Generally when it is said that groundwater is of good quality, it is considered to be safe for human and animal consumption, taste good, has no colour or odour and is not chemically "very hard" (very high concentrations of calcium and magnesium).
Water quality testing will determine the health and safety of a water supply and the results will reflect the quality of the natural environment within the capture zone of the water well and may be reflective of land use in the immediate vicinity of the source.
Groundwater acquires the water quality characteristics of the geological materials it passes through, by dissolving chemical constituents (iron, manganese, calcium, magnesium, sulphate, nitrate, arsenic, etc.). To ensure water is safe for use, water quality tests generally assess the following:
- Physical Characteristics (colour, pH, sediment)
- Chemical Characteristics (iron, arsenic, calcium, magnesium)
- Biological Characteristics (bacteria, parasites, viruses)
- Radiological Characteristics (uranium, radon)
Rural water well owners must accept the responsibility of monitoring the quality of water and maintaining the integrity of their well and distribution systems. Agricultural producers should ensure the water quality is safe for its intended use (livestock, irrigation, dairy, food processing, domestic use). Local health departments can assist in selecting tests important for assessing a domestic water supply.
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Water quality testing
It is highly recommended that bacteriological analysis and chemical analysis should 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.
Groundwater quality must be tested regularly, as water quality varies over time. Ideally, rural agricultural wells should be tested in the spring and fall, after a major weather event or after alterations to the well or distribution system to ensure the water is safe for its intended use (livestock, irrigation, dairy, food processing, domestic use). For rural water wells that are not under the direct influence of surface water, it is important to consult with your local health or environment department for further guidance to develop a sampling regime for bacteriological analysis and routine chemical analysis specific to the intended use of your groundwater supply.
Water quality guidelines and standards
Water quality standards for drinking water vary from country to country. In Canada, the Canadian Council of the Ministers of the Environment (federal and provincial) establish the Canadian Environmental Quality Guidelines for the protection of agriculture, aquatic life, environmental resources (water, soil), and the protection of human health. Health Canada, working with provinces and territories, establish the Guidelines for Canadian Drinking Water Quality (GCDWQ). Provincial governments establish guidelines and/or regulations for public and private drinking water supplies. The GCDWQ 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 important for many agricultural water uses including food processing, dairy and milk production, livestock watering, irrigation, wash water, heating, animal misting and pesticide application. Federal and provincial water quality guidelines 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.
The Rural Water Quality Information Tool developed by Alberta and Canada is an online tool to assist in the assessment of the quality and suitability of raw water sources for privately owned and operated rural and agricultural water supplies.
Measurement and reporting
When you have your water tested, the laboratory will provide you with the concentrations of the parameters (mostly dissolved minerals) that were analyzed. Concentrations will generally be shown in:
mg/L = milligrams per litre or parts per million (ppm)
Sometimes smaller concentrations are reported in:
µg/L = micrograms per litre or parts per billion (ppb)
Parameter specific maximum numbers are based upon Canada's GCDWQ and provincial regulations and guidelines. Maximum Acceptable Concentrations (MAC) are related to health and safety and Aesthetic Objective (AO) guideline numbers indicate desirable levels of odour, taste or colour. The laboratory report may also indicate parameters that are either not detected or are below a detectible limit.
If you have your water tested for microbial indicators you should discuss the results with a public health official to better understand the process, the results of the test, and any potential implications.
Physical and chemical characteristics
Physical characteristics of water may be assessed in a laboratory analysis; however, these are best determined at source. A change in taste, colour, turbidity or odour from a groundwater source can indicate that contamination of the supply is occurring or that nuisance bacteria such as iron-related or sulphate-reducing bacteria are present.
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. Provincial agencies provided recommended acceptable concentrations of these various parameters.
Some water quality parameters of concern for human health, if the recommended limit is exceeded, include nitrates, arsenic, selenium, sulphate and sodium.
- The Health Canada guideline for nitrate + nitrite is 45 mg/L as Nitrate) or 10 mg/L Nitrogen as nitrate. The Maximum Allowable Concentration for nitrate has been established to protect the most vulnerable consumers, who are infants under six months of age or adults with abnormal stomach enzymes, from developing methemoglobinemia.
- Arsenic MAC guidelines are under constant review and have been lowered to 0.010 mg/L and possibly to 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 1.0 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 recommended guideline 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 recommended guidelines, excess concentrations may lead to staining, taste, odour, scaling or other problems, but generally will have no effect on user health.
Bacteriological characteristics
Coliforms
Coliform bacteria are a frequently tested parameter. The Total Coliform test, if positive, indicates the possible presence of pathogenic organisms in the groundwater. This may also show that surface water is entering the well, because these organisms are also present on vegetation and in the soil.
Most coliform bacteria do not cause disease, but 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. An expansion of micro-biological monitoring may logically follow detection of the indicator bacteria in a water sample.
Additional monitoring
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 an accidental spill (fuel, chemicals) in the vicinity of the well can also trigger a higher degree of monitoring. For example, a routine test of electrical conductivity or 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, odour or turbidity of the water likely indicates a change in water chemistry or bacteriological quality.