Sulfide inhibition on polyphosphate accumulating organisms and glycogen accumulating organisms: Cumulative inhibitory effect and recoverability

Sulfate in wastewater can be reduced to sulfide and its impact on the stability of enhanced biological phosphorus removal (EBPR) is still unclear. In this study, the metabolic changes and subsequent recovery of polyphosphate accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs) were investigated at different sulfide concentrations. The results showed that the metabolic activity of PAOs and GAOs was mainly related to H2S concentration. Under anaerobic conditions, the catabolism of PAOs and GAOs was promoted at H2S concentrations below 79 mg/L S and 271 mg/L S, respectively, and inhibited above these concentrations; whereas anabolism was consistently inhibited in the presence of H2S. The phosphorus (P) release was also pH-dependent due to the intracellular free Mg2+ efflux from PAOs. H2S was more destructive to the esterase activity and membrane permeability of PAOs than those of GAOs and prompted intracellular free Mg2+ efflux of PAOs, resulting in worse aerobic metabolism and subsequent recovery of PAOs than GAOs. Additionally, sulfides facilitated the production of extracellular polymeric substances (EPS), especially tightly bound EPS. The amount of EPS in GAOs was significantly higher than that in PAOs. The above results indicated that sulfide had a stronger inhibition to PAOs than GAOs, and when sulfide was present, GAOs had a competitive advantage over PAOs in EBPR.

Automated summary

This study investigated the impact of sulfide generated from sulfate reduction in wastewater on the stability of enhanced biological phosphorus removal (EBPR). The results showed that the metabolic activity of polyphosphate accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs) was mainly influenced by hydrogen sulfide (H2S) concentration. H2S promoted the catabolism of PAOs and GAOs at lower concentrations but inhibited it at higher concentrations. PAOs were more significantly affected by H2S, resulting in poorer aerobic metabolism and recovery compared to GAOs. Additionally, sulfides facilitated the production of extracellular polymeric substances (EPS), with GAOs having a higher amount of EPS than PAOs. Overall, sulfide had a stronger inhibitory effect on PAOs, giving GAOs a competitive advantage in EBPR when sulfide was present.