Section 16Water Quality Testing
There is no single measure that constitutes good water quality ... it depends on its use. Also, keep in mind that some water quality problems (iron, manganese and turbidity) can be treated (see Appendix M). Water quality is defined by analyzing it in terms of its:
Good quality (potable) drinking water is free from disease-causing organisms, harmful chemical substances and radioactive matter, tastes good, is aesthetically appealing and is free from objectionable colour or odour. It should be emphasized that there is a difference between "pure water" and "safe drinking water". Pure water, often defined as water containing no minerals or chemicals, does not exist naturally in the environment. Safe drinking water, on the other hand, may retain naturally occurring minerals and chemicals such as calcium, potassium, sodium or fluoride which are actually beneficial to human health. These will impart a taste to the water that may take some getting used to.
In some cases, however, groundwater can be contaminated with chemicals or bacteria. For example, a recent study has found that the health of many people has been put at risk due to the presence of naturally occurring arsenic in drinking water wells!
Recommended Sampling Program
Often, however, many communities with Lifewater wells do not have reasonable access to commercial laboratories. In these cases, it is still desirable to sample but it must be done at the well site for minimum cost.
Tests for nitrate-nitrogen (NO3-N), pH, turbidity, total dissolved solids (TDS), odours, total coliform (the most important test), aerobic and sulphate reducing bacteria can be performed with minimal equipment and cost and provide accurate information on the state of the well water. Ideally, these tests should be done every 6-12 months to ensure that the water is still safe to drink. The tests will indicate if the well water quality is staying the same or will give an early indication that some activity is impacting it. Any indication of quality deterioration can then be corrected at an early stage.
Recommended Test Methods
Water samples should be taken in the following manner:
- make visual observations concerning the turbidity.
- make statements about any odours observed in the water.
If the water is turbid or cloudy, contaminated surface run-off may be entering the aquifer through cracks in the casing or the cement pump pad or through surrounding soil which is very permeable. While turbidity is not dangerous, it reduces the effectiveness of disinfection and indicates the presence of other conditions that need to be further investigated.
Odours should not be present in the drinking water. If present, potentially harmful substances may be entering the water from households (washing activities), agricultural sources (animal fecal matter), or natural sources (sulphates from springs or aquifers).
If total dissolved solids (TDS) exceed 500 mg/l, objectionable taste may drive people to use unsanitary water supplies. Increasing TDS concentrations over time indicates that the well is drawing groundwater from deeper in the earth or that contaminants (such as salt water if the well is near the ocean) are leaching into the aquifer. Serious TDS changes over time will require reducing pumping volumes and/or drilling a new well (likely at a higher elevation).
Readings of pH should be in the range of 5.5 to 8.5 for well waters. If readings are outside this range, the source and corrections may be difficult. The worse effect may be premature corrosion of metal surfaces contacting the water.
Nitrate concentrations above 10 mg/L can cause blood disorders in infants (blue baby disease). Elevated levels indicate that manure, sewage, or nitrogen fertilizers are reaching the water source. One elevated test reading (greater than 50 mg/l nitrate) must be followed up with more frequent testing (weekly). If nitrate levels above 45 mg/l (10 mg/l nitrate as nitrogen) persist, the source of the nitrate (animal confinement areas, privies etc) should be determined and relocated.
Nitrite readings (can be measured with the same test strip) should always be less than 1 mg/l. If nitrite concentrations are above 1 mg/l, the water must not be given to infants and a different source (boiled for disinfection) must be used.
Specific disease-producing organisms are difficult to identify in water. Therefore, while total coliform and aerobic/anaerobic bacteria are themselves not harmful, their presence signals that bacterial contamination from either human or animal fecal sources may be present. If total coliform and/or active aerobic or anaerobic bacteria are found, the water supply should be re-tested with extra careful attention given to all the sampling details.
If bacteria problems are still found, try to get local health professionals to conduct more thorough testing of the water supply. In addition, the well and surrounding area should be carefully examined to determine possible entry points for contaminated water. Note that the same sources that cause nitrate problems are probably responsible for bacterial contamination (see Section 2.6). However, bacterial contamination can also indicate a cracked well casing. Each circumstance will require its unique solution to improve the water quality. If problems persist and cannot be corrected, each individual user should disinfect the water they need for drinking, cooking, brushing teeth (see Appendix T: Learn how to make water safe to drink!).
Footnotes & References
1 Coliform bacteria detect both non-pathogenic and disease-producing bacteria. Since the identification of specific disease-producing micro-organisms is difficult, total coliform is often used as an indicator of the water possibly containing disease-producing organisms that normally live in the intestinal tracts of man and warm-blooded animals (Driscoll, 1986). The four major types of pathogenic organisms that can affect the safety of drinking water are bacteria, viruses, protozoa and occasionally worm infections. Typhoid, cholera and dysentery are caused by bacteria and protozoa. Diseases caused by viruses include infectious hepatitis and polio.
2 The Biological Activity Reaction Tests (BART) by Dryocon Bioconcepts inc. include the nutrient media as a sterile dried matrix on the floor of the tubes (test vials). For the HACH pathoscreen test, the media is contained in small plastic tubes ("pillows") which must be cut and poured into the vial in the field. Only the BART tests do NOT require incubation.