MBBR vs SBR vs MBR: Choosing a Sewage Treatment Plant for a Housing Society, Hotel or Campus

Sewage generation in Indian residential buildings is typically 80–90 % of water supply — about 100–135 litres per person per day. A 300-flat society at 4.5 persons per flat generates roughly 1,350 × 0.85 × 135 ≈ 155 KLD; the STP is sized for that with a peak factor built into the equalisation tank, not by multiplying everything by two. Hotels are sized per room (400–600 litres per occupied room per day including kitchen and laundry), hospitals per bed (450–600 L), offices per person (45 L per shift). Oversizing an STP costs money twice: in capital, and in a biological process that starves at low load and smells.

1. What will the treated water be used for?Flushing and gardening → MBBR or SBR is enough. Cooling-tower make-up, car wash or any visible-water use → MBR. Discharge to a drain under a tight consent → SBR or MBR.
2. How much space is there — really?Basement STPs in cities with 60–70 % of the theoretical footprint available → MBR. Ground-level plant with room → MBBR.
3. Who operates it?A facility-management contractor with one semi-skilled operator → MBBR. A plant with SCADA and a trained supervisor → SBR or MBR are fine.
4. What is the power situation?Frequent outages and DG-run hours → prefer MBBR; MBR membranes suffer when aeration stops for long.
5. Life-cycle cost, not quote priceAdd 15 years of power, chemicals, membrane or media replacement and manpower. MBBR usually wins on total cost; MBR wins where reuse value is high or land is priceless.

• Show me the design calculations: F/M ratio or surface loading, hydraulic retention time, aeration sizing, clarifier surface loading. If they cannot, walk away.
• What is the guaranteed outlet — BOD, COD, TSS, ammonia, faecal coliform — and at what inlet?
• What happens to the sludge? Where does it go, how often, who pays?
• What is the odour control design — covered tanks, biofilter, or nothing?
• How much operator time per day, and what training is included?
• Power consumption in kWh per m³ at design load, in writing.
• Reference plants of the same size running for more than three years, with contact numbers.

For most housing societies, campuses and hotels with normal reuse needs, a well-designed MBBR with tube-settler clarifier, pressure sand filter, activated carbon filter and chlorination gives the best combination of cost, robustness and outlet quality. Where space is the constraint, or treated water has a high-value reuse, MBR earns its premium. SBR sits between them and suits municipal and institutional plants with trained operators. What matters more than the acronym is the sizing, the equalisation, the aeration margin and the sludge plan — that is where 80 % of STP problems come from. See the sewage treatment plant page for the process description.