1
|
Ayotte SH, Allen CR, Parker A, Stein OR, Lauchnor EG. Greenhouse gas production from an intermittently dosed cold-climate wastewater treatment wetland. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 924:171484. [PMID: 38462002 DOI: 10.1016/j.scitotenv.2024.171484] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 02/23/2024] [Accepted: 03/03/2024] [Indexed: 03/12/2024]
Abstract
This study explores the greenhouse gas (GHG) fluxes of nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) from a two-stage, cold-climate vertical-flow treatment wetland (TW) treating ski area wastewater at 3 °C average water temperature. The system is designed like a modified Ludzack-Ettinger process with the first stage a partially saturated, denitrifying TW followed by an unsaturated nitrifying TW and recycle of nitrified effluent. An intermittent wastewater dosing scheme was established for both stages, with alternating carbon-rich wastewater and nitrate-rich recycle to the first stage. The system has demonstrated effective chemical oxygen demand (COD) and total inorganic nitrogen (TIN) removal in high-strength wastewater over seven years of winter operation. Following two closed-loop, intensive GHG winter sampling campaigns at the TW, the magnitude of N2O flux was 2.2 times higher for denitrification than nitrification. CH4 and N2O emissions were strongly correlated with hydraulic loading, whereas CO2 was correlated with surface temperature. GHG fluxes from each stage were related to both microbial activity and off-gassing of dissolved species during wastewater dosing, thus the time of sampling relative to dosing strongly influenced observed fluxes. These results suggest that estimates of GHG fluxes from TWs may be biased if mass transfer and mechanisms of wastewater application are not considered. Emission factors for N2O and CH4 were 0.27 % as kg-N2O-N/kg-TINremoved and 0.04 % kg-CH4-C/kg-CODremoved, respectively. The system had observed seasonal emissions of 600.5 kg CO2 equivalent of GHGs estimated over 130-days of operation. These results indicate a need for wastewater treatment processes to mitigate GHGs.
Collapse
Affiliation(s)
- S H Ayotte
- Center for Biofilm Engineering, Montana State University, Bozeman, MT 59717, USA; Department of Civil Engineering, Montana State University, Bozeman, MT 59717, USA; Thermal Biology Institute, Montana State University, Bozeman, MT 59717, USA
| | - C R Allen
- Center for Biofilm Engineering, Montana State University, Bozeman, MT 59717, USA; Department of Civil Engineering, Montana State University, Bozeman, MT 59717, USA
| | - A Parker
- Center for Biofilm Engineering, Montana State University, Bozeman, MT 59717, USA; Department of Mathematical Sciences, Montana State University, Bozeman, MT 59717, USA
| | - O R Stein
- Center for Biofilm Engineering, Montana State University, Bozeman, MT 59717, USA; Department of Civil Engineering, Montana State University, Bozeman, MT 59717, USA
| | - E G Lauchnor
- Center for Biofilm Engineering, Montana State University, Bozeman, MT 59717, USA; Department of Civil Engineering, Montana State University, Bozeman, MT 59717, USA; Thermal Biology Institute, Montana State University, Bozeman, MT 59717, USA.
| |
Collapse
|
2
|
Wang H, Miao J, Sun Y. Aerobic nitrous oxide emission in anoxic/aerobic and intermittent aeration sequencing batch reactors. ENVIRONMENTAL TECHNOLOGY 2024; 45:1449-1458. [PMID: 36331189 DOI: 10.1080/09593330.2022.2144467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 10/28/2022] [Indexed: 06/16/2023]
Abstract
This study characterized nitrogen removal and nitrous oxide (N2O) emissions from lab-scale anoxic/aerobic sequencing batch reactor (AOSBR) and intermittent aeration sequencing batch reactor (IASBR), respectively, for treating synthetic municipal wastewater. The N2O emission was evaluated in a simulated cycle, and batch conditions of aerobic nitrification, simultaneous nitrification and denitrification (SND), and aerobic denitrification. The results show that nitrogen removal was enhanced in IASBR compared to AOSBR, with 94.2% and 67.9% of total inorganic nitrogen removal efficiency in IASBR and AOSBR, respectively. In the simulated cycle, the emission factors (of oxidized ammonium) were 4.9% and 0.6% in AOSBR and IASBR, respectively. Under batch conditions, the N2O emission factors during SND were obviously higher than that during aerobic nitrification and denitrification. The N2O emission factors during SND ranging 0.68-11.68% in AOSBR and 1.25-5.13% in IASBR. Furthermore, N2O emission under batch conditions was affected by the aeration ratios. Moderate and high aeration ratios used in this study stimulated the N2O emission from SND. The N2O emission was enhanced with the nitrite accumulation during aerobic nitrification when the nitrite-oxidizing bacteria was inhibited by a chemical inhibitor. Aerobic denitrification via nitrite could be the main pathway of N2O generation from SND processes. The findings from our study can help further understand N2O emission mechanisms and guide the optimization of the current wastewater treatment process for minimizing N2O emission.
Collapse
Affiliation(s)
- Huoqing Wang
- State Environmental Protection Key Laboratory of Drinking Water Source Management and Technology, Shenzhen Academy of Environmental Science, Shenzhen, People's Republic of China
| | - Jia Miao
- Japan Research Center for Environmental Quality Management, Graduate School of Engineering, Kyoto University, Kyoto, Japan
| | - Yuepeng Sun
- Department of Chemical and Environmental Engineering, University of California, Riverside, Riverside, CA, USA
| |
Collapse
|
3
|
Chen H, Zeng L, Wang D, Zhou Y, Yang X. Recent advances in nitrous oxide production and mitigation in wastewater treatment. WATER RESEARCH 2020; 184:116168. [PMID: 32683143 DOI: 10.1016/j.watres.2020.116168] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 06/17/2020] [Accepted: 07/10/2020] [Indexed: 05/21/2023]
Abstract
Nitrous oxide (N2O) emitted from wastewater treatment plants has caused widespread concern. Over the past decade, people have made tremendous efforts to discover the microorganisms responsible for N2O production, elucidate metabolic pathways, establish production models and formulate mitigation strategies. The ultimate goal of all these efforts is to shed new light on how N2O is produced and how to reduce it, and one of the best ways is to find key opportunities by integrating the information obtained. This review article critically evaluates the knowledge gained in the field within a decade, especially in N2O production microbiology, biochemistry, models and mitigation strategies, with a focus on denitrification. Previous research has greatly deepened the understanding of the N2O generation mechanism, but further efforts are still needed due to the lack of standardized methodology for establishing N2O mitigation strategies in full-scale systems. One of the challenges seems to be to convert the denitrification process from a net N2O source into an effective sink, which is recommended as a key opportunity to reduce N2O production in this review.
Collapse
Affiliation(s)
- Hongbo Chen
- College of Environment and Resources, Xiangtan University, Xiangtan 411105, China.
| | - Long Zeng
- College of Environment and Resources, Xiangtan University, Xiangtan 411105, China
| | - Dongbo Wang
- College of Environmental Science and Engineering, Hunan University, Changsha 410082, China.
| | - Yaoyu Zhou
- Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China
| | - Xiao Yang
- Korea Biochar Research Center, O-Jeong Eco-Resilience Institute & Division of Environmental Science and Ecological Engineering, Korea University, Seoul 02841, South Korea
| |
Collapse
|