Water and wastewater · Worked step by step
How many pounds of chlorine for 0.5 MGD at 2 mg/L?
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The problem
You treat 0.5 MGD of water at a dose of 2 mg/L. How many pounds of chlorine per day?
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The written version, step by step
- 1
Write the numbers
flow = 0.5 MGD • dose = 2 mg/L
- Half a million gallons a day, so 0.5 MGD.
- We want 2 mg/L of chlorine.
- Then the usual 8.34.
Quick trick: 0.5 MGD is just half a million gallons a day. The decimal does not change the formula.
- 2
Multiply it out
pounds = 0.5 × 2 × 8.34 • pounds ≈ 8.3 lb/day
- 0.5 × 2 = 1.
- 1 × 8.34 = 8.34.
- So about 8.3 pounds of chlorine a day.
Quick trick: 0.5 times 2 is 1, so the answer is just the 8.34. Handy shortcut.
Remember this for good
Pounds per day = flow (MGD) times dose (mg/L) times 8.34, even when the flow is a decimal like 0.5.
The pounds formula never changes: flow times dose times 8.34. A half-MGD flow just means multiplying by 0.5, which is the same as taking half.
Solve it fast next time
- Pounds per day = flow times dose times 8.34.
- A flow under 1 MGD is fine; 0.5 MGD just halves the result.
- Keep flow in MGD and dose in mg/L.
The answer: About 8.3 pounds per day.