From Waste Water to Tap Water

Each day, 60 million gallons of recycled water is dumped into the Los Angeles River on its journey to the Pacific Ocean. Except for higher-than-allowed levels of nitrogen, the water meets drinking water standards.

However, work is well underway on the equipment that will get rid of the extra nitrogen so that this huge natural resource can be tapped.

Plans call for firing up a new pumping station in Van Nuys in December that will carry the recycled sewer water to basins near Hansen Dam where it will seep into the soil and collect in the aquifer. As it percolates 200 feet down through the ground, microbes will take care of the excess nitrogen. Five years later, the water will reach the city’s Department of Water and Power pumping wells that will draw it to the surface for its eventual comeback through faucets citywide.

By replenishing the ground water beneath the San Fernando Valley, the East Valley Water Recycling Project will supply enough water for 200,000 city residents annually. Construction of the pumping station at the Donald C. Tillman Water Reclamation Plant began last August and pipes leading to Hansen Dam will soon be laid, followed by a two-mile stretch of pipe to basins in Pacoima.

Eventually, a storage tank capable of holding up to 2 million gallons of water will be built near Hansen Dam.

Although this is the biggest such project for the DWP, water recycling is not an original idea. In eastern Los Angeles County, the Montebello Forebay ground-water recharge project has been using reclaimed water to replenish ground water since 1962.

Here’s a look at the way such water is recycled.

1. Waste Water Is treated at Donald C. Tillman Plant

A: Seventy percent of solids removed by passing water through grates and screens.

B: Organic materials in water converted to such harmless by-products like water and air. Remaining solids like pebbles, grit and sand removed.

C: Chemicals added to help pull together remaining organic matter for easier removal.

D: Water passes through sand filters to prevent passage of organic matter and viruses.

E: Chlorine added for disinfection.

F: Water is dechlorinated

G: Treated water goes to the plant’s pumping station.

2. Aquifer Is Recharged With Treated Waste Water

A: Recycled water piped 10 miles to Hansen spreading grounds near Hansen Dam.

B: The water filters through 100 to 300 feet of soil before it reaches the aquifer, a layer of porous rock and sand where water settles.

C: Waste water mixes with ground water in the aquifer.

D: DWP wells tap the aquifer to supplement water imported by aqueduct from Northern California, the Owens Valley and the Colorado River.

E: Mixed ground water is brought to the surface and disinfected before being piped to customers.

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Cost of project: estimated $55 million

Length of pipeline: 10.2 miles (to Hansen Dam); 2.2 miles (to Pacoima)

Size of spreading grounds: 105.3 acres (Hansen); 107.3 acres (Pacoima)

Pumping capacity: 100 gallons per second into Hansen spreading grounds

Pipe capacity: 11,397 million gallons

Time for reclaimed water to travel 6,000 feet to DWP pumping wells: 5 years

Sources: Los Angeles Department of Water and Power. Researched by STEPHANIE STASSEL / Los Angeles Times