154Long-term column performance has been possible through the efforts of community-elected water
committees that collect a local water tax for funding operations and maintenance. It has also been
used to remove undesirably high concentrations of fluoride.
Ion Exchange has long been used as a water-softening process, although usually on a single-
home basis. Traditional anion exchange is effective in removing As(V), but not As (III), or arsenic
trioxide, which doesn't have a net charge. Effective long-term ion exchange removal of arsenic
requires a trained operator to maintain the column.
Both Reverse osmosis and electrodialysis (also called electrodialysis reversal) can remove
arsenic with a net ionic charge. (Note that arsenic oxide, As 2 O 3 , is a common form of arsenic in
groundwater that is soluble, but has no net charge.) Some utilities presently use one of these
methods to reduce total dissolved solids and therefore improve taste. A problem with both methods
is the production of high-salinity waste water, called brine, or concentrate, which then must be
disposed of.
Subterranean Arsenic Removal (SAR) Technology
In subterranean arsenic removal (SAR), aerated groundwater is recharged back into the aquifer to
create an oxidation zone which can trap iron and arsenic on the soil particles through adsorption
process. The oxidation zone created by aerated water boosts the activity of the arsenic-oxidizing
microorganisms which can oxidize arsenic from +3 to +5 state SAR Technology.
No chemicals are used and almost no sludge is produced during operational stage since iron and
arsenic compounds are rendered inactive in the aquifer itself. Thus toxic waste disposal and the
risk of its future mobilization is prevented. Also, it has very long operational life, similar to the long
lasting tube wells drawing water from the shallow aquifers.
Six such SAR plants, funded by the World Bank and constructed by Ramakrishna Vivekananda
Mission, Barrackpore & Queen's University Belfast, UK are operating in West Bengal. Each plant
has been delivering more than 3,000 liters of arsenic and iron-free water daily to the rural
community. The first community water treatment plant based on SAR technology was set up at
Kashimpore near Kolkata in 2004 by a team of European and Indian engineers led by Dr. Bhaskar
Sen Gupta of Queen's University Belfast for TiPOT.
SAR technology had been awarded Dhirubhai Ambani Award, 2010 from IChemE UK for Chemical
Innovation. Again, SAR was the winner of the St. Andrews Award for Environment, 2010. The SAR
Project was selected by the Blacksmith Institute - New York & Green Cross- Switzerland as one of
the "12 Cases of Cleanup & Success" in the World's Worst Polluted Places Report 2009.
The Hungarian Solution
Hungarian engineer László Schremmer has recently discovered that by the use of chaff-based
filters it is possible to reduce the arsenic content of water to 3 microgram/liter. This is especially
important in areas where the potable water is provided by filtering the water extracted from the
underground aquifer.