Reverse Osmosis Recovery Calculator

Work out reverse osmosis recovery instantly with clear inputs, formula shown and shareable results.

About Reverse Osmosis Recovery Calculator

Recovery is permeate divided by feed flow. Salt rejection is the fraction of dissolved solids kept out of the permeate, typically 97-99.5% for brackish water membranes. High recovery concentrates the reject stream — at 75% recovery the concentrate is four times feed salinity, which is where scaling risk arises.

Formulas

Recovery and rejection

Recovery % = permeate / feed x 100; rejection % = (feed TDS - permeate TDS) / feed TDS x 100

Concentration factor

CF = 1 / (1 - recovery)

Worked example

With the default values below, Reverse Osmosis Recovery Calculator returns Recovery of 75.000%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Feed Flowminimum 0 m3/h: 100 m3/h
Permeate Flowminimum 0 m3/h: 75 m3/h
Feed TDSminimum 0 mg/L: 1,500 mg/L
Permeate TDSminimum 0 mg/L: 45 mg/L

Results

Recovery: 75.000%
Salt Rejection: 97.0000%
Concentrate TDS: 5,865.00
Concentration Factor: 3.9100

Step by step

1Values used
2Recovery and rejection
3Concentration factor
4Recovery= 75.000
5Salt Rejection= 97.0000
6Concentrate TDS= 5,865.00
7Concentration Factor= 3.9100

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

What limits recovery?

Scaling of sparingly soluble salts — calcium carbonate, calcium sulphate, barium sulphate and silica — in the concentrate. Antiscalant dosing and acid addition raise the achievable recovery.

Why does permeate quality worsen at high recovery?

Because the average feed concentration along the array rises, and salt passage is proportional to concentration. The last element sees the most concentrated water and produces the poorest permeate.