Chemical Dosing Calculator
Calculate PPM dosing, pump rates (LPH), chemical consumption & costs • Continuous & Batch Mode • Cooling Tower, RO, Boiler, ETP Applications
Calculate chemical dosing for continuous flow systems (cooling towers, RO feed, boiler feedwater). Enter flow rate in m³/hr.
Formulas Used
Continuous Flow Dosing:
\[ \text{Chemical Mass (kg/hr)} = \frac{\text{Flow (m³/hr)} \times 1000 \times \text{Target (ppm)}}{1,000,000 \times \text{Concentration (\%)}/100} \]
Where 1 ppm ≈ 1 mg/L for water-based systems.
Batch Tank Dosing:
\[ \text{Chemical Mass (kg)} = \frac{\text{Tank Volume (m³)} \times 1000 \times \text{Target (ppm)}}{1,000,000 \times \text{Concentration (\%)}/100} \]
Dosing Pump Rate (LPH):
\[ \text{Pump Rate (L/hr)} = \frac{\text{Mass Flow (kg/hr)}}{\text{Density (kg/L)}} \]
Chemical Cost:
\[ \text{Daily Cost} = \text{Mass (kg/day)} \times \text{Unit Cost (₹/kg)} \]
Chemical Dosing Calculator: Complete Guide for Water Treatment
Chemical dosing is a critical process in water treatment systems including cooling towers, reverse osmosis (RO) plants, boilers, and effluent treatment plants (ETP). This calculator helps you determine the exact chemical consumption, dosing pump rates, and operational costs.
Understanding PPM in Water Treatment
PPM (Parts Per Million) is the standard unit for measuring chemical concentration in water. For water-based systems, 1 ppm is approximately equal to 1 mg/L (milligram per liter) because the density of water is approximately 1 kg/L at standard conditions.
Applications of Chemical Dosing
- Cooling Towers: Biocides (0.5-5 ppm), antiscalants (2-10 ppm), corrosion inhibitors (5-20 ppm)
- RO Plants: Antiscalants (2-5 ppm), pH adjusters (10-100 ppm), biocides (0.5-2 ppm)
- Boilers: Oxygen scavengers (10-40 ppm), alkalinity builders (50-200 ppm), antifoams (1-5 ppm)
- ETP/WWTP: Coagulants (10-100 ppm), flocculants (0.5-5 ppm), pH adjusters (50-500 ppm)
Common Mistakes to Avoid
- Ignoring active concentration: A 30% HCl solution is not the same as pure HCl. Always divide by the concentration fraction.
- Confusing ppm with mg/kg: In water treatment, ppm is usually mg/L because water density ≈ 1 kg/L.
- Forgetting density: Suppliers sell by volume (L), but dosing pumps may be calibrated in mass (kg).
- Overdosing "just to be safe": This wastes chemicals and can cause scaling, corrosion, or environmental issues.
- Not accounting for dilution: In batch systems, ensure proper mixing time before measuring concentration.
Typical Dosing Ranges
| Application | Chemical | Typical ppm |
|---|---|---|
| Cooling tower — biocide | NaOCl / Isothiazolinone | 0.5 – 5 |
| Cooling tower — antiscalant | Phosphonate / Polymer | 2 – 10 |
| RO feed — antiscalant | Polyacrylate / Phosphonate | 2 – 5 |
| RO feed — acid (pH adjust) | HCl / H₂SO₄ | 10 – 100 |
| Boiler — oxygen scavenger | Sodium sulfite / Hydrazine | 10 – 40 |
| ETP — coagulant | Alum / Ferric chloride / PAC | 10 – 100 |
| ETP — flocculant | Polyacrylamide (PAM) | 0.5 – 5 |
Tips to Optimize Chemical Consumption
- Monitor residual concentrations: Use online analyzers or regular lab testing to maintain optimal levels.
- Calibrate dosing pumps monthly: Actual output often drifts due to wear, temperature, or pressure changes.
- Use stroke-length control: Fine-tune dosing rates rather than on/off control for better precision.
- Track daily consumption: Sudden changes can indicate leaks, theft, process upsets, or pump failures.
- Consider chemical compatibility: Some chemicals react with each other; dose at separate points if needed.
- Optimize pH first: Many chemicals work better at specific pH ranges; adjust pH before adding other chemicals.
Dosing Pump Selection Guide
When selecting a dosing pump, consider:
- Flow rate (LPH): Choose a pump with 20-30% higher capacity than calculated for flexibility.
- Pressure rating: Must exceed system pressure at injection point.
- Chemical compatibility: Ensure wetted parts (diaphragm, valves) are compatible with your chemical.
- Control type: Manual, timer-based, or proportional (4-20mA) control based on automation needs.
- Accuracy: Typical dosing pumps have ±2-5% accuracy; metering pumps offer ±1%.