Method for directionally culturing diatom by utilizing culture tail water and application

Abstract

The invention discloses a method for directionally culturing diatom by using culture tail water and application, and belongs to the crossing field of aquaculture and wastewater treatment.The method for directionally culturing diatom in the culture tail water comprises the following steps: S1, precipitation: discharging the culture tail water into a precipitation tank to precipitate silt and large particles; s2, sterilization and algae removal: ultraviolet rays are adopted to irradiate the culture tail water to kill bacteria and original algae in the culture tail water; s3, adjusting the nutrition structure: adjusting the total salinity of the culture tail water to 20-30% o, the silicate content to 500-1000 [mu] mol / L, the phosphate content to 0.6-0.9 mg / L and the ammonium salt content to 4-6 mg / L; s4, algae species and bacteria inoculation and culture: diatom and diatom symbiotic bacteria are inoculated into culture tail water. By using the method provided by the invention, the directional regulation and control of the microalgae community in the culture tail water can be realized, and the removal rate of nutritive salts in the culture tail water and the resource recovery rate are greatly improved. Meanwhile, by-product shellfish organisms can appear on the market through subsequent culture, the economic benefit is improved, and the purification cost is reduced.

Description

Technical Field

[0001] The invention relates to the intersecting field of aquaculture and wastewater treatment, and in particular to a method and application of directional cultivation of diatoms using aquaculture tail water. Background Art

[0002] In order to obtain high yields and high returns during marine aquaculture, a large amount of feed is often required. These unused feeds and animal feces will degrade in the water body, which will lead to an increase in nitrogen and phosphorus in the water body. At present, my country has imposed restrictions on the discharge of marine aquaculture tailwater, and marine aquaculture tailwater must be treated before it can be discharged. Marine aquaculture tailwater is not as toxic as industrial wastewater, so it is very important to achieve resource recycling while treating it. At present, the combination of microalgae and shellfish filter feeding is a commonly used aquaculture tailwater treatment and resource recovery model. This model uses microalgae to grow and absorb nutrients in aquaculture tailwater, and then uses seawater economic shellfish such as razor clams, clams and other beach shellfish to filter and absorb microalgae and other particles, thereby achieving the purpose of nitrogen and phosphorus purification and resource recovery. However, in the current aquaculture tailwater treatment application, the nutrient structure of aquaculture tailwater is not suitable for diatom growth in most cases. At present, the microalgae growth area in the aquaculture tailwater treatment lacks nutrient salt regulation, and is only equipped with aeration and oxygenation facilities. Aeration alone cannot meet the growth of algae, and the absorption of nutrients is insufficient. After subsequent shellfish filtration, the inorganic salts still exceed the standard, and other treatment processes are required, which is time-consuming and labor-intensive. At the same time, the algae and bacteria in the aquaculture tail water are very complex. Directly adding diatom species often has poor effects. It is often difficult for the added algae species to become dominant species. Bacteria and algae compete for nutrients and ecological niches, which can easily lead to the collapse of the microalgae community. Summary of the invention

[0003] The problem to be solved by the present invention is how to improve the survival rate and biomass of diatoms in aquaculture tail water.

[0004] In order to solve the above problems, the present invention provides an ecological purification method for aquaculture tail water, comprising the following steps:

[0005] S1. Sedimentation: discharge the aquaculture tail water into the sedimentation tank to settle the silt and large particles;

[0006] S2. Sterilization and algae elimination: Use ultraviolet light with a wavelength of 254nm to irradiate the aquaculture tail water to kill bacteria and original algae in the aquaculture tail water;

[0007] S3, nutritional structure adjustment: adjust the salt content in the aquaculture tail water, the parameters for adjusting the salt content in the aquaculture tail water include total salinity, silicate content, phosphate content, and ammonium salt content, the total salinity is 20-30‰, the silicate content is 500-1000 μmol / L, the phosphate content is 0.6-0.9 mg / L, and the ammonium salt content is 4-6 mg / L;

[0008] S4. Inoculation and cultivation of algae species and bacteria: Plant diatoms and diatom symbiotic bacteria in aquaculture tail water, culture for 3-7 days under a light intensity of not less than 4000 lux and a light duration of not less than 12 hours per day.

[0009] Compared with traditional aquaculture tail water, the purification method provided by the present invention adds a sterilization and algae elimination link, in which most of the indigenous algae and indigenous microorganisms in the aquaculture tail water are killed by ultraviolet rays, which lays the foundation for diatoms and diatom symbionts to gain advantages and obtain ecological niches in the subsequent competition between diatoms and indigenous algae, and between diatom symbionts and indigenous bacteria. At the same time, ultraviolet irradiation of aquaculture tail water can convert part of the organic matter in the aquaculture tail water into absorbable nutrients. The present invention also adds a nutritional structure adjustment step, in which the present invention optimizes the total salt content and the content ratio of various salts, so that the nutritional structure in the aquaculture tail water is balanced.

[0010] Preferably, in step S4, the diatom species is selected from any one or more of Chaetoceros muehii, Thalassiosira wissensis, Nitzschia closterium, and Cyclotella.

[0011] Preferably, in step S4, the diatom implantation density is determined by the following parameters: the concentration of diatom chlorophyll in the diatom in the aquaculture tail water is 300-500 μg / L.

[0012] Preferably, in step S4, the diatom symbiotic bacteria are selected from any one or more of Marinobacter sp., Alteromonasmacleodii, and Muricauda sp.

[0013] Preferably, in step S4, the planting density of the diatom symbiotic bacteria is 10 4 ~10 6 cell / mL.

[0014] Preferably, in step S1, the precipitation time is greater than or equal to 24 hours.

[0015] Furthermore, the second aspect of the present invention provides an application of the aforementioned method for directional cultivation of diatoms using aquaculture tail water, wherein the application is to co-cultivate diatoms with shellfish so that the diatoms are used as shellfish feed.

[0016] Preferably, when using a shellfish culture pond for polyculture, the height of the shellfish culture pond is not less than 20 cm.

[0017] Preferably, the density of the shellfish in the aquaculture tail water is 50,000 to 200,000 grains / m 2 .

[0018] Preferably, the shellfish is selected from one or more of razor clams, mud clams, green clams, Manila clams, and Meretrix meretrix.

[0019] Existing aquaculture tail water has the following defects:

[0020] 1. The nutrient structure in aquaculture tailwater is unbalanced, and in most cases it is not suitable for diatom growth. At present, the microalgae growth area in aquaculture tailwater treatment lacks nutrient salt regulation, and is only equipped with aeration and oxygenation facilities. Aeration alone cannot meet the growth of algae, and nutrient salt absorption is insufficient. After subsequent shellfish filtration, inorganic salts still exceed the standard, and other treatment processes need to be added, which is time-consuming and labor-intensive.

[0021] 2. The algae and bacteria in the tail water of aquaculture are very complex. Directly adding diatom species often has poor effects. It is often difficult for the added algae species to become dominant species. Bacteria and algae compete for nutrients and ecological niches, which can easily lead to the collapse of the microalgae community. When the tail water of aquaculture is centrally treated, there are tail waters from different aquaculture ponds and factories. Some algae in the tail water may not be suitable for shellfish digestion and absorption, such as cyanobacteria and naked dinoflagellates. In addition, there are pathogens in the tail water of aquaculture. These harmful algae and bacteria are harmful to shellfish treated with tail water of aquaculture.

[0022] The beneficial effects of the present invention are as follows: the aquaculture tailwater purification method provided by the present invention regulates the nutrients and microorganisms of the aquaculture tailwater, including sterilization and algae elimination, nutrient regulation, inoculation of exogenous high-efficiency algae species, diatom symbiotic bacteria regulation and other processes for directional cultivation of diatoms in aquaculture tailwater. In response to defect 1, the present invention uses a nutrient regulation scheme to regulate silicates, phosphates, nitrogen salts, and salinity to achieve the most suitable nutritional state of diatoms, and at the same time, the diatoms can utilize these nitrogen and phosphorus after 3-7 days of growth; in response to defect 2, the present invention performs UV sterilization and algae elimination to reduce the impact of original bacteria and microalgae, and then adds exogenous diatom algae species and diatom symbiotic bacteria to ensure the dominant growth of diatoms. After regulation by the method of the present invention, the proportion of bait diatoms in aquaculture tailwater will be more than 90%, and the diatom biomass will increase by 5-10 times. Combined with the treatment process of shellfish filtering in tailwater, the nutrient removal rate and resource recovery rate of tailwater will be greatly improved.

[0023] In addition, in the ecological purification method of aquaculture effluent provided by the present invention, the final product includes, in addition to aquaculture effluent that meets the discharge standards, shellfish organisms. The shellfish organisms can eventually be cultivated again to become adult shellfish and put on the market, which is beneficial to improving the economic benefits of aquaculture. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a graph showing the growth trend of diatom chlorophyll content in the experimental group and the control group when the factory aquaculture tail water is used as the aquaculture tail water in Example 1 of the present invention;

[0025] Figure 2 This is a graph showing the growth trend of chlorophyll content of green algae in the experimental group and the control group when the factory aquaculture tail water is used as the aquaculture tail water in Example 1 of the present invention;

[0026] Figure 3 It is a detection diagram of the growth trend of diatom chlorophyll content in the experimental group and the control group when the soil pond tail water is used as aquaculture tail water in a specific embodiment of the present invention;

[0027] Figure 4 It is a detection diagram of the growth trend of diatom chlorophyll content in the experimental group and the control group when the soil pond tail water is used as aquaculture tail water in a specific embodiment of the present invention;

[0028] Figure 5 It is a detection diagram of the growth trend of diatom chlorophyll content in the experimental group and the control group when the mixed tail water of industrial tail water and earth pond tail water is used as aquaculture tail water in a specific embodiment of the present invention;

[0029] Figure 6 It is a detection diagram of the growth trend of diatom chlorophyll content in the experimental group and the control group when the mixed tail water of industrial tail water and earth pond tail water is used as aquaculture tail water in a specific embodiment of the present invention;

[0030] Figure 7 The present invention is a flowchart of an ecological purification method for aquaculture tail water provided in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation method and typical parameters of the present invention, and are not used to limit the parameter range described in the present invention. Reasonable changes derived therefrom are still within the scope of protection of the claims of the present invention.

[0032] It should be noted that the endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0033] Example 1

[0034] In this embodiment, the tail water of shrimp factory is used as the aquaculture tail water. After measurement, the original salinity of the aquaculture tail water is 22‰, the silicate is 132 μmol / L, the phosphate is 0.2 mg / L, the ammonium nitrogen is 3.1 mg / L, the nitrite is 0.5 mg / L, the nitrate is 2.2 mg / L, the diatom chlorophyll is 170 μg / L, and the green algae chlorophyll is 421 μg / L.

[0035] S1: The aquaculture tail water was discharged into the sedimentation tank through the ditch and settled for 24 hours, and then divided into a control group and an experimental group.

[0036] S2: The tail water of the control group was not treated, and the tail water of the experimental group was transferred to the sterilization and algae removal pool. There were 5 350W ultraviolet lamps in the sterilization and desiccation pool. The wavelength of the ultraviolet lamp was 254nm. The tail water of the experimental group was irradiated with ultraviolet lamps for 10 minutes. After treatment, the chlorophyll of diatoms and green algae in the tail water of the experimental group was 68μg / L and 102μg / L. The chlorophyll of untreated diatoms and green algae in the control group was 150μg / L and 330μg / L.

[0037] S3: The silicate in the aquaculture tail water of the experimental group and the control group treated in step S2 is adjusted to 500 μmol / L, the phosphate is adjusted to 0.9 mg / L, and the ammonium salt is adjusted to 6 mg / L. The nutritional adjustment is completed.

[0038] S4: After completing step S3, add Chaetoceros algae solution to the control group and the experimental group to control the final diatom chlorophyll to 500 μg / L, add diatom symbiotic bacteria solution Marinobacter sp., Alteromonas macleodii, Muricauda sp., and control the addition concentration to 10 4 cell / mL. After inoculation, the chlorophyll content of diatoms, green algae, nitrogen and phosphorus salts in the aquaculture tail water was tested daily. The test results were as follows: Figure 1 and Figure 2 As shown, the diatoms in the aquaculture tail water have been on an upward trend for 7 days, and increased from 170μg / L to 2500μg / L after 7 days. The green algae in the UV-treated group has remained at a low level, and the nitrogen and phosphate salts in the tail water have dropped to below 0.01mg / L. The control group also carried out nutrient salt regulation and diatom and bacteria addition, but without UV irradiation treatment, the green algae has been on an upward trend, reaching 1100μg / L, while the diatoms have remained at a low level.

[0039] Green algae cannot be consumed by shellfish and the diatom content in the control group was too low; therefore, the shellfish consumption diatom experiment could not be conducted in the control group.

[0040] S5: Build a shellfish culture pond with a length, width and height of 4*3*0.5 meters. Put 55,000 grains / m into the shellfish culture pond. 2 After adding the razor clams, the aquaculture tail water containing diatoms treated in step S4 is added. It is determined that the aquaculture tail water rich in diatoms enters the razor clam shellfish plane flow pond for utilization, and the diatoms are fully utilized after the tail water stays in the shellfish aquaculture pond for 1 hour.

[0041] Example 2

[0042] In this embodiment, soil pond tail water is used as aquaculture tail water. After measurement, the original salinity of the aquaculture tail water is 23‰, the silicate is 85 μmol / L, the phosphate is 0.32 mg / L, the ammonium nitrogen is 0.85 mg / L, the nitrite is 0.3 mg / L, the nitrate is 2.0 mg / L, the diatom chlorophyll is 89 μg / L, and the green algae chlorophyll is 35 μg / L.

[0043] S1: The aquaculture tail water was discharged into the sedimentation tank through the ditch and settled for 24 hours, and then divided into a control group and an experimental group.

[0044] S2: The tail water of the control group was not treated, and the tail water of the experimental group was transferred to the sterilization and algae removal pool. There were 5 350W ultraviolet lamps in the sterilization and desiccation pool. The wavelength of the ultraviolet lamp was 254nm. The tail water of the experimental group was irradiated with ultraviolet lamps for 10 minutes. After treatment, the chlorophyll of diatoms and green algae in the tail water of the experimental group was 19μg / L and 18μg / L. The chlorophyll of untreated diatoms and green algae in the control group was 93μg / L and 30μg / L.

[0045] S3: The silicate in the aquaculture tail water of the experimental group and the control group treated in step S2 is adjusted to 500 μmol / L, the phosphate is adjusted to 0.6 mg / L, and the ammonium salt is adjusted to 4 mg / L. The nutritional adjustment is completed.

[0046] S4: After completing step S3, add Chaetoceros algae solution to the control group and the experimental group to control the final diatom chlorophyll to 323 μg / L, and add diatom symbiotic bacteria solution Marinobacter sp., Alteromonas macleodii, and Muricauda sp., and the added concentration is controlled at 2×10 5 cell / mL. After inoculation, the chlorophyll content of diatoms, green algae, nitrogen and phosphorus salts in the aquaculture tail water was tested daily. The test results were as follows: Figure 3 and Figure 4 As shown in the figure, the diatoms in the aquaculture tail water have been on an upward trend for 7 days, and increased to 2348μg / L after 7 days. The green algae in the UV-treated group has remained at a low level, and the nitrogen and phosphate salts in the tail water have dropped to below 0.01mg / L. The control group also carried out nutrient salt regulation and diatom and bacteria addition, but without UV irradiation treatment. After 2 days of growth, the diatoms rose to about 830μg / L and then began to decline, eventually falling to about 300μg / L, and the green algae remained at a low level.

[0047] The green algae bait value was low and the diatom content in the control group was too low, so the shellfish consumption of diatoms experiment could not be conducted in the control group.

[0048] S5: Build a shellfish culture pond with a length, width and height of 4*3*0.5 meters. Put 150,000 grains / m into the shellfish culture pond.2 After the mud clams are added, the aquaculture tail water containing diatoms treated in step S4 is added. It has been determined that the aquaculture tail water rich in diatoms enters the mud clams shellfish plane flow pond for utilization, and the diatoms are fully utilized after the tail water stays in the shellfish aquaculture pond for 1 hour.

[0049] Example 3

[0050] In this embodiment, mixed tail water of factory tail water and earth pond tail water is used as aquaculture tail water, and the aquaculture tail water is affected by rain water and mixed with some natural precipitation. It has been measured that the original salinity of the aquaculture tail water is 15‰, the silicate is 53 μmol / L, the phosphate is 0.28 mg / L, the ammonium nitrogen is 1.1 mg / L, the nitrite is 0.48 mg / L, the nitrate is 1.9 mg / L, the diatom chlorophyll is 90 μg / L, and the cyanobacteria chlorophyll is 20 μg / L.

[0051] S1: The aquaculture tail water was discharged into the sedimentation tank through the ditch and settled for 24 hours, and then divided into a control group and an experimental group.

[0052] S2: The tail water of the control group was not treated, and the tail water of the experimental group was transferred to the sterilization and algae removal pool. There were 5 350W ultraviolet lamps in the sterilization and algae removal pool. The wavelength of the ultraviolet lamp was 254nm. The tail water of the experimental group was irradiated with ultraviolet lamps for 10 minutes. After treatment, the chlorophyll of diatoms in the tail water of the experimental group was 22μg / L, and the chlorophyll of cyanobacteria was 0μg / L. The chlorophyll of untreated diatoms in the control group was 60μg / L, and the chlorophyll of cyanobacteria was 5.7μg / L.

[0053] S3: The total salinity of the aquaculture tail water of the experimental group and the control group treated in step S2 is adjusted to 22‰, the silicate is adjusted to 1000 μmol / L, the phosphate is adjusted to 0.8 mg / L, and the ammonium salt is adjusted to 5 mg / L. The nutritional adjustment is completed.

[0054] S4: After completing step S3, add Chaetoceros algae solution to the control group and the experimental group to control the final diatom chlorophyll to 470 μg / L, add diatom symbiotic bacteria solution Marinobacter sp., Alteromonas macleodii, Muricauda sp., and control the addition concentration to 10 6 cell / mL. After the cultivation is completed, the chlorophyll content of diatoms, chlorophyll content of cyanobacteria, and nitrogen and phosphorus salts in the aquaculture tail water are tested daily. The test results are as follows: Figure 5 and Figure 6As shown in the figure, the diatoms in the aquaculture tail water have been on an upward trend for 7 days, and increased to 3016μg / L after 7 days. The cyanobacteria in the UV-treated group have remained at a low level, and the nitrogen and phosphate salts in the tail water have dropped to below 0.01mg / L. The control group also carried out nutrient salt regulation and diatom and bacteria addition, but without UV irradiation treatment. The diatoms began to decline after reaching 1500μg / L on the third day, and were only around 400μg / L on the seventh day. The cyanobacteria have remained at a low level.

[0055] Cyanobacteria cannot be consumed by shellfish and the diatom content in the control group was too low; therefore, the shellfish consumption diatom experiment could not be conducted in the control group.

[0056] S5: Build a shellfish culture pond with a length, width and height of 4*3*0.5 meters. Put 55,000 grains / m into the shellfish culture pond. 2 After the green clams, the aquaculture tail water containing diatoms treated in step S4 is added. It is determined that the aquaculture tail water rich in diatoms enters the green clam shellfish plane flow pond for utilization, and the diatoms are fully utilized after the tail water stays in the shellfish aquaculture pond for 1 hour.

[0057] It can be seen from the above three embodiments that the contents of elements such as nitrogen and phosphorus in the aquaculture tail water treated by the aquaculture tail water ecological purification method provided by the present invention are greatly reduced, and the treated aquaculture tail water can be directly discharged.

[0058] Unless otherwise defined, all terms, symbols and other scientific terms used herein are intended to have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. In some cases, the terms with conventionally understood meanings are defined herein for the purpose of illustrating or facilitating reference, and such definitions herein should not be construed as indicating significant differences from conventional understandings in the art. The technical methods described or cited herein are generally well understood by those skilled in the art and are adopted by conventional methods. Unless otherwise stated, the use of commercially available reagents and instruments is carried out in accordance with the schemes and parameters given by the manufacturer.

[0059] Although the disclosure is disclosed as above, the protection scope of the disclosure is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for directional cultivation of diatoms using aquaculture tail water, characterized in that: The following steps are involved: S1. Sedimentation: discharge the aquaculture tail water into the sedimentation tank to settle the silt and large particles; S2. Sterilization and algae elimination: Use ultraviolet light with a wavelength of 254nm to irradiate the aquaculture tail water to kill bacteria and original algae in the aquaculture tail water; S3, nutritional structure adjustment: adjust the salt content in the aquaculture tail water, the parameters for adjusting the salt content in the aquaculture tail water include total salinity, silicate content, phosphate content, and ammonium salt content, the total salinity is 20-30‰, the silicate content is 500-1000 μmol / L, the phosphate content is 0.6-0.9 mg / L, and the ammonium salt content is 4-6 mg / L; S4. Inoculation and cultivation of algae species and bacteria: Inoculate diatoms and diatom symbiotic bacteria into the aquaculture tail water, and cultivate for 3-7 days under a light intensity of not less than 4000 lux and a lighting time of not less than 12 hours / day.

2. The method for directional cultivation of diatoms using aquaculture tail water according to claim 1, characterized in that: In step S4, the diatom species is selected from any one or more of Chaetoceros muelleri, Thalassiosira wiseri, Nitzschia closterium, and Cyclotella.

3. The method for directional cultivation of diatoms using aquaculture tail water as claimed in claim 1, characterized in that: In step S4, the diatom inoculation density is determined by the following parameters: the concentration of diatom chlorophyll in the aquaculture tail water is 300-500 μg / L.

4. The method for directional cultivation of diatoms using aquaculture tail water according to claim 1, characterized in that: In the step S4, the diatom symbiotic bacteria are selected from any one or more of Marinobacter sp., Alteromonas macleodii, and Muricauda sp.

5. The method for directional cultivation of diatoms using aquaculture tail water according to claim 1, characterized in that: In step S4, the planting density of the diatom symbiotic bacteria is 10 4 ~10 6 cell / mL.

6. The method for directional cultivation of diatoms using aquaculture tail water according to claim 1, characterized in that: In the step S1, the precipitation time is greater than or equal to 24 hours.

7. An application of the method for directional cultivation of diatoms using aquaculture tail water according to any one of claims 1 to 6, characterized in that: The application is to culture diatoms together with shellfish so that the diatoms can be used as shellfish bait.

8. The use of the method for directional cultivation of diatoms using aquaculture tail water as claimed in claim 7, characterized in that: When using shellfish culture ponds for polyculture, the height of the shellfish culture ponds shall not be less than 20 cm.

9. The use of the method for directional cultivation of diatoms using aquaculture tail water as claimed in claim 7, characterized in that: The density of the shellfish in the aquaculture tail water is 50,000 to 200,000 grains / m 2 .

10. The use of the method for directional cultivation of diatoms using aquaculture tail water as claimed in claim 7, characterized in that: The shellfish is selected from one or more of razor clams, mud clams, green clams, Manila clams, and Meretrix meretrix.

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