rapid assessment of drinking-water quality in the republic of tajikistan

3 Results
3.1 Microbiological parameters
A variety of microorganisms may be found in water, including pathogenic and non-pathogenic species.
Non-pathogenic microorganisms may cause taste and odour problems with water supplies, which can
influence whether people use the water for consumption, but the principle concern for microbiological
quality is contamination by pathogenic species. Most water-borne pathogens derive from faeces, and
to analyse the microbiological quality of drinking-water the usual practice is to test for the presence of
indicator organisms, normally bacteria such as E. coli and thermotolerant coliforms.
The following microbial parameters were included in the RADWQ project:
Thermotolerant coliforms. The ease of use and rapidity of tests for thermotolerant coliforms
justify their use, but it is recommended that confirmation tests for E. coli be undertaken for each
type of water source whenever possible.
Faecal streptococci. Some 10% of all water-source samples were tested for faecal streptococci.
This was designed to provide a small-scale within-study investigation to evaluate the usefulness
of these bacteria.
Thermotolerant coliforms
The thermotolerant coliforms are a group of coliform bacteria that grow at 44°C and include E. coli as
well as other species that may have an environmental source. In temperate climates, it has been
estimated that approximately 95% of thermotolerant coliforms are E. coli, but in tropical climates this
proportion may be significant lower. This shows that the results of analyses should be interpreted
cautiously, and highlights the need for other data collection methods. Thermotolerant coliforms
analysis can be performed using a variety of different techniques and results can be obtained within
1424 hours using relatively inexpensive methods.
E. coli derives almost exclusively from human and animal faeces and some strains are pathogenic (e.g.
E. coli О157:Н7). There is some evidence that E. coli is able to multiply in nutrient-rich tropical soils,
although it is generally recognized that this ability is limited and in most case the indigenous bacteria
would out-compete the E. coli. The identification of E. coli is simple but time consuming, as it
typically requires a two-stage process of presumptive and confirmative testing.
In the RADWQ project, a total of 1620 sites from utility piped supplies and protected springs were
selected to be tested for thermotolerant coliforms. As shown in Table 3.1, 87.2% of all samples tested
in Tajikistan met the requirements of both the national standard and the WHO guideline value.
Compliance was generally higher for utility piped supplies (88.6%) than for protected springs (82.0%).
The difference in compliance likely derived from the fact that water from springs was not disinfected.
The cumulative frequency of thermotolerant coliform counts is shown in Table 3.2. Most of the test
results ranged between 110 cfu/100 ml. Fewer than 14 samples (less than 1% of the sampling points)
showed counts or more than 10 cfu/100 ml, most from protected springs.
For utility piped supplies, compliance varied between broad areas and ranged from 66.7% in GBAO
to 93.3% in RRS and Dushanbe. The variation between broad areas was largely due to differences in
the quality of the supply infrastructure and in regular maintenance activities, particularly in Dushanbe.
It was also assumed that the supply of chlorine (or hypochlorite) for disinfection was better in
Dushanbe and RRS than in other regions of the Republic.
As mentioned in Section 2.2, we used a repeat sampling approach for utility piped supplies (i.e. each
site was visited twice). The time between the two sampling rounds varied between rayons, from one
week to four months. The results in Table 3.1 and Table 3.2 include all sampling points, regardless of
when they were taken (in the first or second sampling round), whereas the data in Table 3.3 provide a
comparison of the results between the two sampling rounds.
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