CN112047585A - VFL sewage treatment equipment - Google Patents

Abstract

The invention provides VFL sewage treatment equipment which comprises an anaerobic zone, an anoxic zone, an aerobic zone, a settling zone and a control system for controlling sludge to flow in the anaerobic zone, the anoxic zone, the aerobic zone and the settling zone, wherein the anaerobic zone, the anoxic zone, the aerobic zone and the settling zone are sequentially connected. The VFL sewage treatment equipment provided by the invention adopts an automatic operation mode, the operation process is completely and automatically controlled and completed by the control unit according to the data collected by the online monitoring unit, the operation process is automatic in the whole process, manual interference is not needed, and in the operation process of the equipment, professional technicians are not needed to perform manual operation, so that the labor is saved, and the operation cost is reduced.

Description

A VFL sewage treatment equipment

technical field

The invention relates to the technical field of environmental protection, in particular to a VFL sewage treatment equipment.

Background technique

my country is a big water country, but water pollution is also very serious. At present, most of the local sewage collection and treatment adopts the centralized collection and treatment method, but it is far away from towns, residential quarters built by remote industrial and mining enterprises, rural gathering areas and other residential areas. Only simple sewage treatment methods such as septic tanks can be used, which cannot meet the standard of reuse water. In particular, the construction of sewage treatment facilities and pipe networks in the vast rural areas and small towns in my country is seriously lagging behind, and a large number of domestic sewage is not completely treated, and even untreated domestic sewage is directly discharged, which has caused a great burden on the local water resources and ecological environment. One of the reasons why the drinking water of the rural population is not up to standard can easily lead to the occurrence and spread of certain epidemic diseases. The discharge of domestic sewage in rural areas is the main reason for the eutrophication of rivers and lakes and the deterioration of water environment.

Biological treatment of sewage is a common sewage treatment method. This method utilizes the metabolic growth of microorganisms to decompose and oxidize dissolved or colloidal organic substances in sewage into stable inorganic substances to purify sewage. The traditional biological sewage treatment equipment is mainly composed of anaerobic tank, anoxic tank, aerobic tank and sedimentation tank. Among them, a submersible mixer is installed at the bottom of the anaerobic tank and anoxic tank. In order to prevent the deposition of activated sludge, the submersible mixer is usually Continuous operation, an aeration device is installed at the bottom of the aerobic tank, and the aeration is provided by a fan. The aeration fan is usually operated continuously, and a nitrifying liquid return pump is also installed at the bottom to return the sludge of the aerobic tank to the anoxic tank and the sedimentation tank. For mud-water separation, a sludge return pump is installed at the bottom of the tank to return the sedimented sludge to the anaerobic tank. In order to ensure the normal operation of traditional integrated sewage treatment equipment, at least 2 submersible mixers, 1 fan and 2 return pumps are required.

However, since the aeration pipes and submersible stirring motors are installed in the pools of the above-mentioned sewage treatment equipment, the construction cost of the sewage treatment equipment is increased, and it needs to be repaired and maintained irregularly. The activated sludge is removed, or the submersible stirring motor is taken out of the tank, and then maintenance is performed. The maintenance operation is complicated, and the maintenance cost of the equipment is increased, and the utilization rate of the sewage treatment device is seriously reduced. At the same time, the maintenance of the sewage treatment facility requires professional technical management personnel, and the lack of professional technical management personnel causes problems such as low management level, large fluctuation of sewage treatment effect, and difficulty in maintenance and maintenance. So that the water pollution of villages and towns in my country has not been effectively controlled.

SUMMARY OF THE INVENTION

The present invention is made to solve the above problems, and aims to provide a VFL sewage treatment equipment.

The technical scheme for realizing the object of the present invention is as follows: The present invention provides a VFL sewage treatment equipment, which has the following technical characteristics: the treatment equipment includes an anaerobic zone, an anoxic zone, an aerobic zone, a sedimentation zone and a A control system for controlling the flow of sewage in the anaerobic zone, anoxic zone, aerobic zone and sedimentation zone.

A VFL sewage treatment equipment provided by the present invention may also have the following characteristics: the control system includes:

an aeration unit for controlling the aeration of the aerobic tank;

a reflux unit for controlling the reflux between the anaerobic zone, the anoxic zone, the aerobic zone and the precipitation zone;

an online monitoring unit, arranged in the anaerobic zone, the anoxic zone, the aerobic zone and the precipitation zone, for monitoring the anaerobic zone, the anoxic zone, the aerobic zone and the the working data of the settling zone;

A control unit, connected with the aeration unit, the reflux unit and the online monitoring unit, for receiving the working data monitored by the online monitoring unit, and generating a control unit for controlling the aeration unit and the reflux unit work order.

The VFL sewage treatment equipment provided by the present invention may also have the following characteristics: the aeration unit includes:

an aeration device, arranged in the aerobic zone, for aeration;

a fan, connected to the aeration device, and used for supplying gas to the aeration device.

The VFL sewage treatment equipment provided by the present invention may also have the following characteristics: the return unit includes one or more selected from the following return flows: a return flow for increasing the sludge circulation at the inlet end ; The return flow of the sludge cycle used to complete the system biological phosphorus removal; The return flow of the sludge cycle used to complete the system biological denitrification; The return flow used to increase the sludge concentration in the front section of the anoxic zone; Used to supplement the sludge in the anoxic zone The return flow of sludge concentration is used to supplement the return flow of sludge concentration in the aerobic zone, and the return flow used to discharge the excess sludge in the system.

The VFL sewage treatment equipment provided by the present invention may also have the following characteristics: the control system further includes a valve group box, the valve group box is connected with the aeration unit, the return unit and the control unit connection for executing the work command issued by the control unit.

The VFL sewage treatment equipment provided by the present invention may also have the following characteristics: the control unit controls the aeration intensity and aeration time of the aeration unit, and the return intensity and return time of the return unit.

The VFL sewage treatment equipment provided by the present invention may also have the following characteristics: the control unit adjusts the aeration cycle and intensity, and the return cycle and intensity through the measurement data of the online measurement device.

The VFL sewage treatment equipment provided by the present invention may also have the following characteristics: the shape of the treatment equipment formed by the anaerobic zone, the anoxic zone, the aerobic zone and the precipitation zone One selected from circle, oval, square and polygon.

The VFL sewage treatment equipment provided by the present invention may also have the following characteristics: the equipment is circular, the anaerobic zone and the anoxic zone are arranged at the outermost periphery; the aerobic zone is two semicircles The shape structure is arranged in the middle of the anaerobic zone and the anoxic zone; the sedimentation zone is arranged in the center of the middle of the two aerobic zones.

The VFL sewage treatment equipment provided by the present invention may also have the following characteristics: a plurality of upper baffles and lower baffles are arranged in the anaerobic zone, and the upper baffles and the lower baffles Alternately installed in the anaerobic zone, the lower end of the upper baffle is fixedly connected to the bottom of the anaerobic zone, so that the upper end of the upper baffle forms the upper flow channel of sewage; the lower baffle The lower end of the plate is spaced from the bottom of the anaerobic zone, so that the lower end of the lower baffle plate forms a lower flow channel of sewage.

The VFL sewage treatment equipment provided by the present invention may also have the following characteristics: a plurality of upper baffles and lower baffles are arranged in the oxygen-deficient area, and the upper baffles and the lower baffles Alternately installed in the anoxic zone, the lower end of the upper baffle is fixedly connected with the bottom of the anoxic zone, so that the upper end of the upper baffle forms an upper flow channel for sewage; the lower baffle The lower end of the plate is spaced apart from the bottom of the oxygen-deficient zone, so that the lower end of the lower baffle plate forms a lower flow channel for sewage.

The VFL sewage treatment equipment provided by the present invention may also have the following characteristics: an upper baffle is formed between the anoxic zone and the aerobic zone, and the sewage enters the aerobic zone from the upper channel.

The VFL sewage treatment equipment provided by the present invention may also have the following characteristics: a mud-water separator and a water outlet tank are provided at the end of the sedimentation zone.

The VFL sewage treatment equipment provided by the present invention can also have the following characteristics: the shape of the mud-water separator is an inverted cone, the bottom is upward, the top of the cone is connected with the bottom of the sedimentation zone, a trapezoidal hole is opened on the side wall, and the hole is equipped with a The baffle, the baffle and the side wall have a certain angle, for the sludge to enter.

The VFL sewage treatment equipment provided by the present invention may also have the following characteristics: the mud-water separator is made of PP plate or carbon steel plate.

The VFL sewage treatment equipment provided by the present invention may also have the following characteristics: the water outlet tank is placed on the upper part of the mud-water separator.

Compared with the prior art, the beneficial effects of the present invention:

1. The VFL sewage treatment equipment provided by the present invention adopts an automatic operation mode. The operation process is all automatically controlled by the control unit according to the data collected by the online monitoring unit. The operation process is fully automated without manual intervention. Equipped with professional and technical personnel for manual operation, saving labor and reducing operating costs.

2. The VFL sewage treatment equipment provided by the present invention only needs one fan to complete all the sewage treatment processes, which reduces a number of power equipment compared with the traditional equipment, and the VFL sewage treatment equipment provided by the present invention The fan in the equipment is operated intermittently according to the detection data of the online monitoring unit, instead of the continuous operation of multiple power equipment in the traditional equipment, which is more energy-saving and consumption-reducing.

3. The VFL sewage treatment equipment provided by the present invention only needs one fan to complete all sewage treatment processes, which solves the problem of irregular maintenance and repair of the aeration pipes and submersible stirring motors installed in the pool in the prior art. This reduces the cost of maintenance and repair, and at the same time solves the problem of dependence on professional technicians required for maintenance in the prior art, further reducing the cost.

4. The fan operation mode of the VFL sewage treatment equipment provided by the present invention is program control, and there are 4 groups of operation programs inside, and the aeration intensity and duration of the 4 groups of automatic operation programs are continuously adjusted through the detection value of the online monitoring unit, There is no need for manual operation by personnel during the operation of the equipment, the degree of automation is high, and the control is more intelligent under the premise of ensuring the processing effect of the equipment.

Description of drawings

1 is a schematic structural diagram of a VFL sewage treatment equipment with a circular pool type provided by an embodiment of the present invention;

2 is a schematic structural diagram of a VFL sewage treatment equipment with a square pool type provided by an embodiment of the present invention;

3 is a schematic structural diagram of a VFL sewage treatment equipment with an oval pool type provided by an embodiment of the present invention;

Among them, 1: anaerobic zone; 2: anoxic zone; 3: aerobic zone; 4: sedimentation zone; 5: aeration membrane; 6: outlet tank; 7: valve group box; 8: fan; 9: electric control cabinet; 10: upper baffle; 11: lower baffle; 12: equipment room; 13: mud-water separator; 14: online monitoring unit.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments, and the advantages and characteristics of the present invention will become more apparent with the description. However, these examples are only exemplary and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solutions of the present invention can be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the protection scope of the present invention.

In the description of this embodiment, it should be understood that the terms "center", "portrait", "horizontal", "top", "bottom", "front", "rear", "left", "right", The orientation or positional relationship indicated by "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention The description is created and simplified rather than indicating or implying that the device or element referred to must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as limiting the invention.

In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first", "second", etc., may expressly or implicitly include one or more of that feature. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

As shown in FIG. 1, a VFL sewage treatment equipment has the following technical features: the treatment equipment includes an anaerobic zone 1, anoxic zone 2, an aerobic zone 3, and a sedimentation zone 4, which are connected in sequence. The control system for the flow of the anaerobic zone 1, anoxic zone 2, aerobic zone 3 and precipitation zone 4. The equipment is circular, and the anaerobic zone 1 and the anoxic zone 2 are arranged at the outermost periphery; the aerobic zone 3 is two semicircular structures, which are arranged in the anaerobic zone 1 and the anoxic zone In the middle of zone 2; the precipitation zone 4 is arranged in the middle of the two aerobic zones 3.

The control system includes an aeration unit, a return unit, an online monitoring unit and a control unit.

The aeration unit is used to control the aeration of the aerobic tank, and includes an aeration device and a fan 8 . The aeration device includes an aeration tube and an aeration membrane 5 , and the aeration membrane 5 and the aeration tube are evenly laid on the bottom of the aerobic zone 3 . The air volume for aeration is generated by the fan 8 . The aeration pipe is a channel for transmitting the air volume, from the outlet of the fan to the aeration membrane 5 for aeration. The aeration membrane 5 is a plastic film with micropores, which can generate tiny air bubbles. The aeration membrane 5 is set outside the aeration pipe with holes, and the aeration air volume passes through the holes and is transmitted from the micropores of the aeration membrane. Aeration.

The reflux unit is used to control the reflux between the anaerobic zone 1, the anoxic zone 2, the aerobic zone 3 and the precipitation zone 4. The return unit includes the return flow for increasing the sludge circulation at the water inlet; the return flow for the sludge circulation for completing the biological phosphorus removal of the system; the return flow for the sludge circulation for completing the biological denitrification of the system; for increasing the anoxic zone The return flow of the sludge concentration in the previous stage; used to supplement the return flow of the sludge concentration in the anoxic zone, used to supplement the return flow of the sludge concentration in the aerobic zone, and used to discharge the excess sludge in the system.

It is used to supplement the return of sludge concentration in the anaerobic zone, and to complete the return of sludge circulation for biological phosphorus removal in the system. At the same time, it increases the amount of sludge circulation at the inlet end, reduces the load at the inlet end, and increases the impact resistance of the VFL process. . The return flow used to increase the sludge concentration in the front section of the anoxic zone and the return flow used to supplement the amount of sludge in the anoxic zone increases the sludge concentration in the anoxic zone. The return flow of the sludge cycle used to complete the biological denitrification of the system enhances the microbial denitrification and denitrification. It is used to supplement the return flow of sludge concentration in the aerobic zone, and strengthens the absorption of phosphorus sources and nitrification by microorganisms. It is used to discharge the backflow of excess sludge in the system, so that the activated sludge in the equipment can be maintained within a certain range.

The online monitoring unit 14 is arranged in the aerobic zone 3 and is used for monitoring the working data of the aerobic zone 3 . The working data of the aerobic zone 3 is the ORP value, that is, the redox potential.

a control unit, connected with the aeration unit, the return flow unit and the online monitoring unit 14, for receiving the working data monitored by the online monitoring unit 14, and generating and controlling the aeration unit and the return flow The unit's work order. The control unit includes aeration program, U cycle program, return sludge cycle program and N cycle program. The aeration program controls the aeration of the aerobic zone 3, the U cycle program, the return sludge cycle program, and the N cycle program are used to control different returns.

In the cycle time period of the aeration program, the U cycle program, the return sludge cycle program and the N cycle program, each cycle period is provided with a fixed-length work cycle and at least one algorithm cycle, and the algorithm cycle depends on the measurement of the online monitoring unit 14. data. In a time period, according to the work data monitored by the online monitoring unit 14, the intensity and work duration of each cycle are selected.

work process:

The sewage to be treated enters the anaerobic zone 1, the anoxic zone 2, the aerobic zone 3 and the sedimentation zone 4 in turn for biological deammonia and phosphorus removal treatment. Under aerobic conditions, the microorganisms convert the ammonia nitrogen in the sewage into nitrate nitrogen or nitrous acid. Salt nitrogen, under anoxic conditions, microorganisms convert nitrate nitrogen and nitrite nitrogen into nitrogen gas, which escapes the water surface to complete denitrification. The dissolved oxygen in the water in the anaerobic zone 1 is less than 0.2 mg/L, the dissolved oxygen in the water in the anoxic zone 2 is less than 0.5 mg/L, and the dissolved oxygen in the water in the aerobic zone 3 is more than 2 mg/L. The online monitoring unit 13 set in the aerobic zone 3 monitors the ORP value, that is, the redox potential. After the ORP value is transmitted to the control unit, the control unit generates different work commands to control the aeration program, the U cycle program, and the return sludge. The work of cycle programs and N cycle programs. The work of the aeration equipment laid at the bottom of the aerobic zone 3 controlled by the aeration program, the U cycle program, the return sludge cycle program, and the N cycle program control the return flow of the return unit.

In the above-mentioned embodiment, a control unit is provided, and all the running programs are automatically controlled and completed by the control unit according to the data collected by the online monitoring unit. The entire running process is automated without manual intervention. During the operation of the equipment, there is no need for professional technicians to perform manual operations. , saving labor and reducing operating costs. Moreover, the operation mode is program control, and there are 4 groups of operation programs inside. The aeration intensity and duration of the 4 groups of automatic operation programs are continuously adjusted through the detection value of the online monitoring unit. There is no need for manual operation by personnel during the operation of the equipment, and the degree of automation is high. In addition, the running period between programs is calculated by the work data obtained by online monitoring, and different programs are performed at different times, which can effectively utilize the fan 8 and avoid the fan 8 from doing useless work, thereby saving energy consumption.

In another embodiment of the present invention, on the basis of the above-mentioned embodiment, a control system of a VFL sewage treatment equipment provided by the present invention further includes a valve group box 7, which is used for performing aeration procedures, U Cycle program, return sludge cycle program and N cycle program. In addition, the valve group box 7 also includes valves with different strengths arranged on each return pipe and aeration pipe. The valve group box 7 executes the work orders generated by the aeration program, the U cycle program, the return sludge cycle program and the N cycle program. When , open and close different valves to control the intensity and time of aeration and reflux.

In the above embodiment, the valve group box 7 is provided in the control system, which can better execute the execution of each program in the control system, and valves with different strengths are provided, which can maximize the use of the fan 8 and avoid the fan 8 Do useless work.

As shown in FIG. 2, in another embodiment of the present invention, on the basis of any of the above embodiments, the anaerobic zone 1, the anoxic zone 2, the aerobic zone 3 and the precipitation The shape of the processing apparatus formed by the combination of zones 4 is square. The anaerobic zone 1 is provided with a plurality of upper baffles 10 and lower baffles 11, the upper baffles 10 and the lower baffles 11 are alternately installed in the anaerobic zone 1, and the upper baffles 10 and 11 are alternately installed in the anaerobic zone 1. The lower end of the baffle 10 is fixedly connected to the bottom of the anaerobic zone 1, so that the upper end of the upper baffle 10 forms an upper flow channel for sewage; the lower end of the lower baffle 11 is connected to the anaerobic zone. The bottom of 1 is spaced so that the lower end of the lower baffle plate 11 forms a lower circulation channel for sewage. A plurality of upper baffles 10 and lower baffles 11 are arranged in the anoxic zone 2, and the upper baffles 10 and the lower baffles 11 are alternately installed in the anoxic zone 1, and the upper baffles 10 and the lower baffles 11 are alternately installed in the anoxic zone 1. The lower end of the baffle 10 is fixedly connected to the bottom of the anoxic zone 1, so that the upper end of the upper baffle 10 forms an upper flow channel for sewage; the lower end of the lower baffle 11 is connected to the anoxic zone. The bottom of 1 is spaced so that the lower end of the lower baffle plate 11 forms a lower circulation channel for sewage.

In the above embodiment, the equipment provided by the present invention is alternately arranged with upper and lower baffles in the middle of the anaerobic zone 1 and the anoxic zone 2 according to the content of dissolved oxygen, and the alternate arrangement of the upper and lower baffles makes the adjacent baffles The height of the liquid between the two parts is different, and the pages decrease in turn in the direction of the water flow. Therefore, the pressure generated by the difference in liquid level makes the sewage flow up and down along the upper and lower gaps flowing out of the baffle plate, which can prevent the activated sludge from settling. At the same time, the denitrification and phosphorus removal of the sewage treatment process is completed with the backflow procedure, and there is no need to set up a mixer under water to stir the water body, which reduces the difficulty of equipment maintenance and maintenance. In addition, the processing equipment with a square structure is more convenient for transportation and is suitable for remote areas that need to be transported.

In another embodiment of the present invention, on the basis of any of the above-mentioned embodiments in which the tank type is square, the end of the sedimentation tank of a VFL sewage treatment equipment provided by the present invention is provided with a mud-water separator 13, which is arranged at the end of the sedimentation tank. The sludge return equipment and the water outlet tank 6 at the bottom of the mud-water separator 13. The shape of the mud-water separator 13 is an inverted cone, the bottom is upward, the top of the cone is connected to the bottom of the sedimentation zone, a trapezoidal hole is opened on the side wall, and a baffle plate is installed outside the hole. Sludge enters. The mud-water separator is made of PP plate or carbon steel plate. The water outlet groove is placed on the upper part of the mud-water separator 13, and the water outlet groove 6 is in the shape of a long strip with a zigzag water outlet weir around it.

In the above embodiment, a mud-water separator 13 is set at the end of the sedimentation zone 4 to separate the activated sludge and water in the sewage, the water is discharged from the sewage treatment equipment through the water outlet 6, and the activated sludge sinks, and the mud-water separator 13 is installed. The inverted cone shape ensures that all the activated sludge flows back and does not accumulate in the mud-water separator 13 . The angle of the baffle plate and the side wall controls the amount, angle and speed of the mud-water mixture entering, so that the sewage can be effectively separated in the mud-water separator 13, and the inlet pollution caused by the low flow rate will not occur, or the flow rate is too fast. Turbulent flow affects sludge sedimentation.

In another embodiment of the present invention, the fan 8 and the electric control cabinet 9 are arranged in the equipment room 12, which prevents the fan 8 and the electric control cabinet 9 from being exposed to the outside and is exposed to the wind and the sun, and increases the number of fans 8 and 9. The service life of the electric control cabinet 9.

In another embodiment of the present invention, as shown in FIG. 3 , a VFL sewage treatment equipment provided by the present invention is annularly arranged, the anaerobic zone 1 and the anoxic zone 2 are arranged at the outermost periphery, and the aerobic zone 3 is arranged In the annular interval formed by the anaerobic zone 1 and the anoxic zone 2, the precipitation zone 4 is arranged in the center of the aerobic zone 3. The annular treatment equipment has a more stable structure and is more suitable for large-scale sewage treatment.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range. The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the technical principles of the present invention, several improvements and modifications can also be made. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (17)

1. The VFL sewage treatment equipment is characterized by comprising an anaerobic zone, an anoxic zone, an aerobic zone, a settling zone and a control system for controlling sewage and activated sludge to flow in the anaerobic zone, the anoxic zone, the aerobic zone and the settling zone, wherein the anaerobic zone, the anoxic zone, the aerobic zone and the settling zone are sequentially connected.

2. The VFL sewage treatment plant of claim 1, wherein the control system comprises:

the aeration unit is arranged in the aerobic zone and is used for aeration of the aerobic zone;

a reflux unit for refluxing a sludge-water mixture among the anaerobic zone, the anoxic zone, the aerobic zone and the settling zone;

the online monitoring unit is arranged in the aerobic zone and used for monitoring the working data of the aerobic zone;

and the control unit is connected with the aeration unit, the backflow unit and the online monitoring unit and used for receiving the working data monitored by the online monitoring unit and generating a working command for controlling the aeration unit and the backflow unit.

3. A VFL sewage treatment plant according to claim 2, characterized in that the aeration unit comprises:

the aeration device is arranged in the aerobic zone and is used for aeration;

and the fan is connected with the aeration device and used for providing gas for the aeration device.

4. A VFL water treatment plant according to claim 3, characterized in that said aeration means comprises:

the aeration membrane is laid at the bottom of the aerobic zone and is used for aeration of the aerobic zone;

and the aeration pipe is connected with the aeration membrane and the fan and used for conveying the air quantity provided by the fan to the aeration membrane.

5. A VFL sewage treatment plant according to claim 2, characterized in that the reflux unit comprises one or more of the following reflux streams:

used for increasing the backflow of the sludge circulation at the water inlet end; the return flow of sludge circulation for completing the biological phosphorus removal of the system; the return flow of the sludge circulation for completing the biological denitrification of the system; a reflux for increasing the sludge concentration in the front section of the anoxic zone; the return flow for supplementing the sludge concentration of the anoxic zone is used for supplementing the return flow of the sludge concentration of the aerobic zone and is used for discharging excess sludge of the system.

6. A VFL sewage treatment plant according to claim 2, characterized in that the control system further comprises a valve stack box connected to the aeration unit, the recirculation unit and the control unit for executing the operating commands issued by the control unit.

7. A VFL sewage treatment plant according to claim 2, characterized in that the control unit controls the aeration intensity and aeration time of the aeration unit and the reflux intensity and reflux time of the reflux unit.

8. A VFL sewage treatment plant according to claim 7, wherein said control unit adjusts said aeration period and intensity, and said respective reflux periods and intensities, by means of said on-line measurement device measurement data.

9. A VFL sewage treatment plant according to any one of claims 1, wherein the shape of the treatment plant in which the anaerobic zone, the anoxic zone, the aerobic zone and the settling zone are combined comprises one selected from a circle, an ellipse, a square and a polygon.

10. A VFL sewage treatment plant according to claim 9, wherein when the tank type is circular, the anaerobic zone and the anoxic zone are disposed at the outermost periphery; the aerobic zone is of two semicircular structures and is arranged between the anaerobic zone and the anoxic zone; the settling zone is arranged between the two aerobic zones.

11. The VFL sewage treatment plant of claim 1, wherein a plurality of upper and lower baffles are provided in the anaerobic zone, said upper and lower baffles being alternately mounted in said anaerobic zone,

the lower end of the upper baffle plate is fixedly connected with the bottom of the anaerobic zone, so that an upper circulation channel of sewage is formed at the upper end of the upper baffle plate;

the lower end of the lower baffle plate is spaced from the bottom of the anaerobic zone, so that a lower circulation channel for sewage is formed at the lower end of the lower baffle plate.

12. The VFL sewage treatment plant of claim 1, wherein a plurality of upper baffles and lower baffles are provided in the anoxic zone, said upper baffles and said lower baffles being alternately installed in said anoxic zone,

the lower end of the upper baffle plate is fixedly connected with the bottom of the anoxic zone, so that an upper circulation channel of sewage is formed at the upper end of the upper baffle plate;

the lower end of the lower baffle plate is spaced from the bottom of the anoxic zone, so that a lower circulation channel for sewage is formed at the lower end of the lower baffle plate.

13. A VFL sewage treatment plant according to claim 12, wherein between the anoxic zone and the aerobic zone is an upper baffle, the sewage entering the aerobic zone from an upper flow path.

14. A VFL sewage treatment plant as claimed in claim 1, wherein the settling zone is terminated by a mud-water separator and a water outlet tank.

15. A VFL sewage treatment plant as claimed in claim 14 wherein the sludge-water separator is in the form of an inverted cone with the bottom facing upwards and the apex of the cone connected to the bottom of the settling zone, the side wall having a trapezoidal aperture, the aperture being externally fitted with a baffle which is angled to the side wall for the ingress of sludge from the aerobic zone.

16. The VFL sewage treatment plant of claim 15, wherein the sludge-water separator is made of PP plate or carbon steel plate.

17. A VFL sewage treatment plant as claimed in claim 15, wherein the effluent tank is located above the mud-water separator.

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