| Conventional Design | | | | energy in the concentrate stream to an equal |
| Previously, the standard Hydropro design for | | | | amount of feed water. The result is a side feed |
| SWRO with energy recovery incorporated a | | | | stream equal in flow to the concentrate stream |
| single multistage centrifugal pump (or positive | | | | (minus bearing leakage) that is boosted to near |
| displacement) with a Hydraulic Turbo Booster. This | | | | membrane feed pressure by the Pressure |
| design is fairly simple and generally does not | | | | Exchanger. A small high pressure booster pump is |
| require a significant increase in system controls or | | | | then required to boost the high pressure feed |
| instrumentation and is for the most part a sound, | | | | exiting the PE so that it equals the discharge |
| and energy efficient SWRO design. | | | | pressure of the high pressure feed pump and the |
| | | | two feed streams can be combined. This |
| This HTB energy recovery device provides a | | | | pressure boost accounts for pressure losses |
| substantial reduction in specific energy | | | | associated with inefficiencies of the pressure |
| consumption, which, depending on the duty cycle | | | | exchanger, losses across the membranes, and |
| and cost of power could pay for itself in a | | | | piping and fitting losses throughout the system. By |
| relatively short amount of time. | | | | significantly reducing the size of the high pressure |
| New Technology | | | | feed pump to approximate the flow of permeate, |
| The concept of a work exchanger energy | | | | the horsepower of the high pressure pump can |
| recovery device was certainly not new, and | | | | be reduced by approximately two thirds of the |
| several variations of these devices have come | | | | total pumping power required. This substantial |
| and gone. However, at the time of this proposal, | | | | reduction in horsepower is, for the most part, |
| there seemed to be a new approach to the | | | | specific to the high pressure, low recovery nature |
| design of these positive displacement devices that | | | | of the SWRO system. To illustrate the effect of |
| eliminated many of the problems associated with | | | | this reduction in pumping power required, the |
| previous versions. The PE from Energy Recovery, | | | | following example is used: |
| Inc. (ERI) is an example of a novel work | | | | Although there are other energy considerations |
| exchanger device that was in a position to | | | | besides just pumping power when comparing a |
| profoundly affect the design of SWRO and the | | | | system with no energy recovery and a system |
| energy recovery industry. | | | | with a PE, this simple analysis shows a significant |
| The main idea of the Pressure Exchanger is its | | | | reduction in energy consumption when using a |
| ability to directly transfer most of the hydraulic | | | | Pressure Exchanger. |