Understanding effects of water characteristics on natural organic matter treatability by PACl and a novel PACl-chitosan coagulants

In this study, we investigated the relationship between water characteristics and removal of natural organic matter (NOM) using polyaluminium chloride (PACl) and a newly developed coagulant obtained by hybridising PACl with chitosan (PACl-chitosan) for two different types of water. Using UV-visible spectroscopy analysis, we showed that PACl-chitosan is more effective than PACl for treating water samples that contain higher levels of activated polyhydroxyaromatic moieties. As a result, a lower level of total trihalomethanes formation potential (THMFP) was detected for synthetic water treated with PACl-chitosan coagulant compared to water treated with PACl only. In contrast, no difference was observed for the total THMFP that were formed following coagulation with either coagulant, for water sample containing the same level of organic carbon concentration, but lower levels of polyhydroxyaromatic moieties. Our work shows how the complex characteristics and interactions of organic matter with coagulant component can affect the outcome of the treatment process, and in this case, enhance the treatment. The use of PACl-chitosan was also shown to produce larger floc for both water samples; this again, can lead to better removal.