Optimizing Autotrophic Sulfide Oxidation in the Oxygen-Based Membrane Biofilm Reactor to Recover Elemental Sulfur.

Biological sulfide oxidation is an efficient means to recover elemental sulfur (S) as a valuable resource from sulfide-bearing wastewater. This work evaluated the autotrophic sulfide oxidation to S in the O-based membrane biofilm reactor (O-MBfR). High recovery of S (80-90% of influent S) and high sulfide oxidation (∼100%) were simultaneously achieved when the ratio of O-delivery capacity to sulfide-to S surface loading (SL) (O/S → S ratio) was around 1.5 (g O/m-day/g O/m-day). On average, most of the produced S was recovered in the MBfR effluent, although the biofilm could be a source or sink for S. Shallow metagenomic analysis of the biofilm showed that the top sulfide-oxidizing genera present in all stages were , , , and . or was the most important genus in stages that produced almost only S (i.e., the O/S → S ratio around 1.5 g of the O/m-day/g O/m-day). With a lower sulfide SL, the S-producing genes were and in . With a higher sulfide SL, the S-producing genes were in the system in . Thus, the biofilm community of the O-MBfR adapted to different sulfide-to-S SLs and corresponding O-delivery capacities. The results illustrate the potential for S recovery using the O-MBfR.