The Energy Recovery PX-220 Pressure Exchanger® is a positive-displacement energy recovery device for seawater reverse osmosis, recovering pressure energy from the high-pressure reject stream through a rotating ceramic rotor. It handles 140 - 220 gpm (31.7 - 49.9 m³/h) of brine flow per unit with a minimum guaranteed efficiency of 96.8% at 45.4 m³/h.
Documentation
Technical Specifications
| Performance | |
| Service | Seawater reverse osmosis (SWRO) |
| Flow range per unit (brine flow) | 140 - 220 gpm (31.7 - 49.9 m³/h) |
| Minimum guaranteed efficiency | 96.8% at 45.4 m³/h |
| Operating principle | Positive-displacement rotary pressure exchange |
| Moving parts | One — the ceramic rotor |
| Configuration | |
| Installation | Modular — units run in parallel to serve larger trains |
| Applications | Pilot plants, brackish water, mobile and marine units, small to large SWRO plants |
| Identification | |
| Manufacturer | Energy Recovery, Inc. (San Leandro, CA) |
| Model | PX-220 (legacy) |
| Current equivalent | PX-Q220 |
| Source | ERI Desalination Products Catalog, PX performance chart |
Efficiencies are ERI minimum guaranteed figures based on their factory performance test standards, quoted at the stated mid-flow condition.
How the PX Pressure Exchanger Works
A ceramic rotor turns inside a sleeve. Each duct is alternately opened to the high-pressure brine leaving the membranes and to the low-pressure feed entering the system. The high-pressure brine pushes directly against the feed water inside the duct, transferring its pressure with almost no loss; the duct then rotates, the depressurised brine 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-220 Fits
Note: the PX-220 is a discontinued model. The capacity guidance below still applies to plants running one, but for a new system specify the PX-Q220, which covers the same duty at higher warranted efficiency.
The PX-220 is specified on brine (concentrate) flow, not permeate — the pressure exchanger sits on the reject stream. ERI rates it for 140–220 gpm of brine at up to 1,200 psi, at 96.8% efficiency.
At the 40–45% recovery typical of seawater systems, one unit at full flow supports roughly 211,200–259,200 GPD of permeate (799–981 m³/day). That places a single PX-220 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-220 units cover about 3,198–3,925 m³/day on the same basis. Below 140 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
Is the PX-220 still available?
What replaced the PX-220?
How many units do I need?
Can I get spare parts for it?
Specifications quoted from the Energy Recovery Desalination Products Catalog PX performance chart. PX® and Pressure Exchanger® are registered trademarks of Energy Recovery, Inc. ERI reserves the right to make specification changes without prior notice.
