Optimization of arsenic removal from an acid mine drainage in an anaerobic membrane bioreactor

This study aims at optimizing the arsenic removal performance of a sulfidogenic anaerobic MBR treating acid mine drainage (AMD). The feed sulfate concentration was kept constant at 2,000 mg/L and ethanol concentration was decreased steadily from 1,500 mg COD/L to 500 mg COD/L. Metal concentrations were kept at 75 or 150 mg/L Fe, 25 mg/L Cu, 5 mg/L Zn, 5 mg/L Co, 5 mg/L Mn, 2.5 mg/L Ni and 2.5 mg/L As. High sulfide concentration led to dissolution of orpiment (As2S3) and low As removal efficiency. Later, decrease of sulfide concentration in the bioreactor resulted in increasing As removal efficiency over 99% due to formation of orpiment and co-precipitation of As with amorphous iron precipitates. Flux was increased up to around 10 L/(m2h) (LMH). It was concluded that heavy metals in the AMD behaved as a filtration aid and increased the sludge filterability, which was assessed by the regular analyses of supernatant filterability, specific resistance to filtration and capillary suction time. © 2020 Elsevier B.V