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By defining the combination of high pressure seawater feed pump and energy recovery system as the core hydraulic module of SWRO plants it becomes obvious that this subsystem mainly contributes to the specific water costs by its operational costs and has to be optimized by a complete approach. In the previous paper published at the IDA Conference 2003 [1], different energy recovery systems were analyzed with respect to theire overall life cycle costs. Identifying the core hydraulic module using pressure exchangers as the advantageous ERS-concept the question of appropriate component optimization was discussed for the high pressure pump design. In the current paper, this approach is extended to the pressure exchanger itself, contributing to an overall optimized core hydraulic module. Therefore, inadequacies and limits of conventional pressure exchanger operation are explored and discussed with respect to their impact on reliability. Based on these results, a new pressure exchanger design is presented. This design was realized in a laboratory prototype and tested on a special test rig. The arrangements of the test rig as well as the results of first prototype tests are described.

The use of a pressure exchanger as energy recovery system enables a very low energy consumption for the reverse osmosis process. Low operating costs are a prerequisite for low drinking water prices. Especially for the regions of the Middle East and North Africa receiving little rainfall, the provision of drinking water will become more and more affordable. An operationally reliable pressure exchanger that can be incorporated in any reverse osmosis facility and can cope with each facility’s operating conditions is an important precondition. The design of the product presented has been matched to satisfy these requirements. A new rotating valve technology with an integrated control system was developed, eliminating the burdens of pressure fluctuations with occurring conventional designs. Tests in a test bed simulating a reverse osmosis facility have been conducted with positive results. The test and documentation of the pressure exchanger’s operational reliability in a field test is on the way. The next step will be the instalation of this solution in different projects.