Disclosure of Invention
In order to solve the problems of salinity rise, pH rise and the like caused by adding high-concentration bicarbonate and other nutrients, the invention discloses a floating type photobioreactor with a slow-release material supplementing device. Meanwhile, in order to avoid the problems of high salinity and high pH caused when bicarbonate is replenished, the submerged water part of the photobioreactor is provided with a semipermeable membrane device for releasing salt ions and hydroxide ions accumulated to high concentrations to stabilize the salt concentration and pH in the reactor.
The invention relates to a floating photobioreactor, which consists of a reactor cavity, a semipermeable membrane arranged at the bottom of the reactor cavity and a slow-release material supplementing structural unit, wherein:
1) the slow-release material supplementing structural unit is used for supplementing nutrient substances which are rapidly consumed in the microalgae culture process; in particular to the slow release supplement of bicarbonate and other nutrients for the growth of microalgae; for example: nitrogen sources, phosphorus sources, and other trace element ions required for microalgae growth, such as: bicarbonate, phosphate, nitrate, iron, calcium, magnesium, potassium, manganese, zinc, silicon, boron, cobalt, molybdenum, and the like.
2) The water immersion part of the photobioreactor comprises a semi-permeable membrane structural unit; is used for releasing salt ions and hydroxyl ions accumulated to high concentration in the cavity of the reactor due to slow release and supplement to the external water body so as to stabilize the pH value of the water body in the photobioreactor.
For the floating type photobioreactor as described above, preferably, the slow-release feeding structural unit is a closed container, and the closed container is connected with the photobioreactor cavity in a penetrating manner through a semipermeable membrane, a capillary tube or a valve capable of adjusting flow rate.
For the floating photobioreactor as described above, preferably, the semi-permeable membrane material is selected from CA (cellulose diacetate); CTA (cellulose triacetate); CN (nitrocellulose); EC (ethyl cellulose); and hydrophilic microporous materials such as CN-CA (mixed cellulose), PA-6 (nylon 6) or PA-66 (nylon) microporous membranes.
For the floating photobioreactor as described above, preferably, the semi-permeable membrane of the slow-release feeding structural unit is a semi-permeable membrane with an optimal area calculated by formula (I) to realize material exchange between the culture solution and the water body in the reactor to ensure the growth of microalgae. In addition, the capillary or the valve capable of adjusting the flow rate in the alternative scheme provided by the invention can also control the slow release speed of the nutrient substances in the slow release feeding structural unit, thereby ensuring the growth of microalgae.
For the floating photobioreactor as described above, preferably, the area of the semi-permeable membrane of the slow release feeding building block can be estimated by the following formula (again, how to replace the semi-permeable membrane with a capillary or a flow rate adjustable valve, and also by using the following algorithm to determine the correct flow rate control), and the relationship between the growth rate of a certain nutrient and the membrane area can be expressed as:
for a certain nutrient to pass through the semi-permeable membrane, the rate of entry into the reactor can be expressed as:
wherein V is the volume of liquid in the reactor (L) and K is the membrane permeability coefficient for a substance (m)2min-1) And A is the semi-permeable membrane area (cm)2) D is the film thickness (m), CoutIs the concentration (mol/L) of a certain substance in external environment, CinIs the concentration of nutrients in the reactor (mol/L).
For nutrients, the substrate consumption rate rs in the reactor can be expressed approximately as:
wherein rs may be represented by the formula:
where rx is the cell growth rate and Yx/s is the ratio of producing cells to consumed substrate, for a process of change of nutrient substance inside the reactor, when the rate of substance passing through the semipermeable membrane is equal to the rate of consumption of substrate inside the reactor, this process can be represented by the following formula:
therefore, the relationship between the growth rate and the desired membrane area can be obtained from equations (3) and (4):
for the floating photobioreactor as described above, it is preferable that the nutrient substances for microalgae culture are contained in the sustained-release feeding structural unit at the concentration calculated by formula (I). The nutrient concentration in the slow release feed building block is higher than the concentration of the corresponding nutrient in the reactor cavity, and the nutrient types comprise: nitrogen sources, phosphorus sources, and other trace element ions required for microalgae growth, such as: bicarbonate, phosphate, nitrate, iron, calcium, magnesium, potassium, manganese, zinc, silicon, boron, cobalt, molybdenum, and the like.
For the floating photobioreactor as described above, preferably, the semipermeable membrane structural unit includes a semipermeable membrane detachably connected to the lower cavity wall of the photobioreactor, and a mechanism for fixing the edge of the semipermeable membrane.
For the floating photobioreactor as described above, preferably, the semipermeable membrane structural unit is a frame or tray structural unit which fixes the edge of the semipermeable membrane and is detachably connected with the lower cavity wall of the photobioreactor in a threaded connection, a plug connection, a buckle connection or a chimeric connection manner. Specifically, frame or tray formula constitutional unit's edge is real frame, and inside is net formula, fence formula or hole-type structure, real frame is favorable to fixed pellicle, inside is net formula, fence formula or hole-type structure and assists holding the pellicle on the one hand, and on the other hand, the setting of its hole or net does not hinder the pellicle to the material exchange of nutrient substance and water.
More preferably, the semi-permeable membrane unit structure comprises a screw fixedly connected with the lower cavity wall and a tray device capable of pressing the semi-permeable membrane on the screw by using a nut.
As for the floating photobioreactor, preferably, the photobioreactor is in the shape of a horizontal flat plate, and the reactor cavity has a space for accommodating microalgae culture and can float on the surface of a water body.
In the floating photobioreactor as described above, preferably, the reactor cavity may be made of a rigid material capable of maintaining its shape, or may be made of a flexible material incapable of maintaining its shape; the rigid material includes glass, hard plastic, etc., and the flexible material includes plastic film, etc.
The reactor cavity floats on the water surface through an additional floating device.
In another aspect of the present invention, a method for culturing microalgae is disclosed, wherein the method employs the photobioreactor according to any of the above schemes.
The invention has the beneficial effects that:
when feeding with high concentrations of nutrients, problems arise with the salt concentration in the reactor rising. For example, when sodium bicarbonate is fed, the sodium ion concentration increases due to the feeding, while in the case of bicarbonate, the sodium ion is converted into carbon dioxide and hydroxide, the former is converted into biomass by photosynthesis, and the remaining hydroxide ions cause the pH to increase. The invention has a semipermeable membrane device which exchanges materials with the external water body, can release over-high sodium ion concentration and maintain the salt concentration balance in the reactor; meanwhile, hydroxyl ions can be released, and the pH value in the reactor is kept stable. The semi-permeable membrane device can also release other substances into the water body, preventing the accumulation thereof in the reactor. For example, substances inhibiting the growth of microalgae may be generated during the growth process of microalgae, and the substances may permeate into water through a semi-permeable membrane. Certainly, the nutrient substances in the external water body can also permeate into the reactor for the growth of the microalgae.
Detailed Description
The following non-limiting examples are presented to enable those of ordinary skill in the art to more fully understand the present invention and are not intended to limit the invention in any way. The following is merely an exemplary illustration of the scope of the claims of the present application and various changes and modifications of the invention of the present application may be made by those skilled in the art based on the disclosure, which should also fall within the scope of the claims of the present application.
Example 1.
Slow-release material supplementing structural unit of floating type semi-permeable membrane photobioreactor adopting semi-permeable membrane device
As shown in figure 1, the reactor comprises a cavity 1 for culturing marine chlorella, between the cavity 1 and a slow-release feed supplement structure unit bottle 3 containing high-concentration nutrient substances inside, the cavity 1 is fixed with the cavity 1 through a spiral fixing device 5, the slow-release feed supplement structure unit bottle 3 is communicated with the cavity 1, the joint of the two bottles compresses a semipermeable membrane 2, the nutrient substances in the slow-release feed supplement device enter the cavity 1 through the slow-release feed supplement structure unit bottle 3, in addition, the position corresponding to a semipermeable membrane tray device 4 on the outer wall of the cavity 1 is open, the semipermeable membrane 2 is compressed by the semipermeable membrane tray device 4 at the cavity 1, the cavity 1 passes through the semipermeable membrane 2 on the semipermeable membrane tray device 4, high-concentration salt ions and hydroxyl ions accumulated in the cavity 1 are released into external water, and the pH value of the water inside the photobioreactor is stabilized.
Example 2
The slow-release material supplementing structural unit of the floating bioreactor adopts a semipermeable membrane device to culture microalgae
Three groups of controls, namely a floating photobioreactor only provided with a semipermeable membrane device, a floating photobioreactor only provided with a slow-release feeding structural unit and a common floating photobioreactor, were respectively arranged in the photobioreactor 1 described in example 1 to culture the marine chlorella outdoors, wherein the phosphorus concentration in the slow-release feeding structural unit was 35mmol/L, the nitrogen concentration was 60mmol/L, the carbon concentration was 0.12mol/L, and the formulation of the other culture media was the same as that of the seawater. The temperature and the illumination do not need any artificial treatment and completely depend on natural conditions.
The culture results are shown in fig. 2, the reactor in example 1 of the present invention can successfully culture microalgae under outdoor conditions, and as can be seen from fig. 2(1), among the four reactors, the dry weight of the reactor with the slow-release feeding structural unit and the semipermeable membrane device is much higher than that of the other reactors, and is up to 0.82g/L, the maximum dry weight of the reactor with only the semipermeable membrane device is 0.61g/L, the maximum dry weight of the reactor with only the slow-release feeding structural unit is 0.60g/L, and the dry weight of the blank control group is up to 0.31g/L, so that the dry weight increase is obvious. FIG. 2(2) shows the change of the pH of the medium inside the different reactors, and it can be seen that the pH of the reactor with both the slow release feeding structural unit and the semipermeable membrane device rises slowly, the final pH is 9.58, and the pH in the blank control group reaches 10.01. FIG. 2(3) shows the total inorganic carbon content in the reactor, the total inorganic carbon content in the reactor with the slow-release supplement structural unit and the semipermeable membrane unit maintained at 3mmol/L, the total inorganic carbon concentration in the reactor with the semipermeable membrane unit alone maintained at 1.51mmol/L, the total inorganic carbon concentration in the reactor with the slow-release supplement structural unit alone maintained at 1.31mmol/L, and the blank control group was almost consumed, indicating that the reactor with the slow-release supplement structural unit and the semipermeable membrane unit had the effect of maintaining the total inorganic carbon concentration. Similarly, FIG. 2(4) shows the total nitrogen content in the reactor, and FIG. 2(5) shows the total phosphorus content in the reactor. The total nitrogen of the reactor with the slow-release feed-supplement structural unit and the semipermeable membrane device is maintained at 0.2mmol/L, the total phosphorus is maintained at 0.05mmol/L, the total nitrogen and the total phosphorus of the reactor with only the semipermeable membrane device are completely consumed, the total nitrogen concentration of the reactor with only the slow-release feed-supplement structural unit is 0.20mmol/L, the total phosphorus is 0.03mmol/L, and the total phosphorus is almost completely consumed by the blank control group.
Therefore, the floating bioreactor is suitable for large-scale microalgae culture, well solves the problem of traditional microalgae culture, reduces the cost of nutrient supply in microalgae culture, effectively and stably controls the pH of the reactor, and has good application prospect in the aspect of reducing the cost of large-scale microalgae culture.