E. Coli and Indiana Lakes and Streams

Safe Water for swimming and wading

How do we determine whether water is "swimmable"?

What are potential health effects?

What are the E.coli levels?

What are the most important sources of these microorganisms?

What can be done to reduce E. coli levels?



Safe water for swimming and wading

Lakes and streams usually contain a variety of microorganisms, including bacteria, viruses, protozoa, fungi, and algae. Most of these occur naturally and have little impact on human health. Some microorganisms, however, can cause disease in humans. Diseases most commonly result from certain bacteria, viruses, and protozoa that live in the gastrointestinal tract and are shed in the feces of warm-blooded animals.

Water quality standards are the basis for determining whether or not a certain level of a contaminant such as E. coli is acceptable. Different levels of a contaminant are allowed for different water uses. For drinking water, E.coli must be less than 1 CFU/100 mL. Most surface water in Indiana would not meet this standard, but compliance with the drinking water standard is not required because water is treated before it is used for drinking. However, all Indiana streams and lakes are designated to meet the use of "full body contact recreation", or swimming.


How do we determine whether water is "swimmable"?

The water quality standard for full body contact recreation in Indiana is based on E.coli, as recommended by the EPA. Monitoring results for E. coli are given in terms of number of E. coli colony forming units (or CFU) in 100 mL of water (about half a cup). For water to meet the recreation standards, the geometric mean of 5 samples over a 30-day period is required to be less than 125 CFU/100 mL, with no sample testing higher than 235 CFU/100 mL.

Although viruses and protozoa cause many of the illnesses associated with swimming in polluted water, monitoring is usually done for E. coli, which tend to indicate fecal contamination. Indicators are used rather than the actual disease-causing organisms (pathogens) because pathogens are much more difficult to measure, and because even though the specific pathogen may not be present on a particular day the presence of fecal bacteria indicate that it could be. In addition, there are many different pathogens, and measuring one pathogen does not predict the concentration of another pathogen. The number of fecal bacteria is an indicator of the human health risk associated with swimming in the water.


What are the potential health effects of swimming in water containing pathogens?

Untreated sewage or livestock waste released into the water can expose swimmers to bacteria, viruses, and protozoa. These pathogens (disease-causing organisms) are usually present at or near the site where polluted discharges enter the water. Children, the elderly, and people with weakened immune systems are most likely to develop illnesses or infections after swimming in polluted water.

The most common illness associated with swimming in water polluted by sewage is gastroenteritis. It occurs in a variety of forms that can have one or more of the following symptoms: nausea, vomiting, stomachache, diarrhea, headache, and fever. Other minor illnesses associated with swimming include ear, eye, nose, and throat infections. In highly polluted water, swimmers may occasionally be exposed to more serious diseases like dysentery, hepatitis, cholera, and typhoid fever. Most of these diseases require ingestion (drinking or swallowing) of the infected water, although some can be transmitted through wounds exposed to water. Swimming-related illnesses are usually minor, according to EPA sources. This means that they require little or no treatment, respond readily to treatment, and have no long-term health effects.


What levels of E. coli are typically found in Indiana streams and lakes?

The Indiana Department of Environmental Management samples for bacteria at numerous sites around the state. The 1994-95 Indiana 305(b) Report (the most recent statewide assessment of water quality available) reported that about 81% of assessed waters did not support the "whole body contact recreation" (swimming) use due to frequent high E. coli levels.

Mean values in hundreds of stations measured by IDEM ranged from 0.2 CFU/100mL to 800,000 CFU/100mL. High E. coli values are clearly not unusual in Indiana streams. Sampling in tributaries of Eagle Creek have found levels as high as 160,000 CFU/100 mL, or about 680 times the maximum allowed for recreation. Less than half the samples taken would meet recreation standards. Over 800 samples were taken in the St. Joseph River (the water supply for Fort Wayne) and its tributaries in 1996-1997. The figure below shows the range of values during the sampling season (April-November) in 1996. The average of all samples was about 2000 CFU/100 mL (16 times the maximum allowed), with a maximum of 35,200 CFU/100 mL.

Another indication of water quality problems is the Indiana 303(d) list (.pdf), on which development of TMDLs, or Total Maximum Daily Loads, will be based. Of 208 waterbodies on the 303(d) list, 44 have E. coli as one of the TMDL parameters. High E. coli levels were in fact found in many of the remaining 164 waterbodies, but due to quality control problems in the sampling were taken off the list. It is expected that resampling will identify E. coli in many of the other streams, so that TMDLs for E. coli will eventually be developed in these streams.


What are the most important source of these microorganisms?

E.coli can come from the wastes of any warm-blooded animal, including humans, cattle, hogs, and many other animals including wildlife. Fecal wastes from humans are the greatest health concern since they carry the most human pathogens. Several of the diseases mentioned above, however, can be transmitted from animals to humans.

Human wastes can enter water from improperly functioning septic systems, improperly treated sewage (usually due to combined sewer overflows during storm events), discharges from boats, sewage sludge applied to the land if not properly treated, and in rare instances from a sick person (usually a small child in diapers) swimming. Modern septic systems are designed to discharge wastes to the soil, where pathogens and other contaminants are filtered by the soil before the water enters groundwater or streams. Houses built before 1950, however, were allowed to discharge wastewater from the septic tank directly to field tiles rather than to a leach field. Such systems have a high probability of releasing fecal organisms to streams, particularly when the soil is wet. In many cases home sites do not have adequate space or suitable soils to install a proper septic leach field. High water tables are common near lakes, and soils there may not be suitable for septic systems. Homes built before modern statewide guidelines were instituted in Indiana in 1991 often have undersized systems or no room for expanding the absorption field in case of system failure.

Even well-designed septic systems can contaminate water if they fail due to improper maintenance or simply reaching the end of their design life. When systems have not been pumped regularly, or where soils cannot handle the wastes, or due to poor design, the leach field may not be able to handle the wastewater properly. Wastewater may rise to the surface, where it can stand in the lawn where children play, or flow overland to the nearest ditch or stream.

Many sewage treatment plants are allowed to bypass the sewage treatment system during storms. This is usually because the storm sewers are connected to the sanitary sewers (known as "combined sewers") and the total flow during a storm can far exceed the capacity of the sewage treatment plant. Such bypasses are a major cause of microbial contamination in Indiana. This practice is not allowed in newer construction, but is a common problem in older cities with existing sewer systems. The high cost of bringing communities into compliance is a major obstacle to reducing this source of E. coli.

Livestock waste also contains fecal coliform bacteria such as E. coli. New research may soon allow us to routinely distinguish between E.coli from animal and human origin, but the standard tests do not make that distinction.

Livestock manure that reaches tile drains, ditches, or streams will usually lead to high levels of E.coli. Manure storages or lagoons that are improperly sited or constructed may leak, contaminating surrounding water. It is much more common, however, for contamination to result from land application of manure. When heavy rains follow an application, or where manure is applied to ground that is too wet, overapplied, or applied too near a stream, runoff can carry manure into a nearby stream. It had been widely assumed that subsurface tile drains are protected by the 2 to 4 feet of soil above them, since bacteria are usually adsorbed to soil. However significant quantities of bacteria have been shown to reach tile lines through cracks, root holes, worm holes, or surface inlets or breather vents to tile lines. In a study in New York, fecal coliform concentrations reached 100,000 CFU/100 mL in tile drainage (approximately 500 times the standard for recreation) after a liquid manure application. The most direct pathway occurs when livestock are allowed in the stream itself, however, the extent of contamination here is a function of animal density and streamflow.

In some areas, especially where there are few people or livestock, wildlife can be a significant contributor. The most direct contributors are waterfowl, although deer, raccoons, and other wildlife living anywhere in the watershed can contribute to bacteria levels in streams. In urban areas, pet wastes can be washed off streets and other impervious surfaces and flow through storm drains directly to lakes and streams.


What can be done to reduce E. coli levels?

1. Make sure septic systems are functioning properly.

Septic systems do not function properly when high groundwater tables, shallow limiting layers of bedrock or fragipan, or very slowly or rapidly permeable soil limit the ability of the soil to treat the waste. Lots that are too steep or too small are also unsuitable for septic systems. All systems require that the septic tank be pumped every 5 years or so to ensure maximum life. In many cases, because the original residential siting was poor or lot size is inadequate, the only solution to salvage a failing septic system is to install a treatment system ahead of the filter field to lower the loading. The following publications, available from your county office of Purdue Extension, can provide additional information on septic system installation and maintenance.

  • ID-170: Construction Guidelines for Conventional Septic Systems
  • ID-142: Operating and Maintaining the Home Septic System
  • AY-9-33: Septic System Owner's Guide

2. Support community plans to construct or upgrade sewage treatment plants and eliminate combined sewer overflows.

In many areas of Indiana, particularly around lakes, lots have no suitable land available for proper septic systems. In some cases the best solution may even be to prohibit the residential use of such lots, or to construct a centralized sewage system, which may include conventional sewage treatment, constructed wetlands, or a centralized septic system leachfield properly located and designed. Although the construction and operation of such systems are expensive, they are necessary to protect water quality and public health. Eliminating combined sewer overflows is a difficult and costly operation, and taxpayers need to realize that the costs are ultimately worthwhile to protect water quality.

3. Prevent manure from entering tiles, ditches, and streams.

All large livestock operations are given permits by IDEM. They are required to follow guidelines for storage and have adequate land area for manure application. Good management practices such as applying manure at optimal times for plant uptake, applying when potential for runoff is low, and injecting or incorporating manure when applying greatly reduce the potential for manure runoff that may contaminate streams. Riparian buffer strips where no manure is applied are important where surface runoff is the major pathway for flow. Setbacks should also be implemented from any surface inlets to tile lines. The following publications, available from your county office of Purdue Extension, can provide additional information on livestock manure and water quality protection.

  • WQ-7: Animal Agriculture's Effect of Water Quality: Pastures and Feedlots
  • WQ-8: Animal Agriculture's Effect of Water Quality: Waste Storage
  • WQ-16: Animal Agriculture's Effect of Water Quality: Land Application of Manure
  • ID-205: Swine Manure Management Planning
  • ID-206: Poultry Manure Management Planning
  • ID-208: Dairy Manure Management Planning


Much of Indiana's 36,000 miles of rivers, 106,000 acres of lakes, and 43 miles of Lake Michigan shoreline do not currently meet water quality standards for recreation. The large number of potential E. coli sources make it very difficult to determine the precise value of each source in most waterbodies. Cleaning up these valuable streams and lakes will require addressing all of the potential sources. Since "we are all a source," we all must be part of the solution.


Dr. Jane Frankenberger
Department of Agricultural and Biological Engineering
Purdue University

For more information contact Jane Frankenberger (frankenb@purdue.edu)
or Brent Ladd (laddb@purdue.edu)
or call the Purdue Extension Safe Water office at 765-496-6331

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