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

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Household samples were also analysed for microbiological and chemical parameters, with a focus on how drinking-water quality deteriorated between the distribution system and household taps. In line with the WHO guidelines for drinking-water quality (WHO, 2004), all samples were assessed for sanitary risks by inspections that used a standard set of questionnaires developed for the RADWQ pilot project. Individual water supplies were assigned to risk categories using a “risk-to-health matrix”, which cross-checks a sanitary risk score with the count for thermotolerant coliforms, to give a measure of the potential health risk. The value of proxy parameters for assessing water quality (i.e. turbidity for bacteria, conductivity for chemicals) was also examined. The output of the analysis was Pearson’s r, a linear correlation coefficient that can easily be calculated within MS Excel. A drawback is that the derivation of Pearson’s r assumes the data are distributed normally, and the analysis uses means and standard deviations, so that outlier values 2 can disproportionately influence the results. More rigorous analyses exist, such Spearman's rho, which does not assume the data are normally distributed, and uses a rank transform method that makes it resistant to outliers, but which cannot be calculated within MS Excel. 2 An outlier is a value far from most others in a set of data. 16
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. 17
Page 1: RAPID ASSESSMENT OF DRINKING-WATER
Page 4 and 5: WHO Library Cataloguing-in-Publicat
Page 6 and 7: Annexes Annex 1. Rayon database of
Page 8 and 9: Foreword Among the infectious disea
Page 10 and 11: Acronyms GBAO Gorno-Badakhshan Auto
Page 13 and 14: 1 Introduction 1.1 The WHO/UNICEF J
Page 15 and 16: Measuring gender disparities. Data
Page 17 and 18: Microbial parameters. This involves
Page 19 and 20: 2 Methods 2.1 Survey design The met
Page 21 and 22: Figure 2.2 Steps in the design of t
Page 23 and 24: Cluster size. Cluster sizes ranged
Page 25 and 26: Table 2.2 Country-specific survey d
Page 27: Throughout the field visits, field
Page 31 and 32: Faecal streptococci Faecal streptoc
Page 33 and 34: Water sources were tested for fluor
Page 35 and 36: Table 3.8 Compliance with the Tajik
Page 37 and 38: Table 3.11 Compliance with WHO sugg
Page 39 and 40: Table 3.13 Results of sanitary insp
Page 41 and 42: Faecal contamination (thermotoleran
Page 43 and 44: comparison was possible, 42.5% show
Page 45 and 46: Table 3.23 Compliance of household
Page 47 and 48: protecting the spring (37.7%). Sani
Page 49 and 50: quality. The Republican SES hopes t
Page 51 and 52: Annex 1. Rayon database of utility
Page 53 and 54: Rayon Water supply Working conditio
Page 63 and 64: Annex 4. Primary stratification a S
Page 65 and 66: Rayons included in the RADWQ survey
Page 67 and 68: Annex 6. Example of a sampling plan
Page 69 and 70: Annex 7. Initial fieldwork plan Fie
Page 71 and 72: Annex 8. Example of a monthly progr
Page 73 and 74: Table 3. # Total number of analyses
Page 75 and 76: The following analyses are planned
Page 77 and 78: Remarks: The Sughd team is continui
Page 79 and 80:
No. Description of expense Expense
Page 81 and 82:
RADWQ Daily Report Sheet Chemical d
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