MICROBIOLOGICAL SAMPLING & TESTING

Microbiological sampling and testing

O.Reg 170/03, Schedule 10 provides the requirements for sampling and testing of microbiological parameters.

The schedule states that for large municipal systems serving a population of more than 100,000 people, the required monthly frequency of sampling is 100 distribution samples, plus one additional sample for every 10,000 people served, with at least three samples being taken in each week.

Each of these samples are to be tested for Escherichia coli and total coliform, with a requirement that at least 25 per cent of the samples be tested for general bacteria population, expressed as colony counts on a heterotrophic plate count. Windsor's required sampling frequency is 130 samples monthly.

In 2019, 1,852 samples were collected and analyzed, an average of 154 samples per month. Approximately 52% of the distribution samples were also analyzed for heterotrophic plate count. In addition, each sample was tested for free chlorine residual at the time the sample was taken.

Schedule 10 states that a treated water sample must be taken at least once per week and tested for Escherichia coli, total coliform and general bacteria population, expressed as colony counts on a heterotrophic plate count. Windsor's treated water samples were generally collected on a daily basis and were tested by an accredited third-party laboratory.

The schedule further states that a raw water sample must be taken at least once per week, before any treatment is applied to the water, and that the sample be tested for Escherichia Coli and total coliform. Samples were collected and tested on average five days per week. Chart 5 (above) indicates the number of samples taken on a monthly basis.