NF System Designer
A professional nanofiltration mass-balance tool that tracks monovalent (salt) and divalent (hardness) rejection independently, across single- or multi-stage (up to 3-stage) arrays with 4-, 8-, and 16-inch element sizing. Model net driving pressure, permeate quality, and finished-water hardness for well water, surface water, and scale-control softening applications, including a solver for the bypass blend needed to hit a target finished hardness.
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Our engineering team is actively designing and building this calculator's engine.
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For multi-stage arrays, non-standard feed chemistry, or antiscalant/scaling verification, our engineers can provide a detailed process audit.
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- Professional PDF engineering reports
- Full mass-balance and dual rejection analysis
- Metric / Imperial unit conversion
- Well water, surface water, and scale-control presets
NF System Designer
Nanofiltration mass-balance with selective monovalent/divalent (hardness) rejection tracking, up to 3-stage arrays, membrane-aging projection, and product-water blending — including a solver for the bypass flow needed to hit a target finished hardness.
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 — standard for hitting the 80-90% system recoveries common in NF softening.
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 application type; edit for a specific project. The "Aged" condition (toggle top-right) projects permeate TDS/hardness and required feed pressure at end of the stated membrane age — both monovalent and divalent passage increase by the same compounding rate.
Raw/pretreated water blended directly into the final product stream — the standard NF softening lever for hitting a target finished hardness economically without over-designing rejection. Leave flow at 0 to disable.
Back-solves the bypass flow (at current membrane-train performance, using the on-screen Day-1/Aged condition) needed to blend the membrane permeate up to a target finished hardness. Only valid for a target strictly between the membrane's own permeate hardness and the raw feed hardness.
| Stage | Elements | Recovery | NDP | Flux | Mono. Rej. | Div. Rej. | Perm. Flow | Perm. TDS | Perm. Hardness | Conc. TDS | Conc. Hardness |
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Engineering Methodology
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 the log-mean average shell-side osmotic pressure across the stage.
Monovalent and divalent salt passage are each independently temperature- and flux-normalized against the membrane's bench test-condition baseline, reflecting nanofiltration's defining selective-rejection behavior rather than reverse osmosis's uniform total-salt rejection.
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