| Membrane bioreactor is a new high efficiency water treatment technology which combines membrane separation technology and biological treatment technology.Because of the improvement of national water quality standards and the increasing shortage of water resources,MBR has became the most effective technology to deal with sewage.However,membrane fouling is the most difficult problem in the operation,expansion and upgrading of membrane bioreactor.Membrane fouling can result in a dramatic increase in membrane flux?a sharp increase in operating pressure and increase the frequency of cleaning of MBR.In order to make more economic operation of the MBR membrane flux of chemical cleaning is often used to restore MBR.In this paper,the study of different concentration and different time interval under different conditions and the backwash amount of sodium chlorate next backwash effect and reactor operation,thus the optimum backwashing parameters.And to study the effect of different long-term operation conditions of the reactor backwashing scheme,thus application of sodium hypochlorite backwashing online process to provide some reference.Research results show that:(1)To study the effects of different concentration of backwashing on membrane bioreactor with 0mg/L,0.5mg/L,1mg/L,5mg/L,20mg/L and 100mg/L of NaClO.In the process of 564 hours,when the backwashing sodium hypochlorite concentration was 20mg/L,the reactor of COD and ammonia nitrogen removal rate were 91.2% and 89.9%,TMP increase rate of 0.1kPa/h,MLSS concentration rise late backwash also rebounded,SV30 and SVI compared to before the change backwashing values were-3L/m~2 and 0.9mL/g,the concentration of activated sludge and stability good settling performance,at the same time compared to other anti concentration,the membrane flux decay rate of the slowest.(2)To study the effects of different backwashing interval on membrane bioreactor,12 h,24h,respectively with 48 h and 72 h.In the process of 552 hours,the change of pressure difference between the water quality of the reactor,the reactor integrated across the membrane and activated sludge reactor,sodium hypochlorite can draw the optimal interval for 24 h backwashing.The removal rate of cod and ammonia nitrogen in the reactor was 93.1 % and 91.0 % respectively,the trans-membrane pressure rising rate was 0.15 kPa/h,the activated sludge concentration was stable and sedimentation performance was good,the membrane flux attenuation rate was the slowest.(3)To study the effects of different amount of backwashing on membrane bioreactor,respectively select the 1L/m~2,3L/m~2,5L/m~2 and 10L/m~2 of the four parameters.In the operation process of 720 hours,the change of pressure difference between the water quality of the reactor,the reactor integrated across the membrane and activated sludge in the reactor,it can be the optimal amount of sodium hypochlorite backwashing was 5L/m~2.The removal rates of cod and ammonia nitrogen in the reactor were 92.4 % and 91.0 % respectively,the trans-membrane pressure rising rate was 0.1 kPa/h,the activated sludge concentration was stable and sedimentation performance was good,the membrane flux attenuation rate was the slowest.(4)The long-term effects of different operation conditions on the reactor backwashing program when choosing 0mg/L+24h+500mL and 20mg/L+24h+500mL two kinds of combination backwashing.In the course of 90 days,the comprehensive removal effect of pollutants and the changes of trans-membrane pressure,better use of 20mg/L+24h+500mL combination of reactor water backwashing.The removal rates of cod,ammonia nitrogen,total phosphorus and total nitrogen in the reactor were 91.4 %,97.2 %,57.0 % and 97.0 % respectively,the trans-membrane pressure rising rate was 3.1 kPa/d,the activated sludge concentration was stable and the settlement property was good. |
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