DWP Plans 2 Projects to Put Sewage Plant’s Water to Use
Each day, 35 million gallons of water pour from the city’s new sewage-treatment plant in the Sepulveda Basin into the concrete-banked Los Angeles River. The water runs east for seven miles and, as it passes Forest Lawn Hollywood Hills Memorial Park, flows over a decaying, partially dismantled dam before it courses to the sea.
The Los Angeles Department of Water and Power, eager to ease--even slightly--the growing strain on its limited supply of drinkable water, has planned two projects to capture some of that steady stream of waste water and put it to use.
Water officials have proposed a pilot project to test whether treated water from Donald C. Tillman Water Reclamation Plant might someday be used to replenish ground water beneath the San Fernando Valley, which provides 15% of the city’s drinking water.
In the proposed experiment, the deteriorating dam would be replaced, and river water would be diverted into the Headworks Spreading Grounds, an expanse of shallow basins near Forest Lawn where water is allowed to percolate into the earth.
Approval of Greenbelt Project Expected
The DWP is also expecting final approval of its Los Angeles River Greenbelt Project, which would provide up to 2 million gallons of treated waste water a day for irrigation. Los Angeles and Glendale already use some reclaimed water.
In this project, conceived in 1982, water flowing from the Tillman plant would be diverted by the same dam into a separate basin, where it would be treated and then sold--for watering only--to four customers: Forest Lawn Memorial Park, Mt. Sinai Memorial Park, the Lakeside Golf Club and Universal Studios. All four facilities now irrigate their expansive grounds with water from the city’s regular supply.
The proposals are being assessed by county and state health agencies, which monitor any use of reclaimed water to ensure that there is no risk of the water carrying disease or potentially hazardous concentrations of industrial chemicals.
The DWP started diverting water from the Los Angeles River to the Headworks Spreading Grounds in 1917. The technology used to block the river flow changed in the 1950s from swinging wooden barriers to an inflatable rubber dam, but the idea remained the same: to recharge the natural subterranean reservoir locked in layers of sediment beneath the Valley with water that would otherwise run to the sea.
By 1982, the rubber dam had deteriorated until it needed replacement, said Walter Hoye, director of water engineering for DWP. But DWP left the dam alone, having planned to take it out of service anyway because, he said, the river was scheduled to be taken out of service soon as a source of drinking water.
Plant’s Operations Halted Diversion
In the Sepulveda Basin, construction was about to start on the Donald C. Tillman Water Reclamation Plant, to treat the sewage of the West Valley and dump the treated waste water in the river. The DWP, once the plant was operating, would not be allowed to divert water from the river to replenish ground water.
The Tillman plant, which achieved full operation in September, 1985, removes most of the particles that reduce the clarity of the water, kills viruses and bacteria, and lowers concentrations of most hazardous chemicals to below limits set by the state for drinking water, said Robert Krivak, assistant plant manager.
The eight-stage treatment process at Tillman was not designed to meet all drinking-water standards, Krivak said, but it produces water that meets all standards for irrigation.
The turbidity, or cloudiness, of reclaimed water from Tillman and other waste-treatment plants is usually at least twice that allowed for drinking water, Krivak said. Because about 10% of the sewage treated at Tillman comes from industrial plants rather than homes, it occasionally contains a variety of potentially toxic compounds, including metals such as chromium and other chemicals, including cyanide, Krivak said.
Most of these chemicals are removed by the treatment process, but some are actually created during the process. For example, when some benign compounds are exposed to chlorine, they produce hazardous byproducts, said Peter Rogers, chief of the sanitary engineering branch of the state Department of Health Services.
Both DWP proposals to reuse Tillman water would require that the deteriorated rubber dam in the Los Angeles River below the plant be replaced. The river water diverted by the dam could be channeled either into a clay-lined basin that would be dug for the project or onto the spreading grounds for the pilot project to recharge ground water, said Winston Wu, a DWP water resources planning engineer.
Wu said that DWP is seeking bids for a new dam, which is expected to cost about $500,000 and resemble the previous rubber dam, a tube of rubberized fabric across the cement river bottom that can be inflated, either with air or water, to divert river water into adjacent basins.
In the pilot project, which is “still in the conceptual stages,” according to Wu, water would be channeled onto one of several shallow basins at the Headworks site, where it would be allowed to seep into the earth. This “spreading” process acts to filter out some contaminants, Wu said.
Carbon Filtering Process Planned
An existing well at the site would pump the water from the ground before it could sink deep or seep through the soil away from the area. The water would be passed through a granular activated carbon filter, which is considered to be the best means of removing a large number of toxic compounds, Wu said.
A second well north of the river would take samples of underground water to detect if the waste-water spreading project were causing contaminants to drift from the site. Depending on the quality of the filtered water and on guidelines yet to be set down by state officials, the water would either be returned to the river or pumped into the ground to add to the subterranean supply, Wu said.
Eventually, if no adverse health effects or hazards are detected and DWP gets continued approval from state officials, the water agency plans by 1995 to replenish Valley ground water with as much as 17 million gallons of reclaimed water each day, according to DWP’s Urban Water Management Plan.
The only other project in California where water from sewage treatment has been used to replenish drinkable ground-water supplies is in Montebello, said Rogers of the state Department of Health Services. For the past 20 years, state health officials have closely monitored a Los Angeles County Sanitation Districts project there that pumps 31 million gallons of treated waste water into the ground-water basin each day.
No Adverse Effects on Health
A five-year study of the Montebello water-recharging project has turned up no signs of adverse health effects, Rogers said. As a result, the health department has approved plans gradually to increase the amount of recycled waste water to 44 million gallons a day, Rogers said.
Reclaimed waste water is also pumped into the earth in Orange County, but there, its main purpose is to create an underground wall of water to prevent seawater from encroaching on the county’s drinking-water supply, Rogers said.
Despite the apparent success of the project in Montebello, Rogers said, the state health department is not automatically assuming that new proposals, such as DWP’s, are safe. “In a different situation, you might have a totally different basin and other conditions,” he said. State water-quality officials recently said that DWP’s pilot project is feasible, but are requiring the water agency to prepare a detailed study of every possible impact of the project. A detailed proposal addressing the concerns of health officials will be written in the next couple of months, Wu said.
Irrigation Use Established
The use of reclaimed water for irrigation projects such as the Greenbelt Project is much more established and less controversial than its use for replenishing drinking-water supplies.
One such system in the Los Angeles area involves reusing water from the Los Angeles-Glendale Water Reclamation Plant east of Griffith Park. This sewage-treatment plant produces about 20 million gallons of water a day. About 5% of that is reclaimed and used to irrigate two golf courses in Griffith Park and a section of landscaping along the Golden State Freeway, and is used as cooling water for a power plant in Glendale.
In the Greenbelt Project, water diverted from the river by the dam would enter a narrow basin, where it would be chlorinated and chemically treated and filtered to remove small particles, said DWP’s Hoye. It would then be pumped to its four customers through pipes separate from those carrying the city’s regular water supply, to ensure that no mixing of drinkable and undrinkable water occurs, he said.
The Greenbelt Project will benefit both the city and the customers using the reclaimed water, Hoye said.
First, it will reduce the amount of drinkable water being wasted on keeping plants green. Any substitution of reclaimed waste water for drinking water will help stretch the city’s increasingly strained supplies.
The customers using the reclaimed water will benefit because they will not be constrained from watering plants during drought years, when strict conservation measures would preclude watering with the city’s regular supply, Hoye said. They will also temporarily be charged a discount rate, 10% below what they now pay for city water.
The Greenbelt plan has not been without controversy. County health officials, who must approve any use of reclaimed water for irrigation, support the increased use of Tillman water by DWP, but have been wrangling with water officials over the extent of treatment needed once the river water reaches the diversion site, said Jack Petralia, director of the health department’s Bureau of Environmental Protection.
Petralia’s office has rejected DWP’s proposed treatment system, instead asking for a more thorough--and costly--treatment of the water.
‘We Have No Qualms’
“If they were going to pipe it directly from the reclamation plant, we would have no problems,” Petralia said.
But DWP is proposing to recover the water seven miles downstream from the plant, after it has mingled with storm-drain water, he said.
“It . . . is being exposed to just about anything that can enter the L.A. River,” Petralia pointed out. “Because of chemical spills and runoff, at any one time no one knows what the quality of that water is going to be. We said they’ll have to re-treat the water to the standard it’s at when it comes out of the plant.”
DWP officials have said that this level of treatment would dramatically increase the cost of the project, according to Petralia. As a result, he said, “they have consistently balked at meeting that high a standard.”
A suggestion by county health officials that a pipeline could be laid from Tillman to the irrigation-water customers, eliminating the possibility of contamination, was also rejected as too costly, he said.
Potential customers have also strongly recommended that the Greenbelt Project meet stringent standards for such factors as the concentration of bacteria in the water. “We are interested in using reclaimed water,” said John Clough, vice president for maintenance and construction of the Forest Lawn cemetery. “But we also feel it’s very necessary that it be safe water.”
Water officials have two plans to recycle millions of gallons of waste water that flow daily from the Donald C. Tillman Water Reclamation Plant in the Sepulveda Basin (1). The Greenbelt Project would provide reclaimed water, carried east in the Los Angeles River (2) and diverted by an inflatable rubber dam (3)
into a treatment facility (4), for the irrigation of two cemeteries, a golf course and the Universal Studios grounds (5,6, 7, & 8). RECLAIMED WATER PROGRAM
The second project, in early design stages, would be the first test in Los Angeles of the safety of using
treated waste water to recharge drinkable
ground-water supplies.The water, also diverted by the dam (3), would be spread in a basin (9) near the Greenbelt Project facility, pumped from a nearby well (10), filtered through charcoal, and tested for any hazards.