I agree with Mr. Chand's concern about the economics behind the treatment/filtration of surface water.
The country like Bangladesh and India have several options for drinking water for 100s of years.
We switched from surface water to ground water to avoid bacterial contamination and now after three decades we are again looking towards surface water as one of the best alternative arsenic free water sources.
I think we need to rethink about the way we are thinking to mitigate arsenic problem.
In my opinion we need an integrated approach to solve this issue and need to focus more on the area specific solution.