OCWA performs routine algae observation and monitoring of Lake Ontario as it relates to drinking water supply. Untreated (raw) lake samples are collected as the water enters the Raw Water Pumping Station and are analyzed under a microscope in our laboratory at the Lake Ontario Water Treatment Plant. If algae is detected in a sample, it is identified by species and its apparent quantity is recorded. This information allows OCWA to track the relative progression of algae in the Lake Ontario supply. The laboratory also performs microscopic analysis of the treated (finished) water leaving the plant.
Cyanobacteria (Blue-green algae) can release a chemical called Microcystin, a cyanotoxin. OCWA utilizes a testing kit manufactured by Abraxis to measure low levels of Microcystin, in both its raw and finished water. The test method utilized can measure levels between 0 and 5 parts per billion (ppb) of Microcystin.
(Lake Ontario September 2015)
Should Microcystin be identified in the Lake Ontario water supply, OCWA has multiple barriers of treatment that can mitigate or remove these toxins. The principal barrier is the coagulation/filtration process via OCWA’s six dual media filters. Each filter is comprised of granular activated carbon (GAC) over a fine sand layer. The GAC can adsorb low levels of the cyanotoxins and help prevent them from entering the treated water. The high level of adsorption capacity combined with very high specific surface area allows the GAC to more readily adsorb contaminants. OCWA employs two chemical treatments which are effective at destroying Microcystin. Potassium permanganate is applied to source (raw) water at the Raw Water Pumping Station and chlorine is applied in both source (pre filtration) and treated (post filtration) water. Both chemical treatments in conjunction with the treatment/filtration process are effective in Microcystin control.
It is worth noting that to-date, OCWA has not detected Microcystin in any of its water samples.