Flue gas denitration and wastewater dephenolization method based on microbial synergistic effect

Abstract

The invention discloses a method for flue gas denitrification and wastewater dephenolization based on a microbial synergistic effect, which comprises the following steps: constructing an oxidation absorption coupling biological reduction flue gas denitrification system which comprises a strain JR1, flue gas containing NOx and wastewater containing phenolic compounds; nOx is converted into nitrate and nitrite by the strain JR1 through an oxidation absorption effect, and the nitrate and the nitrite become a nitrogen source required by growth and reproduction of the strain JR1; phenolic compounds in wastewater are used as a carbon source required by the denitrification process of the strain JR1. According to the method, an aerobic denitrification strain JR1 with synchronous phenol and nitrogen removal capability is utilized, the strain JR1 is put into an oxidation absorption coupling biological reduction flue gas denitrification system, phenol-containing wastewater is used for replacing organic nutrient substances required by the strain, a carbon source does not need to be additionally added in the process of denitrification by utilizing aerobic denitrifying bacteria, and the purpose of wastewater dephenolization is achieved; and the aim of synchronously removing phenol and denitrifying is fulfilled.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas and wastewater pollutant prevention and control, and more specifically, to a method for denitrifying flue gas and removing phenol from wastewater based on the synergistic effect of microorganisms. Background Art

[0002] Nitrogen oxides (NO x ) are one of the main pollutants in ambient air, and the flue gas generated by coal-fired power plants is considered to be the main source of NO in the atmosphere. x The large-scale emission of NO x can lead to various ecological and environmental problems such as photochemical smog, acid rain, and ozone layer depletion. Therefore, it is crucial to develop effective NO x control measures.

[0003] Currently, due to its advantages such as low investment and operation costs and no secondary pollution, the biological method has become a research hotspot for NO x removal at home and abroad. However, since the main component NO in flue gas has a low solubility in water, even if the microbial reduction rate is high, it is still limited by the gas-liquid mass transfer rate, resulting in an unsatisfactory actual NO x removal effect.

[0004] To address the shortcomings of the biological denitrification method, an integrated flue gas denitrification system using chemical absorption - biological reduction has been developed. This method is based on the complexing agent Fe(II)EDTA, which complexes NO to form the Fe(II)EDTA-NO complex, and then reduces NO to N 2 through the action of microorganisms in a biological filter to achieve the regeneration of the complexing agent. However, the actual flue gas usually contains 3 - 8 vol% of oxygen, and the complexing agent is particularly prone to oxidation by the oxygen contained in the flue gas itself, thereby losing the ability to complex NO. Therefore, this method is far from being applicable to industrial scale.

[0005] Existing research results show that when the conversion rate of NO in flue gas is 50 - 60%, the absorption efficiency and absorption rate of NO x in alkaline solution are the highest. After NO x is absorbed by water or alkaline solution, nitrates or nitrites are formed in the liquid phase, and aerobic denitrifying bacteria can be used to remove nitrogen oxides in the liquid phase. The inventor has previously successfully constructed an oxidation absorption-coupled biological reduction system for flue gas denitrification, and has conducted a systematic analysis from aspects such as performance optimization and action mechanism, clarified the optimal operating conditions for the stable operation of the oxidation absorption - biological trickling filter tower, revealed the role of microorganisms in the nitrogen metabolism process, and elucidated the reaction mechanism of NO x removal. This denitrification method solves the problems of low NO mass transfer efficiency and aerobic inhibition of NO x removal while achieving high-efficiency NO x removal.

[0006] However, in the process of using an oxidation-absorption coupled biological reduction system for flue gas denitrification, there is a problem, that is, microorganisms in this system must ingest ready-made organic matter to maintain their growth and reproduction. Therefore, when using the oxidation-absorption coupled biological reduction system to remove NO from flue gas x an additional carbon source needs to be added to this system to provide energy for heterotrophic microorganisms. And the way of adding an external carbon source greatly increases the investment cost.

[0007] Considering that many actual industrial wastewaters such as coking wastewater (Table 1-1) itself contain a large amount of organic substances, such as phenolic organic substances, and the most representative one is phenol. Phenolic organic substances such as phenol are highly toxic to animals, plants and humans, seriously disrupting the ecological balance. Therefore, achieving the efficient removal of phenolic organic substances in industrial wastewater is also one of the current research hotspots at home and abroad.

[0008] Table 1-1 Water quality characteristics of wastewater from typical domestic coking enterprises

[0009] Currently, the treatment methods for phenolic wastewater at home and abroad mainly include physical methods, chemical methods and biological methods. In recent years, it has been found that more and more microorganisms can use phenol as the sole carbon source and energy source for metabolism, making the biological method a relatively widespread treatment method. Yamagishi et al. achieved the complete degradation of phenol by activated sludge through cross-flow filtration, and accompanied by the nitrification of ammonia nitrogen into nitrate salts. In addition, this method is also conducive to promoting denitrification. The strain Cupriavidus oxalaticus T2 isolated by Yan et al. can simultaneously remove 69 mg / L of NO 3 - -N and 1000 mg / L of phenol, and pointed out that this strain degrades phenol through the ortho pathway and removes nitrate through two pathways: denitrification and dissimilatory reduction of nitrate nitrogen. These research results provide strong evidence for the denitrification process of heterotrophic bacteria using phenol as a carbon source.

[0010] Existing research on the performance of using heterotrophic denitrifying bacteria to degrade phenol and the performance of flue gas denitrification are all independent and carried out separately. There is no report on the research of using the same denitrifying bacteria to simultaneously remove phenol in wastewater and NO in flue gas x Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide a method for flue gas denitrification and wastewater dephenolization based on the synergistic effect of microorganisms, using phenolic wastewater to replace the organic nutrients required by the strain, achieving the purpose of simultaneous phenol removal and denitrification.

[0012] ​To solve the above technical problems, the present invention provides a method for denitrifying flue gas and removing phenol from wastewater based on the synergistic effect of microorganisms, which constructs an oxidation absorption coupled biological reduction flue gas denitrification system. This system includes Acinetobacter sp strain JR1, flue gas containing NOx, and wastewater containing phenolic compounds. Strain JR1 converts NOx into nitrate and nitrite through oxidation absorption, which becomes the nitrogen source required for the growth and reproduction of strain JR1; phenolic compounds in the wastewater are used as the carbon source required for the denitrification process of strain JR1.

[0013] Furthermore, the gene sequence of strain JR1 is SEQ ID NO: 1.

[0014] Furthermore, in the oxidation absorption coupled biological reduction flue gas denitrification system, 0 < nitrite nitrogen concentration ≤ 1000 mg / L.

[0015] Furthermore, in the oxidation absorption coupled biological reduction flue gas denitrification system, 0 < nitrite nitrogen concentration ≤ 300 mg / L.

[0016] Furthermore, in the oxidation absorption coupled biological reduction flue gas denitrification system, 0 < phenol concentration < 350 mg / L.

[0017] Furthermore, in the oxidation absorption coupled biological reduction flue gas denitrification system, 0 < phenol concentration ≤ 200 mg / L.

[0018] Furthermore, in the oxidation absorption coupled biological reduction flue gas denitrification system, the circulating nutrient solution for bacterial growth includes 0.2 g / L of phenol, NaH 2 PO 4 ·2H 2 O 0.25 g / L, K 2 HPO 4 ·3H 2 O 0.750 g / L, FeSO 4 ·7H 2 O 0.050 g / L, NaCl 0.120 g / L, MgSO 4 ·7H 2 O 0.050 g / L, MnSO 4 ·H 2 O 0.010 g / L, NaHCO 3 1.68 g / L.

[0019] Using the aerobic denitrifying strain JR1 with the ability of synchronous phenol removal and denitrification, the strain JR1 was introduced into the oxidation-absorption coupled biological reduction flue gas denitrification system. Phenol-containing wastewater was used to replace the organic nutrients required by the strain, and no additional carbon source was needed during the denitrification process using aerobic denitrifying bacteria, achieving the purpose of phenol removal from wastewater and synchronous phenol removal and denitrification. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Effect diagram of strain JR1 removing different nitrite nitrogen concentrations; Figure 2 It is the effect diagram of strain JR1 removing different phenol concentrations; Figure 3 It is a schematic diagram of the oxidation-absorption coupled biological reduction flue gas denitrification system involved in the embodiment of the present invention; In the figure, 1 - gas cylinder, 2 - mass flowmeter, 3 - gas mixer, 4 - temperature control system, 5 - pump, 6 - circulating liquid storage tank, 7 - peristaltic pump, 8 - biological trickling filter tower, 9 - flue gas analyzer; Figure 4 It is a comparison diagram before and after the packing is coated with a film. (A) is the packing before film coating, (B) is the packing after film coating, (C) is the electron microscope image of the packing before film coating, and (D) is the electron microscope image of the packing after film coating; Figure 5 It is a mass spectrometry diagram of the substances contained in the outlet gas of the oxidation-absorption coupled biological reduction flue gas denitrification system; Figure 6 It is a mass spectrometry diagram of the substances contained in the outlet gas of the oxidation-absorption coupled biological reduction system. DETAILED DESCRIPTION OF THE INVENTION

[0021] The process of using oxidation-absorption coupled with heterotrophic microbial denitrification is an effective method for removing NOx from flue gas, but the addition of an external carbon source limits its popularization and application. Using phenolic compounds in industrial wastewater such as coking wastewater as a carbon source will provide a new way for the oxidation-absorption coupled biological reduction system to remove NOx from flue gas.

[0022] Based on this, a method for flue gas denitrification and wastewater phenol removal based on microbial synergy provided by a typical embodiment of the present invention can synchronously achieve phenol removal from actual coking wastewater and flue gas denitrification.

[0023] In this embodiment, an oxidation-absorption coupled biological reduction flue gas denitrification system was constructed, which includes strain JR1, flue gas containing NOx, and wastewater containing phenolic compounds. In this system, strain JR1 converts NOx into nitrate and nitrite through oxidation-absorption, which becomes the nitrogen source required for the growth and reproduction of strain JR1; phenolic compounds contained in the wastewater are used as the carbon source required for the denitrification process of strain JR1.

[0024] The gene sequence of the above-mentioned strain JR1 is SEQ ID NO: 1, and the gene sequence characteristics are as shown in the sequence listing.

[0025] The 16S rRNA gene of strain JR1 was obtained by PCR amplification, and its DNA sequence (1451 bp) was deposited in the GenBank database under the accession number MG188323. After gene alignment, strain JR1 was classified as Acinetobacter sp.

[0026] In the prior art, it has been determined that the above-mentioned strain JR1 has excellent aerobic denitrification ability. As Figure 1 shown, in the aerobic denitrification process of strain JR1 using different nitrite nitrogen concentrations as the sole nitrogen source, the results show that when the nitrite nitrogen concentration is lower than 300 mg / L, it can be completely degraded. After that, as the nitrite nitrogen concentration increases, the removal efficiency begins to decline. When the nitrite nitrogen concentration reaches 1000 mg / L, the nitrogen removal efficiency is about 70%. It can be seen that strain JR1 can tolerate high concentrations of nitrogen.

[0027] On this basis, the present invention focuses on studying the phenol removal ability of this strain, and puts this strain into a biotrickling filter to establish an oxidation-absorption coupled biological reduction system, and uses strain JR1 to achieve the synchronous phenol and denitrification process in the oxidation-absorption biotrickling filter.

[0028] Figure 2 It is the effect diagram of strain JR1 removing different phenol concentrations. The results show that when the phenol concentration is lower than 200 mg / L, it can be completely degraded. After that, as the phenol concentration increases, the phenol removal efficiency begins to decline. When the phenol concentration reaches 350 mg / L, the strain cannot grow and reproduce.

[0029] According to the above analysis of using biological methods for flue gas denitrification and phenol degradation, the following examples mainly use a strain JR1 with synchronous phenol and nitrogen removal performance and put it into a biotrickling filter. Through the oxidation-absorption effect, NOx in the gas phase is converted into nitrates and nitrites in the liquid phase, which become the nitrogen source required for the growth and reproduction of strain JR1. Then, the organic pollutant phenol in industrial wastewater is used as the carbon source required for the denitrification process of strain JR1. This method not only solves the problems of low NO mass transfer efficiency and the need to add additional carbon sources to increase operating costs faced in the biological denitrification process at the same time. Most importantly, this method realizes the synchronous removal of the toxic organic substance phenol while achieving denitrification.

[0030] As Figure 3 shown, the oxidation-absorption coupled biological reduction flue gas denitrification system includes a biotrickling filter 8. The inside of the biotrickling filter 8 is provided with polyurethane sponge packing. After the packing is successfully film-coated, flue gas is started to be introduced. The schematic diagrams before and after the packing is film-coated are as Figure 4As shown in the figure, a large number of microorganisms were significantly attached to the surface of the packing after biofilm formation. The phenol-containing circulating nutrient solution was sprayed into the biological trickling filter tower 8 from the top through a peristaltic pump 7 and a spraying device, and flowed back to the circulating liquid storage tank 6 from the bottom of the biological trickling filter tower 8. The bottom and top of the biological trickling filter tower 8 were respectively connected to the inlet flue gas pipeline and the outlet flue gas pipeline, and the gaseous flue gas was input into the biological trickling filter tower 8 from the inlet flue gas pipeline. The flue gas and the phenol-containing wastewater were in countercurrent contact.

[0031] In this embodiment, the strain JR1 was put into the biological trickling filter tower for biofilm formation. After successful biofilm formation, simulated flue gas was introduced. The composition of the simulated flue gas included 250 ppm NO, 250 ppm NO 2 , 5% O 2 , 15% CO 2 , and the rest was N 2 . The flow rate of the simulated flue gas was 1 L / min. Phenol was used instead of organic nutrients, and the synchronous denitrification and phenol removal experiment was carried out using this device.

[0032] The circulating nutrient solution for bacterial growth included 0.2 g / L of phenol, NaH 2 PO 4 ·2H 2 O 0.25 g / L, K 2 HPO 4 ·3H 2 O 0.750 g / L, FeSO 4 ·7H 2 O 0.050 g / L, NaCl 0.120 g / L, MgSO 4 ·7H 2 O 0.050 g / L, MnSO 4 ·H 2 O 0.010 g / L, NaHCO 3 1.68 g / L, and 1.68 g / L of NaHCO 3 (99.5%) was added as a chemical absorbent.

[0033] Figure 5 is the effect diagram of synchronous denitrification and phenol removal. The inlet flue gas contained NO and NO 2 with concentrations of 250 ppm respectively, the phenol concentration in the wastewater was 200 mg / L, and the phenol-containing circulating nutrient solution was 6 L. In the initial stage of operation of the oxidation absorption-biological reduction system, there was about 20 ppm of NO remaining in the outlet flue gas. After 5 days of operation, the NOx concentration in the outlet flue gas was basically zero, and the phenol in the circulating liquid could be completely degraded within 20 days of stable operation. The results showed that the system could operate stably, and almost all of the NOx in the flue gas outlet and phenol in the wastewater could be removed, achieving the purpose of synchronous phenol removal and denitrification.

[0034] As Figure 6As shown, a mass spectrometer was used to qualitatively analyze the gas components at the outlet of the oxidation-absorption biological reduction system. In the figure, 100% relative abundance represents the equilibrium gas argon in the system, that is, m / z of 40 represents the main ion fragment of the equilibrium gas Ar. And m / z of 28 represents the ion fragment of N 2 . As can be seen from the figure, except for the equilibrium gas argon, the highest relative abundance in the gas at the outlet of the system is N 2 . The generation of N 2 is of great significance for understanding the complex NOx conversion path, indicating that NO x is mainly discharged in the form of N 2 after the action of strain JR1. m / z of 44 represents the ion fragment of CO 2 , indicating that phenol in the liquid phase is mainly discharged in the form of CO 2 after the action of strain JR1.

Claims

1. A method for flue gas denitrification and wastewater dephenolization based on microbial synergy, characterized in that: An oxidation-absorption coupled bioreduction flue gas denitrification system was constructed, which included Acinetobacter sp strain JR1, flue gas containing NOx and wastewater containing phenolic compounds; Strain JR1 converts NOx into nitrate and nitrite through oxidation absorption, which becomes the nitrogen source required for the growth and reproduction of strain JR1; and uses phenolic compounds in wastewater as the carbon source required for the denitrification process of strain JR1.

2. The method according to claim 1, characterized in that: The gene sequence of strain JR1 is SEQ ID NO:

1.

3. The method according to claim 1 or 2, characterized in that: In the oxidation-absorption coupled biological reduction flue gas denitrification system, 0<nitrite nitrogen concentration≤1000 mg / L.

4. The method according to claim 3, characterized in that: In the oxidation-absorption coupled biological reduction flue gas denitrification system, 0<nitrite nitrogen concentration≤300 mg / L.

5. The method according to claim 1 or 4, characterized in that: In the oxidation-absorption coupled biological reduction flue gas denitrification system, 0<phenol concentration<350 mg / L.

6. The method according to claim 5, characterized in that: In the oxidation-absorption coupled biological reduction flue gas denitrification system, 0<phenol concentration≤200 mg / L.

7. The method according to claim 1 or 6, characterized in that: In the oxidation-absorption coupled biological reduction flue gas denitrification system, the circulating nutrient solution for bacterial growth includes 0.2 g / L of phenol, 0.25 g / L of NaH2PO4·2H2O, 0.750 g / L of K2HPO4·3H2O, 0.050 g / L of FeSO4·7H2O, 0.120 g / L of NaCl, 0.050 g / L of MgSO4·7H2O, 0.010 g / L of MnSO4·H2O, and 1.68 g / L of NaHCO3.

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