Donohue & Associates and the City of Hutchinson, Minnesota, received a Grand Award in the 2009 ACEC Minnesota Engineering Excellence competition. The project was also an ACEC National Finalist. The award recognizes Donohue’s innovative approach to increasing facility capacity at the City’s wastewater treatment facility (WWTF).

Prior to the upgrade, the City’s WWTF was operating at or over capacity for biological oxygen demand (BOD), total suspended solids (TSS), and ammonia nitrogen, and future phosphorus and mercury limits necessitated upgrades. Conventional methods of increasing capacity were evaluated, such as adding a third oxidation ditch and final clarifier to the existing facilities. However, these options were rejected due to large footprints and considerable operator requirements. Instead, Donohue developed an MBR system that runs in parallel to the existing treatment train and combines modern and conventional technologies to maximize effluent quality while minimizing costs.

This solution is the first in the Midwest and one of just a handful built across the US. Two-thirds of the flow goes to the existing oxidation ditches and final clarifiers, while the remaining one-third is sent to the new MBR process. The effluent is then blended, resulting in superior effluent quality. In order to be eligible for low interest funding, the facilities were designed in less than 10 weeks.