Chlorine CT Value for Disinfection
Easydisinfectionchlorine
A contact tank holds a free chlorine residual of 2.0 mg/L for a contact time of 30 minutes. The CT value achieved is most nearly:
- A15 mg·min/L
- B30 mg·min/L
- C60 mg·min/L
- D120 mg·min/L
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Answer: C. 60 mg·min/L
CT is simply the product of residual concentration and contact time: CT = (2.0 mg/L)(30 min) = 60 mg·min/L. Disinfection credit tables are entered with this product, so halving the concentration and doubling the time gives the same credit.
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