JP2554563B2 - Method and apparatus for biological treatment of organic wastewater - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel biological treatment apparatus and biological treatment method capable of highly purifying various organic sewage such as sewage by a single treatment tank, and particularly biological treatment and SS filtration. The present invention relates to a novel biological treatment apparatus and a biological treatment method that can perform removal simultaneously.

[0002]

2. Description of the Related Art Conventionally, a fixed bed packed with granular solids such as anthracite is soaked and allowed to come into countercurrent contact with oxygen-containing bubbles blown from the lower part of the fixed bed while allowing organic wastewater to flow downward. , A device for simultaneously performing filtration removal of SS while performing biological treatment by a microbial membrane on the surface of a granular solid is known, and an aerobic biological filtration device (Biological Aerated)
Filter: Abbreviated as BAF).

However, the conventional BAF has a drawback that the filter bed is clogged quickly and the filter bed needs to be frequently washed. In particular, direct treatment of organic sewage having a high SS of 100 mg / liter or more such as raw sewage causes the filter bed to be severely clogged in a short time. Therefore, it was indispensable to provide a sedimentation tank before BAF.

Further, in the conventional BAF, since the microorganisms only adhere thinly to the surface of the filter medium, the amount of organisms retained in the filter bed is small, and therefore high-speed treatment cannot be performed. In addition, there is a drawback that microorganisms adhering to the filter at the time of cleaning the filter bed are peeled off and flow out of the system.

[0005]

SUMMARY OF THE INVENTION The present invention is a conventional BAF.
It is an object of the present invention to provide a new type BAF capable of completely solving the above-mentioned drawbacks.

[0006] Specifically, the progress of clogging of the biological filter is remarkably reduced as compared with the conventional case. Even in high SS raw water,
The BAF should be easily processed directly without providing a settling tank before the BAF.

[0007] By increasing the amount of microorganisms that can be retained in the filter bed significantly (10 times or more) as compared with the conventional BAF, high-speed processing becomes possible. According to the present invention, the drawbacks of the conventional BAF can be fundamentally solved, and an epoch-making ideal BAF having high performance can be completed.

[0008]

[Means and Actions for Solving the Problems] The essence of the technical idea of the present invention is to provide a packed bed filled with a granular solid having a three-dimensional network structure and a dipping fixed bed filled with a granular solid having a three-dimensional network structure in a treatment tank. Of two packed fixed beds.

Both the packed bed and the immersion fixed bed are filled with a granular solid having a three-dimensional network structure capable of retaining a high concentration of microorganisms not only on the surface of the filter medium but also in the voids inside.
At least a part of the above-mentioned submerged fixed bed packed with a granular solid having a three-dimensional network structure is exposed to the atmosphere.

It consists of the above three points. That is, the above problems of the present invention are as follows: 1) An immersion fixed bed A filled with a granular solid having a three-dimensional network structure is provided in the treatment tank, and the upper end surface of the immersion fixed bed A is the treated water outflow means of the treatment tank. Above the outflow level ,
Moreover, a part of the immersion fixed bed A is exposed to the atmosphere,
Further, a packed bed B filled with a granular solid having a three-dimensional network structure is provided above the immersion fixed bed A via a supporting bed,
The treatment tank is provided with two mutually switchable raw water supply channels branched from one channel, one of which is a raw water supply means above the immersion fixed bed A, and the other is a packed bed B.
Is connected to the raw water supply means in the upper part of the above, and the aeration means and the treated water outflow means are provided below the immersion fixed bed A,
A biological treatment apparatus for organic sewage, characterized in that filter bed washing water supply means is provided below the treatment tank.

2) An immersion fixed bed A filled with a granular solid having a three-dimensional network structure is provided in the treatment tank, and the upper end surface of the immersion fixed bed A is higher than the outflow level of the treated water outflow means of the treatment tank.
The upper part of the immersion fixed bed A is exposed to the atmosphere.
Further, a packed bed B filled with a granular solid having a three-dimensional network structure is provided above the immersion fixed bed A through a supporting bed, and the raw water is supplied to the treatment tank above the packed bed B. Water is passed through the packed bed B to the immersion fixed bed A , and the acid is added from below the immersion fixed bed A.
A biological treatment method for organic sewage, which comprises diffusing an element-containing gas .

[0012] or, 3) provided with immersion fixed bed A filled with particulate solids having a three-dimensional network structure in the processing bath, the upper end surface of the immersion fixed bed A is above the outflow level of the treated water outlet means of the processing tank And part of the above-mentioned immersion fixed bed A is large.
A packed bed B, which is exposed in the air and is filled with granular solid having a three-dimensional network structure, is provided above the immersion fixed bed A through a supporting bed, and the raw water is supplied to the treatment tank.
At the start of the operation, first, it is performed from above the packed bed B, then raw water is passed through the packed bed B, and after the filtration resistance of the packed bed B reaches a predetermined value, the raw water is supplied from above the packed bed B. Is stopped , and the water is supplied directly to the upper part of the immersion fixed bed A to pass water to the immersion fixed bed A, and the immersion fixed bed A
It is achieved by a method for biological treatment of organic wastewater, which comprises diffusing an oxygen-containing gas from below .

It is desirable that the portion of the immersion fixed bed exposed to the atmosphere is ⅕ or less of the total length of the immersion fixed bed. Further, when the filtration resistance of the packed bed B reaches a predetermined value, it means that the packed bed B is clogged by SS and it becomes difficult to pass the raw water, and the raw water treatment performance of the treatment tank deteriorates. Say. At this point, the level of raw water is usually packed bed B.
Has reached the bottom surface of.

To make the outflow level of the treated water outflow means close to the upper end surface of the immersion fixed bed A, the outlet of the treated water outflow pipe or the level of the pipe installed outside the treatment tank should be above the immersion fixed bed A. It is realized by setting the level close to the end face.

The packed bed B, which is one aspect of the present invention described above.
When the filtration resistance of No. 1 reaches a predetermined value, the supply of raw water from above the packed bed B is stopped and the raw water is directly supplied to the upper part of the immersion fixed bed A. The pipe is branched into two flow passages up to the inlet to the treatment tank, one flow passage is connected to the raw water supply means to the packed bed B via the control valve if necessary, and another flow passage is connected to the control valve if necessary. It is realized by using a device characterized in that it is connected to a raw water supply means provided above the immersion fixed bed A.

In the case of this aspect of the present invention, it is preferable to provide a space portion having an appropriate height above the submerged fixed bed A for providing the raw water supply means. The granular solids packed in the packed bed B and the fixed bed A immersed are more porous than the granular solids such as anthracite which do not have large voids inside, and have a three-dimensional network structure with large voids inside the filter medium itself. Particulate solids of (for example, granular pieces of polyurethane foam) are suitable. However, a part of the granular solid in the lower part of the medium fixed bed filled with the immersion fixed bed A may be replaced with a granular solid such as anthracite or chamotte. In this case, the SS of the treated water is further reduced.

In order to deepen the understanding of the constitution and operation of the present invention, one specific structure of the treatment tank of the present invention is shown in FIG.
Will be explained. However, the present invention is not limited to the following specific examples.

(Specific Structural Example) In FIG. 1, raw water consisting of organic sewage such as sewage is supplied to a treatment tank 1 through a raw water supply pipe 2.

The raw water supply pipe 2 is branched into a branch pipe 21 and a branch pipe 22 in this specific example before reaching the treatment tank 1. The branch pipe 21 and the branch pipe 22 are respectively provided with a valve 11 and a valve 12 for controlling the supply of raw water. The branch pipe 21 is connected to a raw water supply unit (not shown) for the packed bed B, and the branch pipe 22 is
It is connected to a raw water supply means (not shown) for the immersion fixed bed A, which is provided in a space C between the packed bed B and the immersion fixed bed A.

As described above, the structure in which the raw water supply pipe 2 is divided into two paths and arranged is not an essential structure for the apparatus of the present invention, but it is shown in FIG. 1 as a preferred embodiment.
The treatment tank 1 is provided with an immersion fixed bed A filled with a granular solid 25 having a three-dimensional network structure, and the upper end surface a of the immersion fixed bed A is a pipe of a treated water outflow pipe 3 which constitutes a treated water outflow means of the treatment tank. Level b (This level b is equal to the treated water runoff level)
A packed bed B filled with granular solids having a three-dimensional network structure is provided above the immersion fixed bed A and above the immersion fixed bed A via the support bed 4. The immersion fixed bed A is supported by the support floor 5. Both the support floor 4 and the support floor 5 are composed of a porous member (net or the like).

An air diffuser 6 is provided below the immersion fixed bed A supported by the support bed 5 to supply oxygen-containing bubbles to the immersion fixed bed A. The air diffusing means 6 is the immersion fixed bed A.
It may be embedded inside.

At the bottom of the processing tank, there is provided means for supplying backwash water for washing the submerged fixed bed A and the packed bed B. A wash water supply pipe 7 having a supply pump 10 and a control valve 13 is connected to the wash water supply means for backwash from a wash water storage tank (not shown).

A porous member 8 is provided on the upper part of the processing tank in order to prevent the outflow of the granular solid filled during the cleaning of the packed bed B. In addition, a washing water outflow pipe 9 is provided above the treatment tank.
Is provided.

The above is one aspect of the structure of the processing tank of the present invention. Next, the operation of the present invention will be described according to this device. (Operation) In FIG. 1, each valve 12, 13 of the processing tank 1
And 14 are closed, and organic sewage such as sewage is first supplied as raw water to the treatment tank through the raw water supply pipe 1 and the branch pipe 21. Therefore, the raw water flows downward from the upper part of the packed bed B in the treatment tank 1.

On the other hand, the oxygen-containing bubbles from the air diffusing means 6 in the lower part of the processing tank are used as an ascending flow to rise in the immersion fixed bed A. Thus, the raw water is injected into the treatment tank in the immersion fixed bed A while being biologically treated in countercurrent with the oxygen-containing bubbles.

When the level of the treated water (including the raw water being treated) reaches the level a of the submerged fixed bed A in the treatment tank 1, the valve 14 is opened to let the treated water flow out of the treatment tank. Start routine aerobic biotreatment.

The water level of the treated water in the treatment tank at the start of the raw water flow is at the level a of the immersion fixed bed A as described above, and this position is several centimeters to several centimeters from the pipe level b of the external treated water outflow pipe. It is about 10 centimeters higher. Therefore, at the start of raw water flow, a part of the packed solid in the immersion fixed bed A is exposed to the atmosphere. The portion of the packed solid in the immersion fixed bed A exposed to the atmosphere is designated as D.

The granular solid in the packed bed B had a three-dimensional network structure having large holes 26 of 1 to 3 mm as shown in FIG. 2 (so to speak, a sponge having only a skeleton).
Being a granular solid 25, raw water also freely enters the interior of the granular solid. Therefore, the SS in the raw water is effectively trapped on the surface and inside of the granular solid having a three-dimensional network structure that is filled while flowing down the packed bed B.

According to the result of the experiment, the particle size of the granular solid 25 having a three-dimensional network structure is preferably in the range of 5 to 40 mm, and if the particle size is smaller than this, clogging occurs due to SS in the raw water, and the filtration resistance easily rises quickly. On the contrary, if the particle size is larger than this, the SS removal efficiency is deteriorated. Further, the layer thickness of the filling layer B is preferably 30 cm or more.

As described above, in purifying the organic sewage, the organic sewage is first passed through the packed bed where the solid particles 25 having a three-dimensional network structure are exposed to the atmosphere, and SS
It is one of the novel features of the technical idea of the present invention to remove the SS BOD.

Then, it was made to flow from the bottom of the packed bed B (S
The S and SS BOD are removed by 80% or more). The organic wastewater then flows down into the immersion fixed bed A in a downward flow,
Contact with oxygen-containing bubbles from the diffuser in countercurrent.

The immersion fixed bed A is filled with a granular solid 25 having a three-dimensional network structure as shown in FIG. 2, and the voids (holes 26) inside this granular solid have an extremely high concentration (experimental). The result is a microbial concentration of 18 to 20 g / liter)
Are naturally propagated and fixed.

This high concentration of microorganisms is due to the BAF of the present invention.
Is fundamentally different from BAF when using a granular solid such as conventional anthracite. In the conventional BAF filled with granular solids such as anthracite, the immersion fixed bed A
The concentration of microorganisms retained in the plant is at most 1000-1500m
However, the concentration of the microorganisms retained in the immersion fixed bed A filled with the granular solid having a three-dimensional network structure of the present invention is 18,000 to 20,000 mg / liter, which is 10 to 20 times that of the conventional case. Reaches microbial retention.

The organic wastewater flowing out from the lower part of the packed bed B is contacted with the above-mentioned high-concentration microorganisms and oxygen-containing bubbles in the immersion fixed bed A, whereby BOD is removed at a high speed.

At the same time, the colloidal SS that was not removed in the packed bed B was
It is highly removed by the action of biological filtration, and flows out as treated water of clear treated water (SS number mg / l).

Application of the granular solid 25 having a three-dimensional network structure in the present invention (since the porosity is 97% or more, which is much larger than the porosity of 50% of the conventional BAF, the SS trapping capacity can be remarkably increased). And packed bed B and immersion fixed bed A
Due to the two-stage filter bed configuration, the increase in filtration resistance of the present invention is significantly reduced as compared with the conventional BAF.

Conventional BAF (particle size of granular solid is 3-4 m
m anthracite single-stage filter configuration) same raw water,
When operated at the same filtration rate, the rate of increase in filtration resistance of the present invention is significantly reduced to 1/5 to 1/10.

Even so, when raw water is passed through the apparatus of the present invention for a long time, the amount of SS trapped in the packed bed B increases, reaches a limit at a certain point, and raw water cannot be passed through the packed bed B any more. At this time, the valve 12 is opened, the valve 11 is closed, and the raw water is supplied to the immersion fixed bed A from the raw water supply means to the immersion fixed bed A through the branch pipe 22. The timing of this switching can be determined by the water level in the packed bed B.

Even when the SS trapping capacity of the packed bed B reaches its limit, the trapping of SS on the submerged fixed bed A is small because most of the SS trapping has been carried out by the packed bed B until then, so that the submersion is not performed. The SS capture capacity of the fixed bed A still has a sufficient margin. Therefore, raw water can be passed through this route for a longer time.

Immersion fixed bed A when starting water flow to the treatment tank
Providing the portion D in which a part of the packed solid therein is exposed to the atmosphere further increases the SS trapping capacity of the immersion fixed bed A.

As described above, packed bed B and immersion fixed bed A
Taking full advantage of the two-stage filter bed configuration of
It is a feature of the present invention that the treatment capacity (continuous operation time) of the treatment tank of the present invention is greatly expanded.

However, when raw water is passed through the apparatus of the present invention from the route passing through the branch pipe 22 for a long time, the SS trapping ability of the submerged fixed bed A finally reaches its limit, and the filtration resistance is increased to further increase the raw water. At this point, the valves 14 and 12 are closed to stop the supply of the raw water and the outflow of the treated water, and increase the oxygen-containing bubbles in the diffuser 6 to increase the amount of oxygen-containing bubbles. Air cleaning of A and the packed bed B is performed. After air-washing the immersion fixed bed A and the packed bed B for several minutes, the valve 13 is opened and the pump 10 is operated to supply washing water, and backwashing of the immersion fixed bed A and the packed bed B is continued for several minutes. To do.

As a result, the SS trapped in the packed bed B and the submerged fixed bed A flows out of the system through the cleaning drainage outflow pipe 9. After that, the amount of oxygen-containing bubbles in the air diffuser 6 is returned to a normal value, washing water is supplied for a few more minutes, and the remaining SS in the packed bed B and the immersion fixed bed A is completely expelled for cleaning.

When the cleaning is completed by the above operation, the valve 14 is opened, the pump 10 is stopped, the valves 13 and 12 are closed, and the valve 11
When the raw water is opened and the raw water is supplied from the route through the branch pipe 21, clear treated water is obtained again from the treated water outflow pipe 3.

[0045]

【Example】

(Example-1) A verification test of the apparatus of the present invention was performed using the groundwater as the raw water.

Table 1 shows the water quality of the aggregate groundwater. Table 1 Water temperature 21-23 ° C SS 180-260 mg / liter BOD 150-230 mg / liter Table 2 shows the specifications and experimental conditions of the experimental apparatus.

[0047]

[Table 1] Under the conditions shown in Table 2, the raw water having the water quality shown in Table 1 was continuously treated for 6 months. During the first 3 to 4 weeks, a high concentration of microorganisms of 15 to 20 g / liter was immobilized inside the granular solid composed of polyurethane foam.

The water quality of the treated water from one month after the treatment of this experimental apparatus and the treatment performance of the apparatus are as shown in Table 3, and treated water of extremely high quality was stably obtained. Also, 1
Despite the high filtration speed of 22.7 m / day, 3
Continuous filtration for a long time of 2 to 36 hours was possible.

Table 3 Treatment results (range for 6 months) SS 2 to 3.5 mg / liter BOD 8 to 11 mg / liter Filtration duration time 32 to 36 hours Washing wastewater generation ratio 4.0 to 4.2% Above table In the above, the filtration continuation time means the time until the water level in the immersion fixed bed A shown in FIG. 1 rises to the lower surface of the packed bed B.

The washing wastewater generation ratio is a numerical value represented by the following ratio of amounts. Amount of washing wastewater generated (liter) / total amount of raw water passing (liter) (Comparative Example-1) In the conventional BAF (thickness of 3 to 4 mm as an anthracite filling layer, which is filled to a layer thickness of 2.5 m), The sewage of the water quality shown in Table 1 above is used as raw water.
The water was passed at 2.7 m / day, and the time during which filtration could be continued (time until the filtration resistance reached 500 mmH ₂ O), the quality of treated water, and the generation ratio of cleaning wastewater were examined. The experiment was conducted for 6 months.

The results are shown in Table 4 below. Table 4 Treatment results of comparative example SS 5.3 to 8.8 mg / liter BOD 18 to 27 mg / liter Possible time for continuous filtration 32 to 36 hours Cleaning wastewater generation ratio 35 to 38% When Table 3 and Table 4 are compared, Despite the treatment with the same raw water and the same filtration rate, obviously the quality of the treated water obtained by the method of the present invention is good, and the remaining filtration time is 7 when the conventional BAF is used. It was confirmed that it was 8 times longer and the generation ratio of cleaning wastewater was about 1/10.

This shows the outstanding effect of the method of the present invention.

[0053]

According to the present invention, the following great effects can be obtained and all the drawbacks of the conventional BAF can be solved.

Microorganisms were immobilized at a high concentration inside a granular solid having a three-dimensional network structure with a large porosity, and this was used as a fixed bed, and the configuration of the filter bed was multi-staged, so clogging of the filter bed was significantly reduced. , And biological reactions proceed at high speed.

Therefore, the processing tank can be made compact,
When compared at the same filtration speed, the processing time of one cycle from the start of water flow to the start of washing, that is, the filtration duration, can be taken about 8 times longer than that of the conventional one.

The cleaning wastewater generation ratio is 1/100 of that of the conventional BAF.
Since it is reduced to 10, it becomes easier to dispose of sludge separation water,
Treated water production efficiency is also improved. Even with high SS sewage, B
Since it is not necessary to remove the SS in advance by installing a settling tank before the AF, the construction cost and installation space are greatly reduced.

As a result of being able to highly treat organic sewage such as sewage with the apparatus of the present invention and one tank, the maintainability is remarkably improved. Since the microorganisms are immobilized and held inside the filter medium itself, the microorganisms inside the filter medium do not flow out of the system even when the filter bed is washed. Therefore, good treated water can always be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of a downflow type biological filtration device of the present invention.

FIG. 2 is a perspective view of a granular solid having a three-dimensional network structure used in the present invention.

[Explanation of symbols]

 1 Treatment Tank 2 Raw Water Supply Pipe 3 Treated Water Outflow Pipe 4 Supporting Floor 5 Supporting Floor 6 Diffusing Means 7 Washing Water Supply Pipe 8 Porous Member 9 Washing Drainage Outflow Pipe 10 Pump 11 Valve 12 Valve 13 Valve 14 Valve 21 Branch Pipe 22 Branch pipe 25 Granular solid with three-dimensional network structure 26 Pore A Immersion fixed bed B Packed bed C Space part a Immersion fixed bed upper end surface b Treated water outflow level

Claims (3)

(57) [Claims] 1. A dipping fixed bed A filled with a granular solid having a three-dimensional network structure is provided in the treatment tank, and the upper end surface of the dipping fixed bed A is higher than the outflow level of the treated water outflow means of the treatment tank.
And part of the immersion fixed bed A is exposed to the atmosphere.
Further, a packed bed B filled with granular solids having a three-dimensional network structure is provided above the immersion fixed bed A via a supporting bed, and the processing tank can be switched from one flow path to the other. 2 raw water supply channels are provided, one of which is connected to the raw water supply means above the immersion fixed bed A, and the other one is connected to the raw water supply means above the packed bed B. A biological treatment apparatus for organic sewage, characterized in that an aeration means and the treated water outflow means are provided below the floor A, and a filter bed washing water supply means is provided below the treatment tank. 2. An immersion fixed bed A filled with a granular solid having a three-dimensional network structure is provided in the treatment tank, and the upper end surface of the immersion fixed bed A is higher than the outflow level of the treated water outflow means of the treatment tank.
And part of the immersion fixed bed A is exposed to the atmosphere.
And a packed bed B filled with a granular solid having a three-dimensional network structure above the immersion fixed bed A through a supporting bed.
The raw water is supplied to the treatment tank from above the packed bed B, passes through the packed bed B to the immersion fixed bed A, and oxygen is supplied from below the immersion fixed bed A.
A biological treatment method for organic sewage, which comprises dispersing the contained gas . Wherein providing the immersion fixed bed A filled with particulate solids having a three-dimensional network structure in the processing bath, the upper end surface of the immersion fixed bed A is above the outflow level of the treated water outlet means of the processing tank
And part of the immersion fixed bed A is exposed to the atmosphere.
And a packed bed B filled with a granular solid having a three-dimensional network structure above the immersion fixed bed A through a supporting bed.
The raw water is supplied to the treatment tank from above the packed bed B at the start of operation, and then the raw water is allowed to pass through the packed bed B so that the filtration resistance of the packed bed B reaches a predetermined value. After that, the supply from above the packed bed B is stopped, and it is directly supplied to the upper part of the immersion fixed bed A to pass water to the immersion fixed bed A, and from below the immersion fixed bed A.
A method for biological treatment of organic sewage, which comprises diffusing an oxygen-containing gas .