Energy
Energy/resource recovery, Wastewater/waste treatment

Mitigation of ammonium/salinity inhibition of anaerobic digestion throughbioaugmentation with tolerant microbial community
Division of Sustainable Energy and Environmental Engineering, Graduate School of Engineering
Professor Michihiko Ike					https://researchmap.jp/ikemichi?lang=en

Associate Professor Daisuke Inoue		

https://researchmap.jp/DaisukeINOUE?lang=en

Abstract
Methane recovery by anaerobic digestion is considerably reduced by various factors present in wastes and wastewater to betreated, and especially high concentrations of ammonium andsalt are recognized as important inhibitors. In this research, themicrobial reactions that can be inhibited by high concentrations ofammonium and salt in anaerobic digestion were elucidated, andanaerobic microbial communities that are tolerant to high concentrations of ammonium and salt were introduced into the anaerobic
digestion process (bioaugmentation) to mitigate the ammonium/saltinhibition. The bioaugmentation significantly mitigated the inhibitory
effects, and enabled efficient methane production with equivalent
efficiencies to those in the systems without the inhibitory factors.

Energy▍ Background & Results
The bioaugmentation strategy established in this research isexpected to expand the range of waste/wastewater which canbe treated by anaerobic digestion to recover methane as the carbon-neutral energy, thereby making a significant contribution to theenvironmental conservation and a recycling-oriented and decarbonized society. In the subsequent researches, we have also foundthe possibility of alleviating the inhibition of anaerobic digestion forinhibitors other than ammonium and salt by the bioaugmentaion
strategy. We are currently conducting scale-up studies to apply thisstrategy to full-scale facilities.

monium (>3 g-NH4-N/L) or salt (>10 g-NaCl/L) was found to becommonly caused by inhibition of microbial populations involved
in hydrolysis of complex organic compounds, symbiotic propionate oxidation, and aceticlastic methanogenesis, indicating that it
is important to strengthen these microbial reactions to mitigate theinhibition.
Therefore, we acclimated marine sediments to high concentrations of ammonium (5 g-NH4-N/L) and salt (30 g-NaCl/L) underanaerobic conditions to construct tolerant microbial communities,and the established microbial communities were introduced into
anaerobic digestion systems (bioaugmentation). Bioaugmentation
significantly reduced the inhibition of methanogenesis even in thepresence of high concentrations of ammonium or salt, and the final methane production was found to be almost equivalent to thatof the control system without each inhibitory factor. The results of
microbial community analysis strongly suggested that hydrogenotrophic methanogens derived from the introduced tolerant microbial communities contributed to the mitigation of the inhibition on themethane production.
Optimizing the size and timing of the inoculation of tolerant microbial communities into the anaerobic digestion system should
maximize the effectiveness of the bioaugmentation to mitigate theammonium and salt inhibition.

▍ Significance of the research and Future perspective
Inhibition of anaerobic digestion by high concentrations of ammonium and salt is an important problem to be solved in methane
recovery from organic wastes and wastewater. This study aimed toclarify the mechanism of ammonium and salt inhibition in anaerobic
digestion, which takes place through the interactions of diverse microbial populations, and to establish effective inhibition mitigationtechniques.
Inhibition of anaerobic digestion by high concentrations of am[Inhibition by ammonium/salinity]

Biogas(Methane)

Food waste

Anaerobic
digesterLivestock waste

Wastewater,
sewage sludge

Biogas (methane) production from organic waste/wastewater by anaerobic digestion[Mitigation through bioaugmentation]
Bioaugmentation

Organic polymers

Organic polymers

Monomer/Oligomer

Monomer/Oligomer
Key Population

Butyrate, Propionate, etc.
InhibitAcetate

H2 + CO2

Butyrate, Propionate, etc.

AcetateCH4 + CO2

H2 + CO2CH4 + CO2

Key Population

Ammonium/salinity inhibition of metabolic pathways in anaerobic digestion and its mitigation through bioaugmentation with tolerant microbial community
P a t e n t
Tr e a t i s e

Luong Van Duc et al. Identidfication of key steps and associated microbial populations for efficient anaerobic digestion under high ammonium or salinity
conditions. Bioresource Technology. 2022, 360, 127571. doi:10.1016/j.biortech.2022.127571
Luong Van Duc et al. Bioaugmentation with marine sediment-derived microbial consortia in mesophilic anaerobic digestion for enhancing methane
production under ammonium or salinity stress. Bioresource Technology. 2023, 360, 128853. doi:10.1016/j.biortech.2023.128853

URL
K e y w o r d anaerobic digestion, ammonium/salinity inhibition, ammonium-/salt-tolerant microbial community, bioaugmentation