MEP Analysis / Calculator

STP Size Calculator

Estimate sewage flow and BOD load from occupancy, then size the equalization, biological, filtration, chlorination, sludge and storage stages for Extended Aeration, SBR or MBBR — with standard blower and pump sizes at the end.

Flow & load inputs

Build up the design flow either from occupancy, or enter a known average flow directly.

Occupancy type Residential Apartment Villa / Independent House Hotel (with laundry) Hospital Office / Commercial School / Institutional Restaurant Mixed Use / Custom

Population (persons)

Water supply (LPCD)

Litres per capita per day

Sewage generation (%)

Share of water supply that returns as sewage

Average flow (m³/day)

Peak factor

Typical 2–3 for hourly peak

Raw sewage BOD (mg/l)

Treated BOD target (mg/l)

Design goal — for reference only, not a sizing input

 

Occupancy type auto-fills LPCD, sewage % and raw BOD — override any of them freely.

Treatment process

Pick a process — it sets typical retention times and air/sludge factors below, all editable.

Extended AerationSimple, robust, larger footprint

SBRSequencing Batch Reactor, compact cycles

MBBRMoving bed biofilm, smallest footprint

Design factors (auto-filled by process — edit as needed)

Equalization tank HRT (h)

Aeration tank HRT (h)

Clarifier / settling HRT (h)

MBBR media fill (%)

Air supply rate (m³ air / kg BOD)

Sludge yield (kg SS / kg BOD removed)

Sludge storage (days)

Sludge concentration (kg/m³)

Tank side water depth, SWD (m)

Length : width ratio

Treated water storage (h)

Chlorine contact HRT (h)

PSF loading rate (m³/m²/h)

ACF loading rate (m³/m²/h)

Chlorine dose (mg/l)

Chemical strength (% w/v)

Flow & load summary

–

Average flow, m³/day (KLD)

–

Peak flow, m³/hr

–

BOD load, kg/day

Treatment stage sizing

Stage	Basis	Volume / Area	Suggested dimensions

Dimensions assume a rectangular tank at the side water depth (SWD) and length:width ratio set above — round up to convenient civil dimensions on site. Filter areas are shown with an equivalent vessel diameter for FRP/MS pressure vessels.

Standard equipment sizes

Aeration blower

– m³/hr

≈ – CFM

Sludge transfer pump

– LPM

Empties sludge tank in ~30 min

Treated water pump

– LPM

Empties storage tank in ~30 min

Chlorine dosing pump

– LPH

At the dose & strength set above

These figures are typical planning values used in MEP design practice, not a specific published standard — confirm final sizing with your process design engineer and the equipment vendor's actual performance curves before procurement.