A method for magnetic enhancement of sewage carbon source capture

Abstract

The present invention provides a magnetically enhanced method for capturing carbon sources in wastewater, aiming to address the problems of low carbon source resource utilization and high carbon emissions in existing wastewater treatment processes. The method comprises: adding a coagulant and a magnetic medium to wastewater to coagulate into intermediate effluent one; separating intermediate effluent one with a first magnetic separation device to obtain concentrated carbon source one and intermediate effluent two; adding a biological flocculant and a magnetic medium to intermediate effluent two to carry out a biological adsorption reaction to obtain intermediate effluent three; adding a coagulant and activated carbon to carry out flocculation and adsorption to obtain intermediate effluent four; separating intermediate effluent four with a second magnetic separation device to obtain concentrated carbon source two and effluent; subjecting concentrated carbon source one and concentrated carbon source two to anaerobically digestion to obtain methane and a digested mud-water mixture; and dispersing and recovering the digested mud-water mixture with a magnetic recovery device to obtain recovered magnetic media and sludge. This method has a high capture rate of carbon source organic matter and can achieve the effects of low-carbon energy conservation and emission reduction.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a magnetically enhanced carbon source capture method for sewage. Background Art

[0002] Traditional sewage treatment plants mostly use the activated sludge method and its derivative methods to treat urban sewage. Most of these traditional sewage treatment technologies adopt the form of "high energy consumption for water quality" and "energy consumption for energy". They use high-energy aerobic treatment technology to degrade carbon source organic matter, and directly oxidize the carbon source organic matter in the sewage into greenhouse gases such as carbon dioxide and release them into the atmosphere, which is contrary to the current sustainable development concept of low-carbon energy conservation and emission reduction.

[0003] Currently, municipal wastewater treatment plants primarily recover energy through anaerobic digestion of excess sludge, converting the carbon-derived organic matter in the sludge into methane, which is then converted into electricity or heat. However, across the entire sewage sludge treatment process, only approximately 25% of the carbon-derived organic matter is converted into energy. The majority of the carbon-derived organic matter in the wastewater is converted into carbon dioxide through energy-consuming aeration during the treatment process at the sewage plant, without being effectively captured and utilized. Summary of the Invention

[0004] In response to the deficiencies in the above-mentioned prior art, the present invention provides a magnetically enhanced method for capturing carbon sources in sewage. This method captures carbon sources by adding a magnetic medium and combines it with biological adsorption reaction and activated carbon adsorption to achieve the step-by-step capture of particulate, colloidal and dissolved carbon source organic matter in sewage. The method has a high carbon source capture rate, is fast and efficient in processing, and saves drug consumption.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A magnetically enhanced method for capturing carbon sources in wastewater, comprising the following steps:

[0007] Step S100: adding a coagulant and a magnetic medium to the sewage, stirring and coagulating, and forming an intermediate effluent containing flocs;

[0008] Step S200: Using a first magnetic separation device to separate flocs from the intermediate effluent 1 to obtain a concentrated carbon source 1 and intermediate effluent 2;

[0009] Step S300, adding a biological flocculant and a magnetic medium to the intermediate effluent II, stirring and mixing, and performing biological flocculation and adsorption of carbon sources to obtain an intermediate effluent III containing flocs;

[0010] Step S400: adding a coagulant aid and activated carbon to the intermediate effluent three, stirring and mixing to perform flocculation and adsorption, to obtain intermediate effluent four;

[0011] Step S500: using a second magnetic separation device to separate flocs from the intermediate effluent water 4 to obtain a concentrated carbon source 2 and effluent water;

[0012] Step S600: subjecting the concentrated carbon source 1 and the concentrated carbon source 2 to an anaerobic digestion reaction to obtain methane and a digested mud-water mixture;

[0013] Step S700: using a magnetic recovery device to disperse and recover the digested mud-water mixture to obtain recovered magnetic media and sludge.

[0014] In one embodiment of the present application, step S710 is further included, in which the recovered magnetic medium obtained in step S700 is added to the sewage and / or the intermediate effluent 2 as the magnetic medium in step S100 and / or step S300 for recycling.

[0015] In one embodiment of the present application, step S720 is further included, in which part of the sludge obtained in step S700 is added to the second intermediate effluent of step S300 to be used as return sludge; and the other part is discharged.

[0016] In one embodiment of the present application, step S610 is further included, in which part of the digested mud-water mixture obtained in step S600 is transported back to the intermediate effluent 2 of step S300 for biological flocculation and adsorption of carbon sources; and the other part is subjected to the dispersed recovery treatment of step S700.

[0017] In one embodiment of the present application, the concentration of the coagulant added to the sewage in step S100 is 15-50 mg / L, and the stirring coagulation reaction time is 3-5 min.

[0018] In one embodiment of the present application, in the sewage of step S100, the added concentration of the magnetic medium is 0.8 to 2 times the initial solid suspended matter concentration in the sewage.

[0019] In one embodiment of the present application, in step S300, the initial concentration of the added biological flocculant is 5-10 g / L, and the concentration of the biological flocculant after being added to the intermediate effluent two is 0.1-1 g / L; the biological adsorption reaction time is 10-30 min, and the dissolved oxygen concentration is 0-0.5 mg / L.

[0020] In one embodiment of the present application, in the step S300, the concentration of the magnetic medium in the second intermediate effluent is 0.01 to 0.5 times the concentration of the biological flocculant.

[0021] In one embodiment of the present application, in step S400, the concentration of activated carbon added to the intermediate effluent three is 5-20 mg / L, the concentration of the coagulant aid is 1-3 mg / L, and the flocculation and adsorption reaction time is 3-5 min.

[0022] In one embodiment of the present application, the coagulant is one or more of polyaluminium chloride, polyferric sulfate, ferric chloride and aluminium sulfate;

[0023] And / or, the coagulant aid is polyacrylamide;

[0024] And / or, the activated carbon is powdered activated carbon with a mesh size of 150-300;

[0025] And / or, the biological flocculant is one or more of activated sludge, anaerobic digestion sludge, and sludge extract.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The method of the present application first adds a magnetic medium and a coagulant to treat the sewage, quickly captures and separates the particulate and colloidal carbon source organic matter in the sewage, effectively reduces the operating load of the subsequent carbon source treatment, reduces the amount of biological flocculant required for biological adsorption, and reduces the dosage of subsequent unit reagents; secondly, magnetic coagulation is performed to enhance biological flocculation adsorption to capture the remaining colloidal and dissolved carbon source organic matter in the sewage; then, activated carbon and a coagulant aid are used to further capture the remaining dissolved carbon source organic matter in the sewage; that is, the present application adopts a three-stage carbon source capture that combines magnetic loading chemical coagulation, biological adsorption and activated carbon adsorption, which realizes the targeted and step-by-step capture of particulate, colloidal and dissolved carbon source organic matter, gives full play to the technical advantages of the carbon source capture links at all levels, and greatly improves the concentration and capture rate of carbon source organic matter.

[0028] The difference from the existing magnetic loading treatment technology is that the captured carbon source organic matter is anaerobically digested with magnetic media and activated carbon to produce methane, realizing the resource utilization of captured carbon source; and the magnetic media can be used as a carrier of electron transfer between microbial species, improving the efficiency of electron transfer and changing the acetic acid degradation pathway to improve the efficiency of methane production. At the same time, the magnetic media can also release Fe 2+ To promote methane production; in addition, anaerobic digestion first consumes the sticky carbon source organic matter on the surface of the magnetic medium, converting it into low-viscosity inorganic matter, which facilitates subsequent magnetic medium recovery. Activated carbon can improve the stability of the anaerobic digestion system, alleviate ammonia nitrogen inhibition, and also serve as a carrier for microorganisms in anaerobic digestion, providing attachment sites.

[0029] 2. The use of the first magnetic separation device, the second separation device and the magnetic recovery device to separate the concentrated carbon source containing the magnetic medium and the water body greatly shortens the mud-water separation time, shortens the entire sewage treatment process time, increases the operating load, and reduces the equipment footprint.

[0030] 3. After recovery, the magnetic medium is added to the sewage and the second intermediate effluent, which realizes the recycling of the magnetic medium and can effectively reduce the dosage of the magnetic medium and subsequent reagents (coagulants, flocculants, etc.); the mud-water mixture after digestion contains anaerobic sludge and magnetic medium, and the sludge separated by the magnetic recovery device is also anaerobic sludge. Part of the anaerobic sludge is added to the second intermediate effluent and used as return sludge, which can avoid the carbon source organic matter in the sewage from being aerobic degradation and consumption. At the same time, the carbon source organic matter in the sewage can be hydrolyzed and acidified in advance, which is beneficial to subsequent anaerobic digestion.

[0031] 4. The magnetic enhanced wastewater carbon source capture method of the present application can treat urban wastewater with a COD (Chemical Oxygen Demand) concentration of 150~500 mg / L, with a COD capture rate of 77%~85%. The COD concentration of the captured concentrated carbon source reaches 10,000~20,000 mg / L. At the same time, it can effectively capture more than 90% of total phosphorus (TP) and suspended solids (SS), which can effectively reduce the load of subsequent treatment processes and improve treatment efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0033] Figure 1 This is a schematic diagram of the process flow of the magnetically enhanced wastewater carbon source capture method of the present invention. DETAILED DESCRIPTION

[0034] Hereinafter, certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the embodiments of the present invention. Therefore, the drawings and description are to be regarded as illustrative in nature and not restrictive.

[0035] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0036] Example 1

[0037] See also Figure 1 This embodiment discloses a magnetically enhanced carbon source capture method for sewage, which can be used to treat urban sewage. The method comprises the following steps:

[0038] Step S100: The sewage enters the primary carbon source capture tank, a coagulant and a magnetic medium are added to the sewage in the primary carbon source capture tank, and a stirring device is used to stir and coagulate to form flocs, thereby capturing particulate and colloidal carbon source organic matter in the sewage to obtain an intermediate effluent containing flocs.

[0039] Step S200: Input the obtained intermediate effluent 1 into the first magnetic separation device for magnetic floc separation. The first magnetic separation device includes a magnetic disk and a scraping bar. The magnetic disk absorbs the flocs containing the magnetic medium, separates the flocs and water, and obtains concentrated carbon source 1 and intermediate effluent 2.

[0040] Step S300: The obtained intermediate effluent II is fed into a secondary carbon source capture tank. A bioflocculant and a magnetic medium are added to the intermediate effluent II in the secondary carbon source capture tank, and the bioflocculant and magnetic medium are stirred and mixed to form bioflocs containing the magnetic medium. The intermediate effluent II in the secondary carbon source capture tank is aerated or not aerated with or without a blower and an aeration device to control the dissolved oxygen concentration in the water and maintain the biological activity of the bioflocculant for biosorption. This captures the remaining particulate, colloidal, and dissolved carbon source organic matter in the intermediate effluent II, thereby obtaining intermediate effluent III containing flocs. The bioflocculant can be one or more of activated sludge, anaerobic digestion sludge, and sludge extract.

[0041] Step S400: input the obtained intermediate effluent three into the tertiary carbon source capture tank, add a coagulant and activated carbon into the intermediate effluent three in the tertiary carbon source capture tank, and stir and mix. The coagulant makes the biological flocs in the intermediate effluent three larger and denser, and the activated carbon fully contacts the sewage for physical adsorption, thereby capturing the dissolved carbon source organic matter remaining in the intermediate effluent three, and then obtaining intermediate effluent four.

[0042] In step S500, the intermediate effluent (fourth) is fed into a second magnetic separation device for magnetic floc separation. The magnetic disks and scraping strips adsorb and separate the flocs loaded with magnetic media and activated carbon from the water, resulting in a concentrated carbon source (two) and effluent. The effluent is then forwarded to subsequent processing steps or discharged.

[0043] In step S600, the concentrated carbon source 1 obtained in step S200 and the concentrated carbon source 2 obtained in step S500 are transported to an anaerobic digester for anaerobic digestion. After the anaerobic digestion, methane and a digested mud-water mixture are obtained. The methane is collected and utilized as an energy source.

[0044] Step S700: The digested mud-water mixture is transported to a magnetic recovery device for processing, wherein the magnetic recovery device includes a floc disperser and a magnetic hub. The digested mud-water mixture is first dispersed by the floc disperser and then separated and recovered by a magnetic medium to obtain recovered magnetic medium and sludge.

[0045] In summary, this method first adds magnetic media and coagulants to treat sewage, quickly capturing and separating particulate and colloidal carbon source organic matter in the sewage, effectively reducing the operating load of subsequent carbon source treatment, reducing the amount of bioflocculant required for biological adsorption reactions, and reducing the dosage of subsequent unit reagents; secondly, magnetic coagulation is performed to enhance biological adsorption to capture the remaining colloidal and dissolved carbon source organic matter in the sewage; then, activated carbon and coagulants are used to further capture the remaining dissolved carbon source organic matter in the sewage. That is, this method achieves targeted, step-by-step capture of particulate, colloidal, and dissolved carbon source organic matter through a three-stage carbon source capture that combines magnetic loading, chemical coagulation, biological adsorption, and activated carbon adsorption, giving full play to the technical advantages of each level of carbon source capture, and significantly improving the concentration and capture rate of carbon source organic matter.

[0046] Before biological adsorption, magnetic media are combined with coagulants to perform magnetic loading adsorption and separation on carbon source organic matter, so that most of the particulate and colloidal carbon source organic matter can be captured from the sewage before energy-consuming aeration, and the incremental sludge can be used for energy recovery (anaerobic digestion), which greatly improves the carbon source utilization rate in sewage and reduces energy consumption and greenhouse gas emissions.

[0047] In addition, this method is different from the existing magnetic loading treatment technology in that the captured carbon source organic matter enters the anaerobic digester together with the magnetic mediator and activated carbon, undergoes anaerobic digestion reaction to produce methane, and realizes the resource utilization of the captured carbon source; and the magnetic mediator can serve as a carrier of electron transfer between microbial species, improve the efficiency of electron transfer, change the acetic acid degradation pathway to improve the efficiency of methane production, and at the same time, the magnetic mediator can also release Fe 2+ To promote methane production; anaerobic digestion first consumes the sticky carbon source organic matter on the surface of the magnetic medium, converting it into low-viscosity inorganic matter, which facilitates subsequent magnetic medium recovery. Activated carbon can improve the stability of the anaerobic digestion system, alleviate ammonia nitrogen inhibition, and also serve as a carrier for microorganisms in anaerobic digestion, providing attachment sites.

[0048] Example 2

[0049] The magnetically enhanced carbon source capture method for wastewater of this embodiment further includes step S610, step S710 and step S720 based on the first embodiment.

[0050] Among them, step S610: part of the digested mud-water mixture obtained after anaerobic digestion in step S600 is transported back to the secondary carbon source capture tank, and undergoes biological flocculation and carbon source adsorption reaction with the intermediate effluent two in the secondary carbon source capture tank; the other part of the digested mud-water mixture enters the magnetic recovery device for separation and recovery of the magnetic medium.

[0051] The digested mud-water mixture after anaerobic digestion is recycled and reused to supplement the sludge dosage in step S300 and reduce the initial bioflocculant dosage. Furthermore, the sludge in the digested mud-water mixture is anaerobic sludge, and adding it to the secondary carbon source capture tank can reduce the aerobic degradation and consumption of carbon source organic matter in the sewage, and can also pre-hydrolyze and acidify the carbon source organic matter in the sewage, which is beneficial for subsequent anaerobic digestion. Furthermore, the digested mud-water mixture contains a magnetic medium. The carbon source organic matter adsorbed on the surface of the magnetic medium is converted into low-viscosity inorganic matter after anaerobic digestion, giving the magnetic medium a magnetic loading effect. Recycling and reuse can reduce the load on the subsequent magnetic recovery device, achieving the goal of energy conservation and consumption reduction.

[0052] Step S710: The recovered magnetic medium separated and recovered in step S700 is transported to the primary carbon source capture tank and / or the secondary carbon source capture tank for coagulation and adsorption treatment of sewage and / or intermediate effluent 2, thereby realizing the recovery and recycling of the magnetic medium and effectively reducing the input of external magnetic medium.

[0053] Step S720: Part of the sludge separated in step S700 is returned to the secondary carbon source capture tank, and the intermediate effluent is subjected to biological adsorption treatment, that is, part of the sludge is used as return sludge, and the other part of the sludge is discharged.

[0054] The separated sludge is anaerobic sludge, which is returned to the secondary carbon source capture tank for use. It can prevent the carbon source organic matter in the sewage from being consumed by aerobic degradation, and can hydrolyze and acidify the carbon source organic matter in the sewage in advance, which is beneficial to subsequent anaerobic digestion and improves the carbon source recovery rate.

[0055] Example 3

[0056] The magnetically enhanced carbon source capture method for wastewater of this embodiment further includes step S210 based on the first or second embodiment.

[0057] Step S210: A portion of the concentrated carbon source obtained in step S200 is transported to a subsequent biological deep denitrification treatment process to be used as a supplementary carbon source.

[0058] Since deep denitrification in the later stage of biological sewage treatment process requires additional carbon sources, the carbon sources in urban sewage are concentrated and captured in the early stage of treatment and used as a carbon source supplement for the deep denitrification process, which can effectively reduce the total amount of sludge, save costs and reduce carbon emissions.

[0059] In addition, in step S600, other exogenous sludge and organic waste such as food waste can be added to the anaerobic digester to further realize the resource utilization of carbon sources. At the same time, more anaerobic sludge can be generated and added to the secondary carbon source capture tank for biosorption.

[0060] Example 4

[0061] The magnetic enhanced carbon source capture method for wastewater of this embodiment is based on the embodiment 1, embodiment 2 or embodiment 3:

[0062] In step S100, a coagulant and a magnetic medium are added to the sewage in the primary carbon source capture tank. The coagulant is a mixture of one or more of polyaluminium chloride (PAC), polyferric sulfate (PFS), ferric chloride and aluminium sulfate.

[0063] Use mechanical agitation and coagulation to control the coagulant concentration in the wastewater within the range of 15-50 mg / L. The magnetic media dosage is controlled at 0.8-2 times the initial suspended solids (SS) concentration in the wastewater. The stirring speed is 100-150 rpm, and the reaction time is controlled at 3-5 minutes.

[0064] In step S300, the initial bioflocculant concentration is 5 to 10 g / L. After being added to the secondary carbon source capture tank, the bioflocculant concentration in the intermediate effluent second in the secondary carbon source capture tank is controlled within the range of 0.1 to 1 g / L. The concentration of the magnetic medium added to the secondary carbon source capture tank is controlled within the range of 0.01 to 0.5 times the bioflocculant concentration in the secondary carbon source capture tank.

[0065] Aeration or non-aeration and stirring are performed to carry out biological adsorption reaction, the dissolved oxygen concentration of the water in the secondary carbon source capture tank is controlled to be 0-0.5 mg / L, the stirring speed is 70-100 r / min, and the biological adsorption reaction time is 10-30 min.

[0066] In step S400, a coagulant and activated carbon are added to the intermediate effluent (3) in the tertiary carbon source capture tank, and the mixture is stirred at a speed of 70 to 100 r / min. The coagulant is polyacrylamide, and its concentration after addition is controlled within the range of 1 to 3 mg / L. The activated carbon is powdered activated carbon with a mesh size of 150 to 300, and its concentration after addition is controlled within the range of 5 to 20 mg / L. The flocculation and adsorption reaction time of the intermediate effluent (3) in the tertiary carbon source capture tank is controlled within the range of 3 to 5 minutes.

[0067] In summary, when the method of the above embodiment is used to treat urban sewage with a COD concentration of 150~500 mg / L, the COD capture rate can reach 77%~85%, and the COD concentration of the captured concentrated carbon source reaches 10000~20000 mg / L. At the same time, most of the TP and SS in the sewage can be effectively captured, and the capture rates of TP and SS are both above 90%.

Claims

1. A magnetic enhanced carbon source capture method for sewage, characterized in that: The method comprises the following steps: Step S100: adding a coagulant and a magnetic medium to the sewage, stirring and coagulating, and forming an intermediate effluent containing flocs; Step S200: Using a first magnetic separation device to separate flocs from the intermediate effluent 1 to obtain a concentrated carbon source 1 and intermediate effluent 2; Step S300: adding a biological flocculant and a magnetic medium to the intermediate effluent II, stirring and mixing, and performing biological flocculation and carbon source adsorption to obtain an intermediate effluent III containing flocs; the biological flocculant is one or more of activated sludge, anaerobic digestion sludge, and sludge extract; Step S400: adding a coagulant aid and activated carbon to the intermediate effluent three, stirring and mixing to perform flocculation and adsorption, to obtain intermediate effluent four; Step S500: using a second magnetic separation device to separate flocs from the intermediate effluent water 4 to obtain a concentrated carbon source 2 and effluent water; Step S600: subjecting the concentrated carbon source 1 and the concentrated carbon source 2 to an anaerobic digestion reaction to obtain methane and a digested mud-water mixture; Step S700: using a magnetic recovery device to disperse and recover the digested mud-water mixture to obtain recovered magnetic media and sludge; The process further includes step S610, wherein a portion of the digested mud-water mixture obtained in step S600 is transported back to the intermediate effluent 2 in step S300 for biological flocculation and carbon source adsorption; and the other portion is subjected to the dispersion and recovery treatment in step S700; The process further includes step S720, wherein a portion of the sludge obtained in step S700 is added to the second intermediate effluent of step S300 to be used as return sludge; and the remaining portion is discharged externally; In step S300 , the dissolved oxygen concentration of the biosorption reaction is 0-0.5 mg / L.

2. The magnetic enhanced carbon source capture method for sewage according to claim 1, characterized in that: The method further includes step S710, adding the recovered magnetic medium obtained in step S700 as the magnetic medium in step S100 and / or step S300 into the sewage and / or the second intermediate effluent for recycling.

3. The magnetic enhanced carbon source capture method for wastewater according to claim 1, characterized in that: In the sewage of step S100, the concentration of the coagulant added is 15-50 mg / L, and the stirring coagulation reaction time is 3-5 minutes.

4. The magnetic enhanced carbon source capture method for sewage according to claim 1 or 3, characterized in that: In the sewage of step S100, the added concentration of the magnetic medium is 0.8 to 2 times the initial concentration of suspended solids in the sewage.

5. The magnetic enhanced carbon source capture method for sewage according to claim 1, characterized in that: In the step S300, the initial concentration of the added bioflocculant is 5-10 g / L, and the concentration of the bioflocculant after being added to the intermediate effluent II is 0.1-1 g / L; the biological adsorption reaction time is 10-30 min.

6. The magnetic enhanced carbon source capture method for wastewater according to any one of claims 1, 2 or 5, characterized in that: In the step S300, the concentration of the magnetic medium in the second intermediate effluent is 0.01 to 0.5 times the concentration of the biological flocculant.

7. The magnetic enhanced carbon source capture method for wastewater according to claim 1, characterized in that: In step S400, the concentration of activated carbon added to the intermediate effluent three is 5-20 mg / L, the concentration of coagulant aid is 1-3 mg / L, and the flocculation and adsorption reaction time is 3-5 minutes.

8. The magnetic enhanced carbon source capture method for wastewater according to any one of claims 1, 3 or 7, characterized in that: The coagulant is one or more of polyaluminium chloride, polyferric sulfate, ferric chloride and aluminium sulfate; And / or, the coagulant aid is polyacrylamide; And / or, the activated carbon is powdered activated carbon with a mesh size of 150-300.

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