Advanced treatment of coking wastewater by coagulation with PAC

An integrated technique was investigated, aiming to provide an effective method for the treatment of biologically treated coking wastewater and to reduce pollutants to concentration values below the limits imposed by the legislation. Coking wastewater containing 270 mg/L COD and 202 times color was treated by coagulation using PAC as well as PAC +PAM, respectively. The application of coagulation using PAC+PAM resulted to a much more efficient removal of color, COD and SS in comparison with single coagulation without PAC. The optimal condition for coagulation with PAC was pH 8, dosage 75 mg/L and dynamic condition 1-minute high speed stirring followed by 15-minute low speed stirring. The optimal condition for coagulation with PAC and PAM was: PAM dosage of 6 mg/L, PAC dosage of 70 mg/L, pH of 8 and reaction time of 20 minutes. Both processes of coagulation were found to be efficient for removal of COD from coking wastewater, but ineffective in reducing color.