A method for synergizing phytoremediation with resource utilization of black soldier fly conversion

Abstract

The application provides a method for synergistically repairing water body with aquatic plants and converting with black soldier fly, comprising the following steps: 1) harvesting the aquatic plants of yellow flower water dragon which have completed water body repair, fishing them out of the water body, crushing them to a suitable size, and uniformly spreading them on a collection film; 2) uniformly spraying the crushed aquatic plants with a bacterial solution for pre-fermentation to improve the palatability of black soldier fly larvae to the crushed aquatic plants; 3) after the pre-fermentation process is completed, black soldier fly larvae of 3-5 days old are put in, and after the larvae grow by feeding for 2-3 weeks, the larvae are collected; and 4) using a separation device to separate black soldier fly fresh larvae and a mixture of feces. The application innovatively combines water purification and waste resource utilization, first purifies and repairs the water body with the help of aquatic plants, and then uses black soldier fly larvae to efficiently convert the biomass which has completed water body repair, thereby constructing a transfer cycle of water body nutrients from the water environment to black soldier fly protein.

Description

Technical Field

[0001] This invention relates to the field of water pollution control technology, and in particular to a resource utilization method that synergistically combines aquatic plant remediation with black soldier fly transformation. Background Technology

[0002] In recent years, the use of aquatic plants for water quality ecological restoration has attracted attention. Aquatic plants can remove nitrogen, phosphorus, and organic pollutants from water through absorption and assimilation, while their roots and epiphytic microorganisms jointly promote pollutant degradation. For example, Chinese invention patent application CN120864693A discloses a device and method for highly efficient water purification based on aquatic plants. This device dynamically adjusts the root immersion depth according to the water level changes of different aquatic plant species, such as emergent or submerged plants, ensuring that the plant roots fully contact the polluted water to efficiently absorb pollutants such as nitrogen and phosphorus. It also avoids submerging the plants due to excessively high water levels or dehydrating the roots due to excessively low water levels, thus significantly improving purification efficiency. However, there are still shortcomings in using such devices to purify water. For example, if aquatic plants are not harvested in time, their death and decay can release the absorbed pollutants, causing secondary pollution. Even after harvesting, the biomass of these plants that have completed water restoration is still considered pollutant waste. Traditional disposal methods such as composting or incineration not only increase costs but may also lead to the waste of nutrients and organic matter.

[0003] In summary, existing aquatic plant water purification technologies still have problems such as imperfect treatment methods, low resource utilization rate, and easy formation of secondary pollution. Related technical solutions need to be further improved and perfected. Summary of the Invention

[0004] The purpose of this invention is to address the deficiencies and shortcomings of the prior art by providing a resource utilization method that combines synergistic aquatic plant remediation with black soldier fly transformation.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a resource utilization method for synergistic aquatic plant remediation and black soldier fly transformation, comprising the following steps: 1) Harvest the aquatic plants that have completed water body restoration, crush them to a suitable size, and spread them evenly on the collection membrane. The aquatic plants mentioned here are enriched with nitrogen and phosphorus and adsorbed with organic pollutants. They are typical pollutant-enriched biomass raw materials. In addition, in order to reduce transportation costs and improve operational efficiency, the collection membrane is preferably laid in an open area around the eutrophic water body. The collection membrane can effectively avoid direct contact between aquatic plants and soil, thereby preventing the generation of secondary pollution. 2) Spray the crushed aquatic plants evenly with bacterial solution for pre-fermentation to improve the palatability of the feed for black soldier fly larvae. The specific bacterial solution can be selected from one or more of Bacillus, Lactobacillus, yeast, etc., depending on the type of aquatic plant. 3) After the pre-fermentation process is completed, release 3-5 day old black soldier fly larvae. After 2-3 weeks of feeding and growth, stop feeding before they enter the black soldier fly pupal stage. The reason for using 3-5 day old black soldier fly larvae is that the larvae have a strong feeding ability at this stage. In addition, the release density of black soldier fly larvae depends on the amount of aquatic plants. It is best if they can consume all the aquatic plants within the predetermined time (i.e., within 2-3 weeks). 4) Use a separation device to collect the mixture of fresh black soldier fly larvae and their excrement.

[0006] Fresh black soldier fly larvae are collected by screening using a separation device. The collected larvae can be used as high-quality protein feed. The frass left behind by the black soldier fly larvae after feeding, along with incompletely decomposed plant residues, are collected together as a frass mixture and used as organic fertilizer.

[0007] According to the above scheme, nitrogen-rich auxiliary materials can be selectively added to the aquatic plants in step 1). Specifically, the nitrogen-rich auxiliary materials can be protein grass, lake bottom sludge, or others.

[0008] According to the above scheme, the aquatic plants include one or more of the following: water hyacinth, water hyacinth, foxtail grass, hydrangea, or eelgrass.

[0009] According to the above plan, the aquatic plant selected is *Dracaena fragrans*, and the nitrogen-rich supplementary material is *Hygrophorus purpureus*, with a weight ratio of 1:1 between *Dracaena fragrans* and *Hygrophorus purpureus*. Specifically considering the growth and development needs of black soldier fly larvae, especially the nitrogen source required for protein synthesis, single-feeding can easily lead to nutritional imbalance and prolonged growth cycle in the larvae. *Hygrophorus purpureus* is a high-nitrogen biomass raw material with a crude protein content of 30%–48.7%, containing 18 kinds of amino acids, and its nitrogen exists in an organic form, making it easily digestible and absorbable by black soldier flies. The combined use of these two materials optimizes nitrogen supply, enhances the metabolic activity and growth performance of black soldier fly larvae, and achieves synergistic effects.

[0010] According to the above scheme, the bacterial solution is Bacillus subtilis solution, which can effectively improve the feeding efficiency and growth performance of black soldier fly larvae, while its strong environmental adaptability ensures stability in complex aquatic plant substrates.

[0011] According to the above scheme, the bacterial count of the Bacillus subtilis liquid is 5 billion / gram. 50 mL of Bacillus subtilis liquid is sprayed per kilogram of aquatic plants, and fermentation is carried out for 1 to 2 days at a natural temperature of 15 to 35°C.

[0012] According to the above plan, in step 3), the release density of black soldier fly larvae in 3-5 days is 1-3 grams per kilogram of wet aquatic plants.

[0013] According to the above scheme, the collection membrane is made of PE or PP material.

[0014] According to the above scheme, the collecting membrane is supported by pillars on all four sides, forming a box structure with an opening at the top. The interior of the box structure is a black soldier fly breeding area, within which several inflatable blocks are arranged in parallel. The height of the inflatable blocks is less than the height of the box structure. A drain outlet is provided on the box structure. Preferably, the collecting membrane forms a box structure 1.1m long, 1m wide, and 10cm high. Two layers of filter screens are installed at the drain outlet, with pore sizes of 0.5mm and 0.1mm respectively. In actual use, the thickness of the aquatic plants is approximately 2-5cm. Black soldier flies thrive in humid environments but are sensitive to waterlogged conditions. The above structural design maintains a moist environment for the black soldier fly breeding area. During the feeding and growth process, the inflatable blocks provide a supporting surface for the flies to rest on. Simultaneously, excess water in the breeding area flows along the inflatable blocks to the drain outlet and is discharged, effectively avoiding waterlogging.

[0015] According to the above scheme, the separation device in step 4) of this method is a screening device.

[0016] According to the above scheme, the screening device includes a screening trough and an insect receiving trough arranged vertically and vertically. The bottom of the screening trough is provided with a first screen to allow the insects to crawl downwards through the sieve holes. The bottom of the insect receiving trough is provided with a second screen, and the aperture of the second screen is smaller than that of the first screen. Depending on the size and morphology of the black soldier fly larvae at different stages of life, the first screen is preferably 10 mesh (2 mm aperture) to ensure that the fresh black soldier fly larvae, after 2-3 weeks of feeding, crawl through the sieve holes into the insect receiving trough. Specifically, black soldier flies are photophobic and heat-averse; direct sunlight or the temperature rise from indoor photothermal devices promotes downward crawling, and combined with odor induction, this improves separation efficiency. The second screen is preferably 60 mesh (0.28 mm aperture), which prevents the fresh black soldier fly larvae from crawling out while also allowing for air permeability and control of material moisture content.

[0017] The beneficial effects of this invention are: This invention innovatively integrates water purification and waste resource utilization: first, aquatic plants are used to purify the water, and then black soldier fly larvae are used to efficiently degrade and transform the biomass that has completed water body restoration, thus constructing a transfer cycle of water nutrients from the aquatic environment to black soldier fly protein.

[0018] Compared with existing technologies, the present invention has the following significant advantages: The water quality treatment has yielded remarkable results: aquatic plants remove eutrophic substances such as nitrogen and phosphorus, which can significantly improve water quality.

[0019] Resource recycling and efficient utilization: The harvested biomass from the completed water body restoration is not discarded, but is transformed into high-protein insect resources and organic fertilizer by black soldier flies, realizing the transformation of "waste" into "resource" and building an ecological cycle chain of "water nutrients ~ aquatic plants ~ insect protein".

[0020] Completely avoid secondary pollution: Aquatic plants enter the biological transformation process immediately after harvesting, avoiding their decomposition and pollution of the environment; the black soldier fly treatment process is closed and controllable, the output is stable and harmless, and no secondary wastewater or toxic byproducts are generated, which greatly reduces greenhouse gas emissions compared to direct landfill composting.

[0021] Low cost and considerable additional benefits: This invention relies on natural biological processes, requires no chemical additives, and has low energy consumption. The protein feed and excrement produced by black soldier fly farming can be sold to generate economic benefits, partially offsetting the treatment costs and forming a virtuous cycle of "using waste to treat diseases".

[0022] The implementation and promotion are convenient and easy: aquatic plants are easy to reproduce and grow rapidly, black soldier fly farming technology is mature, the whole method has low requirements for site and equipment, and can be widely used in various scenarios such as rural breeding areas, municipal sewage ponds, and agricultural non-point source pollution water bodies. It has broad prospects for promotion and significant ecological benefits.

[0023] This invention innovatively combines aquatic ecological restoration with insect-borne biotransformation technology, effectively solving the challenge of linking water pollution control with waste utilization. Through this technology, eutrophic pollutants in water bodies that would otherwise cause an ecological crisis are transformed into high-value biological proteins and organic fertilizers, achieving a transformation from pollution to resources. Attached Figure Description

[0024] Figure 1 This is a simplified flowchart of the present invention; Figure 2 This is a simplified structural diagram of the collection membrane described in this invention. Figure 3 This is a simplified schematic diagram of the screening device described in this invention.

[0025] In the picture: 1. Black soldier fly breeding area; 2. Inflatable strips; 3. Drainage outlet; 4. Screening tank; 5. First screen; 6. Insect collection tank; 7. Second screen. Detailed Implementation

[0026] The technical solution of the present invention will be further described below through specific embodiments and comparative examples.

[0027] In this embodiment, the collection membrane is supported by pillars on all four sides, forming a box structure with an open top, measuring 1.1m long, 1m wide, and 10cm high. The interior of the box structure is a black soldier fly breeding area, in which several inflatable blocks are arranged in parallel. The height of the inflatable blocks is less than the height of the box structure. A drain outlet is provided on the box structure, and two layers of filter screens are installed at the drain outlet. The pore sizes of the two filter screens are 0.5mm and 0.1mm, respectively. In actual use, the thickness of the aquatic plants is approximately 2-5cm.

[0028] The sieving device in this embodiment is provided with a sieving trough and an insect receiving trough that are distributed vertically and vertically. A first 10-mesh (2mm aperture) screen is fixedly provided at the bottom of the sieving trough, and a second 60-mesh (0.28mm aperture) screen is fixedly provided at the bottom of the insect receiving trough.

[0029] Example 1: Yellow Water Dragon was selected as the aquatic plant. A resource utilization method for synergistic aquatic plant remediation and black soldier fly transformation is implemented according to the following steps: Step 1: Harvest yellow water dragons weighing 10kg fresh from the pond after water body restoration has been completed. Chop them up mechanically and spread them evenly on the impermeable collection membrane that has been placed in advance near the pond in the natural environment.

[0030] Step 2: Spray 0.5L of Bacillus subtilis solution with a content of 5 billion CFU / g for pre-fermentation for 2 days to improve larval feeding efficiency and substrate palatability.

[0031] Step 3: Place approximately 20g of 5-day-old black soldier fly larvae onto the pre-fermented yellow water dragon from Step 2). Initially, each individual larvae weighed 1.0±0.2mg, had a body length of 1.5±0.5mm, and a body width of 0.7±0.2mm. After 21 days of growth, the final state of the black soldier fly larvae is a fresh weight of 64±5mg, a body length of 17±3mm, and a body width of 1.8±0.5mm.

[0032] Step 4: The mixture of black soldier fly larvae and frass is collected manually, and the larvae and frass are separated using a sieving device. Finally, about 614g of fresh insects are harvested.

[0033] The frass left behind by black soldier fly larvae after feeding, along with incompletely decomposed plant residues, are collected together to yield approximately 2.6 kg of frass fertilizer.

[0034] Example 2: Aquatic plants selected include water hyacinth / myriophyllum / hydrilla / valley grass A resource utilization method for synergistic aquatic plant remediation and black soldier fly transformation is implemented according to the following steps: Steps 1 and 2 are the same as steps 1 and 2 in Example 1.

[0035] Step 3: Approximately 20g of 5-day-old black soldier fly larvae were released onto the pre-fermented aquatic plants from Step 2. Initially, each larva weighed 1.0±0.2mg, had a body length of 1.5±0.5mm, and a body width of 0.7±0.2mm. After 28 days of growth, only a small portion of the black soldier fly larvae from the water hyacinth, foxtail, and Vallisneria groups survived. Their final state was a fresh weight of 3±1mg, a body length of 3±1mm, and a body width of 1±0.5mm per larva, showing little increase in fresh weight, with only a small number of larvae showing relatively significant growth. The final state of the Hydrilla verticillata group was a fresh weight of 24±12mg, a body length of 10±5mm, and a body width of 1.2±0.6mm per larva, but again, only a small number of larvae showed relatively significant growth.

[0036] Step 4: First, the mixture of black soldier fly larvae and frass is collected manually. Then, a sieving device is used to separate the larvae from the frass. The water hyacinth group, foxtail algae group, hydrangea group, and valerian group finally yielded approximately 4g, 17g, 149g, and 79g of fresh insects, respectively.

[0037] Compared with Implementation 1, water hyacinth / myriophyllum / hydrilla / valley grass performed significantly worse in terms of adapting biomass characteristics to black soldier fly feeding and utilization, which not only made the growth cycle of black soldier fly larvae longer, but also significantly reduced the survival rate of black soldier fly larvae.

[0038] Example 3: Yellow Water Dragon + Protein Grass Step 1: Mix yellow water dragon and protein grass in three different weight ratios of "1:3, 1:1, 3:1" (the mixed substrate is 10kg), and label them as experimental groups AM1, AM2 and AM3. After mechanical chopping, spread them evenly on the anti-permeability collection membrane in the natural environment.

[0039] Step 2 is the same as step 2 in Example 1.

[0040] In step 3, approximately 20g of 5-day-old black soldier fly larvae were introduced into each experimental group that had completed pre-fermentation in step 2). Their initial size was 1.0±0.2mg body weight, 1.5±0.5mm body length, and 0.7±0.2mm body width per larva. After 21 days of growth, the black soldier fly larvae in each experimental group showed the following growth patterns: Group AM1 had a final individual fresh weight of 65±8mg, a body length of 19±4mm, and a body width of 1.9±0.6mm; Group AM2 had a final individual fresh weight of 76±3mg, a body length of 20±6mm, and a body width of 1.9±0.6mm; and Group AM3 had a final individual fresh weight of 72±3mg, a body length of 19±4mm, and a body width of 1.9±0.6mm.

[0041] Step 4: The mixture of black soldier fly larvae and frass from each experimental group was manually collected, and the larvae and frass were separated using a sieving device. Finally, experimental groups AM1, AM2, and AM3 yielded approximately 780g, 816g, and 792g of fresh larvae, and 2.4, 2.4, and 2.6 kg of frass, respectively.

[0042] Compared to the single *Hemiberlesia argyi* species in Example 1, the combination of *Hemiberlesia argyi* and *Polygonum multiflorum* in Example 3 not only resulted in larger and heavier black soldier fly larvae, but also improved their palatability and survival rate. Furthermore, by mixing *Hemiberlesia argyi* and *Polygonum multiflorum* in three different weight ratios (1:3, 1:1, and 3:1), the optimal ratio was found to be 1:1.

[0043] The above description is only a preferred embodiment of the present invention. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the claims of this patent application are included in the scope of this patent application.

Claims

1. A method for the resource utilization of synergistic aquatic plant remediation and black soldier fly transformation, characterized in that, Includes the following steps: 1) Harvest the aquatic plants that have completed water body restoration, crush them to a suitable size, and spread them evenly on the collection membrane; 2) Spray the crushed aquatic plants evenly with bacterial solution for pre-fermentation to improve the palatability of the food for black soldier fly larvae. 3) After the pre-fermentation process is completed, release 3-5 day old black soldier fly larvae and collect them after they have fed and grown for 2-3 weeks; 4) A mixture of fresh black soldier fly larvae and their excrement was obtained by using a separation device.

2. The resource utilization method for synergistic aquatic plant remediation and black soldier fly transformation according to claim 1, characterized in that, Add nitrogen-rich supplements to the aquatic plants in step 1).

3. The resource utilization method for synergistic aquatic plant remediation and black soldier fly transformation according to claim 2, characterized in that, The aquatic plants include one or more of the following: water hyacinth, water hyacinth, foxtail algae, hydrangea, or eelgrass.

4. The resource utilization method for synergistic aquatic plant remediation and black soldier fly transformation according to claim 3, characterized in that, The aquatic plant is selected as *Dichroa febrifuga*, and the nitrogen-rich auxiliary material is selected as *Hymenochloa chinensis*. The weight ratio of *Dichroa febrifuga* to *Hymenochloa chinensis* is 1:

1.

5. The resource utilization method for synergistic aquatic plant remediation and black soldier fly transformation according to claim 1, characterized in that, The bacterial solution is Bacillus subtilis solution.

6. The resource utilization method for synergistic aquatic plant remediation and black soldier fly transformation according to claim 5, characterized in that, The Bacillus subtilis liquid contains 5 billion bacteria per gram. 50 mL of Bacillus subtilis liquid is sprayed per kilogram of aquatic plants, and fermented for 1 to 2 days at a natural temperature of 15–35°C.

7. The resource utilization method for synergistic aquatic plant remediation and black soldier fly transformation according to claim 1, characterized in that, In step 3), the release density of black soldier fly larvae in 3-5 days is 1-3 grams per kilogram of wet aquatic plants.

8. The resource utilization method for synergistic aquatic plant remediation and black soldier fly transformation according to claim 1, characterized in that, The collection membrane is made of PE or PP material.

9. The resource utilization method for synergistic aquatic plant remediation and black soldier fly transformation according to claim 8, characterized in that, The collection membrane is supported by pillars on all four sides, forming a box structure with an opening at the top. The interior of the box structure is a black soldier fly breeding area, in which several inflatable blocks are arranged in parallel. The height of the inflatable blocks is less than the height of the box structure. The box structure is provided with a drain outlet.

10. The resource utilization method for synergistic aquatic plant remediation and black soldier fly transformation according to claim 1, characterized in that, The separation device in step 4) is a sieving device, which includes a sieving trough and an insect-collecting trough arranged vertically and vertically. The bottom of the sieving trough is provided with a first screen so that the insects can crawl down through the sieve holes. The bottom of the insect-collecting trough is provided with a second screen, and the aperture of the second screen is smaller than that of the first screen.

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