Archive for May, 2011
More than 2000 residents of Ostersund, Sweden, became sick after drinking municipal water contaminated by Cryptosporidium.
The disease-carrying protozoan Cryptosporidium gained public notoriety during the Cryptosporidiosis outbreak in 1993 when thousands of Milwaukee residents were affected resulting in excess of 100 fatalities.
The likely cause of that epidemic was sewage discharge from Milwaukee’s waste-water plants that was able to enter the drinking-water plant intake.
Cysts passed through the coagulation and filtration steps and were not inactivated because they are very resistant to chlorine disinfection.
Cryptosporidium is a protozoan parasite that can cause a gastrointestinal illness called Cryptosporidiosis. The oocyst form of the parasite is protected by an outer shaell that allows it to survice outside a mamallian host for long periods of time. The oocysts live in humans and animal intestines where they multiply and are excreted in feces in the form of dormant, thick walled oocysts, or fertilized eggs.
The parasite occurs in every region on Earth. The primary symptom of Cryptosporidiosis is diarrhea, with symptoms usually appearing within 2-10 days after infection and rarely last more than 2 weeks. Cryptosporidiosis may be fatal to persons with significant immune deficiency.
Why is cryptosporidium parvum resistant to chlorine?
Chlorine triggers a strong defensive molecular response to oxidative stress in the waterborne parasite according to an article in the journal Applied and Environmental Microbiology. The response likely contributes to the high resistance of these waterborne pathogens to chlorination.
These findings will assist in the development of more efficient disinfection protocols and analytical methods for the inactivation of chlorine-resistant micro organisms.
If it happens in the United States and Sweden then you know it can happen on South Africa, because here in South Africa the problem of untreated, or semi-treated sewage spilling from waste water treatment works, has been becoming a national problem.
It has been claimed that only 32 out of approximately 970 water treatment plants around the country complied with the requirements for the safe discharge of sewage.
That’s a compliance level of only 3%, and as a consequence South Africa’s rivers and coastal water are becoming increasingly polluted, posing a danger to human health, as well as the environment.
One of the best ways for municipalities to treat waste water in order to inactivate Cryptosporidium is the use of ultraviolet light treatment at relatively low doses. And then for household use the use of silver impregnated ceramic filter cartridges is recommended.
By: Tony Henfrey – 09/05/2011
H2O International SA is a supplier of Trojan/Viqua UV systems, the world leaders in UV water disinfection systems.
H2O International SA is also a supplier of the world famous Doulton ceramic filter cartridges and candles.