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Water pollution and its prevention

Chapter 17. Water pollution and its prevention . 1. Water pollution. What is water pollution. Water pollution can be defined as

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Water pollution and its prevention

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  1. Chapter 17 Water pollution and its prevention

  2. 1. Water pollution

  3. What is water pollution • Water pollution can be defined as "the presence of a substance in the environment that because of its chemical composition or quantity, prevents the functioning of natural processes and produces undesirable environmental and (human) health effects."

  4. Categories of Water Pollutants

  5. Main groups of water pollutants • Biodegradable • Rapidly degradable (non-persistent) • Slowly degradable (persistent) • Non-biodegradable

  6. Water Pollutants: sources a. Non-point-source pollutants: agricultural runoff, storm-water drainage, atmosphericdeposition. b. Point-source pollutants: dischargesfromfactories, sewagesystems, power plants, underground coal mines, oilwells.

  7. Strategies to bring water pollution under control: • Reduce or remove the sources • Treat the water to remove pollutants or convert them to harmless forms.

  8. Water pollutants: types a.Pathogens b. Organicwastes c.Chemicalpollutants d.Sediments e.Nutrients

  9. Pathogens • Infectious agents that cause sickness and death • Come from excrement from humans and other animals that are infected

  10. Public heath • Before mid 1800s: epidemics were common in cities (typhoid fever, cholera) • After: connection between disease and sewage-carried pathogens • Today: public health measures • Purification and disinfection of public water supplies with chlorine and other agents • Sanitary collection and treatment of sewage wastes • Maintenance of sanitary standards in all facilities in which food is processed or prepared for public consumption • Public education in personal and domestic hygiene practices

  11. Sanitation = good medicine • Good health is a result of the prevention of disease through public-health measures • Population in areas where here is little or no sewage treatment are extremely vulnerable to deadly epidemics.

  12. Organic wastes • Includes leaves, grass clippings, trash, etc. • Enter water as a consequence of runoff or excessive aquatic plant growth • As bacteria and detritus feeders decompose organic matter, they consume dissolved oxygen (DO) in water. • BOD (biochemical oxygen demand): measures the amount of organic material in water in terms of how much oxygen will be required to break it down. • Fishes and shellfish are killed below a DOof 2 to 3 ppm • A BOD value for raw sewage is around 250 ppm

  13. Chemical pollutants • Inorganic chemicals: include heavy metals (lead, mercury, cadmium, nickel, etc), acids from mine drainage and acid precipitation, and road salts. • Organic chemicals: include petroleum products, pesticides, industrial chemicals (PolyChorinated Biphenyls, cleaning solvents and detergents)

  14. Sediments • Erosion from farmlands, deforested slopes, overgrazed rangelands, construction sites, mining sites, stream banks and roads increase the load of sediments.

  15. Nutrients • Inorganic chemicals carried in solution in all bodies of water are classified as nutrients. • Include phosphorus and nitrogen • Stimulate undesirable plant growth in the bodies of water. • Sources include sewage outfalls, agricultural runoff, lawns and gardens, golf courses and storm drains.

  16. Water quality standards • National Recommended Water Quality Criteria (EPA) provides standards for assessing water pollution. • Lists 158 chemicals and substances as criteria pollutants and recommends concentrations for fresh water, salt water and human consumption

  17. Water quality standards • Criteria maximum concentration (CMC): highest single concentration beyond which environmental impacts may be expected • Criterion continuous concentration (CCC): highest sustained concentration beyond which undesirable impacts may be expected • Drinking water standards and health advisories: enforceable under the authority of the Safe Drinking Water Act (SDWA) • Maximum Contaminant levels (MCLs)

  18. Arsenic as a example: • Listed as a human carcinogen • CMC and CCC values are 340 and 150 g/L for freshwater bodies, and 69 and 36 g/L for saltbodies. • Drinking water MCL concentration is 10 g/L

  19. Other applications to the water quality criteria • National pollution discharge elimination system program (NPDES): addresses point-source pollution and issues permits to regulate discharges from industrial sources. • Total maximum daily load program(TMDL): evaluates all sources of pollutants entering a body of water, especially non-point sources

  20. 2. Eutrophication

  21. Types of aquatic plants • Benthic • Submerged aquatic vegetation (SAV) • Emergent vegetation • Phytoplankton (algae, protists, cyanobacteria)

  22. What is an oligo-trophic body of water? • Oligotrophic = low in nutrients

  23. What is a Eutrophic Body of Water? • Eutrophic = well nourished

  24. How do you create a Eutrophic Body of Water? • 1. Nutrient enrichment, natural or cultural • 2. Increased phytoplankton growth resulting in increased turbidity • 3. Loss of sunlight, food and habitat • 4. Depletion of dissolved oxygen from decomposition of phytoplankton by decomposers

  25. How to Stop Eutrophication • Attack the symptoms: • Chemical treatments (with herbicides) • Aeration • Harvest aquatic weeds • Draw water down

  26. How to Stop Eutrophication • Attack the root cause: • Control point-source pollutants • Ban the sale of phosphate detergents • Regulate the maximum alowablelevel of phosphates • NPDES permits

  27. How to Stop Eutrophication • Attack the root cause: • Control non-point-source pollutants • EPA regulationsthrough the TMDL program include: • Identifypollutants • Estimate pollution commingfrom all sources • Estimate the ability of the body of water to assimilatepollutants • Determine the maximum allowable pollution load • Allocate the allowablelevel of pollution among the different sources

  28. How to Stop Eutrophication • Attack the root cause: • Best management practices (BMPs) • Practices used to minimize erosion, runoff and leaching • Methods of soil conservation

  29. When washings from animal facilities are flushed directly into natural waterways, they contribute significantly to eutrophication. This may be avoided by collecting the flushings in ponds from which both the water and the nutrients may be recycled.

  30. How to Stop Eutrophication • Attack the root cause: • Recovery • Governmentpractices for the management of watersheds • Lake washington

  31. 3. Sewage Management and Treatment

  32. History of sewage treatment • Late 1800s: human excrement was disposed in the outdoor privy • Louis Pasteur and other scientists showed that sewage borne bacteria were responsible for many infectious diseases • Human wastes started to be disposed through drain systems • The flush toilet was introduced • Water became unfit to swim in because of sewage contamination • 1900: Sewage treatment systems were developed

  33. What is in Raw Sewage • 1. Debris and grit: plastic bags, coarse sand, gravel • 2. Particulate organic matter: fecal matter, food wastes, garbage, toilet paper • 3. Colloidal and dissolved organic matter: urine, soaps, detergents and cleaning agents. • 4. Dissolved inorganic matter: nitrogen, phosphorus, and other nutrients • 5. Pathogens: bacteria, protozoa, virus • 6. Heavy metals, pesticides, and various other toxic compounds

  34. How Do We Remove These Substances from the Water? • Preliminary Treatment - debris and grit removed by a bar screen and grit chamber

  35. How Do We Remove These Substances from the Water? • Primary Treatment - particulate organic matter removed by primary clarifiers

  36. How Do We Remove These Substances from the Water? • Secondary Treatments - colloidal and dissolved inorganic matter removed by trickling filter systems or activated sludge systems

  37. How Do We Remove These Substances from the Water? • Biological Nutrient Removal - dissolved inorganic matter removed by bacterial denitrification and bacterial uptake of phosphorusa. Can also be done inorganically by using chemical processes·Lime causes phosphate to precipitate as insoluble calcium phosphate ·Ferric chloride causes phosphate to precipitate as insoluble ferric phosphateb. Removal of the dissolved inorganic matter is not standard treatment though it is becoming more common

  38. Final Clarification and Disinfection • Meant to eliminate pathogens • Disinfecting agents • chlorine gas • Sodium hypochlorite (chlorox) • Ozone gas • Ultraviolet light

  39. Discharge • BOD values are 10 to 20 ppm(200 ppm in the incoming sewage) • Many cities are still operating with lower quality treatments or with no treatment at all.

  40. Treatment of sludge • Raw sludge • Most is disposed in landfills with no previous treatment • It is considered a biologically hazardous material • It is a nutrient-rich organic material with potential to be used as organic fertilizer • Methods for treating sludge include: • Anaerobic digestion • Composting • Pasteurization

  41. Anaerobic digestion • Raw sludge is put into large airtight tanks (sludge digesters) • Anaerobic bacteria break down the organic matter • End products include carbon dioxide, methane and water (biogas) • Treated sludge is called biosolid • Dewatered it becomes a sludge cake

  42. Composting • Raw sludge is mixed with wood chips • Placed in piles that allow air circulation • Aerobic bacteria and other decomposers break down organic material to rich humus-like material

  43. Pasteurization • The sludge cake is put through ovens to be pasteurized • The product is dry, odorless organic pellets.

  44. Alternative Treatment Systems • On site wastewater treatment systems • Using effluents for irrigation • Reconstructed wetland systems

  45. 4. Public Policy

  46. Public Policy • EPA is responsible for overseeing water • Depends on laws passed by Congress • Clean water act (CWA) of 1972 • Required permits for all point source discharges of pollutants • Clean water state revolving fund program (SRF) • Gives funds to local governments to build treatment facilities

  47. Problems and progress • Problems • Non point source pollution • Construction of new wastewater treatment facilities • Storm water discharges • Sewer overflows • Wetlands protection • Animal feeding operations • Progress • The number of people served by adequate sewage has increased • Soil erosion has been reduced • Two-thirds of the nation’s waterways are safe for fishing and swimming • Many rivers have been cleaned up and restored

  48. http://www.ewg.org/node/22520 • http://wn.com/Another_dead_body_in_the_Ganges_river_at_Varanasi • http://smkalammegah.wordpress.com/ • http://www.greendiary.com/entry/china-to-impose-hefty-fines-on-polluters/ • http://bio4esobil2010.wordpress.com/2011/06/01/eutrophication/ • http://www.squamlakes.org/programs/phosphorus.php • http://www.sciencephoto.com/media/183928/enlarge • http://epistimograph.blogspot.com/2011/04/blue-waters-of-mediterranean.html • http://en.wikipedia.org/wiki/File:Eutrophic_Armstrong.jpg • http://www.cee-environmental.com/en/company/info/id/2302 • http://www.jleeg.com/2010/04/09/fertilizing-with-milorganite-organic-fertilizer/dsc03501/

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