Evaluation of nitrification kinetics for treating ammonium nitrogen enriched wastewater in moving bed hybrid bioreactor

Abstract

Nitrification kinetics of wastewater characterized by high nitrogen and very low organic carbon was evaluated using a moving bed hybrid bioreactor (MBHBR) in batch mode by varying initial ammonium nitrogen (NH4+-N) concentration in the range of (500–1000) mg L−1 at a pH of 7.8 ± 0.15 and temperature around 28 ± 2°C. A maximum removal efficiency of 89 % in terms of ammonium nitrogen was achieved with initial NH4+-N concentration of 900 mg L−1 having a total biomass concentration around 2000 mg L−1 and at a batch period of 5 days. The experimental results were analyzed in the light of Monod’s kinetic theory and coefficients for nitrification were obtained as maximum substrate removal rate coefficient (μmax) = 0.52 day−1, yield coefficient (Y) = 0.63 mg VSS/mg NH4+-N, half saturation constant (Ks) =603.11 mg NH4+-NL−1 and endogenous decay constant (kd) = 0.008 day−1. The study confirms better nitrification efficiency in presence of attached biomass as compared to suspended growth condition. An interesting observation from the nitrate nitrogen profile establishes the possibility of denitrification, occurring simultaneously even in absence of organic carbon in the wastewater in aerobic MBHBR. This can be supported by the fact that the suspended flocs and/or attached biofilms in hybrid reactor was deep enough for creating necessary conditions for denitrification and the required organic carbon was partially obtained from endogenous degradation of the microorganisms.