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DW Distribution > Disinfection and Microbiology > Flashcards

Disinfection and Microbiology Flashcards

1
Q

Characteristics of chlorine gas.

A
  • Greenish yellow gas
  • Non flammable
  • Heavier than air
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2
Q

One volume of liquified gas chlorine will produce this much volume of gas.

A

Approximately 460 volumes of gas

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3
Q

Turbidity can have these effects on disinfection

A
  • React to produce chlorine demand

- “Hid” bacteria and other micro-organisms from disinfection action

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4
Q

Method used to disinfect tank or reservoir walls

A

Spray or brush a 200 mg/L chlorine solution on the surfaces, and allow to react for 3 hours.

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5
Q

Steps to insure a proper bacteriological sample.

A
  • Allow the tap to run for 1-5 minutes in order to sample from the main
  • Do not rinse the sample bottle
  • Do not touch any part of the bottle that will come in contact with the sample
  • Do not overfill the sample bottle; fill approximately 80% full
  • Transport the sample immediately to the lab; store on ice if longer than one hour
  • Properly label the sample
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6
Q

Where to pick sample locations for coliform test.

A

Representative locations throughout the distribution system

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7
Q

Color reaction of chlorine and DPD

A

Pink to red

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8
Q

Minimum free residual chlorine to be maintained throughout the distribution system.

A

0.2 mg/L

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9
Q

Disinfection CT must be met before this.

A

The first customer tap

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10
Q

Disinfection CT

A

Disinfection concentration (mg/L) x contact time (minutes)

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11
Q

Characteristics of viruses

A
  • Smallest living organism
  • Cause of certain waterborne diseases such as hepatitis A and polio
  • May be more resistant to disinfection than coliform bacteria
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12
Q

Manner of reporting coliform bacteria in drinking water samples.

A

Coliform present of coliform absent

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13
Q

“Rule-of-thumb” for the disinfection of chlorine residuals

A
  • Hypochlorous acid is 100x more effective than hypochlorite ion.
  • Hypochlorous acid is 1000x more effective than mono chloramine.
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14
Q

Bacteria shapes

A
  • Bacillus- “rod”
  • Coccus- “ sphere”
  • Spirillum- “ cork screw”
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15
Q

When using solid chlorine tablets to disinfect water mains, the tablet should be placed here.

A

At the top of the pipe

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16
Q

This material reacts with chlorine to form THM’s

A

Organic material, especially humic material from decayed vegetation

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17
Q

Chlorine dose =

A

Demand + residual

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18
Q

The number of chlorine samples required each month is based on this.

A

Population size

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19
Q

Chlorine left after the demand has been met.

A

Chlorine residual

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20
Q

Minimum number of repeat samples required in response to a positive coliform result.

A

Minimum three repeat samples; one at the original tap, one at a tap “downstream,” and one at a tap “upstream”

21
Q

Free residual chlorine.

A

Hypochlorous acid + hypochlorite ion

22
Q

Indicates a positive fermentation tube during the coliform test.

A

Gas in the fermentation tube

23
Q

Sample volume collected and tested for coliform bacteria.

A

A 100 ml volume is tested for coliform bacteria; therefore at least 100 ml be collected in the sample bottle

24
Q

The presence of total coliform bacteria in drinking water indicates this:

A

Bacteria of intestinal or soil/vegetation origin, which may indicate the presence of disease causing microorganism

25
Q

The presence of fecal coliform bacteria in drinking water indicates this:

A

Bacteria that originate in the intestinal tract of humans or animals, indicating fecal contamination and may indicate the presence of disease causing microorganisms

26
Q

Relationship between E. coli and fecal coliform bacteria.

A

E. coli is a member of the fecal coliform group

27
Q

Able to live in the presence or absence of oxygen.

A

Facultative anaerobe

28
Q

Steps for disinfecting a distribution main before placing it into service.

A
  • Disinfect with chlorine at 50 mg/L for 24 hours. At least 25 mg/L must remain after the 24 hour period
  • Flush the main, and collect a bacteriological sample
  • When the bacteriological sample comes back “negative” the main can be placed into service
29
Q

Bacterium associated with the intestinal tract of animals or humans.

A

Enteric bacteria

30
Q

Define:

  • Disinfection

- Sterilization

A
  • Destruction of harmful or undesirable micro-organisms

- Complete destruction of all life

31
Q

Pathogenic

A

Disease causing

32
Q

Definition of coliform bacteria group.

A

All gram negative, rod shaped, non-spore forming, facultative anaerobic and aerobic bacteria able to ferment lactose to a gas within 48 hours at 35°C

33
Q

Types of coliform bacteria.

A
  • Fecal coliform bacteria, that live in the intestines of warm blooded animals and man
  • Non-fecal coliform bacteria, that live in soil and decaying vegetation.
34
Q

EPA approved methods for determining the presence of coliform bacteria in drinking water.

A
  • Multiple tube fermentation
  • Membrane filter method
  • Presence absence broth
  • MMO-MUG, Colilert
35
Q

Media used in the multiple tube fermentation test for coliform bacteria.

A
  • Presumptive step: Lauryl tryptose broth

- Confirmed step: Brilliant green lactose bile broth

36
Q

Chlorine and ammonia react to for this.

A

Chloramines

37
Q

Approved chemical disinfectants for public water systems.

A
  • Free chlorine
  • Mono chloramine
  • Ozone
  • Chlorine dioxide
38
Q

Field method for measuring chlorine residual.

A

DPD color comparitor

39
Q

Chlorine formulations used in the water industry.

A
  • Molecular chlorine: (gas) Cl2
  • Sodium hypochlorite: (liquid solution, bleach) NaOCl
  • Calcium hypochlorite: (solid) Ca(OCl)2
40
Q

Cl2 + H20 =

A

Hypochlorous acid (†) + hydrochloric acid (†) disinfectant

41
Q

Used dose chlorine bleach into water.

A

Hypochlorinator

42
Q

Action to take if routine bacteriological sample shows the presence of total coliform bacteria.

A
  • Initiate repeat sampling within 24 hours

- Tet positive sample for presence of fecal coliform or E. coli

43
Q

The pH effect when gas chlorine is added to water.

A

The pH may drop slightly

44
Q

Chlorine demand =

A

Dose - residual

45
Q

Requirement for bacteriological sample bottle.

A
  • Plastic or glass
  • Sterile
  • Contain dechlorination agent thiosulfate, also called “thio”
  • Protected with kraft paper or mailing tube
46
Q

Timing for bacteriological sampling.

A
  • Samples should be taken at the same time each month: for instance, on the first Wednesday of the month.
  • If multipule samples are required to be taken, they should be collected at different times during the month. For example, if three samples are collected, they could be collected during the first, second, and third week of the month.
47
Q

reason that a positive presumptive test must be confirmed.

A

Bacteria other than coliform can cause “false presumptive” results.

48
Q

These protozoa can produce cysts that are more resistant to disinfection.

A
  • Giardia sp.

- Cryptosporidum sp.

49
Q

The reaction of chlorine and organic material can have this effect on the taste and odor of the water.

A

Increase the taste and odor of the water

DW Distribution (8 decks)

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