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A bacteriological test for drinking water in remote communities

Nair, Jayalakshmy (2000) A bacteriological test for drinking water in remote communities. PhD thesis, Murdoch University.

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Abstract

Drinking water quality monitoring in remote areas should be viewed in a different way than in metropolitan areas, for many reasons. In remote areas around the world people use treated and untreated water for domestic purposes. Although there are many chances that the water in these systems could become polluted, the water is seldom tested for microbial quality.

The criteria for what can be considered the most suitable indicator organism should be different in remote areas and in developing countries where facilities for microbial analyses are limited. Emphasis needs to be given to indicators which are easy to detect, and to testing methods that are simple to perform. Complicated testing procedures would totally prevent the testing of drinking water totally in such areas. The hypothesis behind this project is that the HzS method, which was developed by Manja et al. (1982), meets the criteria for a good testing method in remote areas. This method is based on the detection of sulphate reducing bacteria (SRB) in the drinking water sample in contrast to standard methods which are based on the detection of coliform bacteria.

The main significance of the project is that the HzS method if found reliable, would facilitate regular testing of drinking water in remote areas throughout the world at very little expense. This could lead to the early detection of any contamination thereby improving the health of the people. Since local people could conduct the test it would help to create awareness of the need for clean drinking water and improve the hygiene of people in remote areas.

A literature review was conducted to analyse the need for an on-site bacteriological water testing method and to examine how efficient the currently used methods are for detecting faecal contamination of drinking water in developed and developing countries. The available literature was also examined to develop criteria for an indicator organism suitable for remote areas. In addition a review was conducted into present understanding of the H2S method.

In order to test whether the H2S method met the criteria for detecting pathogens in samples, experiments were conducted to test the method s efficiency for detecting Salmonella typhimurium, a common pathogen in drinking water. Similarly the efficiency for detecting another common enteric bacteria, Citrobacter freundii was also studied. Since the availability of power and laboratory facilities are limited in remote areas, the temperature range and the incubation period required by the method to detect contamination were studied. This was to test whether the H2S method would work without incubators. Trials were conducted with modified H2S media to try to detect lower levels of contamination and reduce the incubation period.

While conducting experiments to test whether the SRB are consistently present in human faeces, by comparing the H2S method with the coliform method using faeces samples, it was observed that about 18% of the samples lacked coliform bacteria in detectable amounts. It was concluded that if drinking water is contaminated with such a faecal sample, the contamination could go undetected if faecal coliforms are used as indicator organisms. The H2S method was not able to detect contamination at higher dilutions of faeces where low numbers of SRB would be present. The reason for the poor performance of the H2S method was
attributed to the predominance of methanogenic bacteria over SRB and/or the influence of illness and diet on the human intestinal microflora.

The correlation of the H2S method with the membrane Faecal Coliform method (mFC method) in detecting the presence of spiked raw sewage in drinking water was also observed to be low at lower levels of faecal coliforms. Also the correlation was found to be different with the effluent from two sewage treatment plants. A variation in the presence of sulphate reducing bacteria and the influence of illness and diets on the human intestinal microflora is tentatively postulated as a reason for this difference.

Testing various sources of treated and untreated water supplies revealed that the H2S method could be used as a screening test for drinking water. The absence of false negative results compared to the presence of total coliforms at coliform count of <1 OCFU/1 OOmL indicated that the H2S method is a good test for microbial contamination in developing countries where the acceptable level of total coliforms is <10MPN/100ml.

The conclusion in regard to the hypothesis is that the HzS method could be a useful screening test for microbial quality of drinking water in remote areas. However the comparison of the H2S method with the faecal coliform method was found to have some deficiencies. Due to the low numbers of faecal coliforms in many faecal samples it is concluded that comparison of a new method with such an indicator organism might not be valid. Further work is therefore required to assess the reason for the low levels of faecal coliforms, and whether it is related to health, diet or hereditary factors.

Publication Type: Thesis (PhD)
Murdoch Affiliation: School of Environmental Science
Notes: A digital copy of this thesis is not available. Your library can request a copy from Murdoch University Library via Document Delivery. A fee applies to this service.
Supervisor: Mathew, Kuruvilla, Gibbs, Robyn and Ho, Goen
URI: http://researchrepository.murdoch.edu.au/id/eprint/38154
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