CN100389075C - Drainage disposal method and device - Google Patents

Abstract

The present invention provides a drainage method capable of simply and selectively recovering phosphate ions from wastewater containing ions such as nitrate ions, sulfate ions, iodide ions, and phosphate ions. The present invention provides a wastewater treatment method, which is a wastewater treatment method for recovering phosphate ions from wastewater containing at least one ion selected from nitrate ions, sulfate ions, and iodide ions, and phosphate ions. In an acidic state, the wastewater is brought into contact with an anion exchange resin, and the ions in the nitrate ions, sulfate ions, and iodide ions contained in the above wastewater are ion-exchanged, and then contacted with the anion exchange resin again, so that the phosphate ions are exchanged with the anion exchange resin. Ion exchange is used to recover phosphate ions, and the invention also provides a wastewater treatment device used in the method.

Description

Drainage treatment method and drainage treatment device

technical field

The present invention relates to a wastewater treatment method, in particular to a treatment method and a treatment device for acidic wastewater containing phosphate ions.

Background technique

As a substrate of a liquid crystal display panel or the like, a substrate in which a single layer of aluminum or a pattern of a conductive layer formed of two layers of aluminum and molybdenum is formed on an insulating material is used.

When forming the pattern of this conductive layer, a method of etching with an etchant composed of a mixture of nitric acid, phosphoric acid, and acetic acid has been conventionally used.

When producing substrates such as such a liquid crystal display panel, the waste liquid concentration of the etchant produced is high and easy to circulate, so it is easy to divert to other uses. On the other hand, the effluent of the etched liquid crystal substrate has a lower concentration of phosphate ions than the waste liquid of the etchant, so it is not circulated, but is subjected to biological treatment in the same manner as other waste liquids. In this biological treatment, since the amount of phosphate ions consumed per unit time is substantially constant, the water area load is changed according to the concentration of phosphate ions contained in the wastewater. That is, the treatment is performed while changing the treatment amount per unit time according to the drainage.

However, since environmental awareness has increased in recent years, it is also expected to circulate the waste water with a low ion concentration, such as the waste water from which the liquid crystal substrate after etching has been washed. Especially the phosphorus component, because the utilization value is higher, so try to carry out the selective recovery of phosphate ion, disclose in the patent document 1 to add iron ion or aluminum ion to the drainage that contains phosphate ion by electric field, make it with ferric phosphate or Precipitated in the form of aluminum phosphate.

However, in the method described in Patent Document 1, it is necessary to adjust the amount of iron ions or aluminum ions to be generated according to changes in the concentration of ions contained in the wastewater, and the treatment becomes complicated.

Furthermore, because the electric field is used to generate iron ions or aluminum ions, high energy costs are required, and it is particularly difficult to make the concentration of phosphate ions reach the solubility of iron phosphate or aluminum phosphate or below, so the lower the concentration of phosphoric acid, the treatment The lower the efficiency, the more difficult it is to actually use low-concentration drainage such as phosphate ion concentration of 1% or less.

In addition, the precipitate obtained in this way may contain iron or aluminum salts other than phosphate, and it cannot be said that phosphate ions are selectively recovered.

In addition, in order to recover phosphate ions, it is also conceivable to perform ion exchange using an anion exchange resin, etc., but it is known that generally, anions such as nitrate ions, sulfate ions, and iodide ions are easily ion exchanged with anion exchange resins like phosphoric acid ions. Therefore, phosphate ions cannot be recovered by ion-exchanging the wastewater with an anion-exchange resin.

Thus, there is a problem that it is difficult to selectively recover phosphoric acid in conventional wastewater treatment.

In addition, this problem exists not only in the wastewater treatment that selectively recovers phosphate ions from wastewater containing low-concentration phosphate ions, such as wastewater that has washed liquid crystal substrates, but also in wastewater containing nitrate ions, sulfate ions, and iodide ions. In the wastewater treatment of selective recovery of phosphate ions in the wastewater of equal ions and phosphate ions.

[Patent Document 1] Japanese Unexamined Patent Publication No. 10-225690

Contents of the invention

The object of the present invention is to provide a wastewater treatment method in view of the above problems, which simply and selectively recovers phosphate ions from wastewater containing ions such as nitrate ions, sulfate ions, iodide ions, and phosphate ions, and also provides a wastewater treatment method. device.

Phosphate ions, like anions such as nitrate ions, sulfate ions, and iodide ions, are easily ion-exchanged with anion-exchange resins. In the prior art, anion-exchange resins have not been used to separate these ions from phosphate ions.

However, the inventors of the present invention conducted extensive research on this problem and found that when the drainage is acidic, phosphate ions can be regarded as difficult to ionize with anion exchange resins compared with anions such as nitrate ions, sulfate ions, and iodide ions. exchanged ions, thus completing the present invention.

That is, in order to solve the above-mentioned problems, the present invention provides a wastewater treatment method for recovering phosphate ions from wastewater containing at least one ion selected from the group consisting of nitrate ions, sulfate ions, and iodide ions, and phosphate ions. It is characterized in that, in an acidic state, the drain water is brought into contact with an anion exchange resin, the ions in the nitrate ion, sulfate ion, and iodide ion contained in the above drain are ion-exchanged, and then the anion exchange resin is contacted again to make the phosphoric acid The ions are ion exchanged with an anion exchange resin to recover phosphate ions. The present invention also provides a waste water treatment device, which is a waste water treatment device that recovers phosphate ions from waste water that contains at least one ion selected from nitrate ions, sulfate ions, and iodide ions and phosphoric acid ions and is in an acidic state, It is characterized in that two or more anion exchangers equipped with anion exchange resins are arranged in series in order to allow the above-mentioned waste water to pass through and perform anion exchange twice or more.

According to the present invention, in the acidic state of the drainage, compared with nitrate ions, sulfate ions, and iodide ions, it is difficult for phosphate ions to be ion-exchanged with the anion exchange resin. The ions, sulfate ions, and iodide ions are ion-exchanged with an anion-exchange resin, and then the wastewater is brought into contact with the anion-exchange resin again, and phosphate ions are selectively ion-exchanged with the anion-exchange resin for recovery.

Furthermore, even when the concentration of phosphate ions in the waste water varies, since the waste water treatment amount per unit time can be kept constant, stable waste water treatment can be performed.

In addition, there is no need for high energy costs like the precipitation method using an electric field, and it can be applied to wastewater where the concentration of phosphate ions in wastewater is 1% or less, for example, up to several ppm.

Description of drawings

FIG. 1 is a block diagram showing a waste water treatment device used in a first embodiment.

Fig. 2 is a graph showing changes in ion concentration of the discharge water from the first and second anion exchange towers according to the first embodiment.

Fig. 3 is a graph showing changes in ion concentration of the discharge water of the second anion exchange tower according to the first embodiment.

Fig. 4 is a block diagram showing the sodium phosphate salt recovery device of the first embodiment.

Fig. 5 is a block diagram showing a waste water treatment device used in a second embodiment.

Explanation of symbols

1: The first anion exchange tower

2: The second anion exchange tower

3: water injection pipe

4: connecting pipe

5: drain pipe

6: Solenoid valve

11, 12: Anion exchanger

21, 12: Anion exchanger

19, 29: Alkali regeneration liquid storage tank

Detailed ways

Next, preferred embodiments of the present invention will be described.

First, a waste water treatment device used in the waste water treatment method of this embodiment will be described as a first embodiment based on FIG. 1 .

The above-mentioned waste water treatment device has the following structure: a first anion exchange tower 1, which contacts the waste water with an anion exchange resin to exchange ions such as nitrate ions, sulfate ions, iodide ions, etc.; a first storage tank 13, which temporarily stores The drainage that has passed through the first anion exchange tower 1; the second anion exchange tower 2, which makes the drainage that has passed through the first anion exchange tower 1 contact the anion exchange resin again, so that the phosphate ion is ion-exchanged; the second storage tank 23, which is temporarily stored through the drainage of the second anion exchange tower 2.

In addition, the above-mentioned waste water treatment device has a water injection pipe 3 for introducing waste water to the first anion exchange tower 1; The connecting pipe 4; the drain that has undergone anion exchange in the second anion exchange tower 2 is discharged to the discharge pipe 5 outside the system.

Further, the above-mentioned drainage treatment device has the first return pipe 14 that returns the drainage that has passed through the first anion exchange tower 1 to the first anion exchange tower 1 and returns the drainage that has passed through the second anion exchange tower 2 to the second anion exchange tower 2 again. The second return pipe 24 of the two anion exchange tower 2.

The above-mentioned first anion exchange column 1 is equipped with two anion exchangers 11 and 12, which are exchangers filled with a weakly basic anion exchange resin in a container equipped with a water injection port and a discharge port. In addition, the composition of these two anion exchangers 11, 12 is that the water injection ports of the two anion exchangers are connected to the water injection pipes, and the solenoid valve 6 is used to switch the drainage water flow to each anion exchanger, so that when using one anion exchanger Drainage treatment is carried out. When the anion exchange performance of the anion exchange resin tends to decrease with the progress of the drainage treatment, the flow of the drainage can be switched to another anion exchanger to continue the drainage treatment. In addition, each drain port is connected to a first drain pipe 15 that guides drain water into the above-mentioned first storage tank 13 . In addition, although the positions other than the solenoid valve 6 in FIG. 1 are not marked with symbols, the positions with the same symbols as the solenoid valve 6 in FIG. 1 indicate that a solenoid valve is used.

In addition, the above-mentioned second anion exchange tower 2 also has the same structure as the above-mentioned first anion exchange tower 1, two anion exchangers 21, 22, the water injection port is connected to the connecting pipe 4, and the water outlet is connected to the second drain pipe 25. .

In addition, the water injection pipe 3, the first drain pipe 15 and the second drain pipe 25 are equipped with a total organic carbon (TOC) detector, and the first drain pipe 15 and the second drain pipe 25 are further equipped with an electrical conductivity (EC) measuring device. The instrument measures the TOC and EC of the wastewater flowing through the pipes, and is used to determine the ions contained in the wastewater flowing through each pipe.

As the weakly basic anion exchange resin filled in such an anion exchanger, a resin having an ion exchange capacity of 1.1 to 1.7 eq/L-resin can be used.

In addition, the form is not particularly limited, and generally, a bead-like resin having a diameter of several mm or less can be used.

Next, a method for treating acidic waste water generated by washing liquid crystal substrates etched with an etchant with pure water using such a waste water treatment device will be described with reference to FIG. Temporal changes in the ion concentrations of the drains from the first drain pipe and the second drain pipe.

In the acidic drainage produced by washing the liquid crystal substrate with pure water, it usually contains 100-1000ppm of phosphate ions and 5-50ppm of nitrate ions, and furthermore, 10-100ppm is more difficult to combine with anion exchange resin than phosphate ions in acidic drainage. The acetate ions undergo ion exchange, bringing the pH to approximately 2.

The ion concentration of each ion contained in the acid wastewater is measured in advance with an ion concentration meter or the like in order to grasp the ion exchange status of the anion exchanger based on the flow rate of the acid wastewater. Then, the acidic waste water is introduced into the above-mentioned waste water treatment device by a general liquid delivery device such as a pump (not shown).

Utilize above-mentioned solenoid valve, make the acidic drainage that introduces according to water injection pipe, the first anion exchanger of the first anion exchange tower, the first storage tank, connecting pipe, the first anion exchanger of the second anion exchange tower, the second storage The order of the tank and the drain pipe is processed by the drainage treatment device.

In addition, after the above-mentioned treatment of acidic wastewater starts, as shown in time 0-a in Figure 2, in the first anion exchanger of the first anion exchange tower, all nitrate ions, phosphoric acid ions, and acetate ions are ion-exchanged. , to discharge pure water from the first drain. In this way, it can be judged that all ions have undergone ion exchange in the first anion exchange tower by observing that the TOC and EC of the first drainpipe both become very low values, such as TOC<0.1ppm and EC<1μS/cm.

Then, at time a, the ion exchange resin provided in the first anion exchanger of the first anion exchange column is saturated with nitrate ions, phosphate ions and acetate ions. During the next time a~b, by making the acidic drainage undergo ion exchange in the first anion exchange tower, ions with low ion exchange selectivity can be replaced with ions with high ion exchange selectivity, and become discharged state. That is, by using the nitrate ions and phosphate ions contained in the acidic wastewater, the acetate ions that have been ion-exchanged with the above-mentioned anion exchange resin can be detached, and instead, the anion exchange resin that has detached the nitrate ions and phosphate ions and the acetate ions can be ion-exchanged. .

In this way, since the acetate ions contained in the original acidic drainage and the acetate ions detached from the anion exchange resin are discharged from the first drainage pipe, once the TOC of the first drainage pipe is higher than the TOC of the water injection pipe, it will soon be In b, when the acetate ions are completely detached from the anion exchange resin, the TOC of the two shows the same value again.

At this time, it can be judged that acetic acid starts to be discharged from the value of TOC and EC of the first drain pipe rising slightly (for example, TOC=0.7ppm, EC=4μS/cm). However, since the acetate ions discharged from the first anion exchange tower can be ion-exchanged in the second ion exchange tower, pure water can be discharged from the discharge pipe.

Furthermore, after time b, similarly, the wastewater treatment is continued, and the nitrate ions contained in the acidic wastewater detach the phosphate ions ion-exchanged by the anion exchange resin of the first anion exchange tower, and replace them with the nitric acid contained in the acidic wastewater. The ions are ion exchanged with an anion exchange resin.

At this time, since phosphate ions and acetate ions are discharged from the first anion exchange tower, the acetate ions and phosphate ions greatly increase the EC value of the first drainage pipe, for example, EC=100 μS/cm.

Also at this time, the phosphate ions contained in the acidic wastewater and the phosphate ions desorbed from the anion exchange resin are discharged from the first drainage pipe, so that the phosphate ion concentration of the acidic wastewater is higher than that of the acidic wastewater.

In addition, at this time, since the phosphate ions discharged from the first anion exchange tower can perform ion exchange together with acetate ions in the second anion exchange tower, pure water can still be discharged from the discharge pipe.

And then, when continuing to carry out drainage treatment and reach time c, the ion exchange resin of the second anion exchange tower can form the state that is saturated by phosphoric acid ion and acetate ion, and the acetate ion that is introduced into the second anion exchange tower from connecting pipe can be Form the state that is discharged into the second drainpipe by the second anion exchange tower, and further, continue to carry out drainage treatment, can make the acetate ion that ion exchange has been carried out with the anion exchange resin of the second anion exchange tower be detached, replace it, make Phosphate ions are ion exchanged.

At this time, since the acetate ions contained in the original acidic drainage and the acetate ions detached from the anion exchange resin are discharged from the second drain pipe, once the TOC of the second drain pipe is higher than the TOC of the first drain pipe, the Shortly after time d, when the acetate ions are detached from the anion exchange resin, the TOCs of the two become to show the same value again.

That is, at time d, the first anion exchanger of the second anion exchange column can be regarded as being saturated with phosphate ions, and by recovering the anion exchanger, phosphate ions can be selectively recovered.

In addition, during the time c～d, there is also the situation that a small amount of phosphate ions are discharged together with acetate ions, but if necessary, the solenoid valve switch of the discharge pipe and the second return pipe can be switched to make the second storage tank Ion exchange is performed again in the second anion exchange tower without draining the drain to the discharge pipe, whereby phosphoric acid ions are recovered without being discharged out of the system. In addition, the discharged acetate ions can be used as a nutrient source for biological treatment.

In addition, such selective recovery of phosphate ions in the second anion exchange column can be achieved by using the second anion The electromagnetic valve of the exchange tower is used to switch the anion exchanger for ion-exchanging the drain water in the second anion exchange tower, so that it can be repeatedly implemented.

That is, as shown in the graph of the ion concentration of the wastewater discharged from the second drain pipe when the anion exchanger of the second anion exchange tower is switched at time points t2, t4, t6, and t8 shown in FIG. 3 , By switching the anion exchanger, pure water can be recovered during 0~t1, t2~t3, t4~t5, t6~t7, and at the time points of t2, t4, t6, t8, the anions saturated with phosphate ions can be exchanged Replace the phosphate ion with a new one, or use an alkaline aqueous solution to separate the phosphate ions from the anion exchange resin to recover the phosphate ions.

Here, during t1~t2, t3~t4, t5~t6, t7~t8, phosphate ions and acetate ions are discharged, but in this case, the drainage of the second storage tank does not flow into the discharge pipe, but Ion exchange is performed again in the secondary ion exchange tower, whereby phosphate ions can be recovered without being discharged to the outside of the system.

If the anion exchanger for the acid wastewater treatment in the first anion exchange tower is switched when the time e in Fig. 2 is reached, the above-mentioned series of treatments (0-t8) can be repeatedly implemented, and continuous treatment can be carried out without interrupting the treatment. drainage treatment.

In addition, in this embodiment, TOC and EC are set for confirmation, but the actual switching of the anion exchanger in the first anion exchange tower can be based on the ion concentration and flow rate of each ion in the wastewater measured in advance. Determine the amount of water. However, it is not limited to this method, and if necessary, the aforementioned switching time may be determined with reference to the values of EC and TOC. For example, it is also possible to keep the flow rate at a certain value in advance, judge the time b shown in Figure 2 according to the EC value of the first drain pipe, and then use a timer or the like to switch the first drain pipe before reaching the state of time e. In the anion exchange tower, the anion exchanger for ion-exchanging the drain water suppresses the flow of nitrate ions into the first storage tank or the second anion exchange tower.

In addition, similarly, the switching time of the anion exchanger in the second anion exchange tower can also be determined by a timer after the water flow is kept at a certain value.

In addition, the phosphate ions that have been ion-exchanged with the anion-exchange resin of the second anion-exchange tower can be contained in a high-concentration alkaline aqueous solution containing any metal ion in sodium, potassium, and magnesium in the above-mentioned resin. Phosphate is recovered in the form of phosphate aqueous solution. For example, an aqueous solution of sodium hydroxide, potassium hydroxide, magnesium hydroxide, etc. can also be used to regenerate the anion exchange resin, so that the phosphoric acid containing the detached phosphate ion and the above-mentioned metal ions can be recovered. recovered in the form of an aqueous solution of metal salts.

In this case, by using an alkaline aqueous solution containing a higher concentration of metal ions, the concentration of the phosphoric acid aqueous solution can be increased, and the costs for transporting the aqueous phosphate solution or drying and solidifying the phosphate can be reduced.

In addition, among the phosphates obtained in this way, as sodium phosphate, it is usually recovered in the form of a mixture of sodium dihydrogen phosphate and disodium hydrogen phosphate. By adjusting the pH of the aqueous sodium phosphate solution to be recovered, the sodium dihydrogen phosphate, phosphoric acid The content rate of disodium hydrogen or trisodium phosphate.

More specifically, by making the pH 4.3 to 4.9, it can be recovered as sodium dihydrogen phosphate, by making the pH 9.0 to 9.6, it can be recovered as disodium hydrogen phosphate, and by making the pH 11.5 to 12.5, it can be recovered as Trisodium phosphate is recovered as trisodium phosphate.

In particular, the amount of sodium hydroxide used in the recovery can be small, and from the viewpoint of being able to recover more cheaply and utilizing the recovered phosphoric acid as a food additive, it is preferable to use sodium dihydrogen phosphate and hydrogen phosphate recovered in the form of disodium.

In addition, since disodium hydrogen phosphate is easier to precipitate than sodium dihydrogen phosphate, it is preferable to recover phosphoric acid as sodium dihydrogen phosphate from the viewpoint that phosphoric acid can be recovered at a higher concentration.

That is, the recovery of the sodium phosphate aqueous solution is preferably carried out in a pH range of 4.3 to 4.9, and it is recovered as an aqueous solution of sodium dihydrogen phosphate.

In addition, in the recovery of disodium hydrogen phosphate and trisodium phosphate, the pH can be adjusted by adjusting the amount of sodium hydroxide added, etc., and then, when sodium hydroxide is more than the theoretical amount required to recover sodium phosphate, Regeneration of the anion exchange resin can be performed, so it is suitable.

In addition, similarly, among the phosphate salts obtained in the case of utilizing potassium hydroxide, the potassium phosphate salt can usually be recovered in the form of a mixture of potassium dihydrogen phosphate and dipotassium hydrogen phosphate, and by adjusting the concentration of the potassium phosphate aqueous solution to be recovered pH can increase the content of potassium dihydrogen phosphate, dipotassium hydrogen phosphate or tripotassium phosphate.

More specifically, by making the pH 4.4 to 4.9, it can be recovered as potassium dihydrogen phosphate, by making the pH 8.7 to 9.3, it can be recovered as dipotassium hydrogen phosphate, and by making the pH 11.5 to 12.5, It can be recovered as tripotassium phosphate.

In addition, in the recovery of sodium dihydrogen phosphate, as shown in FIG. 4, the regenerated liquid is temporarily stored in the recovery tank 100, and then, the pump 101 is used to introduce the above-mentioned regenerated liquid into the cation exchanger 103 to carry out sodium recovery. ion exchange. Thus, when the pH of the regeneration solution is lowered to a range of 4.3 to 4.9, by closing the solenoid valve 102 and terminating the cation exchange, the mixing of disodium hydrogen phosphate into the regeneration solution of the recovery tank 100 can be further suppressed, and the recovered The purity of the sodium dihydrogen phosphate aqueous solution is very high.

In such regeneration, it is possible to prevent contamination of impurities such as chlorine and sulfur in the sodium dihydrogen phosphate, compared with the case where the pH of the regeneration solution is in the range of 4.3 to 4.9 using hydrochloric acid, sulfuric acid and their salts.

Next, a second embodiment will be described based on FIG. 5 .

Compared with the above-mentioned first embodiment, this second embodiment does not have the first storage tank 13 and the second storage tank 23 provided in the first embodiment in the wastewater treatment device of the second embodiment, but the first The anion exchange tower 1 and the second anion exchange tower 2 are directly connected by pipes, and the drainage discharged from the second anion exchange tower 2 is directly discharged to the outside of the system through the drain pipe 5, which is different in these respects. In addition, means for recirculating the drain water from the first and second storage tanks, so-called first return pipe 14 and second return pipe 24 , are also not provided. That is, in the drainage treatment device of the second embodiment, the first drainage pipe 15 is directly connected to the connection pipe 4 , and the second drainage pipe 25 is directly connected to the drainage pipe 5 . However, the second embodiment differs from the above-mentioned first embodiment in that each of the two anion exchange towers of the first anion exchange tower 1 and the second anion exchange tower 2 has two anion exchangers. Are the same. In addition, it is the same at the point which can switch and use the two anion exchangers with which one anion exchange column is equipped. In addition, although not shown in the figure, a total organic carbon (TOC) detector is equipped in the water injection pipe 3, the first drain pipe 15, and the second drain pipe 25, and the first drain pipe 15 and the second drain pipe 25 is further equipped with an electrical conductivity (EC) measuring device for measuring the TOC and EC of the drainage flowing through the pipes for confirming the ions contained in the drainage flowing through each pipe; and by measuring the concentration of each ion in the drainage in advance, according to the The measurement value and the flow rate of the waste water to the ion exchange towers are calculated to switch the ion exchangers in the respective ion exchange towers, and these points are also the same as those of the waste water treatment apparatus of the first embodiment.

The wastewater treatment device of the second embodiment is further different from the first embodiment in that the anion exchangers of the first and second anion exchange towers can be backwashed with pure water. In addition, the anion exchange resin can be regenerated by passing an aqueous solution containing metal ions of sodium, potassium, and magnesium through the anion exchangers of the first and second anion exchange towers.

As the above-mentioned equipment for reverse washing, it is equipped with pure water tanks 16 and 26 for reverse washing that store pure water for reverse washing, and the pure water in the pure water tanks 16 and 26 for reverse washing is introduced into each anion exchanger 11, 12, 21, 22 in the reverse washing water inlet pipe 17a, 27a, and then used to discharge the reverse washing water discharge pipe 17b, 27b from each anion exchanger 11, 12, 21, 22, and store the The reverse washing pipes 17b, 27b are the reverse washing drain storage tanks 18, 28 of the reverse washing drain discharged from the respective anion exchangers 11, 12, 21, 22.

In addition, the above-mentioned reverse washing water inlet pipes 17a, 27a are connected to the downstream side (outlet side) of each anion exchanger 11, 12, 21, 22, and the above-mentioned reverse washing water discharge pipes 17b, 27b are connected to each anion exchanger. On the upstream side (water injection port side) of the devices 11, 12, 21, 22, washing water can be passed through each anion exchanger 11, 12, 21, 22 from the downstream side to the upstream side for washing.

In addition, as the above-mentioned regeneration equipment for the anion exchange resin, there are alkaline regeneration solution storage tanks 19, 29 which store an alkaline aqueous solution for regeneration of the ion-exchanged anion exchange resin; a pure water storage tank 110 , 210, which stores pure water, and the pure water is used for flushing the alkaline regeneration liquid remaining in each ion exchanger 11, 12, 21, 22 after the regeneration of the alkaline regeneration liquid; the regeneration liquid introduction pipe 111a, 211a, which guides the alkaline regeneration solution or pure water from these alkaline regeneration solution storage tanks 19, 29 and pure water storage tanks 110, 210 to each anion exchanger 11, 12, 21, 22; regeneration solution discharge pipe 111b, 211b, which is used to discharge alkaline regeneration liquid or pure water from each anion exchanger 11, 12, 21, 22; regeneration drainage storage tank 112, 212, which stores the water from each anion exchanger through the regeneration liquid discharge pipe 111b, 211b 11, 12, 21, 22 discharged alkaline regeneration liquid or pure water.

In addition, the regeneration liquid introduction pipes 111a, 211a are connected to the upstream side (water injection port side) of each anion exchanger 11, 12, 21, 22, and the regeneration liquid discharge pipes 111b, 211b are connected to each anion exchanger 11. , 12, 21, 22 on the downstream side (outlet side), in each anion exchanger 11, 12, 21, 22, regeneration liquid or pure water can be circulated from the upstream side to the downstream side, and the regeneration liquid is used for the anion exchanger. The anion exchange resin is regenerated, or the regenerated solution in the anion exchanger is washed with pure water.

Next, the following method will be described by taking an aqueous solution of sodium hydroxide as an alkaline regeneration solution as an example. This method is produced by washing an etched liquid crystal substrate with pure water using such a wastewater treatment device. A method of ion-exchanging acidic wastewater with anion-exchange resin, and at the same time regenerating the phosphate ions ion-exchanged by the anion-exchange resin with alkaline regeneration solution to recover phosphate.

Here, the procedure up to saturating the anion exchanger 21 of the second anion exchange column 2 with phosphoric acid ions is the same as in the first embodiment, except that the following steps are not performed. The drainage discharged from the first and second anion exchange towers is temporarily stored in the first storage tank 13 or the second storage tank 23; backflow in the tube.

Under the situation that an anion exchanger 21 of this second anion exchange tower 2 is saturated by phosphoric acid ion, by closing the electromagnetic valve that is arranged on the water inlet side of this saturated anion exchanger 21, drain outlet side place, open simultaneously The solenoid valves on the water injection port side and the drain port side of the other anion exchanger 22 can switch the flow path of the drain water introduced from the connecting pipe 4 to another anion exchanger 22, and continue ion exchange with this anion exchanger 22. Then, in the anion exchanger 21 saturated with phosphoric acid ions, open the electromagnetic valve provided at the reverse washing pipe 27a and the reverse washing water discharge pipe 27b, and operate the pump provided in the reverse washing pure water tank 26. , open the solenoid valve at the outlet of the pump to supply pure water for reverse washing in the anion exchanger 21, and discharge the drain remaining in the anion exchanger 21, and store it in the reverse washing drainage storage tank 28.

After the reverse washing is completed, stop the pump of the pure water tank 26 for reverse washing, close the electromagnetic valve at the outlet of the pump and the electromagnetic valves of the two pipes of the reverse washing pipe 27a and the reverse washing water discharge pipe 27b, and regenerate the alkaline While the pump of the liquid storage tank 29 is running, open the electromagnetic valve that is arranged on the outlet of the pump, the electromagnetic valve of the regeneration liquid introduction pipe 211a, and the electromagnetic valve of the regeneration liquid discharge pipe 211b, and the sodium hydroxide aqueous solution is introduced into the anion through the regeneration liquid introduction pipe 211a. In the switch 21. Then, the anion exchange resin of the anion exchanger 21 is regenerated, and at the same time, the phosphate ions ion-exchanged with the anion exchange resin are detached, and discharged from the anion exchanger 21 through the regeneration liquid discharge pipe 211b in the form of sodium phosphate, Store in the regeneration drainage storage tank 212 in the form of sodium phosphate aqueous solution.

After the regeneration of the anion exchange resin is completed, stop the pump of the alkaline regeneration solution storage tank 29, close the solenoid valve arranged at the outlet of the pump, instead, open the pump installed at the outlet of the pure water storage tank 210 while running. The solenoid valve at the outlet of the pump introduces pure water into the anion exchanger 21. Then, the sodium hydroxide aqueous solution remaining in the anion exchanger 21 is discharged, the state (initial state) before ion exchange of phosphate ions occurs in the anion exchanger 21 is restored, and the pump of the pure water storage tank 210 is stopped. Then, the solenoid valve provided at the pump outlet of the pure water storage tank 210, and the solenoid valves provided at each of the regeneration liquid introduction pipe 211a and the regeneration liquid discharge pipe 211b are closed. In addition, the sodium hydroxide aqueous solution discharged from the anion exchanger 21 is also stored in the regeneration waste water storage tank 212 through the regeneration liquid discharge pipe 211b using this pure water.

As described above, since the ion exchange of phosphoric acid ions is performed by the other anion exchanger 22 during the regeneration of this anion exchanger 21, the treatment of acidic wastewater can be continuously performed without interruption.

In addition, the regeneration of the anion exchanger 21 ends when all the anion exchange resins are regenerated with aqueous sodium hydroxide solution, but whether all the anion exchange resins are regenerated by aqueous sodium hydroxide solution can be determined according to the ion exchange capacity of the anion exchange resin and the regeneration The concentration and amount of the sodium hydroxide aqueous solution used are determined.

In addition, when the anion exchange resin of the anion exchanger 21 is regenerated with an aqueous solution of sodium hydroxide, such a method can also be adopted: by measuring the temperature of the aqueous sodium hydroxide solution (aqueous sodium phosphate solution) discharged from the anion exchanger 21, the The state of regeneration of the anion exchange resin in the anion exchanger 21 is judged in more detail. That is, due to the sodium hydroxide aqueous solution, an exothermic reaction occurs when phosphate ions are detached from the anion exchange resin, so the temperature of the sodium hydroxide aqueous solution discharged from the anion exchanger 21 rises, but quickly, as the phosphate ions are released from the anion exchange resin The anion exchange resin detaches, and the temperature of the sodium hydroxide aqueous solution discharged from the anion exchanger 21 falls. Therefore, by measuring the temperature of the aqueous sodium hydroxide solution discharged from the anion exchanger 21, the state of regeneration of the anion exchange resin in the anion exchanger 21 can be determined in more detail.

For measuring the temperature of the aqueous sodium hydroxide solution discharged from the anion exchanger 21 , a thermocouple or the like may be installed at the regeneration liquid discharge pipe 211 b immediately after the outlet of the anion exchanger 21 . As a temperature measuring device used for this temperature measurement, generally, as long as the accuracy is about 0.1K, it can be used for judging the regeneration of the anion exchange resin.

In addition, when the anion exchange resin of the other anion exchanger 22 is saturated with phosphate ion, recovery of sodium phosphate can be performed similarly.

Furthermore, in this second embodiment, since the first anion exchange tower 1 is also equipped with equipment for reverse washing and anion exchange resin regeneration, the case where the anion exchanger of the first anion exchange tower 1 is saturated with nitrate ions Also similar to the case where the anion exchanger of the second anion exchange column 2 is saturated with phosphoric acid ions, the regeneration of the anion exchanger may be performed simultaneously with the acid waste water treatment. In addition, the sodium nitrate aqueous solution stored in the regenerated waste water storage tank 112 by regeneration of the anion exchange resin of this 1st anion exchange tower 1 is discarded by another route. In addition, in this disposal treatment, it is preferable to concentrate the sodium nitrate aqueous solution by evaporative concentration or the like, which can reduce the volume of the object to be treated.

In addition, in the above-mentioned first and second embodiments, although the acidic drainage generated by washing the liquid crystal substrate etched with an etching solution with pure water is used for drainage treatment, this drainage treatment method has the advantage that the discharged water Except for nitrate ions, phosphate ions, and acetate ions, substantially free of floating matter and cations, etc., the discharged discharge water can be reused as pure water until acetate ions are discharged from the discharge pipe, but in the present invention It is not limited to acidic drainage generated by washing such a liquid crystal substrate.

In addition, in acidic waste water, waste water containing nitrate ions, which are ions that are more easily ion-exchanged with anion exchange resins than phosphate ions, is used. Drainage of ions and iodide ions.

Furthermore, in terms of being able to more reliably suppress the introduction of nitrate ions into the second anion tower, and when reusing the discharge water of the second anion exchange tower as pure water, the mixing of acetate ions can be suppressed. The ion concentration of each ion contained in the wastewater is measured in advance, and the treatment water volume or treatment time of switching the anion exchanger in the first anion exchange tower is obtained based on the value of the ion concentration measured above and the amount of anion exchange resin However, it is also possible to use a TOC measuring device or an EC measuring device to determine without prior ion concentration measurement. If necessary, a pH meter can also be used to measure pH to determine the ion status of the drainage at this point.

In addition, as the anion exchange resin, any of weakly basic anion exchange resins and strongly basic anion exchange resins can be used.

In addition, from the viewpoint of preventing the interruption of wastewater treatment, the method of using two anion exchangers in each of the first and second anion exchange towers has been adopted, but in the present invention, one anion exchanger can also be used, Drainage treatment using a batch treatment method is adopted. In addition, it can also be implemented using three or more anion exchangers.

Furthermore, the anion exchange tower is not limited to two towers, but may be a multi-stage tower having two or more towers.

If necessary, after removing ions with higher ion selectivity than phosphate ions in advance using a single ion exchange column, the anion exchange resin of the anion exchange column may be regenerated, and then ion exchange of phosphate ions may be performed.

The number and size of these anion exchangers and anion exchange towers can be appropriately changed according to the amount of wastewater to be treated.

In addition, when anion exchange resins are installed in more stages, only phosphate ions can be recovered more reliably.

In addition, although a solenoid valve is used to switch the drain flow path, in the present invention, not only the solenoid valve but also a device for switching a general flow path may be used, and such a device may not be used.

In addition, if necessary, a cation exchanger for cation-exchanging the wastewater in advance, a membrane separation device for removing floating particles, etc. can also be equipped for wastewater treatment.

When the above-mentioned cation exchange resin is used, cations such as aluminum ions, titanium ions, indium ions, and molybdenum ions can be removed.

In addition, although phosphate ions were recovered as sodium phosphate salt or the like, in the present invention, recovery of phosphate ions is not limited to such recovery.

In addition, salts such as sodium phosphate salt can be recovered by precipitation reaction, which is preferable from the viewpoint of easy recovery.

Example

Hereinafter, examples are given to illustrate the present invention in more detail, but the present invention is not limited to these examples.

Example 1

<Wastewater treatment and recovery of sodium phosphate>

In the first and second anion exchange towers, "Rebachitto MP62WS" of Bayer Chemical Co., Ltd. is respectively arranged as an anion exchange resin, and the respective superficial velocity SV=(treatment amount/resin amount)=10[1/h], as For the wastewater to be treated, make the acidic wastewater containing 300ppm phosphate ions, 25ppm acetate ions, and 8ppm nitrate ions pass through the first and second anion exchange towers continuously at a flow rate of 3L/min, then wash with pure water, and then use 2 times the equivalent The 10wt% sodium hydroxide aqueous solution is regenerated to obtain the sodium phosphate aqueous solution.

<result>

Through the above recovery, 80% or more of the phosphate ions in the wastewater can be recovered in the form of an 8 wt% sodium phosphate salt solution. In addition, the above-mentioned sodium phosphate salt was analyzed by ion chromatography, and the molar ratio of phosphorus to sodium was measured, and the result was almost 1.5, thus confirming that the recovered sodium phosphate salt was a mixture of sodium dihydrogen phosphate and disodium hydrogen phosphate.

Furthermore, the regenerated solution was stored in a regenerated tank, and ion exchange was carried out using a circulation pump, "650C-H" from Dow Chemical Karls Co., Ltd. as a cation exchange resin. When the pH reached 4.5, the circulation pump was stopped, and the recovered The above-mentioned sodium phosphate salt was analyzed by ion chromatography, and the molar ratio of phosphorus to sodium was measured, and the result was almost 1, thus confirming that the sodium phosphate salt can be recovered in the state of sodium dihydrogen phosphate.

Example 2

<Wastewater treatment and recovery of sodium phosphate>

Wastewater treatment and recovery of sodium phosphate were performed in the same manner as in Example 1 except that the aqueous sodium hydroxide solution used for regeneration was 25 wt %.

<result>

Through the above recovery, 80% or more of the phosphate ions in the wastewater can be recovered in the form of a 15 wt% sodium phosphate salt solution.

In addition, in the same manner as above, the regenerated solution was contacted with the cation exchange resin to form a sodium phosphate salt with a pH of 4.5, which was analyzed by ion chromatography, and the molar ratio of phosphorus to sodium was measured. The result was basically 1, thus confirming that the recovered Sodium phosphate is sodium dihydrogen phosphate.

Example 3

<Wastewater treatment and recovery of sodium phosphate>

Wastewater treatment and recovery of sodium phosphate were performed in the same manner as in Example 1 except that the aqueous sodium hydroxide solution used for regeneration was 40 wt %.

<result>

By the recovery described above, the phosphate ions in the waste water can be recovered as a 17 wt % sodium phosphate salt solution.

However, it was observed that the ion exchange resin reached 70 to 80° C. due to the heat generation when adding sodium hydroxide, and disodium hydrogen phosphate was very easily precipitated.

Example 4

<Wastewater Treatment and Recovery of Potassium Phosphate>

Recovery was performed in the same manner as in Example 1, except that potassium hydroxide was used instead of sodium hydroxide, and the concentration was 20 wt %, 2.5 times the equivalent for regeneration treatment.

<result>

Through the above recovery, about 80% of the phosphate ions in the wastewater can be recovered in the form of a 15 wt% potassium phosphate aqueous solution.

In addition, when the obtained potassium phosphate salt was analyzed by ion chromatography, and the molar ratio of phosphoric acid to potassium (potassium/phosphoric acid) was measured, it was 2 or more.

Claims (21)

1. A wastewater treatment method is a wastewater treatment method that reclaims phosphoric acid ions from wastewater containing at least one ion selected from nitrate ions, sulfate ions, iodide ions and phosphoric acid ions, characterized in that, in an acidic state Next, make the drainage contact with the anion exchange resin, ion-exchange the ions in the nitrate ions, sulfate ions, and iodide ions contained in the above drainage, and then contact the anion exchange resin again, so that the phosphate ions and the anion exchange resin are ion-exchanged, to recover phosphate ions. 2. The wastewater treatment method according to claim 1, wherein the phosphate ion concentration of the wastewater is 1% or less. 3. The wastewater treatment method according to claim 1, characterized in that, the wastewater is continuously contacted with the anion exchange resin by passing the wastewater through the anion exchange resin arranged in multiple stages, so that the phosphoric acid ion and the anion exchange resin arranged in the second stage or The subsequent anion exchange resin performs ion exchange. 4. The wastewater treatment method according to claim 3, wherein the ion concentration of each ion contained in the wastewater is measured before the wastewater is brought into contact with the anion exchange resins arranged in multiple stages. 5. The wastewater treatment method according to claim 1, wherein the wastewater is acidic wastewater produced by washing a liquid crystal substrate etched with an etchant containing nitric acid and phosphoric acid and washing it with pure water. 6. The wastewater treatment method according to claim 5, wherein the acidic wastewater generated by washing the liquid crystal substrate with an etching solution containing nitric acid and phosphoric acid with pure water passes through an anion exchange resin arranged in multiple stages. , making the waste water continuously contact with the above-mentioned anion exchange resin, and measuring the total organic carbon concentration of the waste water introduced from the upstream side of the anion exchange resin arranged in the second stage or later and the waste water discharged from the downstream side Simultaneously with conductivity, phosphate ions are ion-exchanged. 7. The wastewater treatment method according to claim 3, wherein the wastewater is acidic wastewater produced by washing a liquid crystal substrate etched with an etchant containing nitric acid and phosphoric acid and washing it with pure water. 8. The wastewater treatment method according to claim 7, characterized in that, the acidic wastewater generated by washing the liquid crystal substrate with etching solution containing nitric acid and phosphoric acid with pure water passes through the anion exchange resins arranged in multiple stages. , making the waste water continuously contact with the above-mentioned anion exchange resin, and measuring the total organic carbon concentration of the waste water introduced from the upstream side of the anion exchange resin arranged in the second stage or later and the waste water discharged from the downstream side Simultaneously with conductivity, phosphate ions are ion-exchanged. 9. The wastewater treatment method according to claim 4, wherein the wastewater is acidic wastewater produced by washing a liquid crystal substrate etched with an etchant containing nitric acid and phosphoric acid and washing it with pure water. 10. The wastewater treatment method according to claim 9, wherein the acidic wastewater generated by washing the liquid crystal substrate with etching solution containing nitric acid and phosphoric acid with pure water passes through the anion exchange resins arranged in multiple stages. , making the waste water continuously contact with the above-mentioned anion exchange resin, and measuring the total organic carbon concentration of the waste water introduced from the upstream side of the anion exchange resin arranged in the second stage or later and the waste water discharged from the downstream side Simultaneously with conductivity, phosphate ions are ion-exchanged. 11. The wastewater treatment method according to any one of claims 1 to 10, characterized in that, after phosphate ions and anion exchange resins are ion-exchanged, any one containing sodium ions, potassium ions and magnesium ions The alkaline aqueous solution of the metal ions is brought into contact with the above-mentioned anion exchange resin, so that the phosphoric acid ions are released from the above-mentioned anion exchange resin and recovered as a phosphate metal salt aqueous solution. 12. The wastewater treatment method according to claim 11, wherein phosphate ions are recovered as a sodium phosphate aqueous solution by using an alkaline aqueous solution containing sodium ions as the alkaline aqueous solution. 13. The wastewater treatment method according to claim 12, wherein the recovery is performed while adjusting the pH of the aqueous sodium phosphate solution. 14. The wastewater treatment method according to claim 11, wherein an alkaline aqueous solution containing potassium ions is used as the alkaline aqueous solution to recover phosphate ions as an aqueous potassium phosphate solution. 15. The wastewater treatment method according to claim 14, wherein the recovery is performed while adjusting the pH of the potassium phosphate aqueous solution. 16. A wastewater treatment device for recovering phosphate ions from wastewater containing at least one ion selected from nitrate ions, sulfate ions, and iodide ions, and phosphate ions in an acidic state, wherein: Two or more anion exchangers equipped with anion exchange resins are arranged in series in order to allow the above-mentioned waste water to pass through and perform anion exchange twice or more. 17. The waste water treatment device according to claim 16, which recovers phosphate ions from said waste water containing phosphate ions at a concentration of 1% or less. 18. The wastewater treatment device according to claim 16, wherein the device is used for treating acidic wastewater generated by etching liquid crystal substrates treated with an etchant containing nitric acid and phosphoric acid and washing them with pure water. 19. The wastewater treatment device as claimed in claim 18, characterized in that, at the upstream side and downstream side of at least one anion exchanger among the anion exchangers implementing the second or later anion exchange, further equipment There are a total organic carbon concentration measuring device and a conductivity meter for measuring the total organic carbon concentration and conductivity of the above-mentioned wastewater. 20. The wastewater treatment device according to any one of claims 16 to 19, wherein at least one of the anion exchangers performing the second or subsequent anion exchange is configured so that After passing through and performing anion exchange, the waste water may be brought into contact with an alkaline aqueous solution containing any one of metal ions including sodium ions, potassium ions, and magnesium ions and allowed to pass through. 21. The wastewater treatment device according to claim 20, wherein at least one anion exchanger among the anion exchangers performing anion exchange for the second time or later is configured such that after the above-mentioned wastewater is passed through and After anion exchange, it can be contacted with an alkaline aqueous solution containing any metal ion of sodium ion, potassium ion and magnesium ion and passed through, and a temperature measuring device is further provided so that the temperature of the above-mentioned alkaline aqueous solution after passing can be measured. temperature.

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