ENVS131 Lecture Notes - Disinfectant, Water Cycle, Aquifer

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Published on 25 Nov 2012
Lecture 3
Water (Liquid Natural Capitol)
Water is in the air and in our body (60% of our body)
Earth is a water planet and is 71% percent of it is covered with water
However this water is mostly salt water and this limits its usages and more
expensive to use the limited fresh water.
To convert salt water to drinking water is expensive, corrosive and difficult to
No species can exist without water
Water changes the surfaces of the Earth (e.g. hill, valley, canyons) due to
erosion of the soil, rain, weathering
Water moderates climates
It is also used to remove and dilute wastes and pollutants
Human usage: withdrawal – total amount of water removed from a river,
lake or aquifer for any purpose. Some of this water can be returned to its
oWater cycle is one of the most important cycles on the Earth and reuses
and renews water the supply on Earth
oHumans use 54% of the world’s reliable run-off (surface water). In 2025,
humans would have consumed 70%-90% of available surface water.
oRaises two questions: 1) how much water is available and 2) what is the
quality of available reliable water.
Globally, there is a very low amount of fresh water available. 2.6% of
all available water is fresh water and only 0.14% is readily accessible
Some areas of the planet lack a good amount of water (less than 1700
cubic meters/year/person) (e.g. USA, Africa, and lower Asia). Under
water stress.
Canada has 20% of all freshwater in the world.
oSome World’s Problems:
Some areas have a lot of water but the largest rivers are far from
agricultural and population centres. It is very expensive to transport to
where it is needed.
Lot of precipitation arrives during short periods which cannot and
stored because it is very expensive
Lakes and rivers are shrinking due to climate change
oHow do we use our water?
64% of available water is used for industrial purposes such as power
plant cooling
A lot of water is being used in the agricultural centers of the USA, not
so much in Canada. In China, most of the water is used for agriculture
purposes (87%).
85% of water available is consumed and not returned to its water basin
In Canada, one household would use for showering (35%) and flushing
the toilet.
Majority of world lives in hydrological poverty. 1 of 6 people doesn’t
have access to clean water.
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Poor quality water can lead to diarrhea and kills 2 million children
Water and Your Health
Drinking Water
Municipal government reports annually on local drinking water quality
Is there any naturally pure water? No, all water contains other minerals like
potassium, sodium and magnesium. These minerals are good for one’s
Distillate water is a not good for drinking because it is lacking minerals.
Water percolates with the soil and then rocks and then minerals dilute within
the water. However, some minerals are not good, such as arsenic.
Surface water (e.g. rivers, lakes, and reservoirs) are sources of water for
urban areas. Ground water in rural areas (e.g. wells and water below ground
reservoir) is used to attain water.
Ground water is fed from the ground and moves slowly and thus it is hard to
contaminate. However, once contaminated, it is harder to clean it of
impurities. Ground water can be either deep or shallow.
Water found in different sources undergoes different process and treatments.
Mechanical Aspect
oMechanical impurities are removed (e.g. organic material, plant parts) –
put in tanks to let water settle.
oSome compounds are added to clump impurities and allow settling at the
bottom of the water basin.
oWater undergoes filtration.
Chemical Aspect
oWater undergoes chemical disinfection.
oChlorination is a popular technique in disinfecting water.
oBefore the chlorination technique, in the end of 19th century, many people in
England died from cholera because of microbes in water. When chlorination of
water became a practice, water quality improved greatly.
oResearch found out that a special type of coal can remove many type of
organic materials but cannot remove inorganic materials from water.
However, they are only in use when necessary. For example, used if water is
contaminated with metals and no water supply is around, these treatments
may be used.
Ground Water is naturally filtered water and contains less organic matter. It
often does not need any treatment.
Contaminants in Drinking Water:
oContaminants vs. Pollutants
Contaminants are any agents that can be found in water, soil or other
mediums but does not necessarily hurt an individual but may cause
health effects in high concentrations (e.g. microbes). Calcium can be a
contaminant if it is in extreme concentrations and it is not desired.
Pollutants always hurt individuals and cause human health effects.
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