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Disinfection: Microbiology and Chemistry. J(Hans) van Leeuwen. Introduction. Need for disinfection Alternative disinfectants Disinfection kinetics Disinfectant chemistry. Topics of Discussion. Diseases borne by water Comparison of disinfectants The Ct concept. Viral. Bacterial.
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Disinfection: Microbiology and Chemistry J(Hans) van Leeuwen Disinfection
Introduction • Need for disinfection • Alternative disinfectants • Disinfection kinetics • Disinfectant chemistry Disinfection
Topics of Discussion • Diseases borne by water • Comparison of disinfectants • The Ct concept Disinfection
Viral Bacterial Protozoan Typhoid fever Para-typhoid Bacterial diarrhea Cholera Legionnaires’ disease Hepatitis Rotavirus diarrhea Amoebiasis Giardiasis Crypto- sporidiasis Some common water-borne diseases prevented by disinfection Disinfection
The rate of disinfection Like most biological processes, disinfection follows a first-order reaction with respect to the number of microbes of a certain species surviving as a function of time at a constant level of a disinfectant - dN/dt = kN, which is also known as Chick’s Law dN/N = - kdt (separating variables) ln N/No = - kt or N = No e-kt (from integration) Disinfection
The Ct Concept In disinfection, the ability to inactivate microorganisms is a function of both disinfectant concentration and time. Fractional removal, N/No = Cntm This is generally simplified to N/No= Ct Ct values have been determined for 99.99% virus and 99.9% Giardia removal Disinfection
Ozone Ct values Disinfection
Chlorination Disinfection
Chlorinator Disinfection
Chlorine gas flow control Disinfection
Chlorine contact tank with baffles Disinfection
Gravity fed chlorine solution feeder Disinfection
Gravity fed chlorine solution feeder Disinfection
Ultraviolet Irradiation Disinfection
Simple Solar Disinfection Disinfection
Solar Disinfection Disinfection
Ozonation Disinfection
Biomass bulking control Disinfection
Effect of ozonation on sludge settling Disinfection
Selective oxidation Disinfection
MeBl oxidation Disinfection
Effect on protozoa Disinfection
Ships’ Ballast Water Disinfection NUTECH O3, NOAA, NETSCO, UNCW, UWS, ISU, et al. Disinfection
Alien Invaders in our Coastal Waters - weirder and risky Disinfection
Zebra Mussel Distribution Disinfection
San Francisco Bay:212 exotic species and 140 more suspected Disinfection
Cross section of ships showing ballast tanks and ballast water cycle Disinfection
Propeller exposed under unballasted conditions Disinfection
Into the Tonsina’s ballast tanks Disinfection
View of ballast tanks from below Disinfection
Disinfection Interconnectivity of ballast tanks in sideview