Composite carbon source for removing nitrate in aquarium system as well as preparation method and application of composite carbon source

Abstract

The invention relates to the technical field of water treatment, and provides a composite carbon source for removing nitrate in an aquarium system and a preparation method and application thereof, and the composite carbon source comprises glycerol, a slow-release carbon source, zeolite, citrate, vitamin, HEPES and a binder. Glycerol and a slow-release carbon source in the composite carbon source form synergy, the former can rapidly start microbial action and rapidly reduce nitrate concentration, the latter provides long-term support and ensures sustainability of degradation effect, and the matching not only improves denitrification efficiency, but also avoids side effects caused by excessive carbon source in short time. In addition, glycerol and citrate are synergistic in chemical and biological aspects: the former is a short-term rapid energy source, the latter plays a role in metal buffering and environmental regulation, and both of the former and the latter provide good support for efficient denitrification of microorganisms. And by combining the physical and chemical properties of other components, the denitrification stability and efficiency of the composite carbon source are jointly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and particularly to a composite carbon source for removing nitrates in an aquarium system, a preparation method thereof, and an application thereof. Background Art

[0002] The accumulation of nitrates in an aquarium mainly comes from fish excrement, residual feed, and organisms decomposed by microorganisms. The toxicity of nitrates to aquatic animals increases with the increase in nitrate concentration and exposure time. Freshwater animals seem to be more sensitive to nitrates than marine animals. 10 mg NO3 - / L (the maximum level of federal drinking water in the United States) will have an adverse impact on freshwater invertebrates, fish, and amphibians. Excessive nitrates will have an adverse impact on the health of fish, such as affecting the digestive and respiratory systems, and may even lead to diseases and death. Therefore, it is necessary to control the nitrate concentration in water. For marine animals, a maximum level of 20 mg NO3 - / L is usually acceptable. However, in the early developmental stages of some marine invertebrates, they are well adapted to low concentrations of nitrates. As the removal of ammonia nitrogen and nitrites in the aquarium leads to the continuous accumulation of nitrates in the aquarium, the toxicity to fish becomes greater and greater.

[0003] Currently, there are three major methods for removing nitrates in an aquarium: physical, chemical, and biological. The physical method is mainly water change, which has the problem of cumbersome operation; the chemical method is to add chemical agents to remove nitrates; the biological method is mainly to remove nitrates by microorganisms absorbing and utilizing nitrates. The first two methods have disadvantages such as high cost and cumbersome processes. Therefore, the biological method has become the mainstream. The removal of nitrates in the biological method is mainly denitrification, and sufficient carbon source is required to maintain the reaction during this process. However, different carbon sources will cause problems such as turbidity of water quality, generation of peculiar smells, and excessive growth of algae. Therefore, a carbon source that can remove nitrates without harming the organisms in the aquarium and without causing obvious changes in water quality is needed. Summary of the Invention

[0004] In view of this, the present invention provides a carbon source that will not cause obvious changes in water quality and can remove nitrates, a preparation method thereof, and an application thereof.

[0005] The technical solution of the present invention is realized as follows: In the first aspect, the present invention provides a composite carbon source for removing nitrates in an aquarium system. The components of the composite carbon source include glycerol, slow-release carbon source, zeolite, citrate, vitamins, HEPES, and binder.

[0006] Specifically, glycerol in the composite carbon source and the slow-release carbon source form a synergy. The former can quickly initiate the microbial action and rapidly reduce the nitrate concentration, while the latter provides long-term support to ensure the sustainability of the degradation effect. This combination not only improves the denitrification efficiency but also avoids the side effects caused by excessive carbon source in a short time. Zeolite provides a favorable attachment and habitat environment for microorganisms; at the same time, its adsorption effect on pollutants further reduces the concentration of competitive harmful substances in the solution, indirectly promoting the activity of efficient strains such as nitrifying bacteria and denitrifying bacteria. Vitamins promote the metabolic activity of microorganisms, thus enabling more efficient utilization of glycerol and slow-release carbon source; in addition, vitamins also improve the stability of the overall ecological environment of the fish tank through nutritional supplementation and promote the diversity of the microbial community. HEPES and citrate respectively control the environmental buffering and heavy metal toxicity problems, enhancing the adaptability and sustainability of the carbon source from the perspective of the microbial metabolic environment.

[0007] The key roles of glycerol and citrate in the entire composite carbon source system are reflected in the synergy between chemistry and biology: the former is a short-term rapid energy source, and the latter plays a role in metal buffering and environmental regulation, and both provide good support for the efficient denitrification of microorganisms. Combining the physical and chemical properties of other components together improves the stability and efficiency of the composite carbon source for denitrification.

[0008] During the assimilatory denitrification process, denitrifying bacteria use the carbon source as an electron donor to gradually reduce nitrate nitrogen to ammonium nitrogen, and then synthesize nitrogen-containing organic compounds such as amino acids and proteins for use as components of cells, achieving the assimilation of nitrogen.

[0009] Based on the above technical solutions, preferably, calculated according to 100% by mass fraction, the components of the composite carbon source include 2%-30% of glycerol, 5%-30% of slow-release carbon source, 15%-30% of zeolite, 5%-20% of citrate, 1%-5% of vitamins, 0.1%-0.5% of HEPES, and 20%-30% of binder.

[0010] Based on the above technical solutions, preferably, the zeolite is zeolite modified with iron, manganese, and chitosan.

[0011] Based on the above technical solutions, preferably, the preparation method of the modified zeolite includes the following steps:

[0012] S1. Zeolite pretreatment: Crush the zeolite raw material and soak it in an acid solution or an alkali solution, then wash, dry, and calcine at 400-600 °C for 4-6 h;

[0013] S2. Prepare a solution containing Fe 3+ 、Mn 2+a metal salt solution, then immerse the pretreated zeolite in the metal salt solution, react at 70 - 90 °C for 2 - 4 h, then wash and dry;

[0014] S3. Place the zeolite treated in step S3 in a chitosan solution, soak for 3 - 4 h and then dry, then place it in a CTAB solution, soak for 3 - 4 h and then dry.

[0015] Based on the above technical solutions, preferably, in the metal salt solution, the concentration of FeCl3 is 0.2 - 0.3 mol / L, and the concentration of MnCl2 is 0.1 - 0.2 mol / L; the mass concentration of the chitosan solution is 1 - 2%, and the concentration of the CTAB solution is 0.2 - 0.5 mol / L.

[0016] Modifying zeolite by the above method can provide adsorption / reaction sites, have a slow - release function, and form a synergistic effect with the carbon source. Specifically, introducing metal ions Fe 3+ on the zeolite surface can effectively serve as adsorption sites and improve the treatment ability for phosphate (PO4 3- ) and nitrate nitrogen (NO 3- ). Introducing metal ions Mn 2+ can accelerate the denitrification conversion of nitrate nitrogen (NO 3- ) to nitrogen (N2) through catalytic action, especially when used in combination with a carbon source in an anaerobic environment.

[0017] Furthermore, introducing organic functional groups through organic modifiers such as chitosan and surfactant CTAB can improve the adsorption ability of zeolite for hydrophobic organic pollutants and enhance the biofilm attachment effect at the same time.

[0018] In addition, the combination of chitosan loading and HEPES can regulate the microbial healthy environment, purify water, and accelerate the removal of nitrate nitrogen.

[0019] Based on the above technical solutions, preferably, the slow - release carbon source is one or more of polylactic acid, polyadipic acid, ethylene - vinyl acetate resin, polybutylene succinate, polyhydroxybutyrate, and polycaprolactone.

[0020] Specifically, polylactic acid (PLA), polyhydroxybutyrate (PHB), and polycaprolactone (PCL) form the basis for long - term slow release, while polyadipic acid (PGA) and polybutylene succinate (PBS) provide medium - speed slow - release performance to optimize the slow - release curve. The stability of ethylene - vinyl acetate resin (EVA) complements the high - salt and high - oxygen adaptability of PCL, ensuring the long - term operation of the material under harsh conditions. The addition of EVA can enhance the physical strength of the composite carbon source particles, avoid particle pulverization and premature disintegration, while PLA and PBS provide basic material adhesiveness and slow - release performance.

[0021] All the materials selected for the slow-release carbon source have good biodegradability, and the degradation products such as lactic acid, succinic acid, and acetic acid are all carbon sources that can be directly utilized by microorganisms in the aquarium system, without causing secondary pollution. Through the optimized combination of these components, a balance can be found between rapid start-up of denitrification and long-term stable operation, and the adaptability, stability, and promotion value of the composite carbon source can be improved.

[0022] Based on the above technical solutions, preferably, the binder is one or more of diatomaceous earth, gypsum, polyvinyl alcohol, polyethylene glycol, and paraffin.

[0023] Diatomaceous earth has a large specific surface area, can adsorb harmful substances and nutrients that promote the growth of algae in water, reduce the concentration of toxic substances and inhibit the overgrowth of algae, providing a cleaner and healthier water environment for fish. Its porosity also provides a large number of attachment sites for beneficial microorganisms such as nitrifying bacteria, promoting the reproduction of beneficial microorganisms, accelerating the nitrogen cycle in the fish tank, and converting harmful ammonia nitrogen into relatively harmless nitrates. In addition, diatomaceous earth and gypsum also provide good physical adhesion of particles, improving the mechanical strength and enabling the carbon source particles to maintain a stable structure in the water body; polyvinyl alcohol (PVA) and polyethylene glycol (PEG) provide excellent molecular-level bonding ability and uniformity. Both PVA, PEG, and inorganic materials such as diatomaceous earth and gypsum can achieve biodegradation or non-toxic degradation, ensuring no risk of secondary pollution to the aquarium system. All binders are suitable for various aquarium environments with high salinity, high dissolved oxygen, and variable pH, showing good ecological adaptability.

[0024] Through the combination of the above various binders, the dissolution rate of the carbon source particles can be adjusted. For example, paraffin provides a good coating and slow-release effect, while diatomaceous earth and gypsum act as carriers to adjust the release curve of the particles.

[0025] Based on the above technical solutions, preferably, the vitamin is one or more of ascorbic acid, riboflavin, niacin, biotin, pyridoxine, and calciferol.

[0026] Specifically, the above-mentioned vitamins support the working efficiency of denitrifying bacteria and nitrifying bacteria in multiple aspects through different promoting effects on microbial metabolism, electron transfer, and energy generation. Ascorbic acid can reduce harmful free radicals generated during the denitrification process, thereby maintaining the integrity of the cell structure and function of denitrifying bacteria. Moreover, ascorbic acid indirectly affects the activity of denitrification-related enzymes (such as nitrate reductase, nitrite reductase, etc.) by regulating the intracellular redox state, optimizing the process of the denitrification reaction, and promoting denitrifying bacteria to convert nitrate and nitrite nitrogen into nitrogen gas and discharge it out of the body. Riboflavin can promote the increase of nitrate reductase in the periplasm of the outer membrane of denitrifying bacteria, which is beneficial to improving the denitrification rate and conversion rate of denitrifying nitrogen removal, and then enhancing the denitrification efficiency of denitrifying bacteria. Riboflavin can enhance the interaction between microorganisms, promote cell aggregation and the formation of biofilms, help denitrifying bacteria better adhere and survive in the environment, improve their stability and adaptability in complex environments, and thus play a more effective denitrification role. Under the conditions of low temperature and limited carbon source, riboflavin can also regulate the pH of the system, create an environment suitable for the growth of denitrifying bacteria and denitrification, and then improve the removal rate of nitrate nitrogen and total nitrogen by denitrifying bacteria.

[0027] Nicotinic acid, pyridoxine, etc. help microorganisms maintain reproduction and homeostasis under environmental stress conditions, while ascorbic acid and calciferol improve the overall health of the aquarium system and indirectly enhance the tolerance of the microbial community. The above-mentioned vitamins not only directly promote microbial metabolism, but also indirectly build a balanced and efficient ecosystem by enhancing the growth and health of aquarium organisms.

[0028] In a second aspect, the present invention provides a method for preparing a composite carbon source for removing nitrate in an aquarium system, comprising the following steps:

[0029] S1, mixing glycerol, a slow-release carbon source, citrate, vitamins, HEPES, zeolite, and a binder evenly, and then putting them into a granulator for granulation to obtain a composite carbon source with a particle size of 3-5 mm;

[0030] S2, drying the composite carbon source obtained in step S1 and then cooling it to obtain the finished product.

[0031] In a third aspect, the present invention provides the application of the composite carbon source in removing nitrate in the water quality of an aquarium.

[0032] On the basis of the above technical solutions, preferably, the composite carbon source is placed in the aquarium water, and BQN2 solid nitrifying bacteria and BP102 solid nitrifying bacteria are added.

[0033] On the basis of the above technical solutions, preferably, the dosage of the composite carbon source is 1%-1.5% of the weight of the aquarium water.

[0034] Based on the above technical solutions, preferably, the dosage of the BQN2 solid nitrifying bacteria is 0.1‰ - 0.5‰ of the weight of the fish tank water, and the dosage of the BP102 solid nitrifying bacteria is 0.1‰ - 0.2‰ of the weight of the fish tank water.

[0035] Among them, both the BQN2 and BP102 solid nitrifying bacteria are strains independently developed by the applicant. The BQN2 solid nitrifying bacteria is Bacillus subtilis (CCTCC NO: M 2020551); the BP102 solid nitrifying bacteria is Bacillus pumilus (CCTCC NO: M2020550).

[0036] A composite carbon source for removing nitrates in an aquarium system, its preparation method and application of the present invention have the following beneficial effects compared with the prior art:

[0037] (1) Breaking the traditional denitrification limitation: The traditional nitrate removal technology realizes nitrogen removal under anaerobic or anoxic conditions. Due to the different dissolved oxygen states in different fish tanks, this carbon source combined with composite denitrifying bacteria can remove nitrates under the condition of dissolved oxygen of 0 - 5 mg / L.

[0038] (2) Coupling anaerobic denitrification and aerobic assimilation improves the denitrification efficiency. The composite carbon source of the present invention can not only provide a suitable biofilm growth environment, promote the activity of microorganisms, but also couple denitrification and assimilation, thus fundamentally improving the denitrification efficiency.

[0039] (3) Simplifying the carrier production process flow: Coupling granulation technology and heating technology directly forms a unique production line. The process flow is simple, the operation is easy, and it avoids the limitation of the single raw material content of the carrier.

[0040] (4) The carbon source of the present invention has strong adaptability. Combined with the self-developed composite denitrifying bacteria of the company, it can adapt to different water quality and environmental conditions, especially the applicability to high salt and high dissolved oxygen, which improves the popularization of the technology. Description of the Drawings

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0042] Figure 1 It is a physical diagram of the composite carbon source for removing nitrates in an aquarium system prepared by the present invention;

[0043] Figure 2 It is an effect diagram of the composite carbon source prepared by the present invention for stabilizing the pH value of the water body;

[0044] Figure 3 The effect diagram of nitrate removal by the composite carbon source prepared for the present invention. Detailed implementation manners

[0045] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0046] Example 1

[0047] The components of the composite carbon source in this example include 30% glycerol, 5% polylactic acid, 18.5% polyadipic acid, 15% zeolite, 10% citrate, 0.5% riboflavin, 0.5% nicotinic acid, 0.5% HEPES, 10% gypsum, and 10% polyethylene glycol.

[0048] Prepare 600 g of the composite carbon source according to the above ratio. First, put 300 g of the mixed material into a disk granulator, add atomized water in batches, the single addition amount of atomized water is 2% of the weight of the mixed material. After adding the atomized water, add another 300 g of the mixed material. Repeat this step. By the rotation of the disk, the water and the powdery material continuously roll and agglomerate, and the particles gradually become larger. When the particles in the disk are prepared into particles of 3-5 mm, put the particles into an oven, heat at 130 °C for 4 h, and sieve after cooling at room temperature to obtain the composite carbon source.

[0049] Example 2

[0050] The difference between Example 2 and Example 1 is that the zeolite is modified zeolite, and its preparation method is as follows:

[0051] S1. Zeolite pretreatment: Crush the zeolite raw material (about 1 mm) and soak it in a 1 mol / L HCl acid solution at 80 °C (liquid-solid ratio 10:1), then wash it with water until neutral, dry it at 80 °C, and then calcine it at 500 °C for 6 h;

[0052] S2. Prepare an aqueous metal salt solution containing Fe 3+ , Mn 2+ (FeCl3 0.25 mol / L, MnCl2 0.15 mol / L), then immerse the pretreated zeolite in the metal salt solution (liquid-solid ratio 10:1), stir and react at 70 °C in a water bath for 4 h, then wash and dry it;

[0053] S3. Place the zeolite after the treatment in step S3 into a chitosan solution with a mass concentration of 1.5% (prepared with acetic acid with a volume concentration of 1%), stir and soak for 3 h, then take it out and dry it, and then place it in a 0.4 mol / L CTAB (cetyltrimethylammonium bromide) solution, soak for 4 h and then dry it.

[0054] Example 3

[0055] The components of the composite carbon source in this example include 2% glycerol, 30% polybutylene succinate, 30% modified zeolite, 5% citrate, 2.9% ascorbic acid, 0.1% HEPES, 10% diatomite, and 15% polyvinyl alcohol.

[0056] The preparation method of the modified zeolite is as follows:

[0057] S1. Zeolite pretreatment: Crush the zeolite raw material (about 1 mm) and soak it in a 1 mol / L HCl acid solution or 1 mol / L NaOH alkali solution at 80 °C (liquid-solid ratio 10:1), then wash it with water until neutral, dry it at 80 °C, and then calcine it at 400 °C for 6 h;

[0058] S2. Prepare an aqueous metal salt solution containing Fe 3+ and Mn 2+ (FeCl3 0.2 mol / L, MnCl2 0.2 mol / L), then immerse the pretreated zeolite in the metal salt solution (liquid-solid ratio 10:1), stir and react at 70 °C in a water bath for 4 h, then wash and dry it;

[0059] S3. Place the zeolite after the treatment in step S3 into a chitosan solution with a mass concentration of 1% (prepared with acetic acid with a volume concentration of 1%), stir and soak for 3 h, then take it out and dry it, and then place it in a 0.5 mol / L CTAB (cetyltrimethylammonium bromide) solution, soak for 3 h and then dry it.

[0060] Prepare 600 g of the composite carbon source according to the above ratio. First, put 300 g of the mixed material into a disk granulator, add atomized water in batches, the single addition amount of atomized water is 2% of the weight of the mixed material. After adding the atomized water, add another 300 g of the mixed material. Repeat this step. Through the rotation of the disk, the water and the powdery material are continuously tumbled and agglomerated, and the particles gradually become larger. When the particles in the disk are prepared into particles with a size of 3 - 5 mm, put the particles into an oven, heat at 130 °C for 4 h, and sieve after cooling at room temperature to obtain the composite carbon source.

[0061] Example 4

[0062] The components of the composite carbon source in this embodiment include 20% glycerol, 3% ethylene-vinyl acetate resin, 2% polyhydroxybutyrate, 19.7% modified zeolite, 20% citrate, 2% biotin, 2% pyridoxine, 1% calciferol, 0.3% HEPES, 20% diatomaceous earth, and 10% paraffin.

[0063] The preparation method of the modified zeolite is as follows:

[0064] S1, Zeolite pretreatment: The zeolite raw material is crushed (about 1 mm) and then soaked in a 1 mol / L HCl acid solution or 1 mol / L NaOH alkaline solution at 80°C (liquid-solid ratio 10:1). Subsequently, it is washed with water until neutral, dried at 80°C, and then calcined at 600°C for 4 h;

[0065] S2, Prepare an aqueous metal salt solution containing Fe 3+ , Mn 2+ (FeCl3 0.3 mol / L, MnCl2 0.1 mol / L), and then immerse the pretreated zeolite in the metal salt solution (liquid-solid ratio 10:1). Stir and react at 90°C in a water bath for 2 h, and then wash and dry;

[0066] S3, Place the zeolite treated in step S3 in a 2% chitosan solution (prepared with 1% acetic acid by volume), stir and soak for 4 h, then take it out and dry. Then place it in a 0.2 mol / L CTAB (cetyltrimethylammonium bromide) solution and soak for 4 h, and then dry.

[0067] Prepare 600 g of the composite carbon source according to the above ratio. First, take 300 g of the mixed material and put it into a disk granulator. Add atomized water batch by batch. The single addition amount of atomized water is 2% of the weight of the mixed material. After adding the atomized water, add another 300 g of the mixed material. Repeat this step. Through the rotation of the disk, the water and the powdery material continuously tumble and agglomerate, and the particles gradually become larger. When the particles in the disk are prepared into particles with a size of 3 - 5 mm, put the particles into an oven, heat at 130°C for 4 h, and sieve after cooling at room temperature to obtain the composite carbon source.

[0068] Example 5

[0069] The components of the composite carbon source in this embodiment include 25% glycerol, 10% polylactic acid, 10% polybutylene succinate, 5% polycaprolactone, 15% modified zeolite, 10% citrate, 1% ascorbic acid, 1% riboflavin, 1% nicotinic acid, 1% biotin, 0.9% pyridoxine, 0.1% HEPES, 10% gypsum, and 10% polyvinyl alcohol.

[0070] The preparation method of the modified zeolite is as follows:

[0071] S1, Zeolite pretreatment: Crush the zeolite raw material (about 1 mm) and soak it in a 1 mol / L HCl acid solution or 1 mol / L NaOH alkali solution at 80 °C (liquid-solid ratio 10:1). Then wash it with water until neutral, dry it at 80 °C, and then calcine it at 550 °C for 4.5 h;

[0072] S2, Prepare an aqueous metal salt solution containing Fe 3+ , Mn 2+ (FeCl3 0.2 mol / L, MnCl2 0.1 mol / L). Then immerse the pretreated zeolite in the metal salt solution (liquid-solid ratio 10:1), stir and react at 75 °C in a water bath for 3.5 h, and then wash and dry it;

[0073] S3, Place the zeolite treated in step S3 in a chitosan solution with a mass concentration of 1.8% (prepared with acetic acid with a volume concentration of 1%). Stir and soak for 4 h, then take it out and dry it. Then place it in a 0.3 mol / L CTAB (cetyltrimethylammonium bromide) solution and soak for 4 h, and then dry it.

[0074] Mix the above materials and stir evenly to ensure the quality stability of subsequent granulation. Turn on the disk granulator, put 300 g of the mixed material into the disk, add atomized water in batches. The single addition amount of atomized water is 2% of the weight of the mixed material. After adding the atomized water, add another 300 g of the mixed material. Repeat this step. Through the rotation of the disk, the water and the powdery material continuously tumble and agglomerate, and the particles gradually become larger. When the particles in the disk are prepared to be 3 - 5 mm in size, put the particles into the oven, heat at 130 °C for 4 h, and sieve after cooling at room temperature to obtain the composite carbon source.

[0075] Example 6

[0076] The components of the composite carbon source in this example include 20% glycerol, 5% polylactic acid, 5% polyadipic acid, 5% ethylene-vinyl acetate resin, 5% polybutylene succinate, 5% polycaprolactone, 15% modified zeolite, 15% citrate, 1% riboflavin, 1% biotin, 1% calciferol, 0.5% HEPES, 6.5% diatomite, gypsum, 10% polyvinyl alcohol, 5% paraffin.

[0077] The preparation method of the modified zeolite is as follows:

[0078] S1, Zeolite pretreatment: Crush the zeolite raw material (about 1 mm) and soak it in a 1 mol / L HCl acid solution or 1 mol / L NaOH alkali solution at 80 °C (liquid-solid ratio 10:1). Then wash it with water until neutral, dry it at 80 °C, and then calcine it at 450 °C for 5.5 h;

[0079] S2, Prepare an aqueous solution containing Fe 3+ , Mn2+ An aqueous solution of metal salts (0.3 mol / L FeCl3, 0.2 mol / L MnCl2), and then the pretreated zeolite is immersed in the metal salt solution (liquid-solid ratio 10:1), stirred and reacted at 85 °C in a water bath for 2.5 h, then washed and dried;

[0080] S3. The zeolite treated in step S3 is placed in a chitosan solution with a mass concentration of 1.3% (prepared with acetic acid with a volume concentration of 1%), stirred and soaked for 3 h, then taken out and dried, and then placed in a 0.45 mol / L CTAB (cetyltrimethylammonium bromide) solution, soaked for 3 h and then dried.

[0081] Mix the above materials evenly to ensure the quality stability of subsequent granulation. Turn on the disk granulator, put 300 g of the mixed material into the disk, add atomized water batch by batch, the single addition amount of atomized water is 2% of the weight of the mixed material, after adding the atomized water, add another 300 g of the mixed material, repeat this step, and through the rotation of the disk, the water and the powdery material continuously tumble and agglomerate, and the particles gradually become larger. When the particles in the disk are prepared to 3 - 5 mm particles, put the particles into the oven, heat at 130 °C for 4 h, and sieve after cooling at room temperature to obtain the composite carbon source.

[0082] Comparative Example 1

[0083] Compared with Example 1, Comparative Example 1 lacks propylene glycol, and the rest are the same.

[0084] Comparative Example 2

[0085] Compared with Example 1, Comparative Example 2 lacks citrate, and the rest are the same.

[0086] Comparative Example 3

[0087] Compared with Example 2, the preparation method of the modified zeolite in Comparative Example 3 lacks step S3, and the rest are the same.

[0088] Respectively take the composite carbon sources prepared in the examples and comparative examples. In a 20 L fish tank system, add 1 / 100 of the fish tank volume of the composite carbon source to each fish tank, that is, 200 g of the composite carbon source, add 0.1‰ BQN2 (2 g), 0.1‰ BP102 (2 g), and add the bacteria culture solution (to 100 mg / L nitrate nitrogen), and turn on the fish tank circulation mode. Sampling time: Sampling and measuring the device data once every 24 h, measuring indicators: Measuring NO 3- -N, NO 2- -N, NH4 + -N, pH, TN indicators.

[0089] Table 1 Performance of Composite Carbon Source

[0090] Tolerable conditions Stable load Example 1 Dissolved oxygen 0 - 5 mg / L, salinity 30000 mg / L, pH 5.5 - 6.5 <![CDATA[1.0-1.5kgN / m 3 / d]]> Example 2 Dissolved oxygen 0 - 5 mg / L, salinity 30000 mg / L, pH 5.5 - 6.5 <![CDATA[2.5 - 3.0 kgN / m 3 / d]]> Example 3 Dissolved oxygen 0 - 5 mg / L, salinity 30000 mg / L, pH 5.5 - 6.5 <![CDATA[2.0 - 3.5 kgN / m 3 / d]]> Example 4 Dissolved oxygen 0 - 5 mg / L, salinity 30000 mg / L, pH 5.5 - 6.5 <![CDATA[2.5 - 3.5 kgN / m 3 / d]]> Example 5 Dissolved oxygen 0 - 5 mg / L, salinity 30000 mg / L, pH 5.5 - 6.5 <![CDATA[2.1 - 3.5 kgN / m 3 / d]]> Example 6 Dissolved oxygen 0 - 5 mg / L, salinity 30000 mg / L, pH 5.5 - 6.5 <![CDATA[2.0 - 4.0 kgN / m 3 / d]]> Comparative Example 1 Dissolved oxygen 0 - 5 mg / L, salinity 30000 mg / L, pH 5.5 - 6.5 <![CDATA[0.3 - 0.5 kg N / m 3 / d]]> Comparative Example 2 Dissolved oxygen 0 - 5 mg / L, salinity 30000 mg / L, pH 5.5 - 6.5 <![CDATA[0.5-0.8kgN / m 3 / d]]> Comparative Example 3 Dissolved oxygen 0 - 5 mg / L, salinity 30000 mg / L, pH 5.5 - 6.5 <![CDATA[1.5 - 2.0 kgN / m 3 / d]]>

[0091] As shown in Table 1, the composite carbon source of Examples 1-6 of the present invention can adapt to anaerobic and aerobic environments. When combined with BQN2 and BP102 nitrifying bacteria, it can adapt to a water environment of 30,000 mg / L, and the stable load reaches 1-4 kgN / m 3 / d, with strong adaptability and the ability to remove nitrate nitrogen.

[0092] After modifying zeolite, the stable load is greatly improved. This is because after the zeolite is modified, the ability to remove nitrate is enhanced. If glycerol and citrate are lacking in the composite carbon source, the stable load will decrease significantly. The reasons are as follows: the lack of glycerol leads to a decrease in the rapid response ability of the denitrification process and a delay in initial denitrification. The lack of citrate will inhibit the microbial activity, especially in the long-term operation, due to the deterioration of the metabolic environment, cumulative negative effects will occur. The lack of glycerol and citrate will lead to insufficient carbon source supply (C / N ratio imbalance), directly restricting the denitrification reaction and resulting in a decrease in denitrification efficiency.

[0093] I. Chromaticity test

[0094] In a 20L fish tank system, add 1 / 100 of the fish tank volume of the composite carbon source to each fish tank, that is, 200g of the composite carbon source, add 0.1‰ BQN2 (2g), 0.1‰ BP102 (2g), add the bacteria culture solution (to 100mg / L nitrate nitrogen), control the temperature to 30°C, put 5 grass carps, turn on the internal circulation of the fish tank, and feed 0.5g of feed every day. In addition, add different carbon sources to other groups of fish tanks for experiments, continuously collect data for analysis, and the specific grouping is shown in Table 2.

[0095] Table 2 Grouping conditions for chromaticity test

[0096]

[0097] According to the dilution multiple method for the determination of water quality chromaticity in HJ 1182-2021, detect the change of water quality chromaticity in the experimental fish tanks. At the beginning of the experiment, the colors of all grouped carbon sources are white, the water quality is transparent and colorless, and the chromaticity is 0. The detection results at 7 days and 25 days after startup are shown in Table 3.

[0098] Table 3 Water quality changes

[0099]

[0100] After 25 days of data tracking, there are different changes in the chromaticity of the experimental groups of carbon sources 1-3. The chromaticity of the experimental group adding this composite carbon source has no obvious change during the experiment. In Comparative Example 1, the lack of glycerol will increase the accumulation of amines and incompletely metabolized intermediate products, resulting in a pale yellow or turbid feeling in the water quality.

[0101] II. pH test

[0102] According to the 20L water fish tank system, add 1 / 100 of the fish tank volume of the composite carbon source to each fish tank, that is, 200g of the composite carbon source, add 0.1‰ BQN2 (2g), 0.1‰ BP102 (2g), add the bacteria culture solution (to 100mg / L nitrate nitrogen), control the temperature to 30°C, put 5 grass carps, turn on the internal circulation of the fish tank, and feed 0.5g of feed every day. In addition, add different carbon sources to the fish tanks in other groups for experiments, and adjust the initial pH to 7.5 using sodium hydroxide solution and dilute sulfuric acid solution. Continuously collect data for analysis. The specific grouping is shown in Table 4, and the results are shown in Figure 2 。

[0103] Table 4 Experimental grouping

[0104]

[0105] Figure 2 As shown, the pH of the experimental group using this composite carbon source stabilized between 7.5 and 7.6 after 12 days of experiments, and the pH data of the experimental groups with other carbon sources all increased to varying degrees.

[0106] In Comparative Example 1, the lack of glycerol caused the denitrification rate to decrease, and the accumulation of intermediate alkaline by-products or heavy metal oxidation products led to the final tendency of the water body to be alkaline (pH slightly increased).

[0107] In Comparative Example 2, due to the absence of citrate, the pH buffering effect of the water body was weakened, and it was easily affected by other reactions and fluctuated.

[0108] III. Denitrification test

[0109] According to the 20L water fish tank system, add 1 / 100 of the fish tank volume of the composite carbon source to each fish tank, that is, 200g of the composite carbon source, add 0.1‰ BQN2 (2g), 0.1‰ BP102 (2g), add the bacteria culture solution (to 100mg / L nitrate nitrogen), control the temperature to 30°C, put 5 grass carps, turn on the internal circulation of the fish tank, and feed 0.5g of feed every day. In addition, add different slow-release carbon sources to other fish tanks for experiments, and continuously collect data for analysis. The specific grouping is shown in Table 5, and the results are shown in Figure 3 。

[0110] Table 5 Experimental grouping

[0111]

[0112] Figure 3As shown, after 16 days of experiments, carbon sources 1, 2, and 3 had a certain carbon release capacity in the early stage, and then were utilized by denitrifying microorganisms to remove nitrates. As the experimental time extended, their carbon release capacity decreased, no excess carbon source was released, and the decreasing trend of nitrates gradually stabilized; the carbon release capacity of the composite carbon source was stable, microorganisms continuously had carbon sources to utilize, and the nitrate concentration could continuously decrease.

[0113] If the composite carbon source lacks glycerol and / or citrate, the nitrate removal rate will decrease. The lack of glycerol in the composite carbon source of Comparative Example 1 will significantly affect the nitrogen removal rate during the startup period; the lack of citrate in the composite carbon source of Comparative Example 2 will have an adverse effect on the long-term operation and water quality stability, especially in complex water bodies or high-load operations, and the nitrate removal rate will decrease more significantly.

[0114] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A composite carbon source for removing nitrate in an aquarium system, characterized in that: The components of the composite carbon source include glycerol, slow-release carbon source, zeolite, citrate, vitamins, HEPES, and binder.

2. The composite carbon source for removing nitrate in an aquarium system according to claim 1, wherein: Calculated by 100% of the mass fraction, the components of the composite carbon source include 2%-30% of glycerol, 5%-30% of slow-release carbon source, 15%-30% of zeolite, 5%-20% of citrate, 1%-5% of vitamins, 0.1%-0.5% of HEPES, and 20%-30% of binder.

3. The composite carbon source for removing nitrate in an aquarium system according to claim 1, wherein: The zeolite is the zeolite modified by iron, manganese, and chitosan.

4. A composite carbon source for removing nitrate in an aquarium system according to claim 3, characterized in that: The preparation method of the modified zeolite includes the following steps: S1, Zeolite pretreatment: Crush the zeolite raw material and soak it in an acid solution or an alkali solution, then wash, dry, and calcine at 400-600 °C for 4-6 h; S2. Configure a metal salt solution containing Fe 3+ , Mn 2+ . Then immerse the pretreated zeolite in the metal salt solution, react at 70 - 90 °C for 2 - 4 h, and then wash and dry it. S3, Place the zeolite treated in step S3 in a chitosan solution, soak for 3-4 h and then dry, and then place it in a CTAB solution, soak for 3-4 h and then dry.

5. A composite carbon source for removing nitrate in an aquarium system according to claim 4, characterized in that: In the metal salt solution, the concentration of FeCl3 is 0.2-0.3 mol / L, and the concentration of MnCl2 is 0.1-0.2 mol / L; The mass concentration of the chitosan solution is 1%-2%, and the concentration of the CTAB solution is 0.2-0.5 mol / L.

6. The composite carbon source for removing nitrate in an aquarium system according to claim 1, wherein: The slow-release carbon source is one or more of polylactic acid, polyadipic acid, ethylene-vinyl acetate resin, polybutylene succinate, polyhydroxybutyrate, and polycaprolactone; The binder is one or more of diatomite, gypsum, polyvinyl alcohol, polyethylene glycol, and paraffin; The vitamins are one or more of ascorbic acid, riboflavin, niacin, biotin, pyridoxine, and calciferol.

7. A preparation method of a composite carbon source for removing nitrate in an aquarium system according to any one of claims 1-6, characterized in that: It includes the following steps: S1, Mix glycerol, slow-release carbon source, citrate, vitamins, HEPES, zeolite, and binder evenly, and then put them into a granulator for granulation to obtain a composite carbon source with a particle size of 3-5 mm; S2, Dry and then cool the composite carbon source obtained in step S1 to obtain the finished product.

8. The application of the composite carbon source according to any one of claims 1-6 in removing nitrates in the water quality of fish tanks.

9. The application according to claim 8, wherein: Just place the composite carbon source in the fish tank water and add BQN2 solid nitrifying bacteria and BP102 solid nitrifying bacteria.

10. The application according to claim 9, characterized in that: The dosage of the composite carbon source is 1%-1.5% of the weight of the fish tank water; the dosage of the BQN2 solid nitrifying bacteria is 0.1‰-0.5‰ of the weight of the fish tank water, and the dosage of the BP102 solid nitrifying bacteria is 0.1‰-0.2‰ of the weight of the fish tank water.

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