Effect of source water quality on arsenic (V) removal from drinking water by coagulation/microfiltration

摘要

The effect of the source water quality on As(V) removal by coagulation/microfiltration (C/MF) was investigated systematically using a jar test and a lab-scale test; the results of the lab-scale test coincide with those of the jar test. It showed that the increase of dissolved organic carbon (DOC), HPO₄ 2− and HCO₃ − concentrations would moderately decrease As(V) removal, and the residual As(V) concentration in treated water is no more than 10 μg L−1 when the concentration of DOC, HPO₄ 2− and HCO₃ − in raw water is not beyond 9.22 mg L−1, 1.6 mg L−1 and 300 mg L−1, respectively. Other co-ions, such as Cl−, NO₃ −, F−, SO₄ 2−, and counter-ions including K+, Ca2+ and Mg2+, have little effect on As(V) removal. Both results of the jar test and the lab-scale test demonstrate that Fe3+ dose of 6 mg L−1 is enough to eliminate the influence of HCO₃ − whose concentration changes from 350 mg L−1 to 450 mg L−1. In the lab-scale test, As(V) removal ranged from 92.8 to 98.2% at Fe3+ dose of 4 mg L−1 and 5 mg L−1 when As(V) concentration in raw water was about 100 μg L−1. The results obtained in this study suggest that As(V) removal by C/MF process is sensitive to the quality of raw water, and a jar test needs to be done before C/MF process is used for arsenic removal from drinking water.