Abstract
Autotrophic denitrification with biosulfur (ADBIOS) provides a sustainable technological solution for biological nitrogen removal from wastewater driven by biogenic S0, derived from biogas desulfurization. In this study, the effect of different biofilm carriers (conventional AnoxK™ 1 and Z-200 with a pre-defined maximum biofilm thickness) on ADBIOS performance and microbiomics was investigated in duplicate moving bed-biofilm reactors (MBBRs). The MBBRs were operated parallelly in continuous mode for 309 days, whilst gradually decreasing the hydraulic retention time (HRT) from 72 to 21 h, and biosulfur was either pumped in suspension (days 92–223) or supplied in powder form. Highest nitrate removal rates were approximately 225 (±11) mg/L·d and 180 (±7) mg NO3−-N/L·d in the MBBRs operated with K1 and Z-200 carriers, respectively. Despite having the same protected surface area for biofilm development in each MBBR, the biomass attached onto the K1 carrier was 4.8-fold more than that on the Z-200 carrier, with part of the biogenic S0 kept in the biofilm. The microbial communities of K1 and Z-200 biofilms could also be considered similar at cDNA level in terms of abundance (R = 0.953 with p = 0.042). A relatively stable microbial community was formed on K1 carriers, while the active portion of the microbial community varied significantly over time in the MBBRs using Z-200 carriers.
Highlights
The contamination of water resources is of serious environmental concern, mainly due to industrialization and the rapidly increasing human population
Synthesized elemental sulfur (S0) has been widely used as an electron donor for autotrophic denitrification, but its low water sol ubility resulted in reduced process rates (Christianson et al, 2015; Kostrytsia et al, 2018a;b; Sahinkaya et al, 2014)
Biogenic S0 globules (2–40 μm) are produced as a result of incomplete sulfide oxidation by various S-oxidizing microorganisms, and are hy drophilic (Janssen et al, 1999; Kamyshny et al, 2009; Kostrytsia et al, 2018c). Such hydrophobicity makes biogenic S0 reactive and bioavailable, and preliminary experiments on autotrophic denitri fication with biosulfur (ADBIOS) in batch microcosms showed 10-times faster denitrification kinetics (Kostrytsia et al, 2018c) compared to those obtained with chemically synthesized S0 (Huilinir et al, 2020; Kostrytsia et al, 2018a)
Summary
The contamination of water resources is of serious environmental concern, mainly due to industrialization and the rapidly increasing human population. Biogenic S0 globules (2–40 μm) are produced as a result of incomplete sulfide oxidation by various S-oxidizing microorganisms, and are hy drophilic (Janssen et al, 1999; Kamyshny et al, 2009; Kostrytsia et al, 2018c) Such hydrophobicity makes biogenic S0 reactive and bioavailable, and preliminary experiments on autotrophic denitri fication with biosulfur (ADBIOS) in batch microcosms showed 10-times faster denitrification kinetics (Kostrytsia et al, 2018c) compared to those obtained with chemically synthesized S0 (Huilinir et al, 2020; Kostrytsia et al, 2018a). Further studies on the ADBIOS process are of great interest, mainly if aimed at further increasing the bioprocess rates in continuous-flow bioreactors
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