Technologies Available For Sewage Treatment

Innovations Driving Sustainability in India

India’s sewage treatment landscape is evolving rapidly, with over 72,000 million litres of wastewater generated daily from homes, industries, and institutions. Treating this volume effectively is vital to prevent pollution of rivers, where untreated discharge causes ecological damage costing ₹50,000 crore annually in health and environmental remediation.

Sewage treatment technologies range from simple, low-cost options to advanced systems that ensure high-quality effluent for reuse, aligning with CPCB norms for BOD below 20 mg/L and TSS under 50 mg/L. At SKF Elixer, our energy-efficient sewage treatment systems, including the Vulcan STP with AABR, empower users to achieve compliance and water conservation in diverse settings.

This blog surveys key sewage treatment technologies, their mechanisms, advantages, and applications in Indian contexts. Whether you’re a developer in Bengaluru planning a residential project or an industrialist in Vadodara seeking robust solutions, these options highlight pathways to efficient wastewater management with SKF Elixer’s tailored offerings.

Septic Tank: A Basic On-Site Solution

Septic tanks provide decentralized treatment for small-scale needs, common in rural homes and remote sites generating 1–5 KLD (kilolitres per day). A typical tank (2,000–5,000 litres capacity, costing ₹50,000–₹1 lakh) uses anaerobic digestion to settle solids and break down organics, reducing BOD by 30–50% (from 200–400 mg/L to 100–200 mg/L).

Process: Sewage enters the tank, where solids settle (sludge layer 500–1,000 kilograms over 2–3 years), and effluent flows to a soak pit. In a household of 5 people producing 500 litres daily, it handles basic solids but requires desludging every 2 years (₹5,000–₹10,000 cost).

Advantages: Low energy (zero power), simple installation in areas like village panchayats in Uttar Pradesh.

Limitations: Poor nutrient/pathogen removal (fecal coliform remains 10^6 MPN/100 mL), risking groundwater contamination affecting 10–20 nearby wells.

Oxidation Ditch/Lagoons/Ponds: Natural Aerobic Systems

These facultative systems use extended retention for natural degradation, suited for communities treating 10–100 KLD. An oxidation ditch (circular channel, 5–10 metres wide) or lagoons (1–2 hectares for 50 KLD) employ aeration and algae-bacteria symbiosis.

Process: Inflow mixes with activated sludge; aerators supply oxygen (1–2 kilograms O2/hour), reducing BOD to 20–50 mg/L over 10–20 days retention. A 50 KLD pond costs ₹5–10 lakh, treating sewage from a school with 500 students (50,000 litres daily).

Advantages: Low operational energy (0.2–0.5 kWh/KL, ₹20,000 yearly for 50 KLD at ₹5/kWh), natural polishing. In sunny regions like Rajasthan, algal growth aids nutrient uptake (phosphorus removal 50–70%).

Limitations: Large footprint (0.5–1 hectare), odour issues in urban areas like Chennai, and seasonal efficiency drops in monsoons.

Trickling Filter/Bio-Tower: Attached Growth Classics

Trickling filters use media beds for biofilm growth, ideal for 20–200 KLD in municipalities. A bio-tower (5–10 metres high, plastic media 200 square metres/cubic metre) costs ₹10–20 lakh.

Process: Sewage sprinkles over rocks/plastic (recirculation 1:1 ratio), biofilms degrade organics, achieving 80–90% BOD removal (to <30 mg/L). For a 100 KLD filter, airflow is passive, handling 100,000 litres daily with sludge yield 0.5 kilograms/kg BOD.

Advantages: Energy-efficient (no aeration blowers, saving ₹50,000 yearly), robust against load variations in hotels.

Limitations: Clogging in high-TSS sewage (200–500 mg/L), requiring pre-settling.

Rotating Biological Contactor (RBC): Mechanical Biofilm System

RBCs feature rotating discs (40–50% submerged) for alternating aerobic-anaerobic treatment, for 10–100 KLD. A unit with 1,000 square metres surface costs ₹15–25 lakh.

Process: Discs rotate at 1–2 rpm, biofilms oxidize BOD (85–95% removal), treating 50 KLD with power 0.5–1 kWh/KL. Sludge settles in clarifiers (100–200 kilograms monthly).

Advantages: Compact (50 square metres footprint), low sludge (30% less than ASP), suitable for labor camps.

Limitations: Mechanical maintenance (₹10,000 yearly for bearings), sensitivity to toxics.

EADOx – Electro Coagulation: Electrochemical Innovation

EADOx uses electric current for coagulation, targeting industrial sewage with metals/oils in 50–500 KLD. Electrodes (aluminium/iron) cost ₹20–40 lakh initial.

Process: Current (5–10 A/square metre) releases ions, flocculating TSS (90% removal) and phosphorus in 1–2 hours retention. For 100 KLD oily effluent, energy is 1–2 kWh/KL.

Advantages: Chemical-free, handles heavy metals (chromium <0.05 mg/L), quick startup.

Limitations: High power (₹50–₹1 lakh monthly), electrode replacement ₹20,000 yearly.

Activated Sludge Process – Extended Aeration (ASPEA): Aerobic Workhorse

ASPEA extends aeration for complete oxidation, common in 100–1,000 KLD urban STPs costing ₹50 lakh–₹1 crore.

Process: Air blowers supply oxygen (2 kilograms/hour for 100 KLD), MLSS 3,000–5,000 mg/L degrades BOD to <20 mg/L over 24–36 hours. Sludge recycle 50–100%.

Advantages: High efficiency (95% BOD removal), nutrient control in extended mode.

Limitations: High energy (1–1.5 kWh/KL, ₹1 lakh yearly for 200 KLD), sludge 0.8 kg/kg BOD.

Sequencing Batch Reactor (SBR): Batch Flexibility

SBR treats in batches (fill-react-settle-decant), for 50–500 KLD, ₹30–60 lakh.

Process: Cycles 4–6 hours, aeration/decantation achieves BOD <10 mg/L. Automation handles variable loads in apartments.

Advantages: Small footprint (30% less), flexible for resorts with seasonal inflow.

Limitations: Complex controls (₹10,000 yearly PLC maintenance).

Membrane Bio-Reactor (MBR): High-Quality Filtration

MBR combines biology with membranes (0.1–0.4 micron pores), for 50–1,000 KLD premium needs, ₹50 lakh–₹2 crore.

Process: Submerged membranes filter effluent to TSS <1 mg/L, BOD <5 mg/L, with air scouring.

Advantages: Superior quality for reuse (pathogens <10 MPN/100 mL), compact.

Limitations: Membrane fouling (cleaning ₹20,000 quarterly), high energy 1.5 kWh/KL.

Advanced Attached Growth Bio Reactor (AABR): SKF Elixer’s Efficient Choice

SKF Elixer’s Vulcan STP uses AABR, blending attached biofilms for robust treatment in 5–500 KLD, ₹5–50 lakh.

Process: Media (200–300 sqm/cum) supports stable biomass, degrading BOD 95% (<10 mg/L) in compact tanks. Low aeration (0.5 kWh/KL), sludge 30% less.

Advantages: Energy-efficient (saving ₹30,000 yearly for 50 KLD), odour-free, relocatable Stainless Steel modules (20-year life), nitrogen removal 80–90%.In a 100 KLD hospital setup, AABR reuses 90,000 litres daily for gardening, saving ₹1 lakh water bills, with minimal operator (2 hours daily).

Biological Treatment Methods: Core Principles

Biological methods dominate, using microbes to degrade organics:

• Aerobic: Oxygen-loving bacteria in ASPEA/MBR reduce BOD via respiration.
• Anaerobic: In septic tanks, methane-producing microbes handle solids.
• Attached vs. Suspended: AABR/RBC attach biofilms for stability, vs. ASP’s suspended sludge.

In India, biological systems treat 70% of STPs, with AABR’s low sludge (0.3–0.5 kg/kg BOD) cutting disposal ₹20,000 yearly.

Energy-Efficient Sewage Treatment Systems: Future Focus

Efficiency metrics: Power 0.5–1.5 kWh/KL; AABR leads with high oxygen transfer (30–40%), solar integration saving ₹50,000 in sunny areas. Modular designs reduce CAPEX by 20–30%.

Conclusion

Sewage treatment technologies offer varied tools for India’s wastewater needs, from basic septic tanks to advanced AABR in SKF Elixer’s Vulcan. Choose energy-efficient options for compliance and reuse.

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