9.10.5 Field testing

Field testing can be used for operational monitoring of drinking water supplies, and its use is encouraged, particularly for small and remote systems where access to laboratory-based testing is difficult.

Some tests, including those for temperature, free and total chlorine and monochloramine, are always undertaken in the field. Sample storage times and conditions affect results such that unless analysis can be undertaken within a short time of sampling, field testing is the only method of deriving representative results.

Beyond those tests which must be done in the field, it is possible to acquire, at reasonable cost, basic chemical test kits for common physical and chemical characteristics, including hydrogen sulfide (H₂S), pH, dissolved oxygen, electrical conductivity, colour, iron, manganese, turbidity, chlorine and fluoride. These test procedures are well within the capabilities of trained treatment plant operators and system caretakers. The test results should generally, however, be regarded as indicative only, and should complement, but not replace, more reliable laboratory tests.

Recent advances in field tests for indicator microorganisms, such as total coliforms and E. coli, are making such tests feasible as part of drinking water quality monitoring in small and remote locations where it may not be possible to get samples to laboratories within the timeframe required for accurate analysis, or the costs of doing so are prohibitive.

The test results of field testing will not have the standing of those produced by NATA-accredited laboratories, but they do permit regular and frequent monitoring. What the field tests sometimes lack in precision and reliability needs to be balanced against the benefits of the increased frequency of monitoring that is possible. Furthermore, such kits enable many tests to be performed in the field, thus avoiding the need to preserve and transport samples to a laboratory.

In all cases where field testing is undertaken, it is essential that those doing the testing are appropriately trained, that analysers are calibrated as per the manufacturers’ specifications, and that an audited quality assurance program, ideally including proficiency testing, is in place to monitor testing performance. The extent to which a monitoring program relies on the results of field kits should be discussed with the relevant health authority or drinking water regulator.