Show simple item record

Potential Impact of Increasing Ammonia Concentrations upon Microbial Population Dynamics in Anaerobic Meso- and Thermophilic driven Fermenters

dc.contributor.advisorDippold, Michaela Prof. Dr.
dc.contributor.authorAlsouleman, Khulud
dc.titlePotential Impact of Increasing Ammonia Concentrations upon Microbial Population Dynamics in Anaerobic Meso- and Thermophilic driven Fermentersde
dc.contributor.refereeBeneke, Frank Prof. Dr.
dc.description.abstractengAnaerobic digestion is the process of decomposition of organic matter by a microbial consortium in an oxygen-free environment. The produced biogas from this process is composed of methane, carbon dioxide, nitrogen, oxygen, hydrogen sulfide and traces of other gases. Long-term mesophilic and thermophilic anaerobic digestion experiments were investigated to evaluate the reactor performance and the response of the microbial community under consideration of the structure variations due to an increasing content of NH4+-N caused by stepwise addition of nitrogen-rich substrates, in this case studies poultry manure (PM). Therefore, laboratory-scale continuously respectively completely stirred tank reactors (CSTR) with a working volume of eight liter and steady organic loading rate (OLR of 3.0 gVS L−1 d−1) in mesophilic (37°C) and thermophilic (55°C) conditions were operated. The gradual increasing of NH4+-N caused by stepwise addition of nitrogen-rich substrates (poultry manure) will lead to an increase in the free ammonia NH3 concentration. Free ammonia is considered a common inhibitor for the anaerobic digestion process due to its cytotoxic effects, resulting from deprotonation of ammonium (NH4+). As the free ammonia (NH3) concentration depends on the concentration of NH4+-N, the pH-value and the reactor temperature, therefore a NH4+-N and NH3 values of > 3 g kgFM-1 respectively > 0,4 g kgFM-1 which has no impact on the anaerobic digestion process under mesophilic condition caused a serious disturbance and inhibition under thermophilic condition. The anaerobic microbiome acclimated to low PM levels in mesophilic and thermophilic conditions which resulted in a stable anaerobic digestion process. After that, with the consecutive application of medium PM level in mesophilic condition, a process disturbance was induced which was characterized by a shift from a Bacteroidetes-dominanted to a Clostridiales-dominated bacterial community accompanied by a change from the acetoclastic to the hydrogenotrophic pathway of methane formation. However, the “new” microbial community in mesophilic condition was functionally redundant as the overall process rates in terms of biogas yield methane content and volatile fatty acids VFA content were similar to the former one. A further increase of poultry manure (high PM level) resulted in complete process failure due to the ongoing increasing in the total ammonium nitrogen and volatile fatty acid content. Compared to a mesophilic experiment, the thermophilic anaerobic microbiome was much more sensitive for process disturbances. The application of medium PM level resulted in a process disturbance and a final process failure. The microbial community was able to compensate the high cytotoxic ammonia contents only for a short time. The ongoing increase in the total ammonium nitrogen NH4+-N content in combination with an increase of the salt content (quantified as electrical conductivity) are assumed to be the main reasons for the final process failure. Overall, the microbial community structure in this study might be the key factor explaining the adaption capacity, as it highlighted how an anaerobic microbiome in mesophilic condition was enabled to adapt to changing environmental conditions while the thermophilic ones with less diversity was much more sensitive and failed to overcome the prevalent environmental conditions. Thus, these results serve as a basic to understand and monitor the different microbiome responses to a specific environmental disturbance and to contribute to further optimization of biogas production process based on nitrogen rich substrates. Also, the results of this study may facilitate the application of anaerobic digestion of process-risk feedstock (nitrogen-rich manure) as a management technology and bioenergy resource on the full–scale in the
dc.contributor.coRefereeDippold, Michaela Prof. Dr.
dc.contributor.thirdRefereeKlocke, Michael Dr.
dc.subject.engAnaerobic digestionde
dc.subject.engAmmonia inhibitionde
dc.subject.engPoultry manurede
dc.subject.engMicrobial communityde
dc.affiliation.instituteFakultät für Agrarwissenschaftende
dc.subject.gokfullLand- und Forstwirtschaft (PPN621302791)de

Files in this item


This item appears in the following Collection(s)

Show simple item record