Kinetics of denitrification processes and experimental work for denitrification

Suspended growth systems are widely used in the world. In suspended growth system, the microbial culture is maintained in a suspended state and clarif iers are used to separate the suspended biomass. As a result of denitrification in nitrifying activated sludge process, an a ctivated sludge settles poorly due to entrained nitrogen gas. For a combine d 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, st andard simple reaction time (SRT) > 10 days) and must include sufficient an oxic areas to carry out denitrification (Bamard, 1973). If the system has a lready achieved nitrification, additional denitrification. zone may be requ ired either for nitrogen removal or to improve settling properties in settl ing tanks. Several investigators have used the Monod kinetics equation for the denitri fication. The other commonly used mathematical denitrification model is pre dictive equation based on F/M and SRT, zero order equations (with respect t o nitrate). Several researchers have studied biological denitrification rat es both in laboratory and fall scale operations based on empiricial equatio ns derived from the batch rising sludge experiments (Sanoglu, M. and Horan, N.J., 1996). These results show that the relationship between the concentr ation of nitrate, which causes a sludge to rise, and the influencing enviro nmental factors, e.g. temperature and available carbon. This paper will provide an overview of denitrification kinetics in biologic al treatment processes and experimental results.