Formation of Trihalomethanes in Water Distribution Systems and their Removal

Abstract

Disinfection by-products, specifically Trihalomethanes (THMs), are a common problem in Manitoba which uses mainly surface water as the source of drinking water. They are formed when disinfectants, such as chlorine, used to control microbial contaminants, react with organic content, which Manitoba`s surface water is rich in. THMs include four chemicals: Chloroform (CCl3), Bromodichloromethane (CCl2Br), Dibromochloromethane (CClBr2) and Bromoform (CBr3) (Oram, n.d.). Due to their dangerous health risks, such as cancer, the concentration of THMs in the water is regulated, and the guideline in Canada is of 100 µg/L (Health Canada, 2016). However, THM levels in Manitoba, especially along the distribution system, are extremely high and exceed the limit. Water treatment plants should minimize the levels of all disinfection by-products without reducing the effectiveness of the disinfection. There are many methods to combat the proliferation of THMs, such as reducing chlorination before filtering the water and reducing the precursors (organic material that reacts with chlorine and form THMs) in general. However, they only reduce the probability of THMs’ formation at the water treatment plant and are not being used in Manitoba. Therefore, this project presents aeration as a simple and effective post-treatment process to completely or almost completely remove THMs and meet the guidelines.