Mathematical models and bacterial communities for ammonia toxicity in mesophilic anaerobes not acclimated to high concentrations of ammonia

Abstract

In this study, we evaluated ammonia toxicity in mesophilic anaerobic digestion at various pH values and total ammonia nitrogen (TAN) concentrations. We performed anaerobic toxicity assays (ATAs) to evaluate the toxicity effects of TAN and pH on mesophilic anaerobic digestion. Modeling based on the results of the ATAs indicated that the specific methanogenic activity (SMA) decreased by 30% at a TAN concentration higher than 3.0 g/L compared to a TAN concentration of 0 g/L. In addition, the highest SMA for a given TAN level (0.5-10.0 g/L) was observed at a pH of around 7.6. The results of bacterial community analyses showed that the diversity and richness of microorganisms with increasing TAN concentration were decreased. Chloroflexi and Synergistetes were the dominant phyla at TAN concentrations less than 3.0 g/L, and Firmicutes was the dominant phylum at TAN concentrations higher than 3.0 g/L, implying that the ammonia toxicity concentration may influence the kind of dominant species. In conclusion, to start a stable mesophilic anaerobic digestion concerning ammonia toxicity, a TAN concentration less than 3.0 g/L is preferable.

Three-dimensional dynamics of nitrogen from banded enhanced efficiency fertilizers

“…It is postulated that the dependence on microbial degradation of succinic acid for DMPP release (Pacholski et al 2016) may impair the initial effectiveness of DMPSA-urea in banded applications. The hostile conditions of a urea-based band may have a general inhibitory effect (Park et al 2016;Rietz and Haynes 2003) on a range of microorganisms that are required for the 'release' of this inhibitor. Further investigation is required to determine whether this product is effective in banded applications.…”