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St. Cloud, Minnesota

2021 ACEC Minnesota Engineering Excellence Grand Conceptor Award

Donohue and the City of St. Cloud received the 2021 Grand Conceptor Award for their collaborative efforts on the Nutrient Recovery and Reuse (NR2) project. This prestigious award is presented to the highest scoring project in ACEC Minnesota’s engineering excellence competition. Judging criteria include innovation, complexity, client satisfaction, future value to the engineering profession, and social, economic, and sustainable design considerations.

The St. Cloud Nutrient, Energy & Water (NEW) Recovery Facility serves over 120,000 people across six communities. It has become one of the nation’s most sustainable resource recovery facilities and a world-class example of how well-conceived sustainability initiatives can improve cost effectiveness.

St. Cloud has made significant improvements in energy and nutrient recovery and biosolids management at its NEW Recovery Facility over the last decade. These accomplishments, due in large part to its recent NR2 project, are improving the health of the planet and the financial wellbeing of the people and businesses within the NEW Recovery Facility service area.

The engineering design team combined two innovative processes to improve the biosolids program: nutrient harvesting (the Ostara process) and thermal hydrolysis of biosolids (the Lystek process). This is the first time these two processes have been employed together at a resource recovery facility in North America. The Ostara process extracts Struvite, a hard phosphate byproduct that can damage equipment if left untreated, and produces a phosphorus-rich fertilizer pellet.

The new Lystek thermal hydrolysis process, which combines heat, alkali, and mixing to break down biological material in biosolids, results in a high quality liquid fertilizer that is more cost-effective and community-acceptable than other typical processes. The biofuel recovery project components have resulted in a net zero energy facility.

The balance of the NR2 project included biofuel storage, biosolids dewatering, a phosphorus-release reactor, and hauled-in waste receiving and processing improvements. The hauled-in waste improvements have dramatically improved biofuel and renewable energy production, allowing the facility to regularly generate more electricity than it consumes. 

The St. Cloud project team decided to take a calculated risk by installing two new technologies at the same time to keep user rates low, enhance resource recovery, and meet the City’s sustainability goals.

The award-winning project was selected among 31 entrants and 14 Grand Award finalists in the engineering excellence competition.