2021 Water Quality Model Calibration | City of Markham, ON, Canada

The City of Markham’s water distribution system is supplied through the Region of York transmission network with water derived from the City of Toronto and the Region of Peel. Accordingly, the City does not engage in treatment or disinfection operations as raw source water from Lake Ontario is treated by the supplying utilities prior to reaching the City’s system. Moreover, it is understood that the City of Toronto and Peel Region (as well as York Region, where necessary) typically use chloramination for secondary disinfection as it is less volatile (more stable) than chlorination alone, therefore maintaining a long-lasting disinfectant residual. This is particularly important in distribution systems, such as the York Region-Markham system, which may be subject to high water age from long residence times and potentially low turnover via processing through numerous storage facilities.

To protect consumers from microbiological risk, the City monitors a wide range of water quality parameters (e.g., chlorine residuals, temperature, nitrates, pH, etc.) to comply with governing regulations, namely, Ontario Regulation 170/03.1 More specifically, the City of Markham, jointly with York Region, maintains and operates (i) 107 water quality sampling stations; (ii) a total of 8 continuous chlorine analyzers (2 in pumping stations, 3 in reservoirs, 1 at an elevated tank, and 2 in separate pressure districts); and (iii) a dead end flushing program so as to turn over stagnant water where connectivity of the network is limited. As a result of these activities, the City’s Annual Water Quality Reports have been positive, historically indicating an acceptable (very low) number of adverse water quality incidents.

The project task of updating and calibrating the existing water quality model will improve the City’s ability to effectively manage chlorine residuals (a strong indicator of water quality) in the distribution system to inform and optimize flushing programs, locate optimal sampling points, and the potential implementation of re-chlorimantion facilities (if necessary).

Figure 1. Water quality Test Areas and sampling points


Figure 2. Water age map

 



Figure 3. Water quality model calibration task flowchart 

Location: Markham, ON, Canada

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