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Oxygen Transfer Design

Aeration Design

Calculate oxygen transfer, diffuser selection, and blower sizing for wastewater treatment systems.

SOTR/AOTR

Conversion

Diffuser Types

3 Types

Energy Analysis

kWh/kg O2

Cost Estimate

CAPEX/OPEX

Aeration System Design

Design diffuser system, blower sizing, and oxygen transfer calculations.

Quick Power Estimate

Power
8.2 kW
Daily Energy
196 kWh
Specific Energy
0.196 kWh/m³

Design Parameters

Tank Parameters

Oxygen Demand

Conditions

Oxygen Transfer Correction Factors

Diffuser Types Comparison

Fine Bubble

SOTE:25-35%
Alpha:0.4-0.8
Applications:

Activated sludge, deep tanks

Pros:

  • High efficiency
  • Low energy
  • Good for deep tanks

Coarse Bubble

SOTE:10-15%
Alpha:0.6-0.9
Applications:

Mixing, equalization, pre-treatment

Pros:

  • Low fouling
  • Simple maintenance
  • Good mixing

Mechanical Surface

SOTE:1.2-2.4 kg O2/kWh
Alpha:0.8-0.95
Applications:

Oxidation ditches, lagoons

Pros:

  • No diffuser fouling
  • Good for shallow basins

Key Design Factors

Alpha (α)

Wastewater correction factor

Typical:0.4-0.8 for domestic wastewater
αSOTE = OTE in wastewater / OTE in clean water

Beta (β)

Salinity correction factor

Typical:0.95-0.99 for domestic wastewater
Cs* = β × Cs (standard)

Theta (θ)

Temperature correction factor

Typical:1.024 standard value
KLa(T) = KLa(20) × θ^(T-20)

Fouling Factor (F)

Diffuser performance decline

Typical:0.65-0.90 over time
Actual SOTE = Design SOTE × F

Key Formulas

Oxygen Requirement

AOR = Q × (So - S) / (1000 × f)
+ 4.57 × Q × (TKNo - TKN) / 1000
- 2.86 × Q × (NOx) / 1000

SOTR from AOTR

SOTR = AOTR × (Cs,20 / (β × Cs,T - CL))
× (1 / α) × (1 / θ^(T-20))

Size aeration systems: convert standard oxygen transfer (SOTR) to actual field conditions (AOTR), select fine/coarse-bubble diffusers, size blowers with redundancy, and estimate energy cost.

ออกแบบระบบเติมอากาศ: แปลงค่าการถ่ายเทออกซิเจนมาตรฐาน (SOTR) เป็นสภาวะจริง (AOTR), เลือก diffuser แบบฟองละเอียด/หยาบ, เลือกขนาด blower พร้อมสำรอง และประเมินต้นทุนพลังงาน

When to use

  • Determining oxygen demand and blower capacity for an aeration basin
  • Comparing fine- vs coarse-bubble diffuser efficiency and energy
  • Sizing standby blowers for reliability

How to use

  1. 1Enter oxygen demand, basin depth, temperature and elevation.
  2. 2Choose diffuser type and α, β, F (fouling) factors.
  3. 3Read required SOTR, air flow, blower power and energy cost.

Key formulas

Field to standard transfer

AOTR = SOTR · [(β·C_s,T,H − C_L)/C_s,20] · 1.024^(T−20) · α · F

α = transfer factor; β = salinity/surface factor; F = fouling

Blower adiabatic power

P_w = (w·R·T₁)/(k₁·e) · [(p₂/p₁)^k₁ − 1]

k₁ = (k−1)/k, k≈1.395 for air; e = efficiency

AOTR derate

SOTR
100 kg O₂/h
α, β, F
0.50, 0.95, 0.90
T, C_L
28 °C, 2.0 mg/L

AOTR ≈ 100 · (0.95·7.8 − 2.0)/9.08 · 1.024^8 · 0.50 · 0.90 ≈ 26 kg O₂/h

References

  • • Metcalf & Eddy (2014), Wastewater Engineering, 5th ed., Ch. 5
  • • ASCE/EWRI 2-06 — Standard Guidelines for In-Process Oxygen Transfer Testing

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