Improved sulphate removal rates at increased sulphide concentration in the sulphidogenic bioreactor

The product of the biological sulphate reduction is sulphide. High concentrations of molecular H 2 S (g) can be inhibitory for microbial activity, especially at a reactor pH of 6 to 7. This paper focuses on the effect of high sulphide concentrations on the sulphate reduction rates. The results of three investigations operating a continuous reactor, a column reactor and batch-test reactors have shown that increased sulphide concentrations have resulted in improved biological sulphate reduction. In all instances the reactor pH was kept at 7.5 to 8.5. It was shown that when the sulphide concentration was 700 mg/ℓ in a continuously operated reactor, the sulphate reduction rate was 12 gSO 4 /ℓ·d. When operating batch-test reactors the results showed that when the sulphide concentration increased, to 1 400 mg/ℓ, the volumetric and specific sulphate reduction rates correspondingly increased to 4.9 gSO 4 /ℓ·d and 1.5 gS