Method for utilization of spent high water-absorption resin and activated sludge carrier

Abstract

To provide: a method for utilization of a spent high water-absorption resin as a new application of a multivalent metal-substituted high water-absorption resin produced in the course of SAP recycling; and an activated sludge carrier.SOLUTION: In a method for utilization of a spent high water-absorption resin of the present invention, a multivalent metal-substituted high water-absorption resin obtained by introducing a multivalent metal ion into the spent high water-absorption resin is utilized as an activated sludge carrier.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for utilizing used highly water-absorbent resin and an activated sludge carrier. [Background technology]

[0002] Articles designed to absorb bodily fluids, such as disposable diapers, sanitary napkins, and incontinence pads (hereinafter referred to as "absorbent articles for bodily fluids"), are mainly made of pulp, superabsorbent polymers (hereinafter referred to as "SAP"), and plastics, and are widely used. In particular, as we move towards an aging society, the amount of disposable diapers used is increasing year by year in ordinary households, hospitals, and welfare facilities. The large amounts of used absorbent articles that are generated are mainly disposed of by incineration as waste.

[0003] However, incineration of used body fluid absorbent articles containing a large amount of moisture requires high-temperature treatment and large-sized incineration equipment, which places a large burden on the incineration equipment, such as accelerating the deterioration of the furnace. Also, from the viewpoint of effective utilization of resources, there is a demand for separating and recovering components from used body fluid absorbent articles and reusing them, without relying on incineration.

[0004] For example, Patent Document 1 describes a method for recycling used paper diapers, which includes an agitation process in which cut used paper diapers and cleaning water containing a polymer decomposition agent are agitated in a polymer decomposition tank, and a separation process in which the agitated material in the polymer decomposition tank is separated into three components: a mixture of absorbent polymer dehydrated by the polymer decomposition agent and pulp components, packaging material of the paper diapers, and wastewater. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-0151254 A Summary of the Invention [Problem to be solved by the invention]

[0006] When recycling used paper diapers, a major issue is how to recycle SAP, which is used in particular as an absorbent for body fluids. In the SAP recycling process, used disposable diapers are first subjected to a separation process by dissolving them in water. The SAP recovered from the separation process has absorbed waste such as human waste, and further treatment processes such as dehydration, washing, acid reaction, neutralization, and drying are required for recycling. In the dehydration process, the water-absorbed SAP can be dehydrated by adding alkaline earth metals such as calcium chloride or divalent or higher polyvalent metal salts. The dehydrated SAP at this stage has almost no water absorption because the carboxyl groups of the SAP are bound to polyvalent metal salts such as calcium. SAP in this state is called "polyvalent metal substituted SAP." In order to turn the non-water-absorbent polyvalent metal substituted SAP into SAP with restored water absorption sufficient for recycling, further treatments such as washing, acid reaction, neutralization, and drying are required.

[0007] If polyvalent metal-substituted SAP could be effectively utilized, it would be possible to omit the acid reaction and neutralization processes and produce a crude product that reduces the energy consumption required for drying. However, conventionally, polyvalent metal-substituted SAP, which can be considered an intermediate product in the process of regenerating used SAP, was limited to use as a solid fuel or soil improvement material.

[0008] The object of the present invention is to solve the above-mentioned problems and to provide a method for utilizing used SAP and an activated sludge carrier as a new application of polyvalent metal-substituted SAP produced during the regeneration of SAP. [Means for solving the problem]

[0009] As a result of extensive investigations into the above-mentioned problems, the present inventors discovered that the resin properties of polyvalent metal-substituted SAP during regeneration can be utilized as an activated sludge carrier in biological treatment in water treatment, and thus completed the present invention. That is, the present invention relates to a method for utilizing spent SAP in the process of being regenerated and an activated sludge carrier as described below.

[0010] The method for utilizing used SAP according to the present invention, which is intended to solve the above problems, is characterized in that polyvalent metal ions are introduced into used SAP to obtain polyvalent metal-substituted SAP, which is then used as an activated sludge carrier. In the process of recycling used SAP, polyvalent metal salts are added during the separation process of the water-solubilization treatment of used paper diapers, and polyvalent metal ions are introduced into the used SAP to dehydrate it. Although the polyvalent metal-substituted SAP after this dehydration does not regain its original water absorption properties, it can be used as an activated sludge carrier by taking advantage of its properties as a resin that does not swell, and the recycled intermediate product of used SAP can be put to new use as a product.

[0011] In one embodiment of the method for utilizing used SAP of the present invention, a part of the polyvalent metal-substituted SAP is substituted for polyvalent metal ions with hydrogen ions. Polyvalent metal replacement of dehydrated used SAP by introducing polyvalent metal ions. SAP with some of the polyvalent metal ions replaced with hydrogen ions is used as an activated sludge carrier. By replacing some of the polyvalent metal ions with hydrogen ions, the surface of the used SAP becomes sticky, making it an activated sludge carrier that is more suitable for microorganisms.

[0012] The activated sludge carrier of the present invention for solving the above problems comprises polyvalent metal-substituted SAP obtained by introducing polyvalent metal ions into used SAP. The multivalent metal substituted SAP that has been through the dehydration process of used SAP regeneration is made into an activated sludge carrier that makes the most of its resin properties. It is possible to provide a new activated sludge carrier made from a composition product that is an intermediate product of used SAP regeneration.

[0013] One embodiment of the activated sludge carrier of the present invention is characterized in that a portion of the polyvalent metal-substituted SAP has been substituted for the polyvalent metal ions by hydrogen ions. By replacing some of the polyvalent metal ions with hydrogen ions, the surface of the used SAP becomes sticky, providing an activated sludge carrier that is more suitable for microorganisms. Effect of the Invention

[0014] According to the present invention, the polyvalent metal-substituted SAP produced in the process of regenerating used SAP is used as an activated sludge carrier, thereby expanding the effective use of intermediate products in the process of regenerating used SAP. In addition, since the process of generating polyvalent metal-substituted SAP is completed midway through the process of regenerating used SAP, energy consumption can be reduced compared to the entire process of regenerating used SAP. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a flow diagram of a process for recycling used SAP. [Diagram 2] FIG. 1 is a schematic diagram illustrating the basic steps of an activated sludge process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] A method for utilizing used SAP and an activated sludge carrier according to an embodiment of the present invention will be described below with reference to Figures 1 and 2. Figure 1 is a flow diagram of the process for regenerating used SAP. Figure 2 is a schematic diagram of the basic process of the activated sludge method.

[0017] In this specification, recycling of used SAP refers to an operation consisting of a separation process for separating SAP from used absorbent articles and a recycling process for recycling the separated SAP. The purpose is to promote the use of SAP as a new resource by enabling the separation, recovery, and remanufacturing of SAP from used absorbent articles such as used disposable diapers, which are discarded in large quantities.

[0018] In this specification, the term "activated sludge process" refers to one of the aerobic microbial processes, which are a method of wastewater treatment, and is a method of treating wastewater containing organic matter by using a group of organisms, mainly bacteria and protozoa, to absorb dissolved oxygen from the water and oxidize and decompose the organic matter in the wastewater to be treated. Activated sludge is a group of microorganisms that look like mud at first glance, as many different types of microorganisms are aggregated by viscous substances to form fine flocs. These microorganisms take up dissolved oxygen from the water and oxidize and decompose the organic matter in the wastewater to be treated.

[0019] In this specification, the term "activated sludge carrier" refers to a substance that serves as a base for the growth of microorganisms by adhering activated sludge to the surface of the carrier. Microorganisms grow in an attached state on the surface of the sludge retention carrier. A suitable environment for the growth of microorganisms is required, and generally a porous material with high water retention is used.

[0020] [First embodiment] A method for utilizing used SAP according to the first embodiment will be described below with reference to the drawings. Fig. 1 shows the entire process for regenerating used SAP. The steps and operations for obtaining the polyvalent metal-substituted SAP according to the first embodiment of the present invention are shown by solid lines, and the steps and operations not related to the first embodiment of the present invention are shown by dashed lines. The polyvalent metal-substituted SAP in the first embodiment of the present invention is obtained from separation means 10 prior to the SAP regeneration step 1. The SAP regeneration process 1 includes a separation means 10 and a regeneration processing means 20. The separation means 10 is used to perform a separation process for separating used body fluid absorbent articles into pulp, SAP, and plastic. As shown in Fig. 1, the separation means 10 includes a separation section 11 where used body fluid absorbent articles are fed and separation processing is performed, and a dehydration means 12 that dehydrates the SAP separated from the used body fluid absorbent articles fed into the separation section 11. By passing through the dehydration means 12, the SAP becomes polyvalent metal-substituted SAP. The first embodiment of the present invention is a method for utilizing used SAP, which is characterized by using this polyvalent metal-substituted SAP as an activated sludge carrier.

[0021] In order to regenerate the used SAP into water-absorbent regenerated SAP, it is necessary to pass the used SAP through a regeneration treatment means 20 shown by the broken line in FIG. The regeneration treatment means 20 includes a washing section 21 consisting of a washing apparatus 100A, an acid reaction section 22, a concentration section 23, a neutralization section 24, and a drying section 25, which are connected to each other through lines L2 to L5. SAP that has been regenerated (regenerated SAP) is discharged from the drying section 25 through line L6. The SAP neutralized (alkali-substituted) in the neutralization section 24 is introduced through line L5 into the drying section 25. The SAP neutralized in the neutralization section 24 is in a water-containing state, and by drying this in the drying section 25, it becomes possible to use it as a regenerated product (product) with sufficient water absorption ability restored.

[0022] SAP is, for example, a three-dimensional cross-linked polyacrylic acid polymer, which consists of carboxyl groups (-COOH) and neutralized carboxyl groups (-COO - and A + A group consisting of + A is a cation. + is a monovalent cation, for example, the sodium ion (Na + ) Thus, SAP is a polymer with carboxyl groups that are partially neutralized with an alkali metal salt, such as sodium hydroxide. The SAP contained in the used body fluid absorbent article is in a swollen state after absorbing liquid (excrement, etc.), and the SAP in the swollen state dissociates into dissociated A + The osmotic pressure and dissociated carboxyl group (-COO - ) absorbs and retains liquids (such as human waste) due to electrostatic repulsion. The osmotic pressure is determined by the ion concentration inside the SAP [A +, C(=O)O-] is higher than the ion concentration of the liquid present outside the SAP, it acts to eliminate the concentration difference between the inside and outside of the SAP, and the external liquid penetrates into the SAP, i.e., the SAP absorbs and retains the external liquid.

[0023] On the other hand, electrostatic repulsion occurs when dissociated carboxyl groups repel each other inside SAP that has absorbed water and become swollen, and this acts in the direction of increasing the distance between the dissociated carboxyl groups, resulting in the generation of gaps between the dissociated carboxyl groups, into which liquid from the outside can penetrate. At the same time, electrostatic attraction occurs between the dissociated carboxyl groups and the molecules (e.g., water molecules) that compose the external liquid, and the molecules that compose the external liquid are trapped in the gap. Thus, electrostatic repulsion acts on the SAP to absorb and hold the external liquid. As a result, the liquid is absorbed and held in the used SAP. When the swollen SAP comes into contact with a polyvalent metal ion, the polyvalent metal ion (e.g., Ca) is introduced between the multiple dissociated carboxyl groups. 2+ ) are ionically cross-linked. The ionic cross-linking causes the swollen SAP to shrink and release the liquid that it has absorbed. Thus, when the used SAP is treated with the polyvalent metal salt, it comes into contact with the polyvalent metal ions, and as a result, it releases the absorbed liquid and is dehydrated.

[0024] (separation means) The separation means 10 for obtaining the polyvalent metal-substituted SAP will be described in detail below. The separation section 11 is supplied with conditioned water together with the used body fluid absorbent article, and separates the used body fluid absorbent article into each component. The conditioned water is supplied to the separation section 11 in order to make the pulp and SAP into a slurry and to increase the separation efficiency when the used body fluid absorbent article is separated into each component in the separation section 11.

[0025] The separating section 11 is supplied with conditioned water together with the used body fluid absorbent article, and serves to separate the used body fluid absorbent article into its respective constituent components. The adjusted water here refers to water that is supplied to turn pulp and SAP into a slurry and increase separation efficiency when the used body fluid absorbent article is separated into its constituent components in the separation section 11. For this reason, water with slightly lower clarity can be used, and in addition to treated water with relatively low clarity such as sewage treatment water, reclaimed water, and circulated water can be used.

[0026] In the separating section 11, the specific means for separating the used body fluid absorbent article into each component is not particularly limited. The separation section 11 in this embodiment includes a separation tank into which used body fluid absorbent articles are placed, and means for performing various processes related to separating the used body fluid absorbent articles into their respective constituent components are provided in the separation tank.

[0027] The separation section 11 may be, for example, a dispersing means for physically decomposing the used body fluid absorbent articles and dispersing the constituent components in the tank, such as a bag breaking means or a fragmenting means provided inside or outside the separation tank. The separation section 11 also includes a process for separating SAP from pulp and other mixed components. The polyvalent metal-substituted SAP separated and concentrated in the separation section 11 is used as an activated sludge carrier. The bag-breaking means here is a means for breaking the packaging (bag) used when collecting and transporting used body fluid absorbent articles, and the fragmenting means is a means for breaking the surface material and waterproof material of the used body fluid absorbent articles to make them into shapes suitable for subsequent mechanical treatments such as dissolving and stirring, and for releasing the inner water-absorbing materials (pulp and SAP) to the outside. Specific examples of the dispersion means include means for strong stirring, means for cutting with a crushing blade, and means for repeatedly piercing the material with a member having many needles attached thereto.

[0028] The separation section 11 may be provided with a separation and recovery means for separating and recovering each of the constituent components dispersed in the separation tank by the dispersion means. The separation and recovery means is not particularly limited as long as it can separate and recover pulp, SAP, and plastics by their constituent components. For example, in addition to separation by size and separation by specific gravity, separation based on solubility or insolubility in solvents and chemicals can be performed by providing a treatment tank separate from the separation tank. The polyvalent metal-substituted SAP separated by the separation and recovery means is discharged together with the pulp and plastics to the outside of the SAP regeneration process 1 via a line L7 consisting of a piping or a transfer mechanism. The first embodiment of the present invention provides a new method for utilizing regenerated SAP, in which the polyvalent metal-substituted SAP discharged outside the SAP regeneration step 1 system via line L7 is utilized as an activated sludge carrier.

[0029] The dehydration means 12 is for carrying out a dehydration step of SAP by adding a polyvalent metal salt. SAP normally dissociates cations (salt components) in liquid, and as a result, the functional groups of SAP (for example, carboxyl groups, etc.) have a negative charge, and as a result of the difference in ion concentration with the water outside the resin, a force (force based on electrostatic interaction or osmotic pressure) is exerted that draws water into the SAP, thereby absorbing water. On the other hand, by adding polyvalent metal salts (polyvalent metal ions) to the used SAP that has absorbed body fluids, which are taken up by the SAP instead of the body fluids (water), the used SAP can be dehydrated. Therefore, the dehydration means 12 may include adding a polyvalent metal salt to the used SAP in the presence of water.

[0030] The dehydration means 12 is not particularly limited in its specific structure as long as it is capable of adding a polyvalent metal salt to the separation section 11 (separation tank) into which used body fluid absorbent articles and adjusted water are placed, as shown in FIG. 2. For example, the apparatus may include a tank for storing the polyvalent metal salt and a supply pipe connecting the tank to a separation tank. The polyvalent metal salt may be in either a solid state or an aqueous solution state in which the polyvalent metal salt is dissolved in water. The supply pipe may also be provided with a control mechanism for controlling the amount of the polyvalent metal salt supplied.

[0031] The polyvalent metal salt may be a salt of a metal having a valence of two or more, and examples of the salt include alkaline earth metal salts and transition metal salts. When the swollen water absorbent resin comes into contact with a polyvalent metal ion, a plurality of dissociated carboxyl groups are ionically cross-linked via the polyvalent metal ion. By ionically cross-linking, the swollen water absorbent resin shrinks, and the liquid absorbed by the swollen water absorbent resin is released. As the polyvalent metal salt, an alkaline earth metal salt, a transition metal salt, etc. can be used. As the alkaline earth metal salt, a water-soluble salt of beryllium, magnesium, calcium, strontium, and barium can be used. As the preferred alkaline earth metal salt, calcium chloride, calcium nitrate, magnesium chloride, magnesium nitrate, etc. can be mentioned, and among them, calcium chloride is more preferred in terms of cost and dehydration effect. The water-containing SAP is dehydrated by utilizing the fact that the water absorption power of SAP decreases when the salt concentration around SAP is high and the pH is low. Calcium chloride has the highest effect. In addition, calcium chloride is harmless and easily available. Examples of transition metal salts include water-soluble salts of iron, cobalt, nickel, copper, etc. As transition metal salts, inorganic acid salts, organic acid salts, complexes, etc. can be used as long as they are incorporated into water-absorbent polymers. Among them, inorganic acid salts or organic acid salts are preferred as transition metal salts in terms of cost and availability. Examples of inorganic acid salts include iron salts such as iron chloride, iron sulfate, iron phosphate, and iron nitrate; cobalt salts such as cobalt chloride, cobalt sulfate, cobalt phosphate, and cobalt nitrate; nickel salts such as nickel chloride and nickel sulfate; and copper salts such as copper chloride and copper sulfate. Examples of organic acid salts include iron lactate, cobalt acetate, cobalt stearate, nickel acetate, and copper acetate.

[0032] By adding the polyvalent metal salt by the dehydration means 12, the SAP in the separation section 11 releases the absorbed body fluid and loses most of its water absorption ability. As a result, the SAP becomes a particulate state with improved settling properties and separability from water. Therefore, the separation efficiency of the above-mentioned separation and recovery means is improved. After passing through the dehydration means 12 by substitution with polyvalent metal salts, the SAP becomes highly fluid and in a liquefied state. By adding an acidic solution to this fluidized SAP and substituting the bound polyvalent metals with hydrogen, the specific gravity of the SAP can be reduced. This makes it possible to adjust the buoyancy of the SAP as a carrier in the aeration tank 32. Furthermore, SAP in which the bound polyvalent metals have been substituted with hydrogen has increased adhesiveness on the resin surface, making it easier for microorganisms to attach to it, and improving its performance as a carrier for activated sludge.

[0033] Furthermore, the separating means 10 may include, in addition to the above-mentioned separating section 11 and dehydration means 12, a means for effectively and efficiently classifying the used body fluid absorbent articles into their respective constituent components (pulp, SAP, plastic) and a means for introducing them in an appropriate state to each processing step downstream of the separating means 10. For example, a concentration adjustment tank for adjusting the concentration of each constituent component during or after the separation process may be provided.

[0034] Figure 2 shows a standard flow of wastewater treatment using the activated sludge method. Here, the water entering the wastewater treatment process and the water that has been treated by the activated sludge method are collectively called treated water. The basic facility configuration in a wastewater treatment process using the activated sludge method, for example, is equipped with a primary sedimentation tank 31, an aeration tank 32, and a sedimentation tank 33. The treated water flows into the primary sedimentation tank 31 through a screen and a grit tank (not shown). The treated water from the primary sedimentation tank 31 flows continuously into the aeration tank 32 and is mixed with the activated sludge in the aeration tank 32. Air is blown into the aeration tank 32 from a blower, so that the dissolved oxygen concentration is kept high. The organic matter in the treated water is oxidized and decomposed by the action of aerobic microorganisms present in the activated sludge. After a certain amount of mixing in the aeration tank 32, the mixture of the treated water and activated sludge in the aeration tank 32 flows directly into the next sedimentation tank 33. Since the sedimentation tank 33 is left to stand without stirring, the microorganisms form flocs and settle. If further processing is required, the supernatant liquid is sent to the next process. The microorganisms that settle in the settling tank 33 are returned to the aeration tank 32 as returned sludge, and are used to decompose the organic matter in the treated water that flows back in. The activated sludge that corresponds to the microorganisms that have multiplied during this series of processes is treated as excess sludge and sent for sludge treatment.

[0035] The activated sludge carrier according to the embodiment of the present invention is a place where the microorganisms that are the main actors in biological treatment adhere to and grow on its surface in the activated sludge process, which is one of the aerobic microbial treatments that are wastewater treatment methods. The activated sludge carrier is suitably used in the activated sludge treatment process for wastewater and wastewater that contain organic matter. In biological treatment, the rate at which microorganisms settle in the wastewater treatment tank can be improved by using a carrier that serves as a habitat for the microorganisms. Resin carriers are widely used as the carrier for this purpose because of their mechanical strength and durability.

[0036] The carriers also serve as a habitat for the microorganisms, improving the rate of settlement of the microorganisms in the aeration tank 32. The carriers on which activated sludge has grown have a specific gravity slightly greater than that of water, so they settle in the settling tank 33, reducing the amount of activated sludge that flows out with the supernatant liquid. Carriers with microorganisms attached are less likely to flow out as supernatant liquid, making them more suitable for the proliferation of microorganisms than flocs made of sludge alone, and also more likely to produce relatively large organisms such as protozoans. As a result, the carrier contributes to improving the biodegradation capacity of activated sludge, which is a group of microorganisms. By utilizing this capability and incorporating the carrier into the aeration tank 32, the volume of the aeration tank 32 can be made compact.

[0037] Sludge circulates within the aeration tank 32, and the microorganisms contained in the sludge decompose organic matter. If a carrier is filled therein, the rate at which the microorganisms settle in the aeration tank 32 is improved, and the decomposition power is also improved. In addition to separating water and sludge based on their specific gravities, separation efficiency can be improved by packing the sludge with carriers.

[0038] The carrier is mainly made of plastic or sponge-like material. The carrier is likely to be damaged during mixing in the aeration tank 32. As the carriers circulate within the aeration tank 32 due to aeration, they may collide with each other and be damaged by shear forces. The carrier has a special shape to increase the specific surface area, and is not a cheap product.

[0039] By using polyvalent metal-substituted SAP that has been subjected only to the separation means 10 in the SAP regeneration process 1 as an activated sludge carrier, new uses for the regenerated SAP can be provided. Furthermore, if the regenerated SAP can be used by passing it only through the separation means 10 in the SAP regeneration process 1, the regeneration cost can be reduced. Furthermore, as an activated sludge carrier, a commercial carrier can be replaced with the regenerated SAP, which reduces the cost of wastewater treatment using the activated sludge method.

[0040] Polyvalent metal-substituted SAP has almost no water absorption, but is in a particulate state with good settling and water separation properties. When activated sludge adheres to the polyvalent metal-substituted SAP as a carrier, it becomes in a suspended state and easily flows, so it can be said that polyvalent metal-substituted SAP is suitable for use as an activated sludge carrier. Polyvalent metal-substituted SAP can also be used as a microbial carrier for facultative anaerobes and obligate anaerobes used in anaerobic treatment of wastewater.

[0041] [Second embodiment] A method for utilizing used SAP according to the second embodiment will be described below with reference to Fig. 1 and Fig. 2. In the second embodiment, the same components as those in the first embodiment are given the same reference numerals as those in the first embodiment, and detailed description thereof will be omitted. The same applies to the third and fourth embodiments.

[0042] In the second embodiment, the polyvalent metal-substituted SAP obtained through the separation means 10 is subjected to an acid treatment by immersing it in an acidic solution, whereby a part of the polyvalent metal-substituted SAP is substituted with hydrogen ions from the polyvalent metal ions, and then the SAP is used as an activated sludge carrier. The polyvalent metal-substituted SAP obtained through the separation means 10 is immersed in an acidic liquid to lower the pH, thereby replacing the cations (eg, calcium ions) derived from the polyvalent metal salt in the SAP with hydrogen ions. By replacing a portion of the polyvalent metal-substituted SAP with hydrogen ions, some of the regenerated SAP will have a sticky resin surface, which is expected to promote the adhesion of sludge. Another advantage is that the specific gravity of the SAP will be reduced, making it easier to flow in the tank.

[0043] [Third embodiment] The third embodiment is an activated sludge carrier made of polyvalent metal-substituted SAP. The use of polyvalent metal-substituted SAP as an activated sludge carrier is a new application of regenerated SAP.

[0044] [Fourth embodiment] The fourth embodiment is an activated sludge carrier in which a part of the polyvalent metal-substituted SAP is substituted from polyvalent metal ions to hydrogen ions. The use of the polyvalent metal-substituted SAP as an activated sludge carrier is a new application of the regenerated SAP. By substituting a part of the polyvalent metal-substituted SAP with hydrogen ions, the resin surface of the regenerated SAP becomes sticky, and the regenerated SAP becomes an activated sludge carrier that has the effect of promoting the adhesion of sludge.

[0045] [Other embodiments] Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and can be modified without departing from the technical concept of the invention.

[0046] As a first variation, it can also be used as a carrier for retaining microbial aggregates (hereinafter referred to as "sludge") that remove odorous components, as an activated sludge carrier in biological deodorization. The procedure for attaching sludge to the polyvalent metal-substituted SAP is the same, but since it is not used in a suspended state in water, in this case it is mixed into another carrier that can ensure breathability, such as Terralet. It is also possible to promote effective use by using molded products made from plastic obtained at the same facility as the carrier.

[0047] The polyvalent metal-substituted SAP obtained from the regeneration process of used SAP is a resin with very low biodegradability, and therefore exists in a stable state in the aeration tank 32 and the sedimentation tank 33. However, over the long term, it is gradually depleted and consumed due to the shearing action and other factors it receives during the aeration and transport processes. Therefore, it is necessary to periodically replenish the SAP with new polyvalent metal-substituted SAP. [Explanation of symbols]

[0048] 1 SAP regeneration process, 10 separation means, 11 separation section, 12 dehydration means, 20 regeneration treatment means, 21 washing section, 22 acid reaction section, 23 thickening section, 24 neutralization section, 25 drying section, 30 standard process of activated sludge method, 31 primary sedimentation tank, 32 aeration tank, 33 sedimentation tank, 34 blower, 41 excess sludge, 42 return sludge

Claims

1. A method for utilizing used superabsorbent resin, comprising the steps of: introducing a polyvalent metal ion into used superabsorbent resin to obtain a polyvalent metal-substituted superabsorbent resin; and utilizing the resulting polyvalent metal-substituted superabsorbent resin as an activated sludge carrier.

2. 2. The method for utilizing used superabsorbent resin according to claim 1, wherein a portion of the polyvalent metal substituted superabsorbent resin has been substituted for polyvalent metal ions by hydrogen ions.

3. An activated sludge carrier comprising a polyvalent metal substituted superabsorbent resin obtained by introducing polyvalent metal ions into used superabsorbent resin.

4. 4. The activated sludge carrier according to claim 3, wherein a portion of the polyvalent metal ions in the polyvalent metal-substituted superabsorbent resin have been substituted with hydrogen ions.

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