Sewage treatment system and sewage treatment method for low-carbon denitrification and phosphorus removal and their applications

Abstract

The present invention relates to the technical field of sewage treatment, and specifically, to a sewage treatment system for low-carbon denitrification and phosphorus removal, a sewage treatment method, and their applications. The sewage treatment system includes a pretreatment unit, an adsorption tank, an intermediate sedimentation tank, a biochemical tank, a secondary sedimentation tank, and an anaerobic hydrolysis and acidification tank; the biochemical tank includes an anaerobic tank, an anoxic tank, and an aerobic tank; the anaerobic hydrolysis and acidification tank has a supernatant outlet containing VFAs communicated with the anaerobic tank; the intermediate sedimentation tank has an adsorbed sludge outlet and a sewage outlet, the adsorbed sludge outlet is communicated with the adsorption tank and the anaerobic hydrolysis and acidification tank, and the sewage outlet is communicated with the anaerobic tank; the secondary sedimentation tank has a biological sludge outlet and a drainage outlet, and the biological sludge outlet is communicated with the anaerobic tank and the anaerobic hydrolysis and acidification tank. This sewage treatment system can cultivate denitrifying phosphorus-accumulating bacteria, nitrifying bacteria, and hydrolytic acidifying bacteria in different sludge systems, solving the contradiction between their competition for substrates and sludge retention time; and the anaerobic hydrolysis and acidification tank is set to recover the internal carbon source of sewage, which has the advantage of low carbon.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and more specifically, to a sewage treatment system and a sewage treatment method for low-carbon denitrification and phosphorus removal and their applications. Background Art

[0002] A 2 The A / O process is widely used in urban sewage treatment plants due to its convenient operation, simple structure, low operating cost, etc. According to the data of the "Urban Drainage Statistics Yearbook", A 2 The A / O type process has the widest range of use, accounting for 33% of the statistical quantity. A 2 The A / O process is the English abbreviation of Anaerobic-Anoxic-Oxic, and it is the abbreviation of the anaerobic-anoxic-aerobic biological denitrification and phosphorus removal process. A 2 The A / O process is developed on the basis of the anaerobic-aerobic phosphorus process, and this process has the functions of denitrification and phosphorus removal at the same time.

[0003] A 2 The principle of the A / O process is as follows: (1) In the first-stage anaerobic tank, the influent raw sewage and the phosphorus-containing sludge refluxed from the secondary sedimentation tank enter synchronously. The main function of this tank is to release phosphorus, increasing the concentration of P in the sewage, and the soluble organic matter is absorbed by the microbial cells, decreasing the BOD5 concentration in the sewage; in addition, part of the NH 3 -N is removed due to cell synthesis, decreasing the concentration of NH 3 -N in the sewage, but the content of NO 3 -N remains unchanged. (2) In the anoxic tank, the denitrifying bacteria use the organic matter in the sewage as a carbon source to reduce the large amount of NO 3 -N and NO 2 -N in the refluxed mixed liquor to N 2 which is released into the air. Therefore, the BOD5 concentration decreases, and the concentration of NO 3 -N decreases significantly, while the change in phosphorus is small. (3) In the aerobic tank, the organic matter is biochemically degraded by the microorganisms, and continues to decrease; the organic nitrogen is ammoniated and then nitrified, significantly decreasing the concentration of NH 3 -N, but with the nitrification process, the concentration of NO 3 -N increases, and P also decreases at a relatively fast rate with the excessive uptake by the polyphosphate-accumulating organisms. A 2 The A / O process can simultaneously complete functions such as the removal of organic matter, nitrification and denitrification, and the excessive uptake and removal of phosphorus. The prerequisite for denitrification is that NO 3 -N should be completely nitrified, which can be completed in the aerobic tank, and the anoxic tank completes the denitrification function. The anaerobic tank and the aerobic tank jointly complete the phosphorus removal function.

[0004] However, A 2The A / O process itself has problems of competition and symbiosis among 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 2 The A / O process belongs to a single-sludge system, in which polyphosphate-accumulating organisms (PAOs), denitrifying bacteria, and nitrifying bacteria coexist. The sludge ages required by 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 polyphosphate-accumulating organisms require a shorter sludge age.

[0006] Carbon source competition: In the A 2 / O system, the carbon source needs to meet the needs of phosphorus release, denitrification, and heterotrophic bacteria metabolism simultaneously. When the influent carbon source is insufficient, it may inhibit the denitrification process, thereby affecting the nitrogen removal efficiency of the system. At the same time, the influent concentration of sewage treatment plants is generally low. According to relevant information, the average influent BOD5 concentration of sewage treatment plants is 103 mg / L, and the water quality characteristics of actual domestic sewage generally show that COD / ρ(TN) is lower than 8, belonging to low C / N ratio sewage. The lack of carbon source in the sewage further restricts the treatment effect of the traditional A 2 / O process. Generally speaking, the lack of carbon source and carbon source competition problems are the fundamental reasons for the poor simultaneous nitrogen and phosphorus removal effect of the traditional A 2 / O process.

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

[0008] The first object of the present invention is to provide a sewage treatment system for low-carbon nitrogen and phosphorus removal, which has a three-sludge system process. 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. The denitrifying polyphosphate-accumulating organisms, nitrifying bacteria, and hydrolytic acidification bacteria are cultured in different sludge systems, solving the contradictions of their respective substrate competition and sludge age; at the same time, an anaerobic hydrolysis acidification tank is set up to recover the internal carbon source of the sewage, reducing the addition of extra carbon source for low-carbon nitrogen ratio sewage, having the characteristics of low carbonization and resource utilization, and also having advantages such as improving the utilization rate of water treatment equipment and reducing sludge production, solving the problems of carbon source shortage and carbon source competition.

[0009] The second object of the present invention is to provide a sewage treatment method for low-carbon nitrogen and phosphorus removal.

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

[0011] In order to achieve the above objects of the present invention, the following technical solutions are specifically 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] Further, the steps of removing particulate matter from the sewage to be treated by the pretreatment unit include: the sewage to be treated enters a coarse grid with a grid pitch of 10 mm to remove large-sized floating matters, then enters a fine grid with a grid pitch of 5 mm through a lift pump to remove small-sized suspended matters, and then enters a grit chamber to remove sand grains with a particle size greater than 0.2 mm.

[0019] Further, the sludge dehydrated by the sludge dewatering device is transported out, and / or the supernatant liquid dehydrated by the sludge dewatering device is refluxed to the coarse grid.

[0020] Further, the method for enriching and domesticating denitrifying phosphorus-accumulating bacteria includes: in the first stage, it operates in a periodic manner of influent - anaerobic - aerobic - sedimentation - drainage to activate the inoculated sludge in the sewage treatment system to obtain sludge with efficient aerobic phosphorus uptake; in the second stage, it operates in a periodic manner of influent Ⅰ - anaerobic - sedimentation - drainage - influent Ⅱ - anoxic - sedimentation - drainage, where the influent Ⅱ is artificial water without COD, used to remove denitrifying bacteria in the sewage treatment system to select and enrich the denitrifying phosphorus-accumulating bacteria; in the third stage, it operates in a periodic manner of influent - anaerobic - anoxic - sedimentation - drainage, and nitrate is added to the anoxic tank to improve the stability of the system.

[0021] Further, the hydrolytic acidification bacterial agent is cultivated and domesticated using the black water in a septic tank as a substrate.

[0022] Further, the dominant bacterial genera of the hydrolytic acidification bacterial agent include at least one of Lactobacillus, Ralstonia, Pseudomonas, and Stenotrophomonas.

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

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) The sewage treatment system for low-carbon denitrification and phosphorus removal provided by the present invention has a three-sludge system process, in which the sludge systems of the adsorption tank and the middle sedimentation tank, the anaerobic tank, the anoxic tank, the aerobic tank and the secondary sedimentation tank, and the middle sedimentation tank, the secondary sedimentation tank and the anaerobic hydrolytic acidification tank are independent of each other. The denitrifying phosphorus-accumulating bacteria, nitrifying bacteria and hydrolytic acidification bacteria are cultured in different sludge systems, solving the contradiction between their respective competition for substrates and sludge retention time. At the same time, an anaerobic hydrolytic acidification tank is set up to recover the internal carbon source of the sewage, reducing the addition of extra carbon sources for sewage with a low carbon-nitrogen ratio. It has the characteristics of low carbonization and resource utilization, and also has advantages such as 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 sewage treatment system for low-carbon denitrification and phosphorus removal provided by the present invention sets up an anaerobic hydrolysis acidification tank and constructs a reasonable combination of treatment units. Using denitrifying phosphorus-accumulating bacteria as the main activated sludge, it realizes the denitrification and phosphorus removal of sewage. Under the action of hydrolysis acidification bacteria agent, the adsorbed sludge and biological sludge anaerobically hydrolyze and acidify to produce short-chain fatty acids (VFAs) that are more suitable for being absorbed and utilized by denitrifying phosphorus-accumulating bacteria, making full use of the internal carbon source in the sewage. It is a new type of sewage treatment system that conforms to low-carbon and green requirements.

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

[0028] (4) The sewage treatment method for low-carbon denitrification and phosphorus removal provided by the present invention uses denitrifying phosphorus-accumulating bacteria as the main activated sludge, takes nitrate as the electron acceptor, and completes the dual processes of denitrification and phosphorus removal in an anoxic environment, realizing the denitrification and phosphorus removal of sewage. It has the characteristics of high efficiency and low consumption. Under the action of hydrolysis acidification bacteria agent, the adsorbed sludge and biological sludge anaerobically hydrolyze and acidify to produce short-chain fatty acids (VFAs) that are more suitable for being absorbed and utilized by denitrifying phosphorus-accumulating bacteria, making full use of the internal carbon source in the sewage. It is a new type of sewage treatment process that saves energy and carbon sources, has low sludge output, and is environmentally friendly.

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

[0030] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0031] Figure 1 It 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 grille; 12 - Lift pump; 13 - Fine grille; 14 - Sand basin; 2 - Adsorption tank; 3 - Intermediate sedimentation tank; 4 - Biochemical tank; 41 - Anaerobic tank; 42 - Anoxic tank; 43 Aerobic tank; 5 - Secondary sedimentation tank; 6 - Anaerobic hydrolysis acidification tank; 7 - Sludge dewatering device. Detailed implementation manners

[0034] The technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific implementation manners. However, those skilled in the art will understand that the following described embodiments are part of the embodiments of the present invention, rather than all the embodiments, and are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not indicated by the manufacturer can be obtained as conventional products through commercial purchase.

[0035] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is 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 thus cannot be construed as limiting the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0036] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installation", "connection", "connection" 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 directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0037] In a first aspect, the present invention provides a sewage treatment system for low-carbon denitrification and phosphorus removal, as Figure 1 shown in the connection schematic diagram of the sewage treatment system for low-carbon denitrification 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 connected in series along the sewage flow direction; wherein, the biochemical tank 4 includes an anaerobic tank 41, an anoxic tank 42, and an aerobic tank 43 connected in series along the sewage flow direction.

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

[0039] The intermediate sedimentation tank 3 is provided with an adsorbed sludge outlet and a sewage outlet. The adsorbed sludge outlet is respectively communicated with the adsorption tank 2 and the anaerobic hydrolysis acidification tank 6, and the sewage outlet is communicated with the anaerobic tank 41. The adsorbed sludge outlet is used to discharge the adsorbed 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 drainage port. The biological sludge outlet is respectively communicated with the anaerobic tank 41 and the anaerobic hydrolysis acidification tank 6. Among them, 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 communicated with a sludge dewatering device 7. The sludge dewatering device 7 is used to dewater the anaerobic sludge discharged from the anaerobic hydrolysis acidification tank 6.

[0042] The sewage treatment system for low-carbon denitrification and phosphorus removal provided by the present invention has a three-sludge system process. Among them, 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, and the intermediate sedimentation tank 3, the secondary sedimentation tank 5 and the anaerobic hydrolysis acidification tank 6 are independent of each other. The denitrifying phosphorus-accumulating bacteria, nitrifying bacteria and hydrolysis acidification bacteria are cultured in different sludge systems, solving the contradiction between the competition for substrates and the sludge age of each.

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

[0044] Specifically, the sewage treatment system for low-carbon denitrification and phosphorus removal provided by the present invention sets up an anaerobic hydrolysis acidification tank 6 and constructs a reasonable combination of treatment units, uses denitrifying phosphorus-accumulating bacteria as the main active sludge to achieve denitrification and phosphorus removal of sewage; under the action of the hydrolysis acidification bacterium agent, the adsorbed sludge and biological sludge are anaerobically hydrolyzed and acidified to produce short-chain fatty acids (VFAs) that are more suitable for being absorbed and utilized by denitrifying phosphorus-accumulating bacteria, making full use of the internal carbon source in the sewage, and it is a new type of sewage treatment system that conforms to low-carbon and green.

[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 sludge-water separation entering the anaerobic tank 41, the supernatant rich in VFAs after anaerobic hydrolysis and acidification and part of the adsorbed sludge (externally returned phosphorus-containing sludge) separated by the secondary sedimentation tank 5 also enter the anaerobic tank 41. While anaerobic phosphorus release occurs, the biodegradable VFAs organic matter is absorbed and converted into internal carbon source by the microbial flora. In the anoxic tank 42, the denitrifying phosphorus-accumulating bacteria use the nitrate nitrogen in the externally returned sludge as the electron acceptor for the phosphorus-accumulating reaction, achieving simultaneous nitrogen and phosphorus removal. In the aerobic tank 43, aerobic phosphorus uptake and nitrification reactions occur, and the ammonia nitrogen and total phosphorus concentrations in the sewage rapidly decrease. Finally, the second sludge-water separation is carried out in the secondary sedimentation tank 5, and the sewage is discharged after being treated qualified.

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

[0056] The supernatant containing VFAs obtained by hydrolysis and acidification by the hydrolysis and acidification agent in the anaerobic hydrolysis and acidification tank 6 enters the anaerobic tank 41 and is converted into internal carbon source. The sludge residue discharged from the anaerobic hydrolysis and acidification tank 6 enters the sludge dewatering device 7 for dewatering.

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

[0058] The sewage treatment method for low-carbon nitrogen and phosphorus removal provided by the present invention uses denitrifying phosphorus-accumulating bacteria as the main active sludge, uses nitrate as the electron acceptor, and completes the dual processes of nitrogen and phosphorus removal in an anoxic environment, realizing the nitrogen and phosphorus removal of sewage, and having the characteristics of high efficiency and low consumption; the adsorbed sludge and biological sludge are anaerobically hydrolyzed and acidified under the action of the hydrolysis and acidification agent to produce short-chain fatty acids (VFAs) that are more suitable for being absorbed and utilized by denitrifying phosphorus-accumulating bacteria, making full use of the internal carbon source in the sewage, and is a new sewage treatment process that saves energy and carbon source, has low sludge output, is environmentally friendly, and conforms to low-carbon and green.

[0059] The above sewage treatment method for low-carbon nitrogen and phosphorus removal can make the most of the internal carbon source in the raw water, create a suitable environment for the main flora, and realize the stable treatment of nitrogen and phosphorus removal of sewage.

[0060] Among them, denitrifying phosphorus-accumulating bacteria (DPAOs) can use NO 3 - -N or NO 2 --N serves as the terminal electron acceptor, and the poly-β-hydroxyalkanoates (PHA) in the cells are utilized to complete the dual processes of denitrification and phosphorus removal under anoxic conditions, enabling the unification of the denitrification and phosphorus removal processes in terms of time and space. Anaerobic fermentation of sludge (i.e., hydrolysis acidification) can produce VFAs (short-chain fatty acids, also known as volatile fatty acids), which are the most easily utilized carbon sources in the biological denitrification and phosphorus removal processes. Therefore, in the case of insufficient organic matter in water, the 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-denitrification for nitrogen removal, the present invention is a biological nitrogen and phosphorus removal technology based on denitrifying phosphorus accumulation.

[0062] In addition, in the sewage treatment method for low-carbon nitrogen and phosphorus removal of the present invention, the hydraulic retention time of the aerobic tank 43 can be effectively shortened to 3 - 4 hours, which is only 40% - 50% of the hydraulic retention time of the aerobic tank 43 in the traditional A 2 / O process. Specifically, in the conventional A 2 / O, the polyphosphate-accumulating organisms (PAOs) will take O 2 as the electron acceptor for aerobic phosphorus uptake, while the denitrifying phosphorus-accumulating organisms in this application are strains that utilize nitrate nitrogen as the electron acceptor for denitrifying nitrogen removal and phosphorus uptake under anoxic conditions. Therefore, this process does not require a long hydraulic retention time and aeration in the aerobic tank 43 for aerobic phosphorus uptake.

[0063] In some specific embodiments, the steps for the sewage to be treated to remove particulate matters in the pretreatment unit 1 include: the sewage to be treated enters the coarse grille 11 with a grid pitch of 10 mm to remove (intercept) large-sized floating matters in the sewage; then it is lifted by the lift pump 12 to the fine grille 13 with a grid pitch of 5 mm to remove (intercept) small-sized suspended matters in the sewage; and then it enters the grit chamber 14 to remove sand grains in the sewage with a particle size greater than 0.2 mm. After that, the sewage flows to the adsorption tank 2.

[0064] In some specific embodiments, the sludge dehydrated by the sludge dewatering device 7 is transported out, and / or, the clear liquid after dehydration by the sludge dewatering device 7 is refluxed to the coarse grille 11.

[0065] In some specific embodiments, the denitrifying phosphorus-accumulating organisms are enriched and domesticated by a three-stage cultivation method, and the enrichment and domestication method includes:

[0066] In the first stage, it is operated in a periodic manner of influent - anaerobic - aerobic - sedimentation - drainage to activate the inoculated sludge in the sewage treatment system to obtain sludge with efficient aerobic phosphorus uptake.

[0067] In the second stage, it operates in a cyclic manner of influent Ⅰ - anaerobic - sedimentation - drainage - influent Ⅱ - anoxic - sedimentation - drainage. Among them, the influent Ⅰ (anaerobic influent) is artificial water containing COD, and the influent Ⅱ (anoxic influent) is artificial water without COD, which is used to remove the denitrifying bacteria (with only denitrification effect and no phosphorus - accumulating effect) in the sewage treatment system to select and enrich the denitrifying phosphorus - accumulating bacteria. That is, the second stage is divided into two influents, anaerobic influent and anoxic influent. The anaerobic influent is artificial water containing COD, and the COD is converted into reduced coenzyme NADH and ATP for subsequent microbial activities. When entering the anoxic section, no COD is added to the influent, which can quickly make the COD concentration in the mixed mud - water less than 50 mg / L, improving the enrichment efficiency of denitrifying phosphorus - accumulating bacteria. It can be understood that the denitrifying phosphorus - accumulating bacteria will not be removed together because conventional denitrifying bacteria will use the residual COD as an electron donor for denitrification reactions, thus competing with denitrifying phosphorus - accumulating bacteria for electron acceptors. Since denitrifying phosphorus - accumulating bacteria do not require additional COD as an electron donor in the anoxic section and only need the reduced coenzyme NADH produced at the anaerobic end, it is only beneficial for denitrifying phosphorus - accumulating bacteria to use nitrate nitrogen as an electron acceptor for phosphorus uptake when the COD in the system is low.

[0068] In the third stage, it operates in a cyclic manner of influent - 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 phosphorus - accumulating bacteria.

[0069] Compared with the two - stage domestication method, in the three - stage domestication method, an additional link is added after the anaerobic / aerobic domestication is completed and before the anaerobic / anoxic mode starts, that is, after the anaerobic section ends, sedimentation and drainage are carried out, and then simulated water without COD is added again; adding this stage can reduce the COD at the beginning of the anoxic section, eliminate the influence of the COD that has not been absorbed and transformed by phosphorus - accumulating bacteria in the anaerobic stage on the denitrifying phosphorus - accumulating bacteria in the anoxic section, and limit the growth of conventional denitrifying bacteria.

[0070] In some specific embodiments, the hydrolytic acidification bacterium agent is cultivated and domesticated with the black water in the septic tank as the substrate.

[0071] In some specific embodiments, the dominant bacterial genera of the hydrolytic acidification bacterium agent include at least one of Lactobacillus, Ralstonia, Pseudomonas, and Stenotrophomonas, which can effectively degrade large - molecular - weight substances such as cellulose in the sludge.

[0072] Among them, the hydrolytic acidification bacteria strengthen the hydrolysis of some refractory organic matters (such as cellulose) in the adsorbed sludge and biological sludge, promote the dissolution of organic matters, and increase the production of volatile fatty acids (VFAs).

[0073] Thirdly, the present invention provides an application of the above sewage treatment system for low-carbon denitrification and phosphorus removal or the above sewage treatment method for low-carbon denitrification and phosphorus removal in sewage treatment.

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

[0075] Although the present invention has been illustrated and described with reference to specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; those of ordinary skill in the art should understand that: without departing from the spirit and scope of the present invention, the technical solutions described in the foregoing embodiments may be modified, or some or all of the technical features may be equivalently replaced; and 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. A low-carbon denitrification and phosphorus removal sewage treatment system, 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; The anaerobic hydrolysis and acidification tank contains a hydrolysis and acidification bacterial agent, which is cultivated and domesticated using black water in a septic tank as a substrate; the dominant bacterial genus of the hydrolysis and acidification bacterial agent includes at least one of the genera Lactobacillus, Ralstonia, Pseudomonas and Stenotrophomonas; The anoxic pool contains denitrifying polyphosphate bacteria, and 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 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 pool to improve the stability of the system.

2. The low-carbon denitrification and phosphorus removal sewage treatment system according to claim 1 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. The low-carbon denitrification and phosphorus removal sewage treatment system according to claim 2 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 low-carbon denitrification and phosphorus removal sewage treatment system according to claim 1 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, 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 method for treating wastewater by low-carbon nitrogen removal and phosphorus removal according to claim 5, 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 method for treating wastewater by low-carbon nitrogen removal and phosphorus removal according to claim 6, 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. Use of the sewage treatment system for low-carbon nitrogen removal and phosphorus removal as described in any one of claims 1 to 4 in sewage treatment.

9. Application of the sewage treatment method for low-carbon nitrogen removal and phosphorus removal as described in any one of claims 5 to 7 in sewage treatment.

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