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Water Distribution > Laboratory > Flashcards

Laboratory Flashcards

1
Q

What is a Maximum Residual Disinfectant Level (MRDL)?

A

Maximum measurement of disinfection allowed in order to prevent disinfection by-products

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2
Q

What is the MRDL for Chlorine, Chloramines, and Ozone?

A 
Chlorine = 4.0 mg/L
Chloramines = 4.0 mg/L
Ozone = 0.0 mg/L
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3
Q

What is the MRDL for Fluoride?

A
  1. 0 mg/L (Primary)

2. 0 mg/L (Secondary)

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4
Q

What is Modeling in relation to fluoride?

A

Drinking water with too much fluoride causes brown stains on teeth

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5
Q

What is the target fluoride range and optimum level?

A

Range - 0.6 mg/L - 0.8 mg/L

Optimum - 0.7 mg/L

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6
Q

How often must the water be tested for fluoride?

A

Once a day at representative sites

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7
Q

How often must samples be sent to the state lab for fluoride analysis?

A

One sample per month taken from a representative location in the distribution system and submitted to the state laboratory of hygiene. The sample submitted to the state laboratory of hygiene shall be a portion of a split sample so that the operator can determine the fluoride concentration with the operator’s equipment and compare it to the state laboratory results. The fluoride concentration obtained by the operator shall be noted on the data sheet prior to submission to the state laboratory.

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8
Q

Describe the sample container requirements for collecting fluoride samples

A

Glass/Plastic - State will send you bottle.
Rinse initially with distilled water
then rinse with sample water

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9
Q

What lab test is the chemical DPD used to detect?

A

DPD = N,N-diethyl-p-phenylenediamine

Chlorine & Chloramines

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10
Q

What lab test is the chemical SPADNS used to detect?

A

SPADNS = 4,5 Dihydroxyl-3-(p-Sulfophenylazo)-2,7-Naphthalene-Disulfonic Acid Trisodium Salt

Fluoride

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11
Q

What is the specific ion test used for?

A

calibrate to detect specific ion…. probably need more info this is vague

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12
Q

Describe the free chlorine residual test utilizing the DPD method

A 
Calibrate (Zero Out)
Add DPD reagent to bottle(powder)
Add sample
Shake
Test with pocket unit (is this a small spectrophotometer?)

Darker pink = more chlorine
Wavelength will identify Cl2 (530 nm)

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13
Q

Describe the Fluoride procedure test utilizing the SPADNS method

A

Absorbs fluoride and becomes a LIGHTER shade of red (opposite Cl2)

Compare to known fl- sample using a spectrophotometer.

Fl- = 580 nm

Temp of SPADNS, Temp of Sample, Temp of known sample should all be the same

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14
Q

What is the correct way to read a meniscus?

A 
Concave = Water meniscus
Convex = Mercury meniscus
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15
Q

Describe how to run a pH test

A

First add 7 buffer

Then add either 4 or 10 buffer depending on where you think the pH falls (this is called bracketing)
4 buffer if its between 0-7
10 buffer if its between 7-14

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16
Q

When and Where are the samples taken to determine trihalomethanes (THMs) and haloacetic acids (HAA5s)?

A

When - At the warmest water time of the year (August/September)

Where - At the site of the highest recorded THM and highest HAA5 site (if its the same site, use second highest for HAA5

17
Q

What is the MCL for THMs (trihalomethanes) and HAA5s (haloacetic acids) ?

A 
THMs = 80 ppb
HAA5s = 60 ppb
18
Q

What are the 5 methods used to determine the stability of water with respect to calcium carbonate saturation?

A
  1. Langalier Index (LI)
  2. Baylis Curve
  3. Ryznar Stability Index (RSI)
  4. Caldwell Lawrence
  5. AWWA Standards
19
Q

What (5) factors effect the Langalier Index and what does a positive/negative result indicate?

A
  1. Calcium Hardness
  2. Alkalinity
  3. Temperature
  4. pH
  5. TDS (Total Dissolved Solids)
Positive = Scale Forming
Negative = Corrosive (0 --> -2 only slightly corrosive; -3 and below corrosive)
20
Q

Describe the Baylis Curve and what areas above/below curve indicate?

A

pH v.s. Alkalinity (water stability)

stable water does not dissolve nor deposit calcium carbonate

Above curve = scale forming
Below curve = corrosive

21
Q

Describe coliform and pathogenic bacteria

A

Coliform = indicator, not harmful itself, found in intestines of humans/animals

Pathogenic = Harmful ex: Salmonella (Typhoid), Shigella (Dysentary), Vibriocome (Cholera); Cryptosporidium (parasite); Giardia Cyst (parasite)

Also harmful - Viruses

22
Q

Describe the MCL for coliform bacteria

A

Present - POSITIVE
Absent - NEGATIVE

No more than 1/40 or 5% of samples can be positive

If positive for fecal coliform with repeat sample, must have boil order

23
Q

How is the minimum number of routine monthly bacteriological samples of community water systems determined?

A

Proportional to population (according to table in NR809)

Some limits because Milwaukee, can’t do 500 samples

24
Q

Describe a good bacteriological sampling program

A

Aseptic - clean
Representative - flowing, fresh, not dead end
Varying times - not taken at same time every month
Acceptable faucets - don’t allow stuff to grow on them

25
Q

What is an ideal sampling point for bacteriological sample sites?

A
  1. Smooth faucet?? (Does this mean smooth flow??) maybe smooth nose faucet?
  2. Sanitary location
  3. Representative (Allow water to flow for a few seconds to get an accurate sample) I think. or representative location idk
26
Q

What types of faucets are NOT ideal for sampling?

A
  1. Swing faucet (like a kitchen sink) because it has “o” ring that will melt when heated with torch
  2. Aerated
  3. Threaded
  4. Screened
  5. Garden Hoses
  6. Bubblers
  7. Slop Sinks
27
Q

What are the sample container requirements used in collecting bacteriological samples taken from a CHLORINATED DISTRIBUTION SYSTEM?

A

Sterilized, 100 mL, contains sodium thiosulfate (aka Thio)

28
Q

What are the sample container requirements used in collecting bacteriological samples taken from a NON-CHLORINATED DISTRIBUTION SYSTEM?

A

Only needs to be sterilized

29
Q

What is the holding time for bacteriological samples?

A

Must get to lab in 24 hours

Max life of sample is 30 hours (6 hours to test)

30
Q

How are bacteriological samples stored when they cannot be used immediately?

A

In a fridge 40-50 degrees Fahrenheit or 4-10 degrees Celsius.
Cannot freeze or get too hot

31
Q

What labs in Wisconsin where bacteriological samples can be analzyed?

A

Some have their own CERTIFIED labs that have been approved by the Department of Health (Milwaukee)

Otherwise the State Lab of Hygiene for smaller communities

32
Q

What is the procedure when a sample has been deemed unsafe? (presence of bacteria)

A

Three repeat samples

  1. Retake same sample
  2. Take sample upstream within 5 service connections
  3. Take sample downstream within 5 service connections

Must be within 48 hours… or maybe 24?

If connected to a well, take a “triggered” sample of that well - only one time

33
Q

How many bacteriological samples have to be taken after a reservoir has been cleaned/repaired before it is put back in service?

A

one initial Bacti, and one 24 hours later

If it has at least 0.10ppm Cl2 in it, it can be put BIS before 2nd bacti

34
Q

What are the AWWA standards for placing Pipes and Tanks back in service after repairs?

A

C650??

C651 - Pipes - Disinfect with minimum of 50 ppm for 24 hours
C652 - Tanks - Same as Pipes OR 200 ppm for 2 hours, then overflow until it gets to 2 ppm. Then BIS

Water Distribution (8 decks)

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