Technical and social assessment of alternative water supply options in arsenic affected areas

Abstract

Arsenic contamination in groundwater and its toxic effect on human health is a major public health problem in Bangladesh. There are 270 arsenic prone upazillas in the country and the total population exposed to arsenic contamination has been estimated as 24.5 million (around 19 percent of total population). Among 4.95 million tube wells in the 270 upazillas, 29 percent tubewells are contaminated with arsenic. The number of arsenicosis patients has come out as 38,430. Given the fact that any effective treatment for arsenicosis is yet to be developed, supply of arsenic safe drinking and cooking water to the population exposed to arsenic contamination is the principal way of mitigating the problem. Considering the urgency and gravity of the problem, alternative water supply options like dug wells(DW), deep tubewells(DTW), pond sand filters(PSF) and rain water harvesting systems(RWHS) are being installed in arsenic affected areas under arsenic mitigation programme. The study aimed at assessing the water quality in both dry and wet seasons, sanitary integrity, functionality, operation and maintenance, costs and social acceptability of these four altemati,.e water supply options. The study was conducted on II DWs of Charghat, Dohar and Gazaria, 9 DTWs of Dohar and Goumadi, 17 RWHSs of Charghat, Goumadi, Pathorghata and Ghior and 6 PSFs of Pathorghata and Goumadi. The contaminants likely to be present in water from DW, DTW, PSF and RWHS were analyzed adopting standard methods. The presence of arsenic, FC and other selected physical and chemical water quality parameters were examined at each water points. The sanitary integrity of all water points ".as assessed using standard sanitary inspection format. A social acceptability based on a questionnaire survey ""as conducted at each water point. The social survey was conducted on 47 households using DWs, 20 households using DTWs, 25 households using PSFs and 30 household using RWHS as arsenic mitigation options. Besides these, a detailed study was conducted to observe performance of !TN-BVET modified PSFs just after commissioning in October 2002. Perfomlance assessment of the modified PSF was done in terms of quality of filtered water through analysis of water quality test results, ease of operation and maintenance, yield capacity/ efficiency of filter, social acceptability of the modified PSF. Microbial contamination were found in 95 percent water samples of DW, 7 percent of DTW, 43 percent of RWHS and 77 percent of PSF. None of DW water sampled in this study had an arsenic concentration higher than the BDS of 50 Ilg/L but arsenic concentrations exceeding the WHOGV of 10 Ilg/L were found in 35 percent of DW water samples. Arsenic concentrations in DTW, RWHS and PSF water samples were found ".ithin BDS and WHOGV. Both iron and manganese were present in DW water of Dohar and Gazaria in excess of BDS. Manganese was present in DTW water of Dohar in excess of BDS. The concentrations of nitrate in DW, DTW, PSF and RWHS water samples were within BDS. Water quality of DWs of Charghat in all respects was found better than DWs of Dohar and Gazaria. It was observed that cost of installation, operation and maintenance of RWHS per person is high than other three options. Performance of !TN-BUET modified PSF was found quite satisfactory in terms of removal efficiencies of FC, TC, turbidity and colour. Users' satisfaction and social acceptability of the DW, DTW, PSF and RWHS were found area specific depending on the quality and availability of water.