Experimental Research On Aerobic Digestion Of Sludge In Wastewater Treatment Plant

Sewage biological treatment technology which has been existing 100 years so far is the most economical and efficient approach among municipal and degradable industrial sewage treatment due to its high removing ratio of organic material and low running cost.During recent years,with the improvement of people's living standard and rapid development of industry,the releasing amount of domestic and industrial wastewater and sludge has been increasing,and current sewage treatment equipment hasn't been meeting present discharge demand of sludge,which has caused severely environmental pollution and shortage of sludge resource.Therefore,developing new sewage treatment equipment with high efficiency and low expense is extremely urgent.Aerobic digestion is a viable option for the stabilization of sludge produced at municipal and in dust rial wastewater t reatment plant s , especially suitable for small wastewater t reatment plant s (≤20000 m3/d).This paper int roduces the process options (CAD,A/ AD,ATAD),echanical and affecting factors of aero2bic sludge digestion . Based on literatures of both domestic and abroad , the research advance and t rend on aer obic sludge digestion are reviewed and analyzed.The eonventional aerobie digestion Proeess is eonsidered to be suitable for disposal of the sludge from small seale wastewater Plants. The higher power eonsumPtion for aeration and the eost of ehemieal reagent for alkalinity maintenanee with CAD PromPt a seareh for an alternative biologieal aPProaeh to stabilizing raws ludge. The experimental research on primary sludge, excess activated sludge, and mixed activated sludge (with 1:1 primary sludge and excess activated sludge) in urban wastewater treatment plant is studied. They were respectively aerobic-digested for 18 days under the condition of 30℃, and Zn2+ and PO43- were added into the excess activated sludge. It is respectively aerobic-digested for 15 days under the condition of 30℃.The experimental research on primary sludge,experimental is made of plexiglass. Total volume of reactor is 3.5 liter. Air diffuser adopts porous stone aerator. Aerating system consists of air compressor, flowmeter, porous stone aerator , aerated pipes. The trial influent below liquid interface,through raw water tank, flowmeter, valve, effluent pipe.The total running time of this experiment is 30 days, consisting of 12 days of test running and 18 days of formal running.It is also studied that the research on the index change of preliminary sludge and mixed activated sludge TS, TVS, COD, SVI,pH, OUR, TTC-DHA and so on. Results reveal that the removal rates of primary sludge TS,TVS are respectively 47% and 44%,and mixed activated sludge TS,TVS 48% and 47.8%. This proves that it is feasible to aerobic treat primary sludge, and its result is as good as that of sole digestion of excess activated sludge. the removal rates of TS and TVS are imp roved slightly. Supernatant turbidity and COD are decreased. At the same time, the sludge settling and dewatering characteristics are imp roved These results show that during aerobic digestion ismore benefit for next treatment of digested sludge.experimental is made of plexiglass. Total volume of reactor is 5.0 liter. Air diffuser adopts porous stone aerator. Aerating system consists of air compressor, flowmeter, porous stone aerator , aerated pipes. The trial influent below liquid interface,through raw water tank, flowmeter, valve, effluent pipe.The total running time of this experiment is 27 days, consisting of 12 days of test running and 15 days of formal running.The experiment reveals that it is convertible between un-degradable TVS and degradable TVS if Zn2+ and PO43- were added in the Aerobic Digestion system of excess activated sludge. The degradable TVS will increase with added amount of Zn2+,and it will surpass the normal digestion if the amount is over 2mg/L, while the degradable TVS will be lower than the normal digestion with the addition of PO43-,and the amount will get to the lowest point with 50mg/L of PO43-. The experiment also demonstrates that the addition of Zn2+ can improve the removal rate, and can promote the setting property of sludge digestion, and can reduce the COD value of supernatant.According to economic level and water pollution status in our country, developing new sewage treatment equipment with high efficiency , saving energy, abroad cleaning function and readily automatic control is extremely urgent. It is a new sludge treatment technique which has competition in the aspect of technology and economy, suiting the situation of our country. Its application would help to reduce expenses of sludge treatment. It is significant for development of protecting environment career.