A method for biological treatment of nuclear contaminated wastewater

Abstract

The invention discloses a method for biological treatment of nuclear contaminated wastewater, which belongs to the field of environmental protection. The nuclear contaminated wastewater is first pretreated and then treated in two stages; the first stage treatment: adsorption by emergent plants; the second stage treatment: adsorption by marine microalgae. The traditional method has a good effect on removing tritium and carbon 14, but the equipment is complex, the operation is troublesome, the cost is high, and there is secondary pollution. The invention adopts plants and marine microalgae to treat nuclear wastewater in two stages, which not only has simple equipment, convenient operation, low cost, but also has a high pollutant removal rate.

Description

Technical Field

[0001] The invention belongs to the field of environmental protection, and more specifically relates to a method for biologically treating nuclear contaminated wastewater. Background Art

[0002] Nuclear wastewater treatment is a complex and sensitive issue, which requires comprehensive consideration of safety, environmental protection, economy and society. Nuclear wastewater contains a large amount of radioactive substances such as tritium, strontium 90, cobalt 16, iodine 129, carbon 14, technetium 99, etc., and the treatment cost is high.

[0003] Regarding the treatment method of nuclear contaminated wastewater, the Institute of Chemical Defense of the Academy of Military Sciences of the People's Liberation Army has invented a method for enriching tritium and carbon 14 in radioactive wastewater using cyanobacteria (CN202310110694.3). Anabaena, Nostoc, Oscillatoria and Spirulina are inoculated in BG11 culture medium respectively, and cyanobacterial stock solution is obtained by culture, wherein the cyanobacterial stock solution is Anabaena stock solution, Nostoc stock solution, Oscillatoria stock solution or Spirulina stock solution, and the cyanobacterial stock solution is centrifuged and added with BG11 culture medium to obtain cyanobacterial concentrate. After centrifuging the cyanobacterial stock solution, it is mixed with sodium alginate solution, and then CaCl2 solution is added to obtain cyanobacterial agent, and the cyanobacterial concentrate or cyanobacterial agent is added to radioactive wastewater containing tritium and carbon 14. This method is effective in removing tritium and carbon 14, but the equipment is complex, the operation is cumbersome, and the cost is high.

[0004] Jiang Lijun invented a method for treating nuclear wastewater (CN202310316784.8), which first uses clay minerals to adsorb, absorb and solidify the nuclear wastewater, and then uses parallel well technology to permanently seal the solidified nuclear wastewater deep in the stratum and make it harmless. This method is not only labor-intensive, but also will cause soil pollution over time.

[0005] Therefore, how to provide a low-cost and easy-to-operate nuclear wastewater treatment method is a technical problem that technical personnel in this field urgently need to solve. Summary of the invention

[0006] In order to solve the current technical problems, the present invention provides a method for biological treatment of nuclear contaminated wastewater. The nuclear wastewater is treated in two stages. In the first stage, large freshwater plants are used for adsorption, and in the second stage, marine microalgae are used for adsorption. Not only is the equipment simple, the operation is convenient, the cost is low, but also the pollutant removal rate is high.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A method for biologically treating nuclear contaminated wastewater, wherein the nuclear contaminated wastewater is first pretreated and then treated in two stages; specifically, the following steps are included:

[0009] First-level treatment: Adsorption by emergent plants;

[0010] Second level treatment: adsorption by marine microalgae.

[0011] Preferably, the pretreatment is to add alum to the nuclear wastewater, stir and let it stand, then take the supernatant and enter the first stage treatment.

[0012] Add 120-150 grams of alum per cubic meter of nuclear contaminated wastewater.

[0013] Preferably, the emergent plants in the first stage treatment include cattail, water hyacinth and Chinese arrowhead; 1-3 cattails, 3-5 water hyacinths and 2-6 Chinese arrowheads are inoculated per square meter of water surface.

[0014] The invention uses cattail, water hyacinth and Chinese arrowhead for planting in combination, which has a synergistic effect and a significant adsorption effect. Moreover, changes in the proportion and planting density of the three plants will also affect the adsorption effect.

[0015] The nuclear contaminated wastewater after pretreatment is introduced into the first treatment pool, and fertilizer is added to the first treatment pool for the growth of emergent plants. After 45-60 days of cultivation, the emergent plants are cut off and the pool water enters the second-level treatment.

[0016] Preferably, the first treatment pool has an area of ​​1000-4000 square meters and a water depth of 50-75 centimeters. The pool is rectangular with a length-to-width ratio of 2:1. The pool runs east-west, and the volume of the introduced pretreated nuclear wastewater accounts for 15-24% of the total volume of the pool water.

[0017] The amount of fertilizer applied in the first treatment pool: add 1-1.5 kg of NH4NO3 and 0.5-0.8 kg of KH2PO4 per 100 square meters of water surface.

[0018] Preferably, the second-stage treatment adopts a raceway culture pool, each raceway culture pool is equipped with an impeller water wheel, the flow of pool water can make the nutrients in the water evenly distributed, and can also prevent the algae cells from sinking or agglomerating together and causing death. The marine microalgae include Chlorella, Subcordiformes and Isochrysis galbana; the raceway culture pool is inoculated with 6 million to 8 million Chlorella / ml, 120,000 to 180,000 Subcordiformes / ml and 500,000 to 900,000 Isochrysis galbana / ml.

[0019] The present invention compounds three kinds of microalgae, namely, Chlorella vulgaris, Platymonas subcordiformis and Isochrysis galbana, which has a synergistic effect on the pollutant absorption effect. Changes in the inoculation ratio and inoculation amount of the three kinds of microalgae will also affect the adsorption effect.

[0020] Preferably, the racetrack culture pool is filled with a culture solution with a depth of 40-50 cm, and the culture solution components, by mass, are: 80-85 parts of seawater filtered through absorbent cotton, 15-18 parts of pool water after the first stage treatment, 0.03-0.07 parts of NH4NO3, 0.0004-0.0008 parts of KH2PO4, 0.00005-0.00009 parts of ferric citrate, and 0.3-0.8 parts of NaHCO3;

[0021] Preferably, the microalgae are inoculated and cultured for 72-96 hours, and then the algae solution is centrifuged at a speed of 6000-7500 rpm to remove the microalgae, and the supernatant is the treated clean water; the microalgae culture conditions are: light intensity 6000-7500 lux, temperature 23-26°C.

[0022] Beneficial effects of the present invention:

[0023] The nuclear contaminated wastewater treatment method provided by the present invention is easy to operate, has low requirements on production equipment, can be promoted and produced on a large scale, has excellent market benefits, and has a high pollutant removal rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0025] Figure 1 Schematic diagram of the raceway-type culture pool used in the second-stage treatment in the embodiment of the present invention. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] The alum used in the pretreatment of the embodiment of the present invention, the fertilizers NH4NO3 and KH2PO4 used in the first stage treatment, and the NH4NO3, KH2PO4, ferric citrate and NaHCO3 used in the second stage treatment process are all of chemically pure grade;

[0028] In order to prevent radiation, operators must wear leather jackets, leather pants, hats, gloves and goggles during the entire operation (specific implementation shall be in accordance with relevant national regulations).

[0029] Example 1

[0030] A method for biological treatment of nuclear contaminated wastewater, specifically comprising the following steps:

[0031] Pretreatment: The nuclear wastewater is introduced into a cement pool with a length of 4 meters, a width of 3 meters, a depth of 1 meter and a water depth of 75 centimeters. 120 grams of alum is added to each cubic meter of water. The water is stirred for 3 hours and allowed to stand for 24 hours. The supernatant is taken and sent to the first stage of treatment.

[0032] First-level treatment: The pretreated nuclear wastewater is introduced into a pool planted with three freshwater aquatic plants: cattail, water hyacinth, and Chinese arrowhead. The pool area is 1,500 square meters and the water depth is 55 centimeters. The pool is rectangular with a length-to-width ratio of 2:1. The pool is east-west oriented to receive more sunlight. The volume of the introduced nuclear wastewater is 18% of the total pool water volume. The pool has a cement pool wall and a mixed brick structure, and the bottom is a natural soil bottom. As long as there is no seepage or leakage, the inoculation of the three aquatic plants will be fine. The amount of fertilizer is 1 cattail, 3 water hyacinths and 3 Chinese arrowheads per square meter of water surface. The average temperature is 22℃. The pond water is ordinary fresh water. The amount of fertilizer is: 1 kg of NH4NO3 per 100 square meters of water surface, and 0.6 kg of KH2PO4 per 100 square meters of water surface. These two fertilizers are dissolved in water and evenly sprinkled throughout the pond. The pond is an outdoor open pond. The cattail, water hyacinth and Chinese arrowhead planted in it grow naturally under sunlight. The pond is cultivated for 48 days, and then the plants are cut off and the pond water enters the second level of treatment;

[0033] Second level treatment: The microalgae culture pool adopts a raceway culture pool (see attached Figure 1 ), a 42 cm deep culture solution was added to the raceway culture pool, the composition of the culture solution: 80 parts of seawater filtered by cotton wool, 15 parts of pool water after the first stage of treatment, 0.03 parts of NH4NO3, 0.0005 parts of KH2PO4, 0.00006 parts of ferric citrate, 0.4 parts of NaHCO3, inoculated with three kinds of marine microalgae: Chlorella vulgaris, Platymonas subcordiformis, and Isochrysis spherica; 6 million Chlorella vulgaris / ml, 140,000 Platymonas subcordiformis / ml, and 500,000 Isochrysis globosum / ml, three kinds of microalgae are mixed and cultured, the light intensity for culturing microalgae is 6200lux, the temperature is 23℃, each pool is equipped with an impeller waterwheel, the impeller waterwheel is started to make the culture liquid run in the pool, the waterwheel rotates at a speed that makes the algae cells always suspended in the water body without sinking, the culture is for 75 hours, and then the algae liquid is centrifuged in a centrifuge, the centrifuge speed is 6000 revolutions per minute, the microalgae are removed, and the supernatant is the treated clean water, and the treatment is completed.

[0034] Example 2

[0035] A method for biological treatment of nuclear contaminated wastewater, specifically comprising the following steps:

[0036] Pretreatment: The nuclear wastewater is introduced into a cement pool with a length of 4 meters, a width of 3 meters, a depth of 1 meter and a water depth of 75 centimeters. 135 grams of alum is added to each cubic meter of water. The water is stirred for 3 hours and allowed to stand for 24 hours. The supernatant is taken and sent to the first stage of treatment.

[0037] First-level treatment: The pretreated nuclear wastewater is introduced into a pool planted with three freshwater aquatic plants: cattail, water hyacinth, and Chinese arrowhead. The pool area is 2,000 square meters and the water depth is 50 centimeters. The pool is rectangular with a length-to-width ratio of 2:1. The pool is east-west oriented to receive more sunlight. The volume of nuclear wastewater introduced is 20% of the total pool water volume. The pool has a cement pool wall and a mixed brick structure. The bottom is a natural soil bottom. As long as there is no seepage or leakage, the inoculation amount of the three aquatic plants is , 2 cattails, 3 water hyacinths, and 3 Chinese arrowheads were inoculated per square meter of water surface, the average temperature was 23℃, the pond water was ordinary fresh water, the fertilizer amount was: 1.2 kg of NH4NO3 per 100 square meters of water surface, 0.7 kg of KH2PO4 per 100 square meters of water surface, these two fertilizers were dissolved in water and evenly sprinkled throughout the pond, the pond was an outdoor open pond, using sunlight to allow the cattails, water hyacinths, and Chinese arrowheads to grow naturally, and the cultivation lasted for 55 days, after which the plants were cut off and the pond water entered the second level of treatment;

[0038] Second level treatment: The microalgae culture pool adopts a raceway culture pool (see attached Figure 1 ), a 46 cm deep culture solution was added to the raceway culture pool, the composition of the culture solution: 83 parts of seawater filtered by cotton wool, 17 parts of pool water after the first stage of treatment, 0.04 parts of NH4NO3, 0.0006 parts of KH2PO4, 0.00008 parts of ferric citrate, 0.5 parts of NaHCO3, inoculated with three kinds of marine microalgae: Chlorella vulgaris, Platymonas subcordiformis, and Isochrysis spherica; 7 million Chlorella vulgaris / ml, 150,000 Platymonas subcordiformis / ml, and 600,000 Isochrysis globosum / ml, three kinds of microalgae are mixed and cultured, the light intensity for culturing microalgae is 6500lux, the temperature is 25℃, each pool is equipped with an impeller waterwheel, the impeller waterwheel is started to make the culture liquid run in the pool, the waterwheel rotates at a speed that makes the algae cells always suspended in the water body without sinking, the culture is carried out for 85 hours, and then the algae liquid is centrifuged in a centrifuge at a speed of 7000 revolutions per minute to remove the microalgae, and the supernatant is the treated clean water, and the treatment is completed.

[0039] Example 3

[0040] A method for biological treatment of nuclear contaminated wastewater, specifically comprising the following steps:

[0041] Pretreatment: The nuclear wastewater is introduced into a cement pool with a length of 4 meters, a width of 3 meters, a depth of 1 meter and a water depth of 75 centimeters. 145 grams of alum is added to each cubic meter of water. The water is stirred for 3 hours and allowed to stand for 24 hours. The supernatant is taken and sent to the first stage of treatment.

[0042] First-level treatment: The pretreated nuclear wastewater is introduced into a pool planted with three freshwater aquatic plants: cattail, water hyacinth, and Chinese arrowhead. The pool area is 3,000 square meters and the water depth is 60 cm. The pool is rectangular with a length-to-width ratio of 2:1. The pool is east-west oriented to receive more sunlight. The volume of the introduced nuclear wastewater is 24% of the total pool water volume. The pool has a cement pool wall and a mixed brick structure. The bottom is a natural soil bottom. As long as there is no seepage or leakage, the inoculation amount of the three aquatic plants is 3 cattails, 4 water hyacinths, and 5 Chinese arrowheads per square meter of water surface. The average temperature is 24℃. The pool water is ordinary fresh water. Fertilizer amount: NH4NO 3, 1.5 kg per 100 square meters of water surface, 0.8 kg per 100 square meters of KH2PO4. These two fertilizers are dissolved in water and evenly sprinkled throughout the pond. The pond is an outdoor open pond, which uses sunlight to allow the cattail, water hyacinth, and Chinese arrowhead to grow naturally. After 60 days of cultivation, the plants are cut off and the pond water enters the second level of treatment.

[0043] Second level treatment: The microalgae culture pool adopts a raceway culture pool (see attached Figure 1 ), a 48 cm deep culture solution was added to the raceway culture pool, the composition of the culture solution was: 88 parts of seawater filtered by cotton wool, 17 parts of pool water after the first stage treatment, 0.06 parts of NH4NO3, 0.0006 parts of KH2PO4, 0.00009 parts of ferric citrate, 0.7 parts of NaHCO3, and three kinds of marine microalgae were inoculated: Chlorella vulgaris, Platymonas subcordiformis, and Isochrysis spherica; 8 million Chlorella vulgaris / ml, 160,000 Platymonas subcordiformis / ml, 85 Ten thousand Isochrysis galbana / ml, three kinds of microalgae were mixed and cultured, the light intensity for culturing microalgae was 7500lux, the temperature was 26℃, each pool was equipped with an impeller waterwheel, the impeller waterwheel was started to let the culture liquid run in the pool, the waterwheel rotated at a speed that made the algae cells always suspended in the water body without sinking, cultured for 90 hours, and then the algae liquid was centrifuged in a centrifuge, the centrifuge speed was 7000 rpm, the microalgae were removed, and the supernatant was the treated clean water.

[0044] Comparative Example 1

[0045] Pretreatment: The nuclear wastewater is introduced into a cement pool with a length of 4 meters, a width of 3 meters, a depth of 1 meter and a water depth of 75 centimeters. 145 grams of alum is added to each cubic meter of water. The water is stirred for 3 hours and allowed to stand for 24 hours. The supernatant is taken and sent to the first stage of treatment.

[0046] The first level of treatment: the pretreated nuclear wastewater is introduced into a pool planted with three freshwater aquatic plants: Salvinia, Water Celery, and Potamogeton. The pool area is 2400 square meters, the water depth is 60 cm, the pool is rectangular, the length-to-width ratio is 2:1, the pool is east-west, the purpose is to receive more sunlight, the volume of the introduced nuclear wastewater is 18% of the total pool volume, the pool has a cement pool wall, a mixed brick structure, and a natural soil bottom. As long as there is no seepage or leakage, the inoculation amount of the three aquatic plants is 3 Salvinia, 3 Water Celery, and 4 Potamogeton per square meter of water surface. The average temperature is 24℃, the pool water is ordinary fresh water, and the amount of fertilizer is NH4NO 3, 1.2 kg per 100 square meters of water surface, 0.6 kg per 100 square meters of water surface. These two fertilizers are dissolved in water and evenly sprinkled throughout the pool. The pool is an outdoor open pond, which uses sunlight to allow the planted Salvinia, Water celery, and Potamogeton crescentus to grow naturally. The plants are cultivated for 54-60 days, then cut off and the removal rate of the main components in the nuclear wastewater is measured.

[0047] Comparative Example 2

[0048] Pretreatment: The nuclear wastewater is introduced into a cement pool with a length of 4 meters, a width of 3 meters, a depth of 1 meter and a water depth of 75 centimeters. 145 grams of alum is added to each cubic meter of water. The water is stirred for 3 hours and allowed to stand for 24 hours. The supernatant is taken and sent to the first stage of treatment.

[0049] First-level treatment: The microalgae culture pool adopts a raceway culture pool (see attached Figure 1 ), the raceway culture pool was filled with 48 cm deep culture solution and decontaminated with three types of marine microalgae. The culture solution comprises 85 parts of seawater filtered by absorbent cotton, 13 parts of nuclear contaminated wastewater, 0.04 parts of NH4NO3, 0.0006 parts of KH2PO4, 0.00008 parts of ferric citrate, and 0.5 parts of NaHCO3. Three kinds of marine microalgae, namely, Chaetoceros rothenbergii, Skeleton stripe algae, and Brown finger algae, are inoculated; 300,000 Chaetoceros rothenbergii / ml, 250,000 Skeleton stripe algae / ml, and 450,000 Brown finger algae / ml are inoculated, and the three kinds of microalgae are mixed and cultured. The light intensity for culturing the microalgae is 7500±1500lux, and the fluorescent lamp is used for lighting; the temperature is 25±2℃, and the temperature is controlled by air conditioning; an air pump is installed, and the air volume is 6-8 liters / minute, so that the algae cells are always suspended in the water body and do not sink. The culture is carried out for 96 hours, and then the algae solution is centrifuged in a centrifuge at a speed of 6500 revolutions / minute to remove the microalgae. The supernatant is the treated clean water, and the treatment is completed.

[0050] Comparative Example 3

[0051] Pretreatment: The nuclear wastewater is introduced into a cement pool with a length of 4 meters, a width of 3 meters, a depth of 1 meter and a water depth of 75 centimeters. 145 grams of alum is added to each cubic meter of water. The water is stirred for 3 hours and allowed to stand for 24 hours. The supernatant is taken and sent to the first stage of treatment.

[0052] The first level of treatment: the pretreated nuclear wastewater is introduced into a pool planted with three freshwater aquatic plants: Salvinia, Water Celery, and Potamogeton. The pool area is 2400 square meters, the water depth is 60 cm, the pool is rectangular, the length-to-width ratio is 2:1, the pool is east-west, the purpose is to receive more sunlight, the volume of the introduced nuclear wastewater is 18% of the total pool volume, the pool has a cement pool wall, a mixed brick structure, and a natural soil bottom. As long as there is no seepage or leakage, the inoculation amount of the three aquatic plants is 3 Salvinia, 3 Water Celery, and 4 Potamogeton per square meter of water surface. The average temperature is 24℃, the pool water is ordinary fresh water, and the amount of fertilizer is NH4NO 3, 1.2 kg per 100 square meters of water surface, 0.6 kg per 100 square meters of KH2PO4. These two fertilizers are evenly sprinkled in the whole pond after being dissolved in water. The pond is an outdoor open pond, which uses sunlight to allow the planted water spinach, water celery, and pondweed to grow naturally. The cultivation lasts for 54-60 days, and then the plants are cut off and the pond water enters the second level of treatment.

[0053] Second level treatment: The microalgae culture pool adopts a raceway culture pool (see attached Figure 1 ), the raceway culture pool was filled with 48 cm deep culture solution and decontaminated with three types of marine microalgae. The culture solution comprises 85 parts of seawater filtered by absorbent cotton, 13 parts of nuclear contaminated wastewater, 0.04 parts of NH4NO3, 0.0006 parts of KH2PO4, 0.00008 parts of ferric citrate, and 0.5 parts of NaHCO3. Three kinds of marine microalgae, namely, Chaetoceros rothenbergii, Skeleton stripe algae, and Brown finger algae, are inoculated; 300,000 Chaetoceros rothenbergii / ml, 250,000 Skeleton stripe algae / ml, and 450,000 Brown finger algae / ml are inoculated, and the three kinds of microalgae are mixed and cultured. The light intensity for culturing the microalgae is 7500±1500lux, and the fluorescent lamp is used for lighting; the temperature is 25±2℃, and the temperature is controlled by air conditioning; an air pump is installed, and the air volume is 6-8 liters / minute, so that the algae cells are always suspended in the water body and do not sink. The culture is carried out for 96 hours, and then the algae solution is centrifuged in a centrifuge at a speed of 6500 revolutions / minute to remove the microalgae. The supernatant is the treated clean water, and the treatment is completed.

[0054] Table 1 Original concentrations of main components of nuclear waste water in Examples 1-3 and Comparative Examples 1-3

[0055] Element tritium Suspended solids SS Biochemical oxygen demand BOD5 Chemical oxygen demand (COD) Ammonia nitrogen Fluoride unit Bq / LA mg / L mg / L mg / L mg / L mg / L concentration 1956 29.4 46.3 21.3 0.8 7.6

[0056] Table 2 Removal rate of main components of nuclear wastewater after first-stage treatment in Example 1-3 (%)

[0057]

[0058] Table 3 Removal rate of main components of nuclear waste water in Examples 1-3 and Comparative Examples 1-3 (%)

[0059]

[0060]

[0061] It can be seen from Table 3 that the removal rates of wastes in nuclear contaminated wastewater by Comparative Examples 1-3 are not as high as those of Examples 1-3.

[0062] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0063] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for biological treatment of nuclear contaminated wastewater, characterized in that: The nuclear contaminated wastewater is first pretreated and then treated in two stages; the pretreatment is to add alum to the nuclear wastewater, stir it, let it stand, take the supernatant, and enter the first stage of treatment; First-stage treatment: three aquatic plants, namely cattail, water hyacinth and Chinese arrowhead, are used for adsorption; 1-3 cattails, 3-5 water hyacinths and 2-6 Chinese arrowheads are inoculated per square meter of water surface; the pre-treated nuclear contaminated wastewater is introduced into the first treatment pool, fertilizer is added to the first treatment pool for the growth of cattail, water hyacinth and Chinese arrowhead, cattail, water hyacinth and Chinese arrowhead are cut off after 45-60 days of cultivation, and the pool water enters the second-stage treatment; the first treatment pool has an area of ​​1000-4000 square meters, a water depth of 50-75 centimeters, a rectangular pool with a length-to-width ratio of 2:1, and an east-west orientation, and the volume of the pre-treated nuclear wastewater introduced is 15-24% of the total volume of the pool water; The second-stage treatment adopts marine microalgae adsorption. The second-stage treatment adopts a raceway culture pool, and each raceway culture pool is equipped with an impeller water wheel; the marine microalgae include Chlorella, Subcordiformes and Isochrysis galbana; the raceway culture pool is inoculated with 6 million to 8 million Chlorella / ml, 120,000 to 180,000 Subcordiformes / ml and 500,000 to 900,000 Isochrysis galbana / ml.

2. A method for biological treatment of nuclear contaminated wastewater according to claim 1, characterized in that: Add 120-150 grams of alum per cubic meter of nuclear contaminated wastewater.

3. The method for biological treatment of nuclear contaminated wastewater according to claim 1, characterized in that: The amount of fertilizer applied in the first treatment pool: add 1-1.5 kg of NH4NO3 and 0.5-0.8 kg of KH2PO4 per 100 square meters of water surface.

4. The method for biological treatment of nuclear contaminated wastewater according to claim 1, characterized in that: The racetrack culture pool is filled with 40-50 cm deep culture solution. The components of the culture solution, by mass, are: 80-85 parts of seawater filtered through cotton wool, 15-18 parts of pool water after the first stage treatment, 0.03-0.07 parts of NH4NO3, 0.0004-0.0008 parts of KH2PO4, 0.00005-0.00009 parts of ferric citrate, and 0.3-0.8 parts of NaHCO3.

5. The method for biological treatment of nuclear contaminated wastewater according to claim 1, characterized in that: After inoculating the microalgae, the microalgae are cultured for 72-96 hours, and then the algae liquid is centrifuged at a speed of 6000-7500 revolutions per minute to remove the microalgae. The supernatant is the treated clean water. The microalgae culture conditions are: light intensity 6000-7500 lux, temperature 23-26°C.

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