Trophic state, natural organic matter content, and disinfection by-product formation potential of six drinking water reservoirs in the Pearl River Delta, China

This study examined spatial and seasonal variation of nutrients, algal biomass, and natural organic matter (NOM) in six subtropical drinking water reservoirs in the Pearl River Delta region, China, during the period from 2004 to 2006. We also tested the formation of trihalomethanes (THMs) and haloacetic acids (HAAs) as disinfection by-products (DBPs) via chlorination of the water samples from these reservoirs. This study showed that these reservoirs were mesotrophic with the average chlorophyll a (Chl a) levels ranging from 2.31 to 7.79 μg l^-1. The average dissolved organic carbon (DOC) in the six reservoirs was 2.70 mg l^-1, and the degree of aromaticity of NOM indicated by UV₂₅₄ (absorbance at 254 nm) was 0.048 cm^-1. Total phosphorous (TP) was significantly correlated with chlorophyll a, as well as DOC and UV₂₅₄. It suggested that the major component of NOM, with a specific UV₂₅₄ value (SUV₂₅₄) of 1.78 l mg^-1 m^-1, was algal-derived organic matter. Existing models from other studies could be used to predict THM yield from NOM level in the present study, but the relationship between HAAs and NOM suggested that aromatic portion of the NOM in the investigated reservoirs had a greater potential to produce HAAs.