Sulfide removal and sulfur production in a membrane aerated biofilm reactor: Model evaluation

Abstract

Sulfide removal from wastewater is essential, in view of the toxic, malodor and corrosive property of sulfide. The oxidation of sulfide by chemolithotrophic sulfide oxidation bacteria can produce elemental sulfur, an important chemical material. A membrane aerated biofilm reactor (MABR) has been successfully implemented and demonstrated for enhanced sulfide oxidation and sulfur production, owning to its counter-diffusion design of oxygen supply. In this work, a mathematical model was developed to evaluate the sulfide oxidation and sulfur production in the MABR in the presence of residual organics in the influent. The model was calibrated and validated using the experimental data from the long-term operation of the sulfide-oxidation MABR at different operational stages. The results suggested that the developed model could satisfactorily describe sulfide oxidation, sulfur production, sulfate accumulation and organics conversion in the MABR. The modelling results indicated that with the optimal combinations of sulfide loading and oxygen pressure, over 90% of sulfide removal and over 75% of sulfur recovery could be achieved. The sulfide oxidation and sulfur production would also be affected by the biofilm area to reactor volume (A/V) ratio in the MABR, with high A/V ratio might deteriorate the sulfur production efficiency depending on the oxygen pressure applied. Further, the increase of volatile fatty acids in the wastewater would not affect the sulfide oxidation efficiency but could enhance the sulfur production efficiency by decreasing the amount of sulfur oxidized to sulfate.