Photovoltaic fish and vegetable symbiotic system

Abstract

The invention relates to the field of fish and vegetable comprehensive cultivation, in particular to a photovoltaic fish and vegetable symbiotic system which comprises a photovoltaic system, a fishery breeding system and a circulating purification system, a fishpond is arranged below a photovoltaic panel, net cages are arranged in the fishpond for fish breeding, the circulating purification system is arranged around the fishpond, and water is pumped in the fishpond through a pump station; water quality purification and water quality maintenance are carried out on the pumped water through a precipitation filtration system, a microfilter, a hydroponic vegetable system and an ultraviolet disinfection system in sequence, so that the water body in the pond is ensured to fully and circularly flow, and the concentration of chemical substances such as ammonia nitrogen, nitrite nitrogen and the like which are harmful to fishes is reduced. Through the synergistic effect of all parts of the photovoltaic fish and vegetable symbiotic system, the problem that the water quality in the aquaculture environment under the photovoltaic panel is prone to deterioration is effectively solved, and the aquaculture benefits are improved.

Description

Technical Field

[0001] The present invention relates to the field of integrated fish-vegetable cultivation, and in particular to a photovoltaic fish-vegetable symbiotic system. Background Art

[0002] Agriculture / fishery photovoltaic complementarity is a new business model that couples agriculture / fishery (aquaculture) with photovoltaic power generation. This model not only fully utilizes solar thermal resources for power generation and provides clean energy to society, but also effectively integrates the growth requirements and physiological habits of crops and suitable fish species, scientifically allocates solar thermal resources, and improves land use efficiency. This, in turn, leads to bumper harvests in agriculture / fishery (aquaculture) and increased income for farmers, providing a sustainable development path for the coordinated development of the photovoltaic industry, crop production, and fishery.

[0003] However, in actual application scenarios, many agriculture-fishery-photovoltaic complementary projects prioritized photovoltaic energy efficiency at the beginning of their construction, ignoring the systematic consideration of agricultural and fishery production needs. Some projects did not even consider the patterns of crop light and heat demand during the design phase, and only used photovoltaic income to cover agricultural income, making it difficult to truly achieve agriculture / fishery-photovoltaic complementarity, resulting in serious waste of a large amount of resources such as land and light.

[0004] Therefore, it is urgent to study and construct suitable crops and their supporting simplified planting production technology system that match the climatic factors such as light, temperature, and humidity under photovoltaic arrays, explore and construct a new model of efficient and comprehensive utilization of land resources that is suitable for fish pond farming + ecological breeding and farming coupled under photovoltaic arrays, optimize the "fish-light-planting" coordinated configuration, ensure the benefits of photovoltaic power generation, and enhance the added value of agricultural / fishery production, thereby opening up new ways for fishery farmers to increase income and efficiency and promote agricultural development. Summary of the Invention

[0005] The present invention provides a photovoltaic fish-vegetable symbiotic system. By organically combining floating aquaculture cages, floating ecological cages, a pond-bottom MABR (membrane aerated bioreactor), and a pond bank ecological circulation filtration system with a vegetable-growing circulating water system, this system truly achieves the complementary benefits of agriculture, fishery, and solar energy, providing a new model for the efficient and comprehensive utilization of land resources. To achieve the above objectives, the present invention employs the following technical solutions:

[0006] A photovoltaic fish-vegetable symbiotic system includes a photovoltaic system, a fish farming system, and a circulation purification system. The specific structure is as follows:

[0007] A. Photovoltaic system:

[0008] Photovoltaic panels are set above the water surface to provide shade during the aquaculture period;

[0009] B. Fishery farming system:

[0010] The fish pond is located below the photovoltaic panels, with a membrane aeration biofilm reactor purification system laid on the pond bottom and cages set up inside the fish pond;

[0011] C.Circulation purification system

[0012] A circulating purification system is set up around the fish pond: water is pumped out of the fish pond through a pumping station, and the pumped water is purified and maintained through sedimentation filtration, microfiltration machine, hydroponic vegetable system and ultraviolet disinfection system in sequence.

[0013] Furthermore, in step A, the photovoltaic panel is 2-2.5m above the water surface with a slope of 13°, and 30-85% shade is maintained during the breeding period; in step B, the fish pond is 2.4m deep, a membrane aeration biofilm reactor purification system is laid on the pond bottom, and cages are set up in the fish pond. The cages are 4m long and 4m wide, with a net depth of 1.5m. 20-24 cages are set up per acre, and the cages are arranged in rows with a row spacing of 2m; the membrane components of the membrane aeration biofilm reactor purification system are spaced 0.4m apart, covering 25% of the bottom area of ​​the fish pond; the cages are floating cages, one part of which is used for breeding fish, and the other part is not used for breeding fish and aquatic plants; the ratio of ecological cages to breeding cages is 1:6-7; in step C, the hydroponic vegetable system is a pipeline hydroponic vegetable system or a hydroponic box; there are no photovoltaic panels in the hydroponic vegetable area.

[0014] Furthermore, in the step C, a certain amount of water is extracted from a corner of the test pond by a pump station for circulation purification, and the amount of water circulated and purified every day is 1 / 10-1 / 5 of the water in the fish pond.

[0015] Furthermore, the purified pond water in the circulation purification system is transported by pipeline to other locations in the fish pond except the pumping station for oxygenation and discharge, thereby achieving effective circulation of the water in the pond.

[0016] A photovoltaic fish-vegetable symbiotic farming method comprises the following steps:

[0017] (1) Using the photovoltaic fish-vegetable symbiotic system of any one of claims 1 to 5, before the fry are released, water is stored in the fish pond and the circulating purification system therein is activated to purify the water quality;

[0018] (2) After the fry are released, the circulating purification system is continued to be turned on to purify the water quality to ensure that the dissolved oxygen content in the water meets the breeding requirements and the water purification load meets the amount of pollutants removed by regular feeding.

[0019] Furthermore, in the step (1), the water purification treatment is continued for at least 3 days to make the water quality meet the aquaculture standard: dissolved oxygen>5mg / L, ammonia nitrogen<0.2mg / L, nitrite nitrogen<0.1mg / L, pH value 7.0-8.0.

[0020] Furthermore, the fry are channel catfish fry, grass carp fry and / or California sea bass fry; and the stocking density is 120 fry per cubic meter of water.

[0021] Furthermore, the vegetable varieties grown in the hydroponic vegetable system are water spinach, lettuce, spinach, celery, Chinese cabbage and / or cilantro, which are suitable for hydroponics.

[0022] Furthermore, the operating parameters of the circulating purification system were adjusted to operate for 8 hours per day, divided into two periods of 4 hours in the morning and 4 hours in the afternoon, with the flow rate controlled at 0.4m / s; the aeration volume of the MABR purification system was adjusted to 0.3m 3 / h·m 2 , ensure that the dissolved oxygen content in the water is stable at above 5mg / L.

[0023] Furthermore, the amount and frequency of feed feeding were adjusted according to the growth of the fish and the water quality. The fish were fed 2-3 times a day, with each feeding amount being 2-3% of the fish body weight.

[0024] The beneficial effects of the present invention are as follows:

[0025] The photovoltaic fish-vegetable symbiotic system described in the present invention, by laying a MABR system at the bottom of the aquaculture pond and combining it with a circulating purification system, has significantly higher dissolved oxygen levels in the test pond than in the control pond, which is beneficial to the growth and development of fish. The ammonia nitrogen and nitrite levels in the test pond are significantly lower than those in the control pond, and the salt content in the test pond is basically maintained below 0.02 mg / L, reducing the risk of fish poisoning. The water quality purification speed of the test pond is faster than that of the control pond, which can effectively degrade dissolved organic matter in the water. Compared with the control group, the weight gain of the channel catfish in the test group increased by more than 10%, the specific growth rate increased significantly (P < 0.05), and the feed coefficient showed a significant downward trend. Vegetables such as lettuce and celery in the hydroponic vegetable system all grew vigorously, achieving fish-vegetable symbiosis. Through the synergistic effect of the photovoltaic fish-vegetable symbiotic system, the present invention effectively solves the problem of easily deteriorating water quality in the aquaculture environment under photovoltaic panels and improves aquaculture efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is the layout diagram of the photovoltaic fish-vegetable symbiotic system in embodiment 1 of the invention.

[0028] Figure 2These are the graphs showing changes in some water quality parameters during the three stages of Example 2 of the invention: A: pH value change graph; B: ammonia nitrogen change graph; C: nitrite change graph; D: total phosphorus change graph.

[0029] Figure 3 This is the on-site installation diagram of the pond bottom MABR system in Example 2 of the invention (during construction).

[0030] Figure 4 This is a picture of vegetables hydroponically grown in a circulating water pipeline in the second embodiment of the invention (left: lettuce; right: celery). DETAILED DESCRIPTION

[0031] The technical solutions of the present invention will be described clearly and completely below with reference to the accompanying drawings and embodiments. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0032] Example 1

[0033] A photovoltaic fish-vegetable symbiotic system comprises a photovoltaic system, a fishery breeding system and a circulation purification system.

[0034] The photovoltaic system consists of multiple panels installed at a height of 3 meters and a 13° slope. The panels are arranged to provide 30% to 85% shade to the area below during cultivation. The panels are secured around and above the fish ponds using brackets made of hot-dip galvanized steel, which offers excellent corrosion resistance and structural stability. The panels are arranged in an east-west pattern, with rows spaced 6 meters apart to ensure even sunlight distribution. The system also includes an inverter, distribution box, and monitoring system to convert the direct current (DC) electricity generated by the panels into alternating current (AC) for transmission to the grid or for the system's own power consumption.

[0035] The fish farming system, located beneath the photovoltaic panels, includes fish ponds and cages. The pond is 2.4 meters deep, and a MABR (membrane aerated biofilm reactor) purification system is installed at the bottom. The MABR purification system consists of multiple membrane modules, each of which includes a hollow fiber membrane, an aeration device, and a support frame. Air is introduced into the hollow fiber membranes, and oxygen diffuses through the membranes into the water, forming a biofilm on the membrane surface that degrades harmful substances such as organic matter and ammonia nitrogen in the water. The MABR system's membrane modules are spaced 0.4 meters apart, covering 25% of the pond's bottom area.

[0036] Fish ponds are equipped with cages, measuring 4 meters long, 4 meters wide, and 1.8 meters high. Twenty cages are installed per acre, spaced 2 meters apart. They are either floating aquaculture cages or floating ecological cages. The nets are woven from polyethylene, with a mesh size of 1.5 cm x 1.5 cm and a depth of 1.5 meters.

[0037] A circulating purification system is installed around the fish pond (there are no photovoltaic panels above the hydroponic vegetable area). It includes a pump station, sedimentation and filtration device, microfiltration unit, hydroponic vegetable system, and UV disinfection system. The pump station, located in a corner of the pond, uses a 3kW variable frequency pump with a flow rate of 50m³ / h. The pump station draws water from the pond through an inlet pipe, circulating and purifying approximately one-fifth of the pond's total water volume daily. The circulation period is 12 hours per day, with a flow rate of 0.5m / s.

[0038] The pumped water first enters a vertical flow settler for sedimentation and filtration. The vertical flow settler is 1.5 meters high and 1.5 meters in diameter, and is equipped with multiple layers of sedimentation plates, spaced 30 centimeters apart and inclined at a 45° angle. Sedimentation and filtration primarily remove large suspended solids and some organic matter from the water.

[0039] After sedimentation and filtration, the water enters a microfiltration machine for rotary microfiltration. The microfiltration machine uses a rotating filter cartridge structure with a diameter of 0.6 meters and a length of 1 meter, and a filter mesh size of 60 microns. The microfiltration machine uses the rotating filter cartridge to filter out fine particles and suspended solids in the water, further improving the water purification effect.

[0040] The treated water flows through a pipeline hydroponic vegetable system, which consists of multiple PVC pipes with a diameter of 200 mm and a length of 10 meters. Planting holes with a diameter of 5 cm are drilled every 30 cm. These holes are filled with planting baskets filled with substrate for growing a variety of leafy and herbaceous vegetables. This hydroponic vegetable system utilizes plant absorption to further remove nutrients such as nitrogen and phosphorus from the water, reducing the levels of harmful substances such as ammonia nitrogen and nitrite nitrogen. The hydroponic vegetable system is divided into multiple planting areas, allowing the cultivation of different vegetable varieties, such as lettuce, spinach, celery, bok choy, and cilantro, according to seasonal and market demand. The pipeline hydroponic vegetable system can also be used in hydroponic boxes to facilitate the cultivation of different vegetable varieties.

[0041] Finally, in order to ensure the safety of water quality, an ultraviolet disinfection system can be added to sterilize the water. The ultraviolet disinfection system uses a medium-pressure ultraviolet lamp with a power of 240W, a wavelength of 254nm, and an irradiation intensity of 30mW / cm 2 The irradiation time is 6-8 seconds. The UV disinfection system can effectively kill bacteria, viruses and other microorganisms in water.

[0042] The purified water is piped to other locations in the pond for aeration and discharge. The outlet is located far from the water inlet to ensure effective circulation of the pond water. The outlets are distributed at multiple points, each with a diameter of 50 mm and a spacing of 5 meters. An aeration device is installed below the outlets, using microporous aeration discs with a pore size of 0.5 mm and an aeration rate of 0.5 m³ / h·m². The purified water is circulated back to the pond by natural fall, achieving the purpose of aeration.

[0043] The entire photovoltaic fish-vegetable symbiotic system (such as Figure 1 The system (shown in Figure 1) is managed through an intelligent control system, including water quality monitoring, equipment control, and data logging. The water quality monitoring system monitors water temperature, pH, dissolved oxygen, ammonia nitrogen, nitrite nitrogen, and other parameters in real time. When these parameters exceed the set range, the system automatically adjusts the operating parameters of the circulation purification system to ensure stable water quality. The equipment control system adjusts the operating status of the photovoltaic system, MABR system, and circulation purification system based on light intensity, water quality, and aquaculture needs, ensuring efficient system operation. The data logging system records various system operating parameters and data, providing a basis for system optimization and management.

[0044] Example 2

[0045] A photovoltaic fish-vegetable symbiotic farming method comprises the following steps:

[0046] Using the photovoltaic fish-vegetable symbiotic system in Example 1, before the fry are released, water is first stored in the fish pond, the water depth is controlled at 2.2 meters, the water temperature is maintained at 22-25°C, and the pH value is controlled between 7.0-8.0. After the water storage is completed, the circulating purification system is turned on to purify the water quality. The circulating purification system runs for 12 hours a day, divided into two periods of 6 hours in the morning and 6 hours in the afternoon, and the flow rate is controlled at 0.5m / s. At the same time, the MABR purification system is turned on, and the aeration volume is controlled at 0.5m 3 / h·m 2 , ensuring that the dissolved oxygen content in the water reaches above 5mg / L. Water purification treatment lasts for at least 3 days to ensure that the water quality meets the aquaculture standards: dissolved oxygen>5mg / L, ammonia nitrogen<0.2mg / L, nitrite nitrogen<0.1mg / L, pH value 7.0-8.0.

[0047] Once the water quality meets the standards, fish fry are released. The appropriate size of the fry is selected based on the species, with a stocking density of 120 per cubic meter of water. During stocking, the water temperature is maintained to avoid large temperature fluctuations that could cause stress and death in the fry. After the fry are released, the circulating purification system continues to purify the water. The system's operating parameters are adjusted to run for 8 hours per day, divided into two periods: 4 hours in the morning and 4 hours in the afternoon, with a flow rate controlled at 0.4 m / s. The MABR purification system's aeration rate is adjusted to 0.3 m³ / h·m² to ensure a stable dissolved oxygen content above 5 mg / L.

[0048] During the growth of the fry, regularly monitor water quality parameters, including temperature, pH, dissolved oxygen, ammonia nitrogen, and nitrite nitrogen. If water quality parameters become abnormal, promptly adjust the operating parameters of the circulation purification system, increasing the run time or increasing the flow rate to ensure stable water quality. At the same time, adjust the feed amount and frequency appropriately based on the fish's growth and water quality. Generally, feed 2-3 times daily, with each feeding amount representing 2-3% of the fish's body weight.

[0049] In a hydroponic vegetable system, different vegetable varieties are grown according to seasonal and market demand. Before planting, vegetable seeds are grown in seedling trays. Once the seedlings have grown 2-3 true leaves, they are transplanted into the planting holes of the hydroponic pipes. Planting density is determined by the variety, typically 1-2 plants per hole. During the vegetable growth process, regular checks are performed on the plants, mature vegetables are harvested promptly, and new seedlings are planted to maintain continuous system operation.

[0050] Throughout the entire breeding process, an intelligent control system monitors system status in real time, recording data such as water quality parameters, fish growth, and vegetable yields, providing a basis for system optimization and management. The breeding cycle varies depending on the fish species and generally lasts three to six months. After the breeding cycle is completed, the system is cleaned and disinfected to prepare for the next round of breeding.

[0051] 1. Investigation of the effects of photovoltaic fish-vegetable symbiotic system on the breeding of different fish species

[0052] Channel catfish were cultured using the method described in Example 2, and lettuce was grown in a pipeline hydroponic vegetable system. Control group 1, a fish pond near the experimental pond (photovoltaic fish-vegetable symbiotic system), did not have a bottom MABR aeration system. Control group 2, a fish pond with a bottom MABR aeration system but no vegetable cultivation system, followed the same procedures as the experimental group. The experiment was conducted in Zhanjiang, Guangdong Province. The results are as follows.

[0053] ①The first round of channel catfish index analysis

[0054] The growth performance of channel catfish in the experimental pond group was significantly improved (see Table 1). Statistical analysis showed that compared with the control group, the final weight, body weight gain, and specific growth rate of the channel catfish in the experimental group were significantly increased (P < 0.05). The feed conversion rate showed a significant downward trend, but the difference was not statistically significant. These results indicate that the experimental pond group was able to improve the body weight gain and specific growth rate of channel catfish. Conclusion: Compared with the control group, the body weight gain of the channel catfish in the experimental group increased by more than 10%.

[0055] Table 1 Effects of the fish-light complementary aquaponics model on the growth performance of channel catfish in the middle growth period (data from the first round of growth period)

[0056]

[0057] Note: The second round of experiments has a growth period of 35 days, starting from December 1, 2024, and the fish weighing period is January 5, 2025. Insignificant differences are indicated by the same letter, while significant differences are indicated by different letters.

[0058] ② The second round of channel catfish index analysis

[0059] The survival rate of fry in each group was over 99%. The study showed that the overall performance of channel catfish in the experimental pond group improved significantly, outperforming the control group (see Table 2). Statistical analysis showed that compared with the control group, the final weight, body weight gain, and specific growth rate of channel catfish in the experimental group were significantly increased (P < 0.05), and the feed conversion efficiency was significantly decreased (P < 0.05). These results indicate that the experimental pond group significantly promoted the final weight, body weight gain, feed efficiency, and specific growth rate of channel catfish. Conclusion: Compared with the control group, the body weight gain of channel catfish in the experimental group increased by over 30%.

[0060] Table 2 Effects of the fish-light complementary aquaponics model on the growth performance of channel catfish in the middle growth period (data from the second growth period)

[0061]

[0062] Note: The second round of experiments has a growth period of 35 days, starting from December 1, 2024, and the fish weighing period is January 5, 2025. Insignificant differences are indicated by the same letter, while significant differences are indicated by different letters.

[0063] ③The third round of channel catfish index analysis

[0064] The survival rate of fry in each group was over 99%. The study showed that the overall performance of channel catfish in the experimental pond group improved significantly, outperforming the control group (see Table 3). Statistical analysis showed that compared with the control group, the final weight, body weight gain, and specific growth rate of channel catfish in the experimental group were significantly increased (P < 0.05), and the feed conversion efficiency was significantly decreased (P < 0.05). These results indicate that the experimental pond group significantly promoted the final weight, body weight gain, feed efficiency, and specific growth rate of channel catfish. Conclusion: Compared with the control group, the body weight gain of channel catfish in the experimental group increased by over 17%.

[0065] Table 3 Effects of fish-light complementary aquaponics on the growth performance of channel catfish in the middle growth period (data from the third growth period)

[0066]

[0067] Note: The second round of experimental growth cycle is 50 days, starting from December 1, 2024, and the fish weighing period is January 20, 2024. Insignificant differences are indicated by the same letter, while significant differences are indicated by different letters.

[0068] 2) Analysis of grass carp growth indicators

[0069] ① Analysis of the first round of grass carp growth indicators

[0070] The growth performance of grass carp in the experimental pond group was significantly improved, surpassing that of the control group (see Table 4). Statistical analysis showed that compared with the control group, the final weight, body weight gain, and specific growth rate of grass carp in the experimental group were significantly increased (P < 0.05), and the feed conversion rate was significantly reduced (P < 0.05). These results demonstrate that the experimental pond group significantly promoted the growth of grass carp, body weight gain, feed conversion rate, and specific growth rate. Conclusion: Compared with the control group, the body weight gain of grass carp in the experimental group increased by more than 20%.

[0071] Table 4 Effects of fish-light complementary aquaponics on the growth performance of grass carp (data from the first growth period)

[0072]

[0073] Note: The growth period of the first round of the experiment is 15 days, starting from December 1, 2024, and the fish weighing period is December 15, 2024. Insignificant differences are indicated by the same letter, while significant differences are indicated by different letters.

[0074] ②Analysis of the second round of grass carp growth indicators

[0075] The survival rate of fry in each group was over 99%. The study showed that the overall performance of grass carp in the experimental pond group was positive, significantly better than that in the control group (see Table 5). Statistical analysis showed that compared with the control group, the final weight, body weight gain, and specific growth rate of grass carp in the experimental group were significantly increased, with statistically significant differences (P < 0.05), and the feed conversion efficiency was significantly reduced, with statistically significant differences (P < 0.05). These results indicate that the experimental pond group significantly promoted the final weight, body weight gain, feed efficiency, and specific growth rate of grass carp. Conclusion: Compared with the control group, the body weight gain of grass carp in the experimental group increased by more than 30%.

[0076] Table 5 Effects of fish-light complementary aquaponics on the growth performance of grass carp (data from the second growth period)

[0077]

[0078] Note: The second round of experimental growth cycle is 35 days, starting from December 1, 2024, and the fish weighing period is January 5, 2024. Insignificant differences are indicated by the same letter, while significant differences are indicated by different letters.

[0079] ③Analysis of grass carp growth indicators in the third round

[0080] The survival rate of fry in each group was over 99%. The study showed that the overall performance of grass carp in the experimental pond group was positive, significantly better than that in the control group (see Table 6). Statistical analysis showed that compared with the control group, the final weight, body weight gain, and specific growth rate of grass carp in the experimental group were significantly increased (P < 0.05), and the feed conversion efficiency was significantly reduced (P < 0.05). These results indicate that the experimental pond group significantly promoted the final weight, body weight gain, feed efficiency, and specific growth rate of grass carp. Conclusion: Compared with the control group, the body weight gain of grass carp in the experimental group increased by more than 5%.

[0081] Table 6 Effects of fish-light complementary aquaponics on the growth performance of grass carp (data from the third growth period)

[0082]

[0083] Note: The growth period of the third round of experiments is 50 days, starting from December 1, 2024, and the fish weighing period is January 20, 2024. Insignificant differences are indicated by the same letter, while significant differences are indicated by different letters.

[0084] 3) Analysis of California bass growth indicators

[0085] ① Analysis of the first round of growth indicators of California bass

[0086] The growth performance of California bass in the experimental pond group improved significantly, outperforming the control group (see Table 7). Statistical analysis showed that compared with the control group, the final weight, body weight gain, and specific growth rate of California bass in the experimental group were significantly increased (P < 0.05). The feed conversion efficiency showed a decreasing trend, but the difference was not statistically significant. These results suggest that the experimental pond group has a certain effect on promoting the body weight gain and specific growth rate of California bass. Conclusion: Compared with the control group, the body weight gain of California bass in the experimental group increased by more than 10%.

[0087] Table 7 Effects of fish-light complementary aquaponics on the growth performance of juvenile California bass (data from the first growth period)

[0088]

[0089] Note: The growth period of the first round of the experiment is 15 days, starting from December 15, 2024, and the fish weighing period is January 5, 2025. Insignificant differences are indicated by the same letter, while significant differences are indicated by different letters.

[0090] ②Analysis of the growth performance indicators of California bass in the second round

[0091] The survival rate of fry in each group was greater than 99%. The study showed that the growth performance of California bass in the experimental pond group improved slightly, slightly outperforming the control group (see Table 8). Statistical analysis showed that compared with the control group, the final weight, body weight gain, and specific growth rate of California bass in the experimental group were significantly increased (P < 0.05). The feed conversion efficiency showed a downward trend, but the difference was not statistically significant. These results indicate that the experimental pond group has a certain effect on promoting the body weight gain and specific growth rate of California bass. Conclusion: Compared with the control group, the body weight gain of California bass in the experimental group increased by more than 5%.

[0092] Table 8 Effects of fish-light complementary aquaponics on the growth performance of California bass (data from the second growth period)

[0093]

[0094] Note: The growth period of the second round of experiments is 35 days, starting from December 15, 2024, and the fish weighing period is January 20, 2024. Insignificant differences are indicated by the same letter, while significant differences are indicated by different letters.

[0095] 2. Experimental aquaculture water quality management and data analysis

[0096] The following experimental locations are the same as those in "1", all in Zhanjiang City, Guangdong Province.

[0097] ① Water quality data analysis

[0098] Based on basic aquaculture requirements, in order to quickly release fry, only key water quality parameters such as pH, ammonia nitrogen, and nitrite were tested to determine if the conditions for fry entry were met. The test pond was equipped with a photovoltaic aquaculture system based on the structure of Example 1. The control pond also had photovoltaic panels installed, but only ecological floating cages were used as an additional purification method.

[0099] Table 9 Water quality conditions before stocking (November 20-25, 2024)

[0100]

[0101] Note: When the project started to store water, it was discovered that the pond was leaking seriously. On the 25th, a large amount of new water (from a nearby river) was injected, which had a great impact on the water quality and caused fluctuations in relevant data.

[0102] According to the test results, after 3 to 5 days of water purification, the indicators such as sub-salt and ammonia nitrogen in the test pond (photovoltaic fish-vegetable symbiosis system) can meet the requirements for the release of fish fry. In contrast, because the pond only has ecological floating cages as an additional purification method, the degradation of sub-salt in the water is relatively slow, but it can still meet the water quality requirements for the release of fish fry.

[0103] Fish fry were released gradually starting from November 24, 2024. After about two weeks of breeding and water treatment, the water quality parameters in the test pond and the comparison pond changed significantly. The relevant data tested on December 14 are shown in Table 10.

[0104] Table 10 Aquaculture water quality monitoring results for the first phase (December 14, 2024)

[0105]

[0106] The water quality data shows that the dissolved oxygen level in the test pond is significantly higher than that in the control pond, which is beneficial to the growth and development of fish. This is because the MABR membrane in the test pond is laid at the bottom. By aerating the hollow fibers, it not only provides sufficient oxygen for the microbial activity at the bottom of the pond to break down organic matter, but also provides a certain amount of dissolved oxygen to the water in the pond. Similarly, the ammonia nitrogen and total phosphorus levels in the test pond are significantly lower than those in the control pond. This is due to the MABR system and the aquaponics circulating water system in the test pond, which effectively degrade the dissolved organic matter in the water. From these results, it can be seen that the water quality of the test pond is better than that of the control pond due to the additional water treatment measures.

[0107] The temperature in Zhanjiang drops to around 15-18°C in winter. When water quality sampling was carried out on January 7, 2025, the water temperature was only 17°C. The water quality data measured at this time are shown in Table 11.

[0108] Table 11: Monitoring of aquaculture water quality in the second phase (January 7, 2025)

[0109]

[0110] The water quality data shows that the COD in the test pond is significantly higher than that in the control pond. This indicates that the water in the test pond is relatively rich, suitable for algae growth, and can provide more biomass, indirectly serving as bait for filter-feeding fish. At the same time, the amount of harmful ammonia nitrogen in the test pond is slightly lower than that in the control pond, indicating that the MABR system and the aquaponics circulating water system have a certain effect in reducing ammonia nitrogen. The total nitrogen and total phosphorus in the test pond are higher than those in the control pond. This is because during the experiment, the river entered the dry season, and the supplementary water source came from the neighboring shrimp pond, which has high total nitrogen and total phosphorus, and the water quality is relatively rich. After the water level stabilizes, the water quality needs to be retested to ensure that the ecological purification system can process and reduce the total nitrogen and total phosphorus to ensure the survival and growth of fish.

[0111] The third breeding period, from January 6 to January 20, 2025, saw a slight rise in local temperatures, with water temperatures ranging from 17°C to 21°C. Water quality data measured on the 20th are shown in Table 12.

[0112] Table 12: Monitoring of aquaculture water quality in the second phase (January 20, 2025)

[0113]

[0114]

[0115] Similar to the water quality in the previous breeding stage, the test results showed that the COD in the test pond was significantly higher than that in the control pond, and the content of organic matter such as total nitrogen and total phosphorus was significantly higher than that in the control pond. However, indicators such as ammonia nitrogen and nitrite, which are harmful to fish growth and development, were significantly lower in the test pond than in the control pond. This shows that the additional water treatment modules added to the test pond, such as circulating purification and pond bottom MABR systems, can ensure low ammonia nitrogen and salt accumulation in the pond water, which is beneficial to fish breeding and production.

[0116] From the above data summary and comparison, we can see that (such as Figure 2 As shown in the figure, as the breeding process prolonged, the pH in the breeding pond increased from weak alkaline (about 7.4) to between 7.8 and 8.1, which is more suitable for fish breeding. The pH of the water in the experimental pond and the control pond was suitable for breeding.

[0117] From the changes in ammonia nitrogen, it can be seen that the ammonia nitrogen values ​​in the experimental pond and the control pond have been increasing continuously and have stabilized in recent tests. From the numerical point of view, the additional water treatment process in the experimental pond has reduced the ammonia nitrogen content in the pond water, and the water quality is better than that of the control pond. However, the ammonia nitrogen values ​​in the experimental pond and the control pond are currently high, and the risk of fish poisoning is relatively high. The possible reasons are as follows: (1) The water temperature in the pond is low in winter, the activity of ammonia oxidizing bacteria in the pond is low, and the ability to decompose ammonia nitrogen is limited; (2) The oxygen supply and aeration time in the pond is short. Currently, the oxygen supply and aeration time is only 4 to 5 hours a day, and the dissolved oxygen in the water is not enough to decompose the manure and leftover bait deposited at the bottom of the pond; (3) The feeding amount is too large. Due to the low temperature, many fish are less active and eat less, resulting in feed waste and increasing the source of ammonia nitrogen at the bottom of the pond. The measures that can be adopted in the later stage include: (1) Extending the daily aeration time to 6 to 8 hours; (2) Reducing the feeding amount to ensure that there is no leftover bait in the breeding cage.

[0118] from Figure 2 It can be seen that the nitrite content in the experimental pond is significantly lower than that in the control pond, and its value is basically maintained below 0.02 mg / L. However, the nitrite content in the control pond gradually increases and tends to be stable, but its value is still within the normal range of aquaculture.

[0119] from Figure 2 As can be seen, the total phosphorus content in the experimental ponds was significantly higher than that in the control ponds in the later stages, indicating a high level of eutrophication, providing ample nutrients for some algae. This result was caused by the fact that, starting in the second phase, due to the high salinity of the nearby river during the winter dry season, water was replenished from adjacent shrimp ponds to ensure overall water quality stability. This resulted in high total phosphorus and COD levels, representing a type of aquaculture-enriched water. According to water quality standards for fish aquaculture, a total phosphorus content below 0.5 mg / L is considered normal, so the total phosphorus content in both the experimental and control ponds met aquaculture requirements.

[0120] 3. Analysis of water purification function modules

[0121] ①Ecological floating cages

[0122] A number of ecological floating cages were regularly installed in both the experimental and control ponds, housing water hyacinth and duckweed for in-situ water purification. Over the past two months, the water hyacinths have experienced slow growth due to a lack of sunlight beneath the photovoltaic panels and low winter temperatures, with some of them withering and dying in the cages. Duckweed is more adaptable and has grown outside the cages, providing ample food for grass carp stocked in the outer ponds. However, due to lack of sunlight, the duckweed in some cages is struggling to survive, with large areas of it turning white and withering.

[0123] Therefore, from the perspective of actual operation, the lack of sunlight under the photovoltaic panels cannot support the growth of larger aquatic plants. Alternatively, the setting of ecological cages can be cancelled, and some aquatic plants and duckweed and other plants or algae with strong adaptability can be planted directly on the edge of the pond where sunlight can be seen. This will purify the water quality while providing sufficient bait for fish such as grass carp.

[0124] ②Pond bottom MABR system

[0125] MABR (Membrane Aerated Biofilm Reactor) purification system is laid on the bottom of the pond (such as Figure 3 (as shown in the figure), nitrifying and denitrifying bacteria in situ consume leftover bait that is not consumed by fish, thereby reducing the risk of water pollution in the pond and maintaining water quality within a suitable range over the long term. A certain number of MABR membranes and aeration systems have been installed at the bottom of the experimental pond. Current operational data indicates that the MABR system effectively purifies pond water and increases dissolved oxygen concentration, providing favorable living conditions for fish farming. However, the comparison pond, without the MABR system, experienced slower water purification and lower dissolved oxygen levels than the experimental pond, which is not conducive to fish survival.

[0126] ③Aquaponics circulation purification system

[0127] The pipeline circulation purification system extracts a certain amount of water from a corner of the experimental pond through a pump station. The water then passes through sedimentation filtration, a microfiltration machine, a pipeline hydroponic vegetable cultivation system, and a UV disinfection system to purify and maintain the water quality. This ensures sufficient circulation of the pond water and reduces the levels of ammonia nitrogen, nitrite nitrogen, and other chemicals harmful to fish. The purified water is then piped to other locations in the pond for aeration and discharge, achieving effective circulation within the pond.

[0128] After nearly two months of operation, the vertical flow settler and microfiltration machine have limited effect on water purification. They can only remove some particulate matter in the circulating water, and have very limited impact on the suspended matter in the entire pond water quality. In the future optimization system, the corresponding equipment settings can be reduced. The pipeline hydroponic vegetables have screened the vegetable varieties. From the test results, lettuce and celery can survive well and grow vigorously, especially in the winter of the test, their growth rate is ideal, but the effect of hydroponic water spinach is poor. On the one hand, it may be that the wind speed in the test area is high, and the water spinach seedlings are swaying in the pipe, which is not conducive to survival and growth. On the other hand, it may be that the temperature and water quality are not suitable for the survival of water spinach. The current pipeline hydroponics effect is as follows: Figure 4 As shown in .

[0129] Because the experiment took place in winter, hydroponic results showed that lettuce (green and purple) and celery adapted well to the hydroponic environment and temperature, achieving satisfactory growth. However, hydroponic water spinach required a change in cultivation methods, as growing in pipes performed poorly. Furthermore, the results suggest that piped hydroponic vegetable cultivation could be optimized into ecological trenches, utilizing standardized hydroponic tanks for vegetable cultivation (such as celery). This would increase the total volume of hydroponic vegetables and improve water purification capacity, while also reducing construction costs and facilitating operation and harvesting.

[0130] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A photovoltaic fish-vegetable symbiotic system, characterized in that: include: Photovoltaic system, fish farming system and circulation purification system, the specific structure is as follows: A. Photovoltaic system: Photovoltaic panels are set above the water surface to provide shade during the aquaculture period; B. Fishery farming system: The fish pond is located below the photovoltaic panels, with a membrane aeration biofilm reactor purification system laid on the pond bottom and cages set up inside the fish pond; C. Circulation purification system: A circulating purification system is set up around the fish pond: water is pumped out of the fish pond through a pumping station, and the pumped water is purified and maintained through sedimentation filtration, microfiltration machine, hydroponic vegetable system and ultraviolet disinfection system in sequence.

2. The photovoltaic fish-vegetable symbiotic system according to claim 1, characterized in that: In the structure A, the photovoltaic panels are 2-2.5m above the water surface with a slope of 13°, and 30-85% shade is maintained during the breeding period; in the structure B, the fish pond is 2.4m deep, and a membrane aeration biofilm reactor purification system is laid on the pond bottom; the fish pond is provided with cages, each of which is 4m long and 4m wide, with a net depth of 1.5m, and 20-24 cages are arranged per mu, arranged in rows with a row spacing of 2m; the membrane components of the membrane aeration biofilm reactor purification system are spaced 0.4m apart, covering 25% of the bottom area of ​​the fish pond; the cages are floating cages, one part of which is used for breeding fish, and the other part is not used for breeding fish and is used for breeding aquatic plants; the ratio of ecological cages to breeding cages is 1:6-7; in the structure C, the hydroponic vegetable system is a pipeline hydroponic vegetable system or a hydroponic box; there are no photovoltaic panels in the hydroponic vegetable area.

3. The photovoltaic fish-vegetable symbiotic system according to claim 1, characterized in that: In the structure C, a certain amount of water is pumped out by the pump station for circulation and purification. The amount of water circulated and purified every day is 1 / 10-1 / 5 of the water in the fish pond.

4. The photovoltaic fish-vegetable symbiotic system according to claim 3, characterized in that: The purified pond water in the circulation purification system is transported by pipeline to other locations of the fish pond except the pumping station for oxygenation and discharge, thereby realizing effective circulation of the water in the pond.

5. A photovoltaic fish-vegetable symbiotic farming method, characterized in that: The following steps are involved: (1) Using the photovoltaic fish-vegetable symbiotic system of any one of claims 1 to 5, before the fry are released, water is stored in the fish pond and the circulating purification system therein is activated to purify the water quality; (2) After the fry are released, the circulating purification system is continued to be turned on to purify the water quality, and the dissolved oxygen content in the water is continued to be turned on to purify the water quality to ensure that the water purification load meets the pollutant removal amount generated by regular feeding of feed.

6. The photovoltaic fish-vegetable symbiotic farming method according to claim 5, characterized in that: In the step (1), the water purification treatment is continued for at least 3 days to make the water quality reach the aquaculture standard: dissolved oxygen>5mg / L, ammonia nitrogen<0.2mg / L, nitrite nitrogen<0.1mg / L, pH value 7.0-8.

0.

7. The photovoltaic fish-vegetable symbiotic farming method according to claim 5, characterized in that: The fry are channel catfish fry, grass carp fry and / or California sea bass fry; the stocking density is 120 fry per cubic meter of water.

8. The photovoltaic fish-vegetable symbiotic farming method according to claim 5, characterized in that: The vegetable varieties grown in the hydroponic vegetable system are water spinach, lettuce, spinach, celery, Chinese cabbage and / or coriander, etc., which are suitable for hydroponics.

9. The photovoltaic fish-vegetable symbiotic farming method according to claim 5, characterized in that: The operating parameters of the circulating purification system were adjusted to 8 hours per day, divided into two periods of 4 hours in the morning and 4 hours in the afternoon, with the flow rate controlled at 0.4m / s; the aeration volume of the MABR purification system was adjusted to 0.3m 3 / h·m 2 , ensure that the dissolved oxygen content in the water is stable at above 5mg / L.

10. The photovoltaic fish-vegetable symbiotic farming method according to claim 5, characterized in that: Adjust the amount and frequency of feed according to the growth of fish and water quality. Feed 2-3 times a day, with each feeding amount being 2-3% of the fish's body weight.

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