Removal of trihalomethane (THM) precursors from water during coagulation enhanced by ozonation

The aim of the study was to evaluate the effectiveness of the reduction of surface water pollution level in the coagulation process with polyaluminum chloride and coagulation supported by ozonation process. The effectiveness of these processes was evaluated in relation to the decrease in turbidity and color of water, the content of organic compounds (determined by total organic carbon (TOC) and dissolved organic carbon, oxidizability (OXI), ultraviolet absorbance) and the potential for the formation of THM-FP trihalomethanes. The use of pre-ozonation and coagulation with polyaluminum chloride allowed for a reduction in the content of organic matter determined by TOC, OXI, absorbance UV by 28%-38%, 39%-54%, and 48%-73%, respectively. Compared to the effects obtained using only the coagulation process, this was an increase of 4%-8%, 6%-12%, and 10%-18%, for TOC, OXI, and absorbance UV, respectively. The effectiveness of water purification depended on the quality of raw water, month and location of water collection. The potential for THM formation in treated water in the coagulation process was by 50%-56% lower than in untreated surface water after chlorination. The application of additional pre-ozonation resulted in an additional reduction of THM-FP by 1%-10%.