Malt production is a multi-stage process. During the first stage, when the steeping of barley grain occurs, large volumes of water are used. Typically, 4.5– 5.0m3 of water is used for every tonne of malt produced, and two-thirds of this becomes effluent wastewater.
In 1997, the Rahr Malting plant in Minnesota, USA, installed an OMNiFLO sequencing batch reactor (SBR) to treat wastewater before its discharge into the Minnesota River. However, after a decade, increased plant production plus more stringent discharge limits meant a more advanced treatment system was required. Further complicating matters, space at the plant was at a premium, so the chosen solution needed to have a small footprint.
These constraints led to the specification and installation of a DuPont MEMCOR® membrane bioreactor (MBR) system in 2008, allowing for peak flows of up to 355m3 per hour across three biological trains arranged in parallel and three corresponding membrane tanks. A further upgrade in 2019 introduced the newer and more effective MEMCOR® MBR MemPulse process, allowing the system to operate at peak flow capacity for longer periods while reducing system operating costs by 50% because of a more efficient aeration system.
In this case study, discover how DuPont MEMCOR® MBR technology is allowing the plant responsible for producing approximately 20% of commercial malt in the US to efficiently treat wastewater for discharge into the Minnesota River.