A method for deep dewatering of excess sludge and preparation of sludge biochar and applications thereof

Abstract

The present application relates to a kind of residual sludge deep dewatering and the method and application of preparing sludge biochar, first, residual sludge is concentrated and handled, then join iron-based advanced oxidation conditioning reagent after stirring evenly, make it fully react to remove the bound water in residual sludge, and using high-pressure diaphragm plate-and-frame filter press to residual sludge is dewatered, make the water content of dewatered sludge reduce to 50% below;Finally, after dewatering, residual sludge is placed into tube furnace, and pyrolysis is carried out under anaerobic condition, and sludge biochar is prepared;The method not only can make residual sludge be properly disposed, and the sludge biochar generated also has good adsorption and catalytic oxidation performance, has good resource utilization value.The present application has simple structure, green and environmental protection and good treatment effect, and the optimal treatment condition is explored, and the treatment of residual sludge has very high application value.

Description

Technical Field

[0001] This invention relates to the field of waste sludge treatment, and more specifically to a method and application for deep dewatering and resource-based disposal of waste sludge. Background Technology

[0002] Urban waste sludge is a byproduct of urban wastewater treatment plants. Its high water content limits its subsequent disposal; therefore, reducing the water content is crucial for achieving volume reduction, harmless treatment, and resource recovery. However, waste sludge contains various pathogens and pollutants. Its high organic content results in a large specific surface area, strong hydrophilicity, and difficulty in achieving sludge-water separation.

[0003] The first and crucial step in treating excess sludge is dewatering. The purpose of dewatering is to reduce the moisture content of the excess sludge, transforming it from a liquid to a solid state, thereby reducing its volume and quantity. This creates conditions for the transportation, disposal, or recycling of the sludge. Therefore, deep dewatering of excess sludge to reduce its moisture content to below 50%, followed by volume reduction and harmless treatment, is an urgent need in excess sludge treatment.

[0004] Currently, the main methods for disposing of waste sludge are landfill and incineration. These methods not only fail to achieve resource utilization of the waste sludge but may also lead to secondary pollution. Landfilling is inefficient due to its long drying time and high operating costs. Because waste sludge has a high moisture content, incineration results in low furnace temperatures, incomplete combustion, and limited heat recovery. Therefore, high-calorific-value fuels such as coal and petroleum coke are often mixed in, resulting in a significant amount of incompletely burned solid residue and exhaust gases containing large amounts of sulfur oxides, nitrogen oxides, and dioxins. Furthermore, the metal elements in waste sludge, especially heavy metals, form tiny metal oxide particles during high-temperature incineration. These particles are very difficult to collect and capture, easily entering the atmosphere with the exhaust gases, negatively impacting the atmosphere, soil, groundwater, and human health.

[0005] Therefore, current waste sludge suffers from problems such as high water content, low resource utilization rate, and susceptibility to secondary pollution. To solve these problems and achieve deep dewatering and resource utilization of waste sludge, it is necessary to explore suitable treatment methods and appropriate treatment conditions. Summary of the Invention

[0006] The purpose of this invention is to provide a method and application for deep dewatering of excess sludge and preparation of sludge biochar, which solves the problems of high water content, low resource utilization rate, and easy generation of secondary pollution in excess sludge mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for deep dewatering of excess sludge includes the following steps:

[0009] S1. Concentration: The remaining sludge is concentrated to obtain concentrated sludge;

[0010] After thickening, the moisture content of the remaining sludge is reduced to 95-97%, which also reduces the volume of the remaining sludge, reduces the amount of subsequent work, and lowers transportation costs.

[0011] S2. Add iron-based advanced oxidation conditioner: Adjust the initial pH of the concentrated sludge, add iron-based advanced oxidation conditioner to the concentrated sludge, stir it evenly and let it stand for a period of time;

[0012] Iron-based advanced oxidation conditioners can oxidize and decompose large organic molecules into smaller molecules and ultimately mineralize them into substances such as CO2, H2O, and inorganic salts. After adding iron-based advanced oxidation conditioners, the residual sludge is broken down to a certain extent, and the dewatering performance of the residual sludge is improved. In addition, this process has many advantages such as short reaction time, fast reaction speed, process controllability, and non-selectivity, and can completely degrade a variety of organic pollutants in a short time.

[0013] Furthermore, the iron-based advanced oxidation conditioning agent in step S2 is selected from at least one of Fenton's reagent, ferrous activated persulfate reagent, and potassium ferrate and ferric chloride combined reagent.

[0014] Among iron-based oxidizing agents, Fenton's reagent, ferrous activated persulfate reagent, and potassium ferrate and ferric chloride combined reagent have the advantage of high oxidizing power, which is beneficial to improving the dewatering performance of excess sludge.

[0015] Furthermore, the iron-based advanced oxidation conditioning agent in step S2 is Fenton's reagent.

[0016] Fenton's reagent can produce the Fenton reaction, effectively removing cyanide and organic matter in wastewater containing residual sludge at room temperature. The Fenton reaction can oxidize and destroy a variety of toxic and harmful organic compounds, has a wide range of applications, and operates under mild conditions, without requiring high temperature or high pressure. The equipment is simple and can be used alone or in combination with other methods.

[0017] Furthermore, in step S2, the ferrous source in the Fenton reagent is ferrous sulfate, and the concentration of hydrogen peroxide is 20-40%.

[0018] Furthermore, in step S2, the molar ratio of ferrous sulfate to hydrogen peroxide in the Fenton reagent is 1:1 to 1:2, and the amount of ferrous sulfate added is 0.3-0.5 mmol / g volatile suspended matter.

[0019] Further, in step S2, the pH is adjusted to the range of 5-8.

[0020] S3. Dewatering: The conditioned concentrated sludge is dewatered to obtain dewatered sludge.

[0021] After the above treatment, the moisture content of the remaining sludge is reduced to below 50%, which meets the standards for the treatment of remaining sludge. Furthermore, the solids content of the dewatered sludge is increased, which greatly reduces transportation costs.

[0022] Furthermore, the dewatering method in step S3 is to use a high-pressure diaphragm plate and frame filter press. The high-pressure diaphragm plate and frame filter press has a strong dewatering capacity, making the dewatering of the remaining sludge more thorough.

[0023] Furthermore, in step S3, the pressure of the filter press is greater than 1 MPa, and the filtration time is 5-15 minutes.

[0024] In another aspect of the present invention, a method for preparing sludge biochar is proposed, which produces sludge biochar with application value while deeply dewatering the excess sludge, thereby realizing the resource-based disposal of excess sludge. The method specifically includes the following steps:

[0025] S1. Concentration: The remaining sludge is concentrated to obtain concentrated sludge;

[0026] S2. Add iron-based advanced oxidation conditioner: Adjust the initial pH of the concentrated sludge, add iron-based advanced oxidation conditioner to the concentrated sludge, stir it evenly and let it stand for a period of time;

[0027] S3. Dewatering: The conditioned concentrated sludge is dewatered to obtain dewatered sludge;

[0028] S4. Pyrolysis: The dewatered sludge produced is pyrolyzed, and the solid products are ground and sieved to prepare sludge biochar.

[0029] Dewatered sludge, after iron-based oxidation conditioning and dehydration, has a high organic content and contains a suitable amount of Fe, making it an excellent raw material for biochar production. The pyrolysis of excess sludge involves drying and thermally decomposing the sludge under specific temperature and anaerobic conditions, ultimately producing fuel gas, fuel oil, and carbon black. The gas obtained from the conversion of excess sludge is rich in gaseous hydrocarbons, hydrogen, carbon monoxide, and other combustible gases, while the liquid can be separated into oil resources. Therefore, the pyrolysis technology of excess sludge can effectively achieve the reduction, harmlessness, and resource utilization of excess sludge. Because the pyrolysis conditions are anaerobic or anaerobic, the exhaust volume is small, thus causing less secondary pollution to the atmospheric environment. After pyrolysis, the excess sludge produces a large amount of carbon black, which can be used to prepare sludge biochar. After grinding and sieving, it produces sludge biochar with small particles and good uniformity.

[0030] Furthermore, in step S4, the pyrolysis temperature is 800-1200℃ and the pyrolysis time is 1.5-2.5 hours.

[0031] This scheme provides suitable conditions for the pyrolysis of excess sludge. Nitrogen gas is used to create an oxygen-deficient environment, facilitating the pyrolysis process. The nitrogen flow rate is 45-55 mL / min, the pyrolysis temperature is 800-1200℃, and the pyrolysis time is 1.5-2.5 hours. Under these conditions, the pyrolysis effect of excess sludge is good.

[0032] Furthermore, the pyrolysis temperature in step S4 is 800-1200℃.

[0033] This study found through experiments that the removal effect of organic matter in the remaining sludge is best when the pyrolysis temperature is 800-1200℃. Therefore, the pyrolysis temperature of 800-1200℃ is the most suitable.

[0034] This method involves a series of steps to deeply dewater excess sludge. The process includes adding iron-based advanced oxidizing agents and pyrolysis to convert bound water in the sludge into free water and remove it, thus reducing pollution from sludge treatment. The pyrolysis of the excess sludge produces biochar with valuable applications, exhibiting good adsorption and catalytic oxidation capabilities. Adsorbents and catalysts made from the biochar can be used as byproducts of sludge degradation. This method not only harmlessly degrades waste sludge but also generates economic benefits, enhancing the resource utilization value of excess sludge.

[0035] In another aspect of the invention, the application of sludge biochar produced by the above method as an adsorbent and / or catalyst is proposed. Sludge biochar has strong adsorption and catalytic oxidation capabilities, making it a good material for use as an adsorbent and catalyst. Therefore, this solution achieves resource utilization while deeply dewatering excess sludge, obtaining sludge biochar, a product with application value.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] This invention relates to a method and application for deep dewatering of waste sludge and preparing sludge biochar. First, the waste sludge is concentrated, then an iron-based advanced oxidizing conditioner is added and stirred until homogeneous, followed by a reaction time. Next, bound water in the waste sludge is removed, and the sludge is dewatered until its moisture content is reduced to below 50%. Finally, the dewatered waste sludge is pyrolyzed under anaerobic conditions to prepare sludge biochar. This method deeply dewaters waste sludge and reduces secondary pollution during treatment. Simultaneously, sludge biochar with application value is obtained after pyrolysis. The sludge biochar has good adsorption and catalytic oxidation capabilities, generating economic benefits in the harmless degradation of waste sludge and improving the resource utilization value of waste sludge. This method is simple in structure, environmentally friendly, and has good treatment effects. It has also explored optimal treatment conditions and has extremely high application value for waste sludge treatment. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 A flowchart of a method for deep dewatering of residual sludge;

[0040] Figure 2 A line graph showing the experimental results to verify the effect of pH on the dehydration rate;

[0041] Figure 3 A line graph showing the experimental results of the effect of temperature on the dehydration rate;

[0042] Figure 4 A line graph showing the experimental results to verify the effect of standing time on the dehydration rate;

[0043] Figure 5 To verify Fe 2+ Line graph showing the effect of dosage on dehydration rate;

[0044] Figure 6 A line graph showing the experimental results of the effect of H2O2 dosage on the dehydration rate;

[0045] Figure 7 Flowchart of a method for preparing sludge biochar from waste sludge;

[0046] Figure 8 shows the SEM images of the surface morphology of sludge biochar before and after conditioning with iron-based advanced oxidation conditioning agents. Figure 8ASEM images of the surface morphology of untreated RC-1000 biochar. Figure 8B SEM image of the surface morphology of FC-1000 biochar treated with Fenton's reagent;

[0047] Figure 9 shows the experimental results of EDS energy dispersive spectroscopy spot scanning on the surfaces of RC-1000 biochar and FC-1000 biochar. Figure 9A Spot scan of RC-1000 biochar; Figure 9B Spot scan of FC-1000 biochar;

[0048] Figure 10 shows the experimental results of adsorption-desorption curve tests on RC-1000 biochar and FC-1000 biochar, respectively. Figure 10A The N2 adsorption-desorption isotherm curve of RC-1000 biochar; Figure 10B The N2 adsorption-desorption isotherm curve of FC-1000 biochar;

[0049] Figure 11 The XRD patterns of RC-1000 biochar and FC-1000 biochar are shown.

[0050] Figure 12 This is a schematic diagram of a small-scale filter press device;

[0051] Figure 13 A comparison chart showing the adsorption effects of sludge biochar and 100-mesh activated carbon on rhodamine B.

[0052] Figure 14 This is a comparison of the removal effects of H2O2 and sludge biochar on Rhodamine B at a pyrolysis temperature of 1000℃. Detailed Implementation

[0053] The technical solution of this patent will be further described in detail below with reference to specific embodiments. It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0054] Waste sludge has a high organic matter content and strong hydrophilicity, resulting in poor dewatering properties. Therefore, conditioning the waste sludge before dewatering can improve its dewatering performance. Currently, waste sludge disposal mainly relies on centrifugation, landfill, and incineration. However, the high water content of waste sludge makes its treatment difficult, and existing disposal methods not only fail to achieve resource utilization but may also lead to secondary pollution.

[0055] This application provides a method and application for deep dewatering of waste sludge and preparing sludge biochar. The method involves conditioning the waste sludge with an iron-based advanced oxidizing conditioner, followed by dewatering. The resulting waste sludge has a high organic content and contains an appropriate amount of iron, making it an excellent raw material for biochar preparation. This method reduces the moisture content of the waste sludge to below 50%, meeting the requirements of existing treatment methods. Furthermore, the dewatered sludge can be further pyrolyzed to prepare iron-containing sludge biochar. The sludge biochar exhibits good adsorption and catalytic oxidation performance, achieving deep dewatering and resource-based treatment of waste sludge.

[0056] Example 1:

[0057] This embodiment provides a method for deep dewatering of excess sludge and preparing sludge biochar.

[0058] Please refer to the appendix for a method for deep dewatering of residual sludge. Figure 1 The following is a flowchart of a method for deep dewatering of residual sludge, with the specific steps as follows:

[0059] S1. Concentration: The excess sludge from the wastewater treatment plant is concentrated by gravity to obtain concentrated sludge, which has a moisture content of 95-97%.

[0060] Because gravity thickening does not require the use of chemicals and reagents, its environmental impact is often minimal. In this step, the remaining sludge is thickened, reducing its moisture content to 95-97%, thus reducing its volume, subsequent workload, and transportation costs.

[0061] S2. Add iron-based advanced oxidation conditioner: Adjust the initial pH and temperature of the concentrated sludge, add iron-based advanced oxidation conditioner to the concentrated sludge, stir it evenly and let it stand for a period of time;

[0062] In this step, iron-based advanced oxidation conditioners are used to modify the residual sludge. Advanced oxidation technology is employed, where hydroxyl radicals generated during the reaction effectively decompose recalcitrant toxic organic pollutants until they are completely converted into harmless inorganic substances, without secondary pollution—a feat difficult to achieve with other oxidation methods. The iron-based advanced oxidation conditioner oxidizes and decomposes large organic molecules into smaller molecules or ultimately mineralizes them into CO2, H2O, and inorganic salts. The addition of the iron-based advanced oxidation conditioner, to a certain extent, breaks down the residual sludge and improves its dewatering performance. Iron-based advanced oxidation conditioners offer numerous advantages, including good treatment effect, recyclability, a wide pH range, and low sludge production.

[0063] In a preferred embodiment of this solution, the iron-based advanced oxidizing conditioner in step S2 is selected from any one of Fenton's reagent, ferrous activated persulfate reagent, and potassium ferrate and ferric chloride combined reagent. These three reagents have the advantage of high oxidizing power, which is beneficial for improving the dewatering performance of excess sludge.

[0064] In a preferred embodiment of this solution, the iron-based advanced oxidizing conditioner in step S2 is Fenton's reagent. Fenton's reagent can produce a Fenton reaction, effectively removing cyanide and organic matter in residual sludge wastewater at room temperature. The Fenton reaction can oxidize and destroy a variety of toxic and harmful organic compounds, has a wide range of applications, and operates under mild conditions, requiring no high temperature or high pressure; the equipment is simple, and it can be used alone or in combination with other methods.

[0065] As a preferred embodiment of this scheme, the ferrous source in Fenton's reagent is ferrous sulfate, and the concentration of hydrogen peroxide is 20-40%.

[0066] In a preferred embodiment of this scheme, the concentration of hydrogen peroxide in Fenton's reagent is 27.5%. The hydrogen peroxide concentration used in this embodiment is 27.5%. Research has shown that the concentration of hydrogen peroxide has little impact on the experimental results; it is sufficient to ensure that the amount of hydrogen peroxide added meets the requirements.

[0067] Figure 2 To verify the experimental results of pH affecting the dewatering rate, a line graph was used. The horizontal axis represents pH, the bar graph represents the moisture content of the remaining sludge, and the line graph with black dots represents the dewatering rate of the remaining sludge. Figure 2 The data shows that the residual sludge has a lower moisture content when the pH is between 3 and 8, with the lowest moisture content between pH 5 and 8, and a higher moisture content at pH 10. The dewatering rate of the residual sludge is higher when the pH is between 3 and 8, and lower when the pH is between 8 and 10. Therefore, when the pH is between 5 and 8, the moisture content of the residual sludge is maintained at a low level, while the dewatering rate is high, indicating good performance in conditioning sludge dewatering.

[0068] Figure 3 To verify the effect of temperature on the dewatering rate, a line graph was used. The horizontal axis represents temperature, the bar graph represents the moisture content of the remaining sludge, and the line graph with black dots represents the dewatering rate of the remaining sludge. Figure 3 The moisture content of the residual sludge remained stable within the temperature range of 5-45℃, and the dewatering rate of the residual sludge was also relatively stable. This indicates that the dewatering performance of the residual sludge did not change significantly within this temperature range. Therefore, when conditioning concentrated sludge with iron-based oxidizing agents, it is not necessary to change the initial temperature of the sludge.

[0069] As a preferred embodiment of this solution, the pH is adjusted to a range of 5-8, and the temperature is adjusted to a range of 5-45°C.

[0070] Figure 4 To verify the effect of settling time on the dewatering rate, a line graph was used. The horizontal axis represents the settling time, the bar graph represents the moisture content of the remaining sludge, and the line graph with black dots represents the dewatering rate of the remaining sludge. Figure 4 The display shows that the moisture content of the remaining sludge decreases and the dewatering rate of the remaining sludge increases within the range of 0-5 minutes. After the fifth minute, the moisture content of the remaining sludge decreases to a stable state and also stabilizes. This indicates that after adding the iron-based oxidant, the sludge achieves a good dewatering effect within 5 minutes of reaction. Therefore, in order to shorten the sludge residence time and reduce the volume of the reaction structure, the reaction time should be controlled at 5-15 minutes.

[0071] In a preferred embodiment of this solution, the concentrated sludge is left to stand for 5-15 minutes. After adding an iron-based advanced oxidizing conditioner to the concentrated sludge, it is left to stand for a period of time to allow the iron-based advanced oxidizing conditioner to fully react with the concentrated sludge, thereby degrading the concentrated sludge and improving its dewatering properties.

[0072] As a preferred embodiment of this solution, the concentrated sludge is placed for 5 minutes.

[0073] Figure 5 To verify Fe 2+ A line graph showing the effect of dosage on dehydration rate; the horizontal axis represents Fe. 2+ The dosage is shown in the graph. The bar chart shows the moisture content of the residual sludge, and the line graph with black dots shows the dewatering rate of the residual sludge. Figure 5 This shows that with Fe 2+ As the dosage increases, the moisture content of the remaining sludge decreases and the dewatering rate increases. When Fe 2+ The dehydration rate was highest when the dosage reached 0.4 mmol / g TSS, after which it reached a steady state.

[0074] As a preferred embodiment of this scheme, the amount of ferrous sulfate added to Fenton's reagent is 0.3-0.5 mmol / g VSS.

[0075] As a preferred embodiment of this scheme, the amount of ferrous sulfate added to Fenton's reagent is 0.4 mmol / g VSS.

[0076] Figure 6 To verify the effect of H2O2 dosage on the dewatering rate, a line graph was used. The horizontal axis represents the H2O2 dosage, the bar graph represents the moisture content of the remaining sludge, and the line graph with black dots represents the dewatering rate of the remaining sludge. Figure 6The results showed that as the dosage of H2O2 increased, the moisture content of the residual sludge decreased and the dewatering rate increased. The dewatering rate was highest when the H2O2 dosage reached 0.4 mmol / g VSS, after which it reached a steady state. (According to the attached...) Figure 5 With appendix Figure 6 It can be known that Fe 2+ The optimal dosage is 0.4 mmol / g TSS, and the optimal dosage of H2O2 is 0.4 mmol / g VSS. Fe 2+ The optimal molar ratio of H2O2 to H2O2 is 1:1.

[0077] As a preferred embodiment of this scheme, the molar ratio of ferrous sulfate to hydrogen peroxide in Fenton's reagent is 1:1 to 1:2.

[0078] As a preferred embodiment of this scheme, the molar ratio of ferrous sulfate to hydrogen peroxide in Fenton's reagent is 1:1.

[0079] S3. Dewatering: The reaction products are dewatered using a high-pressure diaphragm plate and frame filter press. The pressure of the filter press is greater than 1 MPa, and the filtration time is 5-15 minutes, so that the moisture content of the remaining sludge is reduced to below 50%, and dewatered sludge is obtained.

[0080] High-pressure diaphragm plate and frame filter presses are common dewatering equipment in the treatment of waste sludge, including its preparation and mechanical drying. Compared to other types of waste sludge filter presses, they have a stronger dewatering capacity, resulting in more thorough dewatering. After approximately 10 minutes of filtration, there is virtually no filtrate seepage; therefore, approximately 10 minutes is the optimal filtration time. Considering the potential differences in the properties of various waste sludge types, the filtration time can be further extended to reduce the moisture content of the waste sludge; therefore, the filtration time can be set at 10-15 minutes.

[0081] The above-mentioned deep dewatering treatment reduces the moisture content of the residual sludge to below 50%, which meets the national standards for residual sludge treatment. Furthermore, the solids content of the dewatered sludge is increased, which greatly reduces transportation costs.

[0082] Please refer to the appendix for a method for preparing sludge biochar. Figure 7 , Figure 7 A flowchart of a method for preparing sludge biochar from waste sludge is shown below, with specific steps as follows:

[0083] S1. Concentration: The excess sludge from the wastewater treatment plant is concentrated by gravity to obtain concentrated sludge, which has a moisture content reduced to 95-97%.

[0084] S2. Add iron-based advanced oxidation conditioner: Adjust the initial pH and temperature of the concentrated sludge, add iron-based advanced oxidation conditioner to the concentrated sludge, stir it evenly and let it stand for a period of time to obtain the reaction product;

[0085] S3. Dewatering: The reaction products are dewatered using a high-pressure diaphragm plate and frame filter press. The pressure of the filter press is greater than 1 MPa, and the filtration time is 5-15 minutes, so that the moisture content of the remaining sludge is reduced to below 50%, and dewatered sludge is obtained.

[0086] S4. Pyrolysis: The obtained dewatered sludge is placed in a tubular furnace and pyrolyzed in nitrogen. The nitrogen flow rate is 45-55 ml / min, the pyrolysis temperature is 400-1200℃, and the pyrolysis time is 1.5-2.5 hours. The obtained solid product is ground and sieved to prepare fine sludge biochar.

[0087] Dewatered sludge, after iron-based oxidation conditioning and dehydration, has a high organic content and contains a suitable amount of Fe, making it an excellent raw material for biochar production. The pyrolysis of excess sludge involves drying and thermally decomposing the sludge under specific temperature and anaerobic conditions, ultimately producing fuel gas, fuel oil, and carbon black. The gas obtained from the conversion of excess sludge is rich in gaseous hydrocarbons, hydrogen, carbon monoxide, and other combustible gases, while the liquid can be separated into oil resources. Therefore, the pyrolysis technology of excess sludge can effectively achieve the reduction, harmlessness, and resource utilization of excess sludge. Because the pyrolysis conditions are anaerobic or anaerobic, the exhaust volume is small, thus causing less secondary pollution to the atmospheric environment. After pyrolysis, the excess sludge produces a large amount of carbon black, which can be used to prepare sludge biochar. After grinding and sieving, it produces sludge biochar with small particles and good uniformity.

[0088] In a preferred embodiment of this scheme, the nitrogen flow rate is 50 ml / min, the pyrolysis temperature is 800-1200℃, and the pyrolysis time is 2 hours.

[0089] In a further embodiment of this scheme, the pyrolysis temperature is 1000℃.

[0090] This scheme provides suitable conditions for the pyrolysis of dewatered sludge. Through experimental research, it was found that the removal effect of organic matter in the remaining sludge is best when the pyrolysis temperature is 1000℃. Therefore, the pyrolysis temperature of 1000℃ is the most suitable.

[0091] In this method, the added iron-based advanced oxidizing conditioner enhances dewatering performance. The dewatered sludge after iron-based oxidizing and dewatering has a high organic content and contains an appropriate amount of Fe, making it an excellent raw material for biochar preparation. Subsequently, the solid products are recovered through pyrolysis to prepare sludge biochar. Sludge biochar has good adsorption and oxidation catalytic capabilities and can be used as an adsorbent or catalyst, achieving resource utilization of excess sludge while performing deep dewatering. This method is simple in structure, has good treatment effect, is environmentally friendly, and has explored optimal treatment conditions, making it highly valuable for the treatment of excess sludge.

[0092] It should be noted that, in the embodiments of the present invention, the residual sludge includes municipal residual sludge, steel plant residual sludge, and wastewater treatment plant residual sludge. It is understood that, since steel plant residual sludge is generated from many places, such as cold-rolled and hot-rolled steel mills, blast furnaces, oxygen top-blown furnaces, pickling and electroplating operations, heat treatment plants, etc., the specific source of the residual sludge is not specifically limited. As long as it is residual sludge, whether it is only municipal residual sludge, only steel plant residual sludge, or a combination of both, the residual sludge treatment method provided by the present invention can be used for treatment.

[0093] Example 2:

[0094] This embodiment describes the application of sludge biochar as an adsorbent or catalyst. Experiments demonstrated that the sludge biochar prepared using the method of Example 1 exhibited improved adsorption and catalytic oxidation capabilities. Therefore, sludge biochar can be used as an adsorbent or catalyst, achieving the resource-based disposal of excess sludge.

[0095] By comparing and characterizing the properties of biochar prepared from untreated sludge and biochar prepared from sludge treated with iron-based advanced oxidizing agents, it was concluded that the adsorption and catalytic oxidation performance of the biochar prepared by adding iron-based advanced oxidizing agents was improved. Specific experimental results are as follows:

[0096] 1. SEM Analysis

[0097] The sludge biochar prepared by dewatering residual sludge without the addition of conditioning agents and then pyrolyzing it at 1000℃ was named RC-1000 biochar, and the sludge biochar prepared by dewatering residual sludge with Fenton's reagent and then pyrolyzing it at 1000℃ was named FC-1000 biochar. The surface morphology of RC-1000 biochar and FC-1000 biochar was observed using a scanning electron microscope (SEM), and the results are shown in Figure 8.

[0098] Figure 8A SEM images of the surface morphology of untreated RC-1000 biochar. Figure 8B SEM images show the surface morphology of FC-1000 biochar treated with Fenton's reagent. As can be seen from the images, the surface morphology of RC-1000 biochar differs significantly from that of FC-1000 biochar. Firstly, the surface pores of RC-1000 biochar are large and porous, while those of FC-1000 biochar are small and dense. Therefore, FC-1000 biochar theoretically has more adsorption sites and better adsorption performance. Simultaneously, many irregular needle-like crystals, presumably iron-containing compounds, are clearly embedded in the surface of FC-1000 biochar. The abundant presence of these needle-like compounds increases the roughness and specific surface area of ​​the biochar, further enhancing its adsorption capacity.

[0099] 2. SEM-EDS point scan analysis

[0100] To analyze the elemental composition and content of micro-area components of RC-1000 biochar and FC-1000 biochar, elemental analysis was performed using SEM EDS energy dispersive spectroscopy. EDS spot scans were performed on the surfaces of RC-1000 and FC-1000 biochar, and the experimental results are shown in Figure 9.

[0101] Figure 9A This is a SEM-EDS spot scan of RC-1000 biochar. The horizontal axis represents energy, and the vertical axis represents intensity. The peaks in the waveform represent the inorganic elements on the surface of the RC-1000 biochar. Figure 9A It is known that the surface elemental composition of RC-1000 biochar is relatively complex. In addition to organic elements such as C, O, P, and S, it also contains a large number of inorganic elements such as Na, Mg, Al, Si, and Ca. Figure 9B This is a SEM-EDS spot scan of FC-1000 biochar. The horizontal axis represents energy, and the vertical axis represents intensity. The peaks in the waveform represent the inorganic elements on the surface of FC-1000 biochar. Figure 9B It can be seen that the elemental composition of FC-1000 biochar made from residual sludge conditioned with Fenton's reagent is similar to that of RC-1000 biochar made from unconditioned residual sludge. However, a certain amount of Fe was detected on the surface of FC-1000 biochar, indicating that the Fe residue from the Fenton reaction was successfully loaded onto the biochar. This also confirms the hypothesis that the needle-like crystals on the surface of FC-1000 biochar observed by SEM are iron-containing compounds. Therefore, FC-1000 biochar made from residual sludge conditioned with Fenton's reagent contains more Fe and has a larger specific surface area and stronger adsorption capacity.

[0102] 3. BET Analysis

[0103] To investigate the particulate properties of sludge biochar, the BET method was used to test the specific surface area, pore volume, pore size distribution, and nitrogen adsorption-desorption curves of the sludge biochar. Adsorption-desorption curves were tested for RC-1000 biochar and FC-1000 biochar, and the experimental results are shown in Figure 10.

[0104] Figure 10A The graph shows the N2 adsorption-desorption isotherms of RC-1000 biochar. The horizontal axis represents relative pressure, and the vertical axis represents adsorption capacity. Curves containing squares indicate that the adsorption capacity of RC-1000 biochar for N2 increases with increasing relative pressure. Curves containing cross-shaped circles indicate that the desorption capacity of RC-1000 biochar for N2 increases with increasing relative pressure. At 0-0.5P / P0, the desorption capacity of RC-1000 biochar for N2 is equal to the adsorption capacity of N2. At a relative pressure of 0.5P / P0, the desorption capacity of RC-1000 biochar for N2 is greater than the adsorption capacity of RC-1000 biochar for N2. At a relative pressure of 1P / P0, the desorption capacity of RC-1000 biochar for N2 is equal to the adsorption capacity of RC-1000 biochar for N2. Figure 10B This is an isotherm graph of N2 adsorption-desorption for FC-1000 biochar. The horizontal axis represents relative pressure, and the vertical axis represents adsorption capacity. Curves containing squares indicate that the adsorption capacity of FC-1000 biochar for N2 increases with increasing relative pressure, while curves containing circles indicate that the desorption capacity of FC-1000 biochar for N2 increases with increasing relative pressure. At 0-0.5 P / P0, the desorption capacity of FC-1000 biochar for N2 is equal to the adsorption capacity, and this desorption capacity is constant at a relative pressure of 0.5 P / P0. At P0, the desorption of N2 by FC-1000 biochar is greater than the adsorption of N2. At a relative pressure of 1P / P0, the desorption of N2 by FC-1000 biochar is equal to the adsorption of N2. According to the classification of physical adsorption isotherms by the International Union of Theoretical and Applied Chemistry (IUPAC), the N2 isotherm adsorption curves of both RC-1000 biochar and FC-1000 biochar belong to type V isotherms and are accompanied by H3 type hysteresis loops, indicating that the pores of sludge biochar are mainly irregular flat slit pores.

[0105] contrast Figure 10A and Figure 10B It was found that the adsorption capacity of FC-1000 biochar was higher than that of RC-1000 biochar, further proving that the adsorption capacity of FC-1000 biochar is stronger than that of RC-1000 biochar.

[0106] 4. Specific surface area and pore volume structure analysis

[0107] The changes in specific surface area and pore volume of RC-1000 biochar and FC-1000 biochar were measured, and the experimental results are shown in Table 1.

[0108] Table 1 Specific surface area and pore structure of biochar

[0109]

[0110] As shown in Table 1, the specific surface area of ​​RC-1000 biochar is only 68.04 m². 2 / g, while the specific surface area of ​​FC-1000 biochar can reach 112.19m². 2 The specific surface area of ​​FC-1000 biochar is approximately 1.65 times that of RC-1000 biochar, which is approximately 1.65 times that of RC-1000 biochar. Therefore, the specific surface area of ​​FC-1000 biochar made from residual sludge treated with Fenton's reagent is significantly higher than that of RC-1000 biochar. Furthermore, the total pore volume of FC-1000 biochar is slightly larger than that of RC-1000 biochar, while the average pore size of FC-1000 biochar is slightly smaller than that of RC-1000 biochar.

[0111] Previous adsorption experiments have confirmed that FC-1000 biochar exhibits better adsorption performance than RC-1000 biochar. Based on the data in Table 1, this is likely because the biochar produced from the calcined residual sludge, conditioned with Fenton's reagent, has smaller and denser pores, leading to an increase in its specific surface area and pore volume, thus enabling it to adsorb pollutants more quickly and in greater quantities.

[0112] 5. XRD Analysis

[0113] X-ray diffraction (XRD) is an effective method for studying the microstructure of crystalline and certain amorphous materials, and it is also one of the most commonly used material characterization methods in research. XRD has a wide range of applications; in addition to general phase analysis, it can also be used for single-crystal analysis, structural analysis, determination of crystallite size, and macroscopic and microscopic stress. To investigate the microstructure of sludge biochar, XRD analysis was performed on RC-1000 biochar and FC-1000 biochar, respectively. The experimental results are attached. Figure 11 As shown.

[0114] Figure 11 The x-axis represents angle, and the y-axis represents relative intensity. The upper diffraction pattern represents the diffraction signal of RC-1000 biochar, and the lower diffraction pattern represents the diffraction signal of FC-1000 biochar. Figure 11It was found that SiO2 was present in both types of biochar, with 2θ values ​​at 20.859° and 26.640° corresponding to XRD standard card PDF#79-1906. Furthermore, compared to RC-1000 biochar without Fenton reagent conditioning, FC-1000 biochar also showed characteristic peaks at 2θ values ​​of 40.301°, 44.221°, and 47.311°. Referring to XRD standard card PDF#89-3680, these peaks correspond to Fe2P. Therefore, it is speculated that the residual Fe after Fenton reagent conditioning is mainly in the form of FePO4. During subsequent pyrolysis, due to the N2 reducing atmosphere, FePO4 is gradually reduced to Fe2P, decreasing the valence state of Fe and enhancing catalytic performance. Considering the needle-like irregular crystals observed on the surface of FC-1000 biochar via SEM, these crystals are speculated to be Fe2P.

[0115] The method for preparing sludge biochar in Example 1 was used to treat the excess sludge. The dewatered sludge, after iron-based oxidation conditioning and dewatering, had a high organic content and contained an appropriate amount of Fe, making it an excellent raw material for biochar preparation. After pyrolysis, the solid product, sludge biochar, was recovered, ground, and sieved to obtain fine-volume sludge biochar.

[0116] The experimental results show that the obtained sludge biochar possesses strong adsorption and catalytic oxidation capabilities, making it a suitable material for use as both an adsorbent and catalyst. Therefore, this method achieves resource utilization while simultaneously performing deep dewatering of excess sludge, yielding sludge biochar with practical application value. Sludge biochar can be used as an adsorbent or oxidation catalyst in industrial production, realizing the resource utilization of excess sludge while simultaneously performing deep dewatering.

[0117] Example 3:

[0118] In this embodiment, Fenton's reagent was determined to be the optimal agent for the effect of iron-based oxidation conditioning on the dewatering performance of residual sludge.

[0119] The residual sludge used in this implementation was taken from the concentrated sludge of a municipal wastewater treatment plant. The volatile solids (VSS) content and moisture content of the residual sludge were tested. 900 mL of residual sludge was weighed; the VSS of this residual sludge was 17.6 g / L, and the moisture content was 95%. The residual sludge was poured into 500 mL beakers numbered 1 to 3. Fenton's reagent, ferrous activated persulfate reagent, and potassium ferrate and ferric chloride combined reagent were added to beakers 1 to 3 respectively, and stirred thoroughly to allow for complete reaction. Subsequently, 100 mL of the residual sludge was taken to prepare it, and the following method was used... Figure 12The laboratory-scale plate and frame filter press shown was used for filtration. After ten minutes of filtration, the moisture content of the remaining sludge was measured. Please refer to the appendix. Figure 12 , Figure 12 This is a schematic diagram of a small-scale filter press device.

[0120] By studying the effects of different iron-based oxidation conditioning methods on the dewatering performance of residual sludge under the optimal dosage, and calculating the cost of the chemicals, the optimal iron-based oxidation conditioning agent was selected.

[0121] The specific experimental results are shown in Table 2. The water content of the ferrous activated persulfate reagent with added 0.4 mmol / g VSS decreased to 50%, while the water content of the dewatered sludge using a potassium ferrate and ferric chloride combination reagent with added 0.005 g / g VSS decreased to 56%. Both showed poor dewatering effects, with the water content of the remaining sludge exceeding 50% after use. However, the water content of the dewatered sludge using Fenton's reagent with added 0.4 mmol / g VSS decreased to 45%, demonstrating the best dewatering effect. Furthermore, the cost of Fenton's reagent is 51 yuan / ton of sludge, the cost of ferrous activated persulfate reagent is 203 yuan / ton of sludge, and the cost of the potassium ferrate and ferric chloride combination reagent is 96 yuan / ton of sludge. The cost of Fenton's reagent is significantly lower than that of ferrous activated persulfate reagent and the potassium ferrate and ferric chloride combination reagent. Therefore, Fenton's reagent is the optimal agent for practical application due to its low cost and good dewatering effect, making it suitable for large-scale application in wastewater treatment plants for treating excess sludge.

[0122] This solution proposes a method and application for deep dewatering of excess sludge and preparation of sludge biochar. It also explores suitable conditions for deep dewatering of excess sludge and screens out the best reagent. Fenton's reagent not only enhances the dewatering effect of excess sludge but also reduces the cost of deep dewatering of excess sludge, which is beneficial to industrial production.

[0123] Table 2 Comparison of conditioning effects and reagent costs of different iron-based advanced oxidation conditioning methods

[0124]

[0125] Example 4:

[0126] In this embodiment, the optimal pyrolysis temperature of dewatered sludge was determined to be 1000℃ through experiments.

[0127] The remaining sludge was conditioned with Fenton's reagent and then dewatered using a small plate and frame filter press. The dewatered sludge was then used as raw material to prepare sludge biochar using a tubular furnace. Biochar was prepared by pyrolysis at different temperatures: 400℃, 600℃, 800℃, 1000℃, and 1200℃, with a heating rate of 5℃ / min. Pyrolysis was performed under nitrogen atmosphere at a flow rate of 50 mL / min for 2 hours.

[0128] Rhodamine B is a synthetic dye, readily soluble in water, appearing as a red to violet powder. Its aqueous solution is blue-red and exhibits strong fluorescence upon dilution. It is commonly used as a fluorescent staining agent for cells in laboratories and is widely applied in industries such as colored glass and specialty fireworks. Rhodamine B is listed as a Group 3 carcinogen. This experiment uses Rhodamine B as a representative organic compound. The removal efficiency of activated carbon and biochar in sludge solutions before and after application can be determined by examining their absorbance values. Five 200mL beakers were filled with 100mL of a 20mg / L Rhodamine B solution, and the pH was adjusted to 3. Biochar prepared by pyrolysis at different temperatures was then added to the beakers. After stirring thoroughly, 2mmol / L H₂O₂ was added, and the mixture was allowed to react for 2 hours. After the reaction was complete, 10mL of the Rhodamine B solution from each beaker was transferred to a centrifuge tube and centrifuged at 5000 rpm for 2 minutes. The supernatant was collected, and the concentration of remaining Rhodamine B was measured using a spectrophotometer. This allowed for the determination of the residual Rhodamine B concentration in each beaker, thus illustrating the removal efficiency of biochar prepared at different pyrolysis temperatures on Rhodamine B. By studying the effect of biochar prepared from dewatered sludge at different pyrolysis temperatures on the removal efficiency of Rhodamine B, the optimal pyrolysis temperature could be determined.

[0129] The results are shown in Table 3. At pyrolysis temperatures of 400℃ and 600℃, the removal rate of Rhodamine B was below 56%, indicating poor pyrolysis efficiency within this temperature range. At pyrolysis temperatures of 800℃, 1000℃, and 1200℃, the removal rate of Rhodamine B reached over 80%, indicating good pyrolysis efficiency within this temperature range. The removal efficiency of Rhodamine B reached its highest value of 97.7% at a pyrolysis temperature of 1000℃. Therefore, the suitable temperature range for pyrolysis is 800-1200℃, and the optimal pyrolysis temperature is 1000℃.

[0130] This scheme proposes a method and application for deep dewatering and resource-based disposal of excess sludge, and also explores suitable conditions for the pyrolysis process. The pyrolysis efficiency is relatively high at 800-1200℃, and reaches its highest efficiency at 1000℃. Therefore, in practical applications, setting the pyrolysis temperature to 800-1200℃ can achieve a good pyrolysis effect, while setting the pyrolysis temperature to 1000℃ can achieve the best pyrolysis effect.

[0131] Table 3 Screening of Optimal Pyrolysis Temperatures

[0132]

[0133] Example 5:

[0134] This embodiment experimentally verified the good adsorption performance of sludge biochar prepared from residual sludge.

[0135] Activated carbon is a specially treated carbon with countless tiny pores on its surface, resulting in a large specific surface area and high adsorption activity. It is an excellent material for wastewater treatment, electrodes, and flue gas treatment. Comparing the adsorption performance of sludge biochar and activated carbon allows for the evaluation of the adsorption capacity and application value of sludge biochar. Sludge biochar prepared at 1000℃ pyrolysis temperature and activated carbon with a particle size of 100 mesh were respectively added to a 60 mg / L Rhodamine B solution and adsorbed for 4 hours, comparing their adsorption effects.

[0136] Please refer to the appendix for experimental results. Figure 13 , Figure 13 This is a comparison chart of the adsorption effects of sludge biochar and 100-mesh activated carbon on Rhodamine B. Figure 13 The x-axis represents time, and the y-axis represents the adsorption of Rhodamine B. The curve containing the triangle symbol indicates that the adsorption of Rhodamine B by sludge biochar increases continuously with time, stabilizing after 230 minutes. The curve containing the circle symbol indicates that the adsorption of Rhodamine B by activated carbon increases continuously with time, stabilizing after 230 minutes. The adsorption capacity of activated carbon is slightly higher than that of sludge biochar. After 240 minutes of reaction, the adsorption of both sludge biochar and activated carbon approaches saturation. At this point, the adsorption capacity of activated carbon is 148 mg / g, and that of sludge biochar is 120 mg / g. The saturated adsorption capacity of sludge biochar is approximately 80% of that of commercial activated carbon.

[0137] Furthermore, the effects of sludge biochar as an adsorbent and catalyst for removing rhodamine B were investigated at a pyrolysis temperature of 1000℃. Three 200mL beakers were filled with 100mL of a 20mg / L rhodamine B solution, and the pH was adjusted to 3. Then, 0.2g / L sludge biochar and 1mmol / L H2O2, and 0.2g / L sludge biochar and 1mmol / L H2O2 were added to the three beakers respectively, to investigate the adsorption and catalytic oxidation efficiency of the sludge biochar.

[0138] The experimental results are attached. Figure 14As shown, the horizontal axis represents time, and the vertical axis represents the removal rate of Rhodamine B. Curves with squares represent the experimental groups with added sludge biochar and H2O2, curves with circles represent the experimental group with added sludge biochar, and curves with triangles represent the experimental group with added H2O2. Figure 14 As shown, adding H2O2 alone has almost no removal effect on Rhodamine B; while adding sludge biochar alone, after stirring for about 90 minutes, can remove about 70% of Rhodamine B, indicating that the prepared sludge biochar has a strong adsorption effect, but it is difficult to completely remove Rhodamine from the system; however, when H2O2 and sludge biochar are added together to the Rhodamine B solution and reacted for about 90 minutes, the Rhodamine B removal rate can reach more than 97%, which is significantly higher than the adsorption group alone. This shows that sludge biochar can catalyze H2O2 to generate highly oxidizing hydroxyl radicals, further degrading the residual Rhodamine B in the system.

[0139] Comparing the adsorption effects of the prepared biochar on rhodamine B with those of 100-mesh commercial activated carbon, it was found that the prepared sludge biochar had a better adsorption effect, with an adsorption capacity reaching 80% of that of regular biochar. This indicates that the sludge biochar has good adsorption capacity and can be used as a substitute for activated carbon, demonstrating high practicality and application value. The sludge biochar also exhibits good adsorption and catalytic oxidation capabilities, generating economic benefits in the harmless degradation of waste sludge and improving the resource utilization value of residual sludge.

[0140] Example 6:

[0141] This embodiment verifies that the heavy metal leaching toxicity of sludge biochar prepared from residual sludge meets national standards.

[0142] To verify whether the heavy metal leaching toxicity of sludge biochar complies with regulations, it is necessary to test the heavy metal leaching content. The Toxicity Characteristic Leaching Method (TCLP) is a method used by the U.S. government to manage hazardous and solid waste in accordance with the Resource Conservation and Recycling Act (RCRA). This method uses an extractant to adjust the pH of the solid waste and conducts an agitation extraction experiment.

[0143] The heavy metal leaching toxicity of sludge biochar prepared at 1000℃ was studied using the TCLP method. Partial results are shown in Table 4. Table 4 shows that the heavy metal leaching toxicity of the sludge biochar meets national standards; for example, the leaching toxicity of Cr, Ni, Cu, Zn, and Cd all meet national standards.

[0144] The above experimental results demonstrate that the heavy metal content in sludge biochar produced from surplus sludge is low, meeting national standards. Therefore, sludge biochar produced from surplus sludge is low in toxicity and has application value, meeting market demands. Sludge biochar can be applied in industrial production, and this solution is of great significance for the resource-based disposal of surplus sludge.

[0145] Table 4 Heavy metal leaching toxicity of sludge biochar

[0146]

[0147] In summary, this application provides a method and application for deep dewatering of excess sludge and preparing sludge biochar. First, the excess sludge is concentrated, then an iron-based advanced oxidizing conditioner is added, and the mixture is stirred until homogeneous and reacted for a period of time. Subsequently, the bound water in the excess sludge is removed, and the sludge is dewatered until its moisture content is reduced to below 50%. Finally, the dewatered sludge is pyrolyzed to prepare sludge biochar. This method deeply dewaters the excess sludge and reduces secondary pollution during treatment. Simultaneously, the sludge, after iron-based oxidizing and dewatering, has a high organic content and contains an appropriate amount of Fe element. After pyrolysis, sludge biochar with application value is obtained. The sludge biochar has good adsorption and catalytic oxidation capabilities and can be used as an adsorbent or catalyst, realizing the resource-based disposal of excess sludge. Fenton's reagent is inexpensive and environmentally friendly, suitable for large-scale applications in enterprises, and a pyrolysis temperature of 1000℃ yields the best pyrolysis effect. This solution reduces the moisture content of residual sludge, achieves resource-based and environmentally friendly disposal of residual sludge, and explores the optimal treatment conditions, making it highly valuable for the treatment of residual sludge.

[0148] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for treating excess sludge, characterized in that, Includes the following steps: S1. Concentration: The remaining sludge is concentrated to obtain concentrated sludge; S2. Add Fenton's reagent: Adjust the initial pH of the concentrated sludge to the range of 5-8, add Fenton's reagent to the concentrated sludge, stir it evenly and let it stand for a period of time; S3. Dewatering: The concentrated sludge after conditioning is dewatered to obtain dewatered sludge; S4. Pyrolysis: The dewatered sludge is subjected to pyrolysis treatment, and the solid product is ground and sieved to prepare sludge biochar. The surface of the sludge biochar is covered with needle-shaped irregular crystals.

2. The processing method according to claim 1, characterized in that, The ferrous source in the Fenton reagent is ferrous sulfate, and the concentration of hydrogen peroxide is 20-40%.

3. The processing method according to claim 2, characterized in that, The molar ratio of ferrous sulfate to hydrogen peroxide in the Fenton reagent is 1:1 to 1:2, and the amount of ferrous sulfate added is 0.3-0.5 mmol / g volatile suspended matter.

4. The processing method according to any one of claims 1-3, characterized in that, The dehydration method in step S3 is to use a high-pressure diaphragm plate and frame filter press for dehydration.

5. The processing method according to claim 4, characterized in that, In step S3, the pressure of the filter press is greater than 1 MPa, and the filtration time is 10-15 minutes.

6. The processing method according to claim 1, characterized in that, The pyrolysis temperature is 800-1200℃.

7. The application of sludge biochar prepared by the method for treating excess sludge as described in any one of claims 1-6 as an adsorbent.

8. The application of sludge biochar prepared by the method for treating excess sludge as described in any one of claims 1-6 as a catalyst.

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