A method for separating sludge components

Abstract

The present invention relates to the technical field of sludge, and particularly to a method for separating sludge components. The method includes: performing a primary hydrothermal treatment on the sludge to be treated to obtain the sludge to be sorted; performing a sorting treatment on the sludge to be sorted to obtain an upper-layer product and a lower-layer product; wherein the upper-layer product includes a liquid-phase product and solid carbon, and the lower-layer product includes inorganic components; performing a separation treatment on the upper-layer product to obtain waste liquid and the solid carbon; performing a recovery treatment on the inorganic components to obtain phosphorus; and performing a recovery treatment on the waste liquid to obtain ammonium salts, alkali metal and alkaline earth metal compounds. The technical solution of the present invention can achieve effective separation of each component of the sludge.

Description

Technical Field

[0001] The present invention relates to the technical field of sludge, and in particular to a method for separating sludge components. Background Art

[0002] Sludge is a solid waste generated during the sewage treatment process, mainly composed of inorganic particles, organic fragments, and various pathogenic microorganisms. Its complex organic and inorganic components are important reasons restricting its subsequent resource utilization. Therefore, if the components of sludge can be separated, the difficulty of its treatment and disposal can be greatly reduced, and the potential of its resource utilization can be improved. However, it is difficult to effectively separate the components of sludge in related technologies.

[0003] Therefore, there is an urgent need for a method for separating sludge components to solve the above problems. Summary of the Invention

[0004] Embodiments of the present invention describe a method for separating sludge components, which can effectively separate the components of sludge.

[0005] Embodiments of the present invention provide a method for separating sludge components, including:

[0006] Performing a first hydrothermal treatment on the sludge to be treated to obtain the sludge to be sorted;

[0007] Performing a sorting treatment on the sludge to be sorted to obtain an upper-layer product and a lower-layer product; wherein, the upper-layer product includes a liquid-phase product and solid carbon, and the lower-layer product includes inorganic components;

[0008] Performing a separation treatment on the upper-layer product to obtain waste liquid and the solid carbon;

[0009] Performing a recovery treatment on the inorganic components to obtain phosphorus;

[0010] Performing a recovery treatment on the waste liquid to obtain ammonium salts, alkali metal, and alkaline earth metal compounds.

[0011] According to one embodiment, it further includes:

[0012] Performing an ultrasonic treatment on the sludge to be treated and / or the sludge to be sorted;

[0013] Preferably, the conditions of the ultrasonic treatment are: the ultrasonic power is 100-500 W, and the ultrasonic time is 5-60 min.

[0014] According to one embodiment, the performing an ultrasonic treatment on the sludge to be treated includes:

[0015] Performing a first hydrothermal treatment and an ultrasonic treatment on the sludge to be treated simultaneously; or,

[0016] Perform hydrothermal treatment and ultrasonic treatment on the sludge to be treated in sequence;

[0017] Preferably, the conditions of the first hydrothermal treatment are: the hydrothermal temperature is 100°C to 200°C, and the hydrothermal time is 15 to 90 minutes.

[0018] According to one embodiment, performing the first hydrothermal treatment and ultrasonic treatment on the sludge to be treated simultaneously includes:

[0019] Add a first surfactant to the sludge to be treated;

[0020] Perform the first hydrothermal treatment and ultrasonic treatment on the sludge to be treated after adding the first surfactant simultaneously;

[0021] Preferably, the first surfactant includes at least one of polyoxyethylene non-ionic surfactants, fatty amine cationic surfactants, and sulfonate and phosphate ester anionic surfactants;

[0022] Preferably, the dosage of the first surfactant is 0.1% to 1% of the mass of the sludge to be treated.

[0023] According to one embodiment, performing hydrothermal treatment and ultrasonic treatment on the sludge to be treated in sequence includes:

[0024] Perform the first hydrothermal treatment on the sludge to be treated to obtain a first sludge;

[0025] Add a second surfactant to the first sludge to obtain a second sludge;

[0026] Perform ultrasonic treatment on the second sludge to obtain the sludge to be sorted.

[0027] According to one embodiment, adding the second surfactant to the first sludge to obtain the second sludge includes:

[0028] Cool the first sludge; wherein, the temperature of the first sludge after cooling is 40°C to 80°C;

[0029] Add the second surfactant to the cooled first sludge to obtain the second sludge;

[0030] Preferably, the second surfactant is composed of sodium hexametaphosphate, polyvinylpyrrolidone, and sodium oleate;

[0031] Preferably, the proportion of sodium hexametaphosphate in the second surfactant is 40% to 45%, the proportion of polyvinylpyrrolidone in the second surfactant is 40% to 45%, and the proportion of sodium oleate in the second surfactant is 10% to 20%;

[0032] Preferably, the dosage of the second surfactant is 0.1% - 1% of the mass of the first sludge.

[0033] According to one embodiment, the ultrasonic treatment of the sludge to be sorted includes:

[0034] Performing sorting treatment and ultrasonic treatment on the sludge to be sorted simultaneously.

[0035] According to one embodiment, the sorting treatment is one of heavy medium, hydrocyclone, flotation, and liquid-phase sieve; and / or,

[0036] The separation treatment is one of pressure filtration and centrifugation.

[0037] According to one embodiment, the liquid-phase product includes organic components. The separation treatment of the upper-layer product includes:

[0038] Performing secondary hydrothermal treatment on the upper-layer product to obtain a hydrothermal product; wherein, the hydrothermal product includes waste liquid and low-ash organic carbon formed by the enrichment and transformation of the organic components into solid carbon;

[0039] Performing separation treatment on the hydrothermal product to obtain the waste liquid and the low-ash organic carbon.

[0040] According to one embodiment, the conditions of the secondary hydrothermal treatment are: the hydrothermal temperature is 180°C - 300°C, and the hydrothermal time is 10 - 240 min.

[0041] According to the method for separating sludge components provided by the embodiments of the present invention, by performing primary hydrothermal treatment on the sludge to be treated, the extracellular polymers of the sludge to be treated are damaged to a certain extent, which is beneficial to the disintegration of sludge flocs and the release of internal substances; by performing sorting treatment on the sludge to be sorted, an upper-layer product and a lower-layer product are obtained, then the upper-layer product is separated to obtain waste liquid and solid carbon, the inorganic components included in the lower-layer product are recovered to obtain phosphorus, and the waste liquid is recovered to obtain ammonium salts, alkali metals, and alkaline earth metal compounds. In summary, the above technical solution realizes the effective separation of each component of the sludge, specifically the separation of components such as solid carbon, inorganic components, phosphorus, ammonium salts, alkali metals, and alkaline earth metal compounds. Description of the Drawings

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0043] Figure 1 The flowchart of the separation method of sludge components according to an embodiment is shown. Detailed implementation manners

[0044] The solution provided by the present invention will be described below with reference to the accompanying drawings.

[0045] As Figure 1 shown, an embodiment of the present invention provides a separation method of sludge components, including:

[0046] Step A1: Perform a first hydrothermal treatment on the sludge to be treated to obtain the sludge to be sorted.

[0047] Step A2: Perform a sorting treatment on the sludge to be sorted to obtain an upper-layer product and a lower-layer product; wherein, the upper-layer product includes a liquid-phase product and solid carbon, and the lower-layer product includes inorganic components.

[0048] Step A3: Perform a separation treatment on the upper-layer product to obtain waste liquid and solid carbon.

[0049] Step A4: Perform a recovery treatment on the inorganic components to obtain phosphorus.

[0050] Step A5: Perform a recovery treatment on the waste liquid to obtain ammonium salts, alkali metal compounds, and alkaline earth metal compounds.

[0051] In this embodiment, by performing a first hydrothermal treatment on the sludge to be treated, the extracellular polymer of the sludge to be treated is damaged to a certain extent, which is beneficial to the disintegration of sludge flocs and the release of internal substances; by performing a sorting treatment on the sludge to be sorted, an upper-layer product and a lower-layer product are obtained, then the upper-layer product is separated to obtain waste liquid and solid carbon, the inorganic components included in the lower-layer product are recovered to obtain phosphorus, and the waste liquid is recovered to obtain ammonium salts, alkali metal compounds, and alkaline earth metal compounds. In summary, the above technical solution realizes the effective separation of each component of the sludge, specifically the separation of components such as solid carbon, inorganic components, phosphorus, ammonium salts, alkali metal compounds, and alkaline earth metal compounds.

[0052] In an embodiment of the present invention, the above method further includes:

[0053] Performing an ultrasonic treatment on the sludge to be treated and / or the sludge to be sorted.

[0054] In this embodiment, by means of ultrasonic treatment, the separation effect of each component in the sludge is enhanced, and at the same time, this treatment method does not involve chemical reactions, so that gas-phase loss and the generation of harmful substances can be reduced.

[0055] In one embodiment of the present invention, the conditions for ultrasonic treatment are as follows: the ultrasonic power is 100 - 500 W, and the ultrasonic time is 5 - 60 min. Of course, the ultrasonic power and ultrasonic time can also be other numerical ranges (for example, the ultrasonic power is 50 - 600 W, and the ultrasonic time is 20 - 90 min), and the embodiments of the present invention do not limit them here.

[0056] In the related art, some scholars used sulfuric acid leaching coupled with multi - stage elutriation to dissolve and remove inorganic components such as Fe and Al. In a strong acidic environment (such as pH = 1.1), the organic matter content of the product only increased by 16.7%. Obviously, the traditional "acid leaching and ash removal method" has very limited stripping effect on the main components in the sludge.

[0057] However, the inventor creatively found during the R & D process that: from the perspective of the total proportion, stripping the main organic components and inert inorganic particles in the sludge is the key to source separation. Therefore, the embodiments of the present invention propose a new process of "hydrothermal - ultrasonic - sorting" (whether ultrasonic is coupled in the hydrothermal process, or between the hydrothermal process and the sorting process, or in the sorting process is not limited here). Based on deconstructing the cross - linking effect between the main organic components (such as proteins / polysaccharides / lipids / humic substances, etc.) and inert inorganic particles (such as Si / Al / Fe - based) in the sludge to be treated, the effective stripping of organic components and inorganic components is achieved. That is, the technical solution provided by the embodiments of the present invention aims to separate the sludge with complex components and high utilization difficulty into multiple parts that are easy to process through the new process of "hydrothermal - ultrasonic - sorting", so as to broaden the resource utilization ways of the sludge.

[0058] In one embodiment of the present invention, the step of "performing ultrasonic treatment on the sludge to be treated" may specifically include:

[0059] Performing a hydrothermal treatment and an ultrasonic treatment on the sludge to be treated simultaneously; or,

[0060] Performing a hydrothermal treatment and an ultrasonic treatment on the sludge to be treated in sequence.

[0061] In this embodiment, the sludge to be treated can be placed in a container, and the ultrasonic probe can be directly placed in the container (i.e., direct ultrasonic) or the container can be placed in an ultrasonic transmission medium (such as water) to use the ultrasonic waves transmitted by the medium to act on the sludge to be treated in the container (i.e., indirect ultrasonic), so as to heat the container (i.e., perform a hydrothermal treatment) and apply ultrasonic waves (i.e., perform an ultrasonic treatment) simultaneously; or the sludge to be treated can be first placed in a container and the container can be heated (i.e., perform a hydrothermal treatment), and then the ultrasonic probe can be directly placed in the container or the container can be placed in an ultrasonic transmission medium to apply ultrasonic waves to the container (i.e., perform an ultrasonic treatment). Here, both of the above - mentioned methods are acceptable.

[0062] In one embodiment of the present invention, the conditions for the first hydrothermal treatment are as follows: the hydrothermal temperature is 100°C to 200°C, and the hydrothermal time is 15 to 90 minutes.

[0063] In this embodiment, the first hydrothermal treatment is used as a pretreatment process for the front end of the sludge, which is beneficial to achieving a certain degree of damage to the extracellular polymers of the sludge. Specifically, by setting the hydrothermal temperature to 100°C to 200°C and the hydrothermal time to 15 to 90 minutes, the sludge flocs can be better disintegrated, and most of the internal substances of the sludge can be released from the extracellular polymers.

[0064] Of course, the conditions for the first hydrothermal treatment can also be other numerical ranges (for example, the hydrothermal temperature is 150°C to 250°C, and the hydrothermal time is 30 to 120 minutes), and the embodiments of the present invention do not limit it here.

[0065] In one embodiment of the present invention, the step of "simultaneously performing the first hydrothermal treatment and ultrasonic treatment on the sludge to be treated" can specifically include:

[0066] Adding a first surfactant to the sludge to be treated;

[0067] Simultaneously performing the first hydrothermal treatment and ultrasonic treatment on the sludge to be treated after adding the first surfactant.

[0068] In this embodiment, in order to further enhance the separation effect of the organic components and inorganic components in the sludge, a first surfactant can be first added to the sludge to be treated, and then the sludge to be treated after adding the first surfactant is simultaneously subjected to the first hydrothermal treatment and ultrasonic treatment.

[0069] In one embodiment of the present invention, the first surfactant includes at least one of polyoxyethylene non-ionic surfactants, fatty amine cationic surfactants, and sulfonate and phosphate ester anionic surfactants, and the embodiments of the present invention do not limit it here.

[0070] That is to say, when the type of the first surfactant adopts the above composition, it can ensure that it still has high activity after being added to the sludge after the first hydrothermal treatment.

[0071] In one embodiment of the present invention, the dosage of the first surfactant is 0.1% to 1% of the mass of the sludge to be treated. For example, it can be 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, and 1%, and no specific limitation is made here.

[0072] In one embodiment of the present invention, the step of "sequentially performing the first hydrothermal treatment and ultrasonic treatment on the sludge to be treated" can specifically include:

[0073] Performing a first hydrothermal treatment on the sludge to be treated to obtain a first sludge;

[0074] Add a second surfactant to the first sludge to obtain a second sludge;

[0075] Perform ultrasonic treatment on the second sludge to obtain the sludge to be sorted.

[0076] In this embodiment, in order to further enhance the separation effect of the organic components and inorganic components in the sludge, a second surfactant can be first added to the first sludge obtained by one-step hydrothermal treatment, and then ultrasonic treatment is performed on the second sludge after adding the second surfactant.

[0077] It should be noted that in this embodiment, the sludge is first subjected to one-step hydrothermal treatment and then the second surfactant is added to the sludge. This is because if the second surfactant is added to the sludge before the one-step hydrothermal treatment, it may cause the inactivation of the second surfactant, and thus lose the significance of adding the second surfactant to further enhance the separation effect of the organic components and inorganic components in the sludge.

[0078] In an embodiment of the present invention, the step "add a second surfactant to the first sludge to obtain a second sludge" may specifically include:

[0079] Cool the first sludge; wherein, the temperature of the first sludge after cooling is 40°C to 80°C;

[0080] Add a second surfactant to the cooled first sludge to obtain a second sludge.

[0081] In this embodiment, in order to ensure that the second surfactant still maintains a high activity after being added to the first sludge, it can be considered to first cool the first sludge, and the temperature of the first sludge after cooling can be 40°C to 80°C.

[0082] In an embodiment of the present invention, the second surfactant is composed of sodium hexametaphosphate, polyvinylpyrrolidone and sodium oleate.

[0083] In this embodiment, both sodium hexametaphosphate and polyvinylpyrrolidone have two opposite functional structures of hydrophilicity and lipophilicity in their chemical compositions. Both of them can be adsorbed on different solid surfaces in the liquid phase to prevent sedimentation and aggregation between particles, so as to form a stable suspension; at the same time, sodium oleate can be used to introduce polar anions and cations into the first sludge to enhance the surface hydrophobicity of the first sludge (this can make it easier to combine with bubbles), thereby facilitating the increase of the separation efficiency of different components during subsequent sorting treatment.

[0084] In an embodiment of the present invention, the proportion of sodium hexametaphosphate in the second surfactant is 40% to 45%, the proportion of polyvinylpyrrolidone in the second surfactant is 40% to 45%, and the proportion of sodium oleate in the second surfactant is 10% to 20%. The embodiments of the present invention do not limit this here.

[0085] In this embodiment, the proportions of sodium hexametaphosphate and polyvinylpyrrolidone are roughly the same, while the proportion of the latter is relatively small compared to sodium oleate. By formulating the surfactant in this way, the inventor found that the separation effect of different components in this method is better.

[0086] In summary, since the second surfactant is composed of sodium hexametaphosphate, polyvinylpyrrolidone, and sodium oleate, and the proportions of each substance in the second surfactant are specified, in order to make the second surfactant more active, it is necessary to cool the first sludge. The inventor found that the second surfactant has higher activity in the temperature range of 40°C to 80°C.

[0087] In an embodiment of the present invention, the cooling method includes natural cooling and / or adding wet sludge to the first sludge.

[0088] In this embodiment, the cooling rate of the natural cooling method is slow, but the first sludge will not be doped with wet sludge that has not undergone hydrothermal treatment. Therefore, the effect of separating each part of the components from the first sludge by this method is better; the cooling rate of adding wet sludge to the first sludge is faster, but the first sludge is doped with wet sludge that has not undergone hydrothermal treatment. Therefore, the effect of separating each part of the components from the first sludge by this method is slightly worse.

[0089] In an embodiment of the present invention, the dosage of the second surfactant is 0.1% to 1% of the mass of the first sludge. For example, it can be 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, and 1%. Specific limitations are not provided here.

[0090] In an embodiment of the present invention, the step of "ultrasonically treating the sludge to be sorted" may specifically include:

[0091] Performing sorting treatment and ultrasonic treatment on the sludge to be sorted simultaneously.

[0092] In this embodiment, the sludge to be sorted can be placed in a sorting device, and the ultrasonic probe can be directly placed in the sorting device (i.e., direct ultrasonic treatment. Note: Indirect ultrasonic treatment is difficult to be used in a sorting device) to perform sorting treatment and ultrasonic treatment on the sorting device simultaneously.

[0093] In an embodiment of the present invention, the sorting treatment is one of heavy medium, hydrocyclone, flotation, and liquid-phase screening. The embodiments of the present invention do not limit this here.

[0094] For example, the conditions for flotation treatment are as follows: a flotation agent including rosin oil and / or fatty acid is used, and the dosage of the flotation agent is 0.1% - 1% of the mass of the sludge to be separated;

[0095] For another example, the conditions for heavy medium separation treatment are as follows: a heavy medium including carbon tetrachloride and / or zinc chloride is used, and the density of the heavy medium is 1.6 - 2.3 kg / m 3 , and the mass ratio of the sludge to be separated to the heavy medium is 1:1 - 1:10.

[0096] In an embodiment of the present invention, the separation treatment is one of pressure filtration and centrifugation, and the embodiments of the present invention do not limit it herein.

[0097] It should be noted that the methods for recovering phosphorus by recovering inorganic components include but are not limited to: acid leaching, alkali leaching, biological leaching, precipitation crystallization, high-temperature calcination, electrothermal recovery; and the methods for recovering ammonium salts, alkali metals, and alkaline earth metal compounds from waste liquid include but are not limited to: reverse osmosis membrane method, electrodialysis method, evaporation / concentration crystallization method, ion exchange method. Herein, the embodiments of the present invention do not elaborate on the above recovery treatment methods.

[0098] It is worth noting that by adopting the new idea of "stripping inorganic components to extract phosphorus" to replace the traditional route of "phosphorus extraction from sludge ash", the volatilization loss of phosphorus can be reduced, thereby greatly improving the recovery rate of phosphorus.

[0099] It can be known that the liquid-phase product also includes organic components soluble in water. During the R & D process, the inventor creatively uses the method of secondary hydrothermal treatment of the upper-layer product to recover this part of the organic components soluble in water.

[0100] To achieve the above object, in an embodiment of the present invention, the step of "separating the upper-layer product" may specifically include:

[0101] Performing secondary hydrothermal treatment on the upper-layer product to obtain a hydrothermal product; wherein, the hydrothermal product includes waste liquid and low-ash organic carbon formed by the enrichment and transformation of organic components into solid carbon;

[0102] Separating the hydrothermal product to obtain waste liquid and low-ash organic carbon.

[0103] In this embodiment, performing secondary hydrothermal treatment on the upper-layer product can hydrothermally reconstruct the stripped organic components (i.e., organic components soluble in water and solid carbon insoluble in water), so that the organic components soluble in water in the liquid-phase product can be enriched and transformed into solid carbon insoluble in water. Thus, not only the recovery and utilization of the organic components soluble in water are realized, but also the yield of low-ash organic carbon can be increased and the total COD (i.e., chemical oxygen demand) in the waste liquid can be reduced.

[0104] Organic carbon (i.e., solid carbon) is a solid organic component that can be extracted from sludge. In the relevant technology, the organic carbon extracted from sludge contains more inorganic components (i.e., ash), which is not conducive to the resource utilization of organic carbon (for example, using organic carbon as an adsorbent, fuel, and soil conditioner, etc.). Therefore, more low-ash organic carbon can be obtained by the above-mentioned secondary hydrothermal treatment method. It should be noted that the concept of "low-ash organic carbon" proposed in the embodiment of the present invention is compared with the solid carbon obtained by a single hydrothermal treatment of sludge under the same conditions. The ash content of the former can be reduced by more than 10% compared with the latter. Therefore, in order to distinguish, the inventor calls the organic carbon product obtained by the secondary hydrothermal treatment low-ash organic carbon. The reduction in ash content is beneficial to improving the adsorption capacity, calorific value, and soil fertilizer efficiency of organic carbon, which will not be elaborated here.

[0105] In order to make the organic components more completely and fully enriched and transformed into solid carbon to form organic carbon with lower ash content, the hydrothermal temperature and hydrothermal time of the secondary hydrothermal treatment should be higher than those of the primary hydrothermal treatment.

[0106] In one embodiment of the present invention, the conditions of the secondary hydrothermal treatment are: the hydrothermal temperature is 180° C. to 300° C., and the hydrothermal time is 10 to 240 min.

[0107] Of course, the conditions of the secondary hydrothermal treatment may also be in other numerical ranges (for example, the hydrothermal temperature is 250° C. to 350° C., and the hydrothermal time is 40 to 300 min), which is not limited in this embodiment of the present invention.

[0108] In one embodiment of the present invention, the method further includes:

[0109] The recovered waste liquid is mixed with the sludge to be treated, and step A1 is continued.

[0110] In this embodiment, the main component of the recycled waste liquid is water, so it can be further recycled to reduce the waste of water resources.

[0111] The above describes specific embodiments of the present invention. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in an order different from that in the embodiments and still achieve the desired results. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0112] Each embodiment in the present invention is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the apparatus embodiments, since they are basically similar to the method embodiments, the description is relatively simple. For the relevant parts, reference can be made to the corresponding descriptions in the method embodiments.

[0113] It should be noted that, in this document, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0114] 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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for separating sludge components, characterized in that, Comprising: Performing a first hydrothermal treatment on the sludge to be treated to obtain the sludge to be sorted; wherein, the first hydrothermal treatment is used to destroy the extracellular polymers of the sludge to be treated, so as to facilitate the disintegration of sludge flocs and the release of internal substances; Performing a sorting treatment on the sludge to be sorted to obtain an upper-layer product and a lower-layer product; wherein, the upper-layer product includes a liquid-phase product and solid carbon, and the lower-layer product includes inorganic components; Performing a separation treatment on the upper-layer product to obtain a waste liquid and solid carbon; Performing a recovery treatment on the inorganic components to obtain phosphorus; wherein, the recovery treatment method is any one of the following: acid leaching, alkali leaching, bioleaching, precipitation crystallization, high-temperature calcination, electrothermal recovery; Performing a recovery treatment on the waste liquid to obtain ammonium salts, alkali metal compounds, and alkaline earth metal compounds; Performing an ultrasonic treatment on the sludge to be treated and / or the sludge to be sorted; The conditions of the ultrasonic treatment are: the ultrasonic power is 100 - 500 W, and the ultrasonic time is 5 - 60 min; The liquid-phase product includes organic components, and the separation treatment of the upper-layer product includes: Performing a second hydrothermal treatment on the upper-layer product to obtain a hydrothermal product; wherein, the hydrothermal product includes a waste liquid and low-ash organic carbon formed by the enrichment transformation of the organic components to the solid carbon. The second hydrothermal treatment is used for hydrothermal reconstruction of the stripped organic components, so that the organic components soluble in water in the liquid-phase product can be enriched and transformed into solid carbon insoluble in water, thereby not only realizing the recycling of the organic components soluble in water, but also improving the yield of low-ash organic carbon and reducing the total COD in the waste liquid. The solid carbon is the solid-phase organic components that can be extracted from the sludge; Performing a separation treatment on the hydrothermal product to obtain the waste liquid and the low-ash organic carbon; wherein, the ash content of the low-ash organic carbon is more than 10% lower than the ash content of the solid carbon; The conditions of the second hydrothermal treatment are: the hydrothermal temperature is 180°C - 300°C, and the hydrothermal time is 10 - 240 min.

2. The method according to claim 1, characterized in that, The ultrasonic treatment of the sludge to be treated includes: Performing the first hydrothermal treatment and the ultrasonic treatment on the sludge to be treated simultaneously; or, Performing the first hydrothermal treatment and the ultrasonic treatment on the sludge to be treated sequentially; The conditions of the first hydrothermal treatment are: the hydrothermal temperature is 100°C - 200°C, and the hydrothermal time is 15 - 90 min.

3. The method according to claim 1, wherein The ultrasonic treatment of the sludge to be sorted includes: Performing the sorting treatment and the ultrasonic treatment on the sludge to be sorted simultaneously.

4. The method according to claim 1, characterized in that, The sorting treatment is one of heavy medium, hydrocyclone, flotation, and liquid-phase sieve; and / or, The separation treatment is one of pressure filtration and centrifugation.

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