ch 31 & 32 flashcards.txt

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ch 31 & 32 flashcards.txt
2011-03-22 20:04:04


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  1. 1. Why do we need to treat wastewater before releasing into the natural body of water?
    • To Control nutrients, pollutants released into the ocean.
    • Keep the BOD (biochem OXYGEN Demand) down
  2. 2. Main steps involved in wastewater treatment.
    • Primary Treatment: Removes sludge/materials that settle out of liquid (BOD decrease 25%). Use filter for this
    • Secondary Treatment: Microbial growth encouraged to degrade material in water into CO2 and H20 (95% of BOD killed). Can use activated sludge, artificial wetlands for this.
    • Tertiary Treatment: Expensive, removes ammonia, phosphates and NITrates
  3. 3. What is BOD and what does it signify?
    Biochemical Oxygen Demand: amount of oxygen required for the microbial decomposition of organic matter in the given sample. If this level is high, then there are a HIGH # of microorganisms
  4. 4. Why is it a goal of water treatment to reduce BOD?
    It is necessary because the goal is to remove microorganisms and once the BOD is reduced, the oxygen level requirement is low for decomp of organic material, therefore the level of microorganisms have decreased.
  5. 5. Which step of wastewater treatment removes most of the BOD?
    Secondary Step (95% BOD removed): involves a process that facilitates microbial growth, such as artificial wetlands. This encourages the DEGRADATION of microorganisms into CO2 and H20.
  6. 6. Why would the process of secondary treatment preclude denitrification?
    Secondary treatment involves NITRIFICATION of Ammonia to Nitrite and Nitrate, which can then be DENITRIFIED to Nitrogen gas during the tertiary phase by denitrifying bacteria.
  7. 7. Describe methods of water testing.
    • Presence/Absense Test: Water added to lactose medium, if GAS produced then fecal contamination.
    • Most probable Numbers method (MPN) uses statistics of dilutions of water to detect for contamination.
    • Place sample through a filter which retains bacteria, and place that bacteria on a LACTOSE media to see if growth occurs
    • ONPG/MUG: tests for Coliform and E. coli
  8. 8. Why do water testing procedures look for coliforms rather than pathogens?
    Not possible to test for all pathogens, but these are the known indicator organisms that are routinely found in feces.
  9. 9. Which would be more likely to cause illness- a water sample that tested positive for coliforms or one that tested positive for E. coli O157:H7?
    • E. coli 0157:H7 will cause more illness, as this is a fecal coliform.
    • Positive for coliforms does not necessarily indicate fecal contamination, as there are many different types.
  10. 10. What is the significance of indicator organisms in water testing?
    These indicator organisms (coliforms in the US) are organisms that are routinely found in FECES
  11. 11. Why is testing for presence of fecal coliform a more reliable water test than testing for total coliform?
    Total coliforms may not contain fecal coliform, which is the major type of coliform that causes illness. Not all coliforms produce fecal contamination, as some come from soil or plants.
  12. 12. Give three reasons why pollutants can persist in the environment.
    • Synthetic pollutants can be very stable under many different conditions
    • Synthetic pollutants also may survive due to the lack of any bacteria being able to produce an enzyme required for breakdown of the pollutant. (ie plastic)
  13. 13. What is biological magnification?
    Some pollutants can accumulate INSIDE living organisms and become amplified as they move up the food chain.
  14. 14. What is bioremediation?
    use of microorganisms to degrade or detoxify pollutants in a given environment.
  15. 15. Two strategies used in bioremediation.
    • Biostimulation: enhances growth of microbes by adding nutrients
    • Bioaugmentation: relies on activities of new microorganisms added to contaminated materials
  16. 16. Describe the use of bioremediation in the cleanup of oil spills.
    Involves using microorganisms that specifically breakdown oil into H20 and CO2
  17. 17. Factors affecting growth of microbes in food.
    • Intrinsic: influenced by characteristics of food. Include pH, nutrients, water available
    • Extrinsic: dependent on the STORAGE of the food. Include storage temperature, oxygen avail.
  18. 18. Why is S. aureus more likely to be found in high numbers on ham than on fresh meat?
    Incubation conditions used for fermentation process can support GROWTH of S. aureus. Fresh meats do not support that type of growth as they are stored at different temps and do not go through the fermentation process
  19. 19. Which is more important to refrigerate: homemade stew or bread? Why/
    Homemade stew is more important as it is exposed to the air more than bread, which has an outer covering to help prevent it from spoilage. Also the moisture content of the stew allows for more microorganisms to grow.
  20. 20. Why would the cooking process create anaerobic conditions?
    Cooking allows for all of the release of oxygen from food as it is heated.
  21. 21. How does the use of starter cultures improve the safety of fermented meat products?
    The specific starter cultures for fermenting meats help to INHIBIT growth of pathogens by producing LACTIC ACID
  22. 22. Why does the canning process for low acid foods require higher temperatures than the temperature required in the canning process for acidic foods?
    Spore forming bacteria which cause spoilage and are pathogenic CANNOT grow or produce toxin in high ACID environment. So for low acid, need more heat to kill
  23. 23. Why are nitrates added to cured meats?
    They help kill certain bacterias and give meat the pink/red color
  24. 24. Microorganisms are often grouped according to their optimum growth temperatures. Which of these groups is most likely to spoil refrigerated food?
    Psychrophilic organisms
  25. 25. List the food spoilage microbes.
    Pseudomonas, Streptococcus, Clostridium & Bacillus species
  26. 26. Why do fungi most commonly spoil breads and fruits?
    Due to them growing in HIGH acid, LOW moisture environments
  27. 27. Explain the typical sequence of events that can lead to staphylococcal food poisoning, botulism, Salmonella and E. coli infection.
    • Staphylocccal food poisoning: Food that is left at room temp allowing organisms to grow & produce toxins
    • Botulism: paralytic disease caused by neurotoxin � produced by clostridium. Problem with home canning
    • Salmonella: due to inadequate cooking, salmonella survives and multiplies as food is cooled slowly or @ room temp.
    • E. coli: Due to ground meat, troublesome source of infection