Method for sludge resource and application thereof

Abstract

The application discloses a sludge resource utilization method and application thereof. The sludge resource utilization method comprises the following steps: performing electro-fermentation treatment on sludge to be fermented in an anode chamber of an electrolytic cell; and the anode electrode in the anode chamber comprises a carbon-based material modified by titanium oxide. The anode electrode of the electrolytic cell comprises the carbon-based material modified by titanium oxide, the hydrophilicity of the surface of activated carbon particles can be significantly improved by modifying the carbon material by titanium oxide, the biocompatibility and electrocatalytic activity of the material are improved, the growth of microorganisms is facilitated, the anaerobic fermentation speed of bacteria can be improved, the electro-fermentation process speed and treatment effect are optimized and improved, and the effective recovery of elements such as nitrogen, iron and phosphorus contained in the sludge is realized, so that the application prospect is good.

Description

Technical Field

[0001] This invention belongs to the field of microbial electrochemical technology, specifically relating to a method for sludge resource utilization and its application. Background Technology

[0002] As the three essential elements for living organisms, carbon, nitrogen, and phosphorus are crucial to human metabolism, natural ecology, and industrial production. Their natural forms can be broadly categorized into inorganic and organic forms. How to recover resources such as nitrogen is increasingly becoming a research hotspot in resource recycling.

[0003] Sludge is typically generated in wastewater treatment processes, and anaerobic fermentation is often used to realize sludge resource utilization. Bacterial anaerobic fermentation generally includes four stages: dissolution and hydrolysis, acidification, hydrogen and acetic acid production, and methanogenesis. Currently, the rate-limiting step in bacterial anaerobic fermentation is mainly the dissolution and hydrolysis stage, fundamentally due to the imbalance of intracellular redox potential, which to some extent hinders the application of sludge resource utilization. Summary of the Invention

[0004] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a method for sludge resource utilization, which can improve the rate of bacterial anaerobic fermentation and achieve effective recovery of elements such as nitrogen contained in the sludge, showing promising application prospects.

[0005] The present invention also proposes a wastewater treatment method.

[0006] The present invention also proposes an apparatus for the resource utilization of sludge.

[0007] This invention also proposes the application of the above-mentioned methods and apparatus for sludge resource utilization.

[0008] In a first aspect, the present invention provides a method for sludge resource utilization, comprising the following steps: electro-fermenting sludge to be fermented in the anode chamber of an electrolytic cell; wherein the anode electrode in the anode chamber comprises a carbon-based material modified with titanium oxide.

[0009] The sludge resource utilization method according to embodiments of the present invention has at least the following beneficial effects:

[0010] Electrofermentation of sludge utilizes an electric field environment that regulates the redox state of cells, allowing for the selection of more adaptable microbial populations and enhancing the gene expression of relevant functional enzymes. Electroactive bacteria engage in interspecies electron transfer, either through a medium or directly between the electrodes. In anodic electrofermentation, microorganisms act as electron donors, producing more oxidation products and synthesizing more ATP, shifting cellular metabolism towards an acid-producing pathway. Electrofermentation transforms recalcitrant organic matter into substrates readily available to bacteria, promoting sludge hydrolysis and the production of dissolved COD, VFA, ammonium, and phosphate.

[0011] Furthermore, the difficulty of electron transfer between the biofilm and the electrode during electrofermentation is mainly determined by the electrode material. The hydrophilicity and surface tension of the electrode material affect microbial attachment, distribution, and growth, influencing the system's internal resistance and consequently the electrolytic performance of the electrolytic cell. In this invention, the anode electrode comprises a carbon-based material modified with titanium oxide. Electrodes containing carbon-based materials are superior in terms of specific surface area, porosity, conductivity, and biocompatibility, promoting bioadhesion, facilitating electron transfer by microorganisms, and exhibiting high electrocatalytic activity. Moreover, the titanium oxide modification (TiO2 doping) of the carbon material significantly improves the hydrophilicity of the carbon material (such as activated carbon particles), enhancing its biocompatibility and electrocatalytic activity, which is conducive to microbial attachment and growth. This can increase the rate of anaerobic bacterial fermentation, optimize and improve the electrofermentation process rate and treatment effect, and achieve effective recovery of elements such as nitrogen, iron, and phosphorus contained in the sludge, showing promising application prospects. In addition, compared with precious metals such as platinum, the electrode material of this invention has a lower cost.

[0012] In some embodiments of the present invention, the sludge to be fermented includes at least one of chemically enhanced primary sludge, primary sludge, or digested sludge. Preferably, the sludge to be fermented includes chemically enhanced primary sludge.

[0013] Chemically enhanced primary sedimentation sludge (CEPS) refers to sludge obtained through chemical coagulation and sedimentation in wastewater treatment. CEPS typically has a higher content of carbonaceous organic matter than primary sedimentation sludge and digested sludge, making it effective for anaerobic fermentation.

[0014] Chemically enhanced primary sedimentation (CEPS) involves adding chemical flocculants to wastewater at the upstream stage of wastewater treatment, along with appropriate hydraulic conditions. Charged microparticles coagulate and settle after mutual adsorption, bridging, and entrainment, enriching carbon, nitrogen, and phosphorus in the precipitate. On one hand, CEPS reduces the pollution load of subsequent processes, thereby reducing aeration energy consumption and the amount of external carbon source required. On the other hand, CEPS fixes a significant proportion of carbon, nitrogen, and phosphorus sources, facilitating sludge recycling and reuse.

[0015] In summary, the anode electrode of this invention comprises a carbon-based material modified with titanium oxide, and CEPS is placed in the anode chamber as an electron donor substrate. This can improve the anaerobic fermentation rate of bacteria, enrich and convert iron, phosphorus, nitrogen, and carbon resources from CEPS, and simultaneously recover resources such as iron, nitrogen, phosphorus, and carbon. This process achieves the effective recovery of elements such as iron, nitrogen, phosphorus, and carbon contained in sludge, and provides a solution to the problems of resource shortage, pollution control, and material recycling, with good application prospects.

[0016] In some embodiments of the present invention, the titanium oxide-modified carbon-based material is a titanium dioxide-modified carbon-based material.

[0017] In some embodiments of the present invention, the titanium dioxide-modified carbon-based material includes a carbon-based material and titanium dioxide supported on the carbon-based material.

[0018] In some embodiments of the present invention, 0.01-0.06g of titanium dioxide is loaded onto 1g of carbon-based material.

[0019] In some embodiments of the present invention, the method further includes preparing titanium dioxide modified carbon-based materials, specifically including the following operations: placing carbon materials in TiO2 sol, carbonizing, hydrothermally reacting, and then calcining to obtain the titanium dioxide modified carbon-based materials.

[0020] Through the above embodiments, in the titanium dioxide modification steps, the carbonization step: preferably low-temperature carbonization (carbonization temperatures below 1000℃ are considered low-temperature carbonization) increases the carbon fiber content in the carbon material (such as carbon felt), removes non-carbon components from the fiber, and increases the fiber stress. In the hydrothermal reaction step: optionally, in an autoclave, an aqueous solution is used as the reaction system. By heating and pressurizing the reaction system, a relatively high-temperature and high-pressure reaction environment is created, causing the TiO2 sol to dissolve and obtaining TiO2 crystal-modified carbon material (such as carbon felt) with complete crystal structure, uniform particle size distribution, and good dispersibility. In the calcination step: not only can thermal decomposition be achieved, but also chemically bound water, CO2, and NO can be removed. x Other volatile impurities, under suitable high-temperature conditions, oxides can also undergo solid-phase reactions to form reactive chemical synthesis states; and recrystallization can be achieved: producing certain crystal shapes, crystal sizes, pore structures and specific surface areas; in addition, microcrystals can be appropriately sintered to improve mechanical strength.

[0021] In some embodiments of the present invention, the carbon material includes, but is not limited to, one or more of the following: carbon paper, carbon felt, carbon cloth, carbon brush, etc. Optionally, the carbon material includes at least one of the following: carbon paper, carbon felt, carbon cloth, or carbon brush.

[0022] In some embodiments of the present invention, the carbonization temperature is 300–400°C, and / or the carbonization time is 20–40 min.

[0023] In some embodiments of the present invention, the hydrothermal reaction temperature is 150–250°C, and / or the hydrothermal reaction time is 24–36 h.

[0024] In some embodiments of the present invention, the preparation of titanium dioxide modified carbon-based materials specifically includes the following operations: immersing the carbon material in TiO2 sol, then carbonizing it in a tube furnace, performing a hydrothermal reaction after carbonization, cleaning, and calcining to obtain the titanium dioxide modified carbon-based material.

[0025] In some embodiments of the present invention, the preparation method of TiO2 sol includes the following steps: mixing ethanol and tetrabutyl titanate, adding acetic acid, and stirring until the resulting mixture is milky white to obtain the TiO2 sol.

[0026] In some embodiments of the present invention, the volume ratio of ethanol to tetrabutyl titanate is (1-10):1.

[0027] In some embodiments of the present invention, the volume ratio of tetrabutyl titanate to acetic acid is (1-10):1.

[0028] A second aspect of the present invention provides a wastewater treatment method comprising the following steps:

[0029] S1, Take the sludge to be fermented;

[0030] S2, electro-fermentation treatment of the sludge to be fermented is carried out in the anode chamber of the electrolytic cell; wherein, the anode electrode in the anode chamber comprises a carbon-based material modified with titanium oxide; and the sludge to be fermented comprises chemically enhanced primary sedimentation sludge.

[0031] The wastewater treatment method according to embodiments of the present invention has at least the following beneficial effects:

[0032] Chemically enhanced primary sedimentation (CEPS) involves adding chemical flocculants to wastewater at the upstream stage of wastewater treatment, along with appropriate hydraulic conditions. Charged particles coagulate and settle after mutual adsorption, bridging, and entrainment, enriching carbon, nitrogen, and phosphorus in the precipitate. On one hand, CEPS reduces the pollution load on subsequent processes, thereby decreasing aeration energy consumption and the amount of external carbon source required. On the other hand, CEPS fixes a significant proportion of carbon, nitrogen, and phosphorus sources, facilitating sludge recycling and reuse.

[0033] Electrofermentation of chemically enhanced primary sludge utilizes an electric field environment to regulate the redox state of cells, screening for more adaptable microbial populations and enhancing the gene expression of relevant functional enzymes. Electroactive bacteria engage in interspecies electron transfer, either through a medium or directly between the electrodes. In anodic electrofermentation, microorganisms act as electron donors, producing more oxidation products and synthesizing more ATP, shifting cellular metabolism towards an acid-producing pathway. Electrofermentation transforms recalcitrant organic matter into substrates readily available to bacteria, promoting sludge hydrolysis and the production of dissolved COD, VFA, ammonium, and phosphate.

[0034] In this invention, the anode electrode comprises a carbon-based material modified with titanium oxide, which significantly improves the hydrophilicity of the activated carbon particle surface, enhances the material's biocompatibility and electrocatalytic activity, facilitates microbial attachment and growth, increases the rate of bacterial anaerobic fermentation, and optimizes the treatment effect of the electrofermentation process. Furthermore, compared to precious metals such as platinum, the electrode material of this invention has a lower cost.

[0035] In summary, the anode electrode of this invention comprises a carbon-based material modified with titanium oxide, and CEPS is placed in the anode chamber as an electron donor substrate. The process of enriching and converting iron, phosphorus, nitrogen, and carbon resources from CEPS and simultaneously recovering iron, nitrogen, and phosphorus resources provides a solution to the problems of phosphorus resource shortage, pollution control, and material recycling, and has good application prospects.

[0036] In some embodiments of the present invention, the wastewater treatment method includes the following steps:

[0037] S1, wastewater is taken and treated with chemical coagulation to obtain chemically enhanced primary sludge;

[0038] S2, electro-fermentation treatment of chemically enhanced primary precipitated sludge is carried out in the anode chamber of the electrolytic cell; wherein, the anode electrode in the anode chamber comprises a carbon-based material modified with titanium oxide.

[0039] In some embodiments of the present invention, in step S1, at least one of a chemical coagulant or a coagulant aid is used for chemical coagulation treatment.

[0040] In some embodiments of the present invention, the chemical coagulant includes, but is not limited to, metal coagulants and polymeric coagulants.

[0041] In some embodiments of the present invention, the metal coagulant includes, but is not limited to, iron-containing coagulants, aluminum salt coagulants, etc.

[0042] Through the above implementation methods, the coagulation effect of the coagulant will directly affect the concentration of carbonaceous organic matter and phosphorus in CEPS. Since metals can form complex bonds with phosphorus-containing organic matter, the use of metal coagulants can remove more phosphorus from wastewater.

[0043] In some embodiments of the present invention, the iron-containing coagulant includes, but is not limited to, at least one of iron-containing compounds such as FeCl3, FeSO4, and Fe(OH)3.

[0044] In some embodiments of the present invention, the coagulant aid includes, but is not limited to, various polymeric coagulant aids.

[0045] In some embodiments of the present invention, in step S1, the dosage of iron-containing coagulant in wastewater is 5-35 mg / L, calculated based on iron element.

[0046] In some embodiments of the present invention, in step S1, the chemically enhanced primary sedimentation sludge can be different types of biodegradable sludge.

[0047] In some embodiments of the present invention, in step S2, different sludge can be mixed and fermented to improve the carbon-nitrogen ratio, such as using chemically enhanced primary sedimentation sludge mixed with kitchen waste for co-fermentation.

[0048] Food waste contains a high amount of carbonaceous organic matter. Mixing CEPS with food waste for fermentation can further provide the necessary substances for microbial metabolism.

[0049] In some embodiments of the present invention, in step S1, the volatile matter content (VSS) of the chemically enhanced primary sludge is 4-15 g / L.

[0050] Volatile substances (VS) reflect the content of biodegradable organic matter in the substrate. The higher the content, the more organic matter in the substrate can be utilized by microorganisms. To ensure the growth needs of microorganisms, substrates with low VS content can shorten the sludge retention time, i.e., shorten the influent-effluent interval. In this invention, the VSS in CEPS is 4-15 g / L, which is more conducive to electrofermentation.

[0051] In some embodiments of the present invention, step S2 includes the following operations:

[0052] S2-1, the electrolytic cell includes an anode chamber and a cathode chamber, a titanium oxide modified carbon-based electrode is placed in the anode chamber, a metal electrode is placed in the cathode chamber, and the cathode chamber contains an electrolyte;

[0053] The chemically enhanced primary sedimentation sludge is placed in the anode chamber;

[0054] S2-2 involves supplying power to the electrolytic cell for electro-fermentation, controlling the sludge retention time, acclimating the sludge, and monitoring the pH, VFAs (volatile fatty acids), SCOD (soluble COD), and PO4 levels of the materials in the anode and cathode chambers. 3- and NH4 +As the fermentation and cultivation time increases, the monitoring indicators reach a stable period, the acclimatization ends, and the plant enters the working period for electro-fermentation; carbon, nitrogen, phosphorus, and iron resources are recovered.

[0055] In some embodiments of the present invention, in step S2-2, Fe in the materials in the anode chamber and cathode chamber is also monitored. 2+ Changes in Fe. When the chemical flocculant contains iron salt coagulants, Fe needs to be monitored. 2+ The changes.

[0056] In some embodiments of the present invention, the current efficiency in the electrolytic cell reaches 70% and then reaches a stable period.

[0057] In some embodiments of the present invention, in step S2-1, an ion exchange membrane is used to separate the anode chamber and the cathode chamber.

[0058] In some embodiments of the present invention, in step S2-1, the ion exchange membrane includes a cation exchange membrane.

[0059] In some embodiments of the present invention, in step S2-1, the metal electrode includes, but is not limited to, at least one of titanium, copper, silver, and aluminum, specifically such as titanium sheets, copper sheets, silver sheets, aluminum sheets, and stainless steel sheets. Metal electrodes have high conductivity and provide good electrolytic performance as cathode materials in electrolytic cells.

[0060] In some embodiments of the present invention, the metal electrode comprises at least one of titanium, copper, silver or aluminum.

[0061] In some embodiments of the present invention, the thickness of the metal electrode is 1 to 8 mm, and optionally 1 to 4 mm.

[0062] In some embodiments of the present invention, the electrolyte includes at least one selected from KCl solution, NaCl solution, Na2SO4 solution, or K2SO4 solution. The electrolyte in the electrolyte is relatively stable. Optionally, the solvent in the electrolyte includes water.

[0063] In some embodiments of the present invention, the concentration of the solute in the electrolyte is 0.1 to 3 mol / L, and may be 0.1 to 1.0 mol / L.

[0064] In some embodiments of the present invention, in step S2-1, a stirring device is used to stir the materials in the anode and cathode chambers; wire I is used to connect the positive terminal of the power supply and the titanium oxide-modified carbon-based electrode, and wire II is used to connect the metal electrode and the negative terminal of the power supply. The electrolytic cell with the circuit connected is then incubated at a constant temperature.

[0065] In some embodiments of the present invention, in step S2-1, the temperature of the constant temperature culture is 25-40°C, and / or the rotation speed of the stirring device is 50-400 rpm.

[0066] In some embodiments of the present invention, in step S2-1, the rotational speed is 50 to 200 rpm.

[0067] In some embodiments of the present invention, in step S2-2, the voltage applied by the power supply is in the range of 0.5 to 3V.

[0068] In some embodiments of the present invention, a titanium oxide-modified carbon-based electrode is passed through a conductivity greater than 10. 5 The conductor I (S / m) is connected to the positive terminal of the power supply. Optionally, conductor I comprises a metallic material, such as silver wire, titanium wire, copper wire, aluminum wire, or iron wire, and mainly functions as a conductor. A suitable diameter of metallic material can be selected according to actual needs. Optionally, conductor II comprises the aforementioned metallic material.

[0069] In some embodiments of the present invention, the anode chamber is maintained in an oxygen-deficient environment, with an oxygen content of 5-12 mg / L at one standard atmosphere.

[0070] In some embodiments of the present invention, the volume of chemically enhanced primary sludge in the anode chamber accounts for more than 80% of the total volume of the anode chamber, in order to reduce the volume of top air.

[0071] In some embodiments of the present invention, the acclimatization time in step S2-2 is 8 to 16 days.

[0072] In some embodiments of the present invention, in step S2-2, the sludge retention time (hydraulic retention time) is 5 to 16 days, optionally 5 to 12 days. The sludge retention time can be changed by altering the proportion of the outflowing fermentation broth, and the sludge retention time during the acclimation process and the working period is the same.

[0073] In some embodiments of the present invention, step S2-2, monitoring the materials in the anode and cathode chambers, includes: taking the fermentation broth produced in the anode chamber, centrifuging and filtering it, and then detecting it; and taking the electrolyte in the cathode chamber, centrifuging and filtering it, and then detecting it. Optionally, the centrifugation time is 5 to 15 minutes. The filtration method can be membrane filtration.

[0074] In some embodiments of the present invention, in step S2-2, the nitrogen element in the sludge is converted into NH4. + After being released, iron ions migrate to the cathode chamber, and phosphorus is converted into PO4. 3-The VFAs produced during fermentation accumulate in the anode chamber. Optionally, the VFAs accumulated in the anode chamber can be recovered. Precursors for polymer materials can be obtained. Recovering the electrolyte from the cathode chamber can yield nitrogen fertilizer.

[0075] In some embodiments of the present invention, in step S2-2, Mg is added to the supernatant obtained by filtering the fermentation broth in the anode chamber. 2+ precipitate PO4 3- Mg(NH4)PO4·6H2O (guanostone) can be obtained.

[0076] In some embodiments of the present invention, in step S2-2, the pH of the material in the anode chamber (also referred to as the sludge end) is between 5.3 and 5.7, and the pH of the material in the cathode chamber (also referred to as the electrolyte end) is between 7.5 and 9.5. Due to the interaction of pH and potential, Fe migrates to the cathode chamber... 2+ The precipitation forms brick-red particles, enabling iron recovery. The iron precipitate is mainly Fe(OH)3 and may contain its hydrates.

[0077] In some embodiments of the present invention, in step S2-2, the release rate of iron, phosphorus, and nitrogen refers to the Fe content in the supernatant after filtration of the fermentation broth. 2+ PO4 3- NH4 + The ratio (expressed as a percentage, including molar ratio, mass ratio, etc.) of the concentration of total iron, total phosphorus, and total nitrogen in the chemically enhanced primary sludge reflects the resource conversion efficiency of the system. The iron and nitrogen separation rate (also known as the recovery rate) refers to the ratio of the iron and nitrogen content in the electrolyte to the released Fe. 2+ NH4 + The ratio of contents (expressed as a percentage, which can be a molar ratio, mass ratio, etc.) reflects the resource enrichment and recovery effect of the system. The supernatant obtained after filtering the fermentation broth is also called the fermentation supernatant.

[0078] The formula for calculating the nitrogen separation rate from time t1 to time t2 is as follows:

[0079]

[0080] Y N Nitrogen separation rate (%);

[0081] C0: NH4 in the fermentation supernatant in the anode chamber at time t1 + Concentration, mg / L;

[0082] C A NH4+ in the fermentation supernatant in the anode chamber at time t2 + Concentration, mg / L;

[0083] C CNH4+ in the electrolyte at time t2 + Concentration, mg / L;

[0084] V A : Volume of sludge in the anode chamber, mL;

[0085] V C Volume of electrolyte in the cathode chamber, mL;

[0086] The formula for calculating the iron separation rate is as follows:

[0087]

[0088] Y Fe Iron separation rate (%);

[0089] S A Total iron (Fe) in the anode chamber 2+ Concentration, mg / L;

[0090] S C Total iron (Fe) in the cathode chamber 2+ Concentration, mg / L;

[0091] V A : Volume of sludge in the anode chamber, mL;

[0092] V C Volume of electrolyte in the cathode chamber, mL;

[0093] The formula for calculating current efficiency is as follows:

[0094]

[0095] t1: The start time of a continuous time interval, in seconds (s);

[0096] t2: The end time of the continuous time period, in seconds (s);

[0097] n(NH4 + ): NH4 migrating across the membrane during the time period t1 to t2 + The amount of substance, in mol;

[0098] n(Fe 2+ Fe migrating across the membrane during the time interval t1 to t2 2+ The amount of substance, in mol;

[0099] F: Faraday constant, 96485 C / mol;

[0100] dt: a tiny time interval, in seconds (s);

[0101] I: Current value during time dt, unit: Ampere (A);

[0102] A third aspect of the present invention provides an apparatus for sludge resource utilization, comprising an electrolytic cell including an anode chamber, wherein the anode electrode within the anode chamber comprises a titanium oxide-modified carbon-based material.

[0103] In some embodiments of the present invention, the electrolytic cell is a dual-chamber electrolytic cell, comprising an anode chamber and a cathode chamber.

[0104] In some embodiments of the present invention, the chemically enhanced primary sedimented sludge is subjected to electrofermentation treatment in an anode chamber.

[0105] In a fourth aspect, the present invention provides a method for sludge resource utilization and an apparatus for sludge resource utilization, and its application in wastewater treatment.

[0106] The beneficial effects of this invention include:

[0107] 1) To address the problems of high energy consumption and difficulty in resource recovery in traditional wastewater treatment, a combined process of chemically enhanced coagulation and electro-fermentation to produce acid is proposed. This process enables the efficient enrichment, conversion, and simultaneous separation and recovery of carbon, nitrogen, phosphorus, and other resources in wastewater, and provides a solution to reduce treatment costs and reuse carbon, nitrogen, phosphorus, and other resources.

[0108] 2) The use of electro-fermentation at low voltage for a short time accelerates the hydrolysis and acidification of recalcitrant extracellular polymers, improves the efficiency of acid-producing fermentation, and converts carbon, nitrogen, phosphorus and other substances into industrial products with certain economic value, such as VFAs, nitrogen fertilizer and phosphate fertilizer. Through the device used for sludge resource utilization, simultaneous conversion and separation can be achieved, realizing the recovery of target products and further improving the economic feasibility of sludge resource utilization development.

[0109] 3) Using titanium oxide-modified carbon substrate material as the anode electrode improves hydrophilicity, biocompatibility and electron transfer ability, optimizes bacterial metabolic pathways, promotes microbial acid-producing fermentation, and increases the release ratio of iron, phosphorus and nitrogen in the electrofermentation system. Attached Figure Description

[0110] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0111] Figure 1 A schematic diagram of the main components of CEPS;

[0112] Figure 2 This is a schematic diagram of the electrolytic cell structure and the material reaction principle in Embodiment 1 of the present invention;

[0113] Figure 3 The graph shows the test results of the electrical conductivity of carbon felt and titanium dioxide modified carbon felt in Example 1 of this invention.

[0114] Figure 4This is a graph showing the test results of the hydrophilic properties of the carbon felt in Example 1 of the present invention;

[0115] Figure 5 This is a graph showing the test results of the hydrophilicity of titanium dioxide modified carbon felt in Example 1 of the present invention;

[0116] Figure 6 The graph shows the test results of the substances generated in the reactors of Example 1 and Comparative Example 1 of this invention;

[0117] Figure reference numerals: 1. Anode electrode made of carbon-based material modified with titanium oxide; 2. Metal electrode; 3. Cation exchange membrane. Detailed Implementation

[0118] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0119] Unless otherwise specified, the experimental methods described in the following examples are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used are all commercially available from the conventional market unless otherwise specified.

[0120] The preparation method of TiO2 sol includes the following steps: rapidly stirring 30 mL of ethanol, while slowly adding 5 mL of tetrabutyl titanate, and then adding 0.8 mL of acetic acid. After stirring for 2 days, the solution changes from transparent to milky white. When the liquid color completely turns milky white, the precursor TiO2 gel is obtained.

[0121] Example 1

[0122] This embodiment discloses a wastewater treatment method for municipal wastewater, employing a combination of chemical coagulation sedimentation and electro-fermentation for simultaneous wastewater treatment and resource recovery. The method includes the following steps:

[0123] (I) Prepare CEPS (VSS of 6 g / L) obtained from municipal wastewater coagulated with 8 mg / L FeCl3·6H2O in a wastewater treatment plant and store it in a refrigerator at 4℃. CEPS includes carbon-containing organic matter, nitrogen-containing organic matter, phosphorus-containing organic matter, iron salts, etc. The main components of CEPS are easily perishable macromolecular organic matter (such as proteins, polysaccharides and lipids).

[0124] (II) Soak a 6cm×6cm square carbon felt in TiO2 sol for 10min (for better loading effect, TiO2 sol is in excess and needs to submerge the carbon felt), dry it, take it out and put it into a tube furnace for carbonization at 400℃ for 30min, hydrothermal reaction at 180℃ for 30h, wash it with pure water and dry it, then put it into a tube furnace for calcination at 550℃ under N2 atmosphere for 1h. After completion, titanium oxide modified material (titanium dioxide modified carbon felt) is obtained. In the titanium oxide modified material, the loading of titanium dioxide in 1g of carbon material is 0.02g (the loading can be 0.01-0.06g).

[0125] (III) Insert the material obtained in step (II) into the copper wire and place it in the anode chamber. Place a 1 mm thick titanium sheet in the cathode chamber. Place the cation exchange membrane between the cathode and anode chambers. Place 450 mL of CEPS (CEPS occupying 80-85% of the total volume of the anode chamber, ensuring the top air volume does not exceed 20% of the total volume of the anode chamber, serving as a buffer space for gas production during fermentation) in the anode chamber. Place 450 mL of 0.2 mol / L NaCl solution in the cathode chamber. Place the cathode and anode chambers on a magnetic stirrer and set the speed to 100 rpm. Connect the positive terminal of the power supply to the copper wire with wire A, and connect the negative terminal of the power supply to the titanium sheet with wire B. Set the circuit to constant voltage at 0.5V. Place the reactor in a 28℃ incubator for constant temperature incubation.

[0126] (IV) The hydraulic retention time was 8 days, and pH changes at both the sludge and electrolyte ends were monitored. Half the volume of sludge and electrolyte was discharged every four days, and fresh CEPS and electrolyte were added. The discharged fermentation broth was centrifuged at 4000 rpm for 5 min and filtered through a 0.45 μm filter to obtain sample A. The discharged electrolyte was filtered through a 0.45 μm filter to obtain sample B. VFAs, SCOD, and PO4 were measured in samples A and B. 3- NH4 + and Fe 2+ Once the content stabilizes (the separation rates of nitrogen and iron both reach 80%, and the current efficiency of the electrolytic cell reaches 70%, the acclimation process is complete). Electrofermentation then begins, maintaining the sludge retention time constant. The fermentation broth from the anode chamber and the electrolyte from the cathode chamber are recovered. The calculated separation rates are 82% for iron and 82% for nitrogen, with a current efficiency of 85%.

[0127] In this embodiment, the element separation rate and current efficiency are obtained using the following method:

[0128] The release rate of iron, phosphorus, and nitrogen refers to the amount of Fe in the supernatant (fermentation supernatant) after filtration of the fermentation broth. 2 + PO4 3- NH4 +The ratio (in percentage) of the concentration of total iron, total phosphorus, and total nitrogen in the chemically enhanced primary sludge reflects the resource conversion efficiency of the system. The iron and nitrogen separation rate refers to the ratio of the iron and nitrogen content in the electrolyte to the released Fe. 2+ NH4 + The ratio of content (in percentage) reflects the system's resource enrichment and recovery effect.

[0129] The nitrogen separation rate from t1 to t2 is calculated using the following formula, where t1 usually refers to the start of fermentation:

[0130]

[0131] Y N Nitrogen separation rate (%);

[0132] C0: NH4 in the fermentation supernatant in the anode chamber at time t1 + Concentration, mg / L;

[0133] C A NH4+ in the fermentation supernatant in the anode chamber at time t2 + Concentration, mg / L;

[0134] C C NH4+ in the electrolyte at time t2 + Concentration, mg / L;

[0135] V A : Volume of sludge in the anode chamber, mL;

[0136] V C Volume of electrolyte in the cathode chamber, mL;

[0137] The formula for calculating the iron separation rate is as follows:

[0138]

[0139] Y Fe Iron separation rate (%);

[0140] S A Total iron (Fe) in the anode chamber at the end of fermentation 2+ Concentration, mg / L;

[0141] S C Total iron (Fe) in the cathode chamber at the time of fermentation cessation 2+ Concentration, mg / L;

[0142] V A : Volume of sludge in the anode chamber, mL;

[0143] V C Volume of electrolyte in the cathode chamber, mL;

[0144] The formula for calculating current efficiency is as follows:

[0145]

[0146] t1: The start time of a continuous time interval, in seconds (s);

[0147] t2: The end time of the continuous time period, in seconds (s);

[0148] n(NH4 + ): NH4 migrating across the membrane during the time period t1 to t2 + The amount of substance, in mol;

[0149] n(Fe 2+ ): NH4 migrating across the membrane during the time period t1 to t2 + The amount of substance, in mol;

[0150] F: Faraday constant, 96485 C / mol;

[0151] dt: a tiny time interval, in seconds (s);

[0152] I: Current value during time dt, unit: Ampere (A);

[0153] In some other embodiments of the present invention, iron can be recovered in the form of iron precipitate, which can then be collected.

[0154] In some other embodiments of the present invention, nitrogen recovery can be achieved by fermentation to obtain a solution of ammonium ions, and the solution can be treated to produce nitrogen fertilizer.

[0155] In some other embodiments of the invention, Mg is added to the fermentation supernatant in the anode chamber. 2+ precipitate PO4 3- Mg(NH4)PO4·6H2O (guanostone) can be obtained.

[0156] In some other embodiments of the present invention, different sludge can be mixed and fermented to improve the carbon-nitrogen ratio, such as chemically enhanced primary sludge being mixed and fermented with kitchen waste.

[0157] Example 2

[0158] This embodiment discloses a wastewater treatment method that uses chemical coagulation sedimentation combined with electrofermentation for simultaneous wastewater treatment and resource recovery, comprising the following steps:

[0159] (1) Prepare CEPS (VSS of 8g / L) for coagulation with 15mg / L FeCl3·6H2O in the sewage treatment plant and store it in a refrigerator at 4℃.

[0160] (II) A 5cm×5cm square carbon felt was immersed in TiO2 sol for 10 minutes, dried, and then placed in a tube furnace for carbonization at 350℃ for 30 minutes. After hydrothermal reaction at 180℃ for 24 hours, it was washed with pure water, dried, and then placed in a tube furnace for calcination at 550℃ under N2 atmosphere for 1 hour. After completion, titanium oxide modified material was obtained.

[0161] (III) Insert the material obtained in step (II) into the copper wire and place it in the anode chamber. Place the 2mm thick titanium sheet in the cathode chamber. Place the cation exchange membrane between the cathode and anode chambers. Place 500 mL of CEPS in the anode chamber and 500 mL of 0.5 mol / L KCl solution in the cathode chamber. Place the cathode and anode chambers on a magnetic stirrer and set the speed to 100 rpm. Connect the positive terminal of the power supply to the copper wire with wire A, and connect the negative terminal of the power supply to the titanium sheet with wire B. Set the circuit to constant voltage of 0.8V. Place the reactor in a 40℃ incubator for constant temperature incubation.

[0162] (IV) The hydraulic retention time was 10 days, and pH changes at both the sludge and electrolyte ends were monitored. Every five days, half the volume of sludge and NaCl solution was discharged, and fresh CEPS and electrolyte were added. The discharged fermentation broth was centrifuged at 4000 rpm for 5 min and filtered through a 0.45 μm filter to obtain sample A. The discharged electrolyte was filtered through a 0.45 μm filter to obtain sample B. VFAs, SCOD, and PO4 were measured in samples A and B. 3- NH4 + and Fe 2+ Once the content stabilizes (the separation rates of nitrogen and iron both reach 80%, and the current efficiency of the electrolytic cell reaches 70%, the acclimation process is complete). Electrofermentation is then carried out during the working period, maintaining the sludge retention time unchanged. The fermentation broth from the anode chamber and the electrolyte from the cathode chamber are recovered. Using the same method as in Example 1, the calculated current efficiency is 82%, the iron separation rate is 85%, and the nitrogen separation rate is 85%.

[0163] Example 3

[0164] This embodiment discloses a wastewater treatment method that uses chemical coagulation sedimentation combined with electrofermentation for simultaneous wastewater treatment and resource recovery, comprising the following steps:

[0165] (1) Prepare CEPS (VSS of 10g / L) for coagulation with 20mg / L FeCl3·6H2O in the sewage treatment plant and store it in a refrigerator at 4℃.

[0166] (II) A 7cm×7cm square carbon felt was immersed in TiO2 sol for 10 minutes, dried, and then placed in a tube furnace for carbonization at 350℃ for 30 minutes. After hydrothermal reaction at 180℃ for 24 hours, it was washed with pure water, dried, and then placed in a tube furnace for calcination at 600℃ under N2 atmosphere for 1 hour. After completion, titanium oxide modified material was obtained.

[0167] (III) Insert the material obtained in step (II) into the copper wire and place it in the anode chamber. Place the 1.5 mm thick titanium sheet in the cathode chamber. Place the cation exchange membrane between the cathode and anode chambers. Place 600 mL of CEPS in the anode chamber and 600 mL of 1.0 mol / L Na₂SO₄ solution in the cathode chamber. Place the cathode and anode chambers on a magnetic stirrer and set the speed to 300 rpm. Connect the positive terminal of the power supply to the copper wire with wire A, and connect the negative terminal of the power supply to the titanium sheet with wire B. Set the circuit voltage to 1.0 V. Place the reactor in a 37°C incubator for constant temperature incubation.

[0168] (IV) The hydraulic retention time was 10 days, and pH changes at both the sludge and electrolyte ends were monitored. Half the volume of sludge and electrolyte was discharged every five days, and fresh CEPS and electrolyte were added. The discharged fermentation broth was centrifuged at 4000 rpm for 5 min and filtered through a 0.45 μm filter to obtain sample A. The discharged electrolyte was filtered through a 0.45 μm filter to obtain sample B. VFAs, SCOD, and PO4 were measured in samples A and B. 3- NH4 + and Fe 2+ Once the content stabilizes (the separation rates of nitrogen and iron both reach 80%, and the current efficiency of the electrolytic cell reaches 70%, the acclimation process is complete). Electrofermentation is then carried out during the working period, maintaining the sludge retention time unchanged. The fermentation broth from the anode chamber and the electrolyte from the cathode chamber are recovered. Using the same method as in Example 1, the calculated current efficiency is 75%, the iron separation rate is 90%, and the nitrogen separation rate is 90%.

[0169] Example 4

[0170] This embodiment discloses a wastewater treatment method that uses chemical coagulation sedimentation combined with electrofermentation for simultaneous wastewater treatment and resource recovery, comprising the following steps:

[0171] (1) Prepare CEPS (VSS of 12g / L) for coagulation with 30mg / L FeCl3·6H2O in the sewage treatment plant and store it in a refrigerator at 4℃.

[0172] (II) A 4cm×4cm square carbon felt was immersed in TiO2 sol for 10 minutes, dried, and then placed in a tube furnace for carbonization at 350℃ for 30 minutes. After hydrothermal reaction at 180℃ for 30 hours, it was washed with pure water, dried, and then placed in a tube furnace for calcination at 550℃ under N2 atmosphere for 1 hour. After completion, titanium oxide modified material was obtained.

[0173] (III) Insert the material obtained in step (II) into the copper wire and place it in the anode chamber. Place the 2mm thick titanium sheet in the cathode chamber. Place the cation exchange membrane between the cathode and anode chambers. Place 650 mL of CEPS in the anode chamber and 650 mL of 0.1 mol / L K₂SO₄ solution in the cathode chamber. Place the cathode and anode chambers on a magnetic stirrer and set the speed to 100 rpm. Connect the positive terminal of the power supply to the copper wire with wire A, and connect the negative terminal of the power supply to the titanium sheet with wire B. Set the circuit to constant voltage of 1.5V. Place the reactor in a 40℃ incubator for constant temperature incubation.

[0174] (IV) The hydraulic retention time was 10 days, and pH changes at both the sludge and electrolyte ends were monitored. Half the volume of sludge and electrolyte was discharged every five days, and fresh CEPS and electrolyte were added. The discharged fermentation broth was centrifuged at 4000 rpm for 5 min and filtered through a 0.45 μm filter to obtain sample A. The discharged NaCl solution was filtered through a 0.45 μm filter to obtain sample B. VFAs, SCOD, and PO4 were measured in samples A and B. 3- NH4 + and Fe 2+ Once the content stabilizes (the separation rates of nitrogen and iron both reach 80%, and the current efficiency of the electrolytic cell reaches 70%, the acclimation process is considered complete). Electrofermentation is then carried out during the working period, maintaining a constant hydraulic retention time. The fermentation broth from the anode chamber and the electrolyte from the cathode chamber are recovered. Using the same method as in Example 1, the calculated current efficiency is 72%, the iron separation rate is 83%, and the nitrogen separation rate is 83%.

[0175] Comparative Example 1

[0176] This comparative example discloses a wastewater treatment method, which differs from Example 1 in that the carbon felt is not modified with titanium dioxide.

[0177] Test case

[0178] This experimental example performs performance tests on the embodiments and the obtained materials, specifically including:

[0179] 1) The conductivity of the carbon felt used in Example 1 and the carbon felt modified with titanium dioxide was tested: the carbon felt before and after modification were used as electrodes, and cyclic voltammetry was used to test them respectively. The test results are as follows: Figure 3 As shown, the conductivity of carbon felt increases significantly after modification with titanium dioxide.

[0180] 2) The hydrophilicity of the carbon felt used in Example 1 and the carbon felt modified with titanium dioxide was tested, and the test results are as follows: Figure 4-5 As shown: Figure 4 The contact angle between the medium carbon felt and water is approximately 150°. Figure 5 The contact angle between the modified carbon felt and water is 0°, indicating that the hydrophilicity of the carbon felt increases significantly after modification with titanium dioxide.

[0181] 3) Test the material production in the electrolytic cells of Example 1 and Comparative Example 1, such as... Figure 6 As shown, the use of titanium dioxide-modified carbon felt as an electrode for electro-fermentation of chemically enhanced primary sludge results in good fermentation effect and is more conducive to the recovery of resources such as phosphorus, nitrogen, carbon, and iron in the sludge.

[0182] In summary, this invention employs a dual-chamber electrolytic cell and uses titanium oxide-modified carbon-based materials to treat the chemically enhanced primary sedimentation sludge (CEPS) in the anode chamber. This achieves pollution control while simultaneously producing acid through anaerobic fermentation. Furthermore, it efficiently enriches and converts iron, phosphorus, nitrogen, and carbon resources from the CEPS, simultaneously recovering iron and nitrogen resources. In other words, it simultaneously achieves the conversion and separation of substances, achieving a separation efficiency of 80%. This reduces the treatment cost of sludge carbon, nitrogen, and phosphorus recovery and demonstrates promising application prospects.

[0183] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for sludge resource utilization, characterized in that, The process includes the following steps: electro-fermentation of the sludge to be fermented in the anode chamber of an electrolytic cell; wherein the anode electrode in the anode chamber comprises a titanium oxide-modified carbon-based material, the titanium oxide-modified carbon-based material being a titanium dioxide-modified carbon-based material, the titanium dioxide-modified carbon-based material comprising a carbon-based material and titanium dioxide supported on the carbon-based material; the preparation of the titanium dioxide-modified carbon-based material includes the following operations: immersing the carbon material in TiO2 sol, then carbonizing it in a tube furnace, performing a hydrothermal reaction after carbonization, washing, and calcining to obtain the titanium dioxide-modified carbon-based material; wherein the carbonization temperature is 300~400°C, the carbonization time is 20~40 min, the hydrothermal reaction temperature is 150~250°C, and the hydrothermal reaction time is 24~36 h; the preparation method of the TiO2 sol includes the following operations: mixing ethanol and tetrabutyl titanate, adding acetic acid, and stirring until the resulting mixture is milky white to obtain the TiO2 sol.

2. The method for sludge resource utilization according to claim 1, characterized in that, The sludge to be fermented includes at least one of chemically enhanced primary sedimentation sludge, primary sedimentation sludge, or digested sludge.

3. A wastewater treatment method, characterized in that, Includes the following steps: S1, Take the sludge to be fermented; S2, electro-fermentation treatment of the sludge to be fermented is carried out in the anode chamber of the electrolytic cell; wherein, the anode electrode in the anode chamber comprises a titanium oxide-modified carbon-based material, the titanium oxide-modified carbon-based material is a titanium dioxide-modified carbon-based material, the titanium dioxide-modified carbon-based material comprises a carbon-based material and titanium dioxide supported on the carbon-based material, the preparation of the titanium dioxide-modified carbon-based material includes the following operations: the carbon material is soaked in TiO2 sol, then carbonized in a tube furnace, after carbonization, a hydrothermal reaction is carried out, washed, and calcined to obtain the titanium dioxide-modified carbon-based material; wherein, the carbonization temperature is 300~400°C, the carbonization time is 20~40min, the hydrothermal reaction temperature is 150~250°C, and the hydrothermal reaction time is 24~36h, the preparation method of TiO2 sol includes the following operations: ethanol and tetrabutyl titanate are mixed, acetic acid is added, and the mixture is stirred until the resulting mixture is milky white to obtain the TiO2 sol; the sludge to be fermented includes chemically enhanced primary sedimentation sludge.

4. The wastewater treatment method according to claim 3, characterized in that, In step S1, the volatile matter content of the chemically enhanced primary sedimentation sludge is 4~15g / L.

5. The wastewater treatment method according to claim 3, characterized in that, Step S2 includes the following operations: S2-1, the electrolytic cell includes an anode chamber and a cathode chamber, a titanium oxide modified carbon-based electrode is placed in the anode chamber, a metal electrode is placed in the cathode chamber, and the cathode chamber contains an electrolyte; The chemically enhanced primary sedimentation sludge is placed in the anode chamber; S2-2 involves supplying power to the electrolytic cell for electro-fermentation, controlling the sludge retention time, acclimating the sludge, and monitoring the pH, VFAs, SCOD, and PO4 of the materials in the anode and cathode chambers. 3- and NH4 + As the fermentation and cultivation time increases, the monitoring indicators reach a stable period, the acclimatization ends, and the plant enters the working period for electro-fermentation; carbon, nitrogen, phosphorus, and iron resources are recovered.

6. The wastewater treatment method according to claim 5, characterized in that, The electrolyte includes at least one of KCl solution, NaCl solution, Na2SO4 solution or K2SO4 solution; and / or, in the anode chamber, the volume of chemically enhanced primary precipitated sludge accounts for more than 80% of the total volume of the anode chamber.

7. The wastewater treatment method according to claim 5, characterized in that, In step S2-2, the acclimation time is 8 to 16 days; and / or, in step S2-2, the sludge retention time is 5 to 16 days.

8. The wastewater treatment method according to claim 5, characterized in that, In step S2-2, Mg is added to the supernatant obtained by filtering the fermentation broth in the anode chamber. 2+ precipitate PO4 3- Mg(NH4)PO4·6H2O was obtained.

9. An apparatus for sludge resource utilization, characterized in that, The system includes an electrolytic cell, which includes an anode chamber where the sludge to be fermented is electro-fermented. The anode electrode in the anode chamber comprises a titanium oxide-modified carbon-based material, specifically a titanium dioxide-modified carbon-based material. This titanium dioxide-modified carbon-based material includes a carbon-based material and titanium dioxide supported on it. The preparation of the titanium dioxide-modified carbon-based material includes the following steps: immersing the carbon material in TiO2 sol, followed by carbonization in a tube furnace, and then performing a hydrothermal reaction, washing, and calcining to obtain the titanium dioxide-modified carbon-based material. The carbonization temperature is 300-400°C, the carbonization time is 20-40 min, the hydrothermal reaction temperature is 150-250°C, and the hydrothermal reaction time is 24-36 h. The preparation method of the TiO2 sol includes the following steps: mixing ethanol and tetrabutyl titanate, adding acetic acid, and stirring until the resulting mixture is milky white to obtain the TiO2 sol.

10. The application of the sludge resource utilization method according to any one of claims 1 to 2 or the apparatus for sludge resource utilization according to claim 9 in wastewater treatment.

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