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Assessing the impact of corrosion control and increased dissolved oxygen levels on GVRD member municipality distribution and premise plumbing systems Knox, Gillian Frances

Abstract

A study of the water quality, of water distributed within the Greater Vancouver Regional District (GVRD) was carried out. The effectiveness of previously implemented corrosion control plans on the amount of observed metal concentration at the tap, in the warmest and coldest months of the year was evaluated. The effect of different primary disinfectants at the Seymour and Coquitlam water source was also investigated. The GVRD was divided into four distribution areas, to isolate the effects of water coming from Capilano, Seymour and Coquitlam watersheds, and the Newton Reservoir, on the observed metal concentrations at the tap. The Capilano water has no corrosion control treatment. Seymour, Coquitlam and Newton waters are treated with soda ash, targeting a pH of 6.8, 6.9 and 8.1 resulting in alkalinity levels of 8.2, 6.8, and 20.0 mg/L as CaCC>3, respectively. Standing cold water, and running hot and cold water samples were collected during two samplings sessions from houses within the GVRD study area. Samples were analyzed at the UBC laboratory for their lead, copper and zinc concentrations and the averages compared. The amount of lead coming out at the taps does not appear to be influenced by the source water treatment. Copper appeared to be influenced by the source water treatment, with the highest concentrations found in the water with the lowest pH (Capilano) and the lowest concentrations in the water with the highest pH (Newton). The source water treatment influenced the concentration of zinc in the samples. Samples collected in the Newton distribution area had significantly lower zinc levels than samples collected in the Capilano, Coquitlam and Seymour distribution areas. Samples collected during the warmest month of the year had similar metal levels as samples collected during the coldest months of the year. This suggests that the temperature fluctuations of the water in the GVRD, as a result of changing seasons, don't affect the metal concentrations in the water. The use of ozone, which can increase the dissolved oxygen concentration of the water, as opposed to chlorine as a primary disinfectant, didn't appear to affect the amount of lead, copper or zinc in the samples collected at the tap.

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