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REHS > Water 2017 > Flashcards

Water 2017 Flashcards

1
Q

Define Action Level (AL)

A

the concentration of contaminant that, if exceeded, triggers treatment or other requirements that a water system must follow

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2
Q

Define MCL

A

maximum contaminant level
the highest level of a contaminant that is allowed in drinking water

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3
Q

What are primary MCLs

A

primary MCLs are set as close to the PHGs or MCLGs as is economically or technologically feasible
Most glaring contaminants

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4
Q

What are secondary MCLs?

A

set to protect the odor, taste, and appearance of drinking water
not directly hazardous to overall health

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5
Q

What is MCL G

A

MCL goal
the level of a contaminant in drinking water, below which there is no known or expected health risk
set by the EPA

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6
Q

What is the MRDL?

A

maximum residual disinfectant level
the level of disinfectant added for water treatment that may not be exceeded at the consumer’s tap

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7
Q

What is the MRDLG

A

maximum residual disinfectant level goal
the level of a disinfectant added for water treatment below which there is no known or expected health risk
set by US EPA

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8
Q

What is PHG?

A

Public health goal
level of contaminant in drinking water below which there is no known or expected health risk
Set by California EPA

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9
Q

What are Primary Drinking Water Standards?

A

MCLs and MRDLs for contaminants that affect health along with their monitoring and reporting requirements, and water treatment requirements

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10
Q

When was the Safe Drinking Water Act signed into law?

A

12/16/1974

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11
Q

What did the SDWA give the federal government authority to do? (3)

A

set national standards regulating the levels of contamination in drinking water
require public water systems to monitor and report their levels or identified contaminants
establish uniform guidelines specifying acceptable treatment technologies

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12
Q

What did SDWA give regulating authorities?

A

opportunity to assume primary responsibility for enforcing the new regulations

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13
Q

When did the amendments to SDWA occur and what did they achieve?

A

1986, 1996
deadlines for MCLs, more enforcements, etc

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14
Q

What causes algae blooms in water

A

pollution runoff - phosphate detergents, nitrate fertilizers, sewage
aka Eutrophication

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15
Q

What happens to the water composition after an algae bloom?

A

increase in nutrients = algae blooms
fish die and decompose to bottom creating oxygen loss
new oxygen produced by living algae towards surface

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16
Q

What are the three ages of a lake?

A

oligotrophic - young
mesotrophic - middle-aged
eutrophic - old/mature

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17
Q

What is coagulation?

A

chemical reaction that occurs when a coagulating chemical is added to water
most common - aluminum sulfate

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18
Q

How does coagulation work?

A

coagulant reacts with water and minerals in the water to form floc particles
neutralizes negative charge on suspended particles, forms larger clumps that are heavy enough to settle

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19
Q

What is flocculation?

A

process of slow, gentle mixing of the water to encourage tiny floc particles to clump together and grow to a size that will quickly settle
Flocculant particles at 1.5mm (1/16 inch) are usually heavy enough to settle within a few mins
Mechanical or hydraulic mixers

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20
Q

What is sedimentation?

A

process of holding the water in quiet, low-flow conditions so suspended matter and particles can be settled out by gravity to the bottom of the tank and removed as sludge
this is the final step in pretreatment prior to filtration

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21
Q

What is the purpose of sedimentation?

A

remove as much of the flocculent and other suspended material as possible before water flows to the filters

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22
Q

Describe a slow sand filter

A

variation of gravity filtration
uses biological processes as well as physical straining
simple, cost effective
suitable for small communities

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23
Q

What is the top layer of grime in a slow sand filter referred to as?

A

Schmutzdecke

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24
Q

What is a rapid sand filter?

A

much greater water treatment filtration rate and the ability to clean automatically using back washing
complete filtration cycle occurs sequentially

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25
Q

How do bag filters work?

A

particulates are trapped inside the bag for quick disposal

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26
Q

When are bag filters used?

A

they are a convenient and economical choice for applications that require gross particulate removal

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27
Q

How are bag filters typically available?

A

for low flow
come in welded styles
multiple micron removal efficiencies

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28
Q

When are reverse osmosis filters used?

A

when mineral-free water is the desired end product

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29
Q

How do reverse osmosis filters work?

A

most mineral constituents of water are physically larger than water molecules
they are trapped by the semi-permeable membrane and removed from the drinking water

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30
Q

What do reverse osmosis filters remove?

A

salt
lead
manganese
iron
calcium
fluoride
arsenic

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31
Q

Define disinfection

A

the selective destruction or inactivation of pathogenic organisms

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32
Q

What are the four types of disinfection in drinking water?

A

chlorine
ozone
UV light
boiling

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33
Q

What does ozone remove?

A

iron
bacteria/viruses
hydrogen sulfide
manganese

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34
Q

What is significant about free available residual chlorine?

A

chlorine in this form has the highest disinfecting ability

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35
Q

What is breakpoint chlorination?

A

process of adding chlorine to water until the chlorine demand has been satisfied

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36
Q

What happens if additional chlorine is added after the breakpoint chlorination?

A

results in free available chlorine residual that is directly proportional to the amount of chlorine added beyond the breakpoint

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37
Q

What is the water table?

A

zone of saturation of groundwater
easy to find in flat areas, harder to find in hills

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38
Q

What is an artesian well?

A

well bored into aquifer that has enough pressure to bring water to surface without pump

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39
Q

What are the ground levels in relation to groundwater? Descending order

A

aeration zone
saturation zone
impervious rock
aquifer water

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40
Q

What is significant about aquifers in relation to the world’s water supply?

A

97% of world’s fresh water
water percolates at 3ft/yr into aquifer

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41
Q

What is a cone of depression?

A

caused by overdrilling of an aquifer
creates a cone at the top of a well

42
Q

What is a case driven well?

A

best type for quality
solid casing installed with perforation at bottom of aquifer
large kinetic hammer drives casing into ground past point of saturation
well uses submergible pumps
requires 50’ seal (for public water supply, 20’ domestic in CA)

43
Q

What is a bored well?

A

Use earth augers
depth is limited to length of auger used

44
Q

What is a dug well?

A

manually dug by man, machine
finished well lined with concrete, brick, tile, or clay pipes
not deep

45
Q

What is the purpose of a sanitary seal?

A

prevents contaminants from entering the well casing

46
Q

What is the purpose of a well slab?

A

supports pumping equipment and aids in sealing against surface water

47
Q

What is the purpose of the well casing?

A

metal tube placed in the well to keep the well open

48
Q

What is grout?

A

mixture of cement, water, and sometimes sand

49
Q

What is the annulus of a well?

A

the space between the drilled hole and the casing
grout seals the well against contamination

50
Q

What is the well screen/intake screen of a well?

A

at the bottom of the casing
penetrates the aquifer
screen provides enough open spacing for unrestricted water flow

51
Q

What does gravel packing do for a well?

A

aids in filtering and increasing well efficiency

52
Q

What does a pitless adaptor do?

A

allows you to connect your water pipe from your water well pump to an under ground discharge to go to your house

53
Q

What are the components of a pitless adaptor?

A

two piece brass units that have one half installed into the side of teh well casing below frost level
the other half connects to the pipe coming up from your submersible pump

54
Q

What is the purpose of the threading at the top of a pitless adapton?

A

allows you to screw a piece of pipe into it to lift the pitless adapter and the pump out of the receiver half to disconnect

55
Q

What is the purpose of the annular seal of a well?

A

it acts as a barrier to run-off, surface water, and near-surface waters that could otherwise travel down the outside of the casing and contaminate the aquifer

56
Q

What are common entrained gas impurities of water?

A

CO and O have corrosive effects
H2S (hydrogen sulfide) and CH4 (methane) can effect odor/taste

57
Q

What are common dissolved mineral impurities of water?

A

Salts (Ca, Mg, K, Na)
bicarbonates
nitrates
phosphates
Affect taste, odor, color, corrosion

58
Q

What are common suspended/colloidal solids in water?

A

bacteria
fungi
mold
viruses
algae
clay

59
Q

When is radioactive waste present in water?

A

from mining, improper waste disposal, and contamination

60
Q

What sort of chemical exams of water are performed in a laboratory?

A

suspended solids
BOD
OD
COD
nitrates
H2S
pH

61
Q

What sort of bacterial exams are performed in a lab of water?

A

coliform - most probably number, colilert testing
MPN confirmation
membrane filter

62
Q

What are the concerns of Zinc in drinking water?

A

inorganic
threshold limit value of 5 mg/L
high concentration yields metallic taste
can cause vomiting

63
Q

What are the concerns of chlorides in drinking water?

A

at 250 mg/L, can cause heart disease

64
Q

What are the concerns of sulfate compounds in drinking water?

A

Sodium Sulfate (NaSO4)
Magnesium Sulfate (MgSO4, Epsom salt)
Calcium Sulfate (CaSO4)
high levels cause laxative effects to the human body

65
Q

What are the concerns of Alkyl-Benzene Sulfanate in drinking water?

A

common in detergents
conc limit value 0.5 mg/L
common pollution indicator for human domestic sewage
carcinogenic

66
Q

What are the concerns for nitrates in drinking water?

A

nitrates should not be found in fresh water sources
limit - 10 mg/L
high levels of nitrates can lead to Blue Baby Syndrome - methemoglobinemia

67
Q

How do nitrates react in the human body?

A

convert to nitrites in the stomach
enter bloodstream
convert hemoglobin to met-hemoglobin which carried Nitrogen instead of O2

68
Q

What are the limits of copper in drinking water?

A

1mg/dL

69
Q

What are the limits for iron in drinking water?

A

3 ppm

70
Q

What are the limits for fluoride in drinking water?

A

0.6 - 1.7 ppm

71
Q

What are the two methods for defluoridation?

A

Bone char
activated alumnia

72
Q

What are the two radioactive materials in water and what are their limits?

A

nuclides (Radium Ra226) 3 micro-micro curie/L
Strontium 90 (Sr90) 10 micro-micro curie/L

73
Q

How are water samples taken?

A

Most sampling containers are 300 mL
sterilized with leak proof caps
samples taken 2 ft below water surface

74
Q

What is turbidity?

A

standard for water clarity
indexes of 5 units can be distinguishable
soil, silt, algae, microorganism can effect turbidity

75
Q

What is the Jackson Turbidity Meter?

A

used while itilizing light of flame
sample poured until flame is not seen down tube

76
Q

What is a Secchi disk?

A

used for clarity tests in pools - how deep the disk is seen from the surface
should be min 4 ft

77
Q

Describe a Colilert test

A

provides a media that contains specific indicator nutrients for total coliform and E. coli
as these nutrients are metabolized, yellow color and fluorescence are released, confirming their presence
Noncoliform bacteria are chemically suppressed
identified in 24 hrs or less

78
Q

Describe a membrane filter test

A

uses a cellulose ester filter - pore size is manufactured to close tolerances
pore size selectively traps bacteria from water filtered through the membrane
nutrients are diffused through the membrane to grow bacteria into colonies
colonies are recognizable as coliform because the nutrients contain a dye

79
Q

What is multiple tube fermentation?

A

standard method for determining coliform since 1936
tubes of lauryl tryptose broth are inoculated with a water sample (contains lactose)
coliform density is calculated from statistical probability formulas that predict the most probable number of coliforms in a 100 mL sample necessary to produce certain combinations of gas + and gas - tubes in the series of inoculated tubes
3 distinct test states - presumptive, confirmed, completed

80
Q

What are the five water quality classifications? (simplified into 3)

A

Group 1. water found satisfactory, low to no coliform, does not need treatment to be potable
Group 2. water has low contamination levels but requires disinfection
Group 3-5. contaminated water, requires extensive disinfection process

81
Q

What are the three methods for removing dissolved solids in water?

A

distillation
electrodialysis
ion exchange

82
Q

Describe distillation

A

best type
purest form of water
expensive
time consuming
boil water, condense the steam

83
Q

Describe electrodialysis

A

use of electric current, positive charge placed in water, dissolved solid ions go through +/- membrane

84
Q

Describe ion exchange/water softening

A

removed mineral compounds (Ca, Mg) by increasing [Na] - sodium concentration

85
Q

What is a cross connection in drinking water?

A

any connection between piping that carries potable water and the piping that carry other types of water or substances that may be non-potable

86
Q

How do we prevent contamination from non-potable piping?

A

must be protected with a backflow prevention device
any piping without this could be siphoned back into potable water

87
Q

What is an air gap?

A

physical separation of drain pipe and drain

88
Q

What is backflow?

A

flow of contaminated water into potable water supply caused by back pressure

89
Q

What is back siphonage?

A

form of backflow when pressure in potable water drops below pressure in flow of contaminated water

90
Q

What is an atmospheric vacuum breaker?

A

used in toilet tanks and commercial sink faucets
uses atmospheric pressure in event of backflow to force a valve to close, preventing waste water from entering potable water

91
Q

What backflow prevention device is found in a drinking fountain?

A

safest is diagonal jet fountain
air gap
created when fountain jet used
found most often in schools

92
Q

What is a hose bib vacuum breaker?

A

connects to faucets, protects hose siphonage

93
Q

What is a pressure type vacuum breaker?

A

used as protection connection to all non-potable water supplies where line is not subject to back pressure
under continuous pressure and must be installed above usage point

94
Q

What is a flushometer?

A

valve in toilet tanks
discharges specific water amount activated by water pressure

95
Q

What is a reduced pressure backflow prevention device?

A

commercial water mains to protect municipal water supply
must be certified and checked annually by certified backflow plumber

96
Q

What is a double check valve?

A

used in low hazard situations where water may be polluted but not contaminated

97
Q

What are Trihalomethanes?

A

formed during drinking water chlorination
considered potential human carcinogens

98
Q

What is 1,2-dibromo-3-chloropropane (DBCP)

A

pesticide used to control nematode pests
strong carcinogen
factory workers found to have sterility problems

99
Q

What is Trichloroethylene (TCE)

A

organic solvent, degreasing agent, carcinogen

100
Q

What is Perchloroethylene (PCE)?

A

Similar organic solvent to TCE with toxic effects at 20 PPB

101
Q

What is Carbon Tetrachloride?

A

toxic to humans at high concentration
known carcinogen
used to manufacture chlorofluoromethanes for refrigeration, air conditioners, aerosols
causes ozone depletion in atmosphere

REHS (47 decks)

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