Disinfection By-product (DBP) Formation and Minimisation in Southeast Queensland Drinking Water

Abstract

Chemical by-products arising from water disinfection may be harmful to human health. Although there are potentially innumerable individual chemical species arising from the water disinfection process, the risk to human health is considered small when compared to the risks associated with drinking water which has not been treated for pathogen removal. The purpose of this study was to assess the prevalence of the four regulated trihalomethanes, as well as the potently carcinogenic nitrosamine, N-nitrosodimethylamine (NDMA) (whose regulation has been proposed by the NHMRC in the draft 2010 Australian Drinking Water Guidelines) in South East Queensland (SEQ) drinking water supplies.

Toward this objective, NDMA and trihalomethane (THM) formation potential experiments were undertaken using source waters from a number of SEQ water treatment plants (WTPs), as well as directly from the Logan River, Teviot Brook and Mary River. The relationship between water parameters such as dissolved organic carbon (DOC) and dissolved organic nitrogen (DON), disinfection method, and the final concentration of particular disinfection by-products (DBPs) in the finished water were examined, with a number of general trends becoming apparent. NDMA formation potentials were consistently quite low (5 – 21 ng/L) from chloramination of raw waters, and not detected (< 5 ng/L) in chlorinated waters. NDMA was not detected in any SEQ finished waters (< 5 ng/L).THM formation potentials were consistently below the Australian Drinking Water Guideline of 250 µg/L, however levels were higher for chlorinated waters than for chloraminated waters.