Identifying the rejection mechanism for nanofiltration membranes fouled by humic acid and calcium ions exemplified by acetaminophen, sulfamethoxazole, and triclosan

► Humic acid tended to deposit on the membrane surface and led to cake-layer formation. ► Hindrance layer from foulants increased the rejection of neutral-charged compound. ► Concentration polarization from humic acid/Ca2+ decreased larger compounds rejection. ► The SHP model correlated well for the membrane dominated by size exclusion. ► Electrostatic repulsion could be introduced to correct charged compounds rejection.