Disinfection:
Microbiology and
Chemistry
J(Hans) van Leeuwen
4/8/2015
Disinfection
1
Introduction




Need for
disinfection
Alternative
disinfectants
Disinfection
kinetics
Disinfectant
chemistry
Disinfection
2
Topics of Discussion



Diseases borne by water
Comparison of disinfectants
The Ct concept
Disinfection
3
Some common water-borne diseases
prevented by disinfection
Bacterial
Viral
Protozoan
Typhoid fever
Para-typhoid
Bacterial
diarrhea
Cholera
Legionnaires’
disease
Hepatitis
Rotavirus
diarrhea
Amoebiasis
Giardiasis
Cryptosporidiasis
Disinfection
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
- 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
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
Disinfection
7
Ozone Ct values
Microorganism
Ct (mg min l-1)
T (oC) pH
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
Disinfection
16
Disinfection
17
Ultraviolet Irradiation
Disinfection
18
Disinfection
19
Disinfection
20
Simple Solar Disinfection
Disinfection
21
Solar Disinfection
Disinfection
22
Ozonation
Disinfection
23
Disinfection
24
Disinfection
25
Disinfection
26
Disinfection
27
Disinfection
28
Biomass bulking control
Disinfection
29
Disinfection
30
Disinfection
31
Disinfection
32
Disinfection
33
Disinfection
34
Effect of ozonation
on sludge settling
Disinfection
35
Disinfection
36
Disinfection
37
Selective oxidation
Disinfection
38
MeBl oxidation
Disinfection
39
Effect on protozoa
Disinfection
40
Ships’ Ballast Water Disinfection
NUTECH O3, NOAA, NETSCO,
UNCW, UWS, ISU, et al.
Disinfection
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.
O3 + Br-

OBr- + O2
2.
4.
OBr- + O3
OBr- + O3
BrO2- + O3



2O2 + BrBrO2- + O2
BrO3-
5.
H+ + OBr-

HOBr
3.
HOBr main contribution to total residual oxidant (TRO)
Disinfection
53
TRO Decay with time
Unfiltered Puget Sound TRO Decrease
TRO Decrease (mg/L)
0.00
-0.40
TRO 4.0
TRO 3.0
-0.80
TRO 2.0
-1.20
-1.60
-2.00
0
50
100
150
200
Time (h)
Decrease in TRO (mg/L Br2) in unfiltered Puget Sound seawater over time,
Disinfection
54
starting at 2.0, 3.0 and 4.0 mg/L Br2. Data
are the mean + SD of four replicates.
Disinfection
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Disinfection
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Disinfection
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Disinfection
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Flowdiagram with Cyclones & UV .
UV
Contro l
Panel
To/from
ballast tanks.
11.06.99
Disinfection
Halvor Nilsen
60
1
Disinfection
61