1 / 35

Water Pollution Chapter 19

Water Pollution Chapter 19. Types and Effects. Water pollution: any chemical, biological or physical change in water quality that has a harmful effect on living organisms or makes water unsuitable for use. Table 19-1 Major Categories of Water Pollutants. How do we measure Water Quality?.

ziya
Télécharger la présentation

Water Pollution Chapter 19

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Water PollutionChapter 19

  2. Types and Effects • Water pollution: any chemical, biological or physical change in water quality that has a harmful effect on living organisms or makes water unsuitable for use. • Table 19-1 Major Categories of Water Pollutants

  3. How do we measure Water Quality? • 1) Measure number of coliform bacteria present in 100-mL sample • WHO recommends 0 colonies/100mL drinking • EPA max level of swimming 200 colonies/100mL • 2) Measure oxygen demanding waste • Determined by measuring biological oxygen demand (BOD): the amount of dissolved O needed by decomposers to breakdown waste

  4. Sources • Nonpoint: can’t be traced to any single site of discharge • Acid deposit, runoff of chemicals, pesticides, fertilizer/manure • Point source: discharge at specific locations • Factories, sewage treatment, mines, oil tankers • Easy to identify, monitor and regulate

  5. Pollution of Freshwater Streams • Can recover rapidly from degradable, oxygen-demanding wastes and excess heat through dilution and bacterial decay • These processes do not eliminate nonbiodegradable or slowly degradable • The time and distance needed to recover depend on volume of waste, stream’s volume, flow rate, temp., and pH level.

  6. Cuyahoga River, Ohio 1959/’69

  7. Pollution of Freshwater Lakes • Dilution of pollutants in lakes, reservoirs and ponds less effective • Contain stratified layers with little vertical mixing • Little free flow • Ponds have small volumes of water • More vulnerable to contamination by plant nutrients, oil, pesticides, toxic substances

  8. Eutrophication • Lakes receive inputs of nutrients and silt eroded and running off from surroundings • Eutrophication: natural nutrient enrichment of lakes • Near urban or agricultural areas, human activities accelerate input of plant nutrients • Results in cultural eutrophication • Caused mostly by nitrate and phosphate containing effluents

  9. Groundwater Pollution • More of a problem because numerous sources as we dump wastes into storage lagoons, septic tanks, landfills, hazardous dumps and deep injection wells. • Human health risks from contaminants: petrochemicals (gas, oil) organic solvents (TCE) pesticides and arsenic lead (Pb) and fluoride (F-)

  10. Protecting Groundwater • Contaminated aquifers almost impossible to clean up because of large volume, inaccessibility, and slow movement • Preventing contamination only effective method • Monitor aquifer near landfills and tanks • Leak detection systems on underground tanks • Banning/ strictly regulating hazardous waste

  11. 19.5 Oceans and pollution

  12. Clean Water Act (1972) • 1) Make all waters “fishable and swimmable” • 2) Require discharge permits of major polluters • 3) Identify toxic pollutants and require use of best practices technology (BPT)

  13. 19-5 Ocean Pollution • Oceans can dilute, disperse, and degrade large amounts of raw sewage, sludge, oil and some degradable industrial waste. • Pro: dumping sludge and hazardous waste into deep ocean because some organisms are more resilient in the ocean. • Con: Feel it would delay pollution prevention and promote further degradation of this vital system.

  14. Coastal Areas • Include wetlands, estuaries, coral reefs and mangrove swamps • Sustain most of the damage of waste inputs • Most coastal developing countries dump sewage into the sea without treatment • 85% of sewage from cities along Mediterranean Sea is discharged untreated

  15. Harmful Alga Blooms • Runoff of sewage and agricultural wastes into coastal waters introduce large quantities of nitrates (NO3-) and phosphate (PO43-) plant nutrients that cause explosive growth of algae. • The harmful alga blooms (HAB) are called red, brown, or green tides depending on their color. • HAB’s can release toxins that damage fisheries, kill fish-eating birds, reduce tourism and poison seafood.

  16. Death of the HAB’s deplete dissolved oxygen and cause the death of marine species. • These oxygen-depleted zones form in coastal waters b/c of excessive nonpoint inputs of fertilizers and animal wastes from land runoff and deposition of nitrogen from the atmosphere. • In these zones, aquatic life dies or moves elsewhere • Biggest zone in U.S. waters forms every summer in Gulf of Mexico near Louisiana and Mississippi River Basin (Figure 19-13).

  17. What pollutants do we dump into the Ocean? • Barges and ships still legally dump large quantities of dredge spoils (materials containing toxic metals scraped from bottom of harbors and rivers to maintain shipping channels) into Atlantic, Pacific, and Gulf coast • Many countries dump sewage sludge: gooey mixture of toxic chemicals, infectious agents, solids from wastewater treatment plants • 1992 U.S. banned this practice

  18. Oil Effects on Animals • Depend on type of oil, amount released, distance from shore, time of year, weather, water temperature and currents. • Volatile hydrocarbons immediately kill organisms, some others form globules that float on surface and coat feathers of birds. • This oil coating destroys the natural insulation and buoyancy, causing many to drown or die from loss of body heat • Most life forms recover from crude oil within 3 years, but refined oil recovery up to 10 years

  19. Oil Effects on Oceans • Tanker accidents or offshore drilling blowouts get publicity but are not the main source of oil pollution. • Largest input of oil is released into the ocean during normal operation of offshore wells, washing tankers and releasing oily water and from pipeline and storage tank leaks. • Almost half of oil in the ocean is waste oil dumped, spilled or leaked into sewers by cities, industries or at-home oil changes.

  20. Clean Up Oil Spills • Prevention still best method • Others remove only part of the oil • None work well on large spill • Chemical methods • Coagulating agents to cause oil to clump or sink • Dispersing agents to break up oil slicks • Mechanical methods • Floating blooms to contain the oil spill or keep it from moving • Skimmer boats to vacuum up oil • Absorbent pads or mesh pillows to soak up oil

  21. Bioremediation • Biological method of cleanup • May involve constructing wetlands or involving plants to soak up organic nutrients • Ex: Exxon Valdez oil spill • Using bacteria to digest the oil coating • More effective than artificial methods

  22. 19-7 Drinking Water Quality • If no access to clean water, it is taken from • Shallow groundwater easily contaminated • Nearby polluted river water • Mudholes used by animals and humans • Purification developing countries with no treatment systems • Tropical regions: expose water to the sun • Bangladesh: cloth to strain water • PUR packet: powdered mixture that removes pathogenic microorganisms and suspended matter

  23. U.S. Safe Drinking Water Act of 1974 • Requires EPA to establish national drinking water standards called maximum contaminant levels • Privately owned wells not required to meet standards • Opposition: Congress pressured by water-polluting industries to weaken Act • Eliminate national water tests • No media access of health violations • Allow states to violate the act if they cannot afford to comply • Eliminate water systems use of technology to remove cancer causing agents

  24. 19.6Preventing/Reducing Surface Water pollution

  25. Preventing/Reducing Surface Water Pollution Clean Up of Nonpoint Pollution: • Reducing and controlling runoff • Preserve wetlands to allow nitrate and phosphate to flow through and be absorbed Clean Up of Point Source Pollution • Legal Approach (Basis of efforts to control pollution) • Federal Water Pollution Control Act of 1972 (renamed Clean Water Act when amended in 1977) • 1987 Water Quality Act • Technological Approach

  26. Technological Approach to Point source Pollution • Septic Tanks: sewage from each house goes into holding tank on property • (25% of all homes) • Sewer lines: urban areas; waste flow through series of pipes leading to treatment center • Some cities have separate lines for sewage and storm water; some combined lines so if rains flood system, often discharges untreated sewage into surface water

  27. Sewage Reaches Treatment Plant • Preliminary: large objects screened • Primary Treatment (mechanical process) • Removes 60% of the suspended solids and 30% of oxygen demanding wastes from sewage • Grease and oils removed, organic solids sent to Biosolids treatment Uses screens to filter out debris such as sticks, stones and rags Allow suspended solids to settle out as sludge in settling tank

  28. 2) Secondary Treatment (biological process) • Aeration process (add oxygen) 1) Aerobic bacteria remove 90% of biodegradable, oxygen-demanding organic waste still left over Activated sludge process: pump sewage into large tank and mix for several hours with bacteria-rich sludge and air bubbles Then goes to sedimentation tank where microorganisms and suspended solids settle out as sludge

  29. Sludge produced is incinerated, sent to landfill or treated in biosolids facility • Secondary removes only tiny fraction of radioactive isotopes and persistent organic substances such as pesticides

  30. 3) Advanced Sewage Treatment • Water travel through anthracite coal filters that remove specific pollutants left in water after primary and secondary • Sometimes not used because cost twice as much to build and four times as much to operate as secondary plants • Growing interest in using membrane based technologies reverse osmosis, micro filtration, ultra filtration and nanofiltration

  31. Because of Clean Water Act, most U.S. cities have combined primary and secondary sewage treatment plants • **Figure 19-17 • Before discharge, water from all three processes undergo • 1) bleaching to remove water coloration • 2) disinfection to kill disease-carrying bacteria (chlorination)

  32. Treating Sewage by working with Nature • Sewage Walls • Run along residential block • Channels sewage through terraced planters that progressively filter and purify the waste • Living machines • Look like aquatic botanical gardens, powered by sun • Wastewater garden (Figure 19-19) • Small, low tech artificial wetland to treat sewage • Water flowing out can be used to irrigate gardens or fields or flush toilets

  33. The Living Machine

More Related