MEMBRANE TECHNOLOGY - THE WAY FORWARD

The types of membrane processes available to the water industry are described and discussed. Pressure-driven processes can be divided into membrane filtration, ultrafiltration and reverse osmosis. All are capable of achieving water disinfection. Membrane filtration with backwashing can also be used for particulate removal, ultrafiltration for the removal of larger organic molecules such as colour, and reverse osmosis for desalination procedures such as nitrate removal and softening. The electrical potential driven process of electrodialysis shows advantages for the desalination of brackish waters and is already a competitive process for nitrate removal at some locations. The more recent development of dynamic membrane processes has opened up the possibility of easy replacement of fouled membranes, and the use of membranes built up from treatment chemicals such as iron floc, powdered activated carbon or powdered ion-exchange resins. Such membrane processes can be used for colour, pesticide or nitrate removal. It is concluded that membrane processes have great potential for use within the water industry but that this has not been realized for several reasons such as disposal of the concentrated reject stream containing the material separated from the water. It is expected that as water quality standards become more stringent. and membrane processes advance and become cheaper, they will be installed by the water industry. The first large-scale plants may well be constructed before the turn of the century.