Effluent discharge limits in South Africa
South Africa runs a two-tier system — a General Limit and a much tighter Special Limit that applies where the receiving water is listed. Knowing which one your site falls under changes the treatment plant substantially.
Discharge of wastewater into a water resource under the General Authorisation is limited to COD 75 mg/L, suspended solids 25 mg/L, pH 5.5–9.5 and soap, oil or grease 2.5 mg/L. Where the discharge is into a listed water resource, the Special Limit applies instead: COD 30 mg/L, suspended solids 10 mg/L, pH 5.5–7.5, and soap, oil or grease 0 mg/L.
Discharging outside the General Authorisation conditions requires a water use licence rather than operating under general authorisation. Irrigation with wastewater is a separate regime again, with three volume tiers carrying different limits.
Table 2.1 — discharge into a water resource
| Substance / parameter | General limit | Special limit | Relevance to a flotation plant |
|---|---|---|---|
| Chemical oxygen demand (mg/L) | 75 | 30 | Requires biological treatment behind the DAF |
| Suspended solids (mg/L) | 25 | 10 | DAF plus filtration for the special limit |
| pH | 5.5–9.5 | 5.5–7.5 | General limit is generous; special limit is narrow |
| Soap, oil or grease (mg/L) | 2.5 | 0 | Tight. DAF is the process that gets you there |
| Faecal coliforms (per 100 mL) | 1,000 | 0 | Disinfection required |
| Ammonia, ionised and un-ionised, as N (mg/L) | 6 | 2 | Nitrification required |
| Nitrate / nitrite as N (mg/L) | 15 | 1.5 | Denitrification required for the special limit |
| Chlorine as free chlorine (mg/L) | 0.25 | 0 | Dechlorination may be needed |
| Electrical conductivity (mS/m) | 70 above intake, max 150 | 50 above background, max 100 | Coagulant choice contributes — see below |
| Ortho-phosphate as P (mg/L) | 10 | 1 median, 2.5 maximum | Iron dosing at the DAF handles this |
| Fluoride (mg/L) | 1 | 1 | — |
| Dissolved arsenic (mg/L) | 0.02 | 0.01 | — |
| Dissolved cadmium (mg/L) | 0.005 | 0.001 | Hydroxide precipitation |
| Dissolved chromium VI (mg/L) | 0.05 | 0.02 | Reduce with ferrous sulphate, then precipitate |
| Dissolved copper (mg/L) | 0.01 | 0.002 | Very tight |
| Dissolved cyanide (mg/L) | 0.02 | 0.01 | — |
| Dissolved iron (mg/L) | 0.3 | 0.3 | Tight — constrains iron coagulant overdosing |
| Dissolved lead (mg/L) | 0.01 | 0.006 | — |
| Dissolved manganese (mg/L) | 0.1 | 0.1 | — |
| Mercury and its compounds (mg/L) | 0.005 | 0.001 | — |
| Dissolved selenium (mg/L) | 0.02 | 0.02 | — |
| Dissolved zinc (mg/L) | 0.1 | 0.04 | — |
| Boron (mg/L) | 1 | 0.5 | — |
The dissolved iron limit is the one that catches people
Dissolved iron is capped at 0.3 mg/L under both the general and the special limit. That is tighter than most African jurisdictions — Kenya, for comparison, allows 10 mg/L.
The practical consequence: if you dose ferric chloride or ferric sulphate at a South African plant discharging to a water resource, residual iron becomes a compliance parameter rather than an aesthetic one. Overdosed iron that is not incorporated into floc passes the flotation cell in solution, and 0.3 mg/L is not much headroom.
- Dose to the jar-test optimum, not above it. Iron overdosing is expensive twice over here.
- Check pH — ferric hydroxide solubility rises sharply outside 5–9, and dissolved iron rises with it.
- Where phosphorus removal demands a high iron dose, verify residual iron in the treated effluent rather than assuming it.
- An aluminium coagulant carries no equivalent limit in Table 2.1, which is a point in favour of PAC where iron is not required for phosphorus or sulphide.
Irrigation with wastewater — three tiers
A separate and often cheaper route. The General Authorisation permits irrigation with domestic and biodegradable industrial wastewater at three volume tiers, each with its own conditions. Note that the limits get looser as the permitted volume falls.
| Parameter | Up to 2,000 m³/day | Up to 500 m³/day | Up to 50 m³/day |
|---|---|---|---|
| COD | 75 mg/L | 400 mg/L after removal of algae | 5,000 mg/L after removal of algae |
| pH | 5.5–9.5 | 6–9 | 6–9 |
| Suspended solids | 25 mg/L | — | — |
| Faecal coliforms | 1,000 per 100 mL | 100,000 per 100 mL | 100,000 per 100 mL |
| Ammonia as N | 3 mg/L | — | — |
| Nitrate / nitrite as N | 15 mg/L | — | — |
| Ortho-phosphate as P | 10 mg/L | — | — |
| Soap, oil or grease | 2.5 mg/L | — | — |
| Fluoride | 1 mg/L | — | — |
| Free chlorine | 0.25 mg/L | — | — |
| Electrical conductivity | 70 mS/m above intake, max 150 | 200 mS/m | 200 mS/m |
| Sodium adsorption ratio | — | 5 for biodegradable industrial wastewater | 5 for biodegradable industrial wastewater |
Both routes are conditional on the activity not impacting a water resource or another person’s water use, property or land, and on not being detrimental to public health and safety. Irrigation under this authorisation must be registered with the responsible authority.
What this means for plant design
- Establish which limit applies before designing anything. The gap between COD 75 and COD 30, and between suspended solids 25 and 10, is the gap between a conventional biological plant and one with tertiary filtration.
- Oil and grease at 2.5 mg/L general and 0 special is where flotation earns its place. From a food industry influent of 500–2,000 mg/L that is a 99.5%+ removal, which needs a properly dosed DAF and usually a polishing stage behind it.
- Check the irrigation route before assuming discharge. For a site under 50 m³/day with land available, the arithmetic frequently favours irrigation by a wide margin.
- Monitoring is weekly by grab sampling for substances added or concentrated by the industrial activity, analysed by a SANAS-accredited laboratory under the relevant SABS method or as approved in writing.
- Mining activities and associated infrastructure are excluded from the General Authorisation and require a water use licence.
Source and verification
| Instrument | Revision of General Authorisations in terms of section 39 of the National Water Act, 1998 |
| Citation | Government Notice 665, Government Gazette 36820, 6 September 2013 |
| Parent act | National Water Act 36 of 1998 |
| Regulator | Department of Water and Sanitation |
| Tables used | Table 2.1 (discharge into a water resource); section 2.7 (irrigation with wastewater) |
| Read directly on | 5 August 2026 |
| Sources | SAFLII consolidated text and the gazetted notice |
This page is a working reference, not legal advice. The current text of the law and your responsible authority’s reading of it take precedence. If you spot a discrepancy, tell us and we will recheck it.
Frequently asked questions
What is the COD limit for effluent discharge in South Africa?
75 mg/L under the General Limit for discharge of wastewater into a water resource, and 30 mg/L under the Special Limit where the discharge is into a listed water resource. Both are set in Table 2.1 of the General Authorisations under section 39 of the National Water Act. Irrigation with wastewater is a separate regime allowing up to 400 mg/L at 500 m³/day and up to 5,000 mg/L at 50 m³/day.
What is the difference between the general limit and the special limit?
The special limit applies where wastewater is discharged into a listed water resource — typically catchments identified as sensitive, particularly for phosphate. It is substantially tighter across almost every parameter: COD 30 against 75, suspended solids 10 against 25, oil and grease 0 against 2.5, and a narrower pH band of 5.5–7.5 against 5.5–9.5. Establish which applies to your receiving water before designing the plant.
Do I need a water use licence or can I operate under general authorisation?
General authorisation covers discharge within the Table 2.1 limits and within the stated volumes, subject to registration and to the activity not impacting the water resource or others. Discharging outside those conditions requires a water use licence. Mining activities and associated infrastructure are excluded from general authorisation regardless of quality.
Why is the dissolved iron limit a problem for coagulant selection?
Because 0.3 mg/L is tight, and iron coagulants leave residual dissolved iron when overdosed or when pH drifts outside the range where ferric hydroxide is least soluble. Where iron is genuinely needed — for phosphorus precipitation or sulphide control — dose to the jar-test optimum and verify residual iron in the treated effluent. Where it is not needed, an aluminium coagulant carries no equivalent limit in Table 2.1.
Is irrigating with wastewater cheaper than treating for discharge?
Often substantially, if you have the land. At the 50 m³/day tier the COD limit is 5,000 mg/L after algae removal, against 75 mg/L for discharge — a factor of roughly 67. Even at the 500 m³/day tier it is 400 mg/L. The constraints that bite instead are electrical conductivity at 200 mS/m and sodium adsorption ratio at 5 for biodegradable industrial wastewater, both of which are salinity issues rather than organic ones.