SRB activity is evidenced at acidic pH in acid mine drainage water.
Total arsenic and zinc removal from solution is observed.
As, Zn and Fe are observed to precipitate as biogenic sulfides.
Amorphous orpiment (AsIII2S3) and realgar (AsIIS) are observed as main As-bearing sulfides.
A mechanism is proposed for the reduction of As2S3 to AsS by biogenic H2S under acidic conditions.