Research On The Microbial Characteristics Of Enhancing The Aerobic Digestion Of Excess Sludge

Activated sludge process is the most widely used biological treatment technology. And more than90%of urban sewage treatment is using activated sludge process in our country. But there is a large number of surplus sludge during using activated sludge treatment of sewage. The cost of excess sludge treatment and disposal is expensive, which accounts for about25%-65%of total operation cost in wastewater treatment plant. Sludge aerobic digestion is suitable for sludge treatment of small wastewater treatment plant. Because its operation management is convenient, its cost of capital construction is low. But aerobic digestion treatment of residual sludge has low efficiency of digestion and long digestion time. In order to improve the efficiency of the aerobic digestion, this topic research used microbial enhanced sludge aerobic digestion.There were obtained three strains through the process of separation, purification and selection, respectively named B4, H4, N2in the experiment. The sludge digestion efficiency of experimental group of adding respectively the B4, H4, N2were improving sludge digestion rate 5.06%,3.26%,2.68%relative to the control group. The sludge digestion efficiency of B4in three bacteria was best. When the adding bacteria could improve the efficiency, the dosage amount of the strain had much more significantly influence compared with the sludge concentration. The dissolved oxygen could have an impact on sludge aerobic digestion. There was better efficiency under the condition of high dissolved oxygen (6-7mg·L-1) than that under the condition of low dissolved oxygen. pH was another factor which impacted the efficiency of sludge aerobic digestion. Controlling the pH was favorable to improve the efficiency of sludge aerobic digestion.Adding one of three kinds of beneficial bacteria could improve the long-aged sludge aerobic efficiency. After58days the three experimental groups (adding the N2, adding the H4, adding the B4) digestion experiments MLSS and MLVSS digestibility were increased by6.2%,11.7%,13.2%and9%,20%,18.8%respectively relative the control. The strain which was named B4had best efficiency in the experiment. Adding one of three kinds of beneficial bacteria could improve the short-aged sludge aerobic efficiency. After24days the three experimental groups (adding the N2, adding the H4, adding the B4) digestion experiments MLSS and MLVSS digestibility were increased by1.0%,9.0%,10.0%and3.0%,13.0%,11.0%respectively relative the control. The screened bacteria could intensify the aerobic digestion process of long-aged sludge and short-aged sludge. So adding screened bacteria could improve the digestion efficiency.By the way, different age of sludge had different aerobic digestion.Sludge hydrolysis was the main factor in the early stage of the process of sludge aerobic digestion, but effective microorganism activity and the number of effective microorganism was the main factor in the late process of sludge aerobic digestion. The reason of adding the screened bacteria improving the aerobic digestion efficiency might be due to promote the process of sludge hydrolysis and increase the number of active microbes.