The Anaerobic Digestion Facility, located in the Town of Georgetown, was expanded and upgraded by ASCO to meet the plant's rated capacity of 22,700 m3/d. This digestion process expansion enabled the Georgetown area to continue with planned residential and industrial developments. The Plant wide SCADA upgrades were necessary to bring the process control systems to current-day standards thus ensuring continued reliable and efficient operation of the Plant.
The project consisted of the construction of a 20 meter diameter reinforced concrete digester, complete with a steel floating gas holder cover, and hydraulic mixing system, which can be used as a Primary or Secondary Digester. A new Control Building houses the digester mixing and recirculation pumps, sludge heater, and new higher capacity boilers sized to heat two primary digesters. Equipment upgrades to the existing Primary and Secondary digester facilities and associated Control Buildings and Gas Rooms included replacement of the digester gas mixing compressors, digester gas boosters, and waste biogas burner. Additional construction included an upgrade to the complete Plant SCADA system, comprised of component replacement within the existing five (5) PLC Control Panels and replacement of some instruments and VFDs.
Some challenges to the project included concrete placement for the new digester tank, which had to meet stringent tolerance requirements so as to ensure smooth operation of the floating gas holder cover. As well, the cover concrete ballast weighting had to be closely monitored to ensure the weight requirements as stipulated by the manufacturer were attained. Upgrading to the digester gas piping and electrical and ventilation systems within the existing gas rooms to meet CSA 149.6 and NFPA 820 code requirements and the change-out of the PLC Control Panels, instruments, and VFDs had to be properly scheduled and fully coordinated to minimize the operational impacts to the Plant.