Study Backs City Plan to Reuse Treated Waste Water

Preliminary results of a two-year study support plans to boost city water supplies by using treated water from sewage plants to replenish ground-water basins, Los Angeles water officials said Wednesday.

Engineers with the Department of Water and Power said the study at the Headworks spreading grounds near Griffith Park has confirmed previous findings that treated waste water filtered through the soil can meet drinking water standards for bacteria.

“I’m very happy and pleased with the results we’re getting,” said Steve Ott, DWP’s engineer for water quality and project development. “It shows that reclaimed water is a viable alternative for future water supply.”

The study, which began in June, 1991, has involved diverting Los Angeles River water--most of it effluent from the Tillman sewage plant in the Sepulveda Basin--into the Headworks spreading grounds, a series of shallow earthen basins where the water drains into the ground. Seeping through the earth at a rate of about 10 feet per day, the water travels about 700 feet before being pumped from the ground by an extraction well and discharged back into the river.

It is tested when it is diverted from the river and again when it is extracted by the well. “Comparison of the spread water and the extracted water reveals a significant degree of water quality improvement,” according to a progress report on the first year of the study.

In particular, the report said, levels of coliform bacteria--which are associated with sewage--drop markedly as the water seeps through the porous soil.

None of the samples of river water met drinking water standards for coliform bacteria, but all samples of extracted water did, according to the report.

DWP officials acknowledged that some samples of the extracted water did not meet standards for a few elements, including certain minerals and total dissolved solids.

Nonetheless, they said, the results support their contention that river water filtered through the Headworks could be pumped from the ground and served to customers without costly additional treatment. If necessary, they said, the solids content could be lowered by blending the water with other supplies, as is currently done with water from city wells in North Hollywood and near Griffith Park.

Gary Yamamoto, Los Angeles district engineer for the state health department’s office of drinking water, said he had not reviewed the report. But he said DWP has yet to resolve all health concerns, including potential risks from viruses.

DWP has set a goal of using recycled water to supply 40% of the city’s needs by the year 2010. But whether that ambitious goal will be achieved or even approached may depend on treatment requirements or other restrictions that health regulators may impose.

Officials say the highly treated effluent from Tillman is far cleaner than storm runoff that contains oil and pesticides from streets and yards, which used to make up most of the Los Angeles River flow.

In fact, several years ago, DWP ceased diverting storm water from the river to Headworks because the runoff was too dirty. DWP says that now that Tillman water, in dry weather, comprises 90% of the river’s flow, the Headworks is poised for a comeback.

Co-sponsored by the Metropolitan Water District and scheduled for completion next summer, the study is meant to support a request for permission to begin diverting to the Headworks up to 10,000 acre-feet of river water per year--enough to serve about 20,000 families.

The results would also be used to advance a much larger effort--the proposed East Valley Water Reclamation Project, which would deliver up to 32,000 acre-feet per year from the Tillman plant to spreading basins in Pacoima and Sun Valley.