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Mill Bay Wastewater Treatment Plant

2019-2021 | Mill Bay, British Columbia

Mill Bay is a community of over 7,000 people located within the Cowichan Valley Regional District (CVRD) about 30km north of Victoria. To accommodate the community’s expected growth, CVRD’s Official Community Plan is prepared to densify Mill Bay’s population to ten times its current number. Upgrades and improvements to wastewater treatment were immediately prioritized to prepare for this projected future growth.

Over 60 small water and waste treatment facilities are operated by the CVRD across the district. Upgrading and improving systems in the Mill Bay community would accommodate future growth while also creating an opportunity to minimize the total number of systems required. The existing sewage treatment facility serving the Mill Springs area is one such plant that until recently serviced about 2,200 people. McElhanney was engaged to design a system for Mill Springs facility that would quadruple the population that could be serviced within the main commercial area at Hwy No. 1 and Deloume Rd.

The project team was challenged to complete the upgrade using only the available tankage; no further physical additions were permitted. Using advanced treatment technology, McElhanney met and exceeded CVRD’s expectations.

Project team members prepared a design that retrofitted Mill Bay’s aging, dual-train, extended aeration activated sludge wastewater treatment facility with industry-leading membrane reactor (MBR) technology. The existing tankage was modified to accommodate the membrane technology system additions.

Today, the first round of retrofits has been completed, and the infrastructure is in place to retrofit more tanks as community growth continues.

The process design was based on a suspended growth activated sludge process combined with treated effluent extraction via Toray flat plate membranes.

The process configuration consists of upgraded headworks, equalization tank, MBR for biological nutrient removal, UV disinfection, new blowers / aeration system, effluent storage tank, sludge storage tank, upgraded system controls, and future reclaimed effluent distribution to Brentwood College.


McElhanney provided:

  • Project management
  • Development of flow scenarios
  • Phasing
  • Conceptual / detailed design
  • Tendering and construction support
  • Start-up
  • Commissioning
Mill Bay Wastewater Infrastructure
Mill Bay Wastewater Infrastructure Project Area