Drinking water disinfection efficiency

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Question

What is the efficiency of drinking water disinfection methods, reported in log-clearance?

Answer

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Rationale

Data

References of efficiency of disinfection methods
Method Campylobacter E.coli O157:H7 Rotavirus Norovirus Cryptosporidium Giardia
UV [1] [1] [1] [1] [1] [1]
Ozonization [2] [2] [2] [2]

UV

Drinking water UV disinfection efficiency(mJ/cm^2)
ObsPathogen012345
1campylobacter0 3 7 10 14 NA
2E.coli O157:H70 5 9 14 19 NA
3rotavirus0 10 20 29 39 NA
4norovirus0 NA NA NA NA NA
5cryptosporidium0 3 6 12 NA NA
6giardia0 2 5 11 NA NA
  • E.coli and Campulobacter jejuni corrected for environmental spp.
  • Cryptosporidium and giardia: no correction for environmental spp. (research needed).
  • Rotavirus SA-11
  • For noro: 0.8 log inactivation was estimated for a UV fluence of 20mJ/cm2. At higher fluences (40 and 70mJ/cm^2) all samples were negative. However, it is uncertain to which degree inactivation assessed with RT-PCR is representative for inactivation assessed with infectivity assays.
  • For water with low turbidity and high UV transmission?

The log decreases follow the formula [1]

log10(Nt/N) = -k * Fluence

where Nt is the microbial concentration after contact time t. Fluence is the product of the UV fluence rate (mW/cm2) and the exposure t (mWs/cm2 = mJ/cm2).

OR

log10(Nt/N) = -k * Fluence - b

where b is the y-intercept. This is used in cases where small amounts of UV don't have an effect, and the log linear decrease only begins at a certain level of UV. For some microbes there is also an upper limit to log decrease, after which adding fluence doesn't decrease the microbe concentration.

Ozone

Ozone decay model:[3]

C = (C0 - D)exp(-k*t)

Where D is instantaneous demand, k is decay constant, t is time and C is residual

Ozone has a half-life in pure distilled water of approximately 40 min at pH 7.6, but this decreases to 10 min at pH 8.5 at 14.6°C. Rising temperatures increase the rate of decomposition. [4]

Drinking water ozonization efficiency(mg/min l^-1)
ObsPathogen012345
1campylobacter0 NA NA NA NA NA
2E.coli O157:H70 NA 0.02 NA NA NA
3rotavirus0 NA 0.006-0.06 NA NA NA
4norovirus0 NA NA NA NA NA
5cryptosporidium0 4 11 22 NA NA
6giardia0 NA 1.8-2 NA NA NA
  • E.coli, rota, Giardia muris cysts: temperature 5°C and pH 6-7 [2]
  • Cryptosporidium temperature 13°C, also available for 1°C and 22°C[2]

Calculations

CT-value = concentration * time (min)

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The code below saves the constant for immediate demand and decay constant as well as the time used as the time ozone affects the water. The current constants are from Haas & Kaymak 2003[3], the averages of the constants they found for different experiments. Their water temperature in all experiments was 15°C and pH approximately 8. The value on time is based on nothing, but a value is needed for the model to run

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See also


  • Youxian Wu, Thomas Clevenger,* and Baolin Deng 2005. Impacts of Goethite Particles on UV Disinfection of Drinking Water [3]
  • Charlotte Farrella, Francis Hassarda, Bruce Jefferson, Tangui Leziarta, Andreas Nocker, Peter Jarvis 2018. Turbidity composition and the relationship with microbial attachment and UV inactivation efficacy. [4]
  • John C.H. Chang, Susan F. Ossoff, David C. Lobe, Mark H. Dorfman, Constance M. Dumais, Robert G.Qualls, J. Donald Johnson 1985. UV Inactivation of Pathogenic and Indicator Microorganisms. [5]
  • Charles N.Haas, Baris Kaymak 2003. Effect of initial microbial density on inactivation of Giardia muris by ozone. [6]
  • Drinking Water and Health: Volume 2. II The Disinfection of Drinking Water [7]
  • WHO: Water sanitation and health. Guidelines. 3 Inactivation (disinfection) processes. [8]
  • Agnieszka Joanna Brodowska, Agnieszka Nowak, Alina Kondratiuk-Janyska, Marcin Piatkowski, Krzysztof ́Smigielski 2017. Modelling the Ozone-Based Treatments forInactivation of Microorganisms. [9]

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Hijnen et al. 2006: Inactivation credit of UV radiation for viruses, bacteria and protozoan (oo)cyst in water: a review. Water Research 40(1) p3-22
  2. 2.0 2.1 2.2 2.3 2.4 2.5 World Health Organization 2004 Water Treatment and Pathogen Control: Process Efficiency in Achieving Safe Drinking Water: 3 Inactivation (disinfection) processes. Edited by Mark W LeChevallier and Kwok-Keung Au. ISBN: 1 84339 069 8. Published by IWA Publishing, London, UK. [1]
  3. 3.0 3.1 Haas CN, Kaymak B. 2003. Effect of initial microbial density on inactivation of Giardia muris by ozone.Water Res. 2003 Jul;37(12):2980-8.
  4. Drinking Water and Health, Volume 2. II The Disinfection of Drinking Water. Safe Drinking Water Committee, Board on Toxicology and Environmental Health Hazards, Assembly of Life Sciences. ISBN: 0-309-55406-3, 408 pages, 1980. PDF available from the National Academies Press [2]
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