Advanced treatment processes are often required to address disinfection by-product (DBP) issues in drinking water supply. This paper presents results from our recent pilot plant investigation using the ozone and biological activated carbon (Ozone/BAC) process. This process is known for its wide range of treatment benefits including destruction of organic contaminants such as taste and odour compounds, algal toxins, pesticides and herbicides. However, it has been reported to be less effective in removing DBP precursors responsible for the formation of DBPs such as trihalomethanes. The main objective of this work was to conduct a systematic pilot-scale study to assess the efficacy of this process in reducing DBP precursors from one of the most challenging raw water sources in Australia.

The raw water contains typically 10 - 30 mg/L total organic carbon. In addition to the high levels of the organic carbon, the treatment process is further complicated by moderate levels of soluble manganese and sporadic taste and odour events. The pilot plant was operated in the intermediate ozonation mode, with its feed water drawn from the settled water of the full-scale treatment plant operating in the enhanced coagulation mode. The paper will discuss the impact of key process parameters such as the ozone dose, contact time and filter empty bed contact time on the DBP precursor removal efficiency and degree of DBP reduction. Practical implications for the selection of upgrade options for the full-scale plant in addressing DBP water quality issues will be highlighted.