Method for improving settleability of organic biogas slurry by using electron beam irradiation

Abstract

The invention discloses a method for improving settleability of organic biogas slurry by electron beam irradiation, which comprises the following steps: S1, collecting organic biogas slurry, stirring and uniformly mixing to obtain a to-be-treated liquid; and S2, carrying out electron beam irradiation treatment on the to-be-treated liquid by using an electron accelerator. The organic biogas slurry containing a large amount of EPS is treated through electron beams, an EPS suspended matter system and a biological macromolecular structure in the biogas slurry can be effectively destroyed, the settleability of the organic biogas slurry is improved, and the separation efficiency is improved.

Description

Technical Field

[0001] The invention relates to the field of sewage treatment, and in particular to a method for improving the sedimentation of organic biogas slurry by utilizing electron beam irradiation. Background Art

[0002] Organic biogas slurry is the liquid produced by anaerobic fermentation of organic domestic waste in cities. Due to the wide and dispersed sources of domestic waste, the complex and diverse components, and the influence of geographical location, storage environment, etc., the water quality of organic biogas slurry is relatively complex, rich in biological nutrients such as protein, carbohydrates, fat, cellulose, and other substances such as inorganic salts, organic acids, humus, etc. As the fermentation bacteria grow inside the biogas slurry, a large amount of extracellular polymers (EPS) are produced during the growth and metabolism of microorganisms.

[0003] EPS is mainly composed of PS (polysaccharide) and PN (protein), which account for 70% to 80% of the EPS mass. Most of the urban organic waste is kitchen waste. The rich nutrient residues lead to the proliferation of microorganisms such as sludge bacteria. The sludge contains a large amount of EPS. EPS combines with particles in the biofilm suspension and captures particles, which limits the dispersion of substances and element circulation in the sludge, increases the stability of the sediment, and affects the cohesion and permeability of the sediment. EPS is highly hydrated, complex in configuration, and adheres to each other. It forms a stable suspension system with organic macromolecules such as biomass oil and residual protein in the sludge. Filamentous bacteria grow in the sludge, and the extracellular polymer EPS can connect and adhere to cells through bridging and other effects. The overall viscosity of organic sludge is high, there are many biological suspended solids, the EPS content is high, the bound water content is high, it is difficult to settle, the filtration resistance is large, and it is difficult to mechanically dehydrate.

[0004] At present, the main methods for separating suspended matter from organic biogas slurry include filtration, centrifugation, sedimentation, flotation, screening, etc. Among them, centrifugation and sedimentation are the most effective methods in the application of organic biogas slurry treatment engineering. However, there is a high-viscosity component EPS in organic biogas slurry. During the centrifugation treatment process, it often forms adhesion in the equipment pipeline, causing equipment blockage, affecting equipment performance, and even causing system paralysis; during the sedimentation treatment process, due to the stable suspension system formed by high EPS in organic biogas slurry, the sedimentation time is long, the sedimentation effect is poor, and the treatment efficiency is low. Therefore, it is an urgent problem to destroy the stable suspended matter system in organic biogas slurry, change the sedimentation and viscosity of organic biogas slurry, and improve the sedimentation. Summary of the invention

[0005] In view of the above technical problems, the purpose of the present invention is to improve the sedimentation of organic biogas slurry, make it easier to remove stable suspended matter in the biogas slurry, and provide a method for improving the sedimentation of organic biogas slurry by electron beam irradiation.

[0006] To achieve the above-mentioned purpose, the present application provides a method for improving the sedimentation of organic biogas slurry by electron beam irradiation;

[0007] The following steps are involved:

[0008] S1, collecting organic biogas slurry, stirring and mixing it evenly to obtain a liquid to be treated;

[0009] S2, using an electron accelerator to perform electron beam irradiation treatment on the liquid to be treated;

[0010] Wherein: the organic biogas slurry contains EPS.

[0011] More specifically, the soluble EPS content in the organic biogas slurry is greater than 190 mg / L.

[0012] More specifically, in step S2, the irradiation dose of the electron beam irradiation treatment is 1 to 50 kGy.

[0013] More specifically, in step S2, the irradiation dose of the electron beam irradiation treatment is preferably 10 to 50 kGy.

[0014] More specifically, in step S2, the electron accelerator for the electron beam irradiation treatment is selected to be 0.5-2.0 MeV.

[0015] More specifically, in step S2, the electron accelerator beam current of the electron beam irradiation treatment is 10-50 mA.

[0016] More specifically, in step S2, the electron accelerator beam width for electron beam irradiation treatment is 800-1450 mm.

[0017] More specifically, in step S2, the electron beam irradiation time of the electron beam irradiation treatment is 0.005 to 0.05 s.

[0018] More specifically, in step S2, the electron beam irradiation time of the electron beam irradiation treatment is preferably 0.01 to 0.05 s.

[0019] More specifically, in step S2, during the electron beam irradiation treatment, the water curtain width of the organic biogas slurry is smaller than the beam width of the electron accelerator, and the water curtain width of the organic biogas slurry is 500-1000 mm.

[0020] More specifically, in step S2, during the electron beam irradiation treatment, the thickness of the water curtain of the organic biogas slurry is 1 to 5 mm.

[0021] The beneficial effects of the present invention are as follows: by using the electron beam irradiation treatment method, the electron beam energy acts on the high-viscosity suspension system of organic biogas slurry, which can respond quickly, and the electron beam energy penetrates the extracellular polymer (EPS) coated on the bacteria, causing it to decompose and fall off, disrupting the connection bridge between EPS and filamentous fungi, improving the high viscosity, destroying the high-concentration EPS stable suspension system in the organic biogas slurry, and improving the sedimentation of the organic biogas slurry. The sedimentation of the organic biogas slurry after electron beam irradiation is significantly improved, and a large amount of EPS contained in the original biogas slurry has been destroyed.

[0022] The electron beam irradiation process of the present invention can also generate free radicals e in the organic biogas slurry. aq - OH - and H + , can quickly react with organic macromolecules in the water, destroy the long chain structure of organic macromolecules, and achieve the purpose of degrading and converting high-viscosity organic matter. The use of electron beams to treat high-viscosity organic biogas slurry has the characteristics of convenient operation, small footprint, low investment, and short process flow. After electron beam irradiation treatment, the separation efficiency of organic biogas slurry is improved, which solves the problem of high solid content in organic biogas slurry that is difficult to handle, and can reduce the burden of subsequent equipment processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a test graph of biogas slurry viscosity after the organic biogas slurry in this application is irradiated with electron beams of different irradiation doses;

[0024] Figure 2 It is an apparent diagram of the precipitation of organic biogas slurry after being irradiated with electron beams of different irradiation doses over time;

[0025] Figure 3 This is a graph showing the change in solid content sedimentation rate of organic biogas slurry after being irradiated with electron beams of different irradiation doses and then left to settle over time;

[0026] Figure 4 This is a graph showing the SS content in the upper layer of the organic biogas slurry after being irradiated with electron beams of different irradiation doses and then left to stand for 2 hours;

[0027] Figure 5 This is a comparison chart of SS content in the supernatant of the organic biogas slurry after being irradiated with electron beams of different irradiation doses and then centrifuged;

[0028] Figure 6 These are the test results of the EPS content in the organic biogas slurry in this application and the test results of the EPS content after electron beam irradiation. DETAILED DESCRIPTION

[0029] The specific implementation methods of the present invention are described clearly and completely below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments mentioned in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The purpose of the present invention is to improve the sedimentation of organic biogas slurry, make the organic biogas slurry with high EPS content and complex components more easily separated and sedimented, and provide a method for improving the sedimentation of organic biogas slurry by electron beam irradiation.

[0031] To achieve the above-mentioned purpose, the present application provides a method for improving the sedimentation of organic biogas slurry by electron beam irradiation;

[0032] The following steps are involved:

[0033] S1, collecting organic biogas slurry, stirring and mixing it evenly to obtain a liquid to be treated;

[0034] S2, using an electron accelerator to perform electron beam irradiation treatment on the liquid to be treated;

[0035] Wherein: the organic biogas slurry contains EPS.

[0036] In some embodiments, in step S2, the irradiation dose of the electron beam irradiation treatment is 1 to 50 kGy.

[0037] In some embodiments, in step S2, the electron accelerator energy for electron beam irradiation treatment is selected to be 0.5-2.0 MeV.

[0038] In some embodiments, in step S2, the electron accelerator beam current of the electron beam irradiation treatment is 10-50 mA.

[0039] In some embodiments, in step S2, the electron accelerator beam width of the electron beam irradiation treatment is 800 to 1450 mm.

[0040] In some embodiments, in step S2, the electron beam irradiation time of the electron beam irradiation treatment is 0.005 to 0.05 s.

[0041] In some embodiments, in step S2, during the electron beam irradiation treatment, the water curtain width of the organic biogas slurry is smaller than the beam width of the electron accelerator, and the water curtain width of the organic biogas slurry is 500-1000 mm.

[0042] In some embodiments, in step S2, during the electron beam irradiation treatment, the thickness of the organic biogas slurry water curtain is 1 to 5 mm.

[0043] like Figure 1 As shown in the figure, after the organic biogas slurry was irradiated with electron beam at different irradiation doses, the viscosity of the biogas slurry was tested respectively, and the curve of the biogas slurry viscosity changing with the irradiation dose was obtained, which shows that with the increase of irradiation dose, the organic matter, microorganisms and extracellular polymer suspension system in the organic biogas slurry are decomposed, the long-chain polymer substances are broken, the flocculation effect of microorganisms is reduced, the viscosity of the biogas slurry is reduced, the dehydration effect is increased, and the ability of the organic biogas slurry to remove suspended matter is enhanced, thereby achieving the purpose of rapid precipitation.

[0044] like Figure 2 As shown in the figure, the organic biogas slurry after irradiation was allowed to settle and showed different degrees of stratification over time, indicating that the natural sedimentation effect of the organic biogas slurry after irradiation was obvious, and the sedimentation of the organic biogas slurry was enhanced after electron beam irradiation. Figure 3 As shown in the figure, after the organic biogas slurry was treated with different irradiation doses, the sedimentation rate of suspended matter in the biogas slurry gradually increased with the increase of standing time.

[0045] like Figure 4 As shown, the organic biogas slurry treated with electron beam irradiation of different irradiation doses was left to stand for 2 hours, and the suspended matter content in the supernatant was detected and analyzed. The suspended matter content in the supernatant decreased with the increase of irradiation dose.

[0046] The EPS detection method adopted in this application is: the organic biogas slurry is initially separated by centrifugation, the supernatant after centrifugation is discharged, the remaining precipitate is washed with distilled water and resuspended in 0.9% NaCl solution, and the supernatant is obtained after heating, cooling and centrifugation as EPS solution. The EPS content in the solution can be estimated by measuring the TOC content or the total content of PS (polysaccharide) and PN (protein) in EPS. In this application, the method of measuring TOC content is used to determine the EPS content. Figure 6 As shown, in the tested embodiment, the EPS content in the organic biogas slurry sample is 410 mg / L before electron beam irradiation. After electron beam irradiation, the EPS content in the biogas slurry is significantly reduced. The electron beam energy penetrates the EPS biofilm suspension system, disrupts the biogas slurry suspended particles, separates and decomposes organic macromolecules, and the sedimentation of the organic biogas slurry is greatly improved.

[0047] Some specific embodiments and specific performance test results are listed below:

[0048] Example 1

[0049] 1) Collect the organic biogas slurry with a viscosity of 52.18 mPa·s into the biogas slurry pool and stir and mix it evenly to form a relatively stable liquid to be treated.

[0050] 2) The liquid to be treated is transported to an electron accelerator for irradiation treatment, the irradiation dose is 5 kGy, the electron accelerator is selected as 2.0 MeV, the beam current is 50 mA, the beam width is 1000 mm, the irradiation time is 0.005 s, the water curtain width is 800 mm, and the water curtain thickness is 5 mm. The viscosity of the organic biogas slurry after electron beam irradiation is 10.25 mPa·s.

[0051] 3) The solution after electron beam irradiation was allowed to settle naturally. When the settling time was 60 min, the SS content of the supernatant was 6567 mg / L.

[0052] Example 2

[0053] 1) Collect the organic biogas slurry with a viscosity of 52.18 mPa·s into the biogas slurry pool and stir and mix it evenly to form a relatively stable liquid to be treated.

[0054] 2) The liquid to be treated is transported to an electron accelerator for irradiation treatment, the irradiation dose is 10 kGy, the electron accelerator is selected as 2.0 MeV, the beam current is 50 mA, the beam width is 1000 mm, the irradiation time is 0.01 s, the water curtain width is 800 mm, and the water curtain thickness is 5 mm. The viscosity of the organic biogas slurry after electron beam irradiation is 6.57 mPa·s.

[0055] 3) The organic biogas slurry after electron beam irradiation was allowed to settle naturally. When the settling time was 60 min, the SS content of the supernatant was 6167 mg / L.

[0056] Example 3

[0057] 1) Collect the organic biogas slurry with a viscosity of 52.18 mPa·s into the biogas slurry pool and stir and mix it evenly to form a relatively stable liquid to be treated.

[0058] 2) The liquid to be treated is transported to an electron accelerator for irradiation treatment, the irradiation dose is 20 kGy, the electron accelerator is selected as 2.0 MeV, the beam current is 50 mA, the beam width is 1000 mm, the irradiation time is 0.03 s, the water curtain width is 800 mm, and the water curtain thickness is 5 mm. The viscosity of the organic biogas slurry after electron beam irradiation is 4.34 mPa·s.

[0059] 3) The organic biogas slurry after electron beam irradiation was allowed to settle naturally. When the settling time was 60 min, the SS content of the supernatant was 6133 mg / L.

[0060] Example 4

[0061] 1) Collect the organic biogas slurry with a viscosity of 52.18 mPa·s into the biogas slurry pool and stir and mix it evenly to form a relatively stable liquid to be treated.

[0062] 2) The liquid to be treated is transported to an electron accelerator for irradiation treatment, the irradiation dose is 50 kGy, the electron accelerator is selected as 2.0 MeV, the beam current is 50 mA, the beam width is 1000 mm, the irradiation time is 0.05 s, the water curtain width is 800 mm, and the water curtain thickness is 5 mm. The viscosity of the organic biogas slurry after electron beam irradiation is 3.84 mPa·s.

[0063] 3) The organic biogas slurry after electron beam irradiation was allowed to settle naturally. When the settling time was 60 min, the SS content of the supernatant was 6000 mg / L.

[0064] Centrifugal separation tests were conducted on the organic biogas slurry after irradiation treatment with different irradiation doses in the above embodiments, indicating that the treatment method of the present invention can reduce the burden of subsequent equipment treatment of the organic biogas slurry. The centrifugal speed of the centrifugal separation method is 3000-8000r / min, and the centrifugal time is 1-10min. The coagulation + centrifugal separation method is adopted, and the coagulant PAFC is added in the coagulation process, with a concentration of 1‰-5‰, and the pH value is adjusted to 7-8 after stirring evenly, and the flocculant PAM is added in a concentration of 1‰-4‰ during the stirring process.

[0065] The organic biogas slurry irradiated with electron beams of different irradiation doses in Examples 1-3 was subjected to centrifugation and coagulation + centrifugation treatments respectively. After centrifugation, the suspended matter content of the supernatant was measured to obtain the following: Figure 5 The SS content comparison chart of the supernatant is shown. The centrifugal speed of the centrifuge was set to 5000r / min and the centrifugal time was 5min during the centrifugal treatment. The coagulation + centrifugal separation treatment steps are as follows: first, add coagulant PAFC to the organic biogas slurry at a concentration of 3‰, stir evenly and adjust the pH value to 8, add flocculant PAM at a concentration of 2‰ during the stirring process; then centrifuge at a centrifugal speed of 5000r / min and a centrifugal time of 5min.

[0066] Compared with the organic biogas slurry that was directly centrifuged without electron beam irradiation, the suspended matter concentration decreased by 46.9%, 50.1% and 50.4% after irradiation of 5kGy, 10kGy and 20kGy, respectively. After centrifugation with the addition of coagulants, it was found that the SS content of the supernatant decreased significantly when the coagulant PAFC and flocculant PAM were added at the same irradiation dose. When the irradiation dose increased to 10kGy, the suspended matter content in the solution decreased by 23.1% compared with that without the addition of agents. When the irradiation dose increased to 20kGy, the suspended matter content in the solution decreased by 22.1% compared with that without the addition of agents. This shows that after electron beam irradiation treatment with the increase of irradiation dose, the suspended matter in the organic biogas slurry has better sedimentation performance under the action of centrifugation, achieving the purpose of rapid separation and reducing the burden on equipment. When the structure of organic pollutants in organic biogas slurry is destroyed by electron beams and coagulants and flocculants are added, the colloidal double layer in the water is compressed and loses stability during the coagulation stage to form smaller particles; in the flocculation stage, these particles aggregate with each other (or due to the adsorption and bridging effect of macromolecular substances) to form large flocs, which are separated and removed from the water under centrifugal action, thereby increasing the separation efficiency. Therefore, in actual engineering applications, centrifugal separation equipment and cheap coagulants can be used to efficiently separate organic biogas slurry, and the proportion of coagulants can be appropriately adjusted according to demand.

[0067] The following are the test results of the organic biogas slurry after electron beam irradiation treatment in the above embodiment:

[0068] Example 1 Example 2 Example 3 Example 4 Biogas slurry viscosity (mPa·s) 52.18 52.18 52.18 52.18 Radiation dose (kGy) 5 10 20 50 Equipment selection (MeV) 2 2 2 2 Electron beam current (mA) 50 50 50 50 Beam width(mm) 1000 1000 1000 1000 Irradiation time(s) 0.005 0.01 0.03 0.05 Water curtain width(mm) 800 800 800 800 Water curtain thickness (mm) 5 5 5 5 Viscosity after irradiation (mPa·s) 10.25 6.57 4.34 3.84 Supernatant SS (mg / L) 6567 6167 6133 6000

[0069] According to the test results of the viscosity of the organic biogas slurry after electron beam irradiation and the test results of the SS value of the supernatant in the embodiment, with the increase of electron beam irradiation dose and irradiation time, the viscosity of the organic biogas slurry decreases significantly, the EPS flocculation system in the biogas slurry is destroyed, the sedimentation of the organic biogas slurry is improved, and the suspended matter content of the supernatant after sedimentation is greatly reduced.

[0070] The present application specifically performs electron beam irradiation treatment on urban organic biogas slurry containing a large amount of EPS, utilizing the high energy penetration of the electron beam to destroy the high viscosity EPS system secreted by bacteria, thereby improving the sedimentation performance of the organic biogas slurry, facilitating the implementation of subsequent purification treatment processes for the organic biogas slurry, and reducing the processing pressure on equipment.

[0071] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope of the present invention.

Claims

1. A method for improving the sedimentation of organic biogas slurry by electron beam irradiation, characterized in that: The following steps are involved: S1, collecting organic biogas slurry, stirring and mixing it evenly to obtain a liquid to be treated; S2, using an electron accelerator to perform electron beam irradiation treatment on the liquid to be treated; Wherein: the organic biogas slurry contains EPS.

2. The method according to claim 1, characterized in that In step S2, the irradiation dose of the electron accelerator is 1 to 50 kGy.

3. The method according to claim 2, characterized in that In step S2, the irradiation dose of the electron accelerator is 10 to 50 kGy.

4. The method according to claim 1, characterized in that: In step S2, the electron accelerator of the electron accelerator is selected to be 0.5-2.0 MeV.

5. The method according to claim 1, characterized in that In step S2, the electron accelerator beam current of the electron accelerator is 10-50 mA.

6. The method according to claim 1, characterized in that In step S2, the electron accelerator beam width of the electron accelerator is 800-1450 mm.

7. The method according to claim 1, characterized in that In step S2, the electron beam irradiation time of the electron accelerator is 0.005 to 0.05 s.

8. The method according to claim 7, characterized in that In step S2, the electron beam irradiation time of the electron accelerator is 0.01 to 0.05 s.

9. The method according to claim 1, characterized in that: In step S2, during the electron beam irradiation treatment, the water curtain width of the organic biogas slurry is smaller than the beam width of the electron accelerator, and the water curtain width is 500-1000 mm.

10. The method according to claim 1, characterized in that In step S2, during the electron beam irradiation treatment, the thickness of the water curtain of the organic biogas slurry is 1 to 5 mm.

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