Energy Recovery PX-90SB Low Pressure Exchanger

The Energy Recovery PX 90SB Pressure Exchanger® is a positive-displacement energy recovery device for brackish-water and low-pressure reverse osmosis. A single ceramic rotor transfers pressure energy directly from the high-pressure reject stream to the incoming feed, at up to 93% peak efficiency, handling 60 - 90 gpm (13.6-20.4 m3/h) per device. There is no gearbox, no pistons and no lubricating oil — the rotor is the only moving part.

Documentation & Drawings

Technical Specifications

How the PX Pressure Exchanger Works

A ceramic rotor turns inside a sleeve. Each duct is alternately opened to the high-pressure concentrate leaving the membranes and to the low-pressure feed entering the system. The high-pressure stream pushes directly against the feed water inside the duct, transferring its pressure with almost no loss; the duct then rotates, the depressurised stream is flushed to drain, and the cycle repeats. Because the transfer is direct hydraulic displacement rather than a mechanical conversion, efficiency is very high and the only moving part is the rotor.

Watch the PX in Operation

Where the PX-90SB Fits

The PX-90SB is specified on brine (concentrate) flow, not permeate — the pressure exchanger sits on the reject stream. ERI rates it for 60–90 gpm of brine at up to 400 psi, at 93% efficiency.

At the 70–80% recovery typical of brackish water, wastewater and reuse systems, one unit at full flow supports roughly 302,400–518,400 GPD of permeate (1,145–1,962 m³/day). That places a single PX-90SB in high-recovery BWRO for municipal and industrial supply, large-scale water reuse, and wastewater reclamation.

PX units are installed in parallel arrays, so larger plants simply use more of them — four PX-90SB units cover about 4,579–7,849 m³/day on the same basis. Below 60 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 the Energy Recovery technical data sheet for this model. 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.