Advanced Treatment Of Dop Chemical Wastewater By Coagulation And Reverse Osmosis Coupling Process

High concentration organic wastewater of dioctyl phthalate (DOP) is very difficult to degrade completely by conventional treatments and leads to serious problems to the environment due to its strong biological toxicity. The effective way to treat high concentration industrial wastewater for reutilization is eagerly investigated by researchers all over the world in recent years.In this paper, reverse osmosis (RO) coupling with coagulation was used in advanced treatment of secondary effluent from DOP chemical plant for reutilization. To prevent membrane fouling effectively, the optimal operating conditions for coagulation process were investigated at first. Performance of three different kinds of composite RO membranes BW30, CPA2 and CSM-RE were compared and the membrane surface structure variation during wastewater treatment was analyzed by SEM. Results showed that coagulation as pre-treatment had good performance on removal of turbidity and COD, which could guarantee good quality of feed water for RO. The optimum operating conditions for coagulation process were found at pH 8 and 750 mg/L of PAC. It was also found that permeate flux of CPA2 was higher than CSM-RE and BW30, but BW30 provided better stabilization of flux, lower fouling tendency, and better rejection rate than the others in practical waste treatment. Therefore, the BW30 membrane was better than others in industrial application. All three RO membranes presented good performance in rejecting salt and COD effectively to improve product water quality. The removal of COD can be achieved more than 93% for BW30, compared with more than 75% for CPA2 and CSM-RE. After advanced treatment, the product water quality from the coupling process satisfied State Reuse Qualification and could be successfully reused as cooling water in chemical industry. SEM micrographs were used to compare the membrane properties of surface morphology before and after the treatment during membrane treatment. It was predicted that most pollution could be removed by simple hydraulic cleaning due to coagulation as pretreatment before reverse osmosis.In conclusion, advanced treatment aimed at reutilization by coagulation and membrane coupling process has good value and promising prospect for energy-saving and emission reduction in chemical industry.