A method for treating fecal wastewater by self-forming filter cake

Abstract

This application discloses a method for reusing self-forming filter cakes of fecal wastewater, comprising: conveying fecal wastewater to a preset filter surface for filtration, and utilizing the solid particles in the wastewater to form a self-forming filter cake; when the filtration operation reaches the preset cake discharge conditions, peeling off at least a portion of the self-forming filter cake, and deagglomerating at least a portion of it as reuse filter cake to obtain filter cake aggregate particles; determining the dosage based on the solid content of the reuse filter cake and the suspended solids load in the fecal wastewater of the next filtration cycle, premixing the filter cake aggregate particles with the fecal wastewater of the next filtration cycle to form recombined agglomerated particles; and then conveying the fecal wastewater containing the recombined agglomerated particles to the preset filter surface to form the initial filter cake layer of the next filtration cycle. This application can utilize the fiber overlap structure, floc aggregation structure, and organic solid aggregation structure retained in the filter cake to improve the retention capacity of fine particles in the initial stage of filtration, shorten the filter cake maturation time, and reduce the risk of clogging and local accumulation caused by direct filter cake return.

Description

Technical Field

[0001] This application relates to the field of livestock and poultry breeding wastewater, specifically to a method for the reuse of self-forming filter cakes in manure wastewater. Background Technology

[0002] Large-scale farming generates a large amount of manure and wastewater. This wastewater typically contains manure residue, residual feed particles, animal hair, plant fibers, suspended organic matter, microbial flocs, and colloidal pollutants, and is characterized by high suspended solids concentration, high organic matter content, high viscosity, and significant water quality fluctuations.

[0003] Existing sewage treatment processes typically involve first using screens, sieves, screw presses, screw presses, or other solid-liquid separation equipment to remove large particles of fecal residue. The separated liquid phase is then sent to anaerobic, biological, sedimentation, or membrane treatment units. The solid fecal residue formed during the solid-liquid separation process usually goes directly into composting, fermentation, or off-site disposal processes.

[0004] However, sewage still contains a large number of small suspended particles and colloidal pollutants. If a filter medium with a small pore size is used for filtration, it is prone to rapid clogging; if a filter medium with a large pore size is used, fine particles can easily pass through the filter medium in the early stages of filtration, resulting in a high concentration of pollutants in the filtrate.

[0005] During the filtration process, larger solid particles in sewage gradually deposit on the pre-set filter surface and form a filter cake. As the filter cake thickness increases, the filter cake itself can serve as a secondary filtration medium, further trapping fine particles and colloidal pollutants that subsequently enter. However, existing technologies typically discharge the entire filter cake once it reaches a certain thickness or filtration resistance, failing to fully utilize the fiber overlap structure, floc aggregation structure, and organic solid aggregation structure already formed within the filter cake. Summary of the Invention

[0006] In view of the above problems, this application provides a method for the reuse of self-forming filter cakes in sewage treatment, which shortens the time required for the self-forming filter cakes to reach stable filtration capacity.

[0007] To achieve the above objectives, the inventors provide a method for the self-forming filter cake reuse treatment of fecal wastewater, characterized by comprising: The sewage wastewater to be treated is transported to a preset filter surface for filtration, and solid particles in the sewage wastewater are deposited on the preset filter surface to form a self-forming filter cake. During the formation of the self-forming filter cake, the filtration operation status of the self-forming filter cake is detected. When the filtration operation status reaches the preset cake discharge condition, at least a portion of the self-forming filter cake is peeled off from the preset filtration surface. At least a portion of the stripped self-forming filter cake is used as a reuse filter cake. The reuse filter cake is then deagglomerated to obtain filter cake aggregate particles containing at least one of fiber particles, flocculent particles, and organic solid particles. The dosage of the reused filter cake is determined based on the solids content of the reused filter cake and the suspended solids load in the sewage wastewater of the next filtration cycle. The filter cake aggregate particles are then premixed with the sewage wastewater of the next filtration cycle according to the dosage to form recycled aggregate particles. The fecal wastewater containing the recombined agglomerated particles is transported to the preset filter surface to form the initial filter cake layer for the next filtration cycle. The initial filter cake layer and the solid particles deposited by the subsequent fecal wastewater together form the self-forming filter cake for the next filtration cycle.

[0008] Unlike existing technologies, the above-mentioned technical solution involves peeling, screening, and deagglomerating the self-forming filter cake formed by solid particles in sewage wastewater on a preset filter surface. This yields filter cake aggregates that retain fiber overlap, flocculent aggregation, or organic solid aggregation structures. The dosage is determined based on the solid content of the reused filter cake and the suspended solids load in the sewage wastewater for the next filtration cycle. The filter cake aggregates are then premixed with sewage wastewater from the next filtration cycle to form recombinant agglomerates. These recombinant agglomerates preferentially deposit on the preset filter surface to form an initial filter cake layer. This avoids uneven dispersion, pipeline blockage, and localized accumulation caused by direct return of large filter cake pieces, as well as the destruction of the original aggregation structure due to excessive crushing. Simultaneously, it matches the actual solid dosage of the reused filter cake with the solid load of the influent, improving the initial filtration capacity for fine particles, shortening the time required for the self-forming filter cake to reach stable filtration capacity, and taking into account resistance growth and operational stability during subsequent filtration processes.

[0009] The above description of the invention is merely an overview of the technical solution of this application. In order to enable those skilled in the art to better understand the technical solution of this application and to implement it based on the description and drawings, and to make the above-mentioned objectives and other objectives, features and advantages of this application easier to understand, the following description is provided in conjunction with the specific embodiments and drawings of this application. Attached Figure Description

[0010] The accompanying drawings are only used to illustrate the principles, implementation methods, applications, features, and effects of specific embodiments of the present invention and other related contents, and should not be considered as limitations on this application.

[0011] In the accompanying drawings of the instruction manual: Figure 1 This is a flowchart of a method for treating wastewater that uses self-forming filter cakes in an embodiment; Figure 2This is a data graph showing the transport conditions and the form of fecal wastewater in the embodiments. Detailed Implementation

[0012] To illustrate the possible application scenarios, technical principles, implementable specific solutions, and achievable objectives and effects of this application in detail, the following description, in conjunction with the listed specific embodiments and accompanying drawings, provides a detailed explanation. The embodiments described herein are merely illustrative of the technical solutions of this application and are therefore intended to limit the scope of protection of this application.

[0013] In this document, the term "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The term "embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment, nor does it specifically limit its independence or connection with other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the technical features mentioned in each embodiment can be combined in any way to form corresponding implementable technical solutions.

[0014] The wastewater treated by this invention can be a mixture of manure and urine from pig farms, pigsty flushing wastewater, residual feed flushing liquid, or a mixture of one or more of the above wastewaters. The wastewater may contain manure residue, residual feed particles, plant fibers, animal hair, suspended organic matter, microbial flocs, and colloidal pollutants.

[0015] Before entering the filtration process, the sewage wastewater can be passed through a coarse screen or coarse mesh to remove plastic sheets, stones, long straws, and other larger debris. The pre-treated sewage wastewater can then enter a regulating container to balance the flow rate, suspended solids concentration, and water content at different times.

[0016] In this embodiment, a filtration cycle refers to the process from the start of the sewage being transported to the cleaned preset filter surface until the filtration operation reaches the preset cake discharge condition and at least part of the self-forming filter cake is peeled off. Example 1

[0017] Please refer to Figure 1 This embodiment provides a method for treating manure wastewater by self-forming filter cake recycling.

[0018] S100. The sewage wastewater to be treated is transported to a preset filter surface for filtration, and solid particles in the sewage wastewater are deposited on the preset filter surface to form a self-forming filter cake.

[0019] Specifically, the preset filter surface can be formed of a metal screen, a wedge-shaped screen plate, a fiber filter cloth, a polymer filter screen, or a porous support plate. The preset filter surface is used to intercept at least some of the solid particles in the sewage and to provide support for the self-forming filter cake.

[0020] The pore size of the preset filter surface can be set according to the size and composition of solid particles in the sewage. For example, the pore size of the preset filter surface can be 50-1000 μm, preferably 220-480 μm.

[0021] The sewage wastewater can reach the preset filter surface via gravity, liquid level difference, or low-pressure conveying. After the sewage wastewater comes into contact with the preset filter surface, fecal residue particles, residual feed particles, and organic solid particles with a particle size larger than the filter pore size are first trapped.

[0022] Although some fiber particles with a large aspect ratio have a lateral dimension smaller than the filter pore size, they can cross adjacent filter pores or overlap or entangle with solid particles that have already been trapped, thereby remaining on the preset filter surface.

[0023] As sewage continues to pass through the preset filter surface, the initially trapped solid particles overlap, entangle, adhere, and accumulate to form an initial deposition structure. Subsequent flocculent particles, suspended organic matter, and smaller solid particles continue to deposit on the surface of the initial deposition structure or enter the pores inside the initial deposition structure, causing the initial deposition structure to gradually thicken and form the self-forming filter cake.

[0024] After the self-forming filter cake is formed, the subsequently input sewage first passes through the self-forming filter cake and then through the preset filter surface. The irregular pores in the self-forming filter cake can further trap fine particles with a particle size smaller than the filter pore size of the preset filter surface.

[0025] The self-forming filter cake is formed by the solid particles contained in the sewage itself during the filtration process, and there is no need to pre-lay a sand layer, fiber packing layer or other fixed filter material layer on the preset filter surface.

[0026] S200. During the formation of the self-forming filter cake, the filtration operation status of the self-forming filter cake is detected. When the filtration operation status reaches the preset cake discharge condition, at least a portion of the self-forming filter cake is peeled off from the preset filtration surface.

[0027] Specifically, the filtration operation status may include at least one of the following: filtration pressure difference across the preset filtration surface, filtration flux, filtrate volume per unit time, filter cake thickness, continuous filtration time, filtrate turbidity, and filtrate suspended solids content.

[0028] The filtration pressure difference can be obtained by pressure detection devices respectively installed on the inlet side and the filtrate side of the preset filter surface. The filtration flux can be calculated based on the volume of filtrate passing through a unit preset filter area per unit time. The filtrate volume per unit time can be obtained by a flow meter installed at the filtrate outlet. The filter cake thickness can be obtained by a distance sensor, an image detection device, or manual measurement.

[0029] In the initial stage of filtration, the amount of solid particles deposited on the preset filter surface is small, and the self-forming filter cake has not yet formed a stable retention structure. As solid particles continue to deposit, the filtration capacity of the self-forming filter cake gradually increases, while its filtration resistance gradually increases.

[0030] In one embodiment, the self-forming filter cake can be determined to have entered a stable filtration stage after the turbidity or suspended solids content of the filtrate has decreased to a preset range. During this stable filtration stage, the self-forming filter cake continues to be used to filter the sewage wastewater until the filtration operation reaches the preset cake discharge condition.

[0031] The preset cake arrangement conditions may include at least one of the following conditions: The filtration pressure difference reaches the preset pressure difference; The filtration flux is reduced to a preset flux; The filtration flux is reduced to a preset ratio relative to the initial filtration flux during the stable filtration phase. The filtrate volume per unit time is lower than the preset filtrate volume; The filter cake thickness reaches the preset thickness; The continuous filtering time reaches the preset duration.

[0032] For example, the preset pressure difference can be 20 to 100 kPa, preferably 42 to 68 kPa; the preset ratio can be 63% to 80% of the initial filtration flux in the stable filtration stage; and the preset filter cake thickness can be 8 to 27 mm.

[0033] In one specific implementation, when the filtration pressure difference reaches 60 kPa, or the filtration flux decreases to 65% of the initial filtration flux in the stable filtration stage, the filtration operation state is determined to have reached the preset cake discharge condition.

[0034] Once the filtration operation reaches the preset cake discharge condition, the input of fecal wastewater to the preset filter surface can be stopped, or the input flow rate of fecal wastewater can be reduced. Subsequently, scrapers, flexible scrapers, backflushing gas, reverse filtrate, vibration components, or movable preset filter surfaces are used to separate at least a portion of the self-forming filter cake from the preset filter surface.

[0035] When using a scraper for peeling, the scraper moves along the preset filter surface and scrapes the self-forming filter cake into the filter cake collection tank. When using a backflushing method for peeling, gas or filtrate can be introduced from the filtrate side of the preset filter surface to the inlet side, causing the self-forming filter cake to loosen and detach from the preset filter surface.

[0036] In one embodiment, all the self-forming filter cake on the preset filter surface can be peeled off. In another embodiment, a residual layer of filter cake adhering to the preset filter surface can be retained to reduce the number of fine particles that pass directly through the preset filter surface at the start of the next filtration cycle.

[0037] S300. At least a portion of the stripped self-forming filter cake is used as a reuse filter cake. The reuse filter cake is deagglomerated to obtain filter cake aggregate particles containing at least one of fiber particles, flocculent particles and organic solid particles.

[0038] Specifically, the self-forming filter cake after stripping may include fiber aggregates, flocculent aggregates, residual feed particle aggregates, organic solid lumps, and filter mud with a high content of free fine particles.

[0039] All or part of the self-forming filter cake after peeling can be identified as the reused filter cake. In one embodiment, the portion of the filter cake with a more complete aggregate structure is identified as the reused filter cake.

[0040] The deagglomeration process is used to break down the continuous blocky structure of the recycled filter cake, transforming large pieces of recycled filter cake into aggregated particles that can be conveyed and premixed. The purpose of the deagglomeration process is not to completely pulverize the recycled filter cake into independent, free fine particles.

[0041] The depolymerization process can employ a paddle depolymerizer, a spiral depolymerizer, a low-shear crusher, a low-speed stirring device, or a circulating shear pipeline.

[0042] Before the depolymerization process, the recycled filter cake can be mixed with sewage or filtrate to form a filter cake slurry that can flow within the depolymerization device. The solids content of the filter cake slurry can be 1% to 10%, preferably 3.2% to 6.4%.

[0043] In one embodiment, a paddle-type deagglomerator is used to shear the filter cake slurry, with a paddle rotation speed of 80–300 r / min and a shearing time of 1–10 min. Preferably, the paddle rotation speed is 130–230 r / min and the shearing time is 2–5 min.

[0044] The filter cake aggregate particles obtained after deagglomeration may include aggregate structures formed by intertwined fecal fibers, aggregate structures formed by the adhesion of microbial flocs and organic solid particles, or composite aggregate structures formed by fiber particles, floc particles and residual feed particles.

[0045] The size of the filter cake aggregate particles should be suitable for subsequent conveying and premixing. When the size of the filter cake aggregate particles is too large, it can easily cause pipeline blockage or local accumulation on the preset filter surface; when the size of the filter cake aggregate particles is too small, it can easily lose its original aggregate structure and increase the load of free fine particles in the sewage.

[0046] S400. Based on the solids content of the reused filter cake and the suspended solids load in the fecal wastewater of the next filtration cycle, determine the dosage of the reused filter cake, and premix the filter cake aggregate particles with the fecal wastewater of the next filtration cycle according to the dosage to form recycled aggregate particles.

[0047] Specifically, the solids content of the recycled filter cake is first tested. The solids content can be determined by drying and weighing, using an online solids content detection device, or by density conversion.

[0048] When using the drying and weighing method, a sample of recycled filter cake of a preset mass can be weighed and dried to constant weight at 105°C. The solid content of the recycled filter cake can be determined based on the ratio of the mass of the solid after drying to the mass of the sample before drying.

[0049] The suspended solids load in the sewage wastewater in the next filtration cycle can be determined based on the volume of the sewage wastewater to be treated in the next filtration cycle and the suspended solids concentration of the sewage wastewater.

[0050] For example, the volume of sewage to be treated in the next filtration cycle is 10m³. 3 If the suspended solids concentration is 6000 mg / L, then the suspended solids load in the next filtration cycle will be 60 kg.

[0051] Based on the solids content and suspended solids load of the recycled filter cake, determine the required wet mass of recycled filter cake to be added, so that the actual dry basis solids content in the recycled filter cake matches the suspended solids load of the next filtration cycle.

[0052] After determining the dosage, the filter cake aggregate is added to the sewage wastewater in the next filtration cycle for premixing. This premixing can be carried out in a separately installed premixing container or in a regulating container located at the front end of the filtration device.

[0053] During the premixing process, the filter cake aggregate particles come into contact with fine particles in the sewage. The fine particles may adhere to the surface of the filter cake aggregate particles, enter the pores of the filter cake aggregate particles, or become entangled with the fiber particles in the filter cake aggregate particles, thereby forming agglomerated particles with a particle size larger than the original fine particles.

[0054] The recombined agglomerates may include a filter cake aggregate and multiple fine particles attached to the filter cake aggregate, or may include composite particles formed by multiple filter cake aggregates and multiple fine particles.

[0055] S500, the fecal wastewater containing the recombined agglomerated particles is conveyed to the preset filter surface to form the initial filter cake layer of the next filtration cycle. The initial filter cake layer and the solid particles deposited by the subsequent fecal wastewater together form the self-forming filter cake of the next filtration cycle.

[0056] Specifically, the premixed fecal wastewater is transported to the pre-filtered surface after cleaning. The particle size of the recycled agglomerated particles is usually larger than the original fine particles in the fecal wastewater, so the recycled agglomerated particles can be intercepted by the pre-filtered surface at a relatively early stage after reaching the pre-filtered surface.

[0057] The trapped recombined agglomerated particles overlap and accumulate on the preset filter surface to form the initial filter cake layer for the next filtration cycle. The initial filter cake layer can be formed by a single layer or multiple layers of recombined agglomerated particles.

[0058] When the sewage wastewater is fed into the next filtration cycle, the fecal residue, residual feed particles, fiber particles, floc particles and suspended organic matter in the sewage wastewater continue to deposit on the initial filter cake layer or enter the pores of the initial filter cake layer.

[0059] As subsequent solid particles continue to deposit, the thickness and particle composition of the initial filter cake layer change, and gradually form a self-forming filter cake for the next filtration cycle. Example 2

[0060] This embodiment, based on Embodiment 1, performs particle grading on the self-forming filter cake after peeling.

[0061] S310. The stripped self-forming filter cake is classified into particles. The portion of the filter cake containing aggregated structures of fiber particles, flocculent particles and organic solid particles is identified as the reuse filter cake. The remaining portion of the self-forming filter cake with a free fine particle content higher than a preset content is discharged as a resource-based filter cake.

[0062] Specifically, the self-forming filter cake after peeling can be classified into particles by means of sieving, sedimentation classification, image recognition classification, or a combination of sieving and image recognition.

[0063] In one embodiment, the peeled self-forming filter cake is added to a grading container, along with a small amount of sewage or filtrate obtained from filtration. The filter cake is loosened by low-speed agitation, separating free fine particles from larger aggregates.

[0064] The filter cake portion containing aggregated structures of fiber particles, flocculent particles, and organic solid particles, due to its large size or the presence of internal fiber overlap structures, is retained by the grading screen and identified as the reused filter cake.

[0065] The portion of filter cake with a free fine particle content higher than a preset level can pass through a classifying sieve with the liquid, or form a fine particle enrichment portion during sedimentation and classification. The fine particle enrichment portion is discharged as a resource-based filter cake.

[0066] The content of free fine particles can be determined based on the proportion of the mass of particles smaller than a preset particle size to the total dry solid mass of the corresponding filter cake portion. For example, when the mass of free particles with a particle size of less than 100 μm accounts for more than 40% to 70% of the dry solid mass of the corresponding filter cake portion, the content of free fine particles in the corresponding filter cake portion is determined to be higher than the preset content.

[0067] The resource-based filter cake can be dehydrated, mixed with auxiliary materials, aerobic composting, anaerobic fermentation, or otherwise rendered harmless and recycled.

[0068] S320. The recycled filter cake is mixed with the sewage or the filtrate obtained from filtration to form a filter cake slurry. The filter cake slurry is sheared to obtain initial aggregated particles.

[0069] Specifically, the recycled filter cake is added to a depolymerization container, and then sewage or filtrate obtained from filtration is added to the depolymerization container.

[0070] After adding liquid, a low-speed stirring method can be used to allow the liquid to enter the interior of the recycled filter cake and reduce the apparent viscosity of the recycled filter cake, thereby forming a fluid filter cake slurry.

[0071] The solids content of the filter cake slurry can be 1% to 10%. When the fiber particle content in the recycled filter cake is high, the solids content of the filter cake slurry can be set to 2% to 6%; when the recycled filter cake has high viscosity, the solids content of the filter cake slurry can be appropriately reduced.

[0072] The filter cake slurry is sheared to break up the continuous structure of the large filter cake and form multiple smaller initial aggregated particles.

[0073] The shearing process can be performed using paddle stirring, spiral propulsion, low-speed cutting, or cyclic shearing. The intensity and duration of the shearing process can be adjusted according to the remaining proportion of large filter cake pieces in the filter cake slurry.

[0074] For example, a paddle deagglomerator with a rotation speed of 150-200 r / min can be used to shear the filter cake slurry for 2-5 minutes.

[0075] S330. The initial aggregated particles are screened using a first preset sieve hole, and the initial aggregated particles that have passed through the first preset sieve hole are intercepted using a second preset sieve hole to generate filter cake aggregated particles.

[0076] Specifically, the initial aggregated particles obtained from the shearing process are conveyed to a first screening component having a first preset sieve aperture.

[0077] Initially aggregated particles that can pass through the first preset sieve holes enter the second screening component; excessively large particles that cannot pass through the first preset sieve holes can be returned to the deagglomeration container for further shearing, or discharged as a resource-based filter cake.

[0078] The initial aggregated particles entering the second screening component are intercepted by the second preset sieve holes. The initial aggregated particles intercepted by the second preset sieve holes are identified as the filter cake aggregated particles.

[0079] Free fine particles and liquid that can pass through the second preset sieve can be returned to the regulating container or processed together with the resource-based filter cake.

[0080] Specifically, the aperture of the first preset sieve hole is 2.5 to 4.2 mm, and the aperture of the second preset sieve hole is 0.18 to 0.42 mm.

[0081] Specifically, the first preset sieve hole is used to remove or recycle filter cake lumps that are too large, and the second preset sieve hole is used to remove free fine particles that are too small.

[0082] In one embodiment, the aperture of the first preset sieve hole is 3 mm, and the aperture of the second preset sieve hole is 0.3 mm, so that the main size of the filter cake aggregate particles is in the range of 0.3 to 3 mm. Example 3

[0083] Based on any one of Examples 1 to 2, this embodiment determines the amount of recycled filter cake to be added according to the dry basis solids content in the recycled filter cake.

[0084] S410. Determine the dry basis solids content in the recycled filter cake and the suspended solids load in the sewage to be treated in the next filtration cycle, and determine the dosage of the recycled filter cake based on the dry basis solids content and the suspended solids load.

[0085] Specifically, the dry basis solids content of the recycled filter cake is determined based on its solids content. The suspended solids load in the sewage to be treated in the next filtration cycle can be determined based on the volume and concentration of the sewage to be treated.

[0086] For example, the volume of sewage to be treated in the next filtration cycle is 5m³. 3 If the suspended solids concentration is 8000 mg / L, then the suspended solids load is 40 kg. When the planned amount of recycled filter cake solids added is 6% of the suspended solids load, 2.4 kg of recycled filter cake solids needs to be added. If the solids content of the recycled filter cake is 18%, then the required wet mass of recycled filter cake added is approximately 13.3 kg.

[0087] Determining the amount of recycled filter cake to be added based on dry solids content can reduce the fluctuation in the actual solids addition caused by changes in the moisture content of the recycled filter cake.

[0088] Preferably, the dry solids content in the recycled filter cake is 3.5% to 11.5% of the suspended solids load in the sewage to be treated in the next filtration cycle.

[0089] Specifically, when the dry solids content in the recycled filter cake is less than 2% of the suspended solids load, the number of filter cake aggregates available to form the initial filter cake layer may be insufficient.

[0090] When the dry solids content in the recycled filter cake is higher than 15% of the suspended solids load, a large number of recycled agglomerated particles may rapidly deposit in the early stage of filtration, resulting in excessively rapid increase in filtration resistance.

[0091] During the initial operation phase, the dry solids content in the recycled filter cake can be set to 5% to 10% of the suspended solids load. In subsequent filtration cycles, the addition ratio of the recycled filter cake can be adjusted according to the filter cake maturation time and the growth state of filtration resistance. Example 4

[0092] Based on any one of Examples 1 to 3, this embodiment involves a two-stage premixing of the filter cake aggregate particles and the fecal wastewater from the next filtration cycle.

[0093] The filter cake aggregate particles and the fecal wastewater of the next filtration cycle are first mixed to disperse the filter cake aggregate particles in the fecal wastewater.

[0094] Specifically, the filter cake aggregate obtained according to the stated dosage is added to the fecal wastewater in the premixing container.

[0095] The first mixing is carried out using mechanical stirring or circulating mixing. The first mixing is used to distribute the concentrated filter cake aggregates in different areas of the premixing container, reducing the local accumulation of filter cake aggregates near the feed position.

[0096] The stirring speed for the first mixing can be 100–300 r / min, and the mixing time can be 0.5–3 min. Preferably, the stirring speed for the first mixing is 150–250 r / min, and the mixing time is 1–2 min.

[0097] The first mixing termination condition can be that the particle concentration difference of the filter cake aggregate particles at different sampling locations in the premixing container is less than a preset difference value.

[0098] The sewage wastewater that has undergone the first mixing is then subjected to a second mixing process with a lower mixing intensity than the first mixing.

[0099] Specifically, after the first mixing is completed, the speed of the stirring device is reduced or the circulation flow rate is reduced, and the sewage wastewater is mixed a second time.

[0100] The stirring speed for the second mixing can be 20–100 r / min, and the mixing time can be 3–20 min. Preferably, the stirring speed for the second mixing is 30–80 r / min, and the mixing time is 5–12 min.

[0101] During the second mixing process, the filter cake aggregate particles remain suspended and repeatedly contact with fine particles in the sewage wastewater. The mixing intensity of the second mixing is lower than that of the first mixing to reduce the disintegration of the filter cake aggregate particles due to continuous high shear.

[0102] The fecal wastewater that has undergone the second mixing process is subjected to particle size detection. Once the particle size in the fecal wastewater reaches the preset particle size condition, the premixing process is completed and re-agglomerated particles are formed.

[0103] Specifically, laser particle size detection, image particle size detection, or sieving detection methods can be used to detect the particle size of the fecal wastewater after the second mixing.

[0104] The preset particle size condition may include at least one of the following conditions: The mass ratio of particles with a particle size larger than the preset particle size reaches the preset ratio; The median particle size of the mixed particles reaches the preset median particle size; The median particle size of the mixed particles increases to a preset ratio relative to the end of the first mixing. The mass of particles that can be trapped by the preset detection sieve holes reaches the preset mass ratio.

[0105] For example, the particle size in the sewage wastewater can be determined to meet the preset particle size condition when the proportion of particles with a diameter greater than 0.5 mm to the total mass of suspended solids reaches more than 30%.

[0106] If the particle size still does not meet the preset particle size condition after the second mixing time has been reached, the second mixing time can be extended, or the amount of recycled filter cake added can be appropriately increased.

[0107] Understandably, the fibrous particles in the recycled filter cake have a large aspect ratio, providing overlapping and entanglement sites for fine particles in the sewage. The flocculent particles contain extracellular polymers secreted by microorganisms and adhesive organic matter on their surface, which can enhance the adhesion between fine particles and filter cake aggregates. The rough structure and internal pores of the organic solid particles can accommodate and trap fine particles. Therefore, under the conditions of dispersion achieved by the first mixing and shear reduction and extended contact time by the second mixing, fine particles can form recycled agglomerated particles with the filter cake aggregates.

[0108] To ensure the effective formation of recycled aggregated particles through the first and second mixing processes, a first control group, a second control group, and the group described in this embodiment were established under the same conditions: wastewater volume, suspended solids concentration, filter cake aggregate dosage, premixing container structure, and agitator size. The wastewater volume in each group was 6.5 m³, the suspended solids concentration was 7200 mg / L, the dry basis solids content in the recycled filter cake was 6.8% of the wastewater's suspended solids load, and the main particle size range of the filter cake aggregates was 0.28–3.2 mm.

[0109]

[0110] The first control group did not undergo a first mixing, but only performed a low-intensity mixing at a stirring speed of 55 r / min for 8.9 min; the second control group did not undergo a second mixing, but only performed continuous mixing at a stirring speed of 185 r / min for 8.9 min; the group in this embodiment first performed a first mixing at a stirring speed of 185 r / min for 1.4 min, and then performed a second mixing at a stirring speed of 55 r / min for 7.5 min. Thus, the total mixing time for each group was 8.9 min.

[0111] After each group was mixed, samples were taken from the top, middle and bottom of the premix container, and the concentration of aggregated filter cake particles, median equivalent particle size, mass percentage of free fine particles and mass percentage of particles with a particle size in the range of 0.28 to 3.2 mm were measured at different sampling locations.

[0112] In the first control group, due to the lack of a high-intensity first mixing, the aggregated filter cake particles added in a concentrated manner failed to disperse quickly, and the maximum deviation of particle concentration in the upper, middle and lower parts of the premixing container was 27.6%. After mixing, the median equivalent particle size increased by 8.7% compared with before mixing, the mass ratio of free fine particles was 25.4%, and the mass ratio of particles with a particle size in the range of 0.28 to 3.2 mm was 62.3%.

[0113] In the second control group, although the higher mixing intensity enabled rapid dispersion of filter cake aggregates and reduced the maximum particle concentration deviation at different sampling locations in the premixing container to 9.8%, the filter cake aggregates were continuously subjected to high shear stress throughout the mixing process, resulting in the destruction of some fiber overlap structures and floc aggregation structures. After mixing, the median equivalent particle size decreased by 5.9% compared to before mixing, the proportion of free fine particles increased to 33.8%, and the proportion of particles with a diameter in the range of 0.28–3.2 mm was 54.7%.

[0114] In this embodiment, the first mixing rapidly disperses the filter cake aggregates in the sewage wastewater, while the second mixing, at a lower mixing intensity, ensures continuous contact between the dispersed filter cake aggregates and the fine particles in the sewage wastewater. After mixing, the maximum deviation of particle concentration in the upper, middle, and lower parts of the premixing container is 11.2%, the median equivalent particle size increases by 22.1% compared to the end of the first mixing, the proportion of free fine particles decreases to 17.9%, and the proportion of particles with a size in the range of 0.28–3.2 mm increases to 73.6%.

[0115] The above results indicate that, although the shearing effect is weak when only the second mixing is performed, the dispersion uniformity of the filter cake aggregates in the sewage is poor. While the first mixing alone can improve particle dispersion uniformity, the sustained high shearing effect disrupts the original aggregate structure of the filter cake aggregates and generates more free fine particles. The combined approach of first and second mixing allows for rapid dispersion of the filter cake aggregates first, followed by promotion of adhesion, entanglement, and pore embedding between fine particles and filter cake aggregates at a lower mixing intensity. This balances particle dispersion uniformity and agglomerate structure integrity, while also increasing the proportion of re-agglomerated particles.

[0116] To further verify the parameter ranges of the first and second mixing processes, while keeping other conditions the same, the stirring speeds of the first mixing were set to 90 r / min, 185 r / min, and 320 r / min, and the stirring speeds of the second mixing were set to 15 r / min, 55 r / min, and 120 r / min, respectively. The results showed that when the first mixing speed was below 100 r / min, the dispersion rate of the filter cake aggregates was slow, and the particle concentration differences at different sampling locations were significant. When the first mixing speed was above 300 r / min, the instantaneous shear force on the filter cake aggregates was significantly enhanced, and the proportion of free fine particles increased. When the second mixing speed was below 20 r / min, some filter cake aggregates settled, and the effective contact frequency between fine particles and filter cake aggregates decreased. When the second mixing speed was above 100 r / min, the already formed agglomerated particles were prone to disintegration. Therefore, setting the stirring speed of the first mixture to 100–300 r / min and the mixing time to 0.5–3 min, and setting the stirring speed of the second mixture to 20–100 r / min and the mixing time to 3–20 min, can better balance particle dispersion, agglomeration formation and structure retention. Example 5

[0117] Based on any one of Examples 1 to 4, this embodiment uses a low-shear method to transport fecal wastewater containing recycled agglomerated particles.

[0118] S510. Low-shear conveying is used to transport the fecal wastewater containing the recombined agglomerated particles to the preset filter surface; during the low-shear conveying process, the average flow velocity in the conveying pipeline is 0.05 to 0.8 m / s, and the conveying pressure is not higher than 0.3 MPa.

[0119] Specifically, after premixing, the fecal wastewater containing recycled agglomerated particles is conveyed through a pipeline to the preset filter surface.

[0120] The low-shear conveying can be carried out by gravity conveying, screw pump conveying, diaphragm pump conveying, cam rotor pump conveying, or other low-speed volumetric pump conveying.

[0121] When gravity conveying is used, the premixed container can be placed above the filter device, and the sewage wastewater can be made to flow along the conveying pipeline by using a liquid level difference of 0.2 to 2m.

[0122] When using a screw pump for conveying, the screw pump speed can be 20–120 r / min. When using a diaphragm pump for conveying, the diaphragm pump reciprocating frequency can be 10–60 times / min. When using a low-speed positive displacement pump for conveying, the pump speed can be 30–200 r / min.

[0123] The average flow velocity in the conveying pipeline is controlled to be 0.05–0.8 m / s, preferably 0.18–0.56 m / s. The conveying pressure is controlled to be no higher than 0.3 MPa, preferably 0.06–0.16 MPa.

[0124] The conveying pipeline can reduce right-angle bends and use bends with large curvature radii to reduce the collision between the recombined agglomerates and the pipe wall.

[0125] Please refer to Figure 2 To demonstrate the effects of different conveying velocities and pressures on the integrity of the recombined agglomerated particles, pipeline deposition, and the formation of the initial filter cake layer, the following comparative experiments were conducted:

[0126] The total mass percentage of free fine particles, fiber-overlapping aggregated particles, floc-adhesive aggregated particles, and composite aggregated particles in each group was 100%. Free fine particles refer to fine particles that have not formed a stable attachment, entanglement, or embedding relationship with the filter cake aggregated particles; fiber-overlapping aggregated particles refer to aggregated particles formed primarily by the overlapping or entanglement structure between fiber particles; floc-adhesive aggregated particles refer to aggregated particles formed by fine particles adhering to the surface of floc particles or organic flocs; and composite aggregated particles refer to composite aggregated particles that simultaneously contain fiber-overlapping structures, floc-adhesive structures, and organic solid particles.

[0127] From the above table and Figure 2 It is known that the average flow velocity of Group A is 0.03 m / s, and the conveying pressure is 0.02 MPa. Due to the low conveying velocity, some larger or denser agglomerated particles tend to deposit in horizontal pipe sections and bends, with the solid deposition rate in the pipeline reaching 13.6%. Therefore, although the shearing effect during the conveying process is weak, the number of agglomerated particles that can stably reach the conveying outlet is reduced. The mass percentage of free fine particles at the conveying outlet is 36%, while the mass percentages of fiber-overlapping agglomerated particles, floc-adhesive agglomerated particles, and composite agglomerated particles are 28%, 22%, and 14%, respectively, with a median equivalent particle size of 0.68 mm after conveying.

[0128] The average flow velocity of Group B was 0.32 m / s, and the conveying pressure was 0.11 MPa. Under these conveying conditions, the re-agglomerated particles could stably pass through the conveying pipeline with the sewage wastewater, and the shearing and collision effects during the conveying process were small, with the solid deposition rate in the pipeline being only 2.4%. After conveying, the mass percentage of free fine particles decreased to 18%, while the mass percentages of fiber-overlapping agglomerated particles, floc-adhesive agglomerated particles, and composite agglomerated particles increased to 35%, 27%, and 20%, respectively, with a median equivalent particle size of 0.79 mm. This indicates that the conveying conditions of Group B can reduce the deposition of re-agglomerated particles in the pipeline while effectively maintaining the fiber-overlapping structure, floc-adhesive structure, and composite agglomerated structure.

[0129] The average flow velocity of group C was 0.92 m / s, and the conveying pressure was 0.26 MPa. The higher conveying velocity reduced the deposition of solid particles in the conveying pipeline, lowering the proportion of solid deposition to 1.7%. However, the shearing and collision effects on the recombined agglomerated particles at the pump body, pipe walls, and bends were significantly enhanced. After conveying, the mass percentage of free fine particles increased to 45%, while the mass percentages of fiber-overlapping agglomerated particles, flocculent agglomerated particles, and composite agglomerated particles decreased to 23%, 18%, and 14%, respectively. The median equivalent particle size decreased to 0.57 mm after conveying, indicating that the fiber-overlapping and flocculent adhesion structures of some recombined agglomerated particles were damaged during the conveying process.

[0130] The results from groups A, B, and C show that when the conveying velocity is too low, although the shearing effect on the recombined agglomerated particles is smaller, pipeline deposition is more likely to occur, resulting in a reduction in the number of effective agglomerated particles actually reaching the preset filter surface. When the conveying velocity is too high, although pipeline deposition can be reduced, the shearing and collision effects on the recombined agglomerated particles are enhanced, causing the agglomerated structure to break down and increasing the proportion of free fine particles. Group B, using an average flow velocity of 0.32 m / s and a conveying pressure of 0.11 MPa, can maintain a high proportion of fiber-overlapping agglomerated particles, floc-adhesive agglomerated particles, and composite agglomerated particles while reducing pipeline deposition, thus exhibiting better conveying stability and particle structure retention. This result can be used to illustrate that controlling the average flow velocity in the conveying pipeline between 0.05 and 0.8 m / s and the conveying pressure to no higher than 0.3 MPa is beneficial for balancing the conveying capacity and structural integrity of the recombined agglomerated particles. Example 6

[0131] Based on any one of Examples 1 to 5, this embodiment adjusts the amount of recycled filter cake added in the next filtration cycle according to the filter cake maturity time and the state of filter resistance growth.

[0132] S610. In the next filtration cycle, obtain the filter cake maturation time required for the initial filter cake layer to reach the preset filtration capacity and the filtration resistance growth state of the self-forming filter cake in the next filtration cycle.

[0133] Specifically, the preset filtration capacity can be determined based on the turbidity of the filtrate, the content of suspended solids in the filtrate, or the particle retention rate.

[0134] For example, when the turbidity of the filtrate is below 150 NTU for 10 consecutive minutes, or when the suspended solids content of the filtrate is below 300 mg / L for 10 consecutive minutes, it can be determined that the initial filter cake layer has reached the preset filtration capacity.

[0135] The time elapsed from the start of the next filtration cycle when the sewage is introduced until the initial filter cake layer reaches the preset filtration capacity is determined as the filter cake maturation time.

[0136] The growth state of filtration resistance can be represented by the rate of increase in filtration pressure difference, the rate of decrease in filtration flux, or the rate of decrease in filtrate volume per unit time.

[0137] In one embodiment, a preset time period is selected after the self-forming filter cake enters the stable filtration stage, and the ratio of the increase in filtration pressure difference to time during this time period is calculated to obtain the filtration pressure difference growth rate.

[0138] S620. When the filter cake maturation time is greater than the preset maturation time and the filter resistance growth state does not exceed the preset resistance growth state, increase the amount of recycled filter cake added in the next filtration cycle.

[0139] Specifically, when the filter cake maturation time is greater than the preset maturation time, it indicates that the time required for the initial filter cake layer of the current filtration cycle to reach the preset filtration capacity is longer.

[0140] When the increase in filter resistance does not exceed the preset increase in filter resistance, it indicates that the current amount of recycled filter cake added has not caused an abnormal increase in filter resistance.

[0141] In this case, the dry solids content of the recycled filter cake in the next filtration cycle can be increased by 5% to 30% of the current dosage, or the ratio of the dry solids content of the recycled filter cake to the suspended solids load can be increased by 1 to 3 percentage points.

[0142] S630. When the filter resistance growth exceeds the preset resistance growth, reduce the amount of recycled filter cake added in the next filtration cycle.

[0143] Specifically, when the filter resistance growth state exceeds the preset resistance growth state, it indicates that the initial filter cake layer formed in the current filtration cycle or the subsequent self-forming filter cake may be too dense.

[0144] In this case, the dry solids content of the recycled filter cake in the next filtration cycle can be reduced by 5% to 30% of the current dosage, or the ratio of the dry solids content of the recycled filter cake to the suspended solids load can be reduced by 1 to 3 percentage points.

[0145] When the filter resistance growth exceeds the preset resistance growth, the amount of recycled filter cake added will be reduced regardless of whether the filter cake maturation time is greater than the preset maturation time.

[0146] S640. When the filter cake maturation time is not greater than the preset maturation time and the filter resistance growth state does not exceed the preset resistance growth state, maintain the amount of recycled filter cake added in the next filtration cycle.

[0147] Specifically, when the maturation time of the filter cake is not greater than the preset maturation time, it indicates that the initial filter cake layer can achieve the preset filtration capacity within the target time.

[0148] When the increase in filter resistance does not exceed the preset increase in filter resistance, it indicates that the current amount of recycled filter cake added has not caused an abnormal increase in filter resistance.

[0149] In this case, the amount of recycled filter cake added in the next filtration cycle remains unchanged.

[0150] For example, the preset maturation time is 10 minutes, and the filter resistance growth state is the ratio of the increase in filter pressure difference per unit time to the initial filter pressure difference in the stable filtration stage. The preset resistance growth ratio is 10% to 20% per hour, for example, 15%.

[0151] When the filter cake maturation time of the current filtration cycle is 15 min and the filtration pressure differential growth rate is 1.5 kPa / h, increase the amount of recycled filter cake added in the next filtration cycle.

[0152] When the filter cake maturation time of the current filtration cycle is 8 minutes and the filtration pressure differential growth rate is 3 kPa / h, reduce the amount of recycled filter cake added in the next filtration cycle.

[0153] When the filter cake maturation time of the current filtration cycle is 9 minutes and the filtration pressure differential growth rate is 1.8 kPa / h, maintain the amount of recycled filter cake added in the next filtration cycle. Example 7

[0154] This embodiment controls the cumulative number of times the filter cake is reused and the pollutant content, based on any one of Embodiments 1 to 6.

[0155] Record the cumulative number of times the recycled filter cake is reused, and stop using the corresponding self-forming filter cake as a recycled filter cake when the cumulative number of reuses reaches a preset number or when the preset pollutant content in the recycled filter cake reaches a preset limit.

[0156] Specifically, the filtration cycle in which the first self-forming filter cake is selected for reuse is recorded as the first reuse cycle; each time a filtration cycle is completed where the reused filter cake is used to form a self-forming filter cake and a reused filter cake is selected again, the cumulative reuse count is increased by one.

[0157] When the reused filter cake from the previous filtration cycle forms a self-forming filter cake for the next filtration cycle, and is selected again as a reused filter cake after the next filtration cycle's cake discharge, the cumulative reuse count for the corresponding batch increases by one.

[0158] The preset number of times can be set to 2 to 10 times, preferably 3 to 6 times. When the cumulative number of reuses reaches the preset number, the corresponding filter cake portion will be transferred to a harmless or resource-based treatment process.

[0159] The preset pollutants may include at least one of copper, zinc, antibiotic residues, pathogenic microorganisms, parasite eggs, and other pollutants that need to be controlled.

[0160] The reused filter cake can be sampled according to a preset detection cycle, and the content of preset pollutants can be detected. When the content of any preset pollutant reaches the corresponding preset limit, the corresponding filter cake is no longer used as a reused filter cake. The filter cake that is no longer reused can be dehydrated, mixed with auxiliary materials, and subjected to high-temperature aerobic composting, or it can be sent to anaerobic fermentation, heat treatment, or other harmless treatment processes. Example 8

[0161] This embodiment provides a method for treating manure wastewater by reusing self-forming filter cakes, which is used to treat manure and urine mixtures and pigsty flushing wastewater generated by pig farms.

[0162] In this embodiment, the volume of sewage wastewater to be treated in a single filtration cycle is 6.5 m³. After homogenization in the equalization tank, the suspended solids concentration in the sewage wastewater is 7200 mg / L, and the pH is 7.3. Before entering the filtration device, the sewage wastewater passes through a coarse screen with a pore size of 8 mm to remove plastic sheets, stones, long straw strips, and other large-sized debris.

[0163] The sewage wastewater to be treated is transported to a preset filter surface for filtration, and solid particles in the sewage wastewater are deposited on the preset filter surface to form a self-forming filter cake.

[0164] In this embodiment, the preset filter surface uses a stainless steel wedge-shaped sieve plate with a filter pore size of 280μm, and the effective preset filter area of ​​the stainless steel wedge-shaped sieve plate is 2.4m². 2 .

[0165] The sewage wastewater to be treated is conveyed to the stainless steel wedge screen plate using a low-pressure feeding method. Fecal residue particles, residual feed particles, organic solid particles, and fiber particles in the sewage wastewater are first intercepted by the stainless steel wedge screen plate.

[0166] As the filtration process continues, the trapped fiber particles overlap each other, and fecal sludge particles, floc particles, and organic solid particles adhere to and deposit between the fiber particles, thereby forming an initial deposition structure on the surface of the stainless steel wedge-shaped screen plate.

[0167] The fine particles in the subsequently input sewage further deposit on the surface of the initial deposition structure or enter the pores inside the initial deposition structure, causing the initial deposition structure to gradually thicken and form a self-forming filter cake.

[0168] After the self-forming filter cake is formed, subsequent sewage wastewater passes through the self-forming filter cake and the stainless steel wedge-shaped screen plate in sequence. The self-forming filter cake further retains suspended particles with a particle size of less than 280 μm.

[0169] During the formation of the self-forming filter cake, the filtration operation status of the self-forming filter cake is detected. When the filtration operation status reaches the preset cake discharge condition, at least a portion of the self-forming filter cake is peeled off from the preset filtration surface.

[0170] In this embodiment, pressure sensors are installed on both the inlet and filtrate sides of the stainless steel wedge-shaped screen plate, and the filtration pressure difference is determined based on the detection results of the two pressure sensors. Simultaneously, a flow meter is installed at the filtrate outlet to obtain the filtration flux.

[0171] When the suspended solids content of the filtrate remains within the preset range for 8 consecutive minutes, the corresponding time is determined as the moment when the self-forming filter cake enters the stable filtration stage, and the filtration flux at that moment is recorded.

[0172] In this embodiment, a filtration pressure difference of 52 kPa or a filtration flux reduced to 68% of the initial filtration flux in the stable filtration stage is used as the preset cake discharge condition.

[0173] When the filtration pressure difference reaches 52 kPa, the supply of sewage to the stainless steel wedge screen plate is stopped, and a flexible scraper is used to move along the surface of the stainless steel wedge screen plate to peel off the self-forming filter cake from the stainless steel wedge screen plate.

[0174] At least a portion of the stripped self-forming filter cake is used as a reuse filter cake. The reuse filter cake is then deagglomerated to obtain filter cake aggregates containing at least one of fiber particles, flocculent particles, and organic solid particles.

[0175] The detached self-forming filter cake is conveyed to a grading container, and the filtrate obtained from filtration is added to the grading container. The detached self-forming filter cake is agitated for 2.5 minutes using a low-speed agitator at 35 r / min to separate the free fine particles in the self-forming filter cake from the fiber aggregate structure, floc aggregate structure, and organic solid aggregate structure.

[0176] The filter cake containing interlocking fiber particles, adherent flocculent particles, or aggregated organic solid particles is designated as the reused filter cake. The filter cake enriched with free fine particles is discharged as the resource-based filter cake and sent to the subsequent aerobic composting unit.

[0177] The solid content of the recycled filter cake in this embodiment was found to be 19.5%.

[0178] The recycled filter cake is mixed with the filtrate obtained from filtration to form a filter cake slurry with a solids content of 4.3%. Specifically, taking 16.32 kg of recycled filter cake as an example, the dry basis solids content of the recycled filter cake is approximately 3.18 kg. Approximately 57.7 kg of the filtrate obtained from filtration is added to the recycled filter cake, so that the total mass of the resulting filter cake slurry is approximately 74 kg.

[0179] The filter cake slurry is added to a paddle deagglomerator and sheared at a paddle speed of 175 r / min for 3.2 min, which breaks down the continuous block structure of the recycled filter cake into multiple initially aggregated particles that are separated from each other but still retain the fiber overlap structure or floc aggregation structure.

[0180] The stripped self-forming filter cake is subjected to particle classification. The portion of the filter cake containing aggregated structures of fiber particles, flocculent particles, and organic solid particles is identified as the reuse filter cake. The remaining portion of the self-forming filter cake with a free fine particle content higher than a preset content is discharged as a resource-based filter cake.

[0181] In this embodiment, the proportion of the mass of free fine particles with a particle size of less than 100 μm to the dry solid mass of the corresponding filter cake portion is used as the free fine particle content.

[0182] When the ratio is higher than 55%, the content of free fine particles in the corresponding filter cake portion is determined to be higher than the preset content, and the corresponding filter cake portion is discharged as a resource-based filter cake.

[0183] When the proportion is not higher than 55%, and the corresponding filter cake contains aggregated structures formed by fiber particles, flocculent particles, or organic solid particles, the corresponding filter cake is used as a reuse filter cake.

[0184] The recycled filter cake is mixed with the sewage or the filtrate obtained from filtration to form a filter cake slurry. The filter cake slurry is then sheared to obtain initial aggregated particles.

[0185] In this embodiment, the filtrate obtained from filtration is mixed with the recycled filter cake to form a filter cake slurry, so as to avoid adding additional clean water to the treatment system.

[0186] During the shearing process, samples were taken from the paddle deaggregator every 40 seconds, and the proportion of filter cake blocks that could not pass through the 3.2 mm sieve was detected.

[0187] The shearing process is stopped when the proportion of filter cake blocks that cannot pass through the 3.2mm sieve aperture decreases to below 8%. This avoids insufficient shearing time resulting in too many large filter cake blocks remaining, while also preventing excessive damage to the aggregated structure caused by continuous shearing.

[0188] The initial aggregated particles are screened using a first preset sieve hole, and the initial aggregated particles that pass through the first preset sieve hole are intercepted using a second preset sieve hole to generate filter cake aggregated particles.

[0189] The initial aggregated particles after shearing are conveyed to the first screening component. The first preset sieve aperture of the first screening component is 3.2 mm.

[0190] Excessively large filter cake blocks that cannot pass through the first preset sieve holes return to the paddle deagglomerator and continue to be sheared at a speed of 175 r / min for 0.5 to 1 min.

[0191] The initially aggregated particles that can pass through the first preset sieve aperture can enter the second screening component. The second preset sieve aperture of the second screening component is 0.28 mm.

[0192] The initial aggregated particles that can pass through the first preset sieve aperture of 3.2 mm and are trapped by the second preset sieve aperture of 0.28 mm are identified as filter cake aggregated particles.

[0193] Liquid and free fine particles that can pass through the second preset sieve aperture of 0.28mm are returned to the equalization tank and are not used as filter cake aggregate particles.

[0194] Therefore, the main size of the filter cake aggregate particles obtained in this embodiment is in the range of 0.28 to 3.2 mm.

[0195] The dosage of the reused filter cake is determined based on the solids content of the reused filter cake and the suspended solids load in the sewage wastewater of the next filtration cycle. The filter cake aggregate particles are then premixed with the sewage wastewater of the next filtration cycle according to the dosage to form recombinant agglomerate particles.

[0196] The volume of sewage to be treated in the next filtration cycle is 6.5 m³. 3 The suspended solids concentration is 7200 mg / L. Therefore, the suspended solids load in the sewage to be treated in the next filtration cycle is 46.8 kg.

[0197] In this embodiment, the dry solids content in the recycled filter cake is set to 6.8% of the suspended solids load. Therefore, the dry solids content of the recycled filter cake to be added in the next filtration cycle is approximately 3.18 kg.

[0198] Based on the solid content of 19.5% in the recycled filter cake, the required wet mass of recycled filter cake is approximately 16.32 kg.

[0199] The filter cake aggregate particles obtained by deagglomerating and sieving the 16.32 kg of recycled filter cake are added to 6.5 m³ of sewage wastewater in the next filtration cycle for premixing.

[0200] The dry basis solids content in the recycled filter cake and the suspended solids load in the sewage to be treated in the next filtration cycle are determined, and the dosage of the recycled filter cake is determined based on the dry basis solids content and the suspended solids load.

[0201] In this embodiment, an online suspended solids detection device is used to detect the suspended solids concentration of the fecal wastewater in the next filtration cycle, and the suspended solids load is calculated based on the volume of the fecal wastewater to be treated recorded by the flow meter.

[0202] The solids content of the recycled filter cake was detected using a solids content detection device, and the wet mass of the recycled filter cake was determined according to the following formula: The wet mass of the recycled filter cake is equal to the target dry basis solids content divided by the solids content of the recycled filter cake.

[0203] Therefore, the actual amount of recycled filter cake solids added in different filtration cycles is not affected by changes in the moisture content of the recycled filter cake.

[0204] The dry solids content in the recycled filter cake is 2% to 15% of the suspended solids load in the sewage to be treated in the next filtration cycle.

[0205] In this embodiment, the dry solids content in the recycled filter cake is 6.8% of the suspended solids load, which is within the range of 2% to 15%.

[0206] The 6.8% is used as the initial dosage ratio in this embodiment. In subsequent filtration cycles, this dosage ratio is adjusted according to the filter cake maturation time and the increase in filtration resistance.

[0207] The filter cake aggregate particles and the fecal wastewater of the next filtration cycle are first mixed to disperse the filter cake aggregate particles in the fecal wastewater.

[0208] The filter cake aggregate particles are added to the sewage wastewater in the premixing container, and a paddle agitator is used for the first mixing.

[0209] In this embodiment, the stirring speed of the first mixing is 185 r / min, and the mixing time is 1.4 min.

[0210] At the end of the first mixing, samples were taken from the top, middle, and bottom of the premixing container. The filter cake aggregate concentration was considered to have been dispersed in the sewage wastewater when the maximum deviation of the filter cake aggregate concentration at the three sampling locations did not exceed 12% of the average concentration.

[0211] The sewage wastewater that has undergone the first mixing is then subjected to a second mixing process with a lower mixing intensity than the first mixing.

[0212] After the first mixing is completed, the stirring speed is reduced from 185 r / min to 55 r / min, and mixing continues at 55 r / min for 7.5 min.

[0213] During the second mixing process, the filter cake aggregate particles remain suspended in the sewage wastewater and repeatedly come into contact with fine particles in the sewage wastewater. The fine particles adhere to the surface of the filter cake aggregate particles or enter the pores inside the filter cake aggregate particles, thereby forming re-agglomerated particles.

[0214] The fecal wastewater that has undergone the second mixing process is subjected to particle size detection. Once the particle size in the fecal wastewater reaches the preset particle size condition, the premixing process is completed and re-agglomerated particles are formed.

[0215] In this embodiment, an image particle size detection device is used to detect the particle size at the end of the first mixing and the end of the second mixing.

[0216] The median equivalent particle size at the end of the second mixing is increased by more than 18% compared to the end of the first mixing, which is taken as the preset particle size condition.

[0217] After a second mixing of 7.5 minutes, when the median equivalent particle size of the particles increases by 22% relative to the end of the first mixing, it is determined that the particle size has reached the preset particle size condition, the second mixing is stopped and the premixing is completed.

[0218] Using relative particle size variation as a preset particle size condition can reduce the impact of differences in the original particle size of different batches of sewage on the judgment results.

[0219] The fecal wastewater containing the recombined agglomerated particles is transported to the preset filter surface to form the initial filter cake layer for the next filtration cycle. The initial filter cake layer and the solid particles deposited by the subsequent fecal wastewater together form the self-forming filter cake for the next filtration cycle.

[0220] After premixing, the fecal wastewater containing recycled agglomerated particles is conveyed to the stainless steel wedge screen plate.

[0221] The recombined agglomerated particles are intercepted by the stainless steel wedge sieve plate after reaching it.

[0222] As the recombined agglomerated particles continue to deposit, an initial filter cake layer for the next filtration cycle is formed on the surface of the stainless steel wedge-shaped sieve plate.

[0223] After the initial filter cake layer is formed, sewage wastewater continues to be fed into the stainless steel wedge-shaped screen plate. Subsequent fibrous particles, flocculent particles, fecal sludge particles, and organic solid particles in the sewage wastewater deposit on the initial filter cake layer, forming a self-forming filter cake for the next filtration cycle together with the initial filter cake layer.

[0224] The wastewater containing the recycled agglomerated particles is transported to the preset filter surface using low-shear conveying; during the low-shear conveying process, the average flow velocity in the conveying pipeline is 0.05 to 0.8 m / s, and the conveying pressure is not higher than 0.3 MPa.

[0225] In this embodiment, a screw pump is used to transport the fecal wastewater containing the recombined agglomerated particles. The screw pump rotates at 58 r / min.

[0226] The inner diameter of the conveying pipeline is 65mm, the average flow velocity of the sewage in the conveying pipeline is 0.32m / s, and the conveying pressure is 0.11MPa.

[0227] The conveying pipeline uses bends with a radius of curvature no less than three times the pipe diameter and avoids right-angle bends to reduce the collision and shearing of the agglomerated particles during the conveying process.

[0228] During the next filtration cycle, the filter cake maturation time required for the initial filter cake layer to reach the preset filtration capacity and the filtration resistance growth state of the self-forming filter cake during the next filtration cycle are obtained.

[0229] In this embodiment, based on multiple historical filtration cycles without added recycled filter cake, the historical average time required for the self-forming filter cake to reach the preset filtration capacity is determined to be 14 minutes.

[0230] Set 80% of the historical average time, i.e., 11.2 minutes, as the preset maturity time.

[0231] When the suspended solids content in the filtrate does not exceed the preset influent limit of the subsequent treatment unit for 8 consecutive minutes, the initial filter cake layer is determined to have reached the preset filtration capacity.

[0232] The time elapsed from the start of the next filtration cycle until the preset filtration capacity is reached is determined as the filter cake maturation time.

[0233] In this embodiment, the measured maturation time of the filter cake was 10.6 min, which is less than the preset maturation time of 11.2 min.

[0234] Meanwhile, using the initial filtration pressure difference when the self-forming filter cake enters the stable filtration stage as a benchmark, the ratio of the hourly increase in filtration pressure difference to the initial filtration pressure difference is calculated to characterize the filtration resistance growth state.

[0235] In this embodiment, a preset resistance growth state is set where the hourly filtration pressure differential increase rate does not exceed 15%. The actual measured hourly filtration pressure differential increase rate was 11%, which did not exceed the preset resistance growth state.

[0236] When the filter cake maturation time is longer than the preset maturation time, and the filter resistance growth state does not exceed the preset resistance growth state, the amount of recycled filter cake added in the next filtration cycle is increased.

[0237] If the filter cake maturation time is found to be greater than 11.2 minutes during subsequent operation, and the hourly filtration pressure difference increase rate does not exceed 15%, the proportion of recycled filter cake solids in the suspended solids load will be increased by 0.8 percentage points in the next filtration cycle.

[0238] For example, the proportion could be increased from 6.8% to 7.6%.

[0239] When the filter resistance growth exceeds the preset resistance growth, the amount of recycled filter cake added in the next filtration cycle is reduced.

[0240] When the hourly filtration pressure difference increases by more than 15%, the proportion of recycled filter cake solids in the suspended solids load will be reduced by 0.8 percentage points in the next filtration cycle.

[0241] For example, the percentage could be reduced from 6.8% to 6.0%.

[0242] When the filter resistance growth exceeds the preset resistance growth level, the amount of recycled filter cake added will be reduced regardless of whether the filter cake maturation time exceeds 11.2 minutes.

[0243] When the filter cake maturation time is not greater than the preset maturation time, and the filter resistance growth state does not exceed the preset resistance growth state, the amount of recycled filter cake added in the next filtration cycle is maintained.

[0244] In this embodiment, the filter cake maturation time is 10.6 min, which is no more than the preset maturation time of 11.2 min; the hourly filtration pressure difference increase rate is 11%, which does not exceed the preset 15%.

[0245] Therefore, in the next filtration cycle, the amount of recycled filter cake solids will continue to be set at 6.8% of the suspended solids load of the sewage wastewater.

[0246] Record the cumulative number of times the recycled filter cake is reused, and stop using the corresponding self-forming filter cake as a recycled filter cake when the cumulative number of reuses reaches a preset number or when the preset pollutant content in the recycled filter cake reaches a preset limit.

[0247] In this embodiment, a batch number is set for each batch of recycled filter cake, and the cumulative number of times the corresponding batch is recycled is recorded.

[0248] The maximum cumulative reuse count is set to 5 times. When the cumulative reuse count of the corresponding batch of filter cake reaches 5 times, the corresponding portion of the filter cake will no longer be used as reused filter cake, but will be discharged as resource-based filter cake.

[0249] After each filtration cycle, samples are taken from the recycled filter cake for testing for at least one of the following: copper, zinc, and antibiotic residues. If the content of any preset contaminant reaches the corresponding preset limit, the corresponding portion of the filter cake will be discontinued as recycled filter cake, even if the cumulative number of reuses has not reached 5.

[0250] After the filter cake that is no longer reused is dehydrated, it is mixed with straw powder or sawdust and subjected to high-temperature aerobic composting treatment.

[0251] Finally, it should be noted that although the above embodiments have been described in the text and drawings of this application, this should not limit the scope of patent protection of this application. Any technical solutions that are based on the essential concept of this application and utilize the content described in the text and drawings of this application, resulting in equivalent structural or procedural substitutions or modifications, as well as the direct or indirect application of the technical solutions of the above embodiments to other related technical fields, are all included within the scope of patent protection of this application.

Claims

1. A method for treating and reusing self-forming filter cakes of fecal wastewater, characterized in that, include: The sewage wastewater to be treated is transported to a preset filter surface for filtration, and solid particles in the sewage wastewater are deposited on the preset filter surface to form a self-forming filter cake; During the formation of the self-forming filter cake, the filtration operation status of the self-forming filter cake is detected. When the filtration operation status reaches the preset cake discharge condition, at least a portion of the self-forming filter cake is peeled off from the preset filtration surface. At least a portion of the stripped self-forming filter cake is used as a reuse filter cake. The reuse filter cake is then deagglomerated to obtain filter cake aggregate particles containing at least one of fiber particles, flocculent particles, and organic solid particles. The dosage of the reused filter cake is determined based on the solids content of the reused filter cake and the suspended solids load in the sewage wastewater of the next filtration cycle. The filter cake aggregate particles are then premixed with the sewage wastewater of the next filtration cycle according to the dosage to form recycled aggregate particles. The fecal wastewater containing the recombined agglomerated particles is transported to the preset filter surface to form the initial filter cake layer for the next filtration cycle. The initial filter cake layer and the solid particles deposited by the subsequent fecal wastewater together form the self-forming filter cake for the next filtration cycle.

2. The method for treating and reusing self-forming filter cakes of fecal wastewater according to claim 1, characterized in that, The step of using at least a portion of the stripped self-forming filter cake as a reused filter cake includes: The stripped self-forming filter cake is subjected to particle classification. The portion of the filter cake containing aggregated structures of fiber particles, flocculent particles, and organic solid particles is identified as the reuse filter cake. The remaining portion of the self-forming filter cake with a free fine particle content higher than a preset content is discharged as a resource-based filter cake.

3. The method for treating and reusing self-forming filter cakes of fecal wastewater according to claim 1 or 2, characterized in that, The depolymerization process includes: The recycled filter cake is mixed with the fecal wastewater or the filtrate obtained from filtration to form a filter cake slurry. The filter cake slurry is then sheared to obtain initial aggregated particles. The initial aggregated particles are screened using a first preset sieve hole, and the initial aggregated particles that pass through the first preset sieve hole are retained using a second preset sieve hole to generate filter cake aggregated particles.

4. The method for recycling and treating fecal wastewater using self-forming filter cakes according to claim 3, characterized in that, The aperture of the first preset sieve hole is 2-5 mm, and the aperture of the second preset sieve hole is 0.1-0.5 mm.

5. The method for treating and reusing self-forming filter cakes of fecal wastewater according to claim 1, characterized in that, The step of determining the dosage of the reused filter cake based on its solids content and the suspended solids load in the sewage in the next filtration cycle includes: The dry basis solids content in the recycled filter cake and the suspended solids load in the sewage to be treated in the next filtration cycle are determined, and the dosage of the recycled filter cake is determined based on the dry basis solids content and the suspended solids load.

6. The method for recycling and treating fecal wastewater using self-forming filter cakes according to claim 5, characterized in that, The dry solids content in the recycled filter cake is 2% to 15% of the suspended solids load in the sewage to be treated in the next filtration cycle.

7. The method for recycling and treating fecal wastewater using self-forming filter cakes according to claim 1, characterized in that, The step of premixing the filter cake aggregate particles with the sewage wastewater of the next filtration cycle includes: The filter cake aggregate particles and the fecal wastewater of the next filtration cycle are first mixed to disperse the filter cake aggregate particles in the fecal wastewater. The sewage wastewater that has undergone the first mixing is then subjected to a second mixing process with a lower mixing intensity than the first mixing. The fecal wastewater that has undergone the second mixing process is subjected to particle size detection. Once the particle size in the fecal wastewater reaches the preset particle size condition, the premixing process is completed and re-agglomerated particles are formed.

8. The method for recycling and treating fecal wastewater using self-forming filter cakes according to claim 1, characterized in that, The step of conveying the fecal wastewater containing the recycled agglomerated particles to the preset filter surface includes: The wastewater containing the recombined agglomerated particles is transported to the preset filter surface using low-shear conveying; during the low-shear conveying process, the average flow velocity in the conveying pipeline is 0.05 to 0.8 m / s, and the conveying pressure is not higher than 0.3 MPa.

9. The method for treating and reusing self-forming filter cakes of fecal wastewater according to claim 1, characterized in that, Also includes: During the next filtration cycle, the filter cake maturation time required for the initial filter cake layer to reach the preset filtration capacity and the filtration resistance growth state of the self-forming filter cake during the next filtration cycle are obtained. When the filter cake maturation time is longer than the preset maturation time, and the filter resistance growth state does not exceed the preset resistance growth state, the amount of recycled filter cake added in the next filtration cycle is increased. When the filter resistance growth exceeds the preset resistance growth, the amount of recycled filter cake added in the next filtration cycle is reduced. When the filter cake maturation time is not greater than the preset maturation time, and the filter resistance growth state does not exceed the preset resistance growth state, the amount of recycled filter cake added in the next filtration cycle is maintained.

10. The method for recycling and treating fecal wastewater using self-forming filter cakes according to claim 1, characterized in that, Also includes: Record the cumulative number of times the recycled filter cake is reused, and stop using the corresponding self-forming filter cake as a recycled filter cake when the cumulative number of reuses reaches a preset number or when the preset pollutant content in the recycled filter cake reaches a preset limit.

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