Sulfide Effects on the Anaerobic Kinetics of Phosphorus- Accumulating Organisms

Saline wastewaters can be produced from industrial activities, the use of seawater and brackish water in urban environments, or due to saline water infiltration into the sewer system. This can lead to sulfate-rich wastewater that under anaerobic conditions and the presence of electron donors can result in sulfide production. This study focuses on evaluating the sulfide effects on the biological phosphorus removal process which is a key process to prevent eutrophication on surface-water bodies. In this regard, anaerobic short-term sulfide inhibition tests were executed on an enriched culture of phosphorus-accumulating organisms (PAO) at different pH, and sulfide concentrations. Sulfide had a negative effect on PAO activity, and the effect seemed to be related to un-dissociated H2S concentration. 50% inhibition of the maximum acetate uptake rate of PAO was observed at around 60 mg H2S/l regardless the pH. With increasing H2S concentrations, higher ratios of phosphate release to HAc uptake rate were observed likely due to extra need for energy for cell detoxification. P-release for detoxification energy requirements (Pdet) were estimated relative to the total Prelease rate at zero H2S, assuming a fixed ratio of P-release required for HAc uptake. Increasing H2S increased Pdet until a maximum of 50%. A further increase in H2S caused a decrease in Pdet possibly compensated by higher glycogen utilization. Mathematical expressions to describe the sulfide effect on acetate consumption and P-release have been proposed. These can be used to describe the anaerobic kinetics of PAO under the presence of sulfide when treating saline wastewater in general activated sludge models.