Minimum chlorine concentration
to ensure disinfection
Chlorine inactivation of the mixed
population versus indicator
microorganism
Marjolein Peters
2
Civil Engineering Applied Science Marjolein Peters
Water management Environmental biotechnology m.c.f.m.peters@tudelft.nl
Introduction
•
Minimum free chlorine concentration based on:
•
Mixed microbial population
•
Indicator microorganism
Chlorine experiment
2
4
Civil Engineering Applied Science Marjolein Peters
Water management Environmental biotechnology m.c.f.m.peters@tudelft.nl
Methods
•
Non-chlorinated swimming pool water
•
Shower water 1st minute
•
Different chlorine concentrations
•
Live/dead interpretation of cells
•
Same experiments with indicator organism
•
Shower water +
E.coli
•
Viability of cells
Methods
Flow Cell Cytometry
SG
All cells
Broken cells
(dead)
SG
PI
6
Civil Engineering Applied Science Marjolein Peters
Water management Environmental biotechnology m.c.f.m.peters@tudelft.nl
3
Results
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
110%
0
1
2
3
4
5
6
7
8
9
10
11
%
i
ntact cell
s/
uL
Time (min)
Free Cl = 0.64
Free Cl = 0.69
Free Cl = 0.70
Free Cl = 0.73
Free Cl = 1.25
Free Cl = 1.42
Percentage of intact cells in shower water
after exposure of chlorine
8
Civil Engineering Applied Science Marjolein Peters
Water management Environmental biotechnology m.c.f.m.peters@tudelft.nl
Results
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
110%
0
1
2
3
4
5
6
7
8
9
10
11
%
intact
cells/uL
Time (min)
Free Cl = 0.35
Free Cl = 0.61
Free Cl = 0.88
Free Cl = 1.19
Free Cl = 1.29
Free Cl = 1.99
Percentage of intact E.coli cells in shower
water after exposure to chlorine
Results
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
110%
0,0
0,5
1,0
1,5
2,0
2,5
3,0
%
cell
s/
uL
Time (min)
Free Cl = 0.60 IC
Free Cl = 0.60 PC
Free Cl = 1.40 IC
Free Cl = 1.40 PC
Free Cl = 1.97 IC
Free Cl = 1.97 PC
Percentage of intact E.coli cells (IC) and viable E.coli
cells (PC) in shower water after exposure to chlorine
10
Civil Engineering Applied Science Marjolein Peters
Water management Environmental biotechnology m.c.f.m.peters@tudelft.nl
5
Conclusion
•
Intact cell decay depends on free available
chlorine concentration
•
E.coli
cells more sensitive to chlorine than mixed
population
•
Still no 4-log removal in 30 seconds
•
Decay of intact cell show similar graph to
12
Civil Engineering Applied Science Marjolein Peters
Water management Environmental biotechnology m.c.f.m.peters@tudelft.nl
6
Future work
•
Viability tests
•
Shower water
•
Microscopy
•
Biofilm protection?
•
Pyrosequencing
14
Civil Engineering Applied Science Marjolein Peters
Water management Environmental biotechnology m.c.f.m.peters@tudelft.nl
