Application of enhanced coagulation in drinking water treatment from the degraded catchment to reduce NOM: a major DBP precursor

ABSTRACT The occurrence of dissolved natural organic matter (NOM) in drinking water sources can potentially lead to the formation of disinfection byproducts (DBPs). In regions like the degraded soil of the Ethiopian highlands, which have low humic content, hydrophilic NOM tends to dominate. This study aimed to assess the effectiveness of enhanced coagulation in reducing precursors of DBPs in surface water used for drinking purposes. The Angereb reservoir, part of Gonder City's water supply in the Ethiopian highlands, was chosen as the study area. Jar testing was conducted to evaluate the NOM removal efficiency of enhanced coagulation methods using ferric chloride and aluminum sulfate coagulants. Water samples were collected during both dry and wet seasons in 2023. Various parameters, such as total organic carbon (TOC), ultraviolet absorbance at a wavelength of 254 nm (UVA@254), pH, and other water quality indicators, were analyzed. Results revealed that the NOM present was primarily hydrophilic, as anticipated, with specific ultraviolet absorbance values below 2 L/mg−1 m−1. The existing treatment process, which involved prechlorination and coagulation with aluminum sulfate, removed less than 28% of TOC and 14% of UVA@254. However, using ferric chloride-enhanced coagulation achieved a removal efficiency of 50% for both TOC and UVA@254.