A method for promoting the symbiosis of bacteria and algae and efficient recovery by using the foam generated from fish manure fermentation

Abstract

The present invention discloses a method for promoting the symbiosis of bacteria and algae and efficient recovery by using the foam generated from the fermentation of fish feces, which is characterized in that it includes an anaerobic fermentation tank, an aerobic fermentation tank and a bacteria-algae symbiotic system connected in sequence. The bacteria-algae symbiotic system includes a reactor. The foam generated by the anaerobic fermentation is introduced into the bacteria-algae symbiotic system and slowly stirred to make the bubbles evenly dispersed in the reactor. After stopping the stirring, as the photosynthesis of microalgae continuously proceeds, when the microalgae biomass reaches about 0.8-1.0 g / L, the bubbles gradually accumulate on the surface of the reactor. The bubbles are scraped out by a scraper and subjected to ultrasonic vibration, so as to realize the rupture of the bubbles and the recovery of algae. The water passing through the bacteria-algae symbiotic system returns to the fish pond for fish farming. On the one hand, it provides nutrients for the growth of bacteria and algae, and on the other hand, it can realize the separation of bacteria and algae from the liquid surface, reducing the cost of bacteria-algae recovery. (The cost of bacteria-algae recovery generally accounts for more than 20% of the cost of bacteria-algae cultivation.) The cultivated bacteria and algae are collected and used as fish bait in the fish pond.

Description

Technical Field

[0001] The present invention relates to a method for promoting the symbiosis of bacteria and algae and efficient recycling by using the foam generated from fish manure fermentation, belonging to the field of aquaculture and planting. Background Art

[0002] In recirculating aquaculture, the fish stocking density is high, and the average bait feeding amount is between 1% and 1.2%. A large amount of fecal sewage and residual bait are generated every day. At present, in China, the common method is to increase the circulating water volume and the water replacement volume to remove the fecal sewage and residual bait in the fish pond. A large amount of sewage is filtered by a microfiltration machine and then subjected to aerobic treatment. The treated tail water is used for growing vegetables or purifying in an artificial wetland, and finally discharged up to the standard.

[0003] Due to the large amount of sewage, the energy consumption in the treatment process is high, and the facility capacity is large, resulting in high construction investment and large waste of water resources. These problems comprehensively affect the healthy development of recirculating aquaculture. Therefore, how to better reduce the energy consumption of aerobic treatment and reduce the treatment cost has become a problem that needs to be solved.

[0004] For this reason, we designed a high-density recirculating aquaculture system with one main and two auxiliary units. After the fish manure is concentrated in this system, it undergoes anaerobic fermentation, aerobic fermentation, and then enters the bacteria-algae symbiotic system, and then the water returns to the fish pond.

[0005] Foaming is a stable mucus layer formed when the gas generated in the reactor cannot be discharged smoothly, forms a dispersion system in the liquid, and finally accumulates on the liquid surface. It is a three-phase mixing system composed of bubbles, liquid (wastewater containing surface active substances), and solid particles (microorganisms and suspended solids).

[0006] The abundant surface active substances in the bubbles have an asymmetric molecular structure (including hydrophilic polar groups and hydrophobic non-polar groups), can be adsorbed and oriented on the gas-liquid interface to form a critical layer with a certain mechanical strength, so as to play a buffering role when the bubbles meet and rise to the liquid surface, preventing the bubbles from bursting and causing the formation of concentrated foam in the reactor.

[0007] The characteristics of fish manure, the types of microorganisms it carries, volatile fatty acids (VFAs), raw material carbon-nitrogen ratio, organic load, stirring mode, etc. are all foaming inducers. The surfactants / biosurfactants in the fish manure fermentation system mainly come from extracellular polymeric substances (EPS), except for some substrates or intermediate metabolites generated during the substrate degradation process. EPS can adhere to the cell surface, form a protective barrier, provide resistance to harsh environments, adsorb exogenous organic compounds to store nutrients, and digest exogenous macromolecules to obtain nutrients. Soluble EPS, especially soluble PN, also contributes to the formation of foam.

[0008] The rapid degradation of organic matter and the efficient accumulation and utilization of nitrate nitrogen in the fish-vegetable-algae symbiotic system are the keys to constructing a closed-loop recycling system. In previous experiments, it was found that a large amount of foam was generated during the anaerobic fermentation and aerobic biochemical treatment of high-concentration fish manure. The solid substances entrained in the foam caused blockage and even damage to the stirring device, aeration pipe, and pump. At the same time, it also caused an inverse profile with a high solid concentration at the top and a low fixed concentration at the bottom in the reactor, forming a dead zone, reducing the effective volume of the reactor, seriously affecting the gas-liquid mass transfer efficiency, and destroying the system stability.

[0009] Therefore, how to remove these foams is an urgent problem for us to solve. Summary of the Invention

[0010] Aiming at the above technical problems, the purpose of the present invention is to provide a method for promoting the symbiosis of bacteria and algae and efficient recovery by using the foam generated from the fermentation of fish manure.

[0011] In order to achieve the above purpose, the technical solution of the present invention is: a method for promoting the symbiosis of bacteria and algae and efficient recovery by using the foam generated from the fermentation of fish manure, which is characterized in that: it includes an anaerobic fermentation tank, an aerobic fermentation tank, and a bacteria-algae symbiotic system connected in sequence for fish manure. The bacteria-algae symbiotic system includes a reactor. The foam generated from the anaerobic fermentation is introduced into the bacteria-algae symbiotic system and slowly stirred to make the bubbles evenly dispersed in the reactor. Then, the stirring is stopped. As the photosynthesis of microalgae continues, when the microalgae biomass reaches about 0.8-1.0 g / L, the bubbles gradually accumulate on the surface of the reactor. The bubbles are scraped out by a scraper and vibrated by ultrasonic waves, so that the bubbles can be broken and the algae can be recovered. The water passing through the bacteria-algae symbiotic system returns to the fish pond for fish farming.

[0012] In order to achieve the efficient growth and rapid separation of bacteria and algae, a large amount of foam (especially anaerobic fermentation) generated from the fermentation of fish manure is introduced into the bacteria-algae pond and simply and slowly stirred to ensure that the bubbles are evenly dispersed into the bacteria-algae symbiotic system and the bubbles do not burst. Then, the stirring is stopped. The bubbles contain rich nutrients such as nitrogen, phosphorus, and CO2 and have a certain viscosity (163 mPa·S). On the one hand, it can provide nutrients and carbon dioxide (generated from anaerobic fermentation) for the growth of bacteria and algae, improve the photosynthesis efficiency, and the growth efficiency of microalgae is increased by more than 10%, achieving emission reduction and carbon fixation; on the other hand, it can realize the separation of bacteria and algae from the liquid surface, reduce the cost of bacteria and algae recovery, and compared with traditional membrane separation and flocculation precipitation separation, the cost is reduced by more than 15% (the cost of bacteria and algae recovery generally accounts for more than 20% of the cost of bacteria and algae cultivation). The timely removal of bubbles eliminates the inhibition of the bubbles on the gas-liquid mass transfer efficiency and the destruction of the system stability in the anaerobic fermentation system, and the anaerobic fermentation efficiency is increased by more than 10%.

[0013] In the above solution: the ratio of bacteria to algae in the bacteria-algae symbiotic system is 1:4, and the light-dark ratio is 2:1. The bacteria are nitrifying bacteria separated from the fluidized bed, and the algae are Phaeodactylum tricornutum with high-efficiency light fixation function and can be used as bait for bass. The bacteria come from the fish farming system, and the algae can be used for the cultivation of bass.

[0014] In the above solution: the fish feces coming out from the bottom of the fish pond are precipitated by a vertical flow sedimentation tank, and then the fish feces are collected into a fish feces collection pond. The fish feces in the fish feces collection pond are further concentrated, and the concentrated fish feces enter the anaerobic fermentation tank.

[0015] In the above solution: the solid content after concentration by the fish feces concentrator is 3-5%.

[0016] In the above solution: the algae produced by the bacteria-algae symbiotic system are used in the fish pond as fish bait.

[0017] A "one main and two auxiliary" high-density recirculating aquaculture system studied by the applicant, including a fish pond, characterized in that: the fish pond is equipped with three fish-raising tail water circulation routes, namely the main circulation route, the first auxiliary line and the second auxiliary line;

[0018] The main circulation line includes a microfilter, a fluidized bed, an ozone disinfection device and an ultraviolet disinfection device connected in sequence. The upper pool surface drainage pipeline of the fish pond is connected to the microfilter, and the outlet pipeline of the ultraviolet disinfection device is connected to the fish pond. After the upper pool surface drainage of the fish pond is filtered by the microfilter, it enters the fluidized bed, where ammonia nitrogen and nitrite nitrogen are converted into nitrate nitrogen, and then the fish-raising tail water returns to the fish pond after passing through the ozone disinfection device and the ultraviolet disinfection device;

[0019] The first auxiliary line includes a vegetable cultivation system and a filter. A branch pipe is branched from the liquid outlet of the fluidized bed and connected to the vegetable cultivation system. The water outlet of the vegetable cultivation system is connected to the filter, and the water outlet of the filter is connected to the ozone disinfection device. Part of the water coming out from the fluidized bed enters the vegetable cultivation system to reduce the content of nitrate nitrogen. After the water coming out from the vegetable cultivation system is filtered by the filter, it passes through the ozone disinfection device and the ultraviolet disinfection device and then returns to the fish pond;

[0020] The second auxiliary line includes a vertical flow sedimentation tank, a fish manure collection pond, a fish manure concentrator, an anaerobic fermentation tank, an aerobic fermentation tank, and a bacteria-algae symbiotic system; the fish manure sewage discharge pipeline at the bottom of the fish pond is connected to the vertical flow sedimentation tank, the clear liquid outlet pipeline of the vertical flow sedimentation tank is connected to the microfilter, the fish manure in the vertical flow sedimentation tank and the fish manure filtered out by the microfilter enter the fish manure collection pond, a branch pipe is separated from the filtrate outlet pipeline of the microfilter and connected to the fish manure collection pond, the fish manure in the fish manure collection pond is concentrated by the fish manure concentrator, the concentrated fish manure enters the anaerobic fermentation tank for anaerobic fermentation and the aerobic fermentation tank for aerobic fermentation, the tail water after aerobic fermentation enters the bacteria-algae symbiotic system again, and the water coming out of the bacteria-algae symbiotic system returns to the fish pond after passing through the ozone disinfection device and the ultraviolet disinfection device. An online ammonia nitrogen detector, an online nitrate nitrogen monitor, and an online nitrite nitrogen monitor are respectively arranged on the outlet pipeline of the ultraviolet disinfection device, the outlet pipeline of the fluidized bed, and the filtrate outlet pipeline of the microfilter. In this system, the ammonia nitrogen in the water returning to the fish pond is less than 0.5 mg / L, and the concentration of nitrite nitrogen is less than 0.2 mg / L. The solid content after concentration by the fish manure concentrator is 3-5%. The vegetables planted in the vegetable cultivation system are lettuce. For the treatment line of one main and two auxiliaries, the main circulation route uses the fluidized bed to convert ammonia nitrogen and nitrite into nitrate nitrogen to meet the growth requirements of plants. Part of the water coming out of the fluidized bed is provided for the growth needs of plants, and part of it returns to the fish pond. When bait is put in or the ammonia nitrogen concentration is monitored to increase, at this time, most of the water can pass through the second auxiliary line, and through anaerobic-aerobic biochemical reactions, ammonia nitrogen is converted into nitrate nitrogen, and at the same time, nitrate nitrogen is converted into nitrogen gas to remove nitrogen in the water. The three routes are carried out simultaneously to ensure that the content of nitrate nitrogen in the whole system is lower than 500 mg / L, the ammonia nitrogen is less than 0.5 mg / L, and the concentration of nitrite nitrogen is less than 0.2 mg / L. Ensure the quality of vegetable cultivation and achieve high-density aquaculture.

[0021] Beneficial effects: In order to achieve the efficient growth and rapid separation of bacteria and algae, the present invention introduces a large amount of foam generated by fish manure fermentation into the bacteria-algae pond. The bubbles contain rich nutrients such as nitrogen and phosphorus and have a certain viscosity. On the one hand, they can provide nutrients for the growth of bacteria and algae, and on the other hand, they can achieve the separation of bacteria and algae from the liquid surface, reducing the cost of bacteria-algae recovery. (The cost of bacteria-algae recovery generally accounts for more than 20% of the bacteria-algae cultivation cost.) The cultivated bacteria and algae are collected and used as fish bait in the fish pond.

[0022] The method invented in this project is not limited to the Phaeodactylum tricornutum mentioned in this patent, and is also suitable for the collection of other algae, etc. Brief Description of the Drawings

[0023] Figure 1 It is a flow chart of the high-density fish-vegetable-algae symbiotic breeding and cultivation circulation system designed for the applicant.

[0024] Figure 2Schematic diagram of the removal of ammonia nitrogen and nitrate nitrogen in fishpond tail water by lettuce.

[0025] Figure 3 Monitoring diagram of the growth cycle of lettuce. Detailed implementation manners

[0026] The present invention will be further described below by way of examples in conjunction with the accompanying drawings:

[0027] As Figure 1 shown, a high-density planting and breeding circulation system designed by the applicant includes a fishpond 1, and the fishpond 1 is equipped with three fishpond tail water circulation routes, namely a main circulation route, a first auxiliary line and a second auxiliary line.

[0028] The main circulation line includes a microfilter 2, a fluidized bed 3, an ozone disinfection device 4 and an ultraviolet disinfection device 5 connected in sequence. The upper pool surface drainage pipeline of the fishpond 1 is connected to the microfilter 2, and the outlet pipeline of the ultraviolet disinfection device 5 is connected to the fishpond 1. After the upper pool surface drainage of the fishpond passes through the microfilter 2 for filtration, it enters the fluidized bed 3, and ammonia nitrogen and nitrite nitrogen are converted into nitrate nitrogen in the fluidized bed 3. Part of the water coming out of the fluidized bed returns to the fishpond 1 after being disinfected by the ozone disinfection device 4 and the ultraviolet disinfection device.

[0029] The first auxiliary line includes a vegetable cultivation system 6 and a filter 7. A branch pipe is branched from the liquid outlet of the fluidized bed 3 and connected to the vegetable cultivation system 6. The water outlet of the vegetable cultivation system 6 is connected to the filter 7, and the water outlet of the filter 7 is connected to the ozone disinfection device 4. Part of the water coming out of the fluidized bed 3 enters the vegetable cultivation system 6 to reduce the content of nitrate nitrogen. The water coming out of the vegetable cultivation system returns to the fishpond after passing through the filter 7, the ozone disinfection device 4 and the ultraviolet disinfection device 5.

[0030] The second auxiliary line includes a vertical flow sedimentation tank 8, a fish manure collection tank 9, a fish manure concentrator 10, an anaerobic fermentation tank 11, an aerobic fermentation tank 12, a bacteria-algae symbiotic system 13, and an ecological regulation tank 14. The bottom fish manure sewage discharge pipeline of the fish pond 1 is connected to the vertical flow sedimentation tank 8. The clear liquid outlet pipeline of the vertical flow sedimentation tank 8 is connected to the microfilter 2. The fish manure in the vertical flow sedimentation tank 8 and the fish manure filtered out by the microfilter 2 enter the fish manure collection tank 9. A branch pipe is also branched out from the filtrate outlet pipeline of the microfilter 2 and connected to the fish manure collection tank 9. When the ammonia nitrogen content in the surface drainage is too high, part of the water is discharged into the fish manure collection tank 9. The fish manure in the fish manure collection tank 9 is concentrated by the fish manure concentrator and then the concentrated fish manure enters the anaerobic fermentation tank 11 and the aerobic fermentation tank 12 for biochemical treatment. The tail water after biochemical treatment enters the bacteria-algae symbiotic system 13 again. The water coming out of the bacteria-algae symbiotic system 13 returns to the fish pond 1 after passing through the ozone disinfection device 4 and the ultraviolet disinfection device 5. Valves are provided on all connecting pipelines. An online ammonia nitrogen detector, an online nitrate nitrogen monitor, and an online nitrite nitrogen monitor are respectively provided on the outlet pipeline of the ultraviolet disinfection device, the outlet pipeline of the fluidized bed, and the filtrate outlet pipeline of the microfilter. A branch pipe is branched out from the outlet pipeline of the ultraviolet disinfection device and connected to the fluidized bed. When the ammonia nitrogen detection is unqualified, it returns to the fluidized bed again.

[0031] According to the nitrate nitrogen content of the filtrate coming out of the microfilter monitored by the online ammonia nitrogen detector, the online nitrate nitrogen monitor, and the online nitrite nitrogen monitor, the water volumes flowing to the main circulation route, the first auxiliary line, and the second auxiliary line are adjusted. Under normal circumstances, the main circulation route, the first auxiliary line, and the second auxiliary line operate simultaneously, which can not only meet the needs of fish farming, but also meet the planting needs of fungi and vegetables, and at the same time can dispose of fish manure. When the nitrate nitrogen content of the water coming out of the fluidized bed is between 500 mg / L and 1000 mg / L, most of the water coming out of the fluidized bed enters the vegetable cultivation system to further remove ammonia nitrogen through vegetable cultivation, so as to ensure that the nitrate nitrogen content of the water returning to the fish pond is below 500 mg / L to adapt to the growth of fish. When the nitrate nitrogen content is greater than 1000 mg / L, part of the water coming out of the microfilter enters the third auxiliary line to increase the removal of nitrogen. To ensure that the nitrate nitrogen content of the water returning to the fish pond is controlled below 500 mg / L, preferably 400 - 500 mg / L, which is suitable for the growth of both fish and vegetables. In this system, the ammonia nitrogen of the water returning to the fish pond is less than 0.5 mg / L, and the concentration of nitrite nitrogen is less than 0.2 mg / L. The solid content after concentration by the fish manure concentrator is 3 - 5%.

[0032] The bacteria-algae symbiotic system includes a reactor, which is a raceway pond. The ratio of bacteria to algae in the bacteria-algae symbiotic system is 1:4, and the light-dark ratio is 2:1. Among them, the bacteria are nitrifying bacteria separated from the fluidized bed, and the algae are Phaeodactylum tricornutum with high-efficiency light fixation function and can be used as bait for bass. The foam generated by anaerobic fermentation is introduced into the bacteria-algae symbiotic system, and the algae produced by the bacteria-algae symbiotic system are put into the fish pond as fish bait. In order to achieve the efficient growth and rapid separation of bacteria and algae, a large amount of foam generated by anaerobic fermentation of fish manure is introduced into the reactor (the foam can be fished out and put into the bacteria-algae reactor), and gently stirred slowly to ensure that the bubbles are evenly dispersed into the bacteria-algae symbiotic system and the bubbles do not burst, and then the stirring is stopped. The bubbles contain rich nutrients such as nitrogen, phosphorus, and CO2 and have a certain viscosity (163 mPa·S). On the one hand, it can provide nutrients for the growth of bacteria and algae (the main nutrients are provided by the fish-raising tail water coming out of the aerobic pond) and carbon dioxide (produced by anaerobic fermentation), improve the photosynthesis efficiency, and the growth efficiency of microalgae is increased by more than 10%, realizing emission reduction and carbon fixation; on the other hand, it can realize the separation of bacteria and algae from the liquid surface, reduce the cost of bacteria-algae recovery, and compared with traditional membrane separation and flocculation precipitation separation, the cost is reduced by more than 15% (the cost of bacteria-algae recovery generally accounts for more than 20% of the bacteria-algae cultivation cost). The timely removal of bubbles eliminates the inhibition of the bubbles on the gas-liquid mass transfer efficiency in the anaerobic fermentation system and the destruction of the system stability, and the anaerobic fermentation efficiency is increased by more than 10%. As the photosynthesis of microalgae continues, when the microalgae biomass reaches about 0.8 - 1.0 g / L, the bubbles gradually accumulate on the surface of the reactor. By scraping the bubbles with a scraper and vibrating them with ultrasonic waves, the bubbles can be broken and the algae can be recovered. The cultivated bacteria and algae are collected and then put into the fish pond as fish bait. The bubbles can also be used for the separation of other algae.

[0033] The vegetable cultivation system of the present invention can adopt a vegetable hydroponic NFT system or a vegetable hydroponic DFT system. The influence of this system on the growth of lettuce:

[0034] Through experiments, it is found that lettuce can effectively remove ammonia nitrogen and nitrate nitrogen in the tail water. As Figure 2 shown, we directly use the fish-raising tail water (the water directly coming out of the fish pond) for lettuce hydroponics, and its removal of ammonia nitrogen and nitrate nitrogen is as Figure 2 shown.

[0035] In the vegetable cultivation system, hydroponics is carried out using a vegetable hydroponic NFT system, a vegetable hydroponic DFT system, and ordinary tap water. The growth cycle diagram of the lettuce obtained after hydroponics is as shown in Figure 3, and the detection results of the lettuce are shown in Table 1:

[0036]

[0037] From Figure 3It can be seen that the fresh weight of lettuce grown by NFT using the tail water of the system fish farming (the water of the second auxiliary line) is greater than that of DFT using the tail water of the system fish farming, which is greater than that of NFT using ordinary tap water.

[0038] As can be seen from the table, the tail water of fish farming can appropriately increase the contents of soluble sugar, soluble protein and vitamin C in lettuce, significantly reduce the content of nitrate, and improve the quality of lettuce.

[0039] The influence of this system on the growth of fish: The system contains rich trace elements, such as iron and manganese, which appear in the enzyme systems of biochemical reaction microorganisms as components of coenzymes, prosthetic groups and cofactors, promoting the peristalsis of fish intestines and improving the activity of microorganisms in the intestines. The aquaculture density reaches: 80 - 100 kg / m 3

[0040] Compared with replacing fresh water, the growth cycle of this system for largemouth bass is shortened from 9 - 10 months to 5 - 6 months (500 g), and the fish disease rate is reduced by more than 90%.

[0041] The present invention is not limited to the above embodiments. Those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and purposes of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for promoting the symbiosis of bacteria and algae and efficient recycling by using the foam generated from the fermentation of fish feces, characterized in that: It includes an anaerobic fermentation tank, an aerobic fermentation tank and an algal-bacterial symbiotic system which are connected in sequence. The algal-bacterial symbiotic system includes a reactor. The foam generated by anaerobic fermentation is introduced into the algal-bacterial symbiotic system and slowly stirred to make the bubbles evenly dispersed in the reactor. Then the stirring is stopped. As the photosynthesis of microalgae continues, when the microalgae biomass reaches about 0.8 - 1.0 g / L, the bubbles gradually accumulate on the surface of the reactor. The bubbles are scraped out by a scraper and subjected to ultrasonic vibration, so that the bubbles can be broken and the algae can be recovered. The water passing through the algal-bacterial symbiotic system returns to the fishpond for fish farming.

2. The method for promoting symbiosis of bacteria and algae and efficient recovery by using the foam generated from fish manure fermentation according to claim 1, wherein: The algal-bacterial ratio of the algal-bacterial symbiotic system is 1:4, and the light-dark ratio is 2:

1. The bacteria are nitrifying bacteria separated from the fluidized bed, and the algae are Phaeodactylum tricornutum with high-efficiency light fixation function and can be used as bait for bass.

3. The method for promoting symbiosis of bacteria and algae and efficient recovery by using the foam generated from fish manure fermentation according to claim 2, characterized in that: The fish feces coming out from the bottom of the fishpond are precipitated by a vertical flow sedimentator, and then the fish feces are collected into a fish feces collection pond. The fish feces in the fish feces collection pond are further concentrated, and the concentrated fish feces enter the anaerobic fermentation tank.

4. The method for promoting symbiosis between bacteria and algae and efficient recovery by using the foam generated from fish feces fermentation according to claim 3, wherein: The solid content after concentration by the fish feces concentrator is 3 - 5%.

5. The method for promoting symbiosis of bacteria and algae and efficient recovery by using the foam generated from fish manure fermentation according to claim 4, characterized in that: The algae produced by the algal-bacterial symbiotic system are used as fish bait in the fishpond.

Images