The Village of Slinger’s wastewater treatment facility (WWTF) faced a recurring challenge: maintaining effective phosphorus removal during warm weather when oxygen transfer efficiency drops. In response, the Village completed a strategic upgrade to boost aeration capacity and improve system resilience.
Background: A Growing Community and a Demanding System
Slinger’s WWTF treats domestic, commercial, and industrial wastewater for a population of approximately 6,400. The facility has a design capacity of 1.6 million gallons per day (MGD), with current average flows around 0.9 MGD.
Originally built in 1981 and expanded in 2008–2009, the facility uses a three-channel oxidation ditch to treat organic matter and nutrients. Wastewater flows through concentric channels, where submerged disc aerators introduce oxygen to support biological treatment.
The Problem: Limited Aeration During Warm Weather
Over the past decade, the WWTF adopted enhanced biological phosphorus removal (BPR), which requires precise oxygen levels across the ditch’s channels. Less oxygen is needed in the outer channel (anoxic conditions), while more is needed in the middle and inner channels (aerobic conditions).
During warm weather or when aerators were offline, oxygen levels dropped in the middle and inner channels, reducing BPR effectiveness. The facility had to rely more heavily on chemical phosphorus removal using aluminum salts, which strained permit compliance—even with support from a Water Quality Trading (WQT) program.
The Solution: Strategic Aeration Upgrade
Fortunately, the 2008–2009 expansion had anticipated future needs. It included space and structural provisions for additional aerators and motor control centers (MCCs).
In fall 2023, the Village launched an upgrade project to increase aeration capacity. The improvements included:
New aerator shafts and disc assemblies
Weather hoods and motors (50 HP and 25 HP)
Two MCCs and variable speed drives
SCADA system integration
Aerators were added specifically to the middle and inner channels to support BPR. The outer channel remains unchanged for now, with future expansion possible in 10–15 years.
Results: Improved Performance and Resilience
The new equipment was successfully commissioned in summer 2024. The WWTF now has greater aeration capacity where it’s needed most, ensuring more consistent phosphorus removal—even during warm weather or equipment downtime.
This upgrade strengthens the facility’s ability to meet permit limits and supports long-term environmental stewardship for the Village of Slinger.
Interested in how these upgrades support cleaner water and long-term sustainability? Contact our experts to learn more about the project or discuss future infrastructure solutions tailored to your community.
ABOUT THE AUTHOR
Dave Arnott, P.E.
TEAM LEADER & SR. PROJECT MANAGER
Dave has extensive experience in the planning, design and construction project management of wastewater treatment facility renovation and upgrade projects. Areas of expertise include treatment processes, hydraulics, mechanical equipment, and wastewater disinfection. He also has experience in sanitary and water pumping station design and sanitary sewer wet weather facilities.