Sludge Process

8/13/2019 Sludge Process

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ACTIVATED SLUDGE PROCESS

BASIC DESIGN AND OPERATIONS

Domingo E. Boglosa, Jr.*

ABSTRACT

This paper about the activated sludge process is made toprovide every PCO and WWTP operator and all individual, involve inthe environmental protection particularly in the treatment of thewastewater that at present becomes a great contributor of waterpollution in the rivers, lakes and ocean which are the basic source ofmarine life, the basic design and operation knowledge to be used inmaintaining their respective WWTPs BOD Removal Efficiency as wellas an overview about the life of the microorganism present in the

wastewater treatment system.

The activated sludge process is a wastewater treatment methodin which the carbonaceous organic matter of wastewater prov ides anenergy source for the product ion of new cells for a mixed population ofmicroorganisms in an aquatic aerobic environment. The microbesconvert carbon into cell tissue and oxidized end products that includecarbon dioxide and water. In addition, a limited number ofmicroorganisms may exist in activated sludge that obtains energy byoxidizing ammonia nitrogen to nit rate nitrogen in the process knownas nitrif ication.

Bacteria constitute the majority of microorganisms present inactivated sludge. Bacteria that require organic compounds for theirsupply of carbon and energy (heterotrophic bacteria) predominate,whereas bacteria that use inorganic compounds for cell growth(autotrophic bacteria) occur in proportion to concentrations of carbonand nitrogen. Both aerobic and anaerobic bacteria may exist in theactivated sludge, but the preponderance of species is facultative, ableto live in either the presence of or lack of d issolved oxygen.

Fungi, rotifers, and protozoans are also residents of activatedsludge. The latter microorganisms are represented largely by ciliatedspecies, but flagellated protozoans and amoebae may also be present.Protozoans serve as indicators of the activated sludge condition, andciliated species are instrumental in removing Escherichia coli fromsewage. Additionally, viruses of human origin may be found in rawsewage influent, but a large percentage appears to be removed by theactivated-sludge process.

*Asst. Manager, Sales and Marketing Department/Technical Consultant

Fluid Technologies and Environmental Management, Inc. (FTEMI)


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The success of the activated-sludge process is dependent uponestablishing a mixed community of microorganisms that will removeand consume organic waste material, that wi ll aggregate and adhere ina process known as bio-flocculation, and that will settle in such amanner as to produce a concentrated sludge (return activated sludge,

or RAS) for recycling. Any of several types of activated sludge solidsseparations problems indicate an imbalance in the biologicalcomponent of this process. In the ideal "healthy" system, filamentousorganisms grow within a floc (a large aggregate of adherent, or floc-forming, microorganisms, such as bacteria) and give it strength, withfew filaments protruding out into the surrounding bulk solution. Insuch a system, there is no interference with the compaction andsettling rates of the activated sludge prior to its recycling.

INTRODUCTION

Wastewater is an unavoidable by-product of the modern living. The composition ofaverage Philippine water wastewater is about 99.95% water by weight, but the remaining 0.05%can do unlimited damage to our water ways and if left unchecked, can constitute a hazard to the

public.

In general, wastewater is composed of water, solids (dissolved and suspended) andbacteria. Some of these bacteria are potential disease carriers. If these solids and bacteria are notremoved from the wastewater before it is discharged into a receiving body of water, the receiving

body will become unsightly and give off unpleasant odor and, at worst, fish life will be destroyedand the water will become a health hazard.

A wastewater treatment plant is built for the purpose of removing objectional materialfrom wastewater so the treated plant effluent can be safely discharged to the receiving waters.

The complexity and cost of activated sludge process designs preclude their use in large andsmall plants. For years, there was no satisfactory method to handle large and small wastewaterflows. There was a need for a plant with the following characteristics

1. High efficiency

2. Reliability

3. Odorless

4. Minimum supervision requirements

5. Low initial cost

Rated Aeration was developed to meet these specifications. Continued development of therated aeration concept has led to improvement of the product available from economic and

process efficiency standpoint.


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METHOD: BIOLOGICAL PROCESS (ACTIVATED SLUDGE PROCESS)

BASIC DESIGN PARAMETER DEFINITIONS

Before discussing the activated sludge process, a definition of the terms we will be using is

in order.

Flow - Expressed in million gallons per day (MGD) or for small plants in gallons per day(GPD).This is the total volume of waste water which a given treatment plant musttreat over a 24-hour period.

BOD - The biochemical oxygen demand is define as the amount of oxygen required bybacteria while stabilizing decomposable organic matter under aerobic conditions.The BOD test is widely used to determine the pollution strength of domestic andindustrial waste water in terms of the oxygen that they will require if dischargedinto natural water courses in which aerobic conditions.

Suspended Solids -Suspended solids are those solids which are visible and in suspension inwater, waste water or activated sludge. They are the solids which can be removed

by physical or mechanical means, such as sedimentation or filtration. In wastewater, they will include the larger floating particles and consist of seed, grit, clay,fecal solids, paper, sticks of wood, particles of food and garbage, and similar oftime.

Settle able Solids - Settle able solids constitute that portion of the suspended solids which are ofsufficient size and weight to settle out in a given period of time.

Mixed Liquor Settle able solids (MLSS) - Those solids in an activated sludge mixture this willsettle in thirty minutes.

pH - pH is a term used to express the intensity of the acid or alkaline condition of asolution. It is expressed as a number which ranges from 0 to 14.Below 7, thesolution is acid, above 7 is alkaline, and at 7 the solution is neutral. The pH ofdomestic waste usually nearly neutral.

Aerobic - The term aerobic refers to those organisms which live and function in the presenceof oxygen. The bacteria employed in the activated sludge process are suchorganisms and requires an aerobic environment. This environment is provided for

them in the activated sludge process by supplying diffused air throughout theactivated sludge mixture

BASIC PROCESS

If a sample of a wastewater were placed in a vessel and aerated over a period of time, thewastewater would lose its odor and become slightly brown in color. The development of a brownmass within the wastewater would be an indication of an activated sludge being developed withinthe liquid. The air is introduced to the liquid in order to provide the environment in which anaerobic biological mass would thrive. If a small sample of this brown mass were examined underthe microscope, hundreds of microscopic organism would be seen. This brown floc is called

activated sludge.


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In activated sludge process, a tank is filled with wastewater and is then aerated to providethe aerobic environment required in order to develop an activated sludge. Wastewater iscontinually introduced into the tank and the development of a brown activated sludge isdependent on the amount of waste water that is treated in a particular aeration tank. Over a periodof time, the amount of activated sludge developed within the aeration tank will increase

depending upon the amount and strength of wastewater being treated. The micro-organismsdeveloped or the activated sludge developed utilizes the contaminants in the wastewater for food,growth and reproduction. this activated sludge in the aeration tank which is commonly referred toas mixed liquor is then transferred to a final settling tank where separation of liquid and solids iseffected by gravity sedimentation. the settled solids are quickly returned to the aerobicenvironment of the aeration tank in order to sustain the life of these micro-organisms, and theclarified effluent at the top of the final settling tank is withdrawn for discharge to a receiving bodyof water or for further treatment, if required.

The mixed liquor from the aeration tank is introduced into the final settling tank at somepoint below the surface of the settling tanks. The design of a settling tank is such so that the rising

velocity of the liquid flowing out the settling tank is considerably less than the settling velocity ofthe solid particles in the mixed liquor.

In a continuous process activated sludge plant, the amount of activated sludge solids in thesystem will increase as wastewater is treated. In order to maintain a balance in the system

between the activated sludge and the food (organics in the wastewater) that is coming into theaeration tank, it is necessary to remove some solids from the system. This excess sludge isgenerally wasted to a digester and in most plants aerobic digester is provided. In the aerobicdigester the excess solids are aerated over a long period of time. In the absence of food some ofthese micro-organisms begin to die off and provide food for those micro-organisms which aresustained, but over the extended period of time there is generally a substantial reduction in the

percentage of volatile solids in the waste sludge. The important factor in an aerobic digester is toprovide as an end product a sludge which is readily dewaterable and is non- offensive in odor sothat the plant operator can withdraw digested sludge from aerobic digester and put that sludge ona drying bed and expect a dry product in a reasonable period of time.

BASIC DESIGN BASIS

It should always be considered that the design conditions that have been assumed are fairlytypical, but it should be keep in mind that the quality of a specific wastewater, as well as thevarious factors associated with specific locality, such as air temperature, wastewatertemperature, and altitude may differ substantially from one plant to another.

It was also assumed that the wastewater did not contain any substantial amount of toxicimpurities that would preclude the normal functioning of the activated sludge process, withconsequent removals of BOD and suspended solids that normally associated with this process.

Design Basis - Generally in larger communities having wastewater flows of one (1) MGDor more, a person will generate 100 gallons of wastewater per day containing 0.17 pounds ofBOD5. From a hydraulic loading and organic loading standpoint, this represents "One

population equivalent (P.E.)." This equivalent population flow, 100 gallons per captia per day(gpcd), is generally accepted as the upper limit for domestic flow projection on a daily average

basis for new wastewater systems serving large communities. Suspended solids (SS)


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concentrations from domestic flows can be reasonably assumed to contain 0.2 pounds ofsuspended solids per capita per day. If the use of garbage grinders in a system is significant, thenthe design basis should be increased to 0.22 pounds of BOD5 and 0.25 pounds of suspendedsolids per capita per day. If wastewater flow data are not available, the design average daily flowshall be based on 75gpcd for communities with flows less than 1 MGD. An alternate method to

determine design capacity could be justified by local water consumption records but shall not beless than 60 gpcd. These records should generally be based on the average monthly usage for themonths of December, January, and February. Special consideration may be needed forcommunities with highly varying seasonal consumptive water use such as tourism and certainseasonal industrial uses. Projected wastewater flows for a community could be calculated byusing 80 percent of the actual water consumption. Allowances shall be made for infiltration,inflow and significant commercial/ industrial waste flows which will be added to the per capitaflow rate. If no actual data on infiltration is available, an assumed infiltration design allowancefor existing sewers should be added to the design flow. For existing systems, the minimuminfiltration design allowance for the existing sewers and service lines shall be no less than 200gallons per inch of pipe diameter per mile of pipe per day. It is recommended that actual flow

measurements to determine infiltration rates be conducted for those communities that havecollector sewers that lie below the groundwater table.

DISCUSSION

A. AERATION TANK

The volume requirement of aeration tanks are usually determined on the basis of aprescribed five day BOD loading that will depend upon the type of the activated sludge processbeing employed.

Once the total aeration tank volumetric requirement has been determine, the number andsize of tanks are next determined. Each aeration tank is considered upon as one individualtreatment unit.

A very commonly used cross section for an aeration tank is 15ft liquid depth and 30 ft.width. The 15ft liquid depth and 30 ft. width has more or less become the standard limitation andsimilar 30ft tank width has become the normal limitation on tank width when a wide bandaeration system is utilized.

In order to perhaps better explain the rationale behind these commonly used dimensionallimitations, a review of some of the objectives and requisites of a diffused aeration system are to

be considered.

One of the two major objectives is to efficiently transfer oxygen to the mixed liquor.Although a 30 ft. x 15ft aeration tank is by no means the ideal size in order to accomplish this mostefficiently, if one weighs the other economic factors, primarily the capital cost of the aerationtank structure itself and the associated mechanical equipment, this tank size in most instancesgives a very favorable combination of capital and operation costs. From point of capital cost, itmay be stated that the larger the cross section of an aeration tank, the less its cost per unit volume,but, of course, beyond a certain point, at which the number of treatment units is reduced, theconstruction cost is reduced at the expense of a certain degree of flexibility. This may or may not

be important, depending upon the specific number of treatment units in a particular situation


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aside from the fact that under otherwise identical conditions, that as the cross sectional area isincreased, the oxygen transfer efficiency is decreased, the factor of circulating velocities in anaeration tank must also be considered.

In addition to affecting the transfer of oxygen to the mixed liquor, he diffused aerationsystem also provides the energy for maintaining the solids in the mixed liquor suspended, and ingeneral maintaining the mixed liquor in a substantially homogenous state. In order to maintainthe contents of an aeration tank in a homogenous state, the minimum circulating velocity in anypart of the tank should be at least one foot per second and preferably more.

Therefor, in addition to striving to obtain the best economic balance between oxygentransfer efficiency, and tank size, the design engineer must also make certain that the quantity ofair diffused per unit length of aeration tank at the balance point shall be sufficient to provideadequate velocities.

Standard loading factors for Activated Sludge process design

ACTIVATED SLUDGEPROCESS

BODMLSS

Aerationtank

volume

(106

cu.ft)

MLSS(Dry Bulb)

MLSS(mg/li)

Lbs. solids tofinal settling

tank/clarifier

1.Conventional 0.30 0.42857 50,000 1870 156,000

2.Extended Aeration 0.05 1.20 300,000 4006 350,000

3.Step Aeration 0.30 0.30 50,000 2671 131,000

4.Complete mixing 0.30 0.15 50,000 5342 450,000

*lbs. solids = Net flow (MGD) * 8.34lbs/gal* MLSS (mg/li)

B. BASIC ACTUAL DESIGN DETENTION TIME REQUIREMENTS

a. Detention Time for Aeration Tank : 15 to 17 hours

b. Detention Time for Aerobic Digester : 12 to 24 days

c .Det. Time for Neutralization Tank : 2hrs

d. Det. time for Equalization Tank : 4hrs

e. Det. Time for settling tank : variable

f. Det. Time for Chlorine Contact Tank : 1hr

C. BASIC ACTUAL DESIGN FACTORS

Q = Flow rate in, CMD or MGD (variable)

BOD5 = After pre treatment, in mg/li (Variable)

Altitude = 3000ft

Air Temp = -10: to 100:F

Wastewater temp. = 60: to 85:

Alpha = 0.9 (Assumed)

Beta = 0.85(Assumed)


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Organic Nitrogen = 20mg/li

Chlorides = 300mg/li

Minimum D.O. = 2mg/li

Activated Sludge Allowable Hydraulic Loads:

Allowable Hydraulic Loading

Types of Activated Sludge Process Lbs. BOD5/1000cu.ft Transfer efficiency

1. Conventional 35 11.6%

2. Step Aeration 50 12.75%

3. Contact Stabilization 50 11.6%

4. Extended Aeration 12.5 11.6%

5. Complete mixed aeration 100 13.1%

D. BASIC DESIGN FORMULAS

Oxygen Requirements formula

O2/day = (BOD20) + (MVLSS)

Where:

Alpha () = fraction of BOD20 removed oxidized for energy

Assume alpha =0.50

Beta () = Oxygen for auto oxidation of biological mass

Assume beta =0.125

BOD20 = (BOD5) (1.46)

Lbs. MLSS = lbs. BOD5

0.30

AIR REQUIREMENTS:

CFM = ( lbs. O2/day ) x (1 ) x (1 ) x (1 )

1440 min/day trans.eff #O2/#Air Dens

x (1 ) x O2 Deficit x (1 )

Alt. Alpha

Where:

#O2/#Air = Ratio by weight of oxygen in air =0.23

Den = Density at sea level and Ambient Temperature

Alt = Correction for altitude

O2 deficit = O2 saturation in water @temperature

O2 Saturation in Mixed liquor-D.O. level in mixed liquor

= O2 sat. in water

(O2 sat in water X Beta)-D.O.

Alpha = O2 transfer in Mixed Liquor = 0.9 (assumed)


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O2 sat. in water

Beta = O2 saturation in mixed liquor = 0.85(assumed)

O2 Saturation in water

Den. = 0.07093 lbs./cu.ft (@100:F and sea level)

Alt. = 0.891 (@3000ft)

O2 = sat.of water at 85:F and 3000ft at chloride concentration of 300mg/li

= saturation at sea level x Actual pressure

760mm Hg

Cfm for aerator = 9.55 x lbs. O2per day

% Trans. Eff

Oxygen Needed = (2*lbs. BOD)/24hrs

Oxygen Trans. eff = 1.6 lbs. /shaft hip/hr.

For Aerobic Digester/neutralization and Equalization Tank;

Cfm requirements = 30scfm /1000 cu. ft. of water

E. SETTLING TANKS/CLARIFIER

In order the have a better design of the settling/clarifier tank the two major design criteriain the sizing of the final settling/clarifier tank of an activated sludge system, particularly thesurface area, are the hydraulic loading and the solids loading.

Commonly used hydraulic loading rate shall be in the range of 500 to 1000 gallons per dayper square ft., usually depending upon the size of the plant, sometimes ,usually in relatively smallplants, especially those where only one settling tank will be installed, hydraulic loadings below500 gallons per square foot per day is the generally accepted standard. In the design, referring tothe tabulated results, it may readily be seen that at a hydraulic surface area loading of 1000GPD

per square foot, the solids loading is the determining design parameter for establishing thesettling tank surface area, except in the conventional and step aeration of the activated sludge

process. In contrast, at a hydraulic surface loading of 500GPD per square foot, solids loading arethe controlling parameter, except in the case of the complete mix.

Assume hydraulic surface loading of 500 and 1000 gpd/sq.

For Settling Tank:

ACTIVATED SLUDGE

PROCESS

Settling tank surface

area,sq.ft

20lbs/sq.ft.day


area,sq.ft

500gpd/sq.


area,sq.ft

1000 gpd/sq.

1.Conventional 7,800 20,000 10,000

2.Extended Aeration 17,500 20.000 10,000

3.Step Aeration 6,500*** 20,000 10,000

4. Complete mixing 22,500 20,000 10,000


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SCREENING CHAMBER

F. WWTP OPERATION

1. WASTE WATER TREATMENT PROCESS DESCRIPTION

The waste waster treatment as describe below is Extended Aeration process. The unit

operation involve in the process are:

Supernatant Line

Return Sludge line Excess Sludge Line

Influent)Scree

ning

Cham

ber

Neutralization

Tank

EqualizationTank

Aerat ion

Tank

Settling

Tank

Chlorine

Contact

Tank

Aero bic

Digester

Tank

Effluent(Treated Water)

Filtrate line

Dewatering

Facility

Waste sludge line

Sludge Cake

HORIZONTAL FLOW DIAGRAM

EqualizationTank

Influent

Static Bar Screen


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EQUALIZATION TANK

2. Bar Screen

Raw wastewater (influent) from the slaughter area goes into a sump pit or holding tank bygravity then pumped out into a Bar Screen Chamber where solid materials and large arescreened/prevented from flowing with the influent.

Down feed with Diffusers

RawWater Flowfrom screeningChamber

EqualizationTank

NEUTRALIZATION TANK

3. Neutralization Tank

The raw wastewater enters into neutralization tank wherein the pH is being neutralized.The raw wastewater that has pH below 6 is considered acidic while raw wastewater that has pHover 9 is considered basic and those that as pH between 6-9 is considered neutral. The pH of thewastewater if acidic is being neutralized by adding caustic substance while if the pH of the wateris basic it is being neutralized by adding acid.

Return Sludge canal

Downfeed with Diffusers

RawwaterFlow Aeration

Tank


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CLARIFIER TANK

4. Equalization Tank

Influent does not flow at a uniform rate and its characteristics are not constant with time.Any fluctuations in the influent flow rate and its characteristics will affect the efficiency of thesubsequent treatment processes. Flow equalization is done to control the flow through each stage

of the process allowing adequate time for biological treatment to take place. The pH of water isadjusted if necessary to a value (pH 7-9) that is ideal for subsequent biological treatment.

Supernatant

line

Handrail

From

Equalization

Raw Water enters

Settling

Tank

Activated sludge and

microorganism With

Aeration system

AERATION TANK

5. Aeration Tanks

The blower is allowed to operate continuously where the wastewater is oxidized formingbiomass necessary for degradation process. Organic matter is converted by microorganism intocarbon dioxide and water. Air is supplied uniformly into this tank by means of a positivedisplacement blower through the air bubble diffusers installed at the bottom of the tank. Theupward movement of air bubbles stirs up the contents of the tank thereby preventing anaerobiccondition that can upset the aerobic process.

Influent baffle

Return sludge canalEffluent Baffle

HandrailSludge hopper Static Airlift

ClearWaterCanal

Activated SludgeFrom Aeration tank

Clear waterTo ChlorineContact tank


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8. Aerobic Digester

Excess sludge from the settling tanks will be siphoned into the Aerobic Digester where itshall be stored and stabilized. Aerobic digestion is a method of sludge stabilization in an opentank.

Wasted Sludge

From Aerobic Digester Fine

Sludge cake

Medium

Coarse

Filtrate holding tank

To Aeration orPre-aeration tank

SLUDGE DRYING BED

9. Sludge Drying Beds

Waste sludge from the activated process and from the Aerobic Digester are diverted intothe Sludge Drying Beds where excess water will be drained by gravity. Filtrate will flow backinto the sump. Dried Sludge will be extracted and hauled out as landfill or soil conditioner.

10. MAJOR PROBLEM USUALLY ENCOUNTERED IN THE WWTP OPERATIONS

AND THEIR RESPECTIVE SOLUTIONS

1. PROBLEM:

Aeration tank water becomes light in color compared to the usual brown color.

ANSWER:

The above problem indicates that there is a loss of solids in the aeration tank, probablyfrom over wasting of sludge. The operator must then return to a start- up operation procedureuntil the mixed liquor solids concentration reaches the appropriate level. Sludge wasting should

be adjusted to avoid wasting too many solids to the digester again.


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2. PROBLEM:

Aeration tank water appears black in color as compared to the usual brown color.

ANSWER:

The above problem usually indicates that the solids in the aeration tank are becomingseptic due to an inadequate air supply or that the plant is being overloaded. First of all, check tomake sure that the blower is operating properly and at full speed. Next, check the condition of theaerators (surface or submerge type) to be sure that the aerators are in good operating order. If theblower and diffuser or aerators are in good condition, check if the plant is being overloaded or iftoxic material or substance is entering the plant.

3. PROBLEM:

Solids are being carried over the weir in the plant effluent.

ANSWER:

The above abnormal situation can be the result of several different conditions:

a. The concentration of the mixed liquor suspended solids may be too high. Check thiswith the settle able solids test. If the solids level is high, it will be necessary to wastemore sludge to the aerobic digester. However, if solids are returning to the aerationtank from the digester through the supernatant return port, it will be necessary toremove sludge from the digester

b. The plant may be hydraulically overloaded. If this is the case, and the plant isreceiving flow from a lift station, it may be that enough of the wastewater flow is not

being re-circulated through the wet well. This can be remedied by adjusting the flowsplitter box to return more flow to wet well.

c. The activated sludge may be a poor settling sludge.

4. PROBLEM

Floating sludge solids on the Clarifier or settling tank surface.

ANSWER:

The color of these solids can be immediately be a guide to a solution of this problem

a. The presence of the large quantities of light colored sludge on the final tank is usuallyan indication of over aeration of the mixed liquor suspended solids, and this can beconfirmed by measuring the dissolved oxygen content of the mixed liquor, whichwould be very high. To correct this, the operator must reduce the amount of air beingdelivered to the aeration tank by reducing the blower output.


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b. If there are very dark or black floating solids on the final surface, it is probable thatthese solids are being retained in the final tank for too long a period. Checks theconditions of the sludge discharging from clarifier sludge pump/settling tanktravalift. It should be in a fresh condition, it must be no odor and brown in color. f thesludge is in good condition, it is possible then that rubber scrapper of the clarifier or

the squeegee blades are not keeping the clarifier tank or settling tank slope clean.Probe the slopes, especially at the end of the clarifier or settling tank, to see if there hasbeen any sludge builds up. If there is a build- up, push the sludge down the slope thebuild- up solids. If the problem continue to occur, the tank must be dewatered and thesludge pump must be checked carefully and replace if necessary ,also check theclarifier slope sludge scrapper and adjust it does not function well have it adjusted. Ifsettling tank check the travalift squeegee as well as the intake bell and adjust ifneeded.

CONCLUSION

The basic knowledge about biological treatment particularly the Activated Sludge Processbasic design and actual operation is not commonly available to every individual whom theiradvocacy is to protect the environment by reducing the pollutants present in every receiving bodyof water through an efficient wastewater treatment facility.

The dream of protecting the environment can only be achieved by providing sufficientunderstanding about the problem and giving more venues to access the vital information that canenhance the respective skills in monitoring and maintaining the entire treatment facility.

With this knowledge on basic design and operation of Activated Sludge process, it

enhances the skill of WWTP operators/PCOs in responding immediately with accuracy in casethe WWTP equipment has shut-down in their respective plant. These also give them a chance toenhance the efficiency of their Plants by installing newly purchased/repaired equipment withcorrect Capacity as required by the treatment system particularly for the aeration tank that servesas the heart of the entire WWTP.

By knowing the most common major problems of the plants, it is now easy for the WWTPoperator /PCO or any individual involve in environmental protection, to address the need of theplant and they will be able to modify the WWTP to address the need.

This Technical lecture reveals a trend towards practical way of handling water pollutionand provides the maximum benefit of accumulated experiences, eliminate knowledgeinconsistency and set measures of quality control.


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REFERENCES

I. FEW ACTUAL WWTP REFERENCES :

1. AZUCARERA DE DON PEDRO WWTP

Nasugbu, Batangas

2. PAMAYANAN NG DIEGO SILANG CENTRALIZED STPC-5 Taguig City

3. Wyeth Philippines, Inc. WWTPCanlubang, Laguna

4. Coca cola bottlers Philippines STPa. Davao

b. Gensan

c. Zamboangad. Meycawayan, Bulacane. Pangasinan

5. AMANPULO ISLAND RESORT STP

II. THEORITICAL REFERENCES:

J.E.CALLOS AND ASSOCIATES WEFTEC98 ASIALECTURES AND ACTUAL DESIGNED ON STP/WWTP16M Maya Arcade Building, 678 EDSA, Cubao Quezon City

APHA. Standard methods for the Examination of Water and Wastewater, 19 ed.,American Public Health Association, Washington, DC.1995.

Tchobanoglous G, Burton F.L. & Stensel HD., Introduction to process analysis andselection (Chapter 4). Wastewater Engineering: Treatment and Reuse, ed. G.Tchobanoglous, F.L. Burton & H.D. Stensel, McGraw-Hill: Boston, pp. 215-310, 2003

Water Environment Federation. 1996. Operation of municipal wastewatertreatment plants. Manual of practice no. 11, vol. 2, 5th ed. Alexandria, Va.

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