DeltaUV Commercial | Parasitic Hazard
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Parasitic Hazard


Prevention Against Parasitic Hazards

For several decades, the pathogens detected in the water have been not only of bacterial or viral origin, but also of the parasitic type. These parasites (Giardia lamblia, Cryptosporidium parvum or Toxoplasma gondii) are microscopic protozoans. These organisms, found in surface and recycled water, are the cause of an increasing number of epidemics around the world.

A real hazard that is as yet little known to the public!
Of these pathogens include: aueous diarrhea, cramp, abdominal pains, loss of weight, anorexia, bloated stomach, faintness, nausea, vomiting, fever and myalgia. In immunocompromised patients, these symptoms may last for long periods (chronic diarrhea), increase in intensity and cause complications (attack of biliary duct, cholecystitis, sclerosing cholangitis, severe dehydration, cachectic state). These complications can be the direct cause of death. Toxoplasmosis, one of the parasites found in contaminated water, may be linked to a risk of maternal–foetal transmission.

Sensitivity to disinfectant: these pathogens are resistant to most disinfectants (chlorine, ozone) and it is difficult or even impossible to use the doses that are required and/or this generates toxic byproducts.

Life and survival in the environment: Cryptosporidium oocystes may remain viable and infections in water and in animal faeces for several months in temperatures of between 0 and 30°C. It may remain viable for a year at these temperatures in seawater.

(Source: AFSSA, 2001; l’Eau l’Industrie les Nuisances (Water, Industry, Drawbacks) no. 311, 2008)


  • 1992 | Great Britain | Underwater Spring | 47 Cases
  • 1993 | Milwaukee USA | Public Water | 403,000 Cases
  • 1998 | Sète France | Rivere | 150 Children
  • 2001 | Dracy-le-fort, Saone et Loire France | Public Water | 480 Cases, Large Scale Epidemic gastro-entéritis by Cryptosporidium
  • 2003 | Divonne les Bains (Ain) France | Public Water | Large Scale Epidemic gastro-entéritis by Cryptosporidium
  • 2005 | New York USA | Aquatic Park | 4,000 Cases
  • 2007 | Utah USA | 2,000 Cases
  • 2008 | Phoenix USA | 29 Public Pools | 100 Cases – 1 Death

Note: Paris town council, through the offices of the company Eau de Paris, has taken this risk into account in the treatment of water for human consumption. It is now setting up, alongside the conventional treatment system, medium pressure UV reactors that have a sufficient biocidal effect on Cryptosporidium, Giardia and toxoplasma.

The SEDIF, a drinking water supply company for the greater metropolitan Paris region (excluding Paris itself) has just announced a call for bids to do likewise.

A large number of towns and swimming pools throughout the world have started to install equipment and many others are in the process of doing so or are about to.

Summary of the CRECEP study

“Toxoplasma oocystes appear to be quite resistant to the ozonation conditions that are normally put in place. By way of comparison, cryptosporidium and giardia are also resistant to ozonation. By increasing the time or the concentration of ozonation it may be possible to neutralise the toxoplasma oocystes, but this is not realistic in practise, due to the fact that this step would lead to the formation of toxic by-products such as bromates.

The results obtained in vivo and in vitro show the effectiveness of UVs in neutralizing toxoplasma oocystes. The neutralisation of toxoplasma by UVs is similar to that described for other parasites (Cryptosporidium and Giardia (Hijnen et al, 2006) UV treatment is often the solution used in water production plants to reduce the risk of undesirable microbiological events.

Cryptosporidium oocystes and Giardia cysts are very resistant to chemical disinfection processes and particularly to chlorine and ozone”

The Wall Street Journal, July the 30th of 2008
“Crypto isn’t affected by chlorine (except at levels unsafe for humans)”
“Now, many water parks are installing ultraviolet systems, which kill parasites including crypto when water passes through the systems black light.”

French Health Ministry, CSHPF, Section des Eaux, Feb. the 1st of 2005
“consider that the ultraviolet rays applied to a minimum dose of 40 mJ/cm2 provides a sufficient biocidal effect on Cryptosporidium”, 2008
Chlorination water isn’t enough anymore. “UV are installed … it is an instant kill. It breaks the protein coat around the crypto and it’s killed instantly”.

What type of prevention should be put in place for public swimming pools?

Most community swimming pools or spas are now treated solely with chlorine products. While conventional microbiological risks (bacteria, viruses) are satisfactorily controlled by chlorine treatment, the risk linked to these parasites is not addressed.

The risks arising in community pools with only chemical disinfection:

  • Chemical risk: Level of combined chlorine often near to the limits laid down in the regulations (0.6 ppm in France)
  • Biological risk: Possible presence of bacteria, coliforms, E. coli, streptococcus but also Cryptosporidium, Giardia and Toxoplasma.

    The consequences of not managing these risks properly for:

  • Health: respiratory irritation of lifeguards, swimmers, babies. Epidemics due to parasites
  • Economy: high level of water renewal (heating and treatment costs). Closure of the establishment
  • The Environment: discharge of polluted water
  • The Image of the establishment: poor image, closure.

There are 2 proposed solutions for the problems arising in pools only treated with chemicals : UV and Ozone

Ultraviolet treatment is the only means of effectively addressing :
efficiently reduce the levels of combined chlorine,
deal with the risk of presence of Cryptosporidium, Giardia and toxoplasma,
manage water renewal and discharge more efficiently.