Acidic, metal contaminated waters such as acid mine drainage (AMD) and metallurgy process waters are a severe environmental concern. Sulfide production (sulfidogenesis), either chemically or microbially (biosulfidogenesis), is an attractive technology for metal recovery from these waters by enabling their precipitation as metal sulfides. Process economics can be improved by using sulfur (S80) instead of sulfate (SO42-) for sulfidogenesis, and by expanding the operating parameters to more acidic pH and higher temperature, as this enables combination of sulfidogenesis and metal precipitation in one reactor. In this thesis we discovered a novel chemical process for sulfidogenesis at high temperature and low pH involving catalytic pyrite, and studied biosulfidogenesis from S80 at neutral to acidic pH. We furthermore investigated AMD impacted mine pit lakes for the presence of S80- and SO42–reducing microorganisms able to grow at more acidic pH than previously known, and performed an in-depth study of a novel acidotolerant sulfate-reducing bacterium isolated from AMD sediments.