6.7. Membrane separation processes
Membrane separation or filtration processes have become popular due to their simplicity, high and selective separation efficiency, low energy consumption and so on. currently, the membrane separation process is often used for treatment of dyeing effluent. It is the method in which the micro-pores of membrane are used to filter wherein membrane's selective permeability separates specific substances in the effluent(Hauser, 2011). The process is mainly based on pressuring the effluent through membrane and classified as reverse osmosis, nanofiltration, ultrafiltration and microfiltration. The choice of the particular membrane process depends on the quality of the final product. The microfiltration is not suitable for textile effluent treatment because of its large pore size. Whereas, the reverse osmosis is widely adopted by textile dye- houses. Processes using membranes provide very interesting possibilities for the separation of hydrolyzed dye-stuffs and dyeing auxiliaries which ultimately reduce colour and oxygen demand of the effluent. However, the installation and maintenance of the equipment including membrane fouling is expensive.