The Long Term 2 Enhanced Surface Water Treatment Rule ("LT2ESWTR" or simply "LT2") is a 2006 regulation promulgated by the

United States Environmental Protection Agency The Environmental Protection Agency (EPA) is an independent agency of the United States government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it began operation on De ...

(EPA) pursuant to the

Safe Drinking Water Act The Safe Drinking Water Act (SDWA) is the primary federal law in the United States intended to ensure safe drinking water for the public. Pursuant to the act, the Environmental Protection Agency (EPA) is required to set standards for drinking wa ...

. The rule required

public water system Public water system is a regulatory term used in the United States and Canada, referring to specific utilities and organizations providing drinking water. United States The US Safe Drinking Water Act and derivative legislation define a "public wa ...

s to install more stringent treatment systems to control the microorganism ''

Cryptosporidium ''Cryptosporidium'', sometimes called crypto, is an apicomplexan genus of alveolates which are parasitism, parasites that can cause a respiratory and gastrointestinal illness (cryptosporidiosis) that primarily involves watery diarrhea (inte ...

'' and other pathogens.United States Environmental Protection Agency (EPA)(2006-01-05). "National Primary Drinking Water Regulations: Long Term 2 Enhanced Surface Water Treatment Rule." ''Federal Register,''

Background

EPA began drafting the LT2 rule following the 1993 Milwaukee Cryptosporidiosis outbreak, in which it is believed that municipal sewage infected with ''cryptosporidium'' was accidentally discharged into the city of

Milwaukee, Wisconsin Milwaukee is the List of cities in Wisconsin, most populous city in the U.S. state of Wisconsin. Located on the western shore of Lake Michigan, it is the List of United States cities by population, 31st-most populous city in the United States ...

's drinking water.

Principal requirements

* Public water systems (PWS) must conduct source water monitoring for ''cryptosporidium'' * Filtration systems for PWS with the highest levels of ''cryptosporidium'' * All unfiltered systems must inactivate ''cryptosporidium'' using

disinfection A disinfectant is a chemical substance or compound used to inactivate or destroy microorganisms on inert surfaces. Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores; it is less effective than ...

technologies such as

ozone Ozone () (or trioxygen) is an Inorganic compound, inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , break ...

ultraviolet light Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of th ...

, or

chlorine dioxide Chlorine dioxide is a chemical compound with the formula ClO2 that exists as yellowish-green gas above 11 °C, a reddish-brown liquid between 11 °C and −59 °C, and as bright orange crystals below −59 °C. It is usually ...

Controversy

The LT2 rule was criticized for mandating costly public works projects (such as coverage of open-air reservoirs) that may be unnecessary and/or unlikely to address the kind of problem that was responsible for the Milwaukee incident. William R. MacKenzie, M.D., a

Centers for Disease Control The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency under the Department of Health and Human Services (HHS), and is headquartered in Atlanta, ...

epidemiologist who served as the Epidemic Intelligence Officer on the Milwaukee case, stated, "Standards for water treatment facilities were about to be implemented throughout the nation; but even those would not have stopped the Milwaukee outbreak."

Review of regulatory requirements

In response to criticism that the rule unfairly burdens public water systems that are not exposed to municipal sewage, EPA conducted three public meetings in 2011 and 2012 about the LT2 rule, and invited the public to submit information and data to support future regulatory decisions. In a 2017 ''Federal Register'' notice, EPA stated that it "did not identify new information related to potentially revising" the regulatory requirements for ''cryptosporidium'' and other listed pathogens, and requested additional public comments.EPA (2017-01-11). "National Primary Drinking Water Regulations; Announcement of the Results of EPA's Review of Existing Drinking Water Standards and Request for Public Comment and/or Information on Related Issues."

Background

Principal requirements

Controversy

Review of regulatory requirements

References

Further reading