WO2023080877A1

WO2023080877A1 - Production and application of gas bubbled immobilized microalgae culture in water or wastewater treatment process

Info

Publication number: WO2023080877A1
Application number: PCT/TR2022/051245
Authority: WO
Inventors: Serdar GONCU; Emre TURGUT; Eda Tuna OZTURK
Original assignee: Eskisehi̇r Teknik Universitesi
Priority date: 2021-11-05
Filing date: 2022-11-04
Publication date: 2023-05-11

Abstract

The invention relates to a nozzle for the production of a microalgae culture with a gas bubbled structure in immobilized form and the use of the microalgae culture with a gas bubbled structure in immobilized form produced with this nozzle for nitrogen and phosphorus removal from water or wastewater. Here, it is explained that the microalgae are immobilized using various chemicals and a nozzle, forming gas bubbles in them while immobilizing, thereby reducing their density, and keeping them floating on water or wastewater, and using these microalgea to remove nitrogen and phosphorus pollution from water and/or wastewater.

Description

PRODUCTION AND APPLICATION OF GAS BUBBLED IMMOBILIZED

MICROALGAE CULTURE IN WATER OR WASTEWATER TREATMENT

PROCESS

Technical Field of the Invention

The invention relates to a nozzle for the production of a microalgae culture with a gas bubbled structure in immobilized form and the use of the microalgae culture with a gas bubbled structure in immobilized form produced with this nozzle for nitrogen and phosphorus removal from water or wastewater.

State of the Art

The increase in nutrients, especially nitrogen and phosphorus, in wastewater affects the aquatic ecosystem and surface waters negatively. Today, various processes are used for nutrient removal from wastewater to solve this problem.

The most common processes in the current art in which nitrogen and phosphorus are treated removed from wastewater are anaerobic-anoxic-oxic (A²/O) process, five-stage Bardenpho process, University of Capetown type activated sludge system (UCP) process, Virginia plant type activated sludge system (VIP) process, sequential batch reactor (SBR) process and alternative biological processes used in nutrient removal. Today, there are many methods used for nutrient removal from water/wastewater. However, the fact that these methods have many costs such as operation, maintenance and energy consumption has led to the application of natural treatment processes, which are alternative treatment methods.

The most traditional method used to remove nitrogenous compounds from wastewater is the n itrif ication/den itrification process. In cases in which phosphorus removal cannot be achieved biologically, chemicals containing significant amounts of iron and aluminium are used for phosphorus removal. This results in the formation of high volumes of sewage sludge. In the nitrif ication/den itrif ication process for the removal of nitrogenous compounds, the nitrification process is a restrictive process and the need to establish design criteria according to analytical measurements in determining the aerobic sludge retention time significantly affects the treatment efficiency. The fact that the nitrification process takes place in an aerobic environment and the denitrification process in an anaerobic environment necessitates the execution of these processes in different treatment units during the treatment process. Similar requirements arise in processes with membrane bioreactors. All biological treatment methods have maintenance frequencies and difficulties because they contain physical equipment such as aeration and mixing units. In these systems, there are high costs such as high energy consumption to meet mixing and aeration requirements.

As a result of the use of all the above-mentioned conventional biological treatment processes, the pollution in the water is removed, but depending on the intense bacterial population, the pollution is transformed into another form and serious sludge is produced. Various methods such as sludge thickening, filter press, sludge digestion etc. have to be applied for the disposal of this treatment sludge. For these reasons, microalgae have recently been used for nutrient removal from water or wastewater.

The advantage of choosing microalgae over other methods is that, in addition to nitrogen and phosphorus removal from water, growing microalgae can be used as an energy source. The basis of all processes related to this is based on selected pure microalgae cultures using nitrogen and phosphorus species as nutrients and increasing their biomass while removing these impurities from wastewater. In addition, treatment of wastewater with microalgae has gained great importance in recent years since less by-products are produced compared to other processes. However, there are some deficiencies in the prior art methods containing microalgae, and due to these deficiencies, microalgae cannot be used in treatment with high efficiency. In the treatment methods using microalgae, the most important disadvantage is that the algae biomass that is released as a result of the treatment must be removed in other words, harvested from the environment. The need for a secondary treatment method due to the mixing of microalgae cultures into the water body to be treated and the high cost of the methods to be selected for harvesting microalgae are the factors limiting the use of microalgae. For this reason, using microalgae biomass by stabilizing it with immobilized agents provides an advantage in the method. Since the density of the immobilized microalgae masses is normally very close to the water density, the immobilized microalgae globules tend to remain suspended in water. In this way, the immobilized microalgae are suspended in the water, but being suspended in the water is not enough to fully benefit from sunlight. In order for the microalgae to remain floating on the water, additional devices, floating beds, or floating island structures are required on which the microalgae are located. Additional devices or structures cause both additional cost and difficulty in use. Because these devices or structures contain physical equipment, there are maintenance frequencies and difficulties. Another shortcoming of the methods using microalgae in the prior art is the need for a secondary treatment method to mix the immobilized microalgae cultures into the water or wastewater systems and to remove them from the system after treatment. In the state of the art, there are methods such as immobilization of microalgae biomass brought into immobilized form by being adsorbed with spongy structures (medium), as well as having immobilized structures in the form of sheets (leaf); however, these methods are also insufficient in maximizing the diffusion of pollutants in the water into the immobilized structure.

In the prior art utility model CN2062193111I, an embodiment for the treatment of aquaculture wastewater using immobilized microalgae balls is described. It is stated that the immobilized microalgae balls used here can be used in wastewater treatment by placing them at a certain depth in a basket-shaped medium with a certain sieve opening (10-20 mesh). It is mentioned that the microalgae balls, which fill their capacity in the treatment process, are renewed with another basket, providing a cheap, simple and effective treatment. The method applied in this embodiment is insufficient in wastewater treatment, since the microalgae balls are located at a certain depth, but not floating on the water surface.

Patent no CN107986458B describes the method of treating aquaculture wastewater using immobilized microalgae culture. Microalgae cultures are inoculated into BG11 +Glucose medium, and the purification of aquaculture wastewater containing 0.05% glucose is carried out with the immobilized microalgae culture. Chlorella culture is used as microalgae culture, sodium alginate is used for immobilization of microalgae culture and paraben complex is used as active ingredient. It is mentioned that the immobilized microalgae culture can be placed on the top of the treatment unit in a floating position for use in wastewater treatment. It is mentioned here that only immobilized microalgae culture can be placed on an aquarium or an instrument, however, no information is given on how to do this. Patent application no CN111018127A relates to a treatment method using immobilized microalgae for the treatment of aquaculture wastewater. In said method, Pseudomonas pseudospora microalgae species is used, and the method used is to cultivate the microalgae cells, to prepare the chemical solution that provides the immobilization, to mix the solution and the microalgae culture, to immobilize them in the form of globules, and to carry out the treatment process by adding the formed microalgae spheroids to the wastewater. Although it has been stated that the immobilized microalgae globules created here are used in the treatment of wastewater by placing them in an aquarium or similar equipment and keeping them floating in the water, no information is given about how the microalgae are kept in floating form. Since the density of the immobilized microalgae masses is normally very close to the water density, the immobilized microalgae globules tend to remain suspended in water. For this reason, suspended microalgae can be obtained in this method, but this method will not be sufficient for floating microalgae on the water surface without the use of additional equipment.

In the utility model CN207210076U, an integrated device and application with micropore ventilation, biological-ecological floating bed structure, which can be used in the treatment of domestic or industrial wastewater, is explained. The microorganism used here is the active sludge-based bacterial population. With said micropore ventilated biological-ecological floating bed integrated device, it is aimed to solve the oxygen problem experienced in the treatment of anaerobic and malodorous water bodies by increasing the oxygen concentration in the treatment of water bodies.

Said integrated device includes ventilator, floating bed structure, float system, micropore ventilation pipe, protective net, aquatic plants, and immobilized microorganism pellets. For the preparation of immobilized microorganism balls, 8-12% polyvinyl alcohol by weight is heated in water with 2-5% sodium alginate. The mixture prepared here is dripped into a solution containing 2-3% CaCl2 by weight and 3-8% H3BO3 by weight, and pellets containing microorganisms are obtained by mixing and forming the bond structure. The obtained pellets are filtered and washed and made ready for use. The prepared micropellets are used by being placed under said device and being immersed in water or wastewater environment for 24/48 hours. However, in this method used in treatment, it is not possible to bring microorganisms to a floating position without the use of additional devices and floating beds. In addition, complex and long-term preparation is required before the treatment process, as immobilized pellet structures formed from the roots of aquatic plants positioned on the floating bed and the activated sludge-derived bacterial population in the lower part of the equipment are used here.

In the treatment processes using microalgae in the state of the art, there are disadvantages such as insufficiency in positioning of microalgae to float on water and benefiting from sunlight with full efficiency, requiring additional devices, floating beds or floating island structures on which microalgae are positioned for floating positioning, these devices or structures requiring frequent maintenance and having difficulties of due to their physical equipment, the additional devices or structures used requiring a complex and long-term preparation before the treatment process, suspended microalgae getting mixed into water or wastewater systems and the need for a secondary treatment method to remove microalgae from the system after treatment. Therefore, developing methods that enable microalgae to take full advantage of sunlight, do not require additional devices or structures on which the microalgae are positioned in order to float the microalgae in water, do not require a complex and longterm preparation before the treatment process, ensure that immobilized microalgae do not mix with water or wastewater systems and do not require a secondary treatment method to remove microalgae from the system after treatment, and devices that enable microalgae to be brought into floating form are needed.

Brief Description of the Invention

The invention relates to a nozzle for the production of a microalgae culture with a gas bubbled structure in immobilized form and the use of the immobilized microalgae culture with a gas bubbled structure produced with this nozzle for nitrogen and phosphorus removal from water or wastewater.

The first aim of the invention is to bring the microalgae culture used in treatment to a floating form on the water surface by itself, without being positioned on an additional device or structure, and to ensure that it receives sunlight in the most efficient way. In the invention, the immobilized microalgae culture is made into a gas bubbled structure and thus, the microalgae, the density of which is made lower than the density of the water, are ensured to remain floating on the water surface. In this way, the invention allows microalgae to receive the light they need from the surface, even in wastewater containing high turbidity. With the invention, it is ensured that gas sacs are formed, which will contain gas composition at a rate depending on the need, during the immobilization stage. Thus, the weight of the immobilized microalgae globules in unit volume is reduced and the globules, whose density becomes less than the water density, are kept in a floating form in water or wastewater. Especially in the wastewater treatment process, the light transmittance is very low due to the high suspended solids and turbidity values contained in the wastewater. In this case, the suspended immobilized microalgae provided by the methods in the prior art cannot reach the sufficient light they need for photosynthesis. Microalgae globules brought into floating form on the surface can easily obtain the light energy they need for photosynthesis from a natural light source such as sunlight from the surface or from artificial lighting that can be positioned on the surface. By means of the microalgaes’ spherical form, the microalgae in the invention can have optimum light absorption capacity. In addition, by means of the spherical structure, the surface area of each globule has the largest possible area, so the spherical structure maximizes the diffusion of pollutants in the water into the immobilized structure.

Another aim of the invention is to easily remove the immobilized microalgae mass after treatment without the need for a secondary treatment method. By transforming the immobilized microalgae culture into a gas bubbled structure in the invention, it is ensured that the immobilized microalgae mass is in contact with water or wastewater and is easily removed after treatment. In this way, there is no need for an additional process to remove microalgae from the treated wastewater after treatment.

Another aim of the invention is to harvest the microalgae used in treatment after treatment and use them as raw materials for different processes and products. By means of its bubbled structure, microalgae that remain floating on the water surface are easily harvested after treatment and can be used as a raw material for the production of different products. The microalgae biomass, which grows efficiently by the help of the sunlight during the treatment, is collected and used after treatment. Instead of the treatment sludge generated in the treatment methods in the previous art, a microalgae biomass is obtained that can allow the production of different products and the formation of alternative energy sources such as biofuels as a result of the treatment method that is the subject of the invention. Another aim of the invention is to ensure that microalgae are immobilized so that they can proliferate while maintaining their viability. In the immobilization method provided by the nozzle of the invention, microalgae are immobilized with various polymeric compounds and gelling chemicals. The immobilized microalgae biomass can continue to maintain its viability in this way and can proliferate inside the immobilized structure.

With the use of microalgae in the invention, both nitrogen and phosphorus removal are carried out simultaneously. Especially in nitrogen removal, microalgae can easily absorb nitrogen species in the form of both ammonium and nitrate from water or wastewater as nutrients, and they can quickly remove these two types of nitrogen. In addition, the immobilized microalgae globules that form a layer on the surface can use the relatively high amount of CO2 in the wastewater after the biological treatment process for their photosynthetic needs in nitrogen and phosphorus removal, and they benefit from reducing the greenhouse gas emissions that occur intensively in biological treatment processes.

With the invention, a method that enables microalgae to take full advantage of sunlight, does not require additional devices or structures on which the microalgae are positioned in order to float the microalgae in water, does not require a complex and long-term preparation before the treatment process, maximizes the diffusion of pollutants in the water into the immobilized microalgae culture, ensures that immobilized microalgae culture do not mix with water or wastewater systems and does not require a secondary treatment method to remove microalgae culture from the system after treatment, and a device that enables m icroalgae to be brought into floating form are needed are provided.

Description of Drawings

Figure 1 : General representation of the formation of gas bubbled microalgae globules in immobilized form.

Figure 2: Illustration of coaxial flow nozzle used to form gas bubbled microalgae globules in immobilized form.

Figure 3: Demonstration of the use of gas bubbled microalgae globules in immobilized form in conventional water or wastewater treatment plants. Definition of Elements/Parts Composing the Invention

1 . Gel microalgae transmission line

2. Gas transmission line

3. Mixing zone

4. Outlet pipe

5. Microalgae drop in gas bubbled gel form

6. Gas bubbled microalgae globule in immobilized form

7. Solidifying (cross-linking) liquid

8. Upper stopper

9. Nozzle

10. Nozzle lower end

11 . Separator

12. Collection chamber

Detailed Description of the Invention

The invention relates to a nozzle for the production of a microalgae culture with a gas bubbled structure in immobilized form and the use of the microalgae culture with a gas bubbled structure in immobilized form produced with this nozzle for nitrogen and phosphorus removal from water or wastewater. Here, it is explained that the microalgae are immobilized using various chemicals and a nozzle, that gas bubbles remain in the microalgae while immobilized, thereby reducing their density and keeping them floating on water or wastewater, and using these microalgae to remove nitrogen and phosphorus pollution from water/wastewater.

Production method of microalgae culture described in the invention comprises the process steps of: i. preparing microalgae in gel form by mixing solution and suspended microalgae in polymeric gel form, ii. conveying the microalgae in gel form from the gel microalgae transmission line

(1 ) to the mixing zone (3), iii. converting microalgae in gel form mixed with the gas or gas mixture coming from the gas transmission line (2) into drop form in the outlet pipe (4) and obtaining microalgae drop in the form of a gas bubbled gel (5), and iv. obtaining the gas bubbled microalgae globule (6) in immobilized form by mixing the gas bubbled microalgae drop (5) in gel form with the solidifying (crosslinking) liquid (7) and polymerizing it.

In order to form the gas bubbled microalgae globule (6) in the immobilized form, which is the subject of the invention, production can be made by establishing a simple system as seen in Figure 1 . However, a coaxial flow nozzle is used, as shown in Figure 2, so that the globules are more homogeneous and gas bubbles can be formed in the system in a controlled manner. In this nozzle system, microalgae in gel form nested with the gas bubbled form microalgae drop (5) in the form of a gas bubbled gel and the microalgae drop (5) in the form of a gas bubbled gel dripped into the solidifying (crosslinking) liquid (7) polymerizes here to form gas bubbled microalgae globules (6) in immobilized form.

The nozzle (9) used for the production of immobilized microalgae with gas bubbled structure described in the invention is shown in Figure 2. Said nozzle (9) comprises the gel microalgae transmission line (1 ), which provides the transmission of microalgae in polymeric gel form, the gas transmission line (2), which provides the transmission of gas, the mixing zone (3) where the microalgae in gel form and the gas mixture are mixed, the outlet pipe (4), which ensures that the microalgae and gas bubbles in gel form are sequentially directed to the outlet line and has the mixing zone (3) located at its outlet part, the upper stopper (8) and the nozzle lower end (10) directly connected to the nozzle (9) to fix the gas transmission line (2) and the gel microalgae delivery line (1 ) and connect the nozzle. The opening between the lower end of the gas transmission line (2) and the nozzle lower end (10) is an annular opening of 0.1 -5 millimetres in the preferred embodiment of the invention. This opening can be adjusted according to the position of the nozzle lower end (10) and the gas transmission line (2) on the vertical axis to provide the desired clearance. This opening is the most important point that allows the mixing of the gel-form microalgae and the gas mixture in the nozzle. The lower end of the gas transmission line (2) may be in flat, conical or spherical form. By adjusting the vertical positions of the gas transmission line (2) and the nozzle lower end (10), the gas flow amount and the gel microalgae mass flow, a microalgae drop (5) in the form of an optimum gas bubbled gel is formed. All parts of the nozzle can be separated from each other in order to facilitate the cleaning and sterilization processes that may occur in the nozzle. In addition to this nozzle, solidifying (cross-linking) liquid (7) is used for the production of immobilized microalgae with gas bubbled structure.

In the formation of the gas bubbled microalgae globule (6) in immobilized form, first of all, microalgae in polymeric gel form is formed. In order to form microalgae in polymeric gel form, at least one of the synthetic polymer structures derived from monomeric structures such as agar, sodium alginate, carrageenan and acrylamide is used in the gel content.

In the preferred embodiment of the invention, sodium alginate is preferably used because it can be produced quickly, forms a water-insoluble compound after being immobilized, has a durable structure, is non-toxic, and is transparent enough to pass the light needed by microalgae. In this embodiment, firstly, to prepare the solution containing microalgae in gel form, 1 -5% sodium alginate by volume solution is mixed with the suspended microalgae in a ratio of 1 :5-5: 1 by volume (v/v) to form microalgae: sodium alginate. Pure microalgae culture can be used as microalgae or more than one microalgae species can be used together. All known microalgae species can be used in the invention. In an embodiment of the invention, preferably Tetradesmus obliguus and/or Chlorella vulgaris cultures are used.

In the invention, silicone hoses are preferably used as the gel microalgae transmission line (1 ) and the gas transmission line (2), and Y-type pipe connection apparatus is used as the mixing zone (3). All materials used in the system must be biocompatible and sterilizable if used in the production of pure microalgae cultures. As the gas coming from the gas transmission line (2), atmospheric gas can be used directly, a gas mixture containing carbon dioxide gas in different proportions (such as flue gas) or optionally a gas mixture containing nitrogen gas can be used. In the gas mixture used in an embodiment of the invention, carbon dioxide can be found at the rate of 0.5-10% by volume. The flow rate of microalgae in gel form and the gas mixture rate fed to the system vary according to the pipe diameter and the gas/polymeric gel ratio. The aforementioned gas/gel ratio may vary according to the structure of the nozzle and the microalgae gel structure. In an example of the invention, the gas/polymeric gel ratio is preferably used in the range of 1/50-1/1 by volume.

In the method of producing microalgae culture containing gas bubbled microalgae globule (6) in immobilized form to be used in the simultaneous removal of nitrogen and phosphorus from the water or wastewater that is the subject of the invention; the prepared polymeric gel form microalgae is transmitted from the gel microalgae transmission line (1 ) to the mixing zone (3). At the same time, the gas used in bubble formation is transmitted to the mixing zone (3) from the gas transmission line (2). Depending on the structure and shape of the mixing zone (3) and the diameter of the outlet pipe (4), it is ensured that microalgae in gel form and gas bubbles are sequentially directed to the outlet pipe (4). The diameter of the outlet pipe (4) is preferably between 1 and 10 mm in order to provide gas and liquid medium in succession. In the gel form microalgae, which turns into drop form in the outlet pipe

(4), the gas mixture that follows immediately forms a gas bubbled. The microalgae drop

(5) in the form of gas bubbled gel is dropped into the solidifying (cross-linking) liquid (7), which will transform into a spherical form and immobilize the gel form. In the solidifying (cross-linking) liquid (7), the microalgae drop (5) in the form of a gas bubbled gel is polymerized and turned into gas bubbled microalgae globules (6) in the immobilized form.

Sodium alginate, which is the carrier system in the content of microalgae in gel form, is a naturally occurring anionic polymer typically obtained from brown seaweed. It consists of an unbranched l-guluronate (G) and d-maneuronate (M) in a sequential G, sequential M or alternating sequence of GM monomers. This type of alginate gains a solid gel form with +2 valence ions. Therefore, in an embodiment of the present invention, a solution of calcium lactate at a rate of 0.5-10% by weight by volume is used as the solidifying (cross-linking) liquid (7). Apart from this, different chemical solutions containing +2 charged calcium cations such as calcium chloride can be used as agents in the solidifying (cross-linking) liquid (7). As the thickening liquid (7), calcium lactate or its solution, at least one of the solidifying chemical agents such as calcium chloride, acrylonitrile, urethane, vinyl alcohol and hydroxyethylmethacrylate (HEMA) can be used. By the help of the fact that the gas bubbled microalgae globule (6) in the obtained immobilized form contains a gas bladder, its total density is ensured to be less than the density of water or wastewater, and thus the globules can remain in floating form. This situation enables the microalgae to obtain the necessary light from the surface for the photosynthesis reaction needed by the microalgae. By virtue of this feature gained to immobilized microalgae, the microalgae that are subject of the invention are used for nitrogen and phosphorus removal with minor modifications in the units in conventional water or wastewater treatment plants.

Figure 3 shows an example of such an application in a secondary settling tank used after the activated sludge process in a typical wastewater treatment plant. The produced immobilized form of gas bubbled microalgae globules (6) are added to the wastewater by a transmission line from the middle part of the circular shaped settling tank. Likewise, with the help of the radial flow of wastewater entering from the middle part of the tank, the microalgae globules in the middle part tend to move towards the outside. Depending on the hydraulic waiting time in the tank and the desired nitrogen and phosphorus removal rates of the microalgae, the appropriate amount of immobilized gas bubbled microalgae globules (6) covers the surface of the relevant treatment unit. Since the facility will operate on the basis of continuous treatment, the gas bubbled microalgae globules (6) in the immobilized form, which are added continuously, begin to remove nitrogen and phosphorus at the entrance of the relevant unit. The microalgae population also increases within the immobilized gas bubbled microalgae globules (6), which move towards the outer sides of the settling tank with radial flow, and thus the microalgae globules provide the removal of nitrogen and phosphorus in water or wastewater to a large extent. The gas bubbled microalgae globules (6) used in the treatment process and in immobilized form are harvested with a collection chamber (12) placed in the inner part of the separators (11 ) located in the outermost part of the settling tank. Thus, gas bubbled microalgae globules (6) in immobilized form, which purify nitrogen and phosphorus from water or wastewater during the treatment process, are harvested and removed from water/or wastewater. The removed immobilized form of gas bubbled microalgae globules (6) can be used as raw materials in various industries where these components are used, due to their high amount of microalgae, high organic content, and richness in nitrogen and phosphorus. The treatment technique given as an example in Figure 3 can be easily applied in many treatment units. For example, the invention can be used on the upper surface of the active sludge unit in wastewater treatment. Thus, while nitrogen and phosphorus treatment is carried out, CO2, which is the result of biological treatment with active sludge, can be partially retained on the surface. Apart from these, the use of gas bubbled microalgae globules (6) in the immobilized form in membrane bioreactors can prevent membrane blockages to a great extent.

The treatment efficiency was investigated in a batch reactor using gas bubbled immobilized microalgae globules, which is the subject of the invention, and Tetradesmus obliguus (syn. Scenedesmus obliquus) microalgae culture was used within the scope of the study. In an application of the invention, as working conditions, in the study carried out at a constant pH value of 8, in a 24-hour light environment and at room temperature, while the initial nitrogen and phosphorus concentrations were 12.3mg/L NH4+-N and 7.59 mg/L PO4, the nitrogen and phosphorus removal in the wastewater after 97.5 hours was 71.9% and 93.9%, respectively.

In an application of the invention, bacterial microorganisms used in conventional treatment and immobilized microalgae can be used together. Thus, the oxygen needed by the bacteria can be partially met by the photosynthesis of microalgae. The CO2 generated during the purification process of the bacteria can be used for photosynthesis by the immobilized microalgae.

Claims

1. Microalgae culture for simultaneous removal of nitrogen and phosphorus from water or wastewater, comprising at least one gas bubbled microalgae globule (6) in immobilized form comprising microalgae and gas bubbled in polymeric gel form.

2. Microalgae culture according to claim 1 , wherein said polymeric gel form comprises at least one of agar, sodium alginate, carrageenan and acrylamide as a synthetic polymer structure derived from monomeric structures.

3. Microalgae culture according to claim 1 , wherein said polymeric gel form microalgae comprises suspended microalgae:sodium alginate solution in the ratio 1 :5-5: 1 by volume.

4. Microalgae culture according to claim 3, wherein said sodium alginate solution is 1 -5% sodium alginate solution by volume.

5. Microalgae culture according to claim 1 , wherein said gas is atmospheric gas, nitrogen gas, carbon dioxide gas mixture or flue gas.

6. Microalgae culture according to claim 1 , wherein said gas comprises carbon dioxide at a rate of 0.5-10% by volume.

7. Microalgae culture according to claim 1 , wherein said microalgae is Tetradesmus obliguus and/or Chlorella vulgaris.

8. Microalgae culture according to claim 1 , wherein said gas/polymeric gel ratio in the gas bubbled microalgae globule (6) in immobilized form is in the range of 1/50-1/1 by volume.

9. A method for the production of microalgae culture according to claim 1 , comprising the proses steps of: i. preparing microalgae in gel form by mixing solution and suspended microalgae in polymeric gel form, ii. conveying the microalgae in gel form from the gel microalgae transmission line (1 ) to the mixing zone (3), iii. converting microalgae in gel form mixed with the gas or gas mixture coming from the gas transmission line (2) into drop form in the outlet pipe (4) and obtaining microalgae drop in the form of a gas bubbled gel (5), and iv. obtaining the gas bubbled microalgae globule (6) in immobilized form by mixing the gas bubbled microalgae drop (5) in gel form with the solidifying (cross-linking) liquid (7) and polymerizing it

10. A method according to Claim 9, wherein said polymeric gel form comprises at least one of synthetic polymer structures derived from monomeric structures such as agar, sodium alginate, carrageenan, acrylamide, acrylonitrile, urethane, vinyl alcohol and hydroxyethyl methacrylate (HEMA).

11. A method according to Claims 9 or 10, wherein, 1 -5% sodium alginate solution by volume is mixed with suspended microalgae to form a suspended microalgae:sodium alginate solution at a ratio of 1 :5-5: 1 by volume for the preparation of the aforementioned polymeric gel form solution.

12. Method according to claim 9, wherein said microalgae is Tetradesmus obliguus and/or Chlorella vulgaris.

13. Method according to claim 9, wherein said gas is atmospheric gas, nitrogen gas, carbon dioxide gas mixture or flue gas.

14. Method according to claim 9, wherein said gas mixture comprises carbon dioxide at a rate of 0.5-10% by volume.

15. Method according to claim 9, wherein said solidifying (cross-linking) liquid (7) is a solidifying chemical solution containing +2 charged calcium cation.

16. Method according to Claim 9, wherein said solidifying (cross-linking) liquid (7) comprises at least one of calcium lactate or solution thereof, calcium chloride, acrylonitrile, urethane, vinyl alcohol, and hydroxyethylmethacrylate (HEMA) as the solidifying chemical agent.

17. Method according to Claims 9 or 16, wherein said solidifying (cross-linking) liquid (7) is a 0.5-10% solution of calcium lactate by volume.

18. Method according to claim 9, wherein said gas/polymeric gel ratio in the gas bubbled microalgae globule (6) in immobilized form is in the range of 1/50-1/1 by volume.

19. A nozzle (9) for use in the production of microalgae culture containing a gas bubbled microalgae globule (6) in immobilized form used for the simultaneous removal of nitrogen and phosphorus from water or wastewater, comprising

• gel microalgae transmission line (1 ), which provides the transmission of microalgae in gel form,

• gas transmission line (2), which provides the transmission of gas,

• the mixing zone where the microalgae in gel form and the gas mixture are mixed (3),

• the outlet pipe (4), which ensures that the microalgae and gas bubbles in gel form are sequentially directed to the outlet line and where the mixing zone (3) is located at the outlet,

• upper stopper (8) to fix the gas transmission line (2) and the gel microalgae transmission line (1 ) and to ensure the nozzle connection, and

• nozzle lower end (10).

20. Nozzle according to claim 19, wherein the diameter of said outlet pipe (4) is between 1 -10 mm.

21. Nozzle according to claim 19, wherein the opening between the lower end of said gas transmission line (2) and the nozzle lower end (10) is an annular opening of 0.1-5 millimetres.

22. Nozzle according to claim 19, wherein all parts of said nozzle are separable from one another.

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