Interactive Wizard · 2026
STP Equipment Selection Wizard
Turn a plant capacity into a first-cut equipment schedule. Enter the STP capacity in KLD and the inlet BOD, and get recommended sizes for the blower, feed pump, aeration tank and clarifier — the mechanical core of every sewage treatment plant.
Key equipment sizes at a glance (native units)
Your plant
Design flow in kilolitres per day.
Typical domestic sewage ≈ 250–350 mg/L.
Recommended equipment schedule
First-cut mechanical sizing for a 100 KLD plant.
| Equipment item | Recommended size |
|---|---|
| Aeration blower — air delivery | 1.4 m³/min |
| Aeration blower — motor (indicative) | 0.8 kW |
| Raw sewage / feed pump (peak) | 6.3 m³/hr |
| Aeration tank volume (8 h HRT) | 33.3 m³ |
| Secondary clarifier — surface area | 4.2 m² |
| Average design flow | 4.2 m³/hr |
Key equipment sizes
Blower air, feed pump flow, aeration tank volume and clarifier area — each in its own native unit.
How this is calculated
- Average flow = capacity ÷ 24 = 4.2 m³/hr.
- Blower air — oxygen demand = capacity × BOD ÷ 1000 × 1.5 (≈1.5 kg O₂/kg BOD), converted to air at ≈8% transfer (0.28 kg O₂/m³ air) ÷ 1440 min = 1.4 m³/min.
- Feed pump = average flow × 1.5 peak factor = 6.3 m³/hr.
- Aeration tank = capacity × 8 ÷ 24 (8 h HRT) = 33.3 m³.
- Clarifier area = capacity ÷ 24 (surface overflow rate 24 m³/m²/day) = 4.2 m².
Indicative equipment sizing for concept planning. Final selection depends on the treatment technology, redundancy (standby units), altitude, diffuser type and vendor curves — confirm with a qualified consultant before procurement.
Related Guides — Deep-dive reading
Air Blowers & Diffusers in an STP: How Aeration Actually Works
The blowers that push air and the diffusers that turn it into bubbles are the lungs of your sewage treatment plant. Here is how they work, how they are sized, and why they decide most of your electricity bill.
Sewage Treatment PlantsHow to Size an STP: A Step-by-Step Method (With Worked Example)
The complete sizing methodology for a domestic sewage treatment plant — from headcount and LPCD to sewage generation, peak flow and tank-by-tank volumes — worked end to end with an Indian apartment example.
Sewage Treatment PlantsThe Sewage Treatment Process Flow, Explained: Every Stage From Inlet to Reuse
Follow a drop of sewage through a typical STP — inlet, screening, aeration, clarifier, filtration, disinfection and reuse — as one connected flow, with a block diagram and a unit-by-unit table, in plain language.
Sewage Treatment PlantsRelated Tools — You may also find these useful
Air Requirement Calculator
Estimate the process air an aeration tank needs — enter flow, inlet BOD, O2 demand factor and transfer efficiency to get O2 demand and blower air in m3/day and m3/min.
STP CalculatorSTP Tank Schedule & Layout Generator
Enter a sewage treatment plant's KLD capacity and instantly get a tank schedule — collection, equalization, aeration, clarifier, sludge and treated-water volumes plus total tankage and an approximate footprint for concept layout planning.
GeneratorApartment STP Planner
Plan an apartment complex sewage treatment plant from flats and occupancy — get population load, sewage flow, recommended STP capacity in KLD, treatment technology and approximate space.
Planner