By application of a pressure exchange system (PES), which is already in use in other domains, a considerably higher efficiency of energy recovery in reverse osmosis (RO) systems may be achieved than with the use of reverse running pumps or turbines. The PES is suited, above all, for larger plants, i.e., approx. greater than or equal to 2000 m(3)/d permeate production. It enables a simple, variable adaption of discharge volume and has, due to its design and direct pressure transmission of high pressure brine to the feed, an efficiency value of approximately 98%. Therefrom results an economic energy recovery, amortization times for such systems varying between 2 and 4 years depending on the place of operation. The following are presented and explained: (1) technical details of the PES; (2) practical experience with PES in the mining industry with pressures between 4 and 16 MPa; (3) conception of the application in RO systems with individual and parallel trains; (4) economical calculations at the example of a demonstration system; and (6) concept and design of a demonstration system for an existing RO plant.
