Table of Contents
Residential complexes across India—gated communities, high-rises, and townships—house 50–5,000 families, generating 20,000–5 lakh litres of sewage daily. Treating this domestic wastewater on-site is mandatory under CPCB guidelines to prevent groundwater pollution and enable reuse for flushing, gardening, and cooling.
The best residential STP technology must fit tight spaces, handle variable occupancy, operate silently, and deliver odour-free performance at low cost. SKF Elixer’s Vulcan STP with AABR technology meets these needs in stainless steel modules from 5–500 KLD, making apartment sewage treatment reliable and sustainable.
This domestic STP plant selection guide details sewage characteristics, evaluation criteria, technology comparisons, and long-term economics. Whether you’re a developer planning a 300-unit society in Pune or an RWA upgrading a 100 KLD system in Noida, these insights ensure compliance, water savings, and resident satisfaction.
Role of Modern STPs in Sustainable Industry Practices
Modern STPs transform sewage from liability to asset:
- Water Conservation: Reuse 70–90% treated water for non-potable needs—flushing (40% of total demand), landscaping (50 litres/sqm green area), car washing. A 200-unit society reuses 1.5 lakh litres daily, saving ₹2–3 lakh yearly at ₹50–₹100/KL municipal rates.
- Groundwater Protection: Prevent 1 KL untreated sewage from contaminating 1 lakh litres aquifer. In Delhi-NCR, 60% borewells exceed coliform limits without STPs.
- Green Building Credits: LEED/IGBC points for 50%+ reuse; GRIHA rating adds 5–10% property premium (₹5–10 lakh per flat).
- Regulatory Compliance: Avoid ₹1–5 lakh fines + closure; NOCs mandatory for OC.
- Community Health: Eliminate mosquito breeding, waterborne diseases (20–30% reduction in diarrhea cases).
SKF Elixer’s AABR STP supports all five with compact, odour-free design.
Understanding Sewage Load in Residential Communities
Domestic sewage varies by occupancy, lifestyle, and water use:
- Per Capita Generation: 100–150 litres/person/day (CPCB).
- 4-member flat: 400–600 litres/day.
- 300-unit society (1,200 residents): 1.2–1.8 lakh litres/day (120–180 KLD).
- Peak Factor: Morning/evening spikes 2–3x average (e.g., 8–10 AM: 40% daily flow).
- Pollutant Load:
- BOD: 200–300 mg/L (40–60 grams/person/day).
- COD: 400–600 mg/L.
- TSS: 200–400 mg/L.
- Nitrogen: 30–50 mg/L.
- Phosphorus: 5–10 mg/L.
- Seasonal/Occupancy Variation: Vacant flats reduce load 20–30%; festivals increase 50%.
A 100 KLD STP for 600 residents must handle 1.5 lakh litres peak inflow with BOD <10 mg/L effluent for reuse.
Key Parameters to Evaluate Before Selection
- Space Availability:
- Basement: 0.4–0.6 sqm/KLD.
- Ground: 1–2 sqm/KLD.
- Treatment Efficiency:
- BOD <10 mg/L, TSS <10 mg/L, coliform <100 MPN/100 mL for flushing.
- Energy Consumption:
- 0.4–1.5 kWh/KL; ₹5–7/kWh = ₹40,000–₹1.5 lakh yearly for 100 KLD.
- Sludge Generation:
- 0.3–0.8 kg/kg BOD; disposal ₹10–20/kg.
- Odour & Noise:
- <50 dB, zero smell for resident comfort.
- Scalability:
- Phased occupancy: Add modules in 50 KLD increments.
- CAPEX + OPEX:
- ₹5–50 lakh + ₹1–3 lakh/year.
- Lifespan & Maintenance:
- 15–25 years; ₹10,000–₹1 lakh/year.
Comparing Compact STP Technologies for Apartments
MBBR (Moving Bed Biofilm Reactor)
- Footprint: 0.8–1.2 sqm/KLD (40–60 sqm for 50 KLD).
- Efficiency: 90–95% BOD (<20 mg/L).
- Energy: 0.6–0.8 kWh/KL.
- Sludge: 0.5–0.7 kg/kg BOD.
- Pros: Good shock load (150%).
- Cons: Media clogging, odour in open tanks, ₹20,000–₹30,000 yearly media replacement.
SBR (Sequencing Batch Reactor)
- Footprint: 1–1.4 sqm/KLD (50–70 sqm for 50 KLD).
- Efficiency: 90–95% BOD.
- Energy: 0.8–1.0 kWh/KL.
- Sludge: 0.6–0.8 kg/kg BOD.
- Pros: Batch flexibility.
- Cons: Decanting failures, high automation cost (₹30,000–₹40,000/year).
AABR (Advanced Attached Growth Bioreactor) – SKF Elixer Vulcan
- Footprint: 0.4–0.6 sqm/KLD (20–30 sqm for 50 KLD).
- Efficiency: 95%+ BOD (<10 mg/L), 80–90% nitrogen.
- Energy: 0.4–0.6 kWh/KL.
- Sludge: 0.3–0.5 kg/kg BOD (30% less).
- Pros: Shock load 200%, odour-free SS tanks, modular.
- Cons: None significant.
Winner for Apartments: AABR—half the space, 30% less energy/sludge, reuse-ready effluent.
Operation, Maintenance, and Cost Considerations
Capital Expenditure for 100 KLD Capacity
The initial investment for a 100 KLD MBBR system ranges from ₹25–35 lakh, covering aeration tanks, plastic media carriers (approximately 30–40 cubic metres at ₹500–₹700 per cubic metre), blowers, and mild steel or FRP construction with epoxy coating to resist mild corrosion over 10–12 years.
SBR systems require ₹25–45 lakh due to larger single-tank design, sequential decanters (₹3–5 lakh each), PLC automation panels, and additional piping for batch cycling, which increases structural reinforcement costs in basement installations.
In contrast, SKF Elixer’s AABR Vulcan STP costs ₹20–30 lakh, incorporating stainless steel tanks (SS304, 3–4 mm thickness), pre-fabricated synthetic media modules, fine bubble diffusers, and IoT-ready controls—delivering 20–25 year corrosion-free life and reducing foundation expenses by 15–20% through lighter modular weight (8–10 tonnes vs. 12–15 tonnes for SBR).
Annual Power Consumption for 100 KLD Operation
MBBR systems consume 0.6–0.8 kWh per kilolitre treated, translating to ₹60,000–₹80,000 yearly at ₹5 per kWh, primarily from coarse bubble aeration and media agitation pumps that maintain 30–40% media suspension in turbulent flow.
SBR units demand 0.8–1.0 kWh/KL due to cyclic high-intensity aeration during react phases and decanting pumps, resulting in ₹80,000–₹1 lakh annual electricity bills—exacerbated by 20–30% energy spikes during power failures requiring backup generators.
AABR optimizes at 0.4–0.6 kWh/KL through fine bubble diffusers achieving 30–40% oxygen transfer efficiency and low-head blowers, costing only ₹40,000–₹60,000 yearly; solar integration further cuts grid dependency by 50% in sunny regions, saving an additional ₹20,000–₹30,000.
Annual Maintenance Requirements
MBBR maintenance involves ₹20,000–₹30,000 per year for quarterly media cleaning to prevent clogging from biofilm overgrowth, blower servicing, and screen replacements—plus ₹10,000–₹15,000 in chemical dosing for odour control in open tanks.
SBR systems incur ₹30,000–₹40,000 annually due to PLC calibration, decanter mechanism lubrication, valve replacements, and frequent pump failures from sludge settling issues during power outages.
AABR requires just ₹10,000–₹15,000 yearly, limited to annual media visual inspection, blower filter changes, and lubricant top-ups—no moving parts like decanters or rotating media mean 80% fewer failure points, with IoT sensors providing predictive alerts to prevent downtime.
Annual Sludge Disposal Costs
MBBR generates 0.5–0.7 kilograms of sludge per kilogram of BOD removed, equating to 50–70 kilograms monthly for a 100 KLD plant at ₹15 per kilogram disposal cost (municipal or TSDF rates), totaling ₹40,000–₹60,000 yearly including transportation and dewatering chemicals.
SBR produces 0.6–0.8 kilograms per kilogram BOD due to higher biomass yield in batch cycles, resulting in 60–80 kilograms monthly and ₹50,000–₹70,000 annual expenditure.
AABR yields only 0.3–0.5 kilograms per kilogram BOD through stable attached biofilms and extended solids retention, producing 30–50 kilograms monthly and costing ₹25,000–₹35,000 yearly—30–40% savings that compound with compost revenue if converted to manure.
Annual Water Savings Through Reuse
All systems enable 70–90% water recovery, but AABR consistently achieves 90–95% with effluent quality of BOD below 10 mg/L and TSS below 5 mg/L, allowing reuse of 90,000 litres daily from 100 KLD inflow for flushing and gardening—saving ₹1.8–2.2 lakh annually at ₹50–₹60 per KL municipal charges.
MBBR and SBR typically recover 70–80% (70,000–80,000 litres daily) due to slightly higher residual BOD (15–20 mg/L), requiring tertiary filtration for full reuse and reducing savings to ₹1–1.5 lakh yearly.
Total Lifecycle Cost Over 15 Years for 100 KLD
MBBR totals ₹3.5–4.5 crore over 15 years when factoring CAPEX, escalating OPEX from media replacements every 5–7 years (₹3–5 lakh each cycle), and corrosion repairs in MS tanks.
SBR reaches ₹4–5 crore due to higher energy, frequent automation upgrades (₹2–3 lakh every 5 years), and structural cracking in concrete variants.
AABR lifecycle cost is ₹2.5–3 crore, driven by lower initial investment, 40–50% reduced power and sludge expenses, and zero corrosion in stainless steel—delivering ₹1.5–2 crore net savings, equivalent to funding two additional 50 KLD modules or achieving 6–8% ROI through water reuse alone.
Why AABR Technology Fits Best for Residential Projects
- Ultra-Compact: 25 sqm for 100 KLD—fits under staircase or parking.
- Silent & Odour-Free: <45 dB, enclosed SS tanks—no resident complaints.
- Phased Scaling: Start 50 KLD, add ₹5 lakh/module as flats sell.
- Reuse Excellence: <10 mg/L BOD → 90,000 litres/day for flushing (40% savings).
- Durability: 20–25 year SS life vs. 10–15 years FRP/MS.
- Automation: IoT app for RWA—real-time BOD/TSS, auto-alerts.
- Green Certification: 100% reuse qualifies for IGBC Platinum.
Conclusion
The best STP technology for residential area delivers space efficiency, low energy, minimal maintenance, and high reuse. SKF Elixer’s AABR Vulcan STP outperforms MBBR and SBR with 50% smaller footprint, 30% less power/sludge, and ₹1.5–2 crore lifecycle savings.
Choose AABR for sustainable, compliant domestic STP plants. Contact SKF Elixer today.
FAQs
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1. How much space does a 100 KLD residential STP require?
AABR needs 40–60 sqm (0.4–0.6 sqm/KLD) vs. 80–100 sqm (MBBR) or 100–140 sqm (SBR)—fitting basements/parking in high-rises.
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2. What is the daily sewage load for a 300-unit apartment?
1,200 residents × 135 litres/person = 1.62 lakh litres/day (162 KLD average); peak 2.5 lakh litres—design 200 KLD with 25% buffer.
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3. How much can water reuse save in a residential society?
90,000 litres/day reused for flushing at ₹80/KL municipal rate = ₹72 lakh/year savings for 100 KLD STP (90% recovery via AABR).
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4. Why is low sludge important for apartment STPs?
AABR yields 0.3–0.5 kg/kg BOD (30–50 kg/month for 100 KLD) vs. 60–80 kg in SBR—cutting disposal from ₹60,000 to ₹30,000 yearly at ₹15/kg.
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5. How does AABR ensure odour-free operation in residential areas?
Enclosed stainless steel tanks + bio-scrubbers + controlled aeration prevent H2S release—<45 dB noise, zero smell vs. open MBBR/SBR systems requiring deodorizers (₹20,000/year).
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