Treatment Of High Concentration Oil-Bearing Wastewater In Food Industry With Membrane Biofilm Reactor (MBR)

The high strengthen oil containing wastewater with high concentrated organic contaminants, which charged from food industry, result in serious water resources pollution. And the air floatation-membrane bioreactor (MBR) process was applied for the high strengthen oil containing wastewater treatment.The results shown that the COD and oil removal effect of micro-bubble air floatation pretreatment method was better that of conventional air floatation. The COD and oil removal rate of 65% and 75% were obtained under the following optimum conditions:the flocculant dosage, pH, precipitation time and dissolving pressure were 50mg/L PAFC,8.0, 20min and 0.4 MPa, respectively.The novel type of membrane bioreactor composed of anoxic and aerobic areas was designed. The polyvinylidene fluoride flat membrane with the pore size ranging from 0.2 to 0.4 micron was used. The MBR was successfully started up in 20 days with hydraulic retention time, pH, temperature and reflux ratio were 8h,7.2～7.8,20～30℃and 150%, respectively. The effluent COD, oil and ammonia nitrogen were 100 mg/L,0.5 mg/L and 15 mg/L, respectively.The optimum operation conditions of MBR were as follows:hydraulic retention time, pH, and reflux ratio were 8h,7.5 and 200%, respectively. And removal rates of COD and oil were 97.6% and 99.9%, respectively. The results of stability test which last for 60 days indicated that the operation of the reactor was in a good state with the effluent COD, oil and ammonia nitrogen of about 85 mg/L,0.2 mg/L and 7 mg/L, respectively.The membrane was polluted during the operation of membrane bioreactor, and the flux of membrane was descend while the trans-membrane pressure was increased. It was suggest that the membrane should been cleaning once by strengthening aeration every 15days and by chemical agent every 15days during the operation.