AWWA JAW34914

The Greater Vancouver Regional District commissioned an 18-month planning and predesign study to define the components in a comprehensive water quality improvement plan for its 2,500-ML/d (660-mgd) system. The study included three primary tasks: predesign of disinfection and corrosion control facilities; a 12-month pilot testing program using parallel pilot plants at the Seymour and Capilano water supply reservoirs; and planning for future filtration plants. The results of the study identified chlorine, ammonia, sulfur dioxide, soda ash, and carbon dioxide in a two-stage treatment approach as the recommended disinfection and corrosion control scheme for the low-pH, low-alkalinity water supplies. The pilot-plant studies confirmed that direct filtration using deep-bed monomedium filters operating at a loading rate of 22.5 m/h provided excellent treatment performance and productivity over a wide range of raw-water quality. Ozonation was studied extensively and found not to be beneficial in the overall treatment performance. A major conclusion of the study was that the district could achieve significant cost benefit from a combined 1,900-ML/d (500-mgd) filtration facility for both the Seymour and Capilano supplies even though a 6.7-km rock tunnel would have to be constructed to facilitate this concept. The phased improvement plan for the disinfection, corrosion control, and filtration facilities has an estimated capital cost of about Can $459 million. Includes 3 references, tables, figures.