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Microorganisms |
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There are a variety of microorganisms that can contaminate drinking water supplies. They can be broken down into four main categories including:
To find out more about the most common pathogenic organisms including pictures, infectious doses, and more detailed information, click here.
Not all microorganisms are capable of causing disease. Those that do are called pathogens. The most common include Salmonella, certain strains of Coliform bacteria including E. coli, and the cyst-forming protozoa known as Cryptosporidium and Giardia.
Most Salmonella and pathogenic E. coli can infect humans, domestic animals and many wild animals. Random samples from farms indicate that a significant percentage of farm animals may be infected and that infected animals (including horses, cattle and poultry) are not always visibly sick. However these 'asymptomatic' carrier animals shed billions of virulent organisms in each ounce of their feces.
Because virulent E. coli strains can survive for a few months in animal waste, and Salmonella can persist in untreated farm waste for up to two years, proper utilization and composting of animal wastes are important steps for reducing Salmonella and E. coli contamination, and breaking the cycle of re-infection.
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How Common Is The Problem |
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Microbiological contamination of water has long been a concern to the public. From the 1920's-1960's, Salmonella typhi, the bacillus that causes typhoid fever, was considered a major problem for community water supplies. While rare, outbreaks still do occur.
Michael Beach, a waterborne diseases specialist with the CDC, said that in the past 20 years there have been only six reported instances of Salmonella contamination in municipal water. He said one case involved contaminated groundwater, two were linked to water-distribution system breaches, and three involved disinfection problems.
In March of 2008, state and federal public health officials found themselves managing a large Salmonella outbreak linked to contaminated groundwater that sickened hundreds of people in Alamosa, Colorado. Authorities do not know how the water became contaminated with Salmonella. Ken Carlson, an environmental engineering professor from Colorado State University, said Alamosa's water comes from five deep wells and is untreated. More than half of the US drinking water supply consists of untreated groundwater, he told the Post, adding that groundwater typically never comes in contact with possibly contaminated surface water before reaching consumers.
Worldwide, typhoid fever affects roughly 17 million people annually, causing nearly 600,000 deaths. Little is known about the historical emergence of human S. typhi infections, however it is thought to have caused the deaths of many famous figures such as British author and poet Rudyard Kipling, the inventor of the airplane, Wilbur Wright, and the Greek Empire’s Alexander the Great. The earliest recorded epidemic occurred in Jamestown, VA where it is thought that 6,000 people died of typhoid fever in the early 17th Century. While this disease is rare in the United States and other developed nations, as the episode in Alamosa Colorado demonstrates, typhoid fever always poses the risk of emergence.
In parts of the United States, concern is increasing due to outbreaks of E. coli, giardiasis, cryptosporidiosis, and hepatitis A. Some of these are bacteria, while others are viruses or protozoa.
If you are on a public water supply system and you are concerned about the possibility of microbial contamination, contact your water company. If you use a private water supply, have your water tested by a reputable lab. Treatments do exist for microbial contamination, but it is important to know what is present before treatment is started.
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How Water Can Be Disinfected |
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There are a variety of methods used to disinfect water. Traditionally, water can be disinfected by boiling it, by adding oxidizing agents like chlorine or iodine, and by exposing it to ultraviolet light.
The fourth method is filtration. Up until a few years ago this was not a reliable or practical method, however new technologies that make use of capillary membranes make filtration a highly practical method of disinfecting water supplies in a way that is failsafe as well as environmentally friendly.
For a recap of each of these methods click here.
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