Evaluation of stable isotope ratios (δ15N and δ18O) of nitrate in advanced sewage treatment processes: Isotopic signature in four process types
| Autor: | Kazuaki Syutsubo, Takashi Onodera, Gen Kanaya, Motoyuki Mizuochi, Ayato Kohzu, Kazuhiro Komatsu |
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| Rok vydání: | 2021 |
| Předmět: |
Environmental Engineering
Denitrification 010504 meteorology & atmospheric sciences Chemistry Stable isotope ratio 010501 environmental sciences 01 natural sciences Pollution Anoxic waters Isotopic signature chemistry.chemical_compound Activated sludge Nitrate Environmental chemistry Environmental Chemistry Nitrification Extended aeration Waste Management and Disposal 0105 earth and related environmental sciences |
| Zdroj: | Science of The Total Environment. 762:144120 |
| ISSN: | 0048-9697 |
| Popis: | Stable isotope ratios of nitrate are a powerful tool to evaluate aquatic environment stress from treated and untreated sewage. However, there is generally a lack of knowledge on the change in stable isotope ratios within wastewater treatment plants. We investigated nitrogen and oxygen stable isotope ratios (δ15N and δ18O) of nitrate in four types of advanced treatment processes operated in parallel; (A) extended aeration activated sludge, (B) anaerobic-anoxic-aerobic (A2O), (C) recycled nitrification-denitrification, and (D) modified Bardenpho. The results exhibited spatial variation of δ15N and δ18O for nitrate within the treatment steps. The changes in δ15N and δ18O may result from the reactor conditions (aerobic, anoxic, and anaerobic) and the order of these processes. As decreasing nitrate concentration in the anoxic stages, the δ15N/δ18O ratio for nitrate increased at a rate of 1.3 to 1.6 coupling with the reduction in the nitrate concentration in the anoxic stages. The δ15N and δ18O signatures were attributed to process performance in regard to nitrogen removal. In particular, the modified Bardenpho process has higher nitrogen removal efficiency over other processes, producing effluent with lower nitrate concentration and higher stable isotopes (δ15N: 23.6 to 25.5‰, δ18O: 2.8 to 4.5‰). We concluded that the stable isotope signatures mirrored the treatment efficiency and effluent characteristics. |
| Databáze: | OpenAIRE |
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