STP Capacity Calculator
STP Capacity Calculator — quick estimate
Estimate daily sewage generation and the right sewage treatment plant (STP) capacity in KLD for your building — and how much treated water you can reuse. Adjust the inputs, then get an engineered design.
Your building
Sewage ≈ water demand × return factor. STP capacity is rounded up to a standard size with a peak-flow allowance. CPCB / PCB norms apply for discharge & reuse.
Get an engineered STP design — free
Our team will size and specify the STP (SBR / MBBR / MBR), reuse network and PCB documentation for your project. We'll attach the estimate above automatically.
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Indicative estimates only — not a binding design. Actual STP sizing depends on occupancy pattern, inlet characteristics, technology and PCB consent conditions.
How this calculator works — and where it stops
What it calculates
The sewage-treatment-plant capacity in KLD for a building or campus, the standard plant size to specify, the treated water available for reuse and a suggested treatment technology.
Inputs
- Building type — residential, office, hotel, hospital, school, mall or factory
- Number of occupants
- Return factor — the share of water supplied that reaches the drain
Method
- Sewage flow = occupants × per-capita water demand for the building type (from 45 LPCD for offices, schools, malls and factories to 450 for hospitals, with 135 for residential and 180 for hotels) × the return factor.
- Applies a 1.1 peak factor and selects the next standard plant size from 5 to 1,000 KLD; reports 80% of the flow as treated water available for reuse; suggests MBBR up to 50 KLD, SBR or MBBR to 200 KLD, SBR or MBR above.
Assumptions
- The per-capita figures are the usual Indian design bases for the building type (the NBC and CPHEEO pattern); the return factor is the user's choice.
- Occupancy is the design peak, every day.
- Treated-water reuse at 80% assumes a dual-plumbing network exists to take it.
Limitations
- Process effluent, kitchens and laundries with high organic load, and hospital wards with special waste are not modelled — an ETP or a different design basis may apply.
- Discharge norms in the pollution-board consent, not the tool, decide the treatment train and the tertiary stages.
- Plant footprint, civil tank sizing and equipment selection are outside the tool.
Worked example
Produced by running this calculator with the inputs below.
Inputs
- Building type: office
- Occupancy: 600 people
- Return factor: 0.8
Working
- Per-capita demand for an office is 45 LPCD
- 600 × 45 × 0.8 = 21,600 L/day = 21.6 KLD of sewage
- Peak factor 1.1 → 23.8 KLD; next standard plant size is 25 KLD
- Treated water available for reuse: 80% of 21.6 = 17.3 KLD
Result. 25 KLD plant, MBBR (compact) at this scale, with about 17.3 KLD available for flushing and landscape reuse where dual plumbing exists.
How engineers use the result
To reserve the STP footprint and the consent-to-establish application at concept stage, and to check a proposed plant against the occupancy.
When a professional design must replace it
Before the consent application: the capacity is fixed from the water balance for the actual occupancy and reuse plan, and the process design to the consent's discharge parameters.
Got your number — what next?
A calculator gives you a first figure. These take it further.
The work itself
Read before you specify
The terms behind it
Delivered work with this scope
- MEPF for Advantec Wheels Alloy Plant, Jammu— Advantec Wheels
- Warehouse MEPF Delivered in Just 37 Days— client withheld
Need an exact BOQ, rate analysis or measurement sheet?
This is a quick engineering estimate. For tendering, billing or audit, our QS & estimation team prepares an item-wise BOQ, rate analysis and a verified measurement sheet to IS / CPWD norms — backed by 15+ years and ISO 9001:2015 quality processes.