Microbial Dynamics and Mechanistic Insights into a Hydrogenotrophic Denitrifying Microbial Consortium

The current heterotrophic denitrification processes predominantly used in wastewater treatment plants can lead to the fugitive emission of greenhouse gases (N2O and CO2). This is due to microbial competition for limited organic electron donors such as methanol and acetate. Recently, autotrophic denitrification using hydrogen as a clean electron donor, also known as “hydrogenotrophic denitrification”, has garnered increasing interest. Previous studies reported that hydrogenotrophic denitrification, in comparison to its heterotrophic counterpart, results in significantly lower N2O emissions and no CO2 release. However, persistent challenges associated with this process, such as nitrite accumulation, long-lag phases and relatively slower denitrification rates, require further elucidation. Notably, the impact of microbial interactions within hydrogenotrophic denitrifying consortia on these behaviors has yet to be substantially discussed in the literature. Therefore, this study used a co-culture consortium containing a Paracoccus strain and a Thauera strain to address some of the aforementioned challenges. The study demonstrated that the composition of the consortium could be dynamically altered through the supplementation of nitrite (~20 mg-N/L). This adjustment resulted in a shift towards the dominance of the Paracoccus strain, now representing over 60% of the bacterial population. This shift led to an enhanced system performance by mitigating observed lag phases (from 48 hours down to 24 hours). More interestingly, when exposed to low salinity conditions (1% to 2%), the previously observed lag phases were completely eliminated. The Thauera strain became dominant under saline conditions, accounting for over 70% of the bacterial population. Comparative genomic analyses showed that the Thauera strain’s dominance was likely facilitated by a bicarbonate transporter allowing for more efficient carbon utilization by this strain. The consortium could tolerate a salinity up to 3%, highlighting its robustness and adaptability. Further investigations into this consortium unveiled its utility for nitrogen recovery through the precipitation of 13.5 mg/L of struvite crystals. The precipitates obtained were found to be generated through biologically controlled mineralization (BCM) enabled by the dissimilatory nitrate reduction to ammonium (DNRA) process. By understanding and manipulating specific microbial interactions within a hydrogenotrophic consortium, this thesis research contributes to the advancement of zero-emissions biological denitrification systems in wastewater treatment plants.

Name thesis:degree_name

PhD

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Civil & Environmental Engineering

Grantor dc:publisher

ResearchSpace@Auckland

Year dc:date.issued

2023

Author dc:creator

• Bonnet, Hukerenui

Advisors dc:contributor.advisor

• Zhuang, Wei-Qin
• Yi, Shan
• Fa`aui, Tumanako
• Craggs, Rupert

Statement dc:rights

• Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

Licence dc:rights.uri

• https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm

Handle dc:identifier.uri

https://hdl.handle.net/2292/69258

OAI identifier oai:identifier

oai:researchspace.auckland.ac.nz:2292/69258