Pretreatment Chemical Dose Calculator

Plan dosing for coagulants, disinfectants, and conditioners confidence. See mass, solution volume, and pump settings. Download results, verify assumptions, and document your work clearly.

Inputs

Used for exports and reporting.
Converted internally to m³/day.
For water, ppm ≈ mg/L.
% w/w needs density for volume conversion.
kg/L
Typical: 1.00–1.40 kg/L depending on chemical.
hours/day
Use < 24 if dosing only during operation.
×
Example: 1.05–1.20 for variability.
currency/kg
Leave 0 to skip cost output.
Calculate how much solution to add for stock mixing.
L
Used only when tank mode is enabled.
mg/L
Example: 50,000 mg/L = 5% as active.
Reset

Example data table

Scenario Flow Dose Strength Density Runtime Approx. Pump Setting
Coagulant feed 500 m³/day 25 mg/L 12.5% w/w 1.20 kg/L 24 h/day ~ 578.7 mL/min
Disinfectant feed 120 m³/hour 2 mg/L 10% w/w 1.10 kg/L 16 h/day ~ 181.8 mL/min
pH conditioning 35 L/s 15 mg/L 150 g/L 1.15 kg/L 12 h/day ~ 274.0 mL/min
Example pump settings are illustrative; calculate for your exact inputs.

Formula used

1) Convert flow to liters per day
L/day = (m³/day) × 1000
2) Active chemical required
Active (kg/day) = (L/day × Dose mg/L) ÷ 1,000,000
3) Apply safety factor
ActiveSF = Active × Safety Factor
4) Convert to solution mass and volume
Solution (kg/day) = ActiveSF ÷ Strength Fraction
Solution (L/day) = Solution (kg/day) ÷ Density (kg/L)
5) Pump setting from runtime
L/h = (L/day) ÷ Runtime (h/day)
mL/min = (L/h × 1000) ÷ 60
Strength fraction notes
For % w/w: Fraction = % ÷ 100
For g/L active: Fraction = (g/L) ÷ (Density × 1000)

How to use this calculator

  1. Enter your plant flow using any supported unit.
  2. Set the dose target from jar tests, SOPs, or design criteria.
  3. Provide chemical strength and density from the product sheet.
  4. Choose the daily pump runtime to match operating hours.
  5. Add a safety factor to cover variability and process drift.
  6. Click Calculate. Review kg/day, L/day, and mL/min outputs.
  7. Use Download CSV or Download PDF for records.

Professional guide

1) Why pretreatment dosing matters

Pretreatment chemicals such as coagulants, oxidants, and pH conditioners stabilize upstream water quality so downstream units run consistently. Under-dosing can reduce turbidity and organic removal, while over-dosing can raise sludge volumes, increase corrosion risk, and inflate operating cost. This calculator converts a dose target into daily mass, solution volume, and practical pump settings, helping teams document assumptions and repeat setups across shifts.

2) Key inputs you must verify

Flow and dose drive active demand: liters per day multiplied by mg/L sets the daily active mass. Strength and density convert that active requirement into solution liters per day, which is what dosing pumps deliver. Use current product data sheets and confirm density at site temperature. If strength is provided as g/L active, the tool converts it to a mass fraction using density.

3) Translating results to pump operation

Many plants do not dose for 24 hours. When runtime is reduced, the required feed rate rises, and the calculator outputs both L/h and mL/min to match common pump panels. For commissioning, compare calculated mL/min with a timed drawdown test to confirm actual pump calibration. Apply a safety factor when influent quality swings or when control feedback is limited.

4) Using dilution tanks safely

Some sites prepare a stock solution in a day tank to improve pumpability or reduce handling. The optional dilution section estimates how many liters of delivered chemical solution must be added to reach a target stock mg/L in a known tank volume. Always add chemical to water as specified by the manufacturer, provide mixing, and keep secondary containment available.

5) Quick performance checks

After setting the feed rate, verify process response with simple field indicators: pH, oxidation-reduction potential, turbidity, and jar testing trends. Track daily solution usage against the calculator’s L/day output; large gaps often indicate mis-set runtime, incorrect strength entry, or pump drift. Exporting a CSV or PDF report supports shift handover and audit-ready records.

FAQs

1) Is ppm the same as mg/L here?

For dilute aqueous systems, ppm is commonly treated as mg/L. If your liquid is not water-like or has high solids, confirm the appropriate conversion before relying on ppm equivalence.

2) Why does density affect liters per day?

Pumps deliver volume, but strength is a mass fraction. Density converts solution mass to solution volume, so the same active kg/day can require more or fewer liters depending on product density.

3) What safety factor should I use?

Many operators start with 1.05 to 1.20 when influent quality varies. Use the smallest factor that still maintains performance, and refine it after trending jar tests and process feedback.

4) How do I choose runtime hours?

Set runtime to the hours the dosing pump actually runs each day. If dosing is interlocked with flow or shift schedules, use that net time, not 24, to avoid underfeeding.

5) Can I enter strength as g/L active?

Yes. Select g/L active and provide density. The tool converts g/L into a mass fraction using density, then computes solution liters per day and pump settings from that fraction.

6) What does the dilution tank result represent?

It estimates how much delivered chemical solution to add to a tank to achieve a target stock mg/L as active. It does not replace manufacturer mixing instructions or safety requirements.

7) Why does my actual usage differ from the output?

Differences usually come from flow changes, incorrect strength entry, pump calibration drift, or intermittent runtime. Compare a measured daily drawdown against the calculated L/day and adjust inputs to match reality.

Tip: Always validate dosing with field measurements and safety procedures.

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