Testing the Waters

New monitoring tests can increase our understanding of Michigan's water quality

testing water
Water sampling by Michigan State University researchers requires preliminary field tests and comprehensive laboratory analysis.

Michigan features 3,288 miles of Great Lakes shoreline and 11,000 inland lakes and ponds to which millions of visitors flock to sun and swim. New tests are now available to improve water quality monitoring and thus better protect public health and the environment.

County health departments are authorized under state law to monitor water quality at public beaches. A total of 53 of Michigan’s 83 counties conducted beach monitoring in 2004, the latest year for which figures are available. This represents a dramatic increase in testing compared to 1999, when only 20 counties tested water quality at public beaches.

Proper testing requires a minimum of three water samples taken from one foot below the surface, in water that reaches a depth of between three feet and six feet. According to the Michigan Department of Environmental Quality, no less than five "sampling events" (three samples per event) must be taken within 30 days to reliably evaluate water quality. For the purpose of determining if swimming is safe, Michigan tests for E. coli, the presence of which indicates fecal contamination.

Chart - click to enlarge

E. coli and other coliforms are considered to be "indicator organisms" because they grow in the digestive tracts of both animals and humans, and thus they indicate the presence of other more harmful pathogens. Testing for indicator organisms is less costly and time-consuming than testing for a variety of specific bacteria or other pathogens.

At elevated levels, E. coli and other coliforms may "indicate" the possible presence of pathogens in the water (such as E. coli 0157:H7), which can cause illness such as gastroenteritis, an inflammation of the stomach and intestines. Symptoms include crippling cramps, severe diarrhea, kidney failure and even death in young children and the elderly.

The most common test for E. coli involves filtering water samples and culturing the captured bacteria. The bacteria colonies that result are visible and can be counted. Samples may also be mixed with a liquid media and, when the bacteria grow, the change of water color indicates the presence of coliforms or E. coli in the water. (This method does not reveal the volume of bacteria or E. coli.)

Michigan’s water quality standards are set under the state’s Natural Resources and Environmental Protection Act. To be considered safe for swimming, the value of a daily single sample of E. coli must not exceed 300 colonies per 100 milliliters of water. Each 30-day period, a "geometric mean" is also calculated using all of the samples collected within that time. Under this analysis, the water is considered safe for swimming if the E. coli does not exceed 130 colonies per 100 milliliters of water.

At present, the method of testing is determined by the category of water use, as the chart below indicates.

Water Use

Indicator Testing and Standard

Wastewater treatment discharges to surface water

Fecal coliforms (less than 200 bacteria colonies per 100 ml)

Drinking water after treatment

Total coliforms, including E. coli (zero allowed per 100 ml)

Swimming

E. coli (less than 300 bacteria colonies per 100 ml)

There are many disease-causing pathogens, viruses and parasites that contaminate water when, for example, rainfall washes animal waste into lakes and streams, septic tanks leak or sanitary sewers overflow. Useful as fecal indicator tests can be, they do not always capture the full range of pathogens present or the precise levels of contamination that may pose health risks to swimmers.

Recent research has demonstrated that some indicator bacteria may survive and even multiply under conditions that would otherwise destroy the pathogen that the indicators are designed to measure. Also, the concentration of indicators in the water may change depending upon where and when the contamination occurs, and where and when the water samples are taken. Therefore, the ratio of indicators to actual pathogens can fluctuate depending on a variety of factors, rendering the test results less than precise. Consequently, more precise measurements of water quality would require alternative methods of testing, such as "microbial source tracking" and "pathogen monitoring."

One of the gravest illustrations of the potential inadequacy of single-indicator testing occurred in Milwaukee in 1993. Although indicator tests showed the city’s drinking water to be in compliance with regulatory standards, an outbreak of Cryptosporidium sickened more than 400,000 residents and was blamed for more than 100 deaths (principally among the elderly and immune-compromised individuals). The parasite that caused the outbreak could have been detected by pathogen monitoring.

Water quality standards in Michigan are based on "14 beneficial uses" of water. The Michigan Department of Environmental Quality in 2004 identified 580 water "segments of impairment" in the state[1]. A total of 90 impairments (16 percent) were the result of pathogens, the majority of which were related to the release of untreated waste sewage, according to the agency. The balance of 84 percent resulted from the run-off of nutrients such as fertilizers.

Chart - click to enlarge
Source: Michigan Department of Environmental Quality

As previously noted, the single-indicator method of testing does not identify the full extent of pathogen contamination or all its sources. In a recent study, Michigan State University researchers screened key waters in Michigan using alternative indicators and actual pathogen monitoring, and the results demonstrate the range of information that can be obtained through alternative testing methods.

For example, samples from the St. Marys River in Sault Ste. Marie were collected both upstream and downstream of Michigan and Ontario sewage treatment plants. The samples were tested for indicators and parasite pathogens. Key findings include:

  • Water quality at the Canadian site where sewage is discharged to the river was inferior compared to the U.S. discharge site, indicating the need for better treatment. This has since been undertaken.

  • The pathogen Giardia was detected in samples from the Canadian site as well as downstream.

  • The levels of coliphage (a new fecal indicator) at the U.S. site suggest that more investigation may be warranted to understand and improve sewage treatment.

  • Downstream samples of floating solids had very high concentrations of indicators and the pathogen Giardia compared to the discharge sites. The levels suggest an unidentified sewage source is discharging solids into the waterway.

  • The shoreline water was found to be of good quality as long as the solids did not reach the shore.

Silver Lake, in Mears, Mich., is a popular destination for boating, fishing and swimming. The results of testing with both standard and alternative fecal indicators found that water quality generally failed the standard for safe recreational uses as defined by state law. Leakage from septic tanks and, to a lesser extent, perhaps, birds or other animals are likely contributing to the fecal contamination. Bacteria may also persist by attaching to beach sand and lake foams.

Finally, our testing of 11 other surface water sites near large-scale livestock facilities[2] found Cryptosporidium in all. Giardia was detected at eight sites, and high levels of E.coli were also found.

As our research reveals, the use of alternative indicators and pathogen monitoring can provide important information to communities facing decisions about water quality. Advanced testing equipment and techniques are now available to improve monitoring and, as a result, the water quality in the Great Lakes State.


[1] U.S. E.P.A. 1999. Total maximum load (TMDL) program, EPA 841-F-99003A.

[2] Commonly referred to as Confined Animal Feeding Operations (CAFO).