JPH10180298A - Treatment of waste water and waste water treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively and economically decrease the COD in waste water by flocculating and settling the waste water or floating it under pressure to obtain treated water, treating the treated water by the activated sludge process and further flocculating and settling the treated water under acidic conditions. SOLUTION: The waste water discharged from a magnetic disk producing process is a waste plating or grinding water and contains PVA and an org. matter such as org. chelating agent, surfactant and antifoaming agent in addition to SS. When such a waste water is treated, the waste water is introduced into a flocculating and settling tank 1, then a flocculant is added in a neutral condition, and the SS not dissolved in the waste water and suspended is flocculated and settled and separated from the supernatant water. The supernatant water as the treated water is introduced into an activated-sludge tank 2 along with activated sludge and agitated while supplying oxygen from an aerator to decompose the org. matter in the treated water by the microorganism in the activated sludge. The treated water is separated from sludge and introduced into a biological reaction tank 3, and the soluble org. matter is decomposed by the microorganism.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention effectively reduces COD (chemical oxygen demand) of wastewater from factories containing suspensions, organic substances, organic chelating agents, etc., particularly, magnetic disk production wastewater. The present invention relates to an improvement in a wastewater treatment method and a wastewater treatment device.

[0002]

2. Description of the Related Art Conventionally, a method as shown in FIG. 4 has been employed as a method for treating wastewater such as magnetic disk manufacturing wastewater. That is, the wastewater is treated by the coagulation sedimentation tank 21 or the like to remove suspended matter (SS) in the wastewater, and the treated water is further biologically treated in the activated sludge tank 22. By performing this activated sludge method, BOD (biological oxygen demand) in wastewater can be effectively reduced.

[0003]

However, the SS in the wastewater
Even if the amount and BOD can be reduced to a certain level, it is difficult to reduce COD effectively by the coagulation sedimentation tank 21 and activated sludge tank 22 as described above, and it is difficult to meet the standard level of wastewater. It was difficult.

[0004] Therefore, the treated water treated by the activated sludge tank 22 is further filtered to remove SS and then treated in an activated carbon adsorption process 23 to reduce COD. However, when activated carbon is used as an adsorbent, Requires maintenance since it must be regenerated after use, and it is expensive to dispose of activated carbon,
The labor and cost of the management increase, and there is an economic problem.

The present invention has been made to solve such problems, and has as its object to effectively and economically reduce COD in wastewater.

[0006]

The feature of the wastewater treatment method for solving the above-mentioned problems is that the wastewater is subjected to coagulation sedimentation treatment or pressure flotation treatment to obtain treated water, and the treated water is treated by an activated sludge method. Another object of the present invention is to subject the treated water treated by the activated sludge method to coagulation and sedimentation under acidic conditions.

Another feature is that the treated water treated by the activated sludge method is biologically treated.

Further, as another characteristic, the wastewater is subjected to coagulation sedimentation treatment or pressure flotation treatment to obtain treated water, the treated water is treated by an activated sludge method, and the treated water treated by the activated sludge method is further treated. It is to perform coagulation sedimentation treatment by adding an adsorbent. Further, there is another means for biologically treating the treated water treated by the activated sludge method in this treatment.

A feature of the wastewater treatment apparatus is that a coagulation sedimentation tank 1 or a pressurized floating tank 5 into which wastewater is introduced and treated water separated by the coagulation sedimentation tank 1 or the pressurized floating tank 5 are introduced. An activated sludge tank 2 to be used and a coagulation sedimentation tank 4 for coagulating and sedimenting the treated water from the activated sludge tank under acidic conditions.

That is, as described above, the present invention treats wastewater by coagulation sedimentation or flotation under pressure, treats the treated water by the activated sludge method, and further performs coagulation sedimentation treatment under acidic conditions. The SS in the wastewater is first removed by pressurized flotation, and the other organic matter in the wastewater is further removed by the activated sludge method.Then, the organic matter dissolved in the wastewater is easily removed because the coagulation and sedimentation treatment is performed under acidic conditions. Can be removed. Therefore, the organic matter that could not be removed by the activated sludge method is easily removed, and it is difficult to reduce the COD by the activated sludge treatment.
Can be effectively reduced.

Furthermore, when the treated water treated by the activated sludge method is biologically treated, organic substances that cannot be completely removed by the activated sludge method can be effectively removed.

When the treated water treated by the activated sludge method is subjected to coagulation and sedimentation treatment by adding an adsorbent, when the coagulation and sedimentation treatment is performed at a neutral pH range, Similarly, COD can be easily and effectively reduced.

[0013]

For Embodiment 1 of the Detailed Description of the Invention Embodiment Example 1 This invention will first be described with reference to the drawings from the configuration of the wastewater treatment apparatus.

In FIG. 1, reference numeral 1 denotes a coagulation / sedimentation tank into which waste water is introduced. In the coagulation / sedimentation tank 1, coagulation / sedimentation is performed under neutral conditions.

Reference numeral 2 denotes an activated sludge tank into which the supernatant treatment water is introduced. The activated sludge tank holds activated sludge together with the supernatant treatment water. The activated sludge tank 2 is provided with an aeration device (shown in Sez), and the sludge and the treated water are agitated while supplying oxygen by the aeration device to decompose organic substances in the treated water by microorganisms in the activated sludge.
After that, it is separated into treated water and sludge by a sedimentation tank (Cez shown).

Reference numeral 3 denotes a biological reaction tank for introducing the treated water generated in the activated sludge tank 2. The biological reaction tank 3 is filled with a carrier carrying microorganisms, and the treated water is brought into contact with the carrier. Thus, the treated water is biologically treated. The carrier used in the biological reaction tank 3 can be appropriately selected and used from commonly used carriers for biological treatment such as resin, fiber, and sand. As a treatment method, a carrier such as a floating type or a fixed type is used. Any method can be used as appropriate.

Reference numeral 4 denotes a coagulation sedimentation tank for introducing the treated water treated in the biological reaction tank 3. In the coagulation sedimentation tank 4, a pH adjuster other than the coagulant is injected to adjust the pH to an acidic pH, coagulation sedimentation is performed under the acidic pH conditions, and the supernatant treated water is discharged as purified water.

Next, a description will be given of a case where wastewater discharged from a magnetic disk manufacturing process is treated by the wastewater treatment apparatus 10 having such a configuration. Since the wastewater discharged from the manufacture of the magnetic disk is plating or polishing wastewater, it contains, in addition to SS, organic substances such as polyvinyl alcohol, a grinding liquid, an organic chelating agent, a surfactant and an antifoaming agent.

Such waste water is first introduced into the coagulation sedimentation tank 1 and a coagulant is added under neutral conditions to perform coagulation sedimentation. At this time, the aggregated SS is suspended in the wastewater without being dissolved, and the aggregated SS is settled and separated from the supernatant water.

The supernatant water separated in the flocculation settling tank 1 is introduced into the activated sludge tank 2 together with activated sludge as treated water. Then, the organic matter in the treated water is decomposed by the microorganisms in the activated sludge while stirring while supplying oxygen by an aerator, and the organic matter can also decompose and remove dissolved components that cannot be removed by the coagulation sedimentation. .

[0021] The treated water treated by the activated sludge is separated from the sludge and introduced into the biological reaction tank 3. In the biological reaction tank 3, the decomposing action of the soluble organic matter by the microorganisms carried on the carrier is also performed. receive.

As described above, the treated water treated in the activated sludge tank 2 is treated in the biological reaction tank 3 to perform two-stage biological treatment, whereby organic substances can be reliably decomposed. COD can also be reduced to some extent by removing organic matter from the biological reaction tank 3.

Further, in the biological reaction tank 3,
The treated water thus introduced is introduced into the coagulation sedimentation tank 4. Here
, FeCl_Three・ 6H_TwoCoagulant such as O, coagulant and N
aOH, H _TwoSO_FourPH adjuster is added
The pH is adjusted so as to be preferably around pH 4.
These flocculants and pH adjusters are among those commonly used.
Can be selected as appropriate.

When coagulation and sedimentation are performed in an acidic region, organic substances dissolved in the treated water and not removed in the previous steps can be coagulated and sedimented, and the supernatant water is discharged as purified water.

In particular, wastewater discharged from the manufacture of the magnetic disk contains various organic substances irrespective of solubility or insolubility, and these organic substances can be easily prepared without using an adsorbent such as activated carbon. Can be removed. as a result,
Not only SS and BOD contained in purified water, but also COD
Can also be effectively reduced.

Second Embodiment Next, a second embodiment of the present invention will be described. As shown in FIG. 2, a wastewater treatment apparatus of the second embodiment has the same structure as that of the first embodiment. Coagulation sedimentation tank 1, activated sludge tank 2
And a coagulation sedimentation tank 6 into which the treated water of the biological reaction tank 3 is introduced.

In the coagulating sedimentation tank 6, after adding activated carbon powder as an adsorbent and an aluminum-based coagulant such as polyaluminum chloride as a coagulant, the pH of the treated water is adjusted to a neutral region (around pH 6). And a coagulation sedimentation process.

In the wastewater treatment apparatus having such a configuration, by adding activated carbon powder and an aluminum-based coagulant such as polyaluminum chloride, organic substances which cannot be removed by coagulation and sedimentation in a normal neutral pH range. And the like can be effectively removed, and therefore, the COD in the purified water can be reduced.

The activated carbon powder to be added as an adsorbent is less expensive than spherical activated carbon. Therefore, even if the activated carbon powder is thrown away without being regenerated, the activated carbon powder is more likely to be treated by a conventional activated carbon adsorption process using spherical activated carbon. It is economical and easy to maintain and maintain.

Other Embodiments In the above embodiments, the magnetic disk production wastewater is used as the wastewater, but the wastewater to be treated by the wastewater treatment apparatus of the present invention is the same plating as the other magnetic disk wastewater. Substrate manufacturing wastewater, which is polishing wastewater, or chemical cleaning wastewater, such as boiler or plant wastewater, may be treated.

Further, in each of the above embodiments, the coagulation sedimentation tank 1 for introducing the wastewater to remove the SS is provided, but instead of the coagulation sedimentation tank 1, a pressurized floating tank 5 is provided as shown in FIG. The aggregated SS may be floated to separate the treated water and aggregates.

Furthermore, in each of the above embodiments, the biological reaction tank 3 is provided on the downstream side of the activated sludge tank 2, but the provision of the biological reaction tank 3 is not always a condition. However, when the biological reaction tank 3 is provided and the biological treatment is performed in two stages with the activated sludge tank 2, the organic matter can be reliably removed, so that the quality of the treated water is further improved and the COD is reduced. It can be achieved more.

[0033]

Next, a case where the wastewater treatment apparatus shown in each of the above embodiments is used to treat the wastewater from magnetic disk production will be described more specifically.

Example 1 In Example 1, a coagulation settling tank and an activated sludge tank were provided first.
In a wastewater treatment apparatus for coagulating and sedimenting the treated water of the activated sludge tank in each pH range, a pH of 3.1 to p
COD of purified water when coagulated and settled in the range of H10.5
Was measured and compared with the COD of the treated water discharged from the activated sludge tank of the same wastewater treatment apparatus as in the first embodiment. The results are shown in Table 1.

[0035]

[Table 1]

As shown in Table 1, pH 3.1 to pH 5.3
The COD in the acidic region was reduced as compared with the case where the pH was 6.2 or more. In particular, it was found that a pH around 4.0 was optimal as a pH value for coagulation and precipitation.

Example 2 Next, in the same wastewater treatment apparatus as in the first embodiment, when the pH in the coagulation sedimentation tank was adjusted to 4.0, the injection amounts of the coagulant and the pH adjuster were changed. The COD of the effluent from each treatment was measured at the same time, and the results are shown in Table 2.

[0038]

[Table 2]

As shown in Table 2, it was found that when acidic coagulation precipitation was performed at an acidic pH of 4.0, the COD could be reduced constantly by adding a predetermined amount of coagulant.

Example 3 Next, the contents of SS, COD, and BOD at the time of each treatment in the same wastewater treatment apparatus of the first embodiment were measured, and the results are shown in Table 3. However, the wastewater was treated by pressure flotation instead of coagulation sedimentation.

The conditions for acidic coagulation precipitation were as follows: ferric chloride (200 mg / L) and caustic soda (55 mg / L) were added to the treated water from the biological reaction tank (adjusted to a pH of about 4);
After stirring at 3 rpm for 3 minutes, 1 mg / L of a polymer auxiliary is added, and the mixture is stirred at 120 rpm for 1 minute, and further stirred at 40 rpm for 10 minutes. After that, the mixture was allowed to stand for 15 minutes, and the supernatant water was used as purified water.

[0042]

[Table 3]

As shown in Table 3, the SS and BOD in the biological reaction treated water before the acidic coagulation treatment were 10 and 10 respectively.
Although it is reduced to ２０20 mg / L or less and 5 mg / L or less, the COD at this stage is reduced to only about 50 mg / L or less. However, COD can be reduced to about 30 mg / L or less by performing acidic coagulation precipitation.

Example 4 Next, the contents of SS, COD and BOD at the time of each treatment in the same wastewater treatment apparatus of the second embodiment were measured, and the results are shown in Table 4. However, the wastewater was treated by pressure flotation instead of coagulation sedimentation.

The conditions for coagulation and sedimentation were as follows: 50 mg / L of powdered activated carbon was added to treated water from a biological reaction tank, and the mixture was stirred at 120 rpm for 20 minutes or more.
g / L and sulfuric acid 20 mg / L, pH was adjusted to 6.0, and the mixture was further stirred at 120 rpm for 3 minutes. Further, a polymer auxiliary agent 1 mg / L was added and stirred for 1 minute, and then at 40 rpm for 10 minutes. The mixture was stirred and allowed to stand for 15 minutes, and the supernatant was used as purified water.

[0046]

[Table 4]

As shown in Table 4, when the agglomeration treatment was performed in the neutral region, C was also obtained by aggregation and precipitation in the same manner as in Example 3 above.
OD can be effectively reduced.

[0048]

As described above, the present invention makes it possible to effectively and economically remove COD, which was conventionally difficult to reliably remove, by easily removing organic matter in wastewater, and to further reduce wastewater. Purified water of high quality can be obtained.

[Brief description of the drawings]

FIG. 1 is a flowchart of a wastewater treatment method as an embodiment.

FIG. 2 is a flowchart of a wastewater treatment method as another embodiment.

FIG. 3 is a flowchart of a wastewater treatment method as another embodiment.

FIG. 4 is a flowchart of a conventional wastewater treatment method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coagulation sedimentation tank 2 Activated sludge tank 3 Biological reaction tank 4 Acid coagulation sedimentation tank 5 Pressure flotation tank

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 9/00 504 C02F 9/00 504E 1/24 1/24 A ZAB ZABB 1/28 1/28 F 1/52 1/52 Z 3/12 3/12 VF

Claims (8)

[Claims] 1. A wastewater is subjected to a coagulation sedimentation treatment or a pressure flotation treatment to obtain treated water, and the treated water is treated by an activated sludge method,
Further, a wastewater treatment method characterized by subjecting treated water treated by the activated sludge method to coagulation sedimentation treatment under acidic conditions. 2. The wastewater treatment method according to claim 1, wherein the treated water treated by the activated sludge method is biologically treated. 3. The wastewater is subjected to coagulation sedimentation treatment or pressure flotation treatment to obtain treated water, and the treated water is treated by an activated sludge method,
Further, a wastewater treatment method characterized by adding an adsorbent to treated water treated by the activated sludge method and subjecting the treated water to coagulation sedimentation treatment. 4. The wastewater treatment method according to claim 3, wherein the treated water treated by the activated sludge method is biologically treated. 5. A coagulating sedimentation tank (1) or a pressure floating tank (5) into which waste water is introduced, and the coagulating sedimentation tank (1) or the pressure floating tank (5).
Activated sludge tank into which treated water separated by water is introduced
A wastewater treatment apparatus comprising: (2) a coagulation sedimentation tank (4) for coagulating and sedimenting the treated water from the activated sludge tank under acidic conditions. 6. The wastewater treatment apparatus according to claim 5, further comprising a biological reaction tank (3) for introducing treated water from the activated sludge tank (2) and biologically treating the treated sludge. 7. A coagulating sedimentation tank (1) or a pressure floating tank (5) into which waste water is introduced, and said coagulating sedimentation tank (1) or a pressure floating tank (5).
Activated sludge tank (2) into which treated water is introduced
And a coagulating sedimentation tank (6) for adding an adsorbent to the treated water from the activated sludge tank to perform coagulation sedimentation. 8. The wastewater treatment apparatus according to claim 7, further comprising a biological reaction tank (3) for introducing treated water from the activated sludge tank (2) and biologically treating the treated water.