Pathogens are microbes that cause
disease. They include a few types of bacteria, viruses, protozoa, and other organisms.
Some pathogens are often found in water, frequently as a result of fecal matter from sewage
discharges, leaking septic tanks, and runoff from animal feedlots into bodies of water.
------------------------
Total Coliforms are a group of closely related, mostly
harmless bacteria that live in soil and water as well as the gut of animals. The extent
to which total coliforms are present in the source water can indicate the general quality
of that water and the likelihood that the water is fecally contaminated. Total coliforms
are currently controlled in drinking water regulations (i.e., Total Coliform Rule) because
their presence above the standard indicates problems in treatment or in the distribution
system. EPA requires all public water
systems to monitor for total coliforms in distribution systems. If total coliforms are
found, then the public water system must further analyze that total coliform-positive
sample to determine if specific types of coliforms (i.e., fecal coliforms
or E. coli) are present. EPA is increasing protection from
pathogens in surface water systems as part of the Interim Enhanced Surface Water Treatment Rule,
which becomes effective in December 2001.
------------------------
Cryptosporidium is a single-celled microbe contained in
a group generally known as protozoa. Cryptosporidium may cause a disease, cryptosporidiosis,
when ingested. Cryptosporidiosis symptoms can range from mild stomach upset to life threatening
disease in those who are immunocompromised (e.g., people with severely compromised immune systems).
Oocysts are a stage in the life-cycle of some Cryptosporidium. In this stage, the Cryptosporidium
can infect humans and other animals. EPA regulates Cryptosporidium in drinking water, through the
new Interim Enhanced Surface Water
Treatment Rule, by requiring filtered surface water systems serving at least 10,000 to
physically remove at least 99% of Cryptosporidium. Systems without filtration must adopt a
watershed control program to protect the source water from Cryptosporidium
contamination. This requirement becomes effective in December 2001. The effectiveness of treatment
technologies are used to judge how well removal works since direct measurement of pathogens in
treated water is not feasible. Additional Cryptosporidium information is also available from EPA's
Office of Ground Water and Drinking Water.
------------------------
Giardia lamblia (commonly referred to as Giardia) are
single-celled microbes contained in a group known as protozoa. When ingested, they can cause a
gastrointestinal disease called giardiasis. Giardiasis is a frequent cause of diarrhea. Symptoms
may include diarrhea, fatigue, and cramps. Waterborne giardiasis may occur as a result of
disinfection problems or inadequate filtration procedures. Cysts are a stage in the life-cycle of
some Giardia. In this stage, the Giardia can infect humans and other animals. EPA regulates
Giardia in drinking water by requiring water systems
that use surface water or ground water under the direct influence of surface water to disinfect
and/or filter their water so that at least 99.9% of Giardia are rendered harmless or physically
removed. The effectiveness of treatment technologies are used to judge how well removal works
since direct measurement of pathogens in treated water is not feasible.
------------------------
Protozoa are microscopic, usually single-celled microbes
which live in water and are relatively large in comparison to other microbes. Protozoa eat
bacteria, and many are parasitic.
------------------------
Viruses, including hepatitis A virus, rotaviruses, and
Norwalk and other caliciviruses, are microbes that can cause illness. EPA regulates
viruses in drinking water by requiring water systems that use surface water (or ground water
under the direct influence of surface water) to treat their water to ensure that 99.99% of
viruses are rendered harmless or physically removed.
------------------------
Oocysts (cysts) are a stage in the life-cycle of some protozoa.