Geotextiles in sewage treatment plants (STPs) and water treatment plants (WTPs)
Geotextiles play a critical role in sewage treatment plants (STPs) and water treatment plants (WTPs) in India, providing functions like separation, filtration, reinforcement, protection and drainage. They are used in applications such as lining treatment tanks, protecting geomembranes, controlling erosion around plant infrastructure and stabilizing soil. Given the specific requirements of STPs and WTPs, particularly due to the acidic and alkaline nature of sewage and wastewater, geotextiles must meet stringent specifications for durability, chemical resistance, and performance.
Below is a detailed specification chart for geotextiles commonly used in STPs and WTPs in India, based on typical engineering requirements and standards. The specifications focus on nonwoven needle-punched geotextiles, which are widely used due to their filtration and drainage properties, as well as woven geotextiles for reinforcement. These align with Indian standards (e.g., IS 15351, IS 15909) and international norms (e.g., ASTM, ISO) adapted for local conditions.
Specification Chart for Geotextiles in STPs and WTPs in India
| Property | Nonwoven Needle-Punched Geotextile | Woven Geotextile | Test Standard | Remarks |
|---|---|---|---|---|
| Material | Polypropylene (PP) or Polyester (PET) | Polypropylene (PP) | – | PP preferred for high acid/alkali resistance in STPs/WTPs. PET for specific cases. |
| Mass per Unit Area (gsm) | 200–600 g/m² | 150–400 g/m² | IS 14716 / ASTM D5261 | 500 gsm PP nonwoven common for STP tank buffer layers. |
| Thickness (mm) | 1.5–5.0 mm | 0.5–3.0 mm | IS 13162 / ASTM D5199 | Thicker nonwovens for protection; thinner wovens for reinforcement. |
| Tensile Strength (kN/m) | 8–20 (MD/CD) | 20–100 (MD/CD) | IS 13162 / ASTM D4595 | Higher strength for woven geotextiles used in soil reinforcement. |
| Elongation at Break (%) | 50–100% | 15–25% | IS 13162 / ASTM D4632 | Nonwovens have higher elongation for flexibility in uneven terrains. |
| Puncture Resistance (N) | 1000–3000 N | 500–1500 N | IS 13162 / ASTM D6241 | Critical for protecting geomembranes in STP/WTP tanks. |
| Permeability (m/s) | 10⁻³ to 10⁻⁴ | 10⁻⁴ to 10⁻⁵ | IS 14324 / ASTM D4491 | Nonwovens allow higher water flow for drainage; wovens for separation. |
| Apparent Opening Size (AOS) | 75–150 µm | 150–300 µm | IS 14294 / ASTM D4751 | Ensures filtration without clogging in wastewater |
Recommended Steps to Obtain Specifications
- Start with BIS: Obtain IS 15351:2015 and IS 15909:2010 from the BIS website or regional offices for comprehensive geotextile standards tailored to STPs/WTPs.
- Check CPCB Guidelines: Review CPCB’s STP/WTP guidelines for environmental compliance requirements impacting geotextile selection.
- Engage with Textile Committee: For testing and certification, contact the Textile Committee to ensure geotextiles meet BIS standards.
- Collaborate with IGS: For technical insights, refer to IGS publications or consult experts through their network.
Additional Notes
International Standards: While BIS standards are primary, ASTM (e.g., ASTM D4595, ASTM D4491) and ISO standards are often referenced in Indian tenders for quality assurance.