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The objective of this study was to evaluate the quality of raw and treated water from sixtreatment plants in Quebec whose water supply is affected by cyanobacterial blooms. High levels ofcyanobacteria were identified in raw water samples collected from all six plants from July toNovember 2001-2004. At least one cyanotoxin was detected in 43% of the samples, with up to 5.3g/L of microcystins and 2.3 g/L of anatoxin-a. Given the threat to human health posed by theingestion and inhalation of cyanotoxins and cyanobacteria, their levels in raw water demonstrate theneed for effective treatments to remove them. Samples from the six plants showed that, in general,treated water contained very low levels of cyanobacteria (around 200 cells/mL), and low turbiditylevels (0.5 NTU). Moreover, only 5% of the treated water samples had detectable concentrations ofcyanotoxins, with a maximum value of 0.1 g/L for microcystin-LR (10 to 15 times lower thanrecommended maximum available concentrations). While confirming the safety of the drinking waterproduced by the six treatment plants currently affected in Quebec, the study also showed that the plantsare vulnerable to the impacts of pollution, and pointed to the need to further protect and restore lakesand rivers that serve as drinking water sources. Includes 15 references, tables, figure.

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Edition: Vol. - No. Published: 11/01/2005 Number of Pages: 7File Size: 1 file , 220 KB