Process kinetics of an expanded granular sludge bed reactor treating sulfate-containing wastewater

A laboratory study using expanded granular sludge bed (EGSB) reactors was undertaken to explore the kinetic behavior of sulfate reducers and methanogens in treating sulfate-containing wastewater. A kinetic model was also formulated in a way that accounted for mass fractions of sulfate reducers and methanogens ( f SR, f M) and an inhibiting effect of unionized H 2S on microbial groups. When the EGSB reactor was maintained at the influent COD/SO 4 2− ratio of 0.5 (i.e., acetate was growth-limiting and sulfate was in excess), sulfate reducers kinetically prevailed for acetate over methanogens. In contrast, when the EGSB reactor was maintained at the influent COD/SO 4 2− ratio of 0.8–3.0 (i.e., acetate was in excess and sulfate was growth-limiting), methanogens can utilize the excess acetate and may prevail over sulfate reducers. The values of f SR, f M evaluated at the influent COD/SO 4 2− ratio of 0.5–3.0 and the obtained kinetic parameter values of sulfate reducers and methanogens ( k SR, K I,SR, K sa, K s,SR; k M, K I,M, K s,M) together with the validated kinetic model are of help in predicting the performance of the EGSB reactor treating sulfate-containing wastewater.