A large proportion of Bangladesh has tubewell water with unsafe levels of arsenic. Approximately 50% of Bangladesh’s area has groundwater from shallow tubewells (< 30.5 m or < 100 feet bgs) with an average arsenic concentration greater than the 0.05 mg/L national drinking water standard (see Figure 3). Approximately 32% of Bangladesh’s area has groundwater from deep tubewells (> 30.5 m or > 100 feet bgs) with an average arsenic concentration greater than the 0.05 mg/L national standard (see Figure 4).
The major sources of arsenic in Bangladesh’s groundwater might be the dissolution of non-pyrite minerals in a reducing environment, and the anion exchange of sorbed arsenate or sorbed arsenite. This study does not support the hypothesis that arsenic is released from a pyrite source during oxidation; therefore, it does not begin to support the unproven strategy of restricting irrigation in famine-prone Bangladesh to prevent the release of arsenic from pyrite into groundwater.
The first of 3 strategies to supply Bangladesh drinking water with safe levels of arsenic is to identify, use, and monitor existing tubewells that have less than 0.05 mg of As/L. This strategy is the most promising because it can rapidly and inexpensively provide drinking water with safe levels of arsenic to approximately 85% of this 120,000,000 person country. The remaining 15% of Bangladesh’s villages do not have any tubewells with arsenic concentrations less than the 0.05 mg/L national standard (see Figure 14). This 15% of Bangladesh will require an alternative drinking water source or water treatment.
The second of these strategies is to provide an alternative drinking water source by drilling deeper tubewells. This strategy is moderately promising because the drinking water it yields often has arsenic concentrations greater than the 0.05 mg/L national standard (see Figure 6).
The last of these strategies is groundwater treatment for arsenic removal. Appropriate treatment systems should be effective, inexpensive, and easily operated by even an illiterate person. Such a system for arsenic removal will likely require an oxidant to convert soluble As(III) to poorly soluble As(V), and a process to allow the settling, filtration, or sorption of arsenic from solution. This system might use atmospheric oxygen as the oxidant, and ambient iron as a coagulant (see Table 5). This avoids the long-term expense of purchasing water treatment chemicals.
The contour maps of arsenic concentration in groundwater suggest this toxin extends beyond Bangladesh’s borders into West Bengal, Assam, Meghalaya, and Tripura (the 4 Indian States that border Bangladesh, see Figures 3 and 4). Unsafe levels of arsenic have been identified in groundwater from West Bengal (21). However, the authors are unaware of any systematic survey of tubewell water quality in Assam, Meghalaya, or Tripura. Therefore, the groundwater used for drinking in West Bengal, Assam, Meghalaya, and Tripura should be tested to ensure it is safe.
Arsenic readily leaches from many Bangladesh surface soils (see Figures 12 and 13) and can be uptaken by crops (23). Therefore, the ingestion of domestically grown foods should be evaluated as a human exposure pathway for arsenic and possibly other toxins.
The discovery that tubewells often contain an analytical interference to the 1,10-phenanthroline methods for measuring iron indications that non-arsenic toxins maybe widely distributed in Bangladesh’s drinking water. Therefore, the drinking water from Bangladesh, and quite likely West Bengal, Assam, Meghalaya, and Tripura, should be tested for both arsenic and non-arsenic toxins.
