JP2001225094A - Method and apparatus for treating wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To clean wastewater containing organic matters in high concentration mainly generated in a food factory or the like up to a degree dischargeable to heavily regulated rivers regulation. SOLUTION: Wastewater is treated by a first process for applying anaerobic biological treatment to wastewater and a second process for applying aerobic biological treatment to the wastewater from the first process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment method and a wastewater treatment apparatus suitable for treating wastewater containing high-concentration organic substances mainly in food factories and the like.

[0002]

2. Description of the Related Art Conventionally, there are an anaerobic treatment method and an aerobic treatment method as biological wastewater treatment methods using microorganisms such as bacteria.

[0003] For advanced treatment of wastewater containing high-concentration organic matter, for example, in a food factory that performs meat processing, marine processing and lunch box production, an anaerobic wastewater treatment method is useful from the viewpoint of equipment space and the like. As an example, there is a wastewater treatment method of the upflow anaerobic sludge bed method (UASB method).

[0004] The wastewater treatment of the UASB method is described, for example, in the document "Water Quality Environmental Engineering, Treatment, Disposal, and Reuse of Sewage" (Gihodo Shuppan Co., Ltd., 1st edition, 1st edition published March 31, 1993)
Pages 317 to 318 (Fig. 8-28 (g) of page 317), and the document "Basics of Chemistry and Wastewater Treatment Technology" (published by Information Research Institute, Ltd., 2nd print on November 10, 1996) As described in (4) UASB apparatus on page 217 to 218), the reaction is carried out using a reaction vessel (reactor) in a closed state.

[0005] That is, in the wastewater treatment of the UASB method, as shown in FIG. 2, raw water (drainage) 1 is introduced into a closed (anaerobic) reaction tank 2 from the bottom, and the introduced wastewater is raised.

At this time, anaerobic microorganisms are present in the lower part (sludge bed portion) of the reaction tank 2 as granular sludge, and this high concentration of microorganisms digests a large amount of ascending organic matter in the wastewater, thereby increasing the efficiency of the wastewater. Cleanse well and quickly.

[0007] As a result, the wastewater 1 is discharged to
(Biochemical oxygen demand) value 10 ⁴ milligrams (mg) /
Liter (L) or more, specifically, 2 · 10 ⁴ mg / L to ⁴
-Even with wastewater containing high-concentration organic substances of about 10 ⁴ mg / L, the treated water 3 flowing over the reaction tank 2 is purified to a BOD value of about 200 mg / L, which can be discharged to the sewer.

On the other hand, as an aerobic treatment method, there is a wastewater treatment method of a contact aeration method. This treatment method has a BOD value of 10 mg / L or less by arranging a number of aeration tanks and repeating the aeration treatment. It is also possible to purify wastewater to such an extent that it can be discharged into rivers with strict regulations.

[0009]

In the case of the above-mentioned conventional wastewater treatment using anaerobic biological treatment, the BOD value is 200 mg / day.
L is the limit of water purification, for example, B of food factory etc.
To the extent that high-concentration organic matter-containing wastewater with an OD value of 10 ⁴ mg / L or more can be discharged to rivers with strict discharge regulations (BOD value 10 mg / L
L or less).

On the other hand, in the case of wastewater treatment in which aerobic biological treatment is performed, it is possible to purify the water quality of the wastewater containing high-concentration organic substances to a BOD value of 10 mg / L or less by so-called multistage treatment. The size of the equipment is remarkably large, a large space is required, and the initial cost and operation cost of the equipment are extremely high, which is not practical.

The present invention mainly uses a small-scale, small-space, and inexpensive method to discharge high-concentration organic matter-containing wastewater from a food factory or the like.
Can be discharged to strictly regulated rivers (BOD value 10mg
/ L or less).

[0012]

In order to solve the above-mentioned problems, a wastewater treatment method according to the present invention includes a first step of subjecting wastewater to anaerobic biological treatment, and the first step. And a second step of subjecting the discharged wastewater to an aerobic biological treatment.

Therefore, for example, a wastewater containing a high concentration of organic matter, such as a food factory, has a BOD value of 200 mg, which is the limit of water purification, by anaerobic biological treatment in the first step.
After purification to about / L, it can be sufficiently purified to a BOD value of 10 mg / L or less, which can be discharged into a river, by aerobic biological treatment in the second step.

In this case, the water purification ability is further improved as compared with the case of only the anaerobic biological treatment, and the installation cost and the operating cost are smaller and smaller in space than the case of only the aerobic biological treatment. Becomes cheaper.

The anaerobic biological treatment is UASB
The aerobic biological treatment is preferably a contact aeration treatment.

Further, in the treatment by the contact aeration method, it is desirable to provide a porous body such as a volcanic ash filter medium to which aerobic microorganisms adhere in an aeration tank and to improve its water purification ability.

Next, a wastewater treatment apparatus according to the present invention comprises a reaction tank for subjecting wastewater to anaerobic biological treatment by the UASB method, and a contact aeration provided for the wastewater passing through the reaction tank, which is provided at a subsequent stage of the reaction tank. An aeration tank for performing biological treatment of the method.

Therefore, it is possible to provide a specific wastewater treatment apparatus for realizing the wastewater treatment method of the present invention.

It is desirable to provide a porous body such as a volcanic ash filter medium in the aeration tank to improve its water purification ability.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described.
This will be described with reference to FIG. As shown in FIG. 1, for example, a food factory or the like has a BOD value of 10 ⁴ mg / L or more, specifically 2 ·
10 ⁴ mg / L~4 · 10 ⁴ composed of a high density organic matter containing wastewater of about mg / L draining (raw water) 4, and water conveyance from the bottom to the reaction vessel 5 in the closed state, the lower sludge bed in the reaction vessel 5 The high concentration of anaerobic microorganisms digests a large amount of the rising organic matter in the wastewater, and the wastewater 4 is efficiently subjected to anaerobic biological treatment by the UASB method.

By this anaerobic treatment, the wastewater 4 is promptly treated, and the supernatant treated water 6 flowing over the upper part of the reaction tank 5 is treated.
Is a BOD that can be discharged to sewerage, as in the treated water 3 in FIG.
The value is about 200 mg / L.

Further, the treated water 6 is sent to aeration tanks 7, 7 'provided in a column at the rear of the reaction tank 5, and subjected to a contact aeration treatment as an aerobic biological treatment.

At this time, sufficient air is sent from the blowers 8 to the aeration tubes at the bottom of the aeration tanks 7, 7 '.

In the aeration tanks 7 and 7 ′, a large number of appropriately sized ash filter media (volcanic ash filter media: trade name “Touchstone”) or the like formed by agglomerated volcanic ash (volcanic rubble) are provided. The porous bodies 9, 9 'are provided in a mesh bag or the like.

The aerobic microorganisms adhere to the surface of the porous bodies 9 and 9 'in a film-like manner, and the air is sufficiently supplied from the lower part through the above-mentioned air diffuser or the like, and the microorganisms efficiently remove the organic matter in the wastewater. Ingest well, digest and proliferate.

In addition, protozoa prey on the proliferating microorganisms, and their death is the prey of the microorganisms.

By repeating the food chain, the aeration tank 7
The treated water 6 having a BOD value of about 200 mg / L flowing into the tank is sufficiently contacted and aerated in the aeration tanks 7, 7 ', and the water is purified to 10 mg / L or less at the outlet of the subsequent settling tank 10.

For this reason, the treated water 11 discharged from the sedimentation tank 10 can be discharged as it is to a river or the like where discharge regulations are strict.

Then, the UASB of the first step in the reaction tank 5 is performed.
To the extent that wastewater 4 can be discharged to sewerage, which is the limit of anaerobic treatment, by anaerobic biological treatment by the method (BOD value 2
(About 00 mg / L) for purification, and furthermore, aerobic biological treatment by the contact aeration method of the second step in the aeration tanks 7 and 7 'at the subsequent stage of the reaction tank 5, Since the treated water 6 has been purified to a BOD value of 10 mg / L or less, which can be discharged to rivers, etc., it is a food factory with a small-scale and small space configuration combining anaerobic biological treatment and aerobic biological treatment. And other high-concentration organic matter-containing wastewater can be sufficiently purified so that it can be discharged into rivers, and high-speed treatment and sludge volume reduction can be realized.

At this time, the porous bodies 9 and 7 are placed in the aeration tanks 7 and 7 '.
9 ′ is provided, and aerobic microorganisms are attached to the porous bodies 9 and 9 ′ to efficiently and sufficiently perform aerobic biological treatment. Therefore, the number of aeration treatment stages is reduced as much as possible, and the apparatus scale and space are reduced. As much as possible and the initial and operating costs of the equipment as low as possible.
Value can be purified, and the volume of sludge can be significantly reduced.

Therefore, the discharge of high-concentration organic matter-containing wastewater from a food factory or the like into a river, which has been difficult in the past, can be realized by providing a small-scale, small-space, inexpensive and practical wastewater treatment apparatus.

Incidentally, the biological treatment in the first step is as follows:
An anaerobic biological treatment other than the UASB method may be used, and the biological treatment in the second step may be an aerobic biological treatment other than the contact aeration method.

In the above embodiment, the aeration tanks 7, 7 '
And the number of aeration stages is set to two, but the number of aeration stages may be set appropriately based on the BOD value of the treated water 6 and the regulation of the discharge of rivers. Only the aeration tank 7 is provided to reduce the number of stages. Of course, a single stage may be provided, and a similar aeration tank may be further provided after the aeration tank 7 ′ to increase the number of processing stages to three or more.

Further, when the porous bodies 9, 9 'provided in the aeration tanks 7, 7' are formed of, for example, the above-mentioned volcanic ash filter material, the effect is high, and it is a natural product and safe.
In addition, there is an advantage that maintenance can be performed easily,
Needless to say, various natural and artificial porous materials other than the volcanic ash filter material may be used, and for example, urethane foam or the like may be used.

The shape, size, installation method and the like of the porous bodies 9 and 9 'may be appropriately set so as to improve the state of attachment of microorganisms and the purification ability.

The BOD of the waste water (raw water) 4 before the treatment
The value and the BOD value of the treated wastewater (treated water 11) are not limited to those in the above-described embodiment, and the present invention is applied to the treatment of various industrial wastewater and other wastewater mainly containing high-concentration organic substances. It has a remarkable effect.

[0037]

The present invention has the following effects. First, in the case of claim 1, the BOD value 200, which is the limit of water purification, of the wastewater containing high-concentration organic matter in a food factory or the like by the anaerobic biological treatment in the first step.
After purification to about mg / L, BOD value 10 mg / L that can be discharged to rivers etc. by aerobic biological treatment in the second step
It can be sufficiently purified below.

In this case, the water purification ability can be further improved as compared with the case where only the anaerobic biological treatment is used, and the installation cost is smaller and the space is smaller than when only the aerobic biological treatment is used. , Operation costs can be reduced.

Therefore, it is possible to purify the wastewater containing high-concentration organic substances mainly from food factories and the like in a small scale, small space and at a low cost to such an extent that the wastewater can be discharged to a river or the like where regulation is severe.

In the case of the second aspect, the anaerobic biological treatment is a treatment of an upflow anaerobic sludge bed method (UASB method), and the aerobic biological treatment is a treatment of a contact aeration method. Therefore, it is possible to provide a specific wastewater treatment method having the effect of claim 1.

Further, in the case of claim 3, the aeration tank 7,
The porous body 9, 9 'such as a volcanic ash filter medium to which aerobic microorganisms adhere is provided in 7' and aeration treatment is performed. Therefore, the water purification ability is improved by the aerobic biological treatment by the contact aeration method according to claim 2. The sludge volume can be further improved and remarkable sludge volume reduction can be achieved.

Next, in the case of claim 4, the reaction tank 5
Since the aeration tanks 7, 7 'provided at the subsequent stage of the reaction tank 5 are provided, a specific wastewater treatment apparatus for realizing the wastewater treatment method of claim 2 can be provided.

In the case of claim 5, the aeration tanks 7, 7 '.
Since the porous bodies 9 and 9 'are provided in the first embodiment, a wastewater treatment apparatus having the effect of claim 3 can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a process according to an embodiment of the present invention.

FIG. 2 is a process explanatory view of a conventional example.

[Explanation of symbols]

 2,5 Reaction tank 7,7 'Aeration tank 9,9' Porous body

Claims (5)

[Claims] 1. A method of subjecting wastewater to anaerobic biological treatment.
And a second step of performing aerobic biological treatment on the wastewater passed through the first step. 2. The anaerobic biological treatment is an upflow anaerobic sludge bed method, and the aerobic biological treatment is a contact aeration method. Wastewater treatment method. 3. The wastewater treatment method according to claim 2, wherein the treatment by the contact aeration method is performed by providing a porous body such as a volcanic ash filter medium to which aerobic microorganisms adhere in an aeration tank. 4. A reaction tank for subjecting waste water to anaerobic biological treatment by an upflow anaerobic sludge bed method, and a biological body of a contact aeration method provided at a latter stage of the reaction tank and contacting waste water passing through the reaction tank. A wastewater treatment device comprising an aeration tank for performing a chemical treatment. 5. A porous body such as a volcanic ash filter medium to which aerobic microorganisms adhere is provided in an aeration tank.
The wastewater treatment device as described in the above.