A method for regulating nitrous oxide formation and resource utilization during nitrate wastewater treatment.
By enriching Candidatus Methanoperedens nitroreducens microorganisms and Fe(III), nitrous oxide is generated during the denitrification anaerobic methane oxidation process and co-combusted with biogas, solving the problems of methane emissions and insufficient energy in wastewater treatment, and achieving high efficiency, energy saving and greenhouse gas emission reduction in wastewater treatment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HARBIN INST OF TECH
- Filing Date
- 2024-05-31
- Publication Date
- 2026-06-30
AI Technical Summary
Traditional wastewater treatment processes result in high methane emissions and insufficient energy utilization, as well as low nitrous oxide production, leading to greenhouse effect and energy waste.
By culturing and enriching the microorganism Candidatus Methanoperedens nitroreducens, denitrification and anaerobic methane oxidation were carried out under anaerobic conditions using Fe(III), simultaneously removing nitrates and dissolved methane to generate nitrous oxide, which was then co-combusted with biogas to recover energy.
It achieves simultaneous removal of NO3- and dissolved methane from wastewater, improves energy recovery efficiency, reduces greenhouse gas emissions, and provides an energy self-sufficiency solution for wastewater treatment plants.
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Figure CN118684339B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method for regulating nitrous oxide formation and resource recovery during nitrate wastewater treatment. Background Technology
[0002] Carbon emissions from traditional wastewater treatment already account for 1%–2% of total societal emissions. Therefore, pollution reduction and carbon reduction efforts in the wastewater treatment sector are imperative. Traditional wastewater treatment processes, particularly denitrification, utilize a large amount of organic carbon sources inherent in the wastewater. These organic carbon sources could potentially be converted into methane through anaerobic biological treatment, leading to energy self-sufficiency for wastewater treatment plants. However, 20-60% of the methane produced by anaerobic biological treatment often exists in the effluent, subsequently released into the atmosphere, making wastewater treatment plants significant sources of methane emissions. As a major greenhouse gas, methane contributes 26 times more per mole to the greenhouse effect than CO2. The release of methane from wastewater treatment plants not only causes energy loss but also exacerbates the greenhouse effect. Therefore, energy-efficient and effective denitrification, as well as the effective utilization and control of methane, are essential.
[0003] As a novel, highly efficient, and energy-saving nitrogen removal method, denitrifying anaerobic methane oxidation (DAMO) is a denitrification process that uses methane as an electron donor and nitrate or nitrite as an electron acceptor under anaerobic conditions. It plays a crucial role in global greenhouse gas emission reduction. DAMO utilizes methane as a carbon source to achieve denitrification, providing a solution to the two major problems of methane emissions and insufficient carbon sources in wastewater treatment. New processes developed around DAMO will have significant engineering application value.
[0004] Nitrous oxide (N₂O), as the third largest greenhouse gas in the atmosphere after CO₂ and CH₄, has a global warming potential approximately 298 times that of carbon dioxide on a centennial timescale, exerting a long-term and profound impact on global warming. However, N₂O is also a potential renewable energy source: on the one hand, N₂O itself contains a certain amount of chemical energy, which can be recovered through thermal decomposition; on the other hand, non-flammable N₂O can be used as an oxidizer or additive in co-combustion with other fuels. For example, theoretically, the energy produced by co-combusting nitrous oxide with methane is 37% higher than that produced by co-combusting methane with oxygen. Furthermore, nitrous oxide is also a highly efficient chemical propellant. Nitrous oxide-based oxy-fuel propellants are favored in aerospace propulsion technology due to their numerous superior properties, such as non-toxicity, high specific impulse, and wide temperature range.
[0005] It is worth noting that N2O, as a byproduct of various biological denitrification processes in wastewater, is emitted by urban wastewater treatment plants worldwide at a rate of up to 0.32 Tg annually. Previous studies have shown that N2O production can also be detected during the enrichment culture of DAMO microorganisms, but the amount produced is very low. Summary of the Invention
[0006] The purpose of this invention is to provide a method for controlling nitrous oxide formation and resource recovery during nitrate wastewater treatment. This method can reduce NO3 in wastewater... - Simultaneous removal of dissolved methane generates nitrous oxide, which is then co-combusted with biogas produced from the anaerobic digestion of sludge, increasing energy recovery and providing a solution for achieving energy self-sufficiency in wastewater treatment plants.
[0007] The present invention discloses a method for regulating and recycling nitrous oxide formation during nitrate wastewater treatment, the method comprising the following steps:
[0008] Step 1: Cultivate and enrich to obtain a culture containing Candidatus Methanoperedens nitroreducens;
[0009] Step 2: Add the nitrate wastewater to be treated, the anaerobic digestion effluent containing dissolved methane, Fe(III), and the culture obtained from Step 1 to the reactor for denitrification anaerobic methane oxidation treatment, which removes nitrogen and generates nitrous oxide at the same time.
[0010] Step 3: Monitor the nitrous oxide content in the reactor. When the nitrous oxide content reaches a plateau, it can be recovered and co-combusted with the biogas produced by anaerobic digestion for combined heat and power generation.
[0011] Furthermore, the enrichment and cultivation method described in step one is as follows:
[0012] A mixture of sediment from paddy field ditches, freshwater riverbeds, and activated sludge from secondary sedimentation tanks of wastewater treatment plants was inoculated into a reactor. The inoculum and basal culture medium were stirred and mixed. The reactor pH was maintained at 7.0–8.0, and the temperature at 31–33°C. After adjustment, the reactor was incubated. During incubation, a mixed gas containing 95% CH4 and 5% CO2 was introduced into the reactor to maintain the headspace pressure at 100–110 kPa. The nitrate concentration in the reactor was maintained at 10–250 mg NO3 by adding concentrated nitrate solution to the reactor in batches. - -N·L -1 between.
[0013] Furthermore, the nitrate concentration in the reactor is maintained at 50–200 mg NO3. - N·L -1between.
[0014] Furthermore, the volume ratio of the bottom sediment of the paddy field ditch, the bottom sediment of the freshwater river, and the activated sludge of the secondary sedimentation tank of the sewage treatment plant is 1:1:1.
[0015] Furthermore, the basal culture medium is composed of a concentration of 0.07–0.08 g·L⁻¹. -l KH₂PO₄ at a concentration of 0.2–0.4 g·L⁻¹ -l The CaCl2·2H2O concentration was 0.16–0.17 g·L. -l MgCl2·6H2O, with a concentration of 0.4–0.6 mL·L. -l Acidic trace solutions with concentrations of 0.1–0.3 mL / L -l It consists of a trace amount of alkaline solution.
[0016] Furthermore, during the cultivation process, the reactor culture is collected and sequenced to determine the enriched culture components, ensuring that the culture contains the required Candidatus Methanoperedens nitroreducens.
[0017] Furthermore, during the cultivation period, the basal medium was replaced with fresh basal medium every 15-20 days. After adding fresh basal medium, the gas was first aerated with high-purity nitrogen for 25 minutes, and then a mixed gas of 95% CH4 and 5% CO2 was introduced to replace the nitrogen in the headspace phase of the reactor.
[0018] Furthermore, the amount of Fe(III) added is related to the NO3 in the wastewater. - The molar ratio of the contents is 0.10.
[0019] Furthermore, the denitrification anaerobic methane oxidation treatment is carried out under conditions of pH 7.0-8.0 and temperature 31-33℃.
[0020] Furthermore, during the nitrification anaerobic methane oxidation process, the reactor is flushed with a gas mixture containing 95% CH4 and 5% CO2 to replenish methane.
[0021] The present invention has the following beneficial effects:
[0022] This invention utilizes a DAMO culture, primarily composed of Candidatus Methanoperedens nitroreducens (DAMO archaea), enriched and supplemented with Fe(III), to treat nitrate wastewater and anaerobic digestion effluent, thereby reducing NO3 in the wastewater. - Simultaneous removal of dissolved methane, while generating N2O.
[0023] The N2O generated by this invention can be co-combusted with the biogas produced by the anaerobic digestion of sludge, increasing energy recovery and providing a solution for achieving energy self-sufficiency in wastewater treatment plants.
[0024] After adding ferrous sulfate, all nitrates are removed, with a maximum NO3 content of up to 46.5%. - Reduced to N2O (with) Figure 2 ). Attached Figure Description
[0025] Figure 1 A graph showing the concentration of N2O after adding Fe(III) to a reactor operated under laboratory conditions according to the method of the present invention;
[0026] Figure 2 The following are fitted graphs of N2O consumption and productivity in a denitrifying anaerobic methane oxidation bioreactor: A, N2O consumption curve tested one day before the addition of Fe(III); B, N2O consumption rate fitting based on the Michaelis-Menten model; C, N2O accumulation rate fitting for the first 4 days after the addition of Fe(III).
[0027] Figure 3 This is a schematic diagram illustrating the generation and resource utilization of nitrous oxide in the denitrification anaerobic methane oxidation process of the present invention. Detailed Implementation
[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the spirit of the contents disclosed in the present invention will be described in detail below. After understanding the embodiments of the present invention, any person skilled in the art can make changes and modifications based on the technology taught in the present invention without departing from the spirit and scope of the present invention.
[0029] The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.
[0030] Example:
[0031] The following is a method for controlling nitrous oxide formation and resource recovery during nitrate wastewater treatment in this embodiment:
[0032] 150 mL of DAMO culture, primarily composed of *Candidatus Methanoperedens nitroreducens* (DAMO archaea), was inoculated into a 327 mL CSTR reactor. The reactor was initially fed only with synthetic medium containing nitrate, followed by the addition of Fe(III). The loading rates of nitrate and ferric iron were 16.8 mg N·L. -1 ·d -1and 6.7 mg Fe·L -1 ·d -1 The reactor was continuously mixed using a magnetic stirrer at 300 rpm, with a pH of 7.0–8.0 and a temperature of 32 ± 1.0 °C. Methane was replenished by flushing the reactor with a gas mixture containing 95% CH4 and 5% CO2.
[0033] The N2O concentration in the reactor liquid was continuously measured every 60 seconds using an N2O microelectrode (model: N2O-R, measurement range: 0-500 μM, detection limit: 0.1 μM, Unisense, Denmark). Approximately 1 mL of reactor liquid was collected daily for NH4 analysis. + NO2 - and NO3 - Chemical analysis.
[0034] After the addition of ferric iron, an initial increase in N2O was observed, which continued until day 6, then gradually decreased until it became undetectable on day 14 (see appendix). Figure 1 Based on the simulated N2O consumption and accumulation rate (see appendix) Figure 2 Within 4 days of adding ferric iron, up to 46.5% of the nitrates were reduced to N2O.
Claims
1. A method for regulating nitrous oxide formation and resource utilization during nitrate wastewater treatment, characterized in that... The method is performed according to the following steps: Step 1: Cultivate and enrich to obtain a culture containing Candidatus Methanoperedens nitroreducens; The method for culturing and enriching to obtain a culture containing Candidatus Methanoperedens nitroreducens is as follows: A mixture of sediment from paddy field ditches, freshwater riverbeds, and activated sludge from secondary sedimentation tanks of wastewater treatment plants was inoculated into the reactor. The inoculum and basal culture medium were stirred and mixed. The reactor pH was maintained at 7.0–8.0, and the temperature at 31–33°C. After adjustment, the reactor was incubated. During incubation, a mixed gas containing 95% CH4 and 5% CO2 was introduced into the reactor to maintain the headspace pressure at 100–110 kPa. The nitrate concentration in the reactor was maintained at 10–250 mg NO3 by adding concentrated nitrate solution to the reactor in batches. - -N·L -1 between; Step 2: The nitrate wastewater to be treated, the anaerobic digestion effluent containing dissolved methane, Fe(III), and the culture obtained from Step 1 are added to the reactor for denitrification anaerobic methane oxidation treatment, removing nitrogen while generating nitrous oxide; the amount of Fe(III) added is related to the NO3 in the wastewater. - The molar ratio of the contents is 0.10; Step 3: Monitor the nitrous oxide content in the reactor. When the nitrous oxide content reaches a plateau, it can be recovered and co-combusted with the biogas produced by anaerobic digestion for combined heat and power generation.
2. The method for regulating nitrous oxide formation and resource utilization during nitrate wastewater treatment according to claim 1, characterized in that... Maintain the nitrate concentration in the reactor at 50-200 mg NO3. - -N·L -1 between.
3. The method for regulating nitrous oxide formation and resource utilization during nitrate wastewater treatment according to claim 1, characterized in that... The volume ratio of the bottom mud from paddy field ditches, the bottom mud from freshwater rivers, and the activated sludge from the secondary sedimentation tank of the sewage treatment plant is 1:1:
1.
4. The method for regulating nitrous oxide formation and resource utilization during nitrate wastewater treatment according to claim 1, characterized in that... The basal culture medium is composed of a concentration of 0.07~0.08 g·L⁻¹. -l KH₂PO₄ at a concentration of 0.2–0.4 g·L⁻¹ -l The CaCl2·2H2O concentration was 0.16~0.17 g·L. -l MgCl2·6H2O, with a concentration of 0.4~0.6 mL·L -l Acidic trace solutions with concentrations of 0.1–0.3 mL·L -l It consists of a trace amount of alkaline solution.
5. The method for regulating nitrous oxide formation and resource utilization during nitrate wastewater treatment according to claim 1, characterized in that... During the cultivation process, reactor cultures are collected and sequenced to determine the enriched culture components, ensuring that the cultures contain the required Candidatus Methanoperedens nitroreducens.
6. The method for regulating nitrous oxide formation and resource utilization during nitrate wastewater treatment according to claim 1, characterized in that... During the cultivation period, the basal medium was replaced with fresh basal medium every 15-20 days. After adding fresh basal medium, the gas was first aerated with high-purity nitrogen for 25 minutes, and then a mixed gas of 95% CH4 and 5% CO2 was introduced to replace the nitrogen in the headspace phase of the reactor.
7. The method for regulating nitrous oxide formation and resource utilization during nitrate wastewater treatment according to claim 1, characterized in that... The denitrification anaerobic methane oxidation treatment was carried out under conditions of pH 7.0-8.0 and temperature 31-33℃.
8. The method for regulating nitrous oxide formation and resource utilization during nitrate wastewater treatment according to claim 1, characterized in that... In the denitrification anaerobic methane oxidation process, the reactor is flushed with a gas mixture containing 95% CH4 and 5% CO2 to replenish methane.