There are more than 2,700 public water systems in Missouri. Federal and state laws require public water systems to monitor and test the quality of the water they provide to customers. Summary results are published annually by the Missouri Department of Natural Resources, and detailed reports are published by individual water systems. I reported on the 2011 Annual Compliance Report of Missouri Public Drinking Water here. This post updates the information for 2012, the most recent report available.

A public water system is one that provides water to at least 15 service connections, or to an average of at least 25 people for at least 60 days each year. Community Systems (CWS) supply water to the same population year-round. Non-Transient Non-Community Water Systems (NTNCWS) supplies water to at least 25 of the same people at least 6 months per year, but not year-round. An example might be a school that has its own water system. A Transient Non-Community Water System (TNCWS) provides water in a place where people do not remain for long periods of time. Examples might include gas stations or campgrounds that have their own water systems.

The amount of treatment that water must receive differs depending on the source of the water. Surface water and underground water under the direct influence of surface water are more vulnerable to contamination, so they receive more treatment. Underground water from aquifers not under the direct influence of surface water tend to contain water that is heavily filtered by the rock through which it seeps. Sometimes, the seepage is so slow that the water is old, predating most forms of modern contamination.

The top graph at right shows the percentage of community water systems that meet all health-based requirements by year. The bottom graph shows the number of violations involving E. Coli or acute coliform levels. Non-compliance can result from many factors, from broken pipes, to human error, to systems that are inadequate in the first place. But 95.7% of the population was served by water systems that had no violations during the year. Ninety-five percent is the EPA goal.

Sources:

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

Information regarding the violations in 2007 and 2010 was taken from the 2007 and 2010 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.