AWWA MTC64568

This project will evaluate a demonstration-scale, two-stage reverse osmosis (RO) process for achieving high recovery (95%) for membrane desalination of Colorado River water. The two-stage process involves recovering the concentrate stream from a primary RO process by chemical precipitation followed by further recovery of low-total dissolved solids product water in a smaller, secondary RO. The principal research focus is to evaluate physical/chemical treatment strategies for removing scale-forming ions, which limit recovery in RO processes, using an intermediate chemical demineralization (ICD) process. An earlier pilot-scale ICD unit followed by a secondary RO desalting provided an overall total product water recovery plant of 93.5%. Solubility modeling results indicated that operation at recoveries in excess of 95% would be feasible. Includes 21 references, figures.