Archaea and Bacteria Acclimate to High Total Ammonia in a Methanogenic Reactor Treating Swine Waste.

Sofia Esquivel-Elizondo,Anca G Delgado,Rosa Krajmalnik-Brown,Juan Maldonado,Prathap Parameswaran,Bruce E Rittmann

doi:10.1155/2016/4089684

Sofia Esquivel-Elizondo, Anca G Delgado + Show 4 more

Open Access

https://doi.org/10.1155/2016/4089684

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Abstract

Inhibition by ammonium at concentrations above 1000 mgN/L is known to harm the methanogenesis phase of anaerobic digestion. We anaerobically digested swine waste and achieved steady state COD-removal efficiency of around 52% with no fatty-acid or H2 accumulation. As the anaerobic microbial community adapted to the gradual increase of total ammonia-N (NH3-N) from 890 ± 295 to 2040 ± 30 mg/L, the Bacterial and Archaeal communities became less diverse. Phylotypes most closely related to hydrogenotrophic Methanoculleus (36.4%) and Methanobrevibacter (11.6%), along with acetoclastic Methanosaeta (29.3%), became the most abundant Archaeal sequences during acclimation. This was accompanied by a sharp increase in the relative abundances of phylotypes most closely related to acetogens and fatty-acid producers (Clostridium, Coprococcus, and Sphaerochaeta) and syntrophic fatty-acid Bacteria (Syntrophomonas, Clostridium, Clostridiaceae species, and Cloacamonaceae species) that have metabolic capabilities for butyrate and propionate fermentation, as well as for reverse acetogenesis. Our results provide evidence countering a prevailing theory that acetoclastic methanogens are selectively inhibited when the total ammonia-N concentration is greater than ~1000 mgN/L. Instead, acetoclastic and hydrogenotrophic methanogens coexisted in the presence of total ammonia-N of ~2000 mgN/L by establishing syntrophic relationships with fatty-acid fermenters, as well as homoacetogens able to carry out forward and reverse acetogenesis.

Highlights

Animal wastes contribute more than half of the biomassbased wastes generated in the United States [1, 2]
COD Was Converted into Methane during Bioreactor Operation despite NH3-N > 2000 mg/L
Based on COD removed as CH4, the performance of the reactor approached a pseudo-steady state in cycle 1 of semicontinuous operation, with approximately 52% conversion

Summary

Introduction

Animal wastes contribute more than half of the biomassbased wastes generated in the United States [1, 2]. The organic carbon in animal wastes could be a major source of renewable energy if it were captured as methane gas. Many animal wastes, including swine waste, are rich in organic nitrogen (N) due to the high protein content in the animals’ diet. A challenge arises for treating these wastes (and capturing the organic carbon as energy source) as NH3-N above 1000 mg L−1 is toxic to many groups of microorganisms [7, 8], including methanogenic Archaea [9, 10]

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Conclusion