Impact Of Anaerobic, Aerobic,and Alternative Anaerobic-aerobic Operating Conditions On Sludge Characteristics

The traditional activated sludge process is the most common type of sewage, wastewatertreatment method, which also generates a large quantity of excess sludge daily such as handlingand running cost. Therefore, to achieve effective reduction of excess sludge is one of the hot topicsin wastewater biological treatment system.In this paper, the impacts of anaerobic, aerobic and alternative anaerobic-aerobic operatingconditions on activated sludge characteristics were investigated by using the activated sludgeprocess, and studied the effect of three conditions on activated sludge characteristics andmetabolic capacity. Alternative anaerobic-aerobic conditions reduced the yield coefficient ofactivated sludge and revealed the relationship activated sludge characteristics, microbial activityand the sludge reduction. The results of this study could be achieved to provide evidence andsupport by OSA process to achieve excess sludge reduction, and also provide the basis foreffective control of the system.The main research results are as follows:（1）From activated sludge acclimated to ultimate stability, activated sludge under anaerobic,aerobic and alternative anaerobic-aerobic operating conditions could obtain good coagulationsedimentation.Under the three conditions, the sludge settling ratio (SV%) and the sludge volumeindex(SVI)could be kept18%~25%and62mL·g-1~66mL·g-1. The Extracellular PolymericSubstances (EPS) concentration in the activated sludge presented a tendency of accumulating to amaximum and then declining, except EPSB-protein which continuously increased during the wholeexperiment. The EPS concentration of alternative anaerobic-aerobic condition was the highest andthat of the aerobic condition was the lowest.（2）Under the three conditions, the concentration of ATP showed a gradually increasingtrend in the early stage, then a decreasing to a stable state.The concentration of ATP of alternativeaerobic condition had the highest value followed by anaerobic, alternative anaerobic-aerobiccondition.（3）Under the three conditions,the sludge yield coefficient presented a consequence ofaerobic>anaerobic>alternative anaerobic-aerobic which were from0.35to0.45gVSS/gCOD, from0.07to0.13gVSS/gCOD and from0.04to0.06gVSS/gCOD respectively. Alternativeanaerobic-aerobic condition achieved sludge reduction and the yield coefficient was relative to theenergy state of microorganism closely.（4）Under the three conditions, the removal efficiencies of COD and chroma in printingand dyeing wastewater was more than90%and60%. As the treatment effect increased gradually,dehydrogenase activity of the activated sludge increased persistently throughout the experimentalperiod in all conditions. The dehydrogenase activity of alternative anaerobic-aerobic condition had the highest value followed by aerobic, anaerobic condition, which were31.27,26.63and24.37mg·(g·h)-1respectively at the end of the experiment. Dehydrogenase activity had a significantimpact on the degradation of pollutants.（5）Compared to the temperature and the pH, activated sludge characteristics could changeunder alternative anaerobic-aerobic condition. Therefore, the activated sludge should be controlledat25℃~30℃and the pH value at7~8, had a good performance of pollutants removal efficienciesand sludge stability.