A method for rapid biofilm formation in aquaculture water treatment systems

Abstract

This invention provides a method for rapid biofilm formation in aquaculture water treatment systems, specifically comprising the following steps: Step 1, selecting a biofilm carrier; Step 2, preparing a certain amount of fulvic acid solution; Step 3, immersing the biofilm carrier in the fulvic acid solution for a period of time; Step 4, during Step 3, aerating for a period of time, followed by anaerobic settling; Step 5, replacing a portion of the water after sedimentation; Step 6, replenishing fulvic acid to a predetermined concentration after water replacement; Step 7, after a period of time, forming a biofilm on the surface of the biofilm carrier. The enhanced biofilm reactor prepared by this method can significantly shorten the biofilm formation time, improve water quality remediation, and possess significant economic value and practical benefits.

Description

Technical Field

[0001] This invention relates to the field of aquaculture water treatment, and more particularly to a method for rapid biofilm formation in aquaculture water treatment systems. Background Technology

[0002] In the aquaculture industry, the continuous development and expansion of the sector have generated a large amount of wastewater. Effective treatment of this wastewater before its discharge into the environment is crucial. Currently, biological treatment methods, as a common and important approach, offer significant advantages. First, biological methods demonstrate exceptional efficiency in wastewater treatment. By fully utilizing the metabolic functions of microorganisms, they can precisely and efficiently treat various pollutants in wastewater. For example, microorganisms can transform organic matter and heavy metals into harmless or low-toxic substances, greatly reducing the environmental pollution caused by these pollutants. Furthermore, biological wastewater treatment is environmentally friendly. This method removes pollutants while avoiding secondary pollution problems that may arise from the use of chemical agents, effectively protecting the balance and stability of the ecological environment. More importantly, biological methods achieve resource recycling, highly aligning with the strategic requirements of sustainable development. It allows useful substances in wastewater to be reconstituted and reused, providing a feasible path for resource conservation and reuse. Among numerous biological treatment technologies, biofilm-based treatment technology has been widely applied due to its unique advantages. A biofilm is a complex biological system composed of microorganisms and their secreted extracellular polymers. It possesses an extremely high surface area, meaning it provides more adsorption and reaction sites, resulting in more rapid and efficient adsorption and degradation of pollutants. Simultaneously, the high biological activity of the biofilm further enhances its ability to treat pollutants. Compared to traditional activated sludge processes, biofilm treatment technology exhibits several advantages. In terms of treatment efficiency, it can remove pollutants from wastewater more quickly and thoroughly, ensuring that the treated water meets higher standards. In terms of energy consumption, biofilm treatment technology requires relatively low energy input, helping to reduce treatment costs and energy consumption. Furthermore, in terms of sludge production, biofilm treatment technology significantly reduces the amount of sludge produced, alleviating the burden and cost of subsequent sludge treatment. In conclusion, biofilm-based treatment technology demonstrates broad application prospects and enormous development potential in the field of wastewater treatment, and is of great significance for solving the problem of aquaculture wastewater treatment.

[0003] Biofilm technology, an important method for treating organic wastewater, relies on microorganisms—biofilms—that attach to and grow on the surface of specific solids to biodegrade organic and inorganic matter in wastewater. In this process, the microorganisms within the biofilm play a crucial role, transforming pollutants in wastewater into harmless or less harmful substances through their metabolic activities. Rapid and stable biofilm formation is a prerequisite for the successful start-up and full operation of the biofilm process. However, in practical applications, problems such as long biofilm formation time, loose structure, and easy detachment have consistently plagued treatment efficiency and operating costs. Therefore, researching ways to effectively promote biofilm formation is particularly important. This is of paramount significance for significantly improving wastewater treatment efficiency, reducing treatment costs, and enhancing the stability and reliability of treatment systems. It not only helps promote the wider application of biofilm technology in wastewater treatment but also provides strong technical support for solving the increasingly serious water pollution problem. Summary of the Invention

[0004] The core objective of this invention is to provide an innovative and efficient method for the rapid formation of biofilm in aquaculture water treatment systems, aiming to effectively and efficiently achieve the rapid formation of biofilm on a carrier, thereby improving the overall effect and efficiency of aquaculture water treatment.

[0005] To achieve the above objectives, the technical solution adopted by this invention is: a method for rapid biofilm formation in an aquaculture water treatment system, specifically including the following steps:

[0006] Step 1: Select a biofilm carrier;

[0007] Step 2: Prepare a certain amount of fulvic acid solution;

[0008] Step 3: Completely immerse the selected biofilm carrier in the prepared fulvic acid solution for a period of time.

[0009] Step 4: When performing Step 3, first perform aeration for a period of time, then let it stand for a period of anaerobic time.

[0010] Step 5: After sedimentation, replace a portion of the water. This step aims to remove any impurities and metabolic products, optimize the treatment environment, and create purer and more favorable conditions for the further growth and development of the biofilm. When replacing the water, it is necessary to control the volume and speed of the replacement to avoid excessive impact and damage to the established microbial community and biofilm structure.

[0011] Step 6: After changing the water, add fulvic acid to the predetermined concentration;

[0012] Step 7: After a period of time, a biofilm forms on the surface of the biofilm carrier.

[0013] Preferably, the biofilm carrier is a K5 biofilm reactor packing material.

[0014] Preferably, the concentration of fulvic acid is 20 mg / L to 1500 mg / L.

[0015] Preferably, the concentration of fulvic acid is 500 mg / L to 1500 mg / L.

[0016] Preferably, in step four, the aeration time is controlled to be 10 hours and the anaerobic settling time is 2 hours.

[0017] The present invention also provides a water treatment method for aquaculture, specifically including the following steps:

[0018] Step a: Filter the aquaculture water that needs to be treated, and remove solid particles and impurities from the water through a filter screen or filter media;

[0019] Step b: Allow the filtered aquaculture water to settle;

[0020] Step c: Place the settled aquaculture water into a biofilm reactor. The biofilm reactor uses the above-mentioned method for rapid biofilm formation to form a biofilm.

[0021] Step d: After a period of reaction, the microorganisms on the biofilm decompose the substances in the aquaculture water, thus achieving water treatment.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The method proposed in this invention ingeniously and innovatively utilizes fulvic acid to achieve efficient biofilm formation on a carrier. Fulvic acid, as a naturally occurring organic substance, possesses abundant functional groups and a complex molecular structure, enabling it to interact in various ways with microorganisms and the carrier surface. Through glycolysis and the tricarboxylic acid (TCA) cycle, fulvic acid significantly promotes carbon source metabolism. This means that microorganisms can utilize carbon sources more efficiently, producing more energy and metabolic intermediates, providing a powerful impetus for their growth, reproduction, and biofilm formation. During this process, more usable nicotinamide adenine dinucleotide (NADH) is generated. These NADHs, acting as direct electron donors, play a crucial role in heterotrophic denitrification. They provide essential electrons to denitrifying microorganisms, promoting the conversion of nitrogen from nitrates or nitrites to nitrogen gas, thereby effectively reducing the content of nitrogen pollutants in the water. Furthermore, fulvic acid can stimulate the release of AHL (acylhomoserine lactone) in both aqueous and biological phases. AHL is a quorum sensing signaling molecule; increased release of AHL enhances quorum sensing among microorganisms, enabling better information exchange and synergistic effects, leading to more orderly and efficient biofilm formation and improved overall biofilm performance and stability. Through these mechanisms, the method of this invention not only significantly shortens biofilm formation time and reduces the start-up cycle of water treatment systems but also greatly improves the efficiency and effectiveness of water quality remediation. This has significant practical importance and application value for solving water pollution problems in aquaculture and ensuring the health and sustainable development of the aquaculture environment.

[0024] The mechanism by which fulvic acid accelerates biofilm formation mainly lies in the following aspects:

[0025] Fulvic acid has excellent complexing and chelating abilities, enabling it to bind with metal ions in water, providing essential trace elements for microorganisms and promoting their growth and reproduction. For example, fulvic acid binds with iron ions, providing ample nutrition for iron bacteria and other microorganisms, allowing them to colonize and grow more quickly on the carrier surface, thereby accelerating biofilm formation.

[0026] Fulvic acid can improve the chemical environment of water bodies, regulate pH and redox potential, and create suitable living conditions for microorganisms. For example, in a slightly acidic environment, fulvic acid can buffer pH changes, allowing microorganisms to grow and metabolize in a relatively stable environment, thus accelerating the formation of biofilms.

[0027] Fulvic acid (FA) can also enhance signal transduction and communication among microorganisms, promoting synergistic effects within the microbial community. For example, FA can promote carbon source metabolism through glycolysis and the tricarboxylic acid (TCA) cycle, producing more available nicotinamide adenine dinucleotide (NADH). NADH acts as a direct electron donor, providing electrons for heterotrophic denitrification. Fulvic acid can also stimulate the release of alpha-hydroxyl (AHL) in both aqueous and biological phases, enhancing quorum sensing and thus improving denitrification performance and biofilm formation. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings necessary for the description of the embodiments or the prior art will be briefly introduced below. It is worth noting that the drawings described below are only a part of the embodiments of the present invention. For those skilled in the art, other related drawings can be obtained based on these drawings without any creative effort. Wherein:

[0029] Figure 1 These are state diagrams of different fulvic acid concentrations in the carrier in the experimental example;

[0030] Figure 2 This refers to the biofilm thickness in the reactor at different fulvic acid concentrations in the experimental example.

[0031] Figure 3 These are the water quality index data of the reactor water after treatment generated at different fulvic acid concentrations in the experimental examples. Detailed Implementation

[0032] To make the above-mentioned objectives, features, and advantages of this application clearer and easier to understand, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be clarified that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be specifically noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not all structures. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the protection scope of this application.

[0033] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0034] Example 1

[0035] A method for rapid biofilm formation in an aquaculture water treatment system, specifically including the following steps:

[0036] Step 1: Selecting a biofilm carrier. K5 reactor packing was used as the biofilm carrier. This step requires comprehensive consideration of various factors, including but not limited to the material properties, physical structure, and surface chemical properties of the carrier. The K5 reactor packing used is made of high-molecular-weight polyethylene (HMWPE). This material has excellent chemical stability and will not decompose, swell, or deteriorate under long-term contact with water and various chemicals, maintaining its structural and performance integrity. Furthermore, HMWPE has good corrosion resistance, resisting the erosion of common acids, alkalis, and salts in wastewater, extending the service life of the packing. In addition, the dimensions of K5 reactor packing are typically (D x H) 25 x 8 mm, with a bulk density of 110 kg / m³. 3 Specific surface area ≥600m² 2 / m 3 The large specific surface area provides ample space for microbial attachment and growth, increasing the contact opportunities between microorganisms and pollutants in wastewater, which is beneficial for improving wastewater treatment efficiency. Notably, the K5 reactor packing material has a weak negative charge on its surface. This charge distribution is conducive to attracting positively charged microbial cells, promoting their attachment and growth on the packing surface. Furthermore, the K5 surface typically contains functional groups such as hydroxyl and carboxyl groups. Hydroxyl groups can form hydrogen bonds with proteins and other substances on the surface of microbial cells, enhancing the binding force between microorganisms and the packing material; carboxyl groups can undergo complexation reactions with metal ions in wastewater, helping to remove certain heavy metal ions and also providing some nutrients for microbial growth.

[0037] Step 2: Prepare a certain amount of fulvic acid (FA) solution with a concentration of 500 mg / L. Deionized water or purified water is preferred as the solvent to avoid interference from impurities. Preparation should be carried out at room temperature (20-25℃) to ensure the chemical stability of fulvic acid. A magnetic stirrer or mechanical stirrer should be used to ensure uniform stirring and complete dissolution of the fulvic acid in the solvent. The preparation container should be thoroughly cleaned and sterilized before use to prevent residual substances from affecting the solution concentration and properties. This ensures that the solution concentration and properties meet the requirements of subsequent processing.

[0038] Step 3: Immerse the biofilm carrier in fulvic acid solution for 12 hours;

[0039] Step 4: When performing Step 3, first aerate for 10 hours, and then let it settle under anaerobic conditions for 2 hours.

[0040] Step 5: After settling, replace 80% of the water;

[0041] Step 6: After changing the water, add fulvic acid to the set concentration;

[0042] Step 7: Let the solution sit for at least 7 days, maintaining a temperature of 25-28℃, to allow a biofilm to form on the surface of the biofilm carrier. During this step, close monitoring of biofilm formation is crucial, including parameters such as thickness, density, microbial community structure, and activity. Assessing these parameters allows for evaluation of the biofilm formation progress and quality, enabling timely adjustments to ensure the process meets expectations. Specifically, regarding biofilm thickness, if growth is too slow, check nutrient composition, aeration rate, and fulvic acid concentration. Adding trace metal solutions, increasing aerator power, or increasing fulvic acid supplementation may help. If growth is too rapid or too thick, reduce fulvic acid concentration, adjust aeration strategy, or increase water exchange frequency and volume. For low biofilm density, assess the inoculum size, extend aeration time, and ensure appropriate nutrient ratios. For high density, reduce inoculum size, adjust pH, or increase anaerobic settling time. Regarding microbial community structure, if the proportion of key functional microorganisms is low, supplement necessary growth conditions; if non-target microorganisms proliferate excessively, check nutrients, use selective inhibitors, or fine-tune the temperature. When microbial activity is low, adjust the temperature, pH, and dissolved oxygen, supplement nutrients, and pretreat the biofilm carrier; when activity is too high, reduce the fulvic acid concentration and increase the anaerobic settling time.

[0043] In step two, the concentration of fulvic acid can be 20 mg / L to 1500 mg / L, preferably 500 mg / L to 1500 mg / L.

[0044] The fulvic acid is a humic substance with a size of 3500 Da, which is mainly composed of elements such as carbon, hydrogen, oxygen and nitrogen, and is made up of lignite, tree sap and peat, as well as abiotic organic matter in soil and aquatic ecosystems.

[0045] The solution in step two is an aqueous solution.

[0046] In step seven, the temperature of the solution is 25-28°C.

[0047] When in use, the obtained biofilm reactor is placed in the aquaculture water that needs to be treated. The microorganisms in the biofilm reactor decompose the available and inorganic substances in the aquaculture water.

[0048] Example 2

[0049] A water treatment method for aquaculture specifically includes the following steps:

[0050] Step a: Filter the aquaculture water that needs to be treated, and remove solid particles and impurities from the water through a filter screen or filter media;

[0051] Step b: Allow the filtered aquaculture water to settle;

[0052] Step c: Place the settled aquaculture water into a biofilm reactor. The biofilm reactor uses the above-mentioned method for rapid biofilm formation to form a biofilm.

[0053] Step d: After a period of reaction, the microorganisms on the biofilm decompose the substances in the aquaculture water, thus achieving water treatment.

[0054] The specific steps of microbial decomposition of substances in aquaculture water are as follows: First, the microorganisms attach and adapt to the carrier surface, adapting to water temperature, pH, dissolved oxygen, etc., and secreting sticky substances for stable attachment. Next, in the initial stage of organic matter decomposition, microorganisms secrete extracellular enzymes to break down suspended large organic molecules into smaller molecules, while ammonia-oxidizing bacteria and others convert and dissolve organic matter. Then, in the substance transformation and removal stage, the biofilm matures, microorganisms utilize small molecule nutrients for growth and reproduction, denitrifying bacteria and others convert harmful substances, and microorganisms assimilate phosphorus. Finally, a stable operation and dynamic equilibrium stage is reached, forming a complex ecosystem. The alternation of new and old microorganisms maintains system stability, but in practice, adjustments and optimizations are still needed based on factors such as stocking density.

[0055] Experimental Example

[0056] This experiment simulated an aquaculture water treatment system by establishing 10 1L SBBR reactors, comprising 10 groups (R0 to R9). All reaction systems used high-density polyethylene (HDPE) as the biofilm carrier material, with dimensions of 10×25mm, a specific surface area >500m² / m³, and a carrier packing density of 40%. Fulvic acid (FA) (purchased from McGraw-Grunds, 95% purity) was added at concentrations of 0, 20, 40, 50, 80, 100, 500, 1000, 1200, and 1500 mg / L, corresponding to groups R0, R1, R2, R3, R4, R5, R6, R7, R8, and R9, respectively. (See [link to relevant documentation]). Figure 1 The reactor operates on a 12-hour cycle, including 10 hours of aeration and 2 hours of static anaerobic sedimentation. After sedimentation, 80% of the water is replaced, and fatty acid (FA) is added to the set concentration. The reactor is operated at 25–28℃ for 40 days. To better monitor the changes in the concentration of various pollutants during the experiment, the experimental water was raw wastewater from aquaculture (snakehead pond, 300L, 10 snakeheads). The wastewater parameters were as follows: COD 100±3mg / L, TN 107.9±0.7mg / L, TP 27.1±0.3mg / L, NO3--N 56.76±0.63mg / L, NO2--N 0.27±0.15mg / L, NH4+-N 34.53±0.1mg / L, and C / N ratio 1.8±0.03 (low C / N). When the reactor is operated at 25-28°C for 40 days, the biofilm maturation time is shortened by 50-90%, and the water quality restoration efficiency is increased by 50%-80%, achieving good economic and ecological benefits.

[0057] from Figure 2 As can be seen, after 40 days of operation, the biofilm thicknesses of the other groups were 2.14, 3.33, 0.7, 6.67, 7.53, 7.62, 18.1, 27.4, and 31.55 times that of the control group, respectively. This indicates that different concentrations of fulvic acid had a significant impact on the growth and thickness of the biofilm, greatly promoting its formation and growth.

[0058] from Figure 3 The results show that the TNRR were 12.51%, 12.50%, 12.33%, 14.60%, 2.41%, 12.02%, 27.62%, 57.90%, 55.70%, and 63.48%, respectively, which were 0.999629491, 0.985550202, 1.167098924, 0.192663949, 0.961096701, 2.208595773, 4.62912189, 4.45350129, and 5.075213034 times that of the control group. Starting from 500 mg / L, the efficiency increased by 54.7%, 78.4%, 77.55%, and 80.3%, respectively. This indicates that fulvic acid concentrations greater than 40 mg / L have a certain promoting effect on total nitrogen removal, especially when the fulvic acid concentration is greater than 500 mg / L, it can significantly improve the total nitrogen removal rate.

[0059] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A water treatment method for aquaculture, specifically comprising the following steps: Step a: Filter the aquaculture water that needs to be treated, and remove solid particles and impurities from the water through a filter screen or filter media; Step b: Allow the filtered aquaculture water to settle; Step c: Place the settled aquaculture water into a biofilm reactor; Step d: After a period of reaction, the microorganisms on the biofilm decompose the substances in the aquaculture water, thus achieving water treatment. The biofilm reactor employs the following steps for biofilm attachment: Step 1: Select a biofilm carrier; Step 2: Prepare a certain amount of fulvic acid solution; Step 3: Completely immerse the biofilm carrier in the fulvic acid solution and maintain this immersion for a certain period of time; Step 4: When performing Step 3, first aerate for a period of time, and then let it settle in an anaerobic environment for a period of time. Step 5: After settling is complete, replace some of the water; Step 6: After changing the water, add fulvic acid to the predetermined concentration; Step 7: After a period of time, a biofilm forms on the surface of the biofilm carrier; The biofilm carrier used was K5 biofilm reactor packing material; The fulvic acid is one of the humic substances with a size of <3500 Da, mainly composed of carbon, hydrogen, oxygen and nitrogen, and originates from lignite, tree sap and peat, as well as abiotic organic matter in soil and aquatic ecosystems. The concentration of fulvic acid is 20 mg / L to 1500 mg / L; In step four, the aeration time is 10 hours, and the anaerobic settling time is 2 hours.

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