Pretreatment method for efficient sludge dewatering and antibiotic resistance gene reduction

Abstract

The invention discloses a pretreatment method for efficient sludge dewatering and antibiotic resistance gene reduction, and relates to the technical field of pollutant harmless treatment, and the pretreatment method comprises the following steps: adding ferrate and periodate into sludge, and uniformly stirring and mixing to obtain pretreated sludge. The ferrate and periodate pretreatment method for the sludge has the remarkable technical advantages that high-valence strong iron oxide ions can be generated and stabilized without adjusting a treatment system to be acidic, and the efficient and continuous oxidation process is ensured; the method comprises the following steps of: reducing the abundance of actinomycetes and chloromentholum bacteria carrying ARGs by regulating a two-component regulation and control system, quorum sensing and a IV-type secretion system through microorganisms, promoting transfer of antibiotic resistance genes from inside to outside of cells, exposing the antibiotic resistance genes in an external environment of sludge, and promoting removal of the ARGs in the sludge; the surface morphology of the sludge is optimized, regulated and controlled, the high dehydration performance of the sludge is guaranteed through particle dispersion and aggregation, and efficient dehydration and resistance gene reduction in the sludge pretreatment process are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of harmless treatment of pollutants, and in particular to a pretreatment method for efficient sludge dehydration and reduction of antibiotic resistance genes. Background Art

[0002] With the acceleration of global urbanization, urban sewage treatment has become an important issue in environmental protection. Activated sludge technology is widely used in sewage treatment plants around the world to treat urban sewage, which inevitably produces a large amount of sewage sludge rich in organic matter and microorganisms. However, sewage sludge not only contains recyclable resources, but also contains a variety of harmful pollutants, especially antibiotic resistance genes (ARGs) that can be quickly transferred through mobile genetic elements (MGEs). The presence of these genes poses a serious threat to public health and environmental safety.

[0003] Currently, one of the main challenges of sludge treatment is how to effectively remove harmful pollutants in sludge, especially ARGs, and improve the dewatering performance of sludge to facilitate subsequent resource utilization. Mechanical dewatering is a common method in sludge treatment, but the dehydrated sludge cake still contains a large number of ARGs in intracellular form, which may spread rapidly in the soil environment after land application.

[0004] Extracellular polymers (EPS) in the sludge of sewage treatment plants are the main components of activated sludge flocs. EPS directly covers the outside of the cell membrane. The amount and composition of EPS will affect the surface characteristics of activated sludge flocs, and then affect the adsorption and flocculation performance of activated sludge. Sludge is mainly composed of two parts: cell body and EPS. EPS is mainly composed of protein and polysaccharide. Polysaccharide molecules are rich in hydrophilic functional groups such as hydroxyl and carboxyl groups. They can form a stable and elastic network structure through adsorption and bridging. Cross-linking and fixation of free cells is beneficial to sludge flocculation. Proteins and lipids can maintain the stability of floc structure and improve the biological flocculation of sludge accordingly. These substances form a compact and dense network structure through electrostatic force, hydrogen bonding, ion attraction, biochemistry and other effects, which can serve as a protective layer for microorganisms to resist the invasion of adverse factors such as external heavy metals and toxic compounds. Antibiotic resistance genes exist in large quantities in EPS. EPS absorbs a large number of ARGs through bridging effect, hydrophobic effect and entanglement, accounting for up to 74.2% of the total ARGs. In addition, some sludge resistance genes are also distributed in the genetic material of bacteria. It can be seen that resistance genes in sewage treatment plant sludge exist in large quantities in extracellular polymers (EPS). EPS wraps ARGs to form a high-molecular polymer structure that is difficult to degrade. The removal of this part of ARGs is the core and difficulty of sludge ARGs removal and degradation. Therefore, the development of technology for efficient removal of ARGs in sludge is a technical problem that needs to be solved urgently in the current sludge field. Summary of the invention

[0005] In view of the problems commonly found in sludge treatment in the prior art, such as unsatisfactory dehydration effect, low efficiency of removing antibiotic resistance genes (ARGs), and complicated process, the present invention proposes a ferrate / periodate pretreatment method, which utilizes the synergistic effect of the two to efficiently remove ARGs in sludge without additional acid adjustment, while significantly enhancing the dehydration capacity of sludge. This technology simplifies the treatment process and also achieves efficient dehydration of sludge and effective reduction of ARGs.

[0006] The invention provides a pretreatment method for efficient sludge dehydration and antibiotic resistance gene reduction, wherein ferrate and periodate are added to the sludge, and the pretreated sludge is obtained after stirring and mixing.

[0007] Furthermore, the ferrate and the periodate are added in a manner of adding the ferrate to the sludge, stirring for 1 to 2 minutes and then adding the periodate.

[0008] Furthermore, the stirring speed is 500-1000 rpm / min.

[0009] Furthermore, the pretreatment time is 30 to 45 minutes.

[0010] Furthermore, the weight ratio of the ferrate to the volatile suspended solids in the sludge is 0.01-0.04:1, wherein the amount of ferrate is calculated based on the mass of iron.

[0011] Furthermore, the mass ratio of ferrate to periodate is 5:1-2, wherein the amount of ferrate is calculated based on the mass of iron, and the amount of periodate is calculated based on the mass of iodine.

[0012] Furthermore, the periodate is at least one of potassium periodate and sodium periodate.

[0013] Furthermore, the ferrate is at least one of potassium ferrate and sodium ferrate.

[0014] The present invention has the following beneficial effects:

[0015] 1. During the sludge pretreatment process with ferrate and periodate, ferrate quickly produces Fe(V) and Fe(IV) with high redox potential after entering the sludge. These high-valent iron ions are highly oxidizing, but they are easily self-decomposed and transformed into Fe(III) and Fe(II) with weaker oxidizing properties. The addition of periodate can effectively inhibit this process, thereby maintaining the concentration and activity of high-valent iron ions and prolonging the durability of their strong oxidizing properties. At the same time, the presence of periodate reduces the decay of ferrate under alkaline conditions, gets rid of the limitation of its action under acidic conditions, maintains its oxidizing ability in a wider pH range, and can achieve efficient pretreatment without adjusting the pH value of the sludge, reducing the number of operating steps and saving treatment costs.

[0016] 2. Pretreatment of sludge with ferrate and periodate effectively curbed the spread of ARGs in sludge by significantly reducing the abundance of Actinobacteria and Chloroflexi bacteria carrying ARGs. In addition, pretreatment can also promote the transfer of intracellular antibiotic resistance genes (iARGs) to extracellular antibiotic resistance genes (eARGs) by regulating the two-component system, quorum sensing (QS) and type IV secretion system (T4SS) of microorganisms. This process exposes the iARGs that were originally difficult to handle to the environment outside the sludge, providing favorable conditions for subsequent ARGs removal measures, and significantly enhancing the ability to control antibiotic resistance genes during sludge treatment.

[0017] 3. Pretreatment with ferrate and periodate significantly improves the physical and chemical properties of sludge. By producing a large amount of Fe(V) and Fe(IV) with strong oxidizing ability to act on sludge particles, the surface morphology of sludge is optimized, the stable skeleton structure of sludge and the bond between sludge floc particles are destroyed, and sludge cells can be effectively lysed to release adsorbed water and internal bound water. In addition, the particle size distribution of sludge is also effectively regulated, the breakage of large particles and the aggregation of small particles are reduced, the existence of "drainage channels" is guaranteed, and the dewatering performance of sludge is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0019] Figure 1 (a) is the effect of different doses of ferrate on the moisture content of sludge filter cake in the present invention; (b) is the effect of different doses of ferrate on sludge MLVSS; (c) is the effect of different ferrate / periodate addition ratios on the moisture content of sludge filter cake; (d) is the effect of different ferrate / periodate addition ratios on sludge MLVSS.

[0020] Figure 2 This is the effect of different ferrate / periodate addition ratios on the sludge surface morphology in the present invention.

[0021] Figure 3 This is the effect of different ferrate / periodate addition ratios on sludge particle size in the present invention.

[0022] Figure 4 The figure shows the influence of different ferrate / periodate addition ratios on the sludge transmittance in the present invention.

[0023] Figure 5 This is the effect of different ferrate / periodate addition ratios on the types of extracellular ARGs in the present invention.

[0024] Figure 6 This is the effect of different ferrate / periodate addition ratios on extracellular ARGs in the present invention.

[0025] Figure 7 This is the effect of different ferrate / periodate addition ratios on intracellular ARGs in the present invention.

[0026] Figure 8(a) The effect of different ferrate / periodate addition ratios on microbial phyla in the present invention; (b) The effect of different ferrate / periodate addition ratios on microbial genera; (c) The relationship between microbial genera and ARGs.

[0027] Fig. 9 (a) shows the effect of different ferrate / periodate addition ratios on the two-component system in the present invention; (b) shows the effect of different ferrate / periodate addition ratios on the quorum sensing system.

[0028] Fig.10 The figure shows the effects of different ferrate / periodate addition ratios on the type IV secretion system in the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Unless otherwise specified, the terms used herein have the following meanings. The term "ARGs" used in the present invention refers to antibiotic resistance genes, including "iARGs" intracellular antibiotic resistance genes and "eARGs" extracellular antibiotic resistance genes; "MGEs" refers to mobile genetic elements; "VSS" refers to volatile suspended solids; "MLVSS" refers to volatile suspended solids concentration; "EPS" refers to extracellular polymers, including soluble EPS (S-EPS), loose EPS (LB-EPS) and compact EPS (TB-EPS); "Wc" refers to the moisture content of sludge cake.

[0031] The invention provides a pretreatment method for efficient sludge dehydration and antibiotic resistance gene reduction, wherein ferrate and periodate are added to the sludge, and the pretreated sludge is obtained after stirring and mixing.

[0032] In this scheme, after ferrate enters the sludge, it quickly produces Fe(V) and Fe(IV) with high redox potential. These high-valent iron ions have strong oxidizing properties, but they are easily self-decomposed and transformed into Fe(III) and Fe(II) with weaker oxidizing properties. The addition of periodate can effectively inhibit this process, thereby maintaining the concentration and activity of high-valent iron ions and prolonging the durability of their strong oxidizing properties.

[0033] Fe(V) and Fe(IV) are most active under acidic conditions, but ferrate is prone to decay in alkaline environments, limiting its application range. When used in combination with periodate, the oxidation-reduction balance in the reaction system is adjusted to reduce the decay of ferrate under alkaline conditions, thereby maintaining a certain oxidation capacity in a wider pH range. Efficient pretreatment can be achieved without adjusting the pH value of sludge, reducing the number of operating steps and saving treatment costs.

[0034] PI / Fe(VI) pretreatment produces a large amount of Fe(V) and Fe(IV) with strong oxidizing ability, which will destroy the stable skeleton structure of the sludge and the bonding between the sludge floc particles, making the sludge structure looser. It can effectively lyse the sludge cells, release the adsorbed water and internal bound water, and improve the dewatering performance of the sludge.

[0035] During the PI / Fe(VI) pretreatment process, a large amount of strong oxidizing radicals H2O2, ·O2 - 、H3Fe IV O4 - On the one hand, IO3·, ·OH, etc. destroy the EPS structure of the sludge, break the bonds between the originally tightly distributed large polymer structures in the EPS, and generate smaller molecular and looser organic matter groups. At the same time, they partially or completely destroy the resistance genes bound to the EPS by electrostatic forces, hydrogen bonds, ionic attraction, biochemistry, etc., and further destroy the cell structure originally wrapped by the EPS, enter the cell membrane, oxidize and decompose the intracellular DNA and ARGs in the plasmid.

[0036] In addition, the PI / Fe(VI) pretreatment process regulated the metabolic activities of the two-component system, quorum sensing (QS) and type IV secretion system. On the one hand, it promoted the transport of intracellular ARGs to extracellular ARGs, allowing ARGs to be further oxidatively degraded. On the other hand, under the influence of metabolic regulation, the growth of ARGs host bacteria was inhibited, resulting in a decrease in the abundance of ARGs they carried.

[0037] Furthermore, the ferrate and the periodate are added in a manner of adding the ferrate to the sludge, stirring for 1 to 2 minutes and then adding the periodate.

[0038] This scheme optimizes the addition method of ferrate and periodate, regulates the type and concentration of intermediates in the reaction system, and makes the ferrate added first produce high-valent iron ions Fe(IV) / Fe(V). When further added to the periodate system, high-valent iodine (such as IO3·) can react with Fe(IV) / Fe(V) intermediates, driving these intermediates to participate more in the oxidation reaction of micropollutants rather than decomposing themselves. This synergistic effect improves the removal efficiency of the system for micropollutants and makes the overall oxidation performance more stable.

[0039] Furthermore, the stirring speed is 500-1000 rpm / min.

[0040] This solution optimizes the stirring speed in sludge treatment, ensures that ferrate and periodate are fully mixed with the sludge, accelerates the oxidation of pollutants, promotes the destruction of sludge structure, and avoids excessive energy consumption.

[0041] Furthermore, the pretreatment time is 30 min to 45 min.

[0042] This solution optimizes the pretreatment time of sludge, ensures that the dewatering performance of sludge is fully improved and released, and maximizes the removal of potential antibiotic resistance factors in sludge, thereby improving the subsequent treatment effect. It achieves efficient achievement of treatment goals and avoids energy waste caused by long reaction time.

[0043] Furthermore, the weight ratio of the ferrate to the volatile suspended solids in the sludge is 0.01-0.04:1, wherein the amount of ferrate is calculated based on the mass of iron.

[0044] This scheme optimizes the dosage of ferrate by precisely controlling its dosage to 0.01 to 0.04 times the weight of volatile suspended solids (VSS) in the sludge (based on the mass of iron in ferrate). This optimization method abandons the traditional simple proportional addition method based on the total weight of sludge and focuses on the more representative VSS components in the sludge, thereby ensuring that ferrate can act more effectively on the target pollutants.

[0045] Within this optimal ratio, ferrate produces strong oxidizing Fe(V) and Fe(IV), which destroy the sludge floc structure and gradually form a lamellar structure, destroying the bonding between sludge floc particles, making the sludge structure looser, releasing intracellular organic matter and extracellular EPS, decomposing most macromolecular organic polymers including EPS into small organic molecules, leaching a large amount of hydrophilic substances, releasing a large amount of surface bound water, and even breaking the drainage channel. For example, when the Fe(VI) dosage is 40 mg Fe 6+ / g VSS, the moisture content of the sludge dropped from 89.2% to 70.9%, and MLVSS reached the minimum value of 12.11g / L.

[0046] Furthermore, the mass ratio of ferrate to periodate is 5:1-2, wherein the amount of ferrate is calculated based on the mass of iron, and the amount of periodate is calculated based on the mass of iodine.

[0047] This scheme optimizes the addition ratio of ferrate and periodate in the pretreatment system. Under the condition of PI / Fe(VI)=1 / 5, the sludge floc structure is destroyed, resulting in an increase in fine particles in the filtrate and a decrease in transmittance. The minimum moisture content and MLVSS of the sludge cake after pretreatment are 70% and 10.6 g / L, respectively, and the sludge transmittance drops sharply from 68.9% to 31.9%.

[0048] PI / Fe(VI) pretreatment resulted in a downward trend in total eARGs in sludge. The abundance of ARGs and MGEs in the S-EPS layer decreased significantly by 10.7-31.7 lg (gene copies / g VSS) (p<0.05) and 5.2-5.9 lg (gene copies / g VSS) (p<0.05), respectively. The extent of these reductions increased with the decrease in PI / Fe(VI) dosage. The abundance of ARGs and MGEs in LB-EPS decreased significantly by 1.8-18.9 lg (gene copies / g VSS) (p<0.05) and 0.7-5.8 lg (gene copies / g VSS) (p<0.05), respectively.

[0049] After PI / Fe(VI) pretreatment, the expression of the two-component regulatory system was significantly promoted. The pilR, pilS, pilG, K02484, plnL and glnG genes were significantly upregulated, the key genes of the QS system (sdiA, mqsR, bjaR1, cciR and sinR) were significantly upregulated, and the total abundance of T4SS genes increased by 22.0-35.3%. On the other hand, the removal rates of cphA7, ermF, tet(X), aadA14, ErmB, sul3, tetA(60) and tet(M) were significantly reduced, due to the decrease in the abundance of the corresponding host bacteria PHOS-HE28, NitrospiraA, UBA3362, OLB14, Prosthecobacter and OLB17. It was further verified that PI / Fe(VI) pretreatment could remove sludge ARGs by reducing the abundance of microorganisms carrying ARGs and promoting the transfer of iARGs to eARGs, exposing the difficult-to-treat iARGs to the extra-sludge environment.

[0050] Furthermore, the periodate is at least one of potassium periodate and sodium periodate.

[0051] Furthermore, the ferrate is at least one of potassium ferrate and sodium ferrate.

[0052] The above scheme optimizes the selection of ferrate and periodate, and explicitly adopts at least one of potassium periodate and sodium periodate as the source of periodate, and at least one of potassium ferrate and sodium ferrate as the source of ferrate. This is based on their efficient oxidation performance and fully considers the low price and environmental friendliness of the raw materials.

[0053] Example 1

[0054] Take 500 mL of fresh raw sludge and add it to a glass beaker (1000 mL) placed on a magnetic stirrer. First add 30 mg Fe 6+ / g VSS potassium ferrate was added to make it react evenly at 1000 rpm for 1 min, and then 6 mg I 7+ / g VSS potassium periodate, the two oxidants were pretreated, the total reaction time was 30min. 250mL of mud sample was taken from the beaker with a measuring cylinder at 5min of reaction, which was used to determine the physical and chemical properties of the sludge, such as sludge cake moisture content, MLVSS, surface scanning electron microscopy, supernatant refractive index, sludge particle size and other parameters. 300mL of mud sample was taken from the beaker with a measuring cylinder at 30min of reaction, which was used to evaluate the degradation effect of antibiotic resistance genes in sludge extracellular polymers (EPS) and intracellular antibiotic resistance genes.

[0055] Example 2

[0056] Take 500 mL of fresh raw sludge and add it to a glass beaker (1000 mL) placed on a magnetic stirrer. First add 30 mg Fe 6+ / g VSS potassium ferrate was added to make it react evenly at a speed of 1000 rpm for 1 min, and then 12 mg I 7+ / gVSS of potassium periodate, the two oxidants were pretreated, the total reaction time was 35min. 250mL of mud sample was taken from the beaker with a measuring cylinder at 5min of the reaction, which was used to determine the physical and chemical properties of the sludge, such as sludge cake moisture content, MLVSS, surface scanning electron microscopy, supernatant refractive index, sludge particle size and other parameters. 300mL of mud sample was taken from the beaker with a measuring cylinder at 35min of the reaction, which was used to evaluate the degradation effect of antibiotic resistance genes in sludge extracellular polymers (EPS) and intracellular antibiotic resistance genes.

[0057] Example 3

[0058] Take 500 mL of fresh raw sludge and add it to a glass beaker (1000 mL) placed on a magnetic stirrer. First add 30 mg Fe 6+ / g VSS potassium ferrate was added to make it react evenly at 1000 rpm for 1 min, and then 18 mg I 7+ / gVSS of potassium periodate, the two oxidants were pretreated, the total reaction time was 35min. 250mL of mud sample was taken from the beaker with a measuring cylinder at 5min of the reaction, which was used to determine the physical and chemical properties of the sludge, such as sludge cake moisture content, MLVSS, surface scanning electron microscopy, supernatant refractive index, sludge particle size and other parameters. 300mL of mud sample was taken from the beaker with a measuring cylinder at 35min of the reaction, which was used to evaluate the degradation effect of antibiotic resistance genes in sludge extracellular polymers (EPS) and intracellular antibiotic resistance genes.

[0059] Example 4

[0060] Take 500 mL of fresh raw sludge and add it to a glass beaker (1000 mL) placed on a magnetic stirrer. First add 30 mg Fe 6+ / g VSS potassium ferrate was added to make it react evenly at 1000 rpm for 1 min, and then 24 mg I 7+ / gVSS of potassium periodate, the two oxidants were pretreated, the total reaction time was 40min. 250mL of mud sample was taken from the beaker with a measuring cylinder at 5min of the reaction, which was used to determine the physical and chemical properties of the sludge, such as sludge cake moisture content, MLVSS, surface scanning electron microscopy, supernatant refractive index, sludge particle size and other parameters. 300mL of mud sample was taken from the beaker with a measuring cylinder at 40min of the reaction, which was used to evaluate the degradation effect of antibiotic resistance genes in sludge extracellular polymers (EPS) and intracellular antibiotic resistance genes.

[0061] Example 5

[0062] Take 500 mL of fresh raw sludge and add it to a glass beaker (1000 mL) placed on a magnetic stirrer. First add 30 mg Fe 6+ / g VSS potassium ferrate was added to make it react evenly at a speed of 1000 rpm for 1 min, and then 30 mg I 7+ / gVSS of potassium periodate, the two oxidants were pretreated, the total reaction time was 45min. 250mL of mud sample was taken from the beaker with a measuring cylinder at 5min of the reaction, which was used to determine the physical and chemical properties of the sludge, such as sludge cake moisture content, MLVSS, surface scanning electron microscopy, supernatant refractive index, sludge particle size and other parameters. 300mL of mud sample was taken from the beaker with a measuring cylinder at 45min of the reaction, which was used to evaluate the degradation effect of antibiotic resistance genes in sludge extracellular polymers (EPS) and intracellular antibiotic resistance genes.

[0063] Comparative Example 1

[0064] Take 500mL of fresh raw sludge and add it to a glass beaker (1000mL) placed on a magnetic stirrer, and stir it evenly at a speed of 1000rpm for 30min. Take 250mL of mud sample from the beaker with a measuring cylinder at 5min to determine the physical and chemical properties of the sludge, such as sludge cake moisture content, MLVSS, surface scanning electron microscopy, supernatant refractive index, and sludge particle size. Take 300mL of mud sample from the beaker with a measuring cylinder at 30min of the reaction to evaluate the degradation effect of antibiotic resistance genes in sludge extracellular polymers (EPS) and intracellular antibiotic resistance genes.

[0065] Comparative Example 2

[0066] Take 500 mL of fresh raw sludge and add it to a glass beaker (1000 mL) placed on a magnetic stirrer. First add 10 mg Fe 6+ / g VSS of sodium ferrate and then stirred evenly at 500rpm for 30min. After 5min, 250mL of sludge sample was taken from the beaker with a measuring cylinder to determine the physical and chemical properties of the sludge, sludge cake moisture content, and MLVSS.

[0067] Comparative Example 3

[0068] Take 500 mL of fresh raw sludge and add it to a glass beaker (1000 mL) placed on a magnetic stirrer. First add 20 mg Fe 6+ / g VSS of sodium ferrate and then stirred it evenly at 600rpm for 30min. After 5min, 250mL of sludge sample was taken from the beaker with a measuring cylinder to determine the physical and chemical properties of the sludge, sludge cake moisture content, and MLVSS.

[0069] Comparative Example 4

[0070] Take 500 mL of fresh raw sludge and add it to a glass beaker (1000 mL) placed on a magnetic stirrer. First add 30 mg Fe 6+ / g VSS of potassium ferrate and then stirred it evenly at 750rpm for 30min. After 5min, 250mL of sludge sample was taken from the beaker with a measuring cylinder to determine the physical and chemical properties of the sludge, sludge cake moisture content, and MLVSS.

[0071] Comparative Example 5

[0072] Take 500 mL of fresh raw sludge and add it to a glass beaker (1000 mL) placed on a magnetic stirrer. First add 40 mg Fe 6+ / g VSS of potassium ferrate and then stirred it evenly at 900 rpm for 30 minutes. After 5 minutes, 250 mL of sludge sample was taken from the beaker with a measuring cylinder to determine the physical and chemical properties of the sludge, sludge cake moisture content, and MLVSS.

[0073] Comparative Example 6

[0074] Take 500 mL of fresh raw sludge and add it to a glass beaker (1000 mL) placed on a magnetic stirrer. First add 50 mg Fe 6+ / g VSS of potassium ferrate and then stirred it evenly at a speed of 1000 rpm for 30 minutes. After 5 minutes, 250 mL of mud sample was taken from the beaker with a measuring cylinder to determine the physical and chemical properties of the sludge, the moisture content of the sludge filter cake, and MLVSS.

[0075] The test parameters of each embodiment and comparative example are shown in Table 1:

[0076] Table 1 List of test parameters of various embodiments and comparative examples

[0077]

[0078] Test results and analysis

[0079] (1) Effects of ferrate and periodate pretreatment on sludge dewatering

[0080] The dewatering performance of sludge after pretreatment with pure ferrate, ferrate and periodate was compared through the experiments of Comparative Examples 1 to 6 and Examples 1 to 5. Figure 1 It can be seen that with the increase of ferrate dosage, the water content of the sludge cake (Wc) dropped sharply. 6+ / g VSS treatment, the sludge cake Wc was significantly lower than the original sludge. When the Fe(VI) dosage was 40mg Fe 6+ / g VSS, Wc reaches the minimum value of 70.9%, which is the best dehydration effect. 6+ / g VSS, the Wc of the sludge cake showed a sharp upward trend. Figure 1 b It can be seen that the change of volatile suspended solids concentration (MLVSS) of sludge cake is consistent with Wc. This is because at high concentration, the dewatering performance of sludge changes significantly due to the destruction of floc structure and integrity, as well as the release of intracellular and extracellular substances.

[0081] like Figure 1 As shown in Figure 1c and 1d, in the process of ferrate and periodate pretreatment of sludge, with the increase of periodate (PI), the Wc and MLVSS of the sludge cake first decreased and then increased. 7+ / gVSS, that is, when PI / Fe(VI) is 1 / 5, the Wc and MLVSS of the sludge cake decreased from 89.2% and 11.75g / L to 85.1% and 10.6g / L respectively. This is because the sludge floc structure is destroyed, which promotes the conversion of bound water to free water, thereby improving the dewatering performance of the sludge. 7+ / g VSS dosage, with the increase of PI dosage, the Wc and MLVSS of sludge cake showed an upward trend. During the chemical pretreatment process of high-dose oxidant combined with Fe(VI), excessive Fe(V) and Fe(IV) were released, resulting in excessive destruction of the sludge structure and the release of a large amount of hydrophilic EPS substances. Fine particles were released into the liquid phase, resulting in blockage of the drainage channel and deterioration of the sludge filtration performance.

[0082] The Fe(VI) concentration provided by the present invention is 10 to 40 mg Fe 6+ / g VSS, PI / Fe(VI) is 1-2:5, it has a significant effect on improving the sludge dewatering efficiency. At the same time, during the PI / Fe(VI) pretreatment process, the synergistic effect of the two can accurately control the degree of damage to the sludge structure, which not only avoids the decline in dewatering performance due to excessive damage, but also makes full use of the oxidant's transformation of the sludge internal structure, thereby promoting the effective release of water.

[0083] (2) Effect of PI / Fe(VI) pretreatment on sludge structure

[0084] Figure 2 The SEM images of the sludge samples in Comparative Example 1 and Examples 1 to 5 magnified 5000 times are shown. Figure 2 As shown in a, the RS group of comparative example 1 has a smooth surface and an extremely dense floc structure, indicating that the bound water inside the sludge cannot be released and the sludge dewatering ability is poor. Figure 2 As shown in b, in Example 1, after pretreatment with PI / Fe(VI)=1:5, the structure of the sludge flocs was severely damaged, the sludge structure became looser, and a large number of drainage channels appeared. The serious damage to the sludge flocs is due to the interaction between PI and Fe(VI) to produce a large number of highly oxidizing substances (Fe(V) and Fe(IV)). After treatment with Fe(V) and Fe(IV), a large number of tiny and irregular substances were attached to the surface of the sludge. These substances may be released in the form of intracellular organic matter and extracellular polymers (Extracellular Polymeric Substances, EPS). The leaching of a large amount of hydrophilic substances causes a large amount of surface bound water to be carried and released into the liquid phase. As shown in Figure 2As shown in e to f, as the PI dosage increases, PI / Fe(VI) breaks up the drainage channels through strong oxidation, and a large amount of substances float in the liquid phase, presenting an aggregated block structure, causing the drainage channels inside the sludge to lose their function during the dehydration process.

[0085] Sludge particle size distribution is a key factor in sludge dewatering performance. A large proportion of fine particles in the sludge will increase the viscosity of the sludge and lead to poor dewatering performance. Figure 3 As shown, after pretreatment by the methods in Examples 1 to 5, the D50 of the sludge decreased from 47.7 μm to 42.517 μm, which again showed that the pretreatment effect caused serious damage to the sludge flocs, promoted the denaturation of sludge protein, disintegrated the tightly bound sludge particles and EPS, and caused large particles to degrade into small particles and EPS to leak. The D50 value of the sludge after pretreatment with PI / Fe(VI)=4 / 5 and 5 / 5 increased further, indicating that the partially dissociated EPS recombined with the sludge particles to form larger sludge flocs.

[0086] The changes in the physicochemical properties of the sludge were further characterized by the transmittance of the sludge supernatant. Figure 4 As shown in the figure, after PI / Fe(VI) pretreatment, the transmittance of the sludge supernatant showed a decreasing trend. The transmittance of the supernatant in the PI / Fe(VI)=1 / 5 group was the lowest. Compared with the control group 1, the transmittance of the sludge in the PI / Fe(VI)=1 / 5 group after pretreatment dropped sharply from 68.9% to 31.9%, which was mainly due to the destruction of the sludge floc structure after pretreatment in the PI / Fe(VI)=1 / 5 group, which led to an increase in fine particles in the filtrate and a decrease in the sludge transmittance.

[0087] It can be seen that the PI / Fe(VI) pretreatment strategy achieves a significant improvement in sludge dewatering performance by precisely controlling the destruction and reconstruction of the sludge structure. Its advantage is that it can effectively promote the release of water inside the sludge, and at the same time, by regulating the release and repolymerization of EPS, optimize the sludge particle size distribution, providing more favorable conditions for subsequent sludge treatment and dewatering.

[0088] (3) Effect of Fe(VI) and PI dosage ratio on ARGs removal

[0089] The experiment also studied the effect of PI / Fe(VI) pretreatment system on the abundance of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) in different forms of extracellular polymers (EPS) in sewage sludge - soluble EPS (S-EPS), loose EPS (LB-EPS) and compact EPS (TB-EPS). The results are as follows.

[0090] S-EPS layer: In the untreated sludge in the RS group of comparative example 1, the total abundance of ARGs and MGEs of S-EPS were 105.5lg (gene copies / g VSS) and 18.3lg (gene copies / g VSS), respectively, among which β-lactam and fluoroquinolone ARGs dominated, while integrase gene (int1) and transposase (tnpA-2) were the main contributors to MGEs. PI / Fe(VI) pretreatment significantly reduced the abundance of these genes, with ARGs decreasing by 10.7-31.7lg (gene copies / g VSS) and MGEs decreasing by 5.2-5.9lg (gene copies / g VSS), and this reduction trend was inversely proportional to the increase in PI / Fe(VI) dosage. It is worth noting that the abundance of specific subtypes of aminoglycoside, macrolide, sulfonamide and tetracycline ARGs also decreased with dosage.

[0091] LB-EPS layer: In the LB-EPS of untreated sludge in the RS group of Comparative Example 1, the total abundance of ARGs and MGEs was 98.5lg (gene copies / g VSS) and 18.2lg (gene copies / g VSS), respectively. Macrolide and β-lactam ARGs accounted for a higher proportion, and integrase gene (int1) and transposase (tnpA-2) were still the main types of MGEs. PI / Fe(VI) pretreatment significantly reduced the abundance of these genes, but the reduction was smaller than that of S-EPS, and also showed a trend of decreasing with increasing dose. It is worth noting that in the F5 (Example 5) group, in addition to the reduction of ARGs and MGEs, further reductions in specific ARG subtypes such as β-lactams, macrolides and multidrug resistance were observed.

[0092] TB-EPS layer: The total abundance of ARGs and MGEs in the untreated sludge in the RS group of comparative example 1 was 92.5lg (gene copies / g VSS) and 18.6lg (gene copies / g VSS), respectively. Under PI / Fe(VI) treatment, although the abundance of ARGs and MGEs in the LB-EPS layer in the F1 (Example 1) and F2 (Example 2) groups was significantly reduced, the degradation effect of the TB-EPS layer was weakened with the increase of PI dosage, and even in some cases (such as the F5 group corresponding to Example 5), it increased instead of decreased, which was attributed to the overexpression of ISCR1 under the stimulation of high-dose PI, which promoted the spread and value-added of ARGs.

[0093] It can be seen that PI / Fe (VI) pretreatment under the conditions of optimized addition ratio (such as F1 and F2 groups corresponding to Example 1 and Example 2) can effectively reduce the abundance of ARGs and MGEs in each layer of EPS, showing the role and potential of reducing the spread of resistance genes in sludge treatment.

[0094] (4) Effect of Fe(VI) and PI addition ratio on intracellular and extracellular resistance gene degradation

[0095] like Figure 6 As shown, the total eARGs (extracellular resistance genes) in the sludge reached 351.6lg (gene copies / g VSS) in the RS group (Comparative Example 1), of which the ARGs in the S-EPS, LB-EPS and TB-EPS layers accounted for 35.2%, 33.2% and 31.6%, respectively, highlighting the importance of sludge as an ARG reservoir. The abundance of typical ARGs such as aadA1 and blaTEM ranged from 5.4 to 6.6lg (gene copies / g VSS), of which sul1 and aadA1 were dominant ARGs.

[0096] Ferrate and periodate pretreatment significantly reduced the abundance of total eARGs, and the removal effect varied with the PI / Fe(VI) ratio. Specifically, the total eARG removal rate was as high as 21% under F1 (Example 1), while the removal rates under the other conditions were between 1.6% and 12.8%.

[0097] Regarding the degradation of individual ARGs in different EPS layers, it was found that the degradation patterns of genes such as aac(6')-Ib and aadE were similar to those of total eARGs, and were significantly affected by the PI / Fe(VI) ratio. In particular, blaPSE was completely degraded in S-EPS, and the degradation rates in LB-EPS and TB-EPS increased with increasing PI doses, reaching 100% under the conditions of F3 (Example 3) to F5 (Example 5). In addition, erm(A) was completely degraded in all pretreatment groups except F5 (Example 5).

[0098] Figure 7 The abundance changes of iARGs (intracellular resistance genes) under different ratios of PI / Fe(VI) are shown. Sulfonamide, macrolide, β-lactam and tetracycline resistance genes are highly abundant in WAS cells, which is closely related to the daily use of antibiotics. PI / Fe(VI) pretreatment significantly reduced the abundance of iARGs such as cphA7, ermF, tet(X) (>50%), while genes such as aadA14 and ErmB showed a downward trend but the degradation rate was not significant. It is worth noting that the dynamic changes of genes such as sul1 and sul2 are irregular, and even increase in abundance under certain conditions.

[0099] It can be seen that PI / Fe(VI) pretreatment has a significant effect on the degradation of eARGs and iARGs in sludge, and the degradation efficiency is affected by the PI / Fe addition ratio. The optimized pretreatment conditions of the present invention can achieve more efficient ARGs removal.

[0100] (5) Effects of Fe(VI) and PI dosing ratio on sludge bacterial communities and potential hosts

[0101] To reveal the microbial origin of ARGs, the diversity of microbial communities in sludge was analyzed. Figure 8 As shown in a, Bacteroidetes, Proteobacteria, Nitrospira, Chloroflexi and Actinobacteria are the dominant phyla, accounting for about 87% of the total community. After PI / Fe(VI) pretreatment, the dominant phyla changed to Bacteroidetes, Proteobacteria, Chloroflexi, Actinobacteria and Acidobacteria, among which Proteobacteria and Bacteroidetes play a key role in organic matter transformation, while Actinobacteria and Chloroflexi may carry and spread ARGs.

[0102] At the genus level ( Figure 8 b), the abundance of dominant genera in the original sludge, such as JJ008 and Sulfuritalea, decreased significantly after PI / Fe(VI) treatment, while the abundance of Proteobacteria, such as JAABQG01 and Rubrivivax, increased. Under different treatment ratios, the degradation effects of dominant genera in the original sludge varied, but the overall trend was consistent, that is, Proteobacteria increased and Bacteroidetes decreased.

[0103] Further analysis showed that the abundance changes of ARGs were closely related to the life activities of microorganisms. Figure 8 c), the experiment found that 38 nodes and 167 edges constituted a complex network of microorganisms and ARGs, among which Accumulibacter, OLB14, PHOS-HE28 and other genera were closely related to multiple ARGs. These genera mainly belonged to Proteobacteria, Chloroflexi and Bacteroidetes, and the detected ARGs with higher removal efficiency (such as cphA7, ermF, tet(X), etc.) were significantly positively correlated with the abundance of specific genera. After PI / Fe(VI) pretreatment of sludge, Actinobacteria and Chloroflexi were significantly reduced, resulting in the effective degradation of these ARGs.

[0104] (6) Response of Fe(VI) and PI addition ratio to ARGs propagation metabolic pathways and gene expression

[0105] The propagation and spread of ARGs are regulated by multiple functional metabolic pathways, including two-component regulatory systems, quorum sensing (QS), and type IV secretion system (T4SS). Functional metabolic pathways can transmit cellular signals through the cytoplasm to the bacterial nucleoid, where regulation of gene expression occurs and then mediates drug resistance.

[0106] PI / Fe(VI) treatment affected the metabolic activity of the two-component microbial control system in the sludge system. The metabolic activity of the two-component control system increased from 2154 ppm to 2493 ppm ( Fig. 9 a). The emergence of a two-component regulatory system increases transduced cell signals and gene expression, thereby promoting the transfer of iARGs to eARGs, and transferring refractory iARGs to eARGs exposed to the external environment. Compared with the control group, the abundance of baeS, K02483, kdpE, and narX, which mediate microbial responses to environmental stimuli, increased by 41.5-66.1%, 31.9-60.8, 36.4-52.1%, and 0-34.9%, respectively, promoting the spread of ARGs. In fact, most of the key genes involved in two-component signal transduction (i.e., pilR, pilS, pilG, K02484, plnL, and glnG) were significantly upregulated with increasing PI doses.

[0107] In addition, stimulated ARGs hosts trigger the transfer of MGEs, gene expression, and antibiotic resistance through the QS system, thereby controlling the spread of ARGs. The QS system was also observed to be upregulated by PI / Fe(VI), and QS promotes communication between bacteria by regulating the expression of genes related to the synthesis of signaling molecules. Further analysis showed that most of the key genes involved in the QS system (sdiA, mqsR, bjaR1, cciR, and sinR) were significantly upregulated, and the pattern was consistent with the changes in iARGs ( Fig. 9 b). This indicates that PI / Fe(VI) may promote the intra- or inter-species transmission of ARGs by regulating QS, and that intracellular ARGs are transformed into extracellular ARGs, which are easily oxidized and decomposed by highly oxidizing high-valent iron ions when exposed to the external environment.

[0108] DNA is actively released into the extracellular environment through the type IV secretion system (T4SS), resulting in the transfer of iARGs. The schematic diagram of T4SS is shown in Figure 10. The system consists of 12 proteins (VirB1-11 and VirD4) and forms a large macromolecular complex that spans the bacterial envelope. According to the metagenomic results of each group in the cell, the abundance of genes encoding 9 T4SS proteins increased after PI / Fe(VI) pretreatment, and the total abundance of T4SS genes increased by 22.0-35.3% ( Fig.10). The VirD4 gene showed the highest improvement, increasing by 52% after PI / Fe(VI) pretreatment. The abundance of the VirB1 gene also increased significantly by 33%. VirB1 is a periplasmic protein that carries a transglycosylase motif and "punches holes" in the peptidoglycan to facilitate T4SS assembly.

[0109] It can be seen that PI / Fe(VI) pretreatment can also promote the transfer of iARGs to eARGs by regulating the two-component regulatory system, quorum sensing (QS) and type IV secretion system (T4SS), exposing the difficult-to-treat iARGs to the extra-sludge environment and promoting the removal of sludge ARGs.

[0110] In summary, PI / Fe(VI) pretreatment significantly improves the physical and chemical properties of sludge. By producing a large amount of Fe(V) and Fe(IV) with strong oxidizing ability to act on sludge particles, the surface morphology of the sludge is optimized, the stable skeleton structure of the sludge and the bond between the sludge floc particles are destroyed, and the sludge cells can be effectively lysed to release adsorbed water and internal bound water. In addition, the particle size distribution of the sludge is also effectively regulated, the breakage of large particles and the aggregation of small particles are reduced, ensuring the existence of the "drainage channel" and improving the dewatering performance of the sludge.

[0111] Pretreatment with ferrate and periodate effectively curbed the spread of ARGs in sludge by significantly reducing the abundance of Actinobacteria and Chloroflexi bacteria carrying ARGs. In addition, pretreatment can also promote the transfer of intracellular antibiotic resistance genes (iARGs) to extracellular antibiotic resistance genes (eARGs) by regulating the two-component system, quorum sensing (QS) and type IV secretion system (T4SS) of microorganisms. This process exposes iARGs, which are originally difficult to treat, to the environment outside the sludge, providing favorable conditions for subsequent ARGs removal measures and significantly enhancing the ability to control antibiotic resistance genes during sludge treatment.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pretreatment method for efficient sludge dehydration and reduction of antibiotic resistance genes, It is characterized in that Add ferrate and periodate to the sludge, stir and mix to obtain pretreated sludge.

2. The pretreatment method for efficient sludge dehydration and reduction of antibiotic resistance genes according to claim 1, It is characterized in that The ferrate and the periodate are added in the following manner: the ferrate is added into the sludge, stirred for 1 to 2 minutes, and then the periodate is added.

3. The pretreatment method for efficient sludge dehydration and reduction of antibiotic resistance genes according to claim 2, It is characterized in that The stirring speed is 500-1000 rpm / min.

4. The pretreatment method for efficient sludge dehydration and reduction of antibiotic resistance genes according to claim 3, It is characterized in that The pretreatment time is 30 to 45 minutes.

5. The pretreatment method for efficient sludge dehydration and reduction of antibiotic resistance genes according to claim 4, It is characterized in that The weight ratio of the ferrate to the volatile suspended solids in the sludge is 0.01-0.04:1, wherein the amount of ferrate is calculated based on the mass of iron.

6. The pretreatment method for efficient sludge dehydration and reduction of antibiotic resistance genes according to claim 5, It is characterized in that The mass ratio of ferrate to periodate is 5:1-2, wherein the amount of ferrate is calculated based on the mass of iron, and the amount of periodate is calculated based on the mass of iodine.

7. The pretreatment method for efficient sludge dehydration and reduction of antibiotic resistance genes according to claim 6, It is characterized in that The periodate is at least one of potassium periodate and sodium periodate.

8. The pretreatment method for efficient sludge dehydration and reduction of antibiotic resistance genes according to claim 6, It is characterized in that The ferrate is at least one of potassium ferrate and sodium ferrate.

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