Abstract: Disclosed is a multi-stage degassing unit for degassing waste water, such as effluent from grain milling processes, through impingement upon successive impact plates. The degassing unit has one or more stages of impact plates, which alternate with redistribution trays that receive the waste water that impinges upon the impact plates directly above the trays and then redistributes the waste water through a plurality of apertures in the redistribution tray. The process of impinging the waste water against the impact plates, collecting the water, and redistributing the water into a plurality of streams may be repeated as necessary to sufficiently remove gas clinging to biomass in the waste water. This degassing will promote the settlement of the biomass for reuse in the water treatment process to reduce biological oxygen demand.