JPS586556B2 - Structure of aeration tank in wastewater treatment method and treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wastewater treatment method and a structure of an aeration tank in a treatment device thereof.

In order to prevent pollution, wastewater discharged from various factories is required to be treated to a BOD concentration below a certain value before being discharged, and various wastewater treatment methods are implemented depending on the type of wastewater.

The activated sludge method is also a typical wastewater treatment method, and this method is currently considered to be the most suitable method for treating wastewater containing a large amount of organic matter and having a high BOD concentration, such as wastewater from various food processing factories.

However, with the conventional activated sludge method, it is not possible to directly treat wastewater with a high BOD concentration of 3,000 tons or more, so when treating high-concentration wastewater with the activated sludge method, the wastewater must first be diluted with water. Therefore, it is necessary to reduce the BOD concentration, which requires additional processing costs.

Additionally, although various wastewater treatment methods other than the activated sludge method have been developed, a method that can efficiently treat wastewater with high BOD concentrations has not yet been developed, and such a treatment method is strongly desired. has been done.

In order to meet such demands, the present inventor has conducted various experimental studies with the aim of providing a wastewater treatment method that can efficiently treat high-concentration BOD wastewater discharged from various factories at a relatively low cost. As a result, the aeration treatment (decomposition treatment of organic matter in wastewater) of wastewater in an aeration tank (decomposition tank) in the conventional activated sludge method has been replaced with a specific coal or activated carbon that has a specific particle size distribution and has microorganisms attached to it. It was discovered that when carried out while fluidizing, high-concentration BAD wastewater, which cannot be treated at all by conventional activated sludge methods, can be directly and extremely efficiently treated.

In particular, by using coal grains on which microorganisms have been implanted through a specific method outside the tank, the concentration of B can be further increased.
It has been discovered that OD wastewater can be converted into purified water with an extremely low concentration of BOD.

It has also been found that the above effects can be achieved by treating the wastewater by increasing the amount of dissolved oxygen in the wastewater in the aeration tank to a considerably larger amount than in the conventional activated sludge method.

Furthermore, it has been found that the above effects can be reliably achieved by having a specific structure for the aeration tank that carries out the above wastewater treatment.

The present invention was achieved based on the above knowledge, and the BOD
In a wastewater treatment method in which highly concentrated wastewater is aerated in an aeration tank to lower its BOD concentration, particles with a particle size of 2 to 5 mm are used.
The difference in particle size is O~0.5m when the occupancy rate is 80% or more.
Coal (excluding peat, bituminous coal and anthracite with a carbon content of 84% or more) or activated carbon that has a particle size distribution in which the occupancy rate is 70% or less within the range of The present invention provides a wastewater treatment method characterized in that wastewater is treated while flowing through the aeration tank, and a structure of the aeration tank used to carry out this treatment method.

In the conventional activated sludge method, in order to improve the treatment effect, attention is paid to making the state of the wastewater flowing in the aeration tank as uniform as possible. In order to disperse and flow the activated carbon uniformly in the tank, we use particles with as small a particle size as possible, for example, particles with a particle size of 2 mm or less, or we use particles with a uniform particle size, such as particles with a difference in particle size of 0 to 0. The occupancy rate within the range of .5 mm is 95% or more.

On the other hand, the treatment method of the present invention uses coal grains or activated carbon that have a particle size distribution opposite to that of the conventional method, and can achieve a remarkable effect compared to the conventional method. It is an invention.

Hereinafter, the wastewater treatment method of the present invention having the above characteristics will be described in detail based on its embodiments together with the structure of the aeration tank according to the present invention.

In the following (and above), "being able to treat wastewater" means being able to reduce the BOD concentration of wastewater to a level that allows it to be discharged with industrially viable efficiency.

The wastewater to which the treatment method of the present invention can be applied is not particularly limited, and includes, for example, bean paste manufacturing wastewater, miso brewing wastewater, seafood processing wastewater, pig farming wastewater, and the like.

In addition, high concentration BOD wastewater, that is, BOD3000-3
0000ppm wastewater can be treated without dilution.

Of course, it can be applied to wastewater with low concentration BOD, but
Since wastewater with an OD (200 to 1000 ppm) can be treated by the conventional activated sludge method, the treatment method of the present invention is particularly effective for wastewater with a high concentration of BOD, which cannot be treated with the conventional method.

In addition, in the present invention, the coal to be fluidized in the aeration tank has a particle size of 2 to 5 mm in the proportion of 80% or more, preferably 90% or more, and the particle size difference is within the range of 0 to 0.5 mm. has a particle size distribution of 70% or less, preferably 60% or less, more preferably 50% or less.

If more than 20% of particles have a particle size of 2 mm or less, or if the difference in particle size is within the range of 0 to 0.5 mm, that is, more than 70% of particles have a uniform particle size, the particle size distribution is sufficient. Therefore, it becomes difficult to sufficiently uniformize the flow state of the coal grains in the aeration tank, and the object of the present invention cannot be achieved.

In addition, the above-mentioned coal must have microorganisms attached to it, but peat has low strength and has a carbon content of 84.
% or more, it is difficult for microorganisms to settle on bituminous coal and anthracite coal, so these coal grains are not used, and cutlet coal and lignite are used. In addition, it is preferable that microorganisms settle outside the tank, and in particular, It is preferable to carry out the process so that microorganisms including alcohol-fermenting bacteria are implanted.

As a preferable example of this implantation method, the particle size is 0.2 to 2.
100 parts by weight of coal having a particle size distribution in the range of 0 mm;
An example is a method in which 10 to 80 parts by weight of a nutrient source containing a large amount of protein such as rice bran or oil cake and phosphorus and potassium is blended to a moisture content of 40 to 60%, and the mixture is fermented.

Then, the coal grains on which microorganisms have been implanted in this manner may be made to have a desired particle size distribution depending on the purpose.

Further, when activated carbon is used, it is sufficient to put it into an aeration tank together with the required amount of sludge as MLSS, and as a result, microorganisms settle on the activated carbon in the tank.

Therefore, the present invention is carried out by flowing coal or activated carbon having a specific particle size distribution and having microorganisms attached thereto as described above in an aeration tank. The point is that the raw water is introduced into the aeration tank via the screen tank and raw water storage tank.
This is the same as in the conventional activated sludge method.

However, in the conventional method, wastewater with a high concentration of BOD was diluted with water before being introduced into the aeration tank, but in the method of the present invention, the BOD
It differs in that it can be directly introduced even with a high D concentration of 3000 to 30000 ppm and can be treated under a high load (3 to 30 kg BOD/m3 days).

The amount of coal particles fluidized in the wastewater to be treated introduced into the aeration tank depends on the type of wastewater, but is usually 5 to 25%.
k9/m3 (aeration tank), preferably 10-20 kg/m
3, and the amount is selected to increase as the BOD concentration increases.

Further, it is preferable to use coal having a particle size distribution such that the distribution amount of coal with a large particle size increases as the BOD concentration of the wastewater to be treated increases.

Aeration treatment in the aeration tank is performed by blowing air into the wastewater using an aeration pipe to make the wastewater flow and the coal particles flow.The amount of air blown at this time is determined based on the amount of dissolved oxygen in the wastewater to be treated. is appropriately selected depending on the type of wastewater, etc. so that the amount is 2 to 7 ppm, preferably 3 to 5 ppm.

Next, a preferred structure of an aeration tank used for carrying out the treatment method of the present invention will be described with reference to embodiments shown in the drawings.

First, the embodiment shown in FIGS. 1 and 2 will be described. A is a tank body, B is an aeration pipe, and the tank body A has a pair of long side walls 1, 1 and a pair of short side walls 2, 2. It consists of a bottom wall 3 surrounded by these, and an opening 4 at the top.

Moreover, the lower part of one long side wall 1 is 45° with respect to the bottom part 3.
It has an angle of ~60°, and the width a between the long side walls 11 at the opening 4 of the tank body A and the width b of the bottom wall 3 are b/a = 0.5
The sloped wall 5 has an angle of .about.0.8.

Further, a plurality of air diffusers B are arranged in parallel along the inner wall surface near the bottom wall of the other long side wall 1.

Also, the height h of the inner wall of the tank body A and the above a are a/h=
It is set at 0.4 to 0.8.

Further, to explain the embodiment shown in FIGS. 3 and 4, the tank main body A' in this example has two tank main bodies A having the structure shown in FIGS. The long side walls 1 of the long side walls 1 are removed leaving the slanted walls 5 and are arranged side by side. Therefore, the width a' between the long side walls 1', 1' at the opening 4' is 2a, and the two slanted walls 5 are arranged side by side. A chevron-shaped flow regulating body 6 is provided by the walls 5', 5', and 2b'/
a'=0.5-0.8, 2b''/a'=0.5-0.8
, a,/2h'=0.4 to 0.8, except that the structure is the same as that shown in FIGS. 1 and 2. A plurality of them are arranged in parallel along the inner wall surface near the bottom wall of ', 1'.

In the tank bodies A and A' according to the present invention, b/a, 2b'/
The reason why the angles of a' and 2b'/a' and the inclined wall 5.5 are defined as described above is to allow the coal grains to circulate smoothly in the tank bodies A and A according to the grain size.

Further, in any of the embodiments, the air diffuser pipe B is configured and installed so that the air blown out from the air diffuser pipe rises directly upward, and its structure is not necessarily limited, but the long side walls 1, 1'
It is preferable to install the diffuser tube in a direction perpendicular to the air diffuser, and it is particularly preferable to use one having an H-shaped structure.

In addition, in the figure, 7 and 7' are inlets for wastewater from the raw water storage tank (not shown) to the tank bodies A and A', and 8 and 8' are the separation tanks (not shown) from the tank body A. 9 is the liquid level.

Since the aeration tank according to the present invention is configured as described above,
When the aeration treatment in the present invention is carried out using the above-mentioned tank body A or A', coal grains with small particle size move in the direction of arrow A in the figure, and as the particle size increases, the coal particles move in the direction of arrow A in the figure. The object of the present invention can be achieved more effectively by circulating the fluid in the C direction.

In addition, after passing through the aeration treatment (decomposition treatment) in the treatment method of the present invention, the wastewater that has been made into a low concentration BOD can be subjected to decomposition treatment in a normal activated sludge method as necessary. According to the treatment, surplus sludge that was conventionally transferred to a surplus sludge tank and treated can also be returned to the aeration tank in the present invention for treatment.

Examples of the treatment method of the present invention and examples of producing coal on which microorganisms are attached, which are suitable for carrying out the present invention, are listed below along with reference examples.

Production Example A mixture consisting of 3 kg of lignite, 1 kg of rice bran, and 1.5 kg of water, which has a substantially uniform particle size distribution in the range of 0.2 mm to 10 mm, was placed in a container at room temperature (20 ~35°C).

Fermentation begins after 24 hours and water evaporates rapidly, so spray water on the surface every day and keep the temperature at the center at 50°C.
Stir daily to maintain ±2°C, and complete fermentation 7 days after starting fermentation.

The end of fermentation was defined as the time when the apparently white mold entered the inside of the coal grains and started to destroy the grains.

Example Miso brewing wastewater with BOD 3000 ppm and BOD 90
00 ppm of seafood processing wastewater was treated under the conditions listed in Tables 1 and 2 below to obtain the treated water shown in Tables 1 and 2, respectively.

Note that the reference example shows a case using the conventional activated sludge method.

In Example 1, the microorganism-implanted coal particles obtained in the above production example were cut to a particle size exceeding 5 mm, and
kg/m3 was used.

Reference Example 1...Blue bond type Reference Example 2...Deep aeration type In Example 2, the coal grains used in Example 1 were
kg/m3 was used.

Reference Example 3: Blue bond type Reference Example 4: Deep aeration type Next, a test example showing the effect of specifying the particle size and particle size distribution of the carrier according to the present invention, and the effect of the carrier material according to the present invention is shown. List.

Test Example 1 Four types of lignite (carbon content 55%) adjusted to have the particle size and particle size distribution shown in Table 3 below were prepared, and for every 3 kg of each lignite, 1 kg of rice bran and 1 kg of water were prepared.
kg were blended, and these blends were treated in accordance with the production example described above to obtain four types of microbial implantation carriers.

Note: Samples 1 to 4 all have the above particle size. Different particle sizes are distributed within the range and within the particle size range above. Contains 98% or more.

■ Sample 1 contains all particles within the above particle size range. Particle size difference in the range 0-0.5 10% or less within the mm range. Ru.

Next, using each of the above samples, BO was prepared in the following manner.
Miso brewing wastewater (raw water) containing 3,000 ppm of D was treated.

That is, 3 kg of the above sample was placed in a batch type aeration sedimentation tank (capacity 100 liters) equipped with an aeration pipe near the bottom, and 100 liters of the above raw water, which had been stored in the raw water tank in advance, was supplied with a supply pump, and a blower ( Output 30W, 30l
After aeration and agitation for 20 hours by supplying air at a rate of 10 l/min), the supply of air was stopped and the sludge was allowed to settle for 3 hours, and then the supernatant water (treated water) was transferred from the settling tank to the treatment tank. I pulled it out.

After that, the BOD concentration of each treated water was measured.

The results are shown in Table 4 below. From the results shown in Table 4 above, when sample 1 according to the present invention is used, other samples 2 and 3
It can be seen that the processing effect is much better than when using Samples and Samples 4 and 4.

Test Example 2 Samples of lignite, anthracite, and anthracite each adjusted to have the same particle size range and particle size distribution as Sample 1 used in Test Example 1 were prepared, and these were prepared according to the production example described above. Samples 1', 5 and 6 were obtained.

Next, the same miso brewing wastewater (raw water) as that treated in Test Example 1 was treated under the same conditions as Test Example 1 using each of the above samples.

The results are shown in Table 5 below.

From the results shown in Table 5 above, it can be seen that when sample 1' according to the present invention is used, the treatment effect is much better than when other samples 5 and 6 are used.

As mentioned above, the wastewater treatment method of the present invention is based on a completely different technical idea from conventional methods, and enables direct treatment of high-concentration BOD wastewater, which was impossible to directly treat with conventional methods. B.
Since the OD load can be treated at a high load, a large amount of wastewater can be effectively treated per hour compared to conventional methods, and the running cost of wastewater treatment can be greatly reduced, making maintenance and management easier. Together, they will have a tremendous industrial effect.

[Brief explanation of drawings]

Fig. 1 is a plan view showing one embodiment of the aeration tank of the present invention;
3 is a plan view showing another embodiment, and FIG. 4 is a sectional view taken along the Y-Y line. A, A'... Tank body, B... Diffusion pipe, 1, 1'... Long side wall, 2, 2'... Short side wall, 3, 3'... Bottom wall, 4, 4'
...opening, 5,5'...mountain slope wall.

Claims (1)

[Claims] I. In a wastewater treatment method in which wastewater with a high BOD concentration is aerated in an aeration tank to lower the BOD concentration, the difference in particle size is determined when the occupancy rate of particles with a particle size of 2 to 5 mm is 80% or more. 0
~ 0. 70% occupancy of objects within 5 mm
Wastewater treatment is performed while flowing coal (excluding peat, bituminous coal with a carbon content of 84% or more, and anthracite) or activated carbon that has a particle size distribution as follows and has microorganisms attached to it through the aeration tank. A wastewater treatment method characterized by: 2. The method for treating wastewater according to claim 1, characterized in that air is blown into the aeration tank so that the amount of dissolved oxygen in the wastewater to be treated is 2 to 7 ppm. 3. The wastewater treatment method according to claim 1 or 2, characterized in that the coal used is one on which microorganisms have been implanted outside the tank. 4. The method for treating wastewater according to claim 3, wherein the microorganisms include alcohol-fermenting bacteria. 5. The wastewater treatment method according to claim 1, wherein the amount of the coal particles used is 5 to 25 kg/m3 (aeration tank). 6. The wastewater treatment method according to claim 1, wherein the occupancy rate of coal or activated carbon with a large particle size is increased as the BOD concentration of the wastewater to be treated increases. 7 BOD concentration of wastewater to be treated is 3000 to 30000p
pm, and the wastewater treatment method is performed at a BOD load of 3 to 30 kg/m3 days. 8 In a wastewater treatment method in which wastewater with a high BOD concentration is aerated in an aeration tank to lower the BOD concentration, the occupancy rate of particles with a particle size of 2 to 5 mm is 80% or more and the difference in particle size is 0 to 0. Coal that has a particle size distribution in which the occupancy rate of particles within the range of 5 mm is 70% or less and has microorganisms attached to it (
However, an aeration tank in a treatment device used to implement a wastewater treatment method in which wastewater treatment is performed while flowing peat, bituminous coal and anthracite with a carbon content of 84% or more) or activated carbon through the aeration tank, The tank body is composed of a pair of long side walls, a pair of short side walls, and a bottom wall surrounded by them, with the upper part open.
It has an angle of 5° to 60°, and the width a between the pair of long side walls at the opening of the tank body and the width b of the bottom wall are b/a=0.
5 to 0.8, and a diffuser pipe.
A structure of an aeration tank in a wastewater treatment device, characterized in that it is provided along an inner wall surface near the bottom wall of the other long side wall. 9 In a wastewater treatment method in which wastewater with a high BOD concentration is aerated in an aeration tank to lower the BOD concentration, if the occupancy rate of particles with a particle size of 2 to 5 mm is 80% or more, the particle size difference
~0. Coal (excluding peat, bituminous coal and anthracite with a carbon content of 84% or more) or activated carbon that has a particle size distribution in which the proportion of particles within the range of 5 mm is 70% or less and has microorganisms attached to it, An aeration tank in a treatment device used for implementing a wastewater treatment method in which wastewater is treated while flowing through the aeration tank, the tank body being surrounded by a pair of long side walls and a pair of short side walls, Consisting of two bottom walls and a flow adjustment protrusion protruding between the bottom walls, the upper part of which is open, the flow adjustment protrusion is vertically installed in the center between the pair of long side walls, Each of the pair of long side walls is formed into a chevron shape with two oblique walls facing each other, and each of the oblique walls has an angle of 45° to 60° with respect to the horizontal plane, and a pair of oblique walls at the opening of the tank body d]a' between the long side walls and the width b', b'' of the two bottom walls are 2b'/a'=0.5 to 0.8, 2b
``/a'=0.5 to 0.8, and a diffuser pipe is provided along the inner wall surface near the bottom wall of each of the pair of long side walls. Structure of an aeration tank in a processing device. 10 The height h of the inner wall of the tank body and the width a between the pair of long side walls at the opening of the tank body are a/h = 0.4 to 0.
．． 8. The structure of the aeration tank according to claim 8, characterized in that the aeration tank has the following structure. 11 The height h' of the inner wall of the tank body and the width a' between the pair of long side walls at the opening of the tank body are a'/2h'=
The structure of the aeration tank according to claim 9, characterized in that the aeration tank has an aeration ratio of 0.4 to 0.8.