Flashcards in Water Deck (154):
Humans consume an average of __ to __ lbs of water per day
3 to 5 lbs per day
The ocean contains nearly ______ % of all our water
The _____ powers the hydrological cycle
What is thermal stratification
the change in temperature of water at different depths in a body of water. it occurs because colder water is more dense.
name the three sections of thermal stratification from top to bottom
epilimnion -upper layer
hypolimnion - lower layer
in winter what layers exist in thermal stratification?
ice exists above the water layer
name the three ages of lakes
oligotrophic - young
mesotrophic - middle
eutrophic - old or mature lake
a lake is considered "dead" when it has been depleted of _________
why are plants important to a lake?
because they provide oxygen
What is eutrophication
a lake condition of algal blooms due to over enrichment of nutrients such as phosphates and nitrates.
can be natural or manmade
if left untreated manmade eutrophication can result in a ______ lake because the algae depletes the ______
What chemical can be used to control algae
copper sulfate CuSO4 can be used but in limited concentrations so it doesn't kill fish and other aquatic life
what two chemicals can be used to prevent evaporation from lakes
hexadecanol and octadecanol
they are non toxic
so why don't we convert ocean water into drinking water?
because it's too costly due to the high salinity and minerals in the water
what are some types of surface waters
what is an aquifer?
an underground layer of water with permeable rock or other materials through which a well can be drilled
what is the water table
the area of the start of the zone of saturation
What three things should be considered in the construction of the well
depth of water table
type of construction
why do higher water tables have less potable water?
because the water did not have enough time to naturally filtrate through the soil
What are the 3 types of wells
case driven well
case driven well
bottom of casing is perforated to allow water in
used with a submergible pump that is lowered into the water source
an auger is used to drill into the earth
manual dug by man or machine. lined with concrete, bricks, tile or clay pipes.
what is a rainwater cistern
a tank with a simple filter of sand/gravel to filter rain water.
used for non drinking purposes
What are weep holes?
holes in tanks so that if water freezes it can escape out of the tank to prevent tank damage from expansion
what is the hydraulic gradient?
the movement of water downward by earths gravitational pull
What is an injection well
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?
What is an unconfined aquifer
water confined by both upper and lower impermeable layers (typically clay)
usually not vulnerable to contamination
What is an unconfined aquifer
only confined by a lower impermeable layer
What is the purpose of the well casing
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
What are the two types of casing
blank casing - pvc or steel depending on soil
screened casing - slotted, louvered - to keep sand and gravel out but allow water in
What is an annular seal
a cement or bentonite filling around the open space left around the outside of the well casing.
to prevent contamination
What are two types of pumps used in wells
vertical turbine pump (pump motor is on the surface)
submersible pump (more common)
What percent of Americans are on private wells/drinking water
The recycling of water is known as _________
the hydrologic cycle
Water weights ______ lbs/gallon
_______ gallons of water are in 1 cubic foot volumne
What are some gases that can be found in water?
CO2 in water
corrosion, especially in steam and condensate lines
treatment: aeration, deaeration, neutralize with alkalies
Oxygen gas in water
corrosion of water lines, heat exchange equipment
treatment: deaeration, sodium sulfite, corrosion inhibitors
Hydrogen Sulfide gas in water
Rotten Egg odor, Corrosion
treatment: aeration, chlorination, highly basic anion exchange
What is hard water
Water that has a high dissolved mineral content. Typically has a lot of salts and bicarbonates.
Mainly calcium and magnesium
What is the benefit of hard water and the drawbacks of it?
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.
What are some areas with hard water and why?
limestone areas such as Colorado river, Arizona.
south Carolina has the softest water.
calcium concentration must exceed ____ mg/l to be labeled as hard water
What are the two main ways to soften water?
lime soda process
magnesium soda ash process
Water softening is achieved by increased the ______ concentration which precipitates the calcium and magnesium minerals out of the water
lime soda process to soften water
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
magnesium soda ash process is also called
aka zeolite or ion exchange method
excessively soft water can pull ________ out of the pipes such as ______ and ______ and into the water
pulls metallic ions
such as copper and lead from the pipes into the water
What are some radioactive materials that can get into water? how did they get into the water?
from mining wastes and improper haz waste disposal
What is the MCL for strontium 90 a radioactive nuclide?
What is the MCL for combined Radium (226 and 228)
What is the MCL for Uranium?
Which two elements found in water are most known for causing stains
iron and manganese
What are the secondary standards?
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
What are the some of the elements addressed in secondary drinking water standards
What is the acceptable limit for Iron
1 mg/L = ____ ppm
1 they are the same
What are the metals that are monitored in public drinking water?
There are 12
arsenic, barium, cadmium, chromium, lead, copper, mercury, selenium, nickel, thallium, antimony, and beryllium
Copper in water - what are the effects? What is the MCL
mcl is 1 mg/L
can lead to liver damage
Nitrates in water - effects and MCL
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)
Zinc in water - effects and MCL
MCL 5 mg/L
metallic taste and vomiting
MCL categories are broken down to 4 categories which are
Fluoride in water - effects, MCL
high levels actually mottle (break down enamel) of the teeth
2 mg/L is the MCL
What was the purpose of fluoridating water?
do provide chemical protection against dental decay
what level of fluoride will cause teeth mottling?
What are the tree forms of available fluoride
sodium fluoride - commonly a powder
sodium silico-fluoride - also a powder
fluorosilic acid - liquid form - only 22% available fluoride
What is the idea percent of fluoride in the water
.8 mg/L - 1.7 mg/L
What are two ways to defluoridate water?
What is the maximum units of color allowed in water?
Most major metropolitan cities have ______ units of color in their water
4 to 5 units/L
What is the maximum units of turbidity allowed in water?
What are two devices used to test for turbidity?
the Jackson turbid meter
the secchi disk
Jackson turbid meter
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
the secchi disk
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
What is the odor threshold of water?
What is TDS
total dissolved solids - doesn't necessarily mean that that the water is polluted, some water, like hard water just has more dissolved minerals
What is the MCL for TDS
1,000 mg/L for long term
Chlorides in water - effects and MCL
can cause bad taste and heart problems
MCL 500 mg/L
Sulfates in water - effects and MCL
can give a laxative effect
MCL 500 mg/L
Natural water has a pH range of ___ to ____
5 to 8.3
a chemical examination of water includes determining the following.....
a Bacterial examination of water includes determining the following....
presumptive and confirmed testing for MPN
What are some of the common diseases which can come from contaminated drinking water
bacterial and viral gastroenteritis
lead in water - effects and MCL
in the bloodstream it can cause mental and brain dysfunction
What is the indicator test
a coliform test - will indicate potential contaminated water
Why is e-coli a great indicator organism
because it is excreted in large numbers in feces. you can expect from 30 million organisms in a 100 mL sample.
What is the average number of coliforms in 100 ml of drinking water? and also the maximum acceptable limit for human consumption
1 per 100 ml
1 colony per 100 ml
in polluted water, there is approximately ___ pathogenic bacteria for every ______ coliform bacteria
1 to 1 million
in polluted water there is approximately ___ viruses to every _________ coliforms
1 to 100,000
What chemical is in a water sample bottle and why?
sodium thiosulfate - it dechlorinates the sample so you can keep any potential coliforms alive for testing
most coliforms are what shaped bacteria?
What is the MPN?
most probable number - a bacteriological study looking for possible fecal contamination (coliforms)
How is the presumptive test (multiple tube fermentation) performed?
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
What is the confirmation test
ETT elevated temperature test performed after a presumptive MPN test to determine if the coliforms are of fecal origin
What is the colilert test?
a 24 hour test that detects total coliforms and e-coli
a yellow color change indicates a positive
How does aerating water a form of treatment? What are the tree methods?
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
What treatment is often used to remove odors in water?
activated charcoal process
What are two chemicals that are often added to coagulated/flocculate the water
aluminum sulfate (alum)
How does flocculation/coagulation help in water treatment process
by coagulating organic and inorganic solids and helping them fall to the bottom and get disposed of as sludge
What is the purpose of a sedimentation tank?
for water to travel slowly through it to allow particle matter to gravitate down and settle out
how does sedimentation work in a vertical tank?
water flows in through bottom and its motion is slowed down by a baffle. particulates settle down and cleaner water flows out the top.
how does sedimentation work in a horizontal tank?
the water enters from one side and exits the other. the tank bottom is continuously cleaned for settling solids.
What are some problems with sand filters in water treatment processes?
Alum should not go through filters in high concentration. so alum for flocculation processes should be removed before filtration
What are mud balls?
clumping of dirt on filter media. filters must be backwashed to prevent.
three types of chlorine, and their concentrations
liquid NaOCL 5-15 %
calcium hypochlorite is the dry form 70% available chlorine
chlorine gas can yield 100% available chlorine
What is breakpoint chlorination?
adding enough chlorine so that it doesn't all get used up and there is a residual left
What are chloramines?
a byproduct when organic material is broken down with chlorine ammonia.
in solution chlorine breaks down into ______ and ________ which is the stronger disinfectant and thus chlorine works better when the pH is _____________
hypochlorite ion and hypochlorite acid (better)
most municipal water system require a chlorine residual of_______ mg/l
what are some other types of water disinfection
ozone (expensive, no residual)
iodine (affects color, taste, odor)
UV light (required shallow water and longer duration)
boiling (the best method)
What are two tests that can be used to detect chlorine levels
OT orthotoludene test (ortho test) older test sensitive to heat
DPD N-N-diethyl Phenylene Diamine more accurate
What are the four methods commonly used to remove dissolved solids from water?
ion exchange (water softening)
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
electrodialysis of water
positive charge causes dissolved ions to leave the water
reverse osmosis of water
moves lower concentration of dissolved solids to a higher concentration
What is a cross connection
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
What is an air gap
the physical separation of a drain pipe and a drain.
prevents backflow or negative pressure
an air gap should be _____ times the diameter of a pipe or a minimum of _____
two times the diameter
minimum 1 ''
How does an atmospheric vacuum breaker work
backflow pressure releases atmospheric pressure thus shutting a valve and preventing backflow
common on toilet tanks and food facility sinks fauces
What is the safest type of drinking fountain
a diagonal jet with a guard.
how does a hose bib vacuum breaker work
there is a ball cock inside the hose bib connection. when flow reverses (back pressure) the ball backs up inside the bib preventing flow.
where would one install a pressure type vacuum breaker?
above the usage point
Where is a reduced pressure backflow prevention usually used?
at commercial water mains. must be certified and checked annually
What is a flushometer valve?
usually used in toilet tanks.
What is a double check valve
has to spring or ball valves incase one fails
What is back siphonage
a form of backflow when the pressure in the potable water supply drops below the pressure in the flow of contaminated water
Name 4 organic water contaminants
1, 2-dibromo-3-chloropropane (DBCP)
an organic contaminant
formed during chlorination
10 different types
pesticide used to control nematode parasites
solvent/degreasing agent used in past
an organic contaminant
used to manufacture chlorofluoromethanes (CFC for refrigeration)
What is a public water system
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
When was the safe drinking water act established?
What does VOC stand for
volatile organic chemicals
What does SOC stand for
synthetic organic chemicals
what are three methods used for coliform testing
multiple tube fermentation
what is the most common water disinfectant
three water treatment processes that are normally linked together are ...
______ is required for surface water treatment to insure that no pathogens end up in the water supply
what are the most common types of filters used in potable water treatment
granular media filters
which type of well is least likely to become contaminated
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. should be supplemented by a chlorination system
microbial pollution travels only a short distance through:
what type of filter is recommended for use in small communities and rural places?
all of the following are used to disinfect water except:
backsiphonage may be prevented by all of the following methods except:
air gap separation
which of the following is the least effective method for cadmium removal from drinking water:
before a drinking water sample is taken, the sampling tap should be clean, free of leaks, and flushed for how long?
what contaminant has been associated with learning and cognitive disorders in children who drink contaminated water?
What is EDTA used for
to dissolve limescale in water