Development of acid mine drainage treatment process using arsenic adsorbing bacteria

The excavation of mining sites supports technological advancements and material development by supplying valuable metals. However, this process results in the generation of acid mine drainage (AMD) containing harmful metals. Current neutralization treatments discharge harmful neutralized sludge. In this context, we previously proposed a novel bioprocess and isolated Paenarthrobacter sp. strain H1 with the ability to remove As from AMD (pH 1.95). In this study, the As removal mechanism of this bacterium was investigated, and a laboratory-scale AMD treatment process was developed. The mechanism was clarified based on dead cell As removal ability and cell surface observations. The results indicated that the bacterium adsorbed Fe(III) on the bacterial cell surface, and As(V) was adsorbed on Fe(III). This As adsorption behavior followed the Langmuir isotherm model. Using this bacterium, we established a three-cycle repeated As removal process that effectively reduced the As concentration in AMD from 7.2 to below 0.2 mg/L. Compared to the conventional neutralization process, this process reduces the amount and As concentration of the resulting neutralized sludge. Furthermore, the resulting sludge contained P, an essential plant nutrient, rendering it a potential agricultural fertilizer. Thus, the process using bacterial strain H1 possesses the potential to remove As from AMD and facilitate the restoration of mining sites. Although further studies are required, this study contributes to the establishment of a sustainable AMD treatment process with a low environmental impact and reduces the disposal of harmful sludge.