Chemical Analysis Interpretation of Rural Household Farm Water Supplies

 
 
Download 2,380K mobile version ("716_D04_Chemical_Analysis_Interpretation_of_Rural_Household_Water_Supplies.epub")mobile version
(2,380K)
     Download 217K pdf file ("716d04_2015.pdf")PDF
(217K)
     Subscribe to our free E-Newsletter, "Agri-News" (formerly RTW This Week)Agri-News
This Week
 
 
 
 Water quality criteria | Sodium | Potassium | Calcium | Magnesium | Iron | Sulphate (SO4) | Chloride | NO3 nitrogen (nitrate) | NO2 nitrogen (nitrite) | Fluoride | Total dissolved solids inorganic (TDS inorganic) | Conductivity | pH | Hardness | Alkalinity | Water treatment | Helpful conversions

A routine chemical analysis tests the water for about 15 chemical parameters. Levels for common problems such as hardness, sodium, sulfates, nitrates and nitrites can be determined.

Chemicals, other than those discussed below, can be tested, but arrangements to analyze them should be made with the laboratory before the sample is collected and submitted. These special requests must be arranged before collecting or submitting the sample and should be clearly specified on the request form. Special water sample collection procedures may need to be observed.

Your farm water supply should be analyzed regularly. Testing frequency depends on the type of water source. When a new water source is constructed, or a change in water quality is noticed, or other special circumstances arise, the water should be tested.

To test water for human consumption, your Regional Health Authority can provide the necessary water sample containers and arrange for laboratory testing. Water samples for livestock, irrigation, mortgage approvals and other non-household water usage must be sent to a private lab. Check the Yellow Pages telephone book for major cities under “laboratories” for lab contacts.

The water sample you take should be representative of the household supply. Choose a water outlet you regularly use for household usage. If you want to determine if the water quality of the source itself is an issue, then take a sample as close to the source as possible from an uncontaminated outlet. For most household samples, allow the water to run through the faucet for about five minutes and then fill the sample container. Send the sample to the lab right after collection.

To help you interpret the results after the laboratory analysis is complete, you can use factsheets such as this one, or contact a health inspector or agricultural water specialist. The Rural Water Quality Information Tool on Alberta Agriculture’s website can also assess water quality suitability for human drinking water, livestock, irrigation and spray water.

The comments on water quality below, which refer to particular minerals and other chemicals, pertain to household usage.

Water Quality Criteria

It is not legally required for private supplies to meet federal guidelines. People have different reactions and tolerances to different water quality constituents.

The two major types of guidelines are “aesthetic objectives” (AO) and “maximum acceptable concentrations” (MAC). Aesthetic objectives (AO) relate to effects like taste, odour, staining, etc. MAC levels are assigned when there are known health effects. If a chemical in your water exceeds MAC human drinking water limits, consult your family doctor or local health inspector.

All levels listed below (except pH and conductivity) are listed in milligrams/litre (mg/L), which is practically equivalent to parts per million (ppm) for drinking water.

Sodium

The AO for sodium is less than 200 mg/L. Sodium is not considered a toxic metal, and normal adults may consume 5,000 to 10,000 milligrams per day from liquids and solids without adverse effects. The average intake of sodium from water is only a small fraction of that consumed in a normal diet.

The recommended maximum level for people suffering from certain medical conditions such as hypertension, congestive heart failure or heart disease is much lower. In this case, consult your doctor.

Sodium is a significant factor in assessing water for irrigation and plant watering. High levels affect soil structure and a plant’s ability to take up water.

Potassium

There is no guideline or recommended limit for potassium in water. Alberta water supplies rarely contain more than 20 mg/L.

Water softeners that regenerate using potassium chloride can significantly raise the level of potassium in water. It is recommended that people with kidney disease or other conditions such as heart disease, coronary artery disease, hypertension, diabetes and those who take medication that interferes with how the body handles potassium do not drink water from a water softener that uses potassium chloride.

Calcium

The recommended limit for calcium is 200 mg/L; however, there is no federal or provincial guideline. Calcium is a constituent that can cause “hardness” in water and is not a hazard to health. Calcium is undesirable because it may be problematic for household uses such as washing, bathing and laundering. It also tends to cause encrustations in kettles, coffee makers and water heaters and may impair treatment processes.

Magnesium

Magnesium is a constituent that can cause “hardness” in water. There is no federal or provincial guideline
for magnesium, but a recommended limit of 150 mg/L is suggested because of taste. Higher levels of magnesium may produce a bitter taste but are not normally a health hazard.

Iron

The AO for iron is less than 0.3 mg/L. Levels as low as 0.2 to 0.3 mg/L usually cause staining of laundry and plumbing fixtures. Iron gives water a metallic taste that may be objectionable to some at 1 to 2 mg/L. Most water sources contain less than 5 mg/L iron, but occasionally, levels over 30 mg/L are found. The presence of iron bacteria in water supplies will often cause staining even at levels near 0.1 mg/L. Iron and iron bacteria are not normally a health concern.

Iron bacteria cause a slime that can reduce well flow, cause or increase staining, clog up piping and pumps, and impair treatment processes.

A routine chemical test does not always provide a dependable measurement of the iron concentration. To determine an accurate level of iron, a trace metals analysis should be conducted.

Sulfate (SO4)

The AO for sulfate is less than 500 mg/L. Sulfate concentrations over 500 mg/L can cause a laxative effect, especially for new users, as well as an objectionable taste. People may become accustomed to higher sulfate levels. If your water contains high levels of sulfate and you suspect that it is causing health problems, you should contact a physician. Babies are more susceptible to sulfates than adults.

Chloride

The AO for chloride is less than 250 mg/L. At levels above 500 mg/L, varying degrees of a salty taste are noticeable if certain elements such as sodium, calcium or potassium are present to combine with it. Most water in Alberta contains less than 20 mg/L, although chloride levels around the 2,000 mg/L range exist in some areas.

NO3 Nitrogen (Nitrate)

The MAC is 10 mg/L when reported as the nitrogen component of nitrate (NO3-N) or 45 mg/L when reported as nitrate (NO3).

Nitrates may be an indicator of contamination by human or livestock wastes, excessive fertilization or seepage from dump sites. Nitrates can also occur naturally in some geological formations. Nitrite above the guideline can cause methemoglobinemia (blue baby syndrome) and should not be consumed by infants, pregnant or breastfeeding women or people with health problems.

NO2 Nitrogen (Nitrite)

Due to its toxicity, the MAC for nitrite in drinking water is 1 mg/L when reported as NO2-N (the nitrogen component of nitrite) or approximately 3.28 mg/L when reported as nitrite (NO2). Nitrite is often an indicator of direct contamination by sewage or manure because nitrites are unstable and quickly converted into nitrates. Nitrite above the guideline can cause methemoglobinemia (blue baby syndrome) and should not be consumed by infants, pregnant or breastfeeding women or people with health problems.

Fluoride

The MAC for fluoride is 1.5 mg/L. Levels above this limit may cause white spots on teeth (dental fluorosis) in children 8 years or younger, including newborns. Levels above 2.5 mg/L may cause skeletal fluorosis.

Total Dissolved Solids (TDS)

Total Dissolved Solids (TDS) include both dissolved organic and inorganic components that are small enough to pass through a very fine filter (2.0 microns). The AO for TDS is 500 mg/L. “Dissolved solids” can come from natural or man-made sources.

The TDS value that usually appears in a lab analysis is calculated from adding the measured mass of all inorganic elements dissolved in water. A special request should be made if the dissolved organic components also need to be assessed. Alternatively, TDS can be estimated from another measurement called “conductivity” and is most accurate when organic content in the sample is low.

Ground water sources often contain higher TDS concentrations than surface water. Average Alberta well water has a TDS level closer to 1,000 mg/L. Levels higher than 1,000 mg/L are not necessarily a health problem depending on the specific minerals present; however, they may be somewhat unpalatable. High TDS may be associated with excessive hardness, taste, scaling or corrosion.

Conductivity

Conductivity can be used to estimate the total dissolved solids (inorganic) in the water. Multiplying the conductivity in microSiemens per centimetre by 0.65 will give an approximation of the total dissolved solids in mg/L. Conductivity tests are often used to assess water suitability for irrigation, for which the units used are usually deciSiemens per metre.

1 deciSiemen/metre = 1,000 microSiemens/centimetre

pH

The AO for pH is 6.5 to 8.5. pH is a measure of the concentration of the hydrogen ion, which determines how acidic or basic the water is. The pH scale for household water ranges from 0 to 14, with pH less than 7 being acidic and pH greater than 7 being basic. pH below 6.5 may be corrosive whereas pH above 8.5 may cause encrustation, scaling and a bitter taste.

The measurement of pH varies with temperature and is usually reported to what it would be at 25 degrees C. pH will affect many water treatment processes and needs to be considered when assessing treatment options.

Hardness

Hardness is caused primarily by calcium and magnesium salts in water. It is expressed as a mg/L equivalent of calcium carbonate. Hard water causes soap curd, which makes bathroom fixtures difficult to keep clean and causes graying of laundry. Increased levels above 100 mg/L will require more soap to be used when washing or bathing.

Hard water will also tend to form scale in hot water tanks, kettles, piping systems, etc.

Most labs will report hardness in mg/L. Many water treatment companies will use field test kits that report hardness in grains per US gallon.

one grain per gallon (US) = 17.1 mg/L

Type of water
Amount of hardness
mg/L
Grains per gallon
Soft
0 - 50
0 - 3
Moderately soft
50 - 100
3 - 6
Moderately hard
100 - 200
6 - 12
Hard
200 - 400
12 - 23
Very hard
400 - 600
23 - 35
Extremely hard
over 600
over 35

Alkalinity

Alkalinity is not a specific substance but rather a combined effect of several substances, most importantly carbonates, bicarbonates and hydroxides. It is expressed in units of mg/L of CaCO3. It helps the pH to remain stable while an acid is added to the water. When the alkalinity is gone, the pH will rapidly drop while the acid is being added.

The alkalinity of most Alberta waters is in the range of 100 to 500 mg/L, which is considered acceptable. Water with higher levels is often used. Alkalinity is a factor in corrosion (from low levels) or scale deposition (from high levels) and may also impair or affect treatment processes.

Water Treatment

Water treatment equipment can often improve water quality significantly. Each type of water treatment equipment has its limitations and therefore should be selected carefully.

For more information on water treatment please refer to the Agdex 716 D series of factsheets and the Rural Water Quality Information Tool on Alberta Agriculture’s internet site.
Helpful Conversions

1 mg/L (milligram per litre) = approx. 1 ppm (part per million)
1 gpg (grain per US gallon) = 17.1 mg/L (milligram/litre)

References

Other information sources

Prepared by
Farm Water Supply Branch
Alberta Agriculture and Rural Development

Agdex 716 (D04). Revised April 2015.
 
 
 
 
Share via AddThis.com
For more information about the content of this document, contact Ag Info Centre.
This information published to the web on May 1, 2003.
Last Reviewed/Revised on April 29, 2015.