A short-flow combined denitrification and dephosphorization process for realizing expansion of sewage plant in situ

Abstract

This invention discloses a short-process combined nitrogen and phosphorus removal process for in-situ expansion of wastewater treatment plants. It consists of two systems: a nitrogen and phosphorus removal system I and a nitrogen and phosphorus removal system II. Through an influent diversion system, 40% of the wastewater enters the nitrogen and phosphorus removal system I, and 60% enters the nitrogen and phosphorus removal system II. This invention effectively combines the AAO process based on sedimentation and membrane separation using side-flow functional bacteria screening technology. This process is compact, easy to operate, simple to construct, flexible to control, and occupies a small area. By combining the strengths of both solid-liquid separation technologies, it amplifies the advantages of the AAO process, ensuring in-situ expansion during the dry season while handling excessive expansion during the rainy season, and maintaining efficient simultaneous nitrogen and phosphorus removal.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically a short-process combined nitrogen and phosphorus removal process for in-situ expansion of wastewater treatment plants. Background Technology

[0002] With rapid economic development and continuous urbanization, urban sewage discharge is constantly increasing. Meanwhile, sewage treatment plants in coastal areas and the Taihu Lake basin face challenges such as heavy rainfall, long rainy seasons, and incomplete separation of rainwater and sewage in pipe networks. However, due to the limited design capacity of urban sewage treatment plants, they often have to operate at overcapacity to cope with the increasing hydraulic load each year, as well as the excessive load during the rainy season. This gradually increasing hydraulic load makes the nitrogen and phosphorus removal systems of sewage treatment plants extremely vulnerable to shocks, making it difficult to effectively guarantee the overall pollutant removal capacity of the system. This leads to damage to the nitrogen and phosphorus removal systems during the rainy season, causing them to lose their ability to cope with load shocks, forcing sewage to overflow into rivers and causing problems such as black and odorous water bodies.

[0003] AAO (Alternating Acid-Oxygenation) and its improved variants are among the mainstream technologies used for nitrogen and phosphorus removal in urban wastewater treatment plants in my country. They offer advantages such as high pollutant removal efficiency, strong resistance to shock loads, and low susceptibility to filamentous bulking. The solid-liquid separation process is a key step determining the treatment load of the wastewater treatment plant, and commonly used methods include sedimentation tanks and membrane separation technology.

[0004] Sedimentation tanks maintain a lower biomass through a lower solid-liquid retention time (SRT), ensuring the enrichment of polyphosphate-accumulating bacteria (PABs) with stronger extracellular polymeric substances (EPS) secretion capabilities. This enhances their resistance to hydraulic load shocks, guaranteeing the solid-liquid separation performance of the sedimentation tank. However, to provide sufficient reaction time for the low biomass, the hydraulic retention time (HRT) is extended during the design phase, resulting in a larger footprint. However, with increasing hydraulic loads, the original design HRT is still insufficient to maintain the nitrogen and phosphorus removal process, especially with the impact of rainwater loads. This leads to a significant reduction in the HRT of the biological section, resulting in insufficient anaerobic / aerobic reaction time for PPAs, weakening their activity. Furthermore, the shorter SRT and HRT hinder the nitrification process, leading to a deterioration in sedimentation performance and pollutant removal performance.

[0005] Membrane bioreactor (MBR) technology, based on membrane separation, leverages the high retention capacity of membranes to maintain high biomass concentrations, ensuring biological activity and cultivating and enriching nitrifying bacteria with long sedimentation times (SRTs). It can also directly replace secondary sedimentation tanks, achieving sludge-water separation and significantly reducing land area requirements. However, the long SRT results in weaker phosphorus removal capacity, causing more bacteria to enter a decline phase. Under hydraulic load surges, this can lead to large-scale bacterial death, exacerbating membrane fouling and rendering the system unable to handle high hydraulic loads.

[0006] Side-flow functional bacteria screening technology is a technology that achieves biological screening based on the difference in density and viscosity. It consists of a hydrocyclone and its pump assembly. By setting the configuration parameters and operating parameters of the hydrocyclone, it can effectively achieve the directional screening of functional bacteria. It can screen out polyphosphate-accumulating bacteria and denitrifying bacteria with stronger viscosity, thereby enhancing sludge settling performance, as well as loose and low-viscosity nitrifying bacteria, thereby enhancing nitrification performance. Summary of the Invention

[0007] The purpose of this invention is to address the insufficient design hydraulic load of existing urban wastewater treatment plants by proposing a short-process combined nitrogen and phosphorus removal process for in-situ expansion of wastewater treatment plants. This process effectively combines the AAO process based on sedimentation and membrane separation through side-flow functional bacteria screening technology. This process is compact, easy to operate, simple to construct, flexible to control, and occupies a small area. By leveraging the strengths of both solid-liquid separation technologies, it amplifies the advantages of the AAO process, ensuring in-situ expansion during the dry season while handling excessive expansion during the rainy season, and maintaining efficient simultaneous nitrogen and phosphorus removal.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a short-process combined nitrogen and phosphorus removal process for in-situ expansion of wastewater treatment plants, wherein the system used in the process includes an influent diversion system, a nitrogen and phosphorus removal system one, a nitrogen and phosphorus removal system two, and an intelligent automatic control module;

[0009] The water inlet and outlet diversion system includes a water distribution well, a water distribution gate, and diversion pipelines;

[0010] The intelligent automatic control module includes a flow meter detector, a PLC control cabinet, a sludge concentration detector, and a nitrification performance detector;

[0011] The denitrification and phosphorus removal system includes an anaerobic tank, an anoxic tank, an aerobic tank, a membrane separation component, an internal return pipeline, an external return pipeline, a functional bacteria screener, and a sludge storage tank. The anaerobic tank, anoxic tank, and aerobic tank are connected in sequence. The membrane separation component is installed at the tail end of the aerobic tank and includes an effluent pump set and a membrane cleaning component. The sludge storage tank is connected to the aerobic tank and the functional bacteria screener. The functional bacteria screener includes a US pipeline, an OS pipeline, and an OSE pipeline. The US pipeline is directly connected to the sludge treatment unit, the OS pipeline is connected to the external return pipeline, and the OSE pipeline is connected to the external return pipeline.

[0012] The nitrogen and phosphorus removal system 2 includes an anaerobic tank 2, an anoxic tank 2, an aerobic tank 2, a secondary sedimentation tank, an internal return pipeline 2, an external return pipeline 2, a functional bacteria screener 1, and a sludge storage tank 1. The anaerobic tank 2, anoxic tank 2, aerobic tank 2, and secondary sedimentation tank are connected in sequence. The sludge storage tank 2 is connected to the aerobic tank 2 and the functional bacteria screener 2. The functional bacteria screener 2 includes a US pipeline 2 and an OS pipeline 2. The US pipeline 2 is directly connected to the external return pipeline 2, and the OS pipeline 2 is directly connected to the sludge treatment unit.

[0013] The process specifically includes the following steps:

[0014] Step (1): Raw water enters the denitrification and phosphorus removal system 1 and denitrification and phosphorus removal system 2 respectively at 40% and 60% through the inlet diversion system;

[0015] Step (2): 40% of the raw water flow rate enters the anaerobic tank 1, anoxic tank 1, and aerobic tank 1 of the denitrification and phosphorus removal system 1 sequentially. The sludge leaves the system through the membrane separation unit. Sludge from aerobic tank 1 is pumped into sludge storage tank 1 at 100%–110% of the influent flow rate. Sludge from sludge storage tank 1 is then pumped into functional bacteria separator 1 at 1%–10% of the influent flow rate. The hydrocyclone generates underflow sludge (US) and overflow sludge (OS). OS is enriched with nitrifying bacteria, while US is discharged from the system as excess sludge, with a SRT of 15–15%. The operating time of the 30d control functional bacteria screener is monitored in real time by the intelligent automatic control module. When the US sludge discharge meets the above SRT, the operation of the functional bacteria screener stops. During normal operation, the OS generated is all sent to the external return pipeline 1 through OS pipeline 1 to replenish the sludge concentration and nitrifying bacteria. US is discharged as excess sludge through US pipeline 1. OS pipeline 1 is also directly connected to the OSE pipeline and the external return pipeline 2. The flow direction of OS is selected according to the real-time monitoring of the dinitrification performance of the denitrification and phosphorus removal system by the intelligent automatic control module.

[0016] Step (3): 60% of the raw water flow rate enters the anaerobic tank 2, anoxic tank 2 and aerobic tank 2 of the denitrification and phosphorus removal system 2 in sequence. After solid-liquid separation in the secondary sedimentation tank, it leaves the system. The sludge in aerobic tank 2 is pumped into sludge storage tank 2 at 100% to 110% of the influent flow rate. The sludge in sludge storage tank 2 is pumped into functional bacteria screen 2 at 1% to 10% of the influent flow rate. Through the hydrocyclone, underflow sludge (US) and overflow sludge (OS) are generated. US is rich in polyphosphate-accumulating bacteria and denitrifying bacteria. OS is discharged from the system as excess sludge. The operating time of functional bacteria screen 2 is controlled according to SRT of 8 to 12 days. The operation is monitored in real time by the intelligent automatic control module. After the OS sludge discharge meets the above SRT, functional bacteria screen 2 stops operating. All US generated during operation enters external return pipeline 2 to replenish sludge concentration and polyphosphate and denitrifying bacteria.

[0017] Furthermore, the first denitrification and phosphorus removal system is designed with an HRT of 6-8 hours, an SRT of 15-30 days, and an MLSS of 8-12 g / L; the second denitrification and phosphorus removal system is designed with an HRT of 8-12 hours, an SRT of 8-12 days, and an MLSS of 4-6 g / L.

[0018] Furthermore, the functional bacteria sieve one and functional bacteria sieve two are integrated container-type assemblies, which facilitates transportation and management.

[0019] Furthermore, the hydrocyclone includes a column, a cone, an inlet, an overflow outlet, and an underflow outlet. The column diameter D is between 50 and 120 mm, and the column height-to-diameter ratio L1 / D is 1. The cone height-to-diameter ratio L2 / D is 2 to 6, and the cone angle is 8 to 16°. The inlet has a cuboid configuration, and the ratio of the inlet area S to the square of the column diameter D is 0.067. The inlet tangentially enters the column. The overflow outlet is partially embedded in the column, with an embedded portion length L. v The diameter D of the column is 0.14, and the remaining part of the overflow port protrudes from the column, with a protrusion length L. o The diameter D of the column is 0.57, and the diameter D of the overflow outlet is... o The diameter D of the column is 0.4 to 0.6; the underflow outlet is connected to the conical inlet, and the length L of the underflow outlet is... u The diameter D of the column is 0.57, and the diameter of the bottom outlet is D. u The diameter D of the cylinder is 0.2 to 0.3.

[0020] Furthermore, the functional bacteria screener one and functional bacteria screener two control the screening effect of functional bacteria and the sludge discharge of the system by adjusting the operating parameters of the hydrocyclone, such as the processing flow rate, inlet flow velocity and inlet pressure.

[0021] Furthermore, the specific operating parameters of the hydrocyclone are set according to the on-site operating conditions, namely: processing flow rate: 1% to 10% of the influent flow rate; inlet velocity: 5 to 12 m / s; inlet pressure: 50 to 200 kPa.

[0022] The operating principle of the functional bacteria sieve is as follows:

[0023] Sludge from the sludge storage tank is pumped into a hydrocyclone. The sludge is fed into the hydrocyclone column through a transverse inlet; this portion is the feed sludge (FS). Within the column, the sludge is subjected to high-speed centrifugal force and shear force, causing the already aggregated, denser functional bacteria (such as denitrifying bacteria and polyphosphate-accumulating bacteria), and inert substances to be thrown towards the outer wall. Under gravity, they naturally settle to the bottom outlet and exit. Simultaneously, sludge that has lost its activity and viscosity is broken up by high-speed centrifugal force and shear force and enters the bottom outlet as well. This portion is the US, which has good dewatering performance. The broken sludge serves as an internal carbon source, supplementing the system and enhancing denitrification while simultaneously reducing in-situ sludge volume. Sludge with lower density and higher viscosity (such as nitrifying bacteria) flows upwards from the overflow outlet under the influence of the central vortex; this portion is the OS, which has poorer dewatering performance.

[0024] The principle of this invention is as follows:

[0025] The first denitrification and phosphorus removal system, with its longer designed SRT (Solution Time Retention), is conducive to the enrichment and cultivation of nitrifying bacteria with longer generation times. Therefore, under the enhanced effect of the functional bacteria separator, the OS (Organic Substance) rich in nitrifying bacteria is returned to the first denitrification and phosphorus removal system, further increasing the proportion of nitrifying bacteria in the system. The second denitrification and phosphorus removal system, with its shorter designed SRT, is conducive to the enrichment and cultivation of denitrifying and polyphosphate-accumulating bacteria. Under the enhanced effect of the functional bacteria separator, the US (Underlying Substance) rich in denitrifying and polyphosphate-accumulating bacteria is returned to the second denitrification and phosphorus removal system, further increasing the proportion of denitrifying and polyphosphate-accumulating bacteria in the system. This also improves the settling performance of activated sludge and the denitrification and phosphorus removal capacity. Even with in-situ expansion during the dry season and excessive expansion during the rainy season, 40% of the wastewater still enters the first denitrification and phosphorus removal system to ensure the activity of nitrifying bacteria, while the remaining wastewater enters the second denitrification and phosphorus removal system. Utilizing the rapid settling characteristics of denitrifying and polyphosphate-accumulating bacteria, the system can accept 80% to 160% of the original design wastewater volume. To prevent a significant increase in water volume from reducing the HRT (Heat Reduction Time) of the aerobic tank and weakening the nitrification performance of the system, an intelligent automatic control module is installed to monitor changes in the dinitrification performance of the nitrogen and phosphorus removal system in real time. Before any nitrification risk occurs, the OS (Organic Substance) from the functional bacteria separator is added to the nitrogen and phosphorus removal system, supplementing the nitrifying bacteria in the system and improving its nitrification performance to ensure the overall nitrogen and phosphorus removal capacity of the system. This process is compact, easy to operate, simple in construction, flexible in control, and occupies a small area. By combining the strengths of both solid-liquid separation technologies, it amplifies the advantages of the AAO (Aerobic-Oxygen-Alternating Current) process, ensuring in-situ expansion of the system during the dry season and handling excessive expansion during the rainy season, while maintaining efficient simultaneous nitrogen and phosphorus removal.

[0026] The beneficial effects of this invention are:

[0027] 1. A combined nitrogen and phosphorus removal system is adopted to form a targeted enrichment and screening strategy for functional microbial communities and a targeted reflux strategy. By setting the SRT and the operating conditions of the functional microbial screening device, the advantages of the AAO process based on precipitation and membrane separation technology are amplified, and the corresponding functional microbial communities are flexibly refluxed to meet different actual expansion needs;

[0028] 2. By controlling the inlet flow rate, inlet velocity, and inlet pressure of the hydrocyclone, the sludge crushing and cell dissolution are enhanced on the basis of a general hydrocyclone, which is conducive to improving dewatering performance, realizing in-situ sludge reduction, and releasing soluble COD to replenish the carbon source in the system with the return flow. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the hydrocyclone of the present invention;

[0030] Figure 2 This is a schematic diagram illustrating the principle of the process of the present invention;

[0031] Figure 3 This is a schematic diagram illustrating the change in the settling velocity of activated sludge under the application of this invention;

[0032] Figure 4 This is a schematic diagram illustrating the enrichment capacity of the functional bacterial sieving module for nitrifying bacteria in the application of this invention.

[0033] Figure 5 This is a schematic diagram illustrating the enrichment capacity of the functional bacterial sieving module for denitrifying bacteria in the application of this invention.

[0034] Figure 6 This is a schematic diagram illustrating the enrichment capacity of the functional bacterial screening module for polyphosphate-accumulating bacteria in the application of this invention.

[0035] Figure 7 This is a schematic diagram illustrating the changes in the nitrification, denitrification, and phosphorus release performance of activated sludge under the application of this invention;

[0036] Figure 8 This is a schematic diagram showing the changes in capillary water absorption time and viscosity of activated sludge under the application of this invention;

[0037] Figure 9 This is a schematic diagram illustrating the release of soluble COD from activated sludge under the functional bacteria screening module in the application of this invention.

[0038] Figure 10 This is a schematic diagram illustrating the change in apparent sludge yield of activated sludge under the application of the present invention.

[0039] Figure 11 This is a schematic diagram of the process operation mode of the present invention during the rainy season. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Example 1: As Figure 2 As shown: A short-process combined nitrogen and phosphorus removal process for in-situ expansion of wastewater treatment plant. The system used in this process includes an influent diversion system, a nitrogen and phosphorus removal system one, a nitrogen and phosphorus removal system two, and an intelligent automatic control module.

[0042] The water inlet and outlet diversion system includes a water distribution well, a water distribution gate, and diversion pipelines;

[0043] The intelligent automatic control module includes a flow meter detector, a PLC control cabinet, a sludge concentration detector, and a nitrification performance detector;

[0044] The denitrification and phosphorus removal system includes an anaerobic tank, an anoxic tank, an aerobic tank, a membrane separation component, an internal return pipeline, an external return pipeline, a functional bacteria screener, and a sludge storage tank. The anaerobic tank, anoxic tank, and aerobic tank are connected in sequence. The membrane separation component is installed at the tail end of the aerobic tank and includes an effluent pump set and a membrane cleaning component. The sludge storage tank is connected to the aerobic tank and the functional bacteria screener. The functional bacteria screener includes a US pipeline, an OS pipeline, and an OSE pipeline. The US pipeline is directly connected to the sludge treatment unit, the OS pipeline is connected to the external return pipeline, and the OSE pipeline is connected to the external return pipeline.

[0045] The nitrogen and phosphorus removal system 2 includes an anaerobic tank 2, an anoxic tank 2, an aerobic tank 2, a secondary sedimentation tank, an internal return pipeline 2, an external return pipeline 2, a functional bacteria screener 1, and a sludge storage tank 1. The anaerobic tank 2, anoxic tank 2, aerobic tank 2, and secondary sedimentation tank are connected in sequence. The sludge storage tank 2 is connected to the aerobic tank 2 and the functional bacteria screener 2. The functional bacteria screener 2 includes a US pipeline 2 and an OS pipeline 2. The US pipeline 2 is directly connected to the external return pipeline 2, and the OS pipeline 2 is directly connected to the sludge treatment unit.

[0046] The process specifically includes the following steps:

[0047] Step (1): Raw water enters the denitrification and phosphorus removal system 1 and denitrification and phosphorus removal system 2 respectively at 40% and 60% through the inlet diversion system;

[0048] Step (2): 40% of the raw water flow rate enters the anaerobic tank 1, anoxic tank 1, and aerobic tank 1 of the denitrification and phosphorus removal system 1 sequentially. The sludge leaves the system through the membrane separation unit. Sludge from aerobic tank 1 is pumped into sludge storage tank 1 at 100%–110% of the influent flow rate. Sludge from sludge storage tank 1 is then pumped into functional bacteria screen 1 at 1%–10% of the influent flow rate. Through a specific hydrocyclone and its supporting components, US and OS are generated. OS enriches nitrifying bacteria, while US is discharged from the system as excess sludge, with a SRT of 15–30. The operating time of the functional bacteria screener 1 is controlled by the intelligent automatic control module, which monitors it in real time. When the US sludge discharge meets the above SRT, the operation of the functional bacteria screener 1 is stopped. During normal operation, the OS generated is all sent to the external return pipeline 1 through OS pipeline 1 to replenish the sludge concentration and nitrifying bacteria. The US is discharged as excess sludge through US pipeline 1. OS pipeline 1 is also directly connected to the OSE pipeline and the external return pipeline 2. The flow direction of OS is selected according to the real-time monitoring of the dinitrification performance of the denitrification and phosphorus removal system by the intelligent automatic control module.

[0049] Step (3): 60% of the raw water flow rate enters the anaerobic tank 2, anoxic tank 2 and aerobic tank 2 of the denitrification and phosphorus removal system 2 in sequence. After solid-liquid separation in the secondary sedimentation tank, it leaves the system. The sludge in aerobic tank 2 is pumped into sludge storage tank 2 at 100% to 110% of the influent flow rate. The sludge in sludge storage tank 2 is pumped into functional bacteria screen 2 at 1% to 10% of the influent flow rate. Through a specific hydrocyclone and its supporting components, US and OS are generated. US is enriched with polyphosphate-accumulating bacteria and denitrifying bacteria. OS is discharged from the system as excess sludge. The operating time of functional bacteria screen 2 is controlled according to SRT of 8 to 12 days. The intelligent automatic control module monitors in real time. After the OS sludge discharge meets the above SRT, functional bacteria screen 2 stops operating. All US generated during the operation enters external return pipeline 2 to replenish sludge concentration and polyphosphate-accumulating and denitrifying bacteria.

[0050] The first nitrogen and phosphorus removal system is designed with an HRT of 6–8 hours, an SRT of 15–30 days, and an MLSS of 8–12 g / L; the second nitrogen and phosphorus removal system is designed with an HRT of 8–12 hours, an SRT of 8–12 days, and an MLSS of 4–6 g / L. The first and second functional bacteria sieves are integrated into a container assembly for easy transportation and management. The hydrocyclone includes a column, a cone, an inlet, an overflow outlet, and an underflow outlet, as shown below. Figure 1 As shown, the diameter D of the column is between 50 and 120 mm, and the height-to-diameter ratio L1 / D is 1; the height-to-diameter ratio L2 / D of the cone is 2 to 6, and the cone angle is 8 to 16°; the feed inlet has a cuboid shape, the ratio of the inlet area S to the square of the column diameter D is 0.067, and the feed inlet enters the column tangentially; the overflow port is partially embedded in the column, and the length of the embedded part is L. vThe diameter D of the column is 0.14, and the remaining part of the overflow port protrudes from the column, with a protrusion length L. o The diameter D of the column is 0.57, and the diameter D of the overflow outlet is... o The diameter D of the column is 0.4 to 0.6; the underflow outlet is connected to the conical inlet, and the length L of the underflow outlet is... u The diameter D of the column is 0.57, and the diameter of the bottom outlet is D. u The column diameter D is 0.2–0.3 mm. The functional bacteria screener one and functional bacteria screener two control the screening effect of functional bacteria and the system's sludge discharge rate by adjusting the operating parameters of the hydrocyclone, including the treatment flow rate, inlet velocity, and inlet pressure. The specific operating parameters of the hydrocyclone are set according to the on-site operating conditions: treatment flow rate: 1%–10% of the influent flow rate; inlet velocity: 5–12 m / s; inlet pressure: 50–200 kPa.

[0051] After long-term cyclone treatment, the sludge settling velocity of the nitrogen and phosphorus removal system can be gradually increased from 1 m / h to a maximum of 4 m / h. Figure 3 As shown, this significantly improves sludge settling performance, enhances solid-liquid separation in the secondary sedimentation tank, and thus improves the wastewater treatment plant's ability to cope with high water volume loads.

[0052] The functional microbial sieve effectively sieves functional microbial communities based on differences in density and viscosity. This sieve can effectively increase the bioactivity of nitrifying bacteria in the nitrogen and phosphorus removal system by 29.1% (e.g., ...). Figure 4 (As shown); the functional bacterial sieve effectively increased the bioactivity of denitrifying bacteria and polyphosphate-accumulating bacteria in the denitrification and phosphorus removal system by 24.3% and 15.6%, respectively (e.g., as shown). Figure 5 , 6 (As shown).

[0053] After long-term cyclone treatment, the nitrification, denitrification, and phosphorus release performance of the nitrogen and phosphorus removal system gradually improves (e.g., Figure 7 (As shown).

[0054] After cyclone treatment, the capillary absorption time (CST) of US can be reduced by 17.8%, and the viscosity can be reduced by 18.6% (e.g., Figure 8 As shown in the figure, the denitrification and phosphorus removal system uses US as the residual sludge, which directly improves the dewatering performance of the residual sludge in the system and reduces the cost of sludge treatment and disposal.

[0055] The hydraulic shearing and collision processes generated in the hydrocyclone will break down the activated sludge cells, releasing 25% of the dissolved COD (e.g., ...). Figure 9 As shown), it is returned to the anaerobic tank as an internal carbon source to compensate for the insufficient carbon source in the biological tank, while simultaneously achieving a 50% in-situ sludge reduction in the system (e.g. Figure 10 (As shown).

[0056] Example 2: As Figure 11 As shown: A short-process combined nitrogen and phosphorus removal process for in-situ expansion of wastewater treatment plants. This process, compared to Example 1, is characterized by the following features:

[0057] Maintain the hydraulic load of the denitrification and phosphorus removal system one and continue to operate in the manner of step (2) to maintain a high biomass and high activity level of nitrifying bacteria. In the denitrification and phosphorus removal system two, the in-situ expansion water volume and excess rainwater are directly discharged into the denitrification and phosphorus removal system two. By utilizing the characteristics of rapid settling of the cultivated and enriched denitrifying and polyphosphate-accumulating bacteria, the system's design treatment flow rate can be increased by 20% to 100%. In order to prevent the impact of the reduction of HRT in the aerobic tank on the nitrification performance, the changes in the nitrification performance of the denitrification and phosphorus removal system two are monitored in real time through the intelligent automatic control module. Before the nitrification risk occurs, the OS of the functional bacteria screener one is directly discharged to the external return pipeline two, that is, a large number of nitrifying bacteria are added to the denitrification and phosphorus removal system two to improve the nitrification performance of the nitrification system and ensure the overall denitrification and phosphorus removal capacity of the system.

[0058] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A short-process combined nitrogen and phosphorus removal process for in-situ expansion of wastewater treatment plants, characterized in that: The system used in this process includes an inlet water diversion system, a nitrogen and phosphorus removal system 1, a nitrogen and phosphorus removal system 2, and an intelligent automatic control module; The water inlet and outlet diversion system includes a water distribution well, a water distribution gate, and diversion pipelines; The intelligent automatic control module includes a flow meter detector, a PLC control cabinet, a sludge concentration detector, and a nitrification performance detector; The denitrification and phosphorus removal system includes an anaerobic tank, an anoxic tank, an aerobic tank, a membrane separation component, an internal return pipeline, an external return pipeline, a functional bacteria screener, and a sludge storage tank. The anaerobic tank, anoxic tank, and aerobic tank are connected in sequence. The membrane separation component is installed at the tail end of the aerobic tank and includes an effluent pump set and a membrane cleaning component. The sludge storage tank is connected to the aerobic tank and the functional bacteria screener. The functional bacteria screener includes a US pipeline, an OS pipeline, and an OSE pipeline. The US pipeline is directly connected to the sludge treatment unit, the OS pipeline is connected to the external return pipeline, and the OSE pipeline is connected to the external return pipeline. The nitrogen and phosphorus removal system two includes an anaerobic tank two, an anoxic tank two, an aerobic tank two, a secondary sedimentation tank, an internal return pipeline two, an external return pipeline two, a functional bacteria screener two, and a sludge storage tank two. The anaerobic tank two, anoxic tank two, aerobic tank two, and secondary sedimentation tank two are connected in sequence. The sludge storage tank two is connected to the aerobic tank two and the functional bacteria screener two. The functional bacteria screener two includes a US pipeline two and an OS pipeline two. The US pipeline two is directly connected to the external return pipeline two, and the OS pipeline two is directly connected to the sludge treatment unit. The process specifically includes the following steps: Step (1): Raw water enters the denitrification and phosphorus removal system I and the denitrification and phosphorus removal system II respectively at 40% and 60% through the inlet diversion system; Step (2): 40% of the raw water flow rate sequentially enters the anaerobic tank 1, anoxic tank 1, and aerobic tank 1 of the denitrification and phosphorus removal system 1. It leaves the system through a membrane separation unit. Sludge from aerobic tank 1 is pumped into sludge storage tank 1 at 100% to 110% of the influent flow rate. Sludge from sludge storage tank 1 is then pumped into functional bacteria separator 1 at 1% to 10% of the influent flow rate. A hydrocyclone generates US and OS, where OS enriches nitrifying bacteria, and US is discharged from the system as excess sludge, with a SRT of 15 to 30. The operating time of the functional bacteria screener 1 is controlled by the intelligent automatic control module, which monitors it in real time. When the US sludge discharge meets the above SRT, the operation of the functional bacteria screener 1 is stopped. During normal operation, the OS generated is all sent to the external return pipeline 1 through OS pipeline 1 to replenish the sludge concentration and nitrifying bacteria. The US is discharged as excess sludge through US pipeline 1. OS pipeline 1 is also directly connected to the OSE pipeline and the external return pipeline 2. The flow direction of OS is selected according to the real-time monitoring of the dinitrification performance of the denitrification and phosphorus removal system by the intelligent automatic control module. Step (3): 60% of the raw water flow rate enters the anaerobic tank 2, anoxic tank 2 and aerobic tank 2 of the denitrification and phosphorus removal system 2 in sequence. After solid-liquid separation in the secondary sedimentation tank, it leaves the system. The sludge in aerobic tank 2 is pumped into sludge storage tank 2 at 100% to 110% of the influent flow rate. The sludge in sludge storage tank 2 is pumped into functional bacteria screen 2 at 1% to 10% of the influent flow rate. Through the hydrocyclone, US and OS are generated. US is rich in polyphosphate-accumulating bacteria and denitrifying bacteria. OS is discharged from the system as excess sludge. The operating time of functional bacteria screen 2 is controlled according to SRT of 8 to 12 days. The operation of functional bacteria screen 2 is monitored in real time by the intelligent automatic control module. After the OS discharge meets the above SRT, functional bacteria screen 2 stops operating. All US generated during the operation enters external return pipeline 2 to replenish sludge concentration and polyphosphate and denitrifying bacteria. The hydrocyclone comprises a column, a cone, an inlet, an overflow outlet, and an underflow outlet. The column has a diameter D between 50 and 120 mm and a height-to-diameter ratio L1 / D of 1. The cone has a height-to-diameter ratio L2 / D of 2 to 6 and a cone angle of 8 to 16°. The inlet is a cuboid with an inlet area S in ratio to the square of the column diameter D of 0.067, and the inlet enters the column tangentially. The overflow outlet is partially embedded in the column, with an embedded portion length L. v The diameter D of the column is 0.14, and the remaining part of the overflow port protrudes from the column, with a protrusion length L. o The diameter D of the column is 0.57, and the diameter D of the overflow outlet is... o The diameter D of the column is 0.4 ~ 0.6; the underflow outlet is connected to the conical inlet, and the length L of the underflow outlet is... u The diameter D of the column is 0.57, and the diameter of the bottom outlet is D. u The diameter D of the cylinder is 0.2 ~ 0.3; The functional bacteria screener one and functional bacteria screener two control the screening effect of functional bacteria and the sludge discharge of the system by adjusting the operating parameters of the hydrocyclone, such as the processing flow rate, inlet flow velocity and inlet pressure. The hydrocyclone is configured to handle a flow rate of 1% to 10% of the influent flow rate; an inlet velocity of 5 to 12 m / s; and an inlet pressure of 50 to 200 kPa.

2. The short-process combined nitrogen and phosphorus removal process for in-situ expansion of wastewater treatment plants according to claim 1, characterized in that: The first denitrification and phosphorus removal system is designed with an HRT of 6-8 h, an SRT of 15-30 d, and an MLSS of 8-12 g / L; the second denitrification and phosphorus removal system is designed with an HRT of 8-12 h, an SRT of 8-12 d, and an MLSS of 4-6 g / L.

3. The short-process combined nitrogen and phosphorus removal process for in-situ expansion of wastewater treatment plants according to claim 2, characterized in that: The functional bacteria sieve one and functional bacteria sieve two are integrated container-type assemblies.

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