Process for promoting sludge hydrolysis and medium-chain fatty acid synthesis by using ferrocene

Abstract

The invention relates to the technical field of sludge treatment, in particular to a process for promoting sludge hydrolysis and medium-chain fatty acid synthesis by using ferrocene, which comprises the following steps: S10, adding ferrocene into sludge and adjusting the pH value to 3.0-5.0; s20, hydrogen peroxide is added for a Fenton-like reaction, and ferrocene is subjected to solid-liquid form transformation in the reaction process; s30, adding ethanol, anaerobic seed sludge and a culture medium for anaerobic fermentation and carbon chain extension; the ferrocene generates hydroxyl radicals in the Fenton-like reaction to destroy sludge flocs and cell wall membranes; the converted liquid ferrocene cation is used as an electron mediator in the step S30 to improve the electron transfer efficiency; the liquid ferrocene cations simultaneously inhibit ethanol oxidation and methanogenesis processes. A Fenton-like reaction and a biological anaerobic process are combined, a sludge hydrolysis fermentation-carbon chain extension process based on ferrocene regulation and control is constructed, sludge hydrolysis promotion, medium-chain fatty acid synthesis enhancement and substrate competition reaction inhibition are synchronously realized, and the high-value recovery rate of sludge resources is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of sludge treatment, and particularly relates to a process for promoting sludge hydrolysis and medium-chain fatty acid synthesis by using ferrocene. Background Art

[0002] The resource utilization of municipal surplus sludge has become an inevitable trend. Among them, short-chain fatty acids (C2-C5) are produced through anaerobic fermentation of sludge, and medium-chain fatty acids (C6-C8) are produced through the microbial metabolic carbon chain elongation process with ethanol, showing good application potential. However, constructing an anaerobic fermentation-carbon chain elongation process chain faces the following challenges: First, the biodegradability of sludge is relatively low, resulting in hydrolysis becoming the rate-limiting step in the resource utilization process; Second, the traditional process has problems such as insufficient electron flux or low electron transfer efficiency, which hinders the interaction of carbon chain elongation functional strains and thus limits the production of medium-chain fatty acids; Third, there are over-oxidation reactions of ethanol and methane production processes that competitively consume ethanol and organic acids in the carbon chain elongation process respectively.

[0003] In related technologies, only the first or second deficiency is solved separately. For the first deficiency, existing related technologies mainly focus on physical, chemical, biological, and combined pretreatment methods. Physical methods such as ultrasonic waves and mechanical shearing can destroy the sludge structure and accelerate the release of organic matter; chemical methods can improve the hydrolysis efficiency through alkaline adjustment or oxidant assistance; biological methods use exogenous hydrolases or highly efficient microbial communities to enhance the degradation ability; and combined methods combine physical-chemical or chemical-biological technologies to achieve synergistic enhancement of the hydrolysis effect. These technologies and patents provide diverse solutions for solving the sludge hydrolysis bottleneck and promote the high-efficiency and industrial development of sludge resource utilization. For the second deficiency, the technical progress in enhancing the electron transfer function of the anaerobic biological system mainly focuses on electron mediator optimization, addition of conductive materials, and microbial enhancement. By adding electron mediators such as iron tetroxide and potassium polyferricyanide, the electron transfer efficiency is enhanced; conductive nanomaterials such as carbon nanotubes, graphene, or conductive polymers are used to improve the electron conductivity of the system; and microbial communities with high electron transfer ability, such as electroactive bacteria, are screened and domesticated to enhance the overall performance of the system. For the third deficiency, the existing process only solves the inhibition of methane synthesis by adding expensive 2-bromoethylsulfonic acid sodium, and there is no method for synergistically inhibiting the over-oxidation of ethanol and the methane production process. In summary, there is no process that can simultaneously enhance sludge hydrolysis, inhibit the main competitive processes, and directionally promote the synthesis of medium-chain fatty acids. Summary of the Invention

[0004] To overcome the deficiencies of the prior art, the object of the present invention is to provide a process for promoting sludge hydrolysis and medium-chain fatty acid synthesis using ferrocene. By combining the Fenton-like reaction process and the biological anaerobic process, and using inexpensive ferrocene, a sludge fermentation-carbon chain elongation process regulated by ferrocene is constructed. This process does not require the addition of 2-bromoethylsulfonate to inhibit methane synthesis, and can simultaneously promote sludge hydrolysis, enhance medium-chain fatty acid synthesis, and inhibit substrate competition reactions, thereby expanding the high-value recovery rate of sludge resources.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] The first aspect of the present invention provides a process for promoting sludge hydrolysis and medium-chain fatty acid synthesis using ferrocene, comprising the following steps:

[0007] S10. Add ferrocene to the sludge and adjust the pH to 3.0 - 5.0;

[0008] S20. Add hydrogen peroxide for Fenton-like reaction. During the reaction, the ferrocene undergoes a solid-liquid morphological transformation to form ferrocenium cations;

[0009] S30. Add ethanol, anaerobic inoculum, and culture medium for anaerobic fermentation and carbon chain elongation;

[0010] The ferrocene in step S10 generates hydroxyl radicals in the Fenton-like reaction in step S20 to destroy sludge flocs and cell wall membranes;

[0011] The liquid ferrocenium cations transformed in step S20 act as electron mediators in step S30 to improve the electron transfer efficiency;

[0012] The liquid ferrocenium cations simultaneously inhibit ethanol oxidation and the methane production process.

[0013] In the first aspect of the present invention, as an optional embodiment, in step S10, the addition amount of ferrocene is 2 - 5 g / L.

[0014] In the first aspect of the present invention, as an optional embodiment, in step S20, the molar ratio of hydrogen peroxide to iron in ferrocene is (1.5 - 2):1.

[0015] In the first aspect of the present invention, as an optional embodiment, in step S20, the pH of the reaction system spontaneously rises to 4.5 - 5.5 after the reaction, which is the suitable pH condition range for the carbon chain elongation process.

[0016] In the first aspect of the present invention, as an optional embodiment, in step S30, the addition amount of ethanol is 90 - 150 mM.

[0017] In the first aspect of the present invention, as an alternative embodiment, in step S30, the anaerobic seed sludge is an activated sludge treated by domestication. The steps of the domestication treatment are as follows: taking the sludge from the sewage treatment plant, heating it at 100-110°C for 25-35 minutes to kill the methanogens, and then placing it in an anaerobic environment with a sludge retention time of 25-35 days; the inoculation amount of the anaerobic seed sludge is 5-15% of the system volume.

[0018] In the first aspect of the present invention, as an alternative embodiment, in step S30, the reaction time is 12-20 days.

[0019] In the first aspect of the present invention, as an alternative embodiment, the process is continuously implemented in a single reactor. First, collect the municipal surplus sludge into the reactor. After sequentially completing steps S10 and S20, seal the reactor to form an anaerobic fermentation reactor and place it in a constant temperature shaking incubator at 35±2°C to complete step S30.

[0020] In the first aspect of the present invention, as an alternative embodiment, control the shaking frequency of the constant temperature shaking incubator to be set at 120-180 rpm.

[0021] In the first aspect of the present invention, as an alternative embodiment, after the reaction in step S30 is completed, it further includes S40: centrifugally separating the supernatant and collecting the fermentation broth containing medium-chain fatty acids, which is the high-value resource recovery product.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] The process of the present invention synergistically enhances sludge hydrolysis and directionally regulates the synthesis of medium-chain fatty acids by regulating the morphological transformation of ferrocene. Specifically, by adding ferrocene and hydrogen peroxide to form a Fenton-like reaction, hydroxyl radicals are generated to attack the sludge flocs and cell wall membranes, improving the biodegradability of the sludge. During the Fenton reaction process, solid ferrocene is converted into liquid ferrocene cations. The coexistence of ferrocene and its cations in the system serves as an electron mediator, which can improve the electron transfer efficiency of the system and increase the interaction between bacteria. Finally, the liquid ferrocene cations have the effect of inhibiting ethanol oxidation and methane production, and can optimize the utilization of the substrates ethanol and short-chain fatty acids during the carbon chain elongation process, thereby improving the reaction efficiency of ethanol and short-chain fatty acids in sludge fermentation and directionally strengthening the synthesis of medium-chain fatty acids.

[0024] The process of the present invention is a process with microbial anaerobic metabolism as the reaction main body. By using an anaerobic fermentation tank and a stirring device, the main body of the equipment can be constructed, which has the remarkable advantages of simple operation, low energy consumption, and controllable cost. This process does not require complex equipment configuration. By optimizing the stirring and reaction conditions, the high efficiency of mass transfer and metabolic process can be achieved. At the same time, it has strong adaptability, can treat various organic wastes, and realize resource utilization. In addition, the reaction system operates in a closed manner, effectively reducing the generation of odor and secondary pollution. Combined with the automatic control of feeding and discharging, the operation stability and operation efficiency can be further improved, providing good scalability for large-scale application. The overall process combines economy and environmental friendliness, and has broad application prospects in the fields of energy recovery and pollution control.

[0025] The process of the present invention uses ferrocene to stimulate the Fenton-like reaction to generate highly active free radicals, significantly strengthening sludge hydrolysis, and has high efficiency and environmental protection. From the perspective of the Fenton reaction, ferrocene can be recycled as a catalyst. The traditional Fenton has a limitation on pH (the pH value of the traditional method is 3-4), and it can efficiently generate free radicals in a loose elastic pH range (pH is 3-5), which is beneficial to reducing acid consumption. From the perspective of sludge hydrolysis, the strong oxidizing property of free radicals can destroy the sludge structure, release more soluble organic matter, break through the hydrolysis rate-limiting bottleneck, and the available substrate in the sludge supernatant of this stage has increased by 3.77 times (calculated by COD), significantly improving the decomposition efficiency of refractory organic matter. The overall process is simple to operate and has strong adaptability, and synergistically acts with the biological process, providing an innovative solution for sludge resource utilization.

[0026] The process of the present invention provides multiple advantages for the carbon chain elongation process by flexibly adjusting the morphological transformation of ferrocene, especially the application of liquid ferrocene. Liquid ferrocene effectively reduces its consumption in the side reaction of excessive oxidation of ethanol by directionally regulating the utilization of ethanol in the reaction, and the inhibition rate can reach 50%. Description of the Drawings

[0027] Figure 1 It is a process flow schematic diagram of the process of the present invention;

[0028] Figure 2 It is a graph showing the change of medium-chain fatty acid synthesis in Comparative Example 1 of the present invention;

[0029] Figure 3 It is a graph showing the change of medium-chain fatty acid synthesis in Example 2 of the present invention. Detailed Embodiments

[0030] Next, in combination with the accompanying drawings and specific embodiments, the present invention will be further described. It should be noted that, on the premise of no conflict, the following-described embodiments or technical features can be arbitrarily combined to form new embodiments. Except as otherwise specified, the materials and equipment used in this embodiment can be purchased from the market.

[0031] Please refer to Figure 1 , the first aspect of the present invention provides a process for promoting sludge hydrolysis and medium-chain fatty acid synthesis by using ferrocene, including the following steps:

[0032] S10. Add ferrocene to the sludge and adjust the pH to 3.0 - 5.0;

[0033] S20. Add hydrogen peroxide for a Fenton-like reaction; wherein, the ferrocene undergoes a solid-liquid morphological transformation during the reaction to form ferrocene cations;

[0034] S30. Add ethanol, anaerobic inoculum, and medium for anaerobic fermentation and carbon chain elongation;

[0035] The ferrocene in step S10 generates hydroxyl radicals in the Fenton-like reaction in step S20 to destroy the sludge flocs and cell wall membranes;

[0036] The liquid ferrocene cations transformed in step S20 act as electron mediators in step S30 to improve the electron transfer efficiency;

[0037] The liquid ferrocene cations simultaneously inhibit the ethanol oxidation and methanogenesis processes.

[0038] On the basis of the above scheme, the present invention synergistically enhances sludge hydrolysis and directionally regulates medium-chain fatty acid synthesis by controlling the morphological transformation of ferrocene. Specifically, by adding ferrocene and hydrogen peroxide to form a Fenton-like reaction, hydroxyl radicals (refer to formula 1) are generated to attack the sludge flocs and cell wall membranes, improving the biodegradability of the sludge. After the reaction, solid ferrocene is transformed into liquid ferrocene cations. The coexisting ferrocene and its cations in the system act as electron mediators, which can improve the electron transfer efficiency of the system and increase the interaction between bacteria. Finally, the liquid ferrocene cations have the function of inhibiting ethanol oxidation and methanogenesis, and can optimize the utilization of the substrate ethanol and short-chain fatty acids during the carbon chain elongation (refer to formula 2) process, thereby improving the reaction efficiency of ethanol and short-chain fatty acids in sludge fermentation and directionally strengthening the synthesis of medium-chain fatty acids.

[0039] Formula 1: Fc (ferrocene) + H 2 O 2 → Fc + (ferrocene cation) + OH - + ·OH (hydroxyl radical).

[0040] Formula 2: 5C n H 2n-1 O 2 - +6CH 3 CH 2 OH→5C n+2 H 2n+3 O 2 - +CH 3 COO - +4H 2 O+H + +2H 2 。

[0041] As a preferred embodiment, in step S10, the addition amount of ferrocene is 2-5 g / L. When it is higher than 5 g / L, the production of medium-chain fatty acids is saturated and the converted ferrocene cations produce a bioactivity inhibitory effect.

[0042] As a preferred embodiment, in step S20, the molar ratio of hydrogen peroxide to iron in ferrocene is (1.5-2):1.

[0043] As a preferred embodiment, in step S20, the pH of the reaction system spontaneously rises to 4.5-5.5 after the reaction, that is, the suitable pH condition range for the carbon chain elongation process.

[0044] As a preferred embodiment, in step S30, the addition amount of ethanol is 90-150 mM.

[0045] In the first aspect of the present invention, as an alternative embodiment, in step S30, the anaerobic seed sludge is an activated sludge treated by domestication, and the steps of the domestication treatment are as follows: taking the sludge from the sewage treatment plant, heating it at 100-110 °C for 25-35 min to kill the methanogens, and then placing it in an anaerobic environment, with the sludge retention time of 25-35 d; the inoculation amount of the anaerobic seed sludge is 5-15% of the system volume.

[0046] In the first aspect of the present invention, as an alternative embodiment, in step S30, the steps of the domestication treatment are as follows: taking the sludge from the sewage treatment plant, heating it at 105 °C for 30 min, and then maintaining it in an anaerobic environment, with the sludge retention time of 30 d.

[0047] In the first aspect of the present invention, as an alternative embodiment, the culture medium contains the following substances: 5.04 g / L NaHCO 3 、3.6 g / L NH 4 H 2 PO 4 、0.33 g / L MgC l 2 ·6H 2O, 0.2 g / L CaCl 2 ·2H 2 O, 0.2 g / L MgSO 4 ·7H 2 O, 0.15 g / L KCl, 0.5 mg / L MnCl 2 ·4H 2 O, 0.05 mg / L H 3 BO 3 , 0.05 mg / L ZnCl 2 , 0.03 mg / L CuCl 2 , 0.01 mg / L Na 2 MoO 4 ·2H 2 O, 1 mg / L CoCl 2 ·6H 2 O, 0.1 mg / L NiCl 2 ·6H 2 O, 0.05 mg / L Na 2 SeO 3 , 0.106 mg / L biotin, 0.005 mg / L folic acid, 0.0025 mg / L pyridoxal hydrochloride, 0.266 mg / L vitamin B1, 0.0125 mg / L vitamin B2, 0.413 mg / L Ca-D-pantothenic acid, 0.0125 mg / L vitamin B12, 0.0125 mg / L p-aminobenzoic acid, 0.0125 mg / L nicotinic acid, 0.015 mg / L lipoic acid.

[0048] As a preferred embodiment, in step S30, the reaction time is 12 - 20 days.

[0049] As a preferred embodiment, the process is continuously implemented in a single reactor. First, municipal surplus sludge is collected into the reactor. After sequentially completing steps S10 and S20, the reactor is sealed to form an anaerobic fermentation reactor and placed in a constant temperature shaking incubator at 35 ± 2 °C to complete step S30.

[0050] As a preferred embodiment, the shaking frequency of the constant temperature shaking incubator is controlled to be set at 120 - 180 rpm.

[0051] As a preferred embodiment, after the reaction in step S30 ends, it further includes S40: centrifugally separating the supernatant and collecting the fermentation broth containing medium-chain fatty acids, which is the high-value resource recovery product.

[0052] The following are some examples listed in this application, and the application is further illustrated by the following examples.

[0053] Example 1:

[0054] Reactor configuration: Anaerobic fermentation tank, equipped with a pH probe and an automatic chemical dosing system.

[0055] A process for promoting sludge hydrolysis and medium-chain fatty acid synthesis using ferrocene, comprising the following steps:

[0056] S10. Take municipal sludge (total solids content TS = 5%) in an anaerobic fermentation tank, add 5 g / L of ferrocene to the sludge and adjust the pH to 4.0;

[0057] S20. Add hydrogen peroxide for a Fenton-like reaction, wherein the molar ratio of hydrogen peroxide to iron in ferrocene is 1.5:1; the Fenton-like reaction is completed within 10 minutes, and the pH of the reaction system spontaneously rises to 5 after the reaction;

[0058] S30. Seal the reactor to form an anaerobic fermentation reactor, place it in a constant temperature shaking incubator at 35 °C, add ethanol, anaerobic inoculum sludge and culture medium for anaerobic fermentation and carbon chain elongation, and the fermentation time is 15 days;

[0059] Among them, the dosage of ethanol added is 120 mM; the shaking frequency of the constant temperature shaking incubator is set to 150 rpm.

[0060] Among them, the anaerobic inoculum sludge is a kind of activated sludge treated by domestication. The steps of the domestication treatment are as follows: Take the sludge from the sewage treatment plant, heat it at 105 °C for 30 min, and then keep it in an anaerobic environment. The sludge retention time is 30 d; the inoculation amount of the anaerobic inoculum sludge is 10% of the system volume.

[0061] The culture medium contains the following substances: 5.04 g / L NaHCO 3 、3.6 g / L NH 4 H 2 PO 4 、0.33 g / L MgC l 2 ·6H 2 O、0.2 g / L CaC l 2 ·2H 2 O、0.2 g / L MgSO 4 ·7H 2 O、0.15 g / L KC l、0.5 mg / L MnC l 2 ·4H 2 O、0.05 mg / L H 3 BO 3 、0.05 mg / L ZnC l 2 、0.03 mg / L CuC l 2 、0.01 mg / L Na 2 MoO 4 ·2H2 O, 1 mg / L CoCl 2 ·6H 2 O, 0.1 mg / L NiCl 2 ·6H 2 O, 0.05 mg / L Na 2 SeO 3 , 0.106 mg / L biotin, 0.005 mg / L folic acid, 0.0025 mg / L pyridoxal hydrochloride, 0.266 mg / L vitamin B1, 0.0125 mg / L vitamin B2, 0.413 mg / L Ca-D-pantothenic acid, 0.0125 mg / L vitamin B12, 0.0125 mg / L p-aminobenzoic acid, 0.0125 mg / L nicotinic acid, 0.015 mg / L lipoic acid.

[0062] S40. Centrifuge and separate the supernatant, and collect the fermentation broth containing medium-chain fatty acids, which is the high-value resource recovery product.

[0063] Detect the relevant data in the technological process described in Example 1 above as follows:

[0064] Biological activity inhibition rate (%) : 0;

[0065] Sludge COD release amount (gCOD / L) : 3.27;

[0066] Medium-chain fatty acid production (gCOD / L) is: 5.72;

[0067] Recovery rate of medium-chain fatty acids in the fermentation broth (%) is: 42.75.

[0068] On the basis of Example 1 above, the effects of different ferrocene concentrations on the production of medium-chain fatty acids, the recovery rate of medium-chain fatty acids in the fermentation broth, and the biological activity inhibition rate were further explored. In this process, different ferrocene concentrations were set, but other conditions were kept the same as in Example 1. The specific data are shown in Table 1 below.

[0069] Table 1

[0070]

[0071]

[0072] As can be seen from Table 1 above, when the dosage of ferrocene is 2 - 5 g / L, a relatively high yield and recovery rate of medium-chain fatty acids are obtained. This is because the utilization of ferrocene to stimulate the Fenton-like reaction promotes sludge hydrolysis and, as an electron mediator, directionally regulates the synthesis of medium-chain fatty acids. When the dosage is lower than 2 g / L, the free radical excitation effect is weak, making it difficult to promote sludge hydrolysis, resulting in fewer substrates for medium-chain fatty acid synthesis. When the dosage is higher than 5 g / L, a large amount of soluble ferrocene cations are generated by the ferrocene-based Fenton reaction. In the environment of ferrocene cations, the activity of sludge microorganisms is inhibited, reducing the energy metabolism rate and resulting in hindered synthesis of medium-chain fatty acids.

[0073] On the basis of the above-mentioned Example 1, the effects of different pH values in step S10 on the sludge COD release amount, the yield of medium-chain fatty acids, and the recovery rate of medium-chain fatty acids in the fermentation broth were further explored. During this process, different pH values were set, but other conditions were kept the same as in Example 1. The specific data are shown in Table 2 below.

[0074] Table 2

[0075]

[0076]

[0077] As can be seen from Table 2 above, when the pH is in the range of 3 - 5, a relatively high sludge COD release amount, yield of medium-chain fatty acids, and recovery rate are obtained. This is because a high-level oxidation effect is generated within this range, promoting sludge lysis and hydrolysis by exciting free radicals. The traditional Fenton process generally has a significant effect in the pH range of 3 - 4, while the pH range of the ferrocene-based Fenton reaction is milder and more flexible, which can reduce the acid cost of the process. When pH > 5, no high-level oxidation effect occurs, only the oxidation effect of hydrogen peroxide occurs, and the ferrocene form does not change, making it difficult to play the role of directionally regulating the synthesis of medium-chain fatty acids, so the product recovery rate decreases.

[0078] On the basis of the above-mentioned Example 1, the effects of different molar ratios of hydrogen peroxide to iron in ferrocene on the sludge COD release amount, the yield of medium-chain fatty acids, and the recovery rate of medium-chain fatty acids in the fermentation broth were further explored. During this process, different pH values were set, but other conditions were kept the same as in Example 1. The specific data are shown in Table 3 below.

[0079] Table 3

[0080]

[0081] It can be seen from Table 3 above that when the molar ratio of hydrogen peroxide to iron in ferrocene is in the range of (1 - 2):1, advanced oxidation can occur, promoting the release of sludge COD. Among them, when the molar ratio of hydrogen peroxide to iron in ferrocene is in the range of (1.5 - 2):1, the release of sludge COD and the production of medium-chain fatty acids are more significant, and the recovery rate of medium-chain fatty acids is higher than 40%. When it is lower than 1.5:1, hydrogen peroxide is not sufficient to stimulate the Fenton-like reaction of the ferrocene group, so the synthesis of medium-chain fatty acids is blocked.

[0082] Example 2:

[0083] Example 2 provides a process for promoting sludge hydrolysis and medium-chain fatty acid synthesis using ferrocene. The difference between Example 2 and Example 1 is that the solids content TS of the municipal sludge taken is 3%, and other conditions remain the same as in Example 1.

[0084] Comparative Example 1:

[0085] On the basis of the above Example 2, Comparative Example 1 further explored the case of not adding ferrocene, that is, not adopting the operations related to the sludge hydrolysis and medium-chain fatty acid synthesis process regulated by ferrocene in steps S10 and S10; directly proceeding to step S30: anaerobic fermentation and adding ethanol for carbon chain elongation, and other conditions remained the same as in Example 2.

[0086] At the end of the reaction, the COD of the fermentation broth in Comparative Example 1 increased by 0.91 gCOD / L, while that in Example 2 increased by 3.43 gCOD / L, which was 3.77 times that of Comparative Example 1, indicating that the Fenton-like reaction excited by ferrocene promoted the release of sludge COD.

[0087] Referring to Figures 2 - 3 , in Comparative Example 1, as the reaction proceeded to the 10th day, acetic acid gradually accumulated to 1.80 gCOD / L, which was the result of the over-oxidation of ethanol to acetic acid, resulting in a large amount of ethanol being unable to be directed to the synthesis of medium-chain fatty acids. Subsequently, the reaction reached a steady state, and the production of medium-chain fatty acids was 2.35 gCOD / L, with a recovery rate of 17.72%. Among them, hexanoic acid was the main medium-chain fatty acid, with a production of 1.11 gCOD / L, accounting for 47.05% of the medium-chain fatty acids. In Example 2, no significant accumulation of acetic acid was observed in the first 10 days of the reaction, and the inhibition rate of ethanol over-oxidation was 50%. The production of medium-chain fatty acids was 4.47 gCOD / L, which was 1.90 times that of Comparative Example 1, and the recovery rate was 28.48%. Among them, hexanoic acid was the main medium-chain fatty acid, with a production of 4.13 gCOD / L, which was 3.72 times that of Comparative Example 1, accounting for 92.55% of the medium-chain fatty acids.

[0088] In summary, the process of sludge hydrolysis and medium-chain fatty acid synthesis regulated by ferrocene has the effect of promoting the release of sludge COD and efficiently and directionally synthesizing medium-chain fatty acids (especially hexanoic acid).

[0089] The above embodiments are only the preferred embodiment modes of the present invention, and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection required by the present invention.

Claims

1. A process for promoting sludge hydrolysis and medium-chain fatty acid synthesis using ferrocene, comprising the following steps: S10, adding ferrocene to the sludge and adjusting the pH to 3.0-5.0; S20, adding hydrogen peroxide to carry out a Fenton-like reaction to promote sludge hydrolysis; wherein the ferrocene undergoes a solid-liquid phase transition to form a ferrocene cation during the reaction; S30, adding ethanol, anaerobic seed mud and culture medium for anaerobic fermentation and carbon chain extension; The ferrocene in step S10 generates hydroxyl radicals in the Fenton-like reaction in step S20 to destroy the sludge flocs and cell wall membranes; The liquid ferrocene cation converted in step S20 is used as an electron mediator in step S30 to improve the electron transfer efficiency; The liquid ferrocenium cation inhibits both ethanol oxidation and methanogenesis processes.

2. The process according to claim 1, characterized in that The added amount of ferrocene is 2-5 g / L.

3. The process according to claim 1, characterized in that In step S20, the molar ratio of hydrogen peroxide to iron in ferrocene is (1.5-2):

1.

4. The process according to claim 1, characterized in that In step S20, after the reaction, the pH of the system spontaneously rises to 4.5-5.5, which is the pH condition range suitable for carbon chain extension.

5. The process according to claim 1, characterized in that In step S30, the ethanol dosage is 90-150 mM.

6. The process according to claim 1, characterized in that In step S30, the anaerobic seed sludge is an activated sludge that has been acclimated. The acclimation steps are: taking sludge from a sewage treatment plant, heating it at 100-110°C for 25-35 minutes to kill methanogens, and then placing it in an anaerobic environment with a sludge retention time of 25-35 days; the inoculation amount of the anaerobic seed sludge is 5-15% of the system volume.

7. The process according to claim 1, characterized in that In step S30, the reaction time is 12-20 days.

8. The process according to claim 1, characterized in that The process is continuously implemented in a single reactor. First, the municipal residual sludge is collected into the reactor. After completing steps S10 and S20 in sequence, the reactor is sealed to form an anaerobic fermentation reactor, which is placed in a constant temperature shaking incubator at 35±2°C to complete step S30; the shaking frequency of the constant temperature shaking incubator is controlled to be set to 120-180rpm.

9. The process according to claim 1, characterized in that After the reaction in step S30 is completed, the method further includes S40: centrifuging the supernatant to collect the fermentation liquid containing medium-chain fatty acids, which is a high-value resource recovery product.

Images