Fascinating! I love how they use basically a self-sustaining combination of algae and bacteria to convert the dissolved arsenic into a form that can more easily be filtered from the water. Arsenic is certainly a major problem in many countries, and the problem will only get worse as populations increase and climate patterns change. For example, in a country with a huge arsenic problem like Bangladesh, I believe the major reason why arsenic is a problem is because the flow of surface water from India has been reduced, forcing the downstream people in Bangladesh to turn to groundwater, where the soil is high in arsenic and leaches into the water. If the river flow reduces even more or as the population increases, the problem just gets worse.

This algae-bacteria technique may work for other pollutants, but you'd need to find bacteria that will do something useful for each specific pollutant, and that's not easy, unless you can genetically engineer something specific. Note that this technique does not remove arsenic. It just changes it into a form that can more easily and cheaply be removed from the water.