Novel Sulfate Reduction Coupled to Simultaneous Nitrification and Autotrophic Denitrification Process for Removing Nitrogen and Organics from Saline Wastewater

This study demonstrates novel sulfatereduction coupledto simultaneous nitrification and autotrophic denitrification. Theintegrated process efficiently removed nitrogen and organics fromsaline wastewater having a low COD/N ratio, and it minimizes the footprint,energy consumption, and sludge yield. Highly efficient sulfate reduction coupled to autotrophicdenitrificationplus nitrification is demonstrated by integrating an anaerobic membranebioreactor (AnMBR) with a membrane aerated biofilm reactor (MABR).Concurrent chemical oxygen demand (COD) removal and sulfate reductionwere accomplished in the AnMBR, while simultaneous nitrification andautotrophic denitrification were carried out in the MABR. Separateoperation of the MABR achieved >90% total nitrogen (TN) removalwhenthe N/S ratio was controlled at 0.4 gN/gS. The integrated AnMBR-MABRsystem efficiently resisted influent variability, realizing >95%CODremoval in the AnMBR and >75% TN removal in the MABR when the influentCOD/N ratio was above 4 gCOD/gN. Membrane fouling did not happen during & SIM;170 days of operation. Due to sulfide oxidation, a large amountof elemental sulfur (S-0) accumulated in the MABR biofilm,where it served as an electron donor for denitrification. Microbialcommunity analysis indicated that Nitrospira and Thiobacillus played key roles in nitrification and sulfide-drivendenitrification, respectively, and that they occurred in differentlayers of the biofilm. This novel process offers advantages of a smallland-area footprint, modular operation, and high efficiency electron-donorand oxygen utilizations, particularly for wastewater with a low COD/Nratio.