Organic THMs precursors removal from surface water with low TOC and high alkalinity by enhanced coagulation Available to Purchase

NOM removal from surface waters is needed because of potentially carcinogen compound (trihalomethane, THM) formation due to reaction between NOM and free residual chlorine used for disinfection. The stringent limits for THMs (e.g., 30 μg/l in Italy) force conventional drinking water treatment plants to increase TOC removal efficiency by enhanced coagulation. This study was performed on 17 samples taken from a surface water resource with low TOC content (<3 mg/l) and high alkalinity (190 mg as CaCO₃/l) to remove TOC and other parameters (DOC, UV₂₅₄, SUVA, turbidity), typically used to characterize NOM content. Four different coagulants (Al₂(SO₄)₃·18H₂O, FeCl₃·6H₂O, FeSO₄·7H₂O and PACl) were used in jar test without adding polymer as flocculant. There was no correlation between DOC and SUVA in raw and treated water. TOC removal efficiencies (15–30%) required by the USEPA D/DBPs rule were obtained using 30–50 mg/l alum, 30–50 mg/l of FeCl₃, and less than 20 mg/l of PACl (as Al₂O₃, 10%). The use of PACl is suggested for both lesser TTHMFP and residual Al levels (<100 μg/l) occurrences without any pH adjustment.