Assessment of Dugwell as an Alternative Water Supply Options in Arsenic Affected Areas of Bangladesh

Transcription

1 International Journal of Civil & Environmental Engineering IJCEE-IJENS Vol: 11 No: 1 94 Assessment of Dugwell as an Alternative Water Supply Options in Arsenic Affected Areas of Bangladesh Md. Akramul Alam 1, Md. Mujibur Rahman 2 1 Faculty of Civil Engineering, Dhaka University of Engineering and Technology, Gazipur-17, akramul_alam@yahoo.com 2 Faculty of Civil Engineering, Bangladesh University of Engineering and Technology, Dhaka-1, mujib@ce.buet.ac.bd Abstract-- About 29 million people are either directly or indirectly exposed to arsenic contamination with varying degrees of risk due to extensive arsenic contamination of the groundwater in the alluvial aquifers of Bangladesh. Considering the urgency and gravity of the problem, alternative water supply options like dugwells (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 and social acceptability of dugwells. The study was conducted on 11 dugwells of Charghat, Dohar and Gazaria. Microbial contaminations were found in 95 percent water samples of DWs. None of DW water sampled in this study had an arsenic concentration higher than the Bangladesh drinking water standard (BDS) of 5 µg/l but arsenic concentrations exceeding the WHO guideline value (WHOGV) of 1 µg/l were found in 5 percent of DWs water samples. Both iron and manganese were present in DW water of Dohar and Gazaria in excess of BDS. Water quality of DWs of Charghat in all respects was found better than DWs of Dohar and Gazaria. Users satisfaction and social acceptability of the DWs were found area specific depending on the quality and availability of water. Index Term-- Arsenic, Fecal Coliform, Alternative water supply options, Dugwells, Ground water. 1. INTRODUCTION The arsenic contamination of shallow groundwater in Bangladesh is considered as the most serious drinking water related problem in the world in terms of population exposure [1], [2]. Water supply in Bangladesh is primarily based on groundwater sources. The country achieved a remarkable success by providing 97% of the population with access to improved water supply. However, this success is being overshadowed by the presence of arsenic in excess of acceptable levels in the shallow aquifers. Ground water based water supply programs that provide safe drinking water in order to control diseases like diarrhea, dysentery, typhoid, cholera and hepatitis have exposed population to arsenic related health problems. It has been estimated that about 29 million people in Bangladesh are exposed to drinking water with arsenic exceeding Bangladesh standards of 5 µg/l and 49 million people exceeding provisional WHO guideline value of 1 µg/l []. Thus arsenic contamination has reduced the estimated national population coverage with safe water supply from 97 to 74% [1]. Blanket screening of shallow tubewells in 27 arsenic affected Upazilas has shown that 29% of about 5 million tubewells tested had arsenic concentrations exceeding the Bangladesh standards of 5 µg/l [4]. There are 8,54 villages in Bangladesh where more than 8% tubewells used as only source of drinking water are contaminated with arsenic. Total of 8,4 cases of arsenicosis have been identified under national screening program. In the absence of an alternative source, people in acute arsenic problem areas are drinking arsenic contaminated water without paying much attention to possible consequences. On the other hand, people with arsenic phobia are likely to use unprotected surface water to avoid arsenic poisoning and get sick by water borne/related diseases. Arsenic toxicity has no known effective treatment, but drinking of arsenic free water can help the arsenic affected people to get rid of the symptoms of arsenic toxicity. Hence, provision of arsenic free water is urgently needed to mitigate arsenic toxicity and protect health and well being of rural people living in acute arsenic problem areas of Bangladesh. The options available for water supply in the arsenic affected areas can be brought into two major categories: alternative arsenic-safe water source and treatment of arsenic contaminated water. Groundwater from deep aquifers and dugwells, surface water and rainwater can be potential sources of water supply to avoid arsenic ingestion through shallow tubewell water. Dugwells (DW), pond sand filters (PSF), rain water harvesting systems (RWHS) and deep hand tube wells (DTW) have been installed by BAMWSP, JICA/AAN, Danida, Unicef and some other organizations as alternative arsenic-safe water source in some selected arsenic affected areas [5]. In some areas alternative water supply options are working well but not functioning properly in some other areas. To identify reasons of non-functioning and better understanding of the options, assessment of alternative water supply options in both technical and social aspects are essential. 2. METHODOLOGY 2.1 Selection of study area Two areas were selected on the basis of different hydrogeological conditions and different types of communities IJCEE-IJENS February 211 IJENS

2 International Journal of Civil & Environmental Engineering IJCEE-IJENS Vol: 11 No: 1 95 Charghat of Rajshahi and Gazaria of Munshiganj were selected initially but all the visited dugwells in Gazaria were found in abandoned conditions, for this reason Dohar of Dhaka were selected later for dugwell study. Fig. 1 shows the locations of study area. 2.2 Selection of water quality parameters The two important water quality parameters arsenic and bacteriological quality were selected from health risk point of view. Fecal coliforms (FC) were analyzed to represent bacteriological quality of water, as they are the most commonly used indicator bacteria. Other physical and chemical water quality parameters (Turbidity, colour, ph, iron, manganese, nitrate, and sulfate) were also analyzed. Charghat Gazaria Dohar 2. Collection and analysis of water samples Water samples from 4 dugwells of Charghat and 5 dugwells of Dohar were collected and analyzed in both dry and monsoon (wet) period to observe seasonal variation in water quality parameters. As all the visited dugwells of Gazaria were found in abandoned conditions, water samples from 2 dugwells of Gazaria were collected and analyzed only once in dry season. Samples for bacteriological analysis were collected in sterile bags and transported in ice-box. Fecal coliforms (FC) were analyzed by membrane filtration method. Samples for analysis of turbidity, colour, nitrate, and sulfate were collected in 5 ml plastic bottles. Turbidity of samples was measured by Turbidimeter. Colour, nitrate, manganese, sulfate of samples were determined by Hach DR/4 UV-Visible Spectrophotometer. Samples for analysis of arsenic, iron, manganese were collected in the acidified 25ml plastic bottles. Iron of samples was determined by Nesler methods. Arsenic was determined by graphite furnace atomic absorption method by AA-8 Atomic Absorption Spectrometer of SHIMADZU. ph of water samples were measured with ph meter at the field. Fig. 1. Locations of study area 2.4 Determination of Column of Water and Depth of Dugwell Depth, diameter, column of water of dug well were determined to observe the level of water table in study areas and amount or availability of water in dugwells in dry and wet season. Column of water of 4 dugwells of Charghat and 4 dugwells of Dohar were determined in both dry and monsoon season. Column of water of 4 Dug wells of Gazaria were determined once in dry season. Depths of dugwells were determined by a piece of weight hanging in one end of a nylon chord. Column of water of dugwells were determined by subtracting depth of surface of water from the depth of bottom. 2.5 Sanitary Inspection Sanitary inspection uses observation to assess the sanitary integrity and potential hazards in the environment that may affect water quality, particularly microbiological quality. Its use is well documented in the literature [], [7], [8]. It is generally used in conjunction with microbial analysis to understand the potential causes of contamination when it occurs, to assess the potential for contamination in the future and to develop control measures to microbial water quality. Sanitary inspection forms were prepared in the light of WHO Guidelines for Drinking-Water Quality Volume [] IJCEE-IJENS February 211 IJENS

3 International Journal of Civil & Environmental Engineering IJCEE-IJENS Vol: 11 No: Social Assessment The questionnaires were designed to elicit answers on the key questions like awareness about arsenic, water use pattern, users attitude towards mitigation options, acceptability/nonacceptability of the option by the users (with reason), users comment on water quality, operation and maintenance etc. The questionnaire survey was administered to a 1% sample of households using the mitigation options provided to communities. Five households per mitigation option were interviewed. The first household for interview was selected at random; the subsequent households were picked at an interval of 1 households in a systematic order. Adult women respondents were selected by preference as the principal household water manager, but men and child over the age of 15 were also accepted. Should no adult or child over 15 be available in a selected household or be unwilling to respond the next household was picked. Women as respondent were given preference and more than 5% of the respondents were women.. RESULTS AND DISCUSSIONS.1 Water Quality of Dugwell Dugwells water quality were evaluated considering relevant water quality parameters that include Fecal Coliform, Arsenic, Iron, Manganese, Nitrate, Sulfate, ph, Turbidity, Temperature, Electrical Conductivity, Odour and Total Dissolved Solids. From 4 DWs of Charghat and 5 DWs of Dohar samples were collected and analyzed in both dry and wet season. From 2 DWs of Gazaria samples were collected and analyzed in dry season only, due to all the visited DWs of Gazaria were found in abandoned conditions. Seasonal variation of water quality parameters are shown in Fig. 2 &..1.1 Microbiological quality Fecal coliform (FC) count varied from zero to 98 per 1 ml of water sample of dugwell. Only one sample of dugwell #8 in wet season was recorded as zero FC counts. It was observed that in dry season FC count in DWs water of Charghat were higher than in wet season due to dilution and less contamination from out side. But reverse situation was observed in Dohar, FC count in wet season were higher than in dry season. Wet season samples of Dohar were collected just after flood. The inflow of polluted surface water is likely to be the cause of such increase in the level of microbial contamination of DW water in Dohar..1.2 Chemical Quality Arsenic Arsenic concentration in DW water varied from <1 ppb to 42.9 ppb. None of the water samples of dug well exceeds BDS (5 ppb) [9], but 5% of samples exceed WHO guide line value (1 ppb). Arsenic concentrations in almost all DW water samples of Charghat were below detection limit (<1 ppb). Relatively higher arsenic concentrations were observed in DW of Dohar and Gazaria, all DW water samples except one in dry season of these areas exceed WHO guide line value (1 ppb). It was observed that arsenic content in dry season in DW water of Dohar is relatively higher than in wet season. Higher recharge during wet season may be responsible for lowering of arsenic concentration due to dilution. Iron Iron concentration in DWs varied from negligible (<.2mg/L) to1 mg/l. None of the water samples of dug well of Charghat exceeds BDS (1mg/L) but in dry season 1% water samples of dug well of Dohar exceed BDS. Highest iron content (1 mg/l) was observed in dry season in water sample of dugwell # of Dohar that was fully covered, there was no ventilation for aeration. Iron content in dugwell water of Dohar and Gazaria were much higher than in dug well water of Charghat. It was observed that iron concentrations in dry season were significantly higher than in wet season. Higher recharge during this time may be responsible for lowering of iron concentration due to dilution. Manganese Manganese concentrations in DWs were found to vary from.2 mg/l to.42 mg/l. In dry season 5% and in wet season 75% of water samples of dug well of Charghat and 1% of water samples of dugwell of Dohar and Gazaria exceed BDS (.1 mg/l). Highest manganese content (.42mg/L) was observed in wet season in DW #9 of Dohar. ph ph value in DWs were found to vary from.9 to 7.4. All ph values remain within WHO guide line value and BDS (.5 to 8.5). There is no remarkable seasonal and local variation of ph value of dugwell water was observed. Sulfate Sulfate concentrations in DWs were found to vary from below detection limit (<7 mg/l) to 15 mg/l. None of the water samples of dugwell of Charghat exceeds BDS (4 mg/l), only one water samples of dugwell of Dohar exceeds BDS. Higher sulfate contents were found in wet season than in dry season. Nitrate Nitrate concentrations in DWs were found to vary from.5 mg/l to.8 mg/l. None of the water samples of dugwell exceeds BDS (1 mg/l). Turbidity Turbidity in DWs was found to vary from.44 NTU to 58 NTU. None of the water samples of dugwell of Charghat exceeds BDS (1 NTU) but in dry season 1% and in wet season 2% of water samples of dugwell of Dohar exceeds BDS. Much higher turbidity was observed in dry season in water samples of DWs of Dohar than in wet season. The dugwell water of Dohar seems to be clear at the time of collection but after sometimes it gets turbid and this situation was observed mostly on fully covered dugwell water where ventilation facility is absent or inadequate. The reasons identified for high turbidity in dugwell water of Dohar and Gazaria are presence of high concentration of iron and IJCEE-IJENS February 211 IJENS

4 Sulfate (mg/l) Nitrate (mg/l) Iron (mg/l) Manganese (mg/l) FC/1 ml Arsenic (µg/l) International Journal of Civil & Environmental Engineering IJCEE-IJENS Vol: 11 No: 1 97 manganese in water and improper baseline support of the dugwell and clayey soil in the bottom of dugwell. Total dissolved solids Total dissolved solids in water samples of dugwell were found to vary from 279 mg/l to 195 mg/l. None of the water samples of dugwell of Charghat exceeds BDS (1 mg/l) but TDS of water sample of DW# of Dohar exceeds BDS in both seasons. Relatively higher TDS was found in wet season than in dry season. Colour Colours in water samples of dugwell were found to vary from below detection limit (<2 pt-co unit) to 218 pt-co unit. 25% of water samples of dugwell of Charghat and % of Dohar and 1% of Gazaria in dry season exceed BDS (15 pt-co unit). The reasons identified for high colour in dugwell water of Dohar and Gazaria are presence of high concentration of iron and manganese, decaying organic matter in water and poor maintenance of dugwell. Higher concentration of colour in DW water was found in dry season than in wet season. Temperatures of all the dugwell water were found to vary from 24.7C to 2.8C. From the temperature point of view dugwell water is very good. All the values of temperature remain within WHO guide line value and BDS (2C to C). Odour Odours in water samples of DWs were examined by smell in the field. Little or intense bad smell was observed in most of the dugwell water of Dohar and Gazaria but no bad smell was observed in dugwell water of Charghat. It appeared that smell in dugwell water varied from place to place and probably related to the presence of organic matters in soils..2 Column of Water and Depth of Dugwells Diameters of dugwell were found to vary from.8 m to 1.4 m and depth variation was observed from.81 m to 8.84 m, highest depth (8.84 m) was found in dugwell #4 of Charghat that was installed in 191. Columns of water were found to vary from.1m to 5.4m. Highest column of water (5.4 m) was observed in DW #7 of Dohar in wet season and also lowest column of water (.1 m) was observed in DW #8 of Dohar in dry season. Temperature Legend: Dry Season Wet Season Fig. 2. Seasonal variation of FC, Arsenic, Iron, Manganese, Colour & Sulfate in dugwell water IJCEE-IJENS February 211 IJENS

5 Column of water (m) TDS (mg/l) Conductivity (µs/cm) Colour (pt-co unit) Turbidity(NTU) International Journal of Civil & Environmental Engineering IJCEE-IJENS Vol: 11 No: ph Legend: Dry Season Wet Season Fig.. Seasonal variation of Colour, Turbidity, TDS, Conductivity, ph & Column of water in dugwell water. Sanitary Integrity Sanitary inspection (SI) uses observation to assess the sanitary integrity and potential hazards in the environment that may affect water quality, particularly microbiological quality. Sanitary inspection provides an assessment of the existing sanitary conditions of the water point and quantifies the risk on a scale of (no risk) to 1 (very high risk). The distribution of sanitary risk scores and correlation between FC and SI risk score of dugwells are shown in Table 1 and Fig.4 respectively indicate that overall sanitary conditions of dugwells are very poor. The water points with higher sanitary risk scores are likely to show high microbial counts, although this would usually be seen in the monsoon season. The data suggest that sanitary risk factors can be controlled through compliance with construction protocols, improved training of communities, raising awareness within the community, behavioral changes within the community and ensuring community participation in planning and implementation IJCEE-IJENS February 211 IJENS

6 FC/1 ml International Journal of Civil & Environmental Engineering IJCEE-IJENS Vol: 11 No: 1 99 Risk Score SI Risk Score Fig. 4. Correlation between FC and SI risk score of dugwell T ABLE I DISTRIBUTION OF SI SCORES FOR DUGWELLS Risk Category % Dugwell n = 11 No Risk 1- Low Risk.4 4- Intermediate to high Risk Very high Risk 9.9 For dugwells it is also likely that control of microbial water quality requires disinfection, as discussed by DASCOH [9]. This is a finding that is supported from studies in other countries, for instance in Uganda boreholes with hand pumps were found to be of good quality in most areas despite obvious risks [1]. The reduction in sanitary risks and maintenance of water quality require action by the water supply operators. This is most critical for dugwells where even slight deterioration in operation and maintenance performance leads to increasing contamination. The high number of sanitary risks and poor microbial quality suggests that agencies providing dug wells need to do more to support communities in maintaining their dugwells, if these are to provide safe water in the long-term..4 Functionality of Dugwells In Charghat upazilla of Rajshahi out of 5 dugwells surveyed 4 dugwells were functioning properly and only 1 dugwell was found in abandoned conditions due to unavailability of water for insufficient depth. This dugwell could not be constructed properly for sand boiling. In Dohar upazilla of Dhaka out of 11 dugwells surveyed only 5 were found functioning with poor performance in 24 but only were found functioning with poor performance in 25. It is to be mentioned that dugwells of Dohar were constructed from 22 to 24. In Gazaria Upazilla of Munshiganj 1% of dug wells were found in abandoned conditions that were installed in 22. Poor construction, operation and maintenance, bad odor and taste of water, excessive iron and manganese in water and availability of other source of water like deep tubewell are identified as the reasons of nonfunctioning/ abandonment of dugwells in Dohar and Gazaria..5 Operation and Maintenance of Dugwells Most of DWs users of Charghat were aware of operation and maintenance, reverse case was observed in Dohar and Gazaria. DWs of Charghat were installed or renovated in year 2 and motivation work on use of DW water in drinking and cooking purposes and frequent training on operation and maintenance of water points like disinfection of DWs water by chlorination, repairing of tubewell etc. were done through local NGO named SWALLOWS. One of the caretakers of DWs of Charghat stated that he disinfected DW water by bleaching powder two times from the installation of DW and some caretakers stated that they applied bleaching powder when insects were visible in water. Major works like removing deposited clay in the bottom of DW were done by SWALLOWS. DWs of Dohar and Gazaria were installed in years 22 to 24 by BAMWSP. Users of DWs of Dohar and Gazaria stated that they had no knowledge how to repair and who will repair, as a result all of the visited DWs of Gazaria and 72.7% DWs of Dohar were found in abandoned conditions due to lack of maintenance.. Users Perception and Attitude towards Alternative Water Supply Options The users perception and attitude about the DW, DTW, PSF and RWHS as permanent solution to the arsenic problem were found area specific depending on the quality and availability of water. About 9% of the users of Charghat considered DW as a permanent solution to arsenic problem. But reverse situation was observed in Dohar and Gazaria, Users of Dohar and Gazaria did not like DWs and very much annoyed about installed DWs by BAMWSP. All of the visited DWs of Gazaria were found in abandoned conditions. Some users of DWs of Dohar were using DW water after installation but gradually they were shifted to DTW lefting DW in abandoned conditions. They considered DTW as a permanent solution to arsenic problem instead of DW. Water quality of DWs of Charghat in all respects was found better than DWs of Dohar and Gazaria. The respondents provided with a DW, DTW, PSF and RWHS were generally satisfied with the quality of the water but greater satisfaction was expressed in favour of DTW, RWHS and PSF waters as compared to DW water. There was little difference across the income groups regarding their satisfaction with arsenic mitigation options with respect to quality of water. 4. CONCLUSION The following conclusions are drawn on the basis of results obtained from the technical and social assessment IJCEE-IJENS February 211 IJENS

7 International Journal of Civil & Environmental Engineering IJCEE-IJENS Vol: 11 No: 1 1 Microbial contaminations were found in most of the dugwell water and it was recommended that the water should be properly disinfected. Physico-chemical water quality of dug well varied seasonally and locally. Suitability of alternative water supply options is area specific. Social acceptability of alternative water supply options depends on water quality, water availability throughout the year, ease of operation and maintenance. Caretakers training and community participation is essential for sustainability of the water supply options. REFERENCES [1] Ahmed. M. F., Alternative Water Supply Options for Arsenic Affected Areas of Bangladesh, ITN-Bangladesh and WSP-South Asia, 22. [2] BGS-DPHE, Arsenic Contamination of Groundwater in Bangladesh, BGS Technical Report WC/1/19, British Geological Survey, Keyworth, UK, 21. [] Ahmed, M.F and Ahmed C.M, Arsenic Mitigation in Bangladesh, Local Government Division, Ministry of LGRD & Co-operatives, Government of Bangladesh, 22. [4] BAMWSP, Results of National Screening Program, National Arsenic Mitigation Information Centre, Bangladesh Arsenic Mitigation Water Supply Project, 24. [5] APSU, Progress with Provision of Arsenic Mitigation Options to the end of December, 24, Arsenic Policy Support Unit, 25. [] WHO, Guidelines for Drinking-Water Quality Volume : Surveillance and Control of Community Water Supplies, Second Edition, World Health Organization, Geneva, [7] Howard, G., Water Quality Surveillance A Practical Guide, Geneva WEDC, Loughborough University, UK, 22. [8] WHO, Guidelines for Drinking-Water Quality, Third Edition, World Health Organization, Geneva, 24. [9] GoB, Environmental Conservation Rule-1997, Bangladesh Gazette, Ministry of Environment and Forest, Government of the People s Republic of Bangladesh [1] DASCOH, Evaluation of Dugwell as a Safe Water Alternative Option,Development Association for Self-reliance, Communication and Health, Dhaka, 24. [11] Howard, G., Effective Approaches to Water Supply Surveillance in Urban Areas of Developing Countries, Ph. D. Thesis University of Surrey, UK, IJCEE-IJENS February 211 IJENS