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Wastewater math

Pounds Loading Formula for Wastewater Operators

Pounds per day from flow in MGD, concentration in mg/L and 8.34 lb/gal.

The formula

Formula

  • Find pounds per day

    lb/day = MGD × mg/L × 8.34

    WPI Formula/Conversion Table (2023), Printed page 4 of 10, Loading Rate, lb/day: Flow, MGD × Concentration, mg/L × 8.34 lb/gal

Open the Formula Sheet→

Worked example

Step by Step

Waste activated sludge flows at 0.08 MGD and contains 6,000 mg/L of solids. What is the solids loading in lb/day?

  1. Known Values

    Flow is 0.08 MGD and waste activated sludge solids concentration is 6,000 mg/L.

  2. Find

    Find the waste activated sludge solids loading in pounds per day.

  3. Check Your Units

    Flow is in MGD and concentration is in mg/L, matching the governed US-unit loading relationship.

  4. Choose the Relationship

    Loading = flow × concentration × 8.34.

  5. Put In the Values

    0.08 × 6,000 × 8.34

  6. Perform the Calculation

    480 × 8.34 = 4,003.2.

  7. Check the Units

    MGD × mg/L × 8.34 leaves pounds per day (lb/day).

  8. Answer

    4,003.2 lb/day

Answer: 4,003.2 lb/day

Practice

Try It Yourself

Practice this math in the Math Center, with hints and worked steps.

Practice Loading / PoundsLearn the Pie Wheel

More formulas

Other Wastewater Math

  • Detention Time Formula
  • Chemical Feed Rate Formula
  • Percent Removal Formula
  • Channel Flow Rate Formula
  • Tank Area Formulas
  • MGD to GPD Conversion

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