Device and method for low-carbon nitrogen and phosphorus removal of urban sewage in hot area

Abstract

The invention discloses a device and a method for low-carbon nitrogen and phosphorus removal of town sewage, which are mainly used for town sewage treatment, a continuous flow segmented water inlet three-section anoxic and aerobic alternating process is utilized, precipitated sludge enters a cyclone separator to be separated into heavy sludge and light sludge, the heavy sludge flows back to enter the first two sections of aerobic zones of a biochemical pool, and the light sludge flows back to the second two sections of aerobic zones of the biochemical pool. Part of the light sludge flows back into a first-section anoxic zone of the biochemical pool, and the residual light sludge is discharged as residual sludge; microorganisms in the light sludge store an internal carbon source in the anoxic zone and generate a large amount of extracellular polymeric substances, the polymeric substances promote the activated sludge to form granular sludge in the aerobic zone, and nitrification, endogenous short-cut denitrification-anaerobic ammonia oxidation nitrogen removal and phosphorus uptake are realized in the aerobic zone. According to the invention, low-carbon nitrogen and phosphorus removal of town sewage can be realized, the town sewage treatment efficiency can be effectively improved, the use of an external carbon source for sewage treatment is reduced, and the sewage treatment cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the field of sewage treatment, and more particularly, to an apparatus and method for low-carbon nitrogen and phosphorus removal from urban sewage in hot areas. Background Art

[0002] With the increasingly strict nitrogen and phosphorus discharge standards, the deficiencies of traditional nitrogen and phosphorus removal processes have gradually emerged. In traditional nitrogen and phosphorus removal processes, both biological nitrogen removal and phosphorus removal consume organic matter. However, the concentration of organic matter in urban sewage in China is generally low, and the lack of carbon sources makes it difficult to meet the nitrogen and phosphorus effluent standards simultaneously. To meet the effluent standards, it is often necessary to add exogenous organic matter or chemical phosphorus removal agents, which increases the operating costs. In addition, sewage treatment is a high-energy-consuming industry. Therefore, the development of a low-carbon and low-energy-consuming urban sewage nitrogen removal process is of great significance for energy conservation and emission reduction in urban sewage treatment plants.

[0003] The anaerobic ammonium oxidation process removes nitrogen by converting ammonia nitrogen and nitrite into nitrogen gas. Compared with traditional nitrification / denitrification biological nitrogen removal, it has the advantages of saving aeration energy consumption and organic carbon sources. However, due to two main limiting factors, namely the lack of the electron acceptor nitrite in the influent and the inability to meet the total nitrogen effluent standard, this process is less used in the mainstream treatment of low-substrate-concentration sewage such as urban domestic sewage.

[0004] In the process of sewage treatment, granular sludge has obvious advantages compared with activated sludge. It has excellent sedimentation performance and high-efficiency sludge-water separation; it has a high concentration of microorganisms, high treatment efficiency and strong load capacity, and can adapt to fluctuations in water quality and quantity; it can treat special pollutants, operate stably, produce less sludge, and is not easy to expand and lose, which is more conducive to the stable and efficient operation of the sewage treatment system.

[0005] Therefore, this patent adopts the method of staged influent endogenous short-cut denitrification anaerobic ammonium oxidation, and uses methods such as cyclone separators and calcium ion addition to make activated sludge form granular sludge, providing a favorable growth environment for endogenous denitrifying bacteria, anaerobic ammonium oxidizing bacteria and phosphorus-removing bacteria, enabling the cooperation between various bacterial communities, making full use of the organic matter in the sewage, and simultaneously exerting the roles of autotrophic nitrogen removal and heterotrophic nitrogen removal, so as to achieve the purpose of low-carbon and high-efficiency nitrogen and phosphorus removal. Summary of the Invention

[0006] The purpose of the present invention is to provide an apparatus and method for low-carbon nitrogen and phosphorus removal from urban sewage, which can significantly improve the efficiency of nitrogen and phosphorus removal on the basis of reducing energy consumption and carbon emissions, thereby effectively reducing the treatment cost and reducing the floor area, providing a more economical, efficient and sustainable solution for urban sewage treatment.

[0007] To achieve the above object, the present invention provides the following technical solution: A device for low-carbon denitrification and phosphorus removal from urban sewage, comprising a biochemical pool, a secondary sedimentation tank, an inlet pipe, a solution tank, and a hydrocyclone separator for sorting sludge. The biochemical pool consists of a first anoxic zone, a first aerobic zone, a second anoxic zone, a second aerobic zone, a third anoxic zone, and a third aerobic zone; the solution tank is connected to the inlet pipe; the bottom of the secondary sedimentation tank is connected to the inlet of the hydrocyclone separator, and the bottom of the hydrocyclone separator is respectively connected to the front ends of the first aerobic zone and the second aerobic zone. The muddy water mixture flowing out of the biochemical pool enters the secondary sedimentation tank for sedimentation. The hydrocyclone separator separates into bottom flow heavy sludge and overflow light sludge. The bottom flow heavy sludge enters the front ends of the first aerobic zone and the second aerobic zone; a part of the overflow light sludge enters the front end of the first anoxic zone, and the remaining overflow light sludge is discharged as surplus sludge.

[0008] Further, the six compartments of the biochemical pool are arranged vertically and staggeredly in the water flow direction, the aerobic zones and anoxic zones are arranged alternately, and a stirrer is provided in each compartment of the biochemical pool. Micro-pore aeration heads, dissolved oxygen probes, and on-line sensors are provided in the first aerobic zone, the second aerobic zone, and the third aerobic zone. The lower end of the micro-pore aeration head passes through the compartment and is provided with an air volume regulating valve. A blower is provided at the intersection of the pipelines of the three groups of air volume regulating valves; a peristaltic pump is provided at the lower end of the solution tank.

[0009] Further, a sludge return pump, an inlet valve, a light sludge return valve, a heavy sludge return valve, and a surplus sludge discharge valve are provided in the inlet pipe; the stirrer, the blower, the on-line sensor, and the sludge return pump are all electrically connected to the control cabinet. Inclined plate sedimentation devices are installed on the upper parts of the first aerobic zone and the second aerobic zone; the top of the hydrocyclone separator is connected to the first anoxic zone and the surplus sludge discharge valve; a sludge discharge valve is provided at the bottom of the secondary sedimentation tank, and the bottom of the secondary sedimentation tank is simultaneously connected to the sludge return pump, and the sludge return pump is connected to the control cabinet.

[0010] A method for low-carbon denitrification and phosphorus removal from urban sewage using the above device; comprising the following steps:

[0011] S1: Flow the low-carbon urban sewage into the front ends of the first anoxic zone, the second anoxic zone, and the third anoxic zone respectively through the inlet valve at a ratio of 4:4:2.

[0012] S2: Inoculate the activated sludge from the sewage treatment plant and add it to the biochemical pool.

[0013] S3: Start the blower and use the micro-pore aeration disc to carry out low-oxygen aeration in the first aerobic zone and the second aerobic zone, and normal aeration in the third aerobic zone.

[0014] S4: The muddy water mixture flowing out of the biochemical pool enters the secondary sedimentation tank for sedimentation. After the separation of mud and water, the supernatant is discharged.

[0015] S5: The solution tank adds calcium chloride solution to the water inlet pipe through a peristaltic pump, so that the theoretical concentration of calcium ions in the influent water is 80 - 150 mg / L, and it is continuously added every day.

[0016] S6: The precipitated sludge is separated by a hydrocyclone into underflow heavy sludge and overflow light sludge.

[0017] S7: The underflow heavy sludge enters the front ends of the first aerobic zone and the second aerobic zone through the heavy sludge reflux valve; a part of the overflow light sludge enters the front end of the first anoxic zone through the light sludge reflux valve, and the remaining overflow light sludge is discharged as excess sludge through the excess sludge discharge valve.

[0018] By setting staged influent, each anoxic zone can make full use of the organic matter in the municipal sewage to store internal carbon sources for endogenous denitrification; by setting anoxic zones, polyphosphate-accumulating organisms can decompose the polyphosphate stored in their bodies, releasing inorganic phosphorus, and at the same time using the energy generated by decomposing polyphosphate to absorb volatile fatty acids (VFAs) in the sewage and synthesize organic substances to store in the cells.

[0019] Further, in step S3, the sludge retention time is controlled to be 12 to 14 days. The flow rate of the heavy sludge refluxed to the first aerobic zone and the second aerobic zone is 50% - 70% of the influent flow rate; the flow rate of the light sludge refluxed to the first anoxic zone is 130% - 160% of the influent flow rate.

[0020] Further, the activated sludge from the sewage treatment plant is inoculated into the biochemical pool and the double reflux technology is used, so that the sludge concentration in the first anoxic zone is 3800 mg / L - 4200 mg / L, and the sludge concentrations in the first aerobic zone and the second aerobic zone are 3200 mg / L - 3600 mg / L. The total HRT (total hydraulic retention time) of the biochemical pool system is 10 - 14 h, among which the HRT of the anoxic zone is 3 - 5 h, and the HRT of the aerobic zone is 6 - 9 h%.

[0021] Further; the dissolved oxygen in the first aerobic zone and the second aerobic zone is controlled below 0.5 mg / L during aeration, and the dissolved oxygen in the third aerobic zone is controlled at 2.5 - 3.0 mg / L during aeration; the system discharges part of the light sludge generated by the hydrocyclone every day as excess sludge.

[0022] The first and second aerobic zones adopt low-oxygen aeration. Under this condition, endogenous denitrification anaerobic ammonium oxidation reactions occur. Through low-oxygen nitrification, the generation rate of nitrate nitrogen can be controlled. Since nitrate nitrogen is an important substrate in the denitrification process, controlling the generation rate of nitrate nitrogen can further control the supply rate of nitrate nitrogen in the denitrification process; thereby the generation rate of nitrite can be controlled, providing a low concentration of nitrite for the long-term and stable supply of the anaerobic ammonium oxidation reaction, and at the same time effectively preventing the growth inhibition of anaerobic ammonium oxidation bacteria due to excessive nitrite concentration.

[0023] In addition, low-oxygen aeration reduces the oxidation of internal carbon sources, enabling more carbon sources to be used for endogenous denitrification to produce nitrite and remove nitrogen. In the third aerobic zone, normal aeration can maintain the nitrogen and phosphorus removal effects of the biochemical tank. By setting up a sludge cyclone separator, dual sludge reflux is achieved. Part of the light sludge is refluxed to the first anoxic zone. After passing through the third aerobic zone, these sludges are in a starved state, and they can store the organic matter brought in by the influent in the bacteria to form internal carbon sources, while producing more extracellular polymers, providing conditions for the formation of granular sludge in the subsequent aerobic zone. By adding calcium ions to the biochemical tank, the calcium ions act like a "bridge" to connect the extracellular polymers and microbial cells, making the combination between microorganisms closer. Adding Ca2+ is more conducive to the growth of granules and the stability of the structure, and helps the formation of granular sludge structure. The heavy sludge is refluxed to the first and second aerobic zones (low-oxygen aerobic zones), and the heavy sludge containing more granules is refluxed to the low-oxygen aerobic zone. By adding a short-time sedimentation device to the upper part of the first and second aerobic zones, the granular sludge is sedimented, which is conducive to the retention of anaerobic ammonium oxidation bacteria. Only the light sludge is discharged as excess sludge, improving the sludge sedimentation performance of the system and avoiding sludge bulking.

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

[0025] Compared with the traditional A2O process, this method has the following advantages:

[0026] 1) The step-feed process is adopted to make full use of the organic matter in the influent and strengthen the storage of internal carbon sources.

[0027] 2) Low-oxygen aeration is adopted in the first and second aerobic zones to achieve low-oxygen nitrification, endogenous denitrification and anaerobic ammonium oxidation, and supply low-concentration nitrite stably for the anaerobic ammonium oxidation reaction for a long time. Low oxygen can also reduce the aerobic oxidation of internal carbon sources, strengthen anaerobic ammonium oxidation denitrification, and achieve low-carbon denitrification.

[0028] 3) A sludge cyclone separator is used to achieve dual sludge reflux, and calcium ions are added to promote the formation of granular sludge from activated sludge, while strengthening the storage of internal carbon sources in the sludge in the anoxic zone. In addition, discharging the light sludge as excess sludge can effectively improve the sludge sedimentation performance and avoid sludge bulking in the system.

[0029] 4) Inclined plate sedimentation devices are installed above the first and second aerobic zones to retain the granular sludge in the aerobic zone, thus providing favorable conditions for the growth and enrichment of anaerobic ammonium oxidation bacteria.

[0030] 5) More internal carbon sources of the sludge in this process are used for denitrification, resulting in less sludge production in the system.

[0031] 6) This process realizes endogenous denitrification coupled with anaerobic ammonium oxidation for low-carbon and low-energy consumption nitrogen and phosphorus removal, with low sewage treatment cost. At the same time, there is no need to add additional denitrification filters, etc., and the system occupies a small area. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required in the description of the embodiments. Obviously, the drawings in the following description are only the preferred embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 It is a schematic diagram of the overall device for low-carbon nitrogen and phosphorus removal from urban sewage according to the present invention.

[0034] In the figure: 1, biochemical tank; 2, secondary sedimentation tank; 3, inclined plate sedimentation device; 4, water inlet pipe; 5, solution tank; 6, hydrocyclone separator; 7, control cabinet; 8, first anoxic zone; 9, first aerobic zone; 10, second anoxic zone; 11, second aerobic zone; 12, third anoxic zone; 13, third aerobic zone; 14, sludge return pump; 15, blower; 16, stirrer; 17, on-line sensor; 18, microporous aeration head; 19, gas flow regulating valve; 20, dissolved oxygen probe; 21, peristaltic pump; 22, influent flow regulating valve; 23, effluent valve; 24, secondary sedimentation tank sludge discharge valve; 25, light sludge return valve; 26, heavy sludge return valve; 27, excess sludge discharge valve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] In order to more easily understand the structure of the present invention and the functional features and advantages that can be achieved, the following will describe the preferred embodiments of the present invention in detail in conjunction with the drawings as follows:

[0036] Embodiment 1

[0037] As Figure 1 shown, the present application proposes a device for low-carbon nitrogen and phosphorus removal from urban sewage, including a biochemical tank 1, a secondary sedimentation tank 2, a water inlet pipe 4, a solution tank 5, and a hydrocyclone separator 6 for sorting sludge. The biochemical tank 1 is composed of a first anoxic zone 8, a first aerobic zone 9, a second anoxic zone 10, a second aerobic zone 11, a third anoxic zone 12, and a third aerobic zone 13; the solution tank 5 is communicated with the water inlet pipe 4; the bottom of the secondary sedimentation tank 2 is connected to the inlet of the hydrocyclone separator 6, and the bottom of the hydrocyclone separator 6 is respectively connected to the front ends of the first aerobic zone 9 and the second aerobic zone 11. The muddy water mixture flowing out of the biochemical tank 1 enters the secondary sedimentation tank 2 for sedimentation. The hydrocyclone separator 6 is sorted into bottom flow heavy sludge and overflow light sludge. The bottom flow heavy sludge enters the front ends of the first aerobic zone 9 and the second aerobic zone 11; a part of the overflow light sludge enters the front end of the first anoxic zone 8, and the remaining overflow light sludge is discharged as excess sludge.

[0038] See Figure 1, the six compartments of the biochemical tank 1 are arranged in a vertically staggered manner along the water flow direction, with the aerobic zones and anoxic zones arranged alternately. A stirrer 16 is provided in each compartment of the biochemical tank 1. In the first aerobic zone 9, the second aerobic zone 11, and the third aerobic zone 13, a microporous aeration head 18, a dissolved oxygen probe 20, and an on-line sensor 17 are provided. The lower end of the microporous aeration head 18 passes through the compartment and is provided with a gas flow regulating valve 19. A blower 15 is provided at the junction of the pipelines of the three groups of gas flow regulating valves 19; a peristaltic pump 21 is provided at the lower end of the solution tank 5.

[0039] Among them, overflow holes are arranged in a vertically staggered manner along the water flow direction to connect each compartment, and water inlets are provided in the three compartments of the first anoxic zone 8, the second anoxic zone 10, and the third anoxic zone 12.

[0040] See Figure 1 , a sludge return pump 14, a water inlet valve, a light sludge return valve 25, a heavy sludge return valve 26, and a surplus sludge discharge valve 27 are provided in the water inlet pipe 4; the stirrer 16, the blower 15, the on-line sensor 17, and the sludge return pump 14 are all electrically connected to the control cabinet 7.

[0041] Among them, the water inlet is communicated with the water inlet valve, and the water inlet valve is a flow regulating valve for controlling the water inlet flow rate and the water inlet ratio.

[0042] See Figure 1 , a lamella sedimentation device 3 is installed on the upper parts of the first aerobic zone 9 and the second aerobic zone 11; the top of the hydrocyclone 6 is connected to the first anoxic zone 8 and the surplus sludge discharge valve 27; a sludge discharge valve is provided at the bottom of the secondary sedimentation tank 2, and the bottom of the secondary sedimentation tank 2 is simultaneously connected to the sludge return pump 14, and the sludge return pump 14 is connected to the control cabinet 7.

[0043] Among them, the lamella sedimentation device 3 is installed in the upper half parts of the first aerobic zone 9 and the second aerobic zone 11 to precipitate granular sludge. The granular sludge wraps the anaerobic ammonium oxidation bacteria. Inside the granular sludge, there are gradient distributions of dissolved oxygen, substrate concentration, etc. in different regions, which can create a suitable anaerobic or anoxic environment for the anaerobic ammonium oxidation bacteria and meet their strict requirements for low-oxygen or even anoxic conditions. The precipitation of the granular sludge is beneficial to the retention of the anaerobic ammonium oxidation bacteria.

[0044] Example 2

[0045] A method for low-carbon nitrogen and phosphorus removal from municipal sewage uses the municipal sewage low-carbon nitrogen and phosphorus removal device of Example 1 and includes the following steps:

[0046] S1: Flow the low-carbon municipal sewage into the fronts of the first anoxic zone 9, the second anoxic zone 11, and the third anoxic zone 13 through the water inlet valve in a ratio of 4:4:2.

[0047] S2: Inoculate the activated sludge from the sewage treatment plant and add it to the biochemical tank 1.

[0048] S3: Start the blower 15 to conduct low-oxygen aeration in the first aerobic zone 9 and the second aerobic zone 11 using microporous aeration discs, and conduct normal aeration in the third aerobic zone 13;

[0049] S4: The mud-water mixture flowing out of the biochemical tank 1 enters the secondary sedimentation tank 2 for sedimentation. After the separation of mud and water, the supernatant is discharged;

[0050] S5: The solution tank 5 adds calcium chloride solution to the water inlet pipe 4 through the peristaltic pump 21, so that the theoretical concentration of calcium ions in the influent water is 80 - 150 mg / L, and it is continuously added every day;

[0051] S6: The precipitated sludge is separated by the hydrocyclone 6 into underflow heavy sludge and overflow light sludge;

[0052] S7: The underflow heavy sludge enters the front ends of the first aerobic zone 9 and the second aerobic zone 11 through the heavy sludge reflux valve 26; a part of the overflow light sludge enters the front end of the first anoxic zone 8 through the light sludge reflux valve 25, and the remaining overflow light sludge is discharged as excess sludge through the excess sludge discharge valve 27.

[0053] Among them, low-carbon urban sewage flows into the water inlet pipe 4, and then flows into the front ends of the first anoxic zone 8, the second anoxic zone 10, and the third anoxic zone 12 at a ratio of 4:4:2 through the water inlet flow regulating valve 22. When the low-carbon urban sewage is in the anoxic zone, denitrifying bacteria reduce nitrates and nitrites to gaseous nitrogen compounds such as nitrogen, thereby achieving nitrogen removal. Polyphosphate-accumulating organisms can decompose the polyphosphates stored in their bodies, release inorganic phosphorus, and at the same time use the energy generated by the decomposition of polyphosphates to absorb volatile fatty acids (VFAs) in the sewage and synthesize organic substances and store them in the cells. In the first aerobic zone 8 and the second aerobic zone 10, by controlling the generation rate of nitrate nitrogen through low-oxygen aeration, the supply rate of nitrate nitrogen in the denitrification process can be further controlled. And nitrate nitrogen is converted into nitrite in the denitrification process, and then by controlling the generation rate of nitrite, low-concentration nitrite can be stably supplied to the anaerobic ammonium oxidation reaction for a long time, thereby effectively preventing the growth of anaerobic ammonium oxidation bacteria from being inhibited due to too high nitrite concentration, and realizing the start-up of endogenous denitrification-anaerobic ammonium oxidation in the aerobic zone.

[0054] Using the inclined plate sedimentation device 3, the granular sludge is precipitated. The granular sludge wraps the anaerobic ammonium oxidation bacteria. Inside the granular sludge, there are gradient distributions of dissolved oxygen, substrate concentration, etc. in different regions, which can create a suitable anaerobic or anoxic environment for the anaerobic ammonium oxidation bacteria, meet their strict requirements for low-oxygen or even anaerobic conditions. Therefore, the precipitation of granular sludge is beneficial to the retention of anaerobic ammonium oxidation bacteria. The third aerobic zone 13 conducts normal aeration to ensure the treatment effect of nitrogen and phosphorus.

[0055] The mixed liquid of mud and water flowing out of the biochemical tank enters the secondary sedimentation tank 2 for sedimentation. After the separation of mud and water, the supernatant is discharged. The sedimented sludge enters the hydrocyclone separator 6 for sorting. A part of the light overflow sludge enters the front end of the first anoxic zone 8 of the biochemical tank. These sludges are in a starving state after passing through the third aerobic zone 13 and the subsequent sedimentation tank. After entering the first anoxic zone 8 and the second anoxic zone 10 of the biochemical tank, a large amount of organic matter is brought in by the influent water in this area, making the sludge in a feast state. The organic matter brought in by the influent water can be stored in the bacteria to form an internal carbon source, and at the same time, more extracellular polymers are produced, providing conditions for the formation of granular sludge in the subsequent aerobic zone. The heavy underflow sludge enters the front ends of the first aerobic zone 9 and the second aerobic zone 11 of the biochemical tank, so that the heavy sludge containing more particles flows back to the low-oxygen aerobic zone. Adding calcium ions to the biochemical tank 1 can promote the formation of granular sludge. The remaining light sludge is discharged as excess sludge.

[0056] Example 3

[0057] The effluent from the grit chamber of a certain sewage treatment plant was used as the influent water for the test. The specific water quality was as follows: the influent ammonia nitrogen was 14.82 mg / L - 32.96 mg / L, the influent TN was 15.03 mg / L - 33.17 mg / L, the influent total phosphorus was 2.03 mg / L - 4.46 mg / L, the influent COD was 47.63 mg / L - 124.53 mg / L, and the average C / N was 3.75. The test system was as Figure 1 shown. The total reaction volume of the reactor was 20.2 m3, divided into 6 compartments. Among them, the total volume of the biochemical tank was 16.1 m3, and the volume of the secondary sedimentation tank was 4 m3.

[0058] (1) Start the system: Inoculate the activated sludge from the sewage treatment plant into the biochemical tank and use the double reflux technology to make the sludge concentration in the biochemical tank 4000 mg / L;

[0059] (2) Adjust the operation during operation as follows:

[0060] 1). Flow the low-carbon urban sewage into the front ends of the first anoxic zone 8, the second anoxic zone 10, and the third anoxic zone 12 through the influent valve 22 at a ratio of 4:4:2 respectively

[0061] 2). The flow rate of the heavy sludge refluxed to the first aerobic zone 9 and the second aerobic zone 11 is 60% of the influent flow rate;

[0062] 3). The flow rate of the light sludge refluxed to the first anoxic zone 8 is 140% of the influent flow rate;

[0063] 4). The total HRT (total hydraulic retention time) of the biochemical tank system is 12.35 h, of which the HRT of the anoxic zone is 4.39 h, and the HRT of the aerobic zone is 7.96 h;

[0064] 5) The dissolved oxygen in the first aerobic zone 9 and the second aerobic zone 11 is controlled below 0.5 mg / L during aeration, and the dissolved oxygen in the third aerobic zone 13 is controlled at 2 - 3.0 mg / L during aeration;

[0065] 6) By adding calcium chloride solution to the influent pipe 4, the theoretical concentration of calcium ions in the influent is made 80 - 150 mg / L, and it is continuously added every day;

[0066] 7) Part of the light sludge generated by the hydrocyclone separator 6 is discharged as surplus sludge every day, and the SRT (sludge retention time) is controlled at 14 days.

[0067] The test results show that: after stable operation, the average effluent ammonia nitrogen of the system is 0.05 - 0.6 mg / L, the average effluent TN is 3 - 4.4 mg / L, the average effluent total phosphorus is 0 - 0.4 mg / L, and the average effluent COD is 21.53 - 28.62 mg / L.

[0068] Comparative Research Example 1

[0069] The process of this comparative research example is different from that of Example 3 of this application in that: this comparative example replaces the segmented influent multi - stage AO process with a conventional influent AOA process, adjusts the hydrocyclone separator to a conventional sludge return pump, and adjusts the low - oxygen aeration in the separated aerobic zone to normal aeration in a single aerobic zone, with the dissolved oxygen concentration being 2 - 3.0 mg / L; the total reaction volume of the reactor is 18.6 m 3 , divided into 2 compartments, where the total volume of the aerobic zone and the anoxic zone is 13.3 m 3 , and the volume of the secondary sedimentation tank is 5 m 3 The rest of the process and water quality are the same as those in Example 3;

[0070] This comparative example uses a conventional AOA process treatment device, mainly including an aerobic tank, an anoxic tank, and a secondary sedimentation tank. The water body is introduced into the aerobic tank by a conventional influent method, and an aerobic environment is provided by an aeration disk, so that organic matter is oxidized, ammonia nitrogen is converted into nitrate nitrogen by nitrifying bacteria, and phosphorus - accumulating bacteria absorb phosphorus. Sludge is introduced to make the mixed liquid precipitate in the secondary sedimentation tank, and then the supernatant is discharged, and the sludge is returned to the anoxic tank.

[0071] Under the same influent and environmental conditions, the ammonia nitrogen, TN, and COD in the effluent treated by the process of this comparative research example will increase significantly. Under the same influent and environmental conditions, the average effluent TN is 6.84 mg / L, which is much higher than the effluent TN concentration of 3 mg / L in the process of Example 3.

[0072] For the water TN concentration test methods in Comparative Example 1 and Example 3, the potassium persulfate oxidation-ultraviolet spectrophotometry was used; the water sample was digested by alkaline potassium persulfate at a high temperature (120-124 °C) to convert organic nitrogen, ammonia nitrogen, nitrite nitrogen, etc. in the water into nitrate nitrogen, and then the absorbance of nitrate nitrogen was measured by ultraviolet spectrophotometry to calculate the total nitrogen concentration.

[0073] The above are only the preferred embodiments of the present invention and do not impose any formal restrictions on the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention by using the above technical content within the scope of the technical solution of the present invention, or modify it into an equivalent embodiment with equivalent changes. Therefore, any changes, modifications, equivalent changes and modifications made to the above embodiments based on the technology of the present invention without departing from the content of the technical solution of the present invention all fall within the protection scope of this technical solution.

Claims

1. A device for low-carbon nitrogen and phosphorus removal from urban sewage, characterized in that: The invention comprises a biochemical pool (1), a secondary sedimentation tank (2), a water inlet pipe (4), a solution tank (5) and a cyclone separator (6) for sorting sludge. The biochemical pool (1) is composed of a first anoxic zone (8), a first aerobic zone (9), a second anoxic zone (10), a second aerobic zone (11), a third anoxic zone (12) and a third aerobic zone (13); the solution tank (5) is connected to the water inlet pipe (4); the bottom of the secondary sedimentation tank (2) is connected to the inlet of the cyclone separator (6); the bottom of the cyclone separator (6) is respectively connected to the front ends of the first aerobic zone (9) and the second aerobic zone (11); the sludge-water mixture flowing out of the biochemical pool (1) enters the secondary sedimentation tank (2) for precipitation; the cyclone separator (6) is sorted into underflow heavy sludge and overflow light sludge; the underflow heavy sludge enters the front ends of the first aerobic zone (9) and the second aerobic zone (11); A portion of the overflowing light sludge enters the front end of the first anoxic zone (8), and the remaining overflowing light sludge is discharged as residual sludge.

2. The device for low-carbon denitrification and dephosphorization of urban sewage according to claim 1, characterized in that: The six cells of the biochemical pool (1) are arranged in an up-and-down staggered manner according to the direction of water flow, and the aerobic zone and the anoxic zone are arranged at intervals. A stirrer (16) is arranged in each cell of the biochemical pool (1), and microporous aeration heads (18), dissolved oxygen probes (20) and online sensors (17) are arranged in the first aerobic zone (9), the second aerobic zone (11) and the third aerobic zone (13). An air volume regulating valve (19) is arranged at the lower end of the microporous aeration head (18) passing through the cell, and a blower (15) is arranged at the intersection of the pipelines of the three groups of the air volume regulating valves (19); and a peristaltic pump (21) is arranged at the lower end of the solution tank (5).

3. The device for low-carbon nitrogen and phosphorus removal from urban sewage according to claim 2, characterized in that: The water inlet pipe (4) is provided with a sludge return pump (14), a water inlet valve (22), a light sludge return valve (25), a heavy sludge return valve (26) and a residual sludge discharge valve (27); the agitator (16), the blower (15), the online sensor (17) and the sludge return pump (14) are all connected to the control cabinet (5) by electrical signals.

4. The device for low-carbon nitrogen and phosphorus removal from urban sewage according to claim 3, characterized in that: Inclined plate sedimentation devices (3) are installed on the upper parts of the first aerobic zone (9) and the second aerobic zone (11); the top of the cyclone separator (6) is connected to the first anoxic zone (8) and the residual sludge discharge valve (27); the bottom of the secondary sedimentation tank (2) is provided with a sludge discharge valve (24), and the bottom of the secondary sedimentation tank (2) is also connected to the sludge return pump (14), and the sludge return pump (14) is connected to the control cabinet (7).

5. A method for low-carbon denitrification and phosphorus removal of urban sewage, using the low-carbon denitrification and phosphorus removal device for urban sewage according to claim 4, characterized in that; The following steps are involved: S1: low-carbon urban sewage is respectively flowed into the first anoxic zone (8), the second anoxic zone (10) and the front end of the third anoxic zone (12) through the water inlet valve (22) in a ratio of 4:4:2; S2: adding activated sludge from an inoculated sewage treatment plant into the biochemical pool (1); S3: starting the blower to use the microporous aeration disk to perform low-oxygen aeration on the first aerobic zone (9) and the second aerobic zone (11), and performing normal aeration on the third aerobic zone (13); S4: the muddy and water mixture flowing out of the biochemical pool (1) enters the secondary sedimentation tank (2) for sedimentation, and the supernatant is discharged after the muddy and water are separated; S5: the solution tank (5) adds calcium chloride solution to the water inlet pipe (4) through the peristaltic pump (21), so that the theoretical concentration of calcium ions in the inlet water is 80-150 mg / L, and the solution is added continuously every day; S6: the precipitated sludge is separated into underflow heavy sludge and overflow light sludge by the cyclone separator (6); S7: The bottom flow heavy sludge enters the front end of the first aerobic zone (8) and the second aerobic zone (9) through the heavy sludge return valve (26); a part of the overflow light sludge enters the front end of the first anoxic zone (8) through the light sludge return valve (25), and the remaining overflow light sludge is discharged as residual sludge through the residual sludge discharge valve (27).

6. The method for low-carbon denitrification and dephosphorization of urban sewage according to claim 5, characterized in that: In step S3, the sludge retention time is controlled to be 12 to 14 days.

7. The method for low-carbon denitrification and dephosphorization of urban sewage according to claim 5, characterized in that: The heavy sludge flow rate returned to the first aerobic zone (9) and the second aerobic zone (11) is 50% to 70% of the influent flow rate; the light sludge flow rate returned to the first anoxic zone (8) is 130% to 160% of the influent flow rate.

8. The method for low-carbon denitrification and dephosphorization of urban sewage according to claim 5, characterized in that: The activated sludge of the sewage treatment plant is inoculated into the biochemical pool (1) and the double recirculation technology is used to make the sludge concentration of the first anoxic zone (8) 3800mg / L to 4200mg / L, and the sludge concentration of the first aerobic zone (9) and the second aerobic zone (11) 3200mg / L to 3600mg / L.

9. The method for low-carbon nitrogen and phosphorus removal from urban sewage according to claim 5, characterized in that: The total HRT (total hydraulic retention time) of the biochemical pond system is 10 to 14 hours, of which the HRT of the anoxic zone is 3 to 5 hours and the HRT of the aerobic zone is 6 to 9 hours.

10. The method for low-carbon denitrification and phosphorus removal from urban sewage according to claim 5, characterized in that; The dissolved oxygen in the first aerobic zone (9) and the second aerobic zone (11) is controlled to be below 0.5 mg / L during aeration, and the dissolved oxygen in the third aerobic zone (13) is controlled to be 2.5-3.0 mg / L during aeration; The system discharges part of the light sludge produced by the cyclone separator (6) as residual sludge every day.

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