Investigating Sustainable Mitigation Alternatives for Groundwater in Matlab Upazila, Bangladesh

INVESTIGATING SUSTAINABLE MITIGATION ALTERNATIVES FOR GROUNDWATER IN MATLAB UPAZILA, BANGLADESH A MINOR FIELD STUDY Nicklas Gingborn and Hanna Wåhlén April 2012 TRITA-LWR Degree Project 12:18 ISSN 1651-064X LWR-EX-12-18 Nicklas Gingborn and Hanna Wåhlén TRITA LWR Degree Project 12:18 © Nicklas Gingborn & Hanna Wåhlén 2012 Degree Project in Civil Engineering and Urban Management (S), specialisation Natural Resources Engineering (NRT) Department of Land and Water Resources Engineering Royal Institute of Technology (KTH) SE-100 44 STOCKHOLM, Sweden Reference should be written as: Gingborn, N. & Wåhlén, H., (2012). Investigating sustainable mitigation alternatives for groundwater in Matlab Upazila, Bangladesh - A Minor Field Study. TRITA-LWR Degree Project 12:18, 34p. ii This study has been carried out within the framework of the Minor Field Studies Scholarship Programme, MFS, which is funded by the Swedish International Development Cooperation Agency, Sida. The MFS Scholarship Programme offers Swedish university students an opportunity to carry out two months’ field work, usually the student’s final degree project, in a country in Africa, Asia or Latin America. The results of the work are presented in an MFS report which is also the student’s Master of Science Thesis. Minor Field Studies are primarily conducted within subject areas of importance from a development perspective and in a country where Swedish international cooperation is ongoing. The main purpose of the MFS Programme is to enhance Swedish university students’ knowledge and understanding of these countries and their problems and opportunities. MFS should provide the student with initial experience of conditions in such a country. The overall goals are to widen the Swedish human resources cadre for engagement in international development cooperation as well as to promote scientific exchange between unversities, research institutes and similar authorities as well as NGOs in developing countries and in Sweden. The International Relations Office at KTH the Royal Institute of Technology, Stockholm, Sweden, administers the MFS Programme within engineering and applied natural sciences. Lennart Johansson Programme Officer MFS Programme, KTH International Relations Office KTH, SE-100 44 Stockholm. Phone: +46 8 790 9616. Fax: +46 8 790 8192. E-mail: [email protected] www.kth.se/student/utlandsstudier/examensarbete/mfs Nicklas Gingborn and Hanna Wåhlén TRITA LWR Degree Project 12:18 iv Investigating sustainable mitigation alternatives for groundwater in Matlab Upazila, Bangladesh INVESTIGATING SUSTAINABLE MITIGATION ALTERNATIVES FOR GROUNDWATER IN MATLAB UPAZILA, BANGLADESH A MINOR FIELD STUDY Nicklas Gingborn and Hanna Wåhlén Supervisors: Prosun Bhattacharya Professor Department of Land and Water Engineering Royal Institute of Technology (KTH) Stockholm, Sweden Kazi Matin U. Ahmed Professor Department of Geology University of Dhaka Dhaka, Bangladesh Ashis Biswas PhD Student Department of Land and Water Engineering Royal Institute of Technology (KTH) Stockholm, Sweden STOCKHOLM, Sweden April 2012 v Nicklas Gingborn and Hanna Wåhlén TRITA LWR Degree Project 12:18 vi Investigating sustainable mitigation alternatives for groundwater in Matlab Upazila, Bangladesh SUMMARY Naturally occurring (geogenic) arsenic (As) is one of the most serious water quality issues, second only to microbiological contamination. In Bangladesh and West Bengal, India, the most densely populated area in the world, the problem is widespread and is considered to be one of the worst environmental health disasters of this century. The majority of the Bangladesh population lives in rural areas and use hand pumped tube wells to extract groundwater as their main source of drinking water. Elevated levels of As is mainly associated with groundwater extraction from shallow tube wells (10-50 m). Mitigation options evaluated in this study focus on 1) how to target As safe aquifers and 2) how to identify As safe tube wells. A field study was conducted in Matlab Upazila, in central Bangladesh south east of the capital Dhaka, where access to safe drinking water is still very limited. Old tube wells tested for As reveled that 77% (n=79) of the wells exceed the WHO guideline value for As of 10 µg/L. The national guideline value of 50 µg/L is exceeded in 67% (n=69) of the wells. An attempt to target As-safe shallow aquifers (<100m) based on sediment color was evaluated. The targeted sediment color (off-white) was identified by local drillers in 30 out of 36 newly drilled wells. Arsenic concentrations exceed 10 µg/L in 47% of the wells (n=14) and 50 µg/L in 30% of the wells (n=9). The success rate of the method was thereby 44% (n=16) or 58% (n=21) respectively for the 10 µg/L and 50 µg/L As-guidelines. Therefore the method was not considered to be a sustainable mitigation option for As. Recently, manganese (Mn) has also emerged as a possible widespread problem in the area of Bangladesh and West Bengal. Although not thoroughly investigated, present evidence indicates that a high concentration of Mn in drinking water affects the intellectual function in children. The occurrence of both low As (<10 µg/L )and low Mn (<400 µg/L) concentrations in shallow aquifers was found to be very unlikely since only one out of 133 tested wells had this water chemistry composition. Instead it was showed that the highest Mn concentrations of 1-5 mg/L occurs in these As-safe aquifers, highlighting the need for further research about the effects of chronic exposure to high Mn concentrations. The need to focus efforts to areas with scarce supply of safe drinking water has raised the need to quickly locate and identify these areas and screening platform color/precipitation has been suggested as a solution to this problem. Two different classification methods were tested to develop recommendations for the future use of platform color as an As indicator. The results showed that a finer classification of the platform precipitation based on the strength of the color was inadequate at determining differences in water chemistry, since the distribution of Iron (Fe), Mn and As was too alike. When only 3 color classes were used (red, mixed and black) the red platforms indicated with 76% or 70% certainty that the well exceed 10 µg/L or 50 µg/L respectively. Too few black wells were encountered in the platform survey to confirm low As concentrations in these wells. Based on these results it is difficult to validate platform color as a test for As since the probability of high As in wells with red platforms is very close to the prevalence of high As in all wells within the platform survey, regardless of platform color. vii Nicklas Gingborn and Hanna Wåhlén TRITA LWR Degree Project 12:18 viii Investigating sustainable mitigation alternatives for groundwater in Matlab Upazila, Bangladesh SUMMARY IN SWEDISH Naturligt förekommande arsenik (As) är en av de allvarligaste vattenkvalitetsfrå gorna i världen. I världens mest tätbefolkade område, Bangladesh och Västbengalen i Indien, är problemet utbrett och ansett som en av de största miljörelaterade hälsokatastroferna i modern tid. Majoriteten av befolkningen i Bangladesh lever på landsbygden och använder handpumpade brunnar som huvudsaklig källa till dricksvatten. Förhöjda halter av arsenik är främst kopplade till uttag av vatten från dessa grunda rörbrunnar (10-50 m). Den här studien utvärderar två metoder för att 1) lokalisera As- säkra akvifärer för nya brunnar och 2) identifiera befintliga brunnar som är As- säkra. En fältstudie genomfördes i Matlab Upazila i centrala Bangladesh, sydöst om huvudstaden Dhaka, där tillgången till säkert dricksvatten är väldigt begränsad. Gamla rörbrunnar som testades för As avslöjade att 77 % (n=79) av brunnarna översteg WHO:s gränsvärde för As på 10 µg/L. Bangladeshs lokala gränsvärde på 50 µg/L var i sin tur överstiget i 67 % (n=69) av brunnarna. Ett försök att finna As-säkra grunda akviferer (<100m), baserat på sedimentens färg då nya brunnar borras, utvärderades. Den sökta sedimentfärgen (gulvit, engelska: off-white) identifierades av lokala brunnsborrare i 30 av 36 försök till att borra nya brunnar. I dessa burnnar översteg koncentrationen av As 10 µg/L i 47% av brunnarna (n=14) och 50 µg/L i 30 % av brunnarna (n=9). Andelen lyckade försök att finna As-säkert vatten med hjälp av metoden blev då 44 % (n=16) respektive 58 % (n=21) för de två gränsvärdena. Därmed kan inte metoden anses vara en hållbar lösning för att hitta As-säkra akvifärer. Nyligen har även mangan (Mn) uppmärksammats som ett potentiellt omfattande problem i Bangladesh och Västbengalen. Trots att hälsoeffekterna av Mn inte är fullständigt kända, så har bevis framkommit som tyder på att höga halter i dricksvatten påverkar barns intellektuella funktion. Förekomsten av både låga As-halter (<10 µg/L) och låga Mn-halter (<400 µg/L) var väldigt ovanligt i de undersökta brunnarna då bara en utav 133 testade brunnar hade dessa karakteristika. Istället visade studien att de högsta Mn-halterna förekom i de As-säkra akviferer som eftersöktes, vilket framhäver behovet av ytterligare forskning om effekterna av kronisk exponering av höga Mn-halter. Nödvändigheten av att fokusera åtgärder till områden med dåligt tillgång till säkert dricksvatten har gett upphov till ett behov att snabbt kunna hitta och identifiera dessa områden. Att kontrollera färgen/utfällningen på brunnarnas plattformar har föreslagits som en lösning på problemet. Två olika sätt att klassificera plattformarnas färg testades för att kunna utveckla rekommendationer för hur metoden att hitta brunnar med höga respektive låga halter av As kan förbättras. Resultaten visar att en mer detaljerad klassificering av utfällningen baserad på färgstyrkan inte gav bättre resultat än en enklare klassificering. När endast tre färgklasser (röd, mixad, svart) användes så visade en röd plattform med 76 % eller 70 % sannolikhet att brunnen innehöll As i halter högre än 10 µg/L respektive 50 µg/L. Undersökningen innehöll dock för få svarta brunnar för att kunna bekräfta att en svart brunn innehöll låga halter av As.

Load more