JP3225655B2 - Waste paper deinking pulp wastewater treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating wastepaper deinked pulp wastewater. More specifically, in a method for treating deinked pulp (hereinafter, sometimes referred to as DIP) wastewater of used printing paper, in the method of selecting, dewatering,
Separately from the wastewater from the concentration and washing processes, the floss in the flotation process (Floss, foam containing ink and carbon particles floated and separated by the flotation machine) is treated independently using the pressure flotation method. In particular, the present invention relates to a method for treating wastewater in a DIP manufacturing process for efficiently removing suspended substances (hereinafter referred to as SS) in wastewater.

[0002]

2. Description of the Related Art Conventionally, from the viewpoint of effective use of waste resources, deinking treatment of used printing paper such as newsprint, medium-quality paper, high-quality paper, and coated paper has been widely performed. As a method,
As is well known, waste paper is disintegrated into pulp by a disintegrator with mechanical disintegration such as pulper, and foreign matter is removed and selected by a dust removing device such as a screen and a cleaner, and bleached with peroxide as necessary. Later, further flotation machine (flotator)
, To remove fine carbon and other ink components, and then to wash and dewater to perform deinking.

[0003] Furthermore, combining a flotation step before and after the bleaching step, and performing a kneading (kneading) treatment in the middle of a series of steps are already practiced as known methods.
On the other hand, in the wastewater subjected to the mechanical treatment and the chemical treatment, in addition to carbon and other ink components contained in the waste paper, fillers such as clay, talc and titanium dioxide,
Paper strength enhancers such as starch and polyvinyl alcohol, coating compositions such as latex, oxidized starch and calcium carbonate, and fine fibers are suspended therein. Since the SS in this wastewater reaches 2000 to 4000 ppm, it needs to be clarified before being discharged into public water bodies.

Conventionally, DIP wastewater is used alone or mixed with kraft wastewater and papermaking wastewater, and after adding an inorganic flocculant such as aluminum sulfate and an organic polymer flocculant such as polyacrylamide to the wastewater, a suitable separating apparatus is used. However, in this treatment method, it takes a long time to flocculate SS and fine SS still remains in the treated water. It is treated by appropriately combining known treatment steps such as (simple precipitation, no chemical injection), coagulation (coagulation sedimentation), pressure flotation, and activated sludge.

[0005] Therefore, in order to achieve the desired processing efficiency, there is a problem that it is necessary to increase the size of the apparatus and / or increase the amount of processing chemicals in order to allow a margin for each process. To solve these problems, wastewater treated waste paper is passed through an ion-exchange resin layer to obtain SS, COD (chemical oxygen demand) and BOD (biochemical oxygen demand).
Advanced treatment method for adsorbing components (JP-A-51-1556)
No. 2) A method of electrolyzing deinked wastewater using an aluminum electrode, separating the generated flocs, and adding an oxidizing agent to the treated water to decompose and remove the remaining fine components (Japanese Unexamined Patent Publication No.
2-51754), wastewater pulp production wastewater with high pH
And a method in which the filtrate is treated with an ultrafiltration membrane at a high temperature to reuse the permeate (Japanese Patent Application Laid-Open No. 58-143883), a method in which calcium soap is added to waste paper wastewater, and the printing ink particles are separated ( Japanese Patent Application Laid-Open No. Sho 54-110652, a method of oxidizing a high-quality waste paper treating solution with an oxidizing agent, adding a ferric salt to cause coagulation and sedimentation under weak alkalinity (Japanese Patent Application Laid-Open No. Sho.
8-70883), and waste paper wastewater is introduced into a three-phase flow-type wastewater treatment device having a fluid carrier ascending flow region, a descending flow region and a diffuser pipe in the lower part of the tank, and subjected to aerobic biological treatment. ,
Although a method of coagulating and separating (JP-A-1-189399) and the like are disclosed, there is a drawback that equipment cost and running cost are increased, or removal of particularly fine ink and carbon particles in terms of efficiency. However, it is not enough and has not spread.

[0006] Further, an acid or an acid solution is added to the wastewater of the so-called colored paper pulp to adjust the pH to 1 to 3.5, and the sulfur in the wastewater is removed.
There has been proposed a method of coagulating S and then adding an organic polymer coagulant to perform coagulation separation (Japanese Patent Publication No. 58-34081). According to the present proposal, the S
Although the S, COD and BOD are greatly reduced and the processing efficiency is high, all the processing equipment needs to be made of a strong acid-resistant material, and is not generally adopted.

[0007]

In view of this situation, the present inventors have conducted intensive studies on a method for treating DIP wastewater with a minimum increase in cost. Focusing on the fact that the floss floated and separated by a flotation machine has the highest SS concentration and contains many fine bubbles among various wastewaters, we have found the optimal conditions for treating only the floss alone. Thus, the present invention has been completed. Therefore, an object of the present invention is to separately treat the floss from the flotation machine in the DIP wastewater using a pressurized flotation method, and separately treat the wastewater for other selective, dewatering, concentration and washing steps. Another object of the present invention is to provide a method for efficiently treating wastepaper deinked pulp wastewater while minimizing an increase in total wastewater treatment costs including DIP wastewater.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a method for treating deinked pulp wastewater using waste paper for printing, wherein an acid and an inorganic coagulant are added to the floss separated by flotation by a flotation machine.
A method for treating wastepaper deinked pulp wastewater, characterized in that the floss is reduced to 4 to 7, and further added with an organic polymer flocculant , and then the floss is solely treated using a pressure flotation method.
DIP wastewater contains fine air that is floated and separated by a flotation machine, and has high SS concentration floss that is difficult to settle and relatively sedimentable SS that is discharged from other selective, dewatering, concentration and washing processes. (Hereinafter referred to as floss-separated wastewater).

In the conventional method of treating both wastewaters in a lump, the SS having a contradictory property of levitation and sedimentation is mixed. Therefore, when performing either the levitation treatment or the precipitation treatment, In order to obtain the expected effect, it is necessary to increase the equipment capacity or to add additional chemicals, which is not an appropriate measure. Therefore, floss should be treated alone,
As a processing method, flotation separation is desirable. As a means for levitation separation, a commonly used type such as a pressurized type and a diffuser type may be used, but a pressurized levitation type is more preferable. It is an essential condition of the present invention that only the floss is subjected to the pressure levitation treatment alone.

[0010] An inorganic coagulant such as aluminum sulfate and aluminum chloride is added to the floss, and then an acid is added to the floss.
After adjusting H in the range of 4 to 7, preferably 4 to 6.5, pressurized air is fed. Further, an organic polymer flocculant such as polyacrylamide is added, and separation treatment is performed by a pressure flotation device. If the pH exceeds 7, SS flocculation is insufficient, and adding an organic polymer flocculant has little effect.
If it is less than 4, a coagulation effect can be expected, but the material of the device needs to be acid-resistant, which is not practical.

The kind of acid used for pH adjustment, the kind and amount of inorganic coagulant and organic polymer coagulant, and the condition of pressurized air may be the kind and amount used usually.
Although not particularly limited, the inorganic flocculant is 800 to 12% by converting a sulfate band or aluminum chloride into an aluminum oxide (Al ₂ O ₃ ) 8% by weight solution with respect to the floss amount (m ³ ).
00ppm (g / m ^3), an organic polymer flocculant 0.5 to 2 g / m ³ a nonionic or weakly anionic polyacrylamide as solids, the pressurized air pressure is 3-4 kg / c
m ² , the amount of incoming air (GN) with respect to the amount of floss (Lm ³ )
The G / L ratio represented by the ratio m ³ ) is preferably from 0.2 to 0.3.

On the other hand, of the DIP wastewater, the floss separated wastewater excluding the floss is treated by a known method, for example, a single sedimentation treatment may be performed, and a coagulation sedimentation treatment is more preferable. However, since SS and COD may not be released to public waters as they are, they may be continuously mixed with kraft wastewater and / or papermaking wastewater to settle, pressurize and float, and activate sludge. Processing is performed by appropriately combining the processing steps.
If the pressure flotation device is already installed, it is not possible to prevent the processing of the floss by mixing the treated water of the floss separation wastewater with the floss in order to make the most of the capacity of the equipment.

As described above, according to the present invention, by treating floss alone, clearer treated water can be efficiently obtained, and the pressure flotation and the single sedimentation or sedimentation apparatus can be made compact. On the other hand, in the case where the apparatus is already installed, there is an advantage that the processing capacity can be afforded, and in particular, in a case where a plurality of pressure flotation apparatuses are provided, about half of the apparatuses can be stopped. Further, by efficiently treating the DIP wastewater, it is possible to reduce the amount of SS and COD brought into the coagulation and activated sludge processes, which are the latter processes of the wastewater treatment. Therefore, it is possible to minimize the increase in total wastewater treatment cost including DIP wastewater.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited thereto. Note that p in Examples and Comparative Examples
pm indicates parts per million by weight of volume, ie mg / l. The test method is as follows. Both pressure flotation and simple precipitation were performed at room temperature.

[0015] of the floatation on 2l capacity floatation on the test device (Prince Engineering営製) was used. While stirring the raw waste water (140 rpm), aluminum chloride (an 8 wt% solution in terms of Al ₂ O ₃ ) was added thereto, sulfuric acid was added to adjust the pH to a predetermined value, and an organic polymer flocculant (Hi Holder 353, manufactured by Kurita Industries) ) Was added and 1 minute later, stirring was stopped.
After sealing the floating tank, air at a pressure of 3.5 kg / cm ² was sealed so that the G / L ratio was 0.22. After 2 minutes, the pressure was released, and the treated water at the lower part of the floating tank after standing still for 5 minutes was sampled, and SS and COD were measured.

2 L of single sediment (simple sediment) raw wastewater is placed in a beaker and stirred with a jar tester for 3 minutes (140 rpm), followed by low speed stirring for 7 minutes (40 rpm).
pm), and after standing for 30 minutes, the supernatant was collected to measure SS and COD. -SS measurement method: According to JIS K0102 (Factory wastewater test method-14.1, suspended substances). -COD measurement method: It depends on JIS K0102 (Factory wastewater test method-17, oxygen consumption by potassium permanganate at 100 ° C). However, the sample was no. 5A
The soluble COD in the filtrate filtered with filter paper was measured.

Example 1 Of waste paper deinked pulp drainage made from used waste paper, such as newsprint and flyers such as medium quality paper, high quality paper and coated paper,
The floss floated and separated by the flotation machine was used as raw wastewater. The wastewater had a pH of 10.1 and an SS of 3940 ppm.
Take 2 l of the drainage into a pressure flotation tester, add aluminum chloride while stirring, adjust the pH to a predetermined value by adding sulfuric acid, and use a high holder 353 (manufactured by Kurita Kogyo Co., Ltd., weak anionic polyacrylamide, hereinafter referred to as PAA). And stop stirring. Then, the floating tank was sealed, and the pressure was 3.5 kg.
/ Cm ² of air was sealed so that the G / L ratio was 0.22. After 2 minutes, the pressure was released, and the treated water at the lower part of the floating tank after standing still for 5 minutes was sampled and SS was measured.
Shown in Aluminum chloride is 8% by weight in terms of Al ₂ O ₃
500 or 1000 ppm as solution, PAA 0.1
1.0% or 5.0 in terms of solid content.
ppm, respectively.

Example 2 In the same manner as in Example 1, the floss of the flotation machine was treated as raw waste water in a pressure flotation tester. The pH of the wastewater was 10.0, SS4280ppm, and COD520ppm. The amount of the coagulant added was 10% in aluminum chloride solution.
It was fixed at 00 ppm and PAA at 1 ppm. The SS and COD of the treated water at each pH value were measured, and the results are shown in Table 1.

Example 3 From the same waste paper deinking pulp wastewater as in Example 1, 4 volumes by volume of supernatant obtained by subjecting floss separated wastewater except floss to simple sedimentation with a jar tester, and used in Example 2 The pressure flotation treatment was performed in the same manner as in Example 2 except that the sample in which 6 parts by volume of the floss was mixed was used as raw wastewater. Table 1 shows the measurement results.
Shown in The raw wastewater was pH 9.8, SS2740pp
m, COD was 525 ppm. The pH of the floss separation wastewater was 9.7, and the SS before and after the single sedimentation treatment was 244.
0 ppm and 441 ppm, also COD is 539 pp
m and 533 ppm.

Comparative Example 1 The same sample as in Example 1 was used as raw waste water, and in order to confirm the effect of only pH, SS was measured without adding a flocculant and treating with a pressure flotation tester. Table 1 shows the results.

COMPARATIVE EXAMPLE 2 A pressure flotation treatment was carried out in the same manner as in Example 2, except that the same waste paper deinked pulp waste water as in Example 1 was used as raw waste water including floss. Table 1 shows the measurement results.
The raw wastewater was pH 9.9, SS3550ppm, COD
It was 530 ppm.

[0022]

[Table 1]

As is clear from the results of Example 1 in Table 1,
By adding sulfuric acid to the floss to lower the pH and adding aluminum chloride and PAA, the SS removal effect appears. Inferior, no effect of co-aggregation was observed. Further, from the results of Comparative Example 1 in Table 1, it is clear that reducing the pH alone has little effect on pressurizing and floating the floss alone. As shown in Example 2 in Table 1, when the pH was 7 or less, particularly at pH 6 or less, the SS in the treated water was
Is greatly reduced, and the effect of the present invention is clear.
Further, although less than SS, the effect of removing COD is also recognized.

Further, even when mixed with the treated water after the single sedimentation treatment of the floss separation wastewater, the same effect as when the floss is treated alone is recognized, as is apparent from Example 3 in Table 1. On the other hand, as is apparent from Comparative Example 2 in Table 1, when the DIP wastewater containing floss was treated in a lump, SS
Is less effective.

[0025]

According to the present invention, only the floss floated and separated by the flotation machine from the waste paper deinked pulp waste water which has been conventionally treated in a lump is combined with the waste water of other selective, dewatering, concentration and washing processes. Separation and single treatment using the pressure flotation method provide a more efficient treatment method than the conventional method and reduce the total wastewater treatment costs including wastewater deinking wastewater. Things.

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C02F 1/24 C02F 1/52 D21C 1/00-11/14

Claims (1)

(57) [Claims] 1. A method for treating wastewater in a deinking pulp process using waste paper for printing, wherein an acid and an inorganic coagulant are added to the floss floated and separated by a flotation machine to lower the pH to 4 to 7 and further increase the organic high A method for treating wastepaper deinked pulp wastewater, wherein after the addition of a molecular coagulant , the floss is solely treated using a pressure flotation method.