A method for enhancing methane production from anaerobic fermentation of excess sludge by using pyrroloquinoline quinone

Abstract

A method for enhancing methane production from anaerobic fermentation of excess sludge using pyrroloquinoline quinone, which belongs to the technical field of anaerobic fermentation. The purpose of the present invention is to solve the problem of low methane production efficiency caused by the imbalance between the hydrogen-producing and acetate-producing processes and the methane-producing process during the anaerobic fermentation of existing excess sludge. The present invention provides a method for enhancing methane production from anaerobic fermentation of excess sludge using pyrroloquinoline quinone (PQQ), which uses PQQ to promote methane production during the anaerobic fermentation of excess sludge. The efficiency of PQQ in enhancing the conversion of refractory organic matter in sludge into methane shows a concentration-dependent manner. When the dosage of PQQ increases from 0 g / g to 0.3 g / g, the cumulative methane production continuously increases. When the dosage of PQQ is 0.3 g / g, the highest cumulative methane production is 392 mL, which is 2.3 times that of the blank control group. The present invention can obtain a method for enhancing methane production from anaerobic fermentation of excess sludge using pyrroloquinoline quinone.

Description

Technical Field

[0001] The present invention belongs to the technical field of anaerobic fermentation, and particularly relates to a method for enhancing methane production from excess sludge anaerobic fermentation by using pyrroloquinoline quinone. Background Art

[0002] Municipal sewage treatment plants mainly adopt biological treatment processes, during which a large amount of excess sludge is generated. The output of excess sludge is huge, and the treatment and disposal costs are high, reaching about 60% of the total costs of the sewage treatment plant. The treatment and disposal of sludge generally often adopt methods such as landfill, incineration, agricultural utilization, and anaerobic fermentation. Landfill will lead to waste of land resources, incineration will cause environmental pollution, direct agricultural utilization will generate potential ecological risks, while anaerobic fermentation technology can not only effectively achieve sludge reduction, but also convert the refractory organic matter in sludge into energy resource products such as hydrogen, methane, volatile acids, etc., thereby realizing its resource and energy utilization. Therefore, anaerobic fermentation technology combines economic benefits and environmental benefits, and has become one of the most economical and effective methods for treating sludge in recent years. The improvement of methane production efficiency is the technical bottleneck restricting the further development of this technology, and the construction of a highly efficient and stable functional microbiome is an important scientific issue therein. The hydrolysis of refractory organic matter in sludge is the rate-limiting step of sludge anaerobic fermentation. In order to strengthen sludge hydrolysis, researchers have developed various sludge pretreatment technologies, such as physical pretreatment, chemical pretreatment, and biological pretreatment technologies, etc., to promote the hydrolysis efficiency of refractory organic matter in sludge, thereby improving the methane production efficiency in sludge. However, previous studies mainly strengthened sludge hydrolysis through the development of exogenous intervention technologies, while ignoring the attention to the functional microbiome. The growth rate of hydrolytic acidification bacteria in sludge is much higher than that of methanogens, which may lead to a large accumulation of volatile acids, reduce the pH value of the reaction system, and thus harm the growth and metabolic process of methanogenic bacteria. Therefore, strengthening the growth and metabolic process of methanogens to improve the biological conversion process from volatile acids to methane is also very important. Summary of the Invention

[0003] The purpose of the present invention is to solve the problem of low methane production efficiency caused by the imbalance between the hydrogen production and acetic acid production process and the methane production process during the anaerobic fermentation of existing excess sludge, and to provide a method for enhancing methane production from excess sludge anaerobic fermentation by using pyrroloquinoline quinone.

[0004] A method for enhancing methane production from excess sludge anaerobic fermentation by using pyrroloquinoline quinone is specifically completed according to the following steps:

[0005] I. Sieving the sewage sludge mixture obtained from the secondary sedimentation tank of the sewage treatment plant to remove large particle sand and gravel, and then placing it in a constant temperature room to settle until the sewage and sludge interface are stratified, and removing the upper layer of sewage to obtain excess sludge A;

[0006] The total solid (TS) value of the excess sludge A described in Step 1 is 29 g / L, and the volatile solid (VS) value is 18 g / L;

[0007] II. First, rinse the anaerobic sludge with PBS buffer, and then resuspend the anaerobic sludge with PBS buffer to obtain the inoculum sludge B;

[0008] The total solid (TS) value of the inoculum sludge B described in Step 2 is 36 g / L, and the volatile solid (VS) value is 26 g / L;

[0009] III. First, add the excess sludge A into the anaerobic bottle as the substrate, then add pyrroloquinoline quinone, and then add the inoculum sludge B, and mix evenly to obtain the fermentation system; adjust the pH value of the fermentation system to neutral, remove the oxygen in the anaerobic bottle with nitrogen, seal the anaerobic bottle after removing the oxygen, and transfer it to a constant temperature shaking incubator for anaerobic fermentation at a certain temperature and rotation speed;

[0010] The volume ratio of the excess sludge A to the inoculum sludge B described in Step 3 is 10:1;

[0011] The dosage of pyrroloquinoline quinone described in Step 3 is 0.05 g / g - 0.3 g / g, and the dosage of pyrroloquinoline quinone is the mass ratio of pyrroloquinoline quinone to the volatile solid of the excess sludge A.

[0012] Principle of the present invention:

[0013] Pyrroloquinoline quinone (PQQ) can effectively promote the efficiency of electron transfer between methanogens and humus, and the relevant research results can be extended to the anaerobic fermentation process. PQQ-binding proteins are widely distributed in methanogens. Therefore, the addition of PQQ can effectively strengthen the biochemical metabolic pathway of methanogens, thereby promoting the process of converting small molecule volatile acids into methane.

[0014] The present invention has the following beneficial effects:

[0015] The present invention provides a method for enhancing the anaerobic fermentation of excess sludge to produce methane by using pyrroloquinoline quinone (PQQ), and uses PQQ to promote the production of methane during the anaerobic fermentation of excess sludge. The efficiency of converting refractory organic matter in PQQ-enhanced sludge into methane shows a concentration-dependent manner. When the dosage of PQQ increases from 0 g / g to 0.3 g / g, the cumulative methane production continuously increases. When the dosage of PQQ is 0.3 g / g, the highest cumulative methane production is 392 mL, which is 2.3 times that of the blank control group. Description of the Drawings

[0016] Figure 1 It is a graph showing the change of cumulative methane production over time. Detailed Embodiments

[0017] Specific Embodiment 1: A method for enhancing methane production from anaerobic fermentation of excess sludge using pyrroloquinoline quinone is specifically completed according to the following steps:

[0018] I. Sieve the sewage sludge mixture obtained from the secondary sedimentation tank of the sewage treatment plant to remove large particle sand and gravel, and then place it in a constant temperature chamber to settle until the sewage and sludge interface is stratified. Remove the upper layer of sewage to obtain excess sludge A;

[0019] In Step I, the total solid (TS) value of the excess sludge A is 29 g / L, and the volatile solid (VS) value is 18 g / L;

[0020] II. First, rinse the anaerobic sludge with PBS buffer, and then resuspend the anaerobic sludge with PBS buffer to obtain inoculated sludge B;

[0021] In Step II, the total solid (TS) value of the inoculated sludge B is 36 g / L, and the volatile solid (VS) value is 26 g / L;

[0022] III. First, add the excess sludge A into an anaerobic bottle as a substrate, then add pyrroloquinoline quinone, and then add the inoculated sludge B. Mix them evenly to obtain a fermentation system; adjust the pH value of the fermentation system to neutral, use nitrogen to remove the oxygen in the anaerobic bottle, seal the anaerobic bottle after removing the oxygen, and transfer it to a constant temperature shaking incubator to carry out anaerobic fermentation at a certain temperature and rotation speed;

[0023] In Step III, the volume ratio of the excess sludge A to the inoculated sludge B is 10:1;

[0024] In Step III, the dosage of pyrroloquinoline quinone is 0.05 g / g - 0.3 g / g, and the dosage of pyrroloquinoline quinone is the mass ratio of pyrroloquinoline quinone to the volatile solid of the excess sludge A.

[0025] Specific Embodiment 2: The difference between this embodiment and Specific Embodiment 1 is that in Step I, the sewage sludge mixture obtained from the secondary sedimentation tank of the sewage treatment plant is sieved through a 10 - 20 mesh sieve. Other steps are the same as those in Specific Embodiment 1.

[0026] Specific Embodiment 3: The difference between this embodiment and one of Specific Embodiments 1 or 2 is that in Step I, the temperature of the constant temperature chamber is 3°C - 5°C. Other steps are the same as those in Specific Embodiment 1 or 2.

[0027] Specific Embodiment 4: The difference between this embodiment and one of Specific Embodiments 1 to 3 is that in Step II, the PBS buffer is 1×PBS buffer with a pH value of 7.4. Other steps are the same as those in Specific Embodiments 1 to 3.

[0028] Specific Embodiment 5: The difference between this embodiment and any one of Specific Embodiments 1 to 4 is that in Step 2, the anaerobic sludge is first rinsed 3 to 5 times with PBS buffer solution. Other steps are the same as those in Specific Embodiments 1 to 4.

[0029] Specific Embodiment 6: The difference between this embodiment and any one of Specific Embodiments 1 to 5 is that the diameter of the anaerobic sludge described in Step 2 is 0.3 mm to 3 mm. Other steps are the same as those in Specific Embodiments 1 to 5.

[0030] Specific Embodiment 7: The difference between this embodiment and any one of Specific Embodiments 1 to 6 is that in Step 3, the pH value of the fermentation system is adjusted to 6.9 to 7.1 with 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide. Other steps are the same as those in Specific Embodiments 1 to 6.

[0031] Specific Embodiment 8: The difference between this embodiment and any one of Specific Embodiments 1 to 7 is that in Step 3, nitrogen is aerated for 20 to 25 minutes to remove the oxygen in the anaerobic bottle. Other steps are the same as those in Specific Embodiments 1 to 7.

[0032] Specific Embodiment 9: The difference between this embodiment and any one of Specific Embodiments 1 to 8 is that the temperature of the constant temperature shaking incubator in Step 3 is 34°C to 36°C, and the rotation speed is 145 rpm to 155 rpm. Other steps are the same as those in Specific Embodiments 1 to 8.

[0033] Specific Embodiment 10: The difference between this embodiment and any one of Specific Embodiments 1 to 9 is that the number of days of anaerobic fermentation in Step 3 is 21 days. Other steps are the same as those in Specific Embodiments 1 to 9.

[0034] The following examples are used to verify the beneficial effects of the present invention:

[0035] The experimental methods used in the following examples are all conventional methods unless otherwise specified.

[0036] In the following specific examples, pyrroloquinoline quinone (PQQ) was purchased from Macklin. The secondary sedimentation tank of the sewage treatment plant is the secondary sedimentation tank of Wenchang Sewage Treatment Plant in Harbin. The anaerobic sludge was taken from the expanded granular sludge bed anaerobic reactor.

[0037] Example 1: A method for enhancing anaerobic fermentation of excess sludge to produce methane using pyrroloquinoline quinone is specifically completed according to the following steps:

[0038] 1. Pass the sewage sludge mixture obtained from the secondary sedimentation tank of the sewage treatment plant through a 20-mesh sieve to remove large particles of sand and gravel, and then place it in a 4°C constant temperature room to settle until the sewage and sludge interface are stratified, and remove the upper layer of sewage to obtain excess sludge A;

[0039] The total solid (TS) value of the excess sludge A described in Step 1 is 29 g / L, and the volatile solid (VS) value is 18 g / L.

[0040] II. First, rinse the anaerobic sludge with PBS buffer three times, and then resuspend the anaerobic sludge with PBS buffer to obtain the inoculum sludge B.

[0041] The total solid (TS) value of the inoculum sludge B described in Step 2 is 36 g / L, and the volatile solid (VS) value is 26 g / L.

[0042] The PBS buffer described in Step 2 is 1×PBS buffer with a pH value of 7.4.

[0043] The diameter of the anaerobic sludge described in Step 2 is 0.3 mm to 3 mm.

[0044] III. First, add 200 mL of excess sludge A into an anaerobic bottle as a substrate, then add pyrroloquinoline quinone, and then add 20 mL of inoculum sludge B, and mix evenly to obtain a fermentation system; adjust the pH value of the fermentation system to 7, use nitrogen to aerate for 20 min to remove the oxygen in the anaerobic bottle, seal the anaerobic bottle after removing the oxygen, and transfer it to a constant temperature shaking incubator, and carry out anaerobic fermentation for 21 days at a certain temperature and rotation speed.

[0045] The volume ratio of the excess sludge A to the inoculum sludge B described in Step 3 is 10:1.

[0046] The dosage of pyrroloquinoline quinone described in Step 3 is 0.05 g / g, and the dosage of pyrroloquinoline quinone is the mass ratio of pyrroloquinoline quinone to the volatile solid of the excess sludge A.

[0047] In Step 3, adjust the pH value of the fermentation system to 7 with 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide.

[0048] The temperature of the constant temperature shaking incubator described in Step 3 is 35°C, and the rotation speed is 150 rpm.

[0049] The cumulative methane production after the anaerobic fermentation experiment in Example 1 is 213 mL.

[0050] Example 2: The difference between this example and Example 1 is that the dosage of pyrroloquinoline quinone described in Step 3 is 0.1 g / g, and the dosage of pyrroloquinoline quinone is the mass ratio of pyrroloquinoline quinone to the volatile solid of the excess sludge A. Other steps and parameters are the same as those in Example 1.

[0051] The cumulative methane production after the anaerobic fermentation experiment in Example 2 is 252 mL.

[0052] Example 3: The difference between this example and Example 1 is that the dosage of pyrroloquinoline quinone in step three is 0.3 g / g, and the dosage of pyrroloquinoline quinone is the mass ratio of pyrroloquinoline quinone to the volatile solids of excess sludge A. Other steps and parameters are the same as those in Example 1.

[0053] The cumulative methane production after the anaerobic fermentation experiment in Example 3 was 392 mL.

[0054] Control Example 1: The difference between this example and Example 1 is that the dosage of pyrroloquinoline quinone in step three is 0 g / g, and the dosage of pyrroloquinoline quinone is the mass ratio of pyrroloquinoline quinone to the volatile solids of excess sludge A. Other steps and parameters are the same as those in Example 1.

[0055] The cumulative methane production after the anaerobic fermentation experiment in Control Example 1 was 170 mL.

[0056] According to the above research results, pyrroloquinoline quinone (PQQ) can enhance the conversion of complex organic matter into methane during anaerobic fermentation of sludge, and the promoting effect of PQQ on methane production from sludge fermentation increases with the increase of concentration. When the addition amount of PQQ is 0.3 g / g, the cumulative methane amount can reach up to 392 mL at this time, which is about 130% higher than that of the blank control group. This invention is of great significance for exploring the technical principle of using PQQ to enhance methane production from anaerobic fermentation of excess sludge and developing intervention control strategies.

Claims

1. A method for enhancing the anaerobic fermentation of excess sludge to produce methane using pyrroloquinoline quinone, characterized in that The method is specifically completed according to the following steps:

1. The sewage sludge mixture obtained from the secondary sedimentation tank of the sewage treatment plant is sieved to remove large particles of sand and gravel, and then placed in a constant temperature chamber to settle to the interface of sewage and sludge, and the upper sewage is removed to obtain residual sludge A; The temperature of the constant temperature chamber described in step 1 is 3°C to 5°C; The total solid TS value of the excess sludge A described in step 1 is 29 g / L, and the volatile solid VS value is 18 g / L; 2. First, the anaerobic sludge is washed with PBS buffer, and then the anaerobic sludge is resuspended with PBS buffer to obtain inoculated sludge B; The diameter of the anaerobic sludge in step 2 is 0.3 mm to 3 mm; The total solid TS value of the inoculated sludge B described in step 2 is 36 g / L, and the volatile solid VS value is 26 g / L; 3. First, the residual sludge A is added to the anaerobic bottle as a substrate, and then pyrroloquinoline quinone is added, and then the inoculated sludge B is added, and mixed evenly to obtain a fermentation system; the pH value of the fermentation system is adjusted to neutral, and nitrogen is used to remove oxygen in the anaerobic bottle, and the anaerobic bottle with oxygen removed is sealed, and after sealing, it is transferred to a constant temperature shaking incubator to perform anaerobic fermentation at a certain temperature and speed; The volume ratio of the excess sludge A to the inoculated sludge B described in step 3 is 10:1; The dosage of pyrroloquinoline quinone in step 3 is 0.05 g / g to 0.3 g / g, and the dosage of pyrroloquinoline quinone is the mass ratio of pyrroloquinoline quinone to the volatile solids of the excess sludge A; The number of days for anaerobic fermentation described in step 3 is 21 days; The temperature of the constant temperature shaking table described in step 3 is 34° C. to 36° C., and the rotation speed is 145 rpm to 155 rpm.

2. The method for enhancing anaerobic fermentation of excess sludge to produce methane using pyrroloquinoline quinone according to claim 1, characterized in that In step 1, the sewage sludge mixture obtained from the secondary sedimentation tank of the sewage treatment plant is passed through a 10-20 mesh sieve.

3. The method for enhancing anaerobic fermentation of excess sludge to produce methane using pyrroloquinoline quinone according to claim 1, characterized in that The PBS buffer described in step 2 is 1×PBS buffer with a pH value of 7.

4.

4. The method for enhancing anaerobic fermentation of excess sludge to produce methane using pyrroloquinoline quinone according to claim 1, characterized in that In step 2, the anaerobic sludge is firstly rinsed 3 to 5 times with PBS buffer.

5. The method for enhancing anaerobic fermentation of excess sludge to produce methane using pyrroloquinoline quinone according to claim 1, characterized in that In step 3, the pH value of the fermentation system is adjusted to 6.9-7.1 using 1 mol / L hydrochloric acid or 1 mol / L sodium hydroxide.

6. The method for enhancing anaerobic fermentation of excess sludge to produce methane using pyrroloquinoline quinone according to claim 1, characterized in that In step 3, nitrogen aeration is used for 20 to 25 minutes to remove oxygen from the anaerobic bottle.

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