Rejection of pharmaceutically active and endocrine disrupting compounds by nanofiltration as a function of source water humic substances

• Presence of HSs caused increased rejection of neutral PhAC/EDCs.
• Impact of HS–cation interaction was more prominent in the HS-dominated River water.
• Increased rejection was not linearly related to higher HS concentrations in source waters.
• Additional HS beyond a certain level had no addition effect on PhAC/EDC rejection.

The impact of source water humic substances (HS) on the rejection of selected pharmaceutically active compounds (PhACs) and endocrine disrupting compounds (EDCs) via nanofiltration was investigated using two source waters with significantly different HS concentrations (Lake Ontario and Otonabee River, Ontario, Canada). To remove the effects of colloidal particles, raw waters were pre-treated with ultrafiltration, which removed most (up to 93%) of the colloidal and suspended particles but allowed passage of indigenous HSs. The effect of cation concentrations was examined by spiking beyond ambient levels in UF-pretreated Otonabee River water. There were no significant differences in rejection of the ionic PhAC/EDCs from the raw and UF-pretreated water matrices examined. Rejection of neutral compounds in colloid-free natural waters increased in the presence of HSs. The negative impact of cations on rejection was more prominent in the HS-dominated River water when compared to the Lake water. Increased compound rejection was not linearly related to higher concentrations of humic substances in the source waters. The rejection of neutral compounds increased due to the presence of humic substances up to a certain concentration, above which additional HS had no additional effect on PhAC/EDCs removal via nanofiltration.