Lab-scale Data and Microbial Community Structure Suggest Shortcut Nitrogen Removal as the Predominant Nitrogen Removal Mechanism in Post-Aerobic Digestion (PAD)

Authors

Fabrizio Sabba, Black & Veatch
Patrick J. McNamara, Marquette UniversityFollow
Eric Redmond, Black & Veatch
Mike Young, Trinity River Authority of Texas
Leon Downing, Black & Veatch

Document Type

Article

Publication Date

7-2022

Publisher

Wiley

Source Publication

Water Environment Research

Source ISSN

1061-4303

Original Item ID

DOI: 10.1002/wer.10762

Abstract

Implementing an aerobic digestion step after anaerobic digestion, referred to as “post aerobic digestion” (PAD), can remove ammonia without the need for an external carbon source and destroy volatile solids. While this process has been documented at the lab-scale and full-scale, the mechanism for N removal and the corresponding microbial community that carries out this process have not been established. This research gap is important to fill because the nitrogen removal pathway has implications on aeration requirements and carbon demand, that is, short-cut N-removal requires less oxygen and carbon than simultaneous nitrification–denitrification. The aims of this research were to (i) determine if nitrite (NO₂⁻) or nitrate (NO₃⁻) dominates following ammonia removal and (ii) characterize the microbial community from PAD reactors. Here, lab-scale PAD reactors were seeded with biomass from two different full-scale PAD reactors. The lab-scale reactors were fed with biomass from full-scale reactors and operated in batch mode to quantify nitrogen species concentrations (ammonia, NH₄⁺, NO₂⁻, and NO₃⁻) over time. Experimental results revealed that NO₂⁻ production rates were several orders of magnitude greater than NO₃⁻ production rates. Indeed, nitrite accumulation rate (NAR) was greater than 90% at most temperatures, confirming that shortcut nitrogen removal was the dominant NH₄⁺ removal mechanism in PAD. Microbial community analysis via 16S rRNA sequencing indicated that ammonia oxidizing bacteria (AOB) were much more abundant than nitrite oxidizing bacteria (NOB). Overall, this study suggests that aeration requirements for post-aerobic digestion should be based on NO₂− shunt and not complete simultaneous nitrification denitrification.

Comments

Accepted version. Water Environment Research, Vol. 94, No. 7 (July 2022): e10762. DOI. © 2022 Wiley. Used with permission.

Recommended Citation

Sabba, Fabrizio; McNamara, Patrick J.; Redmond, Eric; Young, Mike; and Downing, Leon, "Lab-scale Data and Microbial Community Structure Suggest Shortcut Nitrogen Removal as the Predominant Nitrogen Removal Mechanism in Post-Aerobic Digestion (PAD)" (2022). Civil and Environmental Engineering Faculty Research and Publications. 356.
https://epublications.marquette.edu/civengin_fac/356