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Volume :21 Issue : 2 1994
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Modeling of nitrification in the BOD test
Auther : ISMAIL I. ESEN
Department of Civil Engineering, University of Kuwait, P.O. Box 5969, Safat 13060, Kuwait
ABSTRACT
Nitrogen compounds present in water exert an oxygen demand when assimilated by auto trophic bacteria. Nitrification is slower than BOD exertion by the carbonaceous material and may take several days until completion. Nitrification is particularly important when wastes introduced into water are already seeded with nitrifying bacteria, and it is affected most by the organism growth rate. Two models are developed to describe the nitrogenous oxygen demand based on microbial growth. The first model is a modification of the Monod model in which growth and decay phases are treated separately. The second is a nonhomogeneous birth and death model with constant birth rate and death rate linearly increasing with time. The model parameters were determined by nonlinear least squares schemes for six sets of nitrogenous BOD data which corresponded to activated sludge effluent, river water mixed with treated effluent, two trickling filter effluent samples, raw sewage, and facultative pond effluent. Both models were observed to represent the BOD exertion due to nitrification reasonably well.