RELATIONSHIPS BETWEEN DISSOLVED ORGANIC NITROGEN (DON) AND BIODEGRADABLE DISSOLVED ORGANIC NITROGEN (BDON) TO HALOACETONITRILE FORMATION POTENTIALIN WATER TREATMENT PLANTS

Abstract

Nitrogenous disinfection by-products (N-DBPs) have become an issue of concern in water treatment plant (WTP) since they have more toxicity more than carbonaceous disinfection by-products (C-DBPs) such as trihalomethanes. Dissolved organic nitrogen (DON) in natural water source is known as precursors of nitrogenous disinfection by-products (N-DBPs). This study investigated the fate of total dissolved nitrogen (TDN), dissolved inorganic nitrogen, DON, and biodegradable DON (BDON) along the water treatment trains of Khon Kaen Municipality (Kota WTP (KWTP) and Tapra WTP (TWTP), and Khon Kaen University (KKU Water Treatment plant (KKUWTP)). Occurrence and formation potential of four haloacetonitriles (HANs) including monochloroacetonitrile (MCAN), dichloroacetonitrile (DCAN), trichloroacetonitrile (TCAN), and dibromoacetonitrile (DBAN) were determined. In addition, the effect of ozonation on HAN formation potential (HANFP) was studied. The result shows that DON concentrations of KWTP, TWTP, and KKUWTP ranged from 0.44 to 0.66 mg-N/L. DON at this level was not effectively removed by conventional water treatment plants. BDON accounted for approximately 50% of DON pool and contributed to HANFP formation based on the formation potential test of three water treatment plants (R2 of 0.34-0.74). Ozonation increased the BDON and HANFP of water samples. Total HANs concentration in finished waters ranged between 4 to 15 µg/L. Among HANs being measured, DCAN was the most abundant HAN species contributing more than 50% in samples. The finding of this research reveals that BDON was an important organic fraction to the HAN formation. Removal of BDON would also reduce the HAN concentrations. Water utilities might find this information useful for controlling N-BDPs in drinking water.