Influences of multi influent matrices on the retention of PPCPs by nanofiltration membranes

Abstract

Nanofiltration (NF) has great potential in removing trace organic micropollutants in wastewater, especially pharmaceuticals and personal care products (PPCPs). However, little information is available on PPCPs rejections under complex feed water matrices, which better represent real wastewater treatment conditions. In this paper, the PPCPs rejection behaviors and the dominating mechanisms by NF membranes were studied under multi mixed influent matrices which contained various inorganic ions, humic acids and sodium alginate. The results showed that the DF30 membrane had the highest rejection of negatively charged indomethacin (95.4%) and diclofenac sodium (94.1%) in pure water. Our study also showed that electrostatic effect and steric hindrance were the primary rejection mechanisms of PPCPs by DF30 membrane in pure water. The predominant fouling of DF30 membrane could be explained by the complete blocking model in the filtration of mixed influent matrices containing both inorganic ions and organic matters. The components in membrane bioreactor (MBR) effluent was beneficial to retention of positively and neutrally charged PPCPs, but had no significant effects on retention of negatively charged PPCPs. Risk quotients of the six target PPCPs in NF effluent were all lower than 0.1, likely indicating low risk to aquatic organisms. This work has potential implications for a deeper understanding of PPCPs rejections by NF in wastewater treatment.