ABSTRACT
While ion exchange is used as a tool in reducing pollution, it can produce polluting effluents if spent regenerant cannot be utilized. This is especially true in water softening and in water demineralization. Legislation is limiting the disposal of regenerant streams in those areas where water supplies are scarce and/or brackish. If the salts are mainly sodium, then they could be used as a regenerant for softening the makeup water by ion exchange. The residual ions in the water can be reduced by ion exchange to any value desired. In this manner the amount of regenerant is limited for the removal of the residual ions. DePree and co-workers at Aerojet General developed a process which combines recovery and recycle of the regenerants and the waste salts as precipitates. The process has been applied for deionization of brackish waters, industrial waste streams, and secondary sewage effluents.
