Inhibition kinetics of ammonium oxidizing bacteria under Cu(II) and As(III) stresses during the nitritation process

Nitritation processes with ammonium oxidizing bacteria (AOB) frequently suffer inhibition from heavy metals in municipal wastewater treatment. In the present study, two frequently detected heavy metals, Cu(II) and As(III), were selected to assess their inhibition effect during the nitritation process. Specific ammonium conversion rate (SACR), specific oxygen uptake rate (SOUR), and specific nitrite production rate (SNPR) in batch tests were first applied to evaluate nitritation kinetics, and simulated by the classic Haldane substrate inhibition kinetic model. The presence of Cu(II) stress imposed a more pronounced inhibition on nitritation process than As(III) with half inhibition concentrations of 6.7 and 86.6 mg L-1, respectively. The kinetic result showed that Cu(II) acts as an uncompetitive inhibitor on nitritation process with reduced affinity (K-s) and specific activity (V-max) values. The difference in the inhibition kinetics between Cu(II) and As(III) can be accounted by the oxidation of As(III) to As (V) and subsequent competition by dissolved oxygen under nitritation condition. Our result indicated that the SNPR method exhibits great performance in describing and modelling the inhibition kinetics of heavy metals on nitritation process.