Kinetic analysis of inhibitory substrate degradation in bioaugmented activated sludge process

A steady-state model coupling Haldane kinetics and mass conservative principles was developed herein to depict the degradation of a single inhibitory substrate in a bioaugmented activated sludge reactor. The substrate toxicity impact on the bioaugmentation was evaluated for three levels of inhibition coefficient Ki: 0.1, 10, and 1000 mg/L. Under high toxicity conditions of Ki = 0.1 mg/L, the input biomass markedly enhanced the substrate removal. However, at less toxicity of Ki > 10 mg/L, the input biomass was ineffective. The sensitivity study confirmed the parameters of k, Ks, and bd has no connection with Ki, but depends on the amounts of degradative bacteria inside the reactor. Alternatively, parameter Y is important only when Ki is greater than 10 mg/L and the bacteria significantly utilize the substrate. In addition, a novel indicator of marginal solids retention time examines the economic advantages of adding biomass as compared to extending the solids retention time.