RO recovery, rejection and concentration factor
Calculate system recovery, salt rejection and concentration factor from feed, permeate and concentrate flows and TDS readings.
Results
| System recovery | 70% |
|---|---|
| Salt rejection | 97% |
| Concentration factor | 3,33× |
| Concentrate flow | 3 m3/h |
| Estimated concentrate TDS | 6 527 mg/L |
At 70% recovery the concentrate carries salts at roughly 3,3× feed concentration. Single-stage arrays typically run 50–60%; 2:1 two-stage arrays reach 70–75% where the water chemistry allows.
Formula used
R = Qp ÷ Qf × 100
SR = (1 − TDSp ÷ TDSf) × 100
CF = 1 ÷ (1 − R ÷ 100)
Qc = Qf − Qp
TDSc = (Qf × TDSf − Qp × TDSp) ÷ Qc
- R
- system recovery, %
- SR
- salt rejection, %
- CF
- concentration factor, assuming complete salt rejection
- Qf
- feed flow, m3/h
- Qp
- permeate flow, m3/h
- Qc
- concentrate (reject) flow, m3/h
- TDSf/p/c
- TDS of feed / permeate / concentrate, mg/L
Straight mass balance around the membrane array, assuming steady state and TDS as a conserved lumped parameter. CF = 1 ÷ (1 − R) is the limiting case where the membrane passes no salt at all; at a real 97–99% rejection it runs a couple of percent high, and the honest concentrate figure is the TDSc row below it, which uses the salt actually measured. Concentrate TDS is an estimate; individual sparingly-soluble salts concentrate at their own rates — check saturation indices against the full analysis.
Equipment for this duty
Send the water analysis and duty point, and the branch confirms exact selections, pricing and lead times — usually within one working day.
Request a quoteResults are indicative engineering estimates based on standard formulas and typical assumptions. They are not a design service; confirm any design against a full water analysis and the relevant manufacturer’s data.