Sherbrooke Sewage Treatment Plant Upgrades - St. Mary’s

completed

The project consists of upgrades to the existing wastewater treatment facility in the community of Sherbrooke. The scope of the work involves the installation of a new ultraviolet (UV) disinfection system, replacement of the coarse bubbler system, and upgrades to the equalization (EQ) and aeration tanks. The project aims to upgrade the wastewater treatment facility such that the quality of the effluent is improved. This is an upgrade to the existing facility - it is not intended to increase capacity. The Sherbrooke Sewage Treatment Plant (STP) is a thirty year old extended aeration activated sludge STP, which was designed to treat around 80,000 usgpd (436,080 cubic metres/day). The Municipality proposes to carry out upgrades to maintain the aging plant as well as to enable compliance with regulatory criteria. Presently the STP has a chlorine gas disinfection system to treat the effluent at the plant. Current Nova Scotia Environment guidelines are requiring effluent to be discharged such that the residual chlorine is 0.0 mg/l which would preclude the use of chlorine gas unless a dechlorination process is included in the treatment regime. Aside from the fact that continued chlorine based disinfection would require dechlorination as part of the treatment stage, the Municipality would like to move away from the chlorine gas due to its inherent danger, and Operator training requirements. The Municipality wishes to proceed with the following upgrades: - the conversion of the wastewater disinfection system from chlorination to UV disinfection to bring the STP into compliance with current guidelines - replace the in-tank coarse bubble diffuser system in the plant’s EQ tank, as the existing piping and diffusers have basically deteriorated - sand blast and re-paint the exposed surfaces of the EQ tank and two aeration tanks which are showing signs of corrosion