Abstract
Two functions were newly developed to model the inhibition of nitrite oxidising bacteria (NOB) for partial nitritation of ammonia to nitrite. Traditional non-competitive and competitive inhibition rate expressions could be applied when NOB were exposed to nitrite for short period of time. On the other hand, in long-term batch tests lasting for over 2 days, it appeared that NOB’s oxygen uptake rate (OUR) recovered within the initial few hours. This recovery was thought to be an adaptation phenomenon from the shock loading that existed on the growth stage of NOB. Upon a peak value, the OUR decreased continuously and this was attributed to poisoning that contributed to the acceleration of decay. To express the growth recovery and the poisoning decay, a new mathematical model was elaborated based on the modification of an existing Activated Sludge Model (ASM). In the model a time-dependent adaptation function on the Monod-type growth process and an additional first-order poisoning function on the decay process were included. The developed model could reproduce the batch OUR curves having various shapes depending on different initial nitrite concentrations (125–2,000 mg-N/l).
