Donohue & Associates and Bush Brothers and Company, located in Augusta, Wisconsin, received a Best of State Award in the 2014 ACEC Wisconsin Engineering Excellence competition. The award recognizes an energy recovery project at Bush Brothers’ wastewater treatment facility that provides odor mitigation and produces enough electricity to power 500 home. Donohue provided planning, design, construction administration and inspection, and startup and training services.

Prior to this project, waste beans were separated from the wastewater by a screening system and then used as cattle feed. Donohue conducted a study to determine the degradability of the waste beans and the amount of biogas produced when mixed with the wastewater. The results showed that the beans are nearly 100% degradable and exhibit a steady pattern of methane generation. Thus, the treatment train was reconfigured to grind the beans and mix them into the waste stream that is pumped to the anaerobic reactor, increasing biogas production by 20% to 50%.

To clean the biogas, which had concentrations of hydrogen sulfide (H₂S) of up to 10,000ppm, Donohue selected a hybrid system consisting of a biofilter followed by a replaceable media scrubber. The biofilter provides efficient H₂S removal at low operating costs but does not have the proven track record that replaceable media does. Therefore, the replaceable media was sized to provide complete treatment if necessary to provide redundancy. At the time of installation, the facility was the first in the Midwest and the second of its kind in the U.S.