Cyanobacteria in Québec’s Water Supplies: is Drinking Water Affected?

摘要

The objective of the present study was to evaluate the quality of raw and treated water from sixrntreatment plants in Québec whose water supply is affected cyanobacterial blooms. High levels ofrncyanobacteria were identified in raw water samples collected from all six plants from July tornNovember 2001-2004. At least one cyanotoxin was detected in 43% of the samples, with up to 5.3rnμg/L of microcystins and 2.3 μg/L of anatoxin-a. Given the threat to human health posed by therningestion and inhalation of cyanotoxins and cyanobacteria, their levels in raw water demonstrate thernneed for effective treatments to remove them. Samples from the six plants showed that, in general,rntreated water contained very low levels of cyanobacteria (around 200 cells/mL), and low turbidityrnlevels (<0.5 NTU). Moreover, only 5% of the treated water samples had detectable concentrations ofrncyanotoxins, with a maximum value of 0.1 μg/L for microcystin-LR (10 to 15 times lower thanrnrecommended maximum available concentrations). While confirming the safety of the drinking waterrnproduced by the six treatment plants currently affected in Québec, the study also showed that the plantsrnare vulnerable to the impacts of pollution, and pointed to the need to further protect and restore lakesrnand rivers that serve as drinking water sources.