Total coliforms are a group of bacteria commonly found in the environment, including soil, vegetation, and the feces of warm-blooded animals. They serve as an indicator of water quality and potential contamination, particularly from fecal matter. The presence of total coliforms in drinking water or recreational water signifies a possible health risk, as it may indicate the possible presence of pathogenic (disease-causing) microorganisms.
Total coliforms consist of several types of bacteria, including:
- Escherichia coli (E. coli): A subgroup of coliforms that indicates fecal contamination and is often associated with gastrointestinal diseases.
- Fecal coliforms: Often specifically refers to E. coli but can also include other bacteria that are typically present in the intestines of warm-blooded animals.
- Environmental coliforms: These are naturally occurring bacteria found in the environment that are not necessarily harmful.
Testing for Total Coliforms
Water testing for total coliforms is a routine procedure for water quality monitoring. Common methods include:
- Membrane Filtration: Water is filtered through a membrane that captures bacteria, which can then be cultured for identification.
- Most Probable Number (MPN): A statistical estimate of the number of bacteria based on growth in a series of dilutions.
- Presence/Absence (P/A) Tests: Simple tests used to determine if coliform bacteria are present.
Significance
The detection of total coliforms can trigger further investigation to assess the safety of the water supply and may necessitate corrections, treatments, or further testing. Water systems are often required to provide routines and protocols for testing and addressing contamination issues if coliform bacteria are found.
Regulatory Standards
In many countries, there are established regulatory limits for allowable levels of total coliforms in drinking water. For instance, in the United States, the Environmental Protection Agency (EPA) establishes the Safe Drinking Water Act (SDWA), which sets standards for water quality, including limits on total coliform bacteria.
Conclusion
Monitoring for total coliforms is crucial for ensuring safe drinking water and protecting public health. Regular testing and adherence to water quality standards help prevent potential health risks associated with contaminated water supplies.