Sewage denitrification method using sulfur-activated carbon composite filler to reinforce microbial electron transfer

Abstract

The invention discloses a sewage denitrification method using sulfur-activated carbon composite filler to reinforce microbial electron transfer, which comprises the following steps: mixing raw materials including sulfur particles, activated carbon powder and a pore-forming agent, and granulating to prepare porous sulfur-activated carbon composite filler; the reactor is filled with porous sulfur-activated carbon composite filler, and sewage denitrification is carried out; wherein the sulfur disproportionating bacteria disproportionate elemental sulfur, generate sulfide and polysulfide and release electrons to the activated carbon, the electrons are conducted through the conductive network and are obtained by the sulfur oxidation denitrifying bacteria, NO3 <-> is reduced into N2, and sewage denitrification is achieved. According to the sulfur-activated carbon composite filler disclosed by the invention, the electron transfer time is shortened, efficient synergy of sulfur disproportionation flora and denitrifying flora is realized, and the reaction rate is increased, so that nitrogen removal is accelerated.

Description

Technical Field

[0001] This invention relates to the field of biological wastewater treatment, and in particular to a wastewater denitrification method using sulfur-activated carbon composite packing to enhance microbial electron transfer. Background Technology

[0002] Biological denitrification is one of the mainstream technologies for treating nitrogen-containing wastewater. Among them, sulfur autotrophic denitrification technology has attracted widespread attention due to its advantages of not requiring external organic carbon sources, low sludge production, and relatively low operating costs, and is especially suitable for deep denitrification of wastewater with low C / N ratios. This technology mainly relies on sulfur-oxidizing bacteria to reduce nitrates to nitrogen gas using reduced sulfur as an electron donor, thereby achieving the purpose of denitrification.

[0003] In existing technologies, based on the electron donor morphology and the construction method of the reaction system, the following main technical paths exist:

[0004] Elemental sulfur autotrophic denitrification: This technology directly uses solid elemental sulfur (such as sulfur) as an electron donor, resulting in slow electron transfer and low denitrification efficiency. Furthermore, the reactor has a long start-up period and is prone to blockage due to sulfur particle caking during operation.

[0005] Sulfur disproportionation coupled with sulfur autotrophic denitrification: Sulfur disproportionating bacteria produce sulfides and polysulfides as electron donors, which are then supplied to sulfur-oxidizing denitrifying bacteria via reflux (including integrated and separate systems) to achieve efficient nitrogen removal. The electron transfer process relies on power input, resulting in complex operation and maintenance and high infrastructure costs.

[0006] Sulfur-based porous packing denitrification: Sulfur disproportionate bacteria and denitrifying bacteria are randomly distributed and spatially separated in the packing, making it difficult to form a directional electron transfer network; and the diffusion distance of nitrate into the interior of the packing is limited, further restricting the denitrification rate. Summary of the Invention

[0007] To overcome the aforementioned shortcomings and deficiencies of the prior art, the present invention aims to provide a wastewater denitrification method using sulfur-activated carbon composite packing to enhance microbial electron transfer. Activated carbon is embedded in a sulfur matrix, forming a structured conductive network. The activated carbon facilitates electron bridging between the two types of microorganisms. The highly efficient electron donors (sulfides and polysulfides) generated by sulfur disproportionation are rapidly transferred to sulfur-oxidizing denitrifying bacteria via the activated carbon, shortening the electron transfer time and achieving efficient synergy between sulfur disproportionating bacteria and sulfur-oxidizing denitrifying bacteria, thereby increasing the reaction rate and accelerating denitrification.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] This invention provides a wastewater denitrification method using sulfur-activated carbon composite packing to enhance microbial electron transfer, comprising the following steps:

[0010] (1) After mixing raw materials including sulfur particles, activated carbon powder and pore-forming agent, the mixture is granulated, dried, calcined and cooled to solidify, and a porous composite filler is prepared; the mass ratio of sulfur particles, activated carbon and pore-forming agent is (55~65): (12~18): (3~8);

[0011] After granulation, the porous composite packing is immersed in a bacterial solution containing sulfur disproportionating bacteria and sulfur oxidizing denitrifying bacteria to colonize the sulfur disproportionating bacteria and sulfur oxidizing denitrifying bacteria, thus obtaining a porous sulfur-activated carbon composite packing.

[0012] In the porous sulfur-activated carbon composite filler, the activated carbon forms a continuous conductive network;

[0013] (2) The porous sulfur-activated carbon composite packing material prepared in step (1) is filled into the reactor for wastewater denitrification; wherein, the sulfur disproportionating bacteria disproportionate sulfur to produce sulfides and polysulfides, and release electrons to the activated carbon. The electrons are conducted through a conductive network and acquired by sulfur-oxidizing denitrifying bacteria, thus removing NO3. - It is reduced to N2, thus achieving denitrification of wastewater.

[0014] In some embodiments of the present invention, the porous sulfur-activated carbon composite filler has a spherical structure with a diameter of 3-6 mm and a porosity of 18-30%.

[0015] In some embodiments of the present invention, the sulfur disproportionating bacteria and sulfur-oxidizing denitrifying bacteria are loaded into the pores of the porous sulfur-activated carbon composite packing.

[0016] In some embodiments of the present invention, the sulfur disproportionating bacteria include at least one of the genera *Dissulfurimicrobium* and *Desulfocapsa*; the sulfur-oxidizing denitrifying bacteria include at least one of the genera *Thiobacillus*, *Sulfurimonas*, *Sulfurovum*, and *Sulfuricurvum*.

[0017] In some embodiments of the present invention, the filling rate of the porous sulfur-activated carbon composite packing in the reactor is 60-90%.

[0018] In some embodiments of the present invention, the granulation of the raw materials comprising sulfur particles, activated carbon, and a pore-forming agent is specifically as follows:

[0019] Sulfur granules and activated carbon powder are ground and mixed, and then granulated into spheres using a roller mill.

[0020] In some embodiments of the present invention, the drying specifically involves placing the item in an oven for low-temperature drying at a temperature of 50-80°C for 3-6 hours.

[0021] In some embodiments of the present invention, the calcination specifically involves placing the dried filler in an oven and calcining it at 120-170°C for 5-30 minutes to complete the melting and pore formation.

[0022] In some embodiments of the present invention, the calcination specifically involves calcining the dried filler at 140-165°C for 8-12 minutes; more preferably, the calcination temperature is 140-150°C, and the ratio of CO bonds to C=O bonds is controlled at (2-2.5):1, thereby achieving dual modification of the carbon skeleton by "conductivity" and "microbial affinity".

[0023] In some embodiments of the present invention, the cooling and shaping specifically involves placing the calcined filler at room temperature for cooling, thereby completing the hardening and shaping of the filler.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] (1) This invention embeds activated carbon into a sulfur matrix to form a structured conductive network, thereby bridging electrons between two types of microorganisms. The highly efficient electron donors (sulfides and polysulfides) generated by sulfur dismutation are rapidly transferred to denitrifying bacteria through activated carbon for denitrification, shortening the electron transfer time and achieving efficient synergy between sulfur dismutating bacteria and sulfur-oxidizing denitrifying bacteria, thus increasing the reaction rate and accelerating denitrification.

[0026] (2) The sulfur-activated carbon composite packing of the present invention provides microbial reaction substrates and maintains the internal anaerobic microenvironment, while activated carbon improves the interfacial electron transfer rate; sulfur disproportionating bacteria and sulfur oxidizing denitrifying bacteria form a symbiotic micro-region, and the electron transfer distance is shortened to the micrometer level.

[0027] (3) In the preparation process of the sulfur-activated carbon composite packing of the present invention, the preferred calcination scheme is adopted: the dried packing is calcined at 120~170℃ for 5~30 min (more preferably at 140~165℃ for 8~12 min). After calcination, the content of CC groups on the surface of the packing increases, and the orderliness and conductivity of the carbon skeleton are improved; the increase of CO bonds indicates that the number of oxygen-containing functional groups such as hydroxyl groups on the surface has increased, which enhances the polarity of the packing and the adhesion ability of microorganisms; the C=O carbonyl content decreases, which reduces the hindrance of some high oxidation state groups to electron migration, making the electron flow path smoother. Therefore, the packing calcined by the scheme of the present invention is more conducive to the adhesion, growth and metabolism of sulfur dismutating bacteria and sulfur-oxidizing denitrifying bacteria, and is more conducive to the electron exchange of the packing micro-interface, thereby further improving the denitrification efficiency and stability. At the same time, the calcination scheme of the present invention can induce partial oxidation of polysulfides into S. 4+ Intermediate sulfur, on the other hand, can retain a certain proportion of low-valent sulfides (S). 2-Intermediate sulfur exhibits excellent reversible electron-donating and accepting properties in the PiSADN sulfur autotrophic denitrification system, acting as an "electron buffer" and a substrate to promote sulfur disproportionation, thereby increasing the coupling rate between sulfur disproportionation and denitrification. Meanwhile, a certain proportion of low-valent sulfides (S...) are retained. 2- To maintain highly conductive sulfur sites on the filler surface and prevent sulfides from converting to the fully oxidized state (S) due to high temperatures. 6+ Excessive conversion maintains the continuity of electron transport channels, making the overall sulfur distribution more conducive to electron coupling between denitrifying bacteria and sulfur-disproportionating bacteria. Attached Figure Description

[0028] Figure 1 The images show the C 1s spectrum (a) and S 2p spectrum (b) of the composite filler before calcination, and the C 1s spectrum (c) and S 2p spectrum (d) after calcination, representing embodiments of the present invention.

[0029] Figure 2 This is a schematic diagram of the electron transport path in the sulfur-activated carbon composite filler according to an embodiment of the present invention.

[0030] Figure 3 The conductivity test results are for the sulfur-based filler and the sulfur-activated carbon composite filler of the present invention, as shown in the embodiments of the present invention.

[0031] Figure 4 The nitrate removal of the sulfur-based filler and the sulfur-activated carbon composite filler of the present invention are shown in the embodiments of the present invention.

[0032] Figure 5 This is a comparison of the total nitrogen removal rates of the sulfur-based packing material in an embodiment of the present invention and the sulfur-activated carbon composite packing material of the present invention.

[0033] Figure 6 This is a comparison of the denitrification rates of the sulfur-based packing material in an embodiment of the present invention and the sulfur-activated carbon composite packing material of the present invention. Detailed Implementation

[0034] The present invention is further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0035] Example

[0036] The preparation process of the sulfur-activated carbon composite filler in this embodiment is as follows:

[0037] A porous sulfur-activated carbon composite filler was prepared by mixing 60g of sulfur granules (purity ≥99.9%), 15g of activated carbon powder, and 5g of sodium bicarbonate and granulating the mixture. The specific process steps are grinding, granulation, drying, melting, pore formation, and molding. The granulation step uses roller granulation to form spheres with a diameter of 3-6 mm. The drying step uses low temperature, specifically drying at 60℃ for 5 hours in an oven. The melting and pore formation steps are achieved by calcination, specifically calcining the dried filler at 145℃ for 10 minutes in an oven to complete melting and pore formation. The molding step is cooling and shaping, specifically cooling the calcined filler at room temperature to complete hardening and shaping.

[0038] The porous sulfur-activated carbon composite filler prepared in this embodiment has a particle size of 3-6 mm, a Mohs hardness of 2, and a porosity of approximately 20%. After granulation, the filler was immersed in a bacterial solution containing sulfur disproportionating bacteria and sulfur-oxidizing denitrifying bacteria for 4 days.

[0039] In the porous sulfur-activated carbon composite packing prepared in this embodiment, the activated carbon forms a continuous conductive network; sulfur disproportionating bacteria (such as Dissulfurimicrobium, Desulfocapsa, etc.) and sulfur-oxidizing denitrifying bacteria (such as Thiobacillus, Sulfurimonas, Sulfurovum, Sulfuricurvum, etc.) coexist and accumulate in the packing to form symbiotic microregions, and the electron transfer distance is shortened to the micrometer level.

[0040] In this embodiment, the activated carbon powder was purchased from Guangdong Yongsheng Activated Carbon Co., Ltd., size 6.0 mm, containing oxygen-containing groups such as C=O and CO. These oxygen-containing functional groups provide polar sites for interfacial redox processes, offering a more convenient way for sulfur-oxidizing denitrifying bacteria (such as Thiobacillus, Sulfurimonas, Sulfurovum, and Sulfuricurvum) attached to the packing material to acquire electrons. This helps microorganisms colonize and form a biofilm on the packing surface more quickly, shortening the system's start-up time. When the influent water quality fluctuates, the electron buffering capacity of the oxygen-containing groups helps maintain the stability of the electron flow within the biofilm, enhancing the system's resistance to shock loads.

[0041] To make the sulfur-activated carbon composite packing easier for microorganisms to attach and grow, shorten the reactor start-up time, and enhance the electronic mediation ability of the packing micro-interface, this invention uses artificially designed short-time high-temperature calcination conditions (120-170℃, 5-30 min, with a particularly preferred calcination scheme of 140-165℃ for 8-12 min) to directionally regulate the thermal stability of carbon and sulfur functional groups on the surface of the activated carbon-sulfur composite packing.

[0042] XPS results showed that at a calcination temperature of 145℃, the surface C=O (carbonyl) functional groups exhibited high thermal sensitivity, easily breaking down or transforming into more conductive CC structures or polar CO structures; while the CO functional groups were more stable at this temperature, with their proportion increasing slightly upon heating, thus achieving a dual enhancement of conductivity and surface hydrophilicity. By controlling the heating time at 145℃ to 10 minutes, excessive degradation of CO groups at excessively high temperatures could be avoided, ensuring the number of polar sites required for microbial attachment.

[0043] Regarding the regulation of sulfur chemical states, this invention utilizes polysulfide states (S... 2- / SS) relative to sulfite (S 4+ The low thermal stability of polysulfides induces partial oxidation of polysulfides to S at 145℃. 4+ Intermediate sulfur. This intermediate sulfur exhibits excellent reversible electron-donating and accepting properties in the PiSADN sulfur autotrophic denitrification system, acting as an "electron buffer" and also as a reaction substrate to promote sulfur disproportionation, thereby increasing the coupling rate between sulfur disproportionation and denitrification. Simultaneously, low-temperature heating can retain a certain proportion of low-valent sulfides (S... 2- To maintain highly conductive sulfur sites on the filler surface and prevent sulfides from converting to the fully oxidized state (S) due to high temperatures. 6+ Excessive conversion maintains the continuity of electron transport pathways. Overall sulfur distribution is more conducive to electron coupling between denitrifying bacteria and sulfur-improving bacteria.

[0044] To better illustrate the effect of the calcination method on the oxide groups on the surface of the composite filler, X-ray photoelectron spectroscopy (XPS) analysis was performed on the composite filler before and after calcination in this embodiment. The results are as follows: Figure 1 As shown, the high-resolution C1s spectra of the composite filler surface before and after calcination show that the filler surface is dominated by CC (284.80 eV), indicating that it has a carbon skeleton structure mainly composed of graphitized carbon, providing a conductive channel basis for interfacial electron migration and electrochemical activity. Simultaneously, CO and C=O related peaks appear at 286.19 eV and 289.08 eV, indicating that the surface contains a certain amount of oxygen-containing functional groups, which can improve the wettability and biofilm adhesion of the filler, and provide polar sites for interfacial redox processes, thus facilitating electron exchange at the microorganism-material interface. These characterization results indicate that the activated carbon filler possesses both a conductive carbon skeleton and oxygen-containing polar sites, which is beneficial for microbial adhesion and film formation and interfacial electron exchange processes. After normalizing the three peaks (CC, CO, and C=O) in the C1s spectra of the composite filler before and after calcination, the relative contents of these groups were analyzed.

[0045] Compared to before calcination, in the C1s spectrum, the peak area ratio of C-C bonds in the calcined sample increased from 67.9% to 68.5%, indicating improved carbon skeleton order, enhanced graphitization, and increased conductivity. The proportion of CO bonds increased from 20.9% to 21.9%, indicating an increase in the number of oxygen-containing functional groups such as hydroxyl groups on the surface, enhancing the filler polarity and microbial adhesion ability. Meanwhile, the proportion of C=O carbonyl groups decreased from 11.1% to 9.6%, reducing the obstruction of electron migration by the high oxidation state structure and making the electron flow path smoother. Calcination achieved a dual modification of the carbon skeleton, namely "conductivity" and "microbiophilicity." At this point, the ratio of CO bonds to C=O bonds was approximately 2.3:1.

[0046] In the S2p spectrum, the low-valence sulfide state (S) in the calcined sample 2- The percentage of CS (sulfur / sulfur) increased from 8.41% to 10.01%, retaining and slightly increasing the conductive sulfur sites, which helps to enhance electron transport ability; the percentage of SS groups decreased from 53.9% to 18.1%, meaning that the proportion of unstable electron donors decreased significantly; intermediate sulfur (S... 4+ The percentage of sulfite (S) increased dramatically from 13.5% to 46.9%, becoming the dominant component and indicative of sulfite content. 4+ A significant increase in ) . Sulfite is an important intermediate in the sulfur disproportionation reaction, exhibiting high electron reversibility and can also serve as a substrate for sulfur disproportionation, promoting the formation of HS by sulfur disproportionation. - and S n 2- Electron circulation is achieved on the surface. 6+ Approximately 18%, maintaining a stable oxide layer helps improve surface hydrophilicity and biofilm stability.

[0047] Overall, this carbon-sulfur synergistic structure obtained through low-temperature calcination has a significant promoting effect on the PiSADN sulfur autotrophic denitrification system:

[0048] 1. Enhanced electronic conductivity: Increased CC ratio and reduced carbonyl groups enhance the conductivity of the carbon skeleton and reduce electron migration resistance. Sulfide sites (S 2- This further forms an electron flow channel, creating a sulfur-carbon synergistic conductive network.

[0049] 2. Improved microbial attachment and interfacial coupling: The increase of CO groups improves surface polarity and hydrophilicity, promotes the co-attachment of sulfur-disproportionating bacteria and denitrifying bacteria and stabilizes biofilm formation, thereby stabilizing the electron exchange process.

[0050] 3. Optimize sulfur cycle activity: convert polysulfide form to sulfite form (S 4+ The process transforms sulfur into highly electronically active sulfur components, significantly enhancing sulfur disproportionation capacity and making it easier for electrons generated during sulfur disproportionation to be transferred to denitrifying bacteria, thereby increasing the denitrification reaction rate.

[0051] In summary, the 145℃ low-temperature short-time calcination process significantly improved the surface chemical composition of the activated carbon-sulfur composite packing, achieving triple optimization of carbon skeleton conductivity, reasonable distribution of sulfur active states, and interfacial polarity regulation. In the PiSADN process, this composite packing can promote efficient electron coupling between sulfur disproportionating bacteria and denitrifying bacteria, thereby improving the system's denitrification efficiency and operational stability.

[0052] A wastewater denitrification method based on the sulfur-activated carbon composite packing material prepared in this embodiment, which enhances microbial electron transfer:

[0053] The reactor is filled with the porous sulfur-activated carbon composite packing material prepared in this embodiment for wastewater denitrification. The sulfur disproportionating bacteria disproportionate sulfur, producing sulfides and polysulfides, and release electrons into the activated carbon. These electrons are conducted through a conductive network and captured by sulfur-oxidizing denitrifying bacteria, converting NO3 into nitrogen. - Reduced to N2, achieving denitrification of wastewater, the electron transfer process is as follows Figure 2 As shown.

[0054] In this embodiment, in order to better reflect the advantages of the sulfur-activated carbon composite filler, a sulfur-based filler without activated carbon was prepared (except for the absence of activated carbon, the preparation is the same as that of the porous sulfur-activated carbon composite filler in this embodiment).

[0055] Figure 3 The conductivity test results are for the sulfur-based filler and the sulfur-activated carbon composite filler of this invention. Current testing was performed using cyclic voltammetry (CV) and Tafel analysis: CV employed a three-electrode system with a platinum electrode as the working electrode, an Ag / AgCl electrode as the reference electrode, and a platinum electrode as the counter electrode. The sulfur-activated carbon composite filler and the sulfur-based filler were added to the three-electrode system, and CV curves were recorded at a scan rate of 100 mV / s. Figure 3 It can be seen that, compared with the sulfur-based filler system, the sulfur-activated carbon composite filler system exhibits higher current response and faster interfacial electron transfer kinetics, indicating that the conductive network of activated carbon and its surface oxygen-containing functional groups can promote electron shuttle and electron transfer between microorganisms.

[0056] An upflow sulfur-autotrophic denitrification filter bed was used as the reactor, filled with sulfur-based packing material and the sulfur-activated carbon composite packing material of this invention, respectively, for wastewater denitrification. Operating conditions: packing material filling rate: 60% (600 ml of packing material in a 1 L reactor); influent nitrate concentration: 42.8 ± 2.51 mg N / L; hydraulic load: 0.96 kg N / m³. 3 ·d, HRT 1 h, temperature 25±2℃, the running results are as follows Figures 4-6 As shown.

[0057] Figure 4 The changes in TN concentration in two reactor groups (the experimental group was filled with sulfur-activated carbon composite packing, and the control group was filled with sulfur-based packing) during operation are shown. As can be seen from the figure, during the start-up period (days 1-3), the effluent TN in the experimental group decreased from 10.0 mg N / L to 6.7 mg N / L, while that in the control group decreased from 20.0 mg N / L to 16.0 mg N / L. From day 4 onwards, the effluent entered a relatively stable phase, with the effluent TN in the experimental group ranging from 0.0 to 5.5 mg N / L, averaging 2.85 ± 1.72 mg N / L; and the effluent TN in the control group ranging from 5.5 to 11.4 mg N / L, averaging 8.52 ± 1.71 mg N / L. Compared with the control group, the steady-state effluent TN in the experimental group decreased by an average of approximately 66.5%.

[0058] Figure 5 The comparison of TN removal rates between the two reactor groups is shown. As can be seen from the figure, during the steady-state phase (days 4-14), the TN removal rate in the experimental group ranged from 87.8% to 100.0%, with an average of 93.30 ± 3.92%; while the TN removal rate in the control group ranged from 71.9% to 86.9%, with an average of 79.59 ± 3.91%. The experimental group showed an average improvement of 13.71% compared to the control group.

[0059] Figure 6 The study compared the total nitrogen (TN) removal rates of the two reactor groups. During the steady-state phase (days 4–14), the TN removal rate in the experimental group ranged from 0.854 to 1.039 kg N / (m³·d), with an average of 0.934 ± 0.056 kg N / (m³·d); while that in the control group ranged from 0.698 to 0.895 kg N / (m³·d), with an average of 0.798 ± 0.070 kg N / (m³·d). The experimental group showed an average increase of approximately 17.0% compared to the control group. This indicates that the sulfur-activated carbon composite packing material can significantly improve the total nitrogen removal rate, contributing to improved effluent quality.

[0060] Those skilled in the art will readily understand that the above description is merely an embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A wastewater denitrification method using sulfur-activated carbon composite packing to enhance microbial electron transfer, characterized in that, Includes the following steps: (1) After mixing raw materials including sulfur particles, activated carbon powder and pore-forming agent, the mixture is granulated, dried, calcined and cooled to solidify, and a porous composite filler is prepared; the mass ratio of sulfur particles, activated carbon and pore-forming agent is (55~65): (12~18): (3~8); After granulation, the porous composite packing is immersed in a bacterial solution containing sulfur disproportionating bacteria and sulfur oxidizing denitrifying bacteria to colonize the sulfur disproportionating bacteria and sulfur oxidizing denitrifying bacteria, thus obtaining a porous sulfur-activated carbon composite packing. In the porous sulfur-activated carbon composite filler, the activated carbon forms a continuous conductive network; (2) The porous sulfur-activated carbon composite packing material prepared in step (1) is filled into the reactor for wastewater denitrification; wherein, the sulfur disproportionating bacteria disproportionate sulfur to produce sulfides and polysulfides, and release electrons to the activated carbon. The electrons are conducted through a conductive network and acquired by sulfur-oxidizing denitrifying bacteria, thus removing NO3. - It is reduced to N2, thus achieving denitrification of wastewater.

2. The wastewater denitrification method using sulfur-activated carbon composite packing to enhance microbial electron transfer according to claim 1, characterized in that, The porous sulfur-activated carbon composite filler has a spherical structure with a diameter of 3-6 mm and a porosity of 18-30%.

3. The wastewater denitrification method using sulfur-activated carbon composite packing to enhance microbial electron transfer according to claim 1, characterized in that, The sulfur-disproportionating bacteria and sulfur-oxidizing denitrifying bacteria are loaded into the pores of the porous sulfur-activated carbon composite packing.

4. The wastewater denitrification method using sulfur-activated carbon composite packing to enhance microbial electron transfer according to claim 1, characterized in that, The sulfur disproportionating bacteria include at least one of the genera *Dissulfurimicrobium* and *Desulfocapsa*; the sulfur-oxidizing denitrifying bacteria include at least one of the genera *Thiobacillus*, *Sulfurimonas*, *Sulfurovum*, and *Sulfuricurvum*.

5. The wastewater denitrification method using sulfur-activated carbon composite packing to enhance microbial electron transfer according to claim 1, characterized in that, In the reactor, the filling rate of the porous sulfur-activated carbon composite packing is 60-90%.

6. The wastewater denitrification method using sulfur-activated carbon composite packing to enhance microbial electron transfer according to claim 1, characterized in that, The process of mixing and granulating raw materials including sulfur particles, activated carbon, and pore-forming agents is specifically as follows: Sulfur granules and activated carbon powder are ground and mixed, and then granulated into spheres using a roller mill.

7. The wastewater denitrification method using sulfur-activated carbon composite packing to enhance microbial electron transfer according to claim 6, characterized in that, The drying process specifically involves placing the item in an oven for low-temperature drying at a temperature of 50-80°C for 3-6 hours.

8. The wastewater denitrification method using sulfur-activated carbon composite packing to enhance microbial electron transfer according to claim 6, characterized in that, The calcination process specifically involves placing the dried filler in an oven and calcining it at 120-170°C for 5-30 minutes to complete the melting and pore formation.

9. The wastewater denitrification method using sulfur-activated carbon composite packing to enhance microbial electron transfer according to claim 6, characterized in that, The calcination process specifically involves calcining the dried filler at 140-165℃ for 8-12 minutes.

10. The wastewater denitrification method using sulfur-activated carbon composite packing to enhance microbial electron transfer according to claim 6, characterized in that, The cooling and shaping process specifically involves placing the calcined filler at room temperature to cool it, thereby completing the hardening and shaping of the filler.

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