Method for relieving ammonia nitrogen inhibition in anaerobic digestion by using signal molecules and biochar and application of method

Abstract

The invention discloses a method for relieving anaerobic digestion ammonia nitrogen inhibition by using signal molecules and biochar and application of the method, and belongs to the field of environmental engineering and organic waste resource treatment. The method for relieving ammonia nitrogen inhibition in the anaerobic digestion process comprises the following steps: in an anaerobic digestion reactor, adding a substrate cyanobacteria liquid, inoculating anaerobic sludge, signal molecules and charcoal, adjusting the pH value to 7-8, then carrying out medium-temperature anaerobic digestion on the anaerobic reactor, setting the temperature to 30-40 DEG C, and setting the oscillation rotating speed to 100-300 rpm; wherein the concentration of ammonia nitrogen in the anaerobic reactor is 5000-7000 mg NH4 < + >-N / L; and the signal molecules are any one or more of C4-HSL, C6-HSL, C8-HSL and 3OC6-HSL. According to the method, the cost is reduced, and meanwhile, the inhibition effect of high ammonia nitrogen concentration on an anaerobic digestion system is effectively relieved by exogenously adding signal molecules and biochar.

Description

Technical Field

[0001] The invention relates to a method for alleviating ammonia nitrogen inhibition in anaerobic digestion by utilizing signal molecules and biochar and application thereof, and belongs to the field of environmental engineering and resource disposal of organic waste. Background Art

[0002] With the intensification of urbanization and industrialization in the Taihu Lake Basin, a large amount of nitrogen and phosphorus nutrients are input into Taihu Lake from agricultural emissions, urban sewage, industrial wastewater, and fertilizer use, and cyanobacteria blooms frequently occur. Currently, anaerobic digestion technology is considered to be a low-cost and relatively mature technology for the resource utilization of organic solid waste. However, it is still challenging to efficiently complete the anaerobic digestion process using Taihu cyanobacteria as substrate.

[0003] The protein content of cyanobacterial biomass is high, which will be degraded into ammonia nitrogen during anaerobic digestion. Excessive ammonia nitrogen will inhibit the activity of microorganisms in the anaerobic digestion process, eventually causing the anaerobic digestion process to be disordered and the biogas production to be significantly reduced. Specifically, the stable operation of the anaerobic digestion system mainly depends on the synergistic effect of microorganisms such as hydrolytic fermentation bacteria, acid-producing bacteria and methanogens under normal physiological activities, among which methanogens have the worst tolerance to the concentration of ammonia nitrogen in the system. High concentrations of ammonia nitrogen will seriously affect the activity of methanogens, resulting in an imbalance in the anaerobic digestion process under the synergistic effect of multiple microorganisms, and a large accumulation of volatile fatty acids (VFAs), which further affects the microbial environment of the anaerobic digestion system. Studies have shown that when the concentration of total ammonia nitrogen in the anaerobic reactor exceeds 3000 mg / L, the system's methanogenic performance decreases significantly, and the relative abundance of acetic acid-trophic methanogens Methanosaeta has been significantly reduced.

[0004] How to alleviate the inhibitory effect of ammonia nitrogen in the anaerobic digestion process with low cost and high efficiency has become a major problem that troubles people. Summary of the invention

[0005] [Technical issues]

[0006] In the prior art, the main measures to alleviate the inhibitory effect of high concentration of ammonia nitrogen on anaerobic digestion include optimizing operating parameters, co-digestion of multiple substrates, supplementing trace elements, adding zeolite, microbial acclimation and bio-augmentation, etc. However, they also have their own shortcomings: complex reaction system operation, increased difficulty in operation and management, limited inhibition alleviation effect, long microbial acclimation time and high operation and processing costs.

[0007] [Technical solution]

[0008] In order to solve the above problems, the purpose of the present invention is to provide a method for alleviating ammonia nitrogen inhibition during anaerobic digestion by using signal molecules and biochar.

[0009] The method specifically regulates the behavior of anaerobic microbial flora and improves the structure of microbial communities by exogenously adding signal molecules, thereby enhancing their ability to resist the toxicity of high concentrations of ammonia nitrogen, thereby alleviating the inhibitory effect of ammonia nitrogen in the anaerobic digestion process. In addition, in order to reduce the cost of exogenously added signal molecules, cyanobacteria biochar prepared from cyanobacteria waste as raw materials was added; while reducing costs, the synergistic effect of exogenous signal molecules and biochar further effectively alleviated the inhibitory effect of high ammonia nitrogen concentrations on the anaerobic digestion system.

[0010] In order to achieve the above purpose, the technical solutions provided are as follows:

[0011] The present invention provides a method for alleviating ammonia nitrogen inhibition during anaerobic digestion by using signal molecules and biochar, the method comprising the following steps:

[0012] In the anaerobic digestion reactor, substrate cyanobacteria liquid, inoculated anaerobic sludge, signal molecules and biochar were added, and the pH was adjusted to 7-8. Then, the anaerobic reactor was subjected to mesophilic anaerobic digestion, the temperature was set to 30-40°C, and the oscillation speed was set to 100-300 rpm; the ammonia nitrogen concentration in the anaerobic reactor was 5000-7000 mg NH 4 + -N / L; the signal molecule is any one or more of C4-HSL, C6-HSL, C8-HSL and 3OC6-HSL.

[0013] In one embodiment, the biochar is any one or more of activated carbon, hydrothermal carbon and cyanobacteria biochar; preferably cyanobacteria biochar.

[0014] In one embodiment, the signaling molecule is 3OC6-HSL.

[0015] In one embodiment, the substrate cyanobacteria liquid is cyanobacteria waste collected from the Taihu algae-water separation station, which is then subjected to alkali pretreatment, with the pH controlled at 10 to 12 for a treatment time of 12 to 24 hours.

[0016] In one embodiment, the inoculated anaerobic sludge is taken from the bottom of an upflow anaerobic sludge reactor (UASB) of Jiangsu Guoxin Xielian Energy Co., Ltd. in Yixing City, which operates at a medium temperature of 30-40°C and uses citric acid industrial wastewater as a substrate; after the sludge is retrieved, it is placed in a shaking incubator at 30-40°C for acclimatization for 7-8 days.

[0017] In one embodiment, the preparation of the cyanobacteria biochar includes: drying the Taihu cyanobacteria at high temperature, grinding it into powder, mixing it with KOH, adding it into a tube furnace and heating it, then washing it with deionized water and drying it, and sieving it to obtain the cyanobacteria biochar.

[0018] In one embodiment, the high temperature drying temperature is 100-110°C.

[0019] In one embodiment, the powder and KOH are mixed in a mass ratio of 2:1, the heating temperature in the tube furnace is 400-600°C for 60-90 minutes, then maintained at 800-900°C for 2-3 hours, and the subsequent drying temperature is 105°C.

[0020] In one embodiment, 50 mL of inoculated anaerobic sludge and 75 mL of substrate cyanobacteria liquid are added to every 200 mL of working volume in the anaerobic digestion reactor.

[0021] In one embodiment, the amount of cyanobacteria biochar added to the anaerobic digestion reactor is 4.0 g / L; the amount of signal molecule 3OC6-HSL added is 0.1 μmol / L.

[0022] In one embodiment, the anaerobic reactor is placed in a constant temperature culture shaker for mesophilic anaerobic digestion, the temperature is set at 37° C., and the shaking speed is set at 125 rpm.

[0023] The invention also provides an application of the method in the anaerobic digestion process of organic solid waste.

[0024] Beneficial effects of the present invention:

[0025] (1) The present invention uses Taihu cyanobacteria with high ammonia nitrogen concentration as a substrate for anaerobic digestion. By adding signal molecules and biochar into the anaerobic digestion reactor, the inhibitory effect of a large amount of ammonia nitrogen produced by Taihu cyanobacteria on the anaerobic digestion process is effectively alleviated; wherein, the exogenously added signal molecules regulate the behavior of the anaerobic microbial flora and improve the microbial community structure, thereby alleviating the inhibitory effect of ammonia nitrogen in the anaerobic digestion process; the addition of cyanobacterial biochar, on the one hand, reduces the cost of adding signal molecules, and at the same time, the cyanobacterial biochar can also cooperate with the exogenous signal molecules to further promote the alleviation of the inhibitory effect of high ammonia nitrogen concentration on the anaerobic digestion system;

[0026] (2) The method of alleviating ammonia nitrogen inhibition in anaerobic digestion of the present invention effectively improves the activity of key functional anaerobic microorganisms, and at the same time achieves an increase in methane production, significantly alleviating the ammonia nitrogen inhibition in the anaerobic digestion process; wherein, in an anaerobic digestion reactor with a working volume of 200 ml, 0.1 μmol / L 3OC6-HSL and 4.0 g / L cyanobacteria biochar are added at the same time, and placed in a constant temperature culture shaker for medium-temperature anaerobic digestion, the temperature is set to 37°C, and the oscillation speed is set to 125 rpm; the methane production is increased by 211.7% compared with the case where no exogenous signal molecules and cyanobacteria biochar are added. The methane production is increased by 65.2%, 24.6% and 14.8% compared with the combination of adding 0.1 μmol / L C4-HSL, 0.1 μmol / L C6-HSL and 0.1 μmol / L C8-HSL and 4.0 g / L cyanobacteria biochar, respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a curve diagram showing the effect of different ammonia nitrogen concentrations on methane production during anaerobic digestion;

[0028] Figure 2 This is a data graph showing the effect of adding different carbon materials on methane production under high concentration ammonia nitrogen conditions;

[0029] Figure 3 Data graph showing the effect of combined addition of different exogenous signal molecules (C4-HSL, C6-HSL, C8-HSL and 3OC6-HSL) and cyanobacterial biochar on methane production under high ammonia nitrogen concentration conditions. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention. The following specific implementation methods further describe the present invention.

[0031] The anaerobic digestion substrate cyanobacteria liquid used in the embodiment of the present invention is cyanobacteria waste collected from the Wuxi Taihu algae water separation station; before the anaerobic digestion reaction, the cyanobacteria waste is pretreated with alkaline solution for 24 hours, and the pH is controlled at 12;

[0032] The inoculated anaerobic sludge was taken from the bottom of the upflow anaerobic sludge reactor (UASB) of Jiangsu Guoxin Xielian Energy Co., Ltd. in Yixing City. The reactor was operated at a medium temperature of 37°C and used citric acid industrial wastewater as the substrate. After the anaerobic sludge was taken back, it was placed in a shaking incubator at 37°C for acclimatization for 7 days.

[0033] The four signal molecules used in the present invention are: N-butyryl-DL-homoserine lactone (C4-HSL), N-hexanoyl-L-homoserine lactone (C6-HSL), N-octanoyl-DL-homoserine lactone (C8-HSL) and N-(β-ketohexanoyl)-DL-homoserine lactone (3OC6-HSL). The standard substances are all chromatographically pure and purchased from Sigma-Aldrich.

[0034] Cyanobacteria biochar was prepared from cyanobacteria waste as raw materials, and activated carbon and hydrothermal charcoal were purchased from Hengwang Activated Carbon (Jiangsu) Co., Ltd.

[0035] Example 1

[0036] The anaerobic digestion reactors with a working volume of 200 ml were used, 50 ml of inoculated anaerobic sludge and 75 ml of anaerobic digestion substrate cyanobacteria solution were added, and the pH was adjusted to 7 with hydrochloric acid. The corresponding ammonia nitrogen concentrations in the control reaction system were 1000 mg NH 4 + -N / L, 3000mg NH 4 + -N / L, 5000mg NH 4 + -N / L and 7000mg NH 4 + -N / L (add NH 4 Cl), and then the anaerobic reactor was placed in a constant temperature incubator for mesophilic anaerobic digestion, the temperature was set at 37 ° C, and the shaking speed was set at 125 rpm.

[0037] After 14 days of anaerobic digestion, the methane production was measured and compared with the ammonia nitrogen concentration of 1000 mg NH 4 + -N / L anaerobic digestion reaction, compared with the high concentration of ammonia nitrogen (7000mg NH 4 + -N / L) The methane production during anaerobic digestion was reduced by 71.8% ( Figure 1 ).

[0038] Example 2 Effect of adding different carbon materials on anaerobic digestion process under high concentration of ammonia nitrogen

[0039] The only difference from Example 1 is that, under high concentration ammonia nitrogen conditions (7000 mg NH 4 +-N / L) were added into an anaerobic digestion reactor (activated carbon, hydrothermal carbon and cyanobacteria biochar), and different addition concentrations (2.0, 4.0 and 8.0 g / L) were set for each carbon material; other conditions or parameters were consistent with those in Example 1.

[0040] The high concentration of ammonia nitrogen in Example 1 (7000 mg NH 4 + -N / L) of anaerobic digestion, when 4.0g / L cyanobacteria biochar was added, the methane production reached the highest (163mL), compared with the addition of 4.0g / L activated carbon, hydrothermal charcoal and Example 1, the methane production increased by 22.6%, 55.2% and 111.7%, respectively ( Figure 2 ).

[0041] Example 3 Effects of different exogenous signal molecules combined with the addition of cyanobacterial biochar on the anaerobic digestion process under high concentration of ammonia nitrogen

[0042] The only difference from Example 1 is that, under high concentration ammonia nitrogen conditions (7000 mg NH 4 + -N / L) were added to an anaerobic digestion reactor at the same time, 0.1 μmol / L C4-HSL and 4.0 g / L cyanobacteria biochar, 0.1 μmol / L C6-HSL and 4.0 g / L cyanobacteria biochar, 0.1 μmol / L C8-HSL and 4.0 g / L cyanobacteria biochar, 0.1 μmol / L 3OC6-HSL and 4.0 g / L cyanobacteria biochar, and other conditions or parameters were the same as those in Example 1.

[0043] Compared with Example 1, when 0.1 μmmol / L 3OC6-HSL and 4.0 g / L cyanobacteria biochar were added at the same time, the methane production reached the highest (238 mL), compared with the addition of 0.1 μmol / L C4-HSL, the combination of C6-HSL and C8-HSL with 4.0 g / L cyanobacteria biochar and the high concentration of ammonia nitrogen in Example 1 (7000 mg NH 4 + -N / L) increased by 65.2%, 24.6%, 14.8% and 211.7% ( Figure 3 ).

[0044] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for alleviating ammonia nitrogen inhibition during anaerobic digestion using signal molecules and biochar, characterized in that: The method comprises the following: In the anaerobic digestion reactor, the substrate cyanobacteria liquid, the inoculated anaerobic sludge, the signal molecule and the biochar were added, and the pH was adjusted to 7-8. Then, the anaerobic reactor was subjected to medium-temperature anaerobic digestion, the temperature was set to 30-40°C, and the oscillation speed was set to 100-300 rpm; the ammonia nitrogen concentration in the anaerobic reactor was 5000-7000 mg NH4 + -N / L; the signal molecule is any one or more of C4-HSL, C6-HSL, C8-HSL and 3OC6-HSL.

2. The method according to claim 1, characterized in that The biochar is any one or more of activated carbon, hydrothermal carbon and cyanobacteria biochar.

3. The method according to claim 1, characterized in that The signal molecule is 3OC6-HSL.

4. The method according to claim 1, characterized in that: The substrate cyanobacteria liquid is cyanobacteria waste collected from the Taihu algae-water separation station, and then subjected to alkali pretreatment, with the pH controlled at 10-12 and the treatment time being 12-24 hours.

5. The method according to claim 1, characterized in that The inoculated anaerobic sludge was taken from the bottom of the upflow anaerobic sludge reactor of Jiangsu Guoxin Xielian Energy Co., Ltd. in Yixing City. The reactor was operated at a medium temperature of 30-40°C and used citric acid industrial wastewater as a substrate. After the sludge was taken back, it was placed in a shaking table at 30-40°C for acclimatization for 7-8 days.

6. The method according to claim 2, characterized in that The preparation of the cyanobacteria biochar comprises: drying the Taihu cyanobacteria at high temperature, grinding them into powder, mixing them with KOH, adding them into a tube furnace for heating, washing them with deionized water, drying them, and sieving them to obtain the cyanobacteria biochar.

7. The method according to claim 1, characterized in that In the anaerobic digestion reactor, 50 mL of inoculated anaerobic sludge and 75 mL of substrate cyanobacteria liquid were added per 200 mL of working volume.

8. The method according to claim 1, characterized in that The amount of cyanobacteria biochar added to the anaerobic digestion reactor was 4.0 g / L; and the amount of signal molecule 3OC6-HSL added was 0.1 μmol / L.

9. The method according to claim 1, characterized in that: The anaerobic reactor was placed in a constant temperature culture shaker for mesophilic anaerobic digestion, the temperature was set at 37° C., and the shaking speed was set at 125 rpm.

10. Use of the method according to any one of claims 1 to 9 in the anaerobic digestion process of organic solid waste.

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