Desalination by Continuous Ion Exchange Based on Thermally Regenerable Magnetic Microresins

Abstract

The removal of small quantities of salt at the 500 to 2000 mg/L level is becoming increasingly necessary to counter one of the most widespread forms of water pollution encountered throughout the world. Ion-exchange resins which can be regenerated with hot water have been used previously in a batch mode for the desalting of both natural waters, and municipal and industrial wastewaters. Continuous operation would offer many advantages, especially for productivity, heat economy and ease of control. Unfortunately existing continuous ion-exchange contactors are intermittent in operation and somewhat complex. This paper describes the unique hydrodynamic and kinetic properties of “Sirotherm” thermally regenerable desalting resins when made in the form of magnetic microbeads, and the development of continuous contacting systems which exploit these properties. A novel multistage contactor has been evaluated on laboratory and pilot-plant scales. A prototype plant, with a throughput of 1 ML/day, is to be installed near Perth, Western Australia, in order to demonstrate the process. It is truly continuous, simple and economic, and does not require preclarification of the raw water.