Method and device for synergistic recovery of chemical energy and phosphorus resources in a wastewater carbon capture process

Abstract

The application discloses a method and device for recovering chemical energy and phosphorus resources in a sewage carbon capture process. Specifically, the effluent from a grit chamber of a municipal sewage treatment plant is subjected to carbon and phosphorus capture through a chemical primary enhanced carbon capture unit and a sedimentation tank, and the captured sludge is subjected to sludge concentration and dissimilatory iron reduction in a sludge conditioning tank, and then enters a sludge acidification tank for release of Fe 2+ and PO4 3‑ , and the supernatant rich in Fe 2+ and PO4 3‑ and the remaining sludge enter an anaerobic fermentation unit and a blue vitriol recovery unit, respectively, for recovery of iron and phosphorus. The application realizes reduction of trivalent iron in the sludge by using anaerobic microorganisms carried by the sewage before anaerobic fermentation, and releases iron and phosphorus through acidification, thereby recovering blue vitriol before anaerobic fermentation. The application solves the problem of inhibition of subsequent methanogenesis in anaerobic fermentation caused by high dosage of iron salt, and realizes rapid recovery of phosphorus.

Description

Technical Field

[0001] This invention belongs to the field of urban domestic sewage treatment technology, specifically relating to a method and apparatus for the synergistic recovery of chemical energy and phosphorus resources in a sewage carbon capture process. Background Technology

[0002] Currently, environmental pollution and energy shortage have become two major challenges facing the world. Under the guidance of my country's "dual-carbon" strategic goals, all sectors are actively exploring low-carbon, zero-carbon, and even negative-carbon development paths, and the wastewater treatment field is no exception. Traditional urban wastewater treatment processes, especially the "aerobic activated sludge process," rely on aeration to mineralize organic matter in wastewater into greenhouse gases such as carbon dioxide and nitrous oxide. This not only consumes a large amount of electricity but also directly increases carbon emissions, essentially achieving pollutant removal in a high-energy-consumption and high-carbon-emission manner.

[0003] Studies have shown that 1 kg of COD (Chemical Oxygen Demand) contains up to 3.86 kWh of chemical energy, approximately 4-5 times the energy required for its actual treatment. Simultaneously, wastewater is also rich in valuable resources such as nitrogen and phosphorus. If these energy and resources can be effectively extracted and recovered from wastewater, the wastewater treatment process can not only achieve energy self-sufficiency but also even export energy and resources. Consequently, scholars and engineers both domestically and internationally have gradually proposed a series of carbon-neutral or energy-self-sufficient technical routes for future wastewater treatment plants. The core of these routes lies in maximizing the enrichment of organic matter in wastewater through "carbon capture" and "carbon relocation" strategies, and extracting the chemical energy and other usable resources contained within through a series of biological or physicochemical methods such as anaerobic digestion.

[0004] Among various carbon capture technologies, chemical primary enhancement is relatively common. This process involves adding coagulants or flocculants to promote the coagulation, flocculation, and sedimentation of suspended and colloidal organic matter in wastewater, thereby efficiently transferring it from the aqueous phase to the sludge phase. However, in practical applications, chemical primary enhancement requires the addition of large amounts of coagulants or flocculants. Conventional coagulants and flocculants are mainly metal salts such as aluminum and iron. High dosages of metal salts can inhibit the subsequent anaerobic fermentation process of captured sludge, reduce the efficiency of organic matter conversion to methane, and directly affect the recovery efficiency of organic matter chemical energy.

[0005] Meanwhile, phosphorus recovery from sludge is receiving increasing attention; crystallization (achieving solid-liquid separation of phosphorus by forming phosphate mineral precipitates) is one of the effective methods for recovering phosphorus from sludge; among them, blue iron ore ( Iron phosphate (Fe) is a poorly soluble iron-phosphorus compound and has attracted attention as an emerging phosphorus recovery mineral due to its potential for natural formation in anaerobic environments and its high economic value. In anaerobic digestion systems, dissimilatory iron-reducing bacteria utilize electron donors to convert Fe... 3+Reduced to Fe 2+ Under suitable pH conditions, Fe 2+ With PO4 3- It can then crystallize to form blue iron ore; although chemically enhanced primary sedimentation (CEPT) sludge has the potential to hydrolyze and release phosphates under anaerobic conditions, making phosphorus recovery through anaerobic fermentation theoretically feasible, traditional anaerobic fermentation usually takes 7 days or longer to complete, resulting in an excessively long phosphorus recovery cycle that is difficult to meet the demand for rapid resource utilization.

[0006] In summary, the core technical problems that urgently need to be solved are: in the existing primary enhanced carbon capture process, the high dosage of coagulant will inhibit the subsequent anaerobic fermentation to produce biogas, reducing the recovery efficiency of organic chemical energy; and the traditional anaerobic fermentation to recover phosphorus has too long a cycle and cannot be efficiently recovered. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention proposes a method and apparatus for the synergistic recovery of chemical energy and phosphorus resources in a wastewater carbon capture process. The aim is to reduce ferric iron in sludge by utilizing anaerobic microorganisms carried by the wastewater itself before anaerobic fermentation, and release iron and phosphorus through acidification, thereby recovering lapis lazuli before anaerobic fermentation. This solves the problem of high iron salt dosage inhibiting methane production during subsequent anaerobic fermentation in existing primary enhanced carbon capture processes, while simultaneously achieving rapid phosphorus recovery and shortening the recovery cycle of lapis lazuli.

[0008] This invention discloses a method for the synergistic recovery of chemical energy and phosphorus resources in a wastewater carbon capture process, comprising the following steps: Step 1, Primary Enhanced Carbon and Phosphorus Capture: The effluent from the grit chamber enters the primary enhanced carbon capture unit, where a capture agent is added to capture carbon and phosphorus. After the capture agent is fully mixed with the wastewater, the suspended organic matter and some dissolved phosphorus in the wastewater aggregate and grow larger. The mixture then flows into the sedimentation tank for solid-liquid separation. The supernatant from the sedimentation tank flows to the subsequent treatment unit, while the carbon and phosphorus-rich captured sludge at the bottom is collected. Step 2, Sludge Thickening and Dissimilar Iron Reduction: The carbon- and phosphorus-rich captured sludge formed after sedimentation in the sedimentation tank enters the sludge equalization tank, which is kept in an anoxic state. The captured sludge is then allowed to settle and thicken. Under these anoxic conditions, the anaerobic microorganisms carried by the wastewater utilize the organic matter in the sludge as electron donors to reduce the ferric ions (Fe3+) in the captured sludge. 3+ The iron is reduced to ferrous ions (Fe2+) via dissimilatory reduction. 2+ The supernatant formed after sludge concentration in the sludge equalization tank enters the subsequent treatment unit along with the effluent from the sedimentation tank. Step 3, Fe 2+ and PO4 3-Rapid release: Sludge that has been further concentrated and reduced by dissimilar iron in the sludge equalization tank enters the sludge acidification tank; Fe in the supernatant 2+ and PO4 3- The release of Fe reaches its maximum, and the acidified sludge will undergo further solid-liquid separation, promoting the release of Fe in the sludge. 2+ and PO4 3- Rapidly released from the solid phase to the liquid phase, forming an Fe-rich environment. 2+ and PO4 3- The supernatant; Step 4, Rapid Phosphorus Recovery: Phosphorus-rich phosphorus separated from the sludge acidification tank... 2+ and PO4 3- The supernatant was separately diverted into the blue iron ore recovery unit; Step 5: Anaerobic fermentation to recover chemical energy: The remaining sludge after being treated and separated in the sludge acidification tank enters the anaerobic fermentation unit to produce biogas.

[0009] Preferably, the capturing agent is an easily reducible iron salt, including at least one of ferric chloride, polyferric sulfate, and polyferric chloride, and its dosage is controlled at 40-120 mg / L.

[0010] Preferably, the sedimentation time of the mixture after carbon and phosphorus capture in the sedimentation tank in step 1 is 0.5-1h.

[0011] Preferably, in step 2, the captured sludge is allowed to settle and thicken for 1-2 days, and the oxygen volume fraction in the tank is controlled to be [value missing]. .

[0012] Preferably, in step 3, the pH of the acidification tank is adjusted to 5 by adding hydrochloric acid or sulfuric acid, and the acidification time is 10-30 minutes.

[0013] Preferably, in step 4, the lapis lazuli recovery unit adjusts the pH to 7 by adding ammonia or sodium hydroxide, so that Fe... 2+ and PO4 3- Crystallization forms lapis lazuli Phosphorus can be rapidly recovered through resuspension or magnetic separation.

[0014] Preferably, the inoculation ratio of the residual sludge after treatment in the sludge acidification tank in step 5 to the seed sludge is 3:1.

[0015] Preferably, in step 5, the anaerobic fermentation unit adopts an intermittent or semi-continuous flow sludge anaerobic fermenter, the fermenter maintains an anaerobic environment, the fermentation temperature is 36±2℃, the stirring speed is 120-160rpm, and the fermentation time is 7-10 days.

[0016] This invention also discloses a device for the co-recovery of chemical energy and phosphorus resources in a wastewater carbon capture process, comprising: Chemical primary enhanced carbon capture unit: used to receive effluent from the grit chamber of a municipal wastewater treatment plant and add a capture agent to capture carbon and phosphorus; the capture agent is fully mixed with the wastewater, causing suspended organic matter and some dissolved phosphorus in the wastewater to aggregate and increase in size; Sedimentation tank: connected after the chemical primary enhanced carbon capture unit, used to perform solid-liquid separation on the mixed liquid after carbon and phosphorus capture, to obtain captured sludge and supernatant rich in carbon and phosphorus; Sludge equalization tank: Connected after the sedimentation tank, it receives the carbon- and phosphorus-rich captured sludge, which is then subjected to static concentration and dissimilar iron reduction reaction under anoxic conditions. Anaerobic microorganisms carried by the wastewater utilize the organic matter in the sludge as electron donors to reduce Fe in the sludge. 3+ Reduced to Fe via dissimilar iron reduction. 2 + ; Sludge acidification tank: Connected after the sludge equalization tank, it receives sludge that has been concentrated and undergone iron reduction, and acidifies the sludge. The acidified sludge undergoes further solid-liquid separation, promoting the removal of Fe from the sludge. 2+ and PO4 3- Rapidly released from the solid phase to the liquid phase, forming an Fe-rich environment. 2+ and PO4 3- The supernatant; Anaerobic fermentation unit: connected after the sludge acidification tank, used to receive the remaining sludge after acidification and solid-liquid separation, and to perform anaerobic methanogenesis to recover chemical energy; The urban domestic sewage being treated is transported through underground pipelines that are in a closed, oxygen-deficient state for a long time, in order to maintain the activity of anaerobic microorganisms in the sewage.

[0017] The beneficial effects of this invention are as follows: Significantly shortens the phosphorus recovery cycle: This invention reduces dissimilar iron and Fe 2+ and PO4 3- The release of phosphorus is brought forward to before anaerobic fermentation. This is achieved through anoxic settling and concentration in the sludge equalization tank and acidification treatment in the sludge acidification tank, allowing lapis lazuli crystallization to be completed before anaerobic fermentation. This significantly shortens the phosphorus recovery cycle and enables rapid resource utilization of phosphorus.

[0018] 2. Significantly Improved Methanogenic Efficiency in Anaerobic Fermentation: Before anaerobic fermentation, this invention reduces iron content in the sludge through dissimilatory iron reduction in the sludge equalization tank and releases phosphorus and iron in the sludge acidification tank, and removes most of the iron and phosphorus in the blue iron ore recovery unit. This reduces the iron content in the anaerobic fermentation sludge, effectively mitigating the inhibitory effect of iron on anaerobic methanogenesis, thereby increasing the methane yield. The sludge treated with this invention exhibits a 16.6% to 22.7% higher methane yield during anaerobic fermentation compared to the control group without prior iron and phosphorus recovery, significantly enhancing the recovery efficiency of the chemical energy of organic matter in wastewater.

[0019] 3. Make full use of the inherent microbial resources of sewage and reduce operating costs: This invention makes full use of the anaerobic microorganisms carried by urban domestic sewage to carry out dissimilar iron reduction reaction; by enriching and utilizing these microorganisms together with the captured sludge, there is no need to add exogenous microorganisms or set up complex bioreactors for iron reduction, which simplifies the process and reduces operating costs and complexity.

[0020] 4. Achieving multiple synergistic recovery of carbon, phosphorus, and chemical energy: Through process integration, this invention achieves synergistic and efficient recovery of organic carbon, chemical energy, phosphorus, and iron from wastewater. This not only transforms pollutants in wastewater into valuable resources and energy, avoiding the high carbon emissions of traditional aerobic treatment, but also achieves energy self-sufficiency through methane production and resource recovery, which meets the requirements of the "dual carbon" strategy.

[0021] 5. Strong process adaptability and low cost of modification and upgrading: This invention is based on chemical primary enhanced carbon capture process, which is simple and easy to operate and has low improvement cost; by adding sludge conditioning tank, sludge acidification tank and blue iron ore recovery unit to the existing process, its enhancement effect can be achieved, which is convenient for production and has a broad application prospect. Attached Figure Description

[0022] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a schematic diagram illustrating the change in iron reduction rate in sludge captured by Example 1 with settling and concentration time; Figure 3 This is a comparison graph showing the methane production efficiency of captured sludge during anaerobic fermentation between Example 1 and Control Group 1. Figure 4 This is a schematic diagram illustrating the change in iron reduction rate in sludge captured by Example 2 with settling and concentration time; Figure 5 This is a comparison chart of the methane production efficiency of captured sludge anaerobic fermentation between Example 2 and Control Group 2. Detailed Implementation

[0023] To better understand the content of this invention, specific embodiments will be used to further illustrate the invention below. The following embodiments are based on the technology of this invention and provide detailed implementation methods and operating steps. However, the scope of protection of this invention is not limited to the following embodiments; that is, all other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0024] The urban domestic sewage treated by this invention refers to sewage transported by underground pipe networks, which are in a closed and oxygen-deficient state for a long time. This environment is conducive to maintaining the activity of anaerobic microorganisms in the sewage, providing a natural microbial basis for subsequent processes. The urban domestic sewage is first pretreated by the sedimentation tank of the sewage treatment plant to remove large suspended solids and sand, and the effluent is used as the influent of this invention.

[0025] This invention discloses a device for the synergistic recovery of chemical energy and phosphorus resources in a wastewater carbon capture process, comprising a primary chemical enhanced carbon capture unit, a sedimentation tank, a sludge equalization tank, a sludge acidification tank, an anaerobic fermentation unit, and a lapis lazuli recovery unit. The effluent from the grit chamber of a municipal wastewater treatment plant undergoes carbon and phosphorus capture in the primary chemical enhanced carbon capture unit and sedimentation tank. The captured sludge enters the sludge equalization tank for sludge thickening and dissimilar iron reduction reaction, and then enters the sludge acidification tank for Fe... 2+ and PO4 3- The release of Fe 2+ and PO4 3- The supernatant and the remaining sludge are respectively fed into the anaerobic fermentation unit and the blue iron ore recovery unit for the recovery of chemical energy and phosphorus.

[0026] The specific method and process are as follows: (1) Primary Enhanced Carbon and Phosphorus Capture: The effluent from the grit chamber enters the primary enhanced carbon capture unit, where easily reducible iron salts are added as capture agents. The capture agent is at least one of ferric chloride, polyferric sulfate, and polyferric chloride, and its dosage is controlled at 40-120 mg / L. After the capture agent is fully mixed with the wastewater, the suspended organic matter and some dissolved phosphorus (combined with iron ions) in the wastewater aggregate and increase in size. Then, it flows into the sedimentation tank for solid-liquid separation, and the sedimentation time is 0.5-1 h. The supernatant (effluent) from the sedimentation tank flows to the subsequent treatment unit, while the capture sludge rich in carbon and phosphorus at the bottom is collected.

[0027] (2) Sludge thickening and dissimilar iron reduction: The carbon- and phosphorus-rich captured sludge formed after sedimentation in the sedimentation tank enters the sludge equalization tank. The sludge equalization tank is kept in an anoxic state, and the oxygen volume fraction in the tank is controlled at [value missing]. The captured sludge is allowed to settle and thicken for 1-2 days. Under these anoxic conditions, anaerobic microorganisms carried by the wastewater itself (such as Bacteroides and other iron-reducing bacteria) utilize the organic matter in the sludge as electron donors to capture ferric ions (Fe3+) from the sludge. 3+ ) is reduced to ferrous ions (Fe2+) through dissimilar iron reduction. 2+ The supernatant formed after sludge concentration in the sludge equalization tank enters the subsequent treatment unit along with the effluent from the sedimentation tank.

[0028] (3) Fe 2+ and PO4 3- Rapid release of Fe: The sludge, after further concentration and reduction of dissimilar iron in the sludge equalization tank, enters the sludge acidification tank. The pH in the acidification tank is adjusted to approximately 5 by adding hydrochloric acid or sulfuric acid, and maintained for 10-30 minutes. Under these conditions, the Fe in the supernatant... 2+ and PO4 3- The release of Fe can reach its maximum. After acidification, the sludge will undergo further solid-liquid separation, promoting the release of Fe in the sludge. 2+ and PO4 3- Rapidly released from the solid phase to the liquid phase, forming an Fe-rich environment. 2+ and PO4 3- The supernatant.

[0029] (4) Rapid recovery of phosphorus: The phosphorus-rich phosphorus separated from the sludge acidification tank is rich in Fe. 2+ and PO4 3- The supernatant is separately diverted into the vivianite recovery unit; in the vivianite recovery unit, the pH is adjusted to 7 by adding ammonia or sodium hydroxide, so that Fe... 2+ and PO4 3- Crystallization forms lapis lazuli And phosphorus can be rapidly recovered by resuspension or magnetic separation. (5) Anaerobic fermentation to recover chemical energy: The remaining sludge (most of the iron and phosphorus have been removed) after being treated and separated in the sludge acidification tank is put into the anaerobic fermentation unit for anaerobic biogas production; the anaerobic fermentation unit adopts an intermittent or semi-continuous flow sludge anaerobic fermentation tank, and the inoculation ratio of the captured remaining sludge to the seed sludge is 3:1; a strict anaerobic environment is maintained in the fermentation tank, the fermentation temperature is controlled at 36±2℃, the stirring speed is 120-160rpm, and the fermentation time is 7-10d.

[0030] During anaerobic fermentation, the organic matter in the remaining sludge is converted into biogas such as methane by anaerobic microorganisms, thereby recovering the chemical energy from the wastewater. Since most of the iron and phosphorus have been removed before fermentation, the inhibitory effect of iron on methanogens is reduced, significantly improving the methane yield and chemical energy recovery efficiency.

[0031] The present invention can be further understood through the following embodiments; Example 1

[0032] The influent water quality in this embodiment is as follows: the effluent from the grit chamber of a municipal wastewater treatment plant is used as the treatment object; the wastewater quality parameters are as follows: pH value is 6.8-7.4, COD (chemical oxygen demand) is 180-250 mg / L, ammonia nitrogen is 30-60 mg / L, and TP (total phosphorus) is 3-6 mg / L.

[0033] Specific operation process: (1) Primary Enhanced Carbon and Phosphorus Capture: The urban wastewater is introduced into a chemical primary enhanced carbon capture unit; ferric chloride (FeCl3) is selected as the capture agent, with a dosage of 80 mg / L and a COD capture rate of 72.6%; through coagulation, the organic matter and phosphate in the wastewater are flocculated and captured. The mixed liquor after primary enhanced treatment enters a sedimentation tank for solid-liquid separation; the supernatant after separation flows into the subsequent treatment unit as effluent; the captured sludge rich in carbon and phosphorus at the bottom is collected and pumped to the sludge equalization tank.

[0034] (2) Sludge thickening and dissimilar iron reduction: The captured sludge, rich in carbon and phosphorus, is introduced into a sludge equalization tank for static thickening; the sludge equalization tank is kept in an anoxic state for 2 days; during this period, through the anaerobic microorganisms carried by the sewage itself, the Fe in the sludge is reduced. 3+ Reduced to Fe 2+ ;like Figure 2 As shown, the iron reduction rate in sludge gradually increased with the increase of settling and thickening time. After 2 days of settling and thickening, the iron reduction rate in sludge reached 84.2%.

[0035] (3) Fe 2+ and PO4 3- Rapid release (sludge acidification): The bottom sludge, after settling and thickening, then enters the sludge acidification tank; in the sludge acidification tank, the pH is adjusted to 5 by adding hydrochloric acid to promote Fe production. 2+ and PO4 3- Rapidly released from sludge into the liquid phase; after acidification, Fe in the supernatant 2+ and PO4 3- The concentrations and release rates of the ions are shown in Table 1. The experimental results show that the recovery rates of iron and phosphorus reached 71.6% and 62.3% respectively after treatment in the sludge acidification tank, and the recovery efficiency was significant.

[0036] Table 1. Fe in the supernatant of sludge acidification tank 2+ and PO4 3- -P concentration and release rate

[0037] (4) Recovery of phosphorus from lapis lazuli and recovery of chemical energy from anaerobic fermentation: After solid-liquid separation in the sludge acidification tank, the sludge is rich in Fe. 2+ and PO4 3- The supernatant is diverted to the blue iron ore recovery unit for phosphorus recovery via blue iron ore crystallization; meanwhile, the remaining bottom sludge (with most of the iron and phosphorus removed) enters the anaerobic digester for anaerobic fermentation to produce biogas.

[0038] To evaluate the effectiveness of the present invention, a control group 1 was set up, in which captured sludge without prior iron and phosphorus recovery (without passing through a sludge equalization tank and a sludge acidification tank) was directly subjected to anaerobic fermentation.

[0039] The anaerobic fermentation methanogenesis efficiency of the captured sludge from Example 1 and Control Group 1 was tested, and the results are as follows: Figure 3 As shown in the figure; the experimental results show that by pre-recovering lapis lazuli using the system of the present invention before anaerobic fermentation, iron and phosphorus are removed in advance, which significantly improves the methane production efficiency of the captured sludge during anaerobic fermentation; specifically, the methane production rate of the captured sludge during anaerobic fermentation in Example 1 was 162.2 ml CH4 / gVS, while the methane production rate of the captured sludge during anaerobic fermentation in Control Group 1 was 132.1 ml CH4 / gVS; the methane production rate of this example was 22.8% higher than that of Control Group 1; this indicates that the present invention has significant advantages in reducing the inhibitory effect of iron on anaerobic fermentation and improving the efficiency of chemical energy recovery. Example 2

[0040] The influent water quality in this embodiment is as follows: the effluent from the grit chamber of a municipal wastewater treatment plant is used as the treatment object; the wastewater quality parameters are as follows: pH value is 7.0-7.2, COD (chemical oxygen demand) is 220-250 mg / L, ammonia nitrogen is 40-50 mg / L, and TP (total phosphorus) is 3-6 mg / L.

[0041] Specific operation process: (1) Primary Enhanced Carbon and Phosphorus Capture: The urban wastewater is introduced into a chemical primary enhanced carbon capture unit; polyferric chloride prepared by laboratory slow alkali titration is selected as the capture agent, with a dosage of 60 mg / L and a COD capture rate of 71.6%; through coagulation, the organic matter and phosphate in the wastewater are flocculated and captured. The mixed liquor after primary enhanced treatment enters a sedimentation tank for solid-liquid separation; the supernatant after separation flows into the subsequent treatment unit as effluent; the capture sludge rich in carbon and phosphorus at the bottom is collected and pumped to the sludge equalization tank.

[0042] (2) Sludge thickening and dissimilar iron reduction: The captured sludge, rich in carbon and phosphorus, is introduced into a sludge equalization tank for static thickening; the sludge equalization tank is kept in an anoxic state for 1 day; during this period, through the anaerobic microorganisms carried by the sewage itself, the Fe in the sludge is reduced. 3+ Reduced to Fe 2+ ;like Figure 4 As shown, the iron reduction rate in sludge gradually increased with the increase of settling and thickening time. After 1 day of settling and thickening, the iron reduction rate in sludge reached 92.6%.

[0043] (3) Fe 2+ and PO4 3- Rapid release (sludge acidification): The bottom sludge, after settling and thickening, then enters the sludge acidification tank; in the sludge acidification tank, the pH is adjusted to 5 by adding hydrochloric acid to promote Fe production. 2+ and PO4 3- Rapidly released from sludge into the liquid phase; after acidification, Fe in the supernatant 2+ and PO4 3- The concentrations and release rates of the ions are shown in Table 2. The experimental results show that the recovery rates of iron and phosphorus reached 75.8% and 55.3% respectively after treatment in the sludge acidification tank, and the recovery efficiency was significant.

[0044] Table 2. Fe content in the supernatant of sludge acidification tank 2+ and PO4 3- -P concentration and release rate

[0045] (4) Recovery of phosphorus from lapis lazuli and recovery of chemical energy from anaerobic fermentation: After solid-liquid separation in the sludge acidification tank, the sludge is rich in Fe. 2+ and PO4 3- The supernatant is diverted to the blue iron ore recovery unit for phosphorus recovery via blue iron ore crystallization; meanwhile, the remaining bottom sludge (with most of the iron and phosphorus removed) enters the anaerobic digester for anaerobic fermentation to produce biogas.

[0046] In this embodiment, the control group 2 is still "captured sludge that has not undergone prior iron and phosphorus recovery (without passing through the sludge equalization tank and sludge acidification tank) directly undergoes anaerobic fermentation".

[0047] The anaerobic fermentation methanogenesis efficiency of the captured sludge from Example 2 and Control Group 2 was tested, and the results are as follows: Figure 5 As shown in the figure; the experimental results show that by pre-recovering lapis lazuli using the system of the present invention before anaerobic fermentation, iron and phosphorus are removed in advance, which significantly improves the methane production efficiency of the captured sludge during anaerobic fermentation; specifically, the methane production rate of the captured sludge during anaerobic fermentation in Example 2 was 201.3 ml CH4 / gVS, while the methane production rate of the captured sludge during anaerobic fermentation in Control Group 2 was 172.6 ml CH4 / gVS; the methane production rate of this example was 16.6% higher than that of the control group; this indicates that the present invention has significant advantages in reducing the inhibitory effect of iron on anaerobic fermentation and improving the efficiency of chemical energy recovery.

[0048] This invention can have other embodiments based on the above preparation method, which will not be listed one by one. Therefore, any simple modifications, equivalent changes and alterations made by any person skilled in the art to the above embodiments without departing from the scope of the technical solution of this invention shall still fall within the scope of the technical solution of this invention.

Claims

1. A method for the co-recovery of chemical energy and phosphorus resources in a wastewater carbon capture process, characterized in that, Including the following methods: Step 1, Enhanced Carbon and Phosphorus Capture: The effluent from the grit chamber enters the enhanced chemical carbon capture unit, where a capture agent is added to capture carbon and phosphorus. After the capture agent is thoroughly mixed with the wastewater, the suspended organic matter and some dissolved phosphorus in the wastewater aggregate and grow larger; then the mixture flows into the sedimentation tank for solid-liquid separation; the supernatant in the sedimentation tank flows to the subsequent treatment unit, while the carbon and phosphorus-rich capture sludge at the bottom is collected. Step 2, Sludge Thickening and Dissimilar Iron Reduction: The carbon- and phosphorus-rich captured sludge formed after sedimentation in the sedimentation tank enters the sludge equalization tank, which is kept in an anoxic state. The captured sludge is then allowed to settle and thicken. Under these anoxic conditions, the anaerobic microorganisms carried by the wastewater utilize the organic matter in the sludge as electron donors to reduce the ferric ions (Fe3+) in the captured sludge. 3+ The iron is reduced to ferrous ions (Fe2+) via dissimilatory reduction. 2+ The supernatant formed after sludge thickening in the sludge equalization tank enters the subsequent treatment unit along with the effluent from the sedimentation tank. Step 3, Fe 2+ and PO4 3- Rapid release of Fe: The sludge, after further concentration and reduction of dissimilar iron in the sludge equalization tank, enters the sludge acidification tank; the acidified sludge undergoes further solid-liquid separation, promoting the release of Fe from the sludge. 2+ and PO4 3- Rapidly released from the solid phase to the liquid phase, forming an Fe-rich environment. 2+ and PO4 3- The supernatant; Step 4, Rapid Phosphorus Recovery: Phosphorus-rich phosphorus separated from the sludge acidification tank... 2+ and PO4 3- The supernatant was separately diverted into the blue iron ore recovery unit; Step 5: Anaerobic fermentation to recover chemical energy: The remaining sludge after being treated and separated in the sludge acidification tank enters the anaerobic fermentation unit to produce biogas anaerobic digestate. The capturing agent is an easily reduced iron salt, including at least one of ferric chloride, polyferric sulfate, and polyferric chloride, and its dosage is controlled at 40-120 mg / L.

2. The method for co-recovery of chemical energy and phosphorus resources in a wastewater carbon capture process as described in claim 1, characterized in that, In step 1, the sedimentation time of the mixed solution after carbon and phosphorus capture in the sedimentation tank is 0.5-1h.

3. The method for co-recovery of chemical energy and phosphorus resources in a wastewater carbon capture process as described in claim 1, characterized in that, In step 2, the captured sludge is allowed to settle and thicken for 1-2 days, and the oxygen volume fraction in the tank is controlled at [value missing]. φ(O2) = 12%~15.9%.

4. The method for co-recovery of chemical energy and phosphorus resources in a wastewater carbon capture process as described in claim 1, characterized in that, In step 3, the pH of the acidification tank is adjusted to 5 by adding hydrochloric acid or sulfuric acid, and the acidification time is 10-30 minutes.

5. The method for co-recovery of chemical energy and phosphorus resources in a wastewater carbon capture process as described in claim 1, characterized in that, In step 4, the lapis lazuli recovery unit adjusts the pH to 7 by adding ammonia or sodium hydroxide, so that Fe... 2+ and PO4 3- The crystallization produces lapis lazuli Fe3(PO4)2∙8H2O, and phosphorus is rapidly recovered through resuspension or magnetic separation.

6. The method for co-recovery of chemical energy and phosphorus resources in a wastewater carbon capture process as described in claim 1, characterized in that, In step 5, the inoculation ratio of the remaining sludge after treatment in the sludge acidification tank to the seed sludge is 3:

1.

7. The method for co-recovery of chemical energy and phosphorus resources in a wastewater carbon capture process as described in claim 6, characterized in that, In step 5, the anaerobic fermentation unit adopts an intermittent or semi-continuous flow sludge anaerobic fermenter. The fermenter maintains an anaerobic environment, the fermentation temperature is 36±2℃, the stirring speed is 120-160rpm, and the fermentation time is 7-10 days.

8. A device for the co-recovery of chemical energy and phosphorus resources in a wastewater carbon capture process, realizing the method for the co-recovery of chemical energy and phosphorus resources in a wastewater carbon capture process as described in any one of claims 1-7, characterized in that, include: Chemical primary enhanced carbon capture unit: used to receive effluent from the grit chamber of a municipal wastewater treatment plant and add capture agents to capture carbon and phosphorus; The capture agent is thoroughly mixed with the wastewater, causing suspended organic matter and some dissolved phosphorus in the wastewater to aggregate and increase in size; Sedimentation tank: connected after the chemical primary enhanced carbon capture unit, used to perform solid-liquid separation on the mixed liquid after carbon and phosphorus capture, to obtain captured sludge and supernatant rich in carbon and phosphorus; Sludge equalization tank: Connected after the sedimentation tank, it receives the carbon- and phosphorus-rich captured sludge, which is then subjected to static concentration and dissimilar iron reduction reaction under anoxic conditions. Anaerobic microorganisms carried by the wastewater utilize the organic matter in the sludge as electron donors to reduce Fe in the sludge. 3+ Reduced to Fe via dissimilar iron reduction. 2+ ; Sludge acidification tank: Connected after the sludge equalization tank, it receives sludge that has been concentrated and undergone iron reduction, and acidifies the sludge. The acidified sludge undergoes further solid-liquid separation, promoting the removal of Fe from the sludge. 2+ and PO4 3- Rapidly released from the solid phase to the liquid phase, forming an Fe-rich environment. 2+ and PO4 3- The supernatant; Anaerobic fermentation unit: connected after the sludge acidification tank, used to receive the remaining sludge after acidification and solid-liquid separation, and to perform anaerobic methanogenesis to recover chemical energy; The urban domestic sewage being treated is transported through underground pipelines that are in a closed, oxygen-deficient state for a long time, in order to maintain the activity of anaerobic microorganisms in the sewage.

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