Environmental Studies IDC3O3 Ms. Nguyen

* More than two thirds of the world’s households must fetch water from outside the home * When water is scarce and difficult to obtain, it discourages proper sanitation * Availability doesn’t always mean affordability * Water sellers offer delivery to homes in most countries, but the quality often is questionable * Price may be more than most families can afford

* A typical family in in Lima, Peru uses one-sixth as much water as a middle class American household but pays three times as much for it * If government recommendations were followed to boil the water to prevent diseases, up to one-third of poor family’s income could be used in acquiring and purifying water

* Water pollution is anything that degrades water quality * Two types of pollution: * Point source: discharge pollution from specific location such as drain pipes, ditches or sewer outfalls * Example: factories, power plants, sewage treatment plants, underground coal mines and oil wells * Nonpoint source: water pollution are scattered or diffuse, having no specific locations where they discharge into a particular body of water * Run-off from farm fields and feedlots, golf courses, lawns and gardens, construction sites, logging areas, roads, streets and parking lots * Difficult to monitor, regulate and treat than point sources

* a major nonpoint pollution is atmospheric deposition of contaminates carried by air currents and precipitated into watersheds or directly onto surface water as snow, rain or dry particles. * For example: * The Great Lakes have been found to be accumulating industrial chemicals such as PCBs, dioxins, and agricultural toxins such as insecticide toxaphene * 26,000 metric tons of PCBs over the past 12 years have “disappeared” from Lake Superior and carried by air currents to other areas

* Amount of oxygen dissolved in water is a good indicator of water quality * Oxygen with a water content above 6 parts per million (ppm) will support many forms of aquatic life * Less than 2ppm, oxygen will only support worms, bacteria, fungi and other detritus feeders and decomposers * We use aquatic microorganisms as bioindicators * Caddisflies and dragonfly larvae = good water quality; worms = poor

* Oxygen is added to water by diffusion from the air, especially when turbulence and mixing rates are high * By photosynthesis of green plants, algae and cyanobacteria (blue –green bacteria) * Oxygen is removed from water by respiration and chemical processes that consume oxygen

* Eutrophication = process by which a body of water acquires a high concentration of nutrients, especially phosphates and nitrates or organic wastes * E.g. Organic waste such as sewage, paper pulp or food waste are rich in nutrients * Impact = Increases plant and algae growth

* With increased growth comes increased rate of death and decay  results in the growth of oxygen demanding decomposing bacteria * Biochemical oxygen demand (BOD) = measure of the oxygen used by microorganisms to decompose organic matter * High levels of BOD mean low levels of dissolved oxygen in the water * Since low levels of DO is available in the water, fish & other aquatic organisms may not survive * The affects of oxygen-demanding wastes on rivers depends to a great extent on the volume, flow and temperature of the river water

* Oxygen decline downstream is called the oxygen sag

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