AWWA WQTC65847

The Greater Vancouver Regional District (GVRD) serves the Greater Vancouver, British Columbia area,delivering water to eighteen lower mainland municipalities, which in turn deliver water toapproximately 2.1 million people. Water is collected from three mountainous watersheds: Capilano,Coquitlam, and Seymour. The GVRD adopted its Drinking Water Management Plan (DWMP) inAugust 2005 and its strategy is to use a risk management multi-barrier approach from source to tap.The Coquitlam watershed is closed to the public, industry, and agriculture to minimize potentialcontamination of the source water. The Coquitlam source is currently using ozone for primarydisinfection and chlorine for secondary disinfection. The GVRD plans to install ultraviolet (UV) disinfection forCryptosporidium control downstream of the ozone treatment for Giardia and viruses. While theCoquitlam source water turbidity is low and filtration can be avoided in accordance with theGuidelines for Canadian Water Quality, there may be infrequent but likely events of high sourcewater turbidity. This study was undertaken to demonstrate the degree to which an elevated turbidityevent would diminish the effectiveness of the disinfection system. Specifically, the question askedwas whether elevated turbidity at the Coquitlam source could directly impair the effectiveness ofeither the UV disinfection of Cryptosporidium or the ozone disinfection of Giardia and viruses. Asecond concern was whether elevated turbidity might minimize the advantage gained when UV isapplied downstream of ozone.In this study, bulk water samples and concentrated suspended material were collected and used toquantify and characterize the microbiological and physical characteristics of Coquitlam sourcewater. Further efforts were directed toward re-suspending subsamples of the collectedconcentrated material into reactor volumes of the bulk water, and evaluating the efficacy of ozoneand UV at disinfecting natural or seeded microorganisms across a range of turbiditiesexperimentally prepared from native Coquitlam particles. Specifically, the study examined thedisinfection by ozone and UV of seeded coliphage MS2, Cryptosporidium oocysts and Giardiacysts. Finally, the study investigated the effect of ozone on UV absorbance to determine whether theoxidant would continue to improve the UV treatability of Coquitlam water under high turbidityconditions, to the degree it has been shown to do so at the lower turbidity levels generally present. Includes 17 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2007

Number of Pages:

19

File Size:

1 file , 390 KB