JP2020082031A - Process for treating waste slurry - Google Patents

Abstract

To provide effective reduction of a volume of suspended matter in separated water when waste slurry is treated by a centrifugal separator.SOLUTION: The process includes step 1 of adding one or more cationic organic coagulants to waste slurry, step 2 of adding one or more anionic organic coagulants to the waste slurry, and step 3 of solid-liquid separating the waste slurry in which the cationic organic coagulant(s) and the anionic organic coagulant(s) have been added, by using a centrifugal separator.SELECTED DRAWING: Figure 15

Description

The present invention relates to a waste liquid treatment method for a stable liquid.

In pile construction and continuous underground wall construction, a stabilizing solution containing water (making water), bentonite, polymer, etc. is used for the purpose of stabilizing the excavation trench wall and transporting and separating the excavated soil. The stable liquid with degraded performance must be disposed of as waste liquid (construction sludge) (hereinafter, the waste liquid of the stable liquid is referred to as waste stable liquid). However, in large-scale construction in urban areas, it is not possible to take time to dispose of waste stabilizing liquid that is generated every day. For this reason, they were collected by vacuum trucks and treated as construction sludge.

Discharging waste stabilization liquid can reduce the treatment cost as construction sludge, but it is necessary to meet the discharge standard for sewerage. At this time, problems are the amount of suspended solids (SS) and pH, and it is particularly difficult to reduce the amount of suspended solids (SS). It is considered that the amount of suspended solids (SS) is reduced by performing solid-liquid separation treatment on site, and suspended solids are aggregated by adding a flocculant to the waste stabilization liquid prior to solid-liquid separation treatment. .. For example, in Patent Document 1, one or more kinds selected from cationic organic coagulants and one or more kinds selected from anionic organic coagulants are preliminarily blended to prepare a solid-liquid separation agent, and the solid-liquid separation is performed. A solid-liquid separation method in which an agent is added to a waste stabilizing solution is disclosed.

JP, 2007-7535, A

Usually, the earth and sand in the waste stabilization liquid are negatively charged, and these earth and sand are considered to be in a dispersed state due to repulsion between particles. Therefore, when the solid-liquid separating agent in which the cationic organic coagulant and the anionic organic coagulant are blended in advance is added to the waste stabilizing liquid stored in the storage tank, as in the technique described in Patent Document 1, Although formation of flocs can be expected in the storage tank, there is a problem that the flocs are destroyed when pumped up by the pump during the transfer process to the centrifuge. If the flocs in the waste stabilization liquid are destroyed, the suspended solids cannot be sufficiently centrifuged by the centrifuge, and the amount of suspended solids per unit volume in the separated water is the discharge standard value (600 mg/L) to the sewer. The following may not be satisfied.

The present invention has been made in view of such circumstances, and an object thereof is to effectively reduce the amount of suspended solids contained in separated water when treating a waste stabilization liquid with a centrifuge. is there.

In order to achieve the above-mentioned object, a method for treating a waste liquid of a stable liquid according to the present invention comprises a first step of adding at least one selected from cationic organic coagulants to a waste liquid of a stable liquid, and an anionic organic liquid in the waste liquid. A second step of adding at least one selected from a flocculant, and a third step of solid-liquid separating the waste liquid to which the cationic organic flocculant and the anionic organic flocculant have been added by a centrifuge. It is characterized by including.

Further, the method for treating a waste liquid of a stable liquid according to the present invention comprises a first step of adding at least one kind selected from anionic organic coagulants to the waste liquid of a stable liquid, and a step 1 selected from a cationic organic coagulant to the waste liquid. A second step of adding at least one species, and a third step of solid-liquid separating the waste liquid to which the anionic organic flocculant and the cationic organic flocculant have been added by a centrifuge. ..

Further, it is preferable to further include a step of stirring and mixing the organic coagulant added in the first step with the waste liquid by a line mixer between the first step and the second step.

Further, it is preferable to further include a step of subjecting the separated water obtained by the solid-liquid separation in the third step to a neutralization treatment with carbon dioxide gas.

Further, it is preferable to further include a step of adding at least bentonite and a polymer agent to the separated water obtained by solid-liquid separation in the third step to prepare a new stabilizing solution.

Further, the cationic organic coagulant preferably has a 10% solution viscosity of 12 cps or less.

The cationic organic coagulant is preferably at least one of a P-DADMAC organic coagulant and a polyamine organic coagulant.

The anionic organic coagulant is preferably an organic coagulant of acrylamide/sodium acrylate copolymer.

According to the present invention, the amount of suspended solids contained in the separated water can be effectively reduced when the waste stabilizing solution is processed by the centrifuge.

It is a figure explaining the physical property about the target cationic organic flocculant. It is a figure explaining the physical property in the waste liquid sample used for the selection test of a cationic organic coagulant. It is a figure explaining the result of the selection test of a cationic organic flocculant. It is a figure explaining the anionic organic flocculant used as object. It is a figure explaining the result of the confirmation test of an anionic organic flocculant. It is a figure explaining the measurement result of the amount of suspended solids (SS) and the addition concentration of the cationic organic coagulant of each test sample. It is a figure explaining the measurement result of the addition density|concentration of the cationic organic coagulant of each test sample, and the amount of supernatant liquids. It is a figure explaining the measurement result of the amount of suspended solids (SS) and the addition concentration of the cationic organic coagulant of a two-step addition sample and a mixed addition sample. It is a figure explaining the measurement result of the addition density|concentration of the cationic organic coagulant of a two-step addition sample, and a mixing addition sample, and the amount of supernatant liquids. It is a figure explaining the aggregation effect by two-step addition of an aggregating agent. It is a figure explaining three kinds of waste stabilization liquid samples used for the verification test. It is a figure explaining the outline of the test device used for the verification test. It is a figure explaining the internal structure of a screw decanter type centrifuge. It is a figure explaining the verification test result of an aggregation effect. It is a flowchart explaining the waste liquid processing method of a stabilizing liquid. It is a flowchart explaining the waste liquid processing method of a stabilizing liquid. It is a figure explaining the result of the reuse test of separated water.

Hereinafter, a waste liquid treatment method for stabilizing liquid according to the present embodiment will be described with reference to the accompanying drawings. As a result of intensive studies, the inventors of the present invention have applied the technology of the present disclosure to sludge generated in civil engineering, in particular, to a waste stabilization liquid, whereby separated water satisfies the discharge standard of sewerage. I found that. Hereinafter, each test was conducted in order to embody this idea.

[Cationic organic flocculant]
First, with reference to FIG. 1, the physical properties of the five target cationic organic coagulants will be described. Regarding the cationic organic coagulant, the viscosity greatly affects the effect, so the viscosity was measured using a B-type viscometer. The viscosities shown below are those of No. B type viscometer. It is a value measured at a rotation speed of 60 rpm using one rotor.

The first cationic flocculant C1 is a Dadomac organic flocculant (for example, a polymer flocculant manufactured by Daimei Chemical Co., Ltd., trade name: TC-7400). This coagulant contains poly-diallyldimethylammonium chloride (P-DADMAC) as a main component. P-DADMAC is a polymer having a structure represented by the following formula (1) and is in a liquid state. In this embodiment, a diluting solution obtained by diluting the stock solution to 10% in volume concentration was used. The viscosity of this diluted solution is 9.5 cps.

_{[[(CH 3) 2 N} + (CH 2 CH = CH 2) 2] Cl -] n ··· (1)

The second cationic flocculant C2 is a polyamine organic flocculant. This aggregating agent is, for example, a liquid polymer having a structure represented by the following formula (2). In this embodiment, a diluting solution obtained by diluting the stock solution to 10% in volume concentration was used. The viscosity of this diluent is 12.0 cps.

_{(C 3 H 5 ClOC 2 H} 8 N 2 C 2 H 7 N) n ··· (2)

The third cationic flocculant C3 is a methacrylate cationic organic polymer flocculant. This coagulant is in powder form. In the present embodiment, a solution that is dissolved in a solvent (water) at a concentration of 0.1% by weight is used. The viscosity of the solution is 44.5 cps.

The fourth cationic flocculant C4 is an acrylate cationic organic polymer flocculant. This coagulant is in powder form. In the present embodiment, a solution that is dissolved in a solvent (water) at a concentration of 0.1% by weight is used. The viscosity of the lysate is 31.0 cps.

The fifth cationic flocculant C5 is an acrylate cationic organic polymer flocculant. This coagulant is in powder form. In the present embodiment, a solution that is dissolved in a solvent (water) at a concentration of 0.1% by weight is used. The viscosity of the solution is 15.0 cps.

[Cationic organic flocculant selection test]
A selection test was conducted using the above-mentioned five types of cationic organic flocculants C1 to C5. In this selection test, the waste liquid sample shown in FIG. 2 was used as the waste liquid of the bentonite-based stabilizing liquid. This waste liquid sample was muddy water containing bentonite, CMC, and a dispersant, had a pH of 10.5, a suspended solid amount (SS) per unit volume of 56000 mg/L, an electric conductivity of 285 mS/m, and a specific gravity of 1. It was 038 g/cm ³ . Further, the dissolved ion concentration was 662 mg/L for Na ⁺ , 13 mg/L for K ⁺ , 28 mg/L for Ca ²⁺ , 309 mg/L for Cl ⁻ , 298 mg/L for SO ₄ ²⁻ , and many bentonites were It remained.

In the selection test, 50 mL of the waste liquid sample was weighed into each of a plurality of centrifuge tubes having a volume of 85 mL. Sulfuric acid (pH adjuster) was added to each of the weighed waste liquid samples to adjust the pH to the neutral range (pH 6 to 8). With respect to each waste liquid sample, the above-mentioned five kinds of cationic organic coagulants C1 to C5 are respectively concentrated to 10000 mg/L (10000 mg/L in terms of undiluted solution) and 20000 mg/L (20,000 mg/L in terms of undiluted solution). So added. Each waste liquid sample was set in a centrifuge and centrifuged at a rotation speed of 2600 rpm for 5 seconds.

The supernatant after centrifugation was collected by decantation as separated water, and the amount of separated water was recorded. The recorded amount was divided by the collected amount (50 mL) to calculate the separated water ratio (%). The turbidity of the separated water was measured, and the suspended matter amount (SS) was converted by applying the relational expression of the previously measured turbidity and the suspended matter amount (SS). In addition, the pH of the separated water was measured.

[Selection results of cationic organic flocculants]
The results of the selection test are shown in FIG. Here, with respect to the separated water ratio, 30% or more was used as the acceptance criterion. Regarding the amount of suspended solids (SS), 600 mg/L or less, which is the standard value for discharge into the sewer, was used as the acceptance criterion. Regarding the ratio of separated water and the amount of suspended solids, when the ratio of separated water is 40% or more and the amount of suspended solids is 600 mg/L or less, an excellent evaluation (⊚) is given, and the separated water ratio is 30% or more. When it is less than 40% and the amount of suspended solids is 600 mg/L or less, it is evaluated as good (○), and when the separated water ratio is less than 30% and the suspended solid amount exceeds 600 mg/L. It was rated as unacceptable (x). Regarding the pH of the separated water, all coagulants showed a neutral range (pH 6 to 8).

The first cationic organic coagulant C1 will be described. The ratio of separated water was 40% when the coagulant addition concentration was 10,000 mg/L, and 60% when it was 20,000 mg/L. All were 40% or more, which satisfied the criterion. Regarding the amount of suspended solids (SS), it was 251 mg/L when the coagulant addition concentration was 10,000 mg/L, and 92 mg/L when it was 20,000 mg/L. Both were 600 mg/L or less, which satisfied the criterion. As a result, the first cationic organic coagulant C1 was evaluated as excellent.

The second cationic organic coagulant C2 will be described. The ratio of separated water was 30% when the coagulant addition concentration was 10,000 mg/L, and 54% when it was 20000 mg/L. All were 30% or more, which satisfied the criterion. Regarding the amount of suspended solids (SS), it was 254 mg/L when the coagulant addition concentration was 10,000 mg/L, and 197 mg/L when it was 20000 mg/L. Both were 600 mg/L or less, which satisfied the criterion. As a result, the second cationic organic coagulant C2 was evaluated as good.

The third cationic flocculant C3 will be described. The ratio of separated water was 10% when the coagulant addition concentration was 10,000 mg/L and 20,000 mg/L, respectively. Both were less than 30% and did not satisfy the criterion. The amount of suspended solids (SS) could not be measured because the amount of separated water (sample) was too small. As a result, the third cationic organic coagulant C3 was not evaluated.

The fourth cationic flocculant C4 will be described. The ratio of separated water was 10% when the coagulant addition concentration was 10,000 mg/L and 20,000 mg/L, respectively. Both were less than 30% and did not satisfy the criterion. The amount of suspended solids (SS) could not be measured because the amount of separated water was too small. As a result, the fourth cationic organic coagulant C4 was not evaluated.

The fifth cationic flocculant C5 will be described. The separated water ratio was 20% when the coagulant addition concentration was 10,000 mg/L and 20,000 mg/L, respectively. Both were less than 30% and did not satisfy the criterion. Regarding the amount of suspended solids (SS), measurement was possible only when the amount was 20000 mg/L, which was 950 mg/L, and did not reach 600 mg/L or less. As a result, the fifth cationic organic coagulant C5 was not evaluated.

From the above, out of these five types of cationic organic coagulants C1 to C5, excellent evaluation was obtained for the first cationic organic coagulant C1 and good evaluation was obtained for the second cationic organic coagulant C2. .. From this result, in this embodiment, the first cationic organic coagulant C1 was selected as the coagulant.

The reasons why the first and second cationic organic coagulants C1 and C2 were evaluated as good or good and the third to fifth cationic organic coagulants C3 to C5 were evaluated as non-evaluable or evaluable will be considered. The flocculant concentration shown in FIG. 1 is a concentration generally used in the field. If the concentration is further increased, the viscosity will increase and the workability will be deteriorated, so it cannot be used. Since the first and second cationic organic coagulants C1 and C2 have relatively low viscosities, a 10% solution and a high-concentration solution than the third to fifth cationic organic coagulants C3 to C5 are applied to the waste stabilization liquid. it can. Further, since the viscosity of the 10% solution is as low as 12 cps, the molecules of the flocculant can be easily dispersed in the waste stabilization liquid. Therefore, it is considered that the clay particles can be efficiently adsorbed and the aggregation is promoted. Although the 10% solution is used in this embodiment, it is considered that the same action and effect can be obtained even if the solution is 10% or less, for example, 2% to 8 solution.

[Anionic organic flocculant]
Next, the anionic organic coagulant used will be described with reference to FIG.

The anionic organic coagulant A1 is a coagulant of an acrylamide/sodium acrylate copolymer (for example, a polymer coagulant manufactured by Daimei Chemical Co., Ltd., trade name: TA-310), and is in powder form. In the present embodiment, a solution that is dissolved in a solvent (water) at a concentration of 0.2% by weight is used.

[Confirmation test of anionic organic coagulant]
A confirmation test was conducted using the above-mentioned anionic organic coagulant A1. The confirmation test was carried out by observing the situation after adding the anionic organic coagulant in combination with the above-mentioned cationic organic coagulant C1 to the artificial waste stabilization liquid produced artificially. The simulated waste stabilizer was prepared by adding 2% bentonite, 0.2% polymer agent, 19% Kasaoka clay, and 2% cement to industrial water and stirring.

In the confirmation test, the cationic organic coagulant C1 was added to each of 200 ml of a plurality of simulated waste stabilizing solution samples weighed in a beaker so that the concentrations thereof were 1000 mg/L, 2000 mg/L, and 3000 mg/L, respectively. Stir for about 10 seconds. The above-mentioned anionic organic coagulant A1 was added to the sample of the simulated waste stabilizing solution after stirring so as to have a concentration of 200 mg/L and 300 mg/L, and the mixture was stirred for about 10 seconds, and the floc diameter was visually confirmed. The sample of the waste waste stabilizing solution in which the floc diameter was confirmed to be 1 mm or more was set in a centrifuge and centrifuged under conditions of a centrifugal force of 200 G and 30 seconds, and the amount of supernatant was measured.

[Results of confirmation test of anionic organic coagulant]
The result of the confirmation test is shown in FIG. Here, with respect to the flock diameter, 1 mm or more was used as the acceptance criterion. In the combination of the cationic organic coagulant C1 and the anionic organic coagulant A1, (1) a case of adding 1000 mg/L of the cationic organic coagulant C1 and 300 mg/L of the anionic organic coagulant A1, (2) cation 2000 mg/L of the organic coagulant C1 and 200 mg/L of the anionic organic coagulant A1 were added, (3) 2000 mg/L of the cationic organic coagulant C1 and 300 mg/L of the anionic organic coagulant A1 were added. In the case, the floc diameter grew to 1 mm or more, and the amount of the supernatant became 98 to 100 mL.

From the above, an appropriate amount of the anionic organic coagulant A1 is approximately 300 mg/L, and both of the cationic organic coagulant and the anionic organic coagulant can grow flocs in a low concentration region (small amount of addition). Results were obtained that could be accelerated.

[Agglutination effect confirmation test. 1]
The confirmation test of the aggregation effect by adding the above-mentioned anionic organic coagulant A1 to the cationic organic coagulant C1 was conducted. In this confirmation test, the coagulation effect of the test sample A to which the cationic organic coagulant C1 and the anionic organic coagulant A1 were added, and the sulfuric acid and the cationic organic coagulant C1 were added to the simulated waste stabilization liquid This was done by comparing the agglutination effect of sample B.

As the cationic organic coagulant C1, a diluting solution prepared by diluting the stock solution to a volume concentration of about 10% was used. The anionic organic coagulant A1 used was a solution dissolved in a solvent (water) at a concentration of 0.2% by weight. The simulated waste stabilizing solution was prepared by adding Kasaoka clay to a stabilizing solution prepared by adding 2% bentonite, 0.2% CMC, and 0.2% dispersant to industrial water to adjust the specific gravity to 1.05 g/cm ³ , and then cement 0. It was prepared by adding 5% and leaving it for a predetermined time.

In the test sample A, the cationic organic coagulant C1 was added to 200 ml of a plurality of simulated waste stabilizing liquids weighed in a beaker, and the cationic organic coagulant C1 was used in the amount of 1000 mg/L, 2000 mg/L, 3000 mg/L, 4000 mg/L, 5000 mg/L, 5500 mg, respectively. /L and 6000 mg/L were added and stirred for 30 seconds, and then 120 mg/L of the anionic organic coagulant A1 was added and stirred for 30 seconds. The test sample A after stirring was centrifuged. The centrifugation conditions were a rotation speed of 2600 rpm and 5 seconds.

The test sample B was prepared by adding sulfuric acid to 200 ml of a plurality of simulated waste stabilizing liquids weighed in a beaker and adjusting the pH to 8, and then adding 1000 mg/L, 2000 mg/L, 3000 mg/L, 4000 mg of the cationic organic coagulant C1 respectively. /L, 5000 mg/L, 5500 mg/L, 6000 mg/L were added and stirred for 30 seconds. The test sample B after stirring was centrifuged. The centrifugation conditions were a rotation speed of 2600 rpm and 5 seconds.

For these test samples A and B, the supernatant liquid after centrifugation was collected by decantation as separation water, and the amount of the supernatant liquid was recorded. The turbidity of the separated water was measured, and it was converted into the amount of suspended matter by applying the relational expression of the previously measured turbidity and the amount of suspended matter (SS).

The results of the aggregation effect confirmation test will be described below. FIG. 6 is a measurement result showing the relationship between the concentration of the cationic organic coagulant C1 added to the test samples A and B and the amount of suspended solids (SS). FIG. 7 is a measurement result showing the relationship between the addition concentration of the cationic organic coagulant C1 of the test samples A and B and the amount of the supernatant liquid.

First, the amount of suspended solids (SS) shown in FIG. 6 will be described. When the addition concentration of the cationic organic coagulant C1 is the same, the amount of suspended solids (SS) in the test sample A in which 120 ppm of the anionic organic coagulant A1 is added is higher than that in the test sample B neutralized with sulfuric acid. ) Showed a tendency to decrease. Regarding the test sample A, when the cationic organic coagulant C1 was added in an amount of 2000 mg/L or more, the amount of suspended solids (SS) satisfied the discharge standard value (600 mg/L or less) into the sewer. On the other hand, in the test sample B, the amount of suspended solids (SS) did not satisfy the discharge standard value (600 mg/L or less) into the sewer unless the cationic organic coagulant C1 was added in an amount of 3000 mg/L or more.

Next, the amount of supernatant liquid shown in FIG. 7 will be described. Regarding the amount of the supernatant liquid, except for the case where 5000 mg/L of the cationic organic coagulant C1 was added, the amount of the supernatant of the cationic organic coagulant C1 and the anion was higher than that of the test sample B in which the cationic organic coagulant C1 was added after neutralization with sulfuric acid. The test sample A to which the organic flocculant A1 was added tended to have a larger amount of supernatant liquid.

From the above results, the aggregating effect is obtained by adding the cationic organic aggregating agent C1 and the anionic organic aggregating agent A1 rather than the aggregating treatment with only the cationic organic aggregating agent C1 after neutralization with sulfuric acid. It was confirmed to be high. That is, as the aggregating agent, it was confirmed that not only the cationic organic aggregating agent C1 but also the anionic organic aggregating agent A1 added to the cationic organic aggregating agent C1 was used to obtain a higher aggregating effect.

[Agglutination effect confirmation test. 2]
A confirmation test of the aggregating effect by the order of addition of the above-mentioned cationic organic aggregating agent C1 and anionic organic aggregating agent A1 was conducted. In this confirmation test, a two-step addition sample A in which a cationic organic coagulant C1 and an anionic organic coagulant A1 are sequentially added to the simulated waste stabilizing liquid, a cationic organic coagulant C1 and an anionic organic coagulant are added. It was carried out by comparing with the mixed addition sample B in which A1 was premixed and added.

As the cationic organic coagulant C1, a diluting solution prepared by diluting the stock solution to a volume concentration of about 10% was used. The anionic organic coagulant A1 used was a solution dissolved in a solvent (water) at a concentration of 0.2% by weight. The simulated waste stabilization liquid was prepared by adding 2% bentonite, 0.2% CMC and 0.2% dispersant to industrial water, adjusting the specific gravity to 1.05 g/cm ³ with Kasaoka clay, and adding 0.5% cement. Then, it was prepared by leaving it for a predetermined time.

The two-stage added sample A was prepared by adding 1,000 mg/L, 2000 mg/L, 3000 mg/L, 4000 mg/L, and 5000 mg/L of the cationic organic coagulant C1 to 200 ml of a plurality of simulated waste stabilizers weighed in a beaker. After adding 5500 mg/L and 6000 mg/L and stirring for 30 seconds, 120 mg/L of anionic organic coagulant A1 was added and stirred for 30 seconds. Centrifugation was performed on the two-stage added sample A after stirring. The centrifugation conditions were a rotation speed of 2600 rpm and 5 seconds.

The mixed addition sample B is 1000 mg/L, 2000 mg/L, 3000 mg/L, 4000 mg/L, 5000 mg/L, 5500 mg/L, 6000 mg/L, and anionic organic coagulation agent C1 in a plurality of beakers, respectively. Agent A1 was added in an amount of 120 mg/L and stirred for 10 minutes to prepare a mixed solution. The prepared mixed solution was added to each of 200 ml of a plurality of simulated waste stabilizers weighed in a beaker, and stirred for 30 seconds. The mixed addition sample B after stirring was centrifuged. The centrifugation conditions were a rotation speed of 2600 rpm and 5 seconds.

For these two-stage added sample A and mixed added sample B, the supernatant after centrifugation was collected by decantation as separated water, and the amount of the supernatant was recorded. The turbidity of the separated water was measured, and it was converted into the amount of suspended matter by applying the relational expression of the previously measured turbidity and the amount of suspended matter (SS).

The results of the aggregation effect confirmation test will be described below. FIG. 8 is a measurement result showing the relationship between the added concentration of the cationic organic coagulant C1 of the two-step addition sample A and the mixed addition sample B, and the amount of suspended solids (SS). FIG. 9 is a measurement result showing the relationship between the addition concentration of the cationic organic coagulant C1 of the two-step addition sample A and the mixed addition sample B, and the amount of the supernatant liquid.

First, the amount of suspended solids shown in FIG. 8 will be described. Regarding the two-step addition sample A, when the cationic organic coagulant C1 was added in an amount of 2000 mg/L or more, the amount of suspended solids (SS) satisfied the discharge standard value (600 mg/L or less) into the sewer. Regarding the mixed addition sample B, the amount of suspended solids (SS) did not satisfy the discharge standard value (600 mg/L or less) into the sewer unless the cationic organic coagulant C1 was added in an amount of 5000 mg/L or more.

Next, the amount of supernatant liquid shown in FIG. 9 will be described. In the case where 5000 mg/L of the cationic organic coagulant C1 was added, the two-step addition sample A and the mixed addition sample B showed almost the same amount of supernatant liquid, but the cationic organic coagulant C1 was 5500 mg/L, 6000 mg. In all cases where /L was added, the amount of supernatant in the two-step addition sample A tended to be larger than that in the mixed addition sample B.

From the above results, the two-step addition of sequentially adding the cationic organic coagulant C1 and the anionic organic coagulant A1 rather than the mixed addition of mixing the cationic organic coagulant C1 and the anionic organic coagulant A1 in advance. It was confirmed that the above can obtain a higher aggregation effect.

[Discussion of results]
The reason why a higher coagulant effect is obtained by adding the coagulant in two stages than by mixing and adding the coagulant will be discussed.

The dirt particles in the muddy water are negatively charged, and these particles repel each other, resulting in a dispersed state as shown in FIG. First, when the cationic organic coagulant C1 having a positive charge is added to the muddy water in which the soil particles are in a dispersed state, the cationic organic coagulant C1 acts on the negative charge of the soil particles to reduce the repulsive force, Fine flocs as shown in FIG. 10(B) are formed (hereinafter, also referred to as a condensation action). Next, when the anionic organic coagulant A1 is further added to the muddy water in which the fine flocs are formed, the anionic organic coagulant A1 cross-links the fine flocs to physically agglomerate them, and thus FIG. (3) Coarse flocs are formed (hereinafter, also referred to as agglomeration action). Coarse flocs have a large apparent flock diameter and therefore settle. That is, it is considered that when the coagulant is added in two steps, both the coagulating action of the cationic organic coagulant C1 and the aggregating action of the anionic organic coagulant A1 are effectively exhibited.

On the other hand, when the coagulant is mixed and added, the positive charge of the cationic organic coagulant C1 and the negative charge of the anionic organic coagulant A1 cancel each other, so that the coagulating action of the cationic organic coagulant C1 and the anionic organic coagulant C1 It is considered that the aggregating action of the aggregating agent A1 is weakened. That is, the cationic organic coagulant C1 and the anionic organic coagulant A1 are not mixed and added, but the cationic organic coagulant C1 and the anionic organic coagulant A1 are added in two stages to obtain the cationic organic coagulant. It is considered that the aggregation action of the aggregating agent C1 and the aggregating action of the anionic organic aggregating agent A1 came to be enhanced, and the aggregation was promoted.

〔Verification test〕
By using the above-mentioned cationic organic coagulant C1 and anionic organic coagulant A1 to perform coagulation treatment in a field-scale test device, (1) a waste liquid obtained by combining a coagulant and a screw decanter centrifuge. A verification test was conducted on the treatment effect and (2) the possibility of reuse of the separated water as a stable liquid material.

As the cationic organic coagulant C1, a diluting solution prepared by diluting the stock solution to a volume concentration of about 10% was used. The anionic organic coagulant A1 used was a solution dissolved in a solvent (water) at a concentration of 0.2% by weight. As the waste stabilizer, three kinds of waste stabilizer samples (1) to (3) shown in FIG. 11 were used. The waste stabilizing solution (1) and the waste stabilizing solution (2) are artificially prepared simulated stabilizing solutions. The waste stabilizing solution (3) is an actual stabilizing solution collected at an actual site.

The waste stabilization liquid (1) was adjusted to a specific gravity of 1.05 g/cm ³ with Kasaoka clay by adding 2% of bentonite and 0.2% of CMC to industrial water, and then added to a mixer and stirred for 1 hour. It was prepared by adding 0.8% of cement after stirring and further stirring for 1 hour. The pH of the waste stabilization liquid (1) is 12.1 and the amount of suspended solids (SS) is 56000 mg/L. The waste stabilization liquid (2) was adjusted to a specific gravity of 1.09 g/cm ³ with Kasaoka clay by adding 2% of bentonite and 0.2% of CMC to industrial water, and then added to a mixer and stirred for 1 hour. It was prepared by adding 0.8% of cement after stirring and further stirring for 1 hour. The pH of the waste stabilization liquid (2) is 11.8 and the amount of suspended solids (SS) is 120,000 mg/L. The waste stabilizing solution (3) has a specific gravity of 1.05 g/cm ³ , a pH of 9.1, and an amount of suspended solids (SS) of 45000 mg/L.

[Test equipment]
Next, based on FIGS. 12 and 13, an outline of the test apparatus used for the verification test will be described. As shown in FIG. 12, the test apparatus 10 includes a storage tank 11, a submersible pump 12, an upstream distribution line 13, a line mixer 14, a downstream distribution line 15, and a screw decanter centrifuge (hereinafter, A centrifugal separator 40), an upstream metering pump 20, and a downstream metering pump 30.

The storage tank 11 stores the waste stabilizing liquid 2a. The submersible pump 12 is immersed in the waste stabilizing liquid 2a stored in the storage tank 11. The upstream port of the upstream supply line 13 is connected to the discharge port of the submersible pump 12. That is, when the submersible pump 12 is driven, the waste stabilizing liquid 2a in the storage tank 11 is pumped up by the submersible pump 12 and pumped to the upstream supply line 13.

An upstream addition line 21 is connected to the upstream distribution line 13, and an upstream metering pump 20 that sends out the cationic organic coagulant C1 is connected to the upstream addition line 21. That is, the cationic organic coagulant C1 is added to the waste stabilization liquid 2a flowing through the upstream distribution line 13 via the upstream addition line 21.

The downstream axis of the upstream addition line 21 is inclined at an angle of approximately 45 degrees with respect to the axis of the upstream distribution line 13, and the cationic organic coagulant C1 is approximately 45 with respect to the waste stabilizing solution 2a. Added at an injection angle of degrees. The upstream addition line 21 is preferably provided with a check valve 22.

The line mixer 14 connects the downstream opening of the upstream distribution line 13 and the upstream opening of the downstream distribution line 15. The line mixer 14 promotes the mixing of the cationic organic coagulant C1 by circulating and stirring the waste stabilization liquid 2b to which the cationic organic coagulant C1 has been added in the upstream distribution line 13. Thus, the line mixer 14 effectively mixes the cationic organic coagulant C1 having a coagulating effect with the waste stabilizing solution 2b, thereby promoting the formation of fine flocs in the waste stabilizing solution 2b'.

A downstream side addition line 31 is connected to the downstream side distribution line 15, and a downstream side fixed pump 30 for sending out the anionic organic coagulant A1 is connected to the downstream side addition line 31. That is, the anionic organic coagulant A1 is added to the waste stabilization liquid 2b' flowing through the downstream distribution line 15 via the downstream addition line 31.

The downstream side axis of the downstream side addition line 31 is inclined at an angle of approximately 45 degrees with respect to the axis of the downstream side distribution line 15, and the anionic organic coagulant A1 is substantially inclined with respect to the waste stabilization liquid 2b′. Added at a 45 degree implant angle. A check valve 32 is preferably provided in the downstream addition line 31.

Fine flocs are formed in the waste stabilization liquid 2b' flowing from the line mixer 14 into the downstream distribution line 15. By adding the anionic organic flocculant A1 having a flocculating effect to such waste stabilizing liquid 2b', the fine flocs are bonded to each other and the flocc coarsening is promoted. The waste stabilization liquid 2c in which the flocs are coarsened is sent from the downstream distribution line 15 to the centrifuge 40.

As shown in FIG. 13, the centrifuge 40 includes an outer cylinder 41 that rotates in a predetermined direction, a screw 42 that is arranged in an inner space of the outer cylinder 41, and that rotates coaxially with the outer cylinder 41, and a downstream distribution line 15. The waste stabilizing liquid 2c (the liquid to be treated) introduced through (see FIG. 12) is provided with a liquid to be treated supply pipe 43 (a liquid supply portion) that supplies between the outer cylinder 41 and the screw 42. In the centrifugal separator 40, the rotation of the outer cylinder 41 causes a centrifugal force in the radial direction from the center of rotation to act on the waste stabilizing liquid 2c. Due to the difference in rotational speed between the outer cylinder 41 and the screw 42, the solid content 3 of the waste stabilizing liquid 2c is pushed by the blade portion of the screw 42 and moves toward the reduced diameter portion 41a of the outer cylinder 41. Thereafter, the solid content 3 is discharged to the outside of the outer cylinder 41 from the solid content discharge port 44 provided at the tip side portion of the reduced diameter portion 41a. On the other hand, the separated water 4 of the waste stabilization liquid 2c is discharged to the outside of the outer cylinder 41 from the liquid component discharge port 45 provided on the side surface 41b opposite to the reduced diameter portion 41a. As a result, the solid content 3 and the separated water 4 contained in the waste stabilization liquid 2c are separated.

In addition, in FIG. 12, the test apparatus 10 is described as adding the coagulant to the waste stabilization liquid in the order of the cationic organic coagulant C1 and the anionic organic coagulant A1 (C1→A1). It is also possible to add the anionic organic coagulant A1 and the cation organic coagulant C1 in this order (A1→C1). In this case, the anionic organic coagulant A1 is added to the waste stabilization liquid 2a flowing through the upstream distribution line 13 by the upstream metering pump 20, and the waste stabilization liquid 2b′ flowing through the downstream distribution line 15 is added. On the other hand, the cationic organic coagulant C1 may be added by the downstream metering pump 30.

〔Test procedure〕
The waste stabilization liquids (1) and (2) described above were respectively charged into the storage tank 11 of the test apparatus 10, and the waste stabilization liquid delivered by the submersible pump 12 was treated with the cationic organic coagulant C1 and the anionic organic flocculant. The separated water obtained by solid-liquid separation was collected by passing through the centrifuge 40 having a centrifugal force of 900 G and 1300 G without adding any coagulant A1.

In addition, the waste stabilizing solutions (1), (2), and (3) described above are respectively put into the storage tank 11 of the test apparatus 10 and the cationic stabilizing agent is added to the waste stabilizing solution delivered by the submersible pump 12. C1 and anionic organic coagulant A1 were sequentially added at optimum values (C1→A1) and passed through a centrifuge 40 having a centrifugal force of 900G and 1300G, and separated water obtained by solid-liquid separation was collected.

Furthermore, the waste stabilization liquids (1) and (2) described above are respectively charged into the storage tank 11 of the test apparatus 10, and the waste stabilization liquid delivered by the submersible pump 12 is treated with an anionic organic coagulant A1 and a cation. The system organic coagulant C1 was added in the order of optimum values (A1→C1) and passed through the centrifuge 40 having a centrifugal force of 900G and 1300G, and the separated water obtained by solid-liquid separation was collected.

For each separated water sampled, the amount of suspended solids (SS), pH, and specific gravity were measured. The optimum value is a concentration at which the addition amount is appropriately adjusted while observing the state of the separated water obtained from the centrifuge 40 (flock, transparency, etc.).

[Results of proof test of aggregation effect]
The results of the proof test of the aggregation effect are shown in FIG. In the case where neither the cationic organic coagulant C1 nor the anionic organic coagulant A1 was added to the waste stabilization liquids (1) and (2), the suspended solid amount (SS) of the separated water was half or less. However, the standard value of discharge into sewer (600 mg/L or less) was not satisfied.

In the case (C1→A1) in which the cationic organic coagulant C1 and the anionic organic coagulant A1 were sequentially added to the waste stabilization liquids (1), (2), and (3) at optimum values, the separated water was separated. The amount of suspended solids (SS) decreased significantly, and the discharge standard value (600 mg/L or less) into the sewer was satisfied. Moreover, it was confirmed that when the centrifugal force of the centrifuge 40 was increased from 900 G to 1300 G, the effect of reducing the amount of suspended solids (SS) was increased. In addition, in the case where the anionic organic coagulant A1 and the cationic organic coagulant C1 were sequentially added to the waste stabilization liquids (1) and (2) at the optimum values (A1→C1), the separated water floated. The substance amount (SS) was greatly reduced, and the discharge standard value (600 mg/L or less) into the sewer was satisfied.

From the above results, when the cationic stabilizing agent C1 and the anionic stabilizing agent A1 are sequentially added to the waste stabilizing solution at the optimum values to perform the flocculation treatment (C1→A1), In both cases where an anionic organic coagulant A1 and a cationic organic coagulant C1 are sequentially added to the liquid at optimal values to perform coagulation treatment (A1→C1), the amount of suspended solids (SS ) Was confirmed to meet the standard value for discharge into sewer (600 mg/L or less). Further, the specific gravity of the separated water was about 1.00 g/cm ³ lower than the initial value (see FIG. 11), and it was also confirmed that there is an effect of reducing the specific gravity of the waste stabilizing solution. The separated water can be adjusted to pH 8.6 or less by performing a neutralization treatment with carbon dioxide gas.

To summarize the above results, in the case of treating waste liquid in the field with the waste liquid, the first step (step S100 of FIG. 15) of adding the cationic organic coagulant C1 to the waste liquid that has been pumped up by the pump is performed. A second step (step S110 in FIG. 15) of adding the anionic organic coagulant A1 to the waste stabilization liquid to which the cationic organic coagulant C1 has been added, and the cationic organic coagulant C1 and the anionic organic coagulant If the third step (step S120 in FIG. 15) of solid-liquid separation of the waste stabilizing solution to which the agent A1 is added by a centrifuge is sequentially performed, aggregation of suspended solids can be effectively promoted, It was confirmed that the amount of suspended solids (SS) in the separated water satisfied the discharge standard value (600 mg/L or less) to the sewer.

Further, in the case of performing waste liquid treatment on the spot, the first step (step S200 of FIG. 16) of adding the anionic organic coagulant A1 to the waste stable liquid pumped by the pump and the anionic organic coagulation The second step (step S210 of FIG. 16) of adding the cationic organic coagulant C1 to the waste stabilization liquid to which the agent A1 is added, and the anionic organic coagulant A1 and the cationic organic coagulant C1 are added. If the third step (step S220 in FIG. 16) of solid-liquid separation of the waste stabilization liquid with a centrifuge is sequentially performed, the flocculation of suspended solids can be effectively promoted, and the suspended solids of separated water It was confirmed that the amount (SS) satisfied the discharge standard value for sewerage (600 mg/L or less).

In any of the treatment methods shown in FIGS. 15 and 16, after the third step (S120, S220), the separated water may be neutralized with carbon dioxide gas to adjust the pH to 8.6 or less. Further, in any of the processing methods, a step of stirring and mixing the coagulant and the waste stabilizing solution using a line mixer or the like is included between the first step (S100, S200) and the second step (S110, S210). Preferably.

[Reuse test of separated water]
By using the separated water obtained in the above-described verification test of the agglomeration effect, it was confirmed whether the separated water can be reused as a material of a stable liquid to be newly made (liquid making water). 2% of bentonite and 0.2% of a polymer agent were added to the separated water of the waste stabilization liquids (1) to (3) obtained in the above verification test to prepare a new stabilization liquid, and the funnel viscosity and The amount of water was measured.

The funnel viscosity is a value indicating the viscosity of the stabilizing liquid that is controlled on site. Regarding the funnel viscosity, 500 ml of the stabilizing solution was charged into a funnel-shaped funnel viscometer, and the time required for the entire amount to flow down was measured. The amount of drainage is a value that is an index of deterioration showing the wall-forming property of the stabilizing solution. The amount of filtered water was measured using a pressure filtration tester of API (American Petroleum Institute). Specifically, 290 ml of the stabilizing solution was introduced into the cylinder cell of the pressure filtration tester, a pressure of 0.3 MPa was applied for 30 minutes, and the amount of filtrate flowing out from the lower end of the container was measured with a graduated cylinder.

The test results are shown in FIG. The funnel viscosity of each of the waste stabilizing liquids (1) to (3) showed a value substantially equal to that of the stabilizing liquid prepared with industrial water. On day 7 of the waste stabilizing solution (3), the funnel viscosity showed a slightly low value of 21, but it is within the range of the control value, and it can be said that there is no problem. The amount of drainage was lower than the control value immediately after the 3rd and 7th days in all of the waste stabilization liquids (1) to (3).

From the above results, all of the waste stabilizing solutions (1) to (3) show that the funnel viscosity and the amount of drainage are within the control values immediately after the 3rd and 7th days, and the new stabilizing solution is obtained. It was confirmed that the water can be reused as the water for producing.

The above description of the embodiments is for facilitating the understanding of the present invention and is not intended to limit the present invention. The present invention can be modified and improved without departing from the gist thereof and the present invention includes equivalents thereof.

For example, regarding the cation-based organic coagulant, the first cation-based organic coagulant C1 is exemplified in the above embodiment, but the second cation-based organic coagulant C2 may be used. That is, as long as the viscosity of the 10% solution is 12 cps or less, other types of organic flocculants can be used. Further, the cationic organic coagulant and the anionic organic coagulant are not limited to those in which one kind is added, respectively, and one or more kinds may be added.

Although the separated water has been described as being neutralized with carbon dioxide gas, it may be neutralized with a pH adjusting agent such as sulfuric acid.

DESCRIPTION OF SYMBOLS 10... Test device, 11... Storage tank, 12... Submersible pump, 13... Upstream distribution line, 14... Line mixer, 15... Downstream distribution line, 20... Upstream metering pump, 21... Upstream addition line, 30... Downstream metering pump, 31... Downstream addition line, 40... Screw decanter centrifuge (centrifuge)

Claims (8)

A first step of adding at least one selected from cationic organic coagulants to a waste liquid of a stabilizing solution;
A second step of adding at least one selected from anionic organic flocculants to the waste liquid;
A third step of solid-liquid separating the waste liquid, to which the cationic organic coagulant and the anionic organic coagulant have been added, by a centrifuge. A first step of adding at least one selected from anionic organic flocculants to the waste liquid of the stabilizing solution;
A second step of adding at least one selected from cationic organic flocculants to the waste liquid,
A third step of solid-liquid separating the waste liquid, to which the anionic organic coagulant and the cationic organic coagulant have been added, by a centrifuge. The stabilizing solution according to claim 1 or 2, further comprising a step of stirring and mixing the organic coagulant added in the first step with the waste liquid by a line mixer between the first step and the second step. Waste liquid treatment method. The waste liquid treatment method for a stable liquid according to claim 1, further comprising a step of subjecting the separated water obtained by solid-liquid separation in the third step to a neutralization treatment with carbon dioxide gas. 4. The method according to claim 1, further comprising a step of adding at least bentonite and a polymer agent to the separated water obtained by solid-liquid separation in the third step to prepare a new stabilizing solution. Wastewater treatment method for stable liquids. The waste liquid treatment method for a stabilizing solution according to claim 1, wherein the 10% solution of the cationic organic coagulant has a viscosity of 12 cps or less. The waste liquid treatment method for a stabilizing solution according to claim 6, wherein the cationic organic coagulant is at least one of a P-DADMAC organic coagulant and a polyamine organic coagulant. The waste liquid treatment method for a stabilizing solution according to any one of claims 1 to 7, wherein the anionic organic coagulant is an organic coagulant of an acrylamide-sodium acrylate copolymer.

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