In this paper, a study on using fixed-film biological denitrification to remove nitrates from water supplies is reported. Fixed-film biological systems have not been used in water supply systems in the U.S. although they are proven to be efficient and economical for removing nitrates with the reason being the possibility of imparting residual organics, suspended solids and bacteria to the treated water. In this research, fixed-film upflow biodenitrification columns were operated under carbon-starved conditions and the effluent was treated with a granular activated carbon (GAC) and sand filter system (combined in one unit) to remove residual organics and suspended matter. The system resulted in an average effluent turbidity of 0.8 NTU, and COD and total suspended solids (TSS) concentrations of 5.7 and 0.6 mg/L, respectively.

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