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How Roseville turns sewage into usable water

7:29 PM, Jan 17, 2014   |    comments
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Roseville treats sewage to be used for irrigation. (Photo by Patrick Walker)

ROSEVILLE, Calif. - While nearly two dozen Central Valley communities are wrestling with 20 percent cuts in water use. But, one city has plenty of water to keep its public areas green year round, regardless of how much rain falls.

Roseville's two water treatment plants treat up to 22 million gallons per day of raw sewage from around much of Placer County, treating it and turning it into water suitable for irrigation and release into Pleasant Grove Creek and Dry Creek.

"The water that is discharged from the plants is cleaner than the creek (it's being dumped into)," Roseville's wastewater utility manager Ken Glotzbach said.

Discharged water must meet Title 22 standards, which means it is suitable for full-body human contact, one step below drinking water, Glotzbach explained.

The plant on the west side of Roseville is currently handling about 7 million gallons of sewage per day. Two storage tanks (each holding 1 million gallons) are filled with treated effluent that can then be pumped into the city's treated wastewater distribution system for irrigation. Another 1-million gallon tank is used keep a nearby power plant cool.

When those tanks are full, the rest of the water is released into Pleasant Grove Creek.

Glotzbach said wastewater usually takes about a day to filter through the plant's 5-part processing system:

First, solid waste that cannot be dissolved by bacteria is skimmed out of the sewage at the head end of the facility. The sewage then moves to a secondary treatment process, which cultivates naturally-growing bacteria to dissolve the solids in the waste.

After a couple of passes, the bacteria-filled water flows into a secondary clarifier, which is a giant pond that lets the bacteria settle on the bottom. The now mostly-clear water overflows off the top of the pond into a collection basin that channels the water into underground sand filters. Most of the remaining bacteria and any non-dissolved solids are filtered out here.

The water emerges from the sand filters clear, and is run under high-intensity ultraviolet lights. The UV lights neutralize any remaining bacteria in the water, Glotzbach explained.

Schools, parks and other public areas around the city are using the treated effluent for irrigation. Nearby Barbara Chilton Middle School's lush, green fields are irrigated solely by reclaimed water, except for the occasional rain shower.

Roseville utility managers are working on plans to allow treated water to be used in construction projects, mostly to fill water trucks for use in dust abatement activities, Glotzbach said.



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