JPH022476Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] This invention relates to a filter medium, and particularly to a filter medium used in a contact aeration method. [Prior art] The contact aeration method involves aerating wastewater and
By passing this wastewater through a filter medium, the wastewater is brought into contact with a microbial film that has formed adhering to the filter medium, and organic pollutants, phosphorus, nitrogen, etc. are adsorbed, oxidized and decomposed, and treated. Conventionally, gravel has been used as a filter medium for contact aeration methods. However, since gravel is a solid body, the surface area is small compared to the volume of the gravel, and therefore the contact area between the wastewater and the gravel is small, resulting in poor treatment efficiency. In addition, it is difficult to obtain gravel of a uniform size, and as a result, the gaps through which wastewater flows become uneven, and the microbial membrane thickens, which tends to cause clogging. Therefore, two annular bodies made of synthetic resin were combined at right angles, and a large number of wings made of synthetic resin were attached to them.
A filter medium has been proposed that can widen the area of contact with wastewater and produce a large amount of filter media of uniform size (Utility Model Publication No. 56-21520). [Problem that the invention aims to solve] However, the above synthetic resin filter media has a specific gravity of
Because it is as small as 0.9, it is easy to float due to sewage flow or the uplifting force of air caused by aeration, causing the filter media to collide with each other, and due to this collision, the microbial film attached to the surface of the filter media may peel off or fall off. As a result, there were problems such as a temporary decrease in the purification ability of the microbial film and an increase in suspended solids (SS) due to fine flocs of the detached microbial film. In addition, in the contact aeration method, the microbial film that adsorbs and retains phosphorus in wastewater tends to thicken over time, and may fall off naturally or become suspended fine flocs when the filter medium is subjected to impact as described above. phosphorus often flows out. Therefore, dephosphorization by contact aeration method is approximately 10-50%.
It is extremely unstable, and methods of adding flocculants, lime, etc. to wastewater are used to increase the dephosphorization rate. As flocculants, flocculants such as sulfuric acid, ferric chloride, and ferrous sulfate are used, but both are expensive and generate a large amount of sludge. Furthermore, the sludge after dephosphorization contains various metal salts, which requires even more expense to dispose of. When adding lime, it is necessary to raise the pH of the wastewater in order to increase the dephosphorization rate, which requires adding a large amount of lime, increasing costs. Another drawback was that it reacted with carbon dioxide in the atmosphere, producing calcium carbonate, which adhered to the inside of the reaction tank and piping, causing problems in the management of the purification equipment. In addition, when trying to increase the dephosphorization rate by adding a flocculant or lime, there was a problem in that the flocculation cost increased. This idea uses cast iron to achieve a high dephosphorization rate, and also prevents the detachment of microbial membranes.
It is an object of the present invention to provide a filter medium which can prevent phosphorus from flowing out due to suspended fine flocs and can also obtain a high dephosphorization effect without adding a flocculant, lime, or the like. [Means for Solving the Problems] This device includes an annular body, a connecting portion, an upper skeleton portion, and a lower skeleton portion, and is cast. The coupling portion is arranged concentrically inside the annular body.
An upper skeleton part is provided above the annular body and the coupling part, and a lower skeleton part is provided below the annular body and the coupling part. Moreover, the upper skeleton part and the lower skeleton part are arranged alternately. The upper skeleton part has an upper wall part extending obliquely upward from the upper surface side of the annular body toward the joint part side, and an upper horizontal part extending horizontally from the distal end of the upper wall part toward the joint part side. The upper arm extends diagonally downward from the tip of the arm and is connected to the joint. Similarly, the lower skeleton part has a lower wall part extending diagonally downward from the lower surface side of the annular body toward the joint part side, and a lower horizontal part extending horizontally from the tip of the lower wall part toward the joint part side. extends, and a lower arm extends obliquely upward from the distal end thereof and is connected to the joint. [Function] Such a filter medium is filled into a purification device, and sewage is introduced and aeration is performed. As a result, the microorganisms attached to the surface of the filter medium adsorb and oxidize and decompose organic pollutants, phosphorus, nitrogen, etc. On this occasion,
Since the filter medium is cast, it has a higher specific gravity than one made of synthetic resin, and will not float due to the flow of sewage or the upward pressure of air caused by aeration. Therefore, there is no possibility that the filter media will collide with each other and the microbial film will be peeled off due to the impact and phosphorus will flow out due to suspended fine flocs. In addition, microorganisms that elute iron coexist within the microbial membrane, and these microorganisms elute iron ions from the cast filter medium into the wastewater. Furthermore, organic phosphorus in wastewater is decomposed into phosphate ions. These iron ions and phosphate ions form an ionic bond, forming a slightly soluble amorphous iron phosphate, which co-precipitates with the microscopic flocs of the exfoliated microbial film to remove phosphorization from wastewater. Clear treated water can be separated. Therefore, dephosphorization can be performed from wastewater. Furthermore, this filter medium includes an annular body, a joint portion, an upper skeleton portion, and a lower skeleton portion, and is hollow. Therefore, the contact area with wastewater is large, and the adsorption and oxidative decomposition of organic pollutants, etc. is promoted, and
The dephosphorization mentioned above is also promoted. [Example] The filter medium of this example has a circular annular body 2 as shown in FIGS. 1 and 2. A coupling part 4 is arranged concentrically within this annular body 2. This joint portion 4 has an outer peripheral edge approximately in a hexagonal shape, and an inner hole 6.
is formed into a circular ring. A total of six upper skeleton parts 8 are arranged on the upper surface side of this annular body 2 at intervals of about 60 degrees. As shown in FIG. 3, the upper skeleton section 8 has an upper wall section 10a that slopes obliquely upward from the annular body 2 side toward the joint section 4 side at a rising angle of about 70 degrees. This wall portion 10a is configured such that the width dimension becomes smaller toward the tip. A recess 12a having a substantially trapezoidal planar shape is formed in this wall portion 10a. This recess 1
2a is for expanding the contact area. An upper horizontal portion 14a extending horizontally toward the coupling portion 4 is provided at the tip of the wall portion 10a. This horizontal portion 14a is also configured such that the width dimension becomes smaller toward the tip. This horizontal portion 14a is also provided with a window 16a having a substantially trapezoidal planar shape and passing through the horizontal portion 14a in the vertical direction.
This window 16a is for improving the circulation of waste water. The distal end of the horizontal portion 14a and the connecting portion 4 are connected to the upper arm 1.
8a is connected. This arm 18a is the horizontal part 1
It is gradually inclined diagonally downward from the tip of 4a toward the joint portion 4 side. As described above, since each upper skeleton part 8 is hollow inside, the contact area with wastewater is large. On the lower surface side of the annular body 2, a total of six lower skeleton parts 20 are arranged approximately so as to be located between each upper skeleton part 8.
They are provided at 60° intervals. Therefore, the upper skeleton part 8 and the lower skeleton part 20 are always located alternately. As shown in FIG. 4, these lower skeleton parts 20 are configured in a shape where the upper skeleton part 8 is turned upside down, so each of the constituent elements of the upper skeleton part 8, such as the wall part 10a, the recessed part 12a, 1 in each of the horizontal portion 14a, the window 16a, and the arm 18a.
The symbols 0b, 12b, 14b, 16b, and 18b are given, and the explanation will be omitted. The adjacent upper skeleton part 8 and lower skeleton part 20 are connected by linear support legs 21 and 22. Adjacent upper skeleton part 8 and lower skeleton part 20
There is a slight gap between the supporting legs 21,
22 is somewhat inclined. The filter medium of this example is manufactured by casting, and although the inside of the filter medium is hollow, the mold used for this casting does not require a core or core mold, and is similar to the mold used for casting. Manufactured by a mold and a lower mold. Further, although not shown in the figure, a large number of minute depressions are formed on the outer surface of this filter medium. This depression is for increasing the contact area. This filter medium is manufactured by pouring metal into the mold as described above, cooling it, and then removing the mold.In order to remove the foundry sand that has adhered to the cast filter medium, shot peening is performed. Let's do it. after that,
Finish with a grinder. However, the refractories and binders mixed in the mold material and graphite-based substances coated on the mold surface are locally attached to the surface of the filter medium, which prevents iron from leaching into wastewater and prevents microorganisms. have a negative chemical effect on the survival conditions of Furthermore, an oxide film is formed on the surface of the filter medium during the cooling period, which also prevents iron from leaching into the wastewater. Therefore, in order to remove these, shot peening is performed again to expose the fabric, but shot peening is also performed after that to form a large number of minute depressions, for example, with a maximum depth of about 0.3 mm. Then 97
This filter medium is immersed in 10% diluted sulfuric acid for 5 to 10 minutes to generate trace amounts of highly water-soluble complex iron sulfate and iron sulfide salts on the surface of the filter medium, and then washed with water. , chemically neutral. This improves the initial dissolution of iron into wastewater and the initial adhesion of microorganisms. For example, a large number of these filter media are filled in a septic tank, and at that time, they are stacked and accommodated so that the lower horizontal portion 14b of another filter media is positioned above the upper horizontal portion 14a. This facilitates accommodation. Sewage is introduced in a contained state and aerated from below. At this time, some of the air particles hit the outer surfaces of the walls 10a, 10b, become fine particles, and dissolve into the waste water.
The remaining air particles enter the inside of the filter medium, and the walls 10a,
It dissolves in the waste water while contacting the inner surface of 10b. The undissolved air similarly contacts the upper filter medium and dissolves in the waste water. On the other hand, wastewater flows turbulently inside and outside the stacked filter media, and since sufficient air is dissolved in the wastewater, it comes into contact with microorganisms efficiently. In addition, the surface of the filter medium has many microscopic depressions, which provides a large contact area and makes contact with microorganisms more efficient. Next, the experimental results using this filter medium are shown below. This experiment was conducted in a contact aeration tank with a capacity of 90 ml with continuous aeration. Synthetic resin filter media having the same shape and size as the above-mentioned cast iron filter media with a diameter of 14 cm and a height of 5 cm were filled in an aeration tank to test the effect of the cast iron filter media on dephosphorization. Experiments 1 and 2 were conducted under the same conditions except for the number of filter media. In Experiment 1, an aeration tank was filled with 15 cast iron filter media and 27 synthetic resin filter media, for a total of 42 filter media, and the experimental results are shown in Table 1. In Experiment 2, a total of 42 filter media (5 cast iron filter media and 37 synthetic resin filter media) were filled, and the experimental results are shown in Table 2. Figures 5a and 5b show the results of Experiment 1 and Experiment 2 in graphs.

【table】

〔effect〕

As described above, according to the filter medium according to this invention, since the inside is hollow, the contact area with wastewater becomes large. For example, a solid filter medium with the same outer shape as shown in the example, 18 cm in diameter and 7 cm in height, has a surface area of 697 cm ² , but a hollow filter medium of the present invention with the same shape has a surface area of 1140 cm ² , which is 1.64 times larger. Therefore, the surface area becomes much larger. Therefore, the area where microbial membranes are formed is also 1.64 times larger. Furthermore, since the inside is hollow, the porosity is also increased. For example, in a 100cm x 100cm x 100cm container,
If you fill the above hollow filter media with a diameter of 18 cm and a height of 7 cm and solid filter media of the same size, you can pack 5 pieces vertically, 5 pieces horizontally, and 14 pieces in the height direction.
It can hold 350 pieces, and 25 pieces can be filled in the remaining gap, and when combined, both can hold 375 pieces. This hollow filter medium with a diameter of 18 cm is 1
Since the volume of each piece is 236 cm ³ , the void is 1000000 cm ³ - (236 cm ² × 375) = 911500 cm ^3. In the case of solid filter media such as gravel, the volume of one piece is 1524 cm ³ , so the void is , 1000000cm ³ - (1524cm ³ × 375) = 428500cm ³ . Expressed in terms of porosity, this hollow filter medium has a porosity of 91.2.
%, and 42.8% for solid filter media. Therefore, this hollow filter medium has a porosity about 2.1 times greater. If the porosity is large, if the water quality is the same and the same volume of wastewater is to be purified, the aeration tank will be approximately 1/2 the size when using a hollow filter medium than when using a solid filter medium. This means that the equipment cost, operating cost, etc. of the device can be reduced. Furthermore, when the porosity is large, even if the microbial membrane becomes thick, it is less likely to become clogged, has less resistance to stirring, and consumes less energy. In addition, since it is cast, its specific gravity is higher than that of synthetic resin, and it will not float due to the uplifting force of air due to sewage flow or aeration.
Phosphorus does not flow out as suspended fine flocs due to peeling or falling off. In addition, even when placed in a narrow and shallow contact sewage purification channel using a flow channel, it does not flow out or float up, and microorganisms adhere well to it, functioning as a stable contact filter medium. Furthermore, when used in conjunction with synthetic resin filter media as shown in Experimental Results 1 and 2, it also acts as a weight.
Prevents flotation of synthetic resin filter media. In addition, since it is cast, the iron will leach into the waste water, combine with the phosphorus in the waste water, and precipitate.
The dephosphorization rate can be increased without using coagulants or lime. This precipitate is an amorphous iron ammonium phosphate salt, and can be reused as a self-fertilizer without any expense for disposal of the precipitate. Moreover, since the filter medium according to the present invention has a horizontal portion on each of the upper and lower sides, it can be easily stacked when stored in a septic tank. Also,
The upper skeleton portion and the lower skeleton portion are located alternately, and since both are hollow, a core or core mold is not required during casting, and casting can be performed easily. Moreover, the mold can be easily manufactured using a continuous molding machine and is suitable for mass production.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of an embodiment of the filter medium according to this invention, Fig. 2 is a plan view of the embodiment, Fig. 3 is a vertical cross-sectional view of the upper skeleton of the embodiment, and Fig. 4 is the embodiment. FIG. 5A is a longitudinal cross-sectional view of the lower skeleton of , and FIG. 5A shows the results of Experiment 1, and FIG. 5B shows the results of Experiment 2. 2...Annular body, 4...Joining part, 8...Upper skeleton part, 10a...Upper side wall part, 10b...Lower side wall part,
14a... Upper horizontal part, 14b... Lower horizontal part,
18a... Upper arm portion, 18b... Lower arm portion, 20
...lower skeletal part.

Claims (1)

[Scope of utility model registration request] an annular body; a joint concentrically arranged inside the annular body; an upper wall extending obliquely upward from the top surface of the annular body toward the joint; and a tip end of the wall. an upper skeleton portion including an upper horizontal portion extending more horizontally toward the joint portion; and an upper arm portion extending obliquely downward from the tip of the upper horizontal portion to the joint portion; a lower surface of the annular body; a lower wall portion extending obliquely downward from the side toward the joint portion side; a lower horizontal portion extending horizontally from the tip of the wall portion toward the joint portion side; a lower skeleton part including a lower arm part extending obliquely upward from the tip part to the joining part, and is cast so that the upper skeleton part and the lower skeleton part are alternately located. Filter media for sewage treatment.