Treatment and Reuse of Wastewater in Synthetic Rubber Production by a Full Scale MBR-UF-RO System

The wastewater produced from a rubber synthesis plant was treated by an advanced process of membrane bioreactor-ultra filtration-reverse osmosis (MBR-UF-RO) for reuse. 1 181 m³/d of the production wastewater flowed in the MBR with influent COD_Cr in the range of 158-451 mg/L (258 mg/L in average). The hydraulic retention time (HRT) of the MBR was 5 h. The MBR effluent, with COD_Cr in the range of 5-101 mg/L (31 mg/L in average) and turbidity less than 0.2 NTU, could meet the influent requirements of UF. On-line chemical cleaning was carried out with alternation of high and low reagent concentration every 15 d, which effectively controlled the membrane fouling. The MBR effluent was mixed with 430 m³/d of circulating cooling wastewater, and further treated by the UF and RO. The conductivity of the RO effluent was steadily 30-45 μS/cm, which was qualified to be reused as circulating cooling water. The reuse rate of total wastewater treated was 62.8% within the plant, and the operation cost of the advanced treatment was 4.34 RMB/m³.