Comparison of biogenic and chemical sulfur as electron donors for autotrophic denitrification in sulfur-fed membrane bioreactor (SMBR)

[Display omitted] •Biogenic and chemical sulfur were compared for denitrification and membrane fouling.•Biogenic sulfur showed 20% higher denitrification rates than chemical sulfur in MBR.•Trans membrane pressures (TMPs) were higher in the MBR fed with biogenic sulfur.•Denitrifying Proteobacteria dominated the microbial communities of both MBRs. Two sulfur-oxidizing membrane bioreactors (SMBRs) performing autotrophic denitrification at different HRTs (6–26 h), one supplemented with biogenic elemental sulfur (S0bio) and the other with chemically-synthesized elemental sulfur (S0chem), were compared in terms of nitrate reduction rates, impact on membrane filtration and microbial community composition. Complete denitrification with higher rates (up to 286 mg N-NO3−/L d) was observed in the SMBR supplemented with S0bio (SMBRbio), while nitrate was never completely reduced in the SMBR fed with S0chem (SMBRchem). Trans membrane pressure was higher for SMBRbio due to smaller particle size and colloidal properties of S0bio. Microbial communities in the two SMBRs were similar and dominated by Proteobacteria, with Pleomorphomonas and Thermomonas being the most abundant genera in both bioreactors. This study reveals that S0bio can be effectively used for nitrate removal in autotrophic denitrifying MBRs and results in higher nitrate reduction rates compared to S0chem.