Enhanced degradation of arsanilic acid and in situ recovery of inorganic arsenic in a two-stage bioelectrochemical process

Arsanilic acid (p-ASA), an organoarsenic additive found in livestock wastewater, can release toxic inorganic arsenic into the environment. While bioelectrochemical systems have proven effective in decomposing organoarsenics, managing the resulting inorganic arsenic remains a challenge. This study demonstrated the feasibility of a two-stage bioelectrochemical process designed to facilitate p-ASA degradation and in situ recover inorganic arsenic from contaminated livestock wastewater. It consisted of two sequential stages: (I) anodic stimulation for p-ASA degradation and (II) reversing electrode polarities for the cathodic reduction of inorganic arsenic. In Stage I, the anode significantly enhanced the degradation of p-ASA, resulting in 18 mu g/L of As(III) and 700 mu g/L of As(V) released into the bulk solution. In Stage II, the cathode further reduced the As(III) and As(V) to 8.9 and 35.5 mu g/L, respectively, through the synergistic action of the cathode and suspended microbes. The inorganic arsenic was recovered as a layer of As(V)-O on the cathode. Microbial analysis indicated that Alcaligenes was responsible for the degradation of p-ASA, while Anaerobacillus and Desulfitibacter played key roles in reducing As(V) and As(III) on the cathode, respectively. This study provided a promising alternative approach for the removal of organoarsenics and in situ recovery of inorganic arsenic from organoarsenic-bearing wastewater.