Water & Desalination Design guide Choose between alternatives

Choosing an RO recovery rate without scaling the membrane

How recovery drives concentrate quality, and why pushing it higher trades water for scaling risk.

The engineering question

A higher recovery means more product water. What does it cost you, and where is the limit set by the membrane rather than by the pump?

Worked example

The figures below were produced by running the RO Recovery Calculator with the same inputs .

These figures are worked by the published method rather than executed at build time, because this tool is a self-contained page calculator without a programmatic engine.

Permeate flow is feed flow multiplied by the recovery fraction.
Concentrate is the remainder, and its concentration is what sets the scaling risk.
Antiscalant dosing and acid treatment extend the range but cannot remove it.

Sanity check

Permeate plus concentrate must equal the feed exactly. If it does not, a flow has been lost between the two.

Tools for this problem

These are the EngiMetric calculators that compute the numbers in this topic. Each one shows its formula, its units and its limits rather than returning a bare result.

Engineering review required

This topic supports professional engineering work; it does not replace a sealed design. The result depends on site data, the governing standard and engineering judgement, and should be confirmed by a competent engineer before it is built.

References & standards

DOWEX — RO membrane design guidelines
Hydranautics — membrane system design
Energy Recovery — ERD sizing