DISINFECTION - DISINFECTION Processes Thermal energy...

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DISINFECTION Processes Thermal energy Ultraviolet Gamma-ray, X-ray, microway Ultrasonic Chemical Pathogenic Organisms Coagulation Sedimentation Filtration All kill rates of pathogens Lime-soda softening Sorption Sterilization kills all microorganisms. Disinfection does not even destroy all pathogenic microorganisms Current measurements techniques M.P.N. Plate Counting - Ceelorey Counting Millipore filter History Pearson Law Copper vessels or Silver vessels Egyptrans Purification by filtration 1854 - Bread Street Well - Lpudan Cholera Epidemic - Sinow & Yock 1892 - Hamburg Germany - Pieuen relationship between infectious disease and infected water Slow sand filtration lessened but did not eliminate - Cholera, typhoid 1904 - First continuous chlorination facility in England 1910 - Supreme Court ruling - municipality to protect public could chlorinate 1912 - Large scale facility at Niagara Falls 1974 - Most recent outbreak of waterhouse disease in Florida due to polluted water supply without chlorination Year 1910 1920 1930 1940 1950 1960 # Plant Chlorinating 0 25 75 125 155 225 Water borne disease outbreaks 250 175 50 10 75
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Mechanisms of Disinfection 1. Depends on type of organism and disinfectant. 2. Not completely known. Act on cell protein, critical enzyme systems. Probably 1. Penetration of cell wall. 2. Enzyme reactions General observation - neutral molecules can penetrate negatively chg. Cell wall and are better bactericides. Can work by direct oxidation such as ozone, chlorine, ClO - but H 2 O 2 , a strong oxidant is not a good batericide agent. Direct application of heat energy, short wave radiation or ultrasonic disruption physically destroy cell - organic and inorganic poison cell by enzyme reaction or disruption of cell wall.
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DISINFECTION - DISINFECTION Processes Thermal energy...

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