Total Coliform Rule

In the US EPA publication Small System Compliance Technology List for the Surface Water Treatment Rule (SWTR) and Total Coliform Rule (ICR) (September 1998), DE is a specifically approved filtration technology for compliance with the SWIR. In its comments the US EPA notes that DE is very effective for the removal of Giardia and Cryptosporidium" (23). 

US EPA, Small System Compliance Technology List for the Surface Water Treatment Rule and Total Coliform Rule, US Environmental Protection Agency, Washington, DC, 1998. 

Implementation of the 1986 Amendments to SDWA led to the development of a number of important rules, including the Total Coliform Rule, the Surface Water Treatment Rule, the Lead and Copper Rule, and regulations for a large number of chemicals of public health concern. All public water systems using surface water sources were required to disinfect and provide specific levels of treatment for microbial pathogens most systems were required to filter their water. In addition, the best available technology was specified for the treatment of contaminants for which an MCL was established. 

The Total Coliform Rule (TCR) was promirlgated by the EPA in lime 1989. A speciAc MCL value was not estab-Ashed for total or fecal coliforms under the TCR. Instead, there are three potential scenarios in which an MCL is violated that depend on the presence and/or absence of total coliforms (and fecal coliforms orE. coli). Public water systems morutor for total coliforms throughout the distri-buAon system to determine compliance with the TCR. 

The primary use of anhydrous ammonia (ammonia gas) in water treatment is to combine with chlorine to form chloramines. Chloramines are used both as primary and secondary disinfectants. Use as a secondary disinfectant (residual in the distribution system) is more common. A typical treatment strategy is to use free chlorine to satisfy the USE PA regulatory CT requirements as a primary disinfectant. Ammonia is then added to combine with the free chlorine residual to form chloramines for use as the secondary distribution system disinfectant. The ammonia added is carefully controlled to ensure that all the free chlorine is combined and little free ammonia remains. This control is necessary because the presence of free chlorine can form regulated by-products. Free ammonia can increase the growth of nitrifying bacteria, thus causing residual demand that could lead to conditions that could violate the Total Coliform Rule. 

The Coliform Rule requires all public water systems to meet the coliform MCL and monitor total coliform with frequencies depending on population served, and requires small systems to conduct a sanitary survey. To comply with the coliform MCL, no more than 50% of all total coliform samples per month can be total coliform-positive. 

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