Denitrification module, water body treatment system and water body treatment method

Abstract

This application provides a denitrification module, a water treatment system, and a water treatment method. A single denitrification unit of the denitrification module includes a pre-treatment chamber, a treatment chamber, and a post-treatment chamber connected sequentially in the direction of water flow. The pre-treatment chamber contains an electron donor housing structure and a flow guiding structure to consume dissolved oxygen. The treatment chamber has an exhaust port and an internal biofilm packing layer to reduce nitrates to nitrogen gas for discharge. The post-treatment chamber contains an iron-based filter media layer, an aeration chamber, a biofilm packing layer, and a pH adjustment layer to ensure stable system operation and safe effluent. A flow-limiting mechanism is provided between the inlet of the pre-treatment chamber and the water system to ensure that the denitrification module only takes a portion of the water from the system at a time, achieving the required standard through multiple purification processes, thus reducing the volume of the denitrification module by trading time for space. The system can adapt to water systems of different volumes by scaling the volume of each chamber or by connecting multiple denitrification units or modules in parallel.

Description

Technical Field

[0001] This application relates to the field of water purification technology, specifically to a denitrification module, water treatment system, and water treatment method applicable to aquariums and other water systems. Background Technology

[0002] In water purification scenarios, nitrate accumulation is a major cause of water aging and water quality deterioration. Therefore, denitrification equipment is installed to remove nitrates.

[0003] Existing denitrification equipment is mainly divided into two categories:

[0004] One type is small denitrifiers used in aquaculture systems (such as aquariums, ornamental fish ponds, and aquaculture ponds), for example, the aquarium water purification device disclosed in CN107279031A. This device's treatment process is sequential: "nitrification, activated carbon deoxygenation, denitrification," with no post-treatment guarantee. The byproducts such as nitrites and sulfides produced during the purification process of this type of denitrification equipment are directly returned to the aquaculture system, resulting in a high risk of biotoxicity in the returned water. Furthermore, it is designed based on the idea of ​​achieving purification standards in a single step, meaning that large-volume aquaculture systems require larger denitrification devices to meet purification needs.

[0005] Another type is large-scale denitrification filters for industrial / municipal use, such as CN11302403A and CN104556376A denitrification technologies. These denitrification devices are designed based on the idea of ​​achieving standards through primary purification. They occupy a large area, require high investment, and are complex to operate and maintain. Moreover, they treat high-concentration industrial wastewater / municipal sewage. The treatment method is mainly anaerobic ammonia oxidation, supplemented by short-cut denitrification / nitrification. The treated water is directly discharged into the environment or recycled for continued use as industrial / municipal water. The treatment goals are deep denitrification, energy saving, and phosphorus removal, without considering the biotoxicity risks of the recycled water. They are fundamentally different from the treatment objects, treatment methods, and treatment goals of aquaculture water purification scenarios and are not suitable for aquaculture water purification scenarios. Summary of the Invention

[0006] One of the objectives of this invention is to design a denitrification module suitable for aquaculture water purification scenarios with low risk of biological toxicity to the returned water. To this end, this application proposes the following solution:

[0007] A denitrification module is applicable to various water systems such as aquariums, landscape fish ponds, and aquaculture ponds. It includes a denitrification unit comprising a denitrification pretreatment chamber, a denitrification treatment chamber, and a denitrification posttreatment chamber arranged sequentially, allowing the treated water to flow through these chambers sequentially. Each chamber is equipped with an exhaust port.

[0008] The denitrification pretreatment chamber is equipped with a dissolved oxygen consumption section, which enables the treated water to form an anaerobic or hypoxic environment.

[0009] The denitrification treatment chamber is equipped with a first biofilm packing layer, which serves as a carrier for denitrifying bacteria, enabling the nitrates in the treated water to be reduced to nitrogen gas by the denitrifying bacteria and discharged from the exhaust port.

[0010] The denitrification post-treatment chamber is sequentially arranged along the water flow direction as follows: an iron-based filter media layer, an aeration chamber, a second biofilm packing layer, and a pH adjustment layer. The iron-based filter media layer is used to adsorb sulfides in the treated water and remove some phosphates. The aeration chamber is equipped with an aeration device to increase the dissolved oxygen content of the treated water to create an aerobic environment. The second biofilm packing layer serves as a carrier for nitrifying bacteria, enabling nitrites in the treated water to be oxidized into nitrates by nitrifying bacteria. The pH adjustment layer is used to adjust the pH value of the treated water.

[0011] The denitrification pretreatment chamber, denitrification treatment chamber, and denitrification posttreatment chamber are all sealed chambers to maintain pressure flow when water flows within them. An exhaust pipe can be connected to the exhaust port. One or more denitrification treatment chambers can be connected in series between the denitrification pretreatment chamber and the denitrification posttreatment chamber. The denitrification pretreatment chamber, denitrification treatment chamber, and denitrification posttreatment chamber can be arranged horizontally or stacked in a tower-like structure.

[0012] The aeration device can be one or a combination of two or more of the following: aeration heads, aeration strips, perforated plates, filter heads, or distribution pipes with air vents on their walls. The aeration device is connected to an air supply device (such as a micro air pump or a Venturi jet injector). When selling denitrification modules, an air supply device may or may not be included. The air supply device is preferably located outside the denitrification post-treatment chamber to avoid corrosion from the water.

[0013] The first and second biofilm packing layers can be porous structures that provide attachment and growth space for denitrifying and nitrifying bacteria, such as K3 packing or composite packing commonly found on the market.

[0014] The iron-based filter media layer is used to adsorb sulfides in the treated water and remove some phosphates. The treated water may already contain sulfides. Furthermore, when a sulfur source (such as elemental sulfur or sodium sulfide) is used as an electron donor, denitrifying bacteria will use the sulfur source as an energy source, decomposing it during denitrification to produce sulfides. Sulfides are toxic; by using an iron-based filter media layer to adsorb sulfides in the water, the harmful effects of sulfides flowing back into the water system on aquaculture organisms can be avoided. Alternatively, an iron-based filter media layer can be installed upstream of the denitrification post-treatment chamber.

[0015] The pH adjustment layer is used to regulate the pH value of the treated water, ensuring that the pH of the water flowing out of the denitrification post-treatment chamber remains stable within the range required for aquaculture (e.g., pH 7.0-8.4), allowing it to be directly returned to the water system. The pH adjustment layer can be made of coral skeleton, whose calcium carbonate has a weakly alkaline property. Furthermore, the porous structure of coral skeleton can enrich nitrifying bacteria, enhancing aerobic nitrification of nitrite. Located downstream of the second biofilm packing layer, the pH adjustment layer allows the treated water to flow through the second biofilm packing layer first, followed by the pH adjustment layer. In other words, nitrification occurs first, followed by pH adjustment. The pH may fluctuate slightly due to the nitrification reaction (producing a small amount of acidic substances), but downstream pH adjustment precisely stabilizes the pH to the neutral-to-alkaline range required for aquaculture. Alternatively, the pH adjustment layer can be placed downstream of the denitrification post-treatment chamber.

[0016] When the aforementioned denitrification module treats water, the water first flows through the denitrification pretreatment chamber. The dissolved oxygen in the pretreatment chamber is not consumed, creating an anaerobic or anoxic environment (e.g., dissolved oxygen levels of 0.2 mg / L to 0.6 mg / L). This provides a stable environment for the subsequent denitrification process, ensuring stable operation and efficient removal of nitrates. Afterward, the water flows through the denitrification chamber, where denitrifying bacteria attached to and growing on the first biofilm packing layer reduce the nitrates in the water to nitrogen gas, which is then discharged. (This process also...) The process involves several steps: first, the process generates nitrite, effectively preventing nitrate accumulation that leads to water aging and quality deterioration; second, the treated water flows through the aeration chamber within the denitrification post-treatment chamber, where aeration devices create an aerobic environment, providing a stable environment for the subsequent nitrification process and ensuring its stable operation and efficient removal of nitrite; third, the treated water flows through the second biofilm packing layer within the denitrification post-treatment chamber, where nitrifying bacteria oxidize the nitrite in the treated water into nitrate, preventing nitrite from flowing back into the water and effectively reducing the biotoxicity of the returned water.

[0017] The aforementioned denitrification modules implement pre-treatment measures such as "dissolved oxygen consumption and aeration" before denitrification and nitrification, ensuring stable operation of both processes under ideal conditions. This guarantees that nitrate and nitrite removal rates remain at high levels. The post-treatment of nitrification after denitrification avoids direct recirculation of the denitrified water, thus solving the problem of high biotoxicity risk in the recirculated water from the currently used small denitrifiers in the water system.

[0018] In the aforementioned denitrification module, when the treated water flows through the denitrification post-treatment chamber, it first flows through the iron-based filter media layer to remove sulfides, then flows through the aeration chamber to increase dissolved oxygen, then flows through the second biofilm packing layer to oxidize nitrite, and then flows through the pH adjustment layer for pH adjustment. The combination of "iron-based filter media adsorbing sulfides, aerobic nitrification oxidizing nitrite, and pH adjustment layer stabilizing pH" ensures the absolute safety of the returned water for aquaculture organisms.

[0019] Optionally, the dissolved oxygen consuming section may include a containment structure for accommodating the electron donor and a flow guiding structure, wherein the flow guiding structure is used to form an aerobic biofilm. By jointly consuming the dissolved oxygen in the treated water through the electron donor and the aerobic biofilm on the flow guiding structure, the dissolved oxygen level in the treated water during denitrification is maintained at 0.2 mg / L to 0.6 mg / L.

[0020] If the oxygen consumption in the denitrification pretreatment chamber is insufficient, resulting in dissolved oxygen levels above 0.6 mg / L, it will significantly reduce the metabolic activity of denitrifying bacteria within the treatment chamber, leading to a decrease in denitrification efficiency. Conversely, if the denitrification pretreatment chamber consumes excessive oxygen, causing dissolved oxygen levels below 0.2 mg / L, it will increase the ineffective consumption of carbon sources (electron donors), raising system operation and maintenance costs. Therefore, a dissolved oxygen range of 0.2-0.6 mg / L is the optimal dissolved oxygen window for the coordinated operation of the pretreatment and treatment chambers. In this application, the dissolved oxygen level is precisely controlled from 4-6 mg / L to the aforementioned optimal range to ensure that the denitrifying bacteria within the denitrification treatment chamber are always in an optimal metabolic state, balancing denitrification efficiency and carbon source utilization efficiency, and guaranteeing a stable and efficient denitrification reaction.

[0021] The electron donor can be stored in granular form within the electron donor housing structure. A feed port can be installed at the top of the denitrification pretreatment chamber to conveniently and quickly replenish the electron donor into the electron donor housing structure periodically without disassembling the pipeline. After replenishment, the feed port can be closed to ensure the airtightness of the denitrification pretreatment chamber.

[0022] The aerobic biofilm on the flow guiding structure continuously consumes residual trace dissolved oxygen in the water through microbial metabolism, especially dissolved oxygen in localized areas where the electron donor has not been fully consumed. The synergistic effect of both allows for uniform, stable, and rapid control of the dissolved oxygen concentration within the anoxic / anaerobic range required for denitrification, ensuring the activity of denitrifying bacteria. Furthermore, the dissolved oxygen concentration in aquaculture recirculating water fluctuates with changes in aquaculture conditions. The combined action of the electron donor and aerobic biofilm allows the electron donor to quickly respond to peak dissolved oxygen concentrations and rapidly consume excess dissolved oxygen, while the aerobic biofilm continuously consumes trace dissolved oxygen, forming a dual consumption mechanism of "rapid emergency response + continuous stability." This adapts to the dynamic changes in aquaculture recirculating water, ensuring the stability of the denitrification environment without the need for frequent adjustments to the electron donor dosage. Moreover, while consuming dissolved oxygen, electron donors can also help degrade some organic pollutants in the water. In addition to consuming dissolved oxygen, aerobic biofilms can further degrade small amounts of residual organic matter, ammonia nitrogen and other pollutants in the water. The combination of the two not only achieves efficient consumption of dissolved oxygen, but also completes the initial purification of the water at the same time, reducing the treatment load of the subsequent denitrification chamber.

[0023] Alternatively, the electron donor can be a solid organic carbon source, such as polycaprolactone (PCL), starch copolymers, or polyhydroxyalkanoates (pHA). Solid organic carbon sources can slowly degrade in water, continuously releasing carbon, avoiding the problems of rapid consumption, uneven dissolved oxygen consumption, and short replenishment cycles associated with liquid carbon sources (such as glucose and sodium acetate). The replenishment cycle can reach 90 days or more, and the slow-release characteristic maintains the carbon source concentration in the water within an appropriate range, preventing both excessive carbon sources leading to organic matter residue and insufficient carbon sources leading to inadequate dissolved oxygen consumption, thus meeting the long-term stable treatment requirements of aquaculture recirculating aquaculture systems. Furthermore, solid organic carbon sources can degrade into carbon dioxide and water, without introducing toxic or harmful impurities into the water, avoiding the potential secondary pollution and microbial inhibition problems associated with inorganic electron donors (such as elemental sulfur and sulfides), thus meeting the low biotoxicity risk requirements of aquaculture recirculating aquaculture systems.

[0024] The carbon source replenishment cycle is precisely calculated based on the daily nitrate removal rate and carbon-nitrogen ratio, so that the carbon source release rate is dynamically matched with the nitrate load, avoiding excessive or insufficient carbon source.

[0025] Optionally, the flow guiding structure can be high-density bio-cotton. High-density bio-cotton has a porosity of over 90%. Its uniform and dense microporous structure provides a large specific surface area, allowing for rapid enrichment of aerobic microorganisms and promoting the rapid acclimatization and stable growth of the aerobic biofilm. It also effectively traps suspended fine impurities and organic debris in the water, achieving preliminary purification. Furthermore, the trapped organic matter can serve as nutrients for the aerobic biofilm, improving its dissolved oxygen consumption efficiency. It also ensures stable water flow, preventing excessively fast flow rates that could lead to biofilm desorption. In addition, high-density bio-cotton is made of non-toxic and biodegradable polymer materials, preventing the introduction of toxic or harmful impurities into the water. This meets the low biotoxicity risk requirements of aquaculture recirculating water systems. Moreover, it is not easily powdered or rotten, maintaining structural integrity even after long-term immersion in water, eliminating the need for frequent replacements, reducing system maintenance costs, and meeting the long-term stable treatment requirements of aquaculture recirculating water systems.

[0026] As needed, corresponding functional layers (such as phosphorus removal material layer, activated carbon layer, maifanite layer, etc.) can be added between the second biofilm packing layer and the pH adjustment layer to meet the customized needs of customers.

[0027] The denitrification post-treatment chamber may include a water distribution chamber. This chamber receives the treated water discharged from the denitrification chamber and distributes it evenly. The water distribution chamber is located upstream of the iron-based filter media layer. After being evenly distributed through the water distribution chamber, the treated water can fully contact the iron-based filter media layer, enhancing the sulfide adsorption effect. The iron-based filter media layer is located upstream of the aeration chamber to prevent sulfide desorption caused by aeration, ensuring stable sulfide adsorption.

[0028] The volume and residence time of the denitrification post-treatment chamber are designed based on the maximum possible yield of toxic byproducts (nitrites, sulfides, etc.) produced by the denitrification treatment chamber to ensure the safety of the effluent.

[0029] The iron-based filter media layer, the second biofilm packing layer, and the pH adjustment layer can be placed in separate layered baskets, so that the whole system can be maintained only once every 2-3 years, greatly reducing the difficulty of maintenance and extending the maintenance cycle.

[0030] Optionally, the denitrification pretreatment chamber, the denitrification treatment chamber, and the denitrification posttreatment chamber are all provided with exhaust ports at their tops. This facilitates the rapid discharge of nitrogen.

[0031] Optionally, the denitrification pretreatment chamber can employ a top-down water flow pattern, the denitrification treatment chamber can employ a bottom-up water flow pattern, and the denitrification posttreatment chamber can employ a bottom-up water flow pattern. Both the denitrification treatment chamber and the denitrification posttreatment chamber are equipped with a water distribution chamber to ensure uniform water flow through the biofilm packing layer. When both chambers employ a bottom-up water flow pattern, the water distribution chamber is located at the bottom of these two chambers. Alternatively, the denitrification pretreatment chamber can also employ a horizontal water flow pattern, an inclined water flow pattern, or a bottom-up water flow pattern, and the denitrification treatment chamber and the denitrification posttreatment chamber can also employ a horizontal water flow pattern, an inclined water flow pattern, or a top-down water flow pattern.

[0032] Optionally, when used to purify water in a water system, the inlet of the denitrification pretreatment chamber is connected to the outlet of the water system, and the outlet of the denitrification posttreatment chamber is connected to the return outlet of the water system.

[0033] As needed, corresponding functional modules (such as filtration modules) can be added between the inlet of the denitrification pretreatment chamber and the outlet of the water system. As needed, corresponding functional layers (such as phosphorus removal material layer, activated carbon layer, maifan stone layer, etc.) can also be added between the outlet of the denitrification posttreatment chamber and the return water outlet of the water system to meet the customized needs of customers.

[0034] A flow-limiting mechanism can be installed between the inlet of the denitrification pretreatment chamber and the outlet of the water system. This mechanism can be a needle valve, flow regulating valve, or electronic flow controller, or any structure capable of limiting the flow rate. The flow-limiting mechanism restricts the denitrification module to process a portion of the water system's volume per hour, ranging from 8.5% to 20% of the system's volume. This flow-limiting ratio, combined with the water system's circulation rate of 5-10 times / hour, allows for the complete purification of the water body 2.0 to 4.8 times per day. This overcomes the limitations of the traditional "one-time purification to meet standards" design concept, innovatively adopting a "multiple purification to meet standards" design approach. It achieves efficient removal through the cumulative effect of time, trading time for space, enabling a denitrification module with a very small volume to treat water bodies several times larger than its water body volume. This overcomes the physical limitation that "the volume of water treated is proportional to the volume of the treatment module."

[0035] Optionally, the inlet of the denitrification pretreatment chamber and the outlet of the denitrification posttreatment chamber are standardized quick-connect interfaces. This allows for rapid assembly with water systems or other functional modules, improving ease of use and making it suitable for industrial production. Alternatively, the inlet of the denitrification pretreatment chamber and the outlet of the denitrification posttreatment chamber can also be non-standard interfaces.

[0036] Optionally, the denitrification pretreatment chamber, denitrification treatment chamber, and denitrification posttreatment chamber can be integrated into the same housing to form an integrated module. An inlet and outlet are provided on the housing surface; users only need to connect these inlets and outlets to the corresponding interfaces of the water system for use, improving ease of use. Furthermore, the integrated module design is suitable for commercial product sales, offering a uniform appearance, convenient transportation, and simple installation.

[0037] The denitrification module can be equipped with a separate drive pump to circulate water between the denitrification module and the water system. Alternatively, the denitrification module can be without a drive pump, with the water system's circulation pump driving the water circulation between the denitrification module and the water system. For example, a bypass can be led from the outlet of the water system's circulation pump to guide the water to the denitrification module. The bypass location can be the outlet of the water system's main circulation pump or the outlet of the water system's clear water return pump. The treated water can be returned to the upstream of the water system's clear water tank, the main tank's nitrification zone, or the aeration zone to ensure that the effluent is reoxygenated and fully mixed with the water in the main tank.

[0038] For small-volume water systems, a single denitrification unit can be used for purification. For medium to large-volume water systems, multiple denitrification units can be connected in parallel. In this case, the denitrification module consists of multiple denitrification units connected in parallel, with each unit's inlet connected to the same inlet pipe and its outlet connected to the same outlet pipe. These parallel denitrification units can be stacked vertically or arranged horizontally. Alternatively, for medium to large-volume water systems, multiple denitrification modules can also be connected in parallel for purification. Each denitrification module's inlet pipe is connected to the same main inlet pipe, and each denitrification module's outlet pipe is connected to the same main outlet pipe. These parallel denitrification modules can be stacked vertically or arranged horizontally. Alternatively, for medium to large-volume water systems, a single denitrification unit with a larger volume can also be used for purification. In this way, it can be applied to water systems of various sizes, from small to large.

[0039] Furthermore, this application also provides a water treatment system, including the above-mentioned denitrification module and a filtration module. The denitrification module is connected downstream of the filtration module, so that the water to be treated first flows through the filtration module and then through the denitrification module. The filtration module includes a filtration chamber, and granular filter media is disposed in the filtration chamber.

[0040] The specific structure of the filtration module can refer to the structure of the filtration unit in the Chinese patent application filed by the applicant on March 13, 2026, entitled "Filtration Unit, Filtration Equipment, Filtration Method, Design Method of Filtration Unit, Design Method of Nitrification Unit". In addition, this denitrification module can also be used in conjunction with the nitrification unit in this patent. The nitrification unit converts ammonia nitrogen into nitrate, and this denitrification module reduces nitrate into nitrogen gas, together realizing the whole process of water purification in closed water bodies.

[0041] The denitrified water can also be directly fed into the upstream of the filtration module, where the nitrification filter media of the nitrification unit of the filtration module can further reduce the nitrite content in the denitrified water.

[0042] Furthermore, this application also provides a water treatment method, including a denitrification treatment step, wherein the denitrification treatment step includes a dissolved oxygen consumption treatment, a denitrification treatment and a post-treatment performed sequentially, wherein the dissolved oxygen consumption treatment consumes the dissolved oxygen in the water to form an anaerobic or hypoxic environment; the denitrification treatment uses denitrifying bacteria to reduce nitrates in the water to nitrogen gas and release it; the post-treatment includes a nitrification treatment, wherein the nitrification treatment uses nitrifying bacteria to oxidize nitrites in the water to nitrates.

[0043] Optionally, electron donors and aerobic biofilms are used to consume dissolved oxygen in the water being treated, and electron donors are replenished in a timely manner to maintain the dissolved oxygen level in the water being treated at 0.2 mg / L to 0.6 mg / L during denitrification.

[0044] The post-treatment includes sequential iron-based filter media adsorption treatment, nitrification treatment, and pH adjustment treatment. The nitrification treatment uses nitrifying bacteria to oxidize nitrite in the water to nitrate. The iron-based filter media adsorption treatment uses iron-based filter media to adsorb sulfides in the water and remove some phosphates. The adjustment treatment adjusts the pH of the water to the range of 7.0-8.4.

[0045] When treating the water in the water system, a portion of the water is taken from the system each time for treatment, and then returned to the system after treatment. This process is repeated multiple times until all the water in the system has been treated. The hourly water intake is 8.5% to 20% of the water volume of the system.

[0046] Optionally, the water treatment method further includes a filtration step, wherein the filtration step involves filtering the water to be treated using granular filter media, and the filtration step is performed before the denitrification step. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of one embodiment of the denitrification module provided in this application.

[0048] The annotations in the attached figures are explained as follows:

[0049] 1. Denitrification pretreatment chamber, 2. Denitrification treatment chamber, 3. Denitrification posttreatment chamber, 4. Water distribution chamber, 5. Aeration chamber, 6. Aeration device, 7. Exhaust pipe, 8. Feed port, 9. Flow guiding structure, 10. First biofilm packing layer, 11. Second biofilm packing layer, 12. pH adjustment layer, 13. Iron-based filter media layer, 14. Clear water chamber, 15. Flow limiting mechanism. Detailed Implementation

[0050] The denitrification module of this application is applicable to various water systems such as aquariums, ornamental fish ponds, and aquaculture ponds. To enable those skilled in the art to better understand the technical solution of this application, the following description, in conjunction with the appendix, is provided. Figure 1 The present application will be further described below with reference to specific embodiments. This description is merely exemplary and does not constitute a limitation on the present application. Any non-substantial modifications to the present application by those skilled in the art based on the prior art fall within the protection scope of the present application.

[0051] like Figure 1 As shown, in this embodiment, the denitrification module includes a denitrification unit. The denitrification unit includes a denitrification pretreatment chamber 1, two denitrification treatment chambers 2, a denitrification posttreatment chamber 3, and a clear water chamber 14, which are connected in sequence and arranged horizontally.

[0052] The denitrification pretreatment chamber 1, denitrification treatment chamber 2, and denitrification posttreatment chamber 3 are all sealed chambers. Each of the three chambers has an exhaust port at the top, from which nitrogen gas can be discharged. An exhaust pipe 7 is connected to the exhaust port.

[0053] The denitrification pretreatment chamber 1 is equipped with a feed port 8 at the top, through which electron donors are supplied to the chamber. The chamber also contains an electron donor receiving structure (not shown in the figure) and high-density bio-cotton (with a porosity of over 90%) serving as a flow guiding structure 9. This high-density bio-cotton is used to form an aerobic biofilm. The electron donors and the aerobic biofilm on the flow guiding structure 9 work together to consume dissolved oxygen in the treated water, creating an anaerobic or anoxic environment (e.g., dissolved oxygen levels of 0.2 mg / L to 0.6 mg / L). This provides a stable environment for the subsequent denitrification process, ensuring stable operation and efficient removal of nitrates. The water flow within the denitrification pretreatment chamber 1 is from top to bottom.

[0054] The denitrification treatment chamber 2 features a bottom-up water flow and includes a water distribution chamber 4 located at its bottom. A first biofilm packing layer 10 serves as a carrier for denitrifying bacteria, allowing nitrates in the treated water to be reduced to nitrogen gas, which is then discharged through the exhaust port. Because dissolved oxygen is consumed before the reduction reaction, maintaining dissolved oxygen levels between 0.2 mg / L and 0.6 mg / L, and considering that the water temperature in aquariums, ornamental fish ponds, and aquaculture ponds is generally between 25℃ and 28℃, this dissolved oxygen and temperature range ensures that the denitrifying bacteria are within their optimal metabolic window. This guarantees efficient and stable operation of the denitrification reduction reaction, resulting in a high nitrate removal rate, such as over 60%, or even over 90%.

[0055] The denitrification post-treatment chamber 3 features a bottom-up water flow pattern, with the following layers arranged sequentially from bottom to top: a water distribution chamber 4, an iron-based filter media layer 13, an aeration chamber 5, a second biofilm packing layer 11, and a pH adjustment layer. When the treated water flows through the denitrification post-treatment chamber 3, it first flows through the water distribution chamber 4 for even distribution, then through the iron-based filter media layer 13 to remove sulfides, then through the aeration chamber 5 to increase dissolved oxygen, then through the second biofilm packing layer 11 to oxidize nitrite, and finally through the pH adjustment layer to adjust the pH to a slightly alkaline level (e.g., pH 7.0-8.4).

[0056] The combined effect of "iron-based filter media adsorbing sulfides, aerobic nitrification oxidizing nitrite, and pH adjustment layer stabilizing pH" ensures the absolute safety of the returned water for aquaculture organisms. Because aeration is performed before the oxidation reaction, the nitrification oxidation reaction operates stably in an aerobic environment, thus maintaining a high nitrite removal rate, even exceeding 98%. The post-nitrification treatment, following denitrification, prevents the direct return of nitrite generated after denitrification, ensuring the safety of the returned water.

[0057] The clear water chamber 14 serves as the clear water supply station for the water system. The treated water from the denitrification post-treatment chamber 3 first enters the clear water chamber 14, mixes with the clear water inside, and is then pumped into the water system together with the clear water. This simplifies the structure by eliminating the need for a separate return pipeline for the treated water. Furthermore, since the dissolved oxygen content of the treated water from the denitrification post-treatment chamber 3 is low, directly returning it to the water system would lead to excessively low dissolved oxygen levels in some areas of the water system. Mixing it with the clear water before returning it to the water system avoids this problem.

[0058] An expansion chamber can be set between the denitrification post-treatment chamber 3 and the clear water chamber 14. Corresponding functional layers (such as phosphorus removal material layer, activated carbon layer, maifan stone layer, etc.) can be added in the expansion chamber as needed to meet the customized needs of customers.

[0059] A valve is installed between the inlet of the denitrification pretreatment chamber 1 and the outlet of the water system, serving as a flow restriction mechanism 15 to limit the inflow of the denitrification module to 8.5% to 20% of the water volume of the water system. This flow restriction ratio works in conjunction with the circulation rate of 5-10 times / h in aquariums, landscape fish ponds, and aquaculture ponds, enabling the complete purification of the water body 2.0 to 4.8 times per day. This breaks through the limitations of the traditional "one-time purification to meet standards" design concept and innovatively adopts the design concept of "multiple purification to meet standards," achieving efficient purification through the cumulative effect of time. By trading time for space, it allows a denitrification module with a very small volume to treat water bodies several times larger than its water volume, overcoming the physical limitation that "the volume of water treated is proportional to the volume of the treatment module."

[0060] The volume and residence time of the denitrification post-treatment chamber 3 are designed based on the maximum possible yield of toxic byproducts (nitrite, sulfides, etc.) produced by the denitrification treatment chamber 2 to ensure the safety of the effluent.

[0061] When the electron donor uses a carbon source, the carbon source replenishment cycle is precisely calculated based on the daily nitrate removal rate and carbon-nitrogen ratio, so that the carbon source release rate is dynamically matched with the nitrate load, avoiding excessive or insufficient carbon source.

[0062] For small-volume water systems, a single denitrification unit can be used for purification. For medium to large-volume systems, multiple denitrification units or modules can be connected in parallel. For example, a water system with a volume of 0.1 m³-0.5 m³ (such as an aquarium) can use a single denitrification unit with a total volume ≤0.01 m³, which can be integrated into the aquarium cabinet or suspended from the tank wall. For water systems of 1 m³-50 m³, multiple denitrification units can be connected in parallel; a failure in one unit will not affect the operation of the others. For water systems of 50 m³-1000 m³, multiple denitrification modules can be connected in parallel; a failure in one module will not affect the operation of the others.

[0063] Alternatively, for water systems with medium to large volumes, a single denitrification unit with a larger volume can be used for purification. For example, for a 0.2 m³ water system, four tanks with an outer diameter of 125 mm and a height of 400 mm can be used, with two forming denitrification treatment chambers 2, one forming a denitrification pretreatment chamber 1, and one forming a denitrification posttreatment chamber 3. For a 10 m³ water system, four tanks with an outer diameter of 400 mm and a height of 1350 mm can be used.

[0064] When designing the above-mentioned denitrification module, the influent flow rate, effective water volume of each chamber, carrier structure in each chamber, and HRT (Hydraulic Retention Time) of each chamber are initially determined. Then, the treatment capacity of each chamber is verified to meet the standards. If not, the effective water volume and / or carrier structure and / or HRT are adjusted until the calculated treatment capacity of each chamber meets the standards. After meeting the standards, the daily required electron donor amount is accurately calculated based on the daily nitrate removal rate and carbon-to-nitrogen ratio to avoid excessive or insufficient electron donors. This allows for the determination of the electron donor replenishment cycle. The following specific embodiment illustrates this design process:

[0065] This embodiment is designed for a water system with a main tank volume of 200L. The main tank volume of the water system is 200L, the circulation frequency is 5 times / h, the circulating water temperature is 25℃~28℃, the dissolved oxygen in the main tank is 4 mg / L~6 mg / L, the daily nitrate accumulation rate is 6.5mg / (L·d), the denitrification volumetric load is 1.0kg N / (m³·d) (determined based on the national standard GB50014-2021), the carbon-nitrogen ratio is 4, and the solid carbon source COD equivalent is 1.8g COD / g.

[0066] The initial determination of the influent flow rate, effective water volume of each chamber, carrier structure within each chamber, and HRT (Hydraulic Retention Time) for each chamber was made: Four tanks were constructed, each with an outer diameter of 125 mm, an inner diameter of 115 mm, a height of 400 mm, and a geometric volume of 4.15 L per tank. One tank constituted denitrification pretreatment chamber 1, containing high-density bio-cotton with 90% porosity and a solid carbon source, with an effective water volume of 3.74 L. Two tanks constituted denitrification treatment chamber 2, containing K3 packing material with 70% porosity, with an effective water volume of 5.82 L. A denitrification post-treatment chamber 3 is constructed within a tank. Within this chamber, from bottom to top, are arranged a 30mm thick water distribution chamber 4, an 80mm thick iron-based filter media layer 13, a 40mm thick aeration chamber 5 (containing microporous aeration strips connected to a 3W silent air pump), a 150mm thick composite packing material with approximately 70% porosity (serving as a second biofilm packing layer 11), and an 80mm thick pH buffer layer. The effective water volume of the denitrification post-treatment chamber 3 is 2.92L. The total effective water volume is 12.48L. Water is drawn from the bypass outlet of the clear water tank return pump, with a flow restriction ratio of 10%, resulting in an influent flow rate of 20L / h. The HRT of the denitrification pretreatment chamber 1 is 11.2 min, the HRT of the denitrification treatment chamber 2 is 17.4 min, the HRT of the denitrification posttreatment chamber 3 is 8.8 min, the total HRT is 37.4 min, and the number of treatments per day is 2.4.

[0067] The treatment capacity of denitrification pretreatment chamber 1 was verified: based on an influent dissolved oxygen content of 6 mg / L and a target dissolved oxygen content of 0.4 mg / L, the oxygen demand is 112 mg O2 / h. The carbon source consumes approximately 48.9 mg O2 / h, and the biofilm consumes approximately 294 mg O2 / h. The total oxygen demand capacity is 343 mg O2 / h, which is greater than 112 mg O2 / h, indicating that the oxygen demand capacity is sufficient.

[0068] The processing capacity of denitrification chamber 2 was verified: the required nitrogen removal amount is 0.294 g N / d, and the actual volumetric load is 0.05 kg N / (m³·d), which is only 6.3% of the standard value, indicating that the processing capacity is sufficient.

[0069] Calculate the daily carbon source requirement: 1.174g of COD is required daily, 0.652g of solid carbon source is required / day, and 58.7g of carbon source is required for a 90-day cycle. The denitrification pretreatment chamber 1 has sufficient volume to hold 58.7g of carbon source. Therefore, the carbon source replenishment cycle can be 90 days or more.

[0070] The above examples illustrate the principles and implementation methods of this application. The descriptions of the embodiments are merely for the purpose of helping to understand the methods and core ideas of this application. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of this application.

Claims

1. A denitrification module, characterized in that, The system includes a denitrification unit, which comprises a denitrification pretreatment chamber (1), a denitrification treatment chamber (2), and a denitrification posttreatment chamber (3) arranged in sequence, so that the water to be treated can flow through the denitrification pretreatment chamber (1), the denitrification treatment chamber (2), and the denitrification posttreatment chamber (3) in sequence. Each chamber is provided with an exhaust port. The denitrification pretreatment chamber (1) is equipped with a dissolved oxygen consumption section, which enables the treated water body to form an anaerobic or hypoxic environment. The denitrification treatment chamber (2) is provided with a first biofilm packing layer (10) as a carrier for denitrifying bacteria, so that the nitrate in the treated water can be reduced to nitrogen gas by the denitrifying bacteria and discharged from the exhaust port. The denitrification post-treatment chamber (3) is provided with an iron-based filter media layer (13), an aeration chamber (5), a second biofilm packing layer (11), and a pH adjustment layer (12) in sequence along its water flow direction. The iron-based filter media layer (13) is used to adsorb sulfides in the treated water and remove some phosphates in the water. The aeration chamber (5) is provided with an aeration device (6) to increase the dissolved oxygen content of the treated water to form an aerobic environment. The second biofilm packing layer (11) serves as a carrier for nitrifying bacteria, enabling nitrites in the treated water to be oxidized into nitrates by nitrifying bacteria. The pH adjustment layer (12) is used to adjust the pH value of the treated water.

2. The denitrification module according to claim 1, characterized in that, The dissolved oxygen consuming part includes an electron donor, an electron donor housing structure, and a flow guiding structure (9). The electron donor and the flow guiding structure (9) are used to form an aerobic biofilm so that the dissolved oxygen content of the treated water body is maintained at 0.2 mg / L to 0.6 mg / L during denitrification treatment.

3. The denitrification module according to claim 2, characterized in that, The electron donor is a solid organic carbon source.

4. The denitrification module according to claim 2, characterized in that, The flow guiding structure (9) is high-density biochemical cotton.

5. The denitrification module according to claim 1, characterized in that, The denitrification post-treatment chamber (3) is provided with a water distribution chamber (4), which is used to receive the treated water discharged from the denitrification treatment chamber (2) and achieve uniform water distribution. The water distribution chamber (4) is located upstream of the iron-based filter media layer (13).

6. The denitrification module according to claim 1, characterized in that, The pH adjustment layer, the iron-based filter media layer (13), and the second biofilm packing layer (11) are placed in separate layered baskets.

7. The denitrification module according to claim 1, characterized in that, The denitrification pretreatment chamber (1) adopts a top-down water flow pattern, the denitrification treatment chamber (2) adopts a bottom-up water flow pattern, and the denitrification posttreatment chamber (3) adopts a bottom-up water flow pattern.

8. The denitrification module according to claim 1, characterized in that, The inlet of the denitrification pretreatment chamber (1) is connected to the outlet of the water system, and the outlet of the denitrification posttreatment chamber (3) is connected to the return outlet of the water system.

9. The denitrification module according to claim 1, characterized in that, A flow limiting mechanism (15) is provided between the inlet of the denitrification pretreatment chamber (1) and the outlet of the water system. The flow limiting mechanism (15) is used to limit the denitrification module to take a portion of the water from the water system for treatment every hour. The hourly water intake is 8.5% to 20% of the water volume of the water system.

10. The denitrification module according to claim 1, characterized in that, The inlet of the denitrification pretreatment chamber (1) and the outlet of the denitrification posttreatment chamber (3) are standardized quick-connect interfaces.

11. The denitrification module according to claim 1, characterized in that, The denitrification pretreatment chamber (1), denitrification treatment chamber (2) and denitrification posttreatment chamber (3) are integrated in the same housing to form an integrated module.

12. The denitrification module according to claim 1, characterized in that, The denitrification module is equipped with a separate drive pump to drive the water to circulate between the denitrification module and the water system. Alternatively, the denitrification module may not be equipped with a drive pump, and the water may be circulated between the denitrification module and the water system by the circulation pump of the water system.

13. The denitrification module according to claim 1, characterized in that, The denitrification module includes multiple denitrification units arranged in parallel.

14. A water treatment system, characterized in that, The device includes the denitrification module according to any one of claims 1-13, and further includes a filtration module, wherein the denitrification module is connected downstream of the filtration module, so that the water to be treated first flows through the filtration module and then through the denitrification module, and the filtration module includes a filtration chamber in which granular filter media is disposed.

15. A water treatment method, characterized in that, The treatment includes a denitrification step, which consists of a series of dissolved oxygen consumption treatments, a denitrification process, and a post-treatment. The dissolved oxygen consumption treatment consumes dissolved oxygen in the water to create an anaerobic or anoxic environment. The denitrification process uses denitrifying bacteria to reduce nitrates in the water to nitrogen gas, which is then released. The post-treatment includes a series of iron-based filter media adsorption treatments, a nitrification process, and a pH adjustment process. The nitrification process uses nitrifying bacteria to oxidize nitrites in the water to nitrates. The iron-based filter media adsorption process uses iron-based filter media to adsorb sulfides in the water and remove some phosphates. The pH adjustment process adjusts the pH of the water.

16. The water treatment method according to claim 15, characterized in that, Electron donors and aerobic biofilms are used to consume dissolved oxygen in the water being treated, and electron donors are replenished in a timely manner to maintain the dissolved oxygen level in the water being treated at 0.2 mg / L to 0.6 mg / L during denitrification.

17. The water treatment method according to claim 15, characterized in that, The pH adjustment process adjusts the pH value of the treated water to the range of 7.0-8.

4.

18. The water treatment method according to claim 15, characterized in that, When treating the water in the water system, a portion of the water is taken from the system every hour for treatment. After treatment, the water is returned to the system. This process is repeated multiple times until all the water in the system has been treated. The hourly water intake is 8.5% to 20% of the water volume of the system.

19. The water treatment method according to any one of claims 15-18, characterized in that, The water treatment method further includes a filtration step, which involves using granular filter media to filter the water to be treated. The filtration step is performed first, followed by the denitrification step.

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