Blog of Bong Seog Jung

This project is to develop a Water Quality Maintenance Plan in the City of Markham for the purposes of ensuring that disinfectant residuals in the watermain system are maintained following its initial construction and commissioning.  This work is largely driven by the implementation of a large diameter (750Ø) trunk watermain along Warden Avenue extending northerly from Major Mackenzie Drive to Street E (see Figure 1 ), and for which there will be a relatively large volume of water with potentially little-to-no turnover until such time that sufficient demand is present in the system and/or connectivity to other parts of the City’s broader system is established. In this project, the residual disinfectant (total chlorine) concentration is determined as the minimum of the last week (7 days) of the 28-day simulation period. If the residual disinfectant concentration is at or below a threshold target (0.75 mg/L for the base case), an iterative process is followed to develop a flus...

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 param...