Comparative Study Of Sludge Reduction Effect Between Biofilm Process And Membrane Bioreactor

Among both domestic and overseas, the sludge reduction technique mainly based on physics and chemistry has some disadvantages that large energy consumption and the production of the secondary pollution, which will increase the difficult of the operation and management. In-situ excess sludge reduction technologies are praised an eco-technology of sludge reduction with low power consumption and no-secondary pollution which could reduce excess sludge production in wastewater treatment system. There are many kinds of the in-situ excess sludge reduction technologies, among which the biofilm process and membrane bioreactor process were researched widely.In this experiment, both of the biofilm reactor and the membrane reactor (MBR) were established. The sludge performance, pollution removal effects and sludge reduction performance were investigated. Based on this, the coupling of the biofilm process and MBR process were used for the comparison of sludge reduction effect. The results showed that the sludge reduction effect of both the biofilm reactor and MBR were very good, with the sludge yield of0.072kg MLVSS/kg COD and0.051kg MLVSS/kg COD, respectively. The removal effects of pollutants of biofilm system were excellent. The nitrification rate of biofilm system was maintained above95%during the stable operational period. The phenomenon of sludge granulation was observed in system, which led to a super settling performance. Microscopic observation revealed abundant microorganism flora attached on the biofilm and aerobic granules, which formed stable micro-ecosystem with large amounts of protozoan and metazoan, such as vorticella, epistylis and rotifer. Because of strong interception effects of MBR, the removal performance of pollutants and the sludge reduction effect were better than biofilm system. The principle of sludge reduction was endogenous respiration in natural sludge ecosystems. The sludge settleability and microbial activity were worse than biofilm system. MBR system wouldn’t be stable for long term operation though with the low level of sludge yield.The combined process maintained the advantages of biofilm process and MBR system such as good sludge performance and microbial activity. Moreover, the better treating performance and lower sludge yield were obtained through combined system. The effluent concentrations of COD and NH4+-N were30mg/L and1mg/L, respectively. The sludge yield was just0.037kg MLVSS/kg COD, which was superior to simple system. The results of this experiments confirmed that the sludge reduction effect of combining of biofilm reactor and MBR was better than each process with IIRT of6h.The sludge in combined system had higher sludge activity and was possessed richer microbial communities. The sludge reduction was realized by the prey of miero-metazoa and endogenous respiration in natural sludge ecosystems.