Comparison of coagulant type on natural organic matter removal using equimolar concentrations

Research has shown that in drinking water sources there is a portion of the natural organic matter (NOM) that is recalcitrant to coagulation, regardless of the treatment conditions applied. Advances in inorganic coagulants have resulted in the emergence of many pre-polymerized formulations which may demonstrate improved coagulation performance. The aim of this study was to determine the effects of several coagulant types on dissolved organic carbon (DOC) removal where the molar concentrations of the metal ions were comparable. In the second stage, this work also investigated selected coagulants to determine whether improvements in coagulation conditions or alternative coagulants will be sufficient to remove problematic components in the organic matter responsible for disinfection demand and disinfection by-product (DBP) formation in a high DOC water source. When compared at equimolar concentrations, advanced coagulants were found to perform equally for DOC removal as traditional inorganic coagulants. While they did not necessarily target or improve removal of recalcitrant NOM and DBP precursors, they successfully demonstrated broader conditions at which coagulation was effective, reducing the reliance on precise optimization strategies. Coagulation remains a well developed and cost effective means of water treatment, with continuing relevance into the foreseeable future.Rolando Fabris, Christopher W. K. Chow and Mary Drika