Water/Wastewater 5
encountered when transporting samples to laboratories and the ability to quickly generate and distribute contamination information at remote well locations.
The authors of one study recommend handheld global positioning satellite (GPS) devices be distributed to locals who are already actively engaged in testing tube wells for arsenic levels. By integrating the results from water quality tests along with basic tube well information into a larger geographic information system (GIS) database, the spatial and geological distribution of the arsenic contamination problem can be put into greater context. This would allow water treatment projects to be targeted to the regions and villages where the arsenic contamination problem is the greatest.
Possible solutions
Several potential solutions exist to the arsenic problem. Some of these potential solutions include: (1) switching households from contaminated wells to surface water sources, such as ponds or rivers, (2) switching households from contaminated wells to non- contaminated wells, (3) installing arsenic-removal filters on contaminated wells. Each of these potential solutions carries costs and benefits that are unique to the solution and to the specific site, household, and community under consideration.
Switching households from well water to treated surface water has encountered several challenges. Households do not always trust that the treated surface water is any more free from contamination than the well water. In some cases, surface water treatment facilities are not properly maintained. This can lead to contamination by microbiological agents and pathogens, which may lead to a return of some of the public health problems that initially motivated the move towards groundwater in the 1970s and 1980s. Relative to using ponds and lakes as sources of surface water, treatment problems may be arguably even more challenging for rivers used as a source of drinking and household water. Rivers are likely to carry industrial and municipal waste and pollutants as the urban economies of Bangladesh and surrounding areas continues to rapidly expand and grow.
Switching households from contaminated wells to non- contaminated wells has been found to be problematic because of local customs and costs incurred on the household. In some cases, local customs discourage women from travelling beyond their home communities, without an escort. This makes acquisition of safe water more challenging if the nearest non-contaminated tube well lies outside the home community. In other cases, switching wells may just not be practical. One study found that households that changed wells increased their time spent acquiring water by a factor of fifteen.
Arsenic-removal water treatment technologies posses a lot of potential to address this problem, as such technologies do not require affected households to completely shift to a new source of water. However, such technologies are not cheap and nor are they permanent. Initial cost of installation and continuing costs of repair, maintenance, and replacement are among the reasons given that these filters are not more prevalent among affected households. In one study, approximately 25% of arsenic-removal filters had fallen into disuse after one to two years.
One potential solution suggested to deal with single households incurring unmanageable maintenance costs is to develop a community-based model of filtered-water supply. In such a case, one or two individuals would be responsible for the upkeep of the community’s filter and would be compensated for their efforts.
For any of these potential solutions, a water quality monitoring program is likely to play an important role. In addition to identifying contaminated wells, a thorough monitoring program may identify the nearest uncontaminated well, thereby reducing travel and transportation burden of those households that choose to switch wells. For wells equipped with arsenic removal devices, the ongoing monitoring of those wells may be used to evaluate the need for equipment maintenance or replacement, and, in general, indicate the effectiveness of the arsenic removal technology.
More on arsenic removal technologies
Within the strategy of applying water treatment technologies to remove arsenic at contaminated wells, an array of choices exist, each with particular costs and benefits. These technologies can be generally divided into four categories: (1) Oxidation/Precipitation, (2) Coagulation Coprecipitation, (3) Sorption Techniques, and (4) Membrane Techniques.
Oxidation technologies are characterized by simple and low cost operations, but are slow and remove only a partial component of
Arsenic distribution in the shallow aquifer in Bangladesh Map prepared by J.W. Rosenbloom (UNICEF-Dhaka).
www.envirotech-online.com AET Annual Buyers’ Guide 2012
the arsenic contamination. Coagulation technologies are also relatively simple, but may produce toxic sludge and may remove all species of arsenic. Sorption technologies are relatively more common and well known, but maintenance and replacement costs can be high. Membrane technologies similarly can incur large operation and maintenance costs.
Progress is being made with all types of water treatment to make the technology more effective at removing arsenic, reducing system costs, and making the technologies appeal in all possible ways to the rural residents of the affected regions. However, the scope of the problem is still unknown and potentially so vast that even as technologies progress and improve, years may pass before the problem is completely resolved and in-hand.
This particular case of arsenic contamination in groundwater makes a fairly strong case about the potential value and importance of thorough water quality monitoring. Testing the water quality of a well prior to full installation and periodically during the useful life of the well can support the management and, in some cases, the prevention of potentially serious health issues related to contaminated water. The water industry has a viable opportunity improve the lives of those affected by this very tragic example of large-scale groundwater contamination.
References and material for further reading
Ahmed, M.F. 2001. An overview of arsenic removal technologies in Bangladesh and India, In M. F. Ahmed, M. A. Ali, and Z. Adeel (Eds.), Technologies for Arsenic Removal from Drinking Water, Bangladesh
Carson, R.T., P. Koundourl, and C. Nauges. 2010. Arsenic mitigation in Bangladesh: A household labor market approach. American Journal of Agricultural Economics 93(2): 407-414.
Hossain, M.F. Arsenic contamination in Bangladesh—An overview. Agriculture, Ecosystems, and Environment 113: 1-16.
Johnston, R.B., S. Hanchett, and M.H. Khan. 2010. The socio- economics of arsenic removal. Nature Geoscience 3: 2-3.
Madajewicz, M., A. Pfaff, A. van Geen, J. Graziano, I. Hussein, H. Momotaj, R. Sylvi, and H. Ahsan. 2007. Can information alone change behavior? Response ot arsenic contamination of groundwater in Bangladesh. Journal of Development Economics 84: 731-754.
Pumping the deep aquifer at 700 gallons a minute to test the aquifer properties
Melamed, D. 2004. Monitoring arsenic in the environment: A review of science and technologies for field measurements and sensors. Technical Report. Office of Solid Waste and Emergency Response, U.S. Environmental Protection Agency, Washington, DC.
Nahar, N. 2009. Causes and distribution of arsenic contamination in Bangladesh: evidence from the literature. Water Policy 11: 362-378.
The World Factbook 2009. Washington, DC: Central Intelligence Agency, 2009. Available online:
https://www.cia.gov/library/publications/the-world- factbook/
index.html.
UNICEF. 2004 (March). Monitoring arsenic in water. Technical Bulletin No. 8.
van Geen, A., Y. Zheng, R. Versteeg, M. Stute, A. Horneman, R. Dhar, M. Steckler, A. Gelman, C. Small, H. Ahsan, J.H. Graziano, I. Hussain, and K.M. Ahmed. 2003. Spatial variability of arsenic in 6000 tube wells in a 25 km2 area of Bangladesh. Water Resources Research 39(5) 1140.
Whitney, J., and D.W. Clark. 2010. Geologic, Hydrologic, and Geochemical Characterization of the Deep Ground Water Aquifer System in the Bengal Delta of Bangladesh. U.S. Department of the Interior, U.S. Geological Survey. Available online:
http://international.usgs.gov/projects/bg_arsenic.htm.
Yunus, M., N. Sohel, S.K. Hore, and M. Rahman. 2011. Arsenic exposure and avserse health effects: A review of recent findings from arsenic and health studies in Matlab, Bangladesh. Kaohsiung Journal of Medical Sciences 27: 371-376.
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