Effluent discharge limits in Nigeria
Nigeria is the country where the question “what is the COD limit?” has no answer. NESREA regulates by sector, so the limit depends on what your factory makes.
Nigeria does not set one national industrial effluent standard. The National Environmental Standards and Regulations Enforcement Agency issues separate regulations for each industrial sector, each with its own Schedule I of effluent limitation standards.
For the chemicals, pharmaceuticals, soaps and detergents sector the verified limits are COD 40 mg/L, BOD₅ 20 mg/L, total suspended solids 10 mg/L, total oil and grease 10 mg/L and pH 6–9. A food or beverage plant, a tannery and a steel mill each face a different table.
Why there is no single Nigerian limit
The NESREA Act 2007 gives the Agency power to set standards, and it has done so through a series of sector regulations rather than one omnibus instrument. Each regulation carries its own Schedule I titled “Effluent Limitation Standards” for that sector alone.
The practical consequence for anyone specifying treatment: establish which regulation your facility falls under before designing anything. A number quoted to you as “the Nigerian limit” is either from a specific sector regulation that may not be yours, or from the older FEPA-era guidelines, or from nowhere at all.
Schedule I — chemicals, pharmaceuticals, soaps and detergents
Reproduced from the gazetted regulation. The Schedule states that these requirements are for direct discharge to surface water and that the liquid effluent should not be coloured.
| Parameter | Maximum permissible limit | Relevance to a flotation plant |
|---|---|---|
| Appearance | Colourless and odourless, not objectionable | Overdosed iron leaves a tint |
| Temperature increase | < 3 °C | Measured at the edge of the mixing zone, or 100 m from discharge where undefined |
| pH | 6–9 | Acidic coagulants consume alkalinity — watch the lower bound |
| Total suspended solids | 10 mg/L | Tight. DAF plus filtration |
| Total oil and grease | 10 mg/L | DAF’s core duty |
| COD | 40 mg/L | Requires biological treatment |
| BODâ‚… | 20 mg/L | Requires biological treatment |
| Total nitrogen as N | 10 mg/L | Nitrification and denitrification |
| Ammonia as nitrogen | 0.5 mg/L | Very tight |
| Chloride | 100 mg/L | Ferric chloride adds chloride — consider ferric sulphate |
| Sodium | 200 mg/L | Caustic dosing contributes |
| Sulphate | 100 mg/L | Alum and ferric sulphate add sulphate |
| Sulphide | 0.2 mg/L | Iron dosing precipitates as FeS |
| Free chlorine | 0.5 mg/L | Dechlorination may be needed |
| Fluoride | 1.0 mg/L | — |
| Phenol | 0.10 mg/L | — |
| Detergent as linear alkylbenzene sulphonate | 15 mg/L | Surfactants also destabilise the float |
| Iron | 2.0 mg/L | More headroom than South Africa’s 0.3 mg/L |
| Aluminium | Not stated in the gazetted table | See note below |
| Arsenic · Cadmium · Lead · Nickel | 0.1 mg/L each | Hydroxide precipitation |
| Chromium, total | 0.5 mg/L | Tannery and plating duty |
| Chromium VI | 0.01 mg/L | Reduce with ferrous sulphate, then precipitate |
| Copper | 1.0 mg/L | — |
| Cobalt | 0.5 mg/L | — |
| Manganese | 1.0 mg/L | — |
| Mercury | 0.01 mg/L | — |
| Molybdenum | 0.01 mg/L | — |
| Zinc | 5.0 mg/L | — |
| Total plate count | 10 MPN/100 mL | Disinfection required |
| E. coli | 0 MPN/100 mL | Disinfection required |
Which regulation applies to your facility
| Sector | Instrument | Status here |
|---|---|---|
| Chemicals, pharmaceuticals, soaps and detergents | National Environmental (Chemical, Pharmaceuticals, Soap and Detergent Manufacturing Industries) Regulations 2009 | Verified — published above |
| Food, beverages and tobacco | National Environmental (Food, Beverages and Tobacco Sector) Regulations — originally 2009, replaced by a 2023 instrument | In verification — the 2023 replacement must be read, not the 2009 version still widely circulated |
| Textiles, wearing apparel, leather and footwear | National Environmental (Textile, Wearing Apparel, Leather and Footwear Industry) Regulations | Scheduled |
| Base metals, iron and steel | National Environmental (Base Metals, Iron and Steel Manufacturing) Regulations | Scheduled |
| Mining and processing of coal, ores and industrial minerals | National Environmental (Mining and Processing of Coal, Ores and Industrial Minerals) Regulations | Scheduled |
| Pulp, paper and paperboard | National Environmental (Pulp and Paper, Wood and Wood Products) Regulations | Scheduled |
What this means for plant design
- Confirm your sector regulation in writing before sizing anything. The gap between sectors is large enough to change the process train.
- Suspended solids at 10 mg/L is tight. Flotation alone will not reliably hold it; plan for filtration behind the DAF.
- Coagulant selection is constrained from both directions. Chloride is capped at 100 mg/L and sulphate at 100 mg/L, so both ferric chloride and the sulphate-based coagulants contribute to a limit. On a high-dose duty, run the arithmetic on the anion before choosing.
- COD 40 mg/L and total nitrogen 10 mg/L require biological treatment. Flotation is the pretreatment stage that protects it.
- Ammonia at 0.5 mg/L is among the tightest figures in any African schedule and is a nitrification design problem, not a flotation one.
Source and verification
| Instrument | National Environmental (Chemical, Pharmaceuticals, Soap and Detergent Manufacturing Industries) Regulations 2009 |
| Parent act | National Environmental Standards and Regulations Enforcement Agency (Establishment) Act 2007 |
| Regulator | NESREA |
| Schedule used | Schedule I — Effluent Limitation Standards |
| Read directly on | 5 August 2026 |
| Source | NESREA gazetted regulation (PDF) · NESREA laws and regulations index |
Frequently asked questions
What is the COD limit for industrial effluent in Nigeria?
There is no single national figure. NESREA regulates by sector. For the chemicals, pharmaceuticals, soaps and detergents sector the limit is 40 mg/L COD and 20 mg/L BOD₅. Other sectors — food and beverages, textiles and leather, iron and steel, pulp and paper — each have their own regulation with a different Schedule I. Establish which regulation covers your facility before relying on any number.
Can a DAF meet Nigerian discharge standards alone?
For oil and grease at 10 mg/L, yes, with correct coagulation. For suspended solids at 10 mg/L, only with filtration behind it. For COD at 40 mg/L and total nitrogen at 10 mg/L, no — those require biological treatment, with flotation as the pretreatment stage protecting it from the FOG and solids load.
Which coagulant suits Nigerian limits?
The schedule caps chloride at 100 mg/L and sulphate at 100 mg/L, so both anions are constrained. On a high coagulant dose either can become the binding parameter. Polyaluminium chloride contributes less chloride per unit of metal than ferric chloride does, and the iron limit at 2.0 mg/L is comparatively generous. Run the anion arithmetic at your design dose before committing.
Do the 2009 food and beverage figures still apply?
No. That sector regulation has been replaced by a 2023 instrument, though the 2009 figures remain in wide circulation in consultancy documents and supplier literature. We have not published either set here until the 2023 text has been read directly.