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

Faecal contamination (thermotolerant coliforms) and turbidity;
Thermotolerant coliforms and faecal streptococci;
Conductivity, and nitrate, fluoride and arsenic.
Pearson’s r was used to measure the strength of association. This correlation coefficient measures the
linear association between two variables. If the data lie exactly along a straight line with positive
slope, then r = 1; if they lie exactly along a straight line with negative slope, then r = -1; if there is no
correlation, then r = 0. The main limitations of Pearson’s r are that it measures only a linear
association between two variables; it assumes a normal data distribution; and it is not resistant to
outliers. The justifications for using it are that r can be easily calculated in Microsoft Excel, and that
the RADWQ snapshot nature does not justify using a more complicated analysis.
The only significant correlation was between thermotolerant coliforms and faecal streptococci (r =
0.52). For the other pairs of variables the correlations were negligible (Table 3.16).
Table 3.16 Analysis of proxy parameters a
Technology
Pearson's r
TTC vs.
Conductivity vs.
Turbidity FS NO 3 F As
Utility piped supplies -0.05 0.42 0.07 0.01 N.A.
Protected springs 0.13 0.99 0.06 0.02 N.A.
a
Totals 0.00 0.52 0.08 0.02 N.A.
FS = faecal streptococci. N.A. = data not available. TTC = thermotolerant coliforms.
3.8 Household water quality
The RADWQ survey also tested the quality of water consumed in households, to assess the extent to
which water was contaminated after leaving the source. Household water was matched to a source,
which meant that this part of the RADWQ survey only tested water from households with a known
water supply. As a result, 10% of the total sample size of 1600 (i.e. 160 households) were included in
the survey, with the households being proportionally distributed by broad area and by water-supply
technology. Testing included in-house or in-yard taps, if the households were connected to a utility
piped supply; and containers in households where water was stored before consumption.
Thermotolerant coliforms
As shown in Table 3.17, 85.4% and 91.6% of household taps and household containers, respectively,
complied with the WHO guideline value and the national standard for thermotolerant coliforms. At
most sites, there was little deterioration in the water quality between source and household (Table
3.18). For example, the microbiological quality of household water samples deteriorated in only 6.9%
of all cases.
Table 3.17 Overall compliance of household water quality with the
Tajikistan national standard and WHO guideline value for
thermotolerant coliforms
Technology No. of samples Compliance
(%)
Household piped water 41 85.4
Household container 119 91.6
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