Preparation method and application of sludge-based biochar loaded with group sensing signal molecules and extracellular polymeric substances

Abstract

The invention discloses a preparation method and application of sludge-based biochar loaded with group sensing signal molecules (AHLs) and extracellular polymeric substances (EPS). The preparation method comprises the following steps: culturing, crushing and concentrating waste anaerobic granular sludge (AnGS) to extract AHLs; the method comprises the following steps: washing AnGS, heating in a water bath, and centrifugally extracting EPS; and then drying and grinding the AnGS, stirring in a constant-temperature water bath, pyrolyzing, washing and grinding to prepare biochar, and finally freeze-drying to load the AHLs and the EPS on the sludge-based biochar. The loaded sludge-based biochar can be used as a redox mediator, is applied to the field of anaerobic digestion of wastewater, and aims to improve extracellular electron transfer and enhance the anaerobic treatment efficiency of refractory wastewater. The method has the advantages that the prepared loaded sludge-based biochar has a good removal effect on organic pollutants, meanwhile, the waste activated sludge can be recycled, waste is treated with waste, environmental pollution is reduced, resources are recycled, and cost is saved. In addition, the method has good application value in the aspects of soil remediation, catalysis and the like.

Description

Technical field:

[0001] The present invention belongs to the field of wastewater anaerobic digestion water treatment, and specifically relates to a preparation method and application of sludge-based biochar loaded with quorum sensing signal molecules (AHLs) and extracellular polymers (EPS). Background technology:

[0002] In recent years, the amount and efficiency of sewage treatment in my country's cities have been continuously improved. In order to achieve low-carbon, environmentally friendly, energy-saving and other harmless disposal of sludge, sewage sludge resource utilization has become a major trend. Pyrolysis methods are widely used in sewage sludge treatment. During the pyrolysis process, the organic matter in the sludge will gradually degrade and its minerals will gradually oxidize, eventually forming biochar based on sewage sludge. Because it contains rich carbon elements and functional groups, sludge-based biochar has a wide range of applications in fields such as anaerobic wastewater treatment.

[0003] Anaerobic digestion of wastewater has become a mainstream technology for wastewater treatment due to its advantages of energy saving, more biogas recovery and low sludge production. However, it has problems such as inefficient interspecies electron transfer. Therefore, in the process of enhanced anaerobic digestion, biochar can be used as a conductive medium to enhance the extracellular electron transfer between microorganisms due to its large surface area, high porosity and redox characteristics. It can also selectively enrich electroactive microorganisms and strengthen the establishment of microbial communities, thereby greatly accelerating the symbiotic metabolism of organic matter. However, for conventional biochar, due to its low surface active sites and other problems, in the process of anaerobic wastewater treatment, there are still problems such as low methanogenesis rate (SMA) and chemical oxygen demand (COD) removal efficiency. There is an urgent need for economical and efficient redox mediator materials to be used in anaerobic digestion wastewater treatment systems. Summary of the invention:

[0004] In view of the deficiencies of the prior art, the purpose of the present invention is to design a method for extracting AHLs and EPS from waste anaerobic granular sludge, loading them with sludge-based biochar to form a new type of redox mediator, thereby realizing a method for recycling waste activated sludge.

[0005] Another object of the present invention is to provide the use of the above-mentioned sludge-based biochar loaded with AHLs and EPS in the anaerobic digestion treatment of azo dye wastewater system. The sludge-based biochar loaded with AHLs and EPS is used as a redox mediator. On the one hand, it regulates the quorum sensing of the microbial system by slow-release AHLs, and on the other hand, it enhances electron transfer through EPS surface functional groups. The sludge-based biochar loaded with AHLs and EPS can achieve synergistic enhancement of quorum sensing and electron transfer, thereby enhancing the efficiency of anaerobic biological treatment of azo dye wastewater.

[0006] The purpose of the present invention is achieved through the following technical solutions.

[0007] A method for extracting AHLs from waste anaerobic granular sludge (AnGS) comprises the following steps:

[0008] 1) The waste AnGS was cultured with artificial water and the obtained supernatant was crushed with an ultrasonic crusher, and then the sample was centrifuged, and the supernatant was taken and filtered through filter membranes in sequence.

[0009] In the step 1), the power of the ultrasonic crusher is 70-90W, the frequency is 3s interval, and the number of times is 300-400 times.

[0010] In the step 1), the sample is centrifuged at a rate of 7500-8500 r / min for 8-12 min.

[0011] In the step 1), the filter diameters of the membranes passed sequentially are 0.45 μm and 0.22 μm respectively.

[0012] 2) The samples were concentrated using HLB solid phase extraction columns to extract AHLs signal molecules from waste AnGS.

[0013] In the step 2), the HLB solid phase column has a specification of 6 ml and a filler weight of 500 mg.

[0014] AHLs obtained by the above extraction method.

[0015] A method for extracting EPS from AnGS comprises the following steps:

[0016] 1) The spent AnGS was washed with NaCl solution.

[0017] In the step 1), the concentration of the NaCl solution is 0.05%, and the washing times are 3-4 times.

[0018] 2) After washing, the sludge is suspended in NaCl solution and heated in a water bath.

[0019] In the step 2), the concentration of the NaCl solution is 0.05%, the water bath temperature is 70-90° C., and the water bath time is 25-35 min.

[0020] 3) The mixture is then placed in a centrifuge for centrifugation, and the supernatant containing EPS is collected and filtered through a filter membrane, thereby extracting EPS from the waste AnGS.

[0021] In the step 3), the sample is centrifuged at a rate of 11000-13000 r / min, and the centrifugation time is 15-20 min.

[0022] In the step 3), the filter diameter passing through the filter membrane is 0.45 μm.

[0023] EPS obtained by the above extraction method.

[0024] A method for preparing sludge-based biochar comprises the following steps:

[0025] 1) Dry the waste AnGS, grind it, mix it thoroughly with KHCO3, and dissolve it with distilled water.

[0026] In the step 1), the drying temperature is 100-110° C. and the drying time is 10-12 hours.

[0027] In the step 1), the mass ratio of the ground sludge to KHCO3 is 2:1.

[0028] 2) The mixture is magnetically stirred in a constant temperature water bath and dried.

[0029] In the step 2), the temperature of the constant temperature water bath is 50-70° C., and the magnetic stirring time is 10-12 h.

[0030] In the step 2), the drying temperature is 100-110° C. and the drying time is also 10-12 hours.

[0031] 3) The dried mixture is placed in a crucible and put into a tubular furnace for carbonization. During the pyrolysis process, N2 is introduced into the tubular furnace to maintain the N2 atmosphere.

[0032] In the step 3), the temperature of the tube furnace is set at 350-450° C., the heating rate is set at 8-12° C. / min, and the carbonization time is 1-2 h.

[0033] In the step 3), the rate of introducing N2 is 100-200 ml / min.

[0034] 4) After the pyrolysis is completed, the tube furnace is taken out after being cooled naturally, and is soaked and rinsed with a hydrochloric acid solution, and then washed with anhydrous ethanol and distilled water in sequence until neutral, dried, ground and sieved, and finally a powdered sludge-based biochar product is obtained.

[0035] In step 4), the concentration of the hydrochloric acid solution is 3 mol / L, and the immersion time therein is 1-2 h.

[0036] In step 4), the drying temperature is 100-110° C. and the drying time is 10-12 h.

[0037] In the step 4), the sieve through which the powder is ground is 70-90 mesh.

[0038] The sludge-based biochar obtained by the above preparation method.

[0039] A preparation method for loading biochar with AHLs and EPS comprises the following steps:

[0040] 1) AHLs and EPS extracted from sludge in advance are added to the prepared sludge-based biochar, and the sludge-based biochar is freeze-dried in a freeze dryer to load the sludge-based biochar with AHLs and EPS.

[0041] In the step 1), the mass ratio of the added AHLs and EPS is 1:1, the precooling temperature of the freeze dryer is set at 5-10°C, the cooling rate is 25-35°C / min, and the final cooling temperature is -1°C.

[0042] In the step 1), the drying time is 8-10 hours.

[0043] The sludge-based biochar loaded with AHLs and EPS obtained by the above preparation method.

[0044] The above-mentioned sludge-based biochar loaded with AHLs and EPS was used as a redox mediator.

[0045] The above redox mediator is used for anaerobic digestion treatment of wastewater.

[0046] The invention discloses an application of sludge-based biochar loaded with AHLs and EPS in an anaerobic digestion system for treating azo dye wastewater. The sludge-based biochar loaded with AHLs and EPS is used as a redox mediator and added into the anaerobic digestion system for treating azo dye wastewater, thereby strengthening the electron transfer process of anaerobic microorganisms and realizing rapid degradation of azo dyes.

[0047] The mass of the sludge-based biochar loaded with AHLs and EPS added per liter volume of the anaerobic reactor in the anaerobic digestion treatment of azo dye wastewater is 0.8-1.2g.

[0048] The dye of the above-mentioned azo dye wastewater is methyl orange or Congo red.

[0049] The beneficial effects provided by the present invention are:

[0050] The process of the present invention is simple, the operation flow is simple, the required reagents are cheap and easy to prepare, and the operating cost is low. The preparation of sludge-based biochar can improve the reuse rate of waste activated sludge, and it has the advantages of large specific surface area and rich surface functional groups. For sludge-based biochar loaded with AHLs and EPS, it can be used as a redox mediator to strengthen the electron transfer process of anaerobic microorganisms and enhance the anaerobic digestion treatment efficiency of wastewater. At the same time, it also has a good effect on the removal of organic pollutants. In addition, it has good application value in contaminated soil remediation and catalysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 The microstructure diagrams are of the sludge-based biochar obtained in control case 1 (a) and the sludge-based biochar loaded with EPS and AHLs obtained in implementation case 1 (b);

[0052] Figure 2 COD removal rates for implementation case 2 and control case 2;

[0053] Figure 3 is the specific methanogenesis rate (SMA) of implementation case 2 and control case 2;

[0054] Figure 4 is the decolorization rate of implementation case 2 and control case 2;

[0055] Figure 5 COD removal rates for implementation case 3 and control case 3;

[0056] Figure 6 is the specific methanogenesis rate (SMA) of implementation case 3 and control case 3;

[0057] Figure 7 It is the decolorization rate of implementation case 3 and control case 3. Specific implementation method:

[0058] The present invention is further described in detail below with reference to the accompanying drawings and specific examples:

[0059] The source of artificial water (for extracting signal molecules) in the following examples is self-prepared, and the formula is as follows:

[0060] Artificial water recipe

[0061] Element concentration glucose 3000mg / L <![CDATA[NH4Cl]]> 900mg / L <![CDATA[KH2PO4]]> 60mg / L <![CDATA[MgSO4]]> 24mg / L <![CDATA[CaCl2]]> 3mg / L <![CDATA[FeSO4-7H2O]]> 1.5mg / L <![CDATA[CuSO4]]> 0.18mg / L <![CDATA[ZnSO4-7H2O]]> 0.3mg / L NaCl 0.18mg / L <![CDATA[CoCl-6H2O]]> 0.24mg / L <![CDATA[NaHCO3]]> 600mg / L

[0062] The source of azo dye wastewater (methyl orange) in the following examples is self-prepared, and the formula is as follows:

[0063] Formula of azo dye wastewater (methyl orange)

[0064]

[0065]

[0066] The source of azo dye wastewater (Congo red) in the following examples is self-prepared, and the formula is as follows:

[0067] Formula of azo dye wastewater (Congo red)

[0068] principal component Concentration (mg / L) Auxiliary ingredients Concentration (mg / L) glucose 3000 Calcium chloride (dihydrate) 4.2 Ammonium chloride 120 Ferrous Sulfate Heptahydrate 3.75 Dipotassium hydrogen phosphate 15 Anhydrous magnesium sulfate 3.75 Potassium dihydrogen phosphate 15 Manganese chloride tetrahydrate 3.75 Sodium bicarbonate 2250 EDTA 0.18 Congo Red 750 Copper sulfate pentahydrate 0.15 - - Nickel chloride hexahydrate 0.18 - - Zinc chloride 0.15 - - Aluminum Chloride 0.38 - - Sodium molybdate dihydrate 0.02 - - Boric acid 0.06

[0069] Implementation Case 1

[0070] A method for extracting AHLs from waste AnGS, comprising the following steps:

[0071] First, waste AnGS was placed in a 500ml serum bottle with a granular sludge concentration of 25gVSS / L, and then cultured in a water bath oscillator with 3000mg / LCOD artificial water, oscillated in a water bath at 35°C, with a frequency of 125r / min, and the culture time was 5 days. 100ml of supernatant was collected every day, and 100ml of influent was added to ensure that the influent COD concentration was continuously 3000mg / L, and finally 500ml of supernatant containing AHLs was obtained. An 80W ultrasonic crusher (3S interval and 3S crushing) was used for 300 times, and then the sample was centrifuged at 8000r / min for 10 minutes, the supernatant was taken and filtered through 0.45μm and 0.22μmn membranes in turn. The sample was concentrated using an HLB solid phase extraction column (6mL, 500mg) to obtain AHLs signal molecules.

[0072] A method for extracting EPS from waste AnGS, the steps are as follows:

[0073] The spent AnGS was washed three times with 0.05% NaCl solution. The sludge was then suspended in 0.05% NaCl solution and heated in a water bath at 80°C for 30 min. The mixture was then centrifuged at 12000 pm for 15 min. The supernatant containing EPS was collected and filtered through a 0.45 μm membrane to obtain EPS.

[0074] A method for preparing sludge-based biochar, the steps of which are as follows:

[0075] The waste AnGS was dried at 105°C for 12 hours, and the dried sludge was ground and mixed with KHCO3 at a mass ratio of 2:1, and dissolved with distilled water. The mixture was magnetically stirred in a 60°C constant temperature water bath for 12 hours, and then dried at 105°C for 12 hours. The dried mixture was placed in a crucible and placed in a tube furnace for carbonization at 400°C for 1 hour. The heating rate of the tube furnace was 10°C / min. During the pyrolysis process, N2 was introduced into the tube furnace at 100ml / min to maintain the N2 atmosphere during the pyrolysis process. After the pyrolysis is completed, the tube furnace is taken out after it is cooled naturally, and it is soaked in 3mol / L hydrochloric acid solution for 1 hour and rinsed to remove residual KHCO3. Then, it is washed with anhydrous ethanol and distilled water to neutrality, and finally dried at 105°C for 12 hours, ground, and passed through an 80-mesh sieve to finally obtain a powdered sludge-based biochar product.

[0076] A method for loading AHLs and EPS onto sludge-based biochar, comprising the following steps:

[0077] AHLs and EPS extracted from the sludge in a mass ratio of 1:1 were added to the prepared sludge activated carbon product, and the product was placed in a freeze dryer with a precooling temperature of 7°C and a cooling rate of 30°C / min until it cooled to -1°C. After freezing, it was dried for 10 hours to finally obtain sludge-based biochar loaded with AHLs and EPS.

[0078] Comparative Case 1

[0079] A method for preparing sludge-based biochar, the steps of which are as follows:

[0080] The waste AnGS was dried at 105°C for 12 hours, ground and mixed with KHCO3 at a mass ratio of 2:1, and dissolved with distilled water. The mixture was magnetically stirred in a 60°C constant temperature water bath for 12 hours, and then dried at 105°C for 12 hours. The dried mixture was placed in a crucible and placed in a tubular furnace for carbonization at 400°C for 1 hour. The heating rate of the tubular furnace was 10°C / min. During the pyrolysis process, N2 was introduced into the tubular furnace at 100ml / min to maintain the N2 atmosphere during the pyrolysis process. After the pyrolysis is completed, the tubular furnace is taken out after cooling naturally, and soaked in 3mol / L hydrochloric acid solution for 1 hour, rinsed to remove residual KHCO3, and then washed with anhydrous ethanol and distilled water to neutrality, and finally dried at 105°C for 12 hours, ground, and passed through an 80-mesh sieve to obtain sludge-based biochar.

[0081] Depend on Figure 1 (a) and Figure 1 (b) It can be seen that many white crystalline particles are attached to the sludge-based biochar loaded with AHLs and EPS. Compared with the sludge-based biochar obtained in control case 1, the pores become more sparse and the surface becomes rougher.

[0082] Implementation Cases 2-3

[0083] The application of sludge-based biochar loaded with AHLs and EPS in the anaerobic digestion treatment of azo dye wastewater system. The sludge-based biochar loaded with AHLs and EPS is used as a redox mediator and added to the azo dye wastewater (1200 mg / L) system treated by anaerobic digestion to enhance the anaerobic microbial electron transfer process and achieve rapid degradation of azo dyes.

[0084] The method for using the sludge-based biochar loaded with AHLs and EPS is as follows: the sludge-based biochar loaded with AHLs and EPS is added to the azo dye wastewater system, and the dye wastewater system is always kept at 30°C, so that the sludge-based biochar loaded with AHLs and EPS is fully mixed with the anaerobic granular sludge in the azo dye wastewater. The mass of the sludge-based biochar loaded with AHLs and EPS added per liter volume of the anaerobic reactor in the anaerobic digestion treatment azo dye wastewater system is 0.8-1.2g, and the dye of the azo dye wastewater is methyl orange or Congo red.

[0085] Comparative Cases 2-3

[0086] The dye wastewater system is always maintained at 30°C, the concentration of azo dye is 1200 mg / L, and the azo dye is methyl orange or Congo red.

[0087] The variation patterns of COD removal rate, specific methanogenesis rate and decolorization rate of implementation case 2 and control case 2 over time were investigated. Figure 2 As shown in the figure, it can be seen that the sludge-based biochar loaded with AHLs and EPS used in the present invention is used in the anaerobic digestion treatment of azo dye wastewater system, and its COD removal rate for methyl orange dye wastewater is stably maintained at about 86.3%, which is 41.2% higher than that of the wastewater treatment system without the addition of sludge-based biochar loaded with AHLs and EPS. Figure 3 As shown, it can be seen that the sludge-based biochar loaded with AHLs and EPS used in the invention can maintain a stable methanogenic rate of about 17.1mL / (gVSS.h) in the anaerobic digestion treatment of azo dye wastewater system, which is 49.2% higher than the wastewater treatment system without the addition of sludge-based biochar loaded with AHLs and EPS. Figure 4 As shown, it can be seen that in the anaerobic digestion treatment system of azo dye wastewater treated with the sludge-based biochar loaded with AHLs and EPS of the present invention, the average methyl orange content along the process was measured to be 27.2 mg / L per day, which was reduced by 68.9% compared with the wastewater treatment system without the sludge-based biochar loaded with AHLs and EPS.

[0088] The variation patterns of COD removal rate, specific methanogenesis rate and decolorization rate of implementation case 3 and control case 3 over time were investigated. Figure 5 As shown, it can be seen that the sludge-based biochar loaded with AHLs and EPS used in the present invention is used in the anaerobic digestion treatment of azo dye wastewater system, and its COD removal rate for Congo red dye wastewater is stably maintained at about 85.9%, which is 39.4% higher than that of the wastewater treatment system without the addition of sludge-based biochar loaded with AHLs and EPS. Figure 6As shown, it can be seen that the sludge-based biochar loaded with AHLs and EPS used in the invention can maintain a stable methanogenic rate of about 16.5mL / (gVSS.h) in the anaerobic digestion treatment of azo dye wastewater system, which is 47.3% higher than the wastewater treatment system without the addition of sludge-based biochar loaded with AHLs and EPS. Figure 7 As shown, it can be seen that the sludge-based biochar loaded with AHLs and EPS in the anaerobic digestion treatment of azo dye wastewater system has an average one-day Congo red content of 27.2 mg / L, which is 66.9% lower than that of the wastewater treatment system without the sludge-based biochar loaded with AHLs and EPS.

Claims

1. A method for extracting quorum sensing signal molecules (AHLs) and extracellular polymeric substances (EPS) from waste anaerobic granular sludge (AnGS), characterized in that: The following steps are involved: (1) First, the waste AnGS is crushed by an ultrasonic crusher, then centrifuged and filtered, the supernatant is collected, and the supernatant is concentrated by an HLB solid phase column to obtain the AHLs. (2) washing the waste AnGS with a NaCl solution and mixing them to obtain an intermediate product; The intermediate product is heated in a water bath, centrifuged, and the supernatant is collected and filtered to obtain the EPS.

2. The extraction method according to claim 1, characterized in that In the step (1), the power of the ultrasonic crusher is 70-90W, the frequency is 3s interval, the number of times is 300-400 times, the centrifugal speed is 7500-8500r / min, and the centrifugal time is 8-12min; the HLB solid phase column specification is 6ml, and the filler weight is 500mg.

3. The extraction method according to claim 1, characterized in that In the step (2), the concentration of the NaCl solution is 0.05%, the number of washing times is 3-4 times, the water bath temperature is 70-90°C, the water bath time is 25-35 min, the centrifugal speed is 11000-13000 r / min, and the centrifugal time is 15-20 min.

4. A method for preparing sludge-based biochar, characterized in that: The waste AnGS is dried, oven-dried, ground, mixed with KHCO3, dissolved in distilled water, magnetically stirred in a constant temperature water bath, and dried; placed in a tubular furnace for carbonization, pyrolyzed in an environment where N2 is introduced, and naturally cooled to obtain an intermediate product; the intermediate product is washed with hydrochloric acid solution, anhydrous ethanol, and distilled water in sequence until it is neutral, and finally dried, ground and sieved to finally obtain the sludge-based biochar.

5. The preparation method according to claim 4, characterized in that: The drying temperature is 100-110°C, the drying time is 10-12h, the mass ratio of the ground sludge to KHCO3 is 2:1, the temperature of the constant temperature water bath is 50-70°C, the magnetic stirring time is 10-12h, the drying temperature is 100-110°C, the drying time is 10-12h, the rate of N2 introduction is 100-200ml / min, the concentration of the hydrochloric acid solution is 3mol / L, the soaking time is 1-2h, and the sieve after grinding is 70-90 mesh.

6. A method for loading biochar with AHLs and EPS, characterized in that: The AHLs and EPS extracted according to claim 1 are added to the sludge-based biochar prepared according to claim 4, and the mixture is freeze-dried in a freeze dryer to obtain sludge-based biochar loaded with AHLs and EPS.

7. The preparation method according to claim 6, characterized in that: The mass ratio of the added AHLs and EPS is 1:1; the precooling temperature of the freeze dryer is set at 5-10°C, the cooling rate is 25-35°C / min, the final cooling temperature is -1°C; and the drying time is 8-10h.

8. Use of the sludge-based biochar loaded with AHLs and EPS as claimed in claim 6 in an anaerobic digestion system for treating azo dye wastewater.

9. The use according to claim 8, characterized in that: The sludge-based biochar loaded with AHLs and EPS is used as a redox mediator and added into an anaerobic digestion system for treating azo dye wastewater, thereby strengthening the electron transfer process of anaerobic microorganisms and realizing rapid degradation of azo dyes.

10. The method according to claim 9, characterized in that: In the anaerobic digestion system for treating azo dye wastewater, the mass of the sludge-based biochar loaded with AHLs and EPS put into the anaerobic reactor per liter volume is 0.8-1.2 g; the azo dye is methyl orange or Congo red.

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