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University of Toronto Scarborough
Environmental Science
Chris Bovaird

1. Water Quality and Water resource • the sustainability of human society depends on the availability of plentiful and potable water • water supply faces a combination of old threats from human and industrial wastes and new threats from demand overload and climate change • updating the means of disposal of human wastes improves human health to greater extent than purveying clean water supplies 2. Sources of water • drinking water is obtained mainly from surface water eg. streams, lakes, rivers or from ground water through artesian or other tupes of wells • other means include desalinating sea water and rainwater • availability, treatment and also contaminates varies depending on the sources of water. • 2 TYPES of water sources • surface water, is prone to more contamination by both microbial pathogens and chemicals since it directly receives industrial and municipal waste • Ground water is less contaminated than surface water because the soil through which it passes through acts as a natural filter • exception however happens when theres a dissect or a short path from the surface to ground water which leads to leaching • Ground water collects slowly and doesnt replenish itself; it remains contaminated for a very long time 3. Uses of water • human consumption is actually the smallest use of water • 70% of total water withdrawal is used for irrigation • also used for industrial uses in developing world • within home, far more water is used during shower, for flushing toilets, dish washing than cooking and drinking 4. Sources of contamination  Contaminants can enter drinking water by a variety of mechanism  Pesticides, fertilizers, enter drinking water sources after being deliberately applies to the land and washing into surface or ground water.  Animal waste also enters in similar fashion  Industrial waste chemical and municipal wastes directly discharged into surface water esp in developing countries  Other chemicals reach surface water after moving through soils  Eg. Cadium, lead can leach out of dumps while gasoline products can contaminate drinking water through leakage from storage tanks  Sources of contaminants that discharges into receiving waters from a pipe or other identifiable device are called “point sources”  Point sources include industrial wastes and sewage treatment plants  Sources of contaminant that cannot be defined by discrete pipes are called “non point sources”  though developed world made tremendous effect in point source water, developing world still faces A SERIOUS problems with point source contamination of water due to poor enforcement of existing laws. 5. Water Treatment process  developed world reduced the burden of waterborne diseases by implementing a process to treat drinking water in the late 19 th th century and early 20 century  FIRST water is pumped from its sources. Surface waters containing sediment and microbial pathogens may be held in settling tanks or pretreated with chlorine at this stage  SECOND, involves the addition of a chemical coagulant, usually containing alum to make small particles stick together in the water.  flocculation, the collecting particles are stirred together to make them adhere and become larger and heavier, making it easier for the particles to sink to the bottom of the holding tanks.  These steps are meant to remove tiny particles including microbes but this step doesn
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