Question 1004 of 229 · California Water Distribution Operator Exam
After the 24-hour contact period of the continuous-feed method, what free chlorine residual must remain in the main?
Exactly one answer is correct.
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Correct answer to question 1004
- B: At least 10 mg/L
Explanation
C651 requires that the heavily chlorinated water still holds at least 10 mg/L after 24 hours, which shows that the dose was not used up by demand. If it drops below 10 mg/L, the main is re-chlorinated.
More questions: Disinfection
- 1005Why should a new main be flushed before the disinfectant is added?
- 1006Heavily chlorinated water flushed from a main must be dechlorinated before it reaches a storm drain or creek. Which chemical is commonly used?
- 1007Approximately what percentage of available chlorine does calcium hypochlorite (HTH) contain?
- 1008Which form of chlorine is 100 percent available chlorine?
- 1009A chlorine dose of 3.0 mg/L produces a free chlorine residual of 0.8 mg/L after the contact time. What is the chlorine demand?
- 1010Which substances commonly create chlorine demand in a distribution system?