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Coliform Problems Are the Most Common Public Water System Violation


In the previous post, I reported that there were more than 4,700 public water supply systems in Missouri, and that 95.7% of the population received water from suppliers that had no violations of safe drinking water standards during the year (an increase from 93.8% in 2011).

This means that 4.3% of the population was served by systems that did have a violation (down from 6.2% in 2011). As Missouri’s population in 2012 was 6,024,522, that means that 259,054 people were served water systems that had a violation during the year. This post looks into the nature of the violations.

Two years, 2007 and 2010, had an increase in the population affected by a violation. The cause in 2007 was an error in backwashing a filter at the Missouri American Water Company South Plant in St. Louis County. The error caused a spike in turbidity that lasted four minutes. During that time the water reached an estimated 24,578 customers, though no reports of illness were associated with this event. Even though only some customers were affected, federal documentation rules require that the entire service population be reported as exposed. In 2010, “the same phenomenon happened again.” (2012 Annual Compliance Report of Missouri Public Drinking Water, p. 4)

A violation does not indicate that public health was affected, but it creates the potential for a public health impact to occur. For this reason, violations are important administrative markers. The DNR monitors two broad kinds of violations. Water contaminants (chemicals and bacteria) can exceed their respective maximum concentration levels (health-based standards), or a water system can fail to meet adequate administrative standards (most often not performing and reporting the testing required by law).

Violations 2012The graph at right shows the percentage of the population served by community water systems that had different types of health-based violations during the year. The most common violation in 2012 had to do with coliform bacteria. Coliform bacteria are a class of many microorganisms that are widespread in the environment. Most do not represent a hazard to human health. However, either the presence of E. Coli, a specific type of coliform bacteria, or of fecal coliform bacteria is a sign the water may have become contaminated with fecal material, which is hazardous to human health. Thus, the presence of either is a violation, and it results in a boil order. All water systems in Missouri are required to test for E. Coli and coliform bacteria, and most violations result from improper testing and/or reporting. However, nineteen water systems in Missouri (less than 1%) received boil orders in 2012, a decrease from 32 in 2011. Most lasted for a few days up to two weeks. But two lasted more than 5 months), and one lasted 10-1/2 months. See the report for details.

Seventeen systems (down from 21 water systems in 2011) had chemical violations, all but one for trihalomethanes. These are water treatment byproducts. They form if disinfectants used to treat the water (chlorine, bromine) react with matter that may be present in the water (e.g. decaying vegetation).

Fourteen systems (down from 16 water systems in 2011) had violations involving excess radiological contaminants. Last year I reported that this problem had to do mostly with radon, but that was an error. In both the 2011 and 2012 reports, the problem mostly had to do with the level of combined radium.

As noted above, some of violations can be quite brief, and the threat they represent to public health can be small. However, some systems experience repeated violations, and then the threat to public health increases. The DNR focuses its efforts on water systems that have a history of repeated contamination, and especially on those with a history of suspected contamination and a history of inadequate testing.

Thirty-one water systems (down from 44 water systems in 2011) were listed as having had three or more major coliform violations and chronic monitoring violations. Many of them received repeated citations. They are listed in Appendix B of the report. In addition, 30 water systems ( down from 34 in 2011) were listed as having repeat monitoring violations. They are listed in Appendix C of the report.


2012 Annual Compliance Report of Missouri Public Drinking Water, Missouri Department of Natural Resources, Pub. 2449, http://www.dnr.mo.gov/env/wpp/fyreports.

Information regarding the violations in 2007, 2010, and 2011 was taken from the 2007, 2010, and 2011 versions of the report, available at the same web address.

Information on trihalomethanes from: Disinfection Byproducts: A Reference Resource, EPA, http://www.epa.gov/envirofw/html/icr/gloss_dbp.html.

Information on coliform bacteria: 5.11 Fecal Bacteria: What Are Fecal Bacteria and Why Are They Important, EPA, http://water.epa.gov/type/rsl/monitoring/vms511.cfm.

Population data from U.S. Census Bureau. State & County QuickFacts, Missouri. http://quickfacts.census.gov/qfd/states/29000.html. Viewed 6/2/2013.


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