Combined sewer overflows (CSO) may contain pathogenic microorganisms that can cause waterborne diseases through contamination of drinking water supplies and through direct contact in areas of high public access such as recreational waters. The Canada-wide Strategy for the Management of Municipal Wastewater Effluent, endorsed by the Canadian Council of Ministers of the Environment, calls for reducing the human and environmental risks associated with combined and sanitary sewer overflows. An NSERC Collaborative Research and Development Grant was recently awarded to a consortium of researchers from universities, government, and private industry to develop a new treatment process for CSO disinfection, ultimately improving the health of Canadians by protecting our water resources against the threat of pathogenic contamination.

The project aims to develop a process based on ultrasound and ultraviolet technologies. Unlike chemical disinfection by chlorine, which increases the risk of toxicity in the receiving waters due to release of chlorinated by-products, ultraviolet disinfection can achieve a high rate of bacterial inactivation without negative impacts on aquatic life. However, the effectiveness of ultraviolet disinfection is adversely affected by suspended particles (flocs). Flocs can shield pathogens and increase the ultraviolet dose required to achieve disinfection targets. Pretreating CSO with ultrasound will break up flocs and thereby reduce the ultraviolet dose demand. This collaborative project will be the first to assess the efficacy of combined ultrasound and ultraviolet technologies for treating CSO.

Contacts: Ian Droppo 905-336-4701, Ian.Droppo@ec.gc.ca; Peter Seto 905-336-6438, Peter.Seto@ec.gc.ca