JPS59222291A - Treatment of waste water - Google Patents

Abstract

PURPOSE:To simplify operation for regenerating adsorbing resins and to shorten the time for regeneration by passing waste water contg. boron and COD component through a salt type resin bed for selective adsorption for salt type boron in the fore stage and a resin bed for selective adsorption of free boron in series. CONSTITUTION:Waste water 1 of stack gas desulphurization is in the first stage through a fore stage ion exchange tower 6 packed with resin 2 for selecive adsorption for salt type boron. In this stage, there is no necessity for the waste water 1 to adjust its pH; the waste water is passed as it is used. Only the COD component in the waste water 1 is removed by exchanging ions by the resin 2 for selective adsorption for salt type boron in the ion exchange tower 6. Further, discharged water 3 is passed through a succeeding ion exchange tower 7 packed with the resin 4 for selective adsorption for free boron without performing adjustment of pH. Boron is removed by the ion exchange with the resin 4 in the ion exchange tower 7.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating wastewater containing boron and OOD components discharged from a flue gas desulfurization process.

To prevent air pollution, the combustion gases generated when coal and oil are burned are led to a flue gas desulfurization system, treated, and then released. This flue gas desulfurization equipment brings combustion gas into contact with an absorbent or absorbent to remove pollutants that cause air pollution, but in this process wastewater containing boron and OOD components (hereinafter referred to as flue gas desulfurization wastewater) is discharged. The boron in this flue gas desulfurization wastewater is mainly boric acid, boron heptadide, etc., and the OOD components are mainly sulfur oxides, but these cannot be treated by coagulation, f-filtration, activated carbon biological treatment, ozone oxidation, etc. Even if this is done, it still contains tens to hundreds of ppm, and it is not desirable from the viewpoint of pollution prevention to discharge it directly into rivers or the like.

Therefore, as one method for treating such flue gas desulfurization wastewater, a treatment method using a weakly basic anion exchange resin has been proposed.

That is, in this treatment method, the liquid passing step saturates the flue gas desulfurization wastewater with alkali to bring the pH to 9, then adjusts the pH of the effluent to 7 or more, and then injects salt form (S04 form) weakly basic anions. The liquid is passed through an exchange resin bed to exchange adsorb and remove COD components. On the other hand, in the regeneration process of the weakly basic anion exchange resin bed whose function has deteriorated due to the liquid passage process, the anion exchange resin bed is a free form weak base that has exchanged and adsorbed boron. An alkali is passed through each of the acid anion exchange resin beds, and a new acid or waste liquid discharged from the free weak base anion exchange resin bed is passed through the salt weak base anion exchange resin bed, and a new alkali is passed through the bed. Alternatively, the waste liquid discharged from the salt-form weakly basic anion-exchange resin bed was passed through the free-form weakly basic anion-exchange resin bed for regeneration.

As described above, in the conventional treatment method using a weakly basic anion exchange resin, it is necessary to adjust the pH of flue gas desulfurization wastewater using an acid and an alkali in the liquid passage step, and an operation in which an acid or alkali is used in the regeneration step. After passing through the resin to remove boron or OOD components, it is necessary to pass through the resin with an alkali or acid to convert the weakly basic anion exchange resin into a free form or a salt form, and the process of passing through the resin and regenerating it is extremely complicated. there were.

Therefore, the present inventors conducted intensive studies on a treatment method using an ion exchange resin for flue gas desulfurization wastewater with the aim of solving the drawbacks of the treatment method using a weakly basic anion exchange resin. The present invention was achieved by discovering that it not only has excellent OOD component removal ability but also has excellent OOD component removal ability.

That is, the present invention provides a wastewater treatment method characterized by passing wastewater containing boron and COD components in series through a topographical boron selective adsorption resin bed in the first stage and a free boron selective adsorption resin bed in the second stage. To regenerate a boron selective adsorption resin bed whose function has deteriorated due to passing wastewater, an alkaline solution is passed through the salt form boron selective adsorption resin bed in the previous stage to regenerate it into a free boron selective adsorption resin bed, and then to regenerate it into a free boron selective adsorption resin bed. Free form boron is selectively adsorbed by passing the mineral acid solution through the Mw oil bed to regenerate the salt form boron selectively adsorbing resin bed, and the next time the liquid is passed, the salt form boron selectively adsorbing resin bed after the regeneration is placed in the front stage, and the free form boron is selectively adsorbed. The gist of the present invention is a method for treating wastewater, which is characterized in that the process is carried out using a resin bed that selectively adsorbs boron.

The present invention will be explained in detail below.

Flue gas desulfurization wastewater contains a large amount of suspended solids, metal salts, organic substances, etc., and its pH is about 2 to A. Before passing it through the ion exchange tower, it is pre-coagulated, e-filtered, activated carbon, and biological. Remove contaminants and contaminants that can be removed by conventional treatment methods such as treatment, ozone oxidation, etc. The flue gas desulfurization wastewater subjected to such pretreatment is passed through an ion exchange tower as follows. FIG. 7 is an explanatory diagram showing an example of the embodiment of the present invention. Flue gas desulfurization wastewater/skeletons are first passed through the ion exchange tower B filled with salt-type boron selective adsorption resin. At this time, there is no need to adjust the pH of the flue gas desulfurization wastewater and it is passed through as is. In the ion exchange tower 6, O in the flue gas desulfurization wastewater is removed by the salt-type boron selective adsorption resin λ.
Only the OD component is ion-exchanged and removed.

In other words, the reason why the COD component in the flue gas desulfurization wastewater exhibits ion exchange properties with respect to the salt-form boron selective adsorption resin is unknown, but the OOD component and boron selectivity of the salt-form boron selective adsorption resin are OOD Since the components are much larger, only the 00D component is ion-exchanged, and the boron flows out together with the effluent water 3. In addition, the effluent water 3 contains acid components such as ion-exchanged SO, OL, etc., so the pH is usually
-! It is about r.

Next, the effluent water 3 is passed through the ion exchange column 7 filled with a free boron selective adsorption resin at the subsequent stage without adjusting the pH value. In the ion exchange tower 7, boron is ion-exchanged and removed by the free boron selective adsorption resin. In other words, the free boron selective adsorption resin has a strong selective adsorption ability for boron, but the lower the pH of the effluent water 3, the more its selectivity increases; Since the pH is 1 d lower, boron is efficiently ion-exchanged and removed. At that time, p
Since acid components such as so, -, and B-' are also neutralized, the treated water S becomes nearly neutral and can be discharged into the river as it is. The flow rate of the flue gas desulfurization waste water in the liquid flow step may be approximately 25 hr-' from the left of the SV for both ion exchange towers B and 7.

In the above-mentioned liquid passage process, the boron selective resin in the topography of ion exchange tower B becomes saturated with COD components and the ion exchange capacity decreases, and when leakage of COD components into the treated water is detected, the liquid passage is stopped. The regeneration process is performed as follows. First, the regenerant-adherent resin is backwashed and allowed to settle. Then, a regenerant is passed through it. Filled with salt-form boron selective adsorption resin 00D
An alkaline solution is passed through the ion exchange tower B as a regenerating agent to remove the ion-exchanged COD components and convert them into free form, that is, OH form. The alkaline solution of the rejuvenating agent contains an alkali such as potassium hydroxide or sodium hydroxide at a concentration of 7 to 7 g, and the regeneration level is i, to ~/AO.
I-alka+)/It-resin is administered at SV for about 2 to 6 hr'.

A mineral acid solution is passed through the ion exchange column 7 filled with unselected free boron resin and boron is ion-exchanged as a regenerating agent to remove the ion-exchanged boron and convert it into salt form, i.e., SO,
Make it into a type, Ol type, etc.

The mineral acid solution used as a regenerant is a mineral acid such as hydrochloric acid or sulfuric acid whose concentration is 0.
．． ! -, 2 left heavy tt 'Z, playback level 10~! i
'OOg-mineral acid/l-resin S V 2~A hr-'
Administer the medicine in moderation.

After passing the regenerant, clean water, industrial water, etc. is passed through each ion exchange tower to extrude and wash the regenerant.

After such a regeneration process, the boron-unselected adsorption resin y in the ion exchange tower B changes from the salt form to the free form, and the boron selection resin y in the ion exchange tower 7 changes from the free form to the salt form. In the water process, the water passing process is performed again with the ion exchange tower 7 in the first stage and the ion exchange tower 6 in the latter stage. When the function deteriorates, an alkaline solution is added to the ion exchange tower 7.
A regeneration process is performed by passing a mineral acid solution through the ion exchange tower 6,
Thereafter, the liquid passing step and regeneration step are performed in the same manner.

Since the regenerated waste liquid discharged in the regeneration step contains a large amount of boron and 00D components, it is treated by evaporation concentration, wet combustion, etc.

As explained above, the present invention uses a salt-type boron selective adsorption resin bed in the first stage and a free-type boron selective adsorption resin bed in the latter stage, and performs a flow process without adjusting the pH of flue gas desulfurization wastewater. In addition, in the regeneration process, the salt-form boron selective adsorption resin bed in the first stage is regenerated into the free form, and the subsequent free-form boron selective adsorption resin bed is regenerated into the salt form. The above-mentioned liquid passing step and regeneration step are alternately repeated by using the first stage as the first stage and the first stage as the second stage. The pH adjustment step for adjusting the pH of flue gas desulfurization wastewater in the process can be omitted, and there is also a step of passing a mineral acid solution in the regeneration step to convert the free weakly basic anion exchange resin into a salt form. Since the step of passing an alkaline solution through which the salt-type weakly basic anion exchange resin is made into a free form can be omitted, the regeneration operation can be simplified, the regeneration time can be shortened, and the amount of regenerant used can be reduced. It can be lowered to a large width.

The boron selective adsorption resin used in the present invention is a polymer compound obtained by chloromethylating a copolymer of styrene and divinylbenzene and reacting it with methylsorbitylamine, and N-methylglucamine is used as an exchange group. have

Amberlight (registered trademark) RA-7? J, Diaion (Mitsubishi Chemical Industries, Ltd., registered trademark) ORB-0,
2 or equivalents can be used.

The present invention will be explained below using Examples and Comparative Examples.

Example Glass columns A and B with an inner diameter of 1000H and a height of 1000H were each filled with 2 goml of the boron selective adsorption resin Diaion (Mitsubishi Chemical Corporation, registered trademark) ORBo, and column A was filled with 10% S V iAr of sulfuric acid SOθml
hr-, and a salt form (S04 form) boron selective adsorption resin bed was prepared.

On the other hand, 500 ml of g-modified sodium hydroxide was passed through the force ram B at 8 V and 2j hr-' to form a free form (OR type).
A selective boron adsorption resin bed was used. Tap water was passed through each column to extrude the drug, and after washing, the flue gas desulfurization wastewater having the composition shown in SV/0''' was passed in order from column A to column B. From column B. Outflow treated water OO
The leakage concentration curve of component D, boron, was as shown in Figure 1.

COD concentration of treated water from column B! When it exceeded i ppm, the flow of liquid was stopped and regeneration was performed. After the liquid flow was stopped, tap water was passed through the column to backwash columns A and B, and then the column was allowed to settle.

Next, add 75ml of sodium hydroxide to column A.
ff S V , 2 J hr' to remove the COD component and regenerate it into a free form.

On the other hand, in column B, add 10qlr sulfuric acid,
The solution was passed through the solution at Jhr-' to eliminate boron and regenerate it into a salt form.

Tap water was passed through the drug-passing descendant column to extrude and wash the drug, and then the flue gas desulfurization wastewater was passed through again. So this time, the table -/
Flue gas desulfurization wastewater was passed from column B to column A in this order. COD components of the treated water flowing out from column A at that time,
The boron leakage concentration curve was almost the same as the previous time.

In Figure 1, the vertical axis shows the leakage concentration (ppm), the horizontal axis shows the treated water cap (ml), and in the figure, / shows the COD component, and here shows the leakage concentration curve of boron.

11 - Table - Comparative Example Using the column used in the example, liquid was passed from the free resin bed to the salt resin bed in order of the conventional method using a weakly basic anion exchange resin and compared with the example. Same conditions as the example,
By the same operation, column A was made into a salt-form (S04 form) boron selective adsorption resin bed, and column B was made into a free-form (OH form) boron selective adsorption resin bed. Tap water was passed through each column to extrude and wash the chemicals, and then flue gas desulfurization wastewater having the composition shown in Table 1 was passed in order from column B to column A under the same conditions as in the example.

COD components of treated water flowing out from column A and 12- The leaked boron concentration curve was as shown in Figure 3.

In the figure, 37 shows the OOD component, and 32 shows the concentration curve of boron.
Because the salt-form boron selective adsorption resin bed in the sample was partially converted into a free-form boron selective adsorption resin bed, the leakage concentration of OOD components increased significantly.

[Brief explanation of the drawing]

Figure - / is an explanatory diagram showing the flow of an example of the embodiment of the present invention. - Boron selective adsorption resin j... Treated water, 6... Ion exchange tower... Indicates an ion exchange tower. Figure 1 shows C when flue gas desulfurization wastewater is treated using the method of the present invention.
It is a leakage concentration curve of OD component and boron, and in the figure, 1:ll...-00D component, -1...-boron are shown. Figure 3 shows leakage concentration curves of OOD components and boron when flue gas desulfurization wastewater is treated according to the conventional liquid flow order. . Applicant: Nippon Rensui Co., Ltd. Agent: Patent attorney Mr. Hase - 7 others Figure-1

Claims (2)

[Claims] (1) A method for treating wastewater, which comprises passing wastewater containing boron and COD components in series through a resin bed for selective adsorption of salt boron in the first stage and a resin bed for selective adsorption of free boron in the latter stage. (2) Wastewater containing boron and OOD components is passed in series through a salt-form boron selective adsorption resin bed in the first stage and a free-form boron selective adsorption resin bed in the latter stage, and selective adsorption of boron whose function has decreased due to the passage of the wastewater. To regenerate the resin bed, an alkaline solution is passed through the resin bed that selectively adsorbs salt-form boron in the first stage to transfer it to the resin bed that selectively adsorbs free boron, and a mineral acid bath is applied to the resin bed that selectively adsorbs free boron in the latter stage. The solution is passed through to regenerate the salt form boron selective adsorption resin bed, and the next time the liquid is passed, the topographical boron selective adsorption resin bed after the regeneration is placed in the first stage and the free form boron selective adsorption resin bed is placed in the second stage. Characteristic wastewater treatment method.