期刊
JOURNAL OF ENVIRONMENTAL MANAGEMENT
卷 294, 期 -, 页码 -出版社
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jenvman.2021.112928
关键词
Autotrophic ammonia oxidation; Autotrophic biofilms; Biological nutrient removal; Carbonate alkalinity; Greenhouse gas emissions; CO2 emissions
资金
- Natural Sciences and Engineering Research Council (NSERC) of Canada
The oxidation of ammonia by autotrophic bacteria is an essential part of the nitrogen cycle and biological nutrient removal during wastewater treatment. This process produces CO2, which can contribute to greenhouse gas emissions if transferred to the atmosphere. Two experimental systems demonstrated the relationship between ammonia removal and gaseous CO2 emissions, highlighting the need for further research on managing CO2 production in engineered systems.
The oxidation of ammonia by autotrophic bacteria is a central part of the nitrogen cycle and a fundamental aspect of biological nutrient removal (BNR) during wastewater treatment. Autotrophic ammonia oxidation produces protons and results in net-CO2 production due to the neutralizing effect of bicarbonate alkalinity. Attention must be paid to the propensity for this produced CO2 to be transferred to the atmosphere where it can act as a greenhouse gas (GHG). In the context of BNR systems, bicarbonate-derived CO2 emissions should be considered distinct from the biogenic CO2 that arises from cellular respiration, though this distinction is not made in current GHG accounting practices. The aim of this study was to evaluate the performance of two experimental systems operated under autotrophic mode and buffered with bicarbonate, to investigate the relationship between ammonia removal and gaseous CO2 emissions. The first system consisted of continuously aerated lab-scale batch reactors, which were effective in demonstrating the important link between ammonia oxidizer activity, pH, and gaseous CO2 production. Depletion of the buffer system always led to a rapid decline in system pH and cessation of CO2 emissions when the pH fell below 7.0. The second system was a tubular continuous-flow biofilm reactor which permitted comparison of ammonia removal and CO2 emission rates. A linear relationship between ammonia removal and CO2 emissions was demonstrated and the quantified CO2 production was relatively close to that which was predicted based on the stoichiometry of nitrification, with this CO2 being detected in the gas phase. It was apparent that this system offered minimal resistance to the mass transfer of CO2 from the liquid to gas, which is an important factor that determines how much of the bicarbonatederived CO2 may contribute to greenhouse gas emissions in engineered systems such as those used for BNR.
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