EESA10 Chapter 3.docx

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University of Toronto Scarborough
Environmental Science
Silvija Stefanovic

CHAPTER 3  Our water supply faces old threats from human and industrial waste and new threats from demand overload and climate change  To fulfill human needs of water, we need to answer “how clean” and “how much” (Quantity and quality)  Diarrheal disease usually caused due to drinking contaminated water  40% of the world population lack access to improve sanitary infrastructure  Updating the means of disposal of human waste improves human health more than providing clean water supplies  Drinking water is obtained from surface water such as streams, rivers, lakes  Other sources include collecting rain water and desalinating sea water  Surface water is more prone to contamination by microbial pathogens and chemicals since it receives industrial and municipal wastewater and runoff from the land  Groundwater is usually less contaminated than surface water because the soil acts as a filter. Exceptions occur when there is a direct path between surface to the groundwater, like under a landfill  Groundwater remains contaminated for a long time because it collects slowly and does not reload itself quickly  Human consumption is the smallest use of water  70% of water used for irrigating agriculture land  In homes, tap water is used most to flush, washing clothes, showering Sources of contamination  Use of pesticides, fertilizers. Other chemicals reach after moving through soils. For eg: cadmium and heavy metals can leach out of dumps and landfills  Arsenic and radon occur naturally in the earth’s crust and contaminate ground water  Point sources: sources of contaminants that discharge into receiving waters from a pipe or other device. Point sources include industrial wastes and sewage treatment plants  Non-Point sources: source of contaminants that cannot be defined by discrete pipes. Eg: agricultural runoff, runoff of oils and chemicals from streets, air borne emissions of mercury that may dissolve in water sources  In developed countries, water undergoes several cleaning processes and then chlorine is added to disinfect any toxins in the water  In developing countries, they rely on point of use methods. Boiling water is the traditional method of water purification but this uses a lot of energy, newer techniques include use of dark plastic bottles that collect solar energy to disinfect water. However, they only reduce microbial pathogens and don’t reduce the concentrations of chemical contaminants Biological threats to water quality  WHO has determined 5 ways water is associated to human diseases: 1. Waterborne: transmitted by microorganisms that survive within water and directly ingested 2. Water-washed: diseases exacerbated by inadequate washing of hands or food, such as trachoma, skin and eye infections and many of fecal-oral pathogens that cause waterborne disease 3. Water-based: caused by organisms that spend part of their life cycle as larval forms within freshwater and comes in contact with humans through bathing or consuming infested water. Eg: schistosmisis, dracunculasis 4. Water-related: caused by organisms that breed or spend part of their life cycle in water but do not come in contact with humans via water exposure. Eg: dengue, malaria 5. Water-dispersed: caused my microorganism (legionella) that proliferate within water supplies and are transmitted to humans by dispersal in air and inhalation  Waterborne pathogens infect the gastrointestinal tract. Microbial pathogens are categorized as bacterial, viral or protozoal. They differ in their life cycles, hosts and survival in the environment  To mea
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