From Water Supply Source to Drinking Vessel – A Detailed Analysis of Drinking Water Quality in Bolivia

Simonne Rufener, Institute of Geography, University of Berne, December 2006
E-mail: simonne.rufener@students.unibe.ch

Water-borne diseases are responsible for about 4 billion cases of diarrhoea every year, of which 2.2 million cases lead to death. Many of the deaths involve children under five years of age. The most important and immediate risks to human health are those from enteric microbes of faecal origin that are often transmitted by drinking water. Between the water supply source and the end consumer, the water travels long distances and there are many occasions for it to get contaminated. The focus of this study was laid on coliform contamination A: from water sources, B: in transport vessels and after disinfection treatment and C: in drinking vessels. The purpose of our study was to determine at what stage of the potential transmission pathway contamination might be taking place.
In order to obtain a representative overview of the drinking water supply situation in Bolivia, three typical geographical regions were studied: Tropics (San Julian), Valley (Cochabamba) and Highlands (Uncía). Each region has its typical water supply system: in the Highlands, pipe tap systems built by UNICEF, in the Valley water is distributed by water bowser trucks, and in the Tropics the traditional dug wells with hand pumps are predominantly used together with pipe tap systems.

A: The monthly water quality monitoring campaign included 23 drinking water supply sources and was accompanied by a sanitary inspection of the site, on-site measurement of basic physical parameters, and field-lab analysis of chemical and microbiological parameters. For microbiological tests a membrane filtration method was applied using the DelAgua® water testing kit. Escherichia coli E. coli served as the indicator for the faecal contamination. Physical parameters were measured with hand-held field meters and chemical indicators were tested with a HACH spectrophotometer.
B and C: Water samples of the sources, transport vessels, treated water and the drinking vessels of 81 households were analysed and questionnaires were applied through interviewers. A particular aspect of the study is related to water treatment through boiling and SODIS, a low-cost, home-based method for disinfecting water through solar radiation.

A: About 61.4% of the analysed primary water sources samples show microbiological contamination. The WHO scale rates more than one fourth of the contaminated sources as high to very high health risk.
B: Insufficient or no cleaning of transport vessels may lead to microbiological contamination. About 76.6% of the analysed samples showed an increase of coliform organisms from source to transport vessel.
Some 44.5% of the analysed households do not treat their drinking water, 18.5% boil water and 37.0% perform SODIS method before consumption. The application of SODIS was performed incorrectly in almost one half of the cases. The most frequently observed incorrect SODIS application was that people did not expose the bottles to sunlight, i.e. in 39.1% of the cases the PET bottles were in the shade.
C: The contamination with E. coli increased significantly from water source to drinking vessel (Wilcoxon signed rank test: N=13, Z=2.2, p=0.02). Households which did not perform any water treatment had especially high drinking vessel contamination (Mann-Whitney-U: N=81, Z=3.3, p=0.01). However, even with boiling or SODIS, water in drinking vessels after disinfection treatment can not be considered as safe. There was a significant increase of E. coli from treated water to drinking vessel (Wilcoxon signed rank test: N=45, Z=2.4, p=0.015). This was traced to be related to insufficiently cleaned drinking vessels.

Keeping drinking water sources and their surroundings clean is highly recommended to avoid direct contamination at the supply sources. But even if the water quality at the water sources is safe, it does not necessarily lead to good drinking water quality at household level. Therefore, hygiene education including washing hands, transport and drinking vessels is highly recommended in order to avoid recontamination after water treatment. The implementation of a water treatment method like SODIS should always contain a hygiene sensitisation and an educational part.

Key words: Drinking water quality, transmission pathway, Bolivia, SODIS

Contact Addresses

Fundación SODIS
M. Encalada, M. Saladin
Universidad Mayor de San Simón, Casilla 5783
Cochabamba, Bolivia
sodis@fundacionsodis.org
msaladin@fundacionsodis.org
www.fundacionsodis.org

Centro de Aguas y Saneamiento Ambiental (CASA)
Lic. Mercedes Iriate
Calle Sucre frente Parque La Torre
Casilla 5783
Cochabamba, Bolivia
mechyi@netscape.net

Geographical Department, University of Berne
Group of Hydrology
Prof. Dr. R. Weingartner
Hallerstrasse 12, 3012 Berne, Switzerland
wein@giub.unibe.ch
www.giub.unibe.ch

EAWAG/SIAM
Prof. Dr. H.-J. Mosler
Postfach 611, 8600 Dübendorf, Switzerland
mosler@eawag.ch
www.sodis.ch