Effects of pH on sulfide toxicity to anaerobic processes

Abstract

Effects of sulfide on anaerobic degradation of lactate, butyrate, propionate (Pr) and acetate (Ac) were studied in batch serum bottles. Maintenance of higher pH = 7.7–7.9 allowed for tolerance of much higher concentrations of sulfide pointing to un‐ionized H₂S as the inhibitory sulfide species. Concentration thresholds of 50% inhibition by total and un‐ionized sulfide were determined. Lactate utilization was the least affected while propionate degradation was the most affected by sulfide. Data analysis using semi‐log graphs of substrate utilization rates vs. sulfide produced retardation coefficients (k) of 0.6 L mg⁻¹ for acetate and 1.2 L mg⁻¹ for propionate. Retardation was more pronounced in a mixed Ac/Pr run than in pure Ac and Pr runs.