among the population. Analyses shockingly evealed that some of the groundwater sources contained high arsenic concentrations. The arsenic originates from river sediments that contain pyrite which is dissolved
in the groundwater under anaerobic conditions. International and national relief organizations are now in the process of assessing the extent of the disaster, informing the affected, mostly rural population, and finding solutions to the problem. Preliminary estimates suggest that 50 –80 million
people are exposed to increased arsenic concentrations. The World Health
Organization expects that in a few years the cause of death for 1 in 10 Bangladeshi will be arsenic poisoning [2]. A possible alternative to solving the arsenic problem is to return to using the focally polluted pond water and applying SODIS as treatment method. The SDC is currently DOC
studying the acceptance and efficiency of SODIS in a large demonstration project in which 16 local organizations (NGOs) are participating. Early indications suggest, however, that people prefer the clear but arsenic-containing groundwater to the often turbid pond water. Furthermore, the toxic substances have different effects on health; i.e., consumption of fecally contaminated surface waters often leads to acute diarrhea, while the effects of arsenic traces in the groundwater insidiously manifest themselves
only after 5–15 years. EAWAG, therefore, aims at developing a simple method for separating arsenic from drinking water. The process, which is substantially funded by the SDC and currently tested in laboratory and field experiments, using sunlight for photo-oxidation and sedimentation
for elimination of arsenic, has been named SORAS (Solar Oxidation and
Removal of ArSenic). Since SORAS also uses the plastic bottle technique, it is complementary to SODIS. To enhance photooxidation, a few drops of lemon juice are added to the arsenic-containing groundwater. Preliminary field experiments reveal that SORAS can reduce arsenic concentrations
by 50 –70%. Therefore, life expectancy of the affected population can be extended substantially.
Help to Self-Help
The upgrading of public water supplies will never be able to keep pace with the increasing population growth in developing countries, especially in the future – the number of people who are poorly supplied
with water will only continue to increase. The affected population has to rely on selfhelp. This fact can, however, also be the beginning of a new economical and sustainable water supply strategy in developing countries. Problems should be solved, as far as possible, by the smallest organizational unit. It is economically absurd to treat large amounts of water if only a small amount is consumed, if at all (see replacement by mineral water). Depending on the available financial resources, provision and
distribution of possibly pretreated water could, thus, be a task for the public sector, and final treatment of drinking water would have to be solved at the household level. To realize such new water supply strategies, appropriate technologies are also required. SODIS and SORAS may provide possible
answers.
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