Kinetics of denitrification processes and experimental work for denitrification

Abstract

Suspended growth systems are widely used in the world. In suspended growth system, the microbial culture is maintained in a suspended state and clarifiers are used to separate the suspended biomass. As a result of denitrification in nitrifying activated sludge process, an activated sludge settles poorly due to entrained nitrogen gas. For a combined activated sludge process, the loading rates must be low enough to provide nitrification (total mass mixed liquor(M)/applied BOD5 (F) = F/M < 0.1, standard simple reaction time (SRT) > 10 days) and must include sufficient anoxic areas to carry out denitrification (Bamard, 1973). If the system has already achieved nitrification, additional denitrification. zone may be required either for nitrogen removal or to improve settling properties in settling tanks. Several investigators have used the Monod kinetics equation for the denitrification. The other commonly used mathematical denitrification model is predictive equation based on F/M and SRT, zero order equations (with respect to nitrate). Several researchers have studied biological denitrification rates both in laboratory and fall scale operations based on empiricial equations derived from the batch rising sludge experiments (Sanoglu, M. and Horan, N.J., 1996). These results show that the relationship between the concentration of nitrate, which causes a sludge to rise, and the influencing environmental factors, e.g. temperature and available carbon. This paper will provide an overview of denitrification kinetics in biological treatment processes and experimental results.