A dual-stage membrane bioreactor (MBR) for advanced treatment of industrial wastewater takes up less space and has lower operating costs than conventional activated sludge processing systems.
The ITT Dual-Stage MBR system, developed by ITT Industries , has been created by combining technologies developed at two of its subsidiary companies: Sanitaire and Aquious. It is targetted at industrial wastewater applications in pharmaceutical and chemical processing, food and beverage manufacturing and other sectors.
The system is a complete and continuous process. It accepts wastewater with high loadings of BOD (biochemical oxygen demand), suspended solids and other contaminants and yields an effluent that can be suitable for direct discharge to surface water bodies (depending on local regulations) and low grade re-use applications. The water can be further treated with polishing processes (for instance, reverse osmosis) to yield potable water.
In a traditional activated sludge process, wastewater is introduced into a biological treatment tank where organic contaminants are reduced and nutrients removed. The resultant biomass or sludge then flows to a clarifier or settling tank where solids separate out and effluent can be taken off and filtered prior to disinfection. If higher levels of effluent quality are required before disposal or re-use, an additional microfiltration or ultrafiltration step may be required.
Membrane bioreactors, on the other hand, use the physical barrier provided by an ultrafiltration membrane instead of a settling tank to separate solids from liquid. Thus the effluent is of significantly higher quality and little, if any, additional treatment is required prior to disposal or re-use.
The growth of membrane bioreactors in the global marketplace is a direct result of water scarcity and the increasing need to reduce levels of solids and nutrients in effluent to meet more stringent treatment requirements and to allow for water re-use. In general, any wastewater source that can be treated using activated sludge can be treated using the MBR process. Until recently, traditional activated sludge processes have been used for most applications because of their relatively low cost. However, MBR costs have been dropping and can be comparable or less than conventional treatment, especially when effluent quality requirements are more stringent.
In the ITT Dual Stage MBR system, the biological treatment portion of the process is kept separate from the membrane filtration stage. Parameters such as aeration rate can be controlled discretely to minimise cleaning and power costs, according to the company.
The unit is designed to have a competitive capital cost and will show a 20 to 30 per cent lower operating cost when compared to other MBRs currently marketed, according to ITT. In a typical 20-year life cycle analysis, the per-1000-gallon cost of the ITT system will be at least 30 per cent lower than other systems, it claims.
Aquious is a new brand that envelopes ITT Industries' existing membrane filtration products and technology, including PCI Membrane Systems. Meantime, Sanitaire develops wastewater treatment technologies used in municipal and industrial wastewater treatment facilities.