CN111533374A

CN111533374A - Synchronous denitrification and dephosphorization double-sludge sewage treatment system

Info

Publication number: CN111533374A
Application number: CN202010380246.1A
Authority: CN
Inventors: 袁思静
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-05-08
Filing date: 2020-05-08
Publication date: 2020-08-14

Abstract

The invention provides a synchronous denitrification nitrogen and phosphorus removal double-sludge sewage treatment system, which comprises a raw water tank; the raw water pool is sequentially connected with the pH adjusting pool, the flocculation pool and the sedimentation pool I through pipelines; the sedimentation tank is respectively connected with the two independent tank bodies through pipelines; the two independent groove bodies are respectively communicated with a first water outlet pipe of the sewage distribution tank and a second water outlet pipe of the sewage distribution tank; a water outlet pipe I of the sewage distribution tank is sequentially connected with an anaerobic tank, a sedimentation tank II, a BAF aeration biological filter tank I, an anoxic tank I and a sedimentation tank III; a water outlet pipe II of the sewage distribution tank is sequentially connected with the aerobic tank, the sedimentation tank IV and the BAF biological aerated filter II; the sedimentation tank III and the BAF biological aerated filter II are both connected with the anoxic tank II, and the anoxic tank II is connected with the sedimentation tank V through a pipeline; the double-sludge sewage treatment system has high operation stability, good nitrogen and phosphorus removal effect, effective removal of nitrogen and phosphorus and good effluent quality.

Description

Synchronous denitrification and dephosphorization double-sludge sewage treatment system

Technical Field

The invention relates to the technical field of sewage treatment, in particular to a synchronous denitrification and dephosphorization double-sludge sewage treatment system.

Background

Sewage treatment: the sewage is purified to reach the water quality requirement of being discharged into a certain water body or being reused. Sewage treatment is widely applied to various fields such as buildings, agriculture, traffic, energy, petrifaction, environmental protection, urban landscape, medical treatment, catering and the like, and is increasingly used in daily life of common people.

The sewage treatment is generally classified into production sewage treatment and domestic sewage treatment according to the classification of sewage sources. The production sewage comprises industrial sewage, agricultural sewage, medical sewage and the like, and the domestic sewage is sewage generated in daily life, and refers to complex mixtures of various forms of inorganic matters and organic matters, and comprises the following steps: floating and suspended large and small solid particles; ② colloidal and gelatinous dispersions; ③ pure solution.

There are two types of water pollution, based on the nature of the water pollution: one is natural pollution; the other is artificial pollution, and the current water body is greatly damaged by the artificial pollution. Water pollution can be mainly classified into chemical pollution, physical pollution and biological pollution according to different pollution impurities. The pollutants are mainly: industrial waste water discharged without treatment; ② domestic sewage discharged without treatment; thirdly, farmland sewage which uses a large amount of chemical fertilizer, pesticide and herbicide; fourthly, industrial waste and domestic garbage stacked beside the river; water and soil loss; sixthly, mine sewage.

The traditional single-sludge process is adopted in the sewage treatment plant in China, such as A₂The single sludge process has two main contradictions, namely ① sludge age contradiction, nitrifying bacteria are aerobic autotrophic bacteria and need longer sludge age, while phosphorus accumulating bacteria need shorter sludge age, ② system carbon source competition contradiction, denitrifying bacteria and phosphorus accumulating bacteria compete for carbon source in an anaerobic tank, and the phosphorus accumulating bacteria have weaker competition capability than the denitrifying bacteria, so that the anaerobic tank releases insufficient phosphorus and further causes incomplete phosphorus absorption.

The double-sludge process developed based on the denitrifying phosphorus removal principle can well solve two main contradictions existing in the single-sludge process: firstly, nitrifying bacteria and denitrifying phosphorus accumulating bacteria are separately cultured by a double-sludge method, so that the contradiction of different sludge ages of the nitrifying bacteria and the denitrifying phosphorus accumulating bacteria is solved. Secondly, the denitrifying phosphorus-accumulating bacteria both utilize an in-vivo carbon source for denitrification and phosphorus uptake, so that one-carbon dual-purpose can be realized, and the carbon source competition contradiction of the denitrifying bacteria and the phosphorus-accumulating bacteria is further reduced. Particularly, in areas with lower carbon source of inlet water, the process has strong advantages compared with the traditional activated sludge nitrogen and phosphorus removal process.

The domestic patent with the application number of 201821761355.2 discloses a synchronous denitrification nitrogen and phosphorus removal double-sludge sewage treatment system, which comprises a front-end activated sludge sewage treatment and rear-end biomembrane sewage treatment double-sludge enhanced microorganism system, wherein the two systems are communicated; the front-end activated sludge sewage treatment system consists of an anaerobic tank, an anoxic tank and a middle sedimentation tank, and realizes synchronous denitrification nitrogen and phosphorus removal; the rear end biomembrane sewage treatment system consists of an aerobic tank and a secondary sedimentation tank, and the activated sludge and biomembrane sludge system double-membrane reinforced microorganism system realizes deep nitrogen and phosphorus removal. The utility model discloses a can resist and hit hydraulic shock load, realize that the synchronous degree of depth of nitrogen and phosphorus in the sewage is got rid of to low carbon-nitrogen ratio. However, the above-mentioned double-sludge sewage treatment system has a weak sewage treatment capability, and therefore, it is necessary to optimize the double-sludge sewage treatment system to have a higher sewage treatment capability.

Disclosure of Invention

The invention provides a synchronous denitrification nitrogen and phosphorus removal double-sludge sewage treatment system which is high in operation stability, good in nitrogen and phosphorus removal effect, capable of effectively removing nitrogen and phosphorus and good in effluent quality.

In order to achieve the purpose, the invention provides the following technical scheme:

a synchronous denitrification dephosphorization double-sludge sewage treatment system comprises a raw water tank, a pH adjusting tank, a flocculation tank, a first sedimentation tank, a sewage distribution tank, an anaerobic tank, a second sedimentation tank, a first anoxic tank, a third sedimentation tank, an aerobic tank, a fourth sedimentation tank, a second anoxic tank, a fifth sedimentation tank, a first BAF biological aerated filter and a second BAF biological aerated filter;

the raw water pool is sequentially connected with the pH adjusting pool, the flocculation pool and the sedimentation pool I through pipelines; the sewage distribution tank is divided into two independent tank bodies by a partition plate; the sedimentation tank is respectively connected with two independent tank bodies through pipelines; the two independent groove bodies are respectively communicated with a first water outlet pipe of the sewage distribution tank and a second water outlet pipe of the sewage distribution tank;

the first water outlet pipe of the sewage distribution tank is connected with an anaerobic tank, the anaerobic tank is connected with a second sedimentation tank through a pipeline, the second sedimentation tank is communicated with a second water outlet pipe of the sedimentation tank, the bottom end of the second sedimentation tank is communicated with a second sludge outlet pipe of the sedimentation tank, the second water outlet pipe of the sedimentation tank is connected with the feed end of the first BAF aeration biological filter, and the second sludge outlet pipe of the sedimentation tank is connected with the first anoxic tank; the BAF biological aerated filter I is connected with the anoxic tank I through a pipeline, and the anoxic tank I is connected with the sedimentation tank III through a pipeline; the third bottom end of the sedimentation tank is communicated with a third sludge return pipe of the sedimentation tank, and the third sludge return pipe of the sedimentation tank is connected with the anaerobic tank;

the second water outlet pipe of the sewage distribution tank is connected with an aerobic tank, the aerobic tank is connected with a fourth sedimentation tank through a pipeline, the fourth sedimentation tank is communicated with a fourth water outlet pipe of the sedimentation tank, the bottom end of the fourth sedimentation tank is communicated with a fourth sludge return pipe of the sedimentation tank, and the fourth sludge return pipe of the sedimentation tank is connected with the aerobic tank; a water outlet pipe of the sedimentation tank IV is connected with the feed end of the BAF biological aerated filter II;

the sedimentation tank III and the BAF biological aerated filter II are both connected with the anoxic tank II through pipelines, and the anoxic tank II is connected with the sedimentation tank V through a pipeline.

Preferably, the device also comprises a photocatalytic tank, and the sedimentation tank is connected with the photocatalytic tank through a pipeline; the photocatalyst added into the photocatalytic tank is zeolite fine particles for adsorbing nano titanium dioxide.

Preferably, a flocculating agent adding pipe is connected to the flocculation tank; the flocculating agent added into the flocculation tank is prepared from polyaluminium sulfate, polyferric chloride and polyferric silicate sulfate flocculating agent according to the mass ratio of 1: 0.3-0.5: 1.5-2.5.

Preferably, be equipped with the agitating unit of vertical setting in the flocculation basin, be fixed with the support on the flocculation basin, fixed mounting has the motor on the support, agitating unit is rotated by motor drive.

Preferably, submersible stirrers are arranged in the anaerobic tank, the first anoxic tank, the second anoxic tank and the pH adjusting tank.

Preferably, a micropore aeration head is arranged in the aerobic tank for aeration, and the solubility of dissolved oxygen is 3.5-4 mg/L.

Preferably, five bottom ends of the sedimentation tank are communicated with five sludge return pipes of the sedimentation tank, and the five sludge return pipes of the sedimentation tank are connected with the anaerobic tank.

Preferably, the volume ratio of the sewage led into the anaerobic tank and the aerobic tank from the sewage distribution tank is 2-4: 1.

preferably, flow regulating valves are respectively arranged on the pipeline between the second sedimentation tank and the first BAF biological aerated filter and the pipeline between the fourth sedimentation tank and the second BAF biological aerated filter.

Preferably, the sludge returned by the second sedimentation tank is aged for 15-20 days; the sludge age of the third reflux of the sedimentation tank is 10-15 days; the sludge returned by the sedimentation tank IV is 16-19 days old.

The invention has the beneficial effects that:

1. before the sewage treatment system is used for treating sewage by the double-sludge method, the pH value of the sewage is adjusted, then the sewage is subjected to flocculation treatment in the flocculation tank, solid suspended matters are almost removed after flocculation precipitation, and the performance of the sewage is more stable after flocculation treatment, so that the effect of treating the sewage by the subsequent double-sludge method is enhanced.

2. The sewage after flocculation treatment is divided into two parts, namely an anaerobic/anoxic tank route and an aerobic tank route, the sewage led into the anaerobic/anoxic tank route is sequentially treated by an anaerobic tank, a BAF aeration biological filter I and an anoxic tank I, denitrifying phosphorus accumulating bacteria release phosphorus in the anaerobic tank and suck carbon sources in the sewage into the body to be converted into carbon sources in the body, then nitrate radicals and nitrite are used as electron acceptors of reaction in the environment of the anoxic tank I, the carbon sources in cells are used as electron donors, and the phosphorus is excessively sucked while denitrification reaction is carried out, so that synchronous denitrifying phosphorus suction is realized. And the sewage led into the aerobic tank line is sequentially treated by the aerobic tank and the BAF biological aerated filter II, and organic matters are oxidized and decomposed and absorbed by phosphorus accumulating bacteria. Through the separate treatment, the sewage is guided into the anoxic tank II together, the denitrification phosphorus-accumulating reaction is carried out again, and the denitrification phosphorus-accumulating reaction is carried out by combining the BAF biological aerated filter II, so that the effects of nitrogen and phosphorus removal are very excellent.

3. The double-sludge method of the invention is used for treating sewage and then carrying out photocatalysis treatment, which can decompose residual chemical substances in a certain amount and kill certain bacteria, thus further reducing the pollution of the discharged wastewater after treatment.

4. The double-sludge sewage treatment system has high operation stability, good nitrogen and phosphorus removal effect, effective removal of nitrogen and phosphorus and good effluent quality.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic structural diagram of a synchronous denitrification dephosphorization and denitrification double-sludge sewage treatment system in embodiment 1 of the present invention;

FIG. 2 is a schematic structural diagram of a synchronous denitrification and dephosphorization sludge-water treatment system in embodiment 2 of the present invention;

in the figure: 1. a raw water pool; 2. a pH adjusting tank; 3. a flocculation tank; 4. a first sedimentation tank; 5. a photocatalytic cell; 51. a first water outlet pipe of the photocatalytic tank; 52. a second water outlet pipe of the photocatalytic tank; 6. an anaerobic tank; 7. a second sedimentation tank; 71. a second water outlet pipe of the sedimentation tank; 72. a sludge outlet pipe of the sedimentation tank II; 8. a first anoxic tank; 9. a sedimentation tank III; 91. a third sludge return pipe of the sedimentation tank; 10. an aerobic tank; 11. a sedimentation tank IV; 111. a fourth water outlet pipe of the sedimentation tank; 112. a sludge return pipe of the sedimentation tank; 12. a second anoxic pond; 13. a fifth sedimentation tank; 131. a sludge return pipe of the sedimentation tank; 14. a BAF biological aerated filter I; 15. a BAF biological aerated filter II; 16. a photocatalytic cell.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1:

as shown in figure 1, the synchronous denitrification nitrogen and phosphorus removal double-sludge sewage treatment system comprises a raw water tank 1, a pH adjusting tank 2, a flocculation tank 3, a first sedimentation tank 4, a sewage distribution tank 5, an anaerobic tank 6, a second sedimentation tank 7, a first anoxic tank 8, a third sedimentation tank 9, an aerobic tank 10, a fourth sedimentation tank 11, a second anoxic tank 12, a fifth sedimentation tank 13, a first BAF biological aerated filter 14 and a second BAF biological aerated filter 15.

The raw water tank 1 is sequentially connected with a pH adjusting tank 2, a flocculation tank 3 and a sedimentation tank I4 through pipelines. The flocculation tank 3 is connected with a flocculating agent adding pipe. Be equipped with the agitating unit of vertical setting in the flocculation basin 3, be fixed with the support on the flocculation basin 3, fixed mounting has the motor on the support, agitating unit is rotated by motor drive.

The sewage distribution tank 5 is divided into two independent tank bodies by a partition plate; the sedimentation tank I4 is respectively connected with the two independent tank bodies through pipelines; the two independent tank bodies are respectively communicated with a first water outlet pipe 51 of the sewage distribution tank and a second water outlet pipe 52 of the sewage distribution tank.

The first water outlet pipe 51 of the sewage distribution tank is connected with the anaerobic tank 6, the anaerobic tank 6 is connected with the second sedimentation tank 7 through a pipeline, the second sedimentation tank 7 is communicated with a second water outlet pipe 71 of the sedimentation tank, the bottom end of the second sedimentation tank is communicated with a second sludge outlet pipe 72 of the sedimentation tank, the second water outlet pipe 71 of the sedimentation tank is connected with the feed end of the first BAF biological aerated filter 14, and the second sludge outlet pipe 72 of the sedimentation tank is connected with the first anoxic tank 8; the BAF biological aerated filter I14 is connected with an anoxic tank I8 through a pipeline, and the anoxic tank I8 is connected with a sedimentation tank III 9 through a pipeline; the bottom end of the third sedimentation tank 9 is communicated with a third sludge return pipe 91 of the sedimentation tank, and the third sludge return pipe 91 of the sedimentation tank is connected with the anaerobic tank 6.

The second water outlet pipe 52 of the sewage distribution tank is connected with the aerobic tank 10, and a micropore aeration head is arranged in the aerobic tank 10 for aeration. The aerobic tank 10 is connected with the fourth sedimentation tank 11 through a pipeline, the fourth sedimentation tank 11 is communicated with a fourth sedimentation tank water outlet pipe 111, the bottom end of the fourth sedimentation tank is communicated with a fourth sedimentation tank sludge return pipe 112, and the fourth sedimentation tank sludge return pipe 112 is connected with the aerobic tank 10; a water outlet pipe 111 of the sedimentation tank four is connected with the feed end of the BAF biological aerated filter two 15. Flow regulating valves are respectively arranged on the pipeline between the second sedimentation tank 7 and the first BAF biological aerated filter 14 and the pipeline between the fourth sedimentation tank 11 and the second BAF biological aerated filter 15.

The third sedimentation tank 9 and the second BAF biological aerated filter 15 are both connected with the second anoxic tank 12 through pipelines, and the second anoxic tank 12 is connected with the fifth sedimentation tank 13 through pipelines. The bottom end of the sedimentation tank five 13 is communicated with a sedimentation tank five sludge return pipe 131, and the sedimentation tank five sludge return pipe 131 is connected with the anaerobic tank 6.

As shown in fig. 1, the pipes according to the present embodiment are each provided with a delivery pump. Submersible mixers are arranged in the anaerobic tank 6, the first anoxic tank 8, the second anoxic tank 12 and the pH adjusting tank 2.

The sewage treatment process corresponding to the synchronous denitrification and dephosphorization double-sludge sewage treatment system comprises the following steps: leading the sewage to be treated into a raw water tank, and then leading the sewage into a pH adjusting tank to adjust the pH to a proper value so as to be more suitable for flocculation treatment; leading-in flocculation basin of sewage, add the flocculating agent from flocculating agent filling tube to flocculation basin 3, stir at certain speed through agitating unit, make the solid suspended solid flocculation. And after flocculation is finished, the sewage is guided into a first sedimentation tank 4 for sedimentation treatment.

And after precipitation, one part of supernatant is led into an independent groove body of the sewage distribution tank through a pipeline, and the other part of supernatant is led into an independent groove body of the sewage distribution tank through a pipeline. One of the grooves is larger. The other is smaller. The large tank body is connected with the anaerobic tank 6 through a water outlet pipe I51 of the sewage distribution tank, sewage is guided into the anaerobic tank 6 for treatment and then is guided into a second sedimentation tank 72 for sedimentation treatment, supernatant after sedimentation is guided into a BAF biological aerated filter 14 for treatment through a pipeline, the treated sewage is guided into a first anoxic tank 8 for treatment, and the treated sewage is guided into a third sedimentation tank 9 for sedimentation treatment. The smaller tank body is connected with the aerobic tank 10 through a water outlet pipe II 52 of the sewage distribution tank, sewage is treated by the aerobic tank 10 and then is guided into a sedimentation tank IV 11 for sedimentation treatment, and supernatant after sedimentation is guided into a BAF biological aerated filter 15 for treatment through a pipeline.

And then, introducing the supernatant in the third sedimentation tank 9 and the sewage in the BAF biological aerated filter 15 into the second anoxic tank 12 for anoxic treatment, and introducing the sewage after the anoxic treatment into the fifth sedimentation tank 13 for sedimentation. The supernatant sewage after precipitation reaches the sewage discharge standard.

In this embodiment, the flocculating agent added to the flocculation tank 3 is prepared from polyaluminium sulfate, polyferric chloride and polyferric silicate sulfate flocculating agent according to a mass ratio of 1: 0.3-0.5: 1.5-2.5. The concentration of the flocculation treatment is 10-100 mg/L.

The solubility of dissolved oxygen is 3.5-4mg/L when the aerobic tank 10 is used for treating sewage. The sewage volume ratio of the sewage distribution tank 5 to the anaerobic tank 6 and the aerobic tank 10 is 2-4: 1.

the sludge returned by the second sedimentation tank 7 is 15-20 days old; the sludge returned by the third 9 sedimentation tank is 10 to 15 days old; the sludge returned by the fourth 11 sedimentation tanks is 16-19 days old. The sludge returned from the fourth 11 sedimentation tanks is 9-13 days old.

Example 2:

as shown in fig. 2, a synchronous denitrification nitrogen and phosphorus removal double-sludge sewage treatment system, which is different from embodiment 1, further comprises a photocatalytic tank 16, and a sedimentation tank five 13 is connected with the photocatalytic tank 16 through a pipeline.

The photocatalyst added in the photocatalytic cell 16 is zeolite fine particles adsorbing nano titanium dioxide.

By subjecting the finally obtained wastewater to photocatalytic treatment, a certain amount of residual chemical substances can be decomposed, certain bacteria can be killed, and the pollution of the treated discharged wastewater can be further reduced.

And (3) testing the treatment performance:

the results of the examination of the raw sewage water to be treated are shown in Table 1.

Table 1:

item	The result of the detection
		Suspended substance (mg/L)	326
CODcr(mg/L)	298
		BOD₅(mg/L)	302
Ammonia nitrogen (mg/L)	38
		Total nitrogen (mg/L)	52
Total phosphorus (mg/L)	5.5
		pH	6.5

The synchronous denitrification nitrogen and phosphorus removal double-sludge sewage treatment system in the embodiment 1 is adopted to treat the sewage, 3 groups of treatment are set, and in the 3 groups of treatment, the added flocculating agents are different, and the concentrations of the flocculating agents are different; the solubility of dissolved oxygen is different when the aerobic tank 10 is used for treating sewage; the sewage volume ratio of the sewage distributed tank 5 led into the anaerobic tank 6 and the aerobic tank 10 is different; the sludge ages of the sedimentation tanks which flow back to the corresponding anoxic tank I8, the aerobic tank 10 and the anaerobic tank 6 are different. The method comprises the following specific steps:

treatment 1: the flocculating agent added into the flocculation tank 3 is prepared from polyaluminium sulfate, polyferric chloride and polyferric silicate sulfate flocculating agent according to the mass ratio of 1: 0.5: 2. The concentration of the flocculation treatment was 50 mg/L. The solubility of dissolved oxygen is 4mg/L when the aerobic tank 10 is used for treating sewage. The sewage volume ratio of the sewage distribution tank 5 led into the anaerobic tank 6 and the aerobic tank 10 is 4: 1.

the sludge returned by the second sedimentation tank 7 is aged for 20 days; the sludge returned by the third 9 sedimentation tank is 12 days old; the sludge returned from the fourth 11 sedimentation tanks is 19 days old. The sludge returned from the fourth 11 sedimentation tanks is aged for 10 days.

And (3) treatment 2: the flocculating agent added into the flocculation tank 3 is prepared from polyaluminium sulfate, polyferric chloride and polyferric silicate sulfate flocculating agent according to the mass ratio of 1: 0.3: 1.5. The concentration of the flocculation treatment was 20 mg/L. The solubility of dissolved oxygen is 3.8mg/L when the aerobic tank 10 is used for treating sewage. The volume ratio of the sewage led into the anaerobic tank 6 and the aerobic tank 10 from the sewage distribution tank 5 is 3: 1.

the sludge returned by the second sedimentation tank 7 is 15 days old; the sludge returned by the third 9 sedimentation tank is aged for 10 days; the sludge returned from the fourth 11 sedimentation tanks is 16 days old. The sludge returned from the fourth 11 sedimentation tanks is 9 days old.

And (3) treatment: the flocculating agent added into the flocculation tank 3 is prepared from polyaluminium sulfate, polyferric chloride and polyferric silicate sulfate flocculating agent according to the mass ratio of 1: 0.4: 2.5. The concentration of the flocculation treatment was 70 mg/L. The solubility of dissolved oxygen is 3.5mg/L when the aerobic tank 10 is used for treating sewage. The sewage volume ratio of the sewage distribution tank 5 led into the anaerobic tank 6 and the aerobic tank 10 is 2: 1.

the sludge returned by the second sedimentation tank 7 is 18 days old; the sludge returned by the third 9 sedimentation tank is 15 days old; the sludge returned from the fourth 11 sedimentation tanks is 18 days old. The sludge returned from the fourth 11 sedimentation tanks is 13 days old.

After the three groups of treatments, the final effluent is detected, and specific detection results are shown in table 2.

Table 2:

as shown in Table 2, the double-sludge sewage treatment system has good nitrogen and phosphorus removal effect, effectively removes nitrogen and phosphorus, and has good effluent quality.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. A synchronous denitrification dephosphorization double-sludge sewage treatment system is characterized by comprising a raw water tank (1), a pH adjusting tank (2), a flocculation tank (3), a first sedimentation tank (4), a sewage distribution tank (5), an anaerobic tank (6), a second sedimentation tank (7), a first anoxic tank (8), a third sedimentation tank (9), an aerobic tank (10), a fourth sedimentation tank (11), a second anoxic tank (12), a fifth sedimentation tank (13), a first BAF biological aerated filter (14) and a second BAF biological aerated filter (15);

the raw water tank (1) is sequentially connected with the pH adjusting tank (2), the flocculation tank (3) and the sedimentation tank I (4) through pipelines; the sewage distribution tank (5) is divided into two independent tank bodies by a partition plate; the first sedimentation tank (4) is respectively connected with the two independent tank bodies through pipelines; the two independent tank bodies are respectively communicated with a first sewage distribution tank water outlet pipe (51) and a second sewage distribution tank water outlet pipe (52);

the sewage distribution tank is characterized in that a first water outlet pipe (51) of the sewage distribution tank is connected with an anaerobic tank (6), the anaerobic tank (6) is connected with a second sedimentation tank (7) through a pipeline, a second water outlet pipe (71) of the sedimentation tank is communicated with the second sedimentation tank (7), the bottom end of the second sedimentation tank is communicated with a second sludge outlet pipe (72) of the sedimentation tank, the second water outlet pipe (71) of the sedimentation tank is connected with the feed end of a first BAF biological aerated filter (14), and the second sludge outlet pipe (72) of the sedimentation tank is connected with a first anoxic tank (8); the BAF biological aerated filter I (14) is connected with the anoxic tank I (8) through a pipeline, and the anoxic tank I (8) is connected with the sedimentation tank III (9) through a pipeline; the bottom end of the sedimentation tank III (9) is communicated with a sedimentation tank III sludge return pipe (91), and the sedimentation tank III sludge return pipe (91) is connected with the anaerobic tank (6);

the second water outlet pipe (52) of the sewage distribution tank is connected with an aerobic tank (10), the aerobic tank (10) is connected with a fourth sedimentation tank (11) through a pipeline, the fourth sedimentation tank (11) is communicated with a fourth water outlet pipe (111) of the sedimentation tank, the bottom end of the fourth sedimentation tank is communicated with a fourth sludge return pipe (112) of the sedimentation tank, and the fourth sludge return pipe (112) of the sedimentation tank is connected with the aerobic tank (10); a water outlet pipe (111) of the sedimentation tank IV is connected with the feed end of the BAF biological aerated filter II (15);

the sedimentation tank III (9) and the BAF biological aerated filter II (15) are connected with the anoxic tank II (12) through pipelines, and the anoxic tank II (12) is connected with the sedimentation tank V (13) through pipelines.

2. The synchronous denitrification nitrogen and phosphorus removal double-sludge sewage treatment system as recited in claim 1, further comprising a photocatalytic tank (16), wherein the sedimentation tank five (13) is connected with the photocatalytic tank (16) through a pipeline; the photocatalyst added into the photocatalytic cell (16) is zeolite fine particles adsorbing nano titanium dioxide.

3. The synchronous denitrification dephosphorization double-sludge sewage treatment system as claimed in claim 1, wherein a flocculant adding pipe is connected to the flocculation tank (3); the flocculating agent added into the flocculation tank (3) is prepared from polyaluminium sulfate, polyferric chloride and polyferric silicate sulfate flocculating agent according to the mass ratio of 1: 0.3-0.5: 1.5-2.5.

4. The synchronous denitrification dephosphorization sewage treatment system as claimed in claim 1, wherein a vertically arranged stirring device is arranged in the flocculation tank (3), a bracket is fixed on the flocculation tank (3), a motor is fixedly arranged on the bracket, and the stirring device is driven by the motor to rotate.

5. The synchronous denitrification nitrogen and phosphorus removal double-sludge sewage treatment system as claimed in claim 1, wherein submersible mixers are arranged in the anaerobic tank (6), the first anoxic tank (8), the second anoxic tank (12) and the pH adjusting tank (2).

6. The synchronous denitrification dephosphorization sludge sewage treatment system as claimed in claim 1, wherein a microporous aeration head is arranged in the aerobic tank (10) for aeration, and the solubility of dissolved oxygen is 3.5-4 mg/L.

7. The synchronous denitrification nitrogen and phosphorus removal double-sludge sewage treatment system as claimed in claim 1, wherein the bottom end of the sedimentation tank five (13) is communicated with a sedimentation tank five-sludge return pipe (131), and the sedimentation tank five-sludge return pipe (131) is connected with the anaerobic tank (6).

8. The synchronous denitrification dephosphorization sludge treatment system as claimed in claim 1, wherein the volume ratio of the sewage introduced from the sewage distribution tank (5) into the anaerobic tank (6) and the aerobic tank (10) is 2-4: 1.

9. the synchronous denitrification dephosphorization double-sludge sewage treatment system as claimed in claim 1, wherein flow regulating valves are respectively arranged on the pipeline between the second sedimentation tank (7) and the first BAF aeration biological filter (14) and the pipeline between the fourth sedimentation tank (11) and the second BAF aeration biological filter (15).

10. The synchronous denitrification dephosphorization sludge treatment system as claimed in claim 1, wherein the sludge returned from the second sedimentation tank (7) is aged for 15-20 days; the sludge returned by the third (9) sedimentation tank is aged for 10-15 days; the sludge returned by the fourth sedimentation tank (11) is 16-19 days old.