CN110422971B - Method and device for removing nitrogen and phosphorus from sewage - Google Patents

Method and device for removing nitrogen and phosphorus from sewage Download PDF

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CN110422971B
CN110422971B CN201910821964.5A CN201910821964A CN110422971B CN 110422971 B CN110422971 B CN 110422971B CN 201910821964 A CN201910821964 A CN 201910821964A CN 110422971 B CN110422971 B CN 110422971B
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CN110422971A (en
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张耀宗
庞博
常胜
王昊
杜明辉
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North China University of Science and Technology
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    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/02—Aerobic processes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/28—Anaerobic digestion processes
    • C02F3/286—Anaerobic digestion processes including two or more steps
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/30—Aerobic and anaerobic processes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/30—Aerobic and anaerobic processes
    • C02F3/302—Nitrification and denitrification treatment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F3/00—Biological treatment of water, waste water, or sewage
    • C02F3/34—Biological treatment of water, waste water, or sewage characterised by the microorganisms used
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F2001/007—Processes including a sedimentation step
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/105—Phosphorus compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/16—Nitrogen compounds, e.g. ammonia
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W10/00—Technologies for wastewater treatment
    • Y02W10/10—Biological treatment of water, waste water, or sewage

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Abstract

The invention provides a method and a device for removing nitrogen and phosphorus from sewage, and relates to the technical field of sewage treatment. The sewage denitrification and dephosphorization method provided by the invention comprises the following steps: carrying out first anaerobic treatment on sewage to be treated to obtain first anaerobic treatment effluent; carrying out second anaerobic treatment on the first anaerobic treatment effluent to obtain second anaerobic treatment effluent; carrying out anoxic treatment on the second anaerobic treatment effluent to obtain anoxic treatment mixed liquor; refluxing part of the anoxic treatment mixed liquor to the first anaerobic treatment process, and carrying out aerobic treatment on the rest anoxic treatment mixed liquor to obtain nitrifying liquor and aerobic treatment sludge; refluxing the nitrifying liquid to an anoxic treatment process; carrying out precipitation treatment on the aerobic sludge to obtain effluent reaching the standard and precipitated sludge; and refluxing part of the precipitated sludge to the second anaerobic treatment process, and discharging the rest precipitated sludge. The method provided by the invention has good nitrogen and phosphorus removal effect and stable nitrogen and phosphorus indexes of the effluent.

Description

Method and device for removing nitrogen and phosphorus from sewage
Technical Field
The invention relates to the technical field of sewage treatment, in particular to a sewage nitrogen and phosphorus removal method and a sewage nitrogen and phosphorus removal device.
Background
In the current sewage treatment field, when denitrification and dephosphorization are carried out on sewage, AAO and a sewage denitrification and dephosphorization technology modified by the AAO are mostly adopted. However, this process has two problems, that is, firstly, the generation time of the bacteria having nitrification function (nitrifying bacteria) is different from the generation time of the bacteria having phosphorus absorption function (phosphorus accumulating bacteria) (the generation time of the nitrifying bacteria is 15 days, and the generation time of the phosphorus accumulating bacteria is 5 to 8 days), so that the retention time of the sludge is not controlled well, and the generation times of the two bacteria cannot be optimized simultaneously; secondly, the phosphorus-releasing effect is poor due to the influence of nitrate in the process of releasing phosphorus by the phosphorus-accumulating bacteria anaerobically, so that the phosphorus-absorbing effect of the phosphorus-accumulating bacteria is poor, and the nitrogen and phosphorus removal effect of the whole process is not ideal.
Disclosure of Invention
The invention aims to provide a method and a device for removing nitrogen and phosphorus from sewage.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a sewage nitrogen and phosphorus removal method, which comprises the following steps:
carrying out first anaerobic treatment on sewage to be treated to obtain first anaerobic treatment effluent;
carrying out second anaerobic treatment on the first anaerobic treatment effluent to obtain second anaerobic treatment effluent;
carrying out anoxic treatment on the second anaerobic treatment effluent to obtain anoxic treatment mixed liquor;
refluxing part of the anoxic treatment mixed liquor to the first anaerobic treatment process, and carrying out aerobic treatment on the rest anoxic treatment mixed liquor to obtain nitrifying liquor and aerobic treatment sludge;
refluxing the nitrifying liquid to an anoxic treatment process;
carrying out precipitation treatment on the aerobic sludge to obtain effluent reaching the standard and precipitated sludge;
and refluxing part of the precipitated sludge to the second anaerobic treatment process, and discharging the rest precipitated sludge.
Preferably, the dissolved oxygen of the first anaerobic treatment is less than or equal to 0.2mg/L, and the retention time is 1.5-2 h.
Preferably, the dissolved oxygen of the second anaerobic treatment is less than or equal to 0.2mg/L, and the retention time is 0.5-1.5 h.
Preferably, the dissolved oxygen of the anoxic treatment is 0.2-0.5 mg/L, and the retention time is 2-4 h.
Preferably, the anoxic treatment mixed liquor is refluxed to the first anaerobic treatment process according to a reflux ratio of 100-200%.
Preferably, the dissolved oxygen of the aerobic treatment is 2-4 mg/L, the sludge concentration is 2500-3500 mg/L, and the retention time is 5-7 h.
Preferably, the nitrifying liquid is refluxed to the anoxic treatment process according to the reflux ratio of 100-200%.
Preferably, the precipitated sludge is refluxed to the second anaerobic treatment process according to a reflux ratio of 100-200%.
The invention provides a sewage denitrification and dephosphorization device, which comprises an air blower 6, an anaerobic tank 1, an anaerobic tank 2, an anoxic tank 3, an aerobic tank 4 and a sedimentation tank 5 which are sequentially communicated, wherein the air blower 6 is communicated with the aerobic tank 4 through an air delivery pipe 7-1;
a mixed liquid return pipe 7-2 is arranged between the water outlet of the anoxic tank 3 and the water inlet of the anaerobic tank 1, a nitrifying liquid return pipe 7-3 is arranged between the water outlet of the aerobic tank 4 and the water inlet of the anoxic tank 3, and a sludge return pipe 7-4 is arranged between the sludge discharge port of the sedimentation tank 5 and the feed inlet of the anaerobic tank 2.
Preferably, the aerobic tank 4 comprises an aeration zone 4-1, a clear water zone 4-2 and a muddy water zone 4-3;
the aeration zone 4-1 is arranged at one side close to the anoxic tank 3, and the gas transmission pipe 7-1 extends to the bottom of the aeration zone 4-1;
the clear water area 4-2 and the muddy water area 4-3 are arranged on one side close to the sedimentation tank 5, the water outlet of the clear water area 4-2 is communicated with the water inlet of the anoxic tank 3 through a nitrifying liquid return pipe 7-3, and the mud discharge port of the muddy water area 4-3 is communicated with the sedimentation tank 5.
The invention provides a sewage nitrogen and phosphorus removal method, which comprises the following steps: carrying out first anaerobic treatment on sewage to be treated to obtain first anaerobic treatment effluent; carrying out second anaerobic treatment on the first anaerobic treatment effluent to obtain second anaerobic treatment effluent; carrying out anoxic treatment on the second anaerobic treatment effluent to obtain anoxic treatment mixed liquor; refluxing part of the anoxic treatment mixed liquor to the first anaerobic treatment process, and carrying out aerobic treatment on the rest anoxic treatment mixed liquor to obtain nitrifying liquor and aerobic treatment sludge; refluxing the nitrifying liquid to an anoxic treatment process; carrying out precipitation treatment on the aerobic sludge to obtain effluent reaching the standard and precipitated sludge; and refluxing part of the precipitated sludge to the second anaerobic treatment process, and discharging the rest precipitated sludge. In the invention, part of the precipitated sludge containing dissolved oxygen and nitrate firstly flows back to the second anaerobic treatment process for deoxidation and denitrification, and then is subjected to anoxic treatment, and part of the obtained anoxic treatment mixed liquor flows back to the first anaerobic treatment process, so that the dissolved oxygen does not exist in the returned anoxic treatment mixed liquor, and the content of nitrate nitrogen is relatively low or zero, thereby avoiding the influence on the phosphorus release effect of a large amount of denitrifying phosphorus accumulating bacteria (DPAOs) contained in the anaerobic treatment mixed liquor. Meanwhile, part of the precipitated sludge firstly flows back to the second anaerobic treatment process, and the growth of filamentous bacteria can be inhibited under the conditions of low dissolved oxygen and low carbon source, so that the sludge bulking is prevented. In addition, sludge-water separation is realized in the aerobic treatment process, the obtained nitrified liquid flows back to the anoxic treatment process independently, the obtained sludge subjected to aerobic treatment is subjected to precipitation treatment independently and then flows back to the anaerobic treatment process, sludge-water separation and backflow are realized without mutual influence, the problem that sludge needs to be discharged when the phosphorus removal effect is enhanced due to different generation times of nitrifying bacteria and phosphorus removal bacteria is avoided, and therefore adverse influence on the nitrifying bacteria is generated, and the stability of nitrogen and phosphorus indexes of effluent is ensured.
Drawings
FIG. 1 is a schematic structural diagram of the sewage denitrification and dephosphorization apparatus of the present invention, wherein 1 is an anaerobic tank, 2 is an anaerobic tank, 3 is an anoxic tank, 4 is an aerobic tank, 4-1 is an aeration zone, 4-2 is a clear water zone, 4-3 is a muddy water zone, 5 is a sedimentation tank, 6 is an air blower, 7-1 is a gas pipe, 7-2 is a mixed liquid return pipe, 7-3 is a nitrifying liquid return pipe, 7-4 is a sludge return pipe, 8-1 to 8-3 are mixers, 8-4 is a nitrifying liquid return pump, 8-5 is a sludge lift pump, and 9 is an air release valve.
Detailed Description
The invention provides a sewage nitrogen and phosphorus removal method, which comprises the following steps:
carrying out first anaerobic treatment on sewage to be treated to obtain first anaerobic treatment effluent;
carrying out second anaerobic treatment on the first anaerobic treatment effluent to obtain second anaerobic treatment effluent;
carrying out anoxic treatment on the second anaerobic treatment effluent to obtain anoxic treatment mixed liquor;
refluxing part of the anoxic treatment mixed liquor to the first anaerobic treatment process, and carrying out aerobic treatment on the rest anoxic treatment mixed liquor to obtain nitrifying liquor and aerobic treatment sludge;
refluxing the nitrifying liquid to an anoxic treatment process;
carrying out precipitation treatment on the aerobic sludge to obtain effluent reaching the standard and precipitated sludge;
and refluxing part of the precipitated sludge to the second anaerobic treatment process, and discharging the rest precipitated sludge.
The invention carries out first anaerobic treatment on the sewage to be treated to obtain first anaerobic treatment effluent. The source of the sewage to be treated is not specially limited, and the sewage which needs to be subjected to nitrogen and phosphorus removal can be any; in the embodiment of the present invention, the indexes of the sewage to be treated are preferably: CODCr150 to 400mg/L, BOD580-200 mg/L of ammonia Nitrogen (NH)3-N) concentration of 15-40 mg/L, Total Nitrogen (TN) concentration of 20-50 mg/L, and Total Phosphorus (TP) concentration of 3-10 mg/L. In the present invention, in the actual operation process, the wastewater to be treated is mixed with a part of the mixed solution of the anoxic treatment (which will be described in detail later) generated from the anoxic treatment process, and then the first anaerobic treatment is performed. In the invention, the dissolved oxygen of the first anaerobic treatment is preferably less than or equal to 0.2mg/L, and the retention time is preferably 1.5-2 h, and more preferably 2 h.
After the first anaerobic treatment effluent is obtained, the invention carries out second anaerobic treatment on the first anaerobic treatment effluent to obtain second anaerobic treatment effluent. In the present invention, in the actual operation process, the first anaerobic treatment effluent is mixed with a part of the precipitated sludge (which will be described in detail later) generated from the precipitation treatment process, and then the second anaerobic treatment is performed. In the invention, the dissolved oxygen of the second anaerobic treatment is preferably less than or equal to 0.2mg/L, and the retention time is preferably 0.5-1.5 h, and more preferably 1 h.
After the second anaerobic treatment effluent is obtained, the anaerobic treatment is carried out on the second anaerobic treatment effluent to obtain an anaerobic treatment mixed solution. In the present invention, in the actual operation process, the second anaerobic treatment effluent is mixed with the nitrification liquid (described in detail later) generated from the aerobic treatment process, and then the anoxic treatment is performed. In the invention, the dissolved oxygen of the anoxic treatment is preferably 0.2-0.5 mg/L, and the retention time is preferably 2-4 h, and more preferably 3 h.
After the anoxic treatment mixed liquor is obtained, part of the anoxic treatment mixed liquor flows back to the first anaerobic treatment process, and the rest anoxic treatment mixed liquor is subjected to aerobic treatment to obtain nitrifying liquid and aerobic treatment sludge. The anaerobic treatment mixed solution is preferably refluxed to the first anaerobic treatment process according to the reflux ratio of 100-200%. In the invention, the dissolved oxygen of the aerobic treatment is preferably 2-4 mg/L, the sludge concentration is preferably 2500-3500 mg/L, and the retention time is preferably 5-7 h, and more preferably 7 h.
After the nitrification liquid is obtained through aerobic treatment, the invention reflows the nitrification liquid to the anoxic treatment process. According to the invention, the nitrifying liquid is preferably refluxed to the anoxic treatment process according to the reflux ratio of 100-200%.
After aerobic treatment is carried out to obtain aerobic treatment sludge, the invention carries out precipitation treatment on the aerobic treatment sludge to obtain effluent reaching the standard and precipitation sludge. In the invention, the residence time of the precipitation treatment is preferably 2-3.5 h, and more preferably 2.5 h.
After the precipitated sludge is obtained through the precipitation treatment, part of the precipitated sludge is refluxed to the second anaerobic treatment process, and the rest precipitated sludge is discharged. According to the invention, the precipitated sludge is preferably refluxed to the second anaerobic treatment process according to the reflux ratio of 100-200%. The volume ratio of the precipitated sludge which flows back to the second anaerobic treatment to the precipitated sludge which is discharged outside is not specially limited, and the requirement of the sludge concentration in the actual production can be met.
In the present invention, the retention time specifically refers to the actual retention time of the sewage in each structure (i.e. each treatment tank), and the calculation method is as follows:
Figure BDA0002187805390000051
the flow rate of the liquid entering the structure is the treated water amount plus the reflux amount.
In the method for removing nitrogen and phosphorus from sewage, part of precipitated sludge containing dissolved oxygen and nitrate firstly flows back to the second anaerobic treatment process for deoxidation and denitrification, and then is subjected to anoxic treatment, part of obtained anoxic treatment mixed liquor flows back to the first anaerobic treatment process, no dissolved oxygen exists in the returned anoxic treatment mixed liquor, and the content of nitrate nitrogen is relatively low or zero, so that the influence on the phosphorus release effect of a large amount of denitrifying phosphorus accumulating bacteria (DPAOs) contained in the anoxic treatment mixed liquor can be avoided. In the first anaerobic treatment process, firstly, organic matters in raw water (sewage to be treated) can be acidified to be easily degraded organic matters, denitrifying phosphorus-accumulating bacteria utilize energy released in the hydrolysis process of glycogen and denitrifying phosphorus-accumulating bacteria in water, and volatile organic matters (VFAs) in the water are converted into carbon source substances (PHA) in bacteria and stored in the bacteria; meanwhile, the denitrifying phosphorus-accumulating bacteria release the phosphate stored in the body into water, and the process is finished, namely the phosphorus release process of the denitrifying phosphorus-accumulating bacteria.
The raw water and part of the precipitated sludge are subjected to first anaerobic treatment and then subjected to second anaerobic treatment, wherein the second anaerobic treatment mainly aims to inhibit growth of filamentous bacteria under anaerobic conditions, inhibit sludge bulking to a certain extent, keep a stable and normal SVI value of an aerobic zone and ensure that the sludge has high settling property and good flocculation property.
Carrying out anoxic treatment on the effluent of the second anaerobic treatment and the nitrifying liquid generated in the aerobic treatment process, wherein the content of dissolved oxygen is low in the anoxic treatment process, and the denitrifying phosphorus accumulating bacteria use nitrate as an electron acceptor to complete denitrificationChemical process to produce N2And N2And O, overflowing from the water, consuming PHA, and providing energy for phosphorus uptake of the denitrifying phosphorus accumulating bacteria by taking the PHA as energy for the proliferation and growth of self cells. In the anoxic treatment process, the denitrifying phosphorus accumulating bacteria complete the denitrifying and phosphorus releasing functions, and realize 'one carbon dual purpose'. Meanwhile, denitrifying bacteria existing in the water also carry out denitrification under the anoxic condition, and complete the denitrification process under the combined action of the denitrifying bacteria and other denitrifying bacteria.
Part of the anoxic mixed liquor obtained after the anoxic treatment flows back to the first anaerobic treatment process, so that the sufficient bacterial concentration is provided for denitrifying phosphorus accumulating bacteria in the first anaerobic treatment, and meanwhile, the sufficient strains are provided for the hydrolytic acidification process. And carrying out aerobic treatment on the residual anoxic treatment mixed liquor, mainly removing COD (chemical oxygen demand), oxidizing ammonia nitrogen in water, carrying out nitrification in sewage, and further finishing the phosphorus absorption effect of denitrifying phosphorus accumulating bacteria.
Performing primary separation on sludge and water in the aerobic treatment process to obtain nitrified liquid and aerobic treatment sludge, wherein the nitrified liquid basically does not contain sludge and flows back to the anoxic treatment process; the aerobic sludge is further subjected to precipitation treatment to obtain effluent reaching the standard and precipitated sludge; part of the precipitated sludge flows back to the second anaerobic treatment process, and the rest precipitated sludge is discharged outside. The nitrification liquid basically has no sludge, the precipitated sludge flows back to the second anaerobic treatment process, the separation of the precipitated sludge and the nitrification liquid is realized in the operation process, the generation time of nitrifying bacteria and phosphorus removing bacteria is different, and the denitrification mode is the denitrification removal mode, so the nitrification and denitrification effects can be effectively ensured, and the phosphorus is discharged from the system in the form of sludge precipitation and removed. In actual production, in order to control lower sludge concentration or emphasize phosphorus removal, a large amount of sludge is discharged to cause a large amount of nitrobacteria in a removal system, so that the process nitrification effect is not ideal and the ammonia nitrogen effluent exceeds the standard, which is often generated in the operation management process of a sewage plant in winter in northern cold regions. In the winter operation process, the method provided by the invention can be used for controlling the removal rate of nitrogen and phosphorus by controlling the reflux ratio of the nitrifying liquid and the precipitated sludge according to the generation time of two bacteria and the removal condition of nitrogen and phosphorus in the actual operation process, and the phosphorus removal and the nitrogen removal of the process are not influenced mutually.
The invention provides a sewage denitrification and dephosphorization device, which comprises an air blower 6, an anaerobic tank 1, an anaerobic tank 2, an anoxic tank 3, an aerobic tank 4 and a sedimentation tank 5 which are sequentially communicated, wherein the air blower 6 is communicated with the aerobic tank 4 through an air delivery pipe 7-1;
a mixed liquid return pipe 7-2 is arranged between the water outlet of the anoxic tank 3 and the water inlet of the anaerobic tank 1, a nitrifying liquid return pipe 7-3 is arranged between the water outlet of the aerobic tank 4 and the water inlet of the anoxic tank 3, and a sludge return pipe 7-4 is arranged between the sludge discharge port of the sedimentation tank 5 and the feed inlet of the anaerobic tank 2.
The sewage denitrification and dephosphorization device provided by the invention comprises an anaerobic tank 1, an anaerobic tank 2, an anoxic tank 3, an aerobic tank 4 and a sedimentation tank 5 which are communicated in sequence; in the invention, the anaerobic tank 1, the anaerobic tank 2, the anoxic tank 3, the aerobic tank 4 and the sedimentation tank 5 are respectively used for carrying out first anaerobic treatment, second anaerobic treatment, anoxic treatment, aerobic treatment and sedimentation treatment.
In the sewage nitrogen and phosphorus removal device provided by the invention, a mixed liquid return pipe 7-2 is arranged between the water outlet of the anoxic tank 3 and the water inlet of the anaerobic tank 1 and is used for returning part of anoxic treatment mixed liquid generated by anoxic treatment to the first anaerobic treatment process; a nitrifying liquid return pipe 7-3 is arranged between the water outlet of the aerobic tank 4 and the water inlet of the anoxic tank 3 and is used for returning nitrifying liquid generated by aerobic treatment to the anoxic treatment process; and a sludge return pipe 7-4 is arranged between the sludge discharge port of the sedimentation tank 5 and the feed inlet of the anaerobic tank 2 and is used for returning part of the precipitated sludge generated by the precipitation treatment to the second anaerobic treatment process.
The sewage denitrification and dephosphorization device provided by the invention comprises an air blower 6, wherein the air blower 6 is communicated with an aerobic tank 4 through an air delivery pipe 7-1; the blower 6 is used for providing air required for the aerobic treatment in the aerobic tank 4.
As an embodiment of the invention, the aerobic tank 4 in the sewage nitrogen and phosphorus removal device comprises an aeration zone 4-1, a clear water zone 4-2 and a muddy water zone 4-3; the aeration zone 4-1 is arranged at one side close to the anoxic tank 3, and the gas transmission pipe 7-1 extends to the bottom of the aeration zone 4-1; the clear water area 4-2 and the muddy water area 4-3 are arranged on one side close to the sedimentation tank 5, the water outlet of the clear water area 4-2 is communicated with the water inlet of the anoxic tank 3 through a nitrifying liquid return pipe 7-3, and the mud discharge port of the muddy water area 4-3 is communicated with the sedimentation tank 5.
As an embodiment of the invention, the clean water area 4-2 and the muddy water area 4-3 are separated by a clapboard to realize the separation of muddy water, wherein the position of the clapboard is set according to the reflux ratio of the nitrifying liquid, and in particular, the distance between the clapboard and the liquid level of the aeration area 4-1 is h1The distance between the partition board and the bottom of the aerobic tank 4 is h2，h1、h2And the reflux ratio of the nitrifying liquid meets the following requirements: reflux ratio of nitrating liquid is h1/h2Therefore, the height of the partition board can be adjusted up and down.
As an embodiment of the invention, a stirrer 8-1 is arranged in the anaerobic tank 1, a stirrer 8-2 is arranged in the anaerobic tank 2, and a stirrer 8-3 is arranged in the anoxic tank 3; the stirrers 8-1 to 8-3 are used for preventing sludge precipitation in each treatment stage and ensuring that each treatment stage is smoothly carried out.
As an embodiment of the invention, a nitrifying liquid reflux pump 8-4 is arranged in the clear water zone 4-2 of the aerobic tank 4 and is used for refluxing nitrifying liquid into the anoxic tank 3; and a sludge lifting pump 8-5 is arranged in the mud-water area 4-3 of the aerobic tank 4 and is used for lifting the aerobic sludge to the sedimentation tank 5.
As an embodiment of the invention, the bottom of the muddy water zone 4-3 of the aerobic tank 4 is provided with an emptying valve 9 for equipment maintenance or emptying.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the 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
FIG. 1 is a schematic structural diagram of a sewage denitrification and dephosphorization apparatus, which is used for performing denitrification and dephosphorization treatment on sewage and comprises the following steps:
mixing the sewage to be treated with part of the anoxic treatment mixed liquor generated from the anoxic tank 3, and then conveying the mixed liquor to the anaerobic tank 1 for first anaerobic treatment to obtain first anaerobic treatment effluent; wherein the dissolved oxygen of the first anaerobic treatment is less than or equal to 0.2mg/L, and the retention time is 2 h;
mixing the first anaerobic treatment effluent with part of precipitated sludge generated from the sedimentation tank 5, and then conveying the mixture to an anaerobic tank 2 for second anaerobic treatment to obtain second anaerobic treatment effluent; wherein the dissolved oxygen of the second anaerobic treatment is less than or equal to 0.2mg/L, and the retention time is 1 h;
conveying the second anaerobic treatment effluent to an anoxic tank 3 for anoxic treatment to obtain an anoxic treatment mixed solution; wherein the dissolved oxygen of the anoxic treatment is 0.2-0.5 mg/L, and the retention time is 3 h;
refluxing part of the anoxic treatment mixed liquor (the reflux ratio is 100-200%) to a first anaerobic treatment process through a mixed liquor reflux pipe 7-2, mixing and conveying the rest anoxic treatment to an aerobic tank 4, carrying out aerobic treatment in an aeration zone 4-1, and respectively obtaining nitrified liquor and aerobic treated sludge in a clear water zone 4-2 and a muddy water zone 4-3; wherein the dissolved oxygen of the aerobic treatment is 2-4 mg/L, the sludge concentration is 2500-3500 mg/L, the retention time is 7h, and the air required by the aerobic treatment is conveyed to the bottom of the aeration zone 4-1 by an air blower 6 through an air conveying pipe 7-1;
refluxing the nitrified liquid to the anoxic treatment process through a nitrified liquid reflux pipe 7-3, wherein the reflux ratio is 100-200%;
conveying the aerobic sludge to a sedimentation tank 5 for sedimentation treatment to obtain effluent reaching the standard and precipitated sludge; wherein the retention time of the precipitation treatment is 2.5 h;
refluxing part of the precipitated sludge (the reflux ratio is 100-200%) to a second anaerobic treatment process, and discharging the rest precipitated sludge;
wherein, a stirrer 8-1 is arranged in the anaerobic tank 1, a stirrer 8-2 is arranged in the anaerobic tank 2, and a stirrer 8-3 is arranged in the anoxic tank 3, and in the running process, the stirrers 8-1-8-3 are in a stirring state to prevent sludge precipitation in each treatment stage; a nitrifying liquid reflux pump 8-4 is arranged in the clear water zone 4-2 of the aerobic tank 4 and is used for refluxing the nitrifying liquid into the anoxic tank 3; a sludge lifting pump 8-5 is arranged in the mud-water area 4-3 of the aerobic tank 4 and is used for lifting the aerobic sludge to the sedimentation tank 5.
In this embodiment, the index data of the sewage to be treated and the effluent reaching the standard are shown in table 1 (in table 1, the inlet water corresponds to the sewage to be treated, and the outlet water corresponds to the effluent reaching the standard).
Table 1 index data of water inlet and outlet in example 1
Figure BDA0002187805390000091
According to the embodiments, after the method provided by the invention is operated normally, the effluent quality index can stably reach the first-class A standard in discharge Standard of pollutants for municipal wastewater treatment plants (GB 18918-2002);
meanwhile, in the anoxic treatment process, the denitrifying phosphorus removal bacteria realize 'one carbon dual purpose', and can normally run particularly under the condition of low carbon nitrogen ratio of inlet water, so that a large amount of carbon sources can be saved;
in the method provided by the invention, the reflux amount of various refluxes is larger, the sludge yield of anaerobic treatment and aerobic treatment at the front section of the process is lower, most degradable COD is degraded at the stage, so the sludge production rate is lower, and the sludge treatment cost can be reduced by about 30%;
the conventional secondary treatment process needs a coagulating sedimentation filtration process, the method provided by the invention does not need the coagulating sedimentation filtration process, and the upgrading and reconstruction can be carried out on the original design process, so that the early-stage investment and the later-stage operation cost of the upgrading and reconstruction are reduced to the greatest extent, and particularly, the early-stage investment cost is reduced by more and approximately accounts for 10%;
the method provided by the invention has no chemical phosphorus removal process, the sludge production amount is less, and the sludge amount is reduced by about 30% compared with the conventional treatment process;
according to the invention, mud-water separation is carried out at the tail end of the aerobic tank 4, the obtained nitrified liquid independently flows back to the anoxic tank 3 for denitrification, the obtained aerobic sludge independently enters the sedimentation tank 5 for sedimentation treatment and flows back to the anaerobic tank 2 from the sedimentation tank 5, so that respective backflow of the mud-water separation dual system is independently controlled without mutual influence, the problem that the denitrification or dephosphorization effect is influenced because the generation time of nitrifying bacteria and phosphorus removal bacteria is different and mud needs to be discharged when the dephosphorization effect is enhanced is solved, and the stability of the nitrogen and phosphorus indexes of the effluent is ensured.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (8)

1. A method for removing nitrogen and phosphorus from sewage is characterized by comprising the following steps:
carrying out first anaerobic treatment on sewage to be treated to obtain first anaerobic treatment effluent;
carrying out second anaerobic treatment on the first anaerobic treatment effluent to obtain second anaerobic treatment effluent;
carrying out anoxic treatment on the second anaerobic treatment effluent to obtain anoxic treatment mixed liquor;
refluxing part of the anoxic treatment mixed liquor to the first anaerobic treatment process, and carrying out aerobic treatment on the rest anoxic treatment mixed liquor to obtain nitrifying liquor and aerobic treatment sludge;
refluxing the nitrifying liquid to an anoxic treatment process;
carrying out precipitation treatment on the aerobic sludge to obtain effluent reaching the standard and precipitated sludge;
returning part of the precipitated sludge to the second anaerobic treatment process, and discharging the rest precipitated sludge;
the dissolved oxygen of the second anaerobic treatment is less than or equal to 0.2mg/L, and the retention time is 0.5-1.5 h;
the aerobic treatment is carried out in an aerobic tank (4);
the aerobic tank (4) comprises an aeration zone (4-1), a clear water zone (4-2) and a muddy water zone (4-3);
the aeration zone (4-1) is arranged at one side close to the anoxic tank (3), and the gas transmission pipe (7-1) extends to the bottom of the aeration zone (4-1);
the clear water area (4-2) and the muddy water area (4-3) are arranged on one side close to the sedimentation tank (5), the water outlet of the clear water area (4-2) is communicated with the water inlet of the anoxic tank (3) through a nitrifying liquid return pipe (7-3), and the mud discharge port of the muddy water area (4-3) is communicated with the sedimentation tank (5);
the clear water zone (4-2) and the muddy water zone (4-3) are separated by a partition board, and the distance between the partition board and the liquid level of the aeration zone (4-1) is h1The distance between the clapboard and the bottom of the aerobic tank (4) is h2，h1、h2And the reflux ratio of the nitrifying liquid meets the following requirements: the reflux ratio of the nitrifying liquid is h1/h 2.
2. The sewage nitrogen and phosphorus removal method of claim 1, wherein the dissolved oxygen of the first anaerobic treatment is less than or equal to 0.2mg/L, and the retention time is 1.5-2 h.
3. The method for removing nitrogen and phosphorus from sewage according to claim 1, wherein the amount of dissolved oxygen in the anoxic treatment is 0.2-0.5 mg/L, and the retention time is 2-4 h.
4. The sewage nitrogen and phosphorus removal method of claim 1 or 3, wherein the mixed liquid of the anoxic treatment is refluxed to the first anaerobic treatment process according to a reflux ratio of 100 to 200%.
5. The sewage nitrogen and phosphorus removal method of claim 1, wherein the dissolved oxygen in the aerobic treatment is 2-4 mg/L, the sludge concentration is 2500-3500 mg/L, and the retention time is 5-7 h.
6. The sewage nitrogen and phosphorus removal method according to claim 1 or 5, wherein the nitrifying liquid is refluxed to the anoxic treatment process according to a reflux ratio of 100-200%.
7. The method for removing nitrogen and phosphorus from sewage according to claim 1, wherein the precipitated sludge is refluxed to the second anaerobic treatment process at a reflux ratio of 100 to 200%.
8. The sewage denitrification and dephosphorization device is characterized by comprising an air blower (6), an anaerobic tank (1), an anaerobic tank (2), an anoxic tank (3), an aerobic tank (4) and a sedimentation tank (5), wherein the anaerobic tank, the anoxic tank, the aerobic tank and the sedimentation tank are sequentially communicated, and the air blower (6) is communicated with the aerobic tank (4) through an air conveying pipe (7-1);
a mixed liquid return pipe (7-2) is arranged between the water outlet of the anoxic tank (3) and the water inlet of the anaerobic tank (1), a nitrified liquid return pipe (7-3) is arranged between the water outlet of the aerobic tank (4) and the water inlet of the anoxic tank (3), and a sludge return pipe (7-4) is arranged between the sludge discharge port of the sedimentation tank (5) and the feed inlet of the anaerobic tank (2); the aerobic tank (4) comprises an aeration zone (4-1), a clear water zone (4-2) and a muddy water zone (4-3);
the aeration zone (4-1) is arranged at one side close to the anoxic tank (3), and the gas transmission pipe (7-1) extends to the bottom of the aeration zone (4-1);
the clear water area (4-2) and the muddy water area (4-3) are arranged on one side close to the sedimentation tank (5), the water outlet of the clear water area (4-2) is communicated with the water inlet of the anoxic tank (3) through a nitrifying liquid return pipe (7-3), and the mud discharge port of the muddy water area (4-3) is communicated with the sedimentation tank (5);
the clear water zone (4-2) and the muddy water zone (4-3) are separated by a partition board, and the distance between the partition board and the liquid level of the aeration zone (4-1) is h1The distance between the clapboard and the bottom of the aerobic tank (4) is h2，h1、h2And the reflux ratio of the nitrifying liquid meets the following requirements: the reflux ratio of the nitrifying liquid is h1/h 2.
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CN101544423A (en) * 2009-04-29 2009-09-30 重庆大学 A/O denitrification sewage treatment process and device capable of realizing sludge reduction
CN101792243A (en) * 2010-04-12 2010-08-04 哈尔滨工业大学 Two-stage biological selection denitrifying phosphorus and nitrogen removal sewage treatment device and method thereof
CN104445798A (en) * 2013-12-10 2015-03-25 中国环境科学研究院 Vertical sewage treatment equipment and method

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CN101544423A (en) * 2009-04-29 2009-09-30 重庆大学 A/O denitrification sewage treatment process and device capable of realizing sludge reduction
CN101792243A (en) * 2010-04-12 2010-08-04 哈尔滨工业大学 Two-stage biological selection denitrifying phosphorus and nitrogen removal sewage treatment device and method thereof
CN104445798A (en) * 2013-12-10 2015-03-25 中国环境科学研究院 Vertical sewage treatment equipment and method

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