Efficient removal of low-arsenic concentrations from drinking water by combined coagulation and adsorption processes

Results indicated that the combined process was very effective in removing low arsenic (V) concentration from drinking water in the range of 25-100 μg/L. Moreover, it was found that, among the tested variables, high-velocity gradient conditions led to an improved removal efficiency which reached 89% under optimized process conditions. Although all treating agents played a statistically significant role in terms of process performance, arsenic (V) co-precipitation by AP was found to be the dominating removal mechanism contributing up to an 85% at 1400 rpm, with Z and PAC co-operating for the remaining 5% and mostly functioning as enhancing agents for ballasted settling. Notably, the process investigated in this study was also found to be robust against variation in initial arsenic concentration, showing similar arsenic (V) removal efficiency (85.9%) when the initial arsenic (V) concentration was further reduced from 100 to 25 μg/L. In conclusion, it was demonstrated that the combined treatment process was able to efficiently and simultaneously remove not only organic micropollutants such as phenols, COD and E. coli (as demonstrated in previous studies) but also inorganic contamination by arsenic (V) from a typical drinking water matrix via co-precipitation on aluminum polychloride, a treating agent that is worldwide accessible and typically used in water treatment applications.