A method for simultaneous capture of carbon and phosphorus from sewage

Abstract

This invention relates to a method for the simultaneous capture of carbon and phosphorus in wastewater. It addresses the problems of high aeration energy consumption, long hydraulic retention time, low phosphorus removal rate, and high carbon, ammonia, and phosphorus levels in existing wastewater treatment processes. The method utilizes the aerobic phosphorus absorption characteristics of microorganisms, employing tightly bound EPS (extracellular polymeric substances) to rapidly store and release phosphorus, capturing it in the sludge phase. This simultaneously and rapidly reduces COD and total phosphorus in the wastewater to low levels, achieving a COD removal rate of over 70%. Furthermore, the proportion of carbon captured and converted into the sludge phase reaches 30%–37%, while the proportion of organic matter oxidized to CO2 is only 22%–31%, resulting in an effective phosphorus capture rate of 70%–75%, achieving highly efficient capture and removal of both phosphorus and organic matter. Simultaneously, for effluent treatment with irrigation potential, the method achieves phosphorus capture ratio control based on efficient carbon capture, thereby obtaining effluent with low COD concentration and dynamically adjustable nitrogen-to-phosphorus ratio to meet target irrigation needs.

Description

Technical Field

[0001] This invention relates to a method for capturing carbon and phosphorus in wastewater. Background Technology

[0002] Urban wastewater treatment plants are crucial infrastructure for protecting urban water environments and ensuring water resource security, playing a significant role in pollutant reduction. Currently, the mainstream urban wastewater treatment technologies both domestically and internationally are still improved biological treatment processes based on the traditional activated sludge process. The processes used in my country's wastewater treatment plants are mainly the traditional activated sludge process and aerobic biological treatment processes developed from it, such as oxidation ditches, A / O processes, and A... 2 The main processes used in urban wastewater treatment are the O / O process and the SBR process. The processes employed in urban wastewater treatment are closely related to wastewater quality and effluent discharge standards. With the increasing stringency of effluent standards, urban wastewater treatment in my country faces challenges such as complex influent water quality characteristics, significant discrepancies between process design and actual operating load, and increased equipment maintenance costs. Wastewater treatment is a relatively energy-intensive industry; compared to the average power consumption of 0.2 kW•h / m³ in US wastewater treatment plants... 3 The average energy consumption of wastewater treatment plants in my country is approximately 0.29 kW•h / m³. 3 In my country, the construction and operation of wastewater treatment plants still primarily focus on ensuring effluent quality, continuing the traditional model of "exchanging energy and chemical inputs for pollutant removal." However, with the increasing stringency of wastewater discharge standards, the excessive energy consumption in wastewater treatment processes will be further exacerbated. The current activated sludge process, based on A... 2 / O-based urban wastewater treatment processes consume large amounts of energy to achieve high emission standards, resulting in high energy consumption and large greenhouse gas emissions from existing wastewater treatment technologies, which do not fully meet the requirements of sustainable development.

[0003] To achieve sustainable development in the wastewater treatment industry, the concepts of "energy self-sufficiency" and "carbon neutrality" have gradually become hot topics. Simultaneously, the concept of upgrading wastewater treatment plants into "resource and energy factories" is gradually taking shape. The abundant resource components in wastewater, such as organic matter, nutrients, and heat energy, provide the foundation for realizing this concept. COD is the preferred indicator for characterizing the organic matter content in wastewater; urban wastewater with a COD of 500 mg / L contains as much as 1.93 kWh / m³ of organic chemical energy. 3The energy consumption for treating wastewater is more than six times that of wastewater treatment. Effective extraction and recovery of energy from wastewater can fully realize low-carbon operation of wastewater treatment plants, and even achieve energy self-sufficiency. Furthermore, wastewater also contains considerable phosphorus resources; recovering phosphorus for use in phosphate fertilizer production will save a significant amount of phosphate rock consumption. Therefore, exploring how to achieve efficient and simultaneous separation and utilization of carbon and phosphorus in urban wastewater while meeting discharge standards is of great research significance, and the extraction and recovery of resources from wastewater has become a hot topic in environmental research. To promote the sustainable development of China's wastewater treatment industry, developing innovative technologies for the future-oriented resource and energy recovery of wastewater is crucial.

[0004] Currently, in the field of municipal wastewater treatment, the treatment of organic pollutants is mainly based on oxidation removal, while phosphorus pollutants are primarily removed through sludge removal and chemical coagulation in aerobic-anaerobic processes. This results in high aeration energy consumption and high phosphorus removal costs or complex processes in the treatment of organic matter in municipal wastewater. Therefore, there is still a need to develop carbon and phosphorus co-capture processes for municipal wastewater to reduce aeration energy consumption, phosphorus capture costs, and process complexity.

[0005] A 2 The anaerobic / anoxic (APO) process is the most common biological carbon and phosphorus removal technology for municipal wastewater. It achieves simultaneous removal of carbon and phosphorus by setting up anaerobic, anoxic, and aerobic zones in the wastewater treatment system. Its working principle is as follows: Raw wastewater first enters the anaerobic zone. In an anaerobic environment, polyphosphate-accumulating bacteria release stored phosphates and simultaneously absorb easily degradable organic matter as a carbon source, storing it as polyhydroxyalkanoates (PHAs). The mixed liquor then enters the anoxic zone, where denitrifying bacteria use organic matter in the water and stored organic matter as a carbon source to reduce nitrates returned from the aerobic zone to nitrogen gas. Finally, it enters the aerobic zone, where aerobic bacteria degrade the remaining organic carbon source, while polyphosphate-accumulating bacteria excessively absorb phosphates to achieve phosphorus removal. The entire process maintains nutrient circulation through sludge recirculation and mixed liquor recirculation, thus efficiently removing organic carbon and phosphorus. However, A 2 The / O process also has some drawbacks in removing carbon and phosphorus: First, sludge recirculation carries nitrates into the anaerobic zone, inhibiting the phosphorus release process of polyphosphate-accumulating bacteria, thus reducing phosphorus removal efficiency; second, both polyphosphate-accumulating bacteria and denitrifying bacteria require easily degradable organic matter as a carbon source, leading to fierce competition for carbon sources. If the influent carbon source is insufficient, it may affect the phosphorus removal effect; furthermore, polyphosphate-accumulating bacteria prefer short sludge ages, which limits the overall system performance. Additionally, A 2 / O still focuses on oxidation removal rather than recycling for pollutants.

[0006] Membrane separation technology is a common physicochemical method for municipal wastewater treatment, primarily removing organic carbon and phosphorus through membrane sieving, adsorption, and selective permeation mechanisms. The working principle of membrane separation technology is as follows: Raw wastewater is first pretreated before entering a membrane system such as a membrane bioreactor (MBR). In this step, organic carbon sources are degraded by microorganisms, while suspended solids, colloidal organic matter, and some phosphorus-containing particulate matter are retained by microfiltration (MF) or ultrafiltration (UF) membranes, achieving initial removal of carbon and phosphorus. Subsequently, nanofiltration (NF) or reverse osmosis (RO) membranes further block small-molecule dissolved organic carbon (such as humic acid) and ionic phosphorus (such as phosphates), enriching them in the concentrate for efficient separation. Membrane separation systems can be combined with chemical coagulation (such as aluminum salt precipitation of phosphorus) to enhance the removal effect, thereby further reducing the carbon and phosphorus concentration in the wastewater. However, membrane separation technology also has some drawbacks in carbon and phosphorus removal: First, the membrane surface is prone to fouling and clogging, leading to a sharp drop in flux and requiring frequent chemical cleaning or replacement of membrane modules, increasing operating costs; second, membrane systems have high energy consumption, especially pressure-driven membranes (such as RO membrane systems), where pumping and regeneration processes consume a large amount of energy; in addition, the initial investment in membrane system construction is expensive, including the cost of membrane materials and system equipment; finally, although the volume of the concentrated wastewater generated is small, the pollutant concentration is high, and improper treatment can cause secondary pollution, and the removal of low-concentration phosphorus relies on auxiliary chemical methods, making the overall efficiency highly susceptible to fluctuations in water quality.

[0007] Carbon capture processes, exemplified by the High-Efficiency Contact-Stabilization (HiCS) process, achieve high organic carbon capture rates by controlling low sludge age, hydraulic retention time, and alternating "fed-starved" states for the sludge. During the low-DO concentration contact stage, the HiCS process rapidly captures organic matter from wastewater. Saturated sludge is then subjected to strong aeration during the stabilization stage, returning it to a "starved" state and restoring its flocculation capacity. This "fed-starved" mechanism helps microorganisms capture organic matter more efficiently and reduces catabolism, thereby maintaining low COD oxidation levels. The HiCS process is characterized by low organic matter mineralization, high carbon-rich sludge production, and high sludge methanogenesis potential. Its application is expected to provide a solution for carbon emission reduction in urban wastewater treatment processes in my country. However, the inability to meet emission standards for effluent COD and total phosphorus is the main problem currently limiting the application of HiCS (High-Intensity Crude Oil) processes. HiCS processes produce poor effluent quality, with sludge capture rates of only 19% for total nitrogen and 30% for total phosphorus, resulting in effluent that is low in carbon, high in nitrogen, and high in phosphorus, making it difficult to meet increasingly stringent wastewater discharge standards. Although autotrophic biological nitrogen removal technologies, such as short-cut nitrification-anaerobic ammonium oxidation, can remove nitrogen from wastewater, how to simultaneously remove and recover phosphorus while removing carbon remains a problem that needs to be solved.

[0008] In summary, some existing municipal wastewater treatment processes, such as A... 2 Processes such as sludge and activated sludge do not aim at carbon and phosphorus resource recovery, resulting in significant energy consumption for aeration during organic matter oxidation and a substantial increase in retention time. Existing wastewater treatment processes aimed at resource recovery, such as carbon capture, do not achieve simultaneous carbon and phosphorus capture within biological treatment systems. Carbon capture processes primarily target organic matter in wastewater, resulting in effluent that is low in carbon, high in ammonia, and high in phosphorus. Although high-ammonia wastewater can be removed through autotrophic denitrification systems, phosphorus treatment and recovery still incur significant reagent costs, representing a major challenge for these systems.

[0009] Some wastewater containing organic carbon, ammonia nitrogen, and phosphorus, such as various relatively safe aquaculture wastewater, has the potential for resource-based irrigation, contributing to the ecological cycle of aquaculture and agriculture, and possessing significant environmental, economic, and industrial importance. However, existing aquaculture wastewater treatment technologies mostly aim to meet discharge standards and lack the ability to precisely control COD for irrigation scenarios. Traditional wastewater treatment indiscriminately removes organic matter, nitrogen, and phosphorus, wasting valuable fertilizer resources, while direct irrigation harms crop growth. If it were possible to controllably intercept pollutants in wastewater and dynamically adjust treatment parameters according to crop type, growth stage, and soil type, achieving on-demand interception, it would far surpass traditional static treatment models. Summary of the Invention

[0010] To address the problems of high aeration energy consumption, long hydraulic retention time, low phosphorus removal rate, low carbon, high ammonia, and high phosphorus in existing municipal wastewater treatment processes, as well as the waste of fertilizer resources in existing tailwater treatment, this invention proposes a method for co-capturing carbon and phosphorus in wastewater.

[0011] The carbon and phosphorus capture method for wastewater of the present invention is carried out according to the following steps: wastewater is transported to an anaerobic contact tank, the effluent from the anaerobic contact tank is transported to an aerobic stabilization tank, and the effluent from the aerobic stabilization tank is transported to a sedimentation tank; part of the sludge and effluent in the sedimentation tank are transported back to the anaerobic contact tank, and the remaining sludge and effluent in the sedimentation tank are discharged, thus completing the capture of carbon and phosphorus in the wastewater.

[0012] The beneficial effects of this invention are:

[0013] 1. The method of phosphorus removal in this invention is to use the aerobic phosphorus absorption characteristics of microorganisms to capture phosphorus into the sludge phase, create phosphorus recovery sites in wastewater, and separate it in the form of residual sludge. Phosphorus in sludge can be recovered through the anaerobic phosphorus release characteristics of microorganisms, or it can be recovered and utilized through physicochemical means.

[0014] 2. Existing HiCS processes directly connect to municipal wastewater raw water or pre-treated effluent, resulting in a large amount of organic matter remaining in the sludge. This invention further enhances this by achieving the co-capture and removal of carbon and phosphorus from wastewater. Simultaneously, leveraging the characteristic of large-scale growth of biomass in the stored sludge, the improved carbon and phosphorus removal process of this invention has a larger phosphorus reservoir. Utilizing TB-EPS for rapid phosphorus release and storage, it can effectively capture organic matter and phosphorus from municipal wastewater simultaneously into the sludge phase with an extremely short hydraulic retention time. Ammonia / carbon and phosphorus separation is achieved through sludge-water separation, resulting in effluent with low carbon, low phosphorus, and high ammonia characteristics. Based on this, it solves the problems of high aeration energy consumption and long hydraulic retention time in traditional water treatment processes for carbon and phosphorus removal. It also addresses the industry challenges of low phosphorus removal rates in carbon capture processes aimed at carbon and phosphorus recovery, and the reliance on physicochemical methods for phosphorus removal in effluent with low carbon, high ammonia, and high phosphorus content. It fundamentally solves the current problems of high decarbonization aeration energy consumption, high treatment energy consumption, large greenhouse gas emissions, large demand for phosphorus removal agents, and insufficient wastewater resource utilization in municipal wastewater treatment.

[0015] 3. This invention can simultaneously and rapidly reduce COD and total phosphorus in wastewater to a low level. Most of the ammonia nitrogen in the wastewater still exists in the form of ammonia nitrogen when it is discharged. It is suitable for subsequent coupling of physical denitrification processes (such as reverse osmosis membrane treatment, forward osmosis membrane treatment, electrodialysis, etc.), chemical treatment processes (such as zeolite bed adsorption, ion exchange resin adsorption, breakpoint chlorination oxidation, electrochemical oxidation, etc.), biological low-carbon denitrification processes (such as anaerobic ammonia oxidation, short-cut nitrification and denitrification, etc.), and ecological low-carbon denitrification processes (such as constructed wetland technology, green bed irrigation co-treatment technology, bacterial and algal denitrification technology, etc.).

[0016] 4. This invention can achieve a COD removal rate of over 70%. On this basis, the carbon capture rate can reach 30%~37%, the proportion of organic matter oxidized to CO2 is only 22%~31%, and the phosphorus capture rate is 70%~75%, thus achieving efficient capture and removal of phosphorus and organic matter.

[0017] 5. The residual sludge obtained by this invention can be further utilized for the resource recovery of carbon and phosphorus in wastewater through combustion, methanogenesis, recovery of polyhydroxy fatty acids (PHA), and sludge dephosphorization. Furthermore, in the carbon and phosphorus capture process of this invention, organic matter is largely captured by microorganisms rather than oxidized into carbon dioxide, resulting in a relatively low oxidation rate. Simultaneously, optimized aeration time reduces the oxidation rate of organic pollutants in the influent, achieving control over the oxidation rate of organic matter and effectively reducing the generation of greenhouse gases (carbon dioxide) during pollutant oxidation.

[0018] 6. The treatment method and apparatus of this invention have the advantages of simple processing technology, low aeration energy consumption, and high resource retention rate. They can be modified based on existing facilities and combined with various enhancement measures to improve efficiency. The process of this invention has a wide range of applications. The reactor of the carbon and phosphorus capture system for municipal sewage can be directly modified from the existing aerobic tank of the sewage treatment plant, replacing the original aerobic system and facilitating widespread implementation. At the same time, this process will save a significant amount of aeration costs required for carbon oxidation, reagent costs for phosphorus removal, and tank volume required for long hydraulic retention times. The saved tank volume can be used for wastewater conditioning or to build an autotrophic denitrification system.

[0019] 7. This invention can achieve controllable COD retention and dynamic adjustment of nitrogen and phosphorus retention ratio. The nitrogen and phosphorus retention ratio is achieved by the hydraulic retention time of the aerobic stabilization tank, matching the nitrogen and phosphorus nutrient requirements of different planting and irrigation. It is suitable for crops with high nitrogen requirements such as forage grass and leafy vegetables, or crops with different phosphorus requirements at different growth stages. It solves the problem of existing technologies being unable to adjust water and fertilizer as needed and the waste of fertilizer resources in wastewater treatment. Attached Figure Description

[0020] Figure 1 For the existing HiCS (High-Contact Stabilized System) process flow diagram;

[0021] Figure 2 This is a process flow diagram of the carbon and phosphorus co-capture process (HiCS-CP) for wastewater in Example 1;

[0022] Figure 3 This is a comparison chart of the effluent quality and COD index of conventional AAO and the effluent quality of carbon and phosphorus from the capture process.

[0023] Figure 4 A comparison chart of sludge COD removal load (F / M value) between conventional AAO and carbon-phosphorus capture processes;

[0024] Figure 5 This is a chart showing the fate of organic carbon in conventional AAO and carbon-phosphorus co-capture processes.

[0025] Figure 6 The graph shows the changes in phosphorus concentration in the effluent from the conventional AAO and Example 1 carbon and phosphorus capture processes.

[0026] Figure 7 The phosphorus removal load diagram is shown for conventional AAO and carbon-phosphorus co-capture processes.

[0027] Figure 8 This graph shows the changes in the system phosphorus uptake and re-release capacity of conventional AAO and carbon-phosphorus co-capture processes within a single cycle.

[0028] Figure 9 This is a distribution diagram of phosphorus among different components in sludge at different times in a single cycle during a conventional AAO process.

[0029] Figure 10 This is a distribution diagram of phosphorus among different components in sludge at different times in a single cycle during the carbon-phosphorus co-capture process.

[0030] Figure 11 This is a process flow diagram of the carbon and phosphorus co-capture process (HiCS-CP) for wastewater in Example 2;

[0031] Figure 12 This is a graph showing the phosphorus capture rate of the high-concentration tailwater from the aquaculture farm in Example 2 under different hydraulic retention times in the aerobic tank. Detailed Implementation

[0032] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any reasonable combination of the specific embodiments.

[0033] Specific Implementation Method 1: The carbon and phosphorus capture method for wastewater in this implementation method is carried out according to the following steps: wastewater is transported to an anaerobic contact tank, the effluent from the anaerobic contact tank is transported to an aerobic stabilization tank, and the effluent from the aerobic stabilization tank is transported to a sedimentation tank; part of the sludge and effluent in the sedimentation tank are transported back to the anaerobic contact tank, and the remaining sludge and effluent in the sedimentation tank are discharged, thus completing the capture of carbon and phosphorus in the wastewater.

[0034] This embodiment has the following beneficial effects:

[0035] 1. The phosphorus removal method in this embodiment is to use the aerobic phosphorus absorption characteristics of microorganisms to capture phosphorus into the sludge phase, create phosphorus recovery sites in wastewater, and separate it in the form of residual sludge. Phosphorus in sludge can be recovered through the anaerobic phosphorus release characteristics of microorganisms, or it can be recovered and utilized through physicochemical means.

[0036] 2. Existing HiCS processes directly connect to municipal wastewater raw water or pre-treated effluent, resulting in a large amount of organic matter remaining in the sludge. This invention further enhances this by achieving the co-capture and removal of carbon and phosphorus from wastewater. Simultaneously, leveraging the characteristic of large-scale growth of biomass in the stored sludge, the improved carbon and phosphorus removal process in this embodiment has a larger phosphorus reservoir. Utilizing TB-EPS for rapid phosphorus release and storage, it can effectively capture organic matter and phosphorus from municipal wastewater simultaneously into the sludge phase with an extremely short hydraulic retention time. Ammonia / carbon and phosphorus separation is achieved through sludge-water separation, resulting in effluent with low carbon, low phosphorus, and high ammonia characteristics. Based on this, it solves the problems of high aeration energy consumption and long hydraulic retention time in traditional water treatment processes for carbon and phosphorus removal. It also addresses the industry challenges of low phosphorus removal rates in carbon capture processes aimed at carbon and phosphorus recovery, and the reliance on physicochemical methods for phosphorus removal in effluent with low carbon, high ammonia, and high phosphorus content. It fundamentally solves the current problems of high decarbonization aeration energy consumption, high treatment energy consumption, large greenhouse gas emissions, large demand for phosphorus removal agents, and insufficient wastewater resource utilization in municipal wastewater treatment.

[0037] 3. This implementation method can simultaneously and rapidly reduce COD and total phosphorus in wastewater to a low level. Most of the ammonia nitrogen in the wastewater still exists in the form of ammonia nitrogen in the effluent. It is suitable for subsequent coupling of physical denitrification processes (such as reverse osmosis membrane treatment process, forward osmosis membrane treatment process, electrodialysis process, etc.), chemical treatment processes (such as zeolite bed adsorption, ion exchange resin adsorption, breakpoint chlorination oxidation, electrochemical oxidation, etc.), biological low-carbon denitrification processes (such as anaerobic ammonia oxidation, short-cut nitrification and denitrification, etc.), and ecological low-carbon denitrification processes (such as constructed wetland technology, green bed irrigation co-treatment technology, bacterial and algal denitrification technology, etc.).

[0038] 4. This implementation method can achieve a COD removal rate of over 70%. On this basis, the carbon capture rate can reach 30%~37%, the proportion of organic matter oxidized to CO2 is only 22%~31%, and the phosphorus capture rate is 70%~75%, thus achieving efficient capture and removal of phosphorus and organic matter.

[0039] 5. The residual sludge obtained in this embodiment can be further utilized for the resource recovery of carbon and phosphorus in wastewater through combustion, methanogenesis, recovery of polyhydroxy fatty acids (PHA), and sludge dephosphorization. Furthermore, in this embodiment, organic matter in the carbon and phosphorus capture process is largely captured by microorganisms rather than oxidized into carbon dioxide, resulting in a relatively low oxidation rate. Simultaneously, optimizing the aeration time reduces the oxidation rate of organic pollutants in the influent, achieving control over the oxidation rate of organic matter and effectively reducing the generation of greenhouse gases (carbon dioxide) during pollutant oxidation.

[0040] 6. The treatment method and apparatus of this embodiment have the advantages of simple treatment process, low aeration energy consumption, and high resource retention rate. It can be modified based on existing facilities and combined with various enhancement measures to improve efficiency. The process of this embodiment has a wide range of applications. The reactor of the carbon and phosphorus capture system for municipal sewage can be directly modified from the existing aerobic tank of the sewage treatment plant, replacing the original aerobic system and facilitating widespread implementation. At the same time, this process will save a significant amount of aeration costs required for carbon oxidation, reagent costs for phosphorus removal, and tank volume required for long hydraulic retention times. The saved tank volume can be used for wastewater conditioning or to build an autotrophic denitrification system.

[0041] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that a mechanical stirring device is installed inside the anaerobic contact tank.

[0042] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 2 in that the mechanical stirring device is an internal circulating water pump, a jet mixer, or a pipeline mixer.

[0043] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the hydraulic retention time in the anaerobic contact tank is 10-30 minutes and the dissolved oxygen concentration is 0-0.5 mg / L.

[0044] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: an aeration device is provided in the aerobic stabilization tank.

[0045] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the dissolved oxygen concentration in the aerobic stabilization tank is ≥ 1.5 mg / L, the oxidation-reduction potential is > +200 mV, and the hydraulic retention time is 1.0~2 h.

[0046] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the sedimentation tank is an inclined plate sedimentation tank, an inclined tube sedimentation tank, or a vertical flow sedimentator.

[0047] Specific Implementation Method Eight: This implementation method differs from one of Specific Implementation Methods One to Seven in that the total volume of sludge and wastewater returned from the sedimentation tank to the anaerobic contact tank is in the ratio of 1 to 2:1 to the volume of the influent to the sedimentation tank.

[0048] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the volume ratio of the excess sludge to the return sludge from the sedimentation tank to the anaerobic contact tank is 1:2~50.

[0049] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Method One in that: wastewater is transported to an anaerobic contact tank, the effluent from the anaerobic contact tank is transported to an aerobic stabilization tank, and the effluent from the aerobic stabilization tank is transported to a sedimentation tank; part of the sludge and effluent in the sedimentation tank are transported to a second aerobic stabilization tank, and after aeration treatment in the second aerobic stabilization tank, the sludge and effluent are transported to the anaerobic contact tank; the remaining sludge and effluent in the sedimentation tank are discharged, completing the capture of carbon and phosphorus in the wastewater; the hydraulic retention time of the aerobic stabilization tank is 1~40 min, and the total hydraulic retention time of the aerobic stabilization tank and the second aerobic stabilization tank is 1.0~2.0 h; the hydraulic retention time in the anaerobic contact tank is 10~40 min.

[0050] In this embodiment, the hydraulic retention time in the anaerobic contact tank is 10-40 min, which can adjust the carbon capture ratio and control the COD concentration in the effluent, thus achieving the standard control of organic matter concentration. When the influent COD is 200-400 mg / L, the proportion of organic pollutants in the effluent is 35%-45%, with 20 min being the optimal time for effluent quality, achieving the best COD capture rate, COD removal rate of 55-65%, total phosphorus removal rate of 30-70%, and ammonia nitrogen removal rate of 5-15%. This achieves the retention of most of the ammonia, a large proportion of COD removal, and controllable phosphorus regulation, ensuring that the effluent quality meets irrigation requirements.

[0051] This invention enables controllable COD retention and dynamic adjustment of the nitrogen and phosphorus retention ratio. The nitrogen and phosphorus retention ratio is achieved through the hydraulic retention time of the aerobic stabilization tank, matching the nitrogen and phosphorus nutrient requirements of different planting and irrigation methods. It is suitable for crops with high nitrogen requirements, such as forage grass and leafy vegetables, or crops with different phosphorus requirements at different growth stages. This invention solves the problem of existing technologies being unable to adjust water and fertilizer as needed and the waste of fertilizer resources in wastewater treatment.

[0052] Example 1

[0053] Example 1 was used to verify the carbon and phosphorus co-capture process (abbreviated as HiCS-CP) of the present invention in terms of carbon and phosphorus co-capture efficiency and mechanism, and compared with the traditional activated sludge process (AAO). The specific parameters are shown in Table 1.

[0054] Table 1. Comparison of operating times between carbon and phosphorus capture processes and AAO processes.

[0055] reactor Anaerobic / Contact Section hypoxia section Aerobic / Stable Section Sludge removal strategy Single cycle duration AAO HRT: 60min HRT: 80 min; DO: 0.2-0.5 mg / L HRT: 180 min DO: 2.0-3.0 mg / L Sludge settling at the end of the aerobic stage for 40 minutes 360min HiCS-CP HRT: 20 min DO: 0.5 mg / L HRT: 60 min DO: 2.0-3.0 mg / L Sludge settling at the end of the stabilization phase for 40 minutes 120min

[0056] The carbon and phosphorus capture method for wastewater in Example 1 is carried out according to the following steps: wastewater is transported to an anaerobic contact tank, the effluent from the anaerobic contact tank is transported to an aerobic stabilization tank, and the effluent from the aerobic stabilization tank is transported to a sedimentation tank; some sludge and effluent in the sedimentation tank are transported back to the anaerobic contact tank, and the remaining sludge and effluent in the sedimentation tank are discharged, thus completing the capture of carbon and phosphorus in the wastewater.

[0057] The anaerobic contact tank is equipped with a mechanical stirring device, which is a jet mixer. The hydraulic retention time in the anaerobic contact tank is 20 min, and the dissolved oxygen concentration is 0.5 mg / L. In the anaerobic contact tank, the wastewater to be treated is uniformly mixed with the returned sludge and wastewater from the sedimentation tank. The function of the anaerobic contact tank is to screen microorganisms, inhibit sludge bulking, and capture organic matter. The anaerobic contact tank has the function of forming an anaerobic reaction zone and receiving influent to form a saturated reaction zone. The anaerobic contact tank and the subsequent aerobic stabilization tank form an alternating anaerobic-aerobic environmental stress, allowing the sludge to continuously pass through the anaerobic-aerobic environmental stress in the cycle, thereby screening microorganisms. The screened microorganisms have the function of resisting sludge bulking and capturing organic matter. Organic matter is captured by the sludge into the cells of the sludge floc, the extracellular adsorbate of the sludge, or the extracellular secretions of the sludge, thereby reducing the dissolved COD in the water. The sludge metabolizes organic matter and consumes dissolved oxygen under high sludge activity, producing an anaerobic environment. Unlike the HiCS process, the carbon and phosphorus co-capture method in this embodiment enhances the adsorption and storage pathway. Loosely bound extracellular polymeric substances (LB-EPS) in sludge serve as migration channels, while tightly bound extracellular polymeric substances (TB-EPS) become the primary phosphorus storage site. This process alters the migration and transformation pathway of traditional AAO biological phosphorus removal, which is dominated by biological oxidation and synthesis. Simultaneously, this process expands the phosphorus storage mode of sludge, transforming the intracellular storage-dominated mode dependent on phosphorus-removing bacteria into a mode dominated by rapid extracellular fixation mediated by TB-EPS, with intracellular storage as a synergistic effect. Based on this, rapid capture and stable storage of phosphorus are achieved in the carbon and phosphorus co-capture process for municipal wastewater. During the phosphorus migration process in the phosphorus removal cycle of the carbon and phosphorus co-capture process in this embodiment, polyphosphate-accumulating bacteria rapidly release phosphorus into the water within a brief 20-minute anaerobic phase, using LB-EPS as the release channel. In the first 5 minutes of the anaerobic stage, the carbon-phosphorus co-capture process mainly involves the rapid release of phosphorus from TB-EPS into the water via LB-EPS. After the concentration difference between "phosphorus in TB-EPS" and "phosphorus in sludge cells" is eliminated, phosphorus in sludge cells begins to migrate synchronously with phosphorus in TB-EPS into the aqueous phase during the 5-20 minute stage. This results in a 4.3-5.6 times increase in phosphorus migration rate and a 2.3-3.1 times increase in sludge loading compared to AAO in municipal wastewater co-capture, and successfully enriches bifunctional bacteria such as unclassified_f_Comamonadaceae, Hydrogenophaga, Acinetobacter, Acidovorax, and Candidatus Accumulibacter, which possess carbon storage and polyphosphate accumulation or EPS secretion and polyphosphate accumulation functions. These bacterial communities form an efficient interspecies metabolic network, and the high proportion (92.5-93.6%) of persistent bacterial communities and clear functional module differentiation ensure the stable operation of the system.

[0058] The aerobic stabilization tank is equipped with an aeration device. The dissolved oxygen concentration in the aerobic stabilization tank is 2.0-3.0 mg / L, the oxidation-reduction potential is >+200mV, and the hydraulic retention time is 1.0 h. Sufficient aeration in the aerobic stabilization tank meets the needs of rapid microbial proliferation. Organic matter and phosphorus in the water are captured through a synergistic mechanism of microbial proliferation, phosphorus storage in extracellular secretions, and intracellular phosphorus storage, achieving co-capture of carbon and phosphorus in the process. The function of the aerobic stabilization tank is to form an aerobic reaction zone, creating an alternating anaerobic-aerobic environmental stress with the anaerobic contact tank, allowing the sludge to continuously pass through this anaerobic-aerobic environmental stress during circulation. The aerobic stabilization tank receives wastewater after the sludge in the anaerobic contact tank has captured organic matter, creating a wastewater environment with a relatively low organic matter concentration. In the aerobic stabilization tank, organic matter is captured by sludge and placed into the cells of sludge flocs, into sludge extracellular adsorbates, or into sludge extracellular secretions, thereby reducing the dissolved COD in the water. The sludge in the aerobic stabilization tank consumes the captured organic matter, rapidly proliferates, and consumes a certain amount of dissolved oxygen under high sludge activity. Unlike the HiCs process, after entering the aerobic stage, inorganic phosphorus in the water rapidly migrates to the sludge under the action of polyphosphate-accumulating bacteria. In the first 30 minutes, phosphorus in the water rapidly migrates to EPS, especially TB-EPS. After 30 minutes of aerobic activity, the phosphorus content in the sludge continues to increase, with further phosphorus accumulation in TB-EPS, but the rate of uptake slows down. Simultaneously, phosphorus in LB-EPS further migrates to TB-EPS, reducing its concentration, and under the influence of concentration gradient, some phosphorus in TB-EPS migrates intracellularly, becoming phosphorus in the sludge cells. At the end of 60 minutes of aerobic phosphorus uptake, the phosphorus content in the sludge increases from 38.6 mg-P / g-VSS to 57.8 mg-P / g-VSS. The distribution and content of phosphorus in TB-EPS are restored to the level before anaerobic phosphorus release, which is completely different from the traditional AAO treatment process (which mainly relies on intracellular phosphorus storage to absorb and release phosphorus) and the HiCS process (which does not have significant phosphorus removal capabilities). In this embodiment, the main storage space of phosphorus in the HiCS-CP process has undergone a fundamental change, that is, phosphorus is stored in large quantities and preferentially in TB-EPS.

[0059] The sedimentation tank is an inclined plate sedimentation tank; sludge in the wastewater settles in the sedimentation tank; the total volume of sludge and wastewater returned from the sedimentation tank to the anaerobic contact tank is in a 1:1 ratio to the volume of influent to the sedimentation tank; the total volume of excess sludge discharged daily is in a 1:2 ratio to the volume of sludge returned from the sedimentation tank to the anaerobic contact tank on the same day; thus maintaining the sludge age of the system within 2.0 days. The excess sludge discharged from the sedimentation tank can enter the anaerobic treatment section for energy gas extraction or phosphorus recovery, and the effluent from the sedimentation tank can enter the autotrophic denitrification system for further nitrogen removal.

[0060] Figure 3This is a comparison chart of the effluent quality of conventional AAO and the COD index of effluent quality of carbon and phosphorus versus the capture process; Inf in the chart represents influent and Eff represents effluent. Figure 4 A comparison chart of sludge COD removal load (F / M value) between conventional AAO and carbon-phosphorus capture processes; Figure 5 This diagram shows the fate of organic carbon in conventional AAO and co-capture carbon-phosphorus processes. Experiments showed that the COD removal rate of the AAO process reached 87.4 ± 4.2%, while the COD removal rate of the HiCS-CP process was 71%-72%. Based on the COD removal load of the sludge, HiCS-CP is 5 times that of AAO, exhibiting higher biochemical metabolic activity and pollutant removal capacity. In the AAO system, organic carbon is primarily oxidized to carbon by biological processes, while in HiCS-CP, organic carbon mainly flows to the excess sludge (considered as intercepted wastewater organic carbon).

[0061] Figure 6 This is a graph showing the changes in phosphorus concentration in the effluent of the conventional AAO and Example 1 carbon and phosphorus capture processes; Inf represents the influent and Eff represents the effluent. Figure 7 The phosphorus removal load diagram is shown for conventional AAO and carbon-phosphorus co-capture processes. Figure 8 This graph shows the changes in phosphorus uptake and re-release capacity of the conventional AAO and carbon-phosphorus co-capture processes within a single cycle. After the system stabilizes, under sufficient phosphorus release-uptake HRT and SRT conditions, the conventional AAO process achieves an average influent TP of 4.90 ± 0.37 mg / L and an effluent TP of 0.70 ± 0.11 mg / L, with a TP removal efficiency of 85.6 ± 2.1%.

[0062] In a typical HiCS-C process, both wastewater and excess sludge are discharged in the anaerobic contact section. The discharged wastewater does not participate in the complete phosphorus release-uptake kinetic process of PAOs, resulting in limited PAO function and activity, and a total phosphorus (TP) removal efficiency of only less than 20%. Related studies have reported that HRAS systems, under similar operating conditions, achieve TP removal efficiencies of 17%-37%. In the improved HiCS-CP process of Example 1, phosphorus carried in the wastewater fully participates in the biochemical process of PAOs, and the phosphorus in the influent is largely retained in the excess sludge. Therefore, in the HiCS-CP system, after a complete superphosphate uptake process, the sludge captures phosphorus to the maximum extent in the excess sludge, achieving a TP removal rate of 72.0 ± 3.4%. Thus, HiCS-CP exhibits excellent phosphorus capture efficiency. The TP removal load of the HiCS-CP system is 3-4 times that of AAO, and the phosphorus release and uptake rates of HiCS-CP are 5-6 times that of AAO, indicating that the HiCS-CP process effectively stimulates the activity of phosphorus-capturing bacteria and increases their phosphorus capture limit.

[0063] Figure 9This is a distribution diagram of phosphorus among different components in sludge at different times in a single cycle during a conventional AAO process. Figure 10 This diagram shows the distribution of phosphorus among different components in sludge at different times within a single cycle during the HiCS-CP process. In the diagram, Cell represents phosphorus content within sludge cells; LB-EPS represents phosphorus content in tightly bound sludge extracellular polymeric substances (EBPS); and LB-EPS represents phosphorus content in loosely bound sludge EBPS. The HiCS-CP process uses LB-EPS as the migration channel and TB-EPS as the primary storage site, fundamentally altering the migration and transformation process of biological phosphorus removal and expanding the phosphorus pool in the sludge, achieving rapid phosphorus capture and stable storage. The HiCS-CP process can maximize phosphorus capture with high efficiency and obtain high-grade phosphorus content in excess sludge (57.8 mg-P / g-VSS). HiCS-CP achieves highly efficient and maximized carbon-phosphorus co-capture through the regulation of sludge discharge strategies. In the AAO process, phosphorus capture primarily occurs through phosphorus in sludge cells (Cell-P) at 61.7 ± 8.3%, followed by phosphorus in tightly bound extracellular polymeric substances (TB-EPS-P) at 33.7 ± 1.0%, while loosely bound extracellular polymeric substances (LB-EPS-P) account for a very small proportion (4.8 ± 1.9%). This distribution aligns with the classic biological phosphorus removal theory, where phosphorus in wastewater is mainly stored through polyphosphate (Poly-P) synthesis by polyphosphate-accumulating bacteria within the cells. However, in the HiCS-CP process, under short SRT and high-speed metabolic conditions, phosphorus capture is no longer limited to traditional intracellular biosynthesis. Instead, a novel rapid extracellular fixation pathway, with TB-EPS as the key carrier, emerges, accounting for as much as 51.8 ± 7.0%. In HiCS-CP, LB-EPS serves as the migration channel, and phosphorus migration and transformation mainly occur between the aqueous phase and TB-EPS, forming a unique pathway dominated by rapid extracellular fixation mediated by TB-EPS and synergistically involving intracellular synthesis and storage.

[0064] Example 2:

[0065] Wastewater is transported to an anaerobic contact tank, the effluent from the anaerobic contact tank is transported to an aerobic stabilization tank, and the effluent from the aerobic stabilization tank is transported to a sedimentation tank. Part of the sludge and effluent in the sedimentation tank are transported to a second aerobic stabilization tank. After aeration treatment in the second aerobic stabilization tank, the sludge and effluent are transported to the anaerobic contact tank. The remaining sludge and effluent in the sedimentation tank are discharged, thus completing the capture of carbon and phosphorus in the wastewater.

[0066] The anaerobic contact tank is equipped with a mechanical stirring device, which is a jet mixer; the hydraulic retention time in the anaerobic contact tank is 20 min, and the dissolved oxygen concentration is 0.5 mg / L.

[0067] The aerobic stabilization tank and the second aerobic stabilization tank are equipped with aeration devices; the dissolved oxygen concentration in the aerobic stabilization tank and the second aerobic stabilization tank is 3.0 mg / L, the oxidation-reduction potential is > +200 mV, the hydraulic retention time of the aerobic stabilization tank is 20 min, and the total hydraulic retention time of the aerobic stabilization tank and the second aerobic stabilization tank is 1.0 h.

[0068] The sedimentation tank is an inclined plate sedimentation tank; the total volume of sludge and wastewater transported from the sedimentation tank to the second aerobic stabilization tank is 1:1 with the volume of influent to the sedimentation tank; the total volume of discharged residual sludge is 1:2 with the volume of return sludge transported from the sedimentation tank to the second aerobic stabilization tank; thus maintaining the sludge age of the system at 2.0 days.

[0069] This embodiment targets the high-concentration effluent from large-scale recirculating aquaculture farms. This high-concentration effluent is obtained by further separating uneaten feed and feces from backwash water of a microfiltration machine through gravity sedimentation, and then discharging the high-concentration uneaten feed and feces into a hydrolysis fermentation tank for volume reduction. The water quality characteristics are: COD of 200-300 mg / L, total phosphorus of 8-15 mg / L, and total nitrogen (mostly ammonia nitrogen) of 45-65 mg / L.

[0070] The effluent quality of the carbon and phosphorus co-capture process (HiCS-CP) used in the example is as follows: COD 80-120 mg / L, total removal rate of about 65%, carbon rejection rate of 45%, BOD5 40-50 mg / L, TP 4-10 mg / L, ammonia nitrogen 35-50 mg / L, pH: 7.0 ± 0.5.

[0071] The effluent meets the requirements of GB 5084-2021 for COD < 150 mg / L and BOD < 60 mg / L. TP removal rate can be dynamically adjusted within the range of 20% to 65%. The effluent essentially retains ammonia nitrogen, achieving controllable interception of organic carbon, efficient retention of ammonia nitrogen, and on-demand controlled phosphorus capture. The treated effluent meets the "Standard for Irrigation Water Quality of Farmland GB 5084-2021" and can be directly used for high-nitrogen forage irrigation. The hydraulic retention time in the aerobic stabilization tank is adjusted from 0 to 60 min. The phosphorus capture rate of the high-concentration tailwater from the farm in Example 2 was tested under different hydraulic retention time conditions in the aerobic tank. Figure 12 As shown, different residence times in the aerobic tank can control the proportion of phosphorus captured in the effluent.

Claims

1. A method for capturing carbon and phosphorus from wastewater, characterized in that: The carbon and phosphorus capture method for wastewater is carried out according to the following steps: wastewater is transported to an anaerobic contact tank, the effluent from the anaerobic contact tank is transported to an aerobic stabilization tank, and the effluent from the aerobic stabilization tank is transported to a sedimentation tank; some sludge and effluent in the sedimentation tank are transported back to the anaerobic contact tank, and the remaining sludge and effluent in the sedimentation tank are discharged, thus completing the capture of carbon and phosphorus in the wastewater.

2. The method for carbon and phosphorus co-capture of wastewater according to claim 1, characterized in that: The anaerobic contact tank is equipped with a mechanical stirring device.

3. The method for carbon and phosphorus co-capture of wastewater according to claim 2, characterized in that: The mechanical stirring device is an internal circulating water pump, a jet mixer, or a pipeline mixer.

4. The method for carbon and phosphorus co-capture of wastewater according to claim 1, characterized in that: The hydraulic retention time in the anaerobic contact tank is 10-30 min, and the dissolved oxygen concentration is 0-0.5 mg / L.

5. The method for carbon and phosphorus co-capture of wastewater according to claim 1, characterized in that: An aeration device is installed in the aerobic stabilization tank.

6. The method for carbon and phosphorus co-capture of wastewater according to claim 1, characterized in that: The dissolved oxygen concentration in the aerobic stabilization tank is ≥1.5 mg / L, the oxidation-reduction potential is >+200mV, and the hydraulic retention time is 1.0~2h.

7. The method for carbon and phosphorus co-capture of wastewater according to claim 1, characterized in that: The sedimentation tank is an inclined plate sedimentation tank, an inclined tube sedimentation tank, or a vertical flow sedimentator.

8. The method for carbon and phosphorus co-capture of wastewater according to claim 1, characterized in that: The ratio of the total volume of sludge and wastewater returned from the sedimentation tank to the anaerobic contact tank to the volume of the influent to the sedimentation tank is 1~2:

1.

9. The method for carbon and phosphorus co-capture of wastewater according to claim 1, characterized in that: The volume ratio of the excess sludge to the return sludge from the sedimentation tank to the anaerobic contact tank is 1:2~50.

10. The method for carbon and phosphorus co-capture of wastewater according to claim 1, characterized in that: Wastewater is transported to an anaerobic contact tank, the effluent from the anaerobic contact tank is transported to an aerobic stabilization tank, and the effluent from the aerobic stabilization tank is transported to a sedimentation tank. Part of the sludge and effluent from the sedimentation tank are transported to a second aerobic stabilization tank. After aeration treatment in the second aerobic stabilization tank, the sludge and effluent are transported back to the anaerobic contact tank. The remaining sludge and effluent from the sedimentation tank are discharged, completing the capture of carbon and phosphorus from the wastewater. The hydraulic retention time of the aerobic stabilization tank is 1-40 min, and the total hydraulic retention time of the aerobic stabilization tank and the second aerobic stabilization tank is 1.0-2.0 h. The hydraulic retention time in the anaerobic contact tank is 10-40 min.

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