Study On In-situ Sludge Reduction By Bioaugmentation During Anoxic-Oxic Wastewater Treatment Process

Along with the improvement of China’s sewage treatment capacity, largeamounts of excess sludge is being produced which cause serious challenges topublic health and environment safty. The existing sludge treatment and disposalmethods have defects in environmental or economic aspects. In-situ sludgereduction technology provides a new way to deal with excess sludge problems.In this thesis we have done some research on in-situ sludge reduction bybioaugumention during anoxic-oxic wasterwater treatmen process. First we assesssludge reduction effect of two agents by aerobic pilot test and choose the better oneto do pilot test. The pilot test uses two A/O devices whose capacity is240m3/d.Agents is added into the anaerobic pond and research about sludge reduction effect,sewage treatment efficiency and sludge characteristics are done at the same time.A/O devices run at extending SRT process, high sludge concentration processand low sludge concentration process respectively, and the sludge reduction rate ofMLSS(MLVSS) is30.66%(33.79%)，27.44%(28.69%)and26.26%(28.08%)respectively. As a result of bioaugmentation, the removal of SS, COD, BOD5, TNand ammonia rise while TP removal rate decreases. Adding agents causes the SVI inthe early high, later becomes low; sludge moisture content and standardized CSTdecreased; sludge dewaterability improved; heavy metals, petroleum and cyanideincrease in the excess sludge.Static anaerobic pilot test and component analysis of A/O shows that the agentscontain a large amount hydrolysis-acidification bacetria which strengthen the crackof the granular sludge and acidified hydrolysis process.The amount of acetic acidand propionic acid produced by agents group were4.87and5.73times of the blankgroup. Metal ions and organic substance in the liquid phase of agents group is muchhigher than those of blank group. The dissolved organic matter is reused, andstrengthens the lysis-cryptic growth, leading to sludge reduction.Microbial metabolic activity enhancement of agents group results in increasedenergy consumption for maintenance, which leaves less energy for cell synthesis.High metabolic activity is another cause of sludge recuction.High-throughput DNA sequencing shows that A and B is the main microbialcomposition of the agents. Community composition analysis showed that as a resultof dosing agents, the agents group’s community composition changed significantly,which have much more A and B than the blank group. Community cluster analysisand principal coordinate analysis shows that there are great differences in community structure between agents group and blank group.