Advanced treatment of wastewater by micro-coagulation and membrane coupling process in chemical industry

摘要

Membrane process coupling with micro-coagulation was used in advanced treatment of secondary effluent from dioctyl phthalate (DOP) chemical plant for reutilization. The wastewater from chemical DOP production was first treated by anaerobic and aerobic processes. Because of high solvent and salt content in waste, which was hard to degrade and harm to bacterial, the secondary effluent after sedimentation usually could not meet qualification for discharging very well. Reverse osmosis (RO) was investigated for advanced water treatment and reuse. To prevent membrane fouling effectively, polyaluminium chloride (PAC) was used as pre-treatment. The optimum operating conditions for coagulation process were found at pH 8 and 750 mg/L PAC. Performance of three different kinds of composite RO membranes (BW30, CPA2 and CSM-RE) were tested and compared under different operating pressure, time and temperature etc. Results showed that permeate flux of CPA2 was higher than CSM-RE and BW30, but BW30 provided better stabilization of flux and rejecting ability than the others in practical waste treatment. Although all membranes presented high rejection of SO42-, the rejection of Cl- was rather low for CPA2 and CSM-RE. Concentration polarization in mass-transfer in the RO process was als°Calculated and variation of membrane structure was analyzed by SEM. After treatment, all permeate satisfied State Reuse Qualification and could be reused as cooling water in chemical industry.