Denitrification Inhibition by High Nitrate Wastes

by W. Veydovec, Univ of Colorado, Boulder, CO, USA,
J. Silverstein, Univ of Colorado, Boulder, CO, USA,
N. E. Cook, Jr., Univ of Colorado, Boulder, CO, USA,
L. A. Figueroa, Univ of Colorado, Boulder, CO, USA,
R. Hund, Univ of Colorado, Boulder, CO, USA,
G. D. Lehmkuhl, Univ of Colorado, Boulder, CO, USA,



Document Type: Proceeding Paper

Part of: Critical Issues in Water and Wastewater Treatment

Abstract: The adaptation of activated sludge and inhibition of denitrification at high nitrate concentrations was studied using pH controlled bench-scale sequencing batch reactors (SBRs), operated with 50% of the SBR volume recycled (recycle volume = influent volume). Denitrification of 1,350 and 2,700 mg/l NO3--N was completed after approximately 5 hours and 15 hours, respectively. No denitrification of 5,400 mg/l NO3--N was observed. These results suggest that there is a progressive inhibition of denitrification as nitrate concentrations increase from 1,350 to 5,400 mg/l NO3--N. In a subsequent series of experiments at an initial reactor nitrate concentration of 1,350 mg/l N, a significant accumulation of nitrite was observed, resulting once in destabilization with loss of denitrification and once in successful adaptation of the activated sludge. At a nitrate concentration of 1,350 mg/l N, the adaptation of activated sludge appears to be unstable, resulting sometimes in stable denitrification and sometimes in biomass washout.

Subject Headings: Denitrification | Nitrates | Activated sludge | pH | Recycling | Biomass

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