Chapter 16

Pollution from Biological Sources 

    •  Waterborne diseases in the U.S. are rare. The greater problem is contamination of food sources by 

    • (in order of undesirability): 
        1 Private package sewer plants -unmanned, with daily spot check- often not on weekends
        2. Combined sewer overflows (CSO) - storm water & sewage overwhelm system 
        3. Septic tanks- also susceptible to CSO 
        4. Even municipal wastewater treatment plants can cause pollution when not properly maintained
    • There are 4 main types of pathogenic organisms: 

        1.Viruses: Less than 1/10 th the size of a bacteria. They need a specific host. 
        • Human waste is primary source of all except Reoviruses which inhabit animal waste as well as human waste. 
        • Groundwater probably accounts for about 1/2 of all waterborne-related illnesses as viruses & bacteria survive longer in groundwater. 
        • Viruses are the predominant causes of water-related illnesses in the U.S. 
        • The standard separation of a well & a septic tank is 100 feet, but viruses move over 200 feet. Hepatitis is the major viral water-related disease & is resistant to chlorine. It is bioaccumulated in shellfish. 
        2. Bacteria:
        • Also primarily from human waste, but being larger they are easily filtered out or destroyed. 
        • In U.S. Salmonella types are the most common, 
        • Elsewhere cholera, tuberculosis, & leptospirosis are still problems. 
        • Salmonella cause typhoid, but gastroenteritis, shigellosis & salmonellosis are the main threats in the U.S.
        3. Protozoa: Single-celled. 
        • 10% of U.S. citizens estimated to have amebic cysts, but they easy to filter out. 
        • An amoeba found in the warm water near power plant cooling towers causes meningoencephalitis which can be fatal. 
        • Cryptosporidia infected 300,000 in Milwaukee in 1993. Only 1 died. 
        • Malaria is also a protozoa & though not waterborne, its host is -any of 50 or more species of anopheles mosquito carry the parasite. 
        4. Worms
        • A. Flatworms-
          • Flukes-when humans not natural host penetrate only outer skin-get swimmers itch
          • Tapeworms
        • B. Roundworms- about 1/2 parasitic. Some bore through tissue & get to be 4 feet long.
    • Non-indigenous species
      2. Gause's Principal- no two species can exist indefinitely on a single limiting resource- 
      3. Leibig's Law of the Minimum form the Principal of Competitive Exclusion- two species cannot coexist in the same area if they both need the same resource & it is limited with respect to their ability to use it. 
      4. This competition may occur at any life stage & can include pollution. Examples: water hyacinth in Florida, zebra mussel in Great Lakes, Asiatic clam, carp. 
      5. Introduction of non-indigenous species can be helpful, but results are hard to predict & accidental introduction is rarely beneficial. 

      6. .

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