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Microbiological Contamination Of Pond Water And Associated Drinking Water Risk In Rural Coastal Areas Of Bangladesh

World Water Congress 2015 Edinburgh Scotland
11. Key vulnerabilities and security risks
Author(s): Raju Sarkar (Karlsruhe
Zahid Hayat Mahmud
Rezaul Karim
Joachim Vogt

International Center for Diarrhoeal Disease Research1, Islamic University of Technology2, Karlsruhe Institute of Technology3

Keyword(s): Sub-theme 11: Key vulnerabilities and security risks,


Introduction: Spatially varied availability of sources and related seasonality aspects influence the intensity of stress in managing potable drinking water in rural coastal areas of Bangladesh. In most cases, intolerable limit of salinity accelerates such varied availability. In coastal areas, tube well installation is limitedly successful because of high salinity in shallow aquifers and significant concentration of arsenic and iron. Ponds with or without adjacent filtration facility [pond sand filter (PSF)], household based rainwater harvesting plants and limited number of shallow (<30m) tube wells are the main drinking water sources available here. Compared to the monsoon season, salinity of pond water increases significantly in the four months of dry season. Besides, pond water (generally without PSF) is subject to contamination by microbes. As rainwater has the limitation of seasonal availability, people in this area have very few choices but to pick pond as their drinking water source. In general, they need to move 15-30 minutes of walking distance to fetch water from ponds. Things become worse during natural extreme events like cyclone, and flood, when the surge/flood water inundates the ponds. The increasing frequency and amplitude of such events have made the drinking water management challenging in this area, as it creates the threat of epidemics and other forms of secondary impacts. Even after all these demerits, ponds are till now the mostly used drinking water source here and people are trying to find new ways to make it more safe, effective and sustainable. This study has the objective to contribute in this regard. Previous scientific studies did not considered four critical factors all together to give us a comprehensive picture of the contamination of pond water by microbes. These are the contamination status at source, the contamination status at point of use, the responsible causes, as well as the practiced remedial measures, and the significance of contamination for the drinking water management of the affected community. In our study, we have considered all these four critical factors. Methods: As study area, we have selected nine mauzas (revenue collection unit in Bangladesh) from the three coastal sub districts Sharankhola, Dacope and Shyamnagar. These three sub districts are situated in three south-western coastal districts of Bangladesh and are severely exposed to the adverse effects of tropical cyclones. The overall data collection has been conducted in two stages. In first stage, 62 water samples have been collected from eight mauzas. We did not collect any sample from one mauza of Shyamnagar sub district as the inhabitants there have total tube well coverage. From each of the other eight mauzas, four ponds have been selected to collect samples. From one mauza of Sharankhola sub district, 30 samples have been collected directly from household pitchers. In this mauza, the people do not have any tube well coverage. Necessary other information like geographical location of the collected samples, physical properties of the ponds, use of pond water in other than drinking purpose, maintenance and management of the ponds and water preservation technique in households are enlisted by means of a structured questionnaire survey. All the collected samples were tested for four parameters namely, total coliforms (TC), total bacterial count (TBC), Escherichia coli (Ec), and Vibrio cholera. The samples were collected in sterile plastic bottles and were tested in the laboratory of the International Center for Diarrheal Disease Research, Bangladesh (ICDDR, B). In second phase detail information about the overall drinking water management of these nine mauzas have been collected through household based structured questionnaire survey, qualitative interviews, case studies, focus group discussions and expert interviews. Results and Discussion: Derived result from the collected data revealed the existence of all four types of contaminants in the collected water samples. The recorded maximum concentration of TC, HPC, and Ec in the source-samples is 8300 CFU/100ml, 45000 CFU/ml and 14000 CFU/100ml respectively. The WHO standard for these three parameters is 0, less than 500 CFU/ml and 0 in that order. We have found the point of use concentrations comparatively lower in the cases of alum [KAl(SO4)2*12H2O] use. Presence of Vibrio cholera has been identified in about 42% samples. We have found the absence of functional PSF, the multipurpose use of pond water and the distance of latrines from ponds as the significant causes for the contamination. The stakeholder's awareness regarding the status and causes, of contamination and possible remedial measures are not satisfactory. It indicates the necessity for a regular record keeping, a structured management guideline for drinking water pond, and a communal level awareness campaign to ensure safe water for the 55% households in the area, who use pond as drinking water source.

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