JPS644834B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aerobic biological treatment device for wastewater, and in particular to a wastewater treatment device that biologically purifies wastewater under aerobic conditions using a biofilm. Biological methods are generally used to purify organic wastewater containing nitrogen compounds and other organic substances. In biological methods, organic substances, especially BOD components, whose BOD is indicated by indicators such as COD, are oxidized and removed by microorganisms. In other words, ammonia nitrogen is oxidized (nitrified) to nitrate nitrogen or nitrite nitrogen by nitrifying bacteria under aerobic conditions, and then reduced to nitrogen gas (denitrification) by denitrifying bacteria under anaerobic conditions. removed. By the way, an activated sludge method using suspended sludge is known as a biological treatment method for removing BOD components and nitrifying under aerobic conditions. in this way,
After oxidizing the treated water and floating sludge by bringing them into contact with each other while aerating in the treatment tank, the mixture of treated water and suspended sludge is transferred to a settling tank, where the sludge is allowed to settle and is separated from the treated water. The treated water is either discharged as is or introduced into the next treatment tank, the settled sludge is pulled out and a portion is returned to the original treatment tank for reuse, and the rest is disposed of as surplus sludge. This method has an extremely slow processing speed and requires a long time to process, so large-capacity equipment is required to treat a large amount of wastewater. In addition, a phenomenon called bulking occurs, which worsens the sedimentation of the sludge, causing the sludge to flow out together with the treated water, reducing the quality of the treated water.In severe cases, the sludge in the treatment tank may disappear, resulting in biological treatment itself. There is also the problem that it stops progressing. Furthermore, it has been pointed out that since the oxygen absorption efficiency is low, a large amount of air must be blown in to maintain aerobic conditions, which increases power costs. On the other hand, as a biological treatment method other than the activated sludge method, there is a generated membrane method, and methods for applying a layer to this method include a sprinkle bed method, a soaked bed method, a rotating disk method, and the like. These include plastic fillings, honeycomb tubes, and
This method purifies wastewater using a microbial film attached to the surface of solid particles or disks. Unlike the activated sludge method, there is no need to return sludge, and since bulking does not occur, maintenance is easy. There are advantages such as However, these methods have relatively small biofilm area per tank volume and low treatment capacity.
There are drawbacks such as the need for a separate solid-liquid separation operation because the SS components in the treated water and the microbial film detached from the biofilm medium flow out of the tank together with the treated water. The present invention has been completed as a result of intensive research focusing on the above-mentioned circumstances and in order to solve the problems of treatment capacity and treated water quality that have been pointed out in the biofilm method. A wastewater biological treatment device consisting of a treatment tank with an inlet and a treated water discharge part at the bottom, the treatment tank has a packed bed and a support layer for the packed bed, and the bottom of the support layer. is provided with a treated water collection device and an air introduction device, and the packed bed is filled with a uniform mixture of solid particles with a particle size of 0.2 to 10 mm and a filler sufficiently larger than the solid particles. The gist is something. The structure and effects of the present invention will be explained below based on the drawings showing the embodiments. However, the following are representative examples and do not limit the present invention, and only within the scope that can comply with the spirit of the above and below. It is free to change the shape and structure of the treatment tank body, the configuration of the treated water collection device and air introduction device, or the piping for the treated water, etc., and all of these are included in the scope of the technology of the present invention. . FIG. 1 is an explanatory diagram conceptually showing the treatment apparatus of the present invention, and FIG. 2 is a cutaway diagram of the main parts of the treatment apparatus, in which 1 is a treatment tank, 2 is a treated water storage tank, 3 is a packed bed, 4 is a support layer, 5 is a water collection/air introduction device that collects treated water and introduces air for aeration (details will be described later), 6 is a raw water introduction pipe, 7 is an air pipe, 8 and 9 are treated water Each piping is shown. The bottom of treatment tank 1 not only collects treated water, but also carries backwash water and air to treatment tank 1.
A water collection/air introduction device 5 for dispersing the water throughout is arranged, a support layer 4 is arranged above it, and a packed bed 3, which is the most characteristic feature of the present invention, is arranged above the support layer 4. An abyss 14 is formed at a suitable location at the bottom of the treatment tank 1, and a treated water outlet 15 is provided on the lower wall surface of the abyss 14, and an air pipe 7 for supplying air to the water collection/air introduction device 5 is arranged. do.
In FIG. 1, reference numeral 10 indicates a backwash pump used when backwashing the packed bed 3, 13 indicates a valve, and 11 indicates a discharge pipe for backwash water. FIG. 3 is an enlarged cutaway diagram showing the water collection/air introduction device 5, in which two reinforcing plates 5b are inserted into the rectangular cylindrical body 5a, and the upper wall of the rectangular cylindrical body 5a and the reinforcing plate 5b are arranged. A large number of through holes 5c are bored in the rectangular cylinder body 5.
The water collection/air introduction device 5 is constructed by laying a large number of wafers a on the bottom surface of the treatment tank 1 as shown in FIG. Therefore, as will be described later, the treated water that has been purified while passing through the packed bed 3 and the support layer 4 enters the rectangular cylinder 5a through the through hole 5c, flows along the bottom surface in the direction of the rim 14, and is discharged from the discharge port 15 into the tank. Expelled outside. Moreover, the air sent into the rectangular cylinder 5a from the air pipe 7 is dispersed and rises from the entire lower surface of the processing tank 1 through the through hole 5c. Wastewater treatment using such a device is carried out as follows. First, wastewater containing BOD components, nitrogen components, etc. is made to flow into the treatment tank 1 from the raw water pipe 2, and air is sent into the tank 1 from the pipe 7 through the water collection/air introduction device 5, and the packed bed 3 is Create a moody atmosphere. During the process of wastewater passing through the packed bed 3, BOD components in the wastewater adhere to and grow on the surface of the packing material, forming an aerobic microbial film such as BOD component oxidizing bacteria and nitrifying bacteria, which sequentially flows down inside the packed bed 3. BOD components and the like in the wastewater are decomposed and removed by the action of the aerobic microbial membrane, and ammonia nitrogen and organic nitrogen are oxidized to NO ₃ -N and NO ₂ -N. The treated water purified in this manner is taken out through the water collection/air introduction device 5 and the discharge port 15. By the way, in order to efficiently proceed with the biological purification described above, it is necessary to increase the effective contact area of the aerobic microbial film formed on the surface of each filling material in the packed bed 3 with the wastewater, and to also It is necessary to rise while dispersing the air evenly and create an aerobic atmosphere throughout. Moreover, as the growth of the microbial film progresses, it falls off the surface of the packing and reduces the cleanliness of the treated water, so in order to prevent such problems, it is necessary to give the packing bed 3 itself an overactive effect. be. However, in the conventional packed bed used in this type of equipment, the particle size of the packed material is too large and the effective area of the aerobic microbial membrane cannot be made large enough, resulting in insufficient biological purification effects. There are problems such as excessive heat, or the particle size of the packing material is too small, which prevents the air from rising evenly through the entire packed bed, creating an anaerobic atmosphere in some parts of the bed, reducing the purification effect. I couldn't say that it was. In contrast, in the present invention, the purification effect is significantly enhanced by adjusting the particle size structure of the filler constituting the packed bed. In other words, as a filler, the particle size is
A homogeneous mixture of relatively fine solid particles of 0.2 to 10 mm, particularly preferably 0.4 to 7 mm, and fillers that are significantly larger than the solid particles must be used;
The purpose cannot be achieved with a filler having a substantially single particle size as in the conventional example. However, the inventors have observed through experiments that in the case of only the filling, the rise of the sky is uniform throughout the packed bed, but because the surface area is small, the effective area of the microbial membrane is sufficiently large. Moreover, since the porosity of the packed bed is large, the bubbles tend to grow into large particles during the rising process, which tends to slow down the activity of microorganisms, and the removal effect of microbial membrane debris is poor. On the other hand, in the case of only microfilling, the effective area of the microbial membrane can be increased because the surface area is large, and the removal effect of microbial membrane debris is also high, but the porosity of the filling is small, so air is filled. The entire bed is not raised evenly, and an anaerobic atmosphere is formed locally, reducing the purification effect.The packed bed is likely to become clogged, and backwashing must be performed frequently. However, when a homogeneous mixture of fillers and fine fillers is used, the advantages of both are taken advantage of and the disadvantages are eliminated, resulting in an excellent purifying effect. The reason why the particle size of the solid particles was set at 0.2 to 10 mm is because of the diffusibility of air, the effective surface area of the microbial film, the treatment efficiency,
This is to simultaneously satisfy the overefficiency, etc. If the particle size is less than 0.2 mm, the air diffusivity and treatment efficiency will decrease, and if it exceeds 10 mm, the effective surface area of the microbial film will be insufficient and the overefficiency will also be poor. In either case, the purpose of the present invention cannot be achieved. Further, the filler has the effect of increasing air diffusivity and increasing processing efficiency and backwashing efficiency, and it is sufficient that the filler is sufficiently larger than the solid particles, and it is difficult to specify the particle size. However, the most practical particle size is 25-300mm.
Particularly preferred is 60 to 300 mm, and it is preferable to select from the above particle size range, taking into consideration the size of the treatment tank and the particle size of the solid particles used together. It is essential that the solid particles and filler be mixed uniformly when filling. If the mixing is insufficient, air and raw water will concentrate in uneven parts of the filler, and the purification effect will be extremely reduced. At the same time, the backwashing efficiency also decreases. Also, the blending ratio of both is not particularly limited, but
The apparent volume of the filler is 50 to 100% of the packed bed volume.
Filling is preferred. The porosity of the packed bed 3 varies depending on the blending ratio of the two, but it is approximately 50% for solid particles (sand) alone and 70-95% for the filler alone.
Therefore, the porosity is set to a value between the above-mentioned individual porosity, taking into consideration air diffusivity, biological treatment effect, excess effect, etc. The actual filling method is
It is difficult to form a packed layer all at once, so the process of filling the voids of the filler material with solid particles and adjusting the filling uniformly with water or air is performed in stages to form a layer of a certain height. A method of forming is preferred. The solid particles mentioned above include sand, anthracite,
All conventionally known filling materials such as blast furnace slag and plastic particles can be used, and the shape is not limited to spherical shapes, but can also be used such as pellets, short columns, and irregular shapes that are still crushed. Can be used. In addition, various types of fillers such as Raschig rings and dressings used in gas-liquid contact devices, pipes, spheres, irregularly shaped gravel, and various lattice-shaped containers can all be used. . The support layer disposed below the packed bed is provided to prevent fine solid particles in the packed bed from leaking out from the through holes 5c of the water collection/air introduction device 5. Gravel, etc. with a diameter slightly larger than that is used. In addition, as the water collection/air introduction device 5, an A/W type Leopold block type device developed by Shinko Feudler Co., Ltd. is shown, which has the advantage of being able to feed air from the entire bottom surface of the treatment tank. The most effective methods include, but are not limited to, the perforated block type, perforated pipe type, perforated plate type, boiler type, and T.
Water collection devices such as mold block type and strainer type can also be used. It is also possible to provide a separate air blowing pipe in the support layer or the like to supply aeration air from a location different from the water collection device. The present invention is generally constructed as described above, but the point is that by using a uniform mixture of fine solid particles and fillers as the filling material of the packed bed, it has a high purification effect as listed below. We were able to obtain a wastewater treatment device. (1) Due to the presence of the filler, aeration air is uniformly supplied to the entire packed bed, so the entire bed can be maintained in an aerobic atmosphere, increasing the biological treatment effect. Furthermore, the entire packed bed can be made to have an appropriate porosity, and the efficiency of wastewater treatment and backwashing can also be improved. (2) The presence of fine solid particles expands the effective surface area of the microbial membrane and also promotes the formation of fine bubbles in the aeration air, further increasing biological treatment efficiency. In addition, the solid particle-filled section also exerts a superfluous effect on microbial film droplets and SS components in wastewater, increasing the cleanliness of the treated water. Next, examples will be given to clarify the effects of the present invention. Example 1 A treatment tower with a diameter of 200 mm and a height of 3500 mm was used for the experiment, and a water collection and air introduction device was placed at the bottom.
On top of that, gravel with a grain size ranging from 2 to 20 mmφ was filled according to the grain size to form a supporting layer. In this upper layer, sand with a particle size of 0.4 to 3 mmφ is added as solid particles, and 25 mm is added as a filler.
A mmφ magnetic sphere and a 25mmφ dressing-like filler were used, and the apparent volume of the filler was equal to the packed bed volume.
It was filled 100% and the voids were filled with solid particles (40 dressings were filled to fill the spaces with solid particles). The filling is filled to a bed height of 1300 mm (filling volume 40). Using this processing tower,
Synthetic sewage with a BOD component of 200 ppm, mainly peptone, was treated under the following conditions, and the removal rate of BOD components was investigated. Processed water volume: ^1m2 /day LV: 32m/day Processed water temperature: 25℃ SV: 1 1/h BOD load: 5Kg/ ^m2 /day Air volume: ^1.7Nm2 /day Backwash frequency: 2 times/day Results Shown in Table 1.

[Table] As is clear from Table 1, the BOD removal rate when using sand alone as solid particles is low;
By using a mixture of sand and filler, the BOD removal rate can be significantly increased. Example 2 A dressing-like filling with a diameter of 25 mm as a filler, granulated blast furnace slag with a diameter of 0.4 to 3 mm as solid particles,
A packed bed was formed in the same manner as in Example 1 except that sand or anthracite was used, and sewage 1 was treated under the following conditions.
Next, the treated water was treated. Processed water volume: ^1.73m2 /day LV: 55m/day SV: 1.8 1/h BOV load: 4.6-7.1Kg/m ³ -day air blowing volume: ^2.2Nm2 /day air volume/processed water volume: 1.3 Processed water temperature: 17-21°C Number of backwashing: 3 times/day The results are shown in Table 2.

[Table] As is clear from Table 2, no matter which mixed filler is used, the BOD value of the treated water is 20 ppm or less, the SS content is 15 ppm or less, and a high purification effect can be obtained. In addition, for those using granulated blast furnace slag and sand as solid particles,
BOD load 8.5~10Kg/ ^m2・day and 7.5~8Kg/
Although the treatment was carried out at a higher concentration of ^m3 /day, treated water with a BOD value of 20 ppm or less could be obtained in all cases. Example 3 A water collection/air introduction device was placed at the bottom of a treatment tower with a diameter of 600 mm and a height of 4000 mm, and a particle size of 2 to 20 mm was placed above it.
The supporting layer was filled with gravel of mmφ. In this upper layer, a dressing-like filling with a diameter of 70 mm and a diameter of 0.4 to 3 mm are added.
Using granulated blast furnace slag, the filling material was filled to 100% of the volume of the packed bed, and the voids were filled with solid particles (40 pieces of dressing-like filling were filled, and the spaces were filled with solid particles). fill in). Using this treatment tower, the waste water obtained by dephenolating ammonium water by benzol extraction is used as raw water, and the waste water is treated with miscellaneous water such as cooling water.
Purification treatment was carried out under the following conditions using a diluted product. Processed water volume: ^4.6m2 /day LV: 16m/day SV: 0.5 1/h BOD load: 9.6Kg/ ^m2 /day air blowing volume: ^33Nm3 /day air volume/processed water volume: 7 Processed water temperature: 23-25 °C Number of backwashing: 2 times/day The results are shown in Table 3.

[Table] As is clear from Table 3, the BOD load is 9.6
It can be seen that BOD and phenol can be removed extremely efficiently even under a high load of Kg/m ² ·day. Example 4 A treatment tower was prepared in the same manner as in Example 1, except that a 25 mm diameter dressing-like packing material and 0.4 to 3 mm diameter granulated blast furnace slag were used as solid particles. The treated water was purified. During the treatment, a PH electrode was placed in the treatment tower to prevent a drop in PH in the packed bed, and an aqueous NaOH solution was added so that the PH was 7.0. Processed water amount: 1.2m ² /day LV: 38m / day SV: 1.25 1 / h BOD load: 0.4Kg/m ²・day NH ₃ -N load: 0.6Kg/m ²・day Air blowing amount: 1.2Nm ² / Daily treatment water temperature: 25°C Number of backwashing: 1 time/day The results are shown in Table 4.

[Table] As is clear from Table 4, NH ₃
-99% or more of N is removed, and BOD and SS components can also be removed efficiently. Example 5 0.4 solid particles were impregnated with a phosphate solution adjusted to pH 12 with NaOH to have a dephosphorizing function.
A treatment tower was prepared in the same manner as in Example 4, except that granulated blast furnace slag with a diameter of ~3 mm was used, and secondary treated sewage water was purified. During treatment, the pH inside the tower is
The concentration was adjusted to 9 with a NaOH aqueous solution, and a CaCl ₂ aqueous solution was separately added into the column as a Ca source, and the other treatment conditions were the same as in Example 4. The amount of Ca added is
It was set to 100ppm. The results are shown in Table 5, and if the solid particles are subjected to dephosphorization treatment, phosphorus can be efficiently removed at the same time as nitrification.

【table】 [Brief explanation of drawings]

FIG. 1 is a schematic overall view illustrating the processing apparatus of the present invention, FIG. 2 is a partially cutaway sketch of the treatment tank, and FIG. 3 is a partially cutaway sketch showing an enlarged water collection/air introduction device. 1... Treatment tank, 2... Treated water storage tank, 3... Filled layer, 4... Support layer, 5... Water collection/air introduction device,
6... Raw water (waste water) introduction pipe, 7... Air piping,
8, 9... Treated water piping, 10... Backwash pump,
15... Treated water outlet, 14... Deepwater.

Claims (1)

[Claims] 1 A biological treatment device for wastewater consisting of a treatment tank with a wastewater inlet in the upper part and a treated water discharge part in the lower part, in which a packed bed and a support layer for the packed bed are provided, A treated water collection device and an air introduction device are provided below the bed, and the packed bed has a particle size of
1. An aerobic biological treatment device for wastewater, characterized in that it is filled with a uniform mixture of solid particles of 0.2 to 10 mm and a filler that is sufficiently larger than the solid particles.