CN115385519B

CN115385519B - Rural domestic sewage treatment system and application method thereof

Info

Publication number: CN115385519B
Application number: CN202210877512.0A
Authority: CN
Inventors: 马军; 张瑛洁; 程喜全; 王凯; 宋丹; 隋潇; 徐美庆; 张楠楠; 朱彦磊; 刘鹏程
Original assignee: Weihai Zhijie Environmental Protection Technology Co ltd
Current assignee: Weihai Zhijie Environmental Protection Technology Co ltd
Priority date: 2022-07-25
Filing date: 2022-07-25
Publication date: 2023-06-13
Anticipated expiration: 2042-07-25
Also published as: CN115385519A

Abstract

A rural domestic sewage treatment system and a using method thereof relate to a sewage treatment system and a using method thereof. The invention aims to solve the problems that the existing rural sewage treatment is poor, resources are wasted, the solid-liquid separation technology is difficult to realize good solid-liquid separation for diluted domestic sewage with low solid content, and the water content of solid waste cannot be effectively controlled. A rural domestic sewage treatment system comprises a sewage separation device, a decomposing reactor and a drainage device; the using method comprises the following steps: standing, separating, rotating, separating and decomposing. The invention is used for rural domestic sewage treatment systems and uses thereof.

Description

Rural domestic sewage treatment system and application method thereof

Technical Field

The invention relates to a sewage treatment system and a using method thereof.

Background

With the high-speed development of Chinese social economy, the living standard of people is continuously improved, and compared with urban domestic sewage, rural domestic sewage drainage is lack of a special pipe network for collection, and a special sewage treatment station is also not provided.

The treated excrement can be used as feed raw materials, and after fermentation and degradation, the treated excrement can be used for raising pigs, cattle and the like to form benign ecological cycle, but the treatment of the existing rural sewage is poor, resources are wasted, the water content of common animal excrement is more than 80%, and dilution in the partial flushing process is carried out, if the subsequent treatment is directly carried out, the water content of the excrement needs to be regulated by a conditioner, but the conditioner resources are limited and the price is too high, and the existing solid-liquid separation technology is difficult to realize good solid-liquid separation on diluted domestic sewage with lower solid content, and the water content of solid waste cannot be effectively controlled.

Disclosure of Invention

The invention aims to solve the problems that the existing rural sewage treatment is poor, resources are wasted, the solid-liquid separation technology is difficult to realize good solid-liquid separation for diluted domestic sewage with low solid content, and the water content of solid waste cannot be effectively controlled. Further provides a rural domestic sewage treatment system and a using method thereof.

A rural domestic sewage treatment system comprises a sewage separation device, a decomposing reactor and a drainage device;

the sewage separation device consists of a shell, a rotary cavity, a partition plate, a water collecting cavity, a rotating rod, a connecting rod and a first motor; the shell is internally provided with a rotary cavity, the rotary cavity is internally provided with a water collecting cavity, the rotary cavity is connected with the water collecting cavity through a partition plate, and the partition plate divides the rotary cavity and the water collecting cavity into two cavities;

the water collecting cavity is provided with a through hole, a rotating rod is arranged in the water collecting cavity, the bottom of the rotating rod is connected with the bottom of the water collecting cavity, and the middle part of the rotating rod is connected with the middle part of the water collecting cavity through a plurality of connecting rods; the rotating rod is connected with a motor shaft of the first motor;

the water collecting cavity is internally provided with a water suction pipe, and the shell is internally provided with a buoyancy water suction device and is positioned between the rotary cavity and the water collecting cavity;

the buoyancy water absorbing device consists of a telescopic pipe and an annular floating plate, the annular floating plate is arranged at the bottom of the telescopic pipe, the annular floating plate is an arc-shaped outer edge which is bent upwards along the circumference, and the diameter of the outer edge of the annular floating plate is smaller than the distance between the rotating cavity and the water collecting cavity;

the top of the shell is provided with a water inlet which is positioned above the rotary cavity and is communicated with a water outlet of the domestic sewage discharge device through a first pipeline;

the bottom of the shell is provided with a first discharge hole, the bottom of the rotary cavity is provided with a second discharge hole, the positions of the first discharge hole and the second discharge hole are corresponding, and the first discharge hole is communicated with the feed inlet of the decomposing reactor through a second pipeline;

a first electromagnetic valve is arranged on the first pipeline; the second pipeline is provided with a first suction device, and the second pipelines at the two ends of the first suction device are respectively provided with a second electromagnetic valve and a third electromagnetic valve;

the telescopic pipe is communicated with a third pipeline, a traction rope is arranged on the annular floating plate, a third motor is arranged outside the third pipeline, the traction rope is wound on a motor shaft of the third motor, a second suction device is arranged on the third pipeline, a fourth electromagnetic valve and a fifth electromagnetic valve are respectively arranged on the third pipeline at two ends of the second suction device, and the fifth electromagnetic valve is close to the buoyancy water absorbing device; the water suction pipe is communicated with a third pipeline between the second suction device and the fifth electromagnetic valve; a sixth electromagnetic valve is arranged on the water suction pipe; and a densimeter is arranged in the third pipeline.

The application method of the rural domestic sewage treatment system comprises the following steps:

1. opening a first electromagnetic valve, closing a second electromagnetic valve, a third electromagnetic valve, a fourth electromagnetic valve, a fifth electromagnetic valve and a sixth electromagnetic valve, enabling domestic sewage to enter a sewage separation device from a water inlet through a first pipeline, automatically closing the first electromagnetic valve when the domestic sewage page exceeds the upper limit of a liquid level meter, standing for 12-24 hours, opening a third motor to adjust the rotation direction of a motor shaft, loosening a traction rope, closing the third motor, and enabling an annular floating plate to float on the surface of the domestic sewage through buoyancy;

2. the second suction device is opened to form negative pressure in the vacuum tank, the second suction device is closed, then the fourth electromagnetic valve and the fifth electromagnetic valve are opened, water above the standing domestic sewage is pumped out by utilizing the buoyancy water suction device, when the density of the pumped water is obviously changed as measured by the densimeter in the third pipeline, the fourth electromagnetic valve and the fifth electromagnetic valve are closed, the third motor is opened to adjust the rotation direction of the motor shaft, the traction rope is wound on the motor shaft, the traction rope pulls the annular floating plate upwards, and when the traction rope reaches the upper part of the rotating cavity, the third motor is stopped;

3. opening a first motor, driving a rotating cavity and a water collecting cavity to rotate by a rotating rod under the condition that the rotating speed is 500-2000 r/min, enabling separated water to enter the water collecting cavity through a through hole, opening a second suction device to enable negative pressure to be formed in a vacuum tank under the condition that the rotating speed is kept unchanged, closing the second suction device, then opening a fourth electromagnetic valve and a sixth electromagnetic valve, pumping the water separated in the water collecting cavity by utilizing a water suction pipe, conveying the water to a drainage device, and closing the first motor, the fourth electromagnetic valve and the sixth electromagnetic valve;

4. opening the first suction device to form negative pressure in the vacuum tank, closing the first suction device, opening the second electromagnetic valve and the third electromagnetic valve, and pumping out the solid manure separated in the rotating cavity by using the second pipeline and conveying the solid manure into the decomposing reactor;

5. and adding a decomposing agent and a filler into the decomposing reactor, and performing a decomposing reaction to obtain solid organic fertilizer particles.

The beneficial effects of the invention are as follows:

1. the invention provides a rural domestic sewage treatment system which can be refitted in a traditional toilet (domestic sewage discharge device), excrement and water are separated by a sewage separation device, the water content of the excrement is controlled to be 30-80%, and the excrement is prepared into organic fertilizer along with agricultural straw and the like after being decomposed. After the water body is separated, the water enters a water treatment system, and the irrigation requirements or the water recycling utilization can be met mainly by using the techniques of oxidation ponds, ecological wetlands and floating rice planting.

2. The invention realizes dry-wet separation of rural domestic sewage and high-efficiency resource utilization. The manure straw and the like can be directly prepared into agricultural organic fertilizer and can be returned to the field for planting. The water body can be used for irrigation and landscapes through natural purification, ecological degradation and other processes, so that the water body can be used for the best, and the water demand is saved. The method has low investment cost, can save more than 200t of water per household each year, generates more than 400kg of agricultural fertilizer, and has wide application prospect.

3. In the use process of the system, domestic sewage in the sewage separation device is firstly subjected to standing, so that solid in the sewage is precipitated, further standing and layering are realized, then a third motor is started to adjust the rotation direction of a motor shaft, a traction rope is loosened, a buoyancy water absorption device moves downwards to and stretches a telescopic pipe until an annular floating plate floats on the surface of the domestic sewage, then the buoyancy water absorption device extracts layered water, the buoyancy water absorption device descends along with the water surface along with the descending of the water level, the water extraction effect is kept, the primary separation of a large amount of water can be realized through the process, and the problem that the water absorption device is fixed in position and cannot realize good water separation when the solid content in the domestic sewage is low is solved.

4. After a large amount of water is primarily separated, the rotary cavity and the water collecting cavity are rotated, and the residual solids rotate along with the rotary cavity, so that the solids are stuck to the side wall of the rotary cavity and the partition plate in the rotating process due to different densities of the solids and the water body, the liquid is screwed out and thrown to the central water collecting cavity, enters the water collecting cavity through the through hole on the surface of the water collecting cavity, and finally is sucked out by the water suction pipe to realize separation. And the separation plate gives a solid blocking force, so that the separation of the solid from the side wall of the rotating cavity in the rotating process of the solid is avoided, and a good separation effect cannot be achieved.

The invention is used for a rural domestic sewage treatment system and a using method thereof.

Drawings

FIG. 1 is a schematic diagram of a rural domestic sewage treatment system according to the present invention;

FIG. 2 is a schematic diagram of a sewage separation device according to the present invention;

FIG. 3 is a top view of the sewage separation device of the present invention;

fig. 4 is a schematic structural view of the buoyancy water absorbing device of the present invention.

Detailed Description

The first embodiment is as follows: referring to fig. 1 to 4, a rural domestic sewage treatment system according to the present embodiment includes a sewage separation device 1, a decomposing reactor 2, and a drainage device 3;

the sewage separation device 1 consists of a shell 1-1, a rotary cavity 1-2, a partition plate 1-3, a water collecting cavity 1-4, a rotating rod 1-5, a connecting rod 1-6 and a first motor 1-7; a rotary cavity 1-2 is arranged in the shell 1-1, a water collecting cavity 1-4 is arranged in the rotary cavity 1-2, the rotary cavity 1-2 is connected with the water collecting cavity 1-4 through a partition plate 1-3, and the partition plate 1-3 divides the rotary cavity 1-2 and the water collecting cavity 1-4 into two chambers;

the water collecting cavity 1-4 is provided with a through hole, the water collecting cavity 1-4 is internally provided with a rotating rod 1-5, the bottom of the rotating rod 1-5 is connected with the bottom of the water collecting cavity 1-4, and the middle part of the rotating rod 1-5 is connected with the middle part of the water collecting cavity 1-4 through a plurality of connecting rods 1-6; the rotating rod 1-5 is connected with a motor shaft of the first motor 1-7;

the water collecting cavity 1-4 is internally provided with a water suction pipe 4-3-1, and the shell 1-1 is internally provided with a buoyancy water suction device 4-3-2 and is positioned between the rotary cavity 1-2 and the water collecting cavity 1-4;

the buoyancy water absorbing device 4-3-2 consists of a telescopic pipe 4-3-2-1 and an annular floating plate 4-3-2-2, wherein the annular floating plate 4-3-2-2 is arranged at the bottom of the telescopic pipe 4-3-2-1, the annular floating plate 4-3-2-2 is an arc-shaped outer edge which is bent upwards along the circumference, and the diameter of the outer edge of the annular floating plate 4-3-2-2 is smaller than the interval between the rotary cavity 1-2 and the water collecting cavity 1-4;

the top of the shell 1-1 is provided with a water inlet 1-1-1, the water inlet 1-1-1 is positioned above the rotary cavity 1-2, and the water inlet 1-1-1 is communicated with a water outlet 5-1 of the domestic sewage discharge device 5 through a first pipeline 4-1;

the bottom of the shell 1-1 is provided with a first discharge port 1-1-2, the bottom of the rotary cavity 1-2 is provided with a second discharge port 1-2-1, the first discharge port 1-1-2 corresponds to the second discharge port 1-2-1 in position, and the first discharge port 1-1-2 is communicated with a feed inlet of the decomposing reactor 2 through a second pipeline 4-2;

a first electromagnetic valve 8-1 is arranged on the first pipeline 4-1; the second pipeline 4-2 is provided with a first suction device 7-1, and the second pipeline 4-2 at two ends of the first suction device 7-1 is respectively provided with a second electromagnetic valve 8-2 and a third electromagnetic valve 8-3;

the telescopic pipe 4-3-2-1 is communicated with a third pipeline 4-3, a traction rope 4-3-2-3 is arranged on the annular floating plate 4-3-2-2, a third motor 4-3-2-4 is arranged outside the third pipeline 4-3, the traction rope 4-3-2-3 is wound on a motor shaft of the third motor 4-3-2-4, a second suction device 7-2 is arranged on the third pipeline 4-3, a fourth electromagnetic valve 8-4 and a fifth electromagnetic valve 8-5 are respectively arranged on the third pipeline 4-3 at two ends of the second suction device 7-2, and the fifth electromagnetic valve 8-5 is close to the buoyancy water suction device 4-3-2; the suction pipe 4-3-1 is communicated with a third pipeline 4-3 positioned between the second suction device 7-2 and the fifth electromagnetic valve 8-5; a sixth electromagnetic valve 8-6 is arranged on the water suction pipe 4-3-1; a densitometer is arranged in the third pipeline 4-3.

The telescopic pipe 4-3-2-1 in the specific embodiment is composed of a plurality of sleeves, the resistance among the sleeves is small, the complete stretching can be realized by means of self gravity, and when the annular floating plate 4-3-2-2 floats on the surface of domestic sewage, the stretching is stopped.

The beneficial effects of this embodiment are:

1. the embodiment provides a rural domestic sewage treatment system, which can be refitted in a traditional toilet (a domestic sewage discharge device), and feces and a water body are separated through a sewage separation device, wherein the water content of the feces is controlled to be 30% -80%, and the feces are prepared into organic fertilizer along with agricultural straws and the like after being decomposed. After the water body is separated, the water enters a water treatment system, and the irrigation requirements or the water recycling utilization can be met mainly by using the techniques of oxidation ponds, ecological wetlands and floating rice planting.

2. The method realizes dry-wet separation of rural domestic sewage and efficient resource utilization. The manure straw and the like can be directly prepared into agricultural organic fertilizer and can be returned to the field for planting. The water body can be used for irrigation and landscapes through natural purification, ecological degradation and other processes, so that the water body can be used for the best, and the water demand is saved. The method has low investment cost, can save more than 200t of water per household each year, generates more than 400kg of agricultural fertilizer, and has wide application prospect.

3. In the use process of the system in the embodiment, domestic sewage in the sewage separation device 1 is firstly stood, so that solids in the sewage are precipitated, further standing layering is achieved, then a third motor 4-3-2-4 is started to adjust the rotation direction of a motor shaft, a traction rope 4-3-2-3 is loosened, a buoyancy water absorption device 4-3-2 moves downwards to and stretches a telescopic pipe 4-3-2-1 until an annular floating plate 4-3-2-2 floats on the surface of the domestic sewage, then the buoyancy water absorption device 4-3-2 extracts layered water, along with the lowering of the water level, the buoyancy water absorption device 4-3-2 descends along with the water surface, the water extraction effect is kept, the primary separation of a large amount of water can be achieved through the process, and further the problem that good water separation cannot be achieved due to the fact that the fixed position of the water absorption device is fixed when the solid content in the domestic sewage is small is solved.

4. After a large amount of water is primarily separated, the rotary cavity 1-2 and the water collecting cavity 1-4 are rotated, the residual solids rotate along with the rotary cavity 1-2, because the density of the solids is different from that of the water, the solids are attached to the side wall of the rotary cavity 1-2 and the partition plate 1-3 in the rotating process, the liquid is screwed out and thrown to the central water collecting cavity 1-4, the liquid enters the water collecting cavity 1-4 through the surface through hole of the water collecting cavity 1-4, and finally the water absorbing pipe 4-3-1 is used for absorbing and realizing the separation, and the embodiment can realize the control of the water content of the solids through standing and the adjustment of the rotating speed. And the separation plate 1-3 gives a solid blocking force to avoid separation from the side wall of the rotary cavity 1-2 in the solid rotation process, so that a good separation effect cannot be achieved.

The second embodiment is as follows: the first difference between this embodiment and the specific embodiment is that: the lower parts of the shell 1-1, the rotary cavity 1-2 and the water collecting cavity 1-4 are conical or inverted trapezoids. The other is the same as in the first embodiment.

And a third specific embodiment: this embodiment differs from one or both of the embodiments in that: the first pipeline 4-1 is provided with a sewage temporary storage device 6; and a flowmeter is arranged in the third pipeline 4-3. The other is the same as the first or second embodiment.

The specific embodiment IV is as follows: this embodiment differs from one of the first to third embodiments in that: the first suction device 7-1 and the second suction device 7-2 are composed of a vacuum tank 7-1-1, a pump 7-1-2 and a second motor 7-1-3, wherein the vacuum tank 7-1-1 is communicated with the pump 7-1-2 through a pipeline, and a rotating shaft of the pump 7-1-2 is connected with a motor shaft of the second motor 7-1-3. The others are the same as in the first or third embodiments.

Fifth embodiment: this embodiment differs from one to four embodiments in that: the drainage device 3 is connected with a water treatment system; the decomposing reactor 2 is internally provided with a stirring device 2-1. The other embodiments are the same as those of the first to fourth embodiments.

Specific embodiment six: this embodiment differs from one of the first to fifth embodiments in that: the inner wall of the shell 1-1 above the rotary cavity 1-2 is provided with a position annunciator of an annular floating plate 4-3-2-2; a liquid level meter is arranged in the rotary cavity 1-2. The other embodiments are the same as those of the first to fifth embodiments.

Seventh embodiment: this embodiment differs from one of the first to sixth embodiments in that: the third motor 4-3-2-4 is a servo motor. The others are the same as those of the fourth to sixth embodiments.

Eighth embodiment: the application method of the rural domestic sewage treatment system in the embodiment is carried out according to the following steps:

1. opening a first electromagnetic valve 8-1, closing a second electromagnetic valve 8-2, a third electromagnetic valve 8-3, a fourth electromagnetic valve 8-4, a fifth electromagnetic valve 8-5 and a sixth electromagnetic valve 8-6, enabling domestic sewage to enter the sewage separation device 1 from a water inlet 1-1 through a first pipeline 4-1, automatically closing the first electromagnetic valve 8-1 when a domestic sewage page exceeds the upper limit of a liquid level meter, standing for 12-24 h, opening a third motor 4-3-2-4 to adjust the rotation direction of a motor shaft, loosening a traction rope 4-3-2-3, closing the third motor 4-3-2-4, and enabling an annular floating plate 4-3-2-2 to float on the surface of the domestic sewage through buoyancy;

2. opening the second suction device 7-2 to enable negative pressure to be formed in the vacuum tank 7-1-1, closing the second suction device 7-2, then opening the fourth electromagnetic valve 8-4 and the fifth electromagnetic valve 8-5, pumping out water above the standing domestic sewage by utilizing the buoyancy water absorbing device 4-3-2, closing the fourth electromagnetic valve 8-4 and the fifth electromagnetic valve 8-5 when the density of the pumped water is obviously changed as measured by the densimeter in the third pipeline 4-3, opening the third motor 4-3-2-4 to adjust the rotation direction of a motor shaft, rolling the traction rope 4-3-2-3 on the motor shaft, and pulling the annular floating plate 4-3-2-2 upwards by the traction rope 4-3-2-3, and stopping the third motor 4-3-2-4 when the density of the pumped water reaches the upper part of the rotary cavity 1-2;

3. opening a first motor 1-7, driving a rotary cavity 1-2 and a water collecting cavity 1-4 to rotate by a rotating rod 1-5 under the condition of the rotating speed of 500-2000 r/min, enabling separated water to enter the water collecting cavity 1-4 through a through hole, opening a second suction device 7-2 under the condition that the rotating speed is kept unchanged, enabling negative pressure to be formed in a vacuum tank 7-1-1, closing the second suction device 7-2, opening a fourth electromagnetic valve 8-4 and a sixth electromagnetic valve 8-6, pumping out the separated water in the water collecting cavity 1-4 by utilizing a water suction pipe 4-3-1, conveying the water into a drainage device 3, and closing the first motor 1-7, the fourth electromagnetic valve 8-4 and the sixth electromagnetic valve 8-6;

4. opening the first suction device 7-1 to form negative pressure in the vacuum tank 7-1-1, closing the first suction device 7-1, opening the second electromagnetic valve 8-2 and the third electromagnetic valve 8-3, and pumping out the solid manure separated in the rotary cavity 1-2 by using the second pipeline 4-2 and conveying the solid manure into the decomposing reactor 2;

5. and adding a decomposing agent and a filler into the decomposing reactor 2, and performing a decomposing reaction to obtain solid organic fertilizer particles.

Detailed description nine: this embodiment differs from the eighth embodiment in that: and step five, the filler is one or a mixture of two of rice hulls and straws. The other is the same as in embodiment eight.

Detailed description ten: this embodiment differs from one of the eighth or ninth embodiments in that: the negative pressure in the second step to the fourth step is 2000 Pa-4000 Pa. The others are the same as those of the eighth or ninth embodiment.

The following examples are used to verify the benefits of the present invention:

embodiment one:

a rural domestic sewage treatment system comprises a sewage separation device 1, a decomposing reactor 2 and a drainage device 3;

The lower parts of the shell 1-1, the rotary cavity 1-2 and the water collecting cavity 1-4 are all conical.

The first pipeline 4-1 is provided with a sewage temporary storage device 6; and a flowmeter is arranged in the third pipeline 4-3.

The first suction device 7-1 and the second suction device 7-2 are composed of a vacuum tank 7-1-1, a pump 7-1-2 and a second motor 7-1-3, wherein the vacuum tank 7-1-1 is communicated with the pump 7-1-2 through a pipeline, and a rotating shaft of the pump 7-1-2 is connected with a motor shaft of the second motor 7-1-3.

The drainage device 3 is connected with the constructed wetland; the decomposing reactor 2 is internally provided with a stirring device 2-1.

The inner wall of the shell 1-1 above the rotary cavity 1-2 is provided with a position annunciator of an annular floating plate 4-3-2-2; a liquid level meter is arranged in the rotary cavity 1-2.

The third motor 4-3-2-4 is a servo motor.

The application method of the rural domestic sewage treatment system comprises the following steps of:

And step five, the filler is rice husk.

The negative pressure in the second to fourth steps is 3000Pa.

The domestic sewage discharge device 5 is a toilet.

After static treatment, the concentration of organic matters in the water is reduced, and the water enters a wetland system, so that the obtained water can be directly used for irrigation water in vegetable gardens. Each household can save water resources by more than 230t of water and produce more than 500kg of agricultural fertilizer each year.

When the solid content of the domestic sewage in the first step is about 20%, the water content of the separated solid feces in the fourth step can be adjusted to be 30% -65%.

Embodiment two: the first difference between this embodiment and the first embodiment is that: the drainage device 3 is connected with a floating rice planting system. The other is the same as in the first embodiment.

After static treatment, the concentration of organic matters in water is reduced, the water enters a floating rice planting system, the yield of rice is increased by 12% each year, and the water consumption is reduced by 20%. Each household can save more than 300t of water and produce more than 460kg of agricultural fertilizer.

Embodiment III: the first difference between this embodiment and the first embodiment is that: the drainage device 3 is connected with an oxidation ditch treatment system. The other is the same as in the first embodiment.

After static treatment, the concentration of organic matters in water is reduced, the water enters an oxidation ditch treatment system, continuous oxygenation is realized through water body flow, the purification purpose is realized, and the purified water can be used for irrigating vegetable gardens, so that the water consumption is reduced by 20%. Each household can save more than 300t of water and produce more than 520kg of agricultural fertilizer.

Claims

1. A rural domestic sewage treatment system is characterized by comprising a sewage separation device (1), a decomposing reactor (2) and a drainage device (3);

the sewage separation device (1) consists of a shell (1-1), a rotary cavity (1-2), a partition plate (1-3), a water collecting cavity (1-4), a rotating rod (1-5), a connecting rod (1-6) and a first motor (1-7); a rotary cavity (1-2) is arranged in the shell (1-1), a water collecting cavity (1-4) is arranged in the rotary cavity (1-2), the rotary cavity (1-2) is connected with the water collecting cavity (1-4) through a partition plate (1-3), and the partition plate (1-3) divides the rotary cavity (1-2) and the water collecting cavity (1-4) into two chambers;

the water collecting cavity (1-4) is provided with a through hole, the water collecting cavity (1-4) is internally provided with a rotating rod (1-5), the bottom of the rotating rod (1-5) is connected with the bottom of the water collecting cavity (1-4), and the middle part of the rotating rod (1-5) is connected with the middle part of the water collecting cavity (1-4) through a plurality of connecting rods (1-6); the rotating rod (1-5) is connected with a motor shaft of the first motor (1-7);

the water collecting cavity (1-4) is internally provided with a water suction pipe (4-3-1), and the shell (1-1) is internally provided with a buoyancy water suction device (4-3-2) and is positioned between the rotary cavity (1-2) and the water collecting cavity (1-4);

the buoyancy water absorbing device (4-3-2) consists of a telescopic pipe (4-3-2-1) and an annular floating plate (4-3-2-2), wherein the annular floating plate (4-3-2-2) is arranged at the bottom of the telescopic pipe (4-3-2-1), the annular floating plate (4-3-2-2) is an arc-shaped outer edge which is bent upwards along the circumference, and the diameter of the outer edge of the annular floating plate (4-3-2-2) is smaller than the interval between the rotary cavity (1-2) and the water collecting cavity (1-4);

the top of the shell (1-1) is provided with a water inlet (1-1-1), the water inlet (1-1-1) is positioned above the rotary cavity (1-2), and the water inlet (1-1-1) is communicated with a water outlet (5-1) of the domestic sewage discharge device (5) through a first pipeline (4-1);

the bottom of the shell (1-1) is provided with a first discharge hole (1-1-2), the bottom of the rotary cavity (1-2) is provided with a second discharge hole (1-2-1), the first discharge hole (1-1-2) corresponds to the second discharge hole (1-2-1), and the first discharge hole (1-1-2) is communicated with the feed inlet of the decomposing reactor (2) through a second pipeline (4-2);

a first electromagnetic valve (8-1) is arranged on the first pipeline (4-1); a first suction device (7-1) is arranged on the second pipeline (4-2), and a second electromagnetic valve (8-2) and a third electromagnetic valve (8-3) are respectively arranged on the second pipeline (4-2) at two ends of the first suction device (7-1);

the telescopic pipe (4-3-2-1) is communicated with a third pipeline (4-3), a traction rope (4-3-2-3) is arranged on the annular floating plate (4-3-2-2), a third motor (4-3-2-4) is arranged outside the third pipeline (4-3), the traction rope (4-3-2-3) is wound on a motor shaft of the third motor (4-3-2-4), a second suction device (7-2) is arranged on the third pipeline (4-3), a fourth electromagnetic valve (8-4) and a fifth electromagnetic valve (8-5) are respectively arranged on the third pipeline (4-3) at two ends of the second suction device (7-2), and the fifth electromagnetic valve (8-5) is close to the buoyancy water suction device (4-3-2); the suction pipe (4-3-1) is communicated with a third pipeline (4-3) positioned between the second suction device (7-2) and the fifth electromagnetic valve (8-5); a sixth electromagnetic valve (8-6) is arranged on the water suction pipe (4-3-1); a densimeter is arranged in the third pipeline (4-3).

2. The rural domestic sewage treatment system according to claim 1, wherein the lower parts of the housing (1-1), the rotary cavity (1-2) and the water collecting cavity (1-4) are tapered or inverted trapezoids.

3. The rural domestic sewage treatment system according to claim 1, wherein the first pipeline (4-1) is provided with a sewage temporary storage device (6); a flowmeter is arranged in the third pipeline (4-3).

4. The rural domestic sewage treatment system according to claim 1, wherein the first suction device (7-1) and the second suction device (7-2) are composed of a vacuum tank (7-1-1), a pump (7-1-2) and a second motor (7-1-3), the vacuum tank (7-1-1) is communicated with the pump (7-1-2) through a pipeline, and a rotating shaft of the pump (7-1-2) is connected with a motor shaft of the second motor (7-1-3).

5. A rural domestic sewage treatment system according to claim 1, wherein the water draining device (3) is connected with the water treatment system; the decomposing reactor (2) is internally provided with a stirring device (2-1).

6. The rural domestic sewage treatment system according to claim 1, wherein the position annunciator of the annular floating plate (4-3-2-2) is arranged on the inner wall of the outer shell (1-1) above the rotary cavity (1-2); the rotary cavity (1-2) is internally provided with a liquid level meter.

7. The rural domestic sewage treatment system according to claim 1, wherein the third motor (4-3-2-4) is a servo motor.

8. The method for using a rural domestic sewage treatment system according to claim 1, wherein the method comprises the following steps:

1. opening a first electromagnetic valve (8-1), closing a second electromagnetic valve (8-2), a third electromagnetic valve (8-3), a fourth electromagnetic valve (8-4), a fifth electromagnetic valve (8-5) and a sixth electromagnetic valve (8-6), enabling domestic sewage to enter a sewage separation device (1) from a water inlet (1-1) through a first pipeline (4-1), automatically closing the first electromagnetic valve (8-1) when a domestic sewage page exceeds the upper limit of a liquid level meter, standing for 12-24 h, opening a third motor (4-3-2-4) to adjust the rotation direction of a motor shaft, loosening a traction rope (4-3-2-3), then closing the third motor (4-3-2-4), and floating an annular floating plate (4-3-2-2) on the surface of the domestic sewage through buoyancy;

2. opening a second suction device (7-2) to enable negative pressure to be formed in a vacuum tank (7-1-1), closing the second suction device (7-2), opening a fourth electromagnetic valve (8-4) and a fifth electromagnetic valve (8-5), pumping out water above the standing domestic sewage by using a buoyancy water absorbing device (4-3-2), closing the fourth electromagnetic valve (8-4) and the fifth electromagnetic valve (8-5) when the density of the pumped water is obviously changed by a densimeter in a third pipeline (4-3), opening a third motor (4-3-2-4) to adjust the rotation direction of a motor shaft, rolling a traction rope (4-3-2-3) on the motor shaft, and pulling the annular floating plate (4-3-2-2) upwards by the traction rope (4-3-2-3), and stopping the third motor (4-3-2-4) when the density of the water reaches the upper part of a rotating cavity (1-2);

3. opening a first motor (1-7), driving a rotating cavity (1-2) and a water collecting cavity (1-4) to rotate by a rotating rod (1-5) under the condition of the rotating speed of 500 r/min-2000 r/min, enabling separated water to enter the water collecting cavity (1-4) through a through hole, opening a second suction device (7-2) to enable negative pressure to be formed in a vacuum tank (7-1-1) under the condition that the rotating speed is kept unchanged, closing the second suction device (7-2), opening a fourth electromagnetic valve (8-4) and a sixth electromagnetic valve (8-6), sucking the water separated in the water collecting cavity (1-4) by utilizing a water suction pipe (4-3-1), conveying the water separated in the water collecting cavity to a drainage device (3), and closing the first motor (1-7), the fourth electromagnetic valve (8-4) and the sixth electromagnetic valve (8-6);

4. opening the first suction device (7-1) to enable negative pressure to be formed in the vacuum tank (7-1-1), closing the first suction device (7-1), opening the second electromagnetic valve (8-2) and the third electromagnetic valve (8-3), and pumping out the solid manure separated in the rotary cavity (1-2) by utilizing the second pipeline (4-2) and conveying the solid manure into the decomposing reactor (2);

5. adding a decomposing agent and a filler into the decomposing reactor (2), and performing a decomposing reaction to obtain solid organic fertilizer particles.

9. The method of claim 8, wherein the filler in the fifth step is one or a mixture of rice hulls and straw.

10. The method for using a rural domestic sewage treatment system according to claim 8, wherein the negative pressure in the second to fourth steps is 2000-4000 Pa.