UFC 3-230-08A 16 January 2004

UNIFIED FACILITIES CRITERIA (UFC)

WATER SUPPLY: WATER

TREAMENT

APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED

UFC 3-230-08A 16 January 2004

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UNIFIED FACILITIES CRITERIA (UFC)

WATER SUPPLY: WATER TREATMENT

Any copyrighted material included in this UFC is identified at its point of use. Use of the copyrighted material apart from this UFC must have the permission of the copyright holder. U.S. ARMY CORPS OF ENGINEERS (Preparing Activity) NAVAL FACILITIES ENGINEERING COMMAND AIR FORCE CIVIL ENGINEER SUPPORT AGENCY Record of Changes (changes are indicated by \1\ ... /1/) Change No. Date Location

This UFC supersedes TM 5-813-3, dated 16 September 1985. The format of this UFC does not conform to UFC 1-300-01; however, the format will be adjusted to conform at the next revision. The body of this UFC is the previous TM 5-813-3, dated 16 September 1985.

UFC 3-230-08A 16 January 2004

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FOREWORD \1\ The Unified Facilities Criteria (UFC) system is prescribed by MIL-STD 3007 and provides planning, design, construction, sustainment, restoration, and modernization criteria, and applies to the Military Departments, the Defense Agencies, and the DoD Field Activities in accordance with USD(AT&L) Memorandum dated 29 May 2002. UFC will be used for all DoD projects and work for other customers where appropriate. All construction outside of the United States is also governed by Status of forces Agreements (SOFA), Host Nation Funded Construction Agreements (HNFA), and in some instances, Bilateral Infrastructure Agreements (BIA.) Therefore, the acquisition team must ensure compliance with the more stringent of the UFC, the SOFA, the HNFA, and the BIA, as applicable. UFC are living documents and will be periodically reviewed, updated, and made available to users as part of the Services’ responsibility for providing technical criteria for military construction. Headquarters, U.S. Army Corps of Engineers (HQUSACE), Naval Facilities Engineering Command (NAVFAC), and Air Force Civil Engineer Support Agency (AFCESA) are responsible for administration of the UFC system. Defense agencies should contact the preparing service for document interpretation and improvements. Technical content of UFC is the responsibility of the cognizant DoD working group. Recommended changes with supporting rationale should be sent to the respective service proponent office by the following electronic form: Criteria Change Request (CCR). The form is also accessible from the Internet sites listed below. UFC are effective upon issuance and are distributed only in electronic media from the following source: • Whole Building Design Guide web site http://dod.wbdg.org/. Hard copies of UFC printed from electronic media should be checked against the current electronic version prior to use to ensure that they are current. AUTHORIZED BY: ______________________________________ DONALD L. BASHAM, P.E. Chief, Engineering and Construction U.S. Army Corps of Engineers

______________________________________DR. JAMES W WRIGHT, P.E. Chief Engineer Naval Facilities Engineering Command

______________________________________ KATHLEEN I. FERGUSON, P.E. The Deputy Civil Engineer DCS/Installations & Logistics Department of the Air Force

______________________________________Dr. GET W. MOY, P.E. Director, Installations Requirements and Management Office of the Deputy Under Secretary of Defense (Installations and Environment)

ARMY TM 5-813-3AIR FORCE AFM 88-10, Vol 3

WATER SUPPLY, WATER TREATMENT

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D E P A R T M E N T S O F T H E A R M Y A N D T H E A I R F O R C E16 SEPTEMBER 1985

TM 5-813-3/AFM 88-10, Vol 3●

REPRODUCTION AUTHORIZATION/RESTRICTIONSThis manual has been prepared by or for the Government and, except to the extent indicated below, is public property and not subject to copyright.Copyrighted material included in the manual has been used with the knowledge and permission of the proprietorsand is acknowledged as such at point of use. Anyone wishing to make further use of any copyrighted material, by it-self and apart from this text, should seek necessary permission directly from the proprietors.Reprints or republications of this manual should include a credit substantially as follows: “Joint Departments ofthe Army and Air Force, USA, Technical Manual TM 5-813-3/AFM 88-10, Volume 3, Water Supply, Water Treat-ment.”If the reprint or republication includes copyrighted material, the credit should also state: “Anyone wishing tomake further use of copyrighted material, by itself and apart from this text, should seek necessary permissiondirectly from the proprietors.”

CHAPTER 1. GENERALPurpose and scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Water treatment projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Water quality criteria and standards. . . . . . . . . . . . . . . . . . . . . . . . .

2. WATER TREATMENT PROCESSESProcess selection factor .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Preliminary treatment.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Aeration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Coagulation and flocculation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Sedimentation basins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Filtration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Disinfection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Fluoride adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Taste-and-odor control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Softening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Iron and manganese control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Corrosion and scale control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Special processes. . . . . . . . . . . . . . . . . . . . , . , . . . . . . . , . . . .

3.WATER TREATMENT SYSTEMSGeneral design criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Plant siting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Process selection and design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Reliability, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Operating considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Plant capacity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.MEASUREMENT AND CONTROLlMeasurement of process variables . . . . . . . . . . . . . . . . . . . . . . . . . . .Control, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Design of instruments and controls . . . . . . . . . . . . . . . . . . . . . . . . . .

5.WATER TREATMENT CHEMICALSChemical properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Chemical standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Chemical handling and storage. . . . . . . . . . . . . . . . . . . . . . . . . . . . .Chemical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

6.WATER TREATMENT PLANT WASTESQuantities and characteristics of waste . . . . . . . . . . . . . . . . . . . . . . .Waste management. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

APPENDIX A WATER QUALITY CRITERIA AND STANDARDS . . . . . . . . . . . .

1-11-21-3

2-12-22-32-42-52-62-72-82-92-102-112-122-13

3-13-23-33-43-53-6

4-14-24-3

5-15-25-35-4

6-16-2. . . . .

B DESIGN EXAMPLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .C LABORATORIES AND LABORATORY ANALYSES. . . . . . . . . . . . . . . . . . .D METRIC CONVERSION FACTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .PREFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. BIBLIO

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TM 5-813-3/AFM 88-10, Vol 3

CHAPTER 1

GENERAL

1-1. Purpose and scope.

This manual, intended for planners and design engi-neers, presents information on water quality stand-ards and design criteria for water treatment processes.This manual also establishes criteria to be followed indetermining the necessity for and the extent of treat-ment, and on procedures applicable to the planning ofwater treatment projects. This manual is applicable toall elements of the Army and Air Force responsible forthe planning and design of military construction,

1-2. Water treatment proiects.

State health department, State water resource, andU.S. Environmental Protection Agency personnel, asappropriate, should be consulted in the early stages ofproject planning regarding supply sources and asso-ciated water treatment needs. In addition to the usualtreatment that may be required to insure delivery ofpotable water, consideration will be given to the needfor special treatment to protect pipelines, water heat,-

ers, plumbing fixtures, and other equipment againstscaling, corrosion, and staining, Because of the widelyvarying conditions and the many types of water, it isnot possible to establish criteria for all cases of specialwater treatment. Treatment for prevention of scalingand corrosion may not be entirely effective; and inmany cases a decision as to the necessity of specialtreatment cannot be reached prior to actual operatingexperiences. In general, special treatment will be pro-vided only in cases where a study of water analysesand experience with the water definitely show thatthere will be severe corrosion of the water system orthat severe scaling of hot-water heaters, storage tanks,and other parts of the plumbing system will occur.Marginal cases will be deferred and treatment pro-vided only after operating experience determinestreatment to be necessary.

1-3. Water quality criteria and standards.

Information on current criteria and standards for rawand potable water are presented in appendix A.

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TM 5-813-3/AFM 88-10, Vol 3

CHAPTER 2

WATER TREATMENT PROCESS

2-1. Process selection factors.

The design of treatment facilities will be determinedby feasibility studies, considering all engineering, eco-nomic, energy and environmental factors. All legiti-mate alternatives will be identified and evaluated bylife cycle cost analyses. Additionally, energy use be-tween candidate processes will be considered. For thepurpose of energy consumption, only the energy pur-chased or procurred will be included in the usage eval-uation. All treatment process systems will be com-pared with a basic treatment process system, which isthat treatment process system accomplishing the re-.quired treatment at the lowest first cost. Pilot or labo-ratory analysis will be used in conjunction with pub-lished design data of similar existing plants to assurethe optimal treatment. It is the responsibility of thedesigner to insure that the selected water treatmentplant process complies with Federal EnvironmentalAgency, State or local regulations, whichever is morestringent.

2-2. Preliminary treatment.

Surface waters contain fish and debris which can clogor damage pumps, clog pipes and cause problems inwater treatment. Streams can contain high concentra-tions of suspended sediment. Preliminary treatmentprocesses are employed for removal of debris and partof the sediment load.

a. Screens.(1) Coarse screens or racks. Coarse screens, often

termed bar screens or racks, must be provided to inter-cept large, suspended or floating material. Suchscreens or racks are made of l/2-inch to 3/4-inch metalbars spaced to provide 1- to 3-inch openings.

(2) Fine screens. Surface waters require screens orstrainers for removal of material too small to be inter-cepted by the coarse rack, These may be basket-type,in-line strainers, manually or hydraulically cleaned bybackwashing, or of the traveling type, which arecleaned by water jets. Fine-screen, clear openingsshould be approximately 3/8 inch. The velocity of thewater in the screen openings should be less than 2 feetper second at maximum design flow through thescreen and minimum screen submergence.

(3) Ice clogging. In northern areas screens maybe.clogged by frazil or anchor ice. Exposure of racks orscreens to cold air favors ice formation on submerged

parts and should be avoided to the maximum practi-cable extent. Steam or electric heating, diffusion aera-tion and flow reversal have been used to overcome iceproblems.

(4) Disposal of screenings. Project planning mustinclude provision for the disposal of debris removed bycoarse and fine screens.

b. Flow measurement. Water treatment processes,e.g., chemical application, are related to the rate offlow of raw water, Therefore, it is essential that accu-rate flow-rate measurement equipment is provided.Pressure differential producers of the Venturi type arecommonly used for measurement of flow in pressureconduits. An alternative selection for pressure con-duits is a magnetic flow meter if the minimum velocitythrough the meter will be 5 feet per second or more. AParshall flume can be used for metering in open chan-nels. Flow signals from the metering device selectedshould be transmitted to the treatment plant controlcenter.

c. Flow division. While not a treatment process,flow division (flow splitting) is an important treatmentplant feature that must be considered at an early stageof design. To insure continuity of operation during ma-jor maintenance, plants are frequently designed withparallel, identical, chemical mixing and sedimentationfacilities. No rigid rules can be given for the extent ofduplication required because a multiplicity of factorsinfluence the decision. Normally, aerators are not pro-vided in duplicate. Presedimentation basins may notrequire duplication if maintenance can be scheduledduring periods of relatively low raw water sedimentload or if the following plant units can tolerate a tem-porary sediment overload. If it is determined that pre-sedimentation at all times is essential for reliable plantoperation, then the flow division should be madeahead of the presedimentation basins by means ofldentical splitting weirs arranged so that flow overeither weir may be stopped when necessary, Duringnormal operation, the weirs would accomplish a pre-cise equal division of raw water, regardless of flowrate, to parallel subsequent units; rapid-mix, slow-mixand sedimentation. The water would then be combinedand distributed to the filters. If presedimentationunits are not provided, then the flow is commonly splitahead of the rapid-mix units. If a single treatmenttrain is to be provided initially with the expectation ofadding parallel units in the future, then the flow-split-

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ting facilities should be provided as part of the originaldesign, with provision for Mocking flow over the weirwhich is to serve future units.

d. Sand traps. Sand traps are not normally requiredat surface water treatment plants. Their principal ap-plication is for the removal of fine sand from well wa-ter, The presence of sand in well water is usually a signof improper well construction or development. If sandpumping cannot be stopped by reworking the well, thesand must be removed. Otherwise, it will create seri-ous problems in the distribution system by cloggingservice pipes, meters, and plumbing. Centrifugal sandseparators are an effective means of sand removal.These cyclone-separator devices are available assem-bled from manufacturers and require no power otherthan that supplied by the flowing water. They operateunder system pressure; therefore, repumping is notnecessary. Water from the well pump enters tangen-tially into the upper section of the cone and centrifugalforce moves the sand particles to the wall of the cone.They then pass downwater into the outlet chamber.Sand is periodically drained to waste from this cham-ber through a valve that can be manually or automat-ically operated. The clarified water is discharged fromthe top of the cone, These units are available in diam-eters of 6, 12, 18, 24, and 30 inches. providing a capac-ity range from 15 to 4500 gallons per minute (gpm)and are suitable for operation up to 150 pounds persquare inch (psi). Pressure drop through the unitranges from 3 to 25 psi, depending on unit size andflow rate. These separators will remove up to 99 per-cent of plus 150 mesh sand and about 90 percent ofplus 200 mesh. The units are rubber lined for protec-tion against sand erosion.

e. Plain sedimentation. Plain sedimentation, alsotermed “presedimentation” is accomplished withoutthe use of coagulating chemicals. Whether plain sedi-mentation is essential is a judgment decision influ-enced by the experience of plants treating water fromthe same source. Water derived from lakes or im-pounding reservoirs rarely requires presedimentationtreatment. On the other hand, water obtained fromnotably sediment-laden streams, such as those foundin parts of the Middle West, requires presedimenta-tion facilities for removal of gross sediment load priorto additional treatment. Presedimentation treatmentshould receive serious consideration for water ob-tained from rivers whose turbidity value frequentlyexceeds 1,000 units. Turbidity values of well over10,000 units have been observed at times on some cen-tral U.S. rivers.

(1) Plain sedimentation basins. Plain sedimenta-tion or presedimentation basins may be square, circu-lar, or rectangular and are invariably equipped withsludge removal mechanisms.

(2) Design criteria. Detention time should be ap-

proximately 3 hours. Basin depth should be in the ap-proximate range of 10 to 15 feet, corresponding to up-flow rates of 600 to 900 gallons per day (gpd) persquare foot for a detention period of 3 hours. Short-cir-cuiting can be minimized by careful attention to de-sign of inlet and outlet arrangements. Weir loadingrates should not exceed approximately 20,000 gpd perfoot. Where presedimentation treatment is contin-uously required, duplicate basins should be provided.Basin bypasses and overflows should also be included.

2-3. Aeration.

The term “aeration” refers to the processes in whichwater is brought into contact with air for the purposeof transferring volatile substances to or from water.These volatile substances include oxygen, carbon diox-ide, hydrogen sulfide, methane and volatile organiccompounds responsible for tastes and odor. Aeration isfrequently employed at plants treating ground waterfor iron and manganese removal.

a. Purpose of aeration. The principle objectives ofaeration are:

(1) Addition of oxygen to ground water for theoxidation of iron and manganese. Ground waters arenormally devoid of dissolved oxygen. The oxygen add-ed by aeration oxidizes dissolved iron and manganeseto insoluble forms which can then be removed by sedi-mentation and filtration.

(2) Partial removal of carbon dioxide to reduce thecost of water softening by precipitation with lime andto increase pH.

(3) Reduction of the concentration of taste-and- -

odor producing substances, such as hydrogen sulfidesand volatile organic compounds.

(4) Removal of volatile organic compounds whichare suspected carcinogens, (see para 2-13b.).

b. Types of aerators. Three types of aerators arecommonly employed. These are: waterfall aeratorsexemplified by spray nozzle, cascade, and multiple-tray units; diffusion or bubble aerators which involvepassage of bubbles of compressed air through the wa-ter; and mechanical aerators employing motor-drivenimpellers alone or in combination with air injection de-vices. Of the three types, waterfall aerators, employ-ing multiply trays, are the most frequently used in wa-ter treatment. The efficiency of multiple-tray aeratorscan be increased by the use of enclosures and blowersto provide counterflow ventilation.

c. Design criteria.(1) Multiple-tray, tower aerators.

(a) Multiple-tray aerators. Multiple-tray aera-tors are constructed of a series of trays, usually threeto nine, with perforated, slot or mesh bottoms. The wa-ter first enters a distributor tray and then falls fromtray to tray, finally entering a collection basin at thebase. The vertical opening between trays usually

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ranges from 12 inches to 30 inches. Good distributionof the water over the entire area of each tray is essen-tial. Perforated distributors should be designed to pro-vide a small amount of head, approximately 2 incheson all holes, in order to insure uniform flow. In aera-tors with no provision for forced ventilation, the traysare usually filled with 2- to 6-inch media, such as coke,stone, or ceramic balls to improve water distributionand gas transfer and to take advantage of the catalyticoxidation effect of manganese oxide deposits in themedia. The water loading on aerator trays should be inthe range of 10 to 20 gpm per square foot. Good, nat-ural ventilation is a requirement for high efficiency.For multiple tray aerators designed for natural venti-lation, the following empirical equation can be used toestimate carbon dioxide (CO2) removal:

trayn number of trays, including distribution trayk = 0.11 to 0.16 depending on temperature, tur-

bulence, ventilation, etc.Where icing is a problem and the aerator must behoused, artificial ventilation by fans or blowers is nec-essary. An enclosed induced- or positive-draft aeratorrequires approximately 3.5 to 6 standard cubic feet ofventilating air per gallon of water aerated. Thus, foran enclosed aerator operating at a rate of 1.5 milliongallons per day (mgd), air requirements will be in therange of 3600 to 6200 standard cubic feet of air perminute. Positive-draft aerators employing the higherair-flow rates exhibit the highest efficiency for the ad-dition and removal of dissolved gases and oxidation ofiron, manganese, and sulfide. Power requirements fora natural draft, multiple-tray aerator having an overallheight of 10 feet will be approximately 1.7 kilowattsper mgd of aeration capacity. Power demands forforced draft units will be greater.

(b) Counter-current packed column aeration. Acounter-current parked column aerator tower is simi-lar to operation to counter-current multiple tray aera-tors, but are particularly efficient at the removal ofvolatile organic compounds (VOCs) through air-strip-ping. Packed column aerators consist typically of along thin tower filled with either a random dumpedmedia (Rasching rings, Ber) saddles, Pall rings) or cor-rugated sheet media, held by a packing support plate.Water is pumped to the top of the tower over a distri-bution plate and allowed to fall through the media. Airis blown up through the tower by a fan counter to thefalling water. Redistributor plates are used through-out the column to prevent channeling of the water orair stream. Efficiency of the tower is dependent on theextent of contact between the air and water. Detaileddesign can be found in various chemical engineering

literatures and handbooks or AWWA, EPA publica-tions.

(2) Diffusion aerators. Compressed air is injectedinto the water as it flows through a rectangular basin.A variety of air injection devices may be employed in-cluding perforated pipes, porous plates or tubes andvarious patented sparger devices. Basin size is deter-mined by desired detention time, which commonlyranges from 10 to 30 minutes. Tank depth is usuallyfrom 10 to 15 feet. Air requirements, supplied by acompressor, generally range from 0.1 to 0.2 standardcubic foot per gallon of water aerated. Major advan-tages of a diffusion aeration system include practicallyno head loss and freedom from cold-weather operatingproblems. An additional advantage is that a diffusionaerator may also be used to provide chemical mixing.Power requirements are those associated with air com-pression and range from 1.0 to 2.0 kilowatts per mgdof aerator capacity. Aeration efficiency in terms of ad-dition of oxygen or removal of carbon dioxide is gen-erally similar to that provided by multiple-tray aera-tors employing natural ventilation.

(3) Mechanical aerators. Mechanical aerators typi-cally consist of an open impellar operating on the wa-ters surface. Basin size is determined by detentiontime required. Basin depth can vary from 5 to 17 feetwith the average depth being 10 feet. Major advan-tages of mechanical aerators are practically no headloss and the ability to provide mixing. Mechanicalaerators are generally not as efficient as aeration tow-ers or diffused aerators and longer detention times arerequired.

d. Criteria for installation of aerators. Aeration is agas transfer process which is not needed at all watertreatment plants. A decision as to whether to aerate ornot requires assessment of the economic and waterquality benefits achieved by its use.

(1) Addition of oxygen. Aeration processes arecommonly used in adding oxygen to groundwaters andto oxidize iron, manganese, hydrogen sulfide and to alimited extent, organic matter. Groundwaters areusually deficient in oxygen and acration is an effectivemeans of adding it. Oxygen addition is normally re-quired if iron and manganese removal is a treatmentobjective. Aeration will also help oxidize hydrogen sul-fide and some organic matter.

(2) Partial removal of volatile substances. Aera-tion is a useful method of removing volatile substancesfrom water. Groundwaters while being deficient inoxygen can contain objectionable levels of carbon diox-ide. An efficient aerator will result in near saturationwith oxygen and about 90 percent reduction of the car-bon dioxide content of groundwater. At lime-soda wa-ter softening plants, any carbon dioxide dissolved inthe water at the point of lime application will consumelime without accompanying softening. For high (>50

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mg/L) carbon dioxide concentrations, as encounteredin some groundwaters, aeration for its removal is prob-ably justified. For concentrations on the order of 10mg/L, or less, aeration is probably not economicallyvalid. Before deciding to aerate for carbon dioxide re-moval, the cost of purchasing, maintaining and operat-ing the aerator should be compared to the value of thelime saved. At softening plants, each mg/L of carbondioxide removed will effect a saving of about 1.3 mg/Lquicklime (95 percent calcium oxide). It will also re-duce the quantity of softening sludge produced propor-tionately.

(3) Reduction of hydrogen sulfide. Aeration is alsoused for removing hydrogen sulfide from well water. Itmay be sufficient in itself if the hydrogen sulfide con-centration is not more than about 1.0 or 2,0 mg/L.Otherwise, it maybe used in conjunction with chlorineto oxidize the hydrogen sulfide not removed by aera-tion.

(4) Reduction of Volatile Organic Compounds(VOCs). Recent studies have shown that aeration canbe successfully employed to reduce volatile organiccompounds (VOCs) such as total Trihalomethane(TTHM) concentration in chlorinated water to meetcurrent US EPA regulations limiting TTHM concen-trations. Aeration by diffused air or multiple-trayaerators can reduce TTHM concentration at low cost,with cost increasing with higher concentrations of Tri-halomethane (THM). Counter-current packed toweraeration is most efficient in achieving mass transfer ofVOC.

e. Aeration summary. Where icing is a problem andthe aerator must be housed, artificial ventilation byfans or blowers is necessary. An enclosed induced- orpositive-draft aerator requires approximately 3.5 to 6standard cubic feet of ventilating air per gallon of wa-ter aerated. Thus, for an enclosed aerator operating ata rate of 1.5 mgd, air requirements will be in the rangeof 3600-6200 standard cubic feet of air per minute.Positive-draft aerators employing the higher air-flowrates exhibit the highest efficiency for the additionand removal of dissolved gases and oxidation of iron,manganese, and sulfide. Counter-current packed col-umn aeration is particularly efficient to remove vola-tile organic compounds, Requirements for a naturaldraft, multiple-tray aerator having an overall height of10 feet will be approximately 1,7 kilowatts per mgd ofaeration capacity, Power demands for forced draftunits will be greater. In general, aeration is worthy ofconsideration in connection with the treatment ofgroundwater supplies in conjunction with lime soften-ing and for the removal of some VOCs. Surface watersusually exhibit low concentrations of carbon dioxide,no hydrogen sulfide and fairly high dissolved oxygen.As a consequence, aeration is not required for the re-moval or addition of these gases. However, surfaces

waters contain higher levels of THM precursors thangroundwaters and therefore a need for aeration mayarise to reduce TTHM following chlorination. Waterhigh in the bromine-containing THMs are difficult totreat by aeration and other methods of removal shouldbe used, such as coagulation and flocculation or con-tact with granular activated carbon.

2-4. Coagulation and flocculation.

Coagulation and flocculation processes are defined asfollows: “Coagulation” means a reduction in the forceswhich tend to keep suspended particles apart. Thejoining together of small particles into larger, settle-able and filterable particles is “flocculation.” Thus,coagulation precedes flocculation and the two process-es must be considered conjunctively.

a. Purposes of coagulation and flocculation. Rawwater supplies especially surface water supplies, oftencontain a wide range of suspended matter, includingsuspended minerals, clay, silt, organic debris andmicroscopic organisms ranging in size from about0.001 to 1.0 micrometer. Small particles in this sizerange are often referred to as “colloidal” particles.Larger particles, such as sand and silt, readily settleout of water during plain sedimentation, but the set-tling rate of colloidal particles is so low that removalof colloidal particles by plain sedimentation is notpracticable. Chemical coagulation and flocculationprocesses are required to aggregate these smaller par-ticles to form larger particles which will readily settlein sedimentation basins. The coagulation-flocculationprocesses are accomplished step-wise by short-timerapid mixing to disperse the chemical coagulant fol-lowed by a longer period of slow mixing (flocculation)to promote particle growth.

b. Chemical coagulant. The most frequently usedchemical coagulant is aluminum sulfate (Al2

(SO 4)3 14H 2O). This aluminum coagulant is alsocalled “alum” or “filter alum,” and dissociates in waterfor form S04 =, Al3+ ions and various aluminum hy-droxide complexes. Other aluminum compounds

Magnesium hydroxide (Mg(OH)2), is also an effectivecoagulant, Organic polyelectrolyte compounds, ap-plied in low dosages alone or in combination with themetal coagulant, are also employed, Polyelectrolytesare high-molecular-weight polymers that dissociate inwater to give large highly charged ions, The polyelec-trolytes and dissociated ions destabilize the colloidsand promote their settling, These polymers can be clas-sified an anionic, cationic or nonionic according totheir dissociated polymeric ions being negatively

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charged, positively charged or both negatively andpositively charged,

c. Coagulation for Removal of TrihalomethanePrecursors. Recent US EPA regulations limit allow-able TTHM concentrations in finished potable water(see para 2-13). To help meet the current maximumcontaminant level (MCL) of 0.10 mg/L for TTHM,trivalent metal ion coagulant, such as aluminum sul-fate or ferrous sulfate, and a variety of organic poly-electrolytes have been used to remove THM precursorsbefore chlorination. Naturally-occurring THM precur-sors, such as humic and fulvic compounds, are onlypartially removed by coagulation and filtration. Forcoagulation with alum, a pH of between 5 and 6 is theoptimum for the removal of fulvic and humic acid com-pounds. Ferrous sulfate exhibits an optimum pH forremoving organic compounds of between 3 and 5. Ful-vic acids require twice the dosages of alum needed forhumic acids, The addition of anionic polymers at dosesfrom 1 to 10 mg/L can also provide some removal ofhumic compounds. The efficiency of removal dependsupon the type and concentration of organic compoundspresent in the water supply, pH, coagulant dose, andsolids-liquid separation step. Optimum precursor re-moval can only be estimated using laboratory simula-tion techniques, such as simple jar testing, followed bysettling or removal of precipitated colloids with mem-brane filters. This procedure can provide the informa-tion necessary to determine the optimum conditionsfor the removal of trihalomethane precursor com-pounds. Monitoring of the removal of organic precur-sor compounds by coagulation and filtration can be fa-cilitated by the measurement of total organic carbon.

d. Design criteria for mixing. Criteria for rapid- andslow-mix processes have been developed on the basis ofdetention time, power input, velocity gradient (G) andthe product (Gt) of velocity gradient and detentiontime. The values of G and Gt are computed from:

Gt = product of G and t, a dimensionless numberwhere

P = the power dissipated in the water (ft-lb/see)u =

V = volume of mixing basin (cubic feet)t = mixer detention time (seconds)

e. Rapid mixing. For rapid-mix units, detention pe-riods usually range from 10 to 30 seconds with in-stalled mixer power approximately 0,25 to 1.0 hp permgd. Power and detention time should be matched sothat values of G will be in the approximaterange: 500-1000 see-1. A wire-to-water efficiency of80 percent, a water temperature of 50 ‘F, a power in-put of 1.0 hp per mgd and a detention time of 10 sec-

onds, yield a G value of about 1000 see-l and a Gtvalue of 10,000. Similarly, a 30-second detention timegives a G value of about 600 and a Gt value of 18,000.Long detention period for rapid-mix basins should beavoided because of higher power requirements and in-ferior coagulation results. The rapid-mix basin shouldbe designed to minimize short circuiting.

f. Slow mix, For slow-mix (flocculating) units, de-tention periods should range from 30 minutes to 60minutes, with installed mixer power of approximately0.1 to 3.5 hp per mgd. G values in the range of 20 see -1

to 100 see-l are commonly employed, CorrespondingGt values will, therefore, be in the range of 36,000 to360,000. Tapered, slow mixing with G decreasingfrom a maximum of about 90 see-l down to 50 see-1

and then to 30 sec -1 can be used and will generally pro-duce some improvement in flocculation. Somewhathigher G values, up to 200 see -1, are employed in somewater softening plants. For normal flocculation, usingalum or iron salts, the maximum peripheral speed ofthe mixing units should not exceed about 2.0 fps andprovision should be made for speed variation. To con-trol short circuiting, two to three compartments areusually provided. Compartmentation can be achievedby the use of baffles. Turbulence following flocculationmust be avoided, Conduits carrying flocculated waterto sedimentation basins should be designed to providevelocities of not less than 0.5 fps and not more than1.5 fps, Weirs produce considerable turbulence andshould not be used immediately following flocculation.

2-5. Sedimentation basins.

Sedimentation follows flocculation, The most commontypes of sedimentation basins in general use are shownin figures 2-1 and 2-2. A recent innovation in clari-fiers is a helicai-flow solids contact reactor, consistingof a above ground steel conical basin as shown in fig-ure 2-3. However, these above ground basins require ahigh head and additional pumps may be required. Aminimum of two basins should be provided to allowone unit to be out of service for repair or maintenance.The design must include arrangements that permit useof a single basin when necessary.

a. Design criteria. The design of a sedimentationtank is based on the criterion as listed in table 2-1,The sedimentation basins should have adequate capac-ity to handle peak flow conditions and to prevent ex-cessive deteriorated effluent water qualities. Theabove design data represent common conditions,higher overflow rates may be used at lime softeningplants and at some plants employing upflow clarifica-tion units as indicated in the tables of Water Treat-ment Plant Design by ASCE, AWWA, CSSE (see appE). Unusual conditions may dictate deviation fromthese general criteria. Detention time in the range of 8to 12 hours, or more provided in several stages, maybe

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b. Flocculation-sedimentation basins. Units of thistype, usually circular, combine the functions of floc-culation, sedimentation and sludge removal, Floccula-tion is accomplished in a circular center well, Sedimen-tation occurs in the annular space between the floc-culation section and the perimeter effluent weir. De-sign criteria are generally similar to those applicable

— to separate units.c. Suspended solids contact basins, Basins of this

type combine rapid-mixing, flocculation, sedimenta-tion, and sludge removal in a single unit. Coagulationand flocculation take place in the presence of a slurryof previously formed precipitates which are cycledback to the mixing and reaction zone. Upflow rates atthe point of slurry separation should not exceed about1.0 gpm per square foot for units used as clarifiers fol-lowing coagulation and approximately 1.5-1.75 gpmper square foot for units used in conjunction with limesoftening.

2-6. Fi l tration.

Filtration of water is defined as the separation of col-loidal and larger particles from water by passagethrough a porous medium, usually sand, granular coal,

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on a 50-mesh (U.S. Series) sieve. Approximately 100percent by weight, of the sand should pass the16-mesh sieve and 90 to 100 percent be retained on a50-mesh sieve. Filter sand should be clean silica sandhaving a specific gravity of not less than 2.5. Thehydrochloric acid volubility of the sand should be lessthan 5 percent.

(b) Anthracite. Anthracite is an alternative me-dium consisting of hard anthracite coal particles. Theeffective size commonly ranges from about 0.45 mm to0.6 mm with a uniformity coefficient not to exceed1.7. The hardness should not be less than 2.7 on theMoh scale and the specific gravity not below 1.4. Also,the anthracite should be visibly free of clay, shale, anddirt.

(c) Multimedia. Multimedia filters employ twoor three layers of media of different size and specificgravity. A common arrangement, the dual mediafilter, is 20 inches of anthracite overlaying a sandlayer of approximately 8 to 12 inches. The anthracitelayer has size range of about 0.8 to 2.0 mm; the sandlayer, about 0.4 to 1.0 mm. Tri-media filters employ an18-inch anthracite layer, an 8-inch sand layer, and anunderlying 4-inch layer of garnet or ilmenite having asize range of 0.2 to 0.4 mm. Garnet has a specific grav-it y of about 4, and ilmenite about 4.5.

(3) Filter gravel and underdrains, The filter mediais commonly supported by a 10- to 18-inch layer ofcoarse sand and graded gravel. The gravel depth mayrange from 6 inches to 24 inches, depending on the fil-ter underdrain system chosen. The gravel should con-sist of hard, rounded stones having a specific gravityof at least 2.5 and an acid volubility of less than 5 per-cent. A 3- to 4-inch transition layer of coarse (torpedo)sand, having a size range of about 1.2 to 2.4 mm, isplaced on top of the filter gravel. Gravel size usuallyranges from about 0.1 inch to about 2.5 inches. Filterunderdrains may be constructed of perforated pipegrids or various proprietary underdrain systems. Avariety of the latter are available. Design details forpipe underdrains are given in numerous texts andhandbooks. Manufacturers will furnish design and in-stallation criteria for proprietary systems.

(4) Sand, anthracite, gravel specifications. De-tailed specifications for filter sand, anthracite andgravel are contained in AWWA B100.

(5) Number of filters. Not less than two filtersshould be installed regardless of plant size. For largeplants, rough guidance as to the number of filters to beprovided may be obtained from:

—N = number of filter units–Q = design capacity in mgd

Thus, a 9 mgd plant would require eight filters.(6) Size of filter units. The maximum filter size is

related to wash water flow rate and distribution. Nor-

mally, individual filters sizes do not exceed about 2100square feet corresponding to a capacity of about 6 mgdat a flow rate of 2.0 gpm per square foot. A unit of thissize would require a maximum backwash water rate of about 60 mgd, which is excessive. Consequently, itshould be divided into two parts of equal size arrangedfor separate backwashing. Total filter depth should beat least 9 feet.

(7) Filter backwash. Backwash facilities should becapable of expanding the filter media 50 percent. Thiswill require wash rates in the range of 10 to 20 gpmper square foot. Backwash water can be supplied by abackwash pump or from elevated storage provided spe-cifically for this purpose. Filter down-time duringwash periods commonly average 10 to 20 minutes in-cluding a 5- to 15-minute wash period. For a 15-minutebackwash of a single unit, at maximum rate, the washwater volume will be 300 gallons per square foot of fil-tration area in that unit. In addition to backwashing,auxiliary scour is commonly provided. This aids incleaning the filter and is commonly accomplished byrotary or fixed surface-wash equipment located nearthe top of the bed. It is operated for a time periodequal to that of the backwash, Water pressures of40-100 psi are required for surface-wash operation ata rate of 0.5 gpm per square foot. Air scour may alsobe employed but is not generally used. If an independ-ent washwater storage tank is used, it must refill be-tween washes. Tank capacity should be at least 1.5times the volume required for a single wash.

(8) Wash water troughs. Wash water troughsequalize the flow of wash water and provide a conduitfor removal of used water. Two or more troughs areusually provided. The elevation of the trough bottomsshould be above that of the expended bed. The clearhorizontal distance between troughs should not exceed5 to 6 feet, and the top of the troughs not more than 30inches above the top of the bed.

(9) Filter piping and equipment. Essential filtercontrol valves, etc., are shown schematically in figure2-4. Each filter should be equipped with a rate-of-flowcontroller plus associated equipment for automatic fil-ter water-level control. The latter senses the waterlevel in the main influent conduit and transmits a sig-nal to the flow controllers. The controllers, in responseto this signal, adjust filtration rates to match the in-flow from the sedimentation basins. Thus, within prac-tical limits, total filter outflow always equals total in-flow and the filter water level remains virtually con-stant. A device that will sense maximum permissibleclearwell level should also be provided. This should bearranged so that at maximum allowable clearwellwater level, a shut-off signal will be transmitted to allfilter controllers and also to an audible alarm. Otherdesigns, not involving rate controllers, such as “in- -

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have been developed and may be employed at the dis-cretion of the designer. In general, each filter musthave five operating valves: influent, wash water,drain, surface wash, and filter-to-waste. It is empha-sized that the filter-to-waste piping must not be direct-ly connected to a plant drain or sewer. An effluentsampling tap must be provided for each filter. Valvescan be manually, electrically, hydraulically, or pneu-matically operated. Butterfly type valves are recom-mended for filter service. Design velocities commonlyemployed for major filter conduits are as follows:

The effluent conduit must be trapped to present back-flow of air and provide a seal for the rate controllers.The filter pipe gallery should have ample room andgood drainage, ventilation, and lighting. Dehumidifi-cation equipment for the gallery should receive carefulconsideration. Filters should be covered by a super-structure except under favorable climatic conditions.Drainage from the operating floor into the filtershould be prevented by a curb. Access to the entire bedshould be provided by a walkway at operating floorlevel around the filter. Filters may be manually orautomatically controlled from local or remote loca-tions. Facilities permitting local, manual control arerecommended irrespective of other control features.Used backwash water should be discharged to a washwater recovery basin or to a waste disposal facility.Regulatory agencies generally view filter wash wateras a pollutant and forbid its direct discharge to thenatural drainage.

(10) Essential instrumentation. Minimum essen-tial instrumentation for each filter will be provided asfollows: rate=of-flow indicator; loss-of-head indicator;effluent turbidity indicator; wash water rate-of-flowindicating and totalizing meter. If a wash water stor-age tank is provided, it must be equipped with a water-level indicator. While not absolutely required, a tur-bidity indicator on the main filter influent is desirable.

b. Diatomite filters. Filtration is accomplished by alayer of diatomaceous earth supported by a filter ele-ment termed a septum, This layer of diatomaceousearth is about l/8-inch thick at the beginning of filtra-tion and must be maintained during filtration by aconstant feed of diatomaceous earth (body feed) to theinfluent water. At the conclusion of a filter run, thelayer of diatomaceous earth will have increased inthickness to about 1/2 inch. Filtration rates generallyvary from 0.5 to 2.0 gpm per square foot. The princi-pal use of diatomite filters has been for swimming pool

waters, but some have been installed for the treatmentof potable water.

c. Pressure filters. Pressure filters are similar inconstruction and operating characteristics to rapid sand filters. However, in a pressure filter the media,gravel bed, and underdrains are enclosed in a steelshell. There are a variety of new pressure filters in usetoday. The most common of these are the conventionaldownflow filter, the high-rate downflow filter and theup flow filter. An advantage of any pressure filter isthat any pressure in waterlines leading to the filter isnot lost, as in the case of gravity filters, but can beused for distribution of the filter effluent. Between 3and 10 feet of pressure head are lost through the filter.The primary disadvantage of a pressure filter is that,due to the filter being enclosed in a steel shell, accessto the filter bed for normal observation and mainte-nance is restricted. Also, the steel shells require care-ful periodic maintenance to prevent both internal andexternal corrosion. The use of pressure filters is not ad-vantageous in most systems. However, if the pressurerequirements and conditions in a particular system aresuch that repumping of filtered water can be elim-inated, cost savings will be realized,

(1) Conventional downflow filters. Conventionaldownflow pressure filters consist of a bed of granularmedia or multi-media and are good in removing sus-pended solids comprised of floe. The advantages overgravity filters include lower installation cost andadaptability y to different piping systems. Hydraulicloadings range from 1 to 4 gpm/sq. ft.

(2) High-rate downflow filters. High-rate down-flow filters have filtration rates of 10-20 gpm/sq. ft.The higher downflow velocities require coarser mediawhich allow suspended solids to penetrate deeper intothe medium. As a result, more solids can be stored inthe filter bed before backwashing is required, Manyunits exhibit a 1-4 lbs/sq. ft. solids-loading capacity,The higher filtration rates also allow smaller or fewerfilters to be used over conventional filters. However,the high solids-loading capacity of this filter requireshigher backwashing flow rates and hence larger back-washing water storage tanks.

(3) Upflow filters. Upflow multi-media filtersallow filtration of high solids-loaded liquids in concen-tration up to 1,000 mg/L. The advantage of upflowmulti-media filters is that the coarser material at theinlet collects the heavier particles, while the finer ma-terial collects the smaller particles, thus efficiency ofthe filter is increased.

(4) Upflow continuous backwash sand filters. Up-flow continuous backwash sand filters continuouslyclean the filter medial by recycling the sand internallythrough an air lift pipe and sand washer. The regen-erated sand is then redistributed to the top of the sand –

bed. Once the sand migrates down to the bottom of the

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bed it is again airlifted and repeats the cycle. Upflowcontinuous backwash sand filters require no backwashvalves, storage tanks, or backwash pumps, thereforetheir operation is greatly simplified.

2-7. Disinfection.

Disinfection involves destruction or inactivation oforganisms which may be objectionable from the stand-point of either health or esthetics. Inasmuch as thehealth of water consumers is of principal concern tothose responsible for supplying water, design of facili-ties for disinfection must necessarily be carefullyexecuted.

a. Chlorination. The application of chlorine to wateris the preferred method of disinfecting water suppliesat military installations.

(1) Definitions. Terms frequently used in connec-tion with chlorination practice are defined as follows:

(a) Chlorine demand. The difference betweenthe concentration of chlorine added to the water andthe concentration of chlorine remaining at the end of aspecified contact period. Chlorine demand varies withthe concentration of chlorine applied, time of contact,temperature, and water quality.

(b) Chlorine residual. The total concentration ofchlorine remaining in the water at the end of a speci-fied contact period,

(c) Combined available residual chlorine. Anychlorine in water which has combined with nitrogen.—The most common source of nitrogen is ammonia, andcompounds formed by the reactions between chlorineand ammonia are known as chloramines. The disinfect-ing power of combined available chlorine is about 25 to100 times less than that of free available chlorine.

(d) Free available residual chlorine. That part ofthe chlorine residual which has not combined withnitrogen.

(2) Chlorination practice.(a) Combined residual chlorination, Combined

residual chlorination entails the application of suffi-cient quantities of chlorine and ammonia, if ammoniais not present in the raw water, to produce the desiredamount of combined available chlorine (chloramine) ina water. If enough ammonia is present in raw water toform a combined chlorine residual, only chlorine needbe added to the water. Combined residual chlorinationis generally used only when maintaining an adequatefree chlorine residual in the distribution system isdifficult or when objectionably high levels of TTHMswould be formed as a result of free residual chlorina-tion. Due consideration of other TTHM controlalternatives should be made before using chloramines,(see para 2-13).

(b) Breakpoint chlorination. If a water contains-- ammonia or certain nitrogenous organic matter which

reacts with chlorine, the addition of chlorine causes

the formation of chloramines until the ratio of ele-mental chlorine to ammonia compounds is about 5 to1. Further addition of chlorine results in the oxidationof chloramines to gaseous nitrogen and nitrogenoxides, which decreases the quantity of chloraminespresent. After all of the chloramines have been oxi-dized, additional chlorine added to the water formsonly free available chlorine. The point at which all ofthe chloramines have been oxidized and only free chlo-rine is formed is called the “breakpoint .“ If no am-monia is present in the water, there will be no break-point. The chlorine required to reach the breakpoint isusually about 10 times the ammonia nitrogen contentof the water. However, in certain waters, because ofthe presence of other chlorine consuming substances,as much as 25 times the ammonia nitrogen concentra-tion may be required. Enough chlorine should be addedpast the breakpoint to ensure an adequate freechlorine residual.

(c) Marginal chlorination. Marginal chlorinationinvolves the application of chlorine to produce a de-sired level of total chlorine residual regardless of therelative concentrations of free or combined chlorinepresent. In marginal chlorination the initial chlorinedemand has been satisfied but some oxidizable sub-stances remain.

(d) Chlorine dosages. Figure 2-4 provides mini-mum cysticidal and bactericidal free chlorine residualsand minimum bactericidal combined chlorine residualsfor various pH and temperature levels. Since water-borne bacteria are the major concern at fixed installa-tions, minimum bactericidal levels will be maintainedin treated water in all parts of the distribution systemunder constant circulation. Even at lower pH levels,free chlorine residuals should not fall below 0.2 mg/Land combined chlorine residuals should not fall below2.0 mg/L. If marginal chlorination is practiced, thetotal chlorine residual must not be less than 2.0 mg/l.Whenever epidemological evidence indicates an out-break of a nonbacterial waterborne disease such asamebiasis, infectious hepatitis, or schistosomiasis inthe area of a fixed military installation, cysticidal freechlorine residuals shall be maintained in the watersupply. Further guidance on disinfection requirementsmay be obtained from the Surgeon General’s office.Air Force policy on minimum chlorine levels is estab-lished in AFR 161-44.

(3) Other effects of chlorination. In addition tothe disinfection achieved with chlorination, otherbeneficial effects should be noted. Since the oxidizingpower of chlorine is high, in the presence of free chlo-rine, hydrogen sulfide is oxidized, nitrites are oxidizedto nitrates, and soluble iron and manganese are oxi-dized to their insoluble oxides. Free chlorine also re-acts with naturally occurring taste, odor and color-producing organic substances to form chloro-organic

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compounds, e.g., trihalomethanes (see para 2- 13.b.).The US EPA, after much discussion over costs/benefits, has chosen a maximum contaminant level for

serving above 10,000 persons and has indicated a

water treatment industry to avoid costly modificationsto existing plants. To reach the US EPA’s future maxi-mum contaminant level for TTHM’s, more significantchanges in disinfection practices will be required.

(4) Application of chlorine. Chlorine may be ap-plied to water of two forms: As gaseous elementalchlorine or as hypochlorite salts. Gaseous elementalchlorine shall be used for water disinfection at all fixedinstallations. The cost of hypochlorite salts is prohibi-tive in all plants larger than 0.5 mgd. For remote sites

at fixed installations, some well sources require 5 gpmor less. These sources with small demands can usehypochlorite for disinfection.

(a) Point of application. Chlorine may be ap-plied to water in a variety of locations in the watertreatment plant, storage facilities, or distribution sys-tem. It is absolutely essential that the chlorine appliedto the water be quickly and thoroughly mixed with thewater undergoing treatment. If required, special chlo-rine mixing facilities should be provided. In conven-tional water treatment plants, chlorine may be applied

—.. prior to any other treatment process (prechlorination),following one or more of the unit treatment process(postchlorination), and again in the more distantpoints of the distribution system (dechlorination).

1 Prechlorination., Prechlorination has oftenbeen used so the water would maintain a chlorineresidual for the entire treatment period, thus length-ening the contact time. The coagulation, flocculation,and filtration processes were thought to be improvedby prechlorination of the water, and nuisance algaegrowths in settling basins were reduced. In prechlo-rination, the chlorine was usually injected into the rawwater at or near the raw water intake. Prechlorinationwas the most accepted practice of disinfection in thepast. However, since many surface waters containTHM precursors that will combine with the free chlo-rine during prechlorination and form potentially car-cinogenic THMs, such as chloroform, the point ofapplication has been shifted further down the treat-ment process to take advantage of precursor removalduring treatment.

2 Postchlorination. Postchlorination general-ly involves the application of chlorine immediatelyafter filtration and ahead of the clear well. The designand construction of water treatment plants for mili-tary installations will include the necessary provisionsfor changing the locations of chlorine applications as

may later be desirable for improving treatment or dis-infection processes.

3 Dechlorination. Dechlorination is the prac-tice of adding chlorine to water in the distribution sys-tem to maintain a minimum chlorine residual through-out the system.

(b) Chlorination equipment. Hypochlorite saltsmust be applied to the water in solution form. Hypo-chlorite solutions are pumped by a diaphragm pumpthrough an injection system into the water to be chlo-rinated. If elemental chlorine is used for disinfection,it shall be injected by solution-type chlorinators. Sincechlorine solutions are acidic, many components of achlorination system must be constructed of corrosionresistant materials such as glass, silver, rubber, orplastics. Maintaining the chlorination apparatus in atrouble-free state is essential, Key spare parts and re-pair kits for chlorination systems must be kept onhand. Critical components of the chlorination systemshall be installed in duplicate.

(c) Automatic control. If automatic chlorinationcontrol is utilized, the chlorine feed rate should be con-trolled primarily by the rate of flow of water, with asignal from a downstream residual chlorine analyzerused to trim the feed rate. Provision for manual con-trol during emergency situations must be included.

(5) Superchlorination and dechlorination. Super-chlorination may be necessary if there are large vari-ations in chlorine demand or if available contact timeis brief. Water which has been superchlorinated gen-erally requires dechlorination before discharge to thedistribution system. Dechlorination may be achievedthrough the application of sulfur dioxide, sodium bi-sulfite, or sodium sulfite, or by passing the waterthrough granular activated carbon filters. The de-chlorination process (and subsequent dechlorination, ifnecessary) shall be controlled so that the free residualchlorine remaining in the water is at least 0.2 mg/L.Careful monitoring must be practiced to assure thatpotentially harmful levels of TTHMs are not exceeded.A summary of TTHM regulations are presented intable 2-2.

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(6) Safety precautions for chlorination. TheAWWA manual “Safety Practice for Water Utilities”contains safety recommendations regarding the use ofchlorine. These recommendations shall be followed atall military water treatment facilities. Further discus-sion on safe operation of chlorination facilities forArmy installations are contained in TB MED 576, ap-pendix L.

b. Alternate Disinfectants. If the use of chlorine asa disinfectant causes unacceptably large concentra-

tions of chlorinated organic compounds, and if allother methods for reducing TTHM’s have been ex-hausted, such as moving the point of chlorination,aeration, and special coagulant (as shown in table 2-3 for chloroform which is the main constituent ofTTHMs in many cases) and if an alternate raw watersource, such as a ground water source, is not available,an alternative disinfectant must be considered. Anyalternate disinfectant system installed as the primarymeans of water disinfection shall have chlorination fa-cilities available and operative for stand-by use. Fivealternative disinfectants are discussed below; ozone,chlorine dioxide, chloramines, ultraviolet (UV) radi-ation, and UV and Ozone combined. While chlorine isthe least costly disinfectant, considering dosage andenergy consumption basis. However alternate disin-fectants are not significantly more expensive.

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Table 2-3: Effectiveness of Various Unit Processesfor Reducing Chloroform Formation Potential (Cent ‘d)

(1) Ozone. Ozone is an extremely powerful disin-fectant that has been used in Europe either as a soledisinfectant, or in conjunction with postchlorinationto impart a persistent chlorine residual in the waterdistribution system. United States potable waterplants have in the past used ozone to control taste andodor. Today ozonation is being increasingly used as aprimary disinfectant prior to rapid mixing, floccula-tion and filtration. Ozonation does not produce THMs..It is reduced to oxygen and does not leave any residualdisinfectant. Hence, the need for postchlorination.Ozone is generated electrically, as needed using theelectric discharge gap (corona) technique. Air oroxygen stream, a cooling water stream and alternatingelectric current are required. Efficient cooling is essen-tial to reduce thermal decomposition of ozone. Bubblediffusers appear to be the most economic ozone con-tractors available.

(2) Chlorine Dioxide, Chlorine dioxide is a highlyeffective disinfectant producing minimal THMs in thepresence of their precursors. Chlorine dioxide uses inthe United States have been limited to taste and odorcontrol although it has been used elsewhere as a pri-mary disinfectant and is presently receiving more at-tention in the United States. The common method ofchlorine dioxide production is to react chlorine gasfrom a conventional chlorinator with a sodium chloritesolution. Following the mixing of the chlorine and so-dium chlorite streams and prior to introduction intothe main stream the mixed stream is passed through apacked column contactor to maximize chlorine dioxideproduction. A major disadvantage of chlorine dioxideis the formation of chlorate and chlorite which are po-tentially toxic.

-. (3) Chloramines, The use of chloramines as a dis-infectant fell into disuse after the introduction of

breakpoint chlorination. To achieve the same disinfec-tion ability of chlorine, 10 to 15 times the amount ofchloramines are needed or longer contact time is re-quired. More chloramines are needed if high concen-trations of organic material are found in the influentwater, Chloramines are easy to generate, feed, andproduce a persistant residual that will remain throughthe water distribution system. Chloramines may beproduced by introducing ammonia to the water streamprior to the addition of free chlorine. This process canbe optimized for minimum THM production and maxi-mum disinfection. Recently however there has beensome concern over chloramine toxicity.

(4) Ultraviolet Radiation. Ultraviolet (UV) radi-ation has undergone development, but has not beenused on a large scale for drinking water supply disin-fection. Most of its uses include product or processwater disinfection where high purity, sterile water isneeded. UV radiation has been used to disinfect drink-ing water at remotely located hotels and on cruiseships. Few large scale water processing plants use UVdisinfection, although its application is feasible. UVdisinfection does not leave a disinfectant residual andshould be accompanied by postchlorination. Ultra-violet irradiation is also effective in oxidizing organiccompounds in water, Water turbidity will inhibit theeffectiveness of UV disinfection.

(5) UV and Ozone, Recently there has been someexperimentation in a combined UV and ozone con-tactor. Results from these tests show promise. How-ever, there is no known water treatment plant oper-ating with this method of disinfection.

2-8. Fluoride adjustment.

a. Health effects. An excessive fluoride concentra-tion will damage the teeth of children using the waterfor extended periods. On the other hand, moderateconcentrations, 0.7- 1.2 mg/L, are beneficial to chil-dren’s teeth. Most natural waters contain less than theoptimum concentration of fluoride. Upward adjust-ment of the fluoride concentration can be achieved byapplication of a measured amount of a fluoride chem-ical to the water. For installations where it is desirableand feasible to add fluoride, control limits andoptimum concentrations are as follows:

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b. Fluoridation chemicals. Chemicals most fre-quently used for fluoridation are: Sodium silicofluo-

of chemical will depend principally on delivered costand availability.

(1) Sodium fluoride. This chemical is commercial-ly available as a white crystalline powder having apurity of 95 to 98 percent. (Sometimes it is artificiallycolored nile blue.) Volubility is approximately 4 per-cent at 770 F. The pH of a saturated solution is 6.6.The 100 percent pure material contains 45.25 percentfluoride. It is available in 100-pound bags, 125 to 400pound drums, and bulk.

(2) Sodium silicofluoride. This compound is com-mercially available as a white powder with a purity of98 to 99 percent. Volubility is only about 0.76 percentat 770 F. The pH of a saturated solution is 3.5. The100 percent material contains 60.7 percent fluoride. Itis available in 100 pound bags, 125 to 400 pounddrums, and bulk.

(3) Fluosilicic acid. This chemical is commerciallyavailable as a liquid containing 22 to 30 percent byweight of fluosilicic acid. It is sold in 13 gallon car-boys, 55 gallon drums, and in bulk. The 100 percentpure acid contains 79.2 percent fluoride. The pH of a 1percent solution is 1.2, and the use of fluosilicic acid asa fluoridation agent in a water of low alkalinity willsignificantly reduce the pH of the water. It should notbe used for fluoride adjustment of waters of this typeunless pH adjustment is also provided.

c. Point of application. It is essential that all waterpass the point of injection of the fluoridation chemicaland that the flow rate past this point be known withreasonable accuracy. At a water treatment plant, thepreferred application point is usually the combined ef-fluent of all filters. The fluoride chemical can be fed atan earlier stage of treatment, for example, the com-bined filter influent, but part of the fluoride appliedwill be removed by the filtration process. Coagulationand lime softening will also remove a small amount ofthe applied fluoride. A larger dose is required to offsettreatment process losses. If ground water is the supplysource, the fluoride chemical should be injected intothe discharge pipe of the well pump. Where the supplyis from several wells, each pumping independently tothe distribution system, it will be necessary to providean injection point at each well. If flow past the injec-tion point is variable, automatic equipment that willfeed fluoride chemical at a rate proportional to flow isa requirement.

d. Fluoride feeders. Volumetric or gravimetric dryfeeders equipped with dissolvers are suitable forsodium fluoride or sodium silicofluoride. Feedersshould be equipped with weighing devices that will ac-curately measure the weight of chemical fed each day

and the feed equipment should be designed to mini-mize the possibility of free flow (flooding) of chemicalthrough the feeder. Normally, the feed machine’ssupply hopper should hold no more than 100 to 200pounds of chemical. Large extension hoppers holding ‘- -

much greater quantities of dry fluoride chemical in-crease the danger of flooding and overfeeding and arenot recommended for most installations. Solutions ofsodium silicofluoride are acidic and corrosion-resistantdissolvers and solution piping must be provided wherethis chemical is employed. If fluosilicic acid is used, itcan be applied by means of a small metering pump intoan open channel or a pressure pipe. Storage tanks,feeders, and piping for fluosilicic acid must be made ofcorrosion-resistant material. The acid is slightly vola-tile and the feed system should be enclosed. If not en-closed, special exhaust ventilation should be providedto protect personnel from fluoride fumes.

e. Fluoride removal. Fluoride removal can be accom-plished by passage of the water through beds of acti-vated alumina, bone char, or tricalcium phosphate.When the capacity of the bed to remove fluoride is ex-hausted, it can be regenerated by treatment with acaustic soda solution followed by rinsing and acid neu-tralization of the residual caustic soda. Other methodsof fluoride removal include electrodialysis, reverse os-mosis and ion exchange. Some fluoride reduction canbe obtained by water softening using excess lime treat-ment. Fluoride reduction by this method is associatedwith magnesium precipitation and the extent of fluo-ride removal is a function of the amount of magnesiumprecipitated from the water. All removal processesproduce liquid wastes and suitable provision must bemade for their disposal. Guidance as to the fluoride re-moval process to be employed can be obtained fromlaboratory studies of process effectiveness and fluo-ride removal capacity, using samples of the water thatis to be treated.

2-9. Taste and odor control.

Most taste and odors in surface water are caused bylow concentrations of organic substances derived fromdecomposing vegetation, microscopic organisms, sew-age and industrial waste pollution, etc. Treatment fortaste and odor removal involves destruction of theodorous substance by chemical oxidation or its re-moval by aeration or adsorption or activated carbon.

a. Chemical oxidation. Chemical oxidizing agentswhich have been found effective and which can beused in the treatment of potable water are chlorine,chlorine dioxide, potassium permanganate, and ozone.No single chemical is completely effective under alloperating conditions.

b. Aeration. Aeration is helpful in eliminating odorcaused by hydrogen sulfide, but is ineffective in signif-

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icantly reducing odor associated with dissolvedorganics.

c. Absorption. Powdered activated carbon is com-monly used for removal of tastes, odor and color by ad-sorption. The carbon can be applied to the water at anypoint in the treatment plant prior to filtration, but it isusually advisable to apply it early in the treatmentprocess to prolong contact. For maximum effective-ness, carbon should be applied well ahead of chlorine,and preferably in advance of lime softening, The in-fluent to a presedimentation basin is normally an ef-fective carbon application point. Powdered carbon dos-ages usually range from 5 to 10 mg/L, but as much as50 mg/L may be required. The use of powdered acti-vated carbon adds more suspended solids and increasesthe amount of sludge, thereby creating a sludge dis-posal problem. Powder activated carbon is marginallyeffective in reducing TTHMs. Granular activatedcarbon (GAG) has also been used for taste and odor re-moval. It has been employed as a separate treatmentstep in the form of carbon columns and as a substitutefor sand in the filtration process. Used in this way, thegranular carbon serves in a dual capacity as a filtrationmedium and for taste and odor removal. Granular acti-vated carbon is also excellent at reducing TTHMs.Granular activated carbon must be reactivated on aregular basis to keep its absorptive abilities. Becauseof the cost of reactivation of GAC, other methods oftaste-and-odor control and reduction of TTHMs shouldbe considered. Aeration is generally more cost-effective than GAC contractors.

2-10. Softening.

Whether water softening is provided will depend en-tirely on the type of project and the uses to be made ofthe water. Two general types of processes are used forsoftening: The “lime-soda ash” process and the “cationion exchange” or “zeolite” process.

a. Applications.(1) Permanent posts or bases. Softening of the en-

tire supply for a permanent post or base may be con-sidered if the hardness exceeds 200 mg/l, with hard-ness expressed as equivalent CaCO3. Softening of apost water supply to a total hardness of less than 100mg/L is not required, however, softening to less thanthis amount is justified for the special purposes andservices given in paragraphs (3), (4), (5), and(6) below.

(2) Nonpermanent bases. For Army temporaryconstruction and for Air Force bases not in the perma-nent category, the entire supply will not be softenedunless the total hardness exceeds 300 mg/L. However,when a treatment plant is constructed for the removalof turbidity or iron, the plant may also be designed toaccomplish partial softening.

(3) Laundries. Water for laundries shall have ahardness of 50 mg/l or less. Installation of cation ion

exchange water softeners to reduce the hardness tozero is recommended.

(4) Boiler water. Boiler water for power plantsand heating plants may require softening, but satisfac-tory results can often be obtained by application ofcorrosion and scale inhibitors. Depending on the pres-sure at which the boiler is to operate, partial water-de-mineralization may also be necessary, See paragraph2-13a. for additional information on demineralization.

(5) Dining facilities. The installation of softenersfor small dining facilities, latrines and bathhouses isnot recommended. However, water softeners to reducehardness to 50 mg/L maybe justified for large centraldining facilities to protect equipment and to insuresatisfactory washing of dishes. Each such instance willbe justified separately.

(6) Hospitals. When the water supplied to a hospi-tal has a hardness of 170 mg/L or more, the water willbe softened to approximately 50 mg/L. Where criticalequipment requires water having a hardness of lessthan 50 mg/L, as special study will be made to deter-mine the most feasible means of obtaining water of thenecessary hardness. Zero hardness water may be pipedfrom the main softener or maybe supplied from smallindividual softeners, whichever is the more feasible.The sodium content of the treated water must be takeninto account when selecting a softening method forhospitals.

b. Lime-soda ash process,(1) Softening chemicals and reactions. The princi-

pal chemicals used to effect softening are lime, either

to be softened and react with the calcium carbonateand magnesium in the ater to form insoluble com-pounds of calcium carbonate and magnesium hydrox- .ide. If quicklime is used, it is usually converted to aslurry of hydrated lime by slaking with water prior toapplication. The chemistry of the process can be illus-trated by the following equations:

All of the above reactions can be accomplished in asingle stage of treatment. Lime and soda ash can beadded at the same point and will react with each other;

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however, the net effect will be as illustrated by reac-tions 2 through 7.

(2) Chemical requirements.(a) Lime. A reasonably accurate estimate of lime

requirements for softening can be computed from a

linity and, magnesium. Requirements of quicklime orhydrated lime can be computed as follows:

hardness of the raw water and to establish the amountof noncarbonated hardness to be left in the finished wa-ter. The latter is termed residual noncarbonated hard-ness. Inasmuch as most commercial soda ash is 990/0+

purity of this chemical.lbs soda ash per million gallons = [8.34] [NCH-R]

where— NCH = mg/L of noncarbonated hardness— R = mg/L of residual noncarbonated hardness– (The term [NCH-R] is the mg/L of noncarbonated

hardness removed)(3) Characteristics of lime-softened water. The

carbonate hardness of the water, after application andreaction of the softening chemicals plus sedimentationand filtration, should be approximately 50 mg/L. Thetotal hardness will consist of the carbonate hardness,50 mg/L, plus the residual noncarbonated hardness thatwas intentionally allowed to remain in the water. It isnot advisable to reduce the carbonate hardness to thelowest possible value because such water will be corro-

sive. In lime softened wasters, it is desirable that themagnesium hardness be reduced to 40 mg/L or less.The residual calcium hardness should be approximate-ly 50 mg/L and the alkalinity also about 50 mg/L. Some ground water supplies contain no noncarbonatedhardness. For such waters, lime treatment alone willsuffice for softening.

(4) Sludge production. The lime-soda ash soften-ing process produces chemical sludge composed princi-pally of calcium carbonate and magnesium hydroxide.As withdrawn from sedimentation basins equipped formechanical sludge removal, the proportion of dry sol-ids in the sludge will generally fall within the range of2 to 10 percent. The weight of dry solids produced bysoftening reactions will average approximately 2.5times the weight of commercial quicklime used. Forhydrated lime, softening solids produced will be rough-ly twice the weight of commercial hydrated lime em-ployed. Fairly accurate values of total solids produc-tion at an operating plant can be developed utilizing amass balance which takes into consideration the sus-pended solids in the raw water, the quantity of dis-solved calcium and magnesium in the raw and finishedwater, the quantity and purity of lime applied, thequantity of coagulant used, and the stoichiometry ofthe softening and coagulation reactions. Means of dis-posal of waste solids from softening plants must re-ceive careful consideration at an early stage of treat-ment plant design. See chapter 6.

(5) Lime-caustic soda process. An alternative soft-ening process, sometimes used, is the lime-caustic sodaprocess. The process is worth consideration when con-siderable reduction in noncarbonated hardness is re-quired. Application of the process involves substitu-tion of caustic soda (sodium hydroxide) for soda ashand part of the lime. The remaining lime reacts withcarbonate hardness constituents as previously indi-cated. The caustic soda also reacts with carbonate hardness as follows:

will reduce the noncarbonated hardness as previouslyindicated. All of the reaction products are chemicallyidentical to those obtained by the use of lime and sodaash. The amount of caustic soda required can be calcu-lated from the theoretical quantities of pure lime andsoda ash required. Less calcium carbonate sludge isformed with the lime-caustic soda process. This may bean advantage if softening sludge disposal is a problem.For water softening purposes, caustic soda should bepurchased as a 50 percent solution containing 6.38pounds of pure NaOH per gallon. A 50 percent solutionmust be stored at temperatures above about 600 F. toprevent freezing. As a storage alternative, the 50 per- cent solution may be diluted to 25 to 30 percent

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strength which has a freezing point in the approximate

viewed as a hazardous substance, capable of causingserious burns. Personnel responsible for handling andfeeding the chemical must understand its potentiallydangerous nature, know what precautions should betaken and be supplied with appropriate protectiveclothing, safety showers, etc.

(6) Recarbonation. Recarbonation involves the in-troduction of carbon dioxide and/or bicarbonate ioninto softened water for the purpose of neutralizing ex-cess hydroxide alkalinity and relieving calcium carbon-ate and magnesium hydroxide supersaturation. Car-bon dioxide should either be purchased as liquefiedcarbon dioxide, which must be stored at the plant in arefrigerated storage tank, or generated at the watertreatment plant by the combustion of coke, oil, or gas.Recarbonation can also be achieved by utilizing carbondioxide and bicarbonate available in the raw water.This is the “split” treatment process.

(a) Chemical reactions. The following reactionsillustrate the chemistry of the recarbonation process:

Neutralization of excess lime.

The above reactions are accompanied by importantchanges in the pH of the softened water, and the pHvalue is used as a recarbonation control parameter. Re-carbonation can be practiced in a single-stage or two-stage configuration. If recarbonation is accomplishedin two stages, the first stage is devoted to neutraliza-tion of most of the excess lime. This involves conver-sion of excess lime to calcium carbonate and a pHchange from about 11 to approximately the 9.5-10range. Following the first stage of recarbonation, thewater must be flocculated and settled to remove excesscalcium carbonate. Coagulant such as silica, starch,polymer or ferric sulfate may be employed to assist incoagulation and settling of the calcium carbonate par-ticles. The second stage of recarbonation, usually justahead of filtration, serves principally as a “trim” stagein which final pH adjustments are made, as necessary.Guidance as to the correct pH can be obtained throughcalculation of the saturation index (see para 2-12c).For softened waters of low alkalinity, a plus index isgenerally advisable. Carbon dioxide added in the sec-ond stage converts carbonates to bicarbonates. If onlya single stage of recarbonation is employed, the carbon

---dioxide feed must be adjusted so that the previouslydescribed reactions take place to the extent necessaryat the single point of recarbonation. Single stage recar-

TM 5-813-3/AFM 88-10, Vol 3

The magnesium hardness of the finished water can beestimated from the following:

MgH = magnesium hardness of finished water inmg/L

MgS = magnesium hardness of the first stage sof-tened water in mg/L

MgR = magnesium hardness of the raw water inmg/L

P = ‘/o bypass water(8) Incidental benefits of lime softening.

(a) Disinfection. Excess lime provides excellentbactericidal treatment, especially at pH values above10.5. Lime treatment, while not a substitute for chlori-nation, is an effective supplement,

(b) Reduction of dissolved solids. Removal ofcarbonate hardness by lime treatment results in reduc-tion in the total dissolved solids content of the water.All reaction products of lime softening are relativelyinsoluble. The lime added to the water, as well as thecarbonate hardness constituents in the water, arelargely precipitated.

(c) Iron and manganese removal. Lime softeningis also highly effective as a means of iron and manga-

nese removal. The high pH achieved insured essential-ly complete precipitation of any iron and manganesepresent in the raw water.

(d) Clarification. Lime softening provides excel-lent coagulation and clarification as a result of the pre-cipitation of magnesium hydroxide plus a largeamount of calcium carbonate.

(9) Softening plant design. The equipment, bas-ins, and filters required for lime, lime-soda ash, lime-caustic, or split treatment softening are generallysimilar to the facilities used in conventional coagula-tion-filtration plants. Two stages of treatment areusually advisable. The design of a lime-soda ash orsimilar softening plant is a complex and difficult taskrequiring the services of engineers experienced in proj-ects of this kind. Their assistance should be sought inearly stages of project planning.

(a) Mixing equipment, One problem encoun-tered at softening plants is vibration of rapid mixingdevices due to nonuniform deposits of calcium carbon-ate scale._ Frequent cleaning of the mixer may be re-quired. The frequency of such cleaning can be reducedby recirculation of previously precipitated calcium car-bonate sludge from the settling basin to the rapid-mixchamber. Parshall flumes can serve as mixing devices.

(b) Flocculation and clarification. Each separatestage of flocculation and clarification should have a to-tal detention time at design flow of about 2.5 hours, 30minutes for flocculation and 2 hours for clarification.Average depths of both flocculation and clarificationunits should be 8 to 15 feet. The overflow rate in clari-fiers at design flow should be about 0.75 gpm persquare foot.

(c) Sludge removal and recirculation. First-stagesettling basins shall have mechanical sludge removalequipment. Such equipment is also desirable in the sec-ond-stage basins which follow recarbonation. Sludgerecirculation is generally desirable except during oc-currences of severe taste and odor problems. Recyclingof a portion of the settled sludge, which is high in cal-cium carbonate, to the rapid-mix chamber is effectivein promoting the softening reactions, especially car-bonate precipitation. Where_ presedimentation is em-ployed, recycling sludge to the presedimentation basininfluent will enhance the performance of the presedi-mentation basin.

(d) Solids contact units. Solids contact type ba-sins may be used at many softening plants, particular-ly those treating ground water, These basins providethe functions of mixing, sludge recirculation, sedimen-tation and sludge collection in a simple compact unit.Basins of this type, if properly sized, will provide ef-fective softening and clarification treatment. Overallbasin depths of 10 to 15 feet should be used, and theunit should be designed so that the softening slurry isrecirculated through the center chamber at a rate of

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flow 3 to 5 times as great as the rate of flow throughthe entire unit. The upflow rate at the slurry separa-tion level in the clarification zone should not exceedapproximately 1.5 gpm per square foot.

(e) Chemical application and storage. Lime feed-ers and slakers are key items of equipment at a soften-ing plant and must be selected on the basis of reliabil-ity. Another important item requiring careful consid-eration by the designer is chemical storage. Dependingon the size of the plant, bulk or bag unloading and stor-age for lime and soda ash must be provided. Storageequivalent to at least 30 days average use shall be pro-vided. Caustic soda, if used, will generally be pur-chased as a 50 percent solution and appropriately sizedstorage tanks must be provided for this chemical.

(f) Sludge disposal. A disadvantage of any limesoftening process is the production of a large mass ofsludge of high water content. Provision for its disposalin an environmentally acceptable manner must bemade and this problem must be carefully considered inconnection with softening plant location and design.

c. Cation exchange softening. Hardness is causedprincipally by the cations calcium and magnesium, andcation exchange softening is accomplished by exchang-ing these ions for a cation, usually sodium, which doesnot contribute to hardness. This exchange is achievedby passage of the water through the bed of a granular

change water softeners at fixed military installationshall use polystyrene resins as the softening media.Such resins must have a hardness exchange capacity ofat least 25,000 grains of hardness per cubic foot of res-in.

(2) Regeneration of ion exchange softeners. Theregeneration process generally involves three steps: (1)backwashing, (2) application of regeneration solutions,and (3) rinsing.

(a) Back washing. The purposes of water soften-er backwashing are generally the same as the purposesof filter backwashing. Any turbidity particles filteredout of the water during softening are removed by thebackwashing process. For polystyrene resin media, bedexpansions of from 50 to 100 percent are normally re-quired, which involves backflow rates of 4 to 10 gal-lons per minute per square foot of bed area. Backwashperiods generally range from 2 to 5 minutes. Ion ex-change water softeners which operate upflow ratherthan downflow will not require backwashing, but thewater to be softened must be virtually free of suspend-ed matter.

(b) Application of salt brine. After the unit hasbeen backwashes, a salt solution is applied to the me-dium in order to regenerate its softening capabilities.

Regeneration

TM 5-813-3/AFM 88-10, Voi 3

brines should be 10 to 15 percent solu-tions of salt. The more salt used in the regeneration ofa softener, the more complete the regeneration will be,and the greater the exchange capacity of the regen-erated medium will be. The costs of the extra salt re-quired to obtain the added exchange capacity must beweighed against the advantages of the higher ex-change capacity in order to determine which salt dos-age to use. Salt consumption commonly ranges fromabout 0.3- to 0.5-pound of salt per 1,000 grains ofhardness removed. The contact time of the brine withthe softening medium also has a direct effect on theexchange capacity of the regenerated medium. Con-tact times of 20 to 35 minutes will generally be used.

(c) Rinsing. After regeneration, the brine mustbe rinsed from the unit before softening is resumed.Disposal of backwash water, spent regenerant, andrinse water must be carefully considered.

(3) Ion exchange water softeners. Although mostion exchange softeners at military installations will bedownflow pressure softeners, softening can also beachieved upflow. Larger ion exchange softening facili-ties are often operated upflow in order to avoid the ne-cessity of backwashing. In general, ion exchange soft-eners are of two types; open gravity softeners andpressure softeners.

(a) Open gravity softeners. Open gravity soften-ers are constructed in much the same manner as rapidsand filters, and the modes of operation are very simi-lar. However, the ion exchange medium used in opengravity softeners is much lighter than the sand used infilters, so backwash rates for open gravity softenersmay also be operated upflow, but the softener will notachieve any filtering effects so the influent water mustbe virtually free of suspended matter.

(b) Pressure softeners. A polystyrene resin me-dium used for pressure softening shall have a mini-mum bed depth of 24 inches and physical propertiesapproximately the same as the following:

rate throughto 8 gpm per

square foot but must not exceed 10 gpm per squarefoot under the most severe loadings. Severe reductionsin exchange capacity are experienced if the softeneroperates at rates of flow in excess of 10 gpm per cubicfoot for sustained periods of time. With upflow soften-ing, the rate of flow should be adjusted to maintain abed expansion of from 40 to 60 percent. The degree ofbed expansion is a function of both the flow rate and

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the temperature of the influent water, so the flow ratemust be decreased as water temperature decreases if aconstant bed expansion is to be maintained,

(4) Blending, An ion exchange softener operatingproperly will produce a water having a hardness ap-proaching zero. Inasmuch as it is not generally eco-nomical nor desirable to soften all water to this lowhardness level, provisions, for blending the softenedwater with the unsoftened water are desirable.

(5) Other factors affecting ion exchange soften-ing,

(a) Turbidity, Turbidity particles present in thewater influent to the softener are deposited on thesoftening medium and may cause losses of exchangecapacity and excessive head losses through the soften-er. If turbidity levels are excessive, the particles mustbe removed from the water prior to softening or spe-cial backwashing procedures must be implemented.

(b) Bacterial slimes. Unless proper disinfectionis practiced, bacterial slimes can form in the softeningmedium and cause excessive head losses and loss of ex-change capacity. These slimes can be prevented or re-moved through chlorination of’ feedwater or regenera-tion water.

(c) Temperature. The loss of head through a wa-ter softener is strongly affected by water temperature,with lower head losses occurring at higher tempera-tures. For example, at similar flow rates the head lossthrough a softener at 1220 F. is only about 35 percent

ture affects the exchange capacity of the softener,with a 10 to 15 percent increase at high operating tem-peratures (>860 F.) over the exchange capacity at lowtemperatures (32 to 50° F.)

(d ) I ron , manganese and a luminum. If i ron,manganese, and aluminum are present in the influentwater, precipitates may be formed which coat the me-dium particles and cause a loss of exchange capacity.This problem can be avoided through treatment to re-move the iron, manganese, and aluminum from thewater prior to softening. If iron fouling occurs it maybe possible to overcome it by periodic applications ofsodium bisulfite, sodium hydrosulfite, hydrochloricacid, or sulfuric acid to the softening media. However,these treatments should be implemented only after athorough study of the problem by someone experi-enced in this area.

(e) Total hardness and sodium concentration. Ifthe total hardness exceeds 400 mg/L or the sodium

softener should be sized on the basis of the “compen-sated total hardness” rather than the total hardness.Compensated hardness is calculated as follows:

whereTHC = compensated hardness in mg/L as CaC03

TH = total hardness in mg/L as CaC03

TC = total cations in mg/L, all expressed as CaC03

Compensated hardness (THC) in mg/L is converted tograins per gallon by multiplying by 0.0584 or dividingby 17.1.

(6) Removal of noncarbonated hardness followinglime softening. In some cases, it is more economical toremove noncarbonated hardness in cation exchangesthan by application of soda ash. This method involvesthe use of lime for reduction of carbonate hardness.Following recarbonation, the water is filtered. Then allor part of the water, depending on the final hardnessdesired, is treated in cation exchange softeners for theremoval of noncarbonated hardness. The technique ismost suitable to those areas where regeneration saltcan be obtained at a low cost.

(7) Comparison on lime-soda ash and cation ex-change processes. Although the purpose of both thelime-soda ash process and the cation exchange processis to achieve removal of calcium and magnesium ions,the modes of operation and the quality of the resultantwater are somewhat different.

(a) Turbidity, iron, and manganese. Lime-sodasoftening also effects removal of turbidity and ironand manganese, whereas cation exchange softeningmay have to be preceded by conventional treatmentfor removal of suspended matter and iron and manga-nese.

the water. In contrast, the water entering a cation ex-change softener must be disinfected in order to pre-vent the growth of bacterial slimes within the soften-ing resin.

(c) Total dissolved solids. Total dissolved solidsconcentrations of water are usually lowered by lime-soda ash softening, especially if most of the hardnessinitially present is carbonate hardness. However, ap-plication of soda ash to remove noncarbonated hardnessresults in a slight increase of TDS concentrations.Softening of water by cation exchange processes al-ways results in an increase in TDS levels, because thesodium required to replace calcium and magnesium inthe water has a mass 1.15 times as large as the calciumreplaced and 1.89 times as large as the magnesium re-placed.

2-11. Iron and manganese control.

a. Occurrence of iron and manganese. Dissolvediron and manganese are encountered principally inground waters devoid of dissolved oxygen, Normal,oxygenated surface waters do not contain significantconcentrations of these metals; however, stagnantwater, found in the bottom of thermally-stratified

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reservoirs, sometimes contain dissolved iron and man-ganese. Their presence in solution is associated withanaerobic conditions near the bottom of the reservoir.

b. Effects of iron and manganese. Dissolved iron inexcess of 1 or 2 mg/L will cause an unpleasant taste,and on standing, the water will develop a cloudy ap-pearance. Iron concentrations appreciably greaterthan 0.3 mg/L will cause red stains on plumbing fix-tures and laundry. Similarly, manganese will causeblack stains if present to the extent of more than about0.05 mg/L. Deposits of iron and manganese can buildup in water distribution systems and periodic “flush-outs” of these deposits result in objectionable color andturbidity at the consumer’s tap.

c. Removal by oxidation and filtration. Oxidationcan be accomplished with dissolved oxygen, added byaeration, and by the addition of an oxidizing chemical,such as chlorine, chlorine dioxide, potassium perman-ganate, or ozone. Manganese is more difficult thaniron to oxidize and precipitate. In the absence of man-ganese, iron can often be removed with minimumtreatment, consisting of aeration followed by direct fil-tration. In general, aeration alone will not oxidizemanganese unless the pH is raised to about 9,5. Strongoxidants, such as chlorine or potassium permanganate,are effective at lower pH values. To insure oxidation,precipitation and agglomeration of iron and manga-nese and their essentially complete removal, at leastthree treatment steps are usually necessary: aeration,contact time, and filtration. An aerator containingtrays of coke, limestone, etc., as mentioned in para-graph 2-3c is commonly used. Reaction time is pro-vided by a contact or contact-sedimentation basin hav-ing a detention period of at least 30 minutes. Filtra-tion is accomplished by conventional single or multi-media filters designed for a filtration rate of at least3.0 gpm per square foot. The aeration step is frequent-ly supplemented by a chemical oxidant, such as chlo-rine or permanganate. Flocculation is advantageous inthe contact basin, particularly if iron exceeds about 2mg/L.

d. Removal by ion exchange. The cation exchange(sodium zeolite) softening process, under proper condi-tions, is capable of removing limited amounts of dis-solved (unoxidized) iron and manganese. For applica-tion of this process, it is essential that the raw waterand wash water contain no dissolved oxygen and thatthe sum of the iron and manganese concentrations notexceed about 0.5 mg/L. The presence of oxygen orhigher concentrations of iron and manganese willcause rapid fouling of the exchange resin with conse-quent loss of removal capacity. If fouling occurs, treat-ment of the resin with sodium bisulfite solution anddilute hydrochloric or sulfuric acid will be required torestore capacity.

e. Removal by lime-soda softening. Lime-soda so f-

tening is an effective means of removing both iron andmanganese.

f. Stabilization of iron and manganese. Under somecircumstances, stabilization of iron and manganese byapplication of a polyphosphate compound may be ac-ceptable. The iron and manganese in the water aremaintained in a dispersed state through the complet-ing action of a polyphosphate compound. Dosages ofabout 5 mg/L of sodium hexametaphosphate for eachmg/L of iron and manganese are reasonably effectivehowever, the total polyphosphate dosage should not

phate stabilizing compound must be added to thewater prior to chlorination. If the chlorine is appliedfirst, it will oxidize the iron and manganese to in-soluble forms rendering the stabilizing agent ineffec-tive. Stabilization of concentrations of iron and man-ganese in excess of approximately 1.0 mg/L is general-ly not satisfactory. Also, stabilization will not persistif the water is heated because heating coverts poly-phosphates to orthophosphates which have no stabiliz-ing power. Stabilization, although helpful, is not a sub-stitute for iron and manganese removal, and, in gen-eral, should be viewed as a temporary expedient to beused pending installation of removal facilities.

2-12. corrosion and scale control.

“Corrosion” can be defined as the deterioration ofmetal by direct chemical or electrochemical reactionwith its environment. “Scale” refers to an accumula-tion of solids precipitated out of the water. In watertreatment, corrosion and scale are closely associated.Both must be considered in connection with the designand operation of treatment works. This scale may bedesirable because it can provide a measure of protec-tion against corrosion. However, thick layers of scaleare detrimental in both hot and cold water systems. Itis essential to produce a “balanced” water that isneither highly corrosive nor excessively scale forming.

a. Corrosion.(1) The extent and nature of corrosion reactions

depend upon many factors. Among the most impor-tant are the chemical and physical nature of the water,its velocity, pipe metallurgy and pipe coating. In exist-ing systems, where corrosion is a problem, most ofthese factors, with the exception of the chemicalnature of the water, are not readily susceptible tochange. Consequently, for these situations, emphasismust be placed on adjustment of the water’s chemicalquality as the only practical means of corrosion controlin an existing system. Controllable factors are princi-pally calcium content, alkalinity and PH. Certain cor-rosion inhibitors can also be used, but relatively feware suitable for potable water systems.

(2) Treatment to insure deposition and mainte-nance of a thin layer of calcium carbonate on the pipe

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interior is one widely used means of corrosion control.This control method, while not infallible, has beenfairly successful in minimizing the corrosion rate ofiron pipe. The rate of formation of calcium carbonateis favored by high concentrations of calcium and bi-carbonate and carbonate alkalinity. Protection of thistype cannot be attained in waters containing very lowconcentrations of calcium and alkalinity.

(3) Corrosion rates may also be reduced by the useof certain inhibitors. For potable water systems, themost practical inhibitors are silicates and certain poly-phosphate compounds. Sodium silicate can be used to alimited extent in very soft water. Polyphosphates canbe applied for scale as well as corrosion control. Theyare considered most effective for corrosion control inthe pH range 5.0 to 8.0 and their effectiveness is great-ly influenced by velocity. Low velocity, such as en-countered in dead-end mains, reduces the effectivenessof all corrosion control methods.

(4) Dissolved oxygen and carbon dioxide have asignificant effect on corrosion rates. Carbon dioxidelowers the pH and makes the water more aggressive.Carbon dioxide can be removed chemically, but it isgenerally not feasible to attempt chemical removal ofoxygen from potable water supplies. Most surfacewaters are normally saturated with oxygen whileground waters, initially free of oxygen, usually absorbsome during treatment and distribution. When con-sidering the removal of carbon dioxide by aeration, itshould be kept in mind that while efficient aerationwill remove most of the carbon dioxide, it will, indoing this, practically saturate the water with oxygen.

(5) Corrosion rates are influenced to some extentby all mineral substances found in water, but corrosioneffects are so interrelated that it is not possible to iso-late the quantitative influence of individual ions. It isknown that high concentrations of chloride and sulfateions will produce increased corrosion rates. However,their adverse effects are somewhat mitigated by alka-linity (carbonate, bicarbonate) and calcium ions. To ob-tain appreciable benefit from alkalinity and calcium,the total alkalinity, expressed as calcium carbonate,should be at least 50 mg/L, preferable in the range of50 to 100 mg/L. The calcium concentration, calculatedas calcium carbonate, should also be at least 50 mg/L.In general, the higher the concentrations of alkalinityand calcium, the greater is the water’s capacity for cor-rosion retardation. On the other hand, excessive cal-cium and alkalinity will often result in objectionablescale formation. It is, therefore, necessary to seek acompromise between corrosion on the one hand andscale formation on the other.

(6) Based on the corrosion accelerating effects ofchloride and sulfate and the corrosion inhibiting ef-fects of alkalinity, the following ration, termed the“Corrosion Index,” has been developed.

ing a rippled surface which will produce reductions inpipe carrying capacity as measured by the Hazen-Williams “C” value. The problem is one of “after pre-cipitation” of aluminum hydroxide; i.e., aluminum re-mains in solution until after filtration. Chlorination,which often follows filtration, will reduce the pHslightly and the chemical nature of aluminum is suchthat a slight reduction in pH will result in a significant reduction insolubility.

(2) Magnesium. Magnesium hydroxide depositshave caused serious difficulties in distribution systemsand hot water heaters. Magnesium volubility is highlysensitive to pH and temperature and failure to exercisecareful control over its stabilization following sof-tening will usually lead to deposition problems. In theabsence of detailed information regarding the scalingtendencies of a given water, it is advisable to maintainmagnesium hardness below 40 mg/L and pH below 9.8.Hot water heaters should be operated so that watertemperatures will not exceed 140° F.

(3) Iron and manganese. Hydrous oxide depositsof iron and manganese are inevitable in distributionsystems handling water containing more than about0,3 mg/L of iron and 0.05 mg/L of manganese. Theseverity of the problem is directly related to the con-centration of iron and manganese and the best solutionis to remove them at the source. A less satisfactoryprocedure is to attempt to prevent their precipitationby polyphosphate treatment at the source. Iron de-posits may also be caused by corrosion reactions whichform loose scale or tubercles. In severe cases, cleaningand lining of the pipe may be required. Tubercleformation can be minimized through corrosion control.

c. Chemical Control of corrosion.(1) Calcium carbonate saturation,

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(a) One means of chemical control that has beenreasonably successful is treatment of the water to en-sure deposition and maintenance of a coating of cal-cium carbonate. Prediction of the tendency of a waterto precipitate or dissolve a protective coating of cal-cium carbonate can be based on computation of what istermed the “Langlier Index” (LI). This index is calcu-lated as follows:

(eq 2-1)where:LI = Langlier IndexpH = Actual pH of the water

saturation with calcium carbonate

in the water’s alkalinity, calcium content, dissolved

the actual pH, the LI will be positive, indicative of a

greater than the actual pH, the LI will be negative andthis indicates under saturation or a tendency towarddissolving calcium carbonate, and corrosivity. An LIvalue of O indicates exact saturation with calciumcarbonate and no tendency toward deposition or solu-tion.

(b) The complete equation for the exact calcula-

covering the pH range 6.5 to 9.5, may be used. Thesimplified equation is as follows:

where:

A = constant which is a function of water tem-perature

B = constant which is a’ function of total dissolvedsolids concentration (TDS, mg/L)

log(Ca 2+) = logarithm to the base 10 of the Ca2+

concentration in mg/Llog (Alkalinity) = logarithm to the base 10 of the

total alkalinity expressed asCaCo 3, in mg/L.

Values of Ca2+ and Alkalinity are obtained fromanalytical data.

The values of A and B are obtained from the tables2-4 and 2-5.

A32 2,6039 2,5046 2.4054 2.3061 2.2068 2,10

*Reprinted from Standard Methods, for The Examination ofWater and Wastewater; 14th ed., by permission. Copyright 01976,The American Public Health Association.

Table 2-5 Constant B as a Function of Total Dissolved SolidsTDS mg/L B

0 9.70100 9.77200 9.83400 9.86800 9.89

1,000 9.90Reprinted from Standard Methods, for the Examination of Water

American Public Health Association.(c) Examples of the calculation procedure to be

(d) The LI is not a quantitative index in thesense of providing a numerical measure of the amountof calcium carbonate that will be precipitated or dis-solved. Rather, it merely indicates a tendency in thedirection of precipitating or dissolving calcium carbon-ate. If the water is extremely soft (deficient in calciumions) and has a low alkalinity, the water’s capacity forprotection will be minimal even though a high pH anda positive LI are consistently maintained. The watershould contain at least 50 mg/L of alkalinity and atleast 50 mg/L of calcium hardness in order to take ad-vantage of calcium carbonate protection. For softenedwaters, maintain an LI of about + 1.0, and, in addition,apply about 0.5 mg/L of polyphosphate to the filteredwater in order to prevent excessive deposition inpumps and mains near the treatment plant.

(e) The maintenance of a positive Langlier Indexdoes not preclude the possibility of corrosion. Condi-tions may be such that only a partial coating of cal-cium carbonate is deposited, resulting in a type of cor-rosion at the uncoated areas, known as “pitting.” Pit-ting corrosion results in loss of metal from relativelysmall areas of the pipe rather than informly over theentire surface. As a consequence, the pipe may failfairly quickly because of corrosion penetration of thepipe wall.

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2-13. Special Processes.

In some cases it will be necessary to use raw water sup-plies containing unacceptably large concentrations ofconstituents that cannot be removed by conventionaltreatment processes. The most common of these objec-tionable constituents are mineral salts, such assulfates and chlorides, and volatile organic com-pounds, (VOCs). Special treatment processes are neces-sary to remove these materials,

a. Demineralization. The presence of excessivelyhigh concentrations of dissolved minerals in water isindicated by high chloride (Cl-), sulfate (S042-), andtotal dissolved solids (TDS) levels. The recommendedlimits for these substances are 250 mg/L, 250 mg/L,and 500 mg/L, respectively. These limits are based onesthetic considerations and considerably higher con-centrations, while not desirable, can be tolerated.Where demineralization is required, processes com-monly employed are electrodialysis, reverse osmosis,distillation, and ion exchange. Disposal of waste brinesolutions derived from these processes often poses aserious problem and must be carefully considered at anearly stage in project development. All demineraliza-tion processes are energy intensive, and alternativewater sources should be thoroughly investigatedbefore a commitment to a demineralization project ismade. If the demineralization process selected requireslarge inputs of electricity, consideration should begiven to its operation principally during “off-peak”hours with storage of desalted water until needed,

b. Removal of Volatile Organic Compounds. VOCscan be either halgonated naturally occurring organicsubstances (trihalomethanes), or synthetic organiccompounds (SOCs).

(1) Trihalomethanes. Naturally occurring organicsubstances (precursors), such as humic and fulvic acidsare derived from leaf and soil extract and are notthemselves volatile. When the precursors (usuallyfound in surface waters) enter the treatment facility inthe raw water they react with the free available chlo-rine injected for purposes of disinfection. These halgo-nated organic compounds are known as trihalo-methanes (THMs). Other THMs can be produced by ex-posing precursors to other halogens, such as bromineor iodine. This grouping of total trihalomethanes(TTHMs) is generally comprised of four primary con-stituents: trichloromethane (chloroform), bromodi-chlormethane, chlorodibromomethane, and tribromo-methane (bromoform), Monitoring and analytical re-quirements imposed by the EPA for THMs are to befound in Title 40 CFR 141 Subpart C, sections 141.12(c), 141.30 and Appendix C. These sections of Title 40include MCL’s, monitoring frequencies and the ap-proved method for measuring TTHM’s. THMs aredifficult to remove, hence the need for special proc-

esses to assist in their removal. Three basic approachesto control THMs are:

(a) Use of a disinfectant that does not generateTHMs in water. (Ozone, chlorine dioxide)

(b) Treatment to reduce the concentrations ofprecursor material prior to chlorination (coagulation,flocculation, filtration),

(c) Treatment to reduce THM concentrationssubsequent to their formation (aeration, carbon ad-sorption).These three methods have been presented throughoutthis technical manual.

(2) Synthetic Organic Compounds (SOCs), areVOCs some of which have been found in many ground-water sources used for potable water supplies. SOCsare found in groundwater due to improper disposal ofspent industrial-type solvents, paint thinners, cleaningagents and some household chemicals, Two commonSOCs are trichloroethylene (TCE) and tetrachlo-rethylene. Some VOCs are rather soluable and havelittle affinity for soil materials, and therefore cantravel great distances to an aquifier from an industrialwaste lagoon, industrial, commercial on domestic sep-tic system, landfill, accidental spill or illegal disposal.

(3) Removal Technologies for VOCs. Three differ-ent technologies are available for the removal ofVOCs: aeration, carbon adsorption, or resin absorp-tion. All of these methods have been presented in pre-vious sections of this technical manual, with the excep-tion of resin absorption. Resin absorption involves thephysical separation of the organic compounds fromwater by using a polymeric absorbent or resin filledunit. The resin is specific to the VOC it will remove,therefore great care must be taken in the selection ofthe resin. The resin-filled units also require frequentregeneration with a low pressure backwash and analcohol-wash. The waste from the backwash will con-tain high concentrations of VOCs and may be classi-fied as hazardous waste.

(4) Selection of a removal technology. Importantparameters for removing VOCs are the concentrationsconcerned, the type of VOC, and the cost of theremoval method.

(a) The higher the concentration of VOCs themore expensive removal will become, Higher concen-trations of VOCs will normally require larger equip-ment, e.g. counter-current packed column aerationtowers must increase in either volume or blower andpump horse power for increased removal of VOCs,Low TTHM concentrations may be handled by simplychanging the point of chlorination and allowing coagu-lation and flocculation to remove THM precursors.High TTHM concentrations may require the additionof an aeration tower or a GAC contactor and at the ex-treme an alternate disinfectant such as ozone.

(b) The type of VOC to be removed may dictate

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the method of removal. Most VOCs can be reduced tomeet Federal maximum contaminant levels throughairstripping by an aeration tower. However, someVOCs, such as bromoform cannot be easily removedthrough airstripping and a more expensive method ofremoval such as carbon adsorption must be used.

(c) Airstripping through counter-current packedcolumn aeration towers appear to be a cost-effectivemethod for reducing VOCs. Preliminary analyses sug-gests that it may be more economical than GAC orresin absorption treatment. Predicted capital costs andoverhead and maintenance expenditures for aerationtowers are less than other treatment technologies.However, pilot testing must be performed to prove thefeasibility of any solution to the removal of VOCs.Pilot testing will allow enhancement of a selectedmethod, once that method has been proven feasible,allowing a maximum removal of VOCs for a minimumof cost.

c. Industrial water treatment.(1) Water quantity and quality requirements for

industrial uses can vary greatly from industry to in-dustry, and even from plant to plant within the sameindustry. Also, quality requirements within a large in-

dustrial plant can vary depending on the purpose forwhich the water is to be used (e.g., process needs, cool-ing, sanitary requirements, boiler makeup). Conse-quently, the first step in designing a water treatmentplant for an industrial facility is to define the waterquantity and quality requirements.

(2) The water system serving an industrial facilitywill be sized to supply the maximum anticipated quan-tity of water required during a single day of operation.If hourly water usage rates exceed the average rate forthe day of maximum use, storage tanks will be neces-sary to equalize the rate of flow of water through thetreatment plant (see TM 5-813-4/AFM 88-10, Chap.4).

(3) After the water quality requirements havebeen determined, treatment works will be designedusing the appropriate treatment processes to meetthese quality requirements. Most water quality re-quirements can be met through the use of treatmentprocesses previously described. Approval for the use oftreatment processes not described in this manual mustbe obtained from HQDA (DAEN-ECE-G), WASH DC,20314 or HQ USAF/LEEEU, Washington, D.C. 20332.

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CHAPTER 3

WATER TREATMENT SYSTEMS

3-1. General design criteria.

a. Water treatment plants. Water treatment plantsat military installations must produce high quality wa-ter sufficient in quantity for all intended purposes. Ifthe water is to be used for human consumption, itmust be free at all times of organisms or substancesposing health hazards, and also essentially free of ma-terials that would make it esthetically unsatisfactoryto the consumers. The overall water quality objectivecan be met if the water delivered to service meets thedrinking water standards given in appendix A.

b. Water storage and distribution. The quality ofwater obtained at the user’s tap is not determined sole-ly by water treatment operations. Raw water qualityand conditions in treated water storage and water dis-tribution systems also affect the quality of the water.Consequently, protection of raw water quality and fin-ished water storage and delivery systems to the maxi-mum practicable extent is essential. Excellence in wa-ter treatment is partially nullified unless other watersystem components are adequately designed, main-tained and operated.

3-2. Plant siting.

The following items will be considered inplant site,

choosing a

Proximity to the source of raw water.Proximity to the area to be served.Potential for flooding of the site.Availability and reliability of electric power.Geology and topography of the site.Availability of transportation facilities.Size of the site, both for original and for antici-

pated expansions.h. Legal obligations or restrictions.i. Environmental effects.

3-3. process selection and design.

a. The selection and design of the water treatmentprocesses to be used at a particular facility are dictatedby practicability, reliability, flexibility, and overalleconomics. Engineers experienced in water treatmentplant design are needed to determine the best treat-ment system for any particular situation, and their ad-vice should be obtained in early stages of project plan-ning. Detailed information about major treatmentprocesses is given in chapter 2,

b. State agencies have established design guidelinesbased on local conditions and experiences. Informationregarding these guidelines is available from the divi-sion of engineering within the state agency responsiblefor environmental protection. Consultation with Stateengineers will provide valuable information relative toplant design and water treatment experience in theState or region. It is also advisable to confer with man-agement and operating personnel of nearby water sup-ply utilities.

3-4. Reliabil i ty.

a. Unless the treatment plant can be taken out ofservice for a period of time for maintenance and repairwork, two or more of all essential items, such aspumps, settling basins, flocculators, filters, and chemi-cal feeders must be provided. The degree of impor-tance of each item must be evaluated on a case-by-casebasis, considering that safe water has to be supplied atall times.

b. If there is a definite possibility that lengthy pow-er outages will occur, installation of emergency gener-ating facilities at the water treatment plant should becontemplated. Likewise, if the delivery of crucialchemical supplies is uncertain, larger than normalstores of these chemicals must be kept on hand, whichwould necessitate larger than normal chemical storageareas.

3-5. Operating considerations.

To simplif y plant operations, the following guidelinesshould be observed during the design stage.

a. Unnecessary equipment and operations should beeliminated.

b. Operations requiring frequent attention fromplant operators should be located reasonably close to-gether. The most attention is generally required foroperation of filters, flocculators, and chemical feedingequipment.

c. Chemical handling and feeding should also besimplified as much as possible. Unloading and storageareas for chemicals should be easily maintained andreadily accessible and be close to the point of applica-tion of chemicals.

d. Plants treating river water must be arranged toprovide the flexibility of treatment needed to copewith raw water quality changes.

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3-6. Plant capacity. 5-813-1/AFM 88-10, Vol. 1. Care should be taken not

The water treatment plant will be sized to treat to underestimate special water demands.

enough water to meet the requirements given in TM

TM 5-813-3/AFM 88-10, Vol 3

CHAPTER 4

MEASUREMENT AND CONTROL

4-1. Measurement of process variables.

In order to determine the degree of effectiveness of thedifferent treatment processes, several physical andchemical parameters associated with water treatmentmust be measured. After they are measured, the infor-mation must be evaluated so that necessary adjust-ments can be made in the treatment processes.

a. Minimum analyses. The minimum type, number,and frequency of analyses for military water treat-ment plants will conform to paragraph C-1 of appen-dix C.

b. Laboratories. Laboratories at military watertreatment plants must have the minimum amounts oflaboratory furniture, laboratory equipment, and labo-ratory chemicals prescribed in paragraphs C-2, C-3,and C-4 of appendix C.

c. Records of analyses. Results of laboratory analy-ses will be recorded and maintained in an orderly fil-ing arrangement.

._ 4-2. Control.

Water treatment plant processes may be controlled bymanual, semiautomatic or automatic methods, whichare defined as follows.

a. Manual control. Manual control involves totaloperator control of the various water treatment proc-esses. The personnel at the water treatment plant ob-serve the values of the different variables associatedwith the treatment processes, and make suitable ad-justments to the processes.

b. Semiautomatic control. Semiautomatic controlutilizes instruments to automatically control a func-tion or series of functions within control points thatare set manually. The operator manually starts the au-tomatic sequence of operations. An example of semiau-tomatic control is the automatic backwashing of a fil-ter after operator initiation of the program,

c. Automatic control. Automatic control involvesthe use of instruments to control a process, with neces-sary changes in the process made automatically by thecontrolling mechanisms. When a process variablechanges, the change is measured and transmitted to acontrol device which adjusts the mechanisms control-ling the process. Automatic control systems have beendeveloped which are reliable, but provision for emer-gency manual control must be included.

All instruments and control devices should be placedin readily accessible locations in order to facilitate ob-servation, maintenance, repair, and replacement. In-struments should not be located in environmentswhich might lead to premature failure of the instru-ments. Examples of such environments are areas sub-ject to high temperatures or corrosive vapors. Provi-sions should be made for many of the instruments toactuate alarms if critical process variables exceed orfall below predetermined tolerable levels. Such alarmsshould include both audio and visual signals.

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CHAPTER 5

WATER TREATMENT CHEMICALS

5-1. Chemical properties.

Chemicals are used for a variety of purposes in conven-tional water treatment practice, including coagulationand flocculation, disinfection, fluoridation, taste andodor control, and pH adjustment. The most commonchemicals and some of their characteristics are listedin table 5-1.

5-2. Chemical standards.

Chemicals used at military water treatment plants willmeet the applicable standards of the AWWA. TheAWWA publication number for these standards are:

5-3. Chemical handling and storage.

In the design of water treatment facilities, the selec-tion of methods of chemical handling and storage mustbe based primarily on ease of operation, operating flex-ibility, and safety considerations. If chemicals are tobe received in shipping containers such as bags, boxes,drums, or canisters, equipment required for chemicalhandling may include carts, dollies, fork lifts, cranes,etc. If chemicals are shipped in bulk quantities, themode of unloading depends on the physical character-

istics of the chemical. Bulk liquids are usually unload-ed by pumping from the tank truck or railroad car tothe storage tanks at the treatment plant. Bulk pow-ders can be unloaded by pneumatic unloading and con-veyance devices, or if the powder is to be mixed or dis-solved in water, it can be unloaded directly into a wa-ter eductor in which the powdered chemical and thewater are mixed as the water is flowing to the storagetank, Chemical crystals or granules are usually unload-ed by mechanical devices, such as bucket elevators andconveyor belts. All three forms of bulk chemicals canbe unloaded by gravity if the chemical storage tanks orbins are located below ground near the railroad tracksor roadway. Chemicals shipped in bags, drums, bar-rels, or other shipping containers can usually be storedby placing these containers in a specified storage area,Hazardous chemicals must be stored in separate roomsto avoid reaction of chemical vapors. The supply ofchemicals in storage at a water treatment plant shouldalways be at least equal to the projected 30-day re-quirements. Under some circumstances, it may be de-sirable to maintain larger supplies of essential chemi-cals, such as chlorine or coagulant, and smaller sup-plies of nonessential chemicals, such as fluoridationagents.

5-4. Chemical application.

a. Dry chemicals. Dry chemicals are usually convert-ed to a solution or slurry prior to application to the wa-ter. Measurement of the chemical application rate isaccomplished by the dry-feed machine. The measuredquantity of chemical is then dissolved or slurried in asmall amount of water for transport to the feed point,where the solution or slurry must be rapidly and thor-oughly mixed with water being treated. Before quick-lime can be applied to water, it must be hydrated in aslaker. Either retention-type or paste-type slakers maybe used at military water treatment plants. If a reten-tion-type slaker is used, a temperature of 160° F orgreater will be maintained in the slaker. All slakersmust be equipped with grit removal mechanisms.

b. Liquid chemicals. Chemical solutions or slurriesare applied directly, or after dilution, to the water be-ing treated by volumetric liquid feeders such as meter-ing pumps or rotating wheel feeders. Rapid, thoroughmixing of the chemical solution or slurry with the wa-ter is essential,

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c. Chlorine application. At military water treat- must beat least 2 feet below the surface.ment plants, chlorine will be fed through solution-type d. Corrosion. Special attention should be directed tovacuum feeders. If the concentrated solution from the the materials used for the critical parts of chemicalfeeders is introduced to the water supply in an open feeders. Many chemicals form corrosive environments channel, the point of discharge of the chlorine solution for common metals.

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TM 5-813-3/AFM 88-10, Vol 3

CHAPTER 6

WATER TREATMENT PLANT WASTES

6-1. Quant i t i es and characte r i s t ics o fwastes.

In connection with water treatment plant location anddesign, the disposal of the wastes generated during thevarious treatment processes must receive careful con-sideration. Among these wastes are sludge from pre-sedimentation basins, coagulation and/or softeningsludge, filter wash water, spent regenerant and rinsewater from ion-exchange softeners, diatomite filtersludge, and mineral wastes from desalination facili-ties.

a. Presedimentation sludge. Presedimentation basinsludges reflect the nature of the solids present in theraw water. If the particles in the raw water settle outreadily, the sludge will be of fairly high solids content.Slowly settling particles will produce a thin sludge oflow solids content.

b. Coagulation sludge. The settled residues result-ing from coagulation with alum range in suspendedsolids content from about 1,000 mg/L (0.1%) to about17,000 mg/L (1.70/0). The bulk density of dry alumsludge is usually between 75 and 99 pounds per cubicfoot. In order for alum sludge to be placed in a landfill,it must have a solids content of about 20 percent ormore. Waste sludges produced by coagulation withiron salts are similar to those produced with aluminumsalts.

c. Lime softening sludge. Softening sludges canvary widely in characteristics depending on the rela-tive amounts of calcium carbonate and magnesium hy-droxide in the sludge, the nature and amount of sus-pended particles present in the raw water, and wheth-er or not a coagulant, such as alum, was used. The sol-ids content of softening sludges may vary from 2 to 33percent, and the total sludge volume may range in vol-ume from 0.3 to 6 percent of the water treated. Chemi-cal solids (calcium carbonate and magnesium hydrox-ide) derived from lime softening are roughly 2.5 timesthe weight of quicklime applied.

d. Diatomite sludge. About 300 to 600 pounds ofdiatomite sludge are produced per million gallons ofwater treated. Approximately two-thirds of the sludgeis the diatomaceous earth used for filtration and one-third is the impurities removed from the water. Thedry bulk density of the sludge is about 10 pounds percubic foot.

e. Filter wash water. A variety of suspended substances may be present in filter wash water, including

clay, hydroxides of iron and aluminum, calcium car-bonate, activated carbon, etc. The characteristics of fil-ter wash water at plants using alum for coagulationwill differ considerably from those of wash water de-rived from plants practicing softening or iron andmanganese removal. Filter wash waters invariably arequite diluted, exhibiting average suspended solids con-centrations of less than 200 mg/L (0.020/0).

f. Regeneration brines for ion-exchange softeners.The principal waste products in the waste brines fromion-exchange regeneration are chlorides of calcium,magnesium, and sodium. In addition, small quantitiesof iron, manganese, and aluminum maybe present. To-tal dissolved solids (TDS) concentrations in thesewaste flows commonly range from 35,000 to 45,000mg/L (3.5-4.5%) with maximums of about 95,000 to120,000 mg/L (9.5-12%). The total wastewater flowwill be between 2 to 8 percent of the amount of watersoftened.

g. Desalination waste brines. The waste productsmost often found in desalination waste brines are chlo-ride and sulfate salts of calcium, magnesium and so-dium. TDS concentrations in the waste brines may

pending on the desalination method used and the char-acteristics of the raw water, the volume of the wastebrine flow may be as little as one percent or as much as50 percent of the raw water processed, with an aver-age of 15 to 20 percent. Inasmuch as suspended parti-cles are detrimental to most desalination processes,raw waters intended for desalination are usually treat-ed for turbidity, iron removal, etc., prior to desalina-tion.

6-2. Waste management.

a. Water treatment sludges.(1) Presedimentation sludge. Presedimentation

sludge may be disposed of by returning it to the streamfrom which the raw water was taken, if the appropri-ate regulatory agencies will grant their approval.Otherwise, the sludge should first be dewatered in la-goons or sludge drying beds and then hauled to land-fills or spread on land.

(2) Coagulation sludge,(a) Lagoons. If land is available near the treat-

ment plant, alum sludge can be placed in lagoons to ef-fect further concentration of solids. Depending on thelocal climate and the properties of the sludge, the final

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solids content in the lagoon may be as low as one per-cent or as high as 17.5 percent. A liner of imperviousmaterial may be required within the lagoon by stateauthorities if ground water contamination is a con-cern. Water should be removed from the lagoon by re-cantation. The decanted water may be returned to nat-ural watercourses if state authorities permit, and issometimes returned to the treatment plant for recy-cling. At least two lagoons must be provided so thatfresh alum sludge can be placed in one while the alumsludge in the other is allowed to concentrate. Aftersufficient drying, the sludge should be removed fromthe lagoon and placed in a landfill or spread on suit-able ground. The minimum solids content whichshould be attained before alum sludge can be removedfrom lagoons is generally about 10 percent. In colderclimates, the freeze-thaw cycles to which the liquid inthe lagoon is subjected will aid materially in concen-trating the solids. Sludge lagoons should be enclosedby fencing adequate to exclude children and animals.

(b) Discharge to sanitary sewers. Alum sludgesmay also be discharged to sanitary sewers if disruptionof wastewater treatment processed is not anticipated.If this procedure is chosen, precautions must be takento insure that the sludge does not create a hydraulicoverload in the sewers or form significant deposits inthe sanitary sewer. Inasmuch as a large portion ofalum sludge is not biodegradable, the addition of alumsludge to wastewater will increase the sludge produc-tion at the wastewater treatment plant. Disposal ofalum sludge to storm sewers is equivalent to disposalin natural water courses and should not be attempted.

(c) Sludge beds. Another method of dewateringis application of the sludge to special sludge beds.These beds are usually composed of 6 to 12 inches ofsand ranging in size up to 0.5 mm, with an underdrainsystem of graded gravel 6 to 12 inches deep. Drainpipes 6 to 8 inches in diameter are placed in the gravelto carry away the water from the beds. Sand beds canusually achieve a 20 percent solids concentration inalum sludge within 100 hours at a loading rate of 0.8pounds per square foot. However, the results are high-ly dependent on the characteristics of the sludge andlocal climatic conditions. Warm, dry climates are bestsuited to the use of sand drying beds. The water pass-ing into the drain pipes should be suitable for disposalinto natural watercourses, The dewatered sludge is us-ually removed from the sand bed by mechanicalmeans, but a minimum solids content of approximate-ly 20 percent must be attained before mechanical han-dling is practical. After removal, the dewatered sludgeis usually hauled to a landfill.

(d) Mechanical dewatering devices. Several me-chanical devices have been used for dewatering ofalum sludge, including pressure filters, centrifuges,freeze-thaw devices, vacuum filters, and dual-cell grav-

ity solids concentrators.esses can be used within

Two or more ofthe same system

these proc-to obtain a

higher degree of solids concentration than would be at-tainable using only one process. In order to enchance the performance of some dewatering devices, thesludge can be “conditioned” prior to dewatering.Among the methods of conditioning which have beenused are: application of heat and pressure, freezing,lime treatment, and application of organic polymers.

(e) Alum recovery. Recovery of alum from alumsludge is possible by treatment of the sludge with sul-furic acid followed by sedimentation or filtration to re-move raw water sediment. Recovered alum can be re-cycled, so long as inert material, iron and manganese,toxic metals, and color, do not become unacceptablyconcentrated in the recycled alum solutions. Of thesematerials, iron and manganese usually pose the great-est problem.

(3) Lime-soda softening sludge. In most cases,lime-soda softening sludge will be managed by lagoon-ing. In order to use this method, large areas of landmust be available within a reasonable distance fromthe treatment plant. Lagoon capacity should be atleast 3.5 acre-feet per million gallons daily per 100mg/L of hardness removed. Sized on this basis, thestorage capacity will be sufficient for 2-1/2 to 3 years,after which the accumulated sludge must be removedfor disposal on farm land or in a landfill. If the sludgemust settle through ponded water, a solids concentra-tion of 20 to 40 percent can be anticipated. If theponded water is regularly decanted, the solids contentof the sludge will be about 50 percent. As in the case ofalum sludge lagoons, softening sludge lagoons shouldbe constructed in groups of at least two or three to al-low for alternate filling, drying, and removal of thedried sludge. Lagoon depths will vary from 3 to 10feet. Lagoons will be fenced. The area dimensions ofsludge lagoons should be such that the settled sludgecan easily be removed by cranes or draglines. Thesludge removed from lagoons can be placed in landfills”or used as soil conditioner, although in some cases theapplied sludge has plugged the upper soil layer untilbroken down by winter freezing. The sludge maybe re-calcined for lime recovery, usually after removal ofmost of the magnesium hydroxide by recarbonationand centrifuging. Other methods of dewatering soften-ing sludge prior to recalcining or landfilling includevacuum filtration and centrifugation. Vacuum filtersand centrifuges produce sludge cake having solids con-tent of 50 to 60 percent. Lime-soda softening sludgewill not be discharged to sanitary sewers, and dryingbeds are not recommended because of clogging diffi-culties and potential dust nuisance.

(4) Diatomite sludge. Diatomite sludge dewatersrather easily, so any of several techniques, particularly vacuum filtration and lagooning, may be used to in-

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crease the solids content prior to placement in a land-fill. Inasmuch as diatomite sludges are usually rela-tively innocuous, it may be possible to construct ala-goon, use it until it is filled with sludge, and abandonit. This can be done only if land is readily available forlagoons. If land is not available, lagoons must be al-ternatively filled, dried, and cleaned of settled diato-mite sludge, with the removed sludge taken to a land-fill.

b. Filter wash water. Wash water volumes rangefrom about one to three percent of the raw water proc-essed. Disposal of filter wash water may be by dis-charge to natural receiving waters, by recovery and re-use of the wash water, by lagooning, or by discharge toa sanitary sewer,

(1) Discharge to natural receiving waters. Thismeans of disposal may be practiced only with the ap-proval of the appropriate State and Federal regulatoryagencies.

(2) Recovery and reuse. Recovery and reuse are ac-complished by mixing the filter wash water with theinfluent raw water before or at the rapid-mix basin. Inmost cases, the wash water is collected in a recoverybasin from which it is pumped into the plant raw wa-ter inflow. Suspended solids in the wash water settlealong with other solids in the plant basins and the onlywastewater discharged from the plant is that associ-ated with basin sludge removal. The recycling of filterwash water serves as a water conservation techniqueand may have economic advantages over other meansof disposal. In some instances, the suspended particlesin the filter wash water may not settle out easily, andrecycling may, under some circumstances, cause abbre-viated filter runs. Another potential drawback of washwater recycling, particularly if the raw water has ahigh plankton count, is a build-up of algae in the recy-cled suspended matter and consequent increase oftaste and odor in the water.

(3) Lagooning. Lagooning is an accepted means ofmanaging filter wash water flows. If a separate lagoonis used for the wash water, the supernatant from thelagoon may be recycled through the water treatmentplant.

(4) Discharge to sanitary sewer. Filter wash watermay also be discharged to a sanitary sewer. Rate offlow regulation generally will be required to avoidsewer surcharge. This mode of disposal is most appli-cable if the characteristics of the wash water make itunsuitable for recycling.

c. Waste brines. Two types of brine flows can begenerated at water treatment plants, regenerationbrines from cation-exchange softeners and wastebrines from desalination processes. These brines are

very similar as far as disposal techniques are con-cerned. Methods of brine disposal include regulateddischarge to surface waters, deep well injection,“evaporation” pond disposal, and discharge to a sani-tary sewer. If pond disposal is utilized, the ponds mustbe lined to prevent seepage of brine into the groundwater, Depending on the location of the water treat-ment plant and the volume of brine generated, thesemethods may vary widely in cost, reliability, and en-vironmental acceptability.

(1) Discharge to surface waters. Unregulated dis-charge to surface waters is usually unacceptable. Anexception is that waste brines from a desalting plantnear the ocean can probably be discharged to the oceanif precautions are taken in the design of the outfall toensure that the brine is adequately diluted. On largerivers, it maybe possible to store wastes in watertightponds during low-flow periods and release them at acontrolled rate during high flows. This may be an ac-ceptable procedure if it can be shown that the wastesdo not significantly affect water quality when releasedduring the high-flow period.

(2) Deep well injection. In order to determine thefeasibility of using deep well injection for brine dispos-al, it must first be ascertained whether or not a suit-able subsurface formation is present. Such a formationmust be porous, of large extent, and completely sealedoff from any potential fresh-water aquifiers. Thewastes may require treatment prior to injection toavoid clogging the receiving formation. The costs ofdeep well injection are dependent chiefly on disposalvolumes, treatment requirements, well depths, and in-jection pressures. All deep well injection projects mustmeet appropriate State and Federal regulations.

(3) Evaporation ponds. Evaporation ponds can beused for disposal of waste brines if evaporation ratesare high, precipitation is minimal, and land costs arelow. This method usually involves large capital ex-penditures because of the large surface areas requiredand also because of the pond linings required to retardseepage. In most localities, precautions must be takento insure that brine ponds do not overflow or leak intothe ground water. Watertight ponds are required formost situations.

(4) Discharge to a sanitary sewer. Disposal byregulated discharge to a sanitary sewer may be prac-ticed if wastewater treatment plant operating person-nel and regulatory authorities approve. Conventionalwastewater treatment processes do nothing to removedissolved minerals from water. Hence, all of the dis-solved salts discharged to the sanitary sewer will even-tually be present in the effluent from the wastewatertreatment plant.

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APPENDIX A

WATER QUALITY CRITERIA AND STANDARDS

A-1. Genera l .

In order to evaluate the suitability of water for publicsupply purposes, it is necessary to have numericalquality guidelines by which the water maybe judged.Drinking water standards are of primary concern butit is also valuable to have criteria for assessing thesuitability of a source of raw water for providing waterof drinking water quality after receiving conventionaltreatment. Accordingly, data for evaluating both rawwater and drinking water are given. The raw water cri-teria are those recommended by the National Academyof Sciences-National Academy of Engineering,WASH, DC, and published in “Water Quality Criter-ia.” The Drinking Water Standards are those devel-oped by the U.S. Environmental Protection Agency(EPA) under the provisions of the Safe Drinking WaterAct of 1974. (P. L. 93-523, 93rd Congress). AdditionalArmy guidance and critera are contained in TBMED576, Sanitary Control and Surveillance of Water Sup-plies at Fixed Installations and in TBMED 229, Sani-tary Control and Surveillance of Water Supplies forFixed and Field Installations (currently used only forfield installations). Additional Air Force guidance andcriteria are contained in AFR 161-144, Managementof the Drinking Water Surveillance Program.

A-2. Raw water quality criteria.

Present-day, advanced water treatment processes havedeveloped to the point that a raw water supply of al-most any quality, theoretically, could be used to pro-duce finished water that meets the current standardsfor potable water. However, many of the advancedtreatment processes required to treat a poor qualitywater are complex and costly and should not be in-stalled unless absolutely necessary; i.e., when the soleavailable water source is of inferior quality. Raw watercriteria have been developed by the National Academyof Sciences and National Academy of Engineering andpublished in “Water Quality Criteria.” It is importantto note that these criteria were developed on the basisthat relatively simple, conventional treatment wouldbe given to raw water prior to human consumption.

The criteria are not intended to be definitive bases foracceptance or rejection of a raw water supply. They aremeant to serve as guidelines in determining the ade-quacy of the supply for producing an acceptable fin-ished water supply with conventional treatment -prac-tices.

a. Recommended raw water quality criteria. TableA-1 contains a list of recommended criteria from “Wa-ter Quality Control,” except as otherwise noted. .

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b. Fluoride. Normally, conventional treatment haslittle effect on high fluoride concentrations. Therefore,the criterion for the fluoride concentration in a rawwater supply is practically identical to that for drink-ing water. The drinking water criteria is given in TableA-2.

c. Radioactivity. Table A-3 contains the recom-mended criteria for maximum concentrations of radio-active substances in raw water supplies. Gross alpharadioactivity limits are based on maximum allowableconcentrations of radium-226 (the alpha emitter withthe most critical intake limit).

Table A-2. Maximum contaminant levels for fluoride.

Annual avg. of max. daily Max. contaminantair temp. at system location levels for fluoride

2.42.22.01.81.61.4

A-3. Drinking water standards.

a. Interpretation. It is the responsibility of the Sur-geons General of the Army and Air Force to interpretdrinking water standards established by the USEPA.

b. Bacteriological standards. These standards arebased upon bacteriological tests for oganisms of thecoliform group of bacteria, as specified by the EPA.

(1) Membrane filter technique. When the mem-brane filter technique is used, the number of coliformbacteria will not exceed any of the following:

(a) One per 100 mm as the arithmetic mean ofall samples examined per month; or

(b) Four per 100 mm in more than one samplewhen less than 20 are examined per month; or

(c) Four per 100 mm in more than 5 percent ofthe samples when 20 or more are examined per month.

(2) Fermentation tube method–10 mL portions.When the fermentation tube method using five 10 mLportions per sample is employed, coliform bacteria willnot be present in any of the following:

(a) More than 10 percent of the 10 mL portionsexamined in any month; or

(b) Three or more portions in more than onesample when less than 20 samples are examined permonth; or

(c) Three or more portions in more than 5 per-cent of the samples when 20 or more samples areexamined per month.

(3) Fermentation tube method–100 mL portions.When the fermentation tube method using five 100mL portions per sample is employed, coliform bacteriashall not be present in any of the following:

(a) More than 60 percent of the 100 mL portionsexamined in any month; or

(b) Five portions in more than one sample whenless than five samples are examined per month; or

(c) Five portions in more than 20 percent of thesamples when five or more samples are examined permonth.

(4) Bacteriological samples. The standards alsospecify the minimum number of samples that must beexamined each month. This is based upon the popula-tion served and ranges from one sample per month fora population of 1,000 or less up to 500 per month for

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the largest systems. The standards provide a table set-ting forth the minimum number of samples per monthas a function of population served, The samples mustbe collected at points that are representative of condi-tions in the distribution system.

c. Chemical and physical standards. Tables A-4 andA-5 give standards applicable to all water supplies atfixed facilities used for drinking purposes. Except asdenoted otherwise, these are the standards and cri-teria established by the EPA.

d. Radioactivity standards.(1) The maximum allowable levels for ra-

dium-226, radium-228, and gross alpha particle ra-dioactivity are:

(a) Combined radium-226 and radium-228–5picocuries (pCi)/liter.

(b) Gross alpha particle activity (including ra-dium-226 but excluding radon and uranium)–15pCi/liter.

(2) Maximum levels for beta particles and photonradioactivity from man-made radionuclides are:

(a) The average annual concentration of betaparticle and photon radioactivity from man-made ra-dionuclides in drinking water shall not produce an an-nual dose equivalent to the total body or any internalorgan greater than 4 mrem/year.

(b) Except for the radionuclides listed in tableA-6, the concentration of man-made radionuclidescausing 4 mrem total body or organ dose equivalentsshall be calculated on the basis of a 2 liter per daydrinking water intake using the 168 hour data listed in“Maximum Permissible Body Burdens and MaximumPermissible Concentration of Radionuclides in Air andin Water for Occupational Exposures,” NCRP Pub. No.22-59. If two or more radionuclides are present, thesum of their annual dose equivalent to the total bodyor to any organ shall not exceed 4 mrem/year.

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APPENDIX B

DESIGN EXAMPLES

B-1. Clarification.

This design example is based on the following condi-tions: river water source; no softening required; tur-bidity of raw water is variable, but rarely exceeds 1000units. See plant flow schematic, figure B-1, showingtwo-stage clarification treatment.

a. Facility to be served. The water treatment plantwill serve a permanent installation.

b. Population served.– Resident 6000– Nonresident 1800

1800– Effective population = — = 6000 = 6600

3

c. System design capacity,– Capacity factor: 1.42 (based on effective popu-

lation)– Design population = (1.42)(6600) = 9372– System design capacity, based on population =

(9372)(150) = 1,405,800 gpd. Use 1,41 mgd– Special design capacity for industrial processes,------

independently determined: 0,79 mgd– Total system design capacity = 1.41 + 0.79 =

2.20 mgd= 1530 gpm

= 3.40 cfsIntake structure will be difficult to enlarge at a laterdate, therefore its hydraulic design should be based onat least 4.4 mgd, twice plant capacity.

d. Preliminary treatment.(1) Rack and strainers. Provide coarse rack with 3-

inch clear opening followed by hydraulically cleanedbasket strainers with 3/8-inch clear openings ahead ofeach pump. Strainers sized to provide velocity of lessthan 2 feet per second through 3/8-inch openings.

(2) Pumps. Provide three pumps rated at 1.10mgd each. This gives firm pumping capacity of 2.20mgd. Maximum capacity is 3.30 mgd. Raw waterpumping station design should provide space and piping arrangements that will permit future installationof larger and additional pumps without major struc-tural or piping changes.

(3) Meter. Provide Venturi-type flow meter inpipeline from intake works to treatment plant. Metershould be sized to cover expected flow range, mini-mum to maximum. Flow meter should be equippedwith flushing lines and bayonet cleaning rods.

(4) Presedimentation basins. Not required.(5) Aeration, Not required.(6) Flow division, Normally, flow division is to be

maintained through the second stage of treatment.Provide first-stage flow division structure with twoidentical rectangular weirs which will split flow intotwo equal parts. Hydraulic design of division structureshould be such that flow, corresponding to maximumpumping capacity (3.3 mgd), can be carried througheither half. Provide plates or gates so that either halfof flow from division structure can be stopped. Struc-ture should be designed to permit easy expansion inthe event plant enlargement is required at a futuredate,

e. First-stage mixing and sedimentation.(1) Rapid mix. Provide two identical rapid-mix ba-

sins, each providing a detention time of 20 seconds at50 percent of design flow. Volume each basin is(20)(0.5)(3.4) or 34 cubic feet. Provide one electric mo-tor-driven, rapid-mix unit, each basin, powered toyield a G value of approximately 700 see-l at a water

(2) Flocculation-sedimentation. Provide two me-chanically-equipped, circular flocculator-clarifiers,each sized for 50 percent of design flow. These unitswill normally operate in parallel.

— Detention time in flocculation zone: 30 min-

——

———

satisfactory value.

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– Use double, V-notch, effluent weirs with in-board, effluent launder.

–Approximate total weir length, each basin: 225

Flocculator units should have variable speed drivesand be powered to yield a G value of approximately 50see-l at mid-speed and a water temperature of 50°F.Provide piping and valves so that either basin can bebypassed while maintaining following secondary unitsin service. Provide basin overflow and basin coverstructure if climatic conditions require. Provide basinsludge withdrawal piping to point of sludge disposal.Sludge pumps will be required if gravity sludge flow isnot feasible.

f. Second-stage flow division structure. Provide sec-ond-stage flow division structure identical to first-stage. This structure allows combining the flows fromthe two, parallel-operating, first-stage sedimentationunits followed by their division into two equal flows,which are then directed to the second-stage rapid-mixbasins. Use of this flow division structure providesmaximum flexibility and optimum use of plant facili-ties when one first- or second-stage rapid mix or floc-culator-clarifier is out of service for repair or mainte-nance.

g. Second-stage mixing and sedimentation.(1) Rapid mix. Provide two second-stage rapid-

mix units identical to those used for first-stage rapidmixing.

(2) Flocculation-sedimentation. Provide two me-chanically equipped, circular, flocculator-clarifiersidentical in size to those used in the first-stage. Theseunits will provide 30 minutes flocculation time and 3hours sedimentation time. Total time for flocculation,both stages, is 60 minutes. Total sedimentation time,both stages, is 6 hours.

h. Filtration. Determine number of filter units.

Filter configuration will consist of two filters, side byside, along both sides of a gallery sized to accommo-date filter piping, valves controls, etc. Main influentheader pipe will be sized for a velocity not to exceed1.5 feet per second. Calculated pipe diameter is 20.4inches. Use 24-inch pipe giving actual velocity of 1.08feet per second. Use 12-inch pipes to supply individualfilters. At a rate of 2 gmp per square foot, total filtra-tion area required will be 1530/2 or 765 square feet or191 square feet of medium area per filter. Provide 14feet by 14 feet medium area. Use dual-media filterswith 8 inches of filter-grade sand, 4 inches of coarsesand, and 20 inches of filter-grade anthracite,equipped with rotary surface wash. Actual filter cells,

including gullet, will be approximately 14 feet by 18feet, Use vitrified clay tile or similar underdrains andgravel layer as recommended by manufacturer. Pro-vide rate controllers and filter level control equip-ment. Establish overall depth of filter cell at 15 feet.Assume an arbitrary operating floor elevation of 15feet. Significant filter elevations and related depthswill be approximately as follows:

Elevation, ft.– Filter cell bottom 0.00– Top of underdrains (+ 10”) 0.83– Top of gravel (+ 10”) 1.67– Top of coarse sand (+ 4”) 2.00– Top of filter sand ( + 8”) 2.67– Top of anthracite (+20”) 4.33– Bottom of surface wash equip

ment(+2”) 4.50– Bottom of troughs (+ 14”) 5.67– Operating water level (7’ above

anthracite) 11.33Depth of water above bottom of filter cell =11.33-0.0000 = 11.33 ft.Freeboard = 15.00-11.33 = 3,67 ft.All four filters, each operated at 2 gpm per square

foot, theoretically will produce(4)(14)(14)(2)(1440)

106

or 2.25792 million gallons of water in 24 hours. As-suming two filters washed at 15 gpm per square footfor 15 minutes each in each 24-hour period, wash wa-

million gallons for normal backwash, or about 4 per-cent of production. Surface washing will require an

(2)(14)(14)(0,5)(15)additional

106 or 0.00294 million

gallons. Total down-time, each filter, is assumed to be20 minutes. The theoretical net water production fordelivery to service will be as follows:

— Theoretical total production 2.25792 mgd– Less due to filter down-time 0.01568– Less wash water required– Net theoretical production

available for service 2,1511 mgdUnder actual operating conditions, with the filter-rateand level control equipment specified, the filters re-maining in service will automatically compensate forproduction lost as a result of a filter being out of serv-ice for washing or repair, Level control insures that fil-ter outflow will always match inflow. In addition toflow and level control equipment, provide automaticfilter shut-off and alarm equipment, to be activated atmaximum allowable clearwell level, and also providefilter high-level alarm. Provide all essential piping,

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valves, surface and backwash facilities, and operatingconsoles. provide essential instrumentation for eachfilter. Provide sampling taps for each filter. Plant lay-out and hydraulic design should be such that addition-al filters can be readily added as required.

i. Clearwell. Clearwell (filtered water storage)capacity should be related to the available or proposeddistribution system storage (ground and elevated). Asan approximation for this design example, clearwellcapacity of at least 0.6 million gallons could be pro-vided. This is about 25 percent of the plant’s daily pro-duction when operating at 2.2 mgd (design capacity).Greater clearwell capacity may prove advantageousdepending on water demand patterns and plant oper-ating schedule. The clearwell is commonly locatedadjacent to the filters and at an elevation permittinggravity flow to it. This usually requires an under-ground structure. An alternative arrangement consistsof a sump following the filters, equipped with auto-matically controlled transfer pumps, which dischargeto an above-ground tank or basin. Underground clear-wells are commonly constructed or reinforced con-crete. For above-ground installations, steel tanks canbe used. Regardless of the arrangement, the clearwellshould be an independent structure, watertight, andprotected against birds, animals and insects. Ventsmust be installed and protected against surface andrainwater entry, birds, insects and animals. A pro-tected, free-discharge, overflow should also be pro-vided. The overflow must not be connected to anysewer or drain. Access to the interior of the clearwell isrequired.The access opening should be curbed at least 6 inchesabove the roof surface and be equipped with a hinged,overlapping, watertight, locking cover. As a generalrule, the clearwell should be located at least 50 feetfrom sewers or drains. The area around the clearwellshould be fenced and the site graded so that surfacedrainage is away from the structure. Where wintersare severe, special consideration must be given to thedesign of vents and overflows to prevent freeze-up as aresult of vapor condensation. A water level sensing in-strument with readout in the plant control centershould be provided. This can operate in conjunctionwith the previously described maximum level control-alarm circulation and lengthened chlorine contacttime.

j. Hydraulic profile. The hydraulic interrelationshipof major plant units must be carefully considered. Ingeneral, the hydraulic design of the plant should be onthe side of ample flow capacity so that, under emer-gency conditions, water can be treated and filtered atconsiderably more than the normal rate with all filtersin service. The approximate elevation data, given inthe following tabulation, establish the emergency-operation hydraulic profile:

B-4

LocationWater level upstream, first-stage flow divi-

sion weirWater level downstream, first-stage flow

division weir(Loss: raw water pipe friction + velocity

head in pipeWater level in first-stage rapid-mix basin(Loss: rapid-mix to first-stage flocculator-

clarifierWater level in first-stage flocculator basin(Loss: flocculator to sedimentation basinWater level in first-stage sedimentation

basinFirst-stage sedimentation basin overflow

level(Loss: sedimentation basin weirs, launder

and piping to second-stage division struc-ture

(Loss: second-stage division structureWater level in second-stage rapid-mix basin(Loss: rapid-mix to second-stage floccula-

tor clarifierWater level in second-stage flocculator(Loss: flocculator to sedimentation basinWater level in second-stage sedimentation

basinSecond-stage sedimentation basin overflow

level(Loss: sedimentation basin weirs, launder

and filter influent pipingWater level in filtersTop of anthracite (- 7.00)Filter operating floor level (+3.67)(Filter freeboard at second-stage basin over-

flow levelBottom of filter cells (- 15.00)(Maximum loss through filter media, gravel

underdrains, effluent piping and controlsMaximum water level in clearwell(Overall head loss during emergency oper-

ation: first-stage division structure—maximum clearwell level

By utilizing higher-than-normal chemical dosages, theplant can be operated under emergency overload con-ditions and still produce water meeting drinking waterstandards. In deriving the above data, the followingemergency conditions were assumed:

(1) All raw water pumps are operated, giving araw water flow of 3.3 mgd, which is 1.5 times nominaldesign rate.

(2) Both first- and second-stage rapid mix, floc-culation, and sedimentation units on one side of plantare out of service.

(3) Reference elevation of water in first-stage flow -

TM 5-813-3/AFM 88-10, Vol 3

division structure upstream from flow division weirs isarbitrarily established at the 100 footmark.

(4) Raw water transmission pipe is assumed to bea flow division structure to first-stage rapid mix with a44.5 foot, 16-inch pipe having a C value of 100.

(5) Plant units in service:—Half of first-stage flow division structure.–First-stage rapid mixer and first-stage floccu-

later-clarifier.—Half of second-stage flow division structure.–Second-stage rapid mixer and second-stage floc-

culator-clarifier.–All (4) filters, with filter level control equip-

ment, etc., operating normally.(6) Filters are to be washed when head loss ex-

ceeds approximately 8 feet.k. Wash water. Water supply for filter backwash

can be supplied by a special pump, sized to provide therequired flow. If used, backwash pumps should be pro-vided in duplicate. An alternative is an elevated washwater storage tank providing gravity flow. The capac-ity of this tank should be at least 1.5 times maximumwash water requirement for a single filter. For this ex-ample, it is assumed that two filters will be washed insuccession, each for 15 minutes, at maximum rate. Awater tank having a capacity of three times the washrequirement for a single filter is recommended. Itscapacity will be (3)(15)(14)(14)(15) or 132,000 gallons.The wash water storage tank is refilled by pumping fil-tered water from the clearwell. Duplicate, automat-ically-controlled, refill pumps should be provided. Asingle pump should be capable of refilling the washwater tank in approximately 4 hours. A wash waterrate-of-flow controller should be provided on the mainwash water line serving the filters. Rate of wash waterflow and totalizing instrumentation with readoutvisible during the washing process should also be pro-vided.

l. Wash water recovery. Filter wash water can be re-covered and recirculated through the plant. Solids con-tained in the wash water are removed in the plant sedi-mentation basins. Wash water recovery requires theconstruction of a basin into which the wash water isdischarged. The basin bottom should slope steeplytoward the suction pipe of the recycling pump. Thecapacity of the basin should be approximately equal tothe value of two, maximum rate, 15-minute filterwashes, or about 90,000 gallons. For an assumedschedule of two filter washes every 12 hours, the re-cycle pump should have a capacity of about 125 gpm sothat the recovery tank will be emptied in about 12hours. The recycle pumps should be provided in dupli-cate. The recovery tank should be equipped with anoverflow and a drain connection, both discharging tothe plant waste disposal system. Under unusual cir-cumstances, associated with raw water quality, it may

be undesirable to recycle wash water. For such a sit-uation, the wash water can be discharged to the recov-ery basin and then drained slowly to the plant wastedisposal system.

m. Chemical application. Chemicals required forplant operation and the purpose of each are shown intable B-1. Table B-2 summarizes major features ofchemical application and related factors.

n. Chemical storage space. Chemical storage spacerequirements must be analyzed in terms of requiredapplication rates, shipping schedules and quantities.In general, a 30-day supply of a given chemical, basedon estimated average feed rate, is the minimum stor-age volume that should be provided. If chemicals arepurchased in bulk, the minimum storage volume avail-able should be 150 percent of the volume of one bulkshipment, or about 30 days of storage at average feetrate, whichever is greater. For example, if the chem-ical purchase contract is for liquid alum, depending onlocal conditions, the manufacturer may elect to ship asfollows: rail tank cars, 7,000 to 10,000 gallons; tanktrucks, 3,600,4,000 or 5,000 gallons. For rail delivery,minimum storage should be 1.5 x 10,000 or 15,000gallons. For tank-truck delivery, minimum storageshould be 1.5 x 5,000 or 7,500 gallons. If the esti-mated average alum feed rate is 30 mg/1 and the plantis operated at design rate, 2.2 mgd, daily require-ments, in terms of dry alum, are (30)(8.34)(2.2) or 550pounds per day. Liquid alum, as furnished by themanufacturer, normally contains 5.4 pounds of dryalum per gallon of solution. The daily alum solution re-quirement will, therefore, be about 102 gallons. A stor-age volume of 15,000 gallons provides about 150 daysof storage at average feed rate and design flow rate; astorage volume of 7,500 gallons, about 75 days. In thisexample, standard shipping volumes determine stor-age capacity. If the alum supply is to be purchased andstored in 100 pound bags, minimum bag storage spaceequivalent to (30)(550) or 16,500 lbs. of alum should beprovided. Loosely-packed, dry alum has a bulk densityof about 50 pounds per cubic foot. The minimum bagstorage volume should, therefore, be about 330 cubicfeet arranged so that bags can be handled and storedon pallets. Suppliers should be consulted in advance ofdesign regarding shipping quantities, schedules andcosts. It maybe possible to reduce overall shipping and

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b. Population served.– Resident 12,600– Nonresident 1,200

— Effective population

13,000

1,200=

3+ 12,600 =

c. System, design capacity.– Capacity factor: 1.22– Design population = (1.22)(13,000) = 15,860– System design capacity, based on population =

(15,860)(150) = 2,379,000 gpd. Use 2.38 mgd— Special design capacity for industrial processes

and landscape irrigation: 0.44 mgd– Total system design capacity = 2.38 + 0.44 =

2.82 mgd2.82 mgd = 1,960 gpm = 4.36 cfs

d. Treatment system. Figure B-2 illustrates princi-pally the design of facilities for presedimentation, fol-lowed by lime-soda softening. Intake, pumping, meter-ing, hydraulic profile, filters, chemical feeding, etc.,were discussed in the preceding example and discus-sion and calculations pertaining to them are not re-peated here.

e. Pretreatment. Provide a circular presedimenta-tion basin equipped for mechanical sludge removalwith a detention time of 3 hours at design flow. With aside-water depth of 12 feet, the basin overflow ratewill be about 720 gpd per square foot, a satisfactoryvalue. Basin area will be approximately 3920 squarefeet and diameter about 70 feet. Basin effluent shouldbe collected by a peripheral weir and launder. Theweir’s length will be approximately 220 feet, corre-sponding to a weir loading of about 12,700 gpd perfoot, a satisfactory value. A presedimentation basinbypass should be provided so that plant operation canbe maintained when the presedimentation basin is outof service.

f. Flow-division structures. Refer to figure B-2.Flow division structures, generally similar to those de-scribed in the preceding design example, are requiredfollowing the presedimentation basin. These divisionstructures insure continuity and efficiency of plant operation under emergency conditions; i.e., when amajor unit, such as a solids contact or flocculator-clarifier basin, is out of service for repair or mainte-nance. Hydraulic design of the division structuresshall be such that with all raw water pumps in oper-ation, the full flow can be carried through either halfof the structures.

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g. Solids-contact basins. Provide two identical cir-cular, solids-contact units, equipped for mechanicalsludge removal. Units of this type are available fromseveral manufacturers. While they may differ in cer-tain details, all are generally similar in function anddesign. They combine mixing and flocculation, in con-tact with previously precipitated chemical solids, withclarification and sludge removal in a single basin.Solids-contact basins commonly consist of a central

chamber for mixing, flocculation and slurry recircula-tion. Clarification and sludge removal take place in aperipheral slurry separation basin. Overall basin depthis about 15 feet. Mixing, flocculation and slurry cy-cling equipment should be capable of recirculating theslurry in the center chamber at a rate of 3 to 5 timesthe unit’s design throughout. For this example, eachunit will handle one-half of the plant design flow (980gpm). The internal recirculation capacity should,

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therefore, be in the range of approximately 3000 to4900 gpm. A critical design factor is the upflow rate atthe slurry separation level in the clarification zone.This should not exceed approximately 1.5 gpm persquare foot (2160 gpd per square foot) for lime-sodasoftening plants treating turbid surface water. Forthis example, basin area at the slurry separation levelshould be at least 980/1.5 or 653 square feet. Radiallaunders with submerged orifices are commonly pro-vided to collect the clarified water. Lime and soda ashfor coagulation and softening are added to the mixing—section of each solids-contact basin.

h. First-stage recarbonation. Provide two identical5 feet by 5 feet recarbonation-mixing basins, having awater depth of 5 feet, and located as shown on figureB-2. Flow from the division structure should enternear bottom of each basin where it will be mixed with

tion feeder. The combined flow of softened water and

mechanically mixed. For a G value of 500 see-1 at

(ferric sulfate and polymer) are applied in these mixingbasins. Means for recycling of ferric sulfate-calciumcarbonate sludge to these mixing basins should be pro-vided. This sludge is pumped from the underflow oftack of the secondary flocculator-clarifiers and dis-charged to the corresponding recarbonation-mixingbasin at a maximum rate of approximately 200 gpm.Sludge pumps should be equipped with timers so thatPump operation can be started and stopped at the in-tervals found to be best during plant operation.

i. Secondary flocculation and clarification. Providetwo identical circular center-feed basins with an innerflocculation zone, an outer clarification zone, and me-chanical sludge removal equipment. Each basin shouldProvide at 50 percent of design flow a total detentiontime of 2-1/2 hours, 30 minutes for flocculation and 2hours for sedimentation. Value flocculation zone is(30)(60)(0.5)(4.36) or 3,920 cubic feet. Volume clarifi-cation zone is (120)(60)(0.5)(4.36) or 15,700 cubic feet.For an average depth of 10 feet in the flocculationzone and 12 feet in the sedimentation zone, the re-quired construction diameters are 22 feet for the floc-culation zone and 47 feet for the entire basin. Over-

or 1040 gpd per square foot, (0.72 gpm per squarefoot), The flocculator should have a variable speeddrive and should provide a G value of approximately50 see-l at mid-speed and a water temperature of50°F.

j. Second-stage recarbonation. Prior to filtration,provide an additional stage of recarbonation. Use solu-

tion-type CO2 feeder and apply CO2 solution in conduitcarrying the combined effluents from the secondaryflocculator-clarifier basins. k. Carbon dioxide. In developing this example, it

was assumed that carbon dioxide would be purchasedin liquid form, stored in a refrigerated storage tank,equipped with a vaporizer, and applied by means ofsolution-feed equipment generally similar to that em-ployed for the measurement and application of chlo-rine. Other sources of carbon dioxide could be used.Carbon dioxide may be generated on-site by combus-tion of oil, gas, or coke. A compressor and recarbona-tion basin containing a diffusion system are requiredto apply the CO2 thus generated to the water.

1. Chemical requirements for softening process.(1) Lime.–Lbs. 95%quicklime (CaO)per million gallons

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all of the carbonate alkalinity is converted to bicarbon-ate.

—Maximum CO2required for alkalinity conver-

sin drainage with a much smaller amount in filterwash water. If wash water recovery is practiced, allsolids removed appear in basin drainage. Daily solidsproduction can be estimated from data on suspendedmatter concentration in the raw water and by massbalance calculations based on water softening and co-agulation reactions. An estimate of daily solids pro-duction is developed as follows: (Note that the follow-ing calculations of daily solids production are based onoperation of the treatment plant at the design rate;lower average rates of operation would reduce solidsproduction proportionately.)

(1) Rw water solids, If information on suspendedsolids is available this should be used to estimate solidsderived from the raw water. In the absence of such in-formation, turbidity values can be substituted as arough approximation. Raw water turbidity is assumedto be 1000 units. Raw water solids to sludge is(1000)(8.34)(2,82) or 23,500 pounds per day.

(2) Process solids. Chemical solids produced bysoftening and coagulation are principally calcium car-

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dium is 32 inches, consisting of 8 inches of filter-gradesand, 4 inches of coarse sand, and 20 inches of filter-grade anthracite.

h. Postchlorination, Provide two solution-typechlorinators for application of chlorine to the filteredwater, as required, to supply a suitable residual in thewater delivered to service, Normally, one chlorinatorwill be in use with the other serving as a standby.Maximum dosage capacity of each chlorinator shouldbe approximately 5 mg/L for the total plant flow rate.

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APPENDIX C

LABORATORIES AND LABORATORY ANALYSES

C-1. Minimum analyses for military water tics. For purposes of establishing the required ana-treatment plants. lytical frequency, water treatment plants have been di-

vided into two classes, Class A and Class B. A Class AThe minimum number and frequency of analyses to in- plant is any plant employing treatment beyond chlori-sure drinking water of acceptable quality are deter- nation and fluoride control. A Class B plant is anymined by the size of the system and the treatment re- plant which provides only chlorination and/or fluoridequired. The frequency of analyses must also be ad- addition or control. Minimum analysis frequencies arejusted locally to meet changing raw water characteris- listed in table C- 1.

Table C-1. Minimum Analysis Frequencies

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high; a lead-lined or chemical composition trough, 100inches long, 6 inches wide, and 3 to 6 inches deep; astone or chemical composition sink, 24 inches long, 16inches wide, and 12 inches deep with hot and cold run-ning water; 4 double power outlets (115V). The tabletop should be scored to drain to the drain trough. Thebottle rack should be constructed of material resistantto water, chemicals and wear.

(2) One balance table, 36 inches wide, 30 incheshigh, and 24 inches deep, constructed of marble.

(3) One metal supply case, 72 inches high, 48inches wide, 16 inches deep, constructed of marble.

b. Class A plants practicing both softening andiron/manganese removal. Those Class A plants practic-ing both softening and iron/manganese removal willhave the furniture listed above; and one metal chem-istry laboratory well bench assembly, 72 inches long,38 inches high, 30 inches wide; with one sink, 24inches long, 16 inches wide, and 12 inches deep with

hot and cold running water; 4 double power outlets(115 V); with at least 16 drawers. The table top will beof stone or chemical composition.

c. class B plants. All Class B plants will be fur- nished with:

(1) One metal chemistry laboratory well bench as-sembly, 72 inches long, 38 inches high, 30 inches wide;with one sink, 24 inches long, 16 inches wide, and 12inches deep with hot and cold running water; 4 doublepower outlets (115V); with at least 16 drawers. Tabletop will be of stone or chemical composition.

(2) One metal supply case, 36 inches high, 36inches wide, 16 inches deep, two adjustable shelves.

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APPENDIX D

METRIC CONVERSION FACTORS

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APPENDIX E

REFERENCES

Government Publications

Department of the Army and Air Force

TM 5-660 Operation of Water Supply and Treatment Facilities at Fixed ArmyInstallations

TM 5-813 -1/AFM 88-10, Chap. 1 Water Supply: General ConsiderationsTM 5-813 -4/AFM 88-10, Chap, 4 Water Supply: Water StorageTB MED 229 Sanitary Control and Surveillance of Water Supplies at Fixed and

Field InstallationsTB MED 576 Sanitary Control and Surveillance of Water Supplies at Fixed

InstallationsAFR 161-44 Management of the Drinking Water Surveillance ProgramSafe Drinking Water Act (PL 93-523), (16 December 1979) as amended. Innovative and Alternative TechnologyAssessment Manual, EPA report EPA-430/9 -78-009, Office of Res. Devel., Cincinnati, Ohio (1978).

Environmental Protection Agency

National Interim Primary Drinking Water Regulations. 40 CFR Part 141,(1 July 1982).National Secondary Drinking Water Regulations. 40 CFR Part 143,(1 July 1982).

National Academy of Sciences— National Academy of Engineering Water Quality Criteria, Su-perintendent of Documents, U.S. Government Printing Office, WASH, DC (1974) (EPA. R3.033.March 1973).

National Council on Radiation Protection and Measurementsc/o NCPR Publications, PO Box 30175, WASH, DC 20014Pub, No. 22-1959 Maximum Permissible Body Burdens and Maximum Permissible

Concentrations of Radionuclides in Air and in Water forOccupational Exposures (1959).

Department of the Army

U.S. Army Environmental Hygiene Agency, “Water Quality Information Paper No, 15, Trihalomethanes inDrinking Water,” Department of the Army, (1 April 1982).

U.S. Army Environmental Hygiene Agency, “Water Quality Information Paper No, 35, Volatile OrganicCompounds in Potable Water Supplies,” Department of the Army, (1 February 1982).

Nongovernment Publications

American Water Works Association (AWWA), 6666 West Quincy Avenue, Denver, Colorado 80235Water Treatment Plant Design, ASCE,AWWA, CSSE (1969)Manual M3, Safety Practice for WaterUtilities (1983)

Nongovernment ReferencesStandard Methods for the Examination of Water and Wastewater, 16th Edition, Franson, M. A. (ed,), APHA,AWWA, WPCF, (1984).

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B202 Quicklime and Hydrated LimeB300 HypochloritesB301 Liquid ChlorineB402 Ferrous SulfateB403 Aluminum Sulfate–Lump, Ground or LiquidB404 Liquid Sodium SilicateB405 Sodium AluminateB406 Ferric SulfateB501 Caustic SodaB502 Sodium HexametaphosphateB600 Powdered Activated CarbonB602 Copper SulfateB603 Potassium PermanganateB604 Granular Activated CarbonB701 Sodium FluorideB702 Sodium SilicofluorideB703 Fluosilicic Acid

Non-Government References (cent’d)Chemical Engineers’ Handbook, Perry, J. H., and Clinton, C. H., (Eds.), McGraw-Hill Book Company, New York,

NY (1975).

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—

APPENDIX F

BIBLIOGRAPHY

American Society of Civil Engineers, American Water Works Association, and Conference of State Sanitary Engi-neers, Water Treatment Plant Design, American Water Works Association, Denver, Colorado (1969).

American Public Health Association, Standard Methods for the Examination of Water and Wastewater (13th Edi-tion). American Public Health Association, New York (1971).

American Water Works Association, Water Quality and Treatment. McGraw-Hill Book Co., New York (1971).American Water Works Association Research Foundation, Desalting Techniques for Water Supply Improvement.

Denver, Colorado (1973).American Water Works Association Research Foundation, Disposal of Wastes From Water Treatment Plants. New

York (1969).Ball, W. P., Jones, M. D., and Kavanaugh, M. C., Mass Transfer of Volatile Organic Compounds in Packed Tower

Aeration, 55th Annual Conference of the Water Pollution Control Federation, St. Louis, MO. (1982).Baylis, John R., Elimination of Taste and Odor in Water. McGraw-Hill Book Co., New York (1935).Bellack, Ervin, Fluoridation Engineering Manual. Environmental Protection Agency, Office of Water Programs,

Water Supply Programs Division, Washington, D.C. (1972).The Chlorine Institute, Chlorination Manual. New York (1969).Clark, John W., Viessman, Warren, Jr., and Hammer, Mark J., Water Supply and Pollution Control, International

Textbook. Scranton, Penn (1971).Culp, Gordon L. and Culp, Russell L., New Concepts in Water Purification. Van Nostrand Reinhold Co., New York

(1974).Dickey, George M., Geyer, John C., and Okun, Daniel A., Elements of Water Supply and Wastewater Disposal.

John Wiley & Sons, New York (1971).Eckert, J. S., Design Techniques for Sizing Packed Towers. Chemical Engineering Program, 57,54 (1961).Fair, Gordon M., Geyer, John C., and Okun, Daniel A., Elements of Water Supply and Wastewater Disposal. John

Wiley & Sons, New York (1971).Hager, Donald G. and Flentje, Martin, E., Removal of Organic Contaminants by Granular-Carbon Filtration. Jour-

nal American Water Works Association, 57:1440 (1965).Hammer, Mark J., Water& Wastewater Technology. John Wiley& Sons, Inc., New York (1975).Haney, Paul D. and Hamann, Carl L., Recarbonation and Liquid Carbon Dioxide. Journal American Water Works

Association, 61:512 (1969).Hansen, Robert E., Granular Carbon Filters for Taste and Odor Removal. Journal American Water Works Associa-

tion. 64:176 (1972).Koelzer, Victor A., Desalting, National Water Commission, Arlington, Virginia (1972).Katz, J., Ozone and Chlorine Dioxide Technology of Disinfection of Drinking Water, Noyes Data Corp., Park Ridge,

New Jersey, (1980).Kavanaugh, M. C., Modified Coagulation for Improved Removal of Trihalomethane Precursors. Journal AWWA,

(1978).Kavanaugh, M. C., and Trussell, R. R., Design of Aeration Towers to Strip Volatile Contaminants from Drinking

Water. Journal AWWA. 72 (12), 684 (1980).Langley, K. E., Roberts, W., Drinking Water Disinfection.Larson, T. E., Chemical Control of Corrosion. Journal American Water Works Association. 58:354 (1966).Lobo, W.E. et al, Limiting Capacity of Dumped Tower Packings. Trans Am. Inst. Chem. Engrs., 41,693 (1945).Longely, K. E., Roberts, W., Drinking Water Disinfection, Water/Engineering and Management, Reference Hand-

book. (1982).Maier, F. J., Manual of Water Fluoridation Practice. McGraw-Hill Book Co,, New York (1963).Merten, Ulrich, editor, Desalination by Reverse Osmosis. The M.I.T. Press, Cambridge, Massachusetts (1966).National Association of Corrosion Engineers, NACE Basic Corrosion Course. National Association of Corrosion En-

gineers, Houston, Texas (1970).

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TM 5-813-3/AFM 88-10, Vol 3

National Technical Advisory Committee to the Secretary of the Interior Water Quality Criteria. Superintendent ofDocuments, U.S. Government Printing Office, Washington, D.C. (1968).

Nordell, Eskell, Water Treatment for Industrial and Other Uses (2nd Edition). Reinhold Publishing Co., New York(1961).

Oulman, C. S., Snoeyink, V. C., O’Connor, J.T., Tavas, M. J., Project Summary, Removing Trace Organics fromDrinking Water Using Activated Carbon and Polymeric Absorbents, USEPA, EPA-600 S2-81-077, 078,079,(1981).

Riehl, Merrill L., Water Supply and Treatment (9th Edition). Bulletin 211, National Lime Association, Washing-ton, D.C. (1962).

Roberts, P. V., et al, Removal of Volatile Halogenated Organic Solutes by Gas Transfer in Surface Bubble Aeration.55th Annual Conference of the Water Pollution Control Federation, St. Louis, MO, (1982).

Sherwood, T. K., and Hollaway, F. A., Performance of Packed Towers-Liquid Film Data for Several Packings. TransAm. Inst. Chem. Engrs,, 36, pp. 39-70 (1940).

Sigworth, E. A., Control of Odor and Taste in Water Supplies. Journal American Water Works Association.48:1510 (1956).

Spiegler, K. S., editor, Principles of Desalination. Academic Press, New York (1966).Stumm, W. and Morgan, J. J., Aquatic Chemistry. Wiley Interscience, New York (1970).Symons, J, M., Stevens, A. A., Clark, M. R., Geldrich, E. E., E.E. Love, Jr., O.T., DeMarco, J., Removing Trihalome-

thanes from Drinking Water, Water/Engineering and Management, Vol. 128 No. 8, (1981).Uhlig, Herbert H., Corrosion and Corrosion Control. John Wiley& Sons, Inc., New York (1971).U.S. Department of the Interior, Desalting Handbook for Planners. Bureau of Reclamation and Office of Saline

Water (1972).Whipple, G. C., Fair G. M., and Whipple, M. C., Microscopy of Drinking Water (4th Edition). John Wiley & Sons,

Inc., New York (1947).White, George Clifford, Handbook of Chlorination. Van Nostrand Reinhold Co., New York (1972).Woodward, Richard L., Dostal, Kenneth A., and Robeck, Gordon G., Grannulur Activated-carbon Beds for Odor

Removal. Journal American Water Works Association. 56:287 (1964).Wyness, David Keith, The Helical Flow Reactor Clarifier: A Innovation in Water Treatment, Journal, AWWA,

vol. 71 No. 10 (1979).

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The proponent agency of this publication is the Office of the Chief of Engi-neers, United States Army. Users are invited to send comments and sug-gested improvements on DA Form 2028 (Recommended Changes to publi-cations and Blank Forms) direct to HQDA (DAEN-ECE-G), WASH DC20314-1000.

By Order of the Secretaries of the Army and the Air Force.

JOHN A. WICKHAM, JR.General, United States Army

Official: Chief of StaffROBERT M. JOYCE

Major General, United States ArmyThe Adjutant General

CHARLES A. GABRIELGeneral, United States Air Force

Official: Chief of StaffJAMES H. DELANEY

Colonel, United States Air ForceDirector of Administration

Distribution:Army: To be distributed in accordance with DA Form 12-34B, requirements

for TM 5-800 Series: Construction. Facilities.Air Force: F