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), HPO_4~(2-)and HCO_3~- 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, HPO_4~(2-)and HCO_3~- 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~-, NO_3~-, F , SO_4~(2-), and counter-ions including K~+, Ca~(2+) and Mg~(2+), have little effect on As(V) removal. Both results of the jar test and the lab-scale test demonstrate that Fe~(3+) dose of 6 mg L~(-1) is enough to eliminate the influence of HCO_3~-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 Fe~(3+) 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.