Lake by lake
Resources and references
About the Great Lakes LaMPs study...
Glossary of terms
In most communities, drinking water is treated to remove contaminants before being piped to consumers, and bacterial contamination of municipal water supplies has been largely eliminated by adding chlorine or other disinfectants to drinking water to prevent waterborne disease. By treating drinking water and wastewater, diseases such as typhoid and cholera have been virtually eliminated. Although other disinfectants are available, chlorination still tends to be the treatment of choice. When used with multiple barrier systems (for example, coagulation, flocculation, sedimentation, and/or filtration), chlorine is effective against virtually all infective agents.
Over time, public water systems have been found to supply drinking water of good quality. Monitoring and corrective measures to reduce and eliminate levels of contaminants in treated water are essential components in continuing to assure the safety of drinking water supplies. As the population grows and more people rely on the drinking water supply from the lakes, these control measures must be adequate to reduce the risk from exposure to microbes. Ultimately, however, source water protection (protection of the raw waters) is the key to maintaining the good quality of drinking water supplies. The Lake Erie LaMP has designated the drinking water use of Lake Erie as unimpaired.
In an effort to learn more about microbial contamination and to eliminate sources of pollution, continued monitoring, determination of the source of pathogens, and prevention activities are planned or active around Lake Huron as well as along the tributaries listed above.
Localized outbreaks of water-borne disease have been linked to contamination by bacteria or viruses, probably from human or animal waste. Recently, there has been increasing concern over the presence in drinking water of parasites such as Giardia and Cryptosporidium (the most common source of which is animal feces), which are resistant to common disinfection practices, and may pass through water treatment filtration and disinfection processes in sufficient numbers to cause health problems. For example, in 1993, the city of Milwaukee, Wisconsin, experienced an outbreak of cryptosporidiosis that affected over 400,000 residents, causing severe diarrhoea, nausea, stomach cramps, and other symptoms. The outbreak was caused by Cryptosporidium oocysts that passed through the filtration system of one of the city’s two water-treatment plants.
Cryptosporidium is a one-celled parasite that is spread through human or animal fecal contamination. When the organisms are ingested, they cause an infection and irritation of the digestive track that leads to acute diarrhea. For healthy people, this is generally a short term condition. However, it can be an extremely dangerous for small children and adults with Acquired Immune Deficiency Symdrome (AIDS), cancer, or other health problems. There is no effective drug for the treatment of cryptosporidiosis and currently it is not known whether any concentration of the organisms is safe for human consumption.
Cryptosporidium poses a greater hazard than other potential pathogens in drinking water supplies because of its ability to withstand traditional drinking water treatment. Individual organisms form small hard shelled oocysts when in hostile environments such as surface water. These oocysts are resistant to chlorine and small enough to evade most filter technologies. However, since the Milwaukee outbreak, EPA has strengthened turbidity requirements for finished tap water, to ensure better filtration methods. However, even in water meeting the new standards, small numbers of oocysts may still breach filters.
The largest category of consumer complaints about drinking water, worldwide, is taste and odor problems. Changes in the taste of drinking water may indicate possible contamination of the raw water supply, treatment inadequacies, or contamination of the distribution system. Although there are standards for some parameters that may cause taste and odor problems, such as phenolic compounds, there is considerable variation among consumers as to what is acceptable. Aesthetically acceptable drinking water supplies should not have an offensive taste or smell.
Although there are no drinking water restrictions on the use of Lake Ontario water, some nearshore areas, such as Rochester and the Bay of Quinte, report occasional taste and odor problems. Lake Ontario water suppliers most commonly receive consumer complaints regarding an "earthy" or "musty" taste and odors.
Studies conducted by Lake Ontario water suppliers have shown that these problems are related to naturally occurring chemicals, such as geosmin (trans, trans-1,10-dimethyl-9-decalol) and methylisoborneol (MIB), produced by decaying blue-green algae and bacteria. Using chlorine to clear water supply intakes of zebra mussels may also stimulate the production of these taste and odor-causing chemicals. Geosmin and MIB can cause taste and odor problems for sensitive individuals at levels as low as one part per trillion (ppt), well below the detection limits of the analytical equipment currently available to water authorities (2 to 3 ppt). Once identified, taste and odor problems can be eliminated at water treatment plants by the use of powdered activated carbon or potassium permangenate.
Taste and odor problems are more common during algal blooms. Additionally, storm events precipitate these problems by breaking up mats of the green algae Cladophora from their rocky substrate in nearshore areas. Floating mats of Cladophora located in warm shallow water are ideal habitats for blue-green algae and bacteria growth. The presence of these floating mats contributes to taste and odor problems. Localized eutrophication problems in some nearshore areas may also contribute to taste and odor problems.
In summary, taste and odor problems are considered to be a locally impaired beneficial use in some areas. The causes, however, are poorly understood. Naturally occurring algae, eutrophic conditions, and zebra mussel controls may all be important contributing factors.
Localized beach closings due to occasional high bacteria levels are a problem in some areas and are being addressed by several Remedial Action Plans (RAPs). While some taste and odor problems have been observed, there are no restrictions on drinking water consumption.
In Ontario, beaches are closed when bacterial (E. coli) levels exceed 100 organisms/100mL. During recent years (1995 to 1997) beach closings have continued in heavily urbanized areas in the western part of the basin due to storm events, but are less frequent in the central and eastern regions. Examples of ongoing problems include the beaches of the Bay of Quinte, Toronto, Burlington, Hamilton, Niagara, Pt. Dalhouse, and St. Catherines. Upgrading stormwater controls through the installation of collection tanks so stormwater from Combined Sewer Overflows (CSOs) can be treated in Toronto and Hamilton should reduce beach closings in these areas.
Thunder Bay has two treatment facilities, one drawing its water from Lake Superior (Bare Point Water Treatment Plant), and the other drawing its water from Loch Lomond, an inland lake. The remaining communities within the Lake Superior basin use inland lakes or rivers (surface water) and/or groundwater to supply drinking water. At present none of the eight Areas of Concern (AOCs) in the Lake Superior basin list restrictions on drinking water as a use impairment in their Remedial Action Plans (RAPs).
A variety of contaminants can adversely impact drinking water, such as micro-organisms (for example, bacteria, viruses, and protozoa such as Cryptosporidium), chemical contaminants (including naturally occurring and synthetic chemicals), and radiological contaminants, including naturally-occurring inorganic and radioactive materials.
Some individuals or groups, particularly children and the elderly, may be more sensitive to contaminants in drinking water than the average person. Although drinking water quality guidelines are for the general population, they are based on health effects observed in the most sensitive subgroup of the population (for example, lead and children).
A case in point. In October 1997, the Medical Officer of Health for the Thunder Bay District Health Unit issued a Boil Water Advisory to the residents of the south side of the city of Thunder Bay following the receipt of a laboratory report confirming the presence of Giardia in the water distribution system. The cyst was found on routine testing in the post-treated water supply in the south section of the city. In consultation with the Ministry of Health, Ministry of Environment, and city officials it was agreed that due to lack of a barrier filtration system, the advisory was made to inform the public who were supplied by the compromised system to a potential threat of water-borne disease.
During the 13 months of the Boil Water Advisory, the city undertook the installation of a temporary filtration plant to ensure that water from its Loch Lomond site was safe for its consumers. Once completed, and having met the minimum requirements of the Ministry of the Environment, the Boil Water Advisory was lifted on November 8, 1998. Plans by the city are underway to expand its water treatment facilities in the north end of the city to provide filtered treated water to the entire city from one source.
Boiling water is the best method for killing Cryptosporidium and bacteria in emergency situations. Boil water orders are generally the standard public health protection method when drinking water is found to be contaminated. The EPA has strengthened treatment requirements and standards for public water supplies using surface water. Health Canada, in collaboration with the provinces, is currently developing a drinking water guideline for Giardia and Cryptosporidium, is reviewing its turbidity guideline, and recently published a document titled Guidance for Issuing and Rescinding Boil Water Advisories (November 1998, revised March 1999) as a tool for health and environment authorities who must make the decisions concerning boil water advisories.
Last modified: April 29, 2003