Disinfection Microbiology and Chemistry JHans van Leeuwen 11252020
Disinfection: Microbiology and Chemistry J(Hans) van Leeuwen 11/25/2020 Disinfection 1
Introduction n n Need for disinfection Alternative disinfectants Disinfection kinetics Disinfectant chemistry Disinfection 2
Topics of Discussion n Diseases borne by water Comparison of disinfectants The Ct concept Disinfection 3
Some common water-borne diseases prevented by disinfection Viral Bacterial Protozoan Typhoid fever Para-typhoid Bacterial diarrhea Cholera Legionnaires’ disease Hepatitis Rotavirus diarrhea Disinfection Amoebiasis Giardiasis Cryptosporidiasis 4
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 - d. N/dt = k. N, which is also known as Chick’s Law d. N/N = - kdt (separating variables) ln N/No = - kt or N = No e-kt (from integration) Disinfection 5
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 6
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Ozone Ct values Microorganism Ct (mg min l-1) T (o. C) p. H log reduction E. coli Legionella pneumophila Rotavirus 0, 009 12 * 4 log 1, 05 12 * 2 log 0, 006 -0, 06 5 6 -7 2 log Giardia lamblia (cysts) 0, 17 25 7. 2 2 log Giardia muris (cysts) 0, 27 25 7 2 log Cryptosporidium parvum (oocysts) 5, 39** 20 * 2 log Disinfection 8
Chlorination Disinfection 9
Chlorinator Disinfection 10
Chlorine gas flow control Disinfection 11
Chlorine contact tank with baffles Disinfection 12
Gravity fed chlorine solution feeder Disinfection 13
Gravity fed chlorine solution feeder Disinfection 14
Disinfection 15
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Ultraviolet Irradiation Disinfection 18
Disinfection 19
Disinfection 20
Simple Solar Disinfection 21
Solar Disinfection Disinfection 22
Ozonation Disinfection 23
Disinfection 24
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Biomass bulking control Disinfection 29
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Effect of ozonation on sludge settling Disinfection 35
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Selective oxidation Disinfection 38
Me. Bl oxidation Disinfection 39
Effect on protozoa Disinfection 40
Ships’ Ballast Water Disinfection NUTECH O 3, NOAA, NETSCO, UNCW, Disinfection. UWS, ISU, et al. 41
Alien Invaders in our Coastal Waters - weirder and risky Disinfection 42
Disinfection 43
Zebra Mussel Distribution Disinfection 44
San Francisco Bay: 212 exotic species and 140 more suspected Disinfection 45
Cross section of ships showing ballast tanks and ballast water cycle Disinfection 46
Propeller exposed under Disinfection unballasted conditions 47
Into the Tonsina’s ballast tanks Disinfection 48
View of ballast tanks Disinfection from below 49
Disinfection Interconnectivity of ballast tanks in sideview 50
INSIDE THE OZONE GENERATOR ON THE TONSINA Disinfection 51
Side-stream ozone injection Disinfection 52
Ozone Reactions in Seawater 1. O 3 + Br- OBr- + O 2 2. 4. OBr- + O 3 Br. O 2 - + O 3 2 O 2 + Br. O 2 - + O 2 Br. O 3 - 5. H+ + OBr- HOBr 3. HOBr main contribution to total residual oxidant (TRO) Disinfection 53
TRO Decay with time Decrease in TRO (mg/L Br 2) in unfiltered Puget Sound seawater over time, Disinfection 54 starting at 2. 0, 3. 0 and 4. 0 mg/L Br 2. Data are the mean + SD of four replicates.
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