A method for improving filtration performance of sludge mixed liquor and its application

Abstract

The present invention relates to the field of water treatment technology, and in particular to a method for enhancing the filtration performance of a sludge mixed liquor and its application. The method comprises the following steps: S1, mixing anhydrous sodium sulfate, urea and ferric chloride to obtain a mixed solution; S2, adding carbon fiber to the mixed solution of step S1 to carry out a hydrothermal reaction, taking out carbon fiber after the reaction is completed, drying and crystallizing the carbon fiber at high temperature to obtain an iron-carbon composite material; S3, adding the sludge mixed liquor to an anaerobic reactor, and suspending the iron-carbon composite material obtained in step S2 above the anaerobic reactor or adding it to the sludge mixed liquor; S4, micro-aerating the anaerobic reactor. The present invention improves the hydrolysis efficiency of organic matter in sewage by adding the iron-carbon composite material to the anaerobic reactor and micro-aerating the reactor simultaneously. The method also improves the sedimentation property of the sludge by optimizing the sludge floc cluster structure, thereby helping to improve the filtration performance of the sludge mixed liquor and slowing down the membrane fouling rate. The method has the value of being applied in actual anaerobic membrane bioreactors.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, in particular to a method for improving the filtration performance of sludge mixed liquor and an application thereof. Background Art

[0002] Anaerobic digestion (AD) can not only effectively degrade pollutants, but also recover energy from pollutants, making it a reliable way to treat pollutants. However, the anaerobic digestion process requires a variety of microorganisms to complete a series of biochemical reactions. The inefficiency of electron transfer and energy exchange between microorganisms greatly limits the efficiency of anaerobic digestion. Traditional anaerobic digestion has a series of problems such as long reaction cycle, low organic matter degradation rate, and low methane yield. For example: (1) The hydrolysis efficiency of organic matter is usually low. Even with the action of hydrolytic bacteria, some macromolecular substances can still not be hydrolyzed for a long time; (2) The composition of the produced biogas is complex, and methane production generally only accounts for 50%-60% of the biogas, of which CO2 and H2S still account for a large proportion. These greenhouse gases need to be treated and purified before they can be used; (3) The sludge dewatering performance is poor, and electrolytes or iron-based substances need to be added.

[0003] The anaerobic membrane bioreactor (AnMBR) process is an integrated coupled process that uses micro / ultrafiltration membrane separation to replace gravity sedimentation in traditional anaerobic digestion. The micro / ultrafiltration membrane can completely intercept suspended solids and efficiently intercept large molecular organic matter, thereby extending the interaction time between organic matter and microorganisms, thereby improving COD removal rate and methane recovery rate, and can ensure stable effluent water quality under long-term operation. However, it still faces technical bottlenecks such as membrane fouling that restrict its engineering application.

[0004] Based on this, the present invention is proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for enhancing the filtration performance of sludge mixed liquor and its application, which can improve the efficiency of degrading organic matter in sewage while optimizing the filtration performance of sludge mixed liquor and slowing down the membrane fouling rate.

[0006] The present invention provides a method for improving the filtration performance of a sludge mixed liquor, comprising the following steps:

[0007] S1. Mixing anhydrous sodium sulfate, urea and ferric chloride to obtain a mixed solution;

[0008] S2, adding carbon fiber to the mixed solution of step S1 to carry out a hydrothermal reaction, taking out carbon fiber after the reaction is completed, drying at high temperature and crystallizing it to obtain an iron-carbon composite material;

[0009] S3, adding the sludge mixture to the anaerobic reactor, and hanging the iron-carbon composite material prepared in step S2 above the anaerobic reactor or adding it to the sludge mixture;

[0010] S4. Add micro-aeration to the anaerobic reactor.

[0011] Preferably, in step S1, the concentration of the anhydrous sodium sulfate is 6.94-138.89 mmol / L, the concentration of the urea is 41.67-833.33 mmol / L, and the concentration of the ferric chloride is 12.5-250 mmol / L.

[0012] Preferably, in step S2, the carbon fiber is a sheet-like carbon fiber aggregate.

[0013] Preferably, the amount of the sheet-like carbon fiber aggregate added to the sludge mixture is 7-8 cm 3 / 0.4L; more preferably, the addition amount is 3.5×4×0.5-4×4×0.5cm 3 / 0.4L.

[0014] Preferably, the sheet-like carbon fiber aggregate is carbon felt.

[0015] Preferably, in step S2, the iron-carbon composite material is a composite material of iron oxide and carbon.

[0016] The present invention uses an iron-carbon composite material rather than a single iron or carbon. A composite material of iron oxide and carbon felt is used, but it is not limited to this. People skilled in the art can make adjustments according to actual needs. Any composite material based on carbon-based materials / iron-based materials should fall within the scope of the present invention. Preferably, the carbon-based material uses a flaky carbon material that is easy to separate from the sludge, and the preparation process is to anchor the iron-based material on the surface of the carbon-based material through chemical synthesis.

[0017] Preferably, in step S3, the total solid content in the sludge mixed liquor is 15-25 g / L.

[0018] Preferably, the specific components of the sludge mixture include: chemical oxygen demand: 12-17 g / L, long-term starch culture, and ammonium chloride / disodium hydrogen phosphate as nitrogen and phosphorus sources, but it is not limited to this. People in this field can make adjustments according to actual needs.

[0019] Preferably, in step S4, the micro-aeration is performed by uniformly aerating the anaerobic reactor through an aeration pump and a perforated aeration pipe.

[0020] Preferably, the gas source for uniform aeration of the anaerobic reactor is air or oxygen. Specifically, oxygen is introduced into the AD system by introducing an air source to activate facultative bacteria, but this is not limited to this. Any method of introducing oxygen into the AD system, such as pure oxygen, chemical reaction, or air source, falls within the scope of the invention.

[0021] Preferably, in step S4, the aeration volume of the micro-aeration is controlled by an ORP monitoring device, and the range of the ORP monitoring device is controlled within -300-0mv to achieve precise control of the aeration volume and prevent the collapse of the anaerobic system caused by excessive aeration.

[0022] Beneficial effects:

[0023] The technical solution of the present invention improves the efficiency of organic matter hydrolysis in wastewater by adding an iron-carbon composite material and micro-aeration during anaerobic water treatment. Furthermore, the iron-carbon composite material and micro-aeration significantly improve the sedimentation of sludge, helping to enhance the filtration performance of the sludge mixture and slow membrane fouling. Therefore, the iron-carbon composite material and micro-aeration coupling employed in the present invention has the dual properties of simultaneously degrading organic matter and optimizing the filtration properties of the sludge mixture. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 A schematic structural diagram of an anaerobic reactor provided by the present invention;

[0026] Figure 2 COD content curves under different conditions provided by the present invention;

[0027] Figure 3 This is a structural diagram of the ultrafiltration cup testing system provided by the present invention;

[0028] Figure 4 The relationship curve of the volume of the filtrate and time under different conditions provided by the present invention;

[0029] Figure 5 The sludge particle size distribution diagram under the blank conditions provided by the present invention;

[0030] Figure 6 This is the sludge particle size distribution diagram under the conditions of the iron-carbon composite material of the present invention;

[0031] Figure 7 This is the sludge particle size distribution diagram under the micro-aeration conditions of the present invention;

[0032] Figure 8 This is the sludge particle size distribution diagram under the conditions of the iron-carbon composite material + micro-aeration of the present invention.

[0033] Explanation of the reference numerals: 1. Inlet / exhaust port; 2. Stirring motor; 3. Aeration pump; 4. Stirring paddle; 5. Perforated aeration tube; 6. Connecting rod; 7. Iron-carbon composite material; 8. Biofilm configuration of iron-carbon composite material; 9. ORP monitoring device; 10. Sampling port. DETAILED DESCRIPTION

[0034] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0035] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular also includes the plural. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0036] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment provides a method for improving the filtration performance of a sludge mixed liquor, comprising the following steps:

[0039] S1. Mixing anhydrous sodium sulfate, urea, and ferric chloride to obtain a mixed solution; wherein the concentration of anhydrous sodium sulfate is 6.94-138.89 mmol / L, the concentration of urea is 41.67-833.33 mmol / L, and the concentration of ferric chloride is 12.5-250 mmol / L.

[0040] S2, adding carbon felt to the mixed solution of step S1 for hydrothermal reaction, taking it out after the reaction is completed, drying it at high temperature and crystallizing it to obtain a composite material of iron oxide and carbon (Fe2O3-C); wherein the amount of carbon felt added is 3.5×4×0.5-4×4×0.5cm 3 / 0.4L.

[0041] S3. Add the sludge mixture to the anaerobic reactor, and hang the composite material of iron oxide and carbon obtained in step S2 above the anaerobic reactor or add it to the sludge mixture, wherein the total solid content of the sludge mixture is 15-25 g / L.

[0042] Specifically, the specific components of the sludge mixture include: chemical oxygen demand: 12-17g / L, which is cultivated with starch for a long time, and uses ammonium chloride / disodium hydrogen phosphate as nitrogen source and phosphorus source.

[0043] S4. Add micro-aeration to the anaerobic reactor.

[0044] Air is evenly introduced into the anaerobic reactor through the aeration pump 3 and the perforated aeration pipe 5 to activate the facultative bacteria. The aeration volume of the micro-aeration is controlled by the ORP monitoring device, and the range of the ORP monitoring device is controlled within -300-0mv.

[0045] Example 2

[0046] In this example, actual piggery wastewater was selected as the treatment object to examine the treatment effect of the iron-carbon composite material + micro-aeration on this type of insoluble / refractory wastewater. Seven samples were set up, namely blank, iron-carbon composite material 1, iron-carbon composite material 2, micro-aeration 1, micro-aeration 2, iron-carbon composite material + micro-aeration 1, and iron-carbon composite material + micro-aeration 2. Each group of samples was inoculated with the same activated sludge and added with fully mixed piggery wastewater as the only substrate. After ensuring the addition of an equal amount of COD, the system was operated until no methane gas was produced. The COD of the AD system was examined to evaluate the comprehensive effectiveness of the iron-carbon composite material + micro-aeration. Figure 2 The results show that the COD removal rate of iron-carbon composite material + micro-aeration increased by 22.00-22.55% compared with the blank, increased by 10.65-13.94% compared with the single iron-carbon composite material, and increased by 9.26-20.53% compared with the single micro-aeration condition, which shows that iron-carbon composite material + micro-aeration is more effective than either alone.

[0047] This embodiment also provides an anaerobic reactor (such as Figure 1 As shown), it mainly consists of: an inlet / exhaust port 1, a stirring motor 2, an aeration pump 3, a stirring paddle 4, a perforated aeration tube 5, a connecting rod 6, an iron-carbon composite material 7, a biofilm configuration of the iron-carbon composite material 8, an ORP monitoring device 9, a sampling port 10, etc. The micro-aeration process mainly involves uniformly aerating the AD system through the aeration pump 3 and the perforated aeration tube 5, collecting gas through the exhaust port 1, and controlling the aeration volume through the ORP monitoring device 9, so that the overall environment of the reaction is in the range of -300-0mv, and the dissolved oxygen content in the system is adjusted by ORP to achieve the activation of facultative bacteria. The iron-carbon composite material can be as follows Figure 1As shown, it is suspended above the reactor, but the sludge mixture can also be directly introduced. The stirring motor 2, connecting rod 6, and stirring paddle 4 are used to completely mix the reactor components. The iron-carbon composite material 7 in the iron-carbon composite biofilm configuration 8 may harbor a large number of functional microbial communities associated with direct interspecies electron transfer. These communities have a significant positive effect on accelerating the consumption of organic matter. After sampling through the sampling port 10, the wastewater quality indicators are tested, and the membrane filtration performance is determined using an ultrafiltration cup test system.

[0048] Example 3

[0049] The filtration performance of the sludge mixture (filtration performance refers to the ability to pass through the microfiltration membrane (0.45μm) under the same pressure (10kPa) per unit time) is mainly achieved through Figure 3 The ultrafiltration cup test system shown was used for testing. A mixture of blank control / iron-carbon composite material / micro-aeration / iron-carbon composite material + micro-aeration sludge was placed in an ultrafiltration cup. The pressure in the cup was adjusted to 10 kPa through a nitrogen bottle and a pressure control element. The filtrate was collected through a beaker and the real-time volume change of the filtrate was recorded using a program established between an electronic balance and a computer. Figure 4 The results showed that the filtrate volume increased more significantly under the conditions of iron-carbon composite material + micro-aeration, and the curve rose at a faster rate. This shows that the combination of iron-carbon composite material and micro-aeration can improve the filtration performance of the sludge mixture. However, the curve growth under the conditions of single micro-aeration or iron-carbon composite material was not obvious, and the lowest rising rate was shown under the blank condition. This shows that both micro-aeration and iron-carbon composite material contribute to the filtration performance of the sludge mixture. This result can also be analogized to ordinary anaerobic membrane bioreactors. Improving the filtration performance of the mixed liquor helps to slow the rapid formation of membrane fouling.

[0050] Example 4

[0051] The particle size analysis of the sludge mixed liquid in Example 2 was carried out, and the results were as follows: Figure 5-8 As shown in the blank group, the sludge particle size decreased ( Figure 5 ), while under micro-aeration conditions, the particle size tends to increase ( Figure 7 ), while under the conditions of iron-carbon composite material and iron-carbon composite material + micro-aeration, the sludge particle size was greatly increased ( Figure 6 , Figure 8 ), indicating that the iron-carbon composite combined with micro-aeration significantly improved sludge settleability. The coagulation effect brought about by the dissolution of iron ions and the optimization of sludge floc cluster structure by micro-aeration improved sludge settleability. Combined with the COD removal effect, it is clear that the combination of iron-carbon composite and micro-aeration has the dual properties of simultaneously degrading organic matter and optimizing the filterability of the mixed liquor.

[0052] The above results confirm the feasibility of the iron-carbon composite material + micro-aeration method, which has an actual 1+1>2 effect.

[0053] In summary, the present invention improves the efficiency of organic matter hydrolysis in wastewater by adding an iron-carbon composite material and micro-aeration during anaerobic water treatment. Furthermore, the iron-carbon composite material and micro-aeration significantly improve the sedimentation of sludge, helping to improve the filtration performance of the sludge mixture and slow the rate of membrane fouling. Therefore, the iron-carbon composite material and micro-aeration coupling used in the present invention has the dual properties of simultaneously degrading organic matter and optimizing the filtration properties of the sludge mixture.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for enhancing the filtration performance of sludge mixed liquor in the field of anaerobic wastewater treatment, characterized in that: This method can improve the efficiency of degrading organic matter in sewage while optimizing the filtration performance of sludge mixture and slowing down the membrane fouling rate, and includes the following steps: S1. Mixing anhydrous sodium sulfate, urea and ferric chloride to obtain a mixed solution; S2. Adding carbon fibers to the mixed solution of step S1 to carry out a hydrothermal reaction, taking out carbon fibers after the reaction is completed, drying at high temperature and crystallizing them to obtain an iron-carbon composite material; the iron-carbon composite material is a composite material of iron oxide and carbon; the carbon fibers are a sheet-like carbon fiber aggregate; and the sheet-like carbon fiber aggregate is a carbon felt; S3, adding a sludge mixture to an anaerobic reactor, and hanging the iron-carbon composite material prepared in step S2 above the anaerobic reactor or adding it to the sludge mixture; the total solid content of the sludge mixture is 15-25 g / L; S4. Micro-aeration is performed in the anaerobic reactor. The aeration volume of the micro-aeration is controlled by an ORP monitoring device. The range of the ORP monitoring device is controlled within -300-0 mv. The micro-aeration is performed by uniformly aerating the anaerobic reactor through an aeration pump and a perforated aeration pipe. The gas source for uniform aeration in the anaerobic reactor is air or oxygen.

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