JPH0745037B2 - Method and apparatus for biological treatment of organic wastewater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is a novel biological treatment capable of highly efficiently and highly cleaning organic sewage such as sewage, night soil, industrial wastewater, etc. using a fixed bed. A method and apparatus.

[Conventional technology]

Although biological treatment is widely used in the treatment of organic wastewater, the biological treatment method is as follows: A sprinkler filter in which microorganisms that treat BOD are immobilized as a biofilm on a carrier such as a filter medium. The bed method, the immersion filter bed method, and the activated sludge method in which microorganisms are suspended as flocs and used without a carrier are known. When immobilized as a biofilm on a carrier, the diversity of microorganisms present in the treatment system is large and the ecosystem is stable, and it can withstand fluctuations in wastewater volume and fluctuations in BOD load. Therefore, the activated sludge method that does not use a carrier is more widely used, in addition to the high equipment cost. Therefore, it can be said that the sprinkling filter method and the immersion filter method are superior if the treatment efficiency is increased.

In order to improve the treatment efficiency of the immersion filter bed method, it is necessary to improve the carrier and the device for allowing the organic wastewater to pass through at a high filtration rate and slowing the increase in filtration resistance.

An aerobic immersion biological filter bed apparatus as shown in FIG. 3 is known as a concrete apparatus for the immersion filter bed method. This device is a tank
An immersion filter bed 32 made of granular filter material such as anthracite or chamotte is provided under the water surface of 31, and an air diffusing pipe 33 is provided under the immersion filter bed 32, and an organic wastewater introduced from a raw water supply pipe 35 is supplied. The immersion filter bed 32 is circulated in a downward flow, and aerobic biological treatment is performed in the immersion filter bed 32.

Ancillary equipment of this equipment is settling basin 34, treated water storage tank 3
8. Washing waste water storage tank 40 is installed.

This device is a submerged filter bed composed of a granular mineral filter material such as anthracite, chamotte, or artificial or natural lightweight aggregate under the water surface of a tank 31 while supplying organic wastewater in a downward flow. Is removed by filtration. However, when using this conventional device, SS and BOD of several hundred mg /
When the sewage of the above is passed, SS is trapped on the surface layer of the submerged filter bed such as anthracite, and the biofilm grows excessively, which causes severe clogging, resulting in a sharp increase in filtration resistance and the passage of water. There was a problem that water could not be passed in a short time after the start, and the submerged filter bed 32 had to be frequently washed.

Here, the terms will be explained. In the description of biological treatment by the immersion filter method, anthracite,
A granular filler such as chamotte is generally called a filter medium, and a filter bed composed of such a granular filler is called an immersion filter bed or an immersion fixed bed. However, in the present invention, this filter medium is used not as a material having a filtration function but as a more general material for supporting a biofilm, so that it is particularly referred to as a carrier in the description of the constitution of the present invention, and also in the present invention. The filter bed used does not have to be partially immersed in the organic waste water, so when describing the constitution of the present invention, it is particularly referred to as a fixed bed.

[Problems to be Solved by the Invention]

In the conventional biological treatment method and apparatus using a submerged filter bed, the submerged filter bed is likely to be clogged, so that a sedimentation basin is required as a preparatory step for the precipitation step.

 Inability to pass organic wastewater at a high filtration rate.

A wide filter bed is required to purify certain organic wastewater.

Just as with raw sewage, SS and BOD may cause severe clogging immediately after passing sewage of several hundred mg / m.

 The fixed bed is frequently washed.

There is a drawback that.

The object of the present invention is to improve the above-mentioned drawbacks of the conventional biological treatment method using the immersion filter bed and the apparatus for the immersion filter bed, to allow organic sewage such as raw sewage to pass through at a high filtration rate, and to improve the filtration resistance. It is an object of the present invention to provide a novel biological treatment method and device that can be highly purified with a small increase in the amount of water.

As a result of repeated research, the above-mentioned drawbacks of the conventional biological treatment method using the immersion filter bed and the immersion filter bed apparatus are that the granularity such as anthracite has a small porosity of about 50% at the time of filling. It has come to be recognized that the carrier of the biofilm is composed of minerals.

In consideration of this, the biological treatment method using the immersion filter bed is a carrier as a fixed bed structure (naturally as a carrier) even if the supplied organic wastewater is passed through at a high speed in a downward flow. A wide and efficient contact between the retained biofilm) and the organic wastewater causes a biological reaction to rapidly reduce the BOD,
In addition, even if SS is promptly removed, if the carrier does not become clogged, it is possible to treat wastewater quickly.

As a result of conducting an experimental study on a large number of types of filter media (carriers), a fixed bed is formed by a porous elastic body having large voids (pores) on the surface and inside, for example, small bodies of plastic sponge (urethane foam). It was confirmed that the method of constructing and inflowing organic sewage in a downward flow to bring the sewage into countercurrent contact with diffused bubbles does not cause clogging and enables a quick sewage treatment, and has reached the present invention.

Conventionally, a technique called a sponge activated sludge method has been described in the literature under the title of “fluidized bed biofilm treatment using urethane foam”.

(Water and drainage vo132 No5 pp17-24 (1990)) According to the description of this technology, the sponge activated sludge method is to put the sponge bodies into the aeration tank of the activated sludge method and use aerated air to sponge bodies. The flocs attached to the surface of the sponge body by floating and floating (the flocs referred to in the activated sludge method differ from the biofilm referred to in the biofilm method in terms of size and abundance of the types of microorganisms they contain). .)
This method removes BOD in sewage water, while separating SS in sewage water and suspended microorganisms not attached to sponge bodies in a sedimentation basin following the aeration tank. This technique is obviously one of the activated sludge processes in which light sponge bodies with flocs on the surface float and flow in wastewater.

[Means for Solving the Problems]

 The problems of the present invention are solved by the following means.

(1) A fixed bed made of an open-cell type porous elastic body is provided in a tank, a space is provided above the fixed bed, and organic sewage is supplied from above the fixed bed to downwardly flow the fixed bed. The treated water is made to flow sequentially, and the treated water is raised from the lower side of the fixed bed to flow out at a position below the upper interface of the fixed bed and above the lower interface of the fixed bed, and below the fixed bed and / or the fixed bed. An air diffuser is provided in the middle of the space, air is supplied from the air diffuser to diffuse the air, and the porous elastic body is contacted with organic sewage as a fixed bed structure without flowing, thereby biology. A biological treatment method for organic wastewater, which is characterized by producing a mechanical action and a filtration action.

(2) A fixed bed made of an open-cell type porous elastic body is provided in the tank, a space is provided above the fixed bed, an organic wastewater supply part is provided above the fixed bed, and a lower part of the fixed bed is provided. From the upper interface of the fixed bed and above the lower interface of the fixed bed to set the upper interface of the fixed bed higher than the outflow water level of the treated water. A biological treatment apparatus for organic sewage, comprising an air diffuser for supplying air to a central part or an intermediate part.

(3) First of an open cell type porous elastic body in the tank
Fixed bed (B) is provided, a second fixed bed (C) made of the porous elastic body is provided below the first fixed bed (B), and the fixed bed (B) is provided above the first fixed bed (B). Is provided with an organic sewage supply section, and is raised from the lower part of the second fixed bed (C) so as to be located below the upper interface of the fixed bed and above the lower interface of the fixed bed. And the upper interface of the fixed bed is set higher than the outflow water level of the treated water, and between the first fixed bed (B) and the second fixed bed (C) and / or the second fixed bed (C).
A biological treatment apparatus for organic wastewater, comprising an air diffuser for supplying air to the lower part of the fixed bed (C).

The porous elastic body used in the present invention, for example, a sponge body, is a porous body formed by foaming plastics by a foaming method for forming continuous cells, and the material may be a sponge having water absorbability. However, it is not particularly limited, but particularly preferable materials include urethane resins. Particle size of sponge bodies is 10-30 mm, preferably 15-
It is 20 mm, and its shape can be square, spherical, or various other shapes, but the square is preferable. The diameter of the holes has a distribution, but the maximum is several mm. 90% porosity of sponge bodies
That is all. (Refer to FIG. 2) From the prior art, a porous elastic body having a porosity of 90% or more, for example, a sponge body is used, and this is filled in a treatment tank, and the lower part of the tank filled with this sponge body is used. When air bubbles are raised from the organic sewage by raising air bubbles from the sewage, violent turbulence is generated in the organic sewage, so the sponge bodies float and flow, forming a submerged fixed bed, let alone the effective SS. It is impossible to assume that the sponge bodies can be removed. Therefore, even if the idea of using sponge bodies for biological treatment is used, the light sponge bodies produced by the known prior art in the activated sludge method have already been used as described above. It is just a method of use, in which flocs are attached to the surface of the body and floated in sewage.

In the present invention, using the biological treatment method and biological treatment apparatus of the present invention, a porous elastic body, for example, a carrier made of sponge bodies, is used for a fixed bed of the immersion filter bed method, It is surprising to find that moderate biofilm loading on the surface and inside the voids results in high performance BOD and SS removal.

Other important techniques in the present invention are: a) When starting the passage of organic wastewater (sometimes referred to as raw water for simplicity), the water level of the raw water is a porous elastic body,
For example, a fixed bed formed by using a carrier made of sponge bodies (hereinafter, a porous elastic body, for example, sponge bodies are simply abbreviated as sponge bodies) does not reach the upper surface of the fixed bed and is fixed when blown air is sent. Keep the water level so that the floor does not move. At this time, the sponge bodies above the raw water level contain the raw water, which helps stabilize the fixed bed.

b) By providing an air diffuser also in the middle of the fixed bed, air is mainly supplied from the intermediate air diffuser to diffuse air, and BOD is removed in the first fixed bed (B), and the lower part of the fixed bed The air diffuser at is used for cleaning the fixed bed, and as the air diffusing function, the second fixed bed below the intermediate air diffusing section still needs a BOD removal function. I only use it. Aeration is performed in the first fixed bed (B),
The difference between substantially not performing aeration in the second fixed bed (C) is the biology of sponge bodies in the first fixed bed (B) and sponge bodies in the second fixed bed (C). It makes a difference in the role in the physical treatment, and gives the same effect as that when two kinds of carriers are substantially present in one sponge body.

c) The carrier consisting of sponge bodies has numerous pores with a diameter of several millimeters on the surface and inside, and the porosity reaches 90% or more. Biofilm attaches very easily to these holes,
It can hold various types of microorganisms in high concentrations. Moreover, since the surface of the sponge body is rich in irregularities, SS in the organic wastewater is effectively filtered and captured in combination with the SS adsorption action of the biofilm. Biofilm on the surface and inside of sponge body which was moderately developed in the first fixed bed (B) and was trapped by it
SS stabilizes the fixed bed. As a result, the water level of the raw water rises over time, but the fixed bed stabilizes. It should be further noted that, despite the presence of biofilm on the surface and inside the sponge bodies and the SS trapped in it, this fixed bed allows organic sewage to flow downward at high speed. Even if water is passed at a high speed, the carrier (and of course the biofilm retained on the carrier) and the organic sewage widely and efficiently contact each other to cause a biological reaction, resulting in a rapid decrease in BOD,
It enables fast sewage treatment.

d) In the second fixed bed (C), since there is no rise of air bubbles due to air diffusion, separation occurs due to the shearing action of the air bubbles rising sharply in the first fixed bed (B) and the downward flow of the sewage. Could not be captured by the biofilm fragments and the first fixed bed (B)
The sponge bodies are surprisingly well formed on the surface and in the interior, as SS may bioflocculate during passage through the first fixed bed (B) as described below.
BOD and SS of the effluent can be stably maintained at several mg /.

Up to now, no clear treated water has been obtained by the immersion filter bed method using a carrier consisting of sponge bodies alone in the fixed bed, and this has been made possible by the above a) to d). This is due to the application of new technology, which is completely unexpected.

In the past, it has been believed that in order to enhance the filtration effect of the filter bed and lower the SS of the treated water, it is necessary to employ a dipping fixed bed having a small porosity formed of a filter material having a small particle size. However, in the biological treatment apparatus of the present invention, the porosity of 90% like sponge bodies can be obtained by applying the new technology.
Even with the above filter media, the SS of treated water is sufficiently low (10 mg /
Below)

In the present invention, the filter bed having a porosity of 90% or higher has a high
The SS filtration effect was obtained because the fine SS contained in the organic wastewater was biologically aggregated while passing through the first fixed bed layer (B) to increase the particle size. Therefore, they are trapped in the second fixed bed layer (C).

With reference to FIG. 1, the structure of the submerged filter bed tank and the treatment mode of the present invention will be described below.

The structure of the submerged filter tank is composed of an organic wastewater supply pipe 1, a washing drainage outflow pipe 9, a porous water passage body 10 (mesh, etc.) for preventing the sponge body (A) from flowing out from the top, and an organic wastewater first ( Drain drain pipe that determines the water level when starting the flow of raw water)
11, a first fixed bed layer (B) composed of sponge bodies as a carrier, an intermediate air diffusing section 3, a second fixed bed layer (C), a lower air diffusing pipe 6, a washing water supply pipe 7 and a pump 8, and It is composed of a treated water outflow pipe 4 and a valve 5. In the aspect of the treatment of the present invention, first, organic sewage such as sewage is supplied from the supply pipe 1 to the first fixed bed (B) having sponge bodies as carriers. The water level of the organic wastewater is located slightly above the drain pipe 11.

The organic sewage flows countercurrently in contact with air bubbles discharged from the intermediate diffuser 3 provided between the lower part of the first fixed bed (B) and the second fixed bed (C). However, the BOD in the organic wastewater is decomposed by passing between and inside the carrier and contacting the biofilm in the presence of air. At the same time, SS in organic wastewater is also captured. The first fixed bed (B) removes some of the BOD and SS and the purified organic wastewater enters the second fixed bed (C) with SS still not removed. The layer thickness ratio between the first fixed bed (B) and the second fixed bed (C) depends on the quality of the organic wastewater to be treated, but for example, raw sewage
When SS is 100-200mg / L and BOD is 150-300mg / L,
Assuming that the bed thickness of the first fixed bed (B) is D _B and the bed pressure of the second fixed bed (C) is D _C , a ratio of D _B : D _C = 1: 0.5 to 1 may be set.

The treated water completely filtered by the second fixed bed (C) is stored in a storage tank (not shown) via the outflow pipe 4. When the treated water still contains a small amount of SS, it is filtered in the next step (not shown).

Since the SS trapping capacity of the filter bed mainly comprising the second fixed bed (C) of the present invention is very large, it is remarkably slow that an increase in filtration resistance is recognized as an increase in water level in the immersion filter bed tank. ,
When the operation is continued for a long time, the filtration resistance rises and the water level in the tank reaches the predetermined upper water level (usually 1000 mmH ₂ O). At this point, the fixed beds (B) and (C) are washed as follows. .

Typical Method Procedure for Washing The supply of raw water 1 and the treated water outflow valve 5 are stopped, and air is supplied from the air diffusing pipe 6 below the second fixed bed (C) to the first fixed bed layer (B) and the second fixed bed layer (B). In the fixed bed layer (C), the sponge body carriers flow out in an amount sufficient to vibrate vigorously,
Continue for 15 minutes.

Procedure Next, washing water (using treated water) is pressed from the washing water supply pipe 7 by the pump 8 to fluidize the carrier (at this time, air is also supplied). This operation is continued for a predetermined time to wash out a large amount of SS trapped in the fixed bed layers (B) and (C) from the washing drainage outflow pipe 9 to the outside of the system. Reference numeral 10 is a porous water-permeable body (net etc.) that prevents the sponge body from flowing out. (The porous water body 9 also works to filter out foreign matters in the wastewater when it flows into the treatment tank during the treatment of the wastewater 1.) After washing most of the SS, the washing water 7 and air The water inside the treatment tank is drained from the intermediate drain pipe 11, the water level is lowered to the water level at the start of water passage, and the supply of raw water and the outflow of treated water are restarted.

In addition, in the embodiment, the water level of the organic wastewater is set so as to be located in the first fixed bed layer (B) by the sponge bodies, but it is located above or near the first fixed bed layer (B). You may set it.

Further, the air diffuser indicates the intermediate air diffuser 3 and the lower air diffuser 6,
The lower air diffuser 6 is used only when cleaning the air,
It may also be used for normal processing.

Further, either one of the intermediate air diffusing unit 3 and the lower air diffusing unit 6 may be used as long as it causes a biological action, but in consideration of air cleaning of the fixed bed, only the lower air diffusing unit 6 or the lower air diffusing unit 6 is considered. It is better to provide both the part 6 and the intermediate diffuser 3.

〔Example〕

(Example-1) Using the biological treatment apparatus of the present invention, an experiment was conducted on raw sewage (BOD160-180 mg /, SS96-178 mg /) of F housing complex in Fujisawa City, and the performance of the conventional apparatus was compared. The result of having compared is shown.

The results of the experiment are shown in Table-1.

Comparing Run 1 and Run 3 and Run 2 and Run 4 in Table-1, the filtration continuation time of the present invention is remarkably 10 to 15 times the value of the conventional apparatus. Moreover, the treated water is equal to or slightly superior to that of the conventional device.

Also important as an index of the performance of aerobic biological treatment filter bed, In the present invention, while it is remarkably small at 2.7 to 2.9%, in the case of Run 3 by the conventional device, it reaches 28.5%, and when it is treated, about 30% of the amount of sewage is washed and discharged, and it is completely suitable for practical use. It is clear that this is an ephemeral treatment method.

[Effect of the invention] The present invention, as a result of using a unique material for the filter medium of the biological filter,
The following remarkable effects can be obtained, and the drawbacks of the conventional device can be solved.

Even when treating organic sewage having high SS and BOD, such as raw sewage, it is possible to pass water at a significantly higher filtration rate than in conventional apparatuses, and the filtration duration can be sufficiently long.

Due to the effect described in (1), the former settling basin, which was necessary in the conventional device, is not required, and the installation area of the biological filter bed itself can be greatly reduced (1/4) from the conventional one. As a result, the effect of reducing construction cost and space is remarkable.

The value of the ratio of the amount of cleaning wastewater to the integrated amount of raw water treatment can be made significantly smaller than that of the conventional equipment, the cleaning wastewater can be easily disposed, and the treated water production efficiency can be increased.

Maintenance frequency is greatly improved because the frequency of cleaning is greatly reduced.

During washing, the filter medium stopped flowing out. (In the conventional device, anthracite flows out during cleaning.

[Brief description of drawings]

FIG. 1 is a schematic diagram of the present invention of a type in which a carrier composed of sponge bodies is filled and an air diffuser is provided in the middle thereof. FIG. 2 is a schematic diagram showing an example of a sponge body. FIG. 3 is a schematic diagram showing a biological treatment apparatus having a conventional biological filter bed. Explanation of code 1 …… Organic wastewater supply pipe 2 …… Treatment tank 3 …… Intermediate diffuser 4 …… Treatment water outflow pipe 5 …… Treatment water outflow valve 6 …… Lower diffuser, 7 …… Wash water supply pipe 8 …… Wash water supply pump 9 …… Wash drainage outflow pipe 10 …… Perforated water body, 11 …… Intermediate drain pipe A …… Sponge body B …… First fixed bed, C …… Second fixed bed

Claims (3)

[Claims] 1. A fixed bed made of an open-cell type porous elastic body is provided in a tank, a space is provided above the fixed bed, and organic sewage is supplied from above the fixed bed to fix the same in a downward flow. While letting the bed flow down sequentially, the treated water is raised from below the fixed bed to flow out at a position below the fixed bed upper interface and above the fixed bed lower interface, and below the fixed bed and / or the fixed bed. An air diffuser is provided in the middle of the fixed bed, air is supplied from the air diffuser to diffuse the air, and the porous elastic body is brought into contact with organic wastewater as a fixed bed constituent without flowing. A biological treatment method for organic wastewater, which is characterized by producing a biological action and a filtering action. 2. A fixed bed made of an open-cell type porous elastic body is provided in a tank, a space is provided above the fixed bed, and an organic wastewater supply unit is provided above the fixed bed, The treated water outflow portion is provided at a position below the upper interface of the fixed bed and rising from the lower part, and the upper interface of the fixed bed is set higher than the outflow water level of the treated water. ,
A biological treatment apparatus for organic sewage, comprising an air diffuser for supplying air to a lower portion or an intermediate portion. 3. A first fixed bed (B) made of an open-cell type porous elastic body is provided in the tank, and a second fixed bed (B) made of the porous elastic body is provided below the first fixed bed (B). Of the fixed bed (C), an organic wastewater supply section is provided above the first fixed bed (B), and the organic fixed water is supplied from below the second fixed bed (C). A treated water outflow portion is provided at a position below the upper interface and above the fixed bed lower interface, and the upper interface of the fixed bed is set to be higher than the treated water outflow level, and the first fixed bed (B) Biological property of organic wastewater, characterized in that an air diffuser for supplying air is provided between the second fixed bed (C) and / or in the lower part of the second fixed bed (C). Processing equipment.