"Toilet to tap" returns!

Orange County is now gearing up to do what Los Angeles tried to do some years ago. It makes sense -- the city of Los Angeles pulls in some 600 million gallons of water each day, and dumps 400 million gallons into the sewers and storm drains over the same period. If we could capture and recycle all that water, we could cut our demand on aquifers and snow melt by two thirds.

Some communities have used reclaimed water for decades to recharge their drinking water supplies. In Virginia, recycled water is added to a stream feeding the Occoquan Reservoir. In Los Angeles, treated wastewater is added to the Montebello Forebay, where it percolates through the soil to replenish the groundwater supply. Also in California, the Orange County Water District's (OCWD's) Water Factory 21 facility reclaims wastewater that is then injected into aquifers to provide a pressurized barrier against seawater intrusion into groundwater.

To meet additional need to prevent such intrusion and to meet increased demand for drinking water, the California Department of Public Health, along with the Santa Ana Regional Water Quality Control Board, approved OCWD's new state-of-the-art water reclamation facility on Jan. 10. The Advanced Water Purification Facility (AWPF) will yield 70 million gal of drinkable water per day, or about 10% of the district's daily need for 2.3 million residents. "It will give us a supply unaffected by drought," notes Mehul Patel, OCWD's principal process engineer.

The final treatment step at AWPF removes low-molecular-weight organics by adding hydrogen peroxide and irradiating with ultraviolet light. Hydroxyl radicals or hydroxide anions will oxidize at least some of the remaining organic contaminants.

WHEN WATER exits the plant, it goes to one of two places. About half is pumped to the coast, where it is injected through wells to form a hydraulic barrier to prevent seawater intrusion into groundwater. The other half is destined for a percolation pond, which is essentially a giant lake set in permeable soil that allows water to percolate down to blend with the groundwater table. Additional filtering occurs in the soil, where naturally occurring bacteria may break down any remaining contaminants. Studies done for the original Factory 21 reclamation plant using noble gases as tracers demonstrated that it takes more than six months for water to travel from injection wells or percolation ponds to drinking water well intakes.

AWPF was more than a decade in the making, incorporating design, process validation, construction, and regulatory approval. The facility's end product is water that meets or exceeds all drinking water standards. "There are hundreds of constituents that we have to test for and then report," OCWD's Patel says, "and there are minimum standards for all of them."

The difference between Orange County and Los Angeles? Orange County appears not to have had a mayoral candidate trying to ride the issue into office.