Sulfide‐Induced Inhibition of Anaerobic Digestion

Abstract

Batch anaerobic digestion studies of the effects of pH and sulfide concentration upon lactose utilization, acetate utilization, and sulfate reduction using lactate as a carbon source were performed using 100 ml glass syringes. Increased concentrations of un‐ionized H2S inhibited lactose utilization and acetate utilization whereas total sulfide concentration, more than un‐ionized H2S, inhibited sulfate reduction. Increased retention time was required to carry lactose and acetate utilization to completion in the presence of high concentrations of TS. Almost 90% utilization of lactose at undissociated H2S in excess of 900 mg/L was attained at a retention time of 228 hr. Acetate utilization was 100% complete after 74 days at 175mg/L‐H2S and deteriorated rapidly to zero at higher H2S concentrations. A mechanism is proposed whereby the carbon flow can be diverted from sulfate reduction to methanogenesis in spite of the presence of a high concentration of sulfate.