Treatment method for waste solution

Abstract

To provide a method for treating waste solution capable of improving the dewaterability of low-viscosity waste solution containing few suspended solids, enabling efficient and stable solid-liquid separation treatment.SOLUTION: A method for treating waste solutions characterized by mixing a polymer flocculant, whose 0.2 wt% dilution solution has a viscosity of 150 to 500 mPa*s, into the waste solution containing suspended solids (SS) of 500 to 10,000 mg / L and a viscosity of 0.1 to 20 mPa*s, and then separating a mixture into solid and liquid phases.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for treating a waste solution. [Background technology]

[0002] Waste solutions can contain large amounts of suspended solids (SS). The concentration of suspended solids depends on the type of waste solution and the equipment used. The suspended solids in waste solutions are removed by dehydration using a dehydrator. This dehydration process generates a large amount of solids, and since processing the generated solids is costly, reducing the weight and volume of the solids is a challenge.

[0003] When dehydrating suspended solids, if the concentration of suspended solids in the waste solution is high, it is relatively easy to perform the dehydration treatment using a dehydrator. However, if the concentration of suspended solids in the waste solution is low, dehydration failure is likely to occur, and the operating conditions of the dehydrator may have to be changed frequently.

[0004] One method for solving this problem is to increase the concentration of suspended solids in the waste solution before supplying it to a dehydration treatment device, and then supply the waste solution containing a high concentration of suspended solids to the dehydration device. Methods for increasing the concentration of suspended solids in the waste solution include large equipment such as gravity settling and centrifugation, and screw presses and belt presses, which require labor and effort for maintenance. For example, Japanese Patent Application Laid-Open No. 2016-107265 (Patent Document 1) describes a dehydration system that includes a first thickening section that thickens sludge to produce concentrated sludge, and a dehydration section that receives the concentrated sludge produced in the first thickening section as sludge to be dehydrated and dehydrates the sludge to be dehydrated using a screw press or belt press while heating the sludge using an indirect heating method.

[0005] Japanese Patent Laid-Open Publication No. 2016-55247 (Patent Document 2) describes an example of a belt press type dehydration device that continuously dehydrates sludge generated in water treatment such as water supply and sewage treatment, industrial wastewater treatment, etc. Furthermore, Japanese Patent Laid-Open Publication No. 2023-107035 (Patent Document 3) describes a method in which a polymer flocculant is added to difficult-to-dehydrate organic wastewater containing at least one of human waste and purified water sludge to perform a flocculation treatment, followed by a concentration treatment, and the concentrated sludge is then dehydrated. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-107265 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-55247 [Patent Document 3] Japanese Patent Publication No. 2023-107035 Summary of the Invention [Problem to be solved by the invention]

[0007] The invention described in Patent Document 1 uses a screw press method to produce highly concentrated sludge with relatively low energy consumption, but the energy savings are small and operational management can be difficult due to fluctuations in sludge properties, etc. Furthermore, the invention described in Patent Document 2 describes the possibility of reducing running costs by changing the cleaning mechanism in a belt press dehydration device, but the operational management of a belt press dehydration device places a heavy burden on the user, which can increase the initial cost of the entire device.

[0008] On the other hand, in view of the recent trend toward labor saving and cost reduction, a method of adjusting the waste solution to a state suitable for solid-liquid separation treatment may be more advantageous in terms of cost and treatment efficiency than the method of improving the dehydration apparatus itself as described in Patent Documents 1 and 2. In this regard, Patent Document 3 mentioned above proposes adding a specified polymer flocculant to organic wastewater containing human waste or septic tank sludge, but its use is limited, and its application to low-viscosity waste solutions with little suspended matter has not been fully considered.

[0009] In view of the above problems, the present invention provides a method for treating a waste solution that can improve the dewaterability of a low-viscosity waste solution with a small amount of suspended solids and that can perform an efficient and stable solid-liquid separation treatment. [Means for solving the problem]

[0010] As a result of intensive research to solve the above problems, the inventors have found that by mixing a specific polymer flocculant with a waste solution that has a low viscosity and a small amount of suspended solids, the dewaterability of the waste solution can be improved, and efficient and stable solid-liquid separation treatment can be performed.

[0011] In order to solve the above problems, in one aspect, the present invention provides a method for treating a waste solution, which comprises mixing a waste solution having a suspended solids (SS) of 500 to 10,000 mg / L and a viscosity of 0.1 to 20 mPa·s with a polymer flocculant having a viscosity of 150 to 500 mPa·s when diluted to 0.2 wt%, and then subjecting the mixed solution to solid-liquid separation.

[0012] In one embodiment of the method for treating a waste solution according to the present invention, the polymer flocculant is a cationic polymer flocculant or an amphoteric polymer flocculant.

[0013] In another embodiment of the method for treating a waste solution according to the present invention, the cationic equivalent value of the polymer flocculant at pH 4 is 2.0 to 7.0 meq / g.

[0014] In yet another embodiment of the method for treating a waste solution according to the present invention, the polymer flocculant has a pH of 1.5 to 5.0 when diluted to 0.2 wt %.

[0015] In yet another embodiment of the method for treating a waste solution according to the present invention, the polymer flocculant contains any one of an acrylate monomer, a methacrylate monomer, an acrylamide compound, a methacrylamide compound, a neutralized salt thereof, or a tetrachloride thereof.

[0016] In yet another embodiment of the method for treating a waste solution according to the present invention, the waste solution has a total solids (TS) of 500 to 10,000 mg / L.

[0017] In yet another embodiment of the waste solution treatment method according to the present invention, solid-liquid separation includes concentrating the waste solution to which a polymer flocculant has been added by introducing the mixed liquid into a concentrator that performs a concentration treatment by rotating a plurality of elliptical rotating plates to transport the material to be treated, and discharging separated water from the material to be treated through gaps between the rotating plates.

[0018] In yet another embodiment, the method for treating a waste solution according to the present invention further comprises dehydrating the mixed solution after the concentration treatment.

[0019] In yet another embodiment of the method for treating a waste solution according to the present invention, the separated water separated in the concentration treatment is subjected to an aeration treatment. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide a method for treating a waste solution that can improve the dewaterability of a waste solution containing little suspended matter and perform an efficient and stable solid-liquid separation treatment. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is an explanatory diagram showing an embodiment of a waste solution treatment device suitable for a waste solution treatment method according to an embodiment of the present invention. [Figure 2] FIG. 1 is an explanatory diagram showing another embodiment of a waste solution treatment device suitable for the waste solution treatment method according to the embodiment of the present invention. [Figure 3]FIG. 10 is an explanatory diagram showing yet another embodiment of a waste solution treatment device suitable for the waste solution treatment method according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, identical or similar parts are designated by identical or similar reference numerals. Note that the embodiments shown below are merely examples of devices and methods for embodying the technical concept of the present invention, and the technical concept of the present invention does not limit the structure, arrangement, etc. of component parts to those described below.

[0023] A method for treating a waste solution according to an embodiment of the present invention includes mixing a waste solution having a suspended solids (SS) of 500 to 10,000 mg / L and a viscosity of 0.1 to 20 mPa·s with a cationic polymer flocculant or amphoteric polymer flocculant having a viscosity of 150 to 500 mPa·s when diluted to 0.2 wt%, and then subjecting the mixture to solid-liquid separation.

[0024] The waste solution targeted in this specification has a low suspended solids (SS) of 500 to 10,000 mg / L and a low viscosity of 0.1 to 20 mPa·s. The SS in the waste solution to be treated is preferably 1000 to 8000 mg / L, more preferably 2000 to 7000 mg / L, and even more preferably 3000 to 5000 mg / L. The viscosity of the waste solution is preferably 1.0 to 15 mPa·s, more preferably 1.0 to 10 mPa·s. The pH of the waste solution is not particularly limited, but it is preferable to treat a waste solution with a pH of approximately 5.0 to 8.0, more preferably 6.0 to 7.0.

[0025] The evaporation residue (TS) in the waste solution is 500 to 10,000 mg / L, more preferably 1000 to 8000 mg / L, even more preferably 2000 to 7000 mg / L, and even more preferably 3000 to 5000 mg / L.

[0026] In this embodiment, the effect is fully exerted for waste solutions in which the difference between the total solids (TS) and suspended solids (SS) is 1000 mg / L or less. The difference between the TS and SS of the waste solution is preferably 700 mg / L or less, and more preferably 500 mg / L or less.

[0027] The TS in the waste solution is measured by measuring the weight of the evaporation residue after heating at 105°C for 2 hours, in accordance with the Sewage Testing Method (2012). The SS in the waste solution is measured by measuring the weight of the sediment after 10 minutes at 3000 rpm in a centrifuge, in accordance with the Sewage Testing Method (2012). The viscosity is measured at room temperature (25°C) at 60 rpm using a B-type rotational viscometer.

[0028] The polymer flocculant used has the following physical properties: (1) Viscosity of 0.2 wt% diluted solution is 150 to 500 mPa·s (2) Cationic polymer flocculants or amphoteric polymer flocculants that have the property of being positively charged

[0029] Examples of the cationic polymer flocculant include acrylate monomers, methacrylate monomers, acrylamide compounds, methacrylamide compounds, and neutralized salts or tetrachlorides thereof.

[0030] Examples of acrylate and methacrylate monomers include the following monomers: dimethylamino (methyl, ethyl, propyl, butyl) acrylate or methacrylate, diisobutylamino (methyl, ethyl, propyl, or butyl) acrylate or methacrylate, diethylamino (methyl, ethyl, propyl, butyl) acrylate or methacrylate, di-sec-butylamino (methyl, ethyl, propyl, butyl) acrylate or methacrylate, di-n-propylamino (methyl, ethyl, propyl, butyl) acrylate or methacrylate, diisopropylamino (methyl, ethyl, propyl, butyl) acrylate or methacrylate, di-n-butylamino (methyl, ethyl, propyl, butyl) acrylate or methacrylate, etc.

[0031] Examples of the acrylamide compound or methacrylamide compound include dimethylamino(methyl, ethyl, propyl, butyl)acrylamide or methacrylamide, di-sec-butylamino(methyl, ethyl, propyl, butyl)acrylamide or methacrylamide, diethylamino(methyl, ethyl, propyl, butyl)acrylamide or methacrylamide, diisopropylamino(methyl, ethyl, propyl, butyl)acrylamide or methacrylamide, di-n-propylamino(methyl, ethyl, propyl, butyl)acrylamide or methacrylamide, di-n-butylamino(methyl, ethyl, propyl, butyl)acrylamide or methacrylamide, and diisobutylamino(methyl, ethyl, propyl, butyl)acrylamide or methacrylamide.

[0032] Examples of the neutralized salts include salts with hydrogen halides, sulfuric acid, nitric acid, acetic acid, phosphoric acid, etc. Examples of quaternized salts include quaternized salts with alkyl halides, benzyl halides, dimethyl sulfate, diethyl sulfate, etc.

[0033] The amphoteric polymer flocculant preferably has a polymer in which a vinyl cationic monomer unit, a vinyl anionic monomer unit, and a vinyl nonionic monomer unit are copolymerized in the molecule. Examples of the vinyl cationic monomer copolymerized with the anionic monomer or nonionic monomer include neutralized salts or quaternized products of cationic vinyl monomers. These vinyl cationic monomers may be used alone or in combination of two or more.

[0034] Examples of vinyl-based anionic monomers include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, styrene sulfonic acid, 2-acrylamidoethanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-methacrylamidoethanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, 2-acryloyloxyethanesulfonic acid, 3-acryloyloxypropanesulfonic acid, 4-acryloyloxybutanesulfonic acid, 2-methacryloyloxyethanesulfonic acid, 3-methacryloyloxypropanesulfonic acid, 4-methacryloyloxybutanesulfonic acid, and metal salts or ammonium salts thereof, such as alkali metals and alkaline earth metals. These anionic monomers may be used alone or in combination of two or more.

[0035] Examples of the vinyl-based nonionic monomer to be copolymerized include (meth)acrylamide, (meth)acrylic acid ester, (meth)acrylonitrile, and vinyl acetate, with acrylamide being particularly preferred.

[0036] In the present invention, a polymer flocculant having a crosslinked structure is preferably used. A polymer flocculant having a crosslinked structure creates a greater difference in viscosity from the waste solution, making it easier to form flocs sufficient for treatment. A polymer flocculant having a crosslinked structure can be produced by using a crosslinking agent in combination during polymerization.

[0037] A polymer flocculant having a crosslinked structure can be produced by using a crosslinking agent during polymerization. Examples of crosslinking agents include divinyl compounds such as N,N'-methylenebis(meth)acrylamide, triallylamine, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, and divinylbenzene, vinyl-based methylol compounds such as methylol methacrylamide, vinyl-based aldehyde compounds such as acrolein, and vinyl-based compounds such as methyl acrylamidoglycolate methyl ether. The crosslinking agent is preferably blended in an amount of 0.0005 to 0.003 wt% based on the total amount of monomers.

[0038] Prior to the addition of the polymer flocculant, other inorganic flocculants or organic coagulants may be added to the waste solution. Examples of inorganic flocculants include aluminum sulfate, aluminum chloride, polyaluminum chloride (PAC), ferric chloride, and polyferric sulfate. Examples of organic coagulants include polyamines, dicyandiamides, polydicyandiamides, polydiallyldimethylammonium chlorides (also known as "polyDADMAC"), amino condensation systems, and melamine acid colloids.

[0039] The polymer flocculant can be used in either powder or liquid form. The polymer flocculant having a crosslinked structure may be obtained by drying a crosslinked polymer obtained as an emulsion liquid, granulating or powdering it, to form a dried granule or powder. Typically, the polymer flocculant according to this embodiment is used in the form of an aqueous solution dissolved in water. The concentration of the aqueous solution is not particularly limited, but is usually 0.05 to 0.8 wt%.

[0040] Furthermore, the pH of the polymer flocculant in a 0.2 wt% diluted solution is 1.5 to 5.0, more preferably 2.3 to 4.5, even more preferably 2.8 to 4.3, and even more preferably 2.9 to 3.5. If the pH of the polymer flocculant is lower than 1.5, the polymer flocculant may not be able to exist stably in the diluted solution. If the pH of the polymer flocculant exceeds 5, the charging reaction may be inhibited. In this specification, a 0.2 wt% diluted solution of the polymer flocculant refers to a solution in which the polymer flocculant is diluted with water to 0.2 wt%.

[0041] The polymer flocculant preferably has a cation equivalent value of 2.0 to 7.0 meq / g at pH 4. By using such a polymer flocculant, the frequency of contact between the polymer flocculant and a waste solution with low viscosity and little suspended solids increases, making it possible to produce flocs with relatively large floc diameters. The cation equivalent value of the polymer flocculant at pH 4 is more preferably 2.3 to 5.0 meq / g, even more preferably 2.5 to 4.5 meq / g, and even more preferably 2.8 to 4.3 meq / g.

[0042] The cation equivalent value of a polymer flocculant is measured according to the following procedure. First, dissolve the polymer flocculant in water to prepare a 500 mg / L polymer flocculant sample solution. Next, mix 90 mL of pure water with 10 mL of the polymer flocculant sample solution and adjust the pH to 4.0 with 0.1 N dilute hydrochloric acid or dilute sodium hydroxide, respectively. Add toluidine blue and titrate with a polyvinyl potassium sulfate solution (N / 400 PVSK solution) for colloid titration while stirring with a magnetic stirrer. The titration rate is 2 mL / min. The end point is the point at which the color changes from blue to reddish purple and this color persists for at least 20 seconds, at which point the sample PVSK titer is measured. A blank test is performed using 100 mL of pure water, and the blank PVSK titer is measured. Next, calculate the colloid equivalent based on the sample PVSK titer and the blank PVSK titer, and use this colloid equivalent as the cation equivalent value. Colloid equivalent (meq / g) = {(PVSK titer - blank PVSK titer) x F} / 2 (F is a factor, typically 1.0)

[0043] The amount of polymer flocculant to be added can be appropriately selected by those skilled in the art, but it is preferable to add 0.5 to 90 mg / L of polymer flocculant to the waste solution, and more preferably 5 to 30 mg / L.

[0044] When flocculation treatment is performed using the polymer flocculant according to the embodiment of the present invention, the floc diameter of the flocs in the waste solution organic wastewater is typically more than 2 mm and not more than 10 mm. If flocs having a floc diameter of more than 2 mm and not more than 10 mm can be formed, concentration treatment and dehydration treatment can be performed stably while suppressing the occurrence of dehydration defects in the solid-liquid separation described below.

[0045] The amount of sewage and septic tank sludge received and the sludge properties at the time of delivery vary from moment to moment depending on the receiving situation and the season, so the properties of the sludge used for dehydration treatment can vary greatly. In particular, because sewage contains a large amount of chloride, a high mixing ratio of sewage can lead to poor dehydration. Controlling the amount of coagulant added is one solution, but daily control changes can be practically difficult.

[0046] The polymer flocculant according to the embodiment of the present invention can coarsen fine flocs to produce strong flocs during the flocculation treatment of waste solution with a low viscosity and a small amount of suspended solids. Therefore, the subsequent dewatering treatment can be easily performed without causing dewatering failure. Furthermore, the treatment can be performed stably for a long period of time without strict control of the addition of the polymer flocculant depending on the properties of the waste solution.

[0047] (Waste solution treatment device) Next, a waste solution treatment device according to an embodiment of the present invention will be described with reference to Figures 1 to 3. As shown in Figure 1, the waste solution treatment device according to the embodiment of the present invention includes a mixing tank 12 for mixing a waste solution with a polymer flocculant, and a solid-liquid separation device 1 for performing solid-liquid separation of the mixed liquid containing the polymer flocculant obtained in the mixing tank 12.

[0048] A polymer flocculant adding means 11, which is composed of a pump or the like for adding the polymer flocculant according to the embodiment of the present invention to the waste solution, is connected to the mixing tank 12. A stirring means 13 for stirring the inside of the mixing tank 12 is provided in the mixing tank 12 in order to mix the waste solution and the polymer flocculant and form flocs in the waste solution.

[0049] The solid-liquid separator 1 may be any device capable of performing solid-liquid separation. For example, a preferred solid-liquid separator 1 is a concentrator that can perform a concentration process by rotating multiple elliptical rotating plates to transport the material while discharging separated water from the material through gaps between the rotating plates. Specifically, the solid-liquid separator 1 includes a conveying surface in which multiple elliptical rotating plates are arranged adjacent to each other and parallel to each other in the axial direction. The elliptical rotating plates are configured to periodically alternate between protruding and not protruding upward during rotation. Solid-liquid separation is performed as the material is sequentially transported by the rotation of the rotating plates. A fixed gap is formed between the rotating plates. This concentrator is configured to allow separated water separated from the material to flow down through the gaps between the rotating plates. The polymer flocculant according to this embodiment is particularly suitable for waste solutions supplied to a concentrator having such a configuration. The polymer flocculant according to this embodiment can reduce the leakage of solids from the solid-liquid separator 1 while suppressing excessive leakage of large amounts of solids into the separated water.

[0050] Furthermore, according to the waste solution treatment method of the embodiment of the present invention, the waste solution to which a polymer flocculant has been added is subjected to a concentration treatment using a solid-liquid separation device 1 such as the concentration device described above, and by increasing the solid concentration in the concentrate to a level higher than that before the solid-liquid separation treatment, a waste solution that is more suitable for dehydration treatment and less likely to suffer from dehydration defects during the dehydration treatment described below is obtained.

[0051] 2, the concentrate (including the polymer flocculant) whose solid concentration has been increased by the solid-liquid separator 1 is subjected to a dehydration treatment in a dehydrator 21. The configuration of the dehydrator 21 is not particularly limited. For example, the dehydrator 21 is preferably configured to accommodate the concentrate, to supply a dehydration aid or the like therein as needed, and to perform a dehydration treatment while rotating and heating the concentrate.

[0052] As shown in Fig. 3, the solid-liquid separator 1 may include an aeration tank 31 for aerating the separated water separated in the solid-liquid separation process (concentration process). An aeration pipe 32 is disposed in the aeration tank 31, and an oxygen-containing gas such as air is supplied into the separated water, thereby aerobically treating the separated water in the aeration tank 31. The concentrate separated in the solid-liquid separator 1 is dehydrated and dried in a reaction tank 41.

[0053] According to the waste solution treatment method of the embodiment of the present invention, by adding a high-viscosity polymer flocculant to a low-SS, low-viscosity waste solution, the dewaterability of the low-viscosity waste solution with little suspended solids can be improved, making it possible to perform efficient and stable solid-liquid separation treatment.

[0054] Although the present invention has been described with reference to the above-described embodiments, the descriptions and drawings that form part of this disclosure should not be understood to limit the present invention. The present disclosure is not limited to the above-described embodiments, and components can be combined and modified to be embodied within the scope of the gist of the present disclosure. [Example]

[0055] Examples of the present invention will be described below together with comparative examples. These examples are provided for a better understanding of the present invention and its advantages, and are not intended to limit the invention.

[0056] (Examples 1 to 16) A 100 mL portion of wastewater solution α (viscosity 9.3 mPa·s, pH 6.9, total solids 6,300 mg / L, total solids 6,000 mg / L) delivered to a sewage treatment plant was placed in a 200 mL beaker. A 0.2 wt% aqueous solution of polymer flocculants A–H (listed in Table 1) was added in the amounts shown in Table 2 and stirred with a spatula for 10 seconds. The viscosity of the 0.2 wt% aqueous solution of polymer flocculants was measured at room temperature using a B-type rotational viscometer at 60 rpm, and the pH was measured using a commercially available pH meter. The flocculated sludge obtained after stirring was filtered through a 1.0 mm sieve to evaluate the filtration rate and measure the solids content of the filtrate. The sludge remaining on the sieve was then collected and its moisture content was measured to determine the solids concentration (TS) of the flocculated sludge. The results are shown in Table 2.

[0057] (Examples 17 to 20) In Examples 17 and 18, tests were carried out in the same manner as in Examples 2 and 4, except that waste solution α was changed to waste solution β (viscosity 6.3 mPa s, pH: 6.6, TS: 3,800 mg / L, SS: 3,600 mg / L). In Examples 19 and 20, tests were carried out in the same manner as in Examples 2 and 4, except that the flocculated sludge obtained by stirring was changed to one with a mesh size of 75 μm. The results are shown in Table 2.

[0058] (Comparative Examples 1 to 4) In Comparative Example 1, the test was carried out in the same manner as in Example 2, except that polymer flocculant A was changed to polymer flocculant I. In Comparative Examples 2 and 3, the test was carried out in the same manner as in Examples 2 and 4, except that waste solution γ (viscosity 32.0 mPa·s, pH: 5.3, TS: 29,700 mg / L, SS: 28,200 mg / L) was used. In Comparative Examples 4 and 5, the test was carried out in the same manner as in Examples 2 and 4, except that waste solution δ (viscosity 57.0 mPa·s, pH: 6.2, TS: 37,300 mg / L, SS: 37,000 mg / L) was used. The results are shown in Table 2.

[0059] In Table 2, the filtration rate was evaluated as follows: "◎" if the filtration process of the flocculated sludge obtained by stirring was completed within 10 seconds, "〇" if it was completed within 1 minute, and "△" if it took more than 1 minute. The "concentration" shown in Table 2 was measured by measuring the weight of the evaporation residue after heating at 105°C for 2 hours. The floc diameter was measured by visually inspecting the flocculated sludge after adding each of the polymer flocculants A to I and stirring it, using a spatula.

[0060] [Table 1]

[0061] [Table 2]

[0062] In all of Examples 1 to 20, good flocculation properties and sufficient filtration rates were obtained by adding polymer flocculants A to H, which had a viscosity of 150 to 500 mPa·s when diluted to 0.2 wt%, to waste solutions with little suspended solids and low viscosity. On the other hand, for waste solutions with high viscosity and high SS, the flocs were very small or did not flocculate at all, making it difficult to measure the floc diameter and the SS and solid concentrations of the filtrate. [Explanation of symbols]

[0063] 1: Solid-liquid separator 31: Aeration tank 11: Polymer flocculant addition means 12: Mixing tank 13: Stirring means 21: Dehydration device 32: Diffuser pipe 41: Reactor

Claims

1. A method for treating waste solution, characterized by mixing a polymer flocculant, the viscosity of which when diluted to 0.2 wt%, is 150 to 500 mPa·s, with a waste solution having a suspended solids (SS) content of 500 to 10,000 mg / L and a viscosity of 0.1 to 20 mPa·s, and then subjecting the mixed solution to solid-liquid separation.

2. 2. The method for treating a waste solution according to claim 1, wherein the polymer flocculant is a cationic polymer flocculant or an amphoteric polymer flocculant.

3. 2. The method for treating a waste solution according to claim 1, wherein the polymer flocculant has a cation equivalent value at pH 4 of 2.0 to 7.0 meq / g.

4. 2. The method for treating waste solution according to claim 1, wherein the polymer flocculant has a pH of 1.5 to 5.0 when diluted to 0.2 wt %.

5. 2. The method for treating waste solution according to claim 1, wherein the polymer flocculant contains any one of an acrylate monomer, a methacrylate monomer, an acrylamide compound, a methacrylamide compound, a neutralized salt thereof, and a tetrachloride thereof.

6. 6. The method for treating a waste solution according to claim 1, wherein the waste solution has a residual solid (TS) of 500 to 10,000 mg / L.

7. The method for treating a waste solution according to any one of claims 1 to 5, wherein the solid-liquid separation comprises concentrating the waste solution to which the polymer flocculant has been added by introducing the mixed solution into a concentrator that performs a concentration treatment by rotating a plurality of elliptical rotating plates to transport the material to be treated, and discharging separated water separated from the material to be treated through gaps between the rotating plates.

8. 8. The method for treating a waste solution according to claim 7, further comprising dehydrating the mixed solution after the concentration treatment.

9. 8. The method for treating a waste solution according to claim 7, further comprising aeration of the separated water separated in the concentration treatment.

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