Filter water contaminated with arsenic

10 million people can get sick from drilled wells, especially the risk of arsenic contamination. This seemingly unsolvable problem can be solved by the traditional water purification experience of Bangladesh.

Prof. Gadgil and arsenic filter bag (Photo: TTO)

Actually this problem has been known to scientists 10 years ago. Like in our country, arsenic-contaminated water is assessed as dangerous for wells of poor people in Bangladesh. This problem is even more serious because scientists expect 10% of the country's 130 million people will die from this contaminated well water.

Scientist Askhok Gadgil of Lawrence Berkeley National Laboratory has studied less expensive but effective solutions, helping 60 million Bangladeshis to be assured of using arsenic-contaminated water. Gadgil and his colleagues discovered that in coal ash, ferric hydroxide is contained and this is a substance capable of absorbing arsenic.

These ash are small, very small particles that range in size from 1 to 10 microns (smaller than a 100 micron human hair). So even with a small amount, ash can still react with arsenic. Experiments showed that the samples of arsenic poisoned at 2,400ppb (parts per billion), after filtering, arsenic reduced to 10 ppb. According to Bangladesh standards, safe drinking water is 50ppb. According to calculations, 5 grams of coal ash can filter about 11 liters of water, with an average level of contamination of arsenic 400ppb, into safe water for eating.

In addition, the coal is heated to 800 ^° C, so the ash is a sterile powder. Coal ash is a very simple and abundant material. As calculated, ash accounts for 40% of the mass after burning coal. Filter bags containing tea bag-sized coal ash can clean arsenic in water enough to satisfy drinking water needs for six people a day. Can guide people to make small bags of filtered coal ash, costing about 0.3 USD / person / year.

It is hard to believe that using only the ash Gadgil and his colleagues provided is a safe water for the poor. Currently this system is used by many countries such as Mexico, Philippines, India and some other countries