Mariculture tail water denitrification device and method based on elemental sulfur conversion

Abstract

The invention belongs to the technical field of aquaculture tail water treatment, and discloses a marine aquaculture tail water denitrification device based on elemental sulfur conversion and a method thereof. According to the device, agricultural wastes or high-molecular polymers are added into elemental sulfur to form an anaerobic sulfenyl polyculture denitrification system, and the anaerobic sulfenyl polyculture denitrification system is used for bearing filler and water pressure through a bearing layer arranged from the bottom; a sulfur autotrophy and heterotrophy synergistic polyculture denitrification system is formed through a functional layer arranged in the middle, and the pH value in the polyculture denitrification system is maintained; and intercepting the fallen biological membrane and suspended matters through a filter layer arranged at the top. According to the invention, heterotrophic denitrification and sulfur autotrophic denitrification technologies are combined to form a solid-phase sulfur-based polyculture denitrification system, elemental sulfur is converted into polysulfide / sulfide, conversion of sulfur is promoted, biocompatibility is improved, denitrification efficiency is improved, starting time of equipment is shortened, and the problem of carbon source dependence is effectively solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of aquaculture tail water treatment, and in particular relates to a device and method for denitrifying seawater aquaculture tail water based on elemental sulfur conversion. Background Art

[0002] In recent years, with the intensive development of marine aquaculture, the total volume of tailwater discharge has surged. Direct discharge without treatment can lead to eutrophication and severely impact marine ecosystems. Achieving efficient nitrogen removal has become a key factor in ensuring that marine aquaculture tailwater meets discharge standards. Biological denitrification is the primary method for nitrogen removal, but the high dissolved oxygen concentration and low carbon to nitrogen ratio of marine aquaculture tailwater limit denitrification efficiency. Consequently, the addition of liquid (methanol, sodium acetate, glucose, etc.) or solid (polymers, agricultural waste, sulfur granules, etc.) electron donors is necessary to meet these requirements. While adding traditional carbon sources such as methanol as electron donors significantly improves denitrification, it can lead to wasted electron consumption, requiring large amounts of carbon source supplementation, resulting in high effluent COD concentrations and a high risk of secondary pollution. In contrast, the use of sulfur granules as electron donors avoids carbon source dependence and enables readily available electrons. However, their low solubility and poor mass transfer efficiency result in slow biofilm growth and long startup times for sulfur autotrophic denitrification units, limiting their application for efficient tailwater nitrogen removal. Aiming at the shortcomings of existing biological denitrification. Summary of the Invention

[0003] To overcome the problems existing in the related art, the present invention discloses an apparatus and method for denitrifying marine aquaculture tailwater based on elemental sulfur conversion. Specifically, the apparatus and method for using the apparatus combine heterotrophic denitrification and sulfur autotrophic denitrification technologies to form a solid-phase sulfur-based mixed denitrification system. This system converts elemental sulfur into polysulfides / sulfides, promoting sulfur conversion and enhancing biocompatibility. This system further improves denitrification efficiency, shortens equipment startup time, and effectively addresses carbon source dependence.

[0004] The technical solution is as follows: A marine aquaculture tailwater denitrification device based on elemental sulfur conversion, comprising: an anaerobic sulfur-based mixed culture denitrification system formed by adding agricultural waste or high molecular weight polymers to elemental sulfur; a load-bearing layer arranged at the bottom of the system withstands filler and water pressure, and a functional layer arranged in the middle forms a sulfur autotrophic and heterotrophic mixed culture denitrification system, promoting the conversion of elemental sulfur into polysulfides / sulfides, improving biological affinity, and maintaining the pH in the mixed culture denitrification system; and a filter layer arranged at the top intercepts detached biofilm and suspended matter; The water inlet system is connected to the control instrument system and is used to carry out forward denitrification from top to bottom of the marine aquaculture tail water through the anaerobic sulfur-based polyculture denitrification system; The backwash system is connected to the control instrument system and is used to backwash the suspended solids and detached biofilm in the functional layer from the bottom to the top through the anaerobic sulfur-based polyculture denitrification system using the marine aquaculture tail water; The control instrument system is used to control the denitrification process and backwash process of the water inlet system and backwash system respectively.

[0005] Furthermore, the anaerobic sulfur-based polyculture denitrification system and the backwashing system are separated into upper and lower parts by a load-bearing partition.

[0006] Furthermore, the load-bearing layer arranged at the bottom is pebbles with a particle size of 2-4 cm.

[0007] Furthermore, the functional layer arranged in the middle is composed of sulfur particles with a particle size of 3-5 mm, agricultural waste or high molecular polymer with a particle size of 3-5 mm, and limestone with a particle size of 3-5 mm; The sulfur particles serve as electron donors for sulfur autotrophic denitrifying bacteria, converting nitrate into nitrogen gas; agricultural waste or high molecular weight polymers serve as slow-release carbon sources, promoting the conversion of elemental sulfur into polysulfide / sulfide, and hydrolyzing and consuming DO, providing a carbon source for heterotrophic denitrifying bacteria to utilize, thereby forming a sulfur autotrophic and heterotrophic mixed denitrification system; The limestone converts the H produced by the denitrification reaction into + Neutralize and maintain pH.

[0008] Furthermore, the filter layer arranged on the top is gravel with a particle size of 3-5 mm, which intercepts the detached biofilm and suspended matter.

[0009] Furthermore, the volume ratio of the load-bearing layer, the functional layer and the filter layer is 1:20:1, and the volume ratio of the sulfur particles, agricultural waste or high molecular polymer in the functional layer can be in the range of 3:1-9:1.

[0010] Furthermore, the water inlet system includes a water inlet pump, a flow meter, a water distribution pipe, a circular sight glass, and a pressure relief valve. The water is inletted from the top by introducing the seawater aquaculture tail water through the water inlet pump, the flow rate of the inlet water is controlled by the flow meter, and the water flow is evenly distributed to the functional layer of the anaerobic sulfur-based polyculture denitrification system through the water distribution pipe. The water inlet status is obtained through the circular sight glass, and the gas in the tank is released through the pressure relief valve to reduce the pressure in the tank.

[0011] Furthermore, the backwash system includes a backwash pump and a backwash filter head. The backwash pump is used to introduce seawater aquaculture tail water from the lower end, and the backwash filter head is used to remove impurities and detached biofilms in the functional layer of the anaerobic sulfur-based polyculture denitrification system.

[0012] Another object of the present invention is to provide a method for denitrifying marine aquaculture tail water based on elemental sulfur conversion, the method utilizing the above-mentioned marine aquaculture tail water denitrification device based on elemental sulfur conversion, the method comprising: S1: The instrument control cabinet starts the water inlet pump. The water flows through the flow meter and pressure gauge in sequence, and then enters the anaerobic sulfur-based polyculture denitrification system through the water distribution pipe. The aquaculture tail water adopts the top-in and bottom-out mode. After passing through the filter layer, functional layer, and load-bearing layer in sequence, it is discharged through the load-bearing partition. The gas in the tank is discharged through the pressure relief valve. In step S2, when the pressure gauge value exceeds the set threshold, the backwash intelligent control algorithm is triggered. Through the instrument control cabinet, the water inlet pump is turned off and the backwash pump is turned on. The backwash water flows through the load-bearing partition in sequence, backwashes the filter head, and then enters the anaerobic sulfur-based polyculture denitrification system. In the form of bottom-in and top-out, the water flows through the load-bearing layer, functional layer, and filter layer in sequence, flushing away the generated impurities and detached biofilm, and then discharged from the top; S3, after backwashing the anaerobic sulfur-based polyculture denitrification system in step S2, when the pressure gauge value is lower than the set threshold, the backwash intelligent control algorithm is triggered, the backwash pump is turned off through the instrument control cabinet, the water inlet pump is started, and step S1 is executed to resume the denitrification process.

[0013] In combination with all the above technical solutions, the beneficial effects of the present invention are as follows: First, the present invention combines heterotrophic denitrification and sulfur autotrophic denitrification by adding sulfur particles and agricultural waste or high molecular weight polymers to form a sulfur-based mixed-culture denitrification system. By promoting the conversion of elemental sulfur to form reduced sulfur (sulfide, polysulfide, etc.) with higher solubility, its biological affinity is improved, the mass transfer efficiency is enhanced, and efficient denitrification of marine aquaculture tail water is achieved.

[0014] The present invention realizes intelligent regulation of the backwash process based on the water inlet pressure of the device, which can effectively solve the problem of biofilm accumulation, optimize the spatial structural characteristics of the biofilm, and greatly improve the denitrification effect.

[0015] Second, by replacing traditional carbon sources (such as methanol and sodium acetate) with sulfur granules, this invention significantly reduces the procurement cost of electron donors. Agricultural waste or high-molecular-weight polymers are used as slow-release carbon sources, requiring far less than traditional carbon sources and avoiding the cumbersome and costly continuous dosing, significantly reducing operating costs. Furthermore, DO is hydrolyzed and consumed, and the hydrolysis products promote sulfur conversion, increasing sulfur utilization and improving mass transfer efficiency. Compared to the lengthy biofilm formation and startup time of pure sulfur autotrophic systems, sulfur-based polyculture systems can more rapidly enrich functional microorganisms, significantly shortening the startup time and enabling faster and more efficient operation.

[0016] Third, the present invention innovatively combines sulfur particles, agricultural waste or high molecular weight polymers in a specific volume ratio (3:1-9:1) and particle size (3-5mm) to construct the core of the "solid-phase sulfur-based polyculture denitrification" functional layer. Using agricultural waste or high molecular weight polymers as a slow-release carbon source can not only hydrolyze and consume dissolved oxygen, providing a carbon source for heterotrophic bacteria, but also effectively promote the growth of low-soluble elemental sulfur (S 0 ) into highly bioavailable reduced sulfur (such as sulfide and polysulfide), breaking through the core bottleneck of poor sulfur mass transfer efficiency in pure sulfur autotrophic denitrification. This synergistic mechanism of using one solid electron donor to promote the conversion of another solid electron donor is significantly original in the field of marine aquaculture tailwater denitrification. It is a new high-efficiency denitrification strategy tailored to the characteristics of marine aquaculture tailwater (high DO, low C / N, high salinity). There are no identical systematic solutions reported in public literature or known engineering applications, filling a technical gap in this niche field. Fourth, the core problem faced by denitrification of marine aquaculture tail water is the contradiction between high dissolved oxygen and low carbon-nitrogen ratio. Relying solely on heterotrophic denitrification requires a large amount of carbon source to be added, which is costly and easily leads to excessive COD; relying solely on sulfur autotrophic denitrification does not have a carbon source problem, but the startup is extremely slow and the efficiency is limited by sulfur mass transfer. The present invention uses sulfur particles and agricultural waste or high molecular polymers as core electron donors, fundamentally avoiding the problem of traditional carbon source addition and the resulting COD increase. The slow-release properties of the added carbon source can promote sulfur conversion and greatly improve the bioavailability and mass transfer efficiency of sulfur, thereby achieving faster startup and more efficient denitrification than pure sulfur autotrophic systems. The present invention closely combines the characteristics of high salt, high DO and low C / N of marine aquaculture tail water to specifically solve the denitrification problem in this specific scenario.

[0017] Fifth, the industry generally believes that the low solubility of elemental sulfur is a physical bottleneck that limits its bioavailability, which is difficult to overcome effectively through conventional means. The present invention creatively introduces agricultural waste or high molecular weight polymers as a slow-release carbon source, and utilizes the reducing environment or specific microbial activity generated during its biodegradation process to convert the insoluble sulfur into 0 The conversion into a more soluble reduced sulfide (such as sulfide, polysulfide) is essentially to convert the electron donor from "solid S 0 ” is converted into “dissolved reduced sulfur” which is more easily utilized by microorganisms, thereby cleverly bypassing the limitation of physical solubility at the biological reaction level, significantly improving the mass transfer efficiency and bioavailability of “sulfur”, and overcoming the prejudice that “sulfur mass transfer efficiency cannot be effectively solved”. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure; Figure 1 This is a schematic diagram of a marine aquaculture tail water denitrification device based on elemental sulfur conversion provided by an embodiment of the present invention; Figure 2 This is a flow chart of denitrification of marine aquaculture tail water based on elemental sulfur conversion provided by an embodiment of the present invention; Figure 3 This is a graph showing changes in total inorganic nitrogen concentration at different HRTs according to the present invention; Figure 4 This is a diagram showing the change in denitrification effect before and after backwashing of the present invention; Figure 5 This is a schematic diagram of the intelligent backwashing control process provided by an embodiment of the present invention; In the figure: 1. Water distribution pipe; 2. Round sight glass; 3. Long sight glass; 4. Instrument control cabinet; 5. Backwash filter head; 6. Load-bearing partition; 7. Pressure gauge; 8. Flow meter; 9. Water inlet pump; 10. Backwash pump; 11. Pressure relief valve. DETAILED DESCRIPTION

[0019] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0020] The innovation of this invention lies in the construction of a sulfur-based mixed denitrification system, achieving efficient nitrogen removal through the coordinated sulfur autotrophic and heterotrophic denitrification processes. Specifically, the functional layer is filled with a composite of sulfur granules, agricultural waste, or high-molecular-weight polymers in a specific volume ratio (3:1-9:1). The agricultural waste or high-molecular-weight polymers accelerate the conversion of elemental sulfur into highly biocompatible reduced sulfur (such as sulfide and polysulfide), improving mass transfer efficiency and denitrification rate, while also providing a carbon source for heterotrophic bacteria. Limestone neutralizes the acidity generated by the reaction, maintaining system stability. This design significantly shortens system startup time and addresses the poor mass transfer, slow startup, and carbon source dependence associated with traditional heterotrophic and sulfur autotrophic denitrification systems. Furthermore, a backwash mechanism, intelligently triggered by an inlet pressure threshold, optimizes the spatial structural characteristics of the biofilm, ensuring long-term stable operation of the system.

[0021] Example 1, as Figure 1As shown, the marine aquaculture tailwater denitrification device based on elemental sulfur conversion, provided in an embodiment of the present invention, aims to combine sulfur particles with agricultural waste or high-molecular-weight polymers to effectively address the low denitrification efficiency and high carbon source consumption caused by the low C / N ratio in marine aquaculture tailwater. It also addresses the problem of biofilm accumulation in the later stages of traditional denitrification devices that affects treatment effectiveness. The device includes an anaerobic sulfur-based polyculture denitrification system, a water inlet system, a backwash system, and a control instrument system.

[0022] For example, an anaerobic sulfur-based mixed denitrification system is formed by adding agricultural waste or high molecular weight polymers to elemental sulfur, wherein the load-bearing layer arranged at the bottom bears the filler and water pressure; a sulfur autotrophic and heterotrophic mixed denitrification system is formed by a functional layer arranged in the middle, promoting the conversion of elemental sulfur into polysulfide / sulfide, improving biological affinity, and maintaining the pH in the mixed denitrification system; and a filter layer arranged at the top intercepts detached biofilm and suspended matter; The water inlet system is connected to the control instrument system and is used to carry out forward denitrification from top to bottom of the marine aquaculture tail water through the anaerobic sulfur-based polyculture denitrification system; The backwash system is connected to the control instrument system and is used to backwash the suspended solids and detached biofilm in the functional layer from the bottom to the top through the anaerobic sulfur-based polyculture denitrification system using the marine aquaculture tail water; The control instrument system is used to control the denitrification process and backwash process of the water inlet system and backwash system respectively.

[0023] For example, according to the structure and functional characteristics of the device, the device further includes a water distribution pipe 1, a round sight glass 2, a long sight glass 3, an instrument control cabinet 4, a backwash filter head 5, a load-bearing partition 6, a pressure gauge 7, a flow meter 8, a water inlet pump 9, a backwash pump 10, and a pressure relief valve 11; Exemplarily, the device body is cylindrical, the interior of which is divided into an anaerobic sulfur-based polyculture denitrification system (filler filling area) and a backwash system (backwash area) by a load-bearing partition 6, and the outside is fixed with a water inlet system and a control instrument system.

[0024] The anaerobic sulfur-based polyculture denitrification system is on the upper layer of the load-bearing partition 6. The anaerobic sulfur-based polyculture denitrification system is sequentially arranged with a load-bearing layer, a functional layer and a filter layer from bottom to top; The bottom is filled with a load-bearing layer of pebbles (particle size 2-4cm). The high mechanical strength of the pebbles can withstand the upper filler and water pressure, preventing deformation of the device. The middle is filled with a functional layer of sulfur particles (particle size 3-5mm), agricultural waste or high molecular polymers (particle size 3-5mm) and limestone (3-5mm). The sulfur particles act as electron donors for sulfur autotrophic denitrifying bacteria, converting nitrate into nitrogen gas. Agricultural waste or high molecular polymers act as slow-release carbon sources, which can hydrolyze and consume dissolved oxygen. The hydrolysis products promote sulfur conversion and improve sulfur utilization. They can also provide a stable carbon source for heterotrophic denitrifying bacteria to use, forming a sulfur autotrophic and heterotrophic mixed denitrification system. Limestone can convert the H produced by the reaction into nitrogen. + Neutralization is performed to maintain pH stability. The top layer is filled with a filter layer of gravel (particle size 3-5mm). The small-sized gravel forms a dense filter layer, intercepting detached biofilm and suspended solids, preventing effluent turbidity. The volume ratio of the load-bearing layer, functional layer, and filter layer is 1:20:1. The volume ratio of sulfur particles, agricultural waste, or high molecular weight polymers in the functional layer can range from 3:1 to 9:1. The total filler volume accounts for 70% of the device volume, and microbial biofilm formation is achieved through natural biofilm formation.

[0025] The water inlet system includes a water inlet pump 9, a flow meter 8, a water distribution pipe 1, a circular sight glass 2, and a pressure relief valve 11. The water inlet is in the form of upward inlet. The seawater aquaculture tail water is introduced from the upper end through the water inlet pump 9. The flow rate of the inlet water is controlled by the flow meter 8. The water flow is evenly distributed to the functional layer through the water distribution pipe 1. The water inlet status is observed through the circular sight glass 2. The gas in the tank is discharged through the pressure relief valve 11 to reduce the pressure in the tank.

[0026] The backwash system includes a backwash pump 10 and a backwash filter head 5. The backwash pump 10 introduces seawater aquaculture tail water from the lower end, and the backwash filter head 5 regularly removes impurities and detached biofilm in the functional layer. According to the value of the pressure gauge 7, the backwash intelligent control algorithm is triggered, and backwashing is achieved through the instrument control system.

[0027] The control instrument system includes an instrument control cabinet 4, which can operate the water inlet pump 9 according to actual conditions, and has a built-in backwash intelligent control algorithm to operate the backwash pump 10.

[0028] Example 2, as Figure 2 The method for denitrification of marine aquaculture tail water based on elemental sulfur conversion provided by an embodiment of the present invention includes: S1, the instrument control cabinet 4 starts the water inlet pump 9, and the water flows through the flow meter 8 and the pressure gauge 7 in sequence, and then enters the anaerobic sulfur-based polyculture denitrification system through the water distribution pipe 1. The aquaculture tail water adopts the top-in and bottom-out mode. It passes through the filter layer, the functional layer, the load-bearing layer in sequence and is discharged through the load-bearing partition 6. The gas in the tank is discharged through the pressure relief valve 11; S2, when the value of the pressure gauge 7 exceeds the set threshold, the backwash intelligent control algorithm is triggered. Through the instrument control cabinet 4, the water inlet pump 9 is turned off and the backwash pump 10 is turned on. The backwash water flows through the load-bearing partition 6 and the backwash filter head 5 in sequence, and then enters the anaerobic sulfur-based polyculture denitrification system. In the form of bottom-in and top-out, the water flows through the load-bearing layer, functional layer, and filter layer in sequence, flushing away the generated impurities and detached biofilm, and then discharged from the top; S3, after backwashing the anaerobic sulfur-based polyculture denitrification system in step S2, when the value of the pressure gauge 7 is lower than the set threshold, the backwashing intelligent control algorithm is triggered, the backwashing pump 10 is turned off through the instrument control cabinet 4, the water inlet pump 9 is started, and step S1 is executed to resume the denitrification process.

[0029] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0030] To further illustrate the effects of the embodiments of the present invention, the following experiments were conducted.

[0031] The present invention describes a highly efficient denitrification device for marine aquaculture tailwater based on efficient elemental sulfur conversion, and its method of use. By passing marine aquaculture tailwater through the device, efficient nitrogen removal is achieved. Conventional denitrification systems typically require a hydraulic retention time exceeding six hours to achieve efficient nitrogen removal. However, the present invention combines sulfur granules with agricultural waste or high-molecular-weight polymers to form a sulfur-based polyculture denitrification system. This system promotes the conversion of elemental sulfur into more soluble reduced sulfur (sulfides, polysulfides, etc.), enhancing its biocompatibility and improving denitrification effectiveness. With a hydraulic retention time of only one hour, the device ensures that treated aquaculture tailwater meets discharge standards, significantly reducing treatment time.

[0032] This device uses a limestone buffer system to continuously neutralize the acid-producing reaction, maintaining the pH of the effluent at around 6.5, and no sulfide is produced in the effluent, reducing secondary pollution.

[0033] The sulfur particles, limestone, gravel, etc. used in this device are common materials with low prices, which effectively saves the cost of tail water treatment.

[0034] Aiming at the problem of periodic failure and poor denitrification effect caused by biofilm accumulation during long-term operation of traditional devices, this device integrates an intelligent backwash control system. 2 , triggering the backwash intelligent control algorithm, starting backwash through the instrument control system, and increasing the denitrification effect from 67% to 94%.

[0035] like Figure 5 As shown, the backwash intelligent control process: normal denitrification → pressure gauge detection (P ≥ 0.3kg / cm 2) → trigger backwash → turn off the water inlet pump → turn on the backwash pump → reverse flush (through the load-bearing layer, functional layer, and filter layer in sequence) → backwash for 10 minutes → monitor the pressure → stop backwash → restart the water inlet pump; The backwash intelligent control algorithm is as follows: class DenitrificationSystem: def __init__(self): # System status variables self.mode = "DENITRIFICATION" # Initial mode: Denitrification self.pressure = 0.0 # Current pressure value (kg / cm²) self.backwash_timer = 0# Backwash timer self.is_inlet_pump_on = 1# Inlet pump status self.is_backwash_pump_on = 0# Backwash pump status # Control parameters self.P_HIGH = 0.3# Pressure threshold for triggering backwash self.P_LOW = 0.2# Pressure threshold for stopping backwashing self.BACKWASH_DURATION = 10# Backwash duration (minutes) def update_pressure(self, new_pressure): """Update system pressure and execute control logic""" self.pressure = new_pressure # Control logic in denitrification mode if self.mode == "DENITRIFICATION": if self.pressure>= self.P_HIGH: self.activate_backwash() # Control logic in backwash mode elif self.mode == "BACKWASH": self.backwash_timer += 1 # Check if backwash is complete if self.backwash_timer>= self.BACKWASH_DURATION: if self.pressure<= self.P_LOW: self.deactivate_backwash() else: # The pressure has not dropped below the threshold and manual intervention is required self.mode = "ALARM" print("Warning: The pressure is still high after backwashing, manual inspection is required!") def activate_backwash(self): """Start backwash program""" print(f"Pressure reaches {self.pressure} kg / cm², triggering backwash") self.mode = "BACKWASH" self.is_inlet_pump_on = 0 self.is_backwash_pump_on = 1 self.backwash_timer = 0 print("→ Water inlet pump is turned off, backwash pump is started") def deactivate_backwash(self): """Stop backwash program""" print(f"Pressure drops to {self.pressure} kg / cm², stop backwashing") self.mode = "DENITRIFICATION" self.is_inlet_pump_on = 1 self.is_backwash_pump_on = 0 print("→ Backwash pump shuts down, feed pump restarts") The high-efficiency denitrification device for marine aquaculture tail water based on high-efficiency conversion of elemental sulfur described in the present invention, when started, presses the instrument control cabinet 4 to start the water inlet pump 9, and the water flows through the flow meter 8 and the pressure gauge 7 in sequence, and then enters the anaerobic sulfur-based polyculture denitrification system through the water distribution pipe 1. The aquaculture tail water adopts a top-in and bottom-out form. It passes through the top filter layer composed of gravel, the functional layer composed of sulfur particles, agricultural waste or high molecular polymers, and limestone, and the load-bearing layer composed of pebbles, and then is discharged through the load-bearing partition 6. The gas in the tank is discharged through the pressure relief valve 11. The above device was used to treat the tail water of a certain aquaculture plant. The tail water of aquaculture enters the anaerobic sulfur-based polyculture denitrification system through the water inlet system. The hydraulic retention time is 5-1h, the water temperature is 23℃, the salinity is 20ppt, the dissolved oxygen in the tail water is 3-4mg / L, and the total inorganic nitrogen is 8.7-38.63mg / L. The denitrification performance of the denitrification device with continuous water inflow is as follows: Figure 3 The change of total inorganic nitrogen concentration under different HRT is shown in the figure. like Figure 3 As shown, the anaerobic sulfur-based polyculture denitrification system, after treatment, has met the Shandong Province marine aquaculture tailwater discharge concentration secondary standard. The uniform mixing of functional layer sulfur particles (3-5 mm) with agricultural waste or high molecular weight polymers (3-5 mm) promotes efficient sulfur conversion, increases electron transfer rate, and converts nitrate nitrogen into nitrogen gas, achieving denitrification. When the hydraulic retention time (HRT) is 5 hours, the inlet concentration is (22.98-33.123 mg / L), and the outlet concentration is (0.20-1.19 mg / L), the removal load reaches a maximum of 108.13 gSN m 3 d -1 When the hydraulic retention time (HRT) is 2.5 h, the inlet concentration is 26.55-30.99 mg / L, the outlet concentration is 1.26-4.67 mg / L, and the removal load reaches a maximum of 199.39 g N m 3 d -1 When the hydraulic retention time (HRT) is 1 h, the inlet concentration is 31.32-35.54 mg / L, the outlet concentration is 3.84-5.82 mg / L, and the removal load reaches a maximum of 198.18 g N m 3 d -1 And because of the limestone filling, the H in the denitrification reaction is continuously neutralized. + , and the pH of the effluent was maintained at around 6.5.

[0036] As water continues to flow in, the biofilm on the surface of the microorganisms will continue to age and fall off. If the blockage is not cleaned in time, it will affect the denitrification effect of the device. When the biofilm is blocked and accumulated, the water pressure increases. Experiments have shown that when the pressure exceeds 0.3kg / cm 2When the value of pressure gauge 7 exceeds 0.3kg / cm 2 , triggering the backwash intelligent control algorithm, through the instrument control cabinet 4, shutting off the water inlet pump 9, turning on the backwash pump 10, the backwash water flows through the load-bearing partition 6 in turn, after the backwash filter head 5, it enters the anaerobic sulfur-based polyculture denitrification system, using the bottom-in and top-out form, the water flows through the load-bearing layer composed of pebbles, the functional layer composed of sulfur particles, agricultural waste or high molecular polymers, and limestone, and the filter layer composed of gravel, washing away the generated impurities and detached biofilm, and discharging from the top end, restoring the device flux and denitrification effect. Figure 4 As shown in the figure below, the denitrification efficiency increased from 67% to 94% after the backwash system was turned on for 10 minutes. This effectively avoided the problem of biofilm accumulation, optimized the spatial structure of the biofilm, and significantly improved the denitrification effect.

[0037] The above description is only a preferred specific implementation method of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A marine aquaculture tail water denitrification device based on elemental sulfur conversion, characterized in that: The device comprises: an anaerobic sulfur-based mixed denitrification system formed by adding agricultural waste or high molecular weight polymers to elemental sulfur; a load-bearing layer arranged at the bottom of the system bears the filler and water pressure; a functional layer arranged in the middle forms a sulfur autotrophic and heterotrophic mixed denitrification system, promotes the conversion of elemental sulfur into polysulfide / sulfide, improves biological affinity, and maintains the pH in the mixed denitrification system; and a filter layer arranged at the top intercepts detached biofilm and suspended matter; The water inlet system is connected to the control instrument system and is used to carry out forward denitrification from top to bottom of the marine aquaculture tail water through the anaerobic sulfur-based polyculture denitrification system; The backwash system is connected to the control instrument system and is used to backwash the suspended solids and detached biofilm in the functional layer from the bottom to the top through the anaerobic sulfur-based polyculture denitrification system using the marine aquaculture tail water; The control instrument system is used to control the denitrification process and backwash process of the water inlet system and backwash system respectively.

2. The marine aquaculture tail water denitrification device based on elemental sulfur conversion according to claim 1, characterized in that: The anaerobic sulfur-based polyculture denitrification system and the backwashing system are separated into upper and lower parts by a load-bearing partition (6).

3. The marine aquaculture tail water denitrification device based on elemental sulfur conversion according to claim 1, characterized in that: The load-bearing layer at the bottom is pebbles with a particle size of 2-4 cm.

4. The marine aquaculture tail water denitrification device based on elemental sulfur conversion according to claim 1, characterized in that: The functional layer in the middle is composed of sulfur particles with a particle size of 3-5mm, agricultural waste or high molecular polymer with a particle size of 3-5mm, and limestone with a particle size of 3-5mm; The sulfur particles serve as electron donors for sulfur autotrophic denitrifying bacteria, converting nitrate into nitrogen gas; agricultural waste or high molecular weight polymers serve as slow-release carbon sources, promoting the conversion of elemental sulfur into polysulfide / sulfide, and hydrolyzing and consuming DO, providing a carbon source for heterotrophic denitrifying bacteria to utilize, thereby forming a sulfur autotrophic and heterotrophic mixed denitrification system; The limestone converts the H produced by the denitrification reaction into + Neutralize and maintain pH.

5. The marine aquaculture tail water denitrification device based on elemental sulfur conversion according to claim 1, characterized in that: The filter layer on the top is gravel with a particle size of 3-5mm, which intercepts the detached biofilm and suspended matter.

6. The marine aquaculture tail water denitrification device based on elemental sulfur conversion according to claim 1, characterized in that: The volume ratio of the load-bearing layer, the functional layer and the filter layer is 1:20:1, and the volume ratio of the sulfur particles, agricultural waste or high molecular polymer in the functional layer can be in the range of 3:1-9:

1.

7. The marine aquaculture tail water denitrification device based on elemental sulfur conversion according to claim 1, characterized in that: The water inlet system comprises a water inlet pump (9), a flow meter (8), a water distribution pipe (1), a circular sight glass (2), and a pressure relief valve (11). Water is inletted from the top by introducing seawater aquaculture tail water through the water inlet pump (9). The flow rate of the inlet water is controlled by the flow meter (8). The water flow is evenly distributed to the functional layer of the anaerobic sulfur-based polyculture denitrification system through the water distribution pipe (1). The water inlet state is obtained through the circular sight glass (2). The gas in the tank is released through the pressure relief valve (11) to reduce the pressure in the tank.

8. The marine aquaculture tail water denitrification device based on elemental sulfur conversion according to claim 1, characterized in that: The backwashing system comprises a backwashing pump (10) and a backwashing filter head (5). The backwashing pump (10) is used to introduce seawater aquaculture tail water from the lower end, and the backwashing filter head (5) is used to remove impurities and detached biofilm in the functional layer of the anaerobic sulfur-based polyculture denitrification system.

9. A method for denitrification of marine aquaculture tail water based on elemental sulfur conversion, characterized in that: The method utilizes the marine aquaculture tail water denitrification device based on elemental sulfur conversion according to any one of claims 1 to 8, and the method comprises: S1, the instrument control cabinet (4) starts the water inlet pump (9), and the water flows through the flow meter (8) and the pressure gauge (7) in sequence, and then enters the anaerobic sulfur-based polyculture denitrification system through the water distribution pipe (1). The aquaculture tail water passes through the filter layer, the functional layer, and the load-bearing layer in sequence, and is discharged through the load-bearing partition (6). The gas in the tank is discharged through the pressure relief valve (11); S2, when the value of the pressure gauge (7) exceeds the set threshold, the backwash intelligent control algorithm is triggered, and the water inlet pump (9) is turned off and the backwash pump (10) is turned on through the instrument control cabinet (4). The backwash water flows through the load-bearing partition (6) and the backwash filter head (5) in sequence, and then enters the anaerobic sulfur-based polyculture denitrification system. In the form of bottom-in and top-out, the water flows through the load-bearing layer, the functional layer, and the filter layer in sequence, washes away the generated impurities and detached biofilm, and is discharged from the top; S3, after backwashing the anaerobic sulfur-based polyculture denitrification system in step S2, when the value of the pressure gauge (7) is lower than the set threshold, the backwashing intelligent control algorithm is triggered, the backwashing pump (10) is turned off through the instrument control cabinet (4), the water inlet pump (9) is started, and step S1 is executed to resume the denitrification process.

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