Effects of Molybdate on Sulfate Reduction and Benzoate Degradation

Abstract

Molybdate inhibited both sulfidogenesis and benzoate degradation in anaerobic treatment of wastewater, but the impact was more severe to the former reaction. In batch reactors, molybdate inhibition increased progressively with concentration; biogranules lost 50% of methanogenic activity treating wastewater containing 48 mg/L of molybdate. In continuous experiments the molybdate toxicity had a threshold level. Below 0.5–0.8 mM bacterial activities were unaffected, but above this level both sulfidogenic and benzoate degradation were severely inhibited. However, the molybdate toxicity was not permanent. Biogranules were able to gradually regain their bioactivities once molybdate was removed from the wastewater.