How to Calculate Chemical Dosage for Wastewater Treatment After a Jar-Test
Assists wastewater treatment plant operators and Procurement teams in converting Jar-test results (mg/L) into actual chemical consumption based on treatment flow rate (m³/day). Automatically calculates daily and monthly quantities for purchase planning.
⚠️ Margin of error to note: The dosage shown by this tool is an industry-average reference value and does NOT replace an actual Jar-test. Influent wastewater quality (COD, color, TSS, pH, heavy metals, turbidity) varies between plants — even within the same industry — meaning the actual dosage may differ by 30–50% from the reference value. It is recommended to run a Jar-test with an actual wastewater sample from the plant before placing a bulk order.
🧪 Professional Chemical Dosing Calculator
Accurately calculates the quantity of COMMERCIAL PRODUCT required for order (not just the pure active substance) — segmented by industry, based on actual concentration & density per COA.
⚠️ This is the dosage of the PURE ACTIVE SUBSTANCE (Al₂O₃, Fe³⁺...), NOT the diluted commercial solution dosed. If your jar-test result is measured in mL of solution dosed per liter of wastewater, convert first: active substance dose = solution dose × concentration% (e.g. 150mg of 10% PAC solution/L × 0.10 = 15mg active substance/L). Entering the wrong basis here can cause an ordering error of up to 10x.
📐 Technical Calculation Formula (2 Layers)
Many tools only calculate the pure active substance — leading to UNDER-ordering, since industrial chemicals are never sold in 100% form. The Loc Thien tool calculates both layers in full:
Layer 1 — Pure Active Substance (Kg/day) = [ Flow rate Q (m³/day) × Dosage C (mg/L) ] / 1,000 Layer 2 — Actual Commercial Product (Kg/day) = Layer 1 ÷ Concentration % (per batch COA) Example: A textile dyeing plant with a flow rate of 1,500 m³/day, coagulating with FeCl₃ 36–40%, jar-test dosage of 200 mg/L:
- Layer 1 — pure active substance: (1,500 × 200) / 1,000 = 300 Kg/day.
- Layer 2 — actual FeCl₃ 40% product to order: 300 ÷ 0.40 = 750 Kg/day — not 300 kg as under-calculated in Layer 1.
- Monthly (30 days): 750 × 30 / 1,000 = 22.5 Tons/month.
⚠️ Skipping Layer 2 (concentration conversion) is the most common calculation error causing plants to under-order — particularly with NaOH/HCl 32% (under-ordering by ~3x) and Javen 10% (under-ordering by ~10x) when the pure active substance is mistaken for the commercial product.
📊 General Reference Specification & Dosage Range Table by Chemical
⚠️ Important note: This is a GENERAL technical reference dosage range (not segmented by industry), compiled from verified real-world case studies — NOT a legal QCVN standard (QCVN 40:2025/BTNMT — superseding QCVN 40:2011/BTNMT since Sept 1, 2025 — regulates pollutant concentration limits in wastewater DISCHARGED into the environment, not the dosage of chemicals added). When you select the correct Industry/Sector in the calculator above, the suggested dosage range will automatically narrow more precisely to that industry's characteristics — it may differ from the general range shown in the table below.
| Chemical | Specification / Concentration | Main Purpose | Recommended Dosage Range (ppm) | Shipping/Packaging Specification |
|---|---|---|---|---|
| FeCl₃ (Ferric Chloride) | Solution 38% – 40% | Coagulation, textile dyeing wastewater decolorization, Phosphorus removal, post-biogas livestock wastewater treatment | 100 – 400 mg/L | Tanker truck 5-30 tons, IBC 1000L |
| FeCl₂ (Ferrous Chloride) | Solution 30% | Cr⁶⁺ reduction in electroplating wastewater, Fenton/AOP, coagulation of livestock wastewater | 100 – 400 mg/L | Tanker truck 5-30 tons, IBC 1000L |
| PAC (Poly Aluminium Chloride) | Powder 30–31% / Liquid 10–17% | Coagulation-flocculation, sedimentation of wastewater & water supply, post-biogas livestock wastewater | 50 – 400 mg/L | 25kg bags, tanker truck 20-30 tons |
| NaOH (Liquid Caustic Soda) | Solution 32%, 45%, 50% | pH raising/adjustment, acid neutralization, CIP | 50 – 400 mg/L | Tanker truck 5-30 tons, 250kg drums |
| HCl (Hydrochloric Acid) | Solution 32% – 35% | pH lowering, scale removal, resin regeneration | 50 – 200 mg/L | Tanker truck 20-30 tons, 30L jerry cans |
| Javen (Sodium Hypochlorite) | Solution 10% – 12% | Disinfection of wastewater/water supply, textile bleaching, CIP | 2 – 200 mg/L | Tanker truck 5–30 tons, 30L jerry cans |
| Ca(OH)₂ (Lime Powder) | Powder 90% – 96% | pH raising, heavy metal precipitation (electroplating), coagulation support for post-biogas livestock wastewater | 100 – 600 mg/L | 25-40kg bags, truck delivery |
| FeSO₄ (Ferrous Sulfate) | Solution 30% / Solid 98% | Coagulation, Fenton/AOP, azo dye color removal in textile dyeing | 50 – 300 mg/L | Tanker truck 5-30 tons (liquid), 25kg bags (solid) |
❓ Frequently Asked Questions
What is a Jar-test?
A Jar-test is a small-scale simulation experiment (using jars/beakers) to determine the optimal coagulation/neutralization chemical dosage for an ACTUAL WASTEWATER SAMPLE from the plant, before applying it at full treatment-tank scale. This is a mandatory step in professional wastewater treatment plant operation, since each wastewater source has different characteristics.
Is the calculated chemical dosage 100% accurate?
No. The tool calculates an industry-average REFERENCE value, used for initial purchasing/logistics planning. The precise dosage for each plant depends on the characteristics of the influent wastewater (COD, color, TSS, pH, heavy metals) — only a Jar-test with an actual wastewater sample can determine the true optimal dosage.
Why do two plants in the same industry need different dosages?
Because the source of wastewater generation differs (input raw materials, production technology, waste-stream mixing ratio), resulting in different pollutant concentrations even within the same industry. This is why the dosage in the reference table has a fairly wide range (min–max), rather than a fixed number.
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