Drinking water chlorination efficiency

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How does chlorination affect the concentrations of pathogens in drinking water, reported in log-decrese?


Pathogen Log-dercease
Campylobacter 8.837981871
E.coli O157:H7 7.182699561
Rotavirus 11.97117474
Norovirus 13.55252482
Cryptosporidium 0
Giardia 0.095329311


Chloriantion efficiency, or chlorine's capacity to destroy microbes, depends on many factors: the form of the chlorine, temperature, retention period, pH and concentration as well as other chemicals in the water. In some circumstances it might efficiently kill all indicator organisms, but some active viruses, protists or their cysts may remain in the water. The meter to measure the efficiency of chlorination is kloorikokema ⇤--arg5411: . Someone else has to translate this --Heta (talk) 14:31, 4 July 2019 (UTC) (type: truth; paradigms: science: attack), which is the concentration multiplied by retention period, so called CT-value. The required CT-value depends on the temperature: the lower the temperature, the higher the CT-value has to be.



Pathogen sensitivity to chlorine:

The rows tell which pathogen the ct-values on that row are for.

The columns tell the ct-value required to decrease the amount of each pathogen in the drinking water to a certain level on the log-scale. Column 1 means pathogen concentration will drop to 10-1 of the original, column 2 means the concentration will drop to 10-2 and so on.

Drinking water chlorination efficiency((mg/l)*min)
1campylobacter0 0.154 0.294 0.436 NA NA NA
2E.coli O157:H70 0.17 0.34 0.52 1.06 2.06 NA
3rotavirus0 0.12 0.16 0.2 0.3 NA NA
4norovirus0 0.09 0.18 0.245 0.314 NA NA
5cryptosporidium0 NA NA NA NA NA NA
6giardia0 75 150 216 NA NA NA
Pathogen Reference
Campylobacter [2]; [3]
E.coli O157:H7 [2], [4]
Rotavirus [5]
Norovirus [6]
Cryptosporidium [7]
Giardia [5]



logarithmic decrease


CT-value = Chlorine residue concentration (mg/l)* time (min)

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See also


  1. Valve, M ja Isomäki, E. 2007. Klooraus - Tuttu ja turvallinen? Vesitalous 4/2007.
  2. 2.0 2.1 Blaser, M. J., Smith, P. F., Wang, W.‐L. L. and Hoff, J. C. (1986). "Inactivation of Campylobacter jejuni by Chlorine and Monochloramine." Applied and Environmental Microbiology 51(2): 307‐311.
  3. Lund, V. (1996). "Evaluation of E. coli as an indicator for the presence of Campylobacter jejuni and Yersinia enterocolitica in chlorinated and untreated oligotrophic lake water." Water Research 30(6): 1528‐ 1534.
  4. S. R. Petterson & T. A. Stenström 2015. Quantification of pathogen inactivation efficacy by free chlorine disinfection of drinking water for QMRA. J Water Health (2015) 13 (3): 625-644. [1]
  5. 5.0 5.1 Rice, E. W., Hoff, J. C. and III, F. W. S. (1982). "Inactivation of Giardia cysts by chlorine." Applied and Environmental Microbiology 43(1): 250‐251
  6. Keswick, B. H., Satterwhite, T. K., Johnson, P. C., DuPont, H. L., Secor, S. L., Bitsura, J. A., Gary, G. W. and Hoff, J. C. (1985). Inactivation of norwalk virus in drinking water by chlorine. Applied and Environmental Microbiology 50(2): 261-264.
  7. Benito Corona-Vasquez, Amy Samuelson, Jason L. Rennecker and Benito J. Mariñas (2002): Inactivation of Cryptosporidium parvum oocysts with ozone and free chlorine. Water Research 36, 4053-4063
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