skip to content skip to footer
Aerial view of Ashbridges Bay Treatment Plant with digester tanks and the Toronto skyline in the background.

Ashbridges Bay Wastewater Treatment Plant, Cleaning & Rehabilitation of Digesters No. 1 to 4

Recent Bennett Construction Group Project
Bennett Built
Logo representing the city of Toronto, featuring the mayor's emblem.
Contact Value: $39,959,700.00
Aerial view of Ashbridges Bay Treatment Plant with digester tanks and the Toronto skyline in the background.
Aerial view of four large circular digester tanks at Ashbridges Bay Treatment Plant.
Industrial conveyor transporting material between processing equipment at Ashbridges Bay Treatment Plant.

Scope of Work:

Cleaning, dewatering and rehabilitation of Digesters 1–4 including off-site disposal of sludge and debris, inspection, testing, commissioning and return to regular operation.

CFD modelling and design of new sludge mixing systems including new internal suction and discharge piping, scum control piping, mixing nozzles and structural pipe supports.

Full-scale field performance testing of the digester mixing system using lithium chloride tracer testing to identify hydraulic short-circuiting, dead zones and overall mixing efficiency.

Structural rehabilitation of Digesters 1–4 including concrete repairs to walls, floors, ceilings, overflow boxes and columns; crack injection; masonry repairs; steel repairs; and installation of new structural steel framing and pipe supports.

Installation of new structural steel beam systems to strengthen the existing concrete domes of Digesters 1–4.

Complete replacement of digester roof assemblies including waterproofing membrane, rigid insulation, reinforced concrete wearing slabs, structural repairs and new stormwater collection and drainage systems.

Removal and replacement of existing interior gas-proofing and waterproofing systems including concrete surface preparation, repairs, installation and testing.

Replacement and modification of digester gas piping and equipment including new 316 stainless steel ball valves, actuated gas valves, safety selector valves, flame arrestors, pressure relief equipment, piping, fittings and supports.

Replacement of sludge process piping and valves including raw sludge feed, mixing, transfer and recirculation piping together with hot water supply and return piping, valves, fittings, supports, insulation and jacketing.

Removal and replacement of sludge heat exchangers, mixing pumps, recirculation pumps and transfer pumps including associated piping, valves, concrete bases, electrical equipment, controls and instrumentation.

Installation of new magnetic flow meters, sampling systems, pneumatic service-air piping, actuated valves, position indicators, transmitters and associated process instrumentation.

Programming, integration and testing of new process equipment, valves, actuators and instrumentation with the existing plant SCADA system.

Mechanical building upgrades including replacement of exhaust and ventilation fans, modifications to ductwork and upgrades to sump pump systems.

Electrical upgrades including new distribution panels, breakers, pump and equipment cabling, pneumatic valve control panels, classified-area electrical installations, heat tracing and replacement of existing lighting with new LED fixtures.

Hydrostatic and air-pressure leak testing of Digesters 1–4, including TSSA-witnessed testing and certification, followed by start-up, commissioning and assistance with returning the digesters to normal operation.