Lagoon aeration sizing calculator
Enter what you know about your primary cell. This returns a planning-level picture of what it is being asked to do, not an engineering design.
Short answer
Lagoon aeration is sized on pounds of BOD5 applied per day, not on surface acres. Multiply flow in MGD by influent BOD5 in mg/L by 8.34 to get pounds per day, then apply roughly 1.5 pounds of oxygen per pound of BOD5 as a planning factor. In partial-mix cells, mixing horsepower often controls the design instead.
How each number is calculated
| Output | Method |
|---|---|
| Organic load | Flow in MGD multiplied by influent BOD5 in mg/L multiplied by 8.34, the pounds per million gallons per mg/L conversion. |
| Areal loading | Organic load divided by primary cell surface area in acres. Compared against your own design value when you supply one. |
| Oxygen demand | Organic load multiplied by 1.5, the planning factor design references commonly use for pounds of oxygen per pound of BOD5 applied. |
| Nominal detention | Cell volume divided by daily flow. Nominal, because sludge accumulation and short-circuiting both reduce what you actually get. |
| Indicative energy | Oxygen demand converted to kilograms, divided by published transfer efficiency ranges. Diffused shown at roughly half of surface, per manufacturer estimates. |
| Equipment family | Guidance from cell depth and climate, following the selection logic in the aeration guide. Not a specification. |
Nominal detention is worth a second look. It is what the drawing gives you, and the gap between it and your effective retention is exactly what asludge survey measures.
Common questions
Can I use this to specify equipment?
No. This is a screening tool that turns your flow and BOD numbers into a planning-level oxygen demand range so you can have an informed conversation. On a permitted municipal system, your state design standards and a licensed engineer have the final word on what gets built.
Where does the 1.5 figure come from?
Design references commonly size oxygen supply at roughly 1.5 pounds of oxygen per pound of BOD5 applied. It is a widely used planning factor, not a universal constant, and site conditions including elevation, temperature and cell geometry move the real number.
Why does it ask for my design areal loading?
Because comparing your current loading to your own design value is far more meaningful than comparing it to a generic range. One EPA webinar case examined a pond designed for 22 pounds of BOD5 per acre per day that was receiving nearly 64, and it violated its monthly BOD limit about 75 percent of the time.
Why is mixing called out separately from oxygen?
In partial-mix aerated cells, the horsepower needed to keep the cell mixed often controls the design rather than the oxygen transfer. A system sized only on oxygen can look adequate on paper and still show dead zones, thermal streaking and sludge banks.
How accurate is the energy estimate?
It is indicative only. It applies published category efficiency figures to the calculated oxygen demand, and your manufacturer tested transfer numbers govern in reality. Use it to compare the shape of the two options, not to budget a power bill.
Read next
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