Low-carbon nitrogen and phosphorus removal sewage treatment system, sewage treatment method and application thereof

Abstract

The invention relates to the technical field of sewage treatment, in particular to a low-carbon nitrogen and phosphorus removal sewage treatment system, a sewage treatment method and application thereof. The sewage treatment system comprises a pretreatment unit, an adsorption tank, a mid-sedimentation tank, a biochemical tank, a secondary sedimentation tank and an anaerobic hydrolysis acidification tank; the biochemical tank comprises an anaerobic tank, an anoxic tank and an aerobic tank; the anaerobic hydrolysis acidification tank is provided with a VFAs-containing supernate outlet communicated with the anaerobic tank; the mid-sedimentation tank is provided with an adsorbed sludge outlet and a sewage outlet, the adsorbed sludge outlet is communicated with the adsorption tank and the anaerobic hydrolysis acidification tank, and the sewage outlet is communicated with the anaerobic tank; the secondary sedimentation tank is provided with a biological sludge outlet and a water outlet, and the biological sludge outlet is communicated with the anaerobic tank and the anaerobic hydrolysis acidification tank. According to the sewage treatment system, denitrifying phosphorus-accumulating bacteria, nitrifying bacteria and hydrolytic acidification bacteria can be cultured in different sludge systems, and the contradiction between the denitrifying phosphorus-accumulating bacteria, the nitrifying bacteria and the hydrolytic acidification bacteria on substrate competition and sludge age is solved; and the anaerobic hydrolysis acidification tank is arranged to recycle a carbon source in the sewage, so that the advantage of low carbon is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a sewage treatment system and a sewage treatment method for low-carbon nitrogen and phosphorus removal and applications thereof. Background Art

[0002] A 2 The A / O process is widely used in urban sewage treatment plants due to its convenient operation, simple structure and low operating cost. According to the data of the Urban Drainage Statistical Yearbook, 2 I / O type processes are the most widely used, accounting for 33% of the statistics. 2 The A / O process is the abbreviation of Anaerobic-Anoxic-Oxic, which is the abbreviation of anaerobic-anoxic-aerobic biological nitrogen and phosphorus removal process. 2 The / O process was developed based on the anaerobic-aerobic phosphorus process, which also has the functions of removing nitrogen and phosphorus.

[0003] A 2 The principle of the / O process is as follows: (1) The first anaerobic tank flows into the raw sewage and the phosphorus-containing sludge returned from the secondary sedimentation tank. The main function of this tank is to release phosphorus, which increases the concentration of P in the sewage. The dissolved organic matter is absorbed by the microbial cells, which reduces the BOD5 concentration in the sewage. In addition, a part of NH3-N is removed due to the synthesis of the cells, which reduces the NH3-N concentration in the sewage, but the NO3-N content does not change. (2) In the anoxic tank, denitrifying bacteria use the organic matter in the sewage as a carbon source, and reduce a large amount of NO3-N and NO2-N brought into the return mixed liquid to N2 and release it into the air. Therefore, the BOD5 concentration decreases, the NO3-N concentration decreases significantly, and the change in phosphorus is very small. (3) In the aerobic tank, organic matter is biochemically degraded by microorganisms and continues to decrease; organic nitrogen is ammonified and then nitrified, which significantly reduces the NH3-N concentration. However, as the nitrification process increases the NO3-N concentration, P also decreases at a faster rate due to the excessive uptake of polyphosphate bacteria. A 2 The / O process can simultaneously complete the removal of organic matter, nitrification and denitrification, and the removal of excessive phosphorus intake. The premise of denitrification is that NO3-N should be completely nitrified. Aerobic tanks can complete this function, while anoxic tanks complete the denitrification function. Anaerobic tanks and aerobic tanks jointly complete the phosphorus removal function.

[0004] However, A 2 The / O process itself has the problem of competition and symbiosis between polyphosphate-accumulating organisms (PAOs), denitrifying bacteria and nitrifying bacteria, which restricts its simultaneous nitrogen and phosphorus removal effect. Its defects are mainly reflected in:

[0005] Sludge age contradiction: A 2The O process is a single-sludge system in which phosphate accumulating organisms (PAOs), denitrifying bacteria, and nitrifying bacteria grow together. The sludge ages required for these microbial communities are different, making it difficult to optimize their activities simultaneously in actual operation. For example, nitrifying bacteria require a longer sludge age, while phosphate accumulating bacteria require a shorter sludge age.

[0006] Competition for carbon sources: 2 In the A / O system, the carbon source needs to meet the needs of phosphorus release, denitrification and heterotrophic metabolism. When the carbon source of the influent is insufficient, the denitrification process may be inhibited, thereby affecting the denitrification efficiency of the system. At the same time, the influent concentration of the sewage treatment plant is generally low. According to relevant information, the average BOD5 concentration of the influent of the sewage treatment plant is 103 mg / L. The water quality characteristics of actual domestic sewage are generally characterized by COD / ρ(TN) lower than 8, which belongs to low C / N ratio sewage. The lack of carbon source in sewage further limits the traditional A / O system. 2 In general, the lack of carbon source and carbon source competition are the main causes of the traditional A 2 The fundamental reason why the simultaneous nitrogen and phosphorus removal effects of the / O process are poor.

[0007] In view of this, the present invention is proposed. Summary of the invention

[0008] The first purpose of the present invention is to provide a sewage treatment system for low-carbon denitrification and phosphorus removal, which has a three-sludge system process, wherein the sludge systems of the adsorption tank and the intermediate sedimentation tank, the anaerobic tank, the anoxic tank, the aerobic tank and the secondary sedimentation tank, and the intermediate sedimentation tank, the secondary sedimentation tank and the anaerobic hydrolysis acidification tank are independent of each other, and denitrifying polyphosphate bacteria, nitrifying bacteria and hydrolytic acidification bacteria are cultured in different sludge systems, thereby solving the contradiction between their respective competition for substrates and sludge age; at the same time, an anaerobic hydrolysis acidification tank is set to recycle the internal carbon source of sewage, thereby reducing the addition of additional carbon source of low carbon-nitrogen ratio sewage, having the characteristics of low carbonization and resource utilization, and also having the advantages of improving the utilization rate of water treatment equipment and reducing sludge production, thereby solving the problems of insufficient carbon source and carbon source competition.

[0009] The second object of the present invention is to provide a wastewater treatment method for low-carbon denitrification and dephosphorization.

[0010] The third object of the present invention is to provide a sewage treatment system with low-carbon denitrification and phosphorus removal or a sewage treatment method with low-carbon denitrification and phosphorus removal for application in sewage treatment.

[0011] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0012] The present invention first provides a low-carbon denitrification and dephosphorization sewage treatment system, comprising a pretreatment unit, an adsorption tank, a middle sedimentation tank, a biochemical tank and a secondary sedimentation tank which are sequentially connected along the sewage flow direction; the biochemical tank comprises an anaerobic tank, an anoxic tank and an aerobic tank which are sequentially connected; the sewage treatment system also comprises an anaerobic hydrolysis acidification tank; the anaerobic hydrolysis acidification tank is provided with a VFAs-containing supernatant outlet, and the VFAs-containing supernatant outlet is connected to the anaerobic tank; the middle sedimentation tank is provided with an adsorption sludge outlet and a sewage outlet, the adsorption sludge outlet is respectively connected to the adsorption tank and the anaerobic hydrolysis acidification tank, and the sewage outlet is connected to the anaerobic tank; the secondary sedimentation tank is provided with a biological sludge outlet and a drainage outlet, the biological sludge outlet is respectively connected to the anaerobic tank and the anaerobic hydrolysis acidification tank; the anaerobic hydrolysis acidification tank is provided with an anaerobic sludge outlet, and the anaerobic sludge outlet is connected to a sludge dewatering device.

[0013] Furthermore, the pretreatment unit comprises a coarse screen, a lifting pump, a fine screen and a grit chamber which are sequentially connected along the flow direction of the sewage.

[0014] Furthermore, a desludging sewage return pipe is provided between the sludge dewatering device and the coarse screen.

[0015] Furthermore, the sludge dewatering device is provided with a sludge transport pipeline.

[0016] Furthermore, a mixed liquid reflux pipeline is provided between the aerobic tank and the anoxic tank.

[0017] The present invention further provides a wastewater treatment method for low-carbon denitrification and phosphorus removal, which is applicable to the wastewater treatment system for low-carbon denitrification and phosphorus removal, and comprises the following steps: after the particulate matter is removed by the pretreatment unit, the wastewater to be treated enters the adsorption tank, removes part of the organic matter by adsorption, and then enters the intermediate sedimentation tank for the first mud-water separation; a part of the adsorbed sludge after the first mud-water separation is returned to the adsorption tank, and the other part enters the anaerobic hydrolysis acidification tank for hydrolysis and acidification; the wastewater after the first mud-water separation enters the anaerobic tank for anaerobic phosphorus release, and then enters the anoxic tank for denitrification and phosphorus accumulation. The bacteria use nitrate nitrogen as an electron acceptor to perform a phosphorus polymerization reaction to simultaneously remove nitrogen and phosphorus, and then enter the aerobic tank for aerobic phosphorus absorption and nitrification reaction, and then enter the secondary sedimentation tank for the second mud and water separation; the qualified water after the second mud and water separation is discharged, a part of the biological sludge after the second mud and water separation is returned to the anaerobic tank, and the other part enters the anaerobic hydrolysis acidification tank for hydrolysis and acidification; the VFAs-containing supernatant obtained by hydrolysis and acidification with the hydrolysis and acidification bacteria agent in the anaerobic hydrolysis and acidification tank enters the anaerobic tank and is converted into an internal carbon source; the sludge discharged from the anaerobic hydrolysis and acidification tank enters the sludge dewatering device for dehydration.

[0018] Furthermore, the step of removing particulate matter from the sewage to be treated through the pretreatment unit includes: the sewage to be treated enters a coarse grid with a grid pitch of 10 mm to remove large-sized floating objects, then enters a fine grid with a grid pitch of 5 mm through a lifting pump to remove small-sized suspended objects, and then enters a grit chamber to remove sand particles with a particle size greater than 0.2 mm.

[0019] Furthermore, the sludge dehydrated by the sludge dehydration device is transported out, and / or the clear liquid dehydrated by the sludge dehydration device is returned to the coarse screen.

[0020] Furthermore, the enrichment and domestication method of the denitrifying polyphosphate bacteria includes: in the first stage, the inoculated sludge in the sewage treatment system is activated by operating in a periodic manner of water inlet-anaerobic-aerobic-sedimentation-drainage to obtain sludge with high-efficiency aerobic phosphorus absorption; in the second stage, the system is operated in a periodic manner of water inlet I-anaerobic-sedimentation-drainage-water inlet II-anoxic-sedimentation-drainage, wherein the water inlet II is artificial water without COD, which is used to remove the denitrifying bacteria in the sewage treatment system to select and enrich the denitrifying polyphosphate bacteria; in the third stage, the system is operated in a periodic manner of water inlet-anaerobic-anoxic-sedimentation-drainage, and nitrate is added to the anoxic tank to improve the stability of the system.

[0021] Furthermore, the hydrolytic acidifying bacteria agent is cultivated and domesticated using black water in a septic tank as a substrate.

[0022] Furthermore, the dominant bacterial genus of the hydrolytic acidifying bacterial agent includes at least one of the genera Lactobacillus, Ralstonia, Pseudomonas and Stenotrophomonas.

[0023] The present invention also provides the sewage treatment system for low-carbon denitrification and phosphorus removal and the application of the sewage treatment method for low-carbon denitrification and phosphorus removal in sewage treatment.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The low-carbon denitrification and phosphorus removal sewage treatment system provided by the present invention has a three-sludge system process, wherein the sludge systems of the adsorption tank and the intermediate sedimentation tank, the anaerobic tank, the anoxic tank, the aerobic tank and the secondary sedimentation tank, the intermediate sedimentation tank, the secondary sedimentation tank and the anaerobic hydrolysis acidification tank are independent of each other, and the denitrifying polyphosphate bacteria, the nitrifying bacteria and the hydrolysis acidification bacteria are cultured in different sludge systems, which solves the contradiction between their respective competition for the substrate and the sludge age. At the same time, an anaerobic hydrolysis acidification tank is set to recycle the internal carbon source of the sewage, reduce the addition of additional carbon source of the low carbon-nitrogen ratio sewage, have the characteristics of low carbonization and resource utilization, and also have the advantages of improving the utilization rate of water treatment equipment and reducing sludge production, solving the problems of insufficient carbon source and carbon source competition.

[0026] (2) The low-carbon denitrification and phosphorus removal sewage treatment system provided by the present invention is provided with an anaerobic hydrolysis and acidification tank and a reasonable combination of treatment units is constructed, and denitrification and phosphorus removal of sewage is achieved by using denitrifying polyphosphate bacteria as the main activated sludge; under the action of the hydrolysis and acidification bacterial agent, the adsorption sludge and the biological sludge are anaerobically hydrolyzed and acidified to produce short-chain fatty acids (VFAs) that are more suitable for water absorption and utilization by the denitrifying polyphosphate bacteria, thereby making full use of the internal carbon source in the sewage. It is a new sewage treatment system that conforms to the low-carbon and green requirements.

[0027] (3) The low-carbon denitrification and phosphorus removal sewage treatment system provided by the present invention can maximize the use of the internal carbon source in the raw water, create a suitable environment for the main bacterial flora, construct a reasonable combination of treatment units, and achieve stable treatment of denitrification and phosphorus removal of sewage.

[0028] (4) The low-carbon denitrification and phosphorus removal sewage treatment method provided by the present invention utilizes denitrifying polyphosphate bacteria as the main body of activated sludge and nitrate as the electron acceptor to complete the dual process of denitrification and phosphorus removal in an anaerobic environment, thereby realizing the denitrification and phosphorus removal of sewage, and has the characteristics of high efficiency and low consumption; under the action of hydrolysis and acidification bacteria, the adsorption sludge and the biological sludge are anaerobically hydrolyzed and acidified to produce short-chain fatty acids (VFAs) that are more suitable for water absorption and utilization by denitrifying polyphosphate bacteria, and fully utilize the internal carbon source in the sewage. It is a new sewage treatment process that saves energy and carbon source, has low sludge output, and is environmentally friendly.

[0029] (5) The low-carbon denitrification and phosphorus removal sewage treatment method provided by the present invention can effectively shorten the hydraulic retention time of the aerobic tank to 3 to 4 hours, which is only 1.5 hours in the traditional A 2 O process accounts for 40% to 50% of the hydraulic retention time of the aerobic tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 This is a schematic structural diagram of the sewage treatment system for low-carbon denitrification and phosphorus removal provided by the present invention.

[0032] Reference numerals:

[0033] 1-pretreatment unit; 11-coarse screen; 12-lifting pump; 13-fine screen; 14-sand settling tank; 2-adsorption tank; 3-intermediate settling tank; 4-biochemical tank; 41-anaerobic tank; 42-anoxic tank; 43 aerobic tank; 5-secondary settling tank; 6-anaerobic hydrolysis acidification tank; 7-sludge dewatering device. DETAILED DESCRIPTION

[0034] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0035] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0036] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0037] In the first aspect, the present invention provides a wastewater treatment system for low-carbon nitrogen and phosphorus removal, such as Figure 1 The figure shows a connection diagram of a sewage treatment system for low-carbon nitrogen removal and phosphorus removal, which includes a pretreatment unit 1, an adsorption tank 2, an intermediate sedimentation tank 3, a biochemical tank 4 and a secondary sedimentation tank 5 which are sequentially connected along the sewage flow direction; wherein the biochemical tank 4 includes an anaerobic tank 41, an anoxic tank 42 and an aerobic tank 43 which are sequentially connected along the sewage flow direction.

[0038] The sewage treatment system further comprises an anaerobic hydrolysis acidification tank 6, wherein the anaerobic hydrolysis acidification tank 6 is provided with a VFAs-containing supernatant outlet, and the VFAs-containing supernatant outlet is connected to the anaerobic tank 41. The anaerobic hydrolysis acidification tank 6 contains a hydrolysis acidification bacterial agent, which hydrolyzes and acidifies the sludge to obtain a VFAs-containing supernatant. The VFAs-containing supernatant outlet is used to discharge the VFAs-containing supernatant.

[0039] The intermediate settling tank 3 is provided with an adsorption sludge outlet and a sewage outlet, the adsorption sludge outlet is respectively connected to the adsorption tank 2 and the anaerobic hydrolysis acidification tank 6, and the sewage outlet is connected to the anaerobic tank 41. The adsorption sludge outlet is used to discharge the adsorption sludge into the adsorption tank 2 and the anaerobic hydrolysis acidification tank 6 respectively. The sewage outlet is used to discharge sewage.

[0040] The secondary sedimentation tank 5 is provided with a biological sludge outlet and a drain outlet, and the biological sludge outlet is respectively connected to the anaerobic tank 41 and the anaerobic hydrolysis acidification tank 6. The biological sludge outlet is used to discharge the biological sludge into the anaerobic tank 41 and the anaerobic hydrolysis acidification tank 6 respectively.

[0041] The anaerobic hydrolysis acidification tank 6 is provided with an anaerobic sludge outlet for discharging anaerobic sludge, and the anaerobic sludge outlet is connected to a sludge dehydration device 7. The sludge dehydration device 7 is used to dehydrate the anaerobic sludge discharged from the anaerobic hydrolysis acidification tank 6.

[0042] The low-carbon denitrification and phosphorus removal sewage treatment system provided by the present invention has a three-sludge system process, wherein the sludge systems of the adsorption tank 2 and the intermediate sedimentation tank 3, the anaerobic tank 41, the anoxic tank 42, the aerobic tank 43 and the secondary sedimentation tank 5, the intermediate sedimentation tank 3, the secondary sedimentation tank 5 and the anaerobic hydrolysis acidification tank 6 are independent of each other, and the denitrifying polyphosphate bacteria, nitrifying bacteria and hydrolysis acidification bacteria are cultured in different sludge systems, thereby solving the contradiction between their respective competition for substrates and sludge age.

[0043] At the same time, an anaerobic hydrolysis acidification tank 6 is set up to recycle the internal carbon source of the sewage and reduce the addition of additional carbon source to the low carbon-nitrogen ratio sewage. It has the characteristics of low carbonization and resource utilization, and also has the advantages of improving the utilization rate of water treatment equipment and reducing sludge production, thus solving the problems of insufficient carbon source and carbon source competition.

[0044] Specifically, the low-carbon denitrification and phosphorus removal sewage treatment system provided by the present invention is provided with an anaerobic hydrolysis acidification tank 6 and a reasonable combination of treatment units is constructed, and denitrification and phosphorus removal of sewage is achieved by using denitrifying polyphosphate bacteria as the main activated sludge; under the action of the hydrolysis and acidification bacterial agent, the adsorption sludge and the biological sludge are anaerobically hydrolyzed and acidified to produce short-chain fatty acids (VFAs) that are more suitable for water absorption and utilization by the denitrifying polyphosphate bacteria, thereby making full use of the internal carbon source in the sewage, and is a new type of sewage treatment system that conforms to the low-carbon and green concept.

[0045] The above-mentioned low-carbon denitrification and phosphorus removal sewage treatment system can maximize the use of internal carbon sources in raw water, create a suitable environment for the main bacterial flora, construct a reasonable combination of treatment units, and achieve stable treatment of wastewater denitrification and phosphorus removal.

[0046] In some specific implementations, the pretreatment unit includes a coarse screen 11, a lift pump 12, a fine screen 13 and a grit chamber 14 which are sequentially connected along the flow direction of the sewage.

[0047] In some specific implementations, a desludging wastewater return pipe is provided between the sludge dewatering device 7 (eg, a sludge dewatering machine) and the coarse screen 11 , for returning the supernatant obtained after dehydration to the coarse screen 11 .

[0048] In some specific implementations, the sludge dewatering device 7 is provided with a sludge transport pipeline for transporting the dewatered sludge.

[0049] In some specific embodiments, a mixed liquid reflux pipeline is provided between the aerobic tank 43 and the anoxic tank 42, and its function is to return the nitric nitrogen produced by nitrification in the aerobic tank 43 to the anoxic tank 42, so as to facilitate the denitrifying polyphosphate bacteria to carry out polyphosphate reaction using nitric nitrogen as an electron acceptor, thereby achieving synchronous denitrification and phosphorus removal.

[0050] In a second aspect, the present invention provides a wastewater treatment method for low-carbon denitrification and phosphorus removal, which is applicable to the above-mentioned wastewater treatment system for low-carbon denitrification and phosphorus removal. The wastewater treatment method comprises the following steps:

[0051] After the particulate matter is removed from the sewage to be treated by the pretreatment unit 1, it enters the adsorption tank 2. The sludge in the adsorption tank 2 has a certain adsorption capacity, and some organic matter in the sewage is removed by its adsorption effect. Then it enters the intermediate sedimentation tank 3 for the first mud-water separation.

[0052] A part of the adsorption sludge after the first mud-water separation flows back to the adsorption tank 2 to continue to adsorb organic matter in the sewage entering the adsorption tank 2, and another part of the adsorption sludge is discharged into the anaerobic hydrolysis acidification tank 6 for hydrolysis and acidification.

[0053] The sewage after the first mud-water separation enters the anaerobic tank 41 for anaerobic phosphorus release, then enters the anoxic tank 42 for denitrifying phosphorus-accumulating bacteria to perform phosphorus-accumulating reaction with nitric nitrogen as electron acceptor to simultaneously remove nitrogen and phosphorus, then enters the aerobic tank 43 for aerobic phosphorus absorption and nitrification reaction, and then enters the secondary sedimentation tank 5 for the second mud-water separation.

[0054] Among them, in addition to the sewage after the first mud-water separation entering the anaerobic tank 41, the supernatant rich in VFAs after anaerobic hydrolysis and acidification and part of the adsorbed sludge (external return sludge containing phosphorus) separated by the secondary sedimentation tank 5 also enter the anaerobic tank 41. While anaerobic phosphorus release is carried out, the VFAs organic matter that is easily biodegradable is absorbed by the microbial flora and converted into an internal carbon source. In the anoxic tank 42, the denitrifying polyphosphate bacteria use the nitric nitrogen in the external return sludge as an electron acceptor to carry out a polyphosphate reaction, thereby achieving simultaneous nitrogen removal and phosphorus removal. In the aerobic tank 43, aerobic phosphorus absorption and nitrification reactions occur, and the concentrations of ammonia nitrogen and total phosphorus in the sewage drop rapidly. Finally, the second mud-water separation is carried out in the secondary sedimentation tank 5, and the sewage is discharged after being treated to meet the standards.

[0055] The qualified water after the second mud-water separation is discharged, a part of the biological sludge after the second mud-water separation is returned to the anaerobic tank 41, and the other part of the biological sludge enters the anaerobic hydrolysis acidification tank 6 for hydrolysis and acidification.

[0056] The VFAs-containing supernatant obtained by hydrolysis and acidification by the hydrolysis and acidification bacteria in the anaerobic hydrolysis and acidification tank 6 enters the anaerobic tank 41 to be converted into an internal carbon source. The sludge discharged from the anaerobic hydrolysis and acidification tank 6 enters the sludge dehydration device 7 for dehydration.

[0057] That is, the adsorption sludge in the intermediate sedimentation tank 3 and the biological sludge in the secondary sedimentation tank 5 are discharged into the anaerobic hydrolysis acidification tank 6, pre-treated with a hydrolysis acidification bacterial agent to enhance the dissolution of organic matter, and under the action of the anaerobic fermentation bacterial community, they are metabolized to produce a large amount of short-chain volatile fatty acids (VFAs) and returned to the anaerobic tank 41 as a carbon source.

[0058] The low-carbon denitrification and phosphorus removal sewage treatment method provided by the present invention utilizes denitrifying polyphosphate bacteria as the main body of activated sludge, uses nitrate as an electron acceptor, completes the dual process of denitrification and phosphorus removal in an anaerobic environment, realizes the denitrification and phosphorus removal of sewage, and has the characteristics of high efficiency and low consumption; under the action of a hydrolysis and acidification bacterial agent, adsorption sludge and biological sludge are anaerobically hydrolyzed and acidified to produce short-chain fatty acids (VFAs) that are more suitable for water absorption and utilization by denitrifying polyphosphate bacteria, and fully utilizes the internal carbon source in the sewage. The process is a new sewage treatment process that saves energy and carbon source, has low sludge output, is environmentally friendly, and complies with low-carbon and green standards.

[0059] The above-mentioned low-carbon denitrification and phosphorus removal sewage treatment method can maximize the use of the internal carbon source in the raw water, create a suitable environment for the main bacterial flora, and achieve stable treatment of denitrification and phosphorus removal of sewage.

[0060] Among them, denitrifying phosphorus-accumulating bacteria (DPAOs) can use NO3 - -N or NO2 --N is used as the terminal electron acceptor, and polyhydroxyalkanoates (PHA) in the cell are used to complete the dual process of denitrification and phosphorus removal under anaerobic conditions, which can unify the denitrification and phosphorus removal processes in time and space. Anaerobic fermentation of sludge (i.e. hydrolysis and acidification) can produce VFAs (short-chain fatty acids, also known as volatile fatty acids), which are the most easily available carbon source in the process of biological denitrification and phosphorus removal. Therefore, in the case of insufficient organic matter in water, VFAs produced by sludge can be used as a carbon source to improve the efficiency of biological denitrification and phosphorus removal.

[0061] Different from the conventional nitrification and denitrification denitrification, the present invention is a biological nitrogen and phosphorus removal technology based on denitrification and phosphorus accumulation.

[0062] In addition, the low-carbon denitrification and dephosphorization wastewater treatment method of the present invention can effectively shorten the hydraulic retention time of the aerobic tank 43 to 3 to 4 hours, which is only 2 O process in the aerobic tank 43 hydraulic retention time of 40% to 50%. Specifically, conventional A 2 / O, polyphosphate bacteria PAO will use O2 as an electron acceptor to absorb phosphorus, while the denitrifying polyphosphate bacteria in this application is a strain that uses nitrate nitrogen as an electron acceptor to denitrify and absorb phosphorus under anoxic conditions. Therefore, this process does not require too long hydraulic retention time and aeration in the aerobic tank 43 for aerobic phosphorus absorption.

[0063] In some specific embodiments, the step of removing particulate matter from the sewage to be treated by the pretreatment unit 1 includes: the sewage to be treated enters a coarse grid 11 with a grid pitch of 10 mm to remove (intercept) large-sized floating objects in the sewage; then is lifted by a lifting pump 12 to a fine grid 13 with a grid pitch of 5 mm to remove (intercept) small-sized suspended objects in the sewage; and then enters a grit chamber 14 to remove sand particles in the sewage with a particle size greater than 0.2 mm. The sewage then flows to the adsorption tank 2.

[0064] In some specific implementations, the sludge dehydrated by the sludge dehydration device 7 is transported out, and / or the clear liquid dehydrated by the sludge dehydration device 7 is returned to the coarse screen 11 .

[0065] In some specific embodiments, the denitrifying polyphosphate bacteria are enriched and domesticated using a three-stage culture method, and the enrichment and domestication method includes:

[0066] In the first stage, the inoculated sludge in the sewage treatment system is activated by periodically operating in a water inlet-anaerobic-aerobic-sedimentation-drainage mode to obtain sludge with high efficiency aerobic phosphorus absorption.

[0067] In the second stage, the system is operated in the manner of periodic water inlet I-anaerobic-precipitation-drainage-water inlet II-anoxic-precipitation-drainage, wherein the water inlet I (anaerobic water inlet) is artificial water containing COD, and the water inlet II (anoxic water inlet) is artificial water without COD, which is used to remove denitrifying bacteria (only denitrification but no polyphosphate) in the sewage treatment system, so as to select and enrich the denitrifying polyphosphate bacteria. That is, the second stage is divided into two water inlets, anaerobic water inlet and anoxic water inlet, and the anaerobic water inlet is artificial water containing COD, and COD is converted into reduced coenzyme NADH and ATP for subsequent microbial activities. When entering the anoxic stage, no COD is added to the water inlet, which can quickly make the COD concentration in the water after the mud and water are mixed less than 50 mg / L, thereby improving the enrichment efficiency of denitrifying polyphosphate bacteria. It is understandable that denitrifying polyphosphate bacteria will not be removed together, because conventional denitrifying bacteria will use residual COD as an electron donor for denitrification reaction, thereby competing with denitrifying polyphosphate bacteria for electron acceptors. Since denitrifying polyphosphate bacteria do not need additional COD as an electron donor in the anoxic stage, they only need the reduced coenzyme NADH produced at the anaerobic end. Therefore, only when the COD in the system is low will it be beneficial for denitrifying polyphosphate bacteria to use nitrate nitrogen as an electron acceptor to absorb phosphorus.

[0068] In the third stage, the system is operated in a periodic manner of water inlet-anaerobic-anoxic-sedimentation-drainage, and nitrate is added to the anoxic tank 42 to improve the stability of the system. The cultivated sludge is the sludge enriched with denitrifying polyphosphate bacteria.

[0069] Compared with the two-stage acclimation method, the three-stage acclimation method adds an additional link after the anaerobic / aerobic acclimation is completed and before the anaerobic / anoxic mode begins, that is, sedimentation and drainage are carried out after the anaerobic stage, and then simulated water without COD is re-added; adding this stage can reduce the COD at the beginning of the anoxic stage, eliminate the influence of COD that is not absorbed and converted by polyphosphate bacteria in the anaerobic stage on the denitrifying polyphosphate bacteria in the anoxic stage, and limit the growth of conventional denitrifying bacteria.

[0070] In some specific embodiments, the hydrolytic acidifying bacteria agent is cultivated and domesticated using black water in a septic tank as a substrate.

[0071] In some specific embodiments, the dominant bacterial genus of the hydrolytic acidifying bacterial agent includes at least one of the genera Lactobacillus, Ralstonia, Pseudomonas and Oligotrophomonas, which can effectively degrade high molecular weight substances such as cellulose in sludge.

[0072] Among them, hydrolytic acidifying bacteria enhance the hydrolysis of some difficult-to-degrade organic matter (such as cellulose, etc.) in adsorbed sludge and biological sludge, promote the dissolution of organic matter, and increase the production of volatile fatty acids (VFAs).

[0073] In a third aspect, the present invention provides the application of the above-mentioned low-carbon denitrification and phosphorus removal sewage treatment system or the above-mentioned low-carbon denitrification and phosphorus removal sewage treatment method in sewage treatment.

[0074] The low-carbon denitrification and phosphorus removal sewage treatment system and the low-carbon denitrification and phosphorus removal sewage treatment method provided by the present invention have broad application prospects.

[0075] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. Low-carbon nitrogen and phosphorus removal sewage treatment system, It is characterized in that It includes a pretreatment unit, an adsorption tank, a secondary sedimentation tank, a biochemical tank and a secondary sedimentation tank which are sequentially connected along the flow direction of sewage; the biochemical tank includes an anaerobic tank, an anoxic tank and an aerobic tank which are sequentially connected; The sewage treatment system further comprises an anaerobic hydrolysis acidification tank; the anaerobic hydrolysis acidification tank is provided with a VFAs-containing supernatant outlet, and the VFAs-containing supernatant outlet is connected to the anaerobic tank; The intermediate settling tank is provided with an adsorption sludge outlet and a sewage outlet, the adsorption sludge outlet is respectively connected to the adsorption tank and the anaerobic hydrolysis acidification tank, and the sewage outlet is connected to the anaerobic tank; The secondary sedimentation tank is provided with a biological sludge outlet and a drain outlet, and the biological sludge outlet is respectively connected to the anaerobic tank and the anaerobic hydrolysis acidification tank; The anaerobic hydrolysis acidification tank is provided with an anaerobic sludge outlet, and the anaerobic sludge outlet is connected to a sludge dewatering device.

2. According to the low-carbon denitrification and phosphorus removal sewage treatment system of claim 1, It is characterized in that The pretreatment unit comprises a coarse screen, a lifting pump, a fine screen and a grit chamber which are sequentially connected along the flow direction of the sewage.

3. According to the low-carbon denitrification and phosphorus removal sewage treatment system of claim 2, It is characterized in that A desludging sewage return pipe is provided between the sludge dewatering device and the coarse screen; And / or, the sludge dewatering device is provided with a sludge transport pipeline.

4. The sewage treatment system for low-carbon nitrogen and phosphorus removal according to claim 1, It is characterized in that A mixed liquid reflux pipeline is arranged between the aerobic tank and the anoxic tank.

5. A wastewater treatment method for low-carbon denitrification and phosphorus removal, applicable to a wastewater treatment system for low-carbon denitrification and phosphorus removal as claimed in any one of claims 1 to 4, It is characterized in that The steps include: After the wastewater to be treated is treated by the pretreatment unit to remove particulate matter, it enters the adsorption tank to remove some organic matter through adsorption, and then enters the intermediate sedimentation tank for the first mud-water separation; A portion of the adsorption sludge after the first mud-water separation is returned to the adsorption tank, and the other portion enters the anaerobic hydrolysis acidification tank for hydrolysis and acidification; The sewage after the first mud-water separation enters the anaerobic tank for anaerobic phosphorus release, then enters the anoxic tank for denitrifying phosphorus-accumulating bacteria to perform phosphorus-accumulating reaction with nitrate nitrogen as electron acceptor to simultaneously remove nitrogen and phosphorus, then enters the aerobic tank for aerobic phosphorus absorption and nitrification reaction, and then enters the secondary sedimentation tank for the second mud-water separation; The qualified water after the second mud-water separation is discharged, a part of the biological sludge after the second mud-water separation is returned to the anaerobic tank, and the other part enters the anaerobic hydrolysis acidification tank for hydrolysis and acidification; The VFAs-containing supernatant obtained by hydrolysis and acidification by the hydrolysis and acidification bacteria in the anaerobic hydrolysis and acidification tank enters the anaerobic tank and is converted into an internal carbon source; the sludge discharged from the anaerobic hydrolysis and acidification tank enters the sludge dehydration device for dehydration.

6. The sewage treatment method for low-carbon nitrogen removal and phosphorus removal according to claim 5, It is characterized in that The step of removing particulate matter from the sewage to be treated by the pretreatment unit includes: the sewage to be treated enters a coarse grid with a grid pitch of 10 mm to remove large-sized floating objects, then enters a fine grid with a grid pitch of 5 mm through a lifting pump to remove small-sized suspended objects, and then enters a grit chamber to remove sand particles with a particle size greater than 0.2 mm.

7. The sewage treatment method for low-carbon nitrogen removal and phosphorus removal according to claim 6, It is characterized in that The sludge dewatered by the sludge dewatering device is transported out, and / or the clear liquid dewatered by the sludge dewatering device is returned to the coarse screen.

8. The sewage treatment method for low-carbon nitrogen and phosphorus removal according to claim 5, It is characterized in that The enrichment and domestication method of the denitrifying polyphosphate bacteria comprises: In the first stage, the inoculated sludge in the sewage treatment system is activated by periodically operating in a water inlet-anaerobic-aerobic-sedimentation-drainage mode to obtain sludge with high efficiency aerobic phosphorus absorption; In the second stage, the system is operated in a periodic manner of influent I-anaerobic-sedimentation-drainage-influent II-anoxic-sedimentation-drainage, wherein the influent II is artificial water without COD, which is used to remove denitrifying bacteria in the sewage treatment system, so as to select and enrich the denitrifying polyphosphate bacteria; In the third stage, the system is operated in a periodic manner of water inlet-anaerobic-anoxic-sedimentation-drainage, and nitrate is added to the anoxic tank to improve the stability of the system.

9. The sewage treatment method for low-carbon nitrogen removal and phosphorus removal according to claim 5, It is characterized in that The hydrolytic acidifying bacteria agent is cultivated and domesticated using black water in a septic tank as a substrate; And / or, the dominant bacterial genus of the hydrolytic acidifying bacterial agent includes at least one of the genera Lactobacillus, Ralstonia, Pseudomonas and Stenotrophomonas.

10. Use of the sewage treatment system with low-carbon denitrification and phosphorus removal as claimed in any one of claims 1 to 4, or the sewage treatment method with low-carbon denitrification and phosphorus removal as claimed in any one of claims 5 to 9 in sewage treatment.

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