Waste Water Treatment and Water Purification

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Waste Water Treatment and Water Purification
2011-12-08 03:03:33
PMB 112 midterm3

general microbiology midterm 3
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  1. wastewater
    liquid effluent derived from domestic sewage or industrial sources
  2. sewage
    liquid effluent contaminated with human or animal fecal materials
  3. domestic wastewater
    • sewage
    • "gray water"
    • waste water from food processing
  4. industrial wastewater
    • effluent from petrochemical, pesticide, food, dairy, plastics, pharmaceutical, and metallurgical industries
    • may contain toxic substances
  5. goal of wastewater treatment facility
    to reduce organic and inorganic materials to a level that no longer supports microbial growth and to eliminate other potentially toxic materials
  6. *biochemical oxygen demand (BOD)
    • relative amount of dissolved oxygen consumed by microorganisms to completely oxidize all organic and inorganic matter in a waste sample
    • indicator of water purity

    • determined by:
    • taking a sample of water
    • aerating it well
    • placing in a sealed bottle
    • determining the residual oxygen in the water at the end of the incubation

    low BOD indicates unable to support bacterial growth
  7. primary wastewater treatment
    • physical separations
    • grates and screens that remove large objects
    • effluent is left to settle, suspended solids sediment
  8. secondary wastewater treatment
    • anoxic digestion of sludge in sludge digesters/bioreactors - converts insoluble organic material
    • oxidation - activated sludge and trickling filter methods most common

    eluent is typically chlorinated. UV and ozone also used
  9. *Other than treated water, what are the final products of wastewater treatment?
    • digested sludge
    • methane
    • CO2
  10. aerobic secondary wastewater treatment
    • trickling filter method:
    • wastewater sprayed over bed of crushed rocks
    • biofilm on rocks results in mineralization of organic matter

    • activated sludge process:
    • wastewater is mixed and aerated in a large tank
    • slime forming bacteria grow and form flocs
    • other organisms attach to flocs
    • effluent pumped into clarifier, flocs settle
  11. tertiary wastewater treatment
    • expensive, not common
    • employs precipitation, filtration and chlorination similar to drinking water purification
    • greatly reduces levels of inorganic nutrients and is unable to support extensive microbial growth
  12. *drinking water purification
    • 1. sedimentation basin
    • anionic polymers
    • aluminum sulfate
    • chlorine
    • 2. clarifier/coagulation basin
    • aggregates form (flocculation)
    • 3. filtration
    • thick layers of sand and ionic filtration media
    • 4. disinfection
    • chlorine

    • chloramine - used for long distances (stable, not volatile)
    • UV - good for short distances
  13. coliforms
    • indicator organisms
    • usually associated with intestinal tract
    • aerobic and facultatively aerobic
    • gram-negative
    • nonspore-forming
    • rod-shaped
    • ferment lactose with gas formation
    • most are enteric
  14. the coliform test
    • water passed through a sterile membrane
    • filter is placed on the surface of a plate of EMB
    • coliform colonies are counted
    • calculate presence in water
    • test must pass drinking water standards
  15. *How is EMB a selective medium?
    • the dye inhibits growth of most gram-positive bacteria
    • selecting for presence of gram-negative bacteria
  16. *How is EMB a differential medium?
    • lactose-fermenting bacteria acidify the medium turning Eosin (a pH sensitive) dye black
    • colonies of lactose nonfermenters are translucent
  17. *Why is the coliform test useful?
    coliforms are enteric and indicates fecal contamination of the water source
  18. How can the coliform test fail in determining water safety/quality?
    • doesn't see viruses or protists
    • some pathogens are not coliforms
    • some pathogens are not culturable
    • cells may be slow growing
  19. IDEXX Coliliert water quality test (proprietary)
    • a defined substrate test
    • identifies coliforms and specifically E.coli based on actions on specific substrates with one medium
    • can cause media to change color or fluoresce under UV