Pilot Plant Study and Water Treatment Plant Design and Construction
The Town of Hanover selected Weston & Sampson to evaluate treatment of its four Hanover Street and Broadway wells for removal of iron, manganese, and organic color. The work included an evaluation of the following treatment processes:
- Pressure filtration using manganese greensand
- Pressure filtration using synthetic media (Kinetico)
- Pressure filtration using adsorptive media (Pureflow)
- Existing town filtration facilities
Weston & Sampson pilot tested and estimated life-cycle costs for the three pressure filtration treatment processes, including residuals treatment alternatives. Treatment plant locations and transmission main routes were also evaluated. The most feasible and cost-effective solution for good water quality at a reasonable cost was to construct a manganese greensand pressure filtration plant at the Broadway well site to treat all four wells. The Broadway water treatment plant treats 1.4-million gallons per day (mgd) using six to 12 foot diameter manganese greensand pressure filters. The treatment process includes aeration to reduce carbon dioxide in the water, potassium hydroxide to increase the pH of the treated water and enhance oxidation, potassium permanganate to oxidize iron and manganese, and aluminum sulfate to remove organic color in the filtration process. Sodium hypochlorite is also added for disinfection. Clean supernatant from the decant/recycle tank is pumped back to the head of the plant for recycling. The operators recycle at least 80% of the residuals.
As part of the project, a stormwater design was included to minimize impacts from the construction of the 6,500 square foot treatment building and parking area. The stormwater design included the installation of four drywells to collect runoff from the roof of the treatment building. A catch basin, stormwater treatment unit, and detention basin were included to collect and treat stormwater runoff from the site.