Arsenic removal by coagulation and filtration: comparison of groundwaters from the United States and Bangladesh

Arsenic contamination of drinking water is a concern in many parts of the world. In the United States, the Environmental Protection Agency recently reduced the maximum contaminant level of arsenic in drinking water from 50 to 10 μ/L (ppb). In Bangladesh the arsenic concentration in drinking water can be as high as hundreds of parts per billion while the maximum contaminant level is 50 ppb. Consequently, there is a great need for new cost-effective methods to remove arsenic from drinking water. Here arsenic removal by coagulation and filtration was investigated using groundwater from a city in southern Colorado in the United States and from Sonargaon in Bangladesh. The results of the bench-scale experiments conducted indicate that coagulation with ferric ions followed by filtration is effective in reducing arsenic concentration in the water tested. However, the actual efficiency of removal is highly dependent on the raw water quality. Further, addition of a polyelectrolyte coagulant aid may lead to improved permeate fluxes during tangential flow microfiltration but has little effect on the residual arsenic concentration.