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REHS Study > Water > Flashcards

Water Flashcards

1
Q

Humans consume an average of __ to __ lbs of water per day

A

3 to 5 lbs per day

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2
Q

The ocean contains nearly ______ % of all our water

A

97%

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3
Q

The _____ powers the hydrological cycle

A

sun

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4
Q

What is thermal stratification

A

the change in temperature of water at different depths in a body of water. it occurs because colder water is more dense.

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5
Q

name the three sections of thermal stratification from top to bottom

A

epilimnion -upper layer
thermocline
hypolimnion - lower layer

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6
Q

in winter what layers exist in thermal stratification?

A

ice exists above the water layer

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7
Q

name the three ages of lakes

A

oligotrophic - young
mesotrophic - middle
eutrophic - old or mature lake

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8
Q

a lake is considered “dead” when it has been depleted of _________

A

oxygen

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9
Q

why are plants important to a lake?

A

because they provide oxygen

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10
Q

What is eutrophication

A

a lake condition of algal blooms due to over enrichment of nutrients such as phosphates and nitrates.

can be natural or manmade

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11
Q

if left untreated manmade eutrophication can result in a ______ lake because the algae depletes the ______

A

dead

oxygen

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12
Q

What chemical can be used to control algae

A

copper sulfate CuSO4 can be used but in limited concentrations so it doesn’t kill fish and other aquatic life

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13
Q

what two chemicals can be used to prevent evaporation from lakes

A

hexadecanol and octadecanol

they are non toxic

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14
Q

so why don’t we convert ocean water into drinking water?

A

because it’s too costly due to the high salinity and minerals in the water

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15
Q

what are some types of surface waters

A

spring
pond
swamp
stream

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16
Q

what is an aquifer?

A

an underground layer of water with permeable rock or other materials through which a well can be drilled

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17
Q

what is the water table

A

the area of the start of the zone of saturation

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18
Q

What three things should be considered in the construction of the well

A

expensive
depth of water table
type of construction

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19
Q

why do higher water tables have less potable water?

A

because the water did not have enough time to naturally filtrate through the soil

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20
Q

What are the 3 types of wells

A

case driven well
bored well
dug well

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21
Q

case driven well

A

best quality
bottom of casing is perforated to allow water in
used with a submergible pump that is lowered into the water source

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22
Q

bored well

A

an auger is used to drill into the earth

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23
Q

dug well

A

manual dug by man or machine. lined with concrete, bricks, tile or clay pipes.

not deep

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24
Q

what is a rainwater cistern

A

a tank with a simple filter of sand/gravel to filter rain water.

used for non drinking purposes

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25
Q

What are weep holes?

A

holes in tanks so that if water freezes it can escape out of the tank to prevent tank damage from expansion

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26
Q

what is the hydraulic gradient?

A

the movement of water downward by earths gravitational pull

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27
Q

What is an injection well

A

a way to dispose of contaminated water into an isolated well. Typically it’s a well into limestone or sandstone.

not allowed anymore. most are closed?

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28
Q

What is an unconfined aquifer

A

water confined by both upper and lower impermeable layers (typically clay)

usually not vulnerable to contamination

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29
Q

What is an unconfined aquifer

A

only confined by a lower impermeable layer

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30
Q

What is the purpose of the well casing

A

prevents the collapse of the bore hole
keeps surface and subsurface pollutants from entering the water source
provides a column to store water for positive well upmp
houses the pump and discharge pipe

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31
Q

What are the two types of casing

A

blank casing - pvc or steel depending on soil

screened casing - slotted, louvered - to keep sand and gravel out but allow water in

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32
Q

What is an annular seal

A

a cement or bentonite filling around the open space left around the outside of the well casing.

to prevent contamination

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33
Q

What are two types of pumps used in wells

A

vertical turbine pump (pump motor is on the surface)

submersible pump (more common)

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34
Q

What percent of Americans are on private wells/drinking water

A

15%

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35
Q

The recycling of water is known as _________

A

the hydrologic cycle

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36
Q

Water weights ______ lbs/gallon

A

8.34

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37
Q

_______ gallons of water are in 1 cubic foot volumne

A

7.48

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38
Q

What are some gases that can be found in water?

A

CO2
Oxygen
Hydrogen Sulfide
Methane

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39
Q

CO2 in water

A

corrosion, especially in steam and condensate lines

treatment: aeration, deaeration, neutralize with alkalies

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40
Q

Oxygen gas in water

A

O2
corrosion of water lines, heat exchange equipment

treatment: deaeration, sodium sulfite, corrosion inhibitors

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41
Q

Hydrogen Sulfide gas in water

A

H2S
Rotten Egg odor, Corrosion

treatment: aeration, chlorination, highly basic anion exchange

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42
Q

What is hard water

A

Water that has a high dissolved mineral content. Typically has a lot of salts and bicarbonates.

Mainly calcium and magnesium

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43
Q

What is the benefit of hard water and the drawbacks of it?

A

good cleanser for the human circulatory system.

cons: hard water neutralizes soap and makes it hard to lather. stains sinks and bathing areas and calcifies pipes due to electrolysis.

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44
Q

What are some areas with hard water and why?

A

limestone areas such as Colorado river, Arizona.

south Carolina has the softest water.

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45
Q

calcium concentration must exceed ____ mg/l to be labeled as hard water

A

100 mg/l

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46
Q

What are the two main ways to soften water?

A

lime soda process

magnesium soda ash process

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47
Q

Water softening is achieved by increased the ______ concentration which precipitates the calcium and magnesium minerals out of the water

A

sodium

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48
Q

lime soda process to soften water

A

quicklime - CaO and H2O is mixedhe slurry is added to the water and calcium ions are precipitated out as insoluble calcium carbonate CaCO3

can’t be done at home

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49
Q

magnesium soda ash process is also called

A

aka zeolite or ion exchange method

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50
Q

excessively soft water can pull ________ out of the pipes such as ______ and ______ and into the water

A

pulls metallic ions

such as copper and lead from the pipes into the water

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51
Q

What are some radioactive materials that can get into water? how did they get into the water?

name 3

A

from mining wastes and improper haz waste disposal

radium
strontium 90
uranium

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52
Q

What is the MCL for strontium 90 a radioactive nuclide?

A

8 pCi/L

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53
Q

What is the MCL for combined Radium (226 and 228)

A

5 pCi/L

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54
Q

What is the MCL for Uranium?

A

20 pCi/L

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55
Q

Which two elements found in water are most known for causing stains

A

iron and manganese

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56
Q

What are the secondary standards?

A

limits for other elements in water that may not pose a health risk but my adversely affect the appearance, test, or odor of drinking water

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57
Q

What are the some of the elements addressed in secondary drinking water standards

A 
iron
zinc
turbidity
color
odor
manganese
TDS
Sulfates
Chlorides
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58
Q

What is the acceptable limit for Iron

A

.3 mg/L

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59
Q

1 mg/L = ____ ppm

A

1 they are the same

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60
Q

What are the metals that are monitored in public drinking water?

There are 12

A

arsenic, barium, cadmium, chromium, lead, copper, mercury, selenium, nickel, thallium, antimony, and beryllium

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61
Q

Copper in water - what are the effects? What is the MCL

A

mcl is 1 mg/L

can lead to liver damage

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62
Q

Nitrates in water - effects and MCL

A

nitrates are usually the final product of organic decomposition. so if there are nitrates in the water that is an indication of pollution.

MCL is 10 mg/L

effects: blue baby syndrome methemoglobinemia (begins at 45 mg/L)

63
Q

Zinc in water - effects and MCL

A

MCL 5 mg/L

metallic taste and vomiting

64
Q

MCL categories are broken down to 4 categories which are

A

inorganics
radionuclides
VOCs
SOCs

65
Q

Fluoride in water - effects, MCL

A

high levels actually mottle (break down enamel) of the teeth

2 mg/L is the MCL

66
Q

What was the purpose of fluoridating water?

A

do provide chemical protection against dental decay

67
Q

what level of fluoride will cause teeth mottling?

A

3 mg/L

68
Q

What are the tree forms of available fluoride

A

sodium fluoride - commonly a powder
sodium silico-fluoride - also a powder
fluorosilic acid - liquid form - only 22% available fluoride

69
Q

What is the idea percent of fluoride in the water

A

.8 mg/L - 1.7 mg/L

70
Q

What are two ways to defluoridate water?

A

bone char

activated alumnia

71
Q

What is the maximum units of color allowed in water?

A

15 units

72
Q

Most major metropolitan cities have ______ units of color in their water

A

4 to 5 units/L

73
Q

What is the maximum units of turbidity allowed in water?

A

5 units/L

74
Q

What are two devices used to test for turbidity?

A

the Jackson turbid meter

the secchi disk

75
Q

Jackson turbid meter

A

with a flame under a test tube the sample water is poured into the test tube until the flame is no longer visible

a very old style of testing

76
Q

the secchi disk

A

used to test turbidity. common for recreational swimming

the disk is submerged in water until it is no longer visible. the length is then measured.

for swimming it should still be visible at 4 feet from the surface

77
Q

What is the odor threshold of water?

A

3 units/L

78
Q

What is TDS

A

total dissolved solids - doesn’t necessarily mean that that the water is polluted, some water, like hard water just has more dissolved minerals

79
Q

What is the MCL for TDS

A

1,000 mg/L for long term

80
Q

Chlorides in water - effects and MCL

A

can cause bad taste and heart problems

MCL 500 mg/L

81
Q

Sulfates in water - effects and MCL

A

can give a laxative effect

MCL 500 mg/L

82
Q

Natural water has a pH range of ___ to ____

A

5 to 8.3

83
Q

a chemical examination of water includes determining the following…..

A 
suspended solids
BOD
DO
COD
nitrates
hydrogen sulfide
pH
84
Q

a Bacterial examination of water includes determining the following….

A

coliform MPN
presumptive and confirmed testing for MPN
membrane filter

85
Q

What are some of the common diseases which can come from contaminated drinking water

A 
bacterial and viral gastroenteritis
legionella
cryptosporidiosis
giardiasis
infectious hepatitis
shigellosis/dysentery
cholera/vibrio
salmonella/typhoid/paratyphoid
polio
leptospirosis
entamoeba histolytica
86
Q

lead in water - effects and MCL

A

.05 mg/L

in the bloodstream it can cause mental and brain dysfunction

87
Q

What is the indicator test

A

a coliform test - will indicate potential contaminated water

88
Q

Why is e-coli a great indicator organism

A

because it is excreted in large numbers in feces. you can expect from 30 million organisms in a 100 mL sample.

89
Q

What is the average number of coliforms in 100 ml of drinking water? and also the maximum acceptable limit for human consumption

A

1 per 100 ml

1 colony per 100 ml

90
Q

in polluted water, there is approximately ___ pathogenic bacteria for every ______ coliform bacteria

A

1 to 1 million

91
Q

in polluted water there is approximately ___ viruses to every _________ coliforms

A

1 to 100,000

92
Q

What chemical is in a water sample bottle and why?

A

sodium thiosulfate - it dechlorinates the sample so you can keep any potential coliforms alive for testing

93
Q

most coliforms are what shaped bacteria?

A

rod shaped

94
Q

What is the MPN?

A

most probable number - a bacteriological study looking for possible fecal contamination (coliforms)

95
Q

How is the presumptive test (multiple tube fermentation) performed?

A

to test for coliform.

performed with inverted durham tubes to detect fermentation of the sample

if at least 2 of the 5 tubes are positive than it’s said that 1 in 100ml coliform exisists

a confirmation test is performed if 3 or more tubes are positive

96
Q

What is the confirmation test

A

ETT elevated temperature test performed after a presumptive MPN test to determine if the coliforms are of fecal origin

97
Q

What is the colilert test?

A

a 24 hour test that detects total coliforms and e-coli

a yellow color change indicates a positive

98
Q

How does aerating water a form of treatment? What are the tree methods?

A

By oxygenating the water the organic matter will precipitate out

cascade - water falls
blowers - air is blown into water (bubbles)
jet nozzles - water is sprayed into the air

99
Q

What treatment is often used to remove odors in water?

A

activated charcoal process

100
Q

What are two chemicals that are often added to coagulated/flocculate the water

A

aluminum sulfate (alum)

poly-electrolites (Polymers)

101
Q

How does flocculation/coagulation help in water treatment process

A

by coagulating organic and inorganic solids and helping them fall to the bottom and get disposed of as sludge

102
Q

What is the purpose of a sedimentation tank?

A

for water to travel slowly through it to allow particle matter to gravitate down and settle out

103
Q

how does sedimentation work in a vertical tank?

A

water flows in through bottom and its motion is slowed down by a baffle. particulates settle down and cleaner water flows out the top.

104
Q

how does sedimentation work in a horizontal tank?

A

the water enters from one side and exits the other. the tank bottom is continuously cleaned for settling solids.

105
Q

What are some problems with sand filters in water treatment processes?

A

Alum should not go through filters in high concentration. so alum for flocculation processes should be removed before filtration

106
Q

What are mud balls?

A

clumping of dirt on filter media. filters must be backwashed to prevent.

107
Q

three types of chlorine, and their concentrations

A

liquid NaOCL 5-15 %
calcium hypochlorite is the dry form 70% available chlorine
chlorine gas can yield 100% available chlorine

108
Q

What is breakpoint chlorination?

A

adding enough chlorine so that it doesn’t all get used up and there is a residual left

109
Q

What are chloramines?

A

a byproduct when organic material is broken down with chlorine ammonia.

strong smell
undesirable

110
Q

in solution chlorine breaks down into ______ and ________ which is the stronger disinfectant and thus chlorine works better when the pH is _____________

A

hypochlorite ion and hypochlorite acid (better)

lower pH

111
Q

most municipal water system require a chlorine residual of_______ mg/l

A

.2 mg/l

112
Q

what are some other types of water disinfection

A

ozone (expensive, no residual)
iodine (affects color, taste, odor)
UV light (required shallow water and longer duration)
boiling (the best method)

113
Q

What are two tests that can be used to detect chlorine levels

A

OT orthotoludene test (ortho test) older test sensitive to heat

DPD N-N-diethyl Phenylene Diamine more accurate

114
Q

What are the four methods commonly used to remove dissolved solids from water?

A

distillation
electrodialysis
ion exchange (water softening)
reverse osmosis

115
Q

water distillation

A

most expensive and time consuming
gives the purest form of water
water is boiled and vaporized steam is condensed

doesn’t taste good since there are NO minerals at all

116
Q

electrodialysis of water

A

positive charge causes dissolved ions to leave the water

117
Q

reverse osmosis of water

A

moves lower concentration of dissolved solids to a higher concentration

most effective

118
Q

What is a cross connection

A

any connection or arrangement, physical or otherwise, between a potable water supply system and any plumbing fixture through which it may be possible for non-potable contaminated water to enter any part of the potable water system

119
Q

What is an air gap

A

the physical separation of a drain pipe and a drain.

prevents backflow or negative pressure

120
Q

an air gap should be _____ times the diameter of a pipe or a minimum of _____

A

two times the diameter

minimum 1 ‘’

121
Q

How does an atmospheric vacuum breaker work

A

backflow pressure releases atmospheric pressure thus shutting a valve and preventing backflow

common on toilet tanks and food facility sinks fauces

122
Q

What is the safest type of drinking fountain

A

a diagonal jet with a guard.

123
Q

how does a hose bib vacuum breaker work

A

there is a ball cock inside the hose bib connection. when flow reverses (back pressure) the ball backs up inside the bib preventing flow.

124
Q

where would one install a pressure type vacuum breaker?

A

above the usage point

125
Q

Where is a reduced pressure backflow prevention usually used?

A

at commercial water mains. must be certified and checked annually

126
Q

What is a flushometer valve?

A

usually used in toilet tanks.

127
Q

What is a double check valve

A

has to spring or ball valves incase one fails

128
Q

What is back siphonage

A

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

129
Q

Name 4 organic water contaminants

A 
trihalomethanes (THM)
1, 2-dibromo-3-chloropropane (DBCP)
Trichloroethylene (TCE)
Perchloroethylene (PCE)
Carbon Tetrachloride
130
Q

THM

A 
Trihalomethanes
an organic contaminant
formed during chlorination
potential carcinogen
10 different types
131
Q

DBCP

A 
1,2-dibromo, 3-chloropropane
organic contaminant
pesticide used to control nematode parasites
strong carcinogen
sterility problems
132
Q

TCE

A

Trichloroethylene
organic contaminant
solvent/degreasing agent used in past
carcinogen

133
Q

PCE

A

Perchloroethylene
organic contaminant
solvent
carcinogen

134
Q

Carbon Tetrachloride

A

an organic contaminant
used to manufacture chlorofluoromethanes (CFC for refrigeration)
carcinogen
skin cancer

135
Q

What is a public water system

A

piped water for human consumption that has at least 15 service connections, or regularly services an average of at least 25 individuals at least 60 days out of the year

136
Q

When was the safe drinking water act established?

A

1974

137
Q

What does VOC stand for

A

volatile organic chemicals

138
Q

What does SOC stand for

A

synthetic organic chemicals

139
Q

what are three methods used for coliform testing

A

colilert
multiple tube fermentation
plate count

140
Q

what is the most common water disinfectant

A

chlorine

141
Q

three water treatment processes that are normally linked together are …

A

coagulation/flocculation
sedimentation
filtration

142
Q

______ is required for surface water treatment to insure that no pathogens end up in the water supply

A

filtration

143
Q

what are the most common types of filters used in potable water treatment

A

granular media filters

144
Q

which type of well is least likely to become contaminated

drilled
bored
driven
dug

A

drilled

145
Q

diatomaceous earth filters

a. should be supplemented by a chlorination system
b. should be integrated into a rapid sand filtration system.
c. can be used for public water treatment systems
d. can be used in public sewer treatment systems.

A

a. should be supplemented by a chlorination system

146
Q

microbial pollution travels only a short distance through:

sandstone
smooth clay
fissured rock
limestone

A

smooth clay

147
Q

what type of filter is recommended for use in small communities and rural places?

DE
granular
cartridge
slow sand

A

slow sand

148
Q

all of the following are used to disinfect water except:

chlorine
bromine
fluorine
iodine

A

fluorine

149
Q

backsiphonage may be prevented by all of the following methods except:

hydrostatic loops
vacuum breakers
air gap separation
backpressure units

A

hydrostatic loops

150
Q

which of the following is the least effective method for cadmium removal from drinking water:

activated carbon
iron coagulation
lime softening
ion exchange

A

activated carbon

151
Q

before a drinking water sample is taken, the sampling tap should be clean, free of leaks, and flushed for how long?

1-1.5 mins
2-3 mins
4-5 mins
6-7 mins

A

2-3 minutes

152
Q

what contaminant has been associated with learning and cognitive disorders in children who drink contaminated water?

manganese
copper
lead
parathion

A

lead

153
Q

What is EDTA used for

A

to dissolve limescale in water

154
Q

new pipes or wells must be chlorinated with ____ to ____ mg/l for ____ to _____ hours and then flush out until acceptable level is achieved

A

50 to 100

12 to 24 horus

REHS Study (20 decks)

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