▏水污染 英文版[教学学习]

1、Water pollution,1,学习课堂,It covers 71% of the earths surface and makes up 65 % of our bodies. Without the seemingly invaluable compound comprised of hydrogen and oxygen, life on Earth would be non-existent,Water is Essential for Life,2,学习课堂,Three fourths of the surface of the Earth is covered with wat

2、er. Nearly 98% of the water on Earth, though, is seawaterunfit for drinking and not even suitable for most industrial purposes. Something less than 2% of the water is frozen in the polar ice caps, leaving less than 1% available as fresh water.,3,学习课堂,Water: Unusual Properties,Many chemical substance

3、s are soluble in water. Thus, they are easily dispersed and eventually are scattered to nearly infinite dilution in the ocean. Those properties of water that make it uniquely suited for the support of life also make it easy to pollute.,4,学习课堂,Natural Water Isnt All H2O,Rainwater carries dust particl

4、es from the atmosphere to the ground. Rainwater also dissolves a little oxygen, nitrogen, and carbon dioxide as it falls through the atmosphere. During electrical storms, lightning causes nitrogen, oxygen, and water vapor to combine to form nitric acid.,5,学习课堂,As water moves along or beneath the sur

5、face of the Earth, it dissolves minerals and matter from decaying plants and animals. The principal positive ions (cations) in natural water are sodium (Na+), potassium (K+), calcium (Ca2+), magnesium (Mg2+), and sometimes iron (Fe2+ or Fe3+). The negative ions (anions) are usually sulfate (SO42-),

6、bicarbonate (HCO3-), and chloride (Cl-).,6,学习课堂,hard water,Water containing these calcium, magnesium, and iron ions is called hard water. The positive ions react with the negative ions in soap to form a scum that clings to clothes and leaves them dingy looking.,7,学习课堂,Water pollution,Water pollution

7、 is any chemical, physical or biological change in the quality of water that has a harmful effect on any living thing Water pollution caused by human activities is a large set of adverse effects upon water bodies such as lakes, rivers, oceans, and groundwater Pollutants in water include a wide of ch

8、emicals, pathogens 病原体, and physical chemistry or sensory changes.,8,学习课堂,Water pollution,Water pollution is the leading worldwide cause of deaths and diseases, and that it accounts for the deaths of more than 14,000 people daily. Effects of water pollution include poisonous drinking water, poisonou

9、s food animals, unbalanced river and lake ecosystems, deforestation and many other effects,9,学习课堂,Sources of water pollution,The used water of a community is called wastewater, or sewage. If it is not treated before being discharged into waterways, serious pollution is the result. There are two sort

10、s of sources, point and nonpoint sources. Point sources discharge pollutants at specific locations through pipelines or sewers 下水道into the surface water. Nonpoint sources 非点(污染)源are sources that cannot be traced to a single site of discharge.,10,学习课堂,Factories Agriculture Transportation Household,So

11、urces of water pollution,11,学习课堂,Domestic sewage,Domestic sewage refers to waste water that is discarded from households. Also referred to as sanitary sewage. Domestic sewage contains a wide variety of dissolved and suspended impurities: a. organic materials-food and vegetable waste b. plant nutrien

12、ts- chemical soaps, washing powders c. disease-causing microbes微生物,12,学习课堂,Household Chemicals,Example: substances used for houses clean: Soap and synthetic detergents Wax Paints and paint removers Bleaches Disinfectants消毒剂 Polishes,13,学习课堂,Agricultural Run off,Fertilizers: nitrate , phosphates Pest

13、icides: phenol, chlorine diphenyl Eutrophication富营养作用: nutrients artificially supplemented results in an abnormal increase in the growth of water plants,14,学习课堂,Industrial Pollution,Industrial effluent of many kinds of waste, is discharged into streams, lakes, or oceans, which in turn disperse the p

14、olluting substances. The pollutants include grit, asbestos石棉, phosphates and nitrates, mercury, lead, caustic soda and other sodium compounds, sulfur and sulfuric acid, oils, and petrochemicals. Example: Chrome plating on bumpers, grills, and ornaments is a source of pollution,15,学习课堂,Pollutants fro

15、m various industries,The textile industry dumps conditioners, dyes, bleaches, and water effluents containing oils, dirt, and other organic debris. Meat-packing plants dump blood, the contents of entrails 内脏, and other animal wastes. Other food-processing plants discharge fruit and vegetable skins, s

16、eeds, leaves, stems, and other vegetable wastes. Refineries 精炼厂 release dyes, oils, acids 盐水, sulfur compounds, and other wastes. Chemicals plants produce a variety of waste materials.,16,学习课堂,Oil spills,Oil spills from tankers at sea or leaks from underground storage tanks on land are very difficul

17、t to control Oil spills at sea decrease the oxygen level in the water and cause grave harm to the creatures living in the sea. On land crude is transported through pipelines or tankers which can get damaged and spew out crude oil over the land,17,学习课堂,Oil spills are very difficult to control as oil

18、tends to spread very fast, affecting a large area in a very short time.,18,学习课堂,Groundwater and its contamination,Groundwater are contaminated with heavy metals, persistent organic pollutants, and nutrients Pesticides : Run-off from farms, backyards, and golf courses Leachate沥出液from landfill sites U

19、ntreated or inadequately treated municipal sewage :organic material , microbial pathogen Nutrients :phosphorus and nitrogen Synthetic organics :industrial chemicals and pesticides,19,学习课堂,Chemicals in drinking water,Chemicals in drinking water can be both naturally occurring or introduced by human i

20、nterference Fluoride Arsenic Petrochemicals Chlorinated solvents Salts,20,学习课堂,Different types of water pollution,Microbiological : Disease-causing (pathogenic) microorganisms, like bacteria, viruses and protozoa原生动物. Chemicals : A whole variety of chemicals from industry, such as metals, solvents a

21、nd acids,21,学习课堂,Oxygen-depleting Substances Many wastes are biodegradable, they can be broken down and used as food by microorganisms like bacteria. Too much biodegradable material can cause the serious problem of oxygen depletion in waters,22,学习课堂,Aerobic bacteria,Aerobic bacteria that live in wat

22、er use oxygen gas dissolved in the water when they consume their food Aerobic microorganisms-which use dissolved oxygen- convert the nitrogen, sulfur, and carbon compounds present in the wastewater into odorless- and relatively harmless- oxygenated forms like nitrates, sulfates and carbonates,23,学习课

23、堂,Anaerobic bacteria,Once the oxygen is depleted, other (anaerobic) bacteria that do not need dissolved oxygen take over Anaerobic microorganisms produce toxic and smelly ammonia, amines, and sulfides, and flammable methane (swamp gas),24,学习课堂,Biochemical oxygen demand, or BOD,BOD is the amount of o

24、xygen required by micro-organisms to decompose the organic substances in sewage. The more organic material there is in the sewage, the higher the BOD.,25,学习课堂,Nutrients,Water-soluble nitrates and phosphates that cause excessive growth of algae and other water plants, which deplete the waters oxygen

25、supply.,26,学习课堂,Suspended matter,Particulate matter, consist of much larger- but still very small- particles which are just suspended in the water They will eventually settle out and form silt or mud at the bottom :sediments,27,学习课堂,Water-borne disease,Pathogens which include virus, bacteria, protoz

26、oa, and parasitic worms are disease-producing agents found in the faeces of infected persons. Hepatitis 肝炎, cholera霍乱, dysentery痢疾, diarrhoea腹泻, skin irritation , and typhoid伤寒症are common water-borne diseases,28,学习课堂,How do we prevent water pollution?,In urban areas, the wastewater from homes, busin

27、esses and factories is collected by a system of underground pipes- sewers which carry it to one or more central treatment facilities. Homes in non-urban areas that are not connected to a sewer are usually required by their town to have on-site treatment systems.,29,学习课堂,Wastewater treatment plants,C

28、onsists of a train of individual unit processes, with the output (effluent) of one process becoming the input (influent) of the next process. Biological plants are more commonly used to treat domestic or combined domestic and industrial wastewater from a municipality. Physical/chemical plants are mo

29、re often used to treat industrial wastewaters directly, because they often contain pollutants which cannot be removed efficiently by microorganisms,30,学习课堂,A typical treatment plant,The first stages will be made up of physical processes that take out easily removable pollutants. The remaining pollut

30、ants are generally treated further by biological or chemical processes,31,学习课堂,physical process,A physical process usually treats suspended, rather than dissolved pollutants flocculation Filtration :Ultrafiltration, and reverse osmosis adsorption on activated charcoal Air or steam stripping,32,学习课堂,

31、Desalination of seawater by reverse osmosis.,33,学习课堂,A common set of processes,Preliminary treatment : grinders, bar screens, and grit channels. To remove large or hard solids that might clog or damage other equipment.,34,学习课堂,Primary settling basins,The water flows slowly for up to a few hours, to

32、allow organic suspended matter to settle out or float to the surface.,35,学习课堂,Secondary treatment,to remove the remaining dissolved or colloidal organic matter using usually biological method. The most common type of biological treatment process : Activated sludge process,36,学习课堂,Activated sludge process,consists of two parts, an aeration tank and a