Characterization of Arsenic-Containing Water Treatment Residuals

Abstract

The characterization of water treatment residuals containing arsenic was examined and arsenic desorption and leachability from the residuals were focused. Solution pH is a critical variable in controlling arsenic stability in the residuals. The release of arsenic from the residuals was elevated at low and high pH due to the increase dissolution of the adsorbents such as Fe and Al hydroxides. The negatively charged surfaces of the adsorbents at high pH reduced arsenic anion adsorption. Competition with phosphate can play a significant role for the arsenic leaching from residuals because phosphate tends to compete with As(V) on the sorption sites. The cooperative effects of calcium can help to bind arsenic on metal hydroxides. Arsenic leaching from water treatment residuals was found to be underestimated by the toxicity characteristics leaching test (TCLP) due to the pH of the leachates being favorable for As(V) adsorption.