Application of pyritic sludge with an anaerobic granule consortium for nitrate removal in low carbon systems

Bojan Pelivano; Samuel Bryson; Kristopher A Hunt; Martin Denecke; David A Stahl; Mari Winkler

doi:10.1016/j.watres.2021.117933

Application of pyritic sludge with an anaerobic granule consortium for nitrate removal in low carbon systems

Water Res. 2022 Feb 1:209:117933. doi: 10.1016/j.watres.2021.117933. Epub 2021 Dec 4.

Authors

Bojan Pelivano¹, Samuel Bryson², Kristopher A Hunt², Martin Denecke³, David A Stahl², Mari Winkler²

Affiliations

¹ Department of Civil and Environmental Engineering, University of Washington, 616 Northeast Northlake Place, Seattle, Washington 98105, USA; Department of Urban Water and Waste Management, University of Duisburg-Essen, Universitaetsstr. 15, Essen 45141, Germany. Electronic address: bp19@uw.edu.
² Department of Civil and Environmental Engineering, University of Washington, 616 Northeast Northlake Place, Seattle, Washington 98105, USA.
³ Department of Urban Water and Waste Management, University of Duisburg-Essen, Universitaetsstr. 15, Essen 45141, Germany.

PMID: 34923445
DOI: 10.1016/j.watres.2021.117933

Abstract

Granules recovered from a highly reduced anaerobic digester were capable of active nitrogen removal in the absence of exogenous electron donors, averaging 0.25 mg mgNO₃^--N /gVSS/d over 546 days of operation. Electron mass balance indicated that about half the influent nitrate was converted to ammonia via DNRA and another half denitrified. This capacity was associated with an onion-like structure of multiple layers enriched in reduced iron and sulfur, and a complex microbial community shown by metagenomic sequencing to consist of multiple physiological groups and associated activities, including methanogenesis, denitrification, dissimilatory nitrate reduction to ammonia (DNRA), iron oxidation and reduction, and sulfur reduction and oxidation. Nitrate reduction was supported by both entrained organic material and reduced iron and sulfur species, corresponding to 2.13 mg COD/gVSS/d. Batch incubations showed that approximately 15% of denitrified nitrate was coupled to the oxidation of sulfur derived from both sulfate respiration and granular material enriched in iron-sulfide. Inhibition of sulfate reduction resulted in redirection of electron flow to methanogenesis and, in combination with other batch tests, showed that these granules supported a complex microbial community in which cryptic redox cycles linked carbon, sulfur, and iron oxidation with nitrate, sulfate, iron, and carbon dioxide reduction. This system shows promise for treatment of nitrate contaminated ground water without addition of an external organic carbon source as well as wastewater treatment in combination with (granular) sludge elimination leading in a net reduction of solid treatment costs.

Keywords: Electron balance; Granule; Iron cycle; Metagenomics; Nitrate removal; Sulfur cycle.