Enhanced coagulation can remove dissolved organic carbon (DOC) that acts as a precursor to disinfection byproducts (DBPs). However, previous studies have not elucidated the effect of certain coagulation and settling parameters, such as the fast-mixing rate and settling time, on haloacetic acids (HAAs) and trihalomethanes (THMs). Furthermore, coagulant dosage, fast mixing power, and settling time play essential roles in the cost-efficiency of operation and construction of a water treatment plant. This study aims to present a novel investigation of the effects associated with the operational factors of coagulation-flocculation and sedimentation to achieve feasible solutions for management of DBPs. The simultaneous effects of pH (4.5–8.5), coagulant type (Fe3+/Fe3+ + Al3+ ratio), coagulant dosage, fast-mixing rate, and settling time were examined using a response surface methodology design. Accordingly, predictive models were generated by conducting 2 sets of experiments, which comprised 50 runs of jar tests that were performed in triplicate of 2 blocks for 2 natural drinking water sources in Newfoundland, Canada. The results were validated on four natural waters and two synthetic water samples. The multivariate optimization on THM4 and HAA5 resulted in a significant reduction in the fast-mixing energy by 59.9%, and a reduction of 23.4–41.1% in coagulant dosage. The results of natural organic matter fractionation on water samples revealed that the optimized coagulant dosage of 3.83–5.95 mg/mg DOC could remove up to 91.00%, 72.64%, and 70.79% of THM4, HAA5, and DOC, respectively, in natural water samples with a very hydrophobic acid (VHA) fraction of 0.67–0.81 VHA/DOC.
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