Chapter 3 Textbook Notes

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University of Toronto Scarborough
Environmental Science
Jovan Stefanovic

Human Health and Environment: Chapter 3 Water Quality and Water Resources (Textbook reading) Safe drinking water is a need ; we depend on plentiful and drinkable (clean) water but we are facing issues with water quality and quantity Water supply faces old threats and new threats o Old threats: human and industrial wastes o New threats: demand overload and climate change There are lots of waterborne infections that have existed since the 19 century o Diarrhoeal deaths due to waterborne infections kill over 2 million children annually o Diarrhoeal illnesses are the result of drinking contaminated water Widespread use of oral rehydration therapy has reduced waterborne disease related deaths. However, there is very little being done to improve water and sanitary infrastructure in developing countries Updating the means of disposal of human wastes improves human health to a greater extent than providing clean water supplies Sources of Drinking Water Usually comes from surface water (e.g. streams, rivers, and lakes) or ground water through artesian or other types of wells Other sources collecting rain water or desalinating sea water (taking the salt out of salty, seawater) Surface water more prone to contamination by both microbial pathogens and chemicals since it directly receives industrial and municipal wastewater and runoff from the land o Pathogen: any disease-producing agent, especially a virus, bacterium, or other microorganism. Ground water usually less contaminated than surface water bc the soil which it filtersseeps through serves as a filter EXCEPTION: groundwater can get contaminated if o Ex 1: there is a direct or short path from surface to groundwater, when concentrated wastes deep in the soil leach into groundwater, as beneath a landfill o Ex 2: when wastes are injected directly into the ground Once chemicals enter groundwater, it is contaminated for a long period of time bc groundwater collects slowly and doesnt quickly replenish itself Uses of Water Human consumption of water (e.g. drinking and using water to cook) is one of the smallest uses of water 70% of water is used to irrigate agricultural land (88% of irrigational water is used by Africa, 31% in Europe) Industrial uses of water are substantial usually used to cool or flush equipment. The water is then usually returned to streams, rivers or coastal waters (the returned water often ends up being warm or contaminated by chemicals Tap water at home mostly used for flushing toilets, washing clothes, showering , watering lawns and cars Sources of Contamination Many chemical s (e.g. pesticides and fertilizers) enter drinking water sources after being deliberately applied to land or even ponds & streams and washing into surface or ground water Animal wastes enter drinking water in a similar fashion as above Industrial waste chemicals and municipal wastes containing human fecal material and whatever chemicals have entered the system may be directly discharged into surface water (esp. in developing countries) Other chemicals reach drinking water sources after moving through soils a. E.g. cadmium and other heavy metals can leach out of dumps and landfills while gasoline products and additives can contaminate drinking water through leakage from storage tanks b. Toxicants like arsenic and radon occur naturally in the earths crust and contaminate groundwater that is in contact w deposits of these substances
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