GARDEN GROVE, Calif. --The adage "there's no such thing as a free lunch" when referring to environmental dilemmas may not apply here. Friendly bacteria are having their lunch in nitrate-laden drinking water with only a small burp to show for it. A free lunch? It appears to be the case. The burp is harmless nitrogen gas that already makes up 80 percent of the air we breathe.
The Orange County Water District (OCWD) is operating the country's first and only experimental treatment plant using bacteria and sulfur as a nutrient to eliminate virtually all unwanted nitrate from a drinking water well. Faced with the increasingly common problem of high nitrates in groundwater, OCWD researchers developed a sulfur-based biological denitrification facility that uses ThiobaciIlus denitrificans, an autotrophic sulfur oxidizing bacterium, to reduce nitrate levels to 0.3 milligrams per liter, far below acceptable levels. The federal and state maximum contaminant level for nitrate is 45 milligrams per liter. The beauty of the treatment system is the lack of residual materials that require disposal or have the potential to contaminate the air, soil, or another water source, said district officials. By-products are only clean water and harmless nitrogen gas.
This new, biological treatment technology also has the potential to significantly reduce the cost of water denitrification compared to current processes. Initial tests indicate as much as a 60 percent reduction in treatment costs to remove nitrate from water compared to reverse osmosis, and about half the cost of ion exchange processes. These two treatment technologies have been considered state-of-the-art up to this time.
The OCWD pilot plant is located in Garden Grove, California. It treats approximately 25 gallons of water per minute. Preliminary results indicate great success at nitrate removal, although the water currently is discharged to the sewer because of the experimental nature of the project. If the plant meets technical, economic, and reliability goals, the next step will be a facility that produces 250-500 gallons per minute. The current facility will operate as a pilot project for approximately two years in order to determine whether a full production plant is warranted. The project is a cooperative effort among OCWD, Metropolitan Water District of Southern California, and the City of Garden Grove.
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