RESOURCES

Water Reuse Closes Water-Wastewater Loop

Alan B. Nichols

n recent years a new development I has been taking

place in the field of water reuse in the US. In parts of the country where water shortages are becoming critical, water planners are turning to reuse as a technique aimed pri- marily at augmenting or conserving water supplies. This primary emphasis o n water conservation represents a significant change in the long history of wastewater manage- ment, whose principal objective has been the treatment and disposal of wastewater into the environment by the most cost- effective means possible.

According to some engineers, the shift in emphasis from a disposal ethic EO a ccnscpvadon ethic !x.y have far- reaching implications for both the water and wastewater industries, which tradi- tionally have had little to do with one another. Because they focus on oppo- site ends of the pipe, the two industries have tended to feel they don’t have much in conimon.

This long-standing distinction be- k e e n the two industries is becoming blurred, however, as planners try to cope with today’s water imperatives.

m The treatment train at the Denver Potable Reuse Demonstration Plant has 21 separate processes including chemical treatment (left) and ammonia removal and recovery (above), which converts ammonia into a saleabie fertilizer (6iixtmiiii.i~ sulfate).

Such challenges dictate that planners take a fresh look at solving water prob- lems that threaten to become worse over time. The reuse conservation ethic called for by these imperatives focuses on reclaimed water as a valuable re- source that should be preserved and exploited, not a waste product that requires disposal. If such a principle be-

comes the permanent basis for hture water resources manage- ment, it could bring about an era in which the water and wastewa- ter industries work more closely together as co-stewards of the nation’s water re- sources.

In many places across the landscape, nature has left con- spicuous evidence that all is not well with the aquatic environment. Takashi Asano, water reclamation specialist with the California State Water Resources

Control Board, writes in the June 1988 Literature Review edition of the Journal WPCF, “Pockets of inade- quate water supply represent a serious contemporary concern for the water industry.” This concern, he notes, is brought about by three factors: wide- spread contamination of existing water supplies; droughts, which “exacerbate water problems;” and population growth in arid or semi-arid regions of the country. To combat these factors, he continues, water suppliers must de- velop new sources of water, protect current sources, and implement conser- vation measures including water recla- mation and reuse.

November 1988 1931

Conserving limited supplies Three types of water reuse, represent-

ing progressively more complex levels of management, regulatory controls, and technology, are nonpotable reuse, also called dual distribution, that provides reclaimed wastewater for irrigation or industrial sites; indirect potable reuse, such as aquifer or artificial recharge; and direct potable reuse, which provides a direct source of potable water \rithout aquifer intermediation or dilution with another water supply.

Nonpotable reuse is becoming widel!. practiced in states like California, Flor- ida, Texas, Colorado, and Arizona, where water shortages, salt [rater intru- sion of groundwater, or aquifer over- drafting provide compelling reasons to conserve limited water sumlies. Non-

potable reuse projects serve that pur- pose by substituting reclaimed water for high \\~ater-consurning uses.

In California and Texas, nonpotable reuse is not only accepted, it is vimially mandated. California has a water code that forbids the use of potable water for landscape irrigation when suitable re- laimed water is available. The code states, “It is die intention of the Califor- nia Legislature that the State undertake all possible steps to encourage develop- nient of water reclamation facilities so that reclaimed water will be available to help meet the growing water require- ments of the State.”

The result of this rule has been the dramatic increase of nonpotable reuse projects, especially in water-short south- ern California, which depends on

northern California sources and the: Colorado lG\rr for much of its drinking water. Soon, southern California’s do-- cation of Colorado River water will be: cut in half, a conseqtience that \ \ i l l no) doubt contribute to an c \ ~ n greater practice of nonpotable reuse.

California, \vhich has more water reuse projects than any other state, has; already felt the effects of the practice.. The most recent estimates of the state’s Department of \Vatu Resources indi-- cate that 350,000 acre-feet per year off i n u nici pal \\xrewa t e r is being re -- claimed, an amount DWR said couldi increase to 625,000 ac-ft/yr by the yearr 2010. iMeamvhile, the Department off Health Senices in 1984 determined that 240 \raste\vater treatment plants iiii the state were supplying reclaimed

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Florida Cities Adopt Dual- Distribution Systems

In the early 197Os, St. Petersburg had a water supply and a wastewater problem. To meet revised discharge standards to Tampa Bay, the city had to either upgrade its four WWTPs to advanced waste treatment, including nitrogen removal, or cease discharging into the bay, then one of the most polluted water bodies in the nation. Concurrently, groundwater supplies were being severely strained and the city had to find a way to reduce potable demand. The city council solved both problems at once when it authorized a project to reclaim wastewater from the four plants for urban irrigation, including schools, golf courses, parks, and commercial and residential areas.

Between 1977 and 1987, the city spent over $100 million expanding and upgrading the four plants to dvanced secondary treatment (without nitrogen

vat) and constructing 200 miles of pipes i d network which connects the plants in seri ly to customers. Recently, the system, who is also used for supplemental fire protection

s expanded to encompass “water critical” esidential areas. In 1987, the average daily flow of

20 million gallons a day reached over 5,000 customers. When the project is fully complete by the year 2000, the system will have a 42-mgd capacity with the potential to serve 17,000 customers, while irrigating nearly 9,000 acrss.

Residents pay a flat monthly fee of $10.30 for unlimited use and commercial customers pay a fee based on acreage. The system, whose color-coded lines and valve boxes distinguish’it from the potable water system, meets the controversial state reclaimed water standards (currently being revised) for public access use of 90% BOD removal, less than or equal to 5 mg/L of total suspended solids, and no detectable fecal coliforms. Thanks to the system, city water demand has leveled out.

Located 10 miles from Orlando, Altamonte Springs has an equally ambitious project callec “APRICOT.” The name, standing for “A Prototype Realistic Innovative Community of Today,” is E variation of the futuristic motif of Disney World’s EPCOT Center. Impetus for the project is a 1982 citr, ordinance that requires dual distribution systems fori all newly developed areas of the city, which is in thE throes of a “real water crunch,” according to Alisor Marcous, information liaison in the Department 01 Public Works. Marcous said planners will eventuall]) propose to install the system in commercial buildings and factories to be used for toilet flushing, sprinkler systems, and for such other outside uses as call washing. The goal is to provide reclaimed water tar every property in the city, she said.

The reclaimed water meeting state potable wate! standards will be processed by the city’s WWTP’ which was recently upgraded to tertiary treatmeni and which will be expanded to include dual medk filtration with a 12-mgd capacity. The identical filte! process was used in a pilot study of tha Epidemiology Research Center of Florida yielding arr effluent that achieves low turbidity levels, zero fecaa coliforms, and viruses below detectable limits Marcous said.

The project is expected to go on line in 1993 Tnta! cost is estimated at $32 millinn, tn he finance(( through a combination of developer and nevi connection fees and a bond issue. “There is ncc federal money,” Marcous said, “because the cit!: wanted total control over the project.” To spui maximum usage, residents electing not to use thu system will be charged an availability fee. Thu reclaimed water will be unmetered and will bn available to users for a flat rate, to be set at half thic potable rate.

1932 Journal WPCF, Volume 60, Number 11

Irrigating golf courses with reclaimed water is a growing practice in dry states such as Arizona, where water reuse is helping to ease pressure on potable water supplies.

water to 380 use areas. Today the number of n x e r reclamation projects of all kinds could be as high as 500.

In 1980, the Arizona legislature en- acted the Groundn.ater Alanagement Act, \vhich mandates safeyield of its ground\vater supplies by the year 2025. Safe-yield means that \vithdra\vals of groundivater must not excred natural and artificial recharge. The law also re- quires water conscnation goals for ac- tive management xeas (A\&) marked by heavy development. The objective of these goals is to reduce per capita de- inand of potable \Yarer 10% by 2000 arid to achieve additiond reductions by 2025, according to Wallace iunbrose, partner in charge of Greeley and Hansen’s Phoenix office, \rho noted that dl the state’s major cities ;are incor- porating \vatu reuse into their conipre- hensive water resources management plans to meet the goals of the act.

“Cities in Aizona are bu!ing land in agricultiiral counties to gain access to additional n a c r rights.” he said. “They are also recognizing the need to rec1,iim all of their \\mte\\“x-. \\’e are begin- ning to manage our u’ater far niorc effectively than i n the past.” Examples of \\parer reclaniLition initiatives include the Rio Salada Project in the city ot Tempe. The aim of the project is to develop a no rma l ly d n chainel of the Salt lG\.er i n t o a series o f lakes that \vould be supplied t\,i th reclaimed uwcr

from nvo water reclamation plants. Tempe Director of Public JVorks Jim Jones said that the state water conser- vation requirement provides an incen- tive for water reclamation because re- claiined water doesn’t get charged against the city’s current per capita ceiling of 253 gallons a day. “We’re right at the ceiling now, so u,e’re anx- ious to get started,” he said, adding, “If we are going to continue to grow, we’re going to need water reclama- tion.”

Similarly, other cities like Scottsdale, Glendale, Mesa, and Tucson are mov- ing aggressively to reclaim their Ivater for irrigation of golf courses, parks, free- way landscaping, and residential la\vns and gardens. I n what is becoming a coninion practice, the cities are buying water reclamation plants built by devel- opers in newly developed areas or are waiving developer fees in lieu of out- right purchase. In other cases, the city is financing design and construction through general obligation bonds. Tucson currently has a demonstration project in which tertiary treated Lvaste- water percolates into a groundnrater aquifer and is recovered for irrigation. Tucson hopes to eventually supply 14% of its water necds with reclaimed water, according to Am brose.

Economics and public education play a big part in these cities’ ivater rnanage- ment pl,ins. Mesa, for example, has a

sliding water rate schedule that penal- izes users for excessive consumption. And Karl Kohlhoff, Mesa’s water re- sources management coordinator, said that a public education program even reaches down to the grade-school level to teach youngsters the value of conser- vation. The program encourages resi- dents to replace their high water-con- suniing plants with shrubs and trees that require less water. In Tucson, po- table rate payers are subsidizing re- claimed users, according to Kirke GUM, the city’s chief planning engineer, who, on referring to public education, said, “The city plans to walk the community through the pilot project,” adding, “Most residents here are from the east and they are used to wastewater dis- charges which go downstream and be- come a part of the next city’s water sup-

As to the public health aspects of nonpotable water reclamation, Jones said the public response has been “extremely hvorabie. I haven‘t heard of a single concern about the health is- sue. ”

As these etforts demonstrate, a key benefit ofnonpotable reuse projects is that they result in reduced demand on existing water supplies. I n St. Peters- burg, Fla., which has a dual-tiistribudoi~ system that provides reclaimed waste- water for golf course, pwks, and coin- mcrcial and residential areas, potable

ply.”

November 1988 1933

. a I.,

water consumption has leveled out, eliminating the need to acquire new sources bf fresh water, according to Dave Schul- mister, St. Petersburg’s manager of wastewater treatment.

Indirect and direct potable reuse

The second two types of water reclamation, direct and indirect po- table reuse, have stirred considerable controversy because their public health implications are more serious than those of nonpotable reuse. In- direct potable reuse may include recharging a drinking water aquifer or surface water impound- ment with reclaimed wa- ter.

A leading example of indirect potable reuse is the Fred Hervey Water Reclamation Project in El Paso, Tex. In the project, named after a former mayor of the city, waste- water treated to state potable water standards is injected into the Hueco Bolson Aquifer, from which it is withdrawn to meet the city’s severe wa- ter needs. “The city has limited water resources,” said Daniel Knorr of Gstors to the gallery of the Gainey Ranch Water Reclamation Plant in Scottsdale, G z . , Parkhill, Smith & COO- are struck by the low noise level, a leading feature of this “good neighbor” facility, designed per, Inc., designers of the by GrwleY and t-k“n. project. Knorr explained that groundwater overdrafting is 20 times the recharge rate in a climate that has but 8 in. of average annual rainfall. Before project implementation, alterna- tives were explored including other Texas aquifers and the KO Grande, but allotments for river water have already been assigned and are difficult to reas- sign, he said.

Source water for the project is pro- vided by a $26 million wastewater treat- ment plant, which has been 011 line since June 1985. The plant was fi- nanced by an EPA I/A grant at less than 85% because, said Knorr, the project has a multiple (disposal-supply) purpose. Currently, 4 million gallons a day are injected into the aquifer through injection wells and by the end of 1989 that figure is expected to in- crease to 7 million gallons. The plant’s treatment train includes a two-stage PACT@ system that accomplishes car- bonaceous, nitrogen, and trace organ- ics removal; high lime treatment; two-

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stage recarbonation; sand filtration; ozonation; and granular activated car- bon filtration. Wet air regeneration is used to regenerate the powdered acti- vated carbon in the PACT. The treated water is held in storage tanks for 8 hours so that preliminary analysis can be performed on it before injection, ac- cording to Knorr.

A project of this kind, Knorr said, would probably not be approved in other parts of the country where there are more water options. However, he said, “Here people realize they’re living in a desert.” Planning, he added, in- cluded a citizen’s advisory committee and public meetings to discuss the details of the project which were pre- sented in the context o f a total water management plan. “There was nothing but support,” he said, adding that the Texas Water Commission discharge permit for the plant is based on state water quality standards.

A second example of indirect reuse is

the Upper Occoquan Sewage Authott ity (UOSA), located in FairfBx County Va. This state-of-the-art water reclamz tion hcility produces high-quality effln ent that is discharged into the countt drinking water reservoir which, doni with the Potomac River, serves as th county’s water supply. UOSA has bee operating since 1978 under an NPDE permit issued by the state water contrri board. I t continuously meets some (( the most stringent permit limits in tH- country and is a model for other facd ties of its kind. “Reclaiming water fii indirect potable reuse is not only tecll nologically feasible but practical, esp) cially in areas of limited water supp like the Occoquan watershed,” s a Millard Robbins, UOSA executive a rector.

Because ofhealth eEects concerns because ample water supplies mal reuse unecessary, some states will ni permit projects of the UOSA t y ~ however. In fact, according to

Journal WPCF, Volume 60, Number’

American Water Works Association sur- vey, conducted in 1986 as part of that association’s preparation of a manual on dual-distribution systems, eight states prohibit or discourage the reclamation of treated municipal wastewater for any purpose. With the exception ofAlaska, these states are in the eastern third of the U.S., where drinking water supplies, bolstered by average annual precipita- tion of 40 in. or more, are generally abundant.

These states are not immune from the effects of droughts, however. In 1987, South Pumam, W. Va., experi- enced a drought that greatly reduced the water level at the city’s drinking wa- tei ieser\ri i . The South Putiiaiii Pub- lic Service District applied to the state health departnient for a permit to sup- plement reservoir water with reclaimed water, but was flatly turned down. Be- yond the fact that the state prohibits reuse by policy, “There is not enough research to justifp using reclaimed wa- ter for potable water,” said health de- partment spokesman Donald Kuntz.

The health issue is at the core of the debate concerning direct potable reuse.

The controversy will continue until the issue is re- solved, an outcome that some in the engineering and health professions feel may never come about. The Denver Water Board, meanwhile, is doing everything it can to demon- strate that direct potable reuse is both technically feasible and entirely safe.

The Denver Po- table Reuse Dem- onstration Project, sponsored by the board, is the lead- ing project of this kind in the nation. A 1-mgd demon- stration plant con- taining state-of-the- art treatment tech- nology with mul- tiple redundancy and reliability fea- tures has been in full-scale operation since October 1985. The plant treats effluent from the Metropolitan Denver Sewage Disposal District No. 1 Central

Treatment Plant using a treatment train of 21 interrelated unit processes and multiple side-stream processes that in- cludes lime clarification, two-stage car- bon adsorption, RO, chlorine dioxide disinfection, precipitation, ozonation, and air stripping. “This is the cleanest water on the planet,” said plant super- visor Stephen Rogers.

As impressive as the technology is, the outstanding aspect of the $30 mil- lion demonstration project, which in- cludes EPA grants of $7 million, is a S2.5 million health effects and toxico- logical study. The health effects proto- col that includes chronic toxicity, carcinogenicity, and reproductive tox- ic iq resting using coi~lparis~il saiiiples fi-om Denver’s water supply, began last month and is expected to take at least 2 years, according to Rogers, who said, “This level of investigation is unprece- dented.”

Justification for this massive effort was established after the water board conducted a study of the city’s fiiture water needs that projected a serious water shortage by the year 2000. Denver obtains its water from the

South Platte River on the eastem slope of the Rocky Mountains and fkom the Colorado River watershed on the west- ern slope. Under Colorado water law, water is a private property and all water users, including municipalities, must obtain water rights. In times of short- age, advantage goes to permit holders with seniority. Further, the law requires that withdrawals in a river basin be re- turned to that basin for downstream owners, a requirement that discourages water reuse. However, inter-basin trans- fers are permitted, an exception that al- lows Denver and other cities on the eastern plain to reuse western slope water. Reuse of this limited supply, however will not be sufficient to meet Denver’s year 2000 water needs, ac- cording to the water board. Hence the need to study the feasibility of potable reuse, which the board feels has the po-

November 1988 1935

tential to meet 15% of the city’+ de- mand.

Direct potable reuse, even more so than indirect potable reuse, has galva- nized water professionals into two strongly opposed camps. Its defenders, like Rogers, argue that a totally pure source of water doesn’t exist. Even the best available sources, they say, ar4 con- taminated from runoff and unplanned indirect reuse. Furthermore, conven- tional water treatment doesn’t necessar- ily remove these pollutants, whereas po-

table reuse technology has barrier-safe features that allow for a greater degree of control over the product. Beyond that, potable reuse standards in many cases exceed drinking water standards to assure an additional margin of safety. Rogers argues, however, that “TO ap- ply drinking water standards to highly contaminated waters treated by conven- tional water treatment methods simply because i t is unplanned indirect reuse, and then to require more stringent quality standards for direct reclaimed

department concerns, alert users that it is n

1936

water treated by the most advanced tech- nologies available, represents a double standard and an im- pediment to the de- velopment of water reuse.”

Daniel A. Okun, University of North Carolina professor emeritus of environ- mental engineering, is a strong advocate of nonpotable reuse as an option for meeting growing water demands. However, he vehe- mently opposes po- table reuse, which he said is “not necessary and is not likely to ever be necessary. Nonpotable reuse offers the same op- portunity for water conservation and it is well established.” As to the public health issue, he said, ”It will be difficult to estab- lish the safety of di- rect potable reuse over a lifetime of in- gestion, and public acceptance is not likely to come easily.”

Does he feel that the Denver project,, if successful, will put to rest the public health concerns? “Even if (the health, issues associated \\ith synthetic organic: compounds) are resolved in Denver,”’ he wrote in the lMay 1987 WPCF Jour-- nal, “the type and concentration of syn- thetic organics will likely be considera- bly different in the wastewater of other urban areas.” Therefore, he added,, “The extensive research that has been] found necessary in Denver wiU need tcn be produced in every instance where potable reuse is considered.”

Representing a balance betweem these opposing views is Asano, whc: does not endorse direct potable reuse but, on the other hand, feels that indi- rect potable reuse can be a viable waten supply option to meet & m e water sup+ ply. Referring to Water Factory 21 ana similar recharge projects, Asano said1 “Groundwater recharge, properly managed and integrated with a more eff ficient use of existing water supplies5 provides a valuable source of water t(r. help meet the state’s future wate: needs.”

The myth of public resistance The debate about potable reuse ii

likely to go on for some time. In thl meantime, conaoversy surrounding an1 form of water reuse continues, as prc

Journal WPCF, Volume 60, Number 11

fessionals and the public grapple ivith the complexities associated \vith the practice. One of the biggest mispercep- tions is that the public is against nonpo- table reuse. I n fact, according to lhoretta h h m a n , a research social scicnist uith the Chapman Research Group in Litrlc- ton, Colo., “It is a myth that the pub- lic will not acccpt it. All sunseys sho\r that there is sitbstantial public support for reuse right up to direct contact reuse and, with proper education, the public will even support direct potable reuse.”

Contrary to popular belief, resistance to any form of water reuse is coming primarily from the engineering and water professions, Lohman said, con- firming a view shared by Jon DeBoer, technical director of the American Water Works Association. “Those with foresight in the water supply industn have always viewed wastenaer efiluent as a rcsource,” DeBoer said. “But many in ou r industry are not interested in talking about nonpotabie reuse. IVater suppliers and water supply regulators maintain m hat, because public health principles require that the utmost pris- tine water soiirces available be used. they don’t need to concern thenise11.e~ with i t . The problem with this \ie\r is that most of our water sources aie coil- tarninated, even if in small quantities.”

“Reuse used to be prefaced by the word, ‘wastewater’,” said another en$- neer, noting that more and more user districts have begun to “tackle” the is-

sue, nith the result that “The so-called gap ben\.een thc nvo technologies, be- cause ofreuse, is becoming indistinct.” The expansion ofwater will bring the n\ o fields closer together, he said, but “\Ve’re not there yet.”

“The Doint is that water, no matter

w Reclaimed water is being used to recharge groundwater and surface water impoundments such as this lake near Edwards 41r Force Base in California.

\\.hat the prefix, is re- cycled naturally,” added former LWCF \Vater Reuse Chairman Ray Avendt, “and that the loop is being closed by engineering processes.” He stressed that any effort to pro- mote the idea of reuse must be based o n public acceptance nhich can be achieved through public educa- tion involving a thor- ough discussion of the public health aspects of the practice. Putting one’s head in the sand ndl not cause the problem offinding al- temative water supplies to go away, he said, adding, “The days of abundant supplies are over. ” w

Alm B. N i c l d s is News Editor of the Journal.

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Is Reclamation Suppotable? While Title 22 of the California Administrative

Code prohibits direct potable reuse, San Diego is out to prove that one day reclaimed wastewater will be a future water supply source. The city is sponsoring a pilot project called the Total Re- source Recovery Project. The project, which has also received EPA grant assistance, has two phases: In the first phase, scientists are looking to see if an aquaculture comisting of water hyacinths can treat wastewater to secondary standards. The second phase involves experiments with diffarent advanced waste treatment trains to produce po- table water. This phase also includes a 3-year, $4.5 million nealth effects study.

The city has been sued by the federal govern- ment for alleged flagrant violations of the Clean Water Act and faces the possibility of having to spend several billion dollars to upgrade its major wastewater facility, Point Loma, to secondary treat- ment. At the same time, it is desparately looking for new sources of water. Not surprisingly, city leaders see water reclamation as a solution to both problems.

November 1988 1937