Skip to main content
Calcimator

Wastewater Treatment Sizing Calculator

Size key components of an activated sludge wastewater treatment plant: aeration, clarifiers, aeration power, and sludge production.

Inputs

MGD
mg/L

EPA 40 CFR 133: domestic influent 200–300 mg/L; secondary effluent limit ≤30 mg/L

mg/L

EPA 40 CFR 133: secondary standard 30 mg/L monthly avg; advanced treatment <10 mg/L; reuse <5 mg/L

mg/L

Results

BOD Loading

2,085 lb/day

Aeration Power

60 HP

≈ 6 EV chargers

Required Efficiency92%
Clarifier Area1,250 ft²
Sludge Production2,419 lb/day
Aeration Volume277,778 gal
How to Use This Calculator
  1. Enter population served and per-capita daily flow (gpd).
  2. Set infiltration and inflow allowance and target effluent quality.
  3. Review design flow, treatment unit sizing, and required hydraulic retention time.

How the result changes with Design Flow

Design FlowBOD LoadingAeration Power
1020,850 lb/day600 HP
3572,975 lb/day2,099 HP
65135,525 lb/day3,897 HP
90187,650 lb/day5,395 HP

What each input means

Design Flow
Average daily wastewater flow in million gallons per day. Small community ≈ 0.1-1; medium city ≈ 5-20 MGD.
Influent BOD₅
Biochemical oxygen demand of raw wastewater per EPA secondary treatment standards (40 CFR Part 133). Typical domestic wastewater 200–300 mg/L. Industrial wastewater can range 500–2,000+ mg/L.
Effluent BOD₅ Target
Required effluent BOD concentration per NPDES discharge permit (40 CFR Part 133). EPA secondary treatment standard: 30 mg/L monthly avg, 45 mg/L weekly avg. Advanced treatment (nutrient removal): <10 mg/L.
Influent TSS
Total suspended solids concentration in raw wastewater. Typical domestic is 200-350 mg/L.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Design Flow = 1, Influent BOD₅ = 250, Effluent BOD₅ Target = 20, Influent TSS = 250 = 4 input(s) provided
  2. Calculate BOD Loading
    BOD Loading
    2085 = 2085
  3. Calculate Aeration Power
    Aeration Power
    60 = 60
  4. Calculate Required Efficiency
    Required Efficiency
    92 = 92
  5. Calculate Clarifier Area
    Clarifier Area
    1250 = 1250

Related Calculators

The questions that sit next to this one — chosen by subject, including calculators filed under a different category.

Civil Engineering

Storm Drain Sizing Calculator

Size storm drain pipes using the Rational Method for flow estimation and Manning's equation for pipe capacity. Selects nearest standard pipe size.

Civil Engineering

Water Demand Forecasting Calculator

Forecast future water demand based on population growth, per capita usage, and peak factors. Estimates required storage capacity.

Water Treatment

Sludge Volume Calculator

Estimate sludge production from water treatment including turbidity removal and chemical addition. Size lagoons and estimate disposal costs.

Civil Engineering

Beam Load Calculator

Calculate maximum shear, bending moment, and deflection for simply supported and cantilever beams under uniform or point loads.

More in Engineering.