Study On The Effect Of Substrate On Aerobic Granular Sludge And Degradation Kinetics

Aerobic granular sludge is considered to be a special case of biofilm composing of self-immobilized bacteria. This kind of biological granules are compact structured, biologically reactive with wide diverse microbial species and excellent settling capabilities. Substrate has a strong influence on the whole life cycle of aerobic granular sludge.This study consists of three parts. The first part presents the study on the cultivation of aerobic granular sludge with different substrate concentration. The influent substrate concentration was constant for R2 but changed periodically for R1. The results showed that the substrate concentration demand for aerobic granular sludge is different at disparate stages of granulation. Pure aeration without substrate feeding could greatly improve the settling capabilities in early granulation. Gradually increased substrate concentration is conducive to the accumulation of heterotrophic bacteria and nitrification bacteria in the reactor during the middle stage of granulation. At later stage, high substrate concentration stimulated the overgrowth of heterotrophic bacteria, which is harmful to NH₃-N removal. The substrate cost of R1 was 25% lower than that of R2.The second part introduces the study on the effect of substrate on disintegrated aerobic granules during activity recovery. The results reveal that the substrate type greatly influenced the physical characteristics of aerobic granular sludge, TN, TP removal and the specific degradation rate during the recovery period. When the aerobic granular sludge reached the steady state, the aerobic granules fed by sodium acetate showed the best capacity of nitrogen and phosphorus removal. While maximum COD specific degradation rate,10.74kgCOD/(kgMLSS?d), was reached by aerobic granules cultured with glucose-sodium acetate. The nitrification and denitrification ability of aerobic granular sludge got the best recovery with sodium acetate, and the specific degradation rate of NH₃-N and TN reached to 0.335kgNH₃-N/(kgMLSS?d) and 0.272kgTN/(kgMLSS?d) respectively.The kinetics of substrate degradation by aerobic granular sludge was investigated in the third part. In this study, the reaction order of the sodium acetate degradation was 1.38 derived from quadratic expression fitting, the maximum specific degradation rate(V_max) in this process was 5.44d^-1, which showed no significant difference between aerobic granules system and activated sludge in this aspect. The results indicated that aerobic granules technology is clearly superior to activated sludge for high strength organic wastewater disposal. The NH₃-N degradation kinetics equation is V=0.216C/(0.542+C), and the kinetics of NH₃-N degradation is greater than that by using activated sludge, namely the degradation activity of NH₃-N by aerobic granules is much large than that by activated sludge. The enriched nitrifying bacteria in aerobic granular sludge have laid the foundation for the rapid nitrification.