The Research On Application Of Aeration Flocculation In The CEPT For Municipal Wastewater

Wuhan Wastewater Treatment Plant(WWPT) often runs abnormal for lack of funds, because of the high operation energy consumption of secondary treatment uites. According to the long-term detection on the influent of the plant, the concentration of organic substance is insufficient (BODs is about 60 mg/1.). The wastewater is improper for the conventional active sludge system. But, the contamination removal of existed normal primary treatment is inadequate. To solve such problems, Chemical Enhanced Primary Treatment (CEPT) was put forward to treat the wastewater by WWPT and Wuhan University of Technology, to cut down the operation energy consumption and to improve the quality of effluent of the primary treatment process.During the experiments to select coagulants, excellent result was achieved by adding PAC associated with M1011 to treat municipal wastewater. The experiments to search for the influence factors of CEPT showed that the temperature and pH of the influent have little influence on the effect of CEPT.In the CEPT system of WWPT, aeration flocculation was put forward to reform the primary settling tank. Through model experiments, the effect of aeration flocculation was verified ,and the optimal aeration conditions and design parameters are drawn up.During the full-scale experiment, the feasibility to reform the former primary settling tank to CEPT process was further studied through orthogonal test. And the influence factors of CEPT were analyzed again.The tests of the influent showed that the contaminant concentrations change observably with time in a single day, so it was proposed that the dosages of coagulants should vary with the changes of water quality of raw water. It is useful to improve the treatment effect during the periods of high contamination concentration and to reduce the average coagulants doses. When the dose of M1011 was 0.15mg/L and the average dosages of PAC was 35.4mg/L, SS of effluent was less then 30mg/L and the average removal of SS was 79.2%, COD of effluent was less then 85mg/L and the average removal of COD was 62.0%, BOD5 of effluent was less then 30mg/L while BOD5 of influent was less then 75mg/L , the average removal of BOD5 was 60.6%, the average removal of phosphorus was 67.3%.Comparing with the secondary treatment process, CEPT is with lower removal of organic substances and higher removal of phosphorous. It can obtain more environmental effect to apply CEPT then the secondary treatment process.