wastewater reclamation and reuse

GeoJoumal 5.5 483-501/1981 �9 Akademische Verlagsgesellschaft. Wiesbaden

483

Wastewater Reclamation and Reuse

Heaton, R. D., Reuse Project Director, American Water Works Association, Research Foundations, Denver, Colorado 80235, USA

Abstract: Municipal wastewater reclamation and reuse has been practiced for hundreds of years as a beneficial use of a previously wasted product. But it is now becoming recognized as an effective water conservation tool and pollution-control method. This paper describes the status, need, and potential of water reuse in the United States. Current policies are emphasiz- ed with several examples of successful water recycling on a worldwide basis given. The dis- cussion is limited to the treatment and reuse of municipal sewage effluents for agricultural, industrial, recreational and domestic purposes. This is to be distinguished from in-plant water recycling where multiple uses of the same water are evident.

I n t roduc t i on

The application of wastewaters from human habitations to farming areas has been practiced throughout the world for hundreds of years. It is recorded that irrigation of crops with sewage was employed in Athens before the birth of Christ (Metcalf and Eddy, 1972). Sewage farming was com-

mon practice in Germany as early as the 16th century (De Turk and others, 1978) and was practiced in England until the late 1800's (Wolman, 1977). In the United States, agricultural reuse of sewage effluents was first introduced in the 1870's (Rafter, 1899).

Several major benefits of wastewater irrigation have been recognized including plant nutrient recycling, less costly methods of treatment, and increased agricultural productivity.

But in the recent light of public environmental aware- ness and pollution control regulations, water reuse has assumed a more important and diversified role. The attrac- tiveness of reuse results from several circumstances, one or more of which may be appropriate in any situation.

1. Water reuse accomplishes zero-discharge mandates. Re- covery and reusing wastewaters for a beneficial purpose eliminates a potential pollution load to a receiving water.

2. Water recycling optimizes conservation ethics. Legisla- tive directives have asked for more wise use of resources. Extensive wastewater t reatment requirements im- posed for the maintenance of receiving water quality often results in the production of a product that is literally " too good to throw away". This water may serve many purposes in a community.

3. Where there is insufficient potable water of high quality, growth of a community may be limited. Reclaimed water may be utilized for many of the purposes ordina- rily served by the high-quality potable source, thereby permitting the high-quality water to serve increasing populations.

4. Reuse may result in significant economies. These economies can accrue from the postponement of the development of additional potable water supplies and/ or from the lesser requirements for wastewater treatment for nonpotable purposes than for discharge into fragile receiving waters. For example, the nutrients in wastewaters may not need to be removed where reuse is practiced, because nutrients have an intrinsic value for irrigation.

484 GeoJoumal 5.5/1981

5. High-quality sources of water for potable purposes, whether in protected aquifersunderground or in protected upland watersheds, are limited. Communities that require additional water supplies often find it necessary to develop unprotected sources , sources

that drain extensive urban and industrial areas. The health significance of utilizing these polluted sources is only now beginning to be fully appreciated. Con- sequently, non-potable reuse may take the development of these polluted sources unnecessary, thereby giving assurance to the public that they will not need to ingest water containing trace contaminants in great number (Okun, 1979).

6. In coastal areas, recharging highly treated effluents into ground-water aquifers can provide a seawater intrusion barrier, restore depleted supplies, provide a consistent reliable source, and eliminate the need for a secondary distribution system.

Wate r Reuse in t he Un i t ed S t a t e s

The United States generally has an adequate supply of water to provide for national needs (Culp Engineers, 1979). But, surface-water and ground-water supplies in major portions of the west and midwest are either currently in- adequate or are rapidly becoming insufficient to meet demands.

National freshwater withdrawals are shown in Tab 1 for the year 1975. Agriculture accounts for 51% of those withdrawals, with steam electric at 24.5 % and manufactur- ing 14 % respectively.

Tab 1 US Freshwater Withdrawal, 1975 (in billion gallons per day - bgd)

The gross water use in 1975 was 502 bgd (billion gallons per day) but the withdrawal was only 363 bdg (Tab 2). The use was augmented by 139 bgd of reused or recycled water. Water use is expected to increase to almost 1200 bgd by 2000. However, the 1975 withdrawals of 363 bgd are expected to decrease by the year 2000 to 332 bgd because of

Tab 2 US Water Use and Withdrawals (in bgd)

Tab 3 Reuse/Recycle Summary (in bgd)

increased recycling and reuse and agricultural efficiencies. Tab 3 summarizes the reuse component.

It is estimated that wastewater reuse will increase from 0.2 % of freshwater withdrawal in 1975 to 1.5 % in 2000 - close to an 8-fold increase. Reuse of available sewage effluent will increase from 0.4 % to 4 % over that same time span. In-plant recycling will continue to supply the bulk of the nation's total requirements.

Reuse is here defined as wastewater withdrawn by a user other than a discharger; and recycling is the internal use by the original user prior to discharge. So reuse is the use of municipal sewage effluent for agriculture, industry, etc., and recycling means the in-plant use usually associated- with industries.

One of the most comprehensive marketing surveys for reuse application was completed by the East Bay Dis- chargers Authority near San Francisco, California (Murphy, 1979). The first step was a brainstorming approach which listed all of the possible reuse situations that could be con- ceived. Some o f these are shown in Tab 4.

Existing water reuse projects in the United States were determined for the year 1979. The quantity of reused water was calculated on the basis of 21 regions corresponding to significant river basin designations of the US Water Re- sources Council. The results in Tab 5 show the current use of sewage effluent to be 679 mgd (million gallons per day) divided among 536 locations. Irrigational use was almost double that of industry.

The largest number of projects were in California with 283 followed by Texas with 102 and so on (Tab 6). Those areas in the US having the greatest number of reuse projects

Geodoumal 5.5/1981 485

Tab 4 Possible Applications of Reused Water

aesthetic lakes

E. Commerical t . Auto washing 2. Retail nursery 3. Building washdown 4. Landscape irrigation

F. Agriculture 1. Crop irrigation

a) Pasture b) Fiber and seed c) Food crops d) Tree farming

2. Commercial nursery production 3. Land reclamation 4, Washdown 5. Hydroponics

G. Recreation 1. Lakesand ponds 2. Hiking and riding trail maintenance and landscaping

H. Wildlife Enhancement 1. Marsh creation 2. Irrigation of wildlife, forage or feed crops 3. Streamflow enhancement 4. Improvement of land for game

Aquaculture 1. Farming of food and game 2, Sport fishing ponds 3. Fish hatcheries 4. Farming of fish food, animal feed and aquarium plants

have a similar climate to that of Mexico where water reuse would be expected to increase.

Tab 7 shows the actual and estimated potential reuse for the 21 regions. Reuse potentials range from a low of 1 mgd in Alaska to over I bgd in the Missouri River Basin. Over 50 % of the reuse in the year 2000 is projected to occur in the midwest or west. i

Several fac tors will d e t e r m i n e the q u a n t i t y o f waste-

wate r t h a t will ac tua l ly be reused by the year 2000 , in- . . . . . . . . . . Irrigation ; c luding.

and the withdrawals capable of reuse are relatively in balance. In the western states, the need greatly exceeds the available wastewater.

Tab 5 US Municipal Reuse Projects, ] 979

NUmber Of Wastewater PrOjects Reuse (ih mgd)

420 (!50): ( ] 9 9 )

users.

ments of potential users.

There are large regional differences in wastewater

1. The geographical location of discharges and potential

2. The timing of wastewater discharges and the require-

3. The availability and cost of alternative supplies.

availability and reuse potential. In the eastern states and Alaska the quantities of available wastewater discharges

Landscape (60) (33) (260) (Igs)

Industry 29 215


Tab 6 Current Status of Municipal Reuse Projects in the United States

Water Reuse Policies

Water Reuse Policy in the United States

The status of water reuse policy in the US, which changes rapidly, requires a little history.

Policy is often defined as a definite course of action with the means to achieve it. And policy is evident at several levels of national and local governments. It should be indicated that there are several courses of action at all levels, but few means to achieve them are evident.

Emphasis is given to the federal government level and primarily the EPA (Environmental Protection Agency) he- cause of its Construction Grants Program and prime funding role. In terms of federal directives, President Carter's Water Resources Reform Message to Congress in June of 1978 is important because water conservation was made a national issue for the first time. All federal agencies were asked to examine their existing programs and policies so that they could implement appropriate measures to increase water conservation and reuse. Especially important was the request to remove any federal disincentives.

However, the first national legislation to promote reuse was the Water Pollution Control Act, PL 92-500, passed in

Tab 7 Summary of Wastewater Reycle and Reuse in the United States(All Figures are Million Gallons Per Day)

GeoJoumal 5.5/1981 487

1972. The EPA Administrator, in rather weak wording, was authorized to make grants for reclamation projects. He may do so if desired. A mid-course correction to that law oc- curred in 1977 with PL 95-217 known as the Clean Water Act. The wording was strengthened to: "the EPA Admini- strator shah provide financial incentives". EPA then issued its own policy on land treatment of wastewater (Castle, 1977). Incentives were offered for reuse projetcs or in- novative/alternative technologies with grant shares rising from 75 to 85 %. The current EPA position is to emphasize energy saving treatment and get away from the disposal ethic by recycling. Land disposal is encouraged with reuse as a secondary benefit.

In 1974 US Congress passed PL 93-523 more popularly known as the Safe Drinking Water Act. While the primary goal was to protect public health and establish drinking water regulations, the act contained needed research monies for reuse demonstration grants.

To further complicate the picture, certain provisions in the Clean Water Act and Safe Drinking Water Act called for coordination and planning between them. This provision was satisfied in August of 1979 with an EPA sponsored report "Water Supply - Wastewater Treatment Coordination Study" (EPA, 1979). The draft version concluded that:

1. The economics of reuse are marginal.

2. Uncertainties exist with health effects in sub-potable and potable reuse situations.

With all of the stated policy, what is the status today? Several barriers exist in its implementation. As mandated by law, the chief goal of the water-pollution control acts was to bring the entire nation up to the secondary sewage treatment level. States, such as California and others, were able to meet that goal before the deadline, and wanted to go one step further to advanced wastewater treatment (AWT) and reuse the effluent for many purposes. There are simply not enough federal dollars to go around and a recent EPA decision eliminated funding of several reuse projects which were water supply in nature and not pollution control. In California alone, 48 of a planned 69 reuse projects have been curtailed.

What appears very counter productive to the President's conservation goals has some logical points. EPA is reluctant to subsidize reclamation projects with a 75 % to 85 % grant when the effluent is then sold by the water purveyor. And EPA does not want to fund reuse for some communities while others can't get funds to meet minimum discharge requirements. In essence, the current EPA position is this - "we encourage reuse, we think it's great, everyone should look into it. Just don ' t ask us to pay for it".

That doesn't jeopardize the whole future of reuse but it does set it back until EPA and Congress realize that reuse is a pollution control effort. The present Construction Grants Program appears to be the biggest disincentive to reuse. EPA is writing a ten-year strategy for that program

and will address reuse water supply situations. And new legislation may be introduced from western states to specifically fund reuse efforts. Private monies, or state bond issues have eased some of the pain of lost federal support.

Reuse policy is evident at the state, regional, county, city and local levels. But only one state, California, has created an agency to encourage and promote reuse. More is going on in reuse in California than the rest of the US combined. The Office of Water Recycling was formed in 1977 with the objective of tripling water reuse in the state by 1982. That goal will not be reached, however, because of funding limitations.

International Water Reuse Policies

Few countries outside of the US have formal water reuse policies on a national level. Specific policies are in the form of regulations or criteria for reuse applications. Also irrigation or industrial standards have been set.

Japan is expecting and experiencing water resource depletions in its major metropolitan areas. SeveraJ government agencies have formed reuse policies as a counter- measure. Water reuse is viewed as a viable supply alternative and the national government offers economic incentives to industries, office buildings and municipalities that explore and implement reuse. In some cities, buildings can- not be constructed unless a dual or triple distribution system is installed to recover and recycle wastewater.

In March of 1979, the Commonwealth o f Australia issued the following policy:

"The primary constitutional responsibility for water resource matters lies clearly with the states ... but the Commonwealth is firmly committed to cooperation with the states through appropriate forums such as the Australian Water Resources Council. In broadest terms, the Commonwealth's objective is the long-term beneficial use of the country's water resources which can be achieved by encouraging efficient use. There is evidence of inefficiency in both the supply and use of water, in addition, wastewater and water of marginal quality are potentially valuable sources of augmen- tation. Measures are necessary to encourage the more efficient use and reuse of existing supplies and facilitate the integration into supply systems of wastewater and water of marginal quality treated to acceptable standards. Health aspects will need to remain under close surveillance".

A Reclaimed Water Committee was established in Victoria with the goal of establishing requisite technical information, appropriate legal provisions and the social acceptance of reuse for any purpose by the year 2000.

The Water Research Commission of South Africa was established under the 1971 Water Research Act. The

488 GeoJournal 5.5/1981

monia-stripping and recarbonation to occur. The high- quality effluent is then recharged into the aquifer via in- filtration basins in sand dunes. More than a year of detention is evident from recharge to the recovery wells that bring the reclaimed water to agricultural and industrial users. A future stage will reclaim sewage from an additional one million people with an activated sludge-nutrient removal plant instead of the ponds. Throughout the country, the Israelis have been able to turn deserts into productive agricultural lands by combination of water-conservation measures and water-recycling plans.

Fig 1 Israel's Dan Region Project.

objectives of the commission are to coordinate, promote and encourage research on the occurrence, preservation, conservation, utilization, control, supply, purification, pollution or reclamation of water supplies. The Depart- ment of Water Affairs is responsible for effluent standards, policy and reuse guidelines. Criteria have been established for several levels of reclamation effort.

Sub-potable reuse criteria, especially for food production, have been developed in Israel.

In te rna t iona l R e c l a m a t i o n Ef fo r t s

Israel

The Middle East is not only the dry spot on the globe but some interesting research is taking place there. Israel has been blessed since biblical times as the land of milk and honey. But oil and water were not included. With an average precipitation of only 12 inches a year, the country has to make successive use of every precious drop. Reuse is thus mandatory in that arid land where 90% of the existing sources are already being used.

While desalination of seawater is supposedly the ul- timate solution, reuse is regarded as an immediate priority, which is feasible both technically and economically. The patterns of reclamation cover a wide range - from surface storage of effluent for seasonal irrigation to AWT and recharge for unrestricted agriculture, industry and municipal non-potable uses.

The largest scheme, the Dan Region Project, is located south of Tel Aviv. The system is shown schematically in Fig 1. Approximately 11.5 mgd flow into recirculated oxidation ponds. Lime is added at a 600 - 1000 mg/I dose with magnesium chloride. Clarification removes suspended solids, algae, phosphorus, bacteria, viruses and many heavy metals. Detention in polishing ponds allows natural am-

Saudi Arabia

This is the largest Country in the world without a perennial river but the revenues from oil production have purchased a great deal of technology to resolve the problem. Aside from agricultural reuse schemes, an ambitious effort is taking place at a refinery near Riyadh (Fig 2).

The existing sewage plant is a two-stage trickling filter with aerated lagoons as a final polishing step. The effluent approaches a 3000 mg/I TDS level so additional treatment was necessary.

The plant, currently under construction, will produce three grades of water:

1. Utility water for fire fighting.

2. Process waters for crude oil desalting and cooling towers.

3. Boiler feedwater.

Water recovery of 76 % is expected from the 20,000 ma/day facility built at a cost of over $ 50 million.

South Africa

South Africa is a relatively dry country receiving only one- half the world's average rainfall. In addition, the distribution is very uneven. Demand is rising and projections in- dicate that by the year 2000 it will exceed the available supply. Reuse has played a key role in the total water economy.

At present, approximately 37 % of the sewage from 33 major cities, towns and industrial complexes is reused for irrigation, power-plant cooling and industrial processes. A 150 mio ma/yr is used at golf courses, pastures, sports fields and parks. Successful implementation of reclaimed sewage has been evident for 40 years in power plants, pulp and paper mills, chemical and steel plants, gold and dia- mond mines, and the new coal gasification plant at Sasol- burg.

Most of the treatment research has been conducted in Pretoria at the Stander reclamation plant but a full- scale potable reuse project is expected in Cape Town before the turn of the century.

Coo Journal 5 . 5 / 1 9 8 1 4 8 9

r - 7 l ~ HIYADH WTP

j SURGBPONOS "~1 RAPID X ~ B A ~ I ~ i ~ I'~SRTF~AD~s'INS

~' sludge recycle TO SLUDGE CARBONATION TANKS

s~o ~G TOPN~S!CAL i FIER BASINS TREATMENT SYSTEM

SECOND STAGE l r l r "It SECOND STAGE WET WELL UTILITY FLOCOULATION BASINS- ~, ,~ ,~ REOARRONAT]ON BASINS WATER STORAGE TANKS

~ v T TO GRAVITY SLUDGE THICKENERS

FROM CHEMICAL TREATMENT SYSTEM

~ ~ .~ SYSTEM ~ = ~ ~ ,~,

[ r ~ i UPFLOW ' / I COLUMNS I I

I ~ ~ I GRAVITY FILTERS FILTERED WATER | | | ~ ~ ~ RESERVOIR

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~ DOWNFLOW COLUMNS

TO OEM~NERALIZATION SYSTEM

1.1 FROM PHYSICAL TREATMENTSYSTEM ~L

~ ~ PR~MARYR. QSYS~EM ' !

I I _ h r - " COOLING TOWER MAKEUP AND OESALTING WATER STORAGE TANKS

DEOHLORINATION BASIN, CARTRIDGE FILTERS PRJMARY R.O. FIRST secondary FEED WELL STAGE reverse osmosis system brine reject water

brine reject water to evaporation ponds

~ R O ~ �9 FORCED DRAFt AIR WET WELL CATION ANION BO]LER FEEO FEED WATER STAGE ~ STAGE ~ STAGE ~ OECARBONATORS COLUMNS COLUMNS WATER STORAGE

| TANKS brine reiect water ~orlndeecrl~'oeCtr n~t~enrbasm ~ ION EXCHANGE SYSTEM

Fig :2 Riyadh, Saudi Arabia Ref inery Treatment System


Fig 3 The Rhine River Basin

Reclamation of wastewater for human use still occurs at the Windhoek facility in southwest Africa or Namibia. Potable reuse has been practiced intermittently since 1969 simply because no other source was available. The lmgd plant has been modified to include activated sludge, coagulation with alum or ferric chloride, filtration, carbon adsorption and chlorine disinfection.

Reclaimed water accounts for 20% of the city's supply in winter and 10 % in summer because of blinding capability. Extensive epidemiological, toxicological and water-quality studies are taking place.

Netherlands

The Netherlands, which is rich in water, is highly,industrial- ized and has one of the world's highest population densities. Two-thirds of water for domestic and industrial uses is derived from underground sources and one-third from surface supplies. Ground water is rapidly being depleted. The most important Rhine River (Fig 3) is highly polluted. Production of drinking water in the Netherlands comes from the Rhine which receives discharges from 60 million inhabitants along its course from the Alps to the North Sea.

Substantial improvement of the water quality could be achieved by intensive water pollution control within the entire catchment area. However, this is a difficult international political problem.

Taking into consideration climatological, geographical and economical aspects, several alternatives have been con- sidered for additional supplies with the reuse of municipal wastewaters to play a key role.

Reuse for artificial ground-water recharge and salt intrusion control is a very attractive alternative for a number of islands along the Dutch northwest coast. A countrywide research project was begun in the early 1970's to evaluate treatment technologies for removal of hazardous materials and to quantify the risks involved in a direct potable reuse effort or the indirect reuse already occurring. The investigations will provide data for the formulation of quality criteria for different applications of reused water.

Construction of a major pilot facility in Dordrecht (Fig 3) has resulted in considerable data toward full-scale reclamation plant construction. The pilot plant is a combined biological-physical-chemical treatment system with demineralization capability, as shown in Fig 4.

FR Germany The West Germans have had experience for almost 30 years in so-called "sewage farming". Reuse of effluents for agricultural purposes has transformed windblown barren soils into productive lands, allowed double-cropping in a year's time and reliably planned harvests, and stabilized the economic base. Most of the efforts have taken place near Braunschweig.

Berlin is facing critical water problems with declining ground-water levels. This has led to pilot investigations, just getting underway, to recharge treated sewage for eventual recovery and reuse.

Japan

Japan is fortunate to have a mean average rainfall 25 times the world's average but high economic and population growth have caused water demands to surpass available supplies. Reuse of municipal wastewaters has been introduced in the 1940's. In 1973, a Water Reuse Promotion Centre was established to encourage and coordinate water recycling throughout the country.

One project of many is located in a Tokyo suburb. The Minami Senju AWT plant was built in 1964 in the center of a busy residential area to meet industrial water demands. The 10 mgd plant treats secondary effluent with alum coagulation, clarification, and sand filtration before dis- tributing it through a 140 km pipeline to customers. A nearby paper plant has used the effluent and previous secondary effluent since 1951.


Fig 4 Scheme of the Water Treatment System

Dordrecht

SEC. EFFLUENT ~

LIME

LIME PROCESS I RECARBONATION I COCKLE 'AYER FILTRATION

ZEOL,ET AOT,VATEO CARBO. OZONATION ]RECARBONATION] DRY FILTRATION I FILTRATION I FILTRATION

Fig 5 Process

Hong Kong AWT Pilot Plant

EFFLUENT POLISHING

GRANULAR ACTIVATED CAs

' CHLORINATION i

i OZONATION I

So successful has the effort been, that a new 50,000 m3/day activated carbon plant was constructed. The process provides an even higher quality water for more exact- ing industries, and marketing efforts have already contract- ed for all of the water.

Water reuse is encouraged everywhere and one of the more interesting efforts is in new office buildings. Reuse is made to be economically attractive in all new construction. Sanitary wastes are collected in the basement, treated and then used for cooling, toilet flushing, fire protection and floor washing in a dual and even triple distribution system.

Hong Kong

Hong Kong, located at the mouth of the Pearl River estua- ry, includes a mainland area, two large islands, and over one hundred small islands within its boundaries. The total land area of about 1 000 km 2, most of which is steep and rugged, contains over 5 million people. This urban area is one of the most densely populated in the world. There are no perennial

large rivers or natural lakes in Hong Kong, and water supply has been a major problem since the city was founded in the mid-19th century.

The water resources of Hong Kong are derived from two sources: rainwater catchments (including reservoir sites on land and two impounding sites reclaimed from the sea) and importation from mainland China. In 1977, flash distillation of seawater was initiated and proceeded for nearly one year. This energy-intensive facility was taken out of commission in 1978 because the availabKe natural yield from other sources was sufficient to meet demands. Past shortages of water resources have necessitated the restriction of water usage to reduce the draw-off from the system during the dry years of 1963, 1967 and 1976. Water resources, including catchment and present imported supplies from China, will be fully utilized by 1984. Although Hong Kong is currently negotiating to increase imported supplies from China, other potential supplies are being studied as part of an overall program to investigate alternative future water resources.


4- Townships in Western Australia using reclaimed water for landscape watering

4- 4-

WESTERN AUSTRALIA

+

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i �9 t .rokeoH,,,

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,Horsham " ~ ' - - - ~ ' ~ ' ~ [ �9 .Bendigo 2 /

'Ararat. " , .

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Fig 6 Locations Where Reclaimed Water is Used in Austria

The potential reclamation of available degraded stream water and treated wastewater effluent has been identified as a possible source of municipal and industrial supply for Hong Kong. A pilot plant test program was established to determine:

a) the feasibility of reclaiming fresh water from domestic wastewater and stream water of substandard quality using applicable advanced treatment processes,

b) the suitability, reliability and performance of various processes and different levels of treatment,

Tab 8 Summary of Source-Water Quality at the Hong Kong AWT Plant

c) the technical and economic viability for full-scale application of the processes.

An analysis of the goals for the pilot plant indicated that it had to be extremely flexible with near-universal capabilities. This resulted in the process flow diagram shown in Fig 5.

Three different types of water are treated to various levels of quality. Tab 8 presents a raw water-quality summary of the three sources being investigated.

In yet another pilot trial, secondary effluent has been used for toilet flushing in a large public housing block of 5000 people. Irrigation of parks, race courses and public gardens is common and research is continuing on using reclaimed water for office air conditioners and evaporative cooling towers.

Australia

The Australian continent is the driest on earth yet it dis- plays a wide range of climates from tropical rainforest to arid desert. In some areas, full practical utilization of water resources is at hand.

Most of the organized research and investigative work in water recycling is being carried out in the State of Victoria. In 1974, a Reclaimed Water Committee was formed to ensure that the necessary information and expertise is available so that water may be reused for any purpose (including potable) by the end of this century.


The committee believes that the general technology required to produce a high quality water is already available and is concentrating on applying technology developed overseas to Australian conditions.

Several ongoing projects are shown in Fig 6. Primary use of the treated wastewater is for agriculture and landscaping.

The Victoria Forest Commission has been carrying out species trials at a number of locations for the past three years. One site at Mildura involves irrigating 7000 trees for quick growth studies. The trees are to be used for fence posts or eventual commercial timber.

A large research area has been prepared to investigate the growth of vegetables and turf with secondary effluent. Primary concern is given to viruses, bacteria and trace metal uptake in edible crops.

The Werribee Farm near Melbourne has operated since 1897 and until recently received 90 % of the city's sewage. The farm currently covers an area of some 10,800 ha and treats 200 million m 3 ofwastewater per year. Approximate- ly 80 % of the sewage used for irrigation is applied to the land without prior treatment at a rate of 100 mm every 18 days. The farm carries some 20,000 beef cattle and 50,000 sheep, making it the largest pasture activity in Victoria.

Hawaii

It's hard to imagine the Hawaiian Islands having a water problem but limited resources are a fact. Each major island has its characteristic leeward, high temperature, low rainfall, cultivated and/or urban-resort areas that are susceptible to seasonal water shortages as the water demand increases. The Oahu water situation is more serious than that on the other islands because it accomodates over 600,000 or 80 % of the state's resident population, most of the 3 million annual influx of tourists, and the military and associated personnel. The water-supply problems for Oahu assume an island-wide scale.

The major readily-developable water source is the high- quality ground-water which is potable without treatment. It supplies presently, in mgd, agriculture - 220; municipalities - 140; military - 35; and urban-residential - 30; for a total of 425 mgd, leaving only 67 mgd of the ground-water sources that can be recovered to meet additional demand. It is estimated that the developable ground-water supply will be fully committed by the year 2000. Thus, supplemental water sources must be found.

Now, and in the foreseeable future, desalting even brackish ground-water and especially ocean water is not con- sidered economically feasible in view of recent increased energy costs. The catchment of streamflow faces multiple problems, including the limited number of large perennial streams, shortage of reservoir storage space on an island of

limited land area, necessity of water treatment if used for drinking, and uncertain water rights.

The only other possible supplemental water source is municipal wastewater effluent. It is available and de- pendable, has fertilizer value, and may possibly be used for irrigation if its use does not cause ground-water pollution and decrease the crop yield.

Six years of research have been concluded at the Cen- tral Oahu Project to irrigate Hawaii's valuable sugar cane. When secondary effluent was applied for the entire 2-year cycle, sugar cane yield increased by about 11% but the actual sugar yield and the sucrose quality decreased 6 % and 16 % respectively because of excessive nitrogen Ioadings. No clogging or physical/chemical impairments of the soil were noted. Application of wastewater for the first year, then ditch water thereafter, increased sugar yield by about 6 % as compared to control plots.

Additional research is being conducted on AWT and drip irrigation rather than spray techniques.

Canada

Two recycling systems have been developed by the Ontario Research Foundation in Canada. One is an Environmental Research Module designed for the Canadian Defense and Civil Institute of Environmental Medicine. The unit is an integrated facility for the handling of human solid and liquid waste for military or civilian use in remote northern territories. It is air transportable, capable of providing needs for 100 people, contains toilets, showers and laundry area, and produces an innocuous, sterile, compact residue. Extensive water recycling is employed for all purposes except drinking and culinary use.

Several treatment systems were piloted with the final selection, including maceration, wet oxidation (WETOX), lime addition, ammonia stripping, multi-media filtration, reverse osmosis (RO) and UV-ozone disinfection: The heart of the process is the WETOX reactor which operates at 230 ~ and 600 psi. A per capita water use of 47 liters/day has been achieved with conservation devices and vaccuum collection system. What appears to be a rather energy- intensive expensive system is more economical than some conventional systems in small remote villages.

The other research endeavor has been called CANWEL for Canadian Water-Energy Loop developed for their federal government's housing agency. The integrated unit is designed to treat all liquid and solid wastes from a community or building to the point where discharges will exert a minimum load to the environment. As a result, a high quality water suitable for reuse and useful heat is produced. The liquid portion of the treatment system includes biological nitrification -den i t r i f i ca t ion , phosphorus precipitation, carbon filtration, ozone disinfection and reverse osmosis.

494 GeoJournal 5.5/1981

-'~INFLUENT

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OZONE- VIRUSES DESTROYED

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Fig 7 Vascular Plant Sewage Treat- ment Flow

Solid waste handling includes starved air incineration for destruction of garbage, biological chemical sludges and RO brine.

US Reclamation Projects

Several US projects are unique and worth mentioning, with an example from each of the major reuse applications.

Mexico

Sewage treatment is not provided in the capital - Mexico City - unless the water is needed for reuse. But with a population approaching 16 million, pollution control and protection of valuable ground-water sources is imminent. Today, approximately 50 mgd of disinfected secondary effluent is generated from 7 treatment plants and used to irrigate the famous Chapultepec Park, sports grounds, and highway landscaping and maintain lakes at the floating gardens of Xochimilco. Reuse has been a common practice for 25 years. In Monterrey, a large industrial complex uses reclaimed municipal sewage for cooling, process, fire-fighting and boiler purposes.

Water Recycling in Space

One step beyond worldwide reuse experiences is an out-of- this-world project being conducted at NASA's Johnson Space Center in Houston, Texas. Water recovery and recycling has been investigated for prolonged space flights where weight considerations become critical. Several technologies have been developed for reuse and the space shuttle will carry experimental packages.

Industrial Reuse

For over 25 years, the Bethlehem Steel Corporation has been using over 100 mgd of secondary effluent from Balti- more, Maryland, for a wide variety of purposes in the manu- facturing of steel. The only problems have been getting enough water to satisfy demands.

Recreational Reuse

Lubbock, Texas, is constructing its Yellowhouse Canyon Project, a recreational green-belt stretching six miles through the city and covering 1450 acres. This has all been made possible through the wise use of reclaimed wastewater that now provides water-oriented activities in a semiarid area. The project began in 1966 when the city's planning depart-

ment realized the potential of an unsightly canyon to become a linear park containing a series of small lakes and open spaces. Sewage effluent is first used for agricultural irrigation, recovered, then pumped to decorative inlets on several recreational lakes. Public use and acceptance has been phenomenal. While the lakes use only a portion of the available effluent (4 mgd), a nearby power plant uses 7 - g mgd and agriculture 13 mgd.

GeoJoumal 5.5/t981 495

Agricultural Reuse

The Monterey, California, Wastewater Study for Agricul- ture (MWRSA) is an ambitious, long-term research and development effort to show that food crops can be safely irrigated with treated sewage effluents.

Objectives of MWRSA in this important agricultural region are to demonstrate to local farmers:

a) Safety for the public and farm workers with regards to viruses, aerosolized pathogens, bacteria, and trace metals.

b) Long-term soil impacts such as effects on permeability, structure, and salinity.

c) Crops yield, quality and maturity. Food crops such as lettuce, celery, artichokes, cauliflower, broccoli and tomatoes are grown year-round in the Monterey area.

d) Consumer acceptance of food crops grown with reclaimed water.

e) Economic feasibility of reclamation as related to established standards.

A pilot plant was constructed to provide .25 mgd of reclaimed water to numerous agricultural test plots. Three to five years of analysis are expected in the $ 7 million effort. In hundreds of other US locations, non-edible crops, trees, and grasses have been irrigated with reclaimed effluent.

Aquaculture Reuse

One very ambitious scheme with international cooperation is in the planning stages between San Diego, California and Tijuana, Mexico. Three hundred mgd of raw sewage would be collected from both cities and treated to a secondary level on a 1400 acre site between the cities. Then 800 acres of a covered solar-heated aquaculture process with water hyacinths, algae, daphnia, shrimp and fish would provide additional treatment. Additional processes would provide a drinking quality water for both cities (Fig 7). At the same time, the water hyacinths by-products would produce food and energy in the form of shrimp and fish, pet food, cattle feed, soil conditioners, methane gas and precious metals. A demonstration facility is in the planning stages.

Municipal Reuse

Dual distribution systems have been installed success- fully in St. Petersburg, Florida and Irvine Ranch, California.

St. Petersburg's dual system is unique in that it is the first application of wastewater recycling on a regional basis. The city's secondary treatment plants currently serve 400,000 people and are expected to double in capacity by the year 2000. Since 1977, the Southwest Plant has been

operating at 7 -- 8 mgd, using filtration and disinfection to produce the reusable product (Fig 8). The present 14 mile- long distribution pipeline will expand to 80 miles in the future. The demand for recycled water now exceeds the available supply with present users including golf courses parks, parkways and commercial landscaping.

Fig 8 St. Petersburg Treatment System

The Irvine Ranch system southeast of Los Angeles incorporates additional treatment in a 15 mgd plant and distribution through a carefully controlled system. Users include agricultural irrigation (citrus orchards), landscape irrigation of greenbelts, recreational areas, golf courses, a college campus, lawns surrounding private residences, and a military installation. Doubling of the system is expected before 2000.

Potable Reuse

The conversion of sewage effluents into a product for any human use, including consumption, can be accomplished in any of three ways:

a) Direct Potable Reuse

Direct potable reuse (Fig 9) implies a pipe-to-pipe situation where sewage treatment plant effluent enters a water reclamation plant and is then released to the existing distribution system. Such is being planned in Denver and on a home basis by the Purecycle Corporation in Boulder, Colorado. A water-recycling unit is being manufactured and marketed that requires no water or sewer connections. The sophisticated system starts with 1000 gallons of delivered fresh water that is constantly recovered and used for all purposes in the home. Treatment processes include biological oxidation with an RBC, ultrafiltration, organic adsorption on mixed resins, ion-exchange demineralization and


UV-sterilization. Major opposition to the concept has been from no-growth advocates because homes can now be constructed almost anywhere.

b) Planned Indirect Reuse

Planned indirect reuse (Fig I0) implies the purposeful and knowledgeable discharge of a highly treated wastewater upstream of or into a potable water supply. The word "planned" is important to differentiate it from today's unplanned practice.

A good example is the Upper Occoquan Sewage Authority's 11 mgd plant near Washington, DC. Extremely high-quality effluent from the facility enters a tributary to Occoquan Reservoir, the principal water-supply source for close to a million people in northern Virginia. Sophisticated treatment processes include chemical clarification, multi- media filtration, carbon adsorption, and selective ion- exchange (clinoptilolite) for nitrogen removal.

c) Injection of Reclaimed Wastewater

The third method is ground-water recharge into a potable aquifer (Fig 11), with the Water Factory 21 in southern California, one of the best examples. Operated by the Orange County Water District (OCWD) in Fountain Valley, California, the 15 mgd AWT facility serves as a prototype for plants producing supplemental water during the twenty-first century, thus the name Water Factory 21.

Fig 11 Potable Reuse Through Injection. (WTP = water treatment plant; AWT = advanced wastewater treatment)

Fig 9 Direct Potable Reuse, (WTP = water treatment plant; STP = sewage treatment plant; WRP = water reclamation plant)

Fig 10 Planned Indirect Potable Reuse. (WTP = water treatment plant; STP = sewage treatment plant; AWT = advanced wastewater

treatment)

Case S tudy : California

Technology

Water Factory 21, Fountain Valley,

The reclaimed wastewater produced at Water Factory 21 (US OWRT, 1978) must be extremely high quality water because the injected water is eventually withdrawn and reused for domestic, industrial, and irrigation purposes. When the injected water is pumped from the basin, it must meet drinking water standards; therefore, the California Regional Water Quality Control Board and the State of California Department of Public Health have established stringent requirements which must be met before it can be injected. These requirements are summarized in Tab 9. The OCWD is conducting an extensive specific organic identification and virus monitoring research program to evaluate the effectiveness of contaminant removal.

To meet the injection water-quality criteria, the reclamation system requires several advanced treatment unit operations. Fig 12 shows a schematic flow diagram of the AWT facilities which treats municipal secondary effluent. Treatment operations include lime clarification with sludge recalcining, ammonia stripping, recarbonation, breakpoint chlorination, mixed media filtration, activated carbon adsorption with carbon regeneration, post chlorination, and reverse osmosis demineralization.

GeoJournal 5.5/198t 497

Fig 12 Water Factory 21 -Schema- tic Flow Diagram of Wastewater Re- clamation Plant (From: US OWRT Water Research Capsule Report, 1978)

LIQUID PROCESSING

Chemical Clarification

Lime Reu

Nitrogen Removal Recarbonation

Ammonia Stripping Towers

Lime $ Sludge t

R~

Activated Filtration Carbon

Adsorption

Pump Station I

I

1 T I

I I

Injection System

Cart

Recy

W~

@

�9 Observation

Wells

Injection Pump _ ~ Station

Disinfection and Demineralization

Chlorine Contact

Tank

! Reverse Osmosis

Blending 1 Reservoi r

|

The OCWD selected relatively new advanced treatment technology of reverse osmosis to reduce the effluent total dissolved solids to levels below injection requirements.

The 5 mgd RO facility is the largest ever constructed for wastewater demineralization. A flow schematic is shown in Fig 13. The system is designed to remove 90 % of the salts with an 85 % product water recovery.

The pretreatment system provides optimum feedwater conditions to the RO membranes, which is essential for achieving maximum membrane life and performance. It consists of chemical addition and cartridge filtration. Sodium hexametaphosphate at a dosage of 1 - 2 mg/I is added as a scale inhibitor to prevent precipitation of salts of low solubility in the reverse osmosis elements. Acid is added to adjust the feedwater pH to a level between 4.5 - 5.0 to prevent membrane hydrolysis and convert all car-

bonate alkalinity to carbon dioxide for scale control. Chlorine is added to provide a feedwater chlorine residual of 0.5 mg/I to reduce biological fouling of the RO membranes. Cartridge filters (25#) are provided to remove suspended and colloidal solids. A unique feature of the pretreatment system is the injection of acid downstream of the high-pressure feed pumps. This design resulted in both a major cost savings and a reasonable delivery time since the high-pressure feed pumps required only standard materials of construction.

The RO plant is designed as two parallel 2.5 mgd systems. Each is further broken down into three parallel membrane/pressure vessel assemblies which can be operated independent of each other. This design provides greater operational flexibility and permits cleaning to reduce fouling, or maintenance of one section while the others remain


Tab 9 Water Factory 21 -- Requirements for Injection Water (from: US OWRT Water Research Capsule Report, 1978)

After post-treatment the demineralized product water (5 mgd) is transferred to the blending reservoir, where it is mixed with AWT plant effluent (10 mgd) before injection into the barrier system through a series of injection wells.

The reclaimed water produced at Water Factory 21 is injected into the ground-water basin through a series of 23 multi-point injection wells. Fig 14 is a cross-section of the injection barrier designed to prevent seawater intrusion and recharge the existing aquifers. Multi-casing injection wells were constructed to provide better hydraulic control. Each well is spaced on approximately 600 foot centers.

Reclaimed wastewater must be blended at least 50 % with desalted seawater or deep well water. Reclaimed wastewater must be tested for virus.

on-line. Each of the membrane/pressure vessel assemblies is identical and consists of 35 vessels arranged in a 20-10-5 array to attain 85 % water recovery. The feedwater flows through 20 parallel vessels. The concentrate of brine from the first 20 vessels f low through 10 additional vessels in parallel. The second pass concentrate from these I0 vessels flows through five parallel vessels. In this way, optimum hydraulic conditions are preserved throughout each section.

To increase system reliability, three high pressure feed pumps are provided. Two are operational and one is re- served as a standby. The main feed pumps are 900 hp verti- cal turbine type, capable of providing 3 mgd at an operating pressure of 540 psi. Post-treatment consists of degasifica- tion, for removal of dissolved carbon dioxide, in two verti- cal packed bed decarbonators.

Effectiveness and Costs

A summary of the reclained water quality at various points in the treatment system, including the blended injection water, is given in Tab I0.

Comparison of effluent data with regulatory requirements shows the effectiveness of the system:

�9 Heavy metals, pesticides, bacteria and other potential toxic constituents meed drinking water requirements;

�9 No virus detected;

�9 Turbidity is 0.4 TU and suspended solids are virtually eliminated;

�9 The AWT processes incorporating RO reduce the organics found in municipally treated wastewater by 99 %. The effluent concentration of organics is lower than those presently found in some drinking water supplies recently surveyed;

�9 Advanced wastewater treatment processes can reduce specific organic compounds to levels comparable with many surface water supplies;

�9 Nutrients like nitrogen and phosphorus can be removed from wastewater by AWT to levels where discharge will not impair water quality (total nitrogen = 1.5 rag/l, total phosphorus = 0.07 rag/l);

�9 Operation of the world's first large-scale reverse osmosis plant demonstrates the effectiveness of this new process for reducing dissolved solids as well as remov- ing other constituents of public health significance from reclaimed water.

The costs of the advanced wastewater treatment processes and reverse osmosis are summarized in Tab 1 I . These costs include amortization of capital site improvements and structures, and operation and maintenance cost for each unit process. This 15 mgd AWT plant was constructed in 1972 at a total cost of about $12,000,000. Present operating costs are $ 379 per million gallons (mg), which results in a total AWT cost of $ 549/mg.


Tab 10 Water Factory 21 - Mean Characteristics o f Treated Water, Inject ion Water, and Regulatory Requirements

( f rom US OWRT Water Research Capsule Report , 1978)

!iiiii!!i ii �84

ii,Ti:!

~a

2

lad u a

.= j E

E g

u~ p

,o

O ~.a " W

&7 el m

O

5 o

e l

,s

i �84

al~(C

6i~N:

ity

~S/crr

TU

- - - 1 , 4 6 0 70 8.0 -- -- 6.5

1.2 0,34 -- --

784 900 57

7.6 6 . 6 - 8 . 0 -

0.42 1.0 99

mg/I

mgfl mg/I

mg/I

mg/l

mmg/I g/l

mg/I

mg/I

mg/l 1.0 mg[l

210 110 142

24 0.2

2r 280

1 1 0 103 -

280

- 280 300 -- - 116 -

45 37 S .7 0.9 -

s 9 2.9 - Z -_ 1.3 5.0 : 0.08 -

0.84 . . . .

11 108 110

1.0 37 - 66

0,5 98 16 103 120 60

0.8 83- 125

121 60

0.86 1.0 98

0.70 - 88

- - - 98 0.86 1.0 I 4

0.50 0.8

15 1.5 10 30 92 7 - - - - -

0.23 - 0.08 0.5 97

1 .55 1 .0 1.0 95 9.3 9.6 . . . .

0.2 0.3 - - 94

0.01 * - < 10.0 200

.4 m

_ m

m

1.8

31 1.8

41

49

207

4.7 6 2

3.6

< 2.5 1.3

412

2.4 < 2.4 2.6 50 31 < 1.0 14.0 1,000

1.7 0.2 0.6 10

26 < 1.0 8.8 50

32 7.0 12.3 1,000

66 < 1.0 71.0 300

5.3 0.7 2.8 50

4.9 0.4 4.6 50

4.7 -- 2,4 5

<25 <2.'5 I~8 10

1 . 5 0.3 0.8 50 162 -- 156

21 83

98

94

95

78

85

87

73

9 85

59

< 2 < 2 100 ND 100

found in any sample.


Tab 11 Water Factory 21 - Costs and Energy Requirements (from: US OWRT Water Research Capsule Report, 1978)

* AWT Capital cost based on 1972 construction costs.

* * $1/mil gal = $ 0.264/mil I * * * Energy requirements include

primary and secondary energy c o s t s

**** RO Capital cost based on 1975 construct ion costs ,

Product To

Blending Reservoir

Product Transfer Pumps

"-O- XD--

R. O. Units

Product Clearwell

Brine - To Ocean Disposal

Chlorine h ~ ]

Control Room

Cleaning Pumps Flushing Pumps

Modules Modules

I Air Compressor

Acid Pumps

Main Feed Pumps

Decarbonators

~]~ l~ .JC,e~ ning Z~ n]~ I

Filter Feed Pumps

Flushing Tanks

Fig 13 Water Factory 21 - 5 MGD Reverse Osmosis Flow Schematic (From: US OWRT Water Research Capsule Report, 1978)


The 5 mgd reverse osmosis plant was constructed in August 1975, at a total cost of about $ 3,000,000. Opera- tion and maintenance cost is $ 545/mg, for a total cost of $ 715/mg. Because only a port ion of the water is demineralized, the total blended injection-water costs is

$ 844/mg.

Since energy and water are so closely related, Tab 11

gives energy requirements for producing reclaimed water at

Water Factory 21. This table shows that domestic quali ty

water can produced for 9.5 kwh/l I 000 gal.

Water Factory 21 represents a landmark in treatment technology and reuse of wastewater. It serves as a model

and full-scale demonstration o f the potential use of ad-

vanced waste treatment and reverse osmosis technology

in solving future water supply and water qual i ty problems. Fig 14 Water Factory 21 -- Injection Well Process (From: US OWRT Water Research Capsule Report, 1978)

References

Costle, D.: US Environmental Protection Agency policy on land treatment of municipal wastewaters. EPA, Washington, D.C., October 3 (1977)

Culp, Wesner & Culp Engineers: Water reuse and recycling, Volume I - Evaluation of needs and potential. Office of Water Re- search and Technology, US Dept. of Interior, Washington, D.C. 1979.

De Turk, L.R. and others: Adaptability of sewage sludge as a fertilizer. Sewage Works Journal 7,597 (1978)

Metcalf and Eddy, Inc.: Wastewater engineering: Collection, treatment, disposal. New York, McGraw-Hill Book Co. 1972.

Murphy, D.: Marketing potential in the East Bay Dischargers Au- thority service area. EBDA, Hayward, CA 1979.

Okun, D.A.: Uses and quality requirements for municipal reuse. Am. Soc. of Civil Eng., Environmental Engineering Con- ference Proceedings, San Francisco, CA 1979.

Rafter, G.W.: Sewage irrigation, part III. US Geol. Survey Water- Supply and Irrigation Paper 22 (I 899)

US Environmental Protection Agency: Water supply-wastewater treatment coordination study; Report to Congress, Republic Comment and Review Draft. EPA, Office of Drinking Water, Washington, D.C. (I 979)

US Office of Water Research and Technology: Water Factory 21. Water Research Capsule Report, US Govmt. Printing Office, Wasl~ington, DC 1978.

Wolman, A.: Public health aspects of land utilization of wastewater effluents and sludges. Journal of Water Pollution Control Federation 49,2211 (1977)

wastewater reclamation and reuse

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