Important note: The limit values mentioned in this article are compiled from typical ranges published in the SKKY as of 2026. For official reference, always refer to the current SKKY text published in the Official Gazette. Limits are periodically updated; receiving environments and local regulations may impose different values.
What is SKKY and What Does It Regulate?
The Water Pollution Control Regulation (SKKY) is the main regulation governing all wastewater discharges in Turkey, issued under the Environmental Law No. 2872. The first publication was in 1988, and it has been revised multiple times (most comprehensively: updates in 2004, 2010, 2018).
SKKY provides sector limit tables with 3 main annexes:
- Table 1: General parameters and receiving environment standards
- Table 5-25: Discharge limits by sector (food, textile, chemical, metal, automotive, etc.)
- Table 26-30: Urban wastewater, storage, septic tank standards
Receiving Environment Categories
| Category | Receiving Environment | Limit Stringency |
|---|---|---|
| Class I | High-quality water (drinking water basin) | Most stringent |
| Class II | Slightly polluted water (recreation, irrigation) | Stringent |
| Class III | Polluted water (suitable for transboundary dilution) | Moderate |
| Class IV | Highly polluted (industrial) | Loose |
| Marine | Open sea (long marine discharge) | Dependent on dilution rate |
| Sensitive Area | Protected lakes, coastal bays, wetlands | Very stringent + additional conditions |
Typical Discharge Limits by Sector
The following tables are summary information prepared from typical values of SKKY. For investment or facility design decisions, the current SKKY text in the Official Gazette should be taken as the basis.
Table: Urban Wastewater (Municipal Facilities)
| Parameter | < 10,000 PE | 10,000-100,000 PE | > 100,000 PE | Sensitive Area |
|---|---|---|---|---|
| KOİ (mg/L) | 160 | 125 | 125 | 75 |
| BOİ₅ (mg/L) | 40 | 25 | 25 | 15 |
| AKM (mg/L) | 60 | 35 | 35 | 25 |
| Total nitrogen (TN) | — | 15 | 10 | 10 |
| Total phosphorus (TP) | — | 2 | 1 | 1 |
PE: Person equivalent. In sensitive areas, nitrogen and phosphorus removal is mandatory.
Table: Food Sector (Meat, Milk, Beverage, Slaughterhouse)
| Parameter | 2-hour composite | 24-hour composite |
|---|---|---|
| KOİ (mg/L) | 250 | 200 |
| BOİ₅ | 100 | 50 |
| AKM | 100 | 80 |
| Oil-grease | 30 | 15 |
| Total phosphorus | 3 | 2 |
| pH | 6-9 | |
Table: Textile and Dyeing
| Parameter | Typical Limit |
|---|---|
| KOİ (mg/L) | 200-400 |
| BOİ₅ | 50-100 |
| AKM | 100-150 |
| Color (ADMI) | 280 (general) |
| Salinity (chloride) | Varies by receiving environment |
| Sulfur (Cr⁶⁺) | 0.5 |
| pH | 6-9 |
Table: Metal and Surface Coating
| Parameter | Limit (mg/L) |
|---|---|
| Chromium +6 (Cr⁶⁺) | 0.5 |
| Total chromium | 2 |
| Nickel (Ni) | 3 |
| Copper (Cu) | 3 |
| Zinc (Zn) | 5 |
| Cadmium (Cd) | 0.1 |
| Mercury (Hg) | 0.05 |
| Lead (Pb) | 2 |
| Total cyanide | 0.5 |
| Total oil-grease | 20 |
Table: Chemical and Petrochemical
- KOİ: 200-300 mg/L (depending on process type)
- BOİ₅: 50-100 mg/L
- Phenol: 1-5 mg/L (depending on sub-sector)
- Total cyanide: 0.5 mg/L
- Sulfite: 1-2 mg/L
- Active chlorine: 0.3 mg/L
- Total mineral oil: 10-20 mg/L
- Toxicity (fish test): Zero (LC50 test must be negative)
Table: Automotive and Industrial Washing
- KOİ: 250 mg/L
- AKM: 100 mg/L
- Oil-grease: 20 mg/L
- Mineral oil: 10 mg/L
- pH: 6-9
- Surfactant (detergent): 2 mg/L
General Limits Applicable to All Sectors
- pH: 6.0-9.0 (for all sectors)
- Temperature: Dependent on receiving environment <30-40 °C
- Color: Visually natural appearance
- Oil layer: Must not be present (visual test)
- Foam: No continuous foam
- Pathogen (urban reuse): E.coli < 100 CFU/100 mL (irrigation Class A)
Environmental Permit Process Steps
Every facility discharging wastewater is required to obtain an environmental permit under SKKY:
- Filling out the Wastewater Discharge Declaration Form
- Application for Wastewater Treatment Plant Project Approval
- Environmental Impact Assessment (EIA) — for large facilities
- Facility installation + inspection
- Obtaining the Environmental Permit Document (valid for 5 years, renewable)
- Integration of Online Monitoring (SEÇBİS) (for large facilities)
- Annual reporting and inspections
Penalties for Regulatory Violations and Risk Management
Violations of SKKY can lead to serious financial and operational consequences:
- Administrative fines (for each violation, Environmental Law Art. 20)
- Facility activity suspension (for repeated violations)
- Revocation of environmental permit
- Suspension of municipal OSB membership
- Imprisonment (intentional pollution — Environmental Law Art. 21)
- Loss of reputation + media impact + increase in insurance premiums
Trends After 2026
- Compliance with EU Water Framework Directive (WFD) — stricter nitrogen/phosphorus limits
- Monitoring of micropollutants — pharmaceutical residues, PFAS roadmap
- Water recovery incentives — mandatory in arid regions
- Expansion of online monitoring — SEÇBİS for every large facility
- Climate directive package — greenhouse gas monitoring (including N₂O)
Conclusion
SKKY is the initial specification for wastewater treatment plant investment. The receiving environment class, the additional table corresponding to the sector code, and the sensitive area rules should be evaluated together for proper design. The values in this article are summary; for every investment decision, the current SKKY text in the Official Gazette and the opinion of the local Environmental Provincial Directorate should be obtained.
Related guides: KOİ Removal, Nitrogen Removal, Phosphorus Removal, OSB Wastewater Facility. You can request consultancy from our Arsistek engineering team to analyze your facility's current discharge performance or to develop an SKKY compliance strategy.
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