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3 categories of waterborne pathogens regulated in the U.S.
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point and nonpoint sources
point - pipe, localized source
nonpoint - runoff, surface waters, urban streets, homes, cropland
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septic tanks
- purpose is to separate solids and scum from waste water
- provide some degree of anaerobic digestion of organic matter
- deliver the waste water to the subsurface
- must be maintained to prevent from going into neighbor's drinking water
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conventional vs. in-line treatment
in-line treatment only missing 1 step -floc/sed. step
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flocculation
turbulence provided by gentle stirring to keep flocs from settling and form bigger mass of neutral particles
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3 organisms that must be removed from all surface water systems that serve more than 10,000 people
- Cryptosporidium
- Giardia lamblia
- viruses
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chlorine residual
chlorine dose - chlorine demand
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why is it harder to disinfect protozoa?
cysts form thick cell wall
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John Snow
- father of public health/epidemiology
- knew illnesses were water borne when it was commonly thought they were air borne
- analyzed deaths from cholera in certain area were from water company getting water upstream of sewage outlets
- had broad street pump closed which had broken brickwork between pump and cesspool to stop cholera outbreak
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Legionella
- outbreak of severe pneumona caused by a gram-negative rod, spread through the air conditioning ducts
- transmitted by inhalation of infectious aerosols
- facultative intracellular parasite - can multiply in alveolar macrophages and monocytes and in nature in free-living ameobae
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