Earth Tech study helps find better drinking water treatments

Ray Bilevicius, P.Eng. of Earth Tech’s Winnipeg office presented a study at the Canadian Drinking Water Conference in Halifax last month that could have far-reaching ramifications for the future of water treatment plants. Many municipalities are planning to revamp their water treatment plants in an effort to keep up with new government requirements made in the wake of the Walkerton and North Battleford water supply outbreaks. They often want to investigate new treatment technologies to avoid using large amounts of chlorine disinfectant. A traditional disinfectant, chlorine is effective in microbial inactivation but produces THMs as byproducts which have been linked to cancer at prolonged exposure and dangers to pregnant women when consumed in large amounts.

Done for Health Canada and the Federal-Provincial-Territorial Subcommittee on Drinking Water, the Earth Tech study modelled different water treatment methods and processes to compare their ability to control disinfection byproducts. It compared their actual amount of trihalomethanes (THMs) with THMs produced with a model using alternative enhancement treatments. The consulting engineers also compared the capital and operating costs of different potential systems. Doug Peterson, P.Eng. was the primary author.

The alternative treatments studied included ozone, ultraviolet light, chloramines, membrane filtration and granular activated carbon. They found that as the levels of THMs come down, the capital and operating costs of the plant go up. They also concluded that ultra-violet disinfection should be given serious consideration as a primary disinfectant, and chloramines as a secondary disinfectant.