Deborah Liew

Determination of halonitromethanes and haloacetamides: An evaluation of sample preservation and analyte stability in drinking water

Simultaneous quantitation of 6 halonitromethanes (HNMs) and 5 haloacetamides (HAAms) was achieved with a simplified liquid-liquid extraction (LLE) method, followed by gas chromatography-mass spectrometry. Stability tests showed that brominated tri-HNMs immediately degraded in the presence of ascorbic acid, sodium sulphite and sodium borohydride, and also reduced in samples treated with ammonium chloride, or with no preservation. Both ammonium chloride and ascorbic acid were suitable for the preservation of HAAms. Ammonium chloride was most suitable for preserving both HNMs and HAAms, although it is recommended that samples be analysed as soon as possible after collection. While groundwater samples exhibited a greater analytical bias compared to other waters, the good recoveries (>90%) of most analytes in tap water suggest that the method is very appropriate for determining these analytes in treated drinking waters. Application of the method to water from three drinking water treatment plants in Western Australia indicating N-DBP formation did occur, with increased detections after chlorination. The method is recommended for low-cost, rapid screening of both HNMs and HAAms in drinking water.

Formation and control of nitrogenous DBPs from Western Australian source waters: Investigating the impacts of high nitrogen and bromide concentrations

We studied the formation of four nitrogenous DBPs (N-DBPs) classes (haloacetonitriles, halonitromethanes, haloacetamides, and N-nitrosamines), as well as trihalomethanes and total organic halogen (TOX), after chlorination or chloramination of source waters. We also evaluated the relative and additive toxicity of N-DBPs and water treatment options for minimisation of N-DBPs. The formation of halonitromethanes, haloacetamides, and N-nitrosamines was higher after chloramination and positively correlated with dissolved organic nitrogen or total nitrogen. N-DBPs were major contributors to the toxicity of both chlorinated and chloraminated waters. The strong correlation between bromide concentration and the overall calculated DBP additive toxicity for both chlorinated and chloraminated source waters demonstrated that formation of brominated haloacetonitriles was the main contributor to toxicity. Ozone-biological activated carbon treatment was not effective in removing N-DBP precursors. The occurrence and formation of N-DBPs should be investigated on a case-by-case basis, especially where advanced water treatment processes are being considered to minimise their formation in drinking waters, and where chloramination is used for final disinfection.