A method for resource utilization of aquaculture wastewater filter residue through fermentation and insect conversion.

Abstract

This invention provides a method for the resource utilization of aquaculture wastewater filter residue through fermentation and insect conversion, belonging to the field of aquaculture waste resource utilization and environmental protection technology. This method integrates a complete technology chain of "physical reconstruction of multiple auxiliary materials - staged sequential directional fermentation of compound probiotics (T3 process) - black soldier fly bioconversion," forming a complete closed-loop cycle system. It simultaneously achieves the harmless treatment, nutrient enrichment, high-value bioconversion, and resource utilization of by-products from the wastewater filter residue. The entire process has significant advantages such as high conversion efficiency, simple operation, low operating costs, and environmental friendliness. It is applicable to the resource utilization of wastewater filter residue from both freshwater and marine aquaculture, possessing good universality and promising prospects for promotion.

Description

Technical Field

[0001] This invention relates to the field of resource utilization and environmental protection technology for aquaculture waste, specifically to a method for resource utilization of aquaculture wastewater filter residue through fermentation and insect conversion. Background Technology

[0002] Intensive recirculating aquaculture systems (RAS) generate a large amount of solid particulate matter (mainly composed of uneaten feed and fish excrement) during operation. The resulting wastewater filter residue after solid-liquid separation is rich in nitrogen, phosphorus, and organic matter. Direct discharge of this wastewater would cause severe eutrophication stress to surrounding water bodies. However, conventional biological treatment or simple dehydration and landfill not only incurs high environmental regulatory costs but also results in significant loss of artificial nutrients. Therefore, the resource utilization of aquaculture wastewater filter residue into high-value feed or live bait has become an urgent need for the green transformation of aquaculture.

[0003] Currently, research on the resource utilization of aquaculture wastewater filter residue and aquaculture waste mainly focuses on two technical paths: one is to directly improve the nutritional value of the filter residue through microbial fermentation, making it directly edible for fish or economically valuable bait organisms; the other is to use saprophytic insects (such as black soldier flies Hermetia illucens) to convert the wastewater filter residue into high-protein insect biomass.

[0004] In microbial fermentation, probiotics such as yeasts (e.g., Saccharomyces cerevisiae), lactic acid bacteria (e.g., Lactobacillus plantarum), and Bacillus (e.g., Bacillus subtilis) are commonly used. Their combined formulation can complement each other to improve fermentation stability and nutrient conversion efficiency. Studies have shown that factors such as temperature, initial pH, anaerobic / aerobic conditions, carbon-to-nitrogen ratio, and inoculum size directly affect the increase in crude protein, crude fat, and soluble amino acids. However, existing fermentation technologies are mostly designed for conventional agricultural organic waste (e.g., soybean meal, rapeseed meal). When directly applied to high-moisture, high-fat, low-carbon-to-nitrogen ratio wastewater filter residue, the treatment effect is often unsatisfactory.

[0005] In the biotransformation of black soldier fly larvae, these larvae possess a wide feeding range, high conversion efficiency, and strong environmental adaptability. They can efficiently utilize high-moisture-content organic waste, converting low-value organic residues into insect biomass rich in protein and fat. Existing research has shown that black soldier fly larvae can significantly reduce the organic load in aquaculture sludge and achieve the recycling of nutrients such as nitrogen and phosphorus. However, when effluent filter residue is directly used as a substrate for black soldier flies, problems such as poor palatability and insufficient nutrient availability arise, thus affecting conversion efficiency. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for the resource utilization of aquaculture wastewater filter residue through fermentation and insect conversion. This method integrates a complete technological chain of "physical reconstruction of multiple auxiliary materials - staged sequential directional fermentation of compound probiotics (T3 process) - black soldier fly bioconversion," forming a complete closed-loop system that simultaneously achieves the harmless treatment, nutrient enrichment, high-value bioconversion, and resource utilization of by-products from the wastewater filter residue. The entire process has significant advantages such as high conversion efficiency, simple operation, low operating costs, and environmental friendliness. It is applicable to the resource utilization of wastewater filter residue from both freshwater and marine aquaculture, possessing good versatility and promising prospects for widespread application.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for the resource utilization of aquaculture wastewater filter residue through fermentation and insect conversion, the method comprising: S1. Pre-treat the tailwater filter residue until the moisture content is reduced to below 70% to obtain pre-treated tailwater filter residue; mix 313 parts by weight of the pre-treated tailwater filter residue with 187 parts by weight of agricultural waste to obtain a mixture; wherein the carbon-nitrogen ratio of the agricultural waste is >40. S2. Prepare a compound probiotic agent, wherein the compound probiotic agent comprises highly enzyme-producing heterotrophic bacteria, highly efficient fermentation-converting bacteria, and antibacterial acidifying probiotics in a mass ratio of 1:1:1; use the compound probiotic agent to perform staged sequential directional fermentation of the mixture, specifically including: at a fermentation temperature of 28~35℃, inoculating highly enzyme-producing heterotrophic bacteria and highly efficient fermentation-converting bacteria at 0 hours of fermentation for aerobic degradation; inoculating antibacterial acidifying probiotics at 12~36 hours of fermentation for lactic acid accumulation; and sealing and transferring to micro-anaerobic fermentation at 24~48 hours of fermentation to obtain the fermentation product; wherein the total fermentation time is 5~10 days; S3. Using the fermentation product as a substrate, larvae of saprophytic or filter-feeding economic food organisms are raised. S4. Separate the obtained larvae from the insect sand. The larvae are used as a substitute protein source for fishmeal in aquatic compound feed, and the insect sand is used as a high-quality organic fertilizer for direct reuse in crop fertilization or soil improvement.

[0008] Further, in S1, the pretreatment is plate and frame filter press or centrifugal dewatering; the agricultural waste includes one or more of corn stalk powder, crushed rice husks, wheat bran, corn cob powder, peanut shell powder, rice bran, wheat bran, and sawdust; preferably, the agricultural waste is composed of the following raw materials in parts by weight: 90 parts corn stalk powder, 65 parts crushed rice husks, and 32 parts wheat bran; the moisture content of the mixture is adjusted to 60%, and the carbon-nitrogen ratio is adjusted to 15-25.

[0009] Furthermore, in S2, the highly enzyme-producing heterotrophic bacteria include one or more of Bacillus subtilis, Bacillus licheniformis, or Bacillus coagulans; the highly efficient fermentation and conversion bacteria include one or more of Saccharomyces cerevisiae, Saccharomyces cerevisiae strain, or Candida utilis; the antibacterial and acidifying probiotics include one or more of Lactobacillus plantarum, Pediococcus pentosaceus, or Enterococcus faecalis; preferably, the compound probiotic agent is composed of Bacillus subtilis, Saccharomyces cerevisiae, and Lactobacillus plantarum, with each strain having a viable count ≥10⁻⁶. 8 A mixture of CFU / g and a total addition amount of 0.3wt.%.

[0010] Furthermore, in S2, the timing of the phased sequential directional fermentation process is as follows: at 0 hours, highly enzyme-producing heterotrophic bacteria and highly efficient fermentation and transformation bacteria are introduced for aerobic degradation; at 24 hours, antibacterial and acidifying probiotics are introduced; at 36 hours, the mixture is sealed and transferred to micro-anaerobic fermentation at a fermentation temperature of 30°C, with a total cycle of 5-7 days.

[0011] Furthermore, in S2, the crude protein content on a dry basis in the fermentation product is ≥12%, and the total viable count is ≥10. 9 CFU / g, pH≤5.5, Salmonella not detected, coliform bacteria <10 CFU / g, aflatoxin B1 <2 μg / kg.

[0012] Furthermore, in S3, the saprophytic or filter-feeding economic food organisms include one of the following: black soldier flies, mealworms (Tenebrio molitor), or sandworms (Perinereis aibuhitensis); wherein the rearing control parameters are: temperature 27℃±2℃, relative humidity 60%~70%, and rearing density 1 organism / cm². 2 The substrate moisture content is 70%; the rearing cycle is 10-12 days, that is, the larvae are harvested before they enter the prepupal stage; Furthermore, the feeding conversion performance indicators are: wet basis reduction rate ≥50%, fresh insect yield ≥15%, dry matter bioconversion rate (BCR) ≥15%, and larval survival rate ≥90%.

[0013] Furthermore, in S4, the separation method includes: screening, air separation, light separation, or automatic separation using the self-crawling habits of larvae; the obtained larval meal has a crude protein content of 42%~45% and a crude fat content of 31%~35%, and can be used as raw material for aquatic compound feed; the larval sand is rich in active nitrogen, phosphorus, potassium and humus, and can be used as organic fertilizer.

[0014] Furthermore, S2 specifically includes: S2.1 Configuring compound probiotic inoculum: Configuring compound probiotic inoculum with Bacillus subtilis, Saccharomyces cerevisiae and Lactobacillus plantarum; S2.2 Implementation of T3 sequential inoculation directional fermentation process: At a fermentation temperature of 30℃, the total amount of inoculant added is 3 g / kg substrate; the specific sequence is as follows: Bacillus subtilis and Saccharomyces cerevisiae are inoculated at 0 hours of fermentation to carry out aerobic degradation and initiate the hydrolysis and preliminary transformation of organic matter; Lactobacillus plantarum is inoculated after 24 hours of fermentation to begin accumulating lactic acid and moderately reduce the pH of the system; after 36 hours of fermentation, the system is sealed and transferred to the micro-anaerobic fermentation stage; S2.3 The closed fermentation cycle is 5-7 days. During this process, Bacillus and Lactobacillus constitute the main dominant bacterial groups in the fermentation system, playing a synergistic role in the transformation of organic matter in the effluent filter residue and maintaining the stability of the fermentation system; the final fermentation product has a crude protein content of over 12% on a dry basis and a total viable count of over 10. 9 CFU / g or higher, pH drops below 5.5; S2.4 During the fermentation process, Lactobacillus plantarum accumulates a large amount of lactic acid in the middle and late stages of fermentation, causing the pH value to drop from 6.45 on the second day to 5.46 on the fifth day, thus constructing an acidic antibacterial barrier, effectively inhibiting the metabolism of miscellaneous bacteria and reducing the loss of nitrogen through ammoniation and volatilization; Salmonella was not detected in the final fermentation product, the number of coliform bacteria was less than 10 CFU / g, and the content of aflatoxin B1 was less than 2 μg / kg.

[0015] The present invention also provides the application of the above-mentioned method for the resource utilization of aquaculture wastewater filter residue through fermentation-insect conversion in the field of resource utilization treatment of freshwater aquaculture wastewater filter residue with salinity ≤30‰ and marine aquaculture wastewater filter residue.

[0016] Compared with the prior art, the technical solution provided by the present invention has at least the following advantages: (1) Significantly improved nutrient enrichment efficiency: The T3 sequential directional fermentation process described in this invention can increase the crude protein content of the tailwater filter residue from 26.80% to 34.85% (enrichment rate 30.04%) and the crude fat from 4.76% to 6.35% (enhancement rate 33.40%), which is far superior to the 5%~8% protein increase of conventional single fermentation process, thus realizing the efficient nutrient value-added of tailwater filter residue.

[0017] (2) Construction of biosafety barrier: Lactic acid accumulated by Lactobacillus plantarum in the middle and late stage of fermentation is used to reduce the pH to 5.46, thus constructing an acidic antibacterial environment. Salmonella was not detected in the final fermentation product, coliform bacteria were <10 CFU / g (far below the national standard limit of <100 CFU / g), and aflatoxin B1 was <2 μg / kg (significantly below the national standard limit of 10 μg / kg). All indicators strictly comply with GB 13078-2017 "Feed Hygiene Standard".

[0018] (3) Significantly improved bioconversion efficiency of black soldier flies: Compared with the direct feeding of black soldier flies with untreated tailwater filter residue, the present invention uses fermentation products as substrate, which increases the larval survival rate to 94%, the fresh insect yield to 18%, the dry matter bioconversion rate (BCR) to 17.97%, and the feed conversion ratio (FCR) to 5.56, all of which are better than the existing technical solutions.

[0019] (4) Significant volume reduction effect: The wet basis volume reduction rate of the system reaches 52.3%. More than half of the original materials are effectively degraded and transformed by the feeding and metabolism of black soldier fly, which greatly reduces the amount and cost of solid waste disposal in aquaculture.

[0020] (5) Full-scale resource utilization: The coupling process of this invention realizes the full-scale resource utilization of "solid waste → high-protein insect feed + organic fertilizer" without generating secondary waste. Black soldier fly powder (protein content 42%~45%, fat 31%~35%) can be used as a high-quality protein source for aquatic feed, and insect sand can be used as organic fertilizer, realizing the cascade recycling of materials and energy.

[0021] (6) Strong process adaptability: The fermentation system described in this invention can still maintain stable fermentation in a 30‰ high-salt seawater environment. Black soldier fly larvae have a high tolerance to substrate salinity, making this method applicable to the resource utilization of filter residue from both freshwater and seawater aquaculture, with a wide range of applications.

[0022] (7) Simple process and low cost: The fermentation cycle only takes 5 to 7 days, the black soldier fly breeding cycle is 10 to 12 days, and the overall treatment cycle does not exceed 20 days; the amount of bacterial agent added is only 0.3%, and the auxiliary materials are all agricultural waste (straw powder, rice husk, bran). The raw materials are readily available and inexpensive, making it easy to scale up and promote industrialization. Attached Figure Description

[0023] Figure 1 This is a characteristic analysis diagram of tailwater filter residue and agricultural waste (fermentation auxiliary material) provided in the embodiments of the present invention; Figure 2 This is a comparison chart of nutrient content and improvement rate at different fermentation endpoints at different temperatures provided in the embodiments of the present invention; Figure 3This is a comparison chart of nutrient content and improvement rate with different inoculum amounts provided in the embodiments of the present invention; Figure 4 This is a comparison chart of the nutrient content change trends of different microbial groups with the fermentation endpoint content and improvement rate provided in the embodiments of the present invention; Figure 5 This is a graph showing the pH changes during fermentation at different inoculation times, provided in an embodiment of the present invention. Figure 6 This is a diagram showing the nutrient changes during fermentation at different inoculation times, provided in an embodiment of the present invention. Figure 7 This is a graph showing the daily weight variation of black soldier fly larvae at different temperatures, provided in an embodiment of the present invention. Figure 8 This is a graph showing the daily weight change of black soldier fly under different stocking densities provided in an embodiment of the present invention; Figure 9 This is a graph showing the daily weight variation of black soldier fly under different moisture contents, provided in an embodiment of the present invention. Figure 10 This is a process flow diagram provided in an embodiment of the present invention. Detailed Implementation

[0024] The inventors discovered that the fine particulate matter (i.e., wastewater filter residue) produced by solid-liquid separation of aquaculture wastewater has typical characteristics such as high water content (>80%), high crude fat content (about 20%), low carbon-to-nitrogen ratio (about 7.25), and extreme susceptibility to spoilage. These physicochemical properties make it difficult to directly carry out efficient microbial fermentation or biotransformation and utilization. There is an urgent need for a pretreatment and fermentation method that can effectively reconstruct the physicochemical properties of the filter residue.

[0025] In the field of microbial fermentation technology, existing processes for treating this type of wastewater filter residue generally suffer from problems such as long fermentation cycles, low protein enrichment efficiency, susceptibility to rancidity during fermentation, and difficulty in effectively inhibiting harmful microorganisms. Currently, there is a lack of targeted fermentation processes for substrates with high humidity, high fat content, and low carbon-to-nitrogen ratios, which cannot meet the requirements for fermentation efficiency and product quality for the resource utilization of filter residue.

[0026] In the biotransformation of black soldier fly larvae, directly feeding them with untreated wastewater filter residue leads to poor palatability, slow larval growth, and low biotransformation efficiency. Meanwhile, traditional fermentation processes and insect rearing processes are often independent, failing to form an effective technological connection, and a coordinated or integrated technological solution that couples fermentation and insect transformation has not yet been developed.

[0027] In summary, existing technologies struggle to achieve a closed-loop process simultaneously within the same system, encompassing the harmless treatment of wastewater filter residue, nutrient enrichment, high-value bioconversion, and resource utilization of byproducts. Furthermore, the lack of a unified process route applicable to both freshwater and marine aquaculture wastewater filter residue limits the promotion and application of this technology across different aquaculture models.

[0028] In view of this, the present invention addresses the above-mentioned prominent problems in the existing technologies for the resource utilization of aquaculture wastewater filter residue, and provides a highly efficient, low-cost, and comprehensive coupled treatment and resource utilization method.

[0029] The present invention will now be described in detail with reference to specific embodiments.

[0030] Example This invention provides a method for the resource utilization of aquaculture wastewater filter residue through fermentation and insect conversion, comprising: S1. Tailwater filter residue pretreatment and auxiliary material reconstruction S1.1 The filter residue from solid-liquid separation of aquaculture wastewater is subjected to plate and frame filtration or centrifugal dehydration to reduce its moisture content to below 70%.

[0031] S1.2. The auxiliary materials were reconstructed according to the mass ratio of tailwater filter residue: corn stalk powder: crushed rice husk: wheat bran = 313:90:65:32, and thoroughly mixed to adjust the moisture content of the mixture to approximately 60%. Crushed rice husk and corn stalk powder have a high carbon-to-nitrogen ratio and lignocellulose structure, which can effectively improve the system's permeability and dilute the fat content; wheat bran serves as a fast-acting nutrient source to enhance the early-stage proliferation efficiency of microorganisms. Through auxiliary material reconstruction, the carbon-to-nitrogen ratio of the system was adjusted to the optimal range of 15-25 for solid-state fermentation, while simultaneously improving the structural stability of the materials.

[0032] The mixed fermentation substrate has a moisture content of 60%, a carbon-to-nitrogen ratio of 25, and an organic matter content of 87.65%. Among the organic matter, the crude protein content is 9.3%, the crude fat content is 4.76%, and other organic matter (carbohydrates, cellulose, hemicellulose, lignin, etc.) accounts for 73.59% (i.e., 87.65%-9.3%-4.76%).

[0033] S2, staged sequential directional fermentation of compound probiotics (T3 process) S2.1 Preparation of compound probiotic agent: A three-strain combined system consisting of Bacillus subtilis, Saccharomyces cerevisiae, and Lactobacillus plantarum, with each strain having a live count ≥10. 8 CFU / g.

[0034] S2.2 Implementation of T3 sequential inoculation directional fermentation process: At a fermentation temperature of 30℃, the total amount of inoculant added is 3 g / kg substrate (0.3%, mass percentage). The specific sequence is as follows: Bacillus subtilis and Saccharomyces cerevisiae are inoculated at 0 hours of fermentation to carry out aerobic degradation and rapidly initiate the hydrolysis and initial transformation of organic matter; Lactobacillus plantarum is inoculated after 24 hours of fermentation to begin accumulating lactic acid and moderately lowering the pH of the system; after 36 hours of fermentation, the system is sealed and transferred to the micro-anaerobic fermentation stage.

[0035] S2.3 The closed fermentation cycle is 5-7 days. During this process, Bacillus and Lactobacillus constitute the main dominant bacterial groups in the fermentation system, playing a synergistic role in the transformation of organic matter in the effluent filter residue and maintaining the stability of the fermentation system. The final fermentation product has a crude protein content of over 12% (on a dry basis) and a total viable count of over 10. 9 CFU / g or higher, pH drops below 5.5.

[0036] S2.4 During fermentation, *Lactobacillus plantarum* accumulates a large amount of lactic acid in the later stages of fermentation, rapidly driving the system pH value down from 6.45 on day 2 to 5.46 on day 5, constructing an acidic antibacterial barrier, effectively inhibiting the metabolism of miscellaneous bacteria and reducing nitrogen loss through ammoniation and volatilization. Test results showed that Salmonella was not detected in the final fermentation product, the coliform count was below 10 CFU / g, and the aflatoxin B1 content was below 2 μg / kg. All safety indicators were better than the limits required by GB 13078-2017 "Feed Hygiene Standard".

[0037] S3. Black soldier fly rearing and biotransformation S3.1. Using the fermentation product obtained in S2.3 as a substrate, black soldier fly larvae were reared. The rearing environmental parameters were: temperature 27℃±2℃, relative humidity 60%~70%. The larval rearing density was 1 larva / cm². 2 The initial moisture content of the fermentation substrate is adjusted to about 70%.

[0038] S3.2 The rearing cycle is 10-12 days, and harvesting is carried out before the larvae enter the prepupal stage. Under these conditions, black soldier fly larvae can efficiently utilize the fermentation wastewater filter residue, effectively converting organic nutrients into their own biomass. The system achieves a wet-base reduction rate of 52.3%, a fresh larvae yield of 18%, a dry matter bioconversion rate (BCR) of 17.97%, a feed conversion ratio (FCR) of 5.56, and a larval survival rate of 94%.

[0039] S4. Product separation and resource utilization S4.1. Black soldier fly larvae are separated from insect sand by sieving or air separation. The obtained mature black soldier fly larvae are dried and crushed to prepare insect protein powder. The crude protein content of this insect powder is 42%~45%, and the crude fat content is 31%~35%, which can be used as an alternative protein source for fishmeal in aquatic compound feed.

[0040] S4.2 The separated insect sand (yield of about 22%) is rich in active nitrogen, phosphorus, potassium elements and humic components after biomineralization and degradation, and can be directly reused as a high-quality organic fertilizer for crop fertilization or soil improvement.

[0041] Figure 1 This paper displays data on the crude protein, crude fat, crude ash, organic matter content, and carbon-to-nitrogen ratio of the raw material of the wastewater filter residue, as well as the characteristic data of auxiliary materials such as corn stalk powder, crushed rice husks, and wheat bran, illustrating the necessity of auxiliary material reconstruction for wastewater filter residue. This invention selects corn stalk powder, crushed rice husks, and wheat bran as auxiliary materials. Crushed rice husks and corn stalk powder have a high carbon-to-nitrogen ratio and lignocellulose structure, which can effectively improve the system's permeability and dilute the fat content; wheat bran serves as a fast-acting nutrient source to improve the early-stage microbial proliferation efficiency. After optimizing the auxiliary material ratio, the system moisture content is controlled at around 60%, and the fermentation structure stability is significantly improved, providing favorable conditions for subsequent solid-state fermentation.

[0042] Figure 2 The results show a comparison of the crude protein content and its increase rate on day 7 of fermentation under three temperature gradients: 25℃, 30℃, and 40℃. The results indicate that the crude protein content in the 30℃ treatment group increased from the initial 26.80% to 29.86%, an increase of 11.42%, making it the optimal fermentation temperature. Figure 2 'a' represents the crude protein content. Figure 2 b represents the organic matter content. Figure 2 c represents the crude fat content. Experimental results showed significant differences in the fermentation effect of the wastewater filter residue under different temperature conditions, with the 30 ℃ treatment group exhibiting the best overall fermentation effect. On the 7th day of fermentation, the crude protein content in the 30 ℃ group increased from the initial 26.80% to 29.86%, an increase of 11.42%; the crude fat content increased from 4.76% to 5.30%, an increase of 11.34%. Simultaneously, under these conditions, the fermented material exhibited a distinct sour aroma, a loose structure, and no obvious signs of spoilage, indicating the formation of a relatively stable and beneficial fermentation environment within the system.

[0043] The inventors analyzed that 30℃ is within the suitable growth temperature range for functional strains such as *Lactobacillus plantarum*, *Saccharomyces cerevisiae*, and *Bacillus subtilis*, which is conducive to the formation of a stable and synergistic metabolic system among the three bacteria. Specifically, *Bacillus subtilis* can rapidly secrete proteases, amylases, and cellulases in the early stages of fermentation, initially degrading complex organic matter in the wastewater residue and releasing a large amount of small-molecule nutrients. *Saccharomyces cerevisiae* utilizes soluble sugars and amino acids for cell proliferation and produces some vitamins and metabolically active substances, thereby improving the nutritional value of the system. In the middle and later stages of fermentation, *Lactobacillus plantarum* gradually establishes an acidic environment through lactic acid accumulation, further inhibiting the growth of putrefactive bacteria and other microorganisms. Therefore, at 30℃, the three bacteria can form a good metabolic coupling relationship, ultimately achieving a high level of protein enrichment and lipid accumulation.

[0044] In contrast, fermentation at 25 ℃ was significantly less effective. Experimental results showed that the increase in crude protein and crude fat in this group was lower than that in the 30 ℃ group, and the changes in materials were slower during the fermentation cycle. Analysis suggests that lower temperatures reduce the fluidity of microbial cell membranes and enzyme catalytic efficiency, thereby weakening the metabolic activity of the microbial community. In particular, the proliferation rate of Bacillus and yeast decreased at low temperatures, leading to a slowdown in organic matter degradation and nutrient conversion. Furthermore, low temperatures prolong the time it takes for lactic acid bacteria to establish a dominant community, weakening the acidification process and further reducing overall fermentation efficiency. Therefore, while basic fermentation can be maintained at 25 ℃, the overall metabolic intensity of the system is insufficient, making it difficult to achieve efficient nutrient fortification.

[0045] At 40 ℃, a different inhibitory characteristic was observed. Experimental results showed that the improvement in crude protein and crude fat content was significantly reduced in the later stages of fermentation, and some samples even exhibited a slight ammonia and rancid odor, indicating that the system stability was affected. Analysis suggests that while high temperatures can increase the rate of some enzymatic reactions to a certain extent, exceeding the optimal range can lead to heat stress on some sensitive strains. In particular, the cell activity of *Saccharomyces cerevisiae* decreased significantly at 40 ℃, inhibiting its sugar metabolism and lipid accumulation, thus affecting the overall nutrient enrichment effect. Simultaneously, the high temperature environment may also promote the rapid proliferation of some miscellaneous and putrefactive bacteria, disrupting the metabolic balance within the system, leading to protein decomposition and the production of ammonia, which in turn causes nitrogen loss and off-flavors. Furthermore, high temperatures may accelerate the volatilization of organic acids and microbial cell death, thereby reducing the stability of lactic acid bacteria in the later stages and ultimately causing a decline in fermentation quality.

[0046] The results from different temperature treatments show that temperature changes directly affect the microbial community structure and nutrient transformation pathways during the fermentation of wastewater filter residue. Lower temperatures primarily lead to insufficient fermentation efficiency by limiting microbial metabolic activity, while excessively high temperatures cause microbial imbalance and increased putrefaction. In contrast, 30 ℃ balances microbial proliferation efficiency, enzyme activity expression, and system stability, and is more conducive to the synergistic effect of the composite microbial community. Therefore, 30 ℃ can be considered the optimal temperature for solid-state fermentation of the composite microbial community in wastewater filter residue. This result provides important parameter basis for subsequent engineering scale-up and stable operation.

[0047] Figure 3 The effects of different inoculum dosages (1 g / kg, 3 g / kg, 5 g / kg) on ​​the crude protein content and improvement rate of the fermentation products were shown, and the optimal inoculum dosage was determined to be 3 g / kg. Figure 3 'a' represents the crude protein content. Figure 3 b represents the organic matter content. Figure 3 c represents the crude fat content.

[0048] Low-dose group (1 g / kg): In the early stage of fermentation, the microbial succession was insufficient. Due to the large number of native bacteria in the filter residue, the low inoculum amount resulted in an insignificant colonization advantage of the target microbial groups (Bacillus, yeast, etc.), and the fermentation cycle was prolonged. On day 7, the increase rate of crude protein and crude fat was significantly lower than that of the other two groups, and the natural ammonification of the filter residue could not be effectively inhibited.

[0049] Medium-dose group (3 g / kg): The product exhibited the best biochemical activity. Under this gradient, the crude protein content increased from the initial 26.8% to 29.86% (an increase of 11.42%), and the crude fat content increased to 5.30% (an increase of 11.34%). At this point, the target bacterial community rapidly established a niche competitive advantage in the substrate, the organic matter degradation rate reached its peak, and the defibrillation and cell wall disruption of complex macromolecules were effectively achieved.

[0050] High-dose group (5 g / kg): With further increases in inoculum amount, the rate of increase in crude protein and crude fat tended to level off, and even showed a slight decline. Data showed that there was no statistically significant difference in nutritional indicators between the 5 g / kg group and the 3 g / kg group. P>0.05 ).

[0051] Analysis suggests that when the inoculum density reaches 3 g / kg, the number of viable bacteria in the system is sufficient to cover the substrate surface and enter the logarithmic growth phase. Increasing the inoculum density to 5 g / kg triggers a "marginal effect": on the one hand, excessively high initial microbial density intensifies competition for limited available carbon sources (organic matter) within the population, leading to feedback inhibition of individual metabolic activity; on the other hand, if the metabolic heat generated by rapid microbial reproduction cannot be dissipated in time, it may cause localized high temperatures, which in turn limits the enrichment of temperature-sensitive core strains such as yeast. Comparative analysis shows that an inoculum density of 3 g / kg, while ensuring optimal conversion efficiency, can reduce the cost of the microbial agent by approximately 40% compared to the 5 g / kg scheme. In conclusion, considering both bioconversion potential and engineering operational economics, this invention determines 3 g / kg (0.3%) as the optimal level of microbial agent addition for the fermentation of aquaculture wastewater filter residue into feed.

[0052] Figure 4 The dynamic trends and endpoint comparisons of crude protein and crude fat content under three inoculation strategies—natural succession group (CK), intermittent inoculation group (T2), and sequential inoculation group (T3)—were shown, verifying that the T3 sequential inoculation process is the optimal strategy. Among them, Figure 4 'a' represents the trend of crude protein changes. Figure 4 b represents the trend of organic matter change. Figure 4 c represents the trend of crude fat change. Figure 4 d represents the crude protein content and enhancement rate at the fermentation endpoint. Figure 4 e represents the organic matter content and increase rate at the fermentation endpoint. Figure 4 f represents the crude fat content and increase rate at the fermentation endpoint.

[0053] (1) Construction and functional positioning of complex microbial communities Addressing the challenges posed by the complex structure, easy rancidity, and foul odor of aquaculture wastewater residue (compound solid waste such as fish feces and uneaten feed), which consists of large organic molecules, this invention, based on the principle of "functional complementarity and metabolic synergy," introduces an in-situ solid-state fermentation system using carefully selected Bacillus subtilis. subtilis ), brewer's yeast ( Saccharomyces cerevisiae ) and Lactobacillus plantarum ( Lactobacillus plantarum A three-strain co-fermentation system was constructed. The ecological niche and physiological function of each strain in the system are as follows: Bacillus subtilis (function: fibrinolysis and macromolecular degradation): As a highly enzyme-producing heterotrophic bacterium, it highly expresses and secretes efficient extracellular proteases, cellulases, and lipases in the early stages of fermentation. By breaking down the complex non-starch polysaccharides (such as crude fiber) and crude protein macromolecular peptide chains in the filter residue, it converts them into soluble oligosaccharides, amino acids, and short peptides, providing a sufficient carbon and nitrogen source matrix for subsequent bacterial strains.

[0054] Saccharomyces cerevisiae (function: nutritional reconstruction and palatability improvement): It utilizes the assimilative carbon source generated by Bacillus subtilis degradation to carry out vigorous sugar metabolism and proliferation, achieving secondary nitrogen fixation of "microbial protein". At the same time, its metabolic byproducts contain rich B vitamins, trace elements and nucleotides and other nutrients; the ethanol, lower fatty acids and esters produced give the fermentation products a unique aroma and fruitiness.

[0055] Lactobacillus plantarum (function: acid-stable environment and biosafety control): As a typical homolactic fermenting bacterium, it efficiently utilizes free sugars to convert into lactic acid, driving a rapid decrease in the pH of the fermentation system. The low-acid environment not only effectively inhibits the growth of native Salmonella, Escherichia coli, and other miscellaneous bacteria in the filter residue, but also locks in nitrogen (reducing ammonia volatilization loss), creating a highly stable safety barrier for the overall fermentation process.

[0056] (2) Analysis of key nutritional indicators Experimental results show that single-strain treatment has significant limitations in improving the conversion efficiency of complex wastewater filter residue, while the three-strain compound system exhibits a highly significant biological synergistic effect. This compound system forms a spatiotemporal dynamic metabolic pathway during the fermentation cycle: "spore decomposition and cell wall disruption—yeast nitrogen fixation and lipid production—lactic acid-locked environment."

[0057] After optimization through synergistic fermentation, by day 7 of fermentation, the crude protein content in the product of the three-strain compound system reached a maximum of 34.85%. This was not only due to the hydrolysis and enrichment of substrate proteins, but also mainly due to the synthesis of microbial proteins (accumulation of fungal / bacterial biomass). The crude fat content reached 6.35%, and the increase in high-energy lipids provided black soldier flies with a higher-quality energy conversion substrate. With the vigorous respiratory metabolism and mass-energy conversion of carbon sources by microorganisms, the organic matter content in the system decreased significantly from the initial abundance to 57.82%, indicating that a large number of recalcitrant macromolecules had been converted into microbial carbon sources and volatile gases. At the end of fermentation, the dry matter loss rate reached 23.10%. In solid-state fermentation engineering, this indicator directly reflects the degree of degradation and mineralization of materials. Reasonable volume reduction not only indicates that the substrate has been fully biodegraded, but also retains high-value enriched nutrients for subsequent black soldier fly conversion to the greatest extent, significantly improving the resource utilization efficiency of tailwater filter residue.

[0058] Figure 5 The dynamic changes in pH during the T3 fermentation process from day 0 to day 7 are shown. The pH gradually decreased from an initial value of approximately 6.8 to 5.46 on day 5, illustrating the construction process of the acidic antibacterial barrier. The dynamic evolution of pH in the fermentation system is a core biochemical indicator reflecting probiotic colonization, metabolic substrate transformation, and system stability.

[0059] Group CK: The initial pH of the system was 7.23. Due to the lack of colonization control by exogenous dominant probiotics, the complex putrefactive bacteria naturally attached to the substrate proliferated rapidly, strongly hydrolyzing nitrogenous organic matter and releasing large amounts of free ammonia, leading to rapid ammonification of the system. The pH value spiked within the first 3 days and eventually remained in the strongly alkaline range of 8.42, accompanied by a strong foul odor. This indicates that the substrate is extremely prone to malignant putrefaction under natural succession conditions.

[0060] Group T1: Three strains were inoculated simultaneously at 0 h. Due to the extremely rapid initial proliferation rate of lactic acid bacteria, the pH of the system dropped sharply to 6.25 on the first day of fermentation. This premature acidification severely inhibited the secretory activity of Bacillus subtilis, which prefers a neutral to slightly alkaline environment, resulting in the inability to fully express the extracellular macromolecular degradation enzyme spectrum.

[0061] Group T3: Demonstrated precise, phased biochemical control. During the first 24 hours of aerobic synergy, the system pH remained within the neutral range of 7.23. This provided optimal enzymatic reaction conditions for Bacillus subtilis to synthesize and secrete extracellular cellulase and protease, as well as for the assimilation and proliferation of Saccharomyces cerevisiae. After 24 hours of inoculation with Lactobacillus plantarum, the system's metabolism rapidly switched. Lactic acid bacteria utilized the small-molecule sugars produced by the earlier hydrolysis to accumulate large amounts of lactic acid, driving a rapid axial drop in pH from 6.45 on day 2 to a stable acidic steady-state of 5.46 on day 5. This process successfully constructed an absolutely dominant acidic barrier, freezing the metabolism of other microorganisms while blocking the volatilization and loss of free ammonia.

[0062] Figure 6 The study showed the nutrient change trends at different inoculation times and the comparison of the content and increase rate at the fermentation endpoint.

[0063] Figure 7The daily weight dynamics of black soldier fly larvae were displayed at 25℃, 27℃, and 30℃. The results showed that larvae grew fastest at 27℃, with a prepupal period of 10 days and a maximum total weight of 0.2462 g for a single larva. The figures clearly show that temperature significantly affects the daily weight change and prepupal period of black soldier fly larvae. During the larval development stage, 27℃ is the optimal temperature for black soldier fly larvae development. The graph shows that black soldier fly larvae develop fastest at 27°C, requiring 10 days to enter the prepupal stage, and reaching their maximum weight of 0.2462 g / larva at this temperature. As the temperature rises, the larvae's metabolic rate increases, with mature larvae weighing only 0.2216 g / larva at 34°C, requiring 12 days to enter the prepupal stage. Lower temperatures slow down the larvae's metabolic rate; black soldier fly larvae reared for 20 days gain only the same weight as those reared for 2 days at 27°C. This difference is likely due to the reduced activity levels and significantly decreased food intake of the larvae at low temperatures, hindering their ability to obtain nutrients and convert them into energy for basic life functions.

[0064] Figure 8 Different stocking densities (0.5 birds / cm²) were shown. 2 1 strip / cm 2 2 strips / cm 2 4 strips / cm 2 Under certain conditions, the daily weight change of black soldier fly larvae was determined to be 1 larva / cm. 2 The optimal rearing density is shown in the figure. As can be seen from the figure, different rearing densities have different effects on larvae at different stages. The optimal rearing density is 1 larva / cm². 2 The group with the largest average larval weight, reaching a maximum of 0.2465 g / larva, had a larval stage of 11 days; the rearing density was 2 larvae / cm². 2 The maximum weight was 0.2264g / larva, and the larval stage lasted 12 days; the stocking density was 3 larvae / cm². 2 The maximum weight was 0.2018g / larva, and the larval stage lasted 13 days; the group with the highest stocking density had 4 larvae / cm². 2 The maximum weight is 0.1336g / insect, and the larval stage lasts for 13 days.

[0065] In the early stages of rearing, higher density experimental groups showed greater weight gain in black soldier fly larvae, while in the later stages, lower density experimental groups showed greater weight gain. This is related to the black soldier fly's lifestyle; larvae generally live in clumps, and the higher the density, the more pronounced this clumping effect. As the larvae grow older, their independent mobility increases. When the larval density in the feed exceeds a certain value, competition among the larvae reduces the average amount of feed per larva. Therefore, higher densities result in less food intake per larva, leading to a decrease in average weight and a prolonged larval stage.

[0066] Figure 9 The study shows the daily weight changes of black soldier fly larvae under three moisture content gradients: 60%, 70%, and 80%. A 70% moisture content was the optimal condition, with the largest single larva reaching a total weight of 0.2875 g. The initial moisture content of the substrate is a key physical variable regulating the rheological properties, mass transfer efficiency, and dissolved oxygen diffusion flux of solid materials. This study systematically compared the effects of 60%, 70%, and 80% moisture contents on the proliferation of black soldier fly larvae.

[0067] Experimental results show that an initial moisture content of 70% constitutes the optimal physical window for the growth and development of black soldier flies. Under this moisture gradient, the capillary porosity and mechanical support of the material reach equilibrium, which is conducive to efficient feeding and mass transfer by the black soldier fly larvae through body wall peristalsis, while also maintaining microaeric aeration within the material. Under these conditions, larvae can complete nutrient accumulation and enter the prepupal stage in 13 days, with a maximum total weight of 0.2875g for a single larva. When the moisture content is 60%, the prepupal stage lasts for 15 days, and the maximum total weight of a single larva reaches 0.2575g, demonstrating that black soldier flies are more adapted to an environment with a 70% moisture content.

[0068] Black soldier fly larvae are highly sensitive to substrate moisture content, and suitable moisture conditions are crucial for maintaining their normal feeding, growth, metabolism, and organic matter conversion efficiency. Existing research indicates that a moisture content of approximately 70% is generally considered suitable for black soldier fly larvae in processing organic waste. This is because this moisture level effectively coordinates the relationship between water supply, oxygen diffusion, and microbial metabolism within the substrate system. Black soldier fly larvae are typical wet-feeding insects, primarily feeding on semi-fluid or microbially softened organic matter. When the substrate moisture content is low, the material is prone to drying and compaction, restricting larval movement and feeding, thus reducing growth rate and feed conversion efficiency. Simultaneously, low moisture conditions decrease microbial activity, weakening the substrate's pre-degradation capacity and hindering larval nutrient utilization. When the moisture content is maintained at approximately 70%, a suitable gas-liquid-solid three-phase structure can typically form within the substrate. On the one hand, a higher moisture content can maintain the normal metabolism of larvae and the dissolution and migration of nutrients, enhancing the larvae's ability to feed on the substrate. On the other hand, the substrate can still retain a certain degree of porosity, thereby maintaining oxygen diffusion and aerobic microbial growth conditions, which is conducive to the synergistic metabolic effects of functional microorganisms such as lactic acid bacteria, Bacillus, and yeast, promoting the decomposition of organic matter and the release of nutrients. Therefore, under this moisture content condition, black soldier fly larvae usually exhibit higher growth rates, volume reduction efficiency, and biotransformation capabilities.

[0069] Conversely, when the substrate moisture content further increases to over 80%, excess water fills the substrate pores, hindering oxygen diffusion and creating an anaerobic environment in the bottom material. This leads to rancidity, blackening, and the production of unpleasant odors such as hydrogen sulfide. Simultaneously, anaerobic metabolism causes ammonia accumulation and the proliferation of harmful microorganisms, reducing substrate stability and significantly inhibiting larval growth. Excessive free water also keeps the larval surface constantly moist, affecting normal spiracular exchange and accelerating the reproduction of pathogenic microorganisms, thus increasing the risk of larval infection and death. Furthermore, for highly viscous, fine-particle substrates such as tailwater filter residue, high moisture content more easily leads to material compaction and reduced aeration. Therefore, excessively high moisture content not only reduces the black soldier fly's efficiency in converting organic matter but also disrupts the stability of the entire "larva-microorganism" co-degradation system, making it a significant reason for black soldier fly rearing failures. In summary, a moisture content of approximately 70% can meet the growth requirements of black soldier fly larvae while maintaining good aeration conditions and microbial activity in the substrate, thereby achieving a better bioconversion effect of organic waste.

[0070] Figure 10 The complete process flow provided by this invention is shown as "tailwater filter residue → dewatering → auxiliary material reconstruction → T3 sequential directional fermentation → black soldier fly breeding → insect separation → insect protein powder + insect sand organic fertilizer".

[0071] Specifically, the technical principle of this invention is based on the following three levels of synergistic mechanism: Firstly, the physical reconstruction-biotransformation synergistic mechanism: by adding high carbon-nitrogen ratio auxiliary materials such as corn stalk powder and crushed rice husks, the physical framework and chemical composition of the tailwater filter residue are reconstructed, adjusting the carbon-nitrogen ratio of the system from about 7.25 to the optimal range for solid-state fermentation (15~25), while improving the permeability and structural stability of the material, creating suitable conditions for microbial fermentation.

[0072] Secondly, the microbial community regulation mechanism of T3 sequential directional fermentation: A staged inoculation strategy was adopted. In the early stage of fermentation, aerobic Bacillus subtilis and Saccharomyces cerevisiae rapidly hydrolyzed macromolecular organic matter, consumed free oxygen, and produced metabolic intermediates. In the middle stage of fermentation, Lactobacillus plantarum was introduced, which rapidly proliferated and accumulated lactic acid using the metabolic basis established in the early stage, driving the pH down and creating an acidic antibacterial environment. In the later stage of fermentation, the microbial community was transferred to a micro-anaerobic environment through sealing to maintain the stable metabolism of the dominant microbial community. Through sequential control, the functional microbial community was targeted for screening and enrichment. The relative abundance of Lactobacillus and Bacillus species increased significantly, while the abundance of harmful bacteria such as Pseudomonas species decreased significantly.

[0073] Thirdly, the nutrient gradient conversion mechanism of fermentation-insect feeding coupling: The crude protein content of the filter residue after directional fermentation is significantly increased, anti-nutritional factors are effectively degraded, and harmful microorganisms are inhibited. At the same time, a large number of probiotics (live count ≥10) are retained in the fermentation products. 9 CFU / g can improve the intestinal microecological environment of black soldier fly larvae, enhancing substrate palatability and nutrient availability. Black soldier fly larvae further efficiently enrich and convert nutrients from the fermentation products into high-protein insect biomass, thus achieving a tiered value-added process from "low-value solid waste to high-protein feed."

[0074] Furthermore, the embodiments provided in this invention are for illustrative purposes only, and the excipients, strains, fermentation sequence, feed organisms, and separation methods therein can all be replaced by other feasible solutions. The alternative solutions are described in detail below: First, alternative materials: Corn stalk powder, crushed rice husks, and wheat bran in the auxiliary material reconstruction can be replaced or partially replaced by the following materials: corn cob powder, peanut shell powder, rice bran, wheat bran, sawdust, and other agricultural waste. The replacement principle is to use lignocellulosic materials with a high carbon-to-nitrogen ratio (>40) to improve the system's air permeability and adjust the carbon-to-nitrogen ratio, and to use fast-acting carbon sources to promote early microbial proliferation.

[0075] Second, alternative strains: Bacillus subtilis in the compound probiotic preparation can be replaced with... Bacillus licheniformis or Bacillus coagulans; Saccharomyces cerevisiae strain or Candida utilis can be substituted for Saccharomyces cerevisiae strain or Candida utilis; Lactobacillus plantarum can be substituted for Pediococcus pentosaceus or Enterococcus faecalis.

[0076] Third, alternative fermentation sequence: The inoculation sequence for the phased inoculation can be adjusted within the following range: lactic acid bacteria should be introduced within 12-36 hours after the initial inoculation (Bacillus subtilis + yeast), and the time for sealing and transferring to micro-anaerobic fermentation should be within 24-48 hours after the initial inoculation. The fermentation temperature can be adjusted within the range of 28-35℃, and the fermentation cycle can be adjusted within the range of 5-10 days.

[0077] Fourth, alternative feeding organisms: Replace black soldier flies with other saprophytic or filter-feeding economical feed organisms: yellow mealworm (Tenebrio molitor) larvae can be used to process fermentation products and obtain high-protein insect bodies; two-toothed sandworm (Perinereis aibuhitensis) can utilize fermentation products as feed in stratified symbiotic aquaculture systems and has irreplaceable live feed value in shrimp broodstock rearing.

[0078] Fifth, alternative separation methods: In addition to sieving or air separation, black soldier fly larvae can also be separated from insect sand by vibrating sieving, optical separation, or automatic separation by utilizing the larvae's self-crawling habits.

[0079] Those skilled in the art will understand that the above embodiments are specific examples of implementing the present invention, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of the present invention. Any person skilled in the art can make their own modifications and alterations without departing from the spirit and scope of the present invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for resource utilization of aquaculture wastewater filter residue through fermentation and insect conversion, characterized in that, The method includes: S1. Pre-treat the tailwater filter residue until the moisture content is reduced to below 70% to obtain pre-treated tailwater filter residue; The pretreated wastewater filter residue with a mass ratio of 313 parts was mixed with 187 parts of agricultural waste to obtain a mixture; wherein the carbon-nitrogen ratio of the agricultural waste was >40. S2. Prepare a compound probiotic agent, wherein the compound probiotic agent comprises highly enzyme-producing heterotrophic bacteria, highly efficient fermentation and transformation bacteria and antibacterial acidifying probiotics in a mass ratio of 1:1:

1. The mixture is subjected to staged sequential and directional fermentation using the compound probiotic agent, specifically including: at a fermentation temperature of 28~35℃, strong enzyme-producing heterotrophic bacteria and highly efficient fermentation-converting bacteria are introduced at fermentation time 0 hours for aerobic degradation; at fermentation time 12~36 hours, antibacterial acidifying probiotics are introduced to accumulate lactic acid; at fermentation time 24~48 hours, the mixture is sealed and transferred to micro-anaerobic fermentation to obtain the fermentation product; the total fermentation time is 5~10 days. S3. Using the fermentation product as a substrate, larvae of saprophytic or filter-feeding economic food organisms are raised. S4. Separate the obtained larvae from the insect sand. The larvae are used as a substitute protein source for fishmeal in aquatic compound feed, and the insect sand is used as a high-quality organic fertilizer for direct reuse in crop fertilization or soil improvement.

2. The method for resource utilization of aquaculture wastewater filter residue through fermentation and insect conversion according to claim 1, characterized in that, In S1, the pretreatment is plate and frame filter press or centrifugal dewatering; the agricultural waste includes one or more of corn stalk powder, crushed rice husks, wheat bran, corn cob powder, peanut shell powder, rice bran, wheat bran, and sawdust; preferably, the agricultural waste is composed of the following raw materials in parts by weight: 90 parts corn stalk powder, 65 parts crushed rice husks, and 32 parts wheat bran; the moisture content of the mixture is adjusted to 60%, and the carbon-nitrogen ratio is adjusted to 15-25.

3. The method for resource utilization of aquaculture wastewater filter residue through fermentation and insect conversion according to claim 1, characterized in that, In S2, the highly enzyme-producing heterotrophic bacteria include one or more of Bacillus subtilis, Bacillus licheniformis, or Bacillus coagulans. The highly efficient fermentation and conversion bacteria include one or more of Saccharomyces cerevisiae, Bacillus baker's yeast, or Candida utilis. The antibacterial acidifying probiotics include one or more of Lactobacillus plantarum, Pediococcus pentosaceus, or Enterococcus faecalis. Preferably, the compound probiotic agent is composed of Bacillus subtilis, Saccharomyces cerevisiae, and Lactobacillus plantarum, with each strain having a live count ≥10⁻⁶. 8 A mixture of CFU / g and a total addition amount of 0.3wt.%.

4. The method for resource utilization of aquaculture wastewater filter residue fermentation-insect conversion according to claim 1, characterized in that, In S2, the timing sequence of the phased sequential directional fermentation process is as follows: at 0 hours, highly enzyme-producing heterotrophic bacteria and efficient fermentation conversion bacteria are introduced for aerobic degradation; at 24 hours, antibacterial and acidifying probiotics are introduced; at 36 hours, the mixture is sealed and transferred to micro-anaerobic fermentation at a fermentation temperature of 30°C, with a total cycle of 5-7 days.

5. The method for resource utilization of aquaculture wastewater filter residue fermentation-insect conversion according to claim 1, characterized in that, In S2, the fermentation product has a crude protein dry basis content of ≥12% and a total viable count of ≥10. 9 CFU / g, pH≤5.5, Salmonella not detected, coliform bacteria <10 CFU / g, aflatoxin B1 <2 μg / kg.

6. The method for resource utilization of aquaculture wastewater filter residue through fermentation and insect conversion according to claim 1, characterized in that, In S3, the saprophytic or filter-feeding economic food organisms include one of the following: black soldier fly, yellow mealworm, or didentate sandworm; The feeding control parameters are as follows: temperature 27℃±2℃, relative humidity 60%~70%, and stocking density 1 animal / cm². 2 The substrate moisture content is 70%; the rearing cycle is 10-12 days, that is, the larvae are harvested before they enter the prepupal stage.

7. The method for resource utilization of aquaculture wastewater filter residue fermentation-insect conversion according to claim 1, characterized in that, The feeding conversion performance indicators are: wet substrate reduction rate ≥50%, fresh insect yield ≥15%, dry matter bioconversion rate ≥15%, and larval survival rate ≥90%.

8. The method for resource utilization of aquaculture wastewater filter residue through fermentation and insect conversion according to claim 1, characterized in that, In S4, the separation methods include: sieving, air separation, light separation, or automatic separation using the self-crawling habits of larvae; The larval meal contains 42%–45% crude protein and 31%–35% crude fat, making it suitable as a raw material for aquatic compound feed; the larval sand is rich in active nitrogen, phosphorus, potassium, and humus, making it suitable as organic fertilizer.

9. The method for resource utilization of aquaculture wastewater filter residue fermentation-insect conversion according to claim 1, characterized in that, S2 specifically includes: S2.1 Configuring compound probiotic inoculum: Configuring compound probiotic inoculum with Bacillus subtilis, Saccharomyces cerevisiae and Lactobacillus plantarum; S2.2 Implementation of T3 sequential inoculation directional fermentation process: At a fermentation temperature of 30℃, the total amount of inoculant added is 3 g / kg substrate; the specific sequence is as follows: Bacillus subtilis and Saccharomyces cerevisiae are inoculated at 0 hours of fermentation to carry out aerobic degradation and initiate the hydrolysis and preliminary transformation of organic matter; Lactobacillus plantarum is inoculated after 24 hours of fermentation to begin accumulating lactic acid and moderately reduce the pH of the system; after 36 hours of fermentation, the system is sealed and transferred to the micro-anaerobic fermentation stage; S2.3 The closed fermentation cycle is 5-7 days. During this process, Bacillus and Lactobacillus constitute the main dominant bacterial groups in the fermentation system, which have a synergistic effect on the transformation of organic matter in the effluent filter residue and the maintenance of the stability of the fermentation system. The final fermentation product has a crude protein content of more than 12% on a dry basis and a total viable count of 10. 9 CFU / g or higher, pH drops below 5.5; S2.4 During the fermentation process, Lactobacillus plantarum accumulates a large amount of lactic acid in the middle and late stages of fermentation, causing the pH value to drop from 6.45 on the second day to 5.46 on the fifth day, thus constructing an acidic antibacterial barrier, effectively inhibiting the metabolism of miscellaneous bacteria and reducing the loss of nitrogen through ammoniation and volatilization; Salmonella was not detected in the final fermentation product, the number of coliform bacteria was less than 10 CFU / g, and the content of aflatoxin B1 was less than 2 μg / kg.

10. The application of the method for resource utilization of aquaculture wastewater filter residue fermentation-insect conversion according to any one of claims 1 to 9 in the field of resource utilization treatment of freshwater aquaculture wastewater filter residue with salinity ≤30‰ and seawater aquaculture wastewater filter residue.

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