The model on endogenous denitrification in a biofilm, previously presented by the authors, was verified well with bench scale experiments. Production of the secondary substrate due to lysis of microorganisms, which is necessary for the progress of endogenous denitrification, was experimentally proved. In order to investigate metabolic characteristics of the substrate, molecular weight distributions of the substrate on CODcr or carbohydrate bases were measured. The percentage of the secondary substrate with molecular weight less than 10,000, was more than 50% on both bases. The experimental results demonstrated that the production rate of the substrate can be expressed by the first order type expression with respect to the concentration of biomass. The specific constants for microorganisms lysis and maximum endogenous denitrification rate were determined (0.45 day−1 and 0.141 day−1, respectively).

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Author notes

Current address: Department of Civil Engineering, National University of Singapore, 10 Kent Ridge Crescent, 0511 Singapore.