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| Arsenic and Water Supply
Systems |
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Principal Investigators
MIT:
H.Hemond, C.Harvey, S.Islam
ETH: S.Hug, U.von Gunter,
M.Wegelin
UT: R.Ohtsuka, C.Watanabe, K.Yamamoto,
T.Inaoka
In the early 1970’s, one quarter of a million
children died each year in Bangladesh and West Bengal from water
borne diseases. In response to this problem approximately four
million tube-wells have been drilled in the last 30 years, which
supply 90% of the population with water. These same wells however,
may prove to be the largest mass poisoning in history. Groundwater
throughout Bangladesh and West Bengal is contaminated with naturally
occurring arsenic. 35% of the wells are contaminated with levels
above 50 ppb, over WHO’s recommended standard of 10 ppb. It is not
clear what proportion of the population is suffering poisoning, or
will eventually contract cancer as thee result of arsenic.
Goals/Objectives
The overall goal of this project
was to establish scientifically reliable and socioeconomically and
culturally feasible guidelines for sustainable water use systems in
arsenic polluted areas in Asia, focusing on
Bangladesh.
Research Question 1: Identification and
analysis of Arsenic contamination in Bangladesh
To establish
scientifically reliable and socieconomically feasible guild lines
for sustainable water use systems in arsenic polluted areas in Asia,
with a focus on Bangladesh. The research was conducted in 3
parts:
- Identification of the determining and/or modifying factors of
arsenic-contaminated water on health of the local populations;
- Development of hydrologic models to predict the level of
arsenic contamination in groundwater subject to different
long-term management strategies;
- Identification and development of environmentally sound and
socioeconomically feasible technologies for arsenic removal from
drinking water.
Findings/Results
Several
papers have been written on Arsenic contamination of groundwater in
Bangladesh and Vietnam. Papers include results of surveys and white
papers on the threat posed by the contamination as well as treatment
and mitigation techniques that could be used.
Findings
- Dermatological inspection revealed that 60% of examined
children had some skin lesions which may be related to arsenic
exposure.
- Interview survey of adults revealed that the subjective
consciousness of arsenicosis did not arise while the symptoms were
mild or even moderate.
- Monitoring of 8 tube wells showed that the arsenic
concentration was fairly stable with less than twofold of the
max/min ratio
- The removal efficiency of Arsenic is highly dependent on the
concentration of iron. The recommendation is that all wells with
high iron content be treated.
- Four to eight drops of lemon juice per liter of water proved
to be as ample, low cost, relatively high efficacy of arsenic
removal (50-70%) particularly for the Bangladeshi communities.
- The development of the hypothesis that pumping irrigation
wells cause high levels of dissolved arsenic in drinking water
wells. This hypothesis, if proven true, means that installing
drinking-water wells beneath irrigation wells could provide clean
drinking water.
- The field investigation confirmed that three-stage simple
gravel NF filtration for households gave a very good performance
with a minimum cost. Therefore, it is recommended to use the
equipment as an immediate mitigation alternative, while a more
rational community water supply system is developed.
- Intervention trials do bring some beneficial effects on
dermatological conditions, especially for those who are in the
relatively minor stages of the arsenicosis.
- One of the dug-wells in a target community was contaminated,
the implications of which might be sizeable, since it is generally
assumed that the dug well as opposed to the tube well is a safe
alternative.
- The arsenic was dissolved in the water rather than absorbed
onto small particles precipitated in the bottom sediment of the
well, therefore eliminating filtering as a safety measure.
- Rice was found to be the primary source of arsenic intake,
thus chemical speciation of Arsenic in the rise will be conducted.
- One year later, it was found that some households had switched
tube-wells after being notified that their old wells were
contaminated. Many re-sank new tube wells. They also found that
infants less than 12 months old were exposed to Arsenic.
- A study on the timing of arsenic mobilization and why
concentrations vary by orders of magnitude over short distances
within geologic formations questions the notion that arsenic
concentrations have historically been high in groundwater and
raise concerns about future arsenic levels.
Research
Question 2: Mitigation of Arsenic Hazards
This follow-on
project has three purposes:
- To apply the mitigation trials for a larger number of local
communities and examine their effects through follow-up surveys;
- To expand research to the Terai districts of Nepal;
- To expand networking and educate young scientists from
developing Asian countries.
More
Information
Website
Article - MIT News |
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