Pilot study on the removal of TOC, THMs, and HAAs in drinking water using ozone/UV–BAC

Abstract

The contaminated water is a main source of many waterborne diseases such as cholera, typhoid, etc. causing many serious public health crises, especially in developing countries with the low hygiene condition. In Vietnam, previous studies have reported that industrial and domestic waste cause adverted pollution on Saigon River that supplies water for 30% of 10 million residents in Ho Chi Minh City. Annual monitoring water quality data during 2006–2011 showed that concentration of ammonia and organic matter has been significantly increased and over the allowable limit (COD ##xgt; 10 mg/L). In order to reduce these pollutants in the finished water and for disinfection, a large dose of chlorine (about 3–6 mg/L) needs adding in the treatment process at Tan Hiep water treatment plant. A negative effect of using too much chlorine is the formation of disinfection by-products (DBPs) such as trihalo-methanes (THMs) and haloacetic acids (HAAs). The concentration of THMs in finished water of Tan Hiep plant ranged from 50 to 200 μg/L. In this study, a pilot-scale plant using Ozone/UV process combined with biological activated carbon filter (BAC) was studied on eliminating the organic matters and the DBPs formation in drinking water. With the feed water taken after sedimentation, the combination of Ozone/UV–BAC proved to be very effective in TOC, DOC, UV254, and SUVA removals with percentage reduction of 19.1, 17.6, 30.7, and 16.4%, respectively. The removal efficiency of the combined process was always higher than the sum of treatment efficiency of each process (Ozone/UV or BAC) alone. It was confirmed that the pretreatment of Ozone/UV could help to increase the organic removal of BAC filter. According to the organic reduction, the concentration of DBPs in water has decreased considerably with 70.6% (THMs) and 67.7% (HAAs) removal. DBPs formation potential decreased 39.3% (THMFP) and 46.1% (HAAFP).