Combined membrane and sorption process for selective ion removal

Abstract From the Canadian patent

A combined membrane/sorption process is used to selectively remove ions from liquid streams. As an example, nitrate ions can be more effectively removed from an aqueous stream also containing sulfate ions. Sulfate ions normally are not needed or desired to be removed from drinking water, but are typically sorbed by the available ion exchange resins and result in inefficient use of the ion exchange capacity. The disclosed process and apparatus use an ion selective membrane to first remove the sulfate ions from the stream and then remove the nitrate ions by ion exchange.