Controversy Swirls around Toilet-to-Tap Project.
The project was designed to reduce Los Angeles's dependence on water from the Mono Lake watershed, and homes in the North Hollywood area would be the first to receive the reclaimed water. The proposed project would include a three-year trial period, during which about 9 million gallons of wastewater per day would be processed at the Donald C. Tillman Water Reclamation Plant in the Sepulveda basin and spread for percolation into potable water aquifers. Five years after the project begins, after being naturally filtered, the wastewater would begin to be withdrawn. It would be mixed with groundwater pumped from wells to be chlorinated and then piped to consumers. The wastewater would make up about 20% of what pours from the tap.
Supplementing potable water with reclaimed water is not a new concept for California. Some 40 cities now use reclaimed wastewater for urban nonpotable purposes, but not for human consumption. Finding new methods to reduce water consumption has become Los Angeles's main focus following a particularly severe drought in the early 1990s. State officials reduced the city's allotment of water a few years ago, forcing city planners to seek alternative sources to meet its growing demands. Incentives such as volume-based water rates and rebates on low-flow toilets have helped to reduce the heavy water consumption considerably, but with the population growth forecasted for California's future, state officials continue to look for alternate water resources.
Supporters of the controversial potable reclamation method say that California was the fourth fastest growing state in the nation as of 1999, and is expected to continue to have high growth rates, placing heavy demands on its drinking water supply. Supporters also claim that natural filtration and chemical disinfection used together provide reclaimed water that is cleaner than regular tap water. Paul Gagliardo, the water research and development manager for the San Diego Water Department, notes too that existing water supplies have risks of their own, including contamination with pesticides, heavy metals, and pathogens such as Giardia. "There has been no evidence showing any increased incidence of disease on other successful water reclamation projects," he says.
Those who don't support reclaimed wastewater projects aren't convinced. Daniel A. Okun, a professor of environmental engineering at the University of North Carolina at Chapel Hill, says, "Epidemiological studies are not sufficiently robust to reveal the connections between the contamination and disease, which takes decades to show up. [Opponents'] greatest objection is increased health risk." Okun also remarks that the proposed method does not include any processes specifically directed at removing trace organic contaminants, a dangerous omission in the opinion of many opponents.
The County Sanitary Districts of Los Angeles County conducted a study of the health impact of drinking reclaimed water from the Whittier Narrows Water Reclamation Plant, which has been used to recharge an aquifer in the Montebello Forebay area since 1962--a project similar to the proposed Los Angeles project. The study was evaluated by a scientific advisory panel created by the state of California to advise its regulatory agencies. In their 1987 Report of the Scientific Advisory Panel on Groundwater Recharged with Reclaimed Wastewater, the panel concluded, "[B]efore recharge projects are undertaken, other alternatives such as nonpotable reuse, conservation, other nonstructural measures, and modifications to water rights regulations should be thoroughly evaluated."
Public reaction to the proposal has been mixed. Some people support it, while others cannot ignore their unease about the origins of the water. For now, the project is on hold.
To help solve Los Angeles's high water demand, Okun suggests alternatives such as using reclaimed wastewater for nondrinking purposes including irrigation, toilet flushing, and industrial processing. Okun says such uses would save the same volume of water while eliminating the human health risk. He also suggests diverting water that is currently being wastefully used in agricultural irrigation to urban use.
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|Author:||Greene, Lindsey A.|
|Publication:||Environmental Health Perspectives|
|Date:||Oct 1, 2000|
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