Full Description

The Greater Vancouver Water District (GVWD) supplies water to two million people in the Greater Vancouver area of British Columbia, Canada. Faced with water quality concerns that included the potential for waterborne disease, seasonal turbidity, bacterial regrowth and corrosive water, the GVWD, its consultants and a Technical Review Board (TRB) consisting of water quality and treatment specialists from across North America evaluated the use of ozone versus chlorine for primary disinfection without filtration. The superior inactivation of Giardia and Cryptosporidium using ozone, source water turbidity, total organic carbon levels (TOC), and chlorine demand were considered along with the increases to Assimilable Organic Carbon (AOC) and Biodegradable Dissolved Organic Carbon (BDOC) associated with ozone. Improvements to distribution system maintenance such as water main flushing and increased reservoir water turnover plus the addition of chlorine booster stations to assist in maintaining a chlorine residual were needed to control an already existing regrowth problem and were extremely important pre-requisites to ozonation. A Distribution System Water Quality Committee (DSWQC) consisting of water treatment, water supply and laboratory personnel was formed. This committee monitors the effectiveness of enhancements to the system and recommends changes in either treatment or flow strategies to maintain water quality. Chlorine residuals leaving all facilities can be increased or decreased or source water can be switched to respond to changes in water quality both in the source and in the distribution system. In this role the DSWQC uses a Geographic Information System (GIS)-based water quality data system which was specifically developed for this purpose. The user-friendly system geographically summarizes on-line and laboratory data collected over a 2000 square kilometer area. Since the GVWD Coquitlam ozonation facility became operational in the spring of 2000, dissolved oxygen and AOC levels in the distribution system have increased substantially. In spite of that, distribution system improvements and increased chlorine residuals have effectively controlled HPC and coliform levels to acceptable levels. A multi-disciplinary and multi-jurisdictional task team approach has been very effective in developing and implementing the mitigation strategies used. Includes 6 references, tables, figures.

Product Details

Edition: Vol. - No. Published: 01/01/2001 Number of Pages: 19File Size: 1 file , 700 KB