A Conventional Water Treatment Solution Using an Uncommon Method
The Slinger (Wis.) Village Board wanted to provide its citizens with better drinking water by installing an iron removal plant to remove 1.6 parts per million (ppm) of iron from its well water supply.
The village had been using a sequestering agent to control the iron but felt that removal was a better solution, as it would reduce the frequency of flushing the mains and provide rust-free water to residents.
The solution, the village decided on a coached design-build approach to allow the involvement of all parties, reduce design and construction time and reduce overall costs.
It selected the design-build team of engineering firm McMahon & Associates and contractor Oscar Boldt Construction. The village conducted a pilot study to ensure feasibility of the design-build team’s process design. Proposal requirements were also simultaneously produced.
Once the pilot study was complete, the design-build team selected USFilter’s General Filter product line, a part of Siemens Water Technologies, to supply major process equipment. Working together, the team finalized the plant’s design, with each party contributing ideas to provide a balance between overall project cost, initial quality and long-term performance.
"We really liked the team’s creative design proposal," recalled Dean Otte, Slinger’s village clerk. "It considered the village's desire to control cost while providing us with a plant that would perform well for years to come."
Design innovations included:
- Installing a backwash waste-holding tank below the filter floor to save space and excavation;
- Elevating the plant to gravity discharge from the backwash waste-holding tank;
- Using stainless steel filter front piping to minimize painting and reduce maintenance; and
- Reducing backwash waste flow with a six-cell filter.
Construction was completed in just six months. The total project from conception to construction took only 18 months.
According to Otte, having all parties come together at the project’s onset helped bring the system online months earlier and saved the village several hundred thousand dollars in redundant work.
The iron removal plant works as follows: The village water supply provides 1,000 gpm from a groundwater well. Chlorine is added to begin oxidizing the iron and to carry residual disinfection through the treatment system.
Upon entering the plant, the chlorinated water passes through a pressure aerator, where air is injected into the water to oxidize soluble iron.
A 38 by 10-ft horizontal pressure filter with anthracite media provides filtration of the iron floc.
Since startup, the iron removal system has exceeded the village’s expectations, consistently reducing influent iron from 1.6 ppm to less than 0.1 ppm. The village water supply is free of rust, and the flushing frequency for the distribution mains has been reduced, saving the village money on operating costs. A single operator spends approximately one hour per month on routine plant maintenance.