Harnessing Algae to Meet Ultra-Low Phosphorus Limits at Waupun’s Wastewater Treatment Plant
2026 Engineering Excellence Best of State
Entering Firm: Applied Technologies Inc.
Client: Waupun Utilities
The City of Waupun places great importance on protecting its trails, parks, and waterways, and its Wastewater Treatment Plant plays a vital role in maintaining water quality. Although the plant consistently met its phosphorus limit, upcoming regulations required a nearly 97 percent decrease. The plant could not meet this future limit through operational adjustments alone.
Engineers used algae to treat water contaminants, one of the first facilities worldwide to use this method.
Applied Technologies gathered feedback from stakeholders to implement a unique solution. Following a successful pilot program, the team selected the Advanced Biological Nutrient Recovery (ABNR) system. This technology uses algae in a suspended growth system to remove nutrients like phosphorus from wastewater. With this system, phosphorus is purposefully used to grow algae in a controlled environment, rather than in our lakes and rivers in the form of harmful algal blooms. To manage rare high-flow events, the team coordinated with local farmers and landowners to generate phosphorus credits, avoiding the need to oversize the system while still meeting regulatory requirements.
“Applied Technologies delivered an innovative, collaborative solution to Waupun’s phosphorus challenge. The design team’s adaptability through implementation is a true sign of engineering excellence that will benefit Waupun residents and the engineering community for years to come.”
- Awards judge Bridget Henk
As one of the first ABNR installations worldwide, the project required close collaboration and adaptability. Applied Technologies coordinated all stakeholders to keep the effort on track.
The upgraded facility demonstrates how phosphorus can be captured beneficially rather than contributing to harmful algal blooms, symbolized by Waupun’s striking greenhouse lined with bright green piping. The project is the epitome of green engineering!