Pathogen Information

What are Pathogens?
What Regulations Control Pathogens?
What is the Relationship Between Pathogens with Disinfection Byproducts?
Why Do We Collect Samples from Untreated Water (Source Water)?
What Else is Being Done to Encourage Control of Pathogens?

What are Pathogens?

Pathogens are micro-organisms 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.

Infections by pathogens can occur through such non-drinking water means as recreational activities (e.g., swimming and water slides), person-to-person contact (e.g., diaper changing), and consumption of food.

What Regulations Control Pathogens?

One of the key regulations the United States Environmental Protection Agency (USEPA) has developed and implemented to counter pathogens in drinking water is the Surface Water Treatment Rule (SWTR). Among its provisions, the rule requires that a water system, using surface water or ground water under the direct influence of surface water as its source, have sufficient treatment to reduce the source water concentration of Giardia and viruses by at least 99.9% and 99.99%, respectively. The SWTR specifies treatment criteria to assure that these performance requirements are met; they include turbidity limits, residual disinfectant concentration, and disinfectant contact time conditions.

The Interim Enhanced Surface Water Treatment Rule was published in December 1998 to control Cryptosporidium, and to maintain control of pathogens while systems lower disinfection byproduct levels to comply with the Stage 1 Disinfectants/Disinfection Byproducts Rule. EPA established a Maximum Contaminant Level Goal (MCLG) of zero for all water systems and a 99% removal requirement for Cryptosporidium in filtered surface water systems that serve at least 10,000 people. Systems with no filtration are required to have a watershed control program. The new rule will tighten turbidity standards. Turbidity is an indicator of the physical removal concentration of particulates, including pathogens. EPA will be finalizing a Long Term 1 Enhanced Surface Water Treatment Rule, for systems serving fewer than 10,000 people, in November 2000 to improve physical removal of Cryptosporidium, and to maintain control of pathogens while systems comply with Stage 1 Disinfectants/Disinfection Byproducts Rule . Data from the ICR and research will be used to develop the Long Term 2 Enhanced Surface Water Treatment Rule by 2002 to further improve control of microbial pathogen risk, and for simultaneous compliance with the Stage 2 Disinfectants/Disinfection Byproducts Rule.

What is the Relationship Between Pathogens with Disinfection Byproducts?

In addition to pathogen control, there is another potentially counterbalancing public health concern. The disinfectants used to control microbial pathogens may produce toxic or carcinogenic disinfection byproducts when they react with natural organic material in the source water. Thus, an important question facing water supply professionals is how to minimize the risk from both microbial pathogens and disinfection byproducts simultaneously.

Why Do We Collect Samples from Untreated Water (Source Water)?

Knowing what organisms are present in source waters and in what concentrations will help EPA understand what treatment may be required. The pathogen information collected in the ICR is primarily collected in the source water and not the water that has been treated because it is difficult to measure pathogens in the treated water because of the very low levels and the need for well-trained lab personnel. The pathogens found in the source water are not indicative of the conditions at tap.

What Else is Being Done to Encourage Control of Pathogens?