High-speed filtration of municipal and industrial wastewater
Realizes energy savings and compactness in water treatment equipment
|Purpose, feature or effect of the R&D||Energy Saving, Compactness|
Mitsubishi Electric has developed an immersion-type membrane bioreactor that uses ozonated water to clean the membrane filter (the Eco-MBR*1). The unit realizes high-speed filtration with approximately twice the flow rate of permeate per unit of membrane surface area, halving the number of membrane filters required, increasing compactness, and reducing energy consumption by 25%*2 compared to conventional membrane bioreactors.
Immersion-type membrane bioreactors separate activated sludge and treated water using a membrane filter immersed in activated sludge. Continued filtration results in the membrane filter becoming clogged with foulants, increasing pressure loss. In conventional immersion-type membrane bioreactors, the filter foulants are removed and the filter is cleaned by supplying a sodium hypochlorite solution from the opposite direction of filtering. However, since the membrane filter is more prone to become clogged the greater the speed of filtration, it has not been possible to realize high-speed filtration using sodium hypochlorite, which has a limited cleaning effect. In addition, it is necessary to supply a high flow rate of air bubbles from the lower section of the membrane filter in order to scour activated sludge adhering to the membrane surface, and this significantly increases energy consumption.
The developed Eco-MBR uses ozonated water to clean the membrane filter. Ozone demonstrates 1.4 times the oxidation power of sodium hypochlorite. In addition, increasing the concentration of the ozonated water enables effective removal of filter foulants using less water and less ozone.
The Eco-MBR efficiently removes foulants from the membrane filter through repeated washing with ozonated water, reducing the time required for the same amount of water to pass through the membrane. This makes it possible to realize high-speed filtration, and to halve the number of filters employed. As a result, the flow rate of air supplied to the lower section of the membrane filter for cleaning the membrane surface can be halved, which will save energy. The application of the Eco-MBR in the recycling of municipal and industrial wastewater will contribute to the realization of sustainable water-recycling societies both in Japan and throughout the world.