Optimizing Autotrophic Sulfide Oxidation in the Oxygen-Based Membrane Biofilm Reactor to Recover Elemental Sulfur
Anwar Alsanea, Ayoub Bounaga, Mohammed Danouche, Karim Lyamlouli, Youssef Zeroual, Rachid Boulif, Chen Zhou, Bruce E. Rittmann
Abstract
Biological sulfide oxidation is an efficient means to recover elemental sulfur (S 0 ) as a valuable resource from sulfide-bearing wastewater. This work evaluated the autotrophic sulfide oxidation to S 0 in the O 2 -based membrane biofilm reactor (O 2 -MBfR). High recovery of S 0 (80–90% of influent S) and high sulfide oxidation (∼100%) were simultaneously achieved when the ratio of O 2 -delivery capacity to sulfide-to S 0 surface loading (SL) (O 2 /S 2– → S 0 ratio) was around 1.5 (g O 2 /m 2 -day/g O 2 /m 2 -day). On average, most of the produced S 0 was recovered in the MBfR effluent, although the biofilm could be a source or sink for S 0 . Shallow metagenomic analysis of the biofilm showed that the top sulfide-oxidizing genera present in all stages were Thauera, Thiomonas, Thauera_A, and Pseudomonas . Thiomonas or Pseudomonas was the most important genus in stages that produced almost only S 0 (i.e., the O 2 /S 2– → S 0 ratio around 1.5 g of the O 2 /m 2 -day/g O 2 /m 2 -day). With a lower sulfide SL, the S 0 -producing genes were sqr and fccAB in Thiomonas . With a higher sulfide SL, the S 0 -producing genes were in the soxABDXYZ system in Pseudomonas . Thus, the biofilm community of the O 2 -MBfR adapted to different sulfide-to-S 0 SLs and corresponding O 2 -delivery capacities. The results illustrate the potential for S 0 recovery using the O 2 -MBfR.