About this Project
The Groton Utilities (GU) water treatment plant (WTP) treats water from several sources of supply. The primary source of supply is the Poquonnock Reservoir. Smith Lake, a spring-fed source, is located to the east of the Poquonnock Reservoir system and is a secondary source of supply. Groton Utilities also has three production wells near the shores of Smith Lake, only production Well No. 3 is still in use. Production Well No. 3 and Smith Lake share a common transfer line to the treatment plant. The reservoir system has a safe yield of 12.6 MGD. The conventional water treatment process at the WTP has historically produced a good finished water quality; however, as water quality regulations have become ever more stringent, plant operators have found it more difficult to continuously meet all the treatment goals.
Following a comprehensive process evaluation, Dissolved Air Flotation (DAF) followed by deep bed GAC filtration was evaluated at the pilot scale as a possible replacement for the existing sedimentation and filtration process. This would be in either a retrofit or new-build option .
The results of the pilot study showed that the combined processes of DAF followed by deep bed GAC met all the treatment goals.
FST completed a detailed engineer’s opinion of probable construction cost with advantages and disadvantages for an estimated $38 million water treatment plant upgrade. Some of the key components of the plant upgrade include the addition of passive raw water quality management structures in the reservoirs, upgrade of the transfer station, new intake screen controls, installation of a redundant raw water supply line to improve reliability, addition of permanganate for oxidation of iron and manganese, installation of DAF clarifiers, the addition of GAC filters, the addition of an adsorption contactor for manganese control, converting two of the existing clarifiers to spent washwater holding tanks for recycling to the head of the plant, 2 MG storage tank, as well as major upgrades to the building and HVAC, plumbing, electrical and instrumentation and control systems.
Owner: Groton Utilities
Location: Groton, Connecticut
Highlights: As part of a detailed conceptual design report prepared by FST, many issues at the WTP were evaluated outlining cost and associated advantages and disadvantages.