First off, we do not have a problem on Chandos with blue-green algal blooms. However, some lakes in the Muskokas, Haliburton and the Kawarthas have experienced these toxic blue-green blooms. And what with global warming, more lakes will soon do so as well. A clear and present danger from any surface water drinking source is the potential for exposure to microcystins. These are associated with blue-green algal blooms.
Under the right environmental conditions, microcystins and other cyanobacterial toxins are naturally formed in water. They are produced and stored in the cells of cyanobacteria, and released when the cells rupture or die. Most scientific studies on cyanobacterial toxins focus on microcystins, which are generally regarded as the most important of the freshwater cyanotoxins. Options available for individual households obtaining their drinking water from a surface water source affected by a cyanobacterial bloom would include switching to an alternative water supply, changing the location of the water intake pipe and installing a drinking water treatment system. However, the treatment of water supplies for the removal of cyanobacteria and microcystins at the residential scale is complex, and there are no drinking water treatment systems available that are certified for the removal of microcystins. Please be aware that boiling does not remove these toxins. See the Ontario fact sheet on this topic: Ontario fact sheet blue-green algae And if you really want to know more, here is an excellent source from the Government of Canada: cyanobacteria in drinking water.