The state of Colorado has new regulations for allowable levels of nitrogen in wastewater, so the city of Boulder sought an innovative solution. The city is using waste from Avery Brewing in Boulder to feed the microbes that digest nitrates in sewage. To make it happen, the engineering firm and contractor significantly upgraded Boulder’s 75th Street Wastewater Treatment Facility. Included were modifications to the plant’s aeration basins and solids contact tanks, conversion of a pre-dewatering storage tank into a post-aerobic digester and a newly constructed external carbon-storage and feed facility. The project is unprecedented in Boulder for the way it brought together the private sector and the city’s water-treatment staff. It represented a win for both: The city got an innovative way to remove nitrogen from its sewage while purchasing fewer chemicals, the microbrewery found a use for its waste and Boulder Creek became cleaner in the bargain.

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