The Greater Vancouver (B.C.) Water District compared chlorine and chloramine as secondary disinfectants and their effects on bacterial regrowth in a distribution system supplied with disinfected, unfiltered surface water. The selected section of the distribution system was divided into three areas: a control area that received no secondary disinfectant, an area that received free chlorine as the secondary disinfectant, and an area that received chloramine. Water samples were analyzed for chlorine residual, coliform bacteria, heterotrophic plate count (HPC) bacteria, and turbidity. Although both chlorine and chloramine were effective in reducing bacterial growth in the distribution system, chloraminated water had a lower HPC, less taste and odor, fewer positive coliforms, and a more stable residual.

A 12-month pilot plant study was conducted to evaluate a number of corrosion control treatments to reduce metal leaching from typical household plumbing materials. A pipe loop system was used to test six treatment options, with a control loop of the characteristically soft, acidic, Greater Vancouver Water District (GVWD) water. Four pH- alkalinity combinations and two concentrations of zinc orthophosphate (0.37 mg/L and 1.0 mg/L as Zn) were studied. at regular intervals, the flowing, treated, and control waters were allowed to stagnate in the pipe loop system for 8- and 16-h periods. Following the designated standing time, water samples taken from the lead/tin solder jointed, soft copper plumbing coils, the submerged, free standing coils of 50/50 lead/tin solder, and the brass faucets, were measured for lead, copper, and zinc levels. Overall, when compared to the control loop, the pH-alkalinity treatments appeared to exacerbate metal leaching in standing samples. The zinc orthophosphate treated loops were both effective at reducing lead and copper leaching to below control levels. In general, the two standing times showed little difference in the levels of leached metals. The exception to this occurred in the higher dose zinc orthophosphate loop, which had higher copper and zinc levels at the longer standing time. Key words: copper, corrosion, drinking water, lead, zinc orthophosphate.

This study was initiated to evaluate, in Greater Vancouver Water District water, the effectiveness of zinc orthophosphate, type N sodium silicate, and a commercial blend of the two as corrosion inhibitors within the limitations that a seven-loop pilot plant would allow. In all but the raw water control loop, pH and alkalinity were adjusted, and the water was disinfected with 2.5 mg/L of chloramine (NH 2 Cl). Copper and cast iron corrosion rates were measured over the course of 12 months on pipe inserts removed at 3-month intervals and via weekly monitoring using an electrical resistance measuring device. Standing water samples taken regularly from lead/tin solder jointed, soft copper plumbing coils, from submerged free standing coils of 50/50 lead/tin solder, and from faucets on each loop were measured for lead, zinc, and copper levels. The results of the weight loss determinations from the pipe inserts indicated that all of the inhibitors, particularly the zinc orthophosphate, worked very favorably with copper, but they offered no additional benefit over that obtained from the pH and alkalinity adjustments alone, in the case of the cast iron coupons. However, some very high metal levels were measured in the standing water samples from some of the inhibitor loops. Generally, both the coupon and leaching results confirmed that pH and alkalinity adjustment and disinfection with chloramine, instead of chlorine, will reduce pipe metal corrosion.Résumé : Cette étude a été entreprise afin d'évaluer, dans l'eau du Greater Vancouver Water District, l'efficacité de l'othophosphate de zinc, du silicate de sodium de type N et d'un mélange commercial des deux produits comme agents anticorrosifs dans les limites qu'un système pilote ayant sept boucles pourra permettre. Dans toutes les boucles, à l'exception de la boucle de contrôle contenant de l'eau brute, le pH et l'alcalinité ont été ajustés, et l'eau a été désinfectée avec 2,5 mg/L de chloramine (NH 2 Cl). Les taux de corrosion du cuivre et du fer fondu ont été mesurés pendant 12 mois sur des pièces de conduites, enlevées à des intervalles de trois mois, et aussi en utilisant un instrument qui mesure la résistance électrique des conduites. Des échantillons d'eau stagnante récoltés des soudures articulées de plomb/étain, de rouleaux de cuivre tendre de plombage, de rouleaux submergés de soudure 50/50 plomb/étain, et des robinets utilisés dans chaque boucle ont été régulièrement analysés pour le niveau de plomb, zinc et cuivre. Les résultats de perte de masse des pièces de conduites indiquent que tous les agents anticorrosifs, en particulier l'orthophosphate de zinc, ont agit favorablement avec le cuivre, mais n'ont fourni aucun effet bénéfique additionnel à celui obtenu uniquement de l'ajustement du pH et de l'alcalinité pour le cas du fer fondu. Cependant, quelques niveaux très élevés de métal ont été mesurés dans des échantillons d'eau stagnante obtenus des boucles contenant des agents anticorrosifs. Généralement, les résultats ont confirmé que l'ajustement du pH et de l...

Pilot‐testing was undertaken by the Greater Vancouver (B.C.) Water District to determine the feasibility of using direct filtration for treating turbid water. Because episodes of natural high turbidity tended to be of short duration, turbidity spiking was included in the investigation. Results showed that turbid water could be treated successfully with direct filtration when a deep‐bed monomedium filter was used; a shallower dual‐media filter was not acceptable. Even with a high‐turbidity raw water, turbidity and production goals were met. Determining the appropriate dosage of filter aid was a key factor in meeting the performance goals.

The Greater Vancouver Regional District (GVRD) supplies water to 1.9 million people from three coastal mountain watersheds. Water quality concerns identified include waterborne disease risks associated with Giardia and Cryptosporidium, episodes of elevated turbidity, bacterial regrowth in the distribution system, and corrosive water. To address these concerns, the GVRD has initiated a $300 million capital program to upgrade its treatment capabilities that includes two 1200 ML·d–1 ozone and corrosion control facilities, a 1000 ML·d–1 filtration plant, and an ongoing program of rechlorination stations and distribution system improvements. This paper provides an overview of the GVRD's drinking water treatment program and related initiatives. These include the decision-making process related to using ozone without filtration, the process selection and selected project delivery method for the Seymour filtration plant, and, lastly, the ongoing secondary disinfection program which includes unidirectional flushing, reservoir exercising, environmental management, and remote data monitoring and data evaluation using a geographical information system application.Key words: water quality, protozoa, ozone, direct filtration, rechlorination, remote monitoring, GIS.