Removal of arsenic from groundwater by electro-ultrafiltration

The objective of this study was to examine the removal of arsenic from groundwater by a laboratory scale electro-ultrafiltration (EUF) system. Two groundwater samples taken from I-Ian County located in the northeastern part of Taiwan were studied. These well waters were selected based on their As(III) and As(V) contents; the As(III) to As(V) ratios of the well water were 1.8 and 0.4 for Well-#1 and Well-#2, respectively. In the absence of electrical voltage, the total arsenic removal efficiencies were 1% and 14% for Well-#1 and Well-#2 samples, respectively, using 100-kDa membranes. The higher As removal efficiency of Well-#2 than that of Well-#1 sample might be attributed to different charge characteristics of As(V) and As(III). Upon the application of an electrical voltage of 25 V to the ultrafiltration (UF) system, it was able to reduce the total arsenic concentrations in both groundwater samples by over 79%. The result suggested the possible association between As(III) species and dissolved organic matter which enhanced the As removal.

Results demonstrated that EUF could remove arsenic from groundwater effectively. Arsenic concentration was reduced by more than 79% upon the application of an electric voltage of at 25 V. This is a significant improvement over conventional UF treatment, i.e., without application of electric voltage, which only exhibited <20% arsenic removal. The residual arsenic concentrations in permeate were 8.4 and 49 mg/L from initial arsenic concentration of 49 and 304 mg/L for Well-#1 and Well-#2 water samples, respectively. In addition, the presence of electric voltage brings about electro-osmosis which can enhance flux and reduce electrical cost and ultimately make the process more competitive than other conventional arsenic-removing technologies. Although the arsenic content in Well-#2 permeate exceeded the common environmental regulation standard, it is possible to attain a better performance by further optimizing the operation conditions.