A Detailed Guide to STP Outlet Norms Based on NGT's 2019 Order

National Green Tribunal's (NGT) - 2019 Order

STP Outlet Norms are essential in regulating the quality of treated sewage before it is discharged into water bodies, ensuring compliance with stringent standards set by authorities such as the National Green Tribunal (NGT). The NGT's 2019 Order, issued on April 30, introduced rigorous guidelines for sewage treatment plants (STPs) to safeguard cleaner, healthier water resources. This order focuses on regulating the quality of effluent discharged from STPs, specifically setting limits on parameters like Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Suspended Solids (TSS), and other harmful substances that can significantly impact water quality. The aim of these norms is to prevent pollution of India's rivers, lakes, and groundwater, improving public health and safeguarding ecosystems. For municipalities, industries, and other sewage-generating establishments, adhering to these standards is not just a legal requirement but a responsibility to minimize environmental damage.

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STP OUTLET NORMS

HECS Packaged Sewage Treatment Plants (STPs) are designed to meet these stringent regulations. These systems offer efficient wastewater treatment solutions, ensuring that the treated effluent is compliant with NGT’s outlet norms. With advanced filtration technologies and biological treatment processes, these plants reduce harmful pollutants and enhance the quality of discharged water, minimizing the risk of waterborne diseases and environmental damage.

Compliance with NGT’s 2019 STP outlet norms helps reduce the harmful effects of untreated sewage, which can lead to waterborne diseases and disrupt aquatic life. The updated guidelines emphasize advanced treatment methods, including tertiary treatment, to ensure that the treated water is safe for discharge into natural bodies. HECS Effluent Treatment Plants (ETPs) play a crucial role in achieving these standards, offering industries an efficient solution for treating industrial effluent and ensuring regulatory compliance. These plants integrate advanced processes such as chemical treatment, biological treatment, and filtration to effectively reduce contaminants.

Additionally, HECS Wastewater Treatment solutions contribute to sustainability by encouraging the reuse of treated effluent in industrial processes, agriculture, or landscaping, thereby conserving precious water resources. This move also encourages the use of water recycling technologies, allowing for the reuse of treated effluent, reducing the demand for freshwater, and supporting environmentally responsible practices.

Incorporating the latest norms is critical for industries and municipalities aiming to stay compliant with environmental laws, contribute to sustainability, and maintain public trust. Understanding these regulations and implementing effective sewage treatment systems, such as HECS Packaged Sewage Treatment Plants and Effluent Treatment Plants, will ultimately contribute to cleaner, safer water bodies, ensuring the long-term well-being of both the environment and the public.

Revised Effluent Discharge Standards for STPs

The NGT categorised sewage treatment standards by city type and discharge environment, recognizing the unique challenges in each scenario.

ParameterMega/Metropolitan CitiesClass I CitiesOther Cities/Deep MarineRural Areas
Outfall pH Range5.5-9.05.5-9.05.5-9.05.5-9.0
Biochemical Oxygen Demand (BOD)20 mg/L30 mg/L30 mg/L30 mg/L
Chemical Oxygen Demand (COD)50 mg/L100 mg/L150 mg/L150 mg/L
Total Suspended Solids (TSS)20 mg/L30 mg/L50 mg/L50 mg/L
Total Nitrogen (TN)10 mg/L15 mg/LNo LimitNo Limit
Total Phosphorus (TP)<1 mg/L (for ponds/lakes)1 mg/L1 mg/LNo Limit
Fecal Coliform (FC)Desired:100 MPN/100 mL;Permissible:230 MPN/100 mLPermissible:1,0 MPN/100 mLPermissible:1,0 MPN/100 mLPermissible:10,0 MPN/100 mL

What Do These Standards Mean?

1. Mega/Metropolitan Cities

Cities with populations exceeding 10 lakh (metropolitan) or 1 crore (mega) face the strictest limits, as these urban hubs contribute heavily to pollution and often lack natural dilution in water bodies.

2. Class I Cities:

Cities with populations over 1 lakh fall into this category. Standards are moderately relaxed compared to metropolitan cities but still maintain stringent controls.

3. Other Cities and Rural Areas:

Smaller towns and villages have slightly lenient norms, reflecting their typically lower sewage volumes and limited infrastructure.

4. Deep Marine Outfall:

Sewage discharged into oceans benefits from natural dilution, leading to more relaxed standards.

5. Why were these changes necessary?

Untreated sewage is India’s top water pollutant, affecting rivers, lakes, and groundwater. The revised norms aim to:

  • Protect aquatic ecosystems from nutrient overload caused by nitrogen and phosphorus.
  • Improve public health by reducing microbial contamination in downstream water supplies. Promote reuse of treated wastewater in irrigation, industry, etc.

FAQs on STP Outlet Norms

1. Why are the standards stricter for Mega Cities?

These cities produce the highest volume of sewage and often lack the natural dilution capacity to mitigate pollution. Stricter standards ensure better water quality downstream.

2. How do these norms affect marine discharges?

Marine outfalls have higher permissible limits due to the ocean’s natural dilution and higher capacity to absorb pollutants.

3. How do these norms affect rural areas?

Rural areas are subject to slightly relaxed standards due to infrastructure limitations. However, this approach helps them gradually adopt better practices and improve their treatment capacities without immediate economic strain.

4. Can treated wastewater be used for agriculture or industry?

Yes, treated wastewater meeting these standards can be reused for agriculture, industrial processes, or urban non-potable applications like gardening and cleaning. Advanced treatment can make the water safe for even more uses.

5. Are there any exemptions for smaller STPs or older facilities?

The NGT’s order requires uniform compliance from all STPs. No such exemptions are mentioned.

For further details on sewage treatment plant regulations and standards, we recommend consulting with the HECS Sales Experts.Our experts can provide personalized guidance and the latest updates on environmental regulations in India.

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Frequently Asked Questions​​

STP standards are guidelines that ensure wastewater is treated to safe levels before being released or reused. They focus on effluent quality (e.g., BOD, COD, TSS), design (e.g., retention time, aeration), and sludge management. These standards help protect the environment, and public health, and promote sustainable water reuse while ensuring compliance with local and international regulations.

An STP (Sewage Treatment Plant) is a facility that treats wastewater to remove contaminants before it is discharged into the environment or reused. Standards ensure the treated water meets environmental regulations, safeguarding public health and ecosystems.

Treated effluents must meet the following parameters:

  • BOD (Biochemical Oxygen Demand): ≤10-30 mg/L
  • COD (Chemical Oxygen Demand): ≤50-100 mg/L
  • TSS (Total Suspended Solids): ≤10-30 mg/L
  • pH: 6.5-8.5
  • Total Nitrogen: ≤10 mg/L (for sensitive areas)
  • Total Phosphorus: ≤1 mg/L (to prevent eutrophication)

Penalties may include:

  • Heavy fines from environmental authorities.
  • Suspension of industrial operations.
  • Legal actions and environmental damage liabilities.

STP outlet norms refer to the set of standards and guidelines that determine the quality of treated water before it is discharged from a Sewage Treatment Plant (STP) into the environment or reused.

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STP Outlet Norms – National Green Tribunal’s (NGT) 2019