A sulfur autotrophic denitrification system and a method for operating the same

Abstract

The application discloses a sulfur autotrophic denitrification system and a running method thereof, and belongs to the field of water treatment. The sulfur autotrophic denitrification system comprises at least one filter tank body, and the inside of the filter tank body is sequentially provided with a supporting layer, an active main body layer and a water distribution layer from bottom to top. The active main body layer is filled with a mixture of composite filler and activated sludge. The composite filler is composed of porous filter material and elemental sulfur at a mass ratio of 13.5-18:3. The dry weight ratio of the activated sludge to the composite filler is 1:30-50. The optimal compounding of the porous filter material and the elemental sulfur, the accurate inoculation of the activated sludge and the composite filler and the hierarchical filter tank structure design effectively solve the core problems of the traditional sulfur autotrophic denitrification technology, such as insufficient contact between the sulfur source and the biological membrane and easy loss of the sulfur source. The system startup period is shortened, the denitrification efficiency and the system stability are improved, the impact resistance is enhanced, no additional carbon source is needed, secondary pollution is avoided, and the operation cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of water treatment, and in particular relates to a sulfur autotrophic denitrification system and its operation method. Background Technology

[0002] The rapid development of factory-style aquaculture, while ensuring a supply of high-quality protein, has also generated massive amounts of aquaculture wastewater. This wastewater has distinct characteristics: high nitrate concentration, low carbon-to-nitrogen ratio, and its quality and quantity are easily affected by aquaculture operations such as water changes, disinfection, and feeding. Water quality and quantity exhibit periodic or sudden fluctuations and may contain residual antibiotics and other bioinhibitors. Direct discharge and improper treatment can easily lead to eutrophication of receiving water bodies, causing ecosystem degradation.

[0003] Among low-carbon-nitrogen ratio aquaculture wastewater treatment technologies, sulfur autotrophic denitrification technology is considered a highly promising preferred solution due to its core advantages of not requiring an external carbon source and avoiding secondary organic pollution. The key to achieving efficient sulfur autotrophic denitrification lies in ensuring sufficient contact between the electron donor (sulfur source) and the biofilm, which is also the core prerequisite for the large-scale application of this technology. However, while sulfur autotrophic denitrification wetlands, as an early application of this technology, have achieved some practical results, they have also revealed many inherent defects when treating high-load, low-carbon-nitrogen ratio aquaculture wastewater: they require a large area, making them difficult to adapt to the limited space of aquaculture farms; their hydraulic load is too low, and their treatment capacity cannot match the centralized discharge mode; their shock resistance is insufficient, making them unable to cope with water quality fluctuations; they lack pH and by-product control methods, resulting in poor operational stability; the system is exposed to the natural environment, and the water temperature is significantly affected by the seasons, with efficiency dropping sharply in winter; the more critical problem lies in the failure to solve the effective coupling problem between the sulfur source and the biofilm. The sulfur source is easily lost with the water flow and is unevenly distributed, resulting in insufficient contact between the electron donor and the biofilm, which directly restricts the improvement of denitrification efficiency and the long-term stability of the system. Summary of the Invention

[0004] The purpose of this invention is to propose a sulfur autotrophic denitrification system and its operation method to overcome at least one of the above-mentioned defects in the prior art.

[0005] To achieve this objective, the present invention adopts the following technical solution: The present invention provides a sulfur autotrophic denitrification system, comprising at least one filter body. The filter body has, from bottom to top, a support layer, an activated body layer, and a water distribution layer. The activated body layer is filled with a mixture of composite packing and activated sludge. The composite packing is composed of porous filter media and elemental sulfur in a mass ratio of 13.5-18:3. The dry weight ratio of activated sludge to composite packing is 1:30-50.

[0006] Preferably, the porous filter material has a multi-level pore size distribution, with pores of different sizes interconnected to form a three-dimensional pore network. The pore size ranges are 200-500μm, 50-200μm and less than 50μm, respectively, and the particle size of elemental sulfur is 60-180μm.

[0007] Preferably, the porous filter media has a porosity of 60-80% and a specific surface area of ​​15-30 m². 2 / g, the surface and inner walls of the porous filter media are both rough.

[0008] Preferably, the porous filter media is calcium-based filter media, and the elemental sulfur is sulfur powder.

[0009] Preferably, the thickness of the support layer is 20-30cm and filled with 20-40mm pebbles, the thickness of the active body layer is 110-120cm, and the thickness of the water distribution layer is 8-12cm and filled with 5-8mm of functional filter media.

[0010] Preferably, the functional filter media is calcium-based filter media, volcanic rock, zeolite, ceramsite, coconut shell carbon, columnar carbon, fly ash, steel slag, or manganese sand.

[0011] Preferably, it also includes a black film and a rubber and plastic insulation layer. The outer wall of the filter body is covered with a black film, and the outer wall of the filter body is detachably equipped with a rubber and plastic insulation layer. The filter body is a cylindrical plastic shell with a height-to-diameter ratio of 1-2:1, and an exhaust hole is provided at the top.

[0012] Preferably, the filter body further includes a backwash inlet pipe, a sulfur replenishment pipe, a first inlet pipe, a backwash outlet pipe, a first outlet pipe, and an air inlet pipe. The top wall of the filter body is fixedly connected to the first inlet pipe and the air inlet pipe. The outlet end of the first inlet pipe is located above the water distribution layer, and the outlet end of the air inlet pipe is located inside the support layer. The lower part of the filter body is fixedly connected to the backwash inlet pipe and the first outlet pipe. The outlet end of the backwash inlet pipe is located inside the support layer. The sulfur replenishment pipe is fixedly connected to the backwash inlet pipe, and the connection point is located outside the filter body. The backwash outlet pipe is located above the water distribution layer, and the outlet end extends to the outside of the filter body.

[0013] The present invention also provides an operation method for the above-mentioned sulfur autotrophic denitrification system, comprising the following steps: S1: filter media filling, according to the layered distribution requirements, the support layer, the activated substrate layer and the water distribution layer are filled sequentially from bottom to top; wherein, the activated substrate layer is composed of porous filter media and elemental sulfur mixed evenly, and then mixed with activated sludge and filled to achieve rapid microbial biofilm formation; S2: start-up operation, the water to be treated is introduced into the filter body, the water to be treated passes through the water distribution layer, the activated substrate layer and the support layer in sequence, and nitrates are removed through the sulfur autotrophic denitrification reaction of the activated substrate layer, and the treated effluent and the gas generated by the reaction are discharged.

[0014] Preferably, when the denitrification efficiency is detected to drop below a preset threshold, a sulfur powder slurry with a mass concentration of 45-55 g / L is injected from the bottom of the filter body, and backwashing is started simultaneously. The sulfur powder slurry is flushed at high speed and evenly dispersed throughout the entire active body layer by water flow. The sulfur powder is fixed in situ through the interception and adsorption of the porous filter material and its surface biofilm.

[0015] Preferably, backwashing is performed using a combination of air and water, once a month in summer and once every two months in winter.

[0016] Preferably, based on the fluctuations in the nitrate nitrogen concentration in the influent, a modular operation mode with multiple filter bodies connected in series is adopted to dynamically adjust the treatment load and ensure that the effluent consistently meets the standards.

[0017] The beneficial effects of this invention are as follows: 1. By using the optimal blending of porous filter media and elemental sulfur, the precise ratio of composite packing material and activated sludge for inoculation, and the layered and graded filter structure design, the core problems of insufficient contact between sulfur source and biofilm and easy loss of sulfur source in traditional sulfur autotrophic denitrification technology are effectively solved. This not only shortens the system start-up cycle, improves denitrification efficiency and system stability, and enhances shock resistance, but also eliminates the need for external carbon source, avoids secondary pollution, and reduces operating costs.

[0018] 2. The filter tank has a compact structure that can be modularly connected in series, and occupies a small area. It can be flexibly adapted to the site and treatment load requirements of the farm, which is conducive to large-scale engineering applications.

[0019] 3. By adopting a multi-level pore structure of calcium-based filter media, the precise particle size matching of 60-180μm sulfur powder with 50-200μm pores of calcium-based filter media, combined with the spatial interlocking constraint of the three-dimensional pore network, achieves stable fixation of sulfur powder in the pores of calcium-based filter media, effectively avoiding water erosion and loss, ensuring a continuous and stable supply of sulfur source and full contact with electron donors and biofilm, thereby achieving a highly efficient and stable sulfur autotrophic denitrification reaction.

[0020] 4. The rough morphology of calcium-based filter media can simultaneously improve the microbial biofilm formation performance and the physical binding effect of sulfur powder. High porosity combined with strong adsorption achieves stable fixation of sulfur powder from both spatial constraint and surface adsorption dimensions, ensuring a continuous supply of sulfur source. (25-40m) 2 The specific surface area of ​​ / g takes into account the needs of microbial attachment, slow release of alkalinity and adsorption of pollutants, and is adapted to a multi-level pore size functional zoning design, which effectively improves the denitrification efficiency of the filter media for aquaculture effluent and the overall operational stability of the system.

[0021] 5. The three major functions of sulfur powder fixation, microbial enrichment and pH buffering are integrated in situ at the microscale. Combined with the characteristics of high porosity of 60-80% and rough morphology, it fundamentally solves the problems of traditional systems that require external alkalinity and separation of sulfur powder and microorganisms, and realizes the self-balancing and efficient and stable operation of the system.

[0022] 6. The water distribution layer, activated substrate layer, and support layer adopt differentiated particle size, thickness, and material design. The water distribution layer achieves uniform water distribution, allows for flexible selection of filter media, and takes into account multiple auxiliary functions. The support layer provides stable support and ensures smooth water flow. The 110-120cm activated substrate layer serves as the core denitrification zone, providing ample reaction space and improving total nitrogen removal efficiency. The clear functions of each layer and the layered design also avoid filter media mixing and facilitate later operation and maintenance. The synergistic effect of each layer not only ensures the long-term stable operation of the system but also improves water quality adaptability and overall treatment effect, while reducing operation and maintenance costs.

[0023] 7. The filter body is designed with a dual environmental adaptability structure. It is wrapped with a black film all year round to prevent algae growth, and equipped with a removable rubber and plastic insulation layer for winter to buffer the impact of low temperature and ensure the efficiency of low temperature treatment, realizing the transformation of the system from natural dependence to environmental control.

[0024] 8. Abandoning the drawbacks of traditional wetlands that require a large area, the filter body is constructed using a standardized cylindrical plastic shell with a height-to-diameter ratio of 1-2:1. This design combines the advantages of factory prefabrication, convenient transportation and installation, and a small footprint. In addition, considering the large fluctuations in nitrate nitrogen concentration in aquaculture effluent, a multi-stage module flexible series operation mode is designed. The treatment capacity can be dynamically adjusted according to the influent load, which can efficiently treat high-concentration influent while ensuring stable effluent compliance.

[0025] 9. By integrating a sulfur replenishment pipe into the backwash inlet pipe, an online sulfur replenishment process of slurry injection, hydraulic flushing, uniform distribution, and adsorption fixation is achieved, which is the first to solve the problem of sulfur powder consumption and replenishment in sulfur autotrophic filter ponds. This enables in-situ sulfur source replenishment without the need to start the pond or shut down the machine, which greatly reduces operation and maintenance costs and complexity.

[0026] 10. Abandoning the fixed backwashing frequency, a seasonally differentiated air-water combined backwashing strategy was developed, with one backwashing per month in summer and one backwashing every two months in winter. This strategy is optimized based on the differences in microbial activity and clogging risk in different seasons. While effectively preventing clogging and maintaining stable hydraulic flux, it minimizes disturbance to the fragile biofilm in winter, achieving refined and intelligent system operation and maintenance.

[0027] 11. By using an inoculation method that pre-mixes activated sludge with composite packing material when filling the active substrate layer, microorganisms can achieve uniform attachment in the early stage of packing material filling, which greatly shortens the system biofilm start-up time and improves the efficiency of engineering applications. Attached Figure Description

[0028] Figure 1 This is a cross-sectional structural diagram of Embodiment 1 of the present invention.

[0029] Figure 2This is a schematic diagram of the main structure of Embodiment 1 of the present invention (excluding the rubber and plastic insulation layer).

[0030] Figure 3 This is a schematic diagram of the main structure of the present invention.

[0031] Figure 4 This is a schematic diagram of multiple filter bodies operating in series according to the present invention.

[0032] The labels in the attached diagram are as follows: 1-Filter body, 2-Supporting layer, 3-Activated main body layer, 4-Water distribution layer, 5-Black film, 6-Rubber and plastic insulation layer, 7-Exhaust vent, 8-Backwash inlet pipe, 9-Sulfur replenishment pipe, 10-First inlet pipe, 11-Backwash outlet pipe, 12-Air inlet pipe, 13-First outlet pipe. Detailed Implementation

[0033] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0034] Contents not described in detail in this specification are prior art known to those skilled in the art. In the description of this invention, it should be understood that terms such as "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, terms such as "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0035] Example 1: like Figures 1 to 4 As shown in this embodiment, a sulfur autotrophic denitrification system includes at least one filter body 1. The interior of the filter body 1, from bottom to top, comprises a support layer 2, an activated carbon layer 3, and a water distribution layer 4. The activated carbon layer 3 is filled with a mixture of composite packing material and activated sludge. The composite packing material is composed of porous filter media and elemental sulfur at a mass ratio of 13.5-18:3. Specifically, the mixture is prepared by first uniformly mixing the porous filter media and elemental sulfur, and then mixing it with activated sludge. The dry weight ratio of activated sludge to composite packing material is 1:30-50. In this embodiment, the mass ratio of porous filter media to elemental sulfur is 18:3, the dry weight ratio of activated sludge to composite packing material is 1:45, the porous filter media is calcium-based, and the elemental sulfur is sulfur powder. When there are multiple filter bodies 1, they are connected in series.

[0036] This invention effectively solves the core problems of insufficient contact between the sulfur source and biofilm and easy loss of sulfur powder in traditional sulfur autotrophic denitrification technology. It uses calcium-based filter media as a porous filter medium, which combines a porous structure with alkaline properties. Combined with elemental sulfur (sulfur powder) in the optimal mass ratio, it can firmly bind the sulfur powder within the pores of the calcium-based filter media, ensuring continuous and sufficient contact between the electron donor and the biofilm, while also slowly releasing alkalinity to stabilize the system pH, further improving denitrification efficiency and system stability. Precise inoculation of composite packing material and activated sludge can shorten the system start-up cycle and stabilize the denitrifying bacterial community structure. The stratified filter media is adapted to the characteristics of aquaculture effluent, has strong shock resistance, and requires no external carbon source, avoiding secondary pollution and reducing operating costs. The compact filter structure can be modularly connected in series, occupying a small area and flexibly adapting to the site and treatment load requirements of aquaculture farms, facilitating large-scale engineering applications.

[0037] The porous filter media has a multi-level pore size distribution, with pores of different sizes interconnected to form a three-dimensional pore network. The pore size ranges are 200-500μm, 50-200μm and less than 50μm, respectively, and the particle size of elemental sulfur is 60-180μm.

[0038] This multi-level pore structure enables precise functional zoning: pores of 200-500μm serve as channels for the transport and containment of elemental sulfur, pores of 50-200μm are the main attachment and growth areas for denitrifying microorganisms, and pores smaller than 50μm provide a high specific surface area to support the system's slow release of alkalinity and adsorption of pollutants. It can achieve the slow dissolution of calcium components and release of alkalinity, dynamic neutralization reaction to produce acid, and maintain the pH balance of the system.

[0039] The elemental sulfur particle size of 60-180μm is precisely matched with the pore size of the porous filter media. The particle size falls completely within the 50-200μm pore range of the porous filter media, with pore sizes greater than 50μm and smaller than the lower limit of 200-500μm. This ensures that the sulfur powder will not be lost from pores smaller than 50μm due to its small size, nor will it be unable to enter pores of 200-500μm due to its large size. At the same time, the spatial interlocking constraint formed by the three-dimensional network structure of the pores allows the sulfur powder to be stably fixed in the pores of the porous filter media, avoiding loss caused by water erosion, ensuring a continuous and stable supply of sulfur source, and ensuring full contact between the electron donor and the biofilm, thereby achieving a highly efficient and stable sulfur autotrophic denitrification reaction.

[0040] The porous filter media has a porosity of 60-80% and a specific surface area of ​​15-30 m². 2 / g, the surface and inner walls of the porous filter media are both rough.

[0041] The rough morphology simultaneously enhances the biofilm formation performance and sulfur powder fixation capacity of microorganisms, facilitating rapid attachment and stable biofilm formation by denitrifying microorganisms. Furthermore, the surface microstructure increases the contact friction with sulfur powder, strengthening the physical binding effect. High porosity and a rich three-dimensional pore network provide ample space for sulfur powder, and combined with strong adsorption, effectively confines sulfur powder within the pores through both physical spatial constraint and surface adsorption, preventing sulfur powder loss due to water erosion and ensuring a continuous and stable supply of sulfur source for denitrification. (25-40m) 2 With a specific surface area of ​​ / g, it takes into account the needs of microbial attachment sites, alkalinity slow release, and pollutant adsorption. It is adapted to the multi-level pore size functional zoning design, which improves the denitrification efficiency and overall operational stability of the filter media for wastewater such as aquaculture effluent.

[0042] This invention integrates three major functions—sulfur powder fixation, microbial enrichment, and pH buffering—in situ at the microscale. Combined with its high porosity of 60-80% and rough morphology, it fundamentally solves the problems of traditional systems requiring external alkalinity and the separation of sulfur powder and microorganisms, achieving self-balancing and efficient and stable operation of the system.

[0043] The supporting layer 2 is 20-30cm thick and filled with 20-40mm pebbles; the active substrate layer 3 is 110-120cm thick; and the water distribution layer 4 is 8-12cm thick and filled with 5-8mm functional filter media. The functional filter media include calcium-based filter media, volcanic rock, zeolite, ceramsite, coconut shell carbon, columnar carbon, fly ash, steel slag, or manganese sand.

[0044] The water distribution layer 4 uses functional filter media with a small particle size of 5-8mm and a thickness controlled at 8-12cm. This ensures uniform water distribution and prevents filter media loss or biofilm detachment caused by localized water flow. The support layer 2 uses 20-40mm large-particle pebbles, with a 20-30cm thick layer design forming a stable support base. This effectively supports the filter media in the upper activated substrate layer 3, preventing the filter media from settling and clogging the water distribution system. It also provides sufficient water flow channels, reducing system head loss and ensuring long-term stable operation of the reaction system. The 110-120cm activated substrate layer 3 provides ample reaction space for the denitrification reaction, ensuring sufficient contact and reaction between wastewater, filter media, microorganisms, and sulfur sources. This extends the hydraulic retention time, improves total nitrogen removal efficiency, and is the core functional area for achieving wastewater denitrification. The water distribution layer 4 uses a variety of filter media, including calcium-based media, volcanic rock, and zeolite. It allows for flexible selection based on the specific water quality requirements, such as aquaculture effluent, and integrates multiple functions including alkalinity replenishment, pollutant adsorption, and support for microbial biofilm formation. Working synergistically with the active substrate layer 3, it further enhances the system's water quality adaptability and treatment efficiency. The clearly defined functions and differentiated particle size and thickness of each layer effectively prevent mixing of different filter media, facilitating backwashing and media maintenance, and reducing system operation and maintenance costs.

[0045] It also includes a black film 5 and a rubber and plastic insulation layer 6. The outer wall of the filter body 1 is covered with a black film 5. The outer wall of the filter body 1 is detachably equipped with a rubber and plastic insulation layer 6. The filter body 1 is a cylindrical plastic shell with a height-to-diameter ratio of 1-2:1 and an exhaust hole 7 is provided at the top.

[0046] To overcome the shortcomings of traditional systems that are severely limited by light and temperature, a filter body 1 system with dual environmental adaptability was designed. A black film 5 permanently wraps the filter body, preventing algae growth caused by light exposure. A removable rubber-plastic insulation layer 6 serves as a dedicated winter module, which can be flexibly added or removed according to temperature changes. This provides physical insulation for the filter body 1, effectively buffering against low-temperature shocks and enabling the system to transition from natural dependence to environmental control, ensuring treatment efficiency during cold seasons.

[0047] Abandoning the bulky wetland design, this invention adopts a standardized cylindrical plastic shell with a height-to-diameter ratio of 1-2:1. This design gives the filter body 1 advantages such as factory prefabrication, convenient transportation, flexible installation, and a very small footprint. More importantly, addressing the large fluctuations in nitrate nitrogen concentration in aquaculture effluent, this invention specifies a multi-stage module operation mode that can be flexibly connected in series. This mode can dynamically adjust the system's processing capacity according to the influent load, ensuring stable effluent compliance while efficiently treating high-concentration influent.

[0048] The system includes a backwash inlet pipe 8, a sulfur replenishment pipe 9, a first inlet pipe 10, a backwash outlet pipe 11, a first outlet pipe 13, and an air inlet pipe 12. The top wall of the filter body 1 is fixedly connected to the first inlet pipe 10 and the air inlet pipe 12. The outlet end of the first inlet pipe 10 is located above the water distribution layer 4, and the outlet end of the air inlet pipe 12 is located inside the support layer 2. The lower part of the filter body 1 is fixedly connected to the backwash inlet pipe 8 and the first outlet pipe 13. The outlet end of the backwash inlet pipe 8 is located inside the support layer 2. The sulfur replenishment pipe 9 is fixedly connected to the backwash inlet pipe 8, and the connection point is located outside the filter body 1. The backwash outlet pipe 11 is located above the water distribution layer 4, and its outlet end extends to the outside of the filter body 1. In this embodiment, the air inlet pipe 12 is a perforated pipe, and the backwash outlet pipe 11 is a slotted pipe.

[0049] This system innovatively solves the problem of replenishing sulfur powder after long-term operation of sulfur autotrophic filters. By integrating a sulfur replenishment pipe 9 onto the backwash inlet pipe 8, an online replenishment process is constructed, encompassing slurry injection, hydraulic flushing, uniform distribution, and adsorption fixation. This method achieves in-situ sulfur source replenishment without opening the filter or shutting down the system, simplifying complex maintenance operations to pipeline work, significantly reducing operation and maintenance costs and complexity. It is a key innovation ensuring the long-term economic and stable operation of the system. The air inlet pipe 12 uses a perforated pipe for high-resistance air distribution; a backwash outlet pipe 11 is located at the top, which uniformly collects water through pipe slits and discharges it from the system.

[0050] To address the issue of suspended solids in aquaculture wastewater easily causing blockages, a fixed backwashing frequency was not adopted. Instead, a seasonally differentiated air-water combined backwashing strategy was developed, with more frequent backwashing in summer and less frequent backwashing in winter (once a month in summer and once every two months in winter). This strategy is optimized based on the differences in microbial activity and blockage risk in different seasons. While effectively preventing blockages and maintaining hydraulic flux, it minimizes disturbance to the fragile biofilm in winter, demonstrating the precision and intelligence of operation and maintenance.

[0051] Example 2: This embodiment provides an operation method for a sulfur autotrophic denitrification system according to Embodiment 1. This embodiment takes the treatment of industrialized aquaculture wastewater as an example and includes the following steps: S1: Filter media filling, according to the layered and graded requirements, is carried out sequentially from bottom to top: support layer 2, activated substrate layer 3, and water distribution layer 4. The activated substrate layer 3 is composed of porous filter media and elemental sulfur, which are then mixed evenly with activated sludge before filling, enabling rapid microbial biofilm formation. By using an inoculation method that pre-mixes activated sludge with the composite packing material during the filling of the activated substrate layer 3, microorganisms achieve uniform attachment in the initial stage of packing, significantly shortening the system's biofilm start-up time and improving the efficiency of engineering applications.

[0052] S2: Start-up operation, introduce the wastewater from the factory aquaculture to be treated into the filter body 1. The wastewater from the factory aquaculture to be treated passes through the water distribution layer 4, the active body layer 3 and the support layer 2 in sequence. Nitrate is removed through the sulfur autotrophic denitrification reaction of the active body layer 3. The treated effluent and the gas generated by the reaction are discharged.

[0053] When the denitrification efficiency is detected to drop below the preset threshold, sulfur powder slurry with a mass concentration of 50g / L is injected from the lower part of the filter body 1, and backwashing is started simultaneously. The backwashing water flow is used to flush the sulfur powder slurry at high speed and evenly disperse it throughout the entire active body layer 3. The sulfur powder is fixed in situ through the interception and adsorption of the porous filter material and its surface biofilm.

[0054] During long-term operation, elemental sulfur within the filter body 1 is gradually consumed. To overcome the technical bottleneck of difficult sulfur replenishment in traditional filters, this invention designs an in-situ replenishment method based on a pipeline system. This method is achieved by adding a dedicated sulfur replenishment pipe 9 to the backwash inlet pipe 8. When a decrease in denitrification efficiency is detected and sulfur replenishment is needed, a pre-prepared high-concentration sulfur powder slurry (e.g., 50 g / L) is pumped in through the sulfur replenishment pipe 9, and the backwashing process is immediately initiated. At this time, a large flow of water washes the slurry at high speed and evenly disperses it throughout the entire active substrate layer 3. The sulfur powder in the slurry is then effectively intercepted and adsorbed by the porous filter media and the biofilm attached to its surface, thus efficiently and conveniently completing the replenishment and regeneration of the sulfur source without affecting the main structure of the system or interrupting operation.

[0055] The backwashing frequency is adjusted according to the season. Backwashing adopts a combined air and water method, and is performed once a month in summer and once every two months in winter to prevent filter bed clogging and ensure long-term stable operation.

[0056] In response to the large fluctuations in nitrate nitrogen concentration in aquaculture effluent during the aquaculture cycle, this invention adopts a modular operation mode with a multi-stage filter body connected in series. By flexibly combining different influent loads and dynamically adjusting the treatment load, it ensures stable compliance of effluent water quality while efficiently removing high concentrations of nitrates.

[0057] The water quality monitoring data for summer operation in this embodiment are shown in Table 1:

[0058] Table 1. Water Quality Monitoring Table for Sulfur Autotrophic Denitrification System During Summer Operation As shown in Table 1, the total nitrogen removal rate of the system remained consistently high at 90%-98% during the summer, with most periods exceeding 90%. When the influent total nitrogen concentration fluctuated between 44.09-61.54 mg / L, the secondary effluent total nitrogen concentration could be stably reduced to 0.80-6.14 mg / L, demonstrating excellent resistance to shock loads and treatment stability. Under the condition of higher water temperatures in summer, the system exhibited strong sulfur autotrophic denitrification activity, with stable and efficient nitrogen removal, ensuring the stable and compliant discharge of high-nitrogen wastewater such as aquaculture effluent, and providing data support for the reliable operation of the system during the warm season.

[0059] The water quality monitoring data for winter operation in this embodiment are shown in Table 2:

[0060] Table 2. Water Quality Monitoring Table for Sulfur Autotrophic Denitrification System During Winter Operation As shown in Table 2, under low-temperature conditions in winter, the total nitrogen removal rate of the system remained stably at a high level of 89%-94%. When the total nitrogen concentration in the influent fluctuated between 55.47-60.11 mg / L, the total nitrogen concentration in the secondary effluent could be stably reduced to 3.21-6.55 mg / L, proving that the system has excellent low-temperature resistance and achieved stable operation in winter. The stable treatment efficiency in winter directly verifies the effectiveness of the removable rubber and plastic insulation layer 6 and the differentiated backwashing strategy of denser in summer and sparser in winter. The two together ensured the activity of microorganisms and the stability of the system, breaking through the bottleneck of traditional sulfur autotrophic systems that are limited by temperature. Faced with fluctuations in total nitrogen in the influent, the concentration in the secondary effluent remained within a low range, and the removal rate did not fluctuate significantly, demonstrating that the system still has good resistance to shock loads at low temperatures and can adapt to water quality fluctuations in actual engineering projects.

[0061] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sulfur autotrophic denitrification system, characterized in that: Includes at least one filter body; The interior of the filter body consists of a support layer, an active substrate layer, and a water distribution layer, from bottom to top. The active substrate layer is filled with a mixture of composite packing material and activated sludge. The composite packing material is composed of porous filter media and elemental sulfur in a mass ratio of 13.5-18:

3. The dry weight ratio of activated sludge to composite packing material is 1:30-50.

2. The sulfur autotrophic denitrification system according to claim 1, characterized in that: The porous filter material has a multi-level pore size distribution, with pores of different sizes interconnected to form a three-dimensional pore network. The pore size ranges are 200-500μm, 50-200μm and less than 50μm, respectively. The particle size of the elemental sulfur is 60-180 μm.

3. The sulfur autotrophic denitrification system according to claim 1, characterized in that: The porous filter media has a porosity of 60-80% and a specific surface area of ​​15-30 m². 2 / g; The surface and inner walls of the porous filter material are both rough.

4. The sulfur autotrophic denitrification system according to claim 1, characterized in that: The porous filter media is calcium-based filter media, and the elemental sulfur is sulfur powder.

5. The sulfur autotrophic denitrification system according to claim 1, characterized in that: The supporting layer is 20-30cm thick and filled with 20-40mm pebbles; The thickness of the active host layer is 110-120 cm; The thickness of the water distribution layer is 8-12cm, and it is filled with 5-8mm of functional filter media.

6. The sulfur autotrophic denitrification system according to claim 5, characterized in that: The functional filter media are calcium-based filter media, volcanic rock, zeolite, ceramsite, coconut shell carbon, columnar carbon, fly ash, steel slag, or manganese sand.

7. The sulfur autotrophic denitrification system according to claim 1, characterized in that: It also includes a black film and a rubber and plastic insulation layer; The outer wall of the filter body is covered with a black film; The outer wall of the filter body is detachably fitted with a rubber and plastic insulation layer; The filter body is a cylindrical plastic shell with a height-to-diameter ratio of 1-2:1, and an exhaust vent is provided at the top.

8. The sulfur autotrophic denitrification system according to claim 1, characterized in that: It also includes a backwash water inlet pipe, a sulfur replenishment pipe, a first water inlet pipe, a backwash water outlet pipe, a first water outlet pipe, and an air inlet pipe; The top wall of the filter body is fixedly connected to a first water inlet pipe and an air inlet pipe; The outlet end of the first inlet pipe is located above the water distribution layer; The air outlet of the air inlet pipe is located within the support layer; The lower part of the filter body is fixedly connected to a backwash inlet pipe and a first outlet pipe; The outlet end of the backwash inlet pipe is located within the support layer; The sulfur replenishment pipe is fixedly connected to the backwash water inlet pipe, and the connection point is located outside the filter body. The backwash outlet pipe is located above the water distribution layer, and the outlet end extends to the outside of the filter body.

9. A method for operating a sulfur autotrophic denitrification system according to any one of claims 1-8, characterized in that, Includes the following steps: S1: Filter media filling, according to the layered and graded requirements, the support layer, the active substrate layer and the water distribution layer are filled from bottom to top in sequence; among them, the active substrate layer is made by uniformly mixing porous filter media and elemental sulfur, and then mixing it with activated sludge before filling, so as to realize the rapid biofilm formation of microorganisms. S2: Start-up operation, introduce the water to be treated into the filter body, the water to be treated passes through the water distribution layer, the activated main body layer and the support layer in sequence, and removes nitrates through the sulfur autotrophic denitrification reaction of the activated main body layer. The treated water and the gas generated by the reaction are discharged.

10. The method for operating the sulfur autotrophic denitrification system according to claim 9, characterized in that: When the denitrification efficiency is detected to drop below the preset threshold, sulfur powder slurry with a mass concentration of 45-55 g / L is injected from the bottom of the filter body, and backwashing is started simultaneously. The sulfur powder slurry is flushed at high speed and evenly dispersed to the entire active body layer by water flow. The sulfur powder is fixed in situ through the interception and adsorption of porous filter media and its surface biofilm. Backwashing is performed using a combination of air and water, once a month in summer and once every two months in winter. Based on the fluctuations in influent nitrate nitrogen concentration, a modular operation mode with multiple filter bodies connected in series is adopted to dynamically adjust the treatment load and ensure that the effluent consistently meets the standards.

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