Introduction
Water quality is the chemical, physical and biological characteristics of water with respect to its suitability for a particular purpose. Water that is perfectly good to wash a car with may not be good enough to serve as drinking water. When an average person asks about water quality, they probably want to know if the water is good enough to drink, cook, or wash with.
Ground water may contain some natural impurities or contaminants, even with no human activity or pollution. Natural contaminants can come from many conditions in the watershed or in the ground. Since water is an excellent solvent, it contains a lot of dissolved chemicals. Ground water moves through rocks and subsurface soil, therefore it dissolves substances as it moves such as magnesium, calcium, sodium, chlorides etc. For this reason, ground water will often have more dissolved substances than surface water. Some ground water may contain dissolved substances such as arsenic, boron, selenium, lead, or radon, which at high concentrations are detrimental to human health. Whether these natural contaminants are health problems depends on the amount of the substance present.
In addition to natural contaminants, ground water is often polluted by human activities such as:
- Improper use of fertilizers, animal manures, herbicides, insecticides, and pesticides.
- Improperly built or poorly located and/or maintained septic systems for household wastewater.
- Too dip and poorly constructed pit latrines.
- Leaking or abandoned aboveground and/or underground storage tanks and piping.
- Storm-water drains that discharge chemicals to ground water.
- Improper disposal or storage of wastes.
- Improper disposal of household hazardous wastes such as paint, solvents, cleaners etc.
- Road salts.
Noticeable Problems
Visible
-
Scale or scum from calcium or magnesium salts in water.
-
Unclear/ turbid water from dirty, clay salts, silt or rust in water.
-
Green stains on sinks or faucets caused by high acidity.
-
Brown-red stains on sinks, dishwasher, or clothes in wash points to dissolved iron in water.
-
Cloudy water that clears upon standing may have air bubbles from poorly working pump or problem with filters.
-
Green water colour because of algae is caused by high phosphorus in water.
Tastes
- Salty or brackish taste from high sodium content in water.
- Alkali/soapy taste from dissolved alkaline minerals in water.
- Metallic taste from acidity or high iron content in water.
- Chemical taste from industrial chemicals or pesticides.
Smell
-
A rotten egg odour can be from dissolved hydrogen sulphide gas or certain bacteria in your water. If the smell only comes with hot water it is likely from a part in your hot water heater.
-
A detergent odour and water that foams when drawn could be seepage from septic tanks into your ground water well or borehole.
-
A gasoline or oil smell indicates fuel oil or gasoline likely seeping from a tank into the water supply.
-
Methane gas or musty/earthy smell from decaying organic matter in water.
Unnoticeable Problems
Many serious problems can only be found by laboratory testing of water.
- Bacteria
- Heavy metals and minerals
- Nitrates and nitrites
- Radon
- Pesticides, herbicides and other chemicals
Separation Distances
Because of all the above noted forms of contamination it is important to locate wells or boreholes a safe distance from these possible sources or locate the sources of contamination as far as possible from existing wells or boreholes. Boreholes or water wells should be located at least 15 metres (50 feet) from drilled boreholes or wells with watertight castings that extend 6 metres (20 feet) or more below ground level or at least 30 metres (100 feet) for all other wells. Pit latrines depth will depending on the water table and from the bottom to height of at least 6 metres, the pit latrines should be cast with watertight materials such as waterproof cement.
Table 1. The parameters determined for the routine domestic water analysis test |
Parameter |
Recommended limit (mg/l) |
Conductivity ( :S/cm) |
* |
PH |
6.5-8.5 |
Calcium |
* |
Magnesium |
* |
Sodium |
20 |
Potassium |
* |
Carbonate |
* |
Bicarbonate |
* |
Chloride |
250 |
Sulphate |
250 |
Nitrate |
10 |
Total alkalinity as CaCO 3 |
400 |
Hardness as CaCO 3 |
* |
Total dissolved solids |
500 |
Boron |
* |
Arsenic |
0.010 |
Selenium |
0.05 |
Chromium |
0.10 |
Fluoride |
4.0 |
Barium |
2.0 |
Cadmium |
0.005 |
Lead |
0.015 |
Mercury |
0.002 |
Copper |
1.0 |
Nickel |
0.1 |
Beryllium |
0.004 |
Aluminum |
0.05-0.2 |
Manganese |
0.05 |
Silver |
0.1 |
Zinc |
5.0 |
Limits suggested by U.S. Environmental Protection Agency; Drinking Water Regulations and Health Advisories, EPA 822-R-94, May 1994.
*Limits not established.
Table 2. Hardness expressed as mg/l of CaCO 3
mg/l |
Water hardness |
0-75 |
Soft |
75-150 |
Moderately hard |
150-300 |
Hard |
Over 300 |
Very hard |
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