Generally when it is said that groundwater is of good quality, it is considered not only to be safe for human and animal consumption, but also that it tastes good, has no colour or odour and is not chemically "hard".
Although there are many parameters that can be analyzed, there are several chemical constituents that will indicate the health and safety of a water supply. In addition to safeguarding the health of consumers, these water quality tests will reflect the quality of the environment within the capture zone of the water well and may be reflective of land use in the immediate vicinity of the source.
Water quality tests generally assess the following:
Local health departments can assist in selecting tests important for assessing a domestic water supply; however, owners of private systems must accept the responsibility of monitoring the quality of water and maintaining the integrity of their systems.
It is highly recommended that bacteriological analysis and chemical analysis be performed whenever a new water source is constructed or when purchasing a new rural residence with a private water supply. These tests should also be performed before and after any well restoration work or when a change in water quality is noted. However, a single water sample often does not provide enough evidence that a water supply is safe from contamination. Only continued sampling can ensure the integrity of a water supply.
It is also recommended that private water wells, that are under the direct influence of surface water*, be submitted quarterly for bacteriological analysis and yearly for Routine Chemical Analysis, Trace Metal Analysis and Mercury Analysis. Contact you local health or environment department for further guidance.
For private water wells that are not under the direct influence of surface water, generally samples should be submitted semi-annually for bacteriological analysis and every 2 years for routine chemical analysis.
* Groundwater under the influence of surface water is considered to be any water below the surface of the ground with parameters that closely correlate to and immediately influenced by, climatic conditions or surface water conditions.
Water quality standards for potable water vary from country to country. Canada (Health Canada) applies guidelines with each province regulating the quality standards. Standards are determined based upon an estimate of the concentration of a constituent that a person could ingest safely over a lifetime, based upon available toxicological information and allowance for a considerable safety margin.
Water quality is also important for many agricultural uses including livestock watering, irrigation, and spraying. There are federal and provincial water quality guidelines that provide information on the water quality required for specific agricultural uses. Many commercial laboratories offer test packages that are tailored to a particular agricultural application.
AAFC has developed the Rural Water Quality Information Tool (available on the Alberta Agriculture and Rural Development website), an online tool to assist in the assessment of the quality and suitability of raw water sources for privately owned and operated water supplies.
When you have your water tested, the laboratory will provide you with a list of the parameters (mostly dissolved minerals) that were analyzed and their concentrations. Concentrations will generally be shown in:
mg/L = milligrams per litre or ppm = parts per million
However, where concentrations are very small they may be reported in:
ug/L = micrograms per litre or ppb = parts per billion
The laboratory report may also indicate parameters that are either not detected or are below a detectible limit. The laboratory may also provide parameter specific - maximum guideline numbers, based upon Health Canada or Provincial standards, that show a Maximum Acceptable Concentration (MAC) which is health related or Aesthetic Objective (AO) guideline numbers and are related to items such as taste or potential for discoloration by the water.
If you have your water tested for microbial indicators you should discuss the results with a public health official to better understand the process and the results of the test, in order to fully understand any potential implications.
Although the following physical characteristics of water may be assessed in a laboratory analysis, generally only the pH of the sample is given, as many of these are of more concern in surface water sampling. However, a change in taste, colour, turbidity or odour in a groundwater supply can indicate contamination of the supply is occurring or the presence of nuisance bacteria such as iron-related or sulphate-reducing bacteria.
A routine water quality analysis of groundwater for domestic use generally measures the concentration of the main chemical constituents and is reported as total dissolved solids (TDS). Some of the commonly tested parameters include calcium, chloride, iron, manganese, fluoride, magnesium, nitrate, sodium and sulphate. Health Canada and Provincial Agencies provided recommended acceptable concentrations of these various parameters.
Coliform bacteria are one of the most commonly detected parameters of concern and are often the most frequently tested, usually in the same sampling episode. The Total Coliform test, if positive, may indicate the presence of pathogenic organisms in the groundwater since they are always present in animal and human wastes, or alternatively, that surface water is entering the well since these organisms are also present on vegetation and in the soil. Most coliform bacteria don't cause disease but they are used as an indicator organism to indicate the potential presence of disease-causing micro-organisms in the water. The absence of coliform in the sample leads to the assumption that the water is microbiologically safe to drink.
If the coliform test is positive, the water may be tested for faecal coliform, a subgroup of the coliform group that is specific to the intestinal tracts of warm-blooded animals. If present, it may be assumed that the source has been contaminated with sewage or animal waste. Many laboratories are moving towards testing for Escherichia Coli (E. coli) which is a more specific type of faecal coliform bacteria found in the intestines of animals or humans. No water sample from a private water supply should contain E. coli or Total Coliform bacteria.
Another test which may be conducted is the Heterotrophic Plate Count (HPC) formerly known as the Standard Plate Count (SPC). This is a test to measure the level of general bacteria populations in a water supply. From this procedure an estimate of the number of living, heterotrophic bacteria can be determined. Test results are reported as the number of colony forming units per ml of sample (cfu/ml). The Canadian Drinking Water Guidelines developed by Health Canada suggests further testing for total coliform if HPC exceeds 500. High HPC results may be an indication of biofouling in the water well or distribution system.
Other micro-organisms which can cause sickness or disease can also be investigated, however, analyses for these are not routine. An expansion of micro-biological monitoring may logically follow detection of the indicator bacteria in a water sample.
When testing a private water supply for human consumption, some Regional Health Authorities will provide the necessary water sample containers and will perform some of the tests or they may refer the well owner to a private laboratory. Health authorities or laboratories will also provide guidance on how to collect, store and ship the samples for analysis.
If a coliform test is positive, the assumption is made that the water supply may contain pathogenic bacteria and viruses that could cause human illnesses such as typhoid fever, dysentery, hepatitis, and others. The most common immediate responses to such a finding include chlorination of the water supply, using an alternative source of water or boiling the water before use if an alternative supply is not available. Corrective actions should also be taken to remove the source of contamination followed by disinfection of the water well and retesting of the water supply.
Some water quality parameters that can be a concern if the recommended limit is exceeded, include nitrates, arsenic, selenium, sulphate and sodium.
The MAC for nitrate (45 mg/l or equivalent to 10 mg/l as Nitrogen) or for nitrate + nitrite (4.5 mg/l or equivalent to 1 mg/l as nitrogen) has been established to protect the most vulnerable consumers, which are infants under 6 months of age or adults with abnormal stomach enzymes, from developing methemoglobinemia.
As for the inorganics, arsenic MAC guidelines are under constant review and have been lowered to 0.010 mg/L and possibly 0.005 mg/L in the future. Toxic effects include skin lesions, nervous system disorders and cancer. Selenium toxicity may result in health effects to internal organs and the nervous and circulatory systems. Fluoride between 1 and 1.5 mg/L can be beneficial for the prevention of tooth decay however above this amount there is the tendency to cause tooth mottling and excessive amounts may lead to skeletal damage.
Sulphate concentrations in excess of the AO's may have a laxative effect on new users and high levels of sodium may be a concern to people suffering from hypertension. For the remaining parameters which have AO guidelines, excess concentrations may lead to staining, taste, odour or other problems, but generally will have no effect on user health. Further information on the effects of AO exceedance can be found at Health Canada or provincial agency web sites.
In order to consider additional monitoring of groundwater quality, a significant change in the condition of the water is usually required. A change in activity or the occurrence of an accident (e.g. a spill of gasoline) in the vicinity of the well, can also trigger a higher order of monitoring. For example, a routine test of electrical conductivity or total dissolved solids (TDS) may show a significant increase over earlier samplings, creating a need for expansion of the number of parameters tested as a follow-up. Changing colour, taste and odour of the water may also indicate a change in water chemistry or bacteriological quality.