Energy Recovery PX Q140 Pressure Exchanger

The Energy Recovery PX® Q140 Pressure Exchanger® is a positive-displacement energy recovery device for seawater reverse osmosis. It transfers pressure energy directly from the high-pressure reject brine stream to the incoming low-pressure feed through a single rotating ceramic rotor — with up to 98% peak efficiency and no gearbox, pistons or lubricating oil. Handling 90–140 gpm (20.4–31.8 m³/h) per device, the Q140 typically cuts SWRO energy consumption by around 60% compared with a throttled system.

Documentation & Drawings

System arrangement drawings

A 3D STEP model is available for system layout — request it here.

Technical Specifications

How the PX Pressure Exchanger Works

The PX uses a single ceramic rotor turning inside a sleeve. As the rotor spins, each duct is alternately opened to the high-pressure brine leaving the membranes and to the low-pressure feed entering the system. High-pressure brine pushes directly against the feed water inside the duct, transferring its pressure with almost no loss — then the duct rotates, the depressurised brine is flushed to drain, and the cycle repeats. Because the energy transfer is direct hydraulic displacement rather than a mechanical conversion, efficiency reaches 98% and the only moving part is the rotor itself.

In a typical SWRO train the high-pressure pump only has to supply the permeate flow; the PX handles the remaining feed by recycling energy from the brine. A small booster pump makes up the pressure differential across the device.

Watch the PX in Operation

Energy Recovery's animation shows the ceramic rotor cycle in operation — how high-pressure brine transfers its energy directly to the incoming feed water inside the rotor ducts.

Inside the PX Pressure Exchanger

The cutaway below shows the internal arrangement common to the PX range: the ceramic-alumina rotor and sleeve carried between two endcovers, with the low- and high-pressure ports at each end. There are no pistons, gears, timing belts or lubricating oil — the rotor is the only moving part, driven by the flow itself.

Where the PX-Q140 Fits

The PX-Q140 is specified on brine (concentrate) flow, not permeate — the pressure exchanger sits on the reject stream. ERI rates it for 90–140 gpm of brine at up to 1,200 psi, at 98% efficiency.

At the 40–45% recovery typical of seawater systems, one unit at full flow supports roughly 134,400–164,945 GPD of permeate (509–624 m³/day). That places a single PX-Q140 in resort and hotel complexes, small municipal supply, food and beverage process water, and containerised plants at the larger end of the range.

PX units are installed in parallel arrays, so larger plants simply use more of them — four PX-Q140 units cover about 2,035–2,498 m³/day on the same basis. Below 90 gpm of brine, step down to a smaller model rather than run this one under its minimum.

Capacity figures are indicative, derived from the rated brine flow at typical recovery. Actual output depends on your feed salinity, temperature, membrane configuration and recovery rate — send us your design conditions and we will confirm the model and the number of units.

Frequently Asked Questions

Specifications reproduced from Energy Recovery technical data sheet 80658-01 Rev 0. PX® and Pressure Exchanger® are registered trademarks of Energy Recovery, Inc. ERI reserves the right to make specification changes without prior notice; confirm critical values against the current data sheet before purchase.