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Chemical Phosphorus Removal & Carbon Dosing Calculator

Alum / ferric dosing to meet TP limits, plus external carbon for denitrification · Built for tropical conditions & QCVN 14:2025 / QCVN 40:2025 / PERMENLHK 68

iWhat this tool does

Two coupled calculations on one page — the same chemical-dosing skid serves both:

Chemical P removal — your metal-salt dose, alkalinity consumption (with the nitrification gap few designers check), the chemical sludge you add, and the pump / tank you need.
External carbon dosing — the COD you must add when influent carbon can't drive denitrification to your TN target, and which commercial carbon source at what mass.

Regulatory trigger. Vietnam QCVN 14:2025/BTNMT (eff. 2025-09-01, Circular 05/2025) tightens TN/TP for municipal plants and QCVN 40:2025 (Circular 06/2025) does the same for industrial effluent. Indonesia's PERMENLHK 68/2016 caps TP in many sectors. Effluent targets are your permit values — the tool doesn't enforce them, it sizes the chemistry to reach whatever you enter.

Jar test required. Literature metal-to-phosphorus ratios are engineering starting points. Final doses must be confirmed by jar test on your actual wastewater — especially for effluent TP below 0.5 mg/L.

1Wastewater & effluent targets

Start from a regional profile, then adjust. Effluent targets = your permit, not ours.

Design flow Q m³/d

Wastewater temperature^[5] (26–34)°C

Influent BOD₅^[1][5] (150–250)mg/L

Effluent BOD₅^[1]mg/L

Influent TKN^[5] (30–50)mg/L

Effluent NH₃-N^[7]mg/L

Effluent TN target^[7] (≤ 15)mg/L

Effluent organic N^[1] (1–3)mg/L

Influent total P^[5] (4–8)mg/L

Effluent TP target^[3][6] (0.1–2)mg/L

Influent alkalinity^[5] (150–250)mg/L CaCO₃

Biological sludge^[5]kg TSS/d

Include nitrification alkalinity (plant nitrifies)

Allow ferrous (Fe²⁺) in chemical list

2Chemical P removal — your choice

Primary metal salt

Dosing solution strength^[8] (varies)% w/w

Me:P basis^[2][3][6]

Envelope: ratio set by your residual effluent TP (0.1→6.5 … ≥2.0→1.0) — the conservative basis. EPA mapping keys off % removal instead.

Solution density^[8]kg/L

Storage capacity^[1] (7–15)d

Commercial alum is the 14-hydrate (MW 594.4, 9.08 % Al) — the hydrate most design manuals assume.

Me : P ratio — how the tool picks it (advanced)

Stoichiometry says 1:1, but real dose is 2–6× because metal also reacts with alkalinity and organics. What actually sets the ratio is your residual soluble-P concentration, not removal %. Linear interpolation over published points:

Effluent TP (mg/L)	Me:P molar	Basis
≥ 2.0	1.0	MPCA [6]
1.0	1.5	MPCA low band [6] / EPA ≈80 % removal [2]
0.5	2.0	Springer [3]
0.3	3.0	Springer / EPA compromise [2][3]
0.1	6.5	Springer 6–7 [3]

Manual override:

Override Me:P ratio (leave blank = auto)

Alkalinity factor^[3] (150)g CaCO₃/mol Me

3External carbon for denitrification

N-assimilation convention^[1]

Simplified convention: N in sludge = 0.05 × BOD₅ removed. If you sized this plant in the aeration or A²/O tool (kinetic convention), switch above to keep the nitrogen numbers identical across tools.

Carbon source^[9]

COD / NO₃-N ratio^[9] (3.7–6.0)g/g

Internal recycle ratio R^[1] (100–400)% of Q

Aerobic-end DO^[1] (1–3)mg/L

Three numbers, three meanings. Literature quotes 2.86 / 3.70 / 5.0 g COD per g NO₃-N: 2.86 = theoretical electron-equivalent (no biomass); 3.70 = methanol including cell synthesis [1]; 5.0 = DWA-A 131 engineering value that also covers recycle DO, mixing loss and carbon availability [9]. This tool defaults to 5.0 — a design dose, not a stoichiometry demo. Dosing to 2.86 would under-feed by ~40 %.

Carbon-source COD equivalents (advanced)

Source	MW	COD eq. (g/g)
Methanol CH₃OH	32.04	1.50
Ethanol C₂H₅OH	46.07	2.08
Glacial acetic CH₃COOH	60.05	1.07
Sodium acetate anhyd. CH₃COONa	82.03	0.78
Sodium acetate trihydrate	136.08	0.47
Glucose C₆H₁₂O₆	180.16	1.07
Commercial blend	—	0.8–1.2 (product)

Blend COD eq. (if blend selected)

Results — chemical P removalSECTION A

Metal salt (product)

—kg/d

Dose as solution

—L/h

Chem. sludge added

—kg DS/d

Alkalinity make-up

—kg NaOH/d

Item	Value	Unit

Chemical comparison — every option on the same dutySECTION A

Metal salt	Product (kg/d)	Dose (mg/L)	Notes

Doses shown are commercial product at the metal content in the first column's formula (no solution dilution). All fall in common practice bands (alum 30–100, FeCl₃ 20–60 mg/L).

Results — external carbon dosingSECTION B

N to denitrify

—mg/L

COD required

—kg COD/d

Carbon (product)

—kg/d

Dosing pump

—L/h

Item	Value	Unit

Carbon-source comparisonSECTION B

Source	COD eq.	kg/d	mg/L	× per NO₃-N

Dosing room & instrumentationMAPPED TO OUR RANGE

Pumps are sized from the flow above; quantities are 2 duty + 1 standby per dosing line. Peristaltic pumps suit small-to-mid plants — above ~50,000 m³/d verify duty (large plants typically use diaphragm metering pumps, which we source on request).

Duty	Instrument / equipment	Spec / model	Qty

On TP / NO₃ online analyzers. Continuous PO₄ / NO₃ / NH₃-N / COD / TN analysers are not in our standard range. For small-to-mid plants the cost-effective route is a portable 6-parameter unit (MP230Pro-T) with a CR220 digester on a shift basis — roughly one-tenth the online cost. Where true online continuity is required we source it on your behalf at factory-direct price; under our transparent model you carry no sourcing mark-up.

Have this chemical-dosing list quoted at factory price

We quote dosing pumps, pH / ORP / DO / MLSS instruments and flow meters at the manufacturer's ex-works price — our margin comes solely from the export tax rebate, so you see exactly what the equipment costs. Or, if you already have suppliers, we handle only receiving payment, customs and rebate for a fixed service fee.

Request a quote for this duty ← Aeration Oxygen Demand

Response within 24 hours · Your inputs stay in your browser — nothing is uploaded.

Sources & parameter basis

Every default is traceable. Superscript codes refer to the list below; hover an input for its source and range.

[1]	Metcalf & Eddy / AECOM, Wastewater Engineering: Treatment and Resource Recovery, 5th ed., McGraw-Hill, 2014 — reactions, stoichiometry, methanol formula 2.47, assimilation 0.05 BOD, N in biomass 0.123.
[2]	U.S. EPA, Nutrient Control Design Manual, EPA/625/R-09/012, 2009 — Eq. 4-1/4-2, Al:P vs removal %, dosing-point guidance.
[3]	Springer, Treatment for Nutrient Reduction, Ch.13 (2016) — Me:P by residual concentration, 150 g CaCO₃/mol-Me alkalinity, sludge increments.
[4]	Manitoba NEWPCC, Nutrient Removal Study §13 — alum:P 9.6:1 (14-hydrate 594 g/mol), FeCl₃ 5.2:1.
[5]	SUPRA International, Indonesian municipal / industrial applications — tropical sewage 26–34 °C, alkalinity 150–250, TP 4–8, TKN 30–50.
[6]	Minnesota PCA, Phosphorus Treatment and Removal Technologies (wq-wwtp9-02, 2006) — Me:P bands by effluent P.
[7]	Vietnam QCVN 14:2025/BTNMT (Circular 05/2025, eff. 2025-09-01) & QCVN 40:2025 (Circular 06/2025); Indonesia PERMENLHK 68/2016 — effluent limit context.
[8]	Water-operator study guides — commercial alum 48.5 % solution, alkalinity consumption 0.45–0.55 mg/mg, 5.56 mg CaCO₃/mg Al.
[9]	DWA-A 131 (formerly ATV-DVWK) — denitrification 5 kg COD/kg NO₃-N engineering value.

On the C/N number. The tool defaults to the DWA-A 131 engineering value 5.0 g COD/g NO₃-N. Theoretical electron equivalent is 2.86 and methanol-with-synthesis is 3.70. We size to 5.0 because it covers internal-recycle DO, imperfect mixing and carbon bioavailability — and we show you all three in the results so you can see exactly what margin is applied and why.

Questions about a duty, a specification, or transparent sourcing? Contact our application engineers →