Desalination, Vol.108, No.1-3, 159-166, 1997
Desalination of surface water to industrial water with lower impact on the environment .1. New technological concept
The main environmental problems of conventional processes for the production;of desalinated water are caused by the regeneration of ion exchangers, during which waste water with high salt concentration is obtained and by the concentrates from partial membrane desalination, which have to be disposed of. Our new technological concept focuses on the application of improved technologies for the production of industrial desalinated water with lower impact on the environment. This involves an improved pre-treatment stage, a combination of different membrane processes and an ion exchange stage. By the use of electrodialysis with bipolar membranes, a mixed acid and a mixed base from the regenerates of the ion exchangers and/or from concentrates of the membrane stage can be produced. They can be re-used in the pre-treatment stage and for the regeneration of ion exchangers. The pilot plant, which was built up and optimised, includes different stages: pre-treatment; low pressure reverse osmosis for partial desalination; total desalination by ion exchange; reverse osmosis and electrodialysis for the concentration of the retentate from partial membrane desalination; and acid and base production by electrodialysis with bipolar membranes. The first experimental results, which show the feasibility of the new concept, are presented and discussed.