Advanced treatment of the semi-coking wastewater by the combination of chemical pretreatment and biochemical treatment

Biodegradation of the semi-coking wastewater was improved by the combination of pretreatment technologies of the aeration ferric-carbon micro-electrolysis,the enhanced flocculation,and the catalyzed electro-oxidation through on-site pilot test.The feasibility of ensuring semi-coking wastewater to achieve wastewater discharge standards was studied through a combination of chemical pretreatment and biological treatment.The results show that COD was from 25000mg/L down to 10000mg/L,NH3-N was from 3000mg/L down to 1200mg/L,and the COD and NH3-N all reached 60% through the treatment of aeration ferric-carbon micro-electrolysis of 120 min with the adjustment pH value of about 3 of the raw water.Then,after adjustment of pH value to 8~9 for effluent of the aeration ferric-carbon micro-electrolysis,the removal rates of COD and NH3-N of the effluent of the enhanced coagulation all reached about 50% by dosing 200 mg/L of PAM and 4.5mg/L of PAM.Next,the effluent by the treatment of advanced oxidation reactor of catalyzed electro-oxidation of 120 min attained COD removal rate of up to 65% and NH3-N removal rate of 60%.Finally,the effluent by the treatment of biological contact oxidation of the anaerobic/aerobic reached COD150mg/L and NH3-N25mg/L.The results provide a theoretical basis for the treatment technology of the semi-coking wastewater.