What is the acceptable single-sample maximum concentration of E. coli per 100 mL in Canadian recreational water guidelines?

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What is the acceptable single-sample maximum concentration of E. coli per 100 mL in Canadian recreational water guidelines?

Canadian recreational water guidelines use two thresholds for E. coli: a single-sample maximum and a geometric mean over multiple samples. The single-sample maximum is 400 E. coli per 100 mL, meaning a single test result up to 400 is considered acceptable, while exceeding 400 would trigger advisories or actions. The geometric mean over several samples is 200 E. coli per 100 mL, which helps assess overall water quality over time rather than a single test spike. So the value 400 CFU/100 mL is the correct single-sample maximum. The figure 200 corresponds to the geometric mean, not the single-sample limit, and 50 or 1000 are outside the guideline ranges.

Canadian recreational water guidelines use two thresholds for E. coli: a single-sample maximum and a geometric mean over multiple samples. The single-sample maximum is 400 E. coli per 100 mL, meaning a single test result up to 400 is considered acceptable, while exceeding 400 would trigger advisories or actions. The geometric mean over several samples is 200 E. coli per 100 mL, which helps assess overall water quality over time rather than a single test spike.

So the value 400 CFU/100 mL is the correct single-sample maximum. The figure 200 corresponds to the geometric mean, not the single-sample limit, and 50 or 1000 are outside the guideline ranges.

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