The role of aeration and pre-chlorination prior to coagulation-flocculation process in water treatment: A laboratory and field research in Indonesia

Surface water pollution affects the water treatment system. To meet the water quality standard, water treatment plants (WTP) often require more chemical and energy consumption to treat the low quality of raw water. Several water treatment plants in Indonesia have utilized aeration and pre-chlorination before coagulation-flocculation processes to reduce chemical and energy consumption and decrease water treatment costs. This study was conducted to get more understanding on the role of aeration and pre-chlorination in water treatment. The objective is to improve the performance of coagulation-flocculation processes and increase their efficiency in terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), turbidity, and ammonium removal. A comparison between laboratory and field research was carried out in this study. Overall, aeration and pre-chlorination processes have been proven effective in increasing pollutant removal. Higher concentrations of dissolved oxygen (DO) and chlorine injections significantly enhance the chemical oxidation of organic matter and the removal of volatile organic compounds. Furthermore, the effect of water turbulence during aeration induced better mixing of coagulants favorable for solid-liquid separation. After applying aeration and pre-chlorination processes, a ∼60% reduction in coagulant dosage was confirmed in laboratory and field research. In addition, more than 24% of ammonium was removed in the water treatment plant (WTP) that applied both in aeration and pre-chlorination processes.