Mitsubishi Electric Corporation has developed a compact membrane bioreactor (Eco-MBR) that recycles municipal and industrial wastewater with low-energy consumption and increases the quantity of permeated water per membrane filter surface area (flux) by cleaning the filter with ozonated water.

In conventional activated-sludge processes, treated water is separated from activated sludge by sedimentation, which requires a large surface area and produces water quality not suitable for reuse. In the case of conventional MBRs, a sodium hypochlorite solution is commonly used to clean the membrane filtration, but oxidation power is relatively weak so high flux is not possible. Also, the process requires a large number of membrane filters.

The Eco-MBR—which Mitsubishi Electric is jointly developing with Professor Hiroshi Nagaoka, of Tokyo City University’s Faculty of Engineering—achieves a high flux of 1.6 m³/m²/day and cuts the required number of membrane filters by intermittently cleaning the filters with ozonated water to efficiently remove organic substances for increased permeability. The Eco-MBR also features a compact footprint and reduces energy consumption by lowering the air flow rate that the blower uses to clean the membrane surface with bubbles.

Schematic diagram of Eco-MBR. Image credit: Mitsubishi Electric.Mitsubishi Electric says it expects to introduce the Eco-MBR into commercial use in municipal and industrial wastewater reuse systems in 2018.