JPH0657360B2 - Small merged septic tank - Google Patents

Description

The present invention relates to a small combined septic tank for purifying domestic wastewater such as gray water and night soil.

[Prior Art and Problems to be Solved by the Invention] Generally, for a relatively large septic tank, for example, JP-A-60-1
As disclosed in Japanese Patent No. 66092, a plurality of contact material cases are stacked in a contact aeration chamber provided in a septic tank, and each contact material case is filled with a contact material composed of various large and small porous members. , While sewage is flowing through the contact material, aerobic microorganisms attached to the surface of each contact material,
And, anaerobic microorganisms that adhere to the back of the micro hole of the contact material, the sewage dephosphorization, denitrification, de BOD, is intended to de-SS, de-NH ₄ treatment.

Further, in the contact aeration chamber of the septic tank, for the purpose of preventing clogging of the contact material due to thickening of the aerobic microbial film adhering to the surface of each contact material, for example, a backwashing device such as a tubular pipe is arranged. It is set up.

In the contact aeration chamber of the septic tank having such a configuration, it is important to increase the flow velocity of the sewage in the contact material. Generally, the flow velocity inside the contact material tends to be lower than the flow velocity inside the contact material. Aeration is required so that there is no leaning and stirring can be done quickly. Further, it is necessary to prevent retention of peeled sludge and the like from the contact material obtained by the backwashing device and to effectively guide the peeled sludge to the outside of the contact aeration chamber.

In addition, as a contact material, the material is stable, does not corrode or deform even if used for many years, easily attaches microbial membranes, can contact sewage with a contact area as wide as possible, and is not likely to block It is required to have an array and excellent maintainability.

By the way, many small household septic tanks employ a so-called small combined septic tank in which anaerobic microbial treatment of sewage is performed in a precipitation separation chamber and aerobic microbial treatment is performed in a contact aeration chamber.

In many cases, in the contact aeration chamber of this type of small combined septic tank, a contact material formed in a honeycomb shape, such as a synthetic resin, is arranged as an opening end in the vertical direction of the contact aeration chamber,
Using the air discharged from the air diffuser arranged at the bottom of the contact aeration chamber, the waste water is treated with aerobic microorganisms grown on the surface of the contact material.

However, in this conventional small-scale combined septic tank, since the contact material is formed in a honeycomb shape, it is difficult for the waste water to be stirred,
The organic matter in the wastewater is not uniformly dispersed, and the microbial treatment capacity of the wastewater is reduced accordingly.

Further, in Japanese Utility Model Laid-Open No. 58-112499, the contact material has a structure capable of changing the flow path of sewage, and a diffusing pipe is arranged below the contact material whose flow path can be changed. The material is shown.

That is, in the contact aeration chamber in which the air diffuser is arranged below the conventional honeycomb-shaped contact material, the flow path of the sewage is blocked,
Furthermore, since the sewage is difficult to stir, the organic matter in the sewage is not uniformly dispersed, and the microbial treatment capacity of the sewage is reduced by that amount, so the contact material should be provided with an exchange area for the sewage to solve the above problems. It is what

However, the resistance of the water flow becomes large in the AC area of the sewage, and in order to increase the flow rate of the sewage in the contact material, the flow rate generated by the air diffuser must be increased to some extent, resulting in an increase in the size of the device. If the flow velocity of the contact material is increased, turbulence occurs in the flow of the wastewater in the contact material in the alternating current region, and there arises a problem that the uniform contact between the biological film attached to the contact material and the wastewater is disturbed. Therefore, it is difficult to apply the above technique to a small household septic tank that is required to be small.

Further, the techniques disclosed in the above-mentioned techniques all have a problem with the flow path in the contact material, and in addition to the contact material, the total amount in the contact aeration chamber provided with many components such as a backwashing device. It does not improve the flow of
When the contact aeration chamber having a rectangular vertical cross-sectional shape disclosed in the above technology is used, the contact surface obtained in the backwash device is the upright state because the facing surfaces of the contact aeration chamber along the flow path are upright. Separated sludge from the material easily accumulates at the end of the bottom surface where flow is unlikely to occur, making it difficult to effectively collect the separated sludge.In addition, the flow velocity inside the contact aeration chamber is likely to be slowed down and the efficiency of generating flow velocity is improved. Bring about a decline.

Further, in JP-A-57-207594, there is a technique in which an air diffuser is provided below the center of a pair of contact plates arranged in the contact aeration chamber to generate a flow from the central portion of the contact aeration chamber to the outside. It is disclosed.

However, even in this technique, a contact aeration chamber having a rectangular vertical cross-section is used, and since the facing surfaces in the direction along the flow path of the contact aeration chamber are in an upright state, they were obtained in a backwash device. The sludge from the contact material tends to stay at the bottom edge where the flow is unlikely to occur, making it difficult to collect the sludge effectively, and the flow velocity inside the contact aeration chamber is likely to be slowed down. As well as causing a decrease in the efficiency of generating the flow velocity.

[Object of the Invention] The present invention has been made in view of the above circumstances, is small,
It is possible to efficiently increase the flow rate of sewage in the contact material and to aerate the flow rate in the contact material so that there is no deviation and to allow rapid stirring. It is possible to prevent accumulation of peeled sludge and the like, to effectively collect the peeled sludge and guide it to the outside of the contact aeration chamber, to uniformly disperse the organic matter in the wastewater, and to effectively treat the wastewater, and
The purpose is to provide a small combined septic tank that can be efficiently performed.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention forms a compartment in the septic tank main body into a precipitation separation chamber, a contact aeration chamber, and a precipitation chamber through a partition wall, and makes contact with the contact aeration chamber. A pair of opposing members are arranged, and each of the contact members is formed by a plurality of contact plates that are opposed to each other with a constant space therebetween, and stands upright in the contact aeration chamber. In a small combined septic tank in which an air diffuser and a backwash pipe are provided at the bottom of the contact aeration chamber, the pair of contact materials are arranged opposite to each other in a direction orthogonal to a surface connecting the precipitation separation chamber and the precipitation chamber. On the other hand, each of the contact plates forming the pair of contact members is formed in layers by a resin plate and a porous ceramic sheet stretched on both sides of the resin plate, and further between the contact aeration chamber and the precipitation chamber. The return wall that communicates with the air diffuser on the partition wall The trachea is fixed, and the vertical section of the contact aeration chamber is circular, and the air diffuser is arranged at the bottom of the circular contact aeration chamber in a direction orthogonal to the contact plates. The backwash pipe for cleaning the contact plates is arranged in parallel with both surfaces of the backwash pipe.

[Operation] In the above configuration, the sewage treated in the precipitation separation chamber is
From the upper side of the partition wall between the precipitation / separation chamber and the contact / aeration chamber, it flows into the precipitation / separation chamber side of the contact / aeration chamber.

Further, a diffusing pipe provided at the bottom of the contact aeration chamber defined by a partition wall for the precipitation separation chamber and the precipitation chamber is provided with a partition interposed between the contact aeration chamber and the precipitation chamber. Air is sent through a return air pipe fixed to the wall.

When the air is discharged from the air diffuser, the air is absorbed in the liquid, and the floating of the air causes a water flow in the contact aeration chamber. This water flow rises between the pair of facing contact members along the levitation of the air,
Then, they are dispersed in directions opposite to each other on the side orthogonal to the surface connecting the precipitation separation chamber and the precipitation chamber, and are guided by the inner surface of the contact aeration chamber having a circular vertical section to form the respective contact materials. Flow between the contact plates.

Then, when the resin plate and the porous ceramic sheets stretched on both sides of the resin plate are passed between the contact plates formed in layers, they are generated in the porous layer formed of the ceramic sheet. On the existing microbial membrane, the organic substances contained in the wastewater are decomposed and oxidized.

The water stream then flows in the direction of the air diffuser and is again raised by the air discharged from the air diffuser.

That is, two swirling flows having high flow velocities in opposite directions are generated in the contact aeration chamber, and the organic substances introduced into the swirling flow move along the swirling flow and are uniformly dispersed.

Further, the sewage treatment in the contact aeration chamber is carried out by gradually moving from the precipitation separation chamber side to the precipitation chamber side.

Here, at the bottom of the contact aeration chamber, the air diffuser and the backwash pipe for washing the contact plates in parallel to both sides of the air diffuser are arranged, and the contact material faces each other. By arranging a pair of these contact members, each contact member is formed by a plurality of contact plates facing each other with a fixed interval and standing upright in the contact aeration chamber, thereby reducing the flow velocity in the contact aeration chamber. As a result, the flow rate of wastewater in the contact material is efficiently increased, and the aeration is performed so that the flow rate in the contact material does not deviate and the stirring can be performed quickly. Further, the contact aeration chamber has a circular vertical section to prevent the flow velocity from being attenuated as much as possible.

On the other hand, the backwash pipe always separates sludge from the contact material, and the separated sludge moves along the swirl flow inside the contact aeration chamber toward the precipitation chamber inside the contact aeration chamber.

Here, the vertical cross section of the contact aeration chamber is made circular to prevent the attenuation of the flow velocity as much as possible, and the diffusing pipe and the backwash pipe are arranged at the bottom of the contact aeration chamber. The peeled sludge and the like are prevented from accumulating, and the peeled sludge is reliably and effectively moved to the settling chamber side in the contact aeration chamber.

Further, since this swirl flow is generated in the direction orthogonal to the plane connecting the precipitation separation chambers, the untreated wastewater does not flow back into the precipitation separation chamber or flow out into the precipitation chamber.

Embodiments of the Invention Embodiments of the present invention will be described below with reference to the drawings.

The drawings show one embodiment of the present invention. Fig. 1 is a vertical sectional view of a small combined septic tank, Fig. 2 is a II-II sectional view of Fig. 1, and Fig. 3 is a III-III sectional view of Fig. 1. , Fig. 4 is an enlarged view of the contact material,
Fig. 5 is an enlarged view of the sludge return pipe, and Fig. 6 is VI-VI in Fig. 1.
A sectional view and FIG. 7 are plan views of a small combined septic tank.

In these drawings, reference numeral 1 is a septic tank main body, and in the septic tank main body 1, a precipitation separation chamber 2 in which anaerobic microorganisms are grown, a contact aeration chamber 3 in which aerobic microorganisms are grown, and a sedimentation chamber The chamber 4 is partitioned and formed in order from the left in FIG. 1 via the partition walls 5a and 5b.

An inflow pipe 6 communicating with a domestic drainage pipe (not shown) or the like is inserted into the precipitation separation chamber 2 with its outlet facing the bottom of the precipitation separation chamber 2. An advection pipe having an outlet formed on the partition wall 5a on the side of the precipitation separation chamber 2 is exposed above the contact aeration chamber 3 and an inlet is directed to the bottom of the precipitation separation chamber 2. 7 is fixed. A pair of the advection pipes 7 are arranged on both sides of the partition wall 5a with a predetermined interval.

Further, as shown in FIG. 3, the contact aeration chamber 3 has a circular vertical section, and a pair of contact members 8 are mounted inside.
The contact members 8 are arranged so as to face each other in a direction orthogonal to a surface connecting the precipitation separation chamber 2 and the precipitation chamber 4.

Each of the contact members 8 is formed by arranging a plurality of contact plates 11 in parallel at predetermined intervals with a spacer (not shown) or the like.
Are arranged in parallel along the partition walls 5a and 5b. Further, the frame plate 12 is provided on the facing surface of the pair of contact members 8.
Are fixedly provided, and a gap having a predetermined width is formed between the frame plates 12 of the respective contact members 8.

Further, as shown in FIG. 4, the contact material 11 has a layered structure including a non-porous layer 11a formed as an intermediate layer of the contact material 11 and a porous layer 11b formed as a surface layer. ing.

That is, the non-porous layer 11a in the figure has a plate thickness of 0,6 m.
m resin plate, for example, fiber reinforced plastic (FR
P) or the like, and the porous layer 11b has a plate thickness of about 0.3 to 2.0 mm attached to both surfaces of the non-porous layer 11a.
It is made of a ceramic sheet as a ceramic material to some extent, and aerobic microbial film is grown on the micropores formed in the porous layer 11b and on the surface.

An air diffuser pipe 9 is provided at the bottom of the contact aeration chamber 3 and in a gap formed between the facing surfaces of the contact members 8 so as to communicate with a blower (not shown). Further, a backwash pipe 10 as a backwash device is arranged in parallel with the diffuser pipe 9 at the bottom of each contact member 8 and on both sides of the diffuser pipe 9. The backwash pipe 10 is used when the sludge is peeled off from the contact materials 11 and washed.

Further, the partition wall 5 exposed to the contact aeration chamber 3 side
The middle part of the sludge return pipe 18 is fixed to b. The sludge return pipe 18 is faced between the pair of contact materials 8, and an inflow port 18a opened at the lower end of the sludge return pipe 18 is directed to the bottom of the contact aeration chamber 3. There is. The sludge return pipe 18 is formed in an L shape, and an outlet 18b opened at the tip thereof faces the upper part of the precipitation separation chamber 2.

An air blower (not shown) for supplying air to the air diffuser 9 is connected to the sludge return pipe 18 via a return air pipe 18c.

Further, the contact aeration chamber 3 and the precipitation chamber 4 are provided in the both chambers 3, 3.
4 is communicated through an opening 5c formed in a notch at the upper end of a partition wall 5b which divides the contact aeration chamber 3
The supernatant of the treated water that stays in the above flows into the precipitation chamber 4 through the opening 5c.

Further, a sludge hopper 13 is integrally formed on the bottom of the settling chamber 4. The sludge hopper 13 is converged toward the central bottom of the partition wall 5b. The sludge return port 14 communicating with the contact aeration chamber 3 is provided at the bottom of the partition wall 5b facing the sludge hopper 13. Is opened.

The sludge return port 14 faces the inflow port 18a of the sludge return pipe 18.

Further, a disinfection chamber 15 is provided at the center of the upper part of the precipitation chamber 4. The supernatant of the treated water that has flowed into the precipitation chamber 4 flows into the disinfection chamber 15 via the baffle 15a. Reference numeral 16 is a chemical cylinder loaded with chlorine or the like for disinfecting the treated water that has flowed into the disinfection chamber 15.

Further, an inflow end of a discharge pipe 17 communicating with a river or the like is inserted into the supernatant of the disinfection chamber 15.

Further, a manhole 19 communicating with the precipitation separation chamber 2 and the precipitation chamber 4 and another manhole 20 communicating with the contact aeration chamber 3 are formed on the upper surface of the septic tank body 1 (FIG. 7). reference).

Next, the operation of the small-sized septic tank having the above structure will be described.

Sewage discharged from households and sewage such as human waste are first flowed into the sedimentation separation chamber 2 formed in the septic tank main body 1 through the inflow pipe 6, where the sewage contained in the sewage is relatively discharged. A large suspended matter is settled, and the anaerobic microorganisms growing in the sedimentation separation chamber 2 are subjected to dephosphorization, denitrification, BOD removal, SS removal, and NH ₄ removal treatment of the wastewater.

Then, the sewage treated by the anaerobic microorganisms in the sedimentation separation chamber 2 and the sludge floating in the sedimentation separation chamber 2 pass through the advection pipe 7 to the sedimentation separation chamber 2 side of the adjacent contact aeration chamber 3. Be flowed in.

As shown in FIG. 3, in the contact aeration chamber 3, air is blown from a blower (not shown) into a diffuser pipe 9 arranged at the bottom of the contact aeration chamber 3 through a return air pipe 18c. Air is levitated through the gap between the frame plates 12 provided on the facing surfaces of the pair of contact members 8 arranged in the contact aeration chamber 3, and during this time, the air is absorbed in the liquid and The floating of the air causes a water flow in the liquid. This water flow rises along the levitation of the air between the pair of facing contact materials 8 and is then dispersed in directions opposite to each other on the side orthogonal to the surface connecting the precipitation separation chamber 2 and the precipitation chamber 4. , Is guided between the contact plates 11 forming the contact members 8 by being guided by the inner surface of the contact aeration chamber 3 having a circular vertical section.

Then, while flowing between the contact plates 11, the microbial membrane formed on the surface of the contact plates 11 decomposes and oxidizes the organic matter contained in the wastewater.

Then, the water flow flows toward the air diffuser 9 and is again raised by the air discharged from the air diffuser 9.

That is, inside the contact aeration chamber 3, each contact member 8 is
Two swirling flows with high flow velocities opposite to each other flowing along the contact plate 11 forming the swirl flow are generated, and the sewage introduced into the contact aeration chamber 3 is moved along the two high-speed swirling flows. The organic matter contained in the sewage circulates in the contact aeration chamber 3 and is gradually and uniformly dispersed.

Further, the wastewater treatment inside the contact aeration chamber 3 is performed by gradually moving from the precipitation separation chamber 2 side toward the precipitation chamber 4 side.

By the way, since the intermediate layer of the contact plate 11 is the non-porous layer 11a made of a resin such as FRP, the sewage passing through the surface of the contact plate 11 penetrates the contact plate 11 and moves laterally. It does not disturb the swirling flow by flowing, and therefore the environment for microbial film formation is good.

In addition, the organic matter contained in the sewage is the contact plate 11
While flowing down the porous layer 11b on the surface of the
It is decomposed and oxidized by the aerobic microorganisms produced in 1b.

The aerobic microorganisms are hard to flow on the surface of the contact plate 11 because they are attached to the porous layer 11b formed of a ceramic sheet or the like as a ceramic material, and the aerobic microorganisms have the above swirling flow. Since oxygen is sufficiently supplied to the surface of the porous layer 11b, a microbial film due to aerobic microorganisms is easily generated on the surface of the porous layer 11b. As a result, the decomposition and oxidation of the organic matter in the wastewater can be effectively and efficiently performed.

Here, at the bottom of the contact aeration chamber 3, the air diffuser 9 and
The backwash pipes 10 for cleaning the contact plates 11 are arranged in parallel on both sides of the air diffuser 9 and a pair of the contact members 8 are arranged so as to face each other. By forming a plurality of contact plates 11 that are opposed to each other at regular intervals and standing upright in the contact aeration chamber 3, the attenuation of the flow velocity inside the contact aeration chamber 3 is minimized, and as a result,
Efficiently increase the flow velocity of sewage in the contact material 8,
The flow velocity in the contact material 8 does not deviate, and is rapidly stirred and aerated. Further, since the vertical section of the contact aeration chamber 3 is circular to prevent the flow velocity from being attenuated as much as possible, the velocity of the air discharged from the air diffuser 9 can be minimized, and the blower can be downsized. This enables the overall size of the septic tank to be reduced.

Further, by using the resin material in the middle of the contact plate 11, there is no possibility that the dirty water passing through the surface of the contact plate 11 penetrates the contact plate 11 and flows laterally to disturb the swirling flow. It is possible to obtain a stable water flow. Furthermore, by using a ceramic material for the surface of the contact plate 11, the contact plate 1
Microorganisms are easily attached to the surface of 1, and an environment in which microbial membranes are easily generated can be formed. as a result,
Sewage treatment can be performed more effectively and efficiently.

In addition, since the ceramic material on the surface of the contact plate 11 is formed of a ceramic sheet attached to an intermediate resin material, the material is stable and does not corrode or deform even after many years of use, and the contact material is Not only is it lightweight, it can be easily formed at low cost, but it can also be a contact material having excellent handleability and maintainability.

On the other hand, the backwash pipe 10 always separates sludge such as digested sludge from the contact material 8, and the separated sludge flows along the high-speed swirling flow inside the contact aeration chamber 3 to cause the contact aeration. The chamber 3 is moved to the precipitation chamber 4 side. Further, undigested sludge and the like other than the separated sludge are also moved to the settling chamber 4 side in the contact aeration chamber 3 along the high-speed swirling flow.

Here, since the vertical cross section of the contact aeration chamber 3 is formed in a circular shape to prevent the attenuation of the flow velocity as much as possible, and the aeration pipe 9 and the backwash pipe 10 are arranged at the bottom of the contact aeration chamber 3, The separation sludge and the undigested sludge from the contact material 8 are prevented from accumulating, and the sludge is reliably and effectively moved to the precipitation chamber 4 side in the contact aeration chamber 3.

When the peeled sludge and the undigested sludge reach the settling chamber 4 side in the contact aeration chamber 3, they are returned to the settling separation chamber 2 by the sludge return pipe 18 for reprocessing. Therefore, the digested sludge at the bottom of the contact aeration chamber 3, and
Undigested sludge does not accumulate.

By the way, the swirl flow generated in the contact aeration chamber 3 is
Since it is flowing in a direction orthogonal to the plane connecting the precipitation separation chamber 2 and the precipitation chamber 4, this swirling flow causes untreated wastewater to flow out to the precipitation chamber 4 or flow back to the precipitation separation chamber 2. There is no.

Next, the treated water that has been treated with the aerobic microorganisms flows into the adjacent precipitation chamber 4 through the opening 5c that is opened in the upper portion of the partition wall 5b.

When the treated water flows into the settling chamber 4, a small amount of sludge contained in the treated water is settled in the sludge hopper 13 formed at the bottom of the settling chamber 4.

The sludge is guided by the sludge hopper 13 and flows into the bottom of the contact aeration chamber 3 through the sludge return port 14 opened in the partition wall 5b facing the bottom of the sludge hopper 13. Therefore, sludge does not accumulate on the bottom of the settling chamber 4.

Then, the sludge and the treated water that accumulates at the bottom of the contact aeration chamber 3 together with the above-mentioned digested sludge and undigested sludge flow through the sludge return pipe 18 by the air pressure sent from a blower (not shown). As described above, it is returned to the precipitation separation chamber 2 and treated again for anaerobic microorganisms. Further, the anaerobicly treated sludge and the treated water are re-flowed into the contact aeration chamber 3 through the advection pipe 7 and treated with aerobic microorganisms.

In this way, the wastewater and sludge that have flowed into the septic tank body 1 are circulated through the precipitation separation chamber 2, the contact aeration chamber 3 and the precipitation chamber 4 for repeated microbial treatment, so that dephosphorization,
Denitrification, BOD removal, SS removal, and NH ₄ removal treatment can be performed reliably and efficiently.

Then, the supernatant of the treated water that has flowed into the precipitation chamber 4 is introduced into the disinfection chamber 15 provided in the precipitation chamber 4 using the baffle 1.
The water is introduced through 5a, sterilized with chlorine, and then discharged as conditioned water from the discharge pipe 17 to a river or the like.

[Effects of the Invention] As described above, according to the present invention, a pair of contact materials are arranged so as to face each other in a direction orthogonal to a plane connecting the precipitation separation chamber and the precipitation chamber, while forming the pair of contact materials. Each contact plate has a resin plate in the middle, and porous ceramic sheets are stretched on both side faces of the resin plate to form a layer, and a partition wall interposed between the contact aeration chamber and the precipitation chamber. A return air pipe communicating with the air diffuser is fixedly installed, and the vertical cross section of the contact aeration chamber is circular, and the air diffuser is connected to the contact plates at the bottom of the circular contact aeration chamber. Two high-speed swirling flows with little attenuation of the flow velocity are provided by arranging them in orthogonal directions, and further by providing backwash pipes for washing the contact plates in parallel directions on both sides of the diffuser pipe. Is generated in a direction orthogonal to the plane connecting the precipitation separation chamber and the precipitation chamber, It is possible to efficiently increase the flow rate of sewage in the contact material and to aerate the flow rate in the contact material so that it can be stirred rapidly without any deviation. It is possible to prevent the accumulated sludge from accumulating, and to effectively collect this sludge to guide it outside the contact aeration chamber.
The organic substances in the sewage can be uniformly dispersed, and the sewage treatment can be performed effectively and efficiently.

Furthermore, since a porous layer is formed by laminating a ceramic sheet on the surface of the contact plate, there is less variation in products as compared with one in which a porous layer is formed by spraying the surface with a spray, etc. Not only the quality is stable, but the ceramic sheet can be produced separately, which is suitable for mass production.

[Brief description of drawings]

The drawings show one embodiment of the present invention. Fig. 1 is a vertical sectional view of a small combined septic tank, Fig. 2 is a II-II sectional view of Fig. 1, and Fig. 3 is a III-III sectional view of Fig. 1. , Fig. 4 is an enlarged view of the contact material,
Fig. 5 is an enlarged view of the sludge return pipe, and Fig. 6 is VI-VI in Fig. 1.
A sectional view and FIG. 7 are plan views of a small combined septic tank. 1 ... septic tank body, 2 ... sedimentation separation chamber, 3 ... contact aeration chamber, 4 ... sedimentation chamber, 5a, 5b ... partition wall, 8 ... contact material, 9 ... air diffuser, 10 ... reverse Washing pipe, 11 ... Contact plate, 11a ... Resin plate, 11b ... Porous ceramic sheet, 18c. Return air pipe.

Continuation of the front page (56) Reference JP-A-57-59690 (JP, A) JP-A-53-35247 (JP, A) Actual development Shou-52-107059 (JP, U) JP-B-43-21878 (JP , B1) "Sewage Septic Tank Handbook", Industrial Water Inspection Committee, issued November 26, 1981, pages 38-49 and 205-212.

Claims (1)

[Claims] 1. A septic tank main body is divided into a precipitation separation chamber, a contact aeration chamber, and a precipitation chamber through a partition wall, and a pair of contact materials are disposed in the contact aeration chamber so as to face each other. Formed by a plurality of contact plates that are placed opposite to each other with a certain space therebetween, and stand upright in the contact aeration chamber, and at the bottom of the contact aeration chamber between the pair of contact materials, an air diffuser and a backwash pipe are provided. In the small combined septic tank in which the contact plates are arranged, the pair of contact materials are arranged opposite to each other in a direction orthogonal to a surface connecting the precipitation separation chamber and the precipitation chamber, and the contact plates forming the pair of contact materials. A resin plate and a porous ceramic sheet stretched on both sides of the resin plate in a layered form, and a return wall communicating with the air diffusing pipe is connected to a partition wall interposed between the contact aeration chamber and the precipitation chamber. A fixed air pipe is installed, and the vertical section of the contact aeration chamber is circular. As the circular shaped contact aeration chamber, the air diffusing pipes are arranged in the direction orthogonal to the contact plates, and the contact plates are washed in a direction parallel to both sides of the air diffusing pipe. A small combined septic tank characterized by having a washing pipe.