Entering the mid to late 1990s, membrane - bioreactors have entered the practical application stage in foreign countries. The Canadian company Zenon first introduced the ultrafiltration tubular membrane - bioreactor and applied it to municipal wastewater treatment. In order to save energy, the company also developed the immersion hollow fibre membrane module, which has developed a membrane - bioreactor has been applied in the United States, Germany, France and Egypt and more than a dozen places, the scale from 380m3 /d to 7600m3 /d. Japan's Mitsubishi rayon company is also a well-known provider of immersion hollow fibre membrane in the world, its application in the MBR has also accumulated many years of experience, in Japan and other countries with a number of actual MBR projects. Kubota Japan is another company that is competitive in the practical application of membrane - bioreactors, producing plate membranes with high flow rates, resistance to contamination and simplicity of process.
The first wastewater treatment plant using the MBR process was built in 1967 by Dorr-Oliver in the USA, this treatment plant treated 14m3/d of wastewater. In 1977, a wastewater reuse system was put into operation in a high-rise building in Japan, and in 1980, two MBR treatment plants with a capacity of 10 m3 /d and 50 m3 /d were built. 39 such plants were in operation in Japan by the mid-1990s, with a maximum capacity of 500 m3 /d, and more than 100 high-rise buildings were using MBR to reuse wastewater for water in waterways. In 1997 Wessex built the world's largest MBR system at the time in Porlock, UK, with a capacity of 2,000m3 /d, and in 1999 a 13,000m3 /d MBR plant was built at Swanage, Dorset.
Since the 1990s, the treatment targets of MBR have been broadened, and in addition to water reuse and manure wastewater treatment, the application of MBR in industrial wastewater treatment has also gained widespread attention, such as the treatment of food industry wastewater, aquatic processing wastewater, breeding wastewater, cosmetics production wastewater, dye wastewater and petrochemical wastewater, all of which have obtained good treatment results. The MBR system was used to treat industrial wastewater from an automobile manufacturing plant, with a treatment scale of 151m3/d. The organic load of the system reached 6.3kgCOD/m3-d, with a COD removal rate of 94%, and most of the oil and grease were degraded. In the Netherlands, a fat extraction processing plant used conventional oxidation ditch wastewater treatment technology to treat its production wastewater. The expansion of the production scale resulted in sludge expansion and difficult sludge separation, and finally Zenon's membrane modules were used instead of sedimentation tanks, which operated well.
With the widespread use of nitrogen fertilisers and pesticides in agriculture, drinking water has been contaminated to varying degrees, and the company LyonnaisedesEaux developed an MBR process in the mid-1990s which also provides biological denitrification, pesticide adsorption and turbidity removal. The nitrogen concentration in the effluent is less than 0.1mgNO2/L and the pesticide concentration is less than 0.02μg/L.
The high organic content of manure wastewater, the high sludge concentration required by traditional denitrification treatment methods and the unstable solid-liquid separation affect the effectiveness of tertiary treatment. the advent of MBR has solved this problem and made it possible to treat manure wastewater directly without dilution.
The NS system was built in 1985 in Koshigaya, Saitama Prefecture, Japan, with a production scale of 10kL/d. In 1989, new treatment facilities were built in Nagasaki and Kumamoto Prefectures. The membranes in the NS system are installed side by side in groups of several dozen, and are made into a frame that can be opened automatically and flushed automatically. The membrane material is a 20,000 molecular weight polysulfone ultrafiltration membrane. The sludge concentration in the reactor is kept in the range of 15000~18000mg/L. By 1994, more than 1200 MBR systems had been used in Japan to treat the faecal wastewater of more than 40 million people.
Landfill/compost leachate contains high concentrations of pollutants and its quality and quantity vary with climatic conditions and operating conditions. MBR technology has been used in several wastewater treatment plants for this type of effluent since before 1994. The combination of MBR and RO technology not only removes SS, organic matter and nitrogen, but also effectively removes salts and heavy metals. Envirogen in the USA developed an MBR for landfill leachate treatment and built a 400,000 gallon per day (approx. 1500 m3/d) plant in New Jersey, which was commissioned in late 2000. This MBR uses a naturally occurring mix of bacteria to break down hydrocarbons and chlorinated compounds in leachate and can treat pollutants at concentrations 50 to 100 times higher than conventional wastewater treatment plants. This is achieved because the MBR is able to retain highly efficient bacteria and achieve bacterial concentrations of 50,000 g/. In the field pilot test, the feed COD was a few hundred to 40,000 mg/L and the pollutant removal rate was over 90%.
