Membrane cleaning of ultrafiltration in the combined membrane filtration processes and health risk assessment

This study focused on ultrafiltration membrane fouling mitigation and potential secondary pollution induced by membrane chemical cleaning. Based on the single factor experiment, the chemically enhanced backwash (CEB)(1) operating parameters were optimized by response surface methodology in three combined membrane filtration processes, i.e., coagulation/ultrafiltration (Al/UF),(2) adsorption/ultrafiltration (PAC/UF)(3) and oxidation/ultrafiltration (Ozone/UF).(4) Then the optimal control models of CEB membrane cleaning technologies were established, which indicated high credibility and accuracy. According to the quadratic response surface model, the optimum cleaning parameters including backwash duration (BD),(5) reagent concentration (RC),(6) backwash interval (BI)7 and backwash flux (BF)(8) of Al/UF, PAC/UF and Ozone/UF were 4 min, 29 mg L-1, 60 min, 23 L (m(2) h)(-1); 6 min, 69 mg L-1, 60 min, 40 L (m(2) h)(-1); 2.5 min, 40 mg L-1, 93 min, 15 L (m(2) h)(-1). Health risk assessment of the effluent quality showed that the CEB byproducts from the combined Al/UF and PAC/UF process did not pose carcinogenic or non-carcinogenic health risks. Although the CEB byproducts from Ozone/UF were not a non-carcinogenic health risk, some carcinogenic risk is still evident. In order to ensure the safety and quality of drinking water, adjusting the operating parameters or adding other processes is needed to reduce the concentration of byproducts in the effluent.