Reverse Osmosis Rejection Rate Calculator
ANA›Life Services Authority›National Calculator Authority›Reverse Osmosis Rejection Rate Calculator
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Reverse Osmosis Rejection Rate Calculator
Calculate the rejection rate (removal efficiency) of a reverse osmosis membrane by comparing the solute concentration in the feed water versus the permeate (filtered output).
Feed Concentration (Cf)
mg/L (or any consistent unit)
Permeate Concentration (Cp)
mg/L (or any consistent unit)
Calculate Fill in the fields above and click Calculate.
function revCalc() { const resultDiv = document.getElementById('rev-result');
const cf = parseFloat(document.getElementById('rev-feed-conc').value); const cp = parseFloat(document.getElementById('rev-permeate-conc').value);
// --- Input Validation --- if (isNaN(cf) || isNaN(cp)) { resultDiv.innerHTML = 'Please enter valid numbers for both concentrations.'; return; } if (cf Concentrations cannot be negative.'; return; } if (cf === 0) { resultDiv.innerHTML = 'Feed concentration (Cₙ) cannot be zero (division by zero).'; return; } if (cp > cf) { resultDiv.innerHTML = 'Permeate concentration cannot exceed feed concentration. Please check your values.'; return; }
// --- Core Formula --- // Rejection Rate (R) = (1 - Cp / Cf) * 100 const rejectionRate = (1 - cp / cf) * 100;
// --- Observed Salt Passage --- const saltPassage = (cp / cf) * 100;
// --- Qualitative Rating --- let rating = ''; let ratingClass = ''; if (rejectionRate >= 99) { rating = 'Excellent (High-performance RO membrane)'; ratingClass = 'calc-good'; } else if (rejectionRate >= 95) { rating = 'Good (Standard RO membrane performance)'; ratingClass = 'calc-good'; } else if (rejectionRate >= 85) { rating = 'Moderate (Membrane may need inspection or replacement)'; ratingClass = 'calc-warn'; } else { rating = 'Poor (Membrane likely fouled, damaged, or at end of life)'; ratingClass = 'calc-error'; }
resultDiv.innerHTML = 'Rejection Rate (R): ' + rejectionRate.toFixed(2) + ' %' + 'Salt Passage: ' + saltPassage.toFixed(2) + ' %' + 'Performance Rating: ' + rating + '' + 'Feed: ' + cf + ' mg/L → Permeate: ' + cp + ' mg/L'; }
#### Formula
Rejection Rate (R) = (1 − Cp / Cf) × 100
Salt Passage (%) = (Cp / Cf) × 100
Where:
- Cf = Feed water concentration (mg/L or ppm)
- Cp = Permeate (product water) concentration (mg/L or ppm)
- R = Rejection rate expressed as a percentage (%)
Note: Salt Passage + Rejection Rate = 100%
#### Assumptions & References
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