Sludge low-carbon dehydration method based on hydrophobic amino acid selective cleavage and application of sludge low-carbon dehydration method

Abstract

The invention relates to a sludge low-carbon dehydration method based on hydrophobic amino acid selective cleavage and application of the sludge low-carbon dehydration method, to-be-dehydrated sludge and sulfurized zero-valent iron powder are mixed and contacted, and sulfurized zero-valent iron is prepared by sulfurizing zero-valent iron and a sulfur source according to a specific molar ratio and is provided with a FeS coating layer; then slow-release calcium peroxide particles are added in a segmented mode to control the concentration of liquid-phase hydrogen peroxide; the pH and temperature of the system are controlled in the conditioning process; after conditioning is completed, a framework material is added, and mechanical dehydration is conducted. According to the method, hydrophobic amino acid anchor points in extracellular polymeric substances are selectively broken under mild conditions through the synergistic effect of sulfurized zero-valent iron and slow-release calcium peroxide, bound water is efficiently released, the dehydration efficiency is remarkable, and compared with traditional Fenton and other technologies, carbon emission in the whole process is greatly reduced. The method is also suitable for solid-liquid separation of high-water-content organic wastes such as slaughter wastewater sludge, food waste residue slurry and the like.

Description

Technical Field

[0001] This invention belongs to the field of solid waste treatment, disposal and resource utilization technology, specifically relating to a low-carbon dewatering method for sludge based on the selective cleavage of hydrophobic amino acids and its application. Background Technology

[0002] Municipal wastewater treatment plants generate a large amount of excess sludge during operation, which typically has a water content exceeding 95% and exhibits highly water-containing biogels with strong colloidal properties. Studies have shown that a large amount of water in the sludge does not exist as free water, but is bound within a three-dimensional network of extracellular polymers. In particular, the inner extracellular polymers, rich in proteins, carbohydrates, humic substances, and polyvalent cations, form a highly stable colloidal framework through physical entanglement and chemical cross-linking. Among these, the hydrophobic protein network formed by the aggregation of aliphatic hydrophobic amino acid residues plays a dominant role in retaining bound water.

[0003] Traditional sludge conditioning and dewatering technologies mainly include acid / alkali conditioning, hot water hydrolysis, Fenton oxidation, ozone oxidation, and persulfate activation. Their core principle is to improve dewatering performance through non-selective oxidation or destruction of the extracellular polymeric structure. However, these technologies generally suffer from the following drawbacks:

[0004] (1) Free radical attacks lack selectivity and easily degrade hydrophobic skeletons and hydrophilic groups at the same time, generating more short peptides and hydrophilic small molecules, which in turn increases the overall hydrophilicity and water retention capacity of sludge, thus limiting the dewatering effect.

[0005] (2) The addition of strong oxidants and strong acids / bases is huge, which not only leads to high chemical reagent costs, but also causes serious corrosion to the treatment equipment and increases operation and maintenance costs;

[0006] (3) The conditioning process has high energy consumption and the subsequent drying stage has high carbon emission intensity, which is inconsistent with the "dual carbon" target requirements;

[0007] (4) It is impossible to achieve precise control at the molecular level, and it is difficult to destroy the "water-locking anchor" without damaging the overall structure of the extracellular polymer.

[0008] Related research has proposed identifying "water-binding anchors" in extracellular polymers at the molecular level. It suggests that aliphatic hydrophobic amino acids (such as glycine, alanine, valine, leucine, and isoleucine) form localized hydrophobic microdomains within hydrophobic protein networks, serving as key structural units for water binding. However, an effective technical approach remains to selectively cleave these hydrophobic anchors in complex sludge systems without excessively disrupting the overall protein backbone.

[0009] Therefore, there is an urgent need to develop a novel low-carbon sludge dewatering method that can selectively cleave aliphatic hydrophobic amino acids under mild conditions and with low reagent dosage, thereby releasing bound water and significantly reducing subsequent energy consumption and carbon emissions. Summary of the Invention

[0010] Technical Problem Solved: This invention aims to overcome the shortcomings of existing sludge conditioning and dewatering technologies, such as strong non-selectivity, high reagent consumption, high energy consumption, and significant carbon emissions. It proposes a low-carbon sludge dewatering method and its application based on the synergistic conditioning of zero-valent iron sulfide and slow-release calcium peroxide to selectively break hydrophobic amino acid anchor points. By directionally severing the "water-locking and hydrophobic anchor points" in extracellular polymers at the molecular level, the hydrophobic three-dimensional network is disrupted, and bound water is rapidly released. This significantly improves sludge dewatering performance while reducing energy consumption and carbon emissions throughout the entire life cycle, providing a new solution for low-carbon and high-efficiency sludge treatment.

[0011] Technical Solution: A method for low-carbon dewatering of sludge based on selective cleavage of hydrophobic amino acids, comprising the following steps: S1, placing the sludge to be dewatered in a reactor, adding 10-60 mg / g of sulfided zero-valent iron powder based on the dry solids mass of the sludge, wherein the sulfided zero-valent iron is obtained by sulfidation of zero-valent iron and a sulfur source at a Fe:S molar ratio of 1:(0.1-0.5) and has an FeS coating layer on the surface; dispersing under stirring conditions of 50-300 rpm for 1-10 min, then reducing the stirring speed to 20-150 rpm and maintaining it for 2-15 min; S2, adding slow-release calcium peroxide particles to the system after step S1, the amount added being 20-80 mg / g dry solids based on the effective CaO2 content; wherein the slow-release calcium peroxide particles are particles formed by calcium peroxide loaded on a porous carrier or microcapsule particles formed by calcium peroxide coated with an organic or inorganic shell layer; the CaO2 is added in stages, at least twice, with an interval of 2-12 minutes between adjacent additions. S3. Simultaneously or after step S2, control the pH of the system to 5.5~7.5 and the reaction temperature to 5~40 ℃, and carry out a conditioning reaction for 5~40 min; S4. After conditioning, add 10~200 mg / g of dry solid skeleton material, and then carry out mechanical dehydration. The moisture content of the filter cake after dehydration is not higher than 65%.

[0012] In step S2, the concentration of hydrogen peroxide in the liquid phase is maintained at 80-250 mg / L for 5-20 min after the start of the reaction.

[0013] In step S3, the pH of the system is maintained at 5.5 to 7.5 by introducing carbon dioxide and / or adding a buffer solution of acetic acid, citric acid or their salts.

[0014] In step S3, after the conditioning reaction is completed and before mechanical dehydration, a terminator is added to the system. The terminator is selected from at least one of sulfite, thiosulfate, and hydrogen peroxide decomposing enzyme. The amount added is such that the hydrogen peroxide concentration in the filtrate is less than 10 mg / L.

[0015] The particle size D50 of the above-mentioned sulfided zero-valent iron powder is 50 nm to 100 μm.

[0016] The particle size of the above-mentioned slow-release calcium peroxide particles is 0.1~5 mm, and the mass fraction of CaO2 in the particles is 10~70 wt.%.

[0017] The porous carrier is selected from at least one of biochar, activated carbon, zeolite, diatomaceous earth, mesoporous silica, and clay minerals; and / or the coating shell is selected from at least one of alginate gel, polyvinyl alcohol, polydopamine, and silica shell.

[0018] The aforementioned skeleton material is selected from at least one of cellulose fiber, diatomaceous earth, fly ash, and biochar.

[0019] The aforementioned mechanical dewatering methods include screw press filtration, belt press filtration, or centrifugal dewatering.

[0020] The application of the above method in the solid-liquid separation of high-water-content organic waste or biomass slurry containing a similar extracellular polymer colloidal structure is characterized in that the high-water-content organic waste or biomass slurry is selected from slaughterhouse wastewater sludge, food waste slurry, or protein-rich fermentation residue.

[0021] Invention Principle: CaO2 is gradually released into the sludge system via a slow-release mechanism, maintaining the H2O2 concentration at 80-250 mg / L for 5-20 minutes after the reaction begins. This ensures continuous generation of active free radicals and avoids non-selective degradation caused by instantaneous excess of oxidant. The interfacial proton-coupled electron transfer process utilizes aliphatic hydrophobic amino acids in the extracellular polymeric structure as the primary proton donors. These aliphatic hydrophobic amino acids include amino acid residues such as glycine, alanine, valine, leucine, and isoleucine. Under the proton-coupled electron transfer involving active free radicals, their Cα-H bonds undergo hydrogen extraction, β-cleavage, decarboxylation, and deamination reactions. This preferentially breaks down aliphatic amino acids, with relatively less breakage occurring in charged or polar amino acids, achieving molecular-level selective cleavage of hydrophobic anchor points.

[0022] Beneficial effects: (1) The sludge particle D50 increases from 20~80 μm before conditioning to 50~300 μm, increasing internal pore channels and improving filtrate permeability. (2) For typical municipal waste sludge, this method can reduce capillary water absorption time by 40%~60%, bound water content by 30%~60%, and filter cake moisture content by 50%~65%, with dewatering effect far exceeding that of traditional chemical conditioning processes, laying a good foundation for subsequent sludge disposal (such as incineration, resource utilization, etc.). (3) Based on the life cycle assessment results, the carbon emissions of this method can be reduced by about 37% compared with the traditional Fenton system; when the solid content of sludge cake is increased to 40%, the theoretical heat required for drying can be reduced by more than 70%, significantly reducing energy consumption and greenhouse gas emissions in subsequent drying and disposal processes, which is in line with the "dual carbon" development goal. Attached Figure Description

[0023] Figure 1 The graph shows a comparison of the sludge dewatering performance (capillary water absorption time, bound water content, and filter cake moisture content) of the method of the present invention (Examples 1-5 and Comparative Examples 1-10) under different conditioning conditions.

[0024] Figure 2 This is a comparison chart of Example 1 of the present invention and the conventional Fenton Comparative Example 10 in terms of dehydration performance (capillary water absorption time, bound water content and filter cake moisture content) and carbon emission intensity.

[0025] Figure 3 The images show a comparison of the sludge floc structure before and after conditioning in the method of the present invention (Example 1, Comparative Example 1).

[0026] Figure 4 This is a comparison chart showing the improvement effects of the method of the present invention on capillary water absorption time and filter cake moisture content in the treatment of different types of high-moisture organic waste. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0028] Preparation of calcium peroxide-loaded biochar sustained-release particles: 0.5 g of chitosan powder was weighed and dissolved in 50 mL of 1% (w / w) glacial acetic acid solution, and stirred until completely dissolved. 5.0 g of biochar was added, and the mixture was stirred continuously in a 50 ℃ water bath for 4–6 h to allow chitosan intercalation. The slurry was then centrifuged, and the precipitate was washed 2–3 times alternately with deionized water and anhydrous ethanol. The filter cake was dried in a 60 ℃ vacuum drying oven to constant weight, and finally ground into a fine powder to obtain chitosan-modified biochar (CS-BC) carrier, which was then sealed for later use. Next, in-situ synthesis was performed. The first step involved preparing the reaction solution. Under ice-water bath conditions in a fume hood, 2.0 g of commercially available calcium peroxide powder was slowly added in batches to 50 mL of pre-cooled 1 mol / L hydrochloric acid solution. The mixture was stirred until the reaction was complete, and after filtration, a calcium chloride solution was obtained for later use. Separately, 30 mL of 30% hydrogen peroxide solution was placed in an ice-water bath, and concentrated ammonia was slowly added dropwise with stirring. The pH of the solution was adjusted to 10-11 using a pH meter to obtain a hydrogen peroxide-ammonia mixture, which was prepared and used immediately. The second step involved calcium ion adsorption. 3.0 g of the prepared CS-BC carrier powder was weighed, added to 100 mL of deionized water, and ultrasonically dispersed for 10 min. Under stirring at room temperature, the aforementioned calcium chloride filtrate was slowly added dropwise to the carrier suspension. After the addition was complete, stirring was continued for 1 h. The third step involves in-situ precipitation. Under conditions of continuous vigorous stirring and maintaining the system temperature below 10 °C using a water bath, a hydrogen peroxide-ammonia solution is slowly added dropwise at a rate of 1-2 drops per second to the above-mentioned calcium ion-containing suspension. After the addition is complete, the reaction is continued to be stirred at low temperature for 1-2 hours. Finally, post-treatment is performed. The reaction solution is immediately vacuum filtered using a Buchner funnel. The filter cake is washed 3-5 times with pre-cooled deionized water until the filtrate is neutral. Then, the filter cake is placed in a 50 °C vacuum drying oven and dried in the dark for 12-24 hours. After drying, the product is gently ground and sieved to obtain the final calcium peroxide-loaded composite particles, which are then sealed and stored at low temperature in the dark.

[0029] Example 1

[0030] A method for low-carbon dewatering of sludge based on selective cleavage of hydrophobic amino acids includes the following steps: S1. The sludge to be dewatered is placed in a reactor, and 30 mg / g DS of zero-valent iron sulfide (S-ZVI) powder is added based on the dry solids mass (DS) of the sludge. The mixture is dispersed at 180 rpm for 4 min under stirring conditions. Subsequently, the stirring speed is reduced to 90 rpm and maintained for 7 min to allow S-ZVI to fully contact the sludge flocs and adsorb onto the floc surface / extracellular polymer components. S2. After step S1, slow-release calcium peroxide particles are added to the system. The slow-release calcium peroxide particles are calcium peroxide loaded onto porous biochar, and the dosage is 40 mg / g DS based on the effective CaO2 content. The slow-release calcium peroxide particles are added in a segmented / pulsed manner: added in two separate portions, with a 10-min interval between each portion. The concentration of hydrogen peroxide in the liquid phase is maintained at 200 mg / L for 5-20 min after the start of the reaction. S3. During the conditioning process, the pH of the system is controlled at 6.5, and the reaction temperature is controlled at 25°C. Sludge conditioning was carried out at ℃ and the reaction time was controlled at 20 min. After S4 conditioning, 100 mg / g DS of skeleton material (cellulose fiber) was added, and then the sludge was dewatered by screw press filter press to obtain dewatered sludge. The moisture content of the filter cake after dewatering was 54% (solid content 46%).

[0031] The S-ZVI described in step S1 is prepared by sulfidation of zero-valent iron and sulfur source at a Fe:S molar ratio of 1:0.3, and the surface of S-ZVI has an FeS coating layer. The particle size D50 of S-ZVI is 50 nm to 100 μm, and the thickness of its FeS coating layer is 5 to 500 nm.

[0032] The slow-release calcium peroxide particles described in step S2 have a particle size of 0.1~5 mm and a CaO2 mass fraction of 70 wt.%. The porous carrier is selected from biochar.

[0033] The method to maintain pH 6.5 in step S3 is to introduce carbon dioxide to counteract the alkalization caused by the hydrolysis of calcium peroxide.

[0034] After step S3 is completed and before mechanical dewatering, cellulose fibers are added to the sludge to improve the filtration channels and reduce the moisture content of the filter cake.

[0035] After step S3 is completed, a terminator is added to inhibit the residual oxidation reaction. The terminator is selected from hydrogen peroxide decomposing enzyme. The amount of terminator is such that the concentration of hydrogen peroxide in the filtrate is less than 10 mg / L.

[0036] Example 2

[0037] A method for low-carbon dewatering of sludge based on selective cleavage of hydrophobic amino acids includes the following steps: S1. The sludge to be dewatered is placed in a reactor, and 10 mg / g DS of zero-valent iron sulfide (S-ZVI) powder is added based on the dry solids mass (DS) of the sludge. The mixture is dispersed at 180 rpm for 4 min under stirring conditions. Subsequently, the stirring speed is reduced to 90 rpm and maintained for 7 min to allow S-ZVI to fully contact the sludge flocs and adsorb onto the floc surface / extracellular polymer components. S2. After step S1, slow-release calcium peroxide particles are added to the system. The slow-release calcium peroxide particles are calcium peroxide loaded onto porous biochar, and the dosage is 40 mg / g DS based on the effective CaO2 content. The slow-release calcium peroxide particles are added in a segmented / pulsed manner: added in two separate portions with a 10-min interval between each portion. The concentration of hydrogen peroxide in the liquid phase is maintained at 200 mg / L for 5-20 min after the start of the reaction. S3. During the conditioning process, the pH of the system is controlled at 6.5, and the reaction temperature is controlled at 25°C. Sludge conditioning was carried out at ℃ and the reaction time was controlled at 20 min. After S4 conditioning, 100 mg / g DS of skeleton material (cellulose fiber) was added, and then the sludge was dewatered by screw press filter press to obtain dewatered sludge. The moisture content of the filter cake after dewatering was 62% (solid content 38%).

[0038] The S-ZVI described in step S1 is prepared by sulfidation of zero-valent iron and sulfur source at a Fe:S molar ratio of 1:0.3, and the surface of S-ZVI has an FeS coating layer. The particle size D50 of S-ZVI is 50 nm to 100 μm, and the thickness of its FeS coating layer is 5 to 500 nm.

[0039] The slow-release calcium peroxide particles in step S2 have a particle size of 0.1~5 mm and a CaO2 mass fraction of 70 wt.%. The porous carrier in S2 is selected from biochar.

[0040] The method to maintain pH 6.5 in step S3 is to introduce carbon dioxide to counteract the alkalization caused by the hydrolysis of calcium peroxide.

[0041] After step S3 is completed and before mechanical dewatering, cellulose fibers are added to the sludge to improve the filtration channels and reduce the moisture content of the filter cake.

[0042] After step S3 is completed, a terminator is added to inhibit the residual oxidation reaction. The terminator is selected from hydrogen peroxide decomposing enzyme. The amount of terminator is such that the concentration of hydrogen peroxide in the filtrate is less than 10 mg / L.

[0043] Example 3

[0044] A method for low-carbon dewatering of sludge based on selective cleavage of hydrophobic amino acids includes the following steps: S1. The sludge to be dewatered is placed in a reactor, and 60 mg / g DS of zero-valent iron sulfide (S-ZVI) powder is added based on the dry solids mass (DS) of the sludge. The mixture is dispersed at 180 rpm for 4 min under stirring conditions. Subsequently, the stirring speed is reduced to 90 rpm and maintained for 7 min to allow S-ZVI to fully contact the sludge flocs and adsorb onto the floc surface / extracellular polymer components. S2. After step S1, slow-release calcium peroxide particles are added to the system. The slow-release calcium peroxide particles are calcium peroxide loaded onto porous biochar, and the dosage is 40 mg / g DS based on the effective CaO2 content. The slow-release calcium peroxide particles are added in a segmented / pulsed manner: added in two separate portions with a 10-min interval between each portion. The concentration of hydrogen peroxide in the liquid phase is maintained at 200 mg / L for 5-20 min after the start of the reaction. S3. During the conditioning process, the pH of the system is controlled at 6.5, and the reaction temperature is controlled at 25°C. Sludge conditioning was carried out at ℃ and the reaction time was controlled at 20 min. After S4 conditioning, 100 mg / g DS of skeleton material (cellulose fiber) was added, and then the sludge was dewatered by screw press filter press to obtain dewatered sludge. The moisture content of the filter cake after dewatering was 58% (solid content 42%).

[0045] The S-ZVI described in step S1 is prepared by sulfidation of zero-valent iron and sulfur source at a Fe:S molar ratio of 1:0.3, and the surface of S-ZVI has an FeS coating layer. The particle size D50 of S-ZVI is 50 nm to 100 μm, and the thickness of its FeS coating layer is 5 to 500 nm.

[0046] The slow-release calcium peroxide particles in step S2 have a particle size of 0.1~5 mm and a CaO2 mass fraction of 70 wt.%. The porous carrier in S2 is selected from biochar.

[0047] The method to maintain pH 6.5 in step S3 is to introduce carbon dioxide to counteract the alkalization caused by the hydrolysis of calcium peroxide.

[0048] After step S3 is completed and before mechanical dewatering, cellulose fibers are added to the sludge to improve the filtration channels and reduce the moisture content of the filter cake.

[0049] After step S3 is completed, a terminator is added to inhibit the residual oxidation reaction. The terminator is selected from hydrogen peroxide decomposing enzyme. The amount of terminator is such that the concentration of hydrogen peroxide in the filtrate is less than 10 mg / L.

[0050] Example 4

[0051] A method for low-carbon dewatering of sludge based on selective cleavage of hydrophobic amino acids includes the following steps: S1. The sludge to be dewatered is placed in a reactor, and 30 mg / g DS of zero-valent iron sulfide (S-ZVI) powder is added based on the dry solids mass (DS) of the sludge. The mixture is dispersed at 180 rpm for 4 min under stirring conditions. Subsequently, the stirring speed is reduced to 90 rpm and maintained for 7 min to allow S-ZVI to fully contact the sludge flocs and adsorb onto the floc surface / extracellular polymer components. S2. After step S1, slow-release calcium peroxide particles are added to the system. The slow-release calcium peroxide particles are calcium peroxide loaded onto porous biochar, and the dosage is 40 mg / g DS based on the effective CaO2 content. The slow-release calcium peroxide particles are added in a segmented / pulsed manner: added in two separate portions, with a 10-min interval between each portion. The concentration of hydrogen peroxide in the liquid phase is maintained at 200 mg / L for 5-20 min after the start of the reaction. S3. During the conditioning process, the pH of the system is controlled at 6.5, and the reaction temperature is controlled at 25°C. Sludge conditioning was carried out at ℃ and the reaction time was controlled at 20 min. After S4 conditioning, 100 mg / g DS of skeleton material (cellulose fiber) was added, and then the sludge was dewatered by screw press filter press to obtain dewatered sludge. The moisture content of the filter cake after dewatering was 54% (solid content 46%).

[0052] The S-ZVI described in step S1 is prepared by sulfidation of zero-valent iron and a sulfur source at a Fe:S molar ratio of 1:0.1, and the surface of the S-ZVI has an FeS coating layer. The particle size D50 of the S-ZVI is 50 nm to 100 μm, and the thickness of its FeS coating layer is 5 to 500 nm.

[0053] The slow-release calcium peroxide particles in step S2 have a particle size of 0.1~5 mm and a CaO2 mass fraction of 70 wt.%. The porous carrier in S2 is selected from biochar.

[0054] The method to maintain pH 6.5 in step S3 is to introduce carbon dioxide to counteract the alkalization caused by the hydrolysis of calcium peroxide.

[0055] After step S3 is completed and before mechanical dewatering, cellulose fibers are added to the sludge to improve the filtration channels and reduce the moisture content of the filter cake.

[0056] After step S3 is completed, a terminator is added to inhibit the residual oxidation reaction. The terminator is selected from hydrogen peroxide decomposing enzyme. The amount of terminator is such that the concentration of hydrogen peroxide in the filtrate is less than 10 mg / L.

[0057] Example 5

[0058] A method for low-carbon dewatering of sludge based on selective cleavage of hydrophobic amino acids includes the following steps: S1. The sludge to be dewatered is placed in a reactor, and 30 mg / g DS of zero-valent iron sulfide (S-ZVI) powder is added based on the dry solids mass (DS) of the sludge. The mixture is dispersed at 180 rpm for 4 min under stirring conditions. Subsequently, the stirring speed is reduced to 90 rpm and maintained for 7 min to allow S-ZVI to fully contact the sludge flocs and adsorb onto the floc surface / extracellular polymer components. S2. After step S1, slow-release calcium peroxide particles are added to the system. The slow-release calcium peroxide particles are calcium peroxide loaded onto porous biochar, and the dosage is 40 mg / g DS based on the effective CaO2 content. The slow-release calcium peroxide particles are added in a segmented / pulsed manner: added in two separate portions, with a 10-min interval between each portion. The concentration of hydrogen peroxide in the liquid phase is maintained at 200 mg / L for 5-20 min after the start of the reaction. S3. During the conditioning process, the pH of the system is controlled at 6.5, and the reaction temperature is controlled at 25°C. Sludge conditioning was carried out at ℃ and the reaction time was controlled at 20 min. After S4 conditioning, 100 mg / g DS of skeleton material (cellulose fiber) was added, and then the sludge was dewatered by screw press filter press to obtain dewatered sludge. The moisture content of the filter cake after dewatering was 57% (solid content 43%).

[0059] The S-ZVI described in step S1 is prepared by sulfidation of zero-valent iron and sulfur source at a Fe:S molar ratio of 1:0.5, and the surface of S-ZVI has an FeS coating layer. The particle size D50 of S-ZVI is 50 nm to 100 μm, and the thickness of its FeS coating layer is 5 to 500 nm.

[0060] The slow-release calcium peroxide particles in step S2 have a particle size of 0.1~5 mm and a CaO2 mass fraction of 70 wt.%. The porous carrier in S2 is selected from biochar.

[0061] The method to maintain pH 6.5 in step S3 is to introduce carbon dioxide to counteract the alkalization caused by the hydrolysis of calcium peroxide.

[0062] After step S3 is completed and before mechanical dewatering, cellulose fibers are added to the sludge to improve the filtration channels and reduce the moisture content of the filter cake.

[0063] After step S3 is completed, a terminator is added to inhibit the residual oxidation reaction. The terminator is selected from hydrogen peroxide decomposing enzyme. The amount of terminator is such that the concentration of hydrogen peroxide in the filtrate is less than 10 mg / L.

[0064] Comparative Example 1

[0065] A low-carbon dewatering method for sludge based on selective cleavage of hydrophobic amino acids is proposed. Compared with Example 1, this method does not add zero-valent iron sulfide and slow-release calcium peroxide particles. The sludge is placed under the same stirring and reaction conditions for 20 min and then directly subjected to screw press filtration dewatering.

[0066] Comparative Example 2

[0067] A low-carbon dewatering method for sludge based on the selective cleavage of hydrophobic amino acids is disclosed. Compared with Example 1, this method only adds 40 mg / g slow-release calcium peroxide particles to the sludge based on DS (dissolved solids), without adding zero-valent iron sulfide. All other conditions are the same as in Example 1.

[0068] Comparative Example 3

[0069] A method for low-carbon dewatering of sludge based on selective cleavage of hydrophobic amino acids is disclosed. Compared with Example 1, this method only adds 30 mg / g ferrous sulfide (FSS) to the sludge based on dissolved solids (DS), without adding slow-release calcium peroxide particles. The Fe:S molar ratio during the preparation of FSS is 1:0.3. All other conditions are the same as in Example 1.

[0070] Comparative Example 4

[0071] A low-carbon dewatering method for sludge based on the selective cleavage of hydrophobic amino acids is disclosed. Compared with Example 1, this method involves sequentially adding 30 mg / g DS of unsulfurized zero-valent iron powder and 40 mg / g DS of slow-release calcium peroxide particles to the sludge, based on DS (dissolved solids). The zero-valent iron powder is not subjected to sulfidation treatment. All other conditions are the same as in Example 1.

[0072] Comparative Example 5

[0073] A method for low-carbon dewatering of sludge based on selective cleavage of hydrophobic amino acids is disclosed. Compared with Example 1, the Fe:S molar ratio is set to 1:0.05 during the preparation of zero-valent iron sulfide, and 30 mg / g DS is added to the obtained material according to DS. At the same time, 40 mg / g DS of slow-release calcium peroxide particles are added. The other conditions are the same as in Example 1.

[0074] Comparative Example 6

[0075] A low-carbon dewatering method for sludge based on the selective cleavage of hydrophobic amino acids is disclosed. Compared with Example 1, this method involves sequentially adding 5 mg / g zero-valent iron sulfide (DS) and 10 mg / g slow-release calcium peroxide granules to the sludge according to DS (dissolved solids). The Fe:S molar ratio during the preparation of the zero-valent iron sulfide is 1:0.3. All other conditions are the same as in Example 1.

[0076] Comparative Example 7

[0077] A method for low-carbon dewatering of sludge based on selective cleavage of hydrophobic amino acids is disclosed. The difference between this method and Example 1 is that zero-valent iron sulfide and slow-release calcium peroxide particles are added simultaneously in S1 and S2, while the other conditions are the same as in Example 1.

[0078] Comparative Example 8

[0079] A method for low-carbon dewatering of sludge based on selective cleavage of hydrophobic amino acids is disclosed. The difference between this method and Example 1 is that slow-release calcium peroxide particles are added first in step S2, and zero-valent iron is sulfided in step S1. The other conditions are the same as in Example 1.

[0080] Comparative Example 9

[0081] A low-carbon dewatering method for sludge based on selective cleavage of hydrophobic amino acids is disclosed. The difference between this method and Example 1 is that the calcium peroxide added in S2 is pure granular and does not contain biochar carrier, while the other conditions are the same as in Example 1.

[0082] Comparative Example 10

[0083] A conventional Fenton-conditioned sludge dewatering method, compared with Example 1, employs a conventional Fenton system (Fe... 2+ / H2O2) replaces zero-valent iron sulfide / calcium peroxide for synergistic conditioning: Under the same sludge conditions, Fe 2+ Ferrous sulfate was added at a dosage of 30 mg / g DS (based on dissolved solids); H2O2 was added as industrial hydrogen peroxide at a dosage of 50 mg / g DS (based on dissolved solids). All other conditions were the same as in Example 1.

[0084] Comparative Example 11

[0085] A low-carbon dewatering method for sludge based on the selective cleavage of hydrophobic amino acids is disclosed. Compared with Example 1, this method only adds 100 mg / g slow-release calcium peroxide particles to the sludge based on DS (dissolved solids). All other conditions are the same as in Example 1.

[0086] Comparative Example 12

[0087] A method for low-carbon dewatering of sludge based on the selective cleavage of hydrophobic amino acids is disclosed. Compared with Example 1, this method only adds 80 mg / g zero-valent iron sulfide to the sludge based on DS (dissolved solids), wherein the Fe:S molar ratio during the preparation of zero-valent iron sulfide is 1:0.3. All other conditions are the same as in Example 1.

[0088] Comparative Example 13

[0089] A low-carbon dewatering method for sludge based on the selective cleavage of hydrophobic amino acids is disclosed. Compared with Example 1, this method involves adding slow-release calcium peroxide particles to the system after step S1. The slow-release calcium peroxide particles are calcium peroxide loaded onto porous biochar, and the dosage is 40 mg / g DS based on the effective CaO2 content. The slow-release calcium peroxide particles are added only once. All other conditions are the same as in Example 1.

[0090] Table 1. Sludge dewatering performance and carbon emission intensity of Examples 1-5 and Comparative Examples 1-10

[0091]

[0092] The examples and comparative examples in this set jointly demonstrate the effectiveness of the method of the present invention, the key differentiating features, and the necessity of its parameter range: Examples 1, 2, and 3 show that when the dosage of zero-valent iron sulfide is 10~60 mg / g DS and the dosage of calcium peroxide is 20~80 mg / g At DS, both can significantly improve sludge conditioning and mechanical dewatering effects, indicating that the dosing window defined in claim 1 has a stable and repeatable technical effect; Examples 4 and 5, combined with Comparative Example 5, further show that the degree of sulfidation of zero-valent iron sulfide (Fe:S molar ratio 1:0.1~0.5) plays a key role in dewatering performance, and the effect is significantly reduced when it is below this range, thus proving the rationality of the sulfur-iron ratio described in claim 1; Comparative Examples 1, 2, and 3 show that blank or adding only a single agent is difficult to achieve the effect of the examples, proving that the synergistic effect of zero-valent iron sulfide and calcium peroxide is a necessary condition for obtaining efficient dewatering; Comparative Example 4 shows that even when unsulfided zero-valent iron is combined with calcium peroxide, it cannot achieve the same dewatering improvement, indicating that the difference feature of "zero-valent iron sulfide" is the core of the present invention; Comparative Examples 5 and 6, compared with Example 2, prove that when the two agents are below the lower limit of the specified dosage, the dewatering improvement is not significant, thus supporting the necessity of the lower limit of the dosage in claim 1. Comparative Examples 7 and 8, by changing the order of addition, verified that "first sulfidation and adsorption of zero-valent iron, followed by staged addition of slow-release calcium peroxide" is a necessary step to achieve selective fracture and efficient dehydration, demonstrating that reversing the order or adding them simultaneously significantly reduces the dehydration effect. Comparative Example 9, by comparing pure calcium peroxide particles with slow-release carrier particles, proved that the slow-release structure plays an irreplaceable role in maintaining stable H2O2 concentration, achieving controllable oxidation, and reducing carbon emissions, highlighting the necessity of the slow-release carrier in the system of this invention. Comparative Examples 11, 12, and 13 correspond to over-limit / non-optimized operations such as CaO2 over-limit addition, S-ZVI over-limit addition, and single-time CaO2 addition, respectively. Their dehydration performance and carbon emission intensity per unit dry solids are all below the parameter window defined in the claims, further proving the necessity of the dosage upper limit and the staged addition strategy.

[0093] Table 2. Comparison of EPS amino acid composition and hydrophobicity index before and after conditioning in Examples 1-5

[0094]

[0095] As shown in Table 2, the proportion of aliphatic hydrophobic amino acids and the GRAVY / MATH hydrophobicity index in EPS decreased overall after conditioning by the method of the present invention. This indicates that the hydrophobic anchor points were preferentially broken, causing the colloidal network to shift from a hydrophobic-dominant structure to a more hydrophilic structure, which is beneficial to the release of bound water and the improvement of dehydration performance. EPS is an extracellular polymer, and its amino acid composition is expressed as the total amino acid molar percentage measured by high performance liquid chromatography / amino acid analyzer after acid hydrolysis. "Aliphatic hydrophobic amino acids" refers to residues such as Gly, Ala, Val, Leu, and Ile, which are mainly composed of aliphatic side chains and contribute significantly to the hydrophobic network. "Other hydrophobic amino acids" refers to hydrophobic or weakly polar residues such as Phe, Met, and Pro. "Hydrophilic / charged amino acids" refers to polar or charged residues such as Asp, Glu, Lys, Arg, Ser, and Thr. GRAVY is the grand average of hydropathy; the higher the value, the more hydrophobic the protein is overall. MATH method is an apparent hydrophobicity index obtained by microbial adhesion to hydrocarbons test; the higher the value, the easier it is for EPS to combine with hydrophobic substances and the stronger the overall hydrophobicity.

[0096] The dewatering performance of high-water-content organic waste or biomass slurry with a similar extracellular polymer colloidal structure was tested according to the methods described in Example 1, Comparative Examples 1-4, and Comparative Example 10:

[0097] The waste sludge discharged from the secondary biological treatment system of a slaughterhouse wastewater treatment plant was used as the treatment target. The sludge had a moisture content of approximately 96%, a dry solids content of approximately 4%, a pH of approximately 7.3, and volatile solids accounting for approximately 70% of the dry solids. Its protein content was higher than that of municipal waste sludge, classifying it as high-protein industrial sludge. Specific dewatering procedures included the following steps:

[0098] (1) Place the sludge from the proposed slaughterhouse wastewater into the reactor and add the required reagents in sequence;

[0099] (2) Adjusting pH and temperature to condition slaughterhouse wastewater sludge;

[0100] (3) After conditioning, mechanical dehydration is carried out by screw press filtration, belt press filtration or centrifugal dehydration to obtain solid phase and supernatant.

[0101] Table 3. Dewatering performance of slaughterhouse wastewater sludge and carbon emission intensity

[0102]

[0103] As shown in Table 3, the method of the present invention (Example 1) also exhibits excellent dewatering performance and low-carbon advantages when treating high-protein industrial sludge (sludge from slaughterhouse wastewater): compared with the blank control group (Comparative Example 1), the capillary water absorption time is reduced by about 52%, the bound water content is reduced by about 56%, the filter cake moisture content is significantly reduced to 58%, and the carbon emission intensity per unit dry solids is 0.40 kg CO2e / kg DS, which is significantly lower than the traditional Fenton process (Comparative Example 10, 0.55 kg CO2e / kg DS). Comparative Examples 2 and 3 show that the effect of single agent addition is limited. Although the combination of unsulfurized zero-valent iron and calcium peroxide in Comparative Example 4 has some improvement, it is still not as good as Example 1 of the present invention, further confirming the necessity and superiority of the synergistic effect of "sulfurized zero-valent iron" and calcium peroxide. In addition, the method of the present invention can still maintain a good selective fragmentation effect in the protein-rich industrial sludge system, indicating that it has good applicability and stability for high-protein waste with a similar extracellular polymer colloidal structure.

[0104] The dewatering performance of high-water-content organic waste or biomass slurry with a similar extracellular polymer colloidal structure was tested according to the methods described in Example 1, Comparative Examples 1-4, and Comparative Example 10:

[0105] The centrifuged mother liquor fermentation residue slurry produced by an amino acid fermentation company was used as the treatment target. The residue had a water content of approximately 97%, a dry solids content of approximately 3%, a pH of approximately 6.5, and volatile solids accounting for approximately 75% of the dry solids. It was rich in soluble and colloidal proteins and peptides, and exhibited a high-viscosity slurry consistency. Specific dehydration performance included the following steps:

[0106] (1) Place the residue slurry to be treated in the reactor and add the required reagents in sequence;

[0107] (2) Conditioning the residual slurry by adjusting pH and temperature;

[0108] (3) After conditioning, mechanical dehydration is carried out by screw press filtration, belt press filtration or centrifugal dehydration to obtain solid phase and supernatant.

[0109] Table 4. Dewatering performance and carbon emission intensity of amino acid fermentation residue slurry

[0110]

[0111] As shown in Table 4, for amino acid fermentation residue slurries with high viscosity and rich in soluble and colloidal proteins and peptides, the method of the present invention (Example 1) can still effectively improve its dewatering performance: the capillary water absorption time is reduced by about 49% compared with the blank group (Comparative Example 1), the bound water content is reduced by about 49%, the filter cake moisture content is reduced to 61%, and the carbon emission intensity per unit dry solids is 0.45 kgCO2e / kg DS, which is significantly lower than the traditional Fenton process (Comparative Example 10, 0.63 kgCO2e / kg DS). Comparative Examples 2 and 3 again demonstrate that the conditioning effect of a single agent is limited; although the combination of unsulfurized zero-valent iron and calcium peroxide in Comparative Example 4 has a certain improvement in dewatering, the filter cake moisture content and carbon emission are still lower than those of Example 1 of the present invention, further highlighting the key role of sulfurized zero-valent iron in this system. The method of the present invention still shows good structural selectivity regulation ability in slurries with high organic matter and high colloidal strength, confirming that it has good applicability and process stability in the solid-liquid separation of complex biomass slurries.

[0112] Those skilled in the art should understand that various equivalent substitutions or modifications can be made to the above specific embodiments without departing from the spirit and essence of the present invention, and all such substitutions or modifications fall within the protection scope of the present invention.

Claims

1. A method for low-carbon dewatering of sludge based on selective cleavage of hydrophobic amino acids, characterized in that, Includes the following steps: S1. Place the sludge to be dewatered in a reactor and add 10-60 mg / g of sulfided zero-valent iron powder based on the dry solids mass of the sludge. The sulfided zero-valent iron is prepared by sulfidation of zero-valent iron and a sulfur source at a Fe:S molar ratio of 1:(0.1-0.5) and has an FeS coating layer on its surface. Disperse the powder under stirring at 50-300 rpm for 1-10 min, then reduce the stirring speed to 20-150 rpm and maintain this speed for 2-15 min. S2. Add slow-release calcium peroxide particles to the system treated in step S1. The amount added is 20-80 mg / g of dry solids based on the effective CaO2 content. The slow-release calcium peroxide particles are particles formed by calcium peroxide loaded on a porous carrier or microcapsule particles formed by calcium peroxide coated with an organic or inorganic shell. The CaO2 is added in stages, at least twice, with an interval of 2-12 minutes between each addition. S3. Simultaneously or after step S2, control the pH of the system to 5.5~7.5 and the reaction temperature to 5~40 ℃, and carry out a conditioning reaction for 5~40 min; S4. After conditioning, add 10~200 mg / g of dry solid skeleton material, and then carry out mechanical dehydration. The moisture content of the filter cake after dehydration is not higher than 65%.

2. The method according to claim 1, characterized in that, In step S2, the concentration of hydrogen peroxide in the liquid phase is maintained at 80-250 mg / L for 5-20 min after the start of the reaction.

3. The method according to claim 1, characterized in that, In step S3, the pH of the system is maintained at 5.5 to 7.5 by introducing carbon dioxide and / or adding a buffer solution of acetic acid, citric acid or their salts.

4. The method according to claim 1, characterized in that, In step S3, after the conditioning reaction is completed and before mechanical dehydration, a terminator is added to the system. The terminator is selected from at least one of sulfite, thiosulfate, and hydrogen peroxide decomposing enzyme. The amount added is such that the hydrogen peroxide concentration in the filtrate is less than 10 mg / L.

5. The method according to claim 1, characterized in that, The particle size D50 of the sulfided zero-valent iron powder is 50 nm to 100 μm.

6. The method according to claim 1, characterized in that, The slow-release calcium peroxide particles have a particle size of 0.1~5mm and a CaO2 mass fraction of 10~70 wt.%.

7. The method according to claim 1, characterized in that, The porous carrier is selected from at least one of biochar, activated carbon, zeolite, diatomaceous earth, mesoporous silica, and clay minerals; and / or the coating shell is selected from at least one of alginate gel, polyvinyl alcohol, polydopamine, and silica shell.

8. The method according to claim 1, characterized in that, The skeleton material is selected from at least one of cellulose fiber, diatomaceous earth, fly ash, and biochar.

9. The method according to any one of claims 1 to 8, characterized in that, The mechanical dewatering is performed by screw press filtration, belt press filtration, or centrifugal dewatering.

10. The application of the method of claim 1 in the solid-liquid separation of high-water-content organic waste or biomass slurry containing an extracellular polymer colloidal structure, characterized in that, The high-moisture organic waste or biomass slurry is selected from slaughterhouse wastewater sludge, food waste slurry, or protein-rich fermentation residue.

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