Lecture 2 Water

Lecture 2 Water - Water- 2 Water: chemical and biological...

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Water- 2 Water: chemical and biological contamination Pathogenic microorganisms Acid Rain Euthophication and oxygen depletion Groundwater contamination Nitrates Volatile Organic Chemicals Water treatment plants Pumping and containment Flocculation Sedimentation: Filtration Aeration Disinfection Additional treatment options Wastewater treatment plants Primary, secondary and tertiary treatments
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Water: chemical and biological contamination 1) Contamination of water supplies by pathogenic (disease- causing) microorganisms (water-borne diseases). Cholera: Persons infected with cholera have massive diarrhea. This highly-liquid diarrhea is loaded with bacteria that can spread under unsanitary conditions to infect water used by other people. Cholera is transmitted from person to person through ingestion of water contaminated with the cholera bacterium, usually from feces. Typhoid fever: bacterial infection Dysentery: parasitic or bacterial infection. It is estimated that 80% of the cases of diarrheal disease in the world is attributable to unsafe water supply, sanitation and hygiene and is mostly concentrated on children in developing countries.
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2) Acid rain. Acid rain is rain or any other form of precipitation that is unusually acidic. Acid rain is mostly caused by human emissions of sulfur and nitrogen oxides (SOx and NOx) which react in the atmosphere to produce acids. Sulfur and nitrogen oxides mainly come from coal-fired power plants, but also from other industries and automobiles. Both the lower pH and higher aluminum concentrations in surface water that occur as a result of acid rain can cause damage to fish and other aquatic animals. Aluminum is normally tightly bound to clays and other minerals and can be released by acid. Acids are no threat to lakes and streams in areas where the rock is limestone (calcium carbonate), which can neutralize excess acid. CaCO 3 (s) + 2H + (aq) Ca 2+ (aq) + CO 2 (g) + H 2 O
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3) Oxygen depletion. The breakdown of organic matter by bacteria depletes dissolved oxygen in the water and enriches the water with plant nutrients. A measure of the amount of oxygen needed for this degradation is the biochemical oxygen demand or BOD. The greater the quantity of degradable organic wastes, the greater the BOD. A stream can handle a small amount of waste without any difficulty, but when massive amounts of raw sewage are dumped into a waterway, undesirable changes occur. -Eutrophication: it is an increase in chemical nutrients -- typically compounds containing nitrogen or phosphorus -- in an ecosystem. Eutrophication is frequently a result of nutrient pollution such as the release of sewage effluent and run-off from lawn fertilizers into natural waters (rivers or coasts) although it may also occur naturally in situations where nutrients accumulate. Eutrophication
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Lecture 2 Water - Water- 2 Water: chemical and biological...

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