Kinetic study on nitrification of ammonium nitrogen-enriched synthetic wastewater using activated sludge

Nitrification of ammonium nitrogen (NH4+-N)-bearing synthetic wastewater was performed in a batch-activated sludge reactor by varying the initial ammonium nitrogen concentration up to 400 mg/L at a pH of 8.1 +/- 0.2 and temperature of 36 +/- 2 degrees C for developing the process kinetics using acclimatised biomass. Maximum ammonium nitrogen removal efficiency of 98.3% was achieved with initial ammonium nitrogen and mixed liquor suspended solids concentration of 235 mg/L and 2,180 mg/L, respectively, at 48 h batch period. Based on the experimental results, kinetic constants for ammonia nitrogen removal following Monod's approach were obtained as maximum substrate removal rate coefficient = 0.057 per day, yield coefficient = 0.336 mg volatile suspended solids/mg ammonium nitrogen, half velocity constant = 12.95 mg NH4+-N/L and endogenous decay constant = 0.02 per day. Nitrification is a consecutive reaction with ammonium oxidation as the first step followed by nitrite oxidation. The overall rate of nitrite and nitrate formation was observed to be 1.44 per day and 0.34 per day, respectively.