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. 2021 Jun 7:12:678323.
doi: 10.3389/fmicb.2021.678323. eCollection 2021.

Enrichment of Autotrophic Denitrifiers From Anaerobic Sludge Using Sulfurous Electron Donors

M F Carboni  1 , A P Florentino  1 , R B Costa  2 , X Zhan  3 , P N L Lens  1
Affiliations

Enrichment of Autotrophic Denitrifiers From Anaerobic Sludge Using Sulfurous Electron Donors

M F Carboni et al. Front Microbiol. .

Abstract

This study compared the rates and microbial community development in batch bioassays on autotrophic denitrification using elemental sulfur (S0), pyrite (FeS2), thiosulfate (S2O3 2-), and sulfide (S2-) as electron donor. The performance of two inocula was compared: digested sludge (DS) from a wastewater treatment plant of a dairy industry and anaerobic granular sludge (GS) from a UASB reactor treating dairy wastewater. All electron donors supported the development of a microbial community with predominance of autotrophic denitrifiers during the enrichments, except for sulfide. For the first time, pyrite revealed to be a suitable substrate for the growth of autotrophic denitrifiers developing a microbial community with predominance of the genera Thiobacillus, Thioprofundum, and Ignavibacterium. Thiosulfate gave the highest denitrification rates removing 10.94 mM NO3 - day-1 and 8.98 mM NO3 - day-1 by DS and GS, respectively. This was 1.5 and 6 times faster than elemental sulfur and pyrite, respectively. Despite the highest denitrification rates observed in thiosulfate-fed enrichments, an evaluation of the most relevant parameters for a technological application revealed elemental sulfur as the best electron donor for autotrophic denitrification with a total cost of 0.38 € per m3 of wastewater treated.

Keywords: enrichment; microbial diversity; nitrogen removal; pyrite; reduced sulfur compounds.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Profile of NO3– (•) and SO42– (▲) of the last transfer in (A) ThEnr with DS, (B) ThEnr with GS, (C) PyEnr with DS, (D) PyEnr with GS, (E) S0Enr with DS, and (F) S0Enr with GS.
FIGURE 2
FIGURE 2
Comparison of measured and theoretical sulfate concentrations for all enrichments: (A) first incubation with the inocula and (B) last transfer with the enrichments.
FIGURE 3
FIGURE 3
Relative abundance at genus level present in the (A) inocula—in duplicate—and (B) in the last transfer of ThEnr, PyEnr, and S0Enr—in triplicate.
See this image and copyright information in PMC

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