Dissolved organic carbon and potential for disinfection byproducts in Kranji, Pandan and Tengah reservoirs in Singapore

Abstract

Fresh water from three western reservoirs of Singapore was assessed for the formation of trihalomethanes and the removal of precursors in a pilot-scale study. Raw water was processed through flocculation-sedimentation modules in a pilot plant with a capacity of 45 m3/day. Alum was the primary coagulant. Normal coagulation removed 10–60% of THM precursors. Kranji Reservoir, which has a watershed with thick vegetation, had relatively higher levels of dissolved organic matter with correspondingly higher potential for the formation of THM than Pandan Reservoir; Pandan is largely an urban catchment. Land-use pattern and proximity to seashore seem to influence THM formation. UV254 and SUVA were found to be better surrogates than DOC for THM. A benchmark criterion (UV254<0.08 cm−1) for on-line monitoring of THM was deduced from SDS-THM data and this criterion would vary slightly among the water works.