1.
[Effects of Environmental Factors on the Synergy of Functional Bacteria in Completely Autotrophic Granular Sludge].
Chen, X, Qian, FY, Wang, JF, Gao, JJ, Shen, YL, Jia, X
Huan jing ke xue= Huanjing kexue. 2018;(4):1756-1762
Abstract
To obtain experimental evidences for optimizing a completely autotrophic nitrogen removal process based on granules, the effects of dissolved oxygen (DO) concentration, temperature (t), initial ammonium (NH4+-N) concentration, and solution pH conditions on the synergy between the aerobic and anaerobic ammonium-oxidizing bacteria (AOB and AMX) were investigated using a single factor batch experiment, while the analysis of the microbial community structure within them was conducted using MiSeq high-throughput pyrosequencing. Results revealed that AOB (genus Nitrosomonas) and AMX (genus Candidatus Kuenenia) dominated in the granules, representing relative abundances of 32.9% and 9.8%, respectively. For the granules, the highest specific nitrogen removal rate of q(TN)=(17.7±1.0) mg·(g·h)-1 was obtained at a DO concentration of 2 mg·L-1, while the initial NH4+-N concentration was set at 100 mg·L-1. And a lower DO level resulted in partial nitritation became the rate-limiting step of process, otherwise, it would be the ANAMMOX reaction instead. According to the free energy of the reactions, the activity of AMX was more sensitive to low temperature than that of AOB. When the reaction temperature was lower than 30℃, nitrite accumulation could be observed in bulk liquid, with the significant decrease of q(TN) for the granules. Under the same oxygen supply conditions, an initial NH4+-N concentration lower than 100 mg·L-1 could inhibit the activity of AMX partly. However, with an initial NH4+-N concentration over 150 mg·L-1, either oxygen-limiting or high free ammonia concentration could lead to the dramatic decrease of q(TN). In addition, the effective synergy of the two types of ammonium oxidizers in granules was always achieved at solution pH in the range of 7.0-8.5.
2.
Evaluating the Role of Microbial Internal Storage Turnover on Nitrous Oxide Accumulation During Denitrification.
Liu, Y, Peng, L, Guo, J, Chen, X, Yuan, Z, Ni, BJ
Scientific reports. 2015;:15138
Abstract
Biological wastewater treatment processes under a dynamic regime with respect to carbon substrate can result in microbial storage of internal polymers (e.g., polyhydroxybutyrate (PHB)) and their subsequent utilizations. These storage turnovers play important roles in nitrous oxide (N2O) accumulation during heterotrophic denitrification in biological wastewater treatment. In this work, a mathematical model is developed to evaluate the key role of PHB storage turnovers on N2O accumulation during denitrification for the first time, aiming to establish the key relationship between N2O accumulation and PHB storage production. The model is successfully calibrated and validated using N2O data from two independent experimental systems with PHB storage turnovers. The model satisfactorily describes nitrogen reductions, PHB storage/utilization, and N2O accumulation from both systems. The results reveal a linear relationship between N2O accumulation and PHB production, suggesting a substantial effect of PHB storage on N2O accumulation during denitrification. Application of the model to simulate long-term operations of a denitrifying sequencing batch reactor and a denitrifying continuous system indicates the feeding pattern and sludge retention time would alter PHB turnovers and thus affect N2O accumulation. Increasing PHB utilization could substantially raise N2O accumulation due to the relatively low N2O reduction rate when using PHB as carbon source.