Evaluation, Final Design, and Construction for Southbridge WTP Upgrades
The Town of Southbridge selected Weston & Sampson to perform an evaluation, final design, and construction services for upgrades to the Southbridge Water Treatment Plant (WTP). The WTP is used to treat surface water from Reservoir Numbers 3, 4, 5, Hatchet Pond, and Cohasse Reservoir. Prior to the improvements, the WTP was equipped with two treatment units, each rated for 2.0 million gallons per day (MGD), for a maximum capacity of 4.0 MGD. Each treatment unit consisted of a two-stage process, upflow clarification followed by filtration. The upflow clarifiers were equipped with a non-buoyant media that required routine removal and cleaning due to the clogging of the inlet water supply nozzles.
Improvements were completed at the WTP to increase the capacity of the WTF and improve operations by eliminating the clarifier non-buoyant media/nozzle setup. The improvements included the addition of a third upflow clarification/filtration treatment unit that uses a buoyant clarification media, increasing the maximum capacity from 4.0 to 6.0 MGD. In addition to the new treatment unit, the internals of the two existing units were retrofitted to match the new unit. Due to the size of the new treatment unit, the external masonry wall was removed and replaced during construction to bring the new treatment unit inside the WTP.
SCADA (Supervisory Control and Data Acquisition) upgrades were completed to properly control the new and retrofitted treatment units. The existing PC-based computer control system for the plant includes monitoring and automation of the treatment process for several remote sites in town via radio modem. These remote sites include pump stations, storage tanks, and raw water reservoirs.