Forward osmosis dialysate production using spiral-wound reverse-osmosis membrane elements

Presented here is an analysis of a method by which a spiral-wound reverse osmosis (RO) membrane element may be used in forward osmosis (FO) mode to produce dialysate fluid for medical treatment. In this method, dialysate is produced from the draw-side of an FO process by carefully controlling the output concentration, managing the accumulation of salt in the closed, feed-side membrane envelope and using osmotic backwashing to recover the membrane. The analysis shows that a high-quality, spiral-wound, polyamide 4040 RO membrane element may be used to produce un-buffered dialysate when supplied with brackish groundwater and dialysate concentrate. Production is possible for a short period before the membrane needs to be osmotically backwashed to remove accumulated salt. By alternating between production and backwashing cycles, a pair of high-quality 4040 elements may produce dialysate at a rate high enough to enable continuous haemodialysis treatment. The low-cost, compact nature of standard RO elements makes them suitable for water and energy-efficient FO applications. The method proposed here exploits the features of standard RO elements to enable their application in Australian desert regions, where water supplies are slightly brackish and where rates of kidney failure and dialysis treatment are relatively high.