JP6957959B2 - Organic acid salt-containing waste liquid treatment method and organic acid salt-containing waste liquid treatment system - Google Patents

Description

The present invention relates to a method for treating an organic acid salt-containing waste liquid for treating a waste liquid containing a sulfate and an organic acid salt, and a treatment system for the organic acid salt-containing waste liquid.

A paste material containing a metal powder such as nickel powder is used for the internal electrode of the multilayer ceramic capacitor and the electrode of the chip resistor. This metal powder is produced by using a dry reduction method or a wet reduction method. When a metal powder is produced by a wet reduction method, it is common to add a reducing agent or an additive to an aqueous solution containing a salt as a raw material for the metal and carry out a reduction reaction in the aqueous solution to obtain a metal powder. It is done in. Organic acid salts may be used as reducing agents and additives. The waste liquid generated in this case after the production of the metal powder is a waste liquid having a high salt concentration and a high chemical oxygen demand (hereinafter, also referred to as COD). Such waste liquid with high COD causes pollution such as eutrophication, and therefore cannot be drained to public water areas without being treated.

In Japan's environmental standards for organic matter in public water bodies, biochemical oxygen demand (hereinafter also referred to as BOD) is used as an index for rivers, and COD is used as an index for lakes and marshes. Japan's Water Pollution Control Law stipulates that COD and BOD should be 160 mg / L (daily average 120 mg / L) as a uniform wastewater standard.

Furthermore, depending on the prefecture, there are cases where stricter additional standards are set by ordinance. In closed sea areas with significant pollution, in order to secure environmental quality standards for water quality, we impose not a concentration regulation but a total water quality regulation that reduces the total amount of organic pollutants discharged into the sea area below the standard value. .. As described above, in order to prevent pollution such as water pollution, the above-mentioned waste liquid having a high chemical oxygen demand needs to be treated to reduce COD.

Various methods have been conventionally proposed for the decomposition of organic substances in order to reduce COD. When biological treatment using activated sludge, biofilm, etc. (see, for example, Non-Patent Document 1) is applied, organisms contained in activated sludge, biofilm, etc. in a high salt concentration solution such as the above-mentioned waste liquid. There is a risk of death, and it is difficult to apply biological treatment as it is. For this reason, it is necessary to dilute the organism to a viable concentration. However, when diluted, there is a demerit that the equipment becomes large due to the increase in the amount of liquid and the cost increases.

Therefore, as a method for removing organic substances, for example, as described in Patent Document 1, a method has been proposed in which solidification is carried out by evaporation to dryness without decomposition to remove organic substances from the liquid. There is. However, this method has a demerit that the energy cost required for heating is large. Further, since the solidified recovered product has adhesiveness, it adheres to the evaporation kiln and becomes difficult to remove, and there is a big problem of handleability.

As a method for decomposing an organic substance, in addition to biological decomposition, for example, as described in Patent Document 2, a method of chemically oxidatively decomposing using an oxidizing agent such as sodium hypochlorite is known. Since the waste liquid as described above contains an organic acid salt at a high concentration, an extremely large amount of an oxidizing agent is required if all the organic acid salts are to be oxidatively decomposed only by the oxidizing agent. Therefore, this method has a demerit that the cost increases because the oxidizing agent is expensive.

The present inventors have previously proposed the method described in Patent Document 3 in which the amount of an expensive oxidizing agent used is suppressed by combining an inexpensive and simple COD reducing method before chemical oxidative decomposition. This method is characterized in that a metal ion is added to a waste liquid containing an organic acid salt to generate a sparingly soluble metal salt, and the produced sparingly soluble metal salt is separated to reduce COD. An expensive drug with high oxidizing power is used to decompose the COD source that remains slightly after the treatment. However, since the amount of COD remaining is small, the amount of the drug used can be reduced, so that the total amount of the drug used can be reduced. Wastewater treatment costs can be kept low.

For example, if the organic acid salt that is the COD source is citrate, by adding calcium chloride to the waste liquid containing citrate, poorly soluble calcium citrate is generated and precipitated and removed. Calcium citrate has a solubility in water of about 0.85 g / L, and is hardly soluble in water and slightly soluble. Therefore, a slightly residual COD source is oxidatively decomposed by an oxidizing agent such as hypochlorous acid. do.

Japanese Unexamined Patent Publication No. 2009-220047 Japanese Unexamined Patent Publication No. 2000-22088 Japanese Unexamined Patent Publication No. 2016-005825

Hiromutsu Wada, "Understanding the Basics and Mechanisms of the Latest Water Treatment Technology" [2nd Edition] p145-174, Shuwa System Co., Ltd., published on July 10, 2012.

However, in the method of adding calcium ions as metal ions to the waste liquid containing an organic acid salt to generate a sparingly soluble metal salt and separating the produced sparingly soluble metal salt to reduce COD, the waste liquid is a sulfuric acid-based aqueous solution. If this is the case, calcium sulfate (plaster) will also be produced as a precipitate. Therefore, the precipitate containing the poorly soluble metal salt becomes a mixture of calcium citrate and gypsum. When the mixture of the precipitate containing the poorly soluble metal salt is separately treated, it is economically advantageous to reduce the amount of the generated precipitate, but if the amount of the precipitate is reduced, the COD of the treatment liquid increases. .. When the COD of the treatment liquid is high, the cost of the oxidant used for oxidative decomposition of COD is high, so that the effect of reducing the amount of starch is offset. Therefore, it is necessary to suppress the increase in the amount of starch as much as possible while reducing COD.

The present invention has been made in view of the above problems, and when treating an organic acid salt-containing waste liquid containing a sulfate, the COD of the treatment liquid is reduced and the increase in the amount of starch generated is suppressed. It is an object of the present invention to provide a new and improved method for treating an organic acid salt-containing waste liquid and a treatment system for an organic acid salt-containing waste liquid.

One aspect of the present invention is a method for treating an organic acid salt-containing waste liquid in which the sulfate and the organic acid salt are simultaneously treated from a waste liquid containing a sulfate and an organic acid salt, wherein the sulfate ion and the organic salt contained in the waste liquid are treated organically. An adjustment step of adding metal ions to the waste liquid based on the concentration of acid ions to prepare the sparingly soluble metal salt while producing the sparingly soluble metal salt, and a separation step of separating the sparingly soluble metal salt produced in the adjustment step. In the adjusting step, the pH of the waste liquid is adjusted to be 7 or more and 12 or less, and the temperature is adjusted to a constant temperature in the range of 50 to 80 ° C. In the adjusting step, the metal ions to be added are added. The amount is adjusted in the range of 0.2 equivalent to 0.7 equivalent with respect to the total of the sulfate ion and the organic acid ion contained in the waste liquid, the sulfate contains sodium sulfate, and the metal ion is calcium. It is an ion, and the organic acid salt is characterized by being either a citrate, a oxalate, or a tartrate.

According to one aspect of the present invention, when treating an organic acid salt-containing waste liquid containing a sulfate, a predetermined range of metal ions are added to the total of sulfate ions and organic acid ions contained in the waste liquid. It is possible to reduce the COD of the treatment liquid and suppress the increase in the amount of generated starch at a low cost and easily.

By doing so, the crystallinity of the poorly soluble metal salt produced can be increased by adding the metal ion in a stable state at the time of adjustment, and the filterability can be improved.

In this way, a sparingly soluble salt of organic acid and calcium is produced. Therefore, by removing the sparingly soluble salt of organic acid and calcium by solid-liquid separation, COD in the waste liquid can be easily and inexpensively reduced.

By doing so, a sparingly soluble salt of a metal such as an organic acid and calcium is produced. Therefore, by removing the sparingly soluble salt of the organic acid and calcium by solid-liquid separation, COD in the waste liquid can be easily and inexpensively obtained. Can be reduced.

Another aspect of the present invention is a treatment system for an organic acid salt-containing waste liquid that simultaneously treats the sulfate and the organic acid salt from a waste liquid containing a sulfate and an organic acid salt, and the chemistry contained in the waste liquid. An analyzer that analyzes the target oxygen requirement, and an adjusting device that adjusts while producing a sparingly soluble metal salt by adding metal ions to the waste liquid based on the concentrations of sulfate ions and organic acid ions contained in the waste liquid. The adjusting device includes a separating device for separating the poorly soluble metal salt produced by the adjusting device, and the adjusting device has a constant temperature in the range of 50 to 80 ° C. in which the pH of the waste liquid is 7 or more and 12 or less. The adjusting device adjusts the amount of the metal ion to be added to 0.2 to 0.7 equivalents with respect to the total amount of the sulfate ion and the organic acid ion contained in the waste liquid. Controlled to adjust to a range, the sulfate comprises sodium sulfate, the metal ion is a calcium ion, and the organic acid salt is either citrate, oxalate, or tartrate. It is characterized by that.

According to another aspect of the present invention, when treating an organic acid salt-containing waste liquid containing a sulfate, a predetermined range of metal ions is added to the total of sulfate ions and organic acid ions contained in the waste liquid. As a result, it is possible to both reduce the COD of the treatment liquid and suppress the increase in the amount of generated starch.

As described above, according to the present invention, even when the organic acid salt-containing waste liquid contains sulfate, a predetermined range of metal ions is added to the total amount of sulfate ions and organic acid ions contained in the waste liquid. As a result, both reduction of COD in the treatment liquid and suppression of increase in the amount of generated starch can be achieved at low cost and easily.

It is a flow chart which shows the outline of the treatment method of the organic acid salt-containing waste liquid which concerns on one Embodiment of this invention. It is a block diagram which shows the outline of the treatment system of the organic acid salt-containing waste liquid which concerns on one Embodiment of this invention. It is a graph which shows the relationship between the addition amount of calcium chloride dihydrate and the COD concentration of the treatment liquid in an Example and a comparative example of the method of treating the organic acid salt-containing waste liquid which concerns on one Embodiment of this invention. It is a graph which shows the relationship between the addition amount of calcium chloride dihydrate and the weight of the generated precipitate in the Example and the comparative example of the method of treating the organic acid salt-containing waste liquid which concerns on one Embodiment of this invention.

Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unreasonably limit the content of the present invention described in the claims, and all the configurations described in the present embodiment are indispensable as a means for solving the present invention. Is not always the case.

First, an outline of a method for treating an organic acid salt-containing waste liquid according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow chart showing an outline of a method for treating an organic acid salt-containing waste liquid according to an embodiment of the present invention.

The method for treating an organic acid salt-containing waste liquid according to an embodiment of the present invention is a method for treating a waste liquid containing a sulfate and an organic acid salt, and has an adjusting step S11 and a separation step S12. By performing the steps S11 to S12 in the flow shown in FIG. 1, the COD in the waste liquid is reduced. In the present embodiment, the COD in the waste liquid is reduced by adding metal ions to the waste liquid to generate a sparingly soluble salt of the organic acid and the metal, and then removing the sparingly soluble salt of the organic acid and the metal by solid-liquid separation. It is characterized by reduction.

In the adjustment step S11, a predetermined equivalent amount of metal ions is added to the waste liquid based on the concentrations of sulfate ions and organic acid ions contained in the waste liquid to prepare a sparingly soluble metal salt. In the present embodiment, the organic acid salt-containing waste liquid to be treated is the production waste liquid of a metal powder such as nickel powder. Therefore, based on the amount of the organic acid ion and the sulfate ion added at the time of producing the metal powder, these organic acids The amount of metal ion that is the source of metal ion to be added is determined by judging the concentration of ion and the concentration of sulfate ion.

As a result of diligent studies to achieve the above-mentioned object of the present invention, the present inventors, when treating the organic acid salt-containing waste liquid containing a sulfate, the sulfate ion contained in the waste liquid in the adjustment step S11. It has been found that by adding a predetermined range of metal ions to the total amount of organic acid ions, it is possible to both reduce the COD of the treatment liquid and suppress the increase in the amount of generated starch. Then, as a result of further research based on these findings, the present invention has been completed.

Therefore, in the present embodiment, the amount of the metal ion added in the adjusting step S11 is adjusted to the range of 0.2 equivalent to 0.7 equivalent with respect to the total amount of the sulfate ion and the organic acid ion contained in the waste liquid. This reduces the COD of the waste liquid treatment liquid containing sulfates and organic acid salts, and suppresses the increase in the amount of starch generated.

Examples of the metal ion that produces a sparingly soluble salt include calcium ion and the like. The metal ion source is not particularly limited as long as it is a highly soluble water-soluble salt, but in the case of calcium ions, calcium chloride or the like is preferable because it is inexpensive and easily available.

Further, examples of the organic acid that forms a sparingly soluble metal salt with calcium include citric acid, oxalic acid, and tartaric acid. Addition of calcium ions to a effluent containing sulfates and these organic acid salts produces gypsum and calcium organic acid starches.

The solubility of calcium organic acid in water is 0.85 g / L for calcium citrate, 0.0067 g / L for calcium oxalate, and 0.023 g / L for calcium tartrate. As described above, the lower the solubility of calcium organic acid in water, the larger the amount of organic acid removed, and the higher the efficiency of COD reduction.

On the other hand, the solubility of gypsum is about 2 g / L, which is higher than that of these calcium organic acids. Therefore, when calcium ions are added, calcium organic acid is preferentially precipitated, and when the amount of calcium ions added is small, calcium organic acid having low solubility is precipitated in a larger amount than gypsum.

Therefore, in the present embodiment, by adjusting the amount of calcium ions added in the adjusting step S11, it is possible to prepare a treated starch having a high ratio of calcium organic acid, and while lowering the COD of the treated liquid, It becomes possible to reduce the amount of treated starch. As described above, the amount of calcium ions added is preferably in the range of 0.2 equivalents to 0.7 equivalents with respect to the total amount of sulfate ions and organic acid ions in the waste liquid.

Further, in the present embodiment, the organic acid needs to be acid dissociated in order to react the organic acid with a metal ion such as calcium to form a salt in the preparation step S11. Therefore, it is desirable that the pH of the waste liquid is on the alkaline side of the acid dissociation constant. Specifically, when the organic acid is citric acid, its acid dissociation constants are pKa1 = 2.9, pKa2 = 4.35, and pKa3 = 5.69, so that the pH is alkaline higher than about 6. It is desirable to have.

Further, the higher the pH of the waste liquid, the greater the rate of acid dissociation of the organic acid. Therefore, the higher the pH, the better. However, some metal ions generate hydroxides in alkalinity, making it impossible to produce calcium salts of organic acids. For example, when the metal ion is calcium, calcium hydroxide is produced at pH 13 or higher, and the calcium salt of the organic acid cannot be produced. Therefore, when the metal ion is calcium, it is necessary to carry out the reaction at a pH of less than 13.

Therefore, for example, when citric acid is removed as calcium citrate, the pH needs to be more than 6 and less than 13, but the rate of acid dissociation is increased and the formation of calcium hydroxide is prevented. In order to do so, pH 7 or more and pH 12 or less are preferable. The pH of the waste liquid is appropriately adjusted according to the organic acid and the metal ion.

The pH adjusting agent for adjusting the pH is not particularly particular, but an alkali hydroxide such as sodium hydroxide or a mineral acid such as sulfuric acid can be used. The temperature at which the sparingly soluble salt is produced is not particularly particular, but in general, the higher the temperature, the higher the crystallinity and the better the filterability. Therefore, it is preferable that the temperature at the time of producing the poorly soluble salt is high, and industrially, for example, 50 ° C. to 80 ° C. is suitable in consideration of the cost, the amount of capital investment, the material of the reaction vessel, and the like.

In particular, when calcium chloride is added as a metal ion source for producing a sparingly soluble salt in the preparation step S11, it is used as a hexahydrate when the calcium chloride is 30 ° C. or lower, and as a tetrahydrate when the calcium chloride is 30 to 40 ° C. At higher temperatures, they are present as dihydrates, respectively. As described above, in the temperature range of calcium chloride of 30 to 40 ° C., the mode of hydrate changes and the number of grams per mole changes. Therefore, when calcium chloride is added and adjusted in the adjustment step S11. In order to improve the accuracy, it is preferable to adjust the temperature at a constant temperature of 50 ° C. to 80 ° C.

In the present embodiment, the metal ion added in the adjustment step S11 in the method for treating the organic acid salt-containing waste liquid is calcium ion, and the organic acid contained in the waste water is citric acid, oxalic acid, tartaric acid and the like. However, any form can be applied as long as the metal ion and the organic acid form a sparingly soluble salt. Further, the organic acid other than citric acid, oxalic acid, and tartaric acid can be similarly applied as long as it is an organic acid that produces a calcium salt having a lower solubility than gypsum.

In the separation step S12, the poorly soluble metal salt produced in the adjustment step S11 is separated. In the present embodiment, the slurry containing the poorly soluble metal salt produced in the adjustment step S11 is solid-liquid separated by using a rotary filter, centrifugation, filter press, pressure filtration, vacuum filtration, etc. to obtain the poorly soluble metal salt. By separating and removing, the COD contained in the treatment liquid is reduced.

As described above, in the present embodiment, when the organic acid salt-containing waste liquid containing sulfate is treated, a predetermined range of metal ions are added to the total of sulfate ions and organic acid ions contained in the waste liquid. It is inexpensive and easy to reduce the COD of the treatment liquid and suppress the increase in the amount of generated starch.

Next, a treatment system to which the method for treating the organic acid salt-containing waste liquid according to the embodiment of the present invention is applied will be described with reference to the drawings. FIG. 2 is a block diagram showing an outline of a treatment system for an organic acid salt-containing waste liquid according to an embodiment of the present invention.

The organic acid salt-containing waste liquid treatment system 100 according to an embodiment of the present invention has a function of treating a waste liquid containing a sulfate and an organic acid salt. In particular, the treatment system 100 for the organic acid salt-containing waste liquid of the present embodiment is applied to the pretreatment step of the step of oxidatively decomposing the organic acid salt which is the COD source in the waste liquid with an oxidizing agent.

As shown in FIG. 2, the organic acid salt-containing waste liquid treatment system 100 of the present embodiment includes a treatment tank 102, an analyzer 104, an adjustment device 106, a separation device 108, and a control unit 110.

The analyzer 104 has a function of analyzing the COD contained in the waste liquid WL charged into the treatment tank 102. In the present embodiment, the analyzer 104 collects the waste liquid WL to be treated, and then analyzes the COD contained in the waste liquid by using, for example, an acidic high-temperature permanganate method or the like.

The adjusting device 106 has a function of adding metal ions to the waste liquid based on the concentrations of sulfate ions and organic acid ions contained in the waste liquid WL to prepare while producing a sparingly soluble metal salt. In the present embodiment, in order to achieve both reduction of COD of the treatment liquid TW and suppression of increase in the amount of starch generated, the adjusting device 106 includes sulfate ions and organic acids containing the addition amount of metal ions to be added in the waste liquid. It is characterized in that it is controlled so as to be adjusted in the range of 0.2 equivalent to 0.7 equivalent with respect to the total amount of ions.

The separating device 108 has a function of separating the poorly soluble metal salt produced by the adjusting device 106. In the present embodiment, the separation device 108 is a solid-liquid separation means such as a rotary filter, a centrifuge, a filter press, pressure filtration, and vacuum filtration, and produces a slurry WS containing a sparingly soluble metal salt produced in the treatment tank 102. Solid-liquid separation is performed to reduce the COD contained in the treatment liquid TW. The separation liquid IW obtained by solid-liquid separation of the slurry WS by the separation device 108 is returned to the treatment tank 102.

The control unit 110 has a function of controlling the operation of each component provided in the organic acid salt-containing waste liquid treatment system 100. In the present embodiment, the control unit 110 has a function of controlling the operation of the adjusting device 106 based on the concentrations of sulfate ions and organic acid ions contained in the waste liquid WL and controlling the solid-liquid separation operation of the separating device 108. In particular, in the present embodiment, the control unit 110 ^{adds the amount of metal ions such as calcium ion Ca 2+} added by the adjusting device 104 to 0.2 equivalents with respect to the total amount of sulfate ions and organic acid ions contained in the waste liquid. Control to adjust to the 0.7 equivalent range.

As described above, in the method and system for treating the organic acid salt-containing waste liquid according to the embodiment of the present invention, the organic acid and the metal are added to the waste liquid containing the sulfate and the organic acid salt and stirred while stirring. The ions are reacted to form a sparingly soluble metal salt. At that time, the pH of the waste liquid may be adjusted according to the metal ions to be added to facilitate the formation of a sparingly soluble metal salt. Then, since the organic acid salt serving as a COD source can be removed from the waste liquid only by separating and removing the produced poorly soluble metal salt, the organic acid concentration in the waste liquid can be easily reduced.

Further, in the method and system for treating the organic acid salt-containing waste liquid of the present embodiment, the amount of metal ions added to remove the organic acid salt in the waste liquid is the sum of the sulfate ions and the organic acid ions contained in the waste liquid. Since the amount is adjusted in the range of 0.2 equivalent to 0.7 equivalent, the amount of the poorly soluble metal salt generated can be reduced while reducing the COD in the treatment liquid. That is, when treating an organic acid salt-containing waste liquid containing a sulfate, the COD of the treatment liquid is reduced by adding a predetermined range of metal ions to the total of sulfate ions and organic acid ions contained in the waste liquid. It is possible to suppress the increase in the amount of starch such as calcium sulfate generated at the same time.

Further, the method for treating the organic acid-containing waste liquid of the present embodiment is not affected by the chemical salt concentration, and the reaction apparatus or the like is simpler and cheaper than the biological treatment or evaporation to dryness, and the organic acid is used by a chemical method. It can also be used as a pretreatment for a method of oxidatively decomposing a salt. Therefore, when the treatment method and treatment system for the organic acid salt-containing waste liquid of the present embodiment are applied as the pretreatment, an oxidizing agent is added to the waste liquid having a reduced organic acid concentration to oxidize the remaining organic acid. Since it only needs to be decomposed, the amount of oxidizing agent used can be reduced. Therefore, the method of oxidative decomposition using an oxidizing agent in a subsequent step has extremely great industrial value because the cost can be reduced by reducing the amount of expensive oxidizing agent used.

Next, the method for treating the organic acid salt-containing waste liquid according to the embodiment of the present invention will be described in more detail with reference to Examples. The present invention is not limited to these examples.

(Example 1)
0.5 L of a pH 10, COD 30 g / L aqueous solution containing 76 g / L of trisodium citrate and 107 g / L of sodium sulfate was placed in a 1 L beaker and heated to 60 ° C. with mixing and stirring. After reaching 60 ° C., add 0.2 equivalents of calcium chloride dihydrate powder (14 g) equivalent to the reaction, stir and mix for 1 hour while maintaining at 60 ° C., and mix calcium citrate and gypsum. A precipitate was created.

After mixing and stirring, the slurry containing the precipitate was solid-liquid separated with a 5C filter paper, and the precipitate and the precipitate filtrate were separated. The COD concentration in the precipitate filtrate was measured by the CODMn method, and the precipitate was dried at 60 ° C. for 24 hours and weighed. The measured value of COD concentration was 15 g / L, and the weight of the precipitate was 31 g.

(Examples 2 and 3, Comparative Examples 1 to 3)
In Examples 2 and 3 and Comparative Examples 1 to 3, the addition amounts of calcium chloride dihydrate were 0.4 equivalent (28 g), 0.7 equivalent (49 g), 0.1 equivalent (7 g), and 1. A mixed precipitate of calcium citrate and gypsum was prepared in the same manner as in Example 1 except that it was adjusted to 0 equivalent (70 g) and 1.5 equivalent (105 g).

The measured values of COD, the COD residual ratio, and the weight of the precipitate of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1 below.

Further, the relationship between the amount of calcium chloride dihydrate added (equivalent) and the COD concentration of the treatment solution in Examples 1 to 3 and Comparative Examples 1 to 3 is shown in FIG. 3, and the amount of calcium chloride dihydrate added (equivalent) is shown in FIG. ) And the weight of the precipitate are shown in FIG.

As shown in Table 1 and FIG. 3, when the addition amount of calcium chloride dihydrate is 0.2 equivalent or more, the residual rate of COD is 50% or less, which is preferable. That is, as in Comparative Example 1, if the addition amount is less than 0.2 equivalent, the COD of the treatment liquid remains more than 50% of the starting liquid, which is not preferable.

Further, as shown in Table 1 and FIG. 3, when the addition amount of calcium chloride dihydrate is 0.7 equivalent, the COD concentration can be reduced to 1.7 g / L, which is 5.7% of the starting solution. ing. On the other hand, when the addition amount of calcium chloride dihydrate is more than 0.7 equivalent, as shown in Comparative Example 2 and Comparative Example 3, the effect of reducing COD is compared with the increase in the addition amount. Although small, as shown in FIG. 4, the weight of the generated starch increases linearly.

From this, citric acid, which is a COD source, can be sufficiently reduced by adding up to 0.7 equivalents, and even if more than 0.7 equivalents are added, the addition of excess calcium ions mainly causes gypsum. Indicates that it is being used to generate. Therefore, it was found that the addition of more than 0.7 equivalents of calcium chloride dihydrate is not preferable because it only increases the weight of the starch and the effect of reducing COD is small.

From the results of each of the above Examples and Comparative Examples, when treating a waste liquid containing a sulfate and an organic acid salt, the amount is 0.2 to 0 with respect to the total of the sulfate and the organic acid salt contained in the waste liquid. It was found that it is preferable to adjust to the range of 0.7 equivalents, that is, 0.2 equivalents or more and 0.7 equivalents or less.

Although one embodiment of the present invention and each embodiment have been described in detail as described above, those skilled in the art will be able to make many modifications that do not substantially deviate from the novel matters and effects of the present invention. , Will be easy to understand. Therefore, all such modifications are included in the scope of the present invention.

For example, a term described at least once in a specification or drawing with a different term in a broader or synonymous manner may be replaced by that different term anywhere in the specification or drawing. Further, the method for treating the organic acid salt-containing waste liquid and the configuration and operation of the organic acid salt-containing waste liquid treatment system are not limited to those described in one embodiment of the present invention and each embodiment, and various modifications can be carried out. Is.

100 Organic acid salt-containing waste liquid treatment system, 102 treatment tank, 104 analyzer, 106 adjustment device, 108 separation device, 110 control unit, S11 adjustment process, S12 separation process, IW separation liquid, TW treatment liquid, WL waste liquid, WS slurry

Claims (2)

A method for treating an organic acid salt-containing waste liquid in which the sulfate and the organic acid salt are simultaneously treated from a waste liquid containing a sulfate and an organic acid salt.
An adjustment step of adding metal ions to the waste liquid based on the concentrations of sulfate ions and organic acid ions contained in the waste liquid to produce a sparingly soluble metal salt, and an adjustment step.
It has a separation step of separating the poorly soluble metal salt produced in the adjustment step.
In the adjustment step, the pH of the waste liquid is adjusted to be 7 or more and 12 or less, and the temperature is adjusted to a constant temperature in the range of 50 to 80 ° C.
In the adjustment step, the amount of the metal ion to be added is adjusted to a range of 0.2 equivalent to 0.7 equivalent with respect to the total of the sulfate ion and the organic acid ion contained in the waste liquid.
The sulfate contains sodium sulfate, and the metal ion is a calcium ion.
A method for treating an organic acid salt-containing waste liquid, wherein the organic acid salt is any one of citrate, oxalate, and tartrate. A treatment system for an organic acid salt-containing waste liquid that simultaneously treats the sulfate and the organic acid salt from a waste liquid containing a sulfate and an organic acid salt.
An analyzer that analyzes the chemical oxygen demand contained in the waste liquid, and
An adjusting device that adjusts while producing a sparingly soluble metal salt by adding metal ions to the waste liquid based on the concentrations of sulfate ions and organic acid ions contained in the waste liquid.
A separation device for separating the poorly soluble metal salt produced by the adjustment device is provided.
The adjusting device is controlled so that the pH of the waste liquid is 7 or more and 12 or less and the temperature is adjusted to a constant temperature in the range of 50 to 80 ° C.
The adjusting device is controlled so as to adjust the amount of the metal ion to be added in the range of 0.2 equivalent to 0.7 equivalent with respect to the total of the sulfate ion and the organic acid ion contained in the waste liquid. ,
The sulfate contains sodium sulfate, and the metal ion is a calcium ion.
A treatment system for an organic acid salt-containing waste liquid, wherein the organic acid salt is any one of citrate, oxalate, and tartrate.

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