JPH0160313B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention relates to an apparatus for purifying wastewater discharged from household flush toilets, kitchens, bathhouses, etc.
In particular, microorganisms (activated sludge) are attached to a carrier (fixed bed) and sewage is brought into contact with the activated sludge bed, which has been cultured, in order to propagate the activated sludge and oxidize and decompose water pollutants such as BOD and COD. The present invention relates to a sewage treatment device equipped with a treatment tank of a removal type. [Conventional technology] Conventionally, when flushing toilets in areas where sewage treatment facilities were incomplete, a septic tank was buried in each household, and after the septic tank purified the waste water, the purified water was discharged. I try to do that.
However, this septic tank purifies the sewage introduced into the tank by simply blowing air into it, and has very low purification ability, and has major problems such as the production of a large amount of surplus sludge. Therefore, the present applicant previously proposed a sewage treatment device for household flush toilets as disclosed in Japanese Patent Publication No. 60-29319. This sewage treatment equipment first introduces sewage discharged from household flush toilets into a coarse screen to remove coarse, sparsely soluble and insoluble substances, and then uses a compressor equipped with ultra-fine filtration material to remove the sewage from the wastewater. fine suspended solids (hereinafter referred to as
(referred to as "SS") is compressed and separated to remove 85~
After removing 98% of the SS, the dehydrated SS is discharged into the SS storage tank, and the sewage that has been filtered using the filter material is introduced into an aeration treatment tank with a number of sponge activated sludge beds suspended upright. Perform aeration,
This device oxidizes and decomposes water pollutants such as BOD and COD in wastewater, and then completely disinfects them with chlorine. According to this sewage treatment equipment, in the first half of the series of treatment processes, coarse SS and fine SS are separated.
BOD in wastewater by forcibly removing SS and
The concentration is reduced to about 50 ppm, and by further low-load treatment in the activated sludge bed and chlorine sterilization in the latter half, it is possible to finally obtain purified water with a BOD concentration of 3 ppm or less. [Problems to be Solved by the Invention] The sewage treatment device disclosed in Japanese Patent Publication No. 60-29319 has extremely high purification ability compared to conventional septic tanks.
A compressor equipped with ultrafine filter material is installed in the front half of the device, and by operating this compressor, fine particles are removed.
In wastewater that has passed through a filter material after forced removal of SS
After the BOD concentration has been reduced to a certain level, low-load treatment is performed in an aeration treatment tank equipped with an activated sludge bed. Due to the large number of devices installed, maintenance and management of the device is time consuming and equipment failures are apt to occur. This invention was made to solve the above-mentioned problems; it does not require much effort to maintain and manage the equipment, the daily operation management is relatively simple, and it always achieves an extremely high removal rate. The object of the present invention is to provide a sewage treatment device that can treat sewage at a high rate and also generates almost no surplus sludge. [Means for Solving the Problems] The present invention, like the sewage treatment equipment disclosed in Japanese Patent Publication No. 60-29319, filters sewage using a filter material of a compressor in the front half of the equipment. Wastewater is treated with an activated sludge bed, instead of using the method of reducing the BOD concentration in the wastewater to a certain level and then introducing the wastewater into an aeration treatment tank, where the aeration treatment tank exclusively performs low-load treatment. By arranging multiple treatment tanks and changing the shape of the activated sludge bed installed in each sewage treatment tank, it is possible to perform high-load treatment to low-load treatment in the multiple sewage treatment tanks. The main points are as follows. That is, a household flush toilet according to the present invention,
A treatment device for wastewater from a kitchen, etc. is connected to a wastewater introduction pipe, and includes a solid matter removal device that crushes solid aggregates in the introduced wastewater and separates and removes coarse solid matter, and a solid matter removal device that separates and removes coarse solid matter. The flow path is connected,
A sewage treatment tank that removes water pollutants such as BOD and COD in sewage by oxidative decomposition, a sedimentation tank connected to this sewage treatment tank, and a treated water discharge pipe connected to this sedimentation tank. , and a connected sterilization tank, the sewage treatment tank is provided with an aeration pipe connected to the air introduction pipe at the bottom, and a long cylindrical core body whose cylindrical surface is formed in a mesh or lattice shape. A porous material having a predetermined thickness is wound around the outer peripheral surface of the sewage treatment tank, and a plurality of activated sludge beds are fixed by fixing means, and a plurality of activated sludge beds are erected above the aeration pipe. In the sewage treatment apparatus, the elongated cylindrical core in the activated sludge bed is covered with the porous body. The cylindrical surface area is increased sequentially in the sewage treatment tank unit according to the order in which they are installed, or is made equal between adjacent sewage treatment tanks, and at least larger in the last sewage treatment tank than in the first sewage treatment tank, and activated. The present invention is characterized in that the bacterial species constituting the sludge, the growth ratio of aerobic bacteria and anaerobic bacteria, their distribution status, etc. are changed for each sewage treatment tank. [Function] The present invention is constructed as described above, and in the sewage treatment device according to the present invention, sewage discharged from a household flush toilet etc. and introduced into the device through the sewage introduction pipe is first While passing through the solid matter removal device, solid aggregates such as excrement and urine are crushed and made into fine particles and dispersed in the wastewater, and coarse solid matters consisting of poorly soluble and insoluble substances such as sanitary products are separated. After being removed, the wastewater is introduced into a wastewater treatment tank. In this sewage treatment tank, the air sent to the aeration pipe installed at the bottom of the tank via the air introduction pipe becomes bubbles from the many small holes on the surface of the aeration pipe and blows out into the wastewater. Oxygen dissolves into the wastewater. This sewage containing dissolved oxygen comes into contact with an activated sludge bed installed above the aeration pipe, and adheres to the activated sludge bed and is affected by cultured aerobic bacteria and anaerobic bacteria, resulting in water quality such as BOD and COD. The pollutants are decomposed, while aerobic and anaerobic bacteria grow using part of the energy obtained. Here, since the activated sludge bed has a long cylindrical shape, the dissolved oxygen concentration (hereinafter referred to as "DO value") inside and outside the cylinder
Generally, aerobic bacteria grow on the surface layer around the outside of the activated sludge bed, and anaerobic bacteria grow on the surface layer around the inside of the cylinder. In addition, giant microorganisms such as Zoglaea, Spharotailus, Nematoda, and water mites naturally occur in the center of the porous body of the activated sludge bed, and these giant microorganisms eat aerobic and anaerobic bacteria. causes autolysis, which prevents excessive growth of aerobic and anaerobic bacteria and eliminates the generation of excess sludge. A plurality of sewage treatment tanks are arranged, and each activated sludge bed provided in each sewage treatment tank has its own physical environment, that is, the area of the cylinder covering the long cylindrical core with the porous material. Due to the change in each sludge treatment tank, the degree of flow of sewage with an increased DO value between the inside and outside of the cylinder changes from one treatment tank to another. For this reason, the types of bacteria that make up the activated sludge,
The ratio of aerobic bacteria to anaerobic bacteria, the distribution of microorganisms, etc. will change. In addition, by sequentially reducing the amount of air fed from the aeration pipes according to the order in which each sewage treatment tank is connected, the DO
If the value is changed, an activated sludge bed having a growth phase consisting of aerobic bacteria and anaerobic bacteria can be transitioned and formed in each treatment tank more effectively. In this way, activated sludge beds with different growth phases are formed in each sewage treatment tank according to the order in which they are connected, so that the ability of each bacterial species, that is, aerobic bacteria, can be improved in high-load treatment. Anaerobic bacteria are excellent in low-load treatment and nitrogen removal, and their respective abilities are utilized to the fullest, and depending on the degree of purification in each wastewater treatment process, the nutrients of air, nitrogen, and phosphorus are While maintaining a balance, wastewater is efficiently treated from high-load treatment to low-load treatment. The sewage that has been subjected to high-load treatment to low-load treatment while passing through multiple sewage treatment tanks in sequence is further settled and removed in a sedimentation tank, and finally sterilized in a sterilization tank, and then sent to the treated water discharge pipe. It is discharged as treated water through the [Embodiments] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIGS. 1 and 2 show one embodiment of the present invention, with FIG. 1 being a front sectional view showing the overall configuration of a sewage treatment apparatus, and FIG. 2 being a plan view. However, FIG. 2 shows the sewage treatment tank with the lid removed, and for convenience of illustration, various piping, pumps, etc. are omitted. This sewage treatment equipment is used for household flush toilets, kitchens,
Solids removal device 2 connected to the end of sewage introduction pipe 1 connected to a sewage source such as a bathhouse, solids storage tank 3 attached to this solids removal device 2, and solids removed to solids removal device 2. It is composed of a tank body 4 to which a treated water discharge pipe 5 is connected. and,
The tank body 4 includes a solid-liquid separation tank 11, an aeration tank 12, and a first
It is divided into a sewage treatment tank 13, a second sewage treatment tank 14, a third sewage treatment tank 15, a sedimentation tank 16, and a sterilization tank 17. The solid matter removal device 2 crushes solid aggregates such as feces contained in the introduced wastewater, makes them fine, and disperses them in the wastewater, and also removes coarse solids made of poorly soluble and insoluble substances such as sanitary products. It was installed for separation and removal. This solid matter removal device 2 includes a crusher 22 made of a screw-like barrier body arranged inside a cylinder of a cylindrical drum 21 formed of a stainless wire mesh, and these cylindrical drums 21
1 and a crusher 22 are housed in an outer case 23, and cylindrical tubes 24 and 25 are connected to each end of the cylindrical drum 21, respectively.
3, the cylindrical pipe 24 is connected to the waste water introduction pipe 1, and the cylindrical pipe 25 is connected to its end 26.
is open. A solid storage tank 3 is disposed below the open end 26 of the cylindrical tube 25. Further, the cylindrical drum 21 is supported so as to be rotationally driven by a drive motor 27 via a connecting chain 28 . One end of a connecting pipe 30 is connected to an outlet 29 formed near the bottom of the outer box 23, and the other end of the connecting pipe 30 is connected to a sewage inlet 31 of the tank body 4. The sewage inlet 31 communicates with the solid-liquid separation tank 11 , and a chemical solution dripping device 32 is attached to the upper part of the solid-liquid separation tank 11 . The chemical solution dripping device 32 supplies a chemical solution that speeds up the natural decomposition of organic matter and prevents the release of bad odors, as well as stimulates various microorganisms such as aerobic bacteria and anaerobic bacteria to increase their vitality. A chemical solution containing a natural emulsifying surfactant and saponin is constantly dripped. In addition, a stirring rod 33 that is movable in the vertical direction is provided in the solid-liquid separation tank 11.
A stirring blade 34 is fixedly installed at the tip of the stirring blade 34 . The solid-liquid separation tank 11 and the next aeration tank 12 are separated by a partition wall 35, and an overflow window 36 covered with a stainless wire mesh is provided on the top of the partition wall 35.
Further, a cleaning device 37 is provided close to the partition wall 35 to prevent the overflow window 36 from clogging. It has 38. An aeration pipe 41 connected to the air introduction pipe 39 is disposed at the inner bottom of the aeration tank 12 , and an end of the air introduction pipe 39 is connected to a blower 40 . A partition wall 42 separates the aeration tank 12 from the next first sewage treatment tank. Similar to the partition wall 35,
An overflow window 43 covered with a stainless wire mesh is provided at the top of the partition wall 42, and a cleaning device 44 is provided adjacent to the partition wall 42 to prevent the overflow window 43 from clogging. , this cleaning device 44
has a rotating brush 45 made of nylon that rolls while contacting the overflow window 43. The first sewage treatment tank 13 and the next second sewage treatment tank 14 are separated by partition walls 46 and 47, and the second sewage treatment tank 14 and the next third sewage treatment tank 15 are separated by partition walls 46 and 47, respectively. ing. The first sewage treatment tank 13 and the second sewage treatment tank 14 have an overflow window 49 provided at the top of an overflow tube 48 disposed at a corner of the first sewage treatment tank 13.
The flow path is connected through. Further, the second sewage treatment tank 14 and the third sewage treatment tank 15 have an overflow window (not shown) provided at the top of an overflow tube 50 disposed at a corner of the second sewage treatment tank 14. The flow path is connected through the First sewage treatment tank 13, second sewage treatment tank 14
An aeration pipe 51 connected to the air introduction pipe 39 is arranged at the inner bottom of each of the third sewage treatment tanks 15, and above the aeration pipe 51 there are a number of activated sludge beds 5.
2 and 53 are erected with their upper and lower ends supported by support rods (not shown). The activated sludge bed is made of a hard synthetic resin material with a mesh or cylindrical surface that does not deteriorate due to corrosion even when immersed in sewage for a long period of time, as shown in Figure 4, which shows a partially cut-out state. A porous body 72 is coated to a predetermined thickness on the outer peripheral surface of a long cylindrical core body 71 formed in a lattice shape.
Wind it up so that it is usually about 15 to 20 mm, and 3-1.
As shown in the figure and FIG. 3-2, its upper and lower ends are fixed by a fixing ring 73, and
A porous body 72 is fastened and fixed to a long cylindrical core body 71 using fixing bands 74 at appropriate locations on the body. In addition, 75 in the figure is a support hole drilled in the fixed ring 73 for inserting the support rod. The porous body 72 is formed, for example, by intertwining a large number of highly corrosion-resistant vinylidene chloride filaments, or by using a spongy, mesh, or fibrous synthetic resin material. And activated sludge bed 52,5
The form of each of 3 differs depending on each sewage treatment tank. FIG. 3-1 and FIG. 3-2 show an example thereof. Among these, the activated sludge bed 52 shown in FIG. 3-1 is placed in the sewage treatment tank 13, and the porous body 72 is cut out in a spiral shape with a constant width to form a long cylindrical core. The body 71 is exposed. Also,
The activated sludge bed 53 shown in FIG. 3-2 is placed in the sewage treatment tanks 14 and 15, and has a long cylindrical core body 71 entirely covered with a porous body 72. A return pump 54 is disposed in the second sewage treatment tank 14, and the return pump 54 transports a portion of the sewage in the middle of treatment in the second sewage treatment tank 14 through a return pipe 55 to the solid-liquid separation tank. I am trying to send it back to 11. The third sewage treatment tank 15 and the next sedimentation tank 16 are separated by a partition wall 56,
Both tanks 15 and 16 are in fluid communication via an overflow window (not shown) provided at the top of an overflow cylinder 57 disposed at a corner of the third sewage treatment tank 15. Also,
The settling tank 16 and the sterilization tank 17 are separated by a partition wall 58 and a bottom wall 59, and the top side 60 of the partition wall 58 has a continuous chevron shape. Intermediately treated water in the sedimentation tank 16 flows into the sterilization tank 17. A small electrode plate type ozone generator 61 is disposed in the sterilization tank 17 . Note that the sterilizing device installed in the sterilizing tank 17 may be a device other than an ozone generator, and a sterilizing agent injection device may be installed above the sterilizing tank 17. A treated water discharge pipe 5 is connected to the sterilization tank 17, and the treated water is discharged through the treated water discharge pipe 5. In addition, 62 in the figure is a lid part of the tank body 4, and this lid part 62 includes an outlet for taking out the solids piled up in the solid-liquid separation tank 11 using a vacuum suction device, etc., and a port for each sewage treatment. Tank 13,
14, 15, an inspection port used for adjusting the DO value, etc., an outlet for taking out the sediment deposited at the bottom of the sedimentation tank 16, an input port for replenishing the sterilizing agent into the sterilizing tank 17, etc. (not shown) is also provided. In the sewage treatment apparatus configured as described above, sewage treatment is performed as follows. Sewage such as human waste and sewage discharged from a household flush toilet is introduced into the device through the sewage introduction pipe 1,
First, it enters the cylindrical drum 21 of the solids removal device 2. The sewage that has entered the cylindrical drum 21 flows into the outer box 23 through the wire mesh of the cylindrical drum 21, and is discharged from the outlet 29. At this time, the cylindrical drum 2
1 is rotationally driven by a drive motor 27 via a connection chain 28, and a crusher 22 is disposed inside the cylinder of the cylindrical drum 21, so that solid aggregates such as feces are removed from the cylindrical drum 21. As the waste flows from the inlet to the outlet, it is crushed into fine particles, dispersed in the waste water, enters the outer case 23 through the wire mesh of the cylindrical drum 21 together with the waste water, and is discharged from the outlet 29. On the other hand, coarse solids such as sanitary products move within the cylindrical drum 21 without being crushed, are discharged from the open end 26 of the cylinder 25, and are piled up in the solids storage tank 3. The wastewater discharged from the solid matter removal device 2 is introduced into the solid-liquid separation tank 11 from the wastewater inlet 31 of the tank body 4 through the connecting pipe 30. A chemical liquid is constantly dripped into the wastewater that has entered the solid-liquid separation tank 11 from a chemical liquid dripping device 32. In addition, the wastewater in the solid-liquid separation tank 11 is
It is stirred by a stirring rod 33 and stirring blades 34 about once a month. After the solids contained in the wastewater are sedimented and removed in the solid-liquid separation tank 11, the wastewater passes through the partition wall 3.
Naturally overflows into the aeration tank 12 through an overflow window 36 provided at 5. Incidentally, clogging of the wire mesh stretched over the overflow window 36 can be prevented by cleaning by moving the rotary brush 38 of the cleaning device 37 up and down while contacting the wire mesh. In the aeration tank 12, air supplied from the blower 40 to the aeration pipe 41 through the air introduction pipe 39 is blown out into the wastewater from a large number of small holes drilled on the surface of the aeration pipe 41, and flows into the solid-liquid separation tank in the previous stage. The chemical solution introduced in step 11 is emulsified and dispersed in the wastewater, and the wastewater overflows into the first wastewater treatment tank 13 through the overflow window 43 provided in the partition wall 42.
Note that the wire mesh stretched over the overflow window 43 is cleaned by moving the rotating brush 45 of the cleaning device 44 up and down. The sewage that has flowed into the first sewage treatment tank 13 is aerated by the aeration pipe 51 to have its DO value increased, and is also made to flow by a pump (not shown) or the like. In this process, aerobic bacteria are mainly attached and cultured in the voids in the outer surface layer of the activated sludge bed 52, and anaerobic bacteria are mainly attached and cultured in the voids in the inner surface layer. , oxidizes and decomposes water pollutants such as COD, and uses part of the energy acquired during this process to proliferate. On the other hand, in the center of the porous body 72 of the activated sludge bed 52, giant microorganisms such as Zoglaea, Spharotails, Nematoda, and water mites naturally occur, and these giant microorganisms attack the proliferating aerobic and anaerobic bacteria. do. In this way, the activated sludge bed 5
2. Self-digestion as a whole, keeping the film thickness of aerobic bacteria and anaerobic bacteria almost constant, and purifying wastewater without generating excess sludge. At this time, the giant microorganisms move from the center to the surface of the porous body 72 and attack the aerobic and anaerobic bacteria, so the aging bacteria with poor purification efficiency digest them one after another, causing the inside and outside of the cylinder to be digested. New aerobic bacteria and anaerobic bacteria with high purification efficiency are constantly cultivated and proliferated in the surface layer, further increasing the rate of purification of wastewater. Through the treatment process described above, the wastewater that has undergone the first stage of treatment in the first sewage treatment tank 13 is transferred to the overflow tube 48 disposed at the corner of the first sewage treatment tank 13.
The flow flows into the interior from the lower part and flows toward the upper part within the overflow pipe 48, and the overflow window 49 provided at the upper part
It overflows into the second sewage treatment tank 14 through the sewage treatment tank 14. Then, in the second sewage treatment tank 14, the wastewater is subjected to the same second stage treatment as described above. Part of the untreated wastewater treated in the second sewage treatment tank 14 is constantly returned to the first solid-liquid separation tank 11 by a return pump 54 through a return pipe 55. Then again, from the solid-liquid separation tank 11, the aeration tank 1
2. By circulating the sludge to the first sewage treatment tank 13 and the second sewage treatment tank 14, the nitrogen content in particular is repeatedly treated while maintaining the nutritional balance necessary for the sludge to survive. On the other hand, the sewage that flows into the overflow pipe 50 disposed at the corner of the second sewage treatment tank 14 from the lower part flows toward the upper part in the overflow pipe 50, and flows into the overflow pipe provided at the upper part. It overflows into the third sewage treatment tank 15 through a window (not shown) and undergoes the same third stage treatment as described above within the third sewage treatment tank 15. In the treatment process in each sewage treatment tank mentioned above,
The amount of air fed from each aeration pipe 51 to the first, second, and third sewage treatment tanks 13, 14, and 15 is sequentially reduced. In addition to adjusting the amount of air supplied, depending on the form of each activated sludge bed placed in each sewage treatment tank, that is, the presence or absence of the exposed part of the long cylindrical core body 71, the DO The value changes. In this way, as the DO value changes for each sewage treatment tank and inside and outside the cylinder of each activated sludge bed,
Activated sludge beds 52, 53, arranged in 4, 15,
53, the types of bacteria that propagate, the ratio of aerobic bacteria to anaerobic bacteria, the distribution of microorganisms, etc. change. The ratio of aerobic bacteria to anaerobic bacteria in each sewage treatment tank is, for example, 80% aerobic bacteria and 20% anaerobic bacteria in the activated sludge bed 52 in the first sewage treatment tank 13, and 20% in the second sewage treatment tank 14. The activated sludge bed 53 has 60 aerobic bacteria.
%, 40% anaerobic bacteria, and 20% aerobic bacteria and 80% anaerobic bacteria in the activated sludge bed 25 in the third sewage treatment tank 15. The first sewage treatment tank 13 mainly performs high-load BOD treatment, and the second sewage treatment tank 14 mainly processes BOD and COD.
In the third sewage treatment tank 15, BOD and COD low-load treatment and nitrogen removal are mainly performed. The intermediate treated water that has been processed in the third sewage treatment tank 15 flows from the lower part into an overflow pipe 57 disposed at a corner of the third sewage treatment tank 15, and the overflow pipe 57
7 toward the top and overflows into the sedimentation tank 16 through an overflow window (not shown) provided at the top. In this sedimentation tank 16, the solid content contained in the intermediately treated water settles in the water and is deposited at the bottom of the tank. The intermediately treated water then overflows the chevron-shaped upper side 60 of the partition wall 58 and finally flows into the sterilization tank 17, where it is sterilized.
The finally purified treated water is discharged from the sterilization tank 17 through the treated water discharge pipe 5. Finally, the treatment effects obtained by actually treating human waste sewage using the apparatus of the above embodiment are shown in the following table.

〔effect〕

Since the present invention has the above-described configuration and functions, in the sewage treatment device according to the present invention, a plurality of highly concentrated sewage from which solids have been removed by the solids removal device are arranged. Since various treatments ranging from high-load treatment to low-load treatment are performed while passing through the sewage treatment tank, daily operation management is relatively simple, and the equipment has few moving parts and is mechanically efficient. Since it is not very complicated, it does not require much effort to maintain and manage the equipment, and there are fewer failures. Moreover, sewage treatment can always be carried out with an extremely high removal rate, and furthermore, almost no surplus sludge is produced. This invention has such excellent performance,
This provides a device for treating sewage discharged from household flush toilets, kitchens, etc.

[Brief explanation of drawings]

1 and 2 show one embodiment of the present invention, FIG. 1 is a front cross-sectional view showing the overall configuration of the sewage treatment equipment, FIG. 2 is a plan view, and FIG.
Figure-1 and Figure 3-2 are perspective views showing various examples of activated sludge beds used in the above equipment, and Figure 4 is a partial perspective view showing a partially cut away activated sludge bed. be. 1...Sewage introduction pipe, 2...Solid removal device, 3
...Solid storage tank, 5...Treatment water discharge pipe, 11...
...Solid-liquid separation tank, 12...Aeration tank, 13-15...
1st to 3rd sewage treatment tanks, 16... Sedimentation layer, 17...
...Sterilization tank, 39...Air introduction pipe, 41, 51...
Aeration pipe, 52, 53... activated sludge bed, 71... long cylindrical core, 72... porous body.

Claims (1)

[Scope of Claims] 1. A solids removal device connected to a sewage inlet pipe for crushing solid aggregates in the introduced sewage and separating and removing coarse solids, and a flow path connected to this solids removal device. A sewage treatment tank that removes water pollutants such as BOD and COD in the sewage by oxidation and decomposition; a sedimentation tank that has a flow path connected to this sewage treatment tank; a sterilization tank to which a discharge pipe is connected; The sewage treatment tank is constructed by erecting a plurality of activated sludge beds above the aeration pipe, which are formed by winding a porous material having a predetermined thickness around the outer peripheral surface of a core body and fixing it by fixing means. In the sewage treatment apparatus, the elongated cylindrical core in the activated sludge bed is covered with the porous body, in which a plurality of sewage treatment tanks are arranged and adjacent sewage treatment tanks are connected to flow paths, respectively. The cylindrical surface area of each sewage treatment tank is increased sequentially in accordance with the order in which they are installed, or is made equal between adjacent sewage treatment tanks, and is at least larger in the last sewage treatment tank than in the first sewage treatment tank. , domestic flush toilets, kitchens, etc., characterized in that the bacterial species constituting activated sludge, the growth ratio of aerobic bacteria and anaerobic bacteria, and their distribution status change for each sewage treatment tank. Treatment equipment for sewage discharged from. 2. The porous body in the activated sludge bed is formed by intertwining a large number of filamentous bodies made of polyvinylidene chloride, etc. Treatment equipment for wastewater discharged.