Cc604 chapter 2_water_pollution

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  • 1. 9 2.0 WATER POLLUTION 2.1 The types of water pollution: a. point sources:  discharge pollutants at specific locations through pipes, ditches, or  sewers into bodies of surface water  Easily identified, monitored, & regulated b. non-point sources:  Nonpoint sources—sources that cannot be traced to a single site of discharge  Large areas of land that pollute water by runoff or atmospheric deposition  Agricultural runoff includes sediments, inorganic fertilizers, manure, salts from irrigation waters, & pesticides.  Responsible for an estimated 64% of all water pollution in US 2.2 The sources of water pollution and its effects on aquatic life: 2.2.1 Infectious agents: o Examples include bacteria, viruses, protozoa, & parasitic worms o Major human sources—human & animal wastes o Effects—diseases (Typhoid fever, Cholera, Dysentary, Giardiasis, Hepatitis) o Good indicator of water quality in terms of infectious agents is the number of colonies of coliform bacteria present in a 100-mL sample of water � WHO & EPA recommend 0 colonies/100-mL for drinking water & maximum level of 200 colonies for swimming 2.2.2 Oxygen-demanding wastes: o Examples include decomposition of animal & plant matter by aerobic bacteria o Major human sources—sewage, animal feed lots, paper mills o Effects—depletion of dissolved oxygen leading to death of aquatic organisms o Biological Oxygen Demand (BOD)—amount of dissolved oxygen needed by aerobic decomposers to break down the organic matter in a certain volume of water in a 5-day incubation period at 20o C. 2.2.3 Inorganic chemicals: o Examples include acids, toxic metals (Pb, As, Se), & salts (NaCl, Fl-) o Major human sources—surface runoff, industrial effluents, household cleansers o Effects—damage human systems (cancers), harm aquatic life, lower crop yields, accelerate corrosion, make water non-potable o Chemical water analysis is used to determine presence of inorganics in water 2.2.4 Organic chemicals: o Examples—gasoline, oil, plastics, pesticides, detergents o Major human sources—industrial effluents, household cleansers, surface runoff from farms & yards o Effects—threaten human health & harm wildlife o Chemical water analysis & use of indicator species used to determine
  • 2. 10 presence & concentration � Filter-feeding mollusks. 2.2.5 Sediment: o Examples—soil & silt o Major human sources—land erosion o Harmful effects—reduce photosynthesis, disrupt aquatic food webs, destroy spawning grounds of benthic species, clog harbors & lakes 2.2.2 Explain the causes of soil erosion. 2.2.3 Describe the effects of soil erosion on environment. 2.2.4 Identify the ways to control soil erosion. 2.2.6 Heat (Thermal pollution) o Examples include excessive heat o Major sources—water cooling of electric power plants o Lowers DO levels & causes thermal shock in species 2.3 Pollution of Streams & Lakes 2.3.1 The process of self-purification in river. • Streams & rivers have potential to rapidly recover from degradable wastes & excess heat o Depends on volume, flow rate, temperature, & pH o Developing nations deploy about 95% of all sewage directly into rivers & streams 2.3.2 Dilution limits using mass balance equation. 2.3.3 Explain dissolved oxygen profile in river (graph of dissolved oxygen against time). 2.4 The phenomena of eutrophication. 2.4.1 The eutrophication process occurred in a lake and its effects. • Lakes are more vulnerable to pollution o Often stratified with little vertical mixing o Have little flow • Eutrophication—natural nutrient enrichment of lakes leading to excessive algal growth o Human activities accelerate eutrophication (sewage treatment plants, runoff of fertilizers, & accelerated erosion of topsoil)—cultural eutrophication o Accumulation of nitrates can lead to nitrate poisoning as nitrates bind to hemoglobin reducing the capacity for oxygen transport (amphibians) o Leads to a potential algal bloom � Decreases light penetration � Decreases DO levels due to the action of decomposers � Disrupts nitrogen & phosphorus cycles
  • 3. 11 2.4.2 Explain the causes of eutrophication.  Soil retention o Nutrients from human activities tend to accumulate in soils and remain there for years. It has been shown that the amount of phosphorus lost to surface waters increases linearly with the amount of phosphorus in the soil. Thus much of the nutrient loading in soil eventually makes its way to water. Nitrogen, similarly, has a turnover time of decades or more. o  Runoff to surface water and leaching to groundwater o Nutrients from human activities tend to travel from land to either surface or ground water. Nitrogen in particular is removed through storm drains, sewage pipes, and other forms of surface runoff. Nutrient losses in runoff and leachate are often associated with agriculture. Modern agriculture often involves the application of nutrients onto fields in order to maximise production. However, farmers frequently apply more nutrients than are taken up by crops or pastures. Regulations aimed at minimising nutrient exports from agriculture are typically far less stringent than those placed on sewage treatment plants and other point source polluters. It should be also noted that lakes within forested land are also under surface runoff influences. Runoff can wash out the mineral nitrogen and phosphorus from detritus and in consequence supply the water bodies leading to slow, natural eutrophication. o  Atmospheric deposition o Nitrogen is released into the air because of ammonia volatilization and nitrous oxide production. The combustion of fossil fuels is a large human- initiated contributor to atmospheric nitrogen pollution. Atmospheric deposition (e.g., in the form of acid rain) can also affect nutrient concentration in water especially in highly industrialized regions. o  Other causes o Any factor that causes increased nutrient concentrations can potentially lead to eutrophication. In modeling eutrophication, the rate of water renewal plays a critical role; stagnant water is allowed to collect more nutrients than bodies with replenished water supplies. It has also been shown that the drying of wetlands causes an increase in nutrient concentration and subsequent eutrophication blooms. 2.4.3 Identify the methods of eutrophication control. � Planting vegetation along streambeds to slow erosion � Controlling application & timing of fertilizer � Controlling runoff from feedlots, golf courses, & fields � Use of biological control agents such as denitrification
  • 4. 12 2.5 Pollution of Groundwater 2.5.1 The sources ground water pollution: a. industrial waste b. domestic waste c. municipal landfill d. petroleum waste and mining e. agriculture f. saltwater intrusion. • Groundwater supplies 75% of drinking water in Europe & 51% in US • Pollution sources include storage lagoons, septic tanks, landfills, hazardous waste dumps, deep injection wells, and underground storage tanks filled with gasoline, oil, & solvents. • EPA estimates that 4.5 trillion liters of contaminated water seep into US groundwater each day. • Easily polluted because water in aquifers is renewed very slowly (recycling time is 1400 years compared to 16 days for rivers) o Degradable wastes do not break down due to slow flow of water, cold temperatures, & smaller populations of bacteria • Excessive pumping of groundwater leads to saltwater intrusion of an aquifer • Impossible to clean contamination so prevention is the only effective way to protect groundwater resources o Require leak detection devices for underground tanks o Banning disposal of hazardous wastes in deep injection wells & landfills o Storing hazardous wastes above ground 2.6 Sea / Ocean Pollution 2.6.1 The sources of sea pollution: a. domestic and industrial waste b. sludge disposal c. oil spillage • Coastal areas (wetlands, estuaries, coral reefs, etc.) o 40% of world’s population lives within 160 miles of the coast o 14 of the 15 largest metropolitan cities are coastal • Dumping of untreated sewage directly into the ocean along SE Asia • Algal blooms (Red tides)— o Release toxins that kill marine life o Poison seafood • Effects of oil on ocean ecosystems o Operation of offshore wells, washing tankers, pipeline & storage tank leaks
  • 5. 13 • 50% of oil pollution comes from oil dumped on land making its way to sewers o VOCs in oil kill aquatic organisms immediately (especially larvae) o Accumulation of tars on feathers & fur of marine birds & mammals—reduce natural insulation o Cleaning up oil spills • Floating booms to contain coil spill • Absorbent pads to soak up oil on beaches • Coagulating agents that cause oil to clump for easier pickup • Dispersing agents to break up oil slicks • Biological cleanup—oil degrading microbes