Wastewater math
Pounds per day of chemical to feed, including the product's purity.
The formula
lb/day = MGD × mg/L × 8.34 ÷ purity decimalWPI Formula/Conversion Table (2023), Printed page 2 of 10, Feed Rate, lb/day: (Dosage, mg/L × Flow, MGD × 8.34 lb/gal) ÷ Purity expressed as a decimal
Worked example
A plant treats 2 MGD at a chemical dose of 4 mg/L. Product purity is 65%. What is the feed rate in lb/day?
Flow is 2 MGD, dose is 4 mg/L, and product purity is 65%.
Find the chemical-product feed rate in pounds per day.
Flow is in MGD, dose is in mg/L, and purity can be written as a decimal.
Feed rate = dose × flow × 8.34 ÷ purity decimal.
4 × 2 × 8.34 ÷ 0.65
66.72 ÷ 0.65 = 102.65.
The final unit is pounds of product per day (lb/day).
102.65 lb/day
Answer: 102.65 lb/day
Practice
Practice this math in the Math Center, with hints and worked steps.
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