Treatment Plant Improvements

The Town of Colchester selected Weston & Sampson to improve treatment process performance and expand the capacity of the Taintor Hill Road water treatment plant. Constructed in 1989, the greensand filter plant treats groundwater with high levels of iron and manganese that has caused fouling of the wells and increased operating costs. Groundwater from two wells is treated by pH adjustment, pressurized greensand filtration, disinfection, and aeration for volatile organic compounds (VOCs). The facility’s rated capacity is 450 gallons per minute (gpm). The Connecticut Water Diversion permit for the wellfield allows up to a combined 600 gpm withdrawal, with no well greater than 400 gpm.

Over the years, iron concentration has increased up to a range of 6 ppm to 10 ppm. This increased iron concentration lowered the efficiency of the greensand filters resulting in lower production capacity of the filters, as well as more frequent backwashing. Colchester’s Well #5 was located in an aquifer with high iron and manganese concentrations. Due to the age of the well and water quality conditions of the site, capacity of the well had fallen off considerably. Weston & Sampson designed the replacement of Well #5 to increase production capacity and provide pumping system flexibility to its system.

Weston & Sampson completed the conceptual design of improvements to the plant and will provide construction services. Weston & Sampson accomplished the following town objectives:

• Increased well and treatment production to the permitted 600 gpm
• Evaluated other treatment processes and enhancements including roughing filters, other filter media, and membrane filtration
• Minimized potential future impacts to water quality and treatment efficiency due to changes in VOC contaminants
• Reduced backwashing of the filters
• Optimized the efficiency of the treatment processes to reduce chemical and power requirements and costs
• Utilized bulk chemical storage to reduce chemical and delivery costs

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