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Energy Optimized Resource Recovery

Client: Kenosha Water Utility

Location: Kenosha, Wisconsin

The Kenosha Water Utility embraces value-added innovation. The Utility recently completed an innovative project at their Water Resource Recovery Facility (WRRF) that demonstrates commitment to their unique brand of sustainability: protecting the financial well-being of their rate payers and enhancing the environmental benefits offered by their practice.

This WRRF project reduced energy and solids handling costs 20%, reduced dependence on fossil fuel energy by 40%, removed 10,000 tons annually from landfills, and produces a Class A biosolids product that allows for the annual reuse of 500 tons of nitrogen and 250 tons of phosphorus.

Aging infrastructure; rising natural gas, electricity, and landfill costs; and a commitment to sustainability prompted the Utility to seek out and evaluate strategies to reduce operating costs and extract energy and nutrients in the wastewater. The Utility found and implemented such a strategy: a holistic biosolids-reuse strategy that incorporates energy recovery and a biosolids-conditioning system that “unlocks” energy trapped in the cell walls of the biosolids.

Donohue’s design included anaerobic digestion, medium-temperature thermal biosolids drying, combined heat and power (CHP) energy recovery, and North America’s first PONDUS thermal-chemical hydrolysis system to enhance energy recovery. The PONDUS system allowed digester loading rates far exceeding conventional loadings rates, increased energy-laden biogas production from conventional digesters by nearly 20%, reduced digestion heat loss by 50%, improved biosolids dewatering, and reduced the energy consumed by thermal drying.

The Utility elected to utilize a design-build approach due to the complexity and varied technologies associated with this project. Centrisys, an equipment manufacturer located in Kenosha, served as the design-build developer and Donohue served as the engineer of record, providing detailed plans and specifications for the structures, piping, mechanical, electrical, controls, pumps and ancillary equipment; engineering services during construction; and Operations & Maintenance (O&M) and startup documents.