What to test for in the field
Water quality can affect health in the following ways:
- Some can be directly harmful to health, such as microbiological and biological contaminants, fluoride, pesticides and heavy metals;
- Colour, taste, turbidity and odour can make the water objectionable to consumers and cause them to use less objectionable water which may not necessarily be safer;
- Other features, such as pH and turbidity, can reduce the effectiveness of treatment processes such as disinfection.
The presence of pathogenic organisms is far more a frequent problem in developing countries, although sometimes chemicals such as fluoride and arsenic can be. Therefore if a water test has to be done, the priority should usually be for a bacteriological test, especially in emergency settings, with chemical analysis being a longer-term priority and goal (Arbelot, 1994 [ref.01]Ref.01: Arbelot, A. (Ed.) (1994). Public Health Engineering in Emergency Situation. Médecins Sans Frontières, Paris, France, pp. 1.13 – 1.15.). House and Reed (1997 [ref.02]Ref.02: House, S.; Reed, R. (1997). Emergency Water Sources. WEDC, Loughborough, UK, pp. 169-176. Available online.) outline guidelines as to what is acceptable in the short term, as opposed to what is considered acceptable in the long term.
Types of water tests
Direct pathogen testing is possible and has been carried out in various lab studies. Processes and methods for such tests are specialised, expensive and require specific expertise for the interpretation of results. They have not been detailed here.
A good background to water testing and water quality standards and guidelines (including WHO guidelines) can be found in House and Reed (1997 [ref.02]Ref.02: House, S.; Reed, R. (1997). Emergency Water Sources. WEDC, Loughborough, UK, pp. 169-176. Available online.). Water testing complements surveys, but there are various categories of tests:
- Core tests;
- Secondary tests;
- Treatability tests;
- Assessments for industrial pollution.
Core tests are singled out because they provide:
- Key information to determine treatment requirements (turbidity, pH, bacteriological analysis);
- Simple tests to indicate acceptability which can also highlight other potential pollution problems, and hence the need for further tests (odour, colour, conductivity).
The core tests are:
- Bacteriological analysis (E. coli).
Secondary tests mainly determine chemical quality and the features are less common than those measured in the core tests. The secondary tests are for: Chloride, Nitrates, Arsenic, Fluoride, Nitrites, Permanganate value, Iron, Sulphates, Chlorine demand (of raw water), Manganese and Taste.
Treatability tests are an aid to the selection of a suitable water treatment process. The treatability tests are for: Chlorine residual, Temperature, Aluminium and Alkalinity.
Ref.01: Arbelot, A. (Ed.) (1994). Public Health Engineering in Emergency Situation. Médecins Sans Frontières, Paris, France, pp. 1.13 – 1.15.
Ref.02: House, S.; Reed, R. (1997). Emergency Water Sources. WEDC, Loughborough, UK, pp. 169-176. Available online.