EPA funding for Arlington Desalter's biological denitrification

California's Western Municipal Water District (WMWD) confirmed on 10 February 2011 that it had secured a US$ 528,000 federal grant in January for design work on a treatment system that uses naturally occurring bacteria to remove toxic contaminants, including perchlorate and nitrate, from drinking water.

The funding, from the Environmental Protection Agency, will enable the district to proceed with what will be the USA's first full-scale biologically active denitrification facility producing drinking-water at its Arlington Desalter. If successfully implemented at full scale, this biological treatment could replace processes such as ion-exchange (IE), reverse-osmosis (RO) and electrodialysis-reversal (EDR).

WMWD, in cooperation with the California Department of Public Health and Carollo Engineers, conducted six months of tests on a pilot project at Arlington Desalter and completed preliminary design on the full-scale project. The next steps will be to complete final design and prepare construction plans to build new treatment facilities at the desalter.

"Completing the design is a critical step that will maintain momentum to attract state and federal support to complete construction of the project," said John V Rossi, general manager for the district.

Biodenitrification systems use microorganisms that are harmless to humans to remove nitrates from water. The organisms metabolize chemicals like nitrate and perchlorate as a food source, thereby converting them to harmless by-products like nitrogen gas, chloride and water.

While existing nitrate treatment processes, such as IE, RO and EDR, remove nitrate effectively, each creates a nitrate-laden concentrate waste requiring treatment and disposal. The fixed-bed biological treatment (FXB) process converts nitrate to harmless byproducts such as nitrogen gas, thereby also eliminating the need for nitrate-waste handling, making this technology sustainable.

Large amounts of contaminants can be removed quickly and cheaply with an end-yield of drinking water as high as 96%. Operation and maintenance costs are estimated to be 10-20% of those associated with current technology.

Arlington Desalter is a groundwater treatment facility, currently consisting of five production wells and a reverse-osmosis plant, and is being expanded by 3.6 MGD (13,600 m³/d). The new FXB facility will consist of a series of biofilters, polishing filters, chemical disinfection facilities and supply pumps.


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