Microbiological Contaminants

Health Effects & Standards for Microbiological Contaminants

Surface Water Treatment Technique Microbiological Contaminants

The U.S. Environmental Protection Agency (EPA) has determined that the presence of microbiological contaminants are a health concern at certain levels of exposure. If water is inadequately treated, microbiological contaminants in that water may cause disease. Disease symptoms may include diarrhea, cramps, nausea and possibly jaundice, and associated headaches and fatigue. These symptoms, however, are not just associated with disease-causing organisms in drinking water, but also may be caused by a number of factors other than your drinking water. EPA and the state have set enforceable requirements for treating drinking water to reduce the risk of these adverse health effects. Treatment such as filtering and disinfecting the water removes or destroys microbiological contaminants. Drinking water treated to meet EPA requirements is associated with little to none of these risks and should be considered safe.

Total coliform

The EPA has determined that the presence of total coliforms is a possible health concern. Total coliforms are common in the environment and are generally not harmful themselves. The presence of these bacteria in drinking water, however, generally is a result of a problem with water treatment or the pipes that distribute the water, and indicates that the water may be contaminated with organisms that can cause disease. Disease symptoms may include diarrhea, cramps, nausea and possibly jaundice, and associated headaches and fatigue. These symptoms, however, are not just associated with disease-causing organisms in drinking water, but also may be caused by a number of factors other than your drinking water. EPA and the state have set an enforceable drinking water standard for total coliforms to reduce the risk of these adverse health effects. Under this standard, no more than 5.0 percent of the samples collected during a month can contain these bacteria, except that systems collecting fewer than 40 samples/month that have one total coliform-positive sample per month are not violating the standard. Drinking water that meets this standard is usually not associated with a health risk from disease-causing bacteria and should be considered safe.

Fecal coliforms/E. coli

The EPA has determined that the presence of fecal coliforms or E. coli are generally not harmful themselves, but their presence in drinking water is serious because they are usually associated with sewage or animal wastes. The presence of these bacteria in drinking water generally is a result of a problem with water treatment or the pipes that distribute the water, and indicates that the water may be contaminated with organisms that can cause disease. Disease symptoms may include diarrhea, cramps, nausea and possibly jaundice, and associated headaches and fatigue. These symptoms, however, are not just associated with disease-causing organisms in drinking water, but also may be caused by a number of factors other than your drinking water. EPA and the state have set an enforceable drinking water standard for fecal coliforms and E. coli to reduce the risk of these adverse health effects. Under this standard, all drinking water samples must be free of these bacteria. Drinking water that meets this standard is associated with little or none of this risk and should be considered safe.

There are three maximum contaminant levels (MCL) for microbiological contaminants. The first is based on the presence or absence of coliform bacteria. This group of bacteria is very common and is not harmful. The presence of coliform bacteria is used as an indicator that the water system must pay closer attention to its disinfection process. Violation of this MCL is not an emergency situation.

The second MCL is based on the presence of fecal coliform or Escherichia coli (E. coli). Violation of this MCL is an emergency, and the state requires water systems to promptly notify the public.

In addition to the above two MCLs, a third one applies to public water systems that use surface water or ground water that is determined to be under the influence of surface water. Because these type of systems are very susceptible to contamination from bacteria, viruses, and pathogens like Giardia lamblia and Cryptosporidium, they are required to filter the water and disinfect it before sending it to customers. Measures are established to ensure water from surface water plants is clean. Violation of this standard is an emergency, and the state requires water systems to promptly notify the public.

A public water system must determine its compliance with the maximum contaminant level for microbiological contaminants each month (or quarter for non-community water systems that serve 1,000 or fewer persons).

The Standard

1. The maximum contaminant level for coliform bacteria is based on the presence or absence of total coliforms in a sample, rather than coliform density. For the purpose of the public notice requirements in Rule 62-560.410, F.A.C., a violation of the standards in this paragraph poses a non-acute risk to health.
   1.  For a system that collects at least 40 samples per month, if no more than 5.0 percent of the samples collected during a month are total coliform-positive, the system is in compliance with the maximum contaminant level for total coliforms.
   2.  For a system that collects fewer than 40 samples per month, if no more than one sample collected during a month is total coliform-positive, the system is in compliance with the maximum contaminant level for total coliforms.
2. Any fecal coliform-positive repeat sample or E.coli-positive repeat sample or any total coliform-positive repeat sample following a fecal coliform-positive or E.coli-positive routine sample is a violation of the maximum contaminant level for total coliforms. For the purposes of the public notification requirements in Rule 62-560.410, F.A.C., this is a violation that poses an acute risk to health.
3. For surface water systems using conventional or direct filtration, the turbidity level of representative samples of filtered water taken throughout the day must be less than or equal to 0.3 NTU in at least 95 percent of the measurements taken each month. At no time is the turbidity level of the filtered water allowed to exceed 1.0 NTU. In addition to filtration, the water must contain a disinfectant like chlorine for a predetermined amount of time before it can be used by the public. For more detail on this standard, refer to Chapter 62-550.817, Part VIII, Florida Administrative Code.