California Water Distribution Operator Exam, Disinfection: all 31 questions
All questions from the Disinfection section for California Water Distribution Operator Exam, each with the correct answer.
- 1001Why is a new or repaired water main disinfected before it is placed in service?
- 1002Under the AWWA C651 continuous-feed method, what is the minimum chlorine concentration in the new main at the start of the contact period?
- 1003Under the AWWA C651 slug method, which dose and contact time apply?
- 1004After the 24-hour contact period of the continuous-feed method, what free chlorine residual must remain in the main?
- 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?
- 1011The total chlorine residual equals which combination?
- 1012Which test is most often used by operators in the field to measure chlorine residual?
- 1013A sudden drop of chlorine residual at a dead-end hydrant most likely points to what?
- 1014Before a newly disinfected main is placed in service, what must the bacteriological samples show?
- 1015Which standard covers the disinfection of new and repaired water mains?
- 1016A well is most likely to need disinfection in which situation?
- 1017Which of the following is a common source of contamination of a water storage reservoir?
- 1018Chlorine gas is heavier than air. Where should an operator expect leaking gas to collect?
- 1019At which pH is free chlorine the most effective disinfectant?
- 1020Which form of free chlorine is the stronger disinfectant?
- 1021What chlorine to ammonia-nitrogen ratio, by weight, is typically targeted when making chloramines?
- 1022Which is an advantage of using chloramines instead of free chlorine in a distribution system?
- 1023Which problem is specific to chloraminated distribution systems?
- 1024Water that will be used for kidney dialysis or fish tanks needs special treatment when the system uses chloramines. Why?
- 1025On the chlorine dose curve, what is the breakpoint?
- 1026In a breakpoint chlorination curve, what makes up the residual after the breakpoint is passed?
- 1027What is the main cause of disinfection byproducts such as trihalomethanes in a distribution system?
- 1028Which AWWA standard covers disinfection of water storage facilities?
- 1029Which AWWA standard covers disinfection of wells?
- 1030Under 22 CCR 64580, what must be true of the bacteriological samples from a new water main before it is placed into service?
- 1031Which AWWA standard does 22 CCR 64582 require for disinfecting and bacteriological sampling of a distribution reservoir that was taken out of service for repair or inspection?