Impact of Proposed Provincial Well Supply Treatment Guidance Changes on the Region of Waterloo’s Water Supply System

The Region of Waterloo (Region), Water Services Division, hired C3 Water Inc. (C3W) to carry out a system wide review of the level of disinfection achieved at their system supply wells. The scope of work included identifying the impact of the proposed provincial well supply treatment guidance changes on the Region’s well water supplies, given existing system conditions and treatment infrastructure. Both the Terms of Reference for the Assessment of Groundwater Systems Potentially Under the Influence of Surface Water (GUDI-TOR) and the Procedure for Disinfection of Water Supplies in the Province of Ontario (PFD) are currently in the process of being updated. It is anticipated that these documents will echo the Canadian Federal Government’s move from a minimum treatment level of 2-log virus inactivation to 4-log virus inactivation for well supplies. Of this total required 4-log virus inactivation for primary disinfection, at least 2-log virus inactivation much be achieved through chlorine disinfection.

C3W’s analysis included the following components;

  1. Existing Treatment Facility Definition
  2. Definition of Upgrade Alternatives
  3. Evaluation of Upgrade Alternatives

Where additional treatment was identified to be required, the preferred upgrade alternative was selected based on an analysis of lifecycle cost. Lifecycle cost analysis was carried out over a twenty-year time horizon and included upgrade capital costs as well as operational and maintenance (O&M) costs. Facility O&M costs were established by considering electricity costs, person hour costs, and material costs associated with each facility.

Other considerations for determining the optimal upgrade solution included;

  • Existing asset condition and remaining useful life.
  • Raw and treated water chemistry using AWWA’s Tetra Tech RTW Corrosion Model.

In all cases, existing facilities requiring an increase in the level of virus inactivation used UV light for primary disinfection under current configuration. Lifecycle analysis found that the most economical and effective upgrade solutions at these locations included;

  • Installation of chlorine contact chambers to increase contact time and thus virus inactivation credits.
  • The removal and decommissioning of UV disinfection system equipment and associated instruments.

This project evolved from a preliminary study, to conceptual, preliminary and detailed design completed through a separate project with the Region.

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