LECTURE 3 (JANUARY 25, 2012): WATERBORNE HAZARDS AND HUMAN
Liquid natural capitol
The Earth is water planet
Water covers 71% of Earth surface
Mostly salty water
No species can do without water
Sculpting the Earth’s surface
Removing and diluting wastes and pollutants
Quantity of water
Quality of water
Withdrawal- total amount of water removed from a river, lake or aquifer for any purpose.
Some may be returned to the source for reuse
Use about 54 % of the world's reliable runoff of surface water and could be using 70-90%
Quantity of water: How much fresh water is available?
Stress on the world’s major river basins
Some areas have lots of water but the largest rivers are far from agricultural and
population centers – since water is not near agricultural places, the water must be
transported which costs money.
Lots of precipitation arrives during short period but cannot be collected and stored
Lakes and rivers shrinks
How do we use the world’s fresh water?
In Canada we mostly use water for power plant cooling
Agriculture is most responsible for water use
Average water use in Canadian homes (Environment Canada, 2005)
Toilet flushing is second most use of water
Shower and bath is first
One out of six people do not have regular access to clean water
Diarrheal deaths kill over 2 million children annually
Hydrological poverty – not enough water is available Many people do not have access to clean water or need to go to far places to get clean
water – Africa
Diarrhea – microbes are the problem
Water and Your health
Annual reports on local drinking water quality
Tap water & bottled water
Naturally pure water & distilled water
Natural content of minerals in water
Surface water - In urban areas
Ground water- In rural areas
We drink water from Lake Ontario – not from the shore. We have one of the safest
drinking water in the world.
Water without cells is called distilled water – you don’t want to drink distilled water
because your body needs calcium, magnesium, etc.
Main sources of drinking water is surface water and ground water
Ground water mostly used in rural areas
Two different kinds of ground water – one is unconfined ground water and the other is
Confined aquifer is better
How development change the natural flow of water
Quality of Water
Agriculture – pesticides might reach the ground water
Storage tanks (storage of organic solvents, etc) might leak and contaminate the ground
Septic tank from houses or farms – if not properly secured might reach ground water
Quality of water
Water pH – good ph is 7, if higher than 7 then some cells may precipitate and you can get
solid with water, if below 7, acidic water dissolves metals. pH of water affects our health Hardness – total amount of cells mostly calcium, magnesium in the water. If water is soft
there is not enough cells, if hard there is too much cells. You don’t want soft water
because it can dissolve lead.
Color – you don’t want colour. If there is colour, it is an indication of chemicals like
copper, or organic matter
Turbidity – if water turbid it does not necessary mean it’s contaminated.