ADBIOS in MBBRs: autotrophic denitrification with biosulfur in moving-bed biofilm reactors. Denitrification performance and microbial community dynamics in moving-bed biofilm reactors using biogenic sulfur and different biofilm carriers

Two types of biofilm carriers (AnoxKTM 1 and Z-200) were used in four moving bed biofilm reactors (MBBRs) aimed at autotrophic denitrification with biosulfur (ADBIOS) and operated parallelly in continuous mode for 309 days with a decreasing hydraulic retention time (HRT). The highest nitrate removal rates were approximately 225 (± 11) mg/L and 180(± 7) mg NO3--N/L·d in the MBBRs operated with K1 and Z-200 carriers, respectively. The biomass attached onto the K1 carrier reached a final concentration of 1.26 g TSattached/L, i.e. 4.8-fold higher than that on the Z-200 carrier. At cDNA level, K1 and Z-200 biofilms demonstrated temporal similarity only in terms of abundance (R=0.953 with p=0.042) with phylogenic distances being not similar. A relatively stable microbial community was formed in MBBRs with the K1 carrier over time, while the active microbial community (cDNA-based) varied significantly over time in the MBBRs with the Z-200 carrier.