Reverse osmosis mass-balance, temperature correction, and salt-passage performance for single- or two-pass, up-to-3-stage concentrate-staged array configurations, with membrane-aging projection and product-water blending.
2- and 3-stage arrays feed each stage from the prior stage's concentrate, raising overall system recovery beyond what a single stage can reach.
Re-pressurizes Stage 1's concentrate before it enters Stage 2, independent of the main feed pump — useful when this stage would otherwise run short on net driving pressure, especially at high recovery or aged-membrane conditions.
Re-pressurizes Stage 2's concentrate before it enters Stage 3, independent of the main feed pump.
Defaults follow the selected feed water type; edit for a specific project. The "Aged" condition (toggle top-right) projects permeate TDS and required feed pressure at end of the stated membrane age — the design should stay within spec at BOTH Day-1 and Aged conditions.
Pass 2's feed is Pass 1's blended permeate, re-pressurized by an interstage pump (modeled as Pass 2's own feed pressure). Common for high-purity applications (boiler feed, semiconductor, pharma) and RO+EDI trains.
Pass 2 feed is Pass 1's permeate (very low TDS), so this selects the 2nd-pass membrane's own bench baseline and aging defaults, not a feed-water fouling classification.
Fully independent of Pass 1's feed pressure — Pass 1's permeate arrives at Pass 2 already at atmospheric pressure (net of its own permeate back-pressure, effectively an atmospheric break tank), so this is the total pressure Pass 2's own booster pump must supply, not an addition on top of any Pass 1 residual.
Pass 2's final concentrate is already near permeate quality (it started from Pass 1 permeate), so recycling it into the raw feed instead of wasting it is standard practice and materially improves overall system recovery.
Optional raw/pretreated water blended directly into the final product stream to hit a target finished TDS without over-designing rejection. Leave flow at 0 to disable.
| Stage | Elements | Recovery | NDP | Osmotic P. | Flux | Rejection | Perm. Flow | Conc. Flow | Conc. TDS |
|---|
| Stage | Elements | Recovery | NDP | Osmotic P. | Flux | Rejection | Perm. Flow | Conc. Flow | Conc. TDS |
|---|
Inputs changed — click Calculate to refresh results above.
Powered by ATLAS WTS
Mass-balance and flux calculations follow the standard recovery-based form (Qp = Qf·Y), with net driving pressure derived from feed pressure less concentrate-side losses and feed osmotic pressure.
Salt passage is temperature- and flux-normalized against the element's bench test-condition baseline, with a concentration-polarization factor applied to estimate real membrane-wall salt passage.
Application
Scenario
Workflow
