This newly designed pressure recovery pump is an elegant new high pressure pump that has been developed in 2009 for energy efficient, reverse osmosis desalination. This Pump is a breakthrough evolution and enhancement of reciprocating pump design. This unique high pressure pumping system combines feed stream pumping and energy recovery into a single unit.

The “Energy Recovery� feature of the pump takes the energy entrained in the brine reject stream from the RO membranes and recaptures up to 80%, dramatically increasing the overall efficiency, bringing energy requirements down to an impressive 9-11 Watt Hours per Gallon (2.6 KH per Cubic Meter), a major improvement for water desalination.

The recovery pump is scalable for a range of designed applications and product output. The system does not require continuous monitoring and adjustment as it stays inherently in balance at all times, providing a constant product flow and recovery ratio, while the pressure automatically matches membrane and feed water requirements.

The product flow can be controlled via a variable speed drive to the motor. The pump head is manufactured from engineered composites and high quality stainless steel for extreme corrosion resistance and oil filtration allows for long maintenance intervals.

Models are available with capacities to produce from 3700 liters fresh water per day up to 19,000 l/d. Energy consumption will be as low as 11 watt- hours per 3,7 l (1 gallon) in sea water applications and even lower in brackish water.

In conventional Reverse Osmosis systems the high pressure needed in the membranes is created and regulated by a back pressure regulating valve in the high pressure concentrate (brine) discharge line. All of the potential energy in the high pressure concentrate is lost in the back pressure regulator, and the power required to produce that energy is wasted.

This new developed pump is a positive displacement three cylinder reciprocating high pressure pump with the same motors and crankcases used in conventional RO system feed pumps. The pump head delivers water to the membranes in the same way as conventional feed pumps but is capable of recovering the energy in the concentrate. This is done by returning the concentrate to the pump at high pressure, where it flows into the pump cylinders on the undersides of the pistons, transferring its energy to the feed water being discharged to the membranes.

The energy recovered from the concentrate reduces the load on the pump motor, reducing the electrical consumption dramatically.

If the volume of the cylinder under the piston were the same as the volume of the cylinder above the piston all of the water being discharged from the pump could return to the pump and no pressure would be developed. However, part of the volume in the underside cylinder is taken up by the ceramic plunger, reducing the space available for the returning concentrate. Because feed water is being forced out of the cylinder by the upper side of the piston, and only a portion of that water will be able to return to the underside, a “Hydraulic Lock� is created, and flow is only possible if the water displaced by the plunger has somewhere else to go. Because the electric motor is forcing the piston upwards, and that water has no where to go, pressure begins to build up. When the pressure rises high enough water will be forced through the membrane as permeate and flow will begin.

The proportion of the feed water discharged by the pump which will permeate the membrane and become product water is fixed by the percentage of the volume of the underside cylinder taken up by the plunger. If the plunger takes up half the volume of the cylinder, then only 50% of the feed water discharged by the pump can return to the pump, and the other 50% must leave the system as permeate. Thus, this pump based system will be a fixed recovery ratio system, and the operating pressure will vary with pump speed, feed water salinity, and feed water temperature but the percentage of feed recovered as permeate will always be constant.

The pump is available in three fixed and different recovery ratios of 20%, 30% and 50%.

Conventional systems are constant pressure systems, where the back pressure regulator keeps the system at a fixed pressure, and the recovery ratio will vary according to operating conditions.

Because in a conventional system the energy in the concentrate is lost, recovery ratios and operating pressures must be kept as high as possible to reduce the concentrate flow rates to the lowest possible amount. This results in high concentrate densities and the resultant scaling and other problems related to high concentrate density. In a system using this pump, there is little difference in energy efficiency with different recovery ratios because nearly all the energy is recovered. This means that recovery ratios and operating pressures can be kept lower and antiscaling treatments reduced or eliminated, with resulting improvements in maintenance costs.