A sandwich infiltrated semi-arcuate immobilized microalgae membrane reactor and method of use thereof

Abstract

The present application relates to the technical fields of microalgae culture and bioreactor, in particular to a kind of sandwich infiltrated semi-arch fixed microalgae membrane reactor and its using method.The reactor includes support chassis, semi-arch culture main body, top liquid distributor, liquid distribution port, funnel type liquid collection tank, bottom liquid discharge port, circulating pump and return pipe, semi-arch culture main body is defined by the sandwich flow channel between outside fixed carrier material and inside hole stainless steel support structure, culture solution is entered sandwich flow channel from top distributor through liquid distribution port, flows from top to bottom along semi-arch curved surface, infiltrates outside microalgae membrane from carrier back side, then is closed circuit reused through funnel type collection tank and circulating pump.The present application makes culture solution not directly strong to wash the outer surface of algal membrane, reduces shear drop, improves membrane thickness uniformity, reduces evaporation and water consumption, improves the unit area yield of fixed microalgae membrane.

Description

Technical Field

[0001] This invention relates to the field of microalgae cultivation and bioreactor technology, specifically to a sandwich-type semi-arched immobilized microalgae membrane reactor and its usage method. Background Technology

[0002] Microalgae are a class of photosynthetic microorganisms that can use light energy and inorganic carbon to synthesize a variety of products such as proteins, lipids, polysaccharides, pigments, and polyunsaturated fatty acids. Large-scale microalgae cultivation typically employs open raceway tanks, circular tanks, tubular photobioreactors, plate photobioreactors, and various thin-layer culture devices. Microalgae cells attach to the surface of filter cloth, ester fibers, sponges, membrane materials, or other carriers to form a microalgae biofilm. Water and nutrients are then supplied to the algal biofilm through methods such as spraying, drip irrigation, perfusion, intermittent immersion, or carrier rotation. Immobilized culture can reduce the total volume of the culture medium and increase the local cell density. During harvesting, a high concentration of algal biomass can be obtained by scraping, rinsing, or removing the entire carrier.

[0003] However, existing immobilized culture still has the following main problems: Firstly, when the culture medium is supplied by flowing from top to bottom or by spraying from the outer surface of the carrier, the liquid flow will directly wash over the microalgal membrane. Especially in the early stages of inoculation and membrane formation, the binding force between algal cells and the carrier is weak, and excessive shear force can easily cause cell detachment, resulting in prolonged membrane formation period and inoculation loss.

[0004] Secondly, surface flow or external surface liquid supply can easily create obvious differences between upstream and downstream. The top or the initial liquid distribution area is subject to stronger water flow and has a thinner algal film, while the downstream area has a longer retention time of nutrient solution and a thicker algal film. This results in uneven light and nutrient supply, which limits the yield per unit carrier area. Summary of the Invention

[0005] The purpose of this invention is to provide a sandwich-type semi-arched immobilized microalgae membrane reactor and its usage method, in order to solve the problems mentioned in the background art, such as large water consumption, low algal solution density, high harvesting cost, strong surface water flow scouring, difficulty in initial film formation, uneven algal membrane thickness distribution, large water evaporation loss, and easy detachment of the rotating carrier. This solution prevents the culture medium from directly and strongly scouring the outer surface of the algal membrane, thereby reducing shear loss, improving membrane thickness uniformity, reducing evaporation and water consumption, and increasing the yield per unit area of ​​the immobilized microalgae membrane.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a sandwich-type semi-arched immobilized microalgae membrane reactor, comprising a supporting frame, a semi-arched culture body, a liquid distributor, a liquid distribution port, a funnel-shaped liquid collection tank, a bottom drain port, a circulation pump, and a return pipe; The semi-arched culture body is fixedly installed above the support base frame. The semi-arched culture body includes an immobilized carrier material on the outer side, a perforated stainless steel support structure on the inner side, and an interlayer flow channel disposed between the immobilized carrier material and the perforated stainless steel support structure. The reactor is an axisymmetric semi-arched structure with a circular support area at the bottom and a top circular flat structure at the top. The diameter of the top circular flat structure is smaller than the diameter of the bottom circular structure, preferably 1 / 5 to 1 / 10 of the diameter of the bottom circular structure. The top circular flat structure and the bottom circular support area are connected by a gently sloping arc-shaped surface to form the main light-receiving surface for microalgae immobilization culture. The immobilized carrier material is disposed on the outer side of the gently sloping arc-shaped surface of the semi-arched culture body, and is used to attach microalgal cells and form a microalgal membrane. The immobilized carrier material is selected from one or more of nylon cloth, linen, cotton cloth, non-woven fabric, filter cloth, polyester fiber cloth, polypropylene fiber cloth, sponge thin layer, fiber felt, and modified hydrophilic fabric. The immobilized carrier material preferably has a rough surface, good water retention and certain water permeability to facilitate microalgal cell attachment, nutrient salt penetration and subsequent harvesting. The immobilized carrier material is fixed to the outer side of the perforated stainless steel support structure by means of pressure strips, buckles, cable ties, edge clamps, detachable ring pressure frames or corrosion-resistant adhesives.

[0007] Furthermore, the immobilized carrier material adopts a composite carrier structure, which includes an outer microalgae attachment layer, a middle water-retaining capillary layer, and an inner liquid-conducting contact layer arranged sequentially from the outside to the inside. The outer microalgae attachment layer provides a rough surface for providing a surface for microalgae cell attachment. The inner liquid-conducting contact layer contacts the interlayer flow channel. The middle water-retaining capillary layer is used to buffer fluctuations in the culture medium supply and reduce local drying of the microalgae membrane.

[0008] Furthermore, the perforated stainless steel support structure is disposed on the inner side of the immobilized carrier material to support the immobilized carrier material and maintain the semi-arched structure. The perforated stainless steel support structure is a thin-walled structure, which is a perforated stainless steel plate, stainless steel mesh plate, stainless steel perforated plate, or stainless steel wire mesh composite plate. The thickness of the perforated stainless steel support structure is preferably 0.3 mm to 5 mm, more preferably 0.5 mm to 2 mm, the aperture is preferably 0.2 mm to 10 mm, more preferably 0.5 mm to 5 mm, and the porosity is preferably 5% to 50%, more preferably 10% to 30%. The holes on the perforated stainless steel support structure not only allow the culture medium to leak locally into the funnel-shaped liquid collection tank when the flow rate is large, but also allow air to exchange inside and outside the reactor, which is beneficial to reduce local heat and moisture accumulation, promote oxygen dissipation, and maintain gas renewal on the surface of the microalgae film.

[0009] Furthermore, the immobilized carrier material and the perforated stainless steel support structure define the interlayer flow channel. After the culture medium enters the interlayer flow channel, it flows slowly from top to bottom along the semi-arched arc surface and supplies water and nutrients to the microalgae membrane on the outside through the back of the immobilized carrier material. The spacing of the interlayer flow channel is preferably 0.2 mm to 20 mm, more preferably 1 mm to 8 mm.

[0010] Furthermore, the interlayered flow channel is provided with one or more of the following: a liquid guiding net, a capillary liquid guiding layer, spacer protrusions, microgrooves, a hydrophilic fiber layer, or a zoned flow obstruction element, to prevent the formation of local channeling of the culture medium, so that the culture medium is evenly distributed along the arc-shaped surface and the shearing and scouring of the microalgae membrane on the outer surface of the immobilized carrier material is reduced. The interlayered flow channel is divided into sections in the radial or circumferential direction, and each section corresponds to one or more liquid distribution ports in order to adjust the wetting intensity of different areas.

[0011] Furthermore, the liquid distributor is provided on the top circular flat structure. The liquid distributor can be an annular distribution tube, a circular disc distributor, a perforated annular tube, a radial branch tube, or an annular groove distributor. The liquid distributor is provided with a plurality of liquid distribution ports, which can be small holes, short tubes, slits, droppers, or microporous liquid distribution devices. The plurality of liquid distribution ports are evenly arranged along the circumference of the top circular flat structure, so that the culture medium can be evenly introduced into the entire circumference or zoned interlayer flow channel.

[0012] Furthermore, the funnel-shaped liquid collection tank is located below the semi-arched culture body to collect the culture medium flowing down from the entire semi-arched arc surface and the culture medium leaking through the perforated stainless steel support structure. The upper edge of the funnel-shaped liquid collection tank corresponds to the bottom circular area of ​​the semi-arched culture body, and its bottom gradually narrows from the periphery to the center to the bottom drain port. The bottom drain port is connected to the circulation pump via a pipeline, and the outlet of the circulation pump is connected to the top liquid distributor or the liquid distribution port through the return pipe, thereby forming a closed-loop circulation of the culture medium.

[0013] Furthermore, the reactor also includes one or more of the following: a pH sensor, a temperature sensor, a liquid level sensor, a conductivity sensor, a dissolved oxygen sensor, a nutrient sensor, a carrier surface humidity sensor, or a controller. The pH sensor, conductivity sensor, dissolved oxygen sensor, and nutrient sensor are preferably located at the front end of the funnel-shaped liquid collection tank, the bottom drain port, the inlet pipe of the circulation pump, the outlet pipe of the circulation pump, the return pipe, or the inlet pipe near the liquid distributor, for monitoring the pH, salinity, dissolved oxygen, and nutrient status of the recovered culture medium or the culture medium about to enter the jacketed flow channel. When the reactor also includes the controller, the controller is connected to the circulation pump and is used to adjust the start / stop, flow rate, or pulse supply cycle of the circulation pump according to the detection signal.

[0014] Furthermore, the reactor also includes one or more of the following: a scraping component, a flexible scraper, a backwashing pipeline, a carrier disassembly component, or a carrier clamping component, used to harvest microalgae after the immobilized microalgae film reaches the target thickness or target biomass, and to retain a portion of the residual algal film as seed film for the next round of cultivation.

[0015] The present invention also provides a method for cultivating microalgae in a sandwich-wet semi-arched immobilized microalgae membrane reactor, comprising the following steps: S1, the immobilized carrier material is installed on the outside of the perforated stainless steel support structure, and the interlayer flow channel is formed between the immobilized carrier material and the perforated stainless steel support structure; S2, add the culture medium to the funnel-shaped liquid collection tank or the matching liquid storage container; S3, start the circulation pump so that the culture medium enters the top liquid distributor through the reflux pipe and enters the jacketed flow channel through the liquid distribution port; S4, the microalgae seed solution is inoculated onto the outer surface of the immobilized carrier material, or the microalgae cells are attached to the immobilized carrier material by back-side wetting through the sandwich channel; S5, low flow or intermittent interlayer immersion solution is used in the early stage of membrane formation, and continuous or pulsed interlayer immersion solution is used in the growth period, so that microalgae form an immobilized microalgae membrane on the surface of the immobilized carrier material. S6. Once the immobilized microalgae film reaches the target thickness or target biomass, the microalgae are harvested by scraping, using a flexible scraper, increasing the liquid supply flow rate for rinsing, backwashing, or disassembling the immobilized carrier material.

[0016] Furthermore, in the early stage of microalgal membrane formation, the culture medium supply intensity can be lower than that during the growth period to reduce microalgal cell shedding. After the microalgal membrane has been stably formed, the flow rate of the circulation pump can be appropriately increased to enhance nutrient supply.

[0017] Furthermore, during the harvesting period, the flow rate of the circulating pump can be increased briefly, or backflushing can be used to detach some of the microalgal film and allow it to enter the funnel-shaped liquid collection tank and the bottom drain. At harvest, 5% to 30% of the residual algal film can be retained as seed film for the next round of cultivation.

[0018] Furthermore, the culture medium circulation system can be controlled by feedback based on signals such as pH value, temperature, liquid level, conductivity, dissolved oxygen, nutrient salt concentration, or carrier surface humidity. For green algae such as Chlorella and Scenedesmus, the pH of the culture medium can be controlled between 6.0 and 8.5; for Spirulina, the pH of the culture medium can be controlled between 8.5 and 11.0.

[0019] Furthermore, the culture medium can be BG11 medium, Z medium, F / 2 medium, SM medium, D1 medium, aquaculture tail water, agricultural wastewater, food processing wastewater, secondary effluent from domestic sewage, or industrial wastewater that has been adjusted with nutrients.

[0020] Compared with the prior art, the beneficial effects of the present invention are: The culture medium flows downwards along a semi-arched surface in a channel between the immobilized carrier material and the perforated stainless steel support structure, wetting the outer microalgal membrane from the back. This avoids direct and forceful scouring of the outer surface membrane, which is beneficial for the adhesion and uniform membrane formation of microalgal cells in the early stages of inoculation. It also significantly reduces the shear force on the membrane and the slippage caused by gravity. Compared with the inverted V-shaped steep slope structure, the semi-arched gentle slope configuration provides a smoother downward liquid path, which can suppress local scouring zones and improve the uniformity of membrane thickness distribution. The interlayer wetting and back-side liquid supply greatly reduce the exposed area of ​​the culture medium, thereby reducing evaporation loss and salinity. The concentration of nutrients reduces the risk of disease, and immobilized culture significantly reduces the total volume of culture medium, increases the biomass load per unit volume, and reduces the amount of water required for subsequent harvesting and processing. The funnel-shaped liquid collection tank, circulation pump, and return pipe form a closed-loop circulation, which can recover culture medium and nutrients that are not utilized by algae, reducing nutrient loss. The perforated stainless steel support structure has the functions of support, liquid permeability, air permeability, and heat dissipation. It can not only prevent water accumulation in the interlayer when the flow rate is large, but also connect the air inside and outside the reactor, promote gas renewal and heat dissipation, thereby facilitating the long-term stable growth of immobilized microalgae membranes and increasing the microalgae yield per unit carrier area. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall structure of the reactor of the present invention; Figure 2 This is a schematic diagram of the cross-sectional structure of the reactor and the circulation path of the culture medium in this invention.

[0022] In the figure: 1. Immobilized carrier material; 2. Perforated stainless steel support structure; 3. Sandwiched flow channel; 4. Top circular flat structure; 5. Liquid distributor; 6. Liquid distribution port; 7. Funnel-shaped liquid collection tank; 8. Bottom drain port; 9. Circulation pump; 10. Return pipe; 11. Support base frame. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Without departing from the concept of this invention, any equivalent substitutions or conventional adjustments made by those skilled in the art to the structural dimensions, materials, algal species, culture medium, liquid supply method, and harvesting method shall fall within the protection scope of this invention.

[0025] Among the existing methods for cultivating microalgae, the following methods also exist. Firstly, the culture medium is supplied by flowing from top to bottom or by spraying from the outer surface of the carrier. However, in this method, the liquid flow will directly wash away the microalgal membrane. Especially in the early stages of inoculation and membrane formation, the binding force between algal cells and the carrier is weak, and excessive shear force can easily cause cell detachment, resulting in prolonged membrane formation period and inoculation loss.

[0026] Secondly, surface flow liquid supply is adopted, but this method is prone to creating obvious differences between upstream and downstream. The top or the initial liquid distribution area is strongly scoured by the water flow, resulting in a thinner algal film. In the downstream area, the nutrient solution accumulates and stays for a longer time, resulting in a thicker algal film, leading to uneven light and nutrient supply.

[0027] Third, although spray or fountain-type culture can increase the gas-liquid interface and the surface area exposed to light, the large exposed area of ​​the culture medium leads to a significant increase in evaporation loss, which is not conducive to low water consumption and low salinity fluctuation culture.

[0028] Fourth, immobilized culture employs rotating membranes, rotating drums, or moving flexible belts, periodically immersing the carrier in the culture medium while exposing it to air and light. Although such structures can reduce continuous spraying, the movement of the carrier may still cause the microalgal membrane to be mechanically bent, stretched, rubbed, or scraped, resulting in membrane detachment. At the same time, some carriers are immersed in the liquid phase for a long time, and the microalgal cells are in a dynamic balance between attached and free states. The density of suspended cells in the culture medium is not low, which affects the effect of immobilized culture in reducing harvesting costs.

[0029] Fifth, an inverted V-shaped attached-wall reactor is used, which typically forms a steep slope through two plates. Microalgae are inoculated on its outer surface and culture medium is supplied to the outer surface by a sprayer. This structure can increase the area for light-receiving culture, but the slope is steep and the liquid supply mainly acts on the outer surface, so there are still problems such as local scouring, evaporation and uneven film distribution.

[0030] Therefore, to resolve the above issues, please refer to [link / reference]. Figure 1This invention provides a sandwich-type semi-arched immobilized microalgae membrane reactor, comprising an immobilized carrier material 1 and a perforated stainless steel support structure 2 arranged sequentially from the outside to the inside. An interlayer flow channel 3 is formed between the immobilized carrier material 1 and the perforated stainless steel support structure 2. A top circular flat structure 4 is provided at the top of the reactor. A liquid distributor 5 is provided on the top circular flat structure 4. A liquid distribution port 6 is provided on the liquid distributor 5. A funnel-shaped liquid collection tank 7 is provided at the bottom of the reactor. A bottom drain port 8 is provided at the bottom of the funnel-shaped liquid collection tank 7. The bottom drain port 8 is connected to a circulation pump 9 through a pipeline. The circulation pump 9 is connected to the top liquid distributor 5 or the liquid distribution port 6 through a return pipe 10. The entire reactor is supported by a support frame 11.

[0031] The reactor is preferably a symmetrical semi-arched structure composed of a circular bottom structure and a small circular flat top structure. The top circular flat top structure 4 is located in the center of the reactor. Calculated with the diameter of the bottom circular structure as D and the diameter of the top circular flat top structure 4 as d, the ratio of d / D is preferably 1 / 5 to 1 / 10. For example, when D is 2.0m, d can be 0.2m to 0.4m; when D is 3.0m, d can be 0.3m to 0.6m. The height of the semi-arched structure is preferably 0.2D to 0.6D, more preferably 0.25D to 0.45D, so that the immobilized carrier material 1 forms a gently sloping light-receiving surface.

[0032] Please see Figure 2 In this embodiment, the immobilized carrier material 1 is laid on the semi-arched outer surface. The immobilized carrier material 1 can be fixed to the outside of the perforated stainless steel support structure 2 by means of pressure strips, buckles, cable ties, edge clamps, detachable annular pressure frames or corrosion-resistant adhesives. An interlayer flow channel 3 is retained between the immobilized carrier material 1 and the perforated stainless steel support structure 2. The interlayer flow channel 3 can be defined by gaskets, spacers, protrusions, support mesh or corrugated pads.

[0033] After the culture medium is transported to the liquid distributor 5 via the circulation pump 9 and the return pipe 10, it enters the interlayer channel 3 through the liquid distribution port 6. The culture medium slowly flows down from the top to the bottom along the interlayer channel 3 and supplies water and salt to the outer microalgae membrane through the back of the immobilized carrier material 1. Since the culture medium mainly flows in the interlayer channel 3, rather than forming a strong water flow directly on the outer surface of the immobilized carrier material 1, the shear force on the outer surface microalgae membrane can be reduced.

[0034] The holes on the perforated stainless steel support structure 2 can provide drainage channels when the culture medium flow rate is large or when liquid accumulates locally in the jacketed flow channel 3, allowing some of the culture medium to drip directly into the funnel-shaped liquid collection tank 7, preventing local water accumulation or excessive pressure in the jacket. At the same time, the holes also allow air to connect the inside and outside of the reactor, enhancing permeability, cooling, and oxygen dissipation.

[0035] The funnel-shaped liquid collection tank 7 is located below the semi-arched culture surface. Its upper edge corresponds to the bottom circumference of the reactor, and the bottom narrows towards the center to the bottom drain port 8. After the culture medium drips from the lower edge of the immobilized carrier material 1, the bottom end of the interlayer flow channel 3, and the holes of the perforated stainless steel support structure 2, it is collected by the funnel-shaped liquid collection tank 7 and returned to the circulation pump 9 through the bottom drain port 8.

[0036] The circulating pump 9 draws the collected culture medium from the bottom drain port 8 and sends it back to the top liquid distributor 5 through the return pipe 10, forming a closed loop circulation.

[0037] The liquid distributor 5 is an annular tube with an inner diameter of 60% to 95% of the diameter of the top circular flat structure 4. The liquid distribution ports 6 are evenly arranged along the annular tube, with a number of 8 to 200 ports and a diameter of 0.2 mm to 5 mm. Depending on the reactor scale, the liquid distributor 5 can also be configured as a double annular distribution tube, an inner and outer ring combined distribution tube, or a radial multi-branch distribution tube.

[0038] The immobilization carrier material 1 can be selected from nylon cloth, linen, cotton cloth, non-woven fabric, filter cloth, polyester fiber cloth, polypropylene fiber cloth, sponge layer, fiber felt, modified hydrophilic fabric or a combination thereof, preferably nylon cloth, linen or non-woven fabric. Before use, the carrier material is rinsed with clean water, irradiated with ultraviolet light, sterilized by steam, disinfected with sodium hypochlorite or soaked in ethanol. Alternatively, the carrier surface can be modified with chitosan, polylysine, sodium alginate, gelatin, dopamine or inorganic mineral particles to enhance the initial attachment of microalgae cells. The immobilization carrier material 1 can be subdivided into three layers. The composite carrier structure includes an outer microalgae attachment layer, a middle water-retaining capillary layer and an inner liquid-conducting contact layer arranged sequentially from the outside to the inside. The outer microalgae attachment layer provides a rough surface for providing a surface for microalgae cell attachment. The inner liquid-conducting contact layer contacts the interlayer flow channel. The middle water-retaining capillary layer is used to buffer fluctuations in the culture medium supply and reduce local drying of the microalgae membrane.

[0039] The reactor may also include one or more of the following: pH sensor, temperature sensor, liquid level sensor, conductivity sensor, dissolved oxygen sensor, nutrient sensor, carrier surface humidity sensor, or controller. The pH sensor, conductivity sensor, dissolved oxygen sensor, and nutrient sensor are preferably located at the front end of the funnel-shaped liquid collection tank, the bottom drain port, the inlet pipe of the circulation pump, the outlet pipe of the circulation pump, the return pipe, or the inlet pipe near the liquid distributor, to monitor the pH, salinity, dissolved oxygen, and nutrient status of the recovered culture medium or the culture medium about to enter the jacketed flow channel.

[0040] Temperature sensors can be placed in funnel-shaped liquid collection tanks, reflux pipes, jacketed flow channels, near the outer surface of immobilized carrier materials, inside perforated stainless steel support structures, or in the breathable open space inside the reactor to monitor the temperature of circulating culture medium, algal membrane microenvironment, jacketed liquid supply temperature, or the air temperature inside the reactor.

[0041] The liquid level sensor is preferably installed in a funnel-shaped liquid collection tank or a liquid storage container connected to it, or it can be installed above the bottom drain port to monitor the liquid level of the recirculating culture medium, the minimum safe liquid level, and to prevent the circulation pump from running dry.

[0042] The carrier surface humidity sensor is set on the outer surface or near the surface of the immobilized carrier material, preferably in one or more of the top adjacent area, the middle arc area and the bottom edge area. Multiple detection points can also be set along the circumference to monitor the wet state, local dry state or excessively wet liquid state of the carrier surface where the microalgae film is located.

[0043] When the reactor also includes a controller, the controller is connected to the circulating pump and one or more of the sensors respectively, and is used to adjust the start / stop, flow rate or pulse liquid supply cycle of the circulating pump according to the detection signal. When the surface humidity of the carrier is lower than the set threshold or the liquid supply of the jacket is insufficient, the controller increases the flow rate of the circulating pump, extends the liquid supply time or shortens the pump stop interval. When the surface humidity of the carrier is higher than the set threshold, the liquid level of the funnel-shaped liquid collection tank is too high or the dissolved oxygen is too high, the controller reduces the liquid supply intensity or extends the interval time. When the liquid level sensor detects a low liquid level, the controller stops the circulating pump or issues a liquid replenishment alarm.

[0044] The reactor also includes one or more of the following: scraping components, flexible scrapers, backwashing pipelines, carrier disassembly components, or carrier clamping components, used to harvest microalgae after the immobilized microalgae film reaches the target thickness, and to retain a portion of the residual algae film as seed film for the next round of cultivation.

[0045] The method of using this invention includes the following steps: S1, Assembly and Pretreatment: Install the perforated stainless steel support structure 2 on the support base 11, cover and fix the immobilized carrier material 1 on the outside of the support structure to form a sandwich flow channel 3, add culture medium to the system, start the circulation pump 9 to clean and circulate and remove impurities.

[0046] S2, Inoculation and membrane formation: The logarithmic growth phase microalgal seed solution is concentrated to 0.5 g dry weight / L to 5.0 g dry weight / L and inoculated onto the immobilized carrier material 1 by spraying, brushing, wetting or low-flow-rate liquid supply in a sandwich. After inoculation, low or medium light is maintained and low-flow-rate intermittent liquid supply is used to allow algal cells to attach and form an initial algal membrane.

[0047] S3, Stable cultivation: After a continuous algal film forms on the carrier surface, increase the frequency or flow rate of the liquid supply. The culture medium enters the interlayer channel 3 from the top liquid distributor 5 and flows continuously or in a pulsed manner to maintain the moisture of the algal film and the supply of nutrients. During the cultivation process, adjust the flow rate or supply cycle of the circulation pump 9 according to the pH value, temperature, liquid level, conductivity, dissolved oxygen, nutrient concentration or carrier surface humidity signal.

[0048] S4, Harvesting and Regeneration: Once the algal film reaches the target thickness, microalgae are harvested by scraping, using flexible scraping strips, increasing the circulation flow for rinsing, backwashing, or disassembling the substrate. After harvesting, a certain amount of residual algal film is retained or the algae are re-inoculated for the next round of cultivation.

[0049] The microalgae are selected from one or more of the following: Chlorella, Scenedesmus, Spirulina, Dunaliella, Haematococcus pluvialis, diatoms, Euglena, or a mixture of microalgae. The culture medium is selected from one of the following: BG11 medium, Z medium, F / 2 medium, SM medium, D1 medium, aquaculture tailwater, agricultural wastewater, food processing wastewater, secondary effluent from domestic sewage, or industrial wastewater that has been adjusted with nutrients.

[0050] Example 1

[0051] Common Chlorella can be cultured using the reactor of this invention.

[0052] The bottom circular structure of the reactor has a diameter D of 2.0m, and the top circular flat structure 4 has a diameter d of 0.28m, with a d / D ratio of 0.14, close to 1 / 7. The highest point of the semi-arched structure is 0.65m from the bottom circumference plane. The perforated stainless steel support structure 2 is made of 316L stainless steel perforated sheet with a thickness of 1.0mm, a hole diameter of 2.0mm, and an opening rate of about 18%. The immobilization carrier material 1 is made of hydrophilically treated nylon cloth. After the algal cells attach, the nylon cloth is divided into three layers from the inside out: an algal liquid attachment layer, a middle water-retaining layer, and an inner flow guiding contact layer. The spacing between the interlayer flow channels 3 is 4mm. In this embodiment, BG11 medium was used, and the inoculated algae was Chlorella vulgaris. Before inoculation, the seed solution was concentrated to 1.5 g dry weight / L. The circulation pump 9 was stopped during inoculation, and the concentrated algal solution was evenly sprayed onto the outer surface of the immobilized carrier material 1. After standing for 2 hours, the solution was intermittently supplied at a flow rate of 0.03 L / (min·m² carrier area), with a 2-minute run followed by a 10-minute stop, for 12 hours. Subsequently, the supply rate was adjusted to 0.08 L / (min·m² carrier area), with a 5-minute run followed by a 10-minute stop, and the culture was continued for 2 days. From day 3 to day 7, a pulsed sandwich immersion supply of 0.15 L / (min·m² carrier area) was used, and the culture temperature was 25 ± At 2℃, with a light intensity of 150 to 250 μmol / (m²·s), a light-dark cycle of 12h:12h, and pH controlled at 6.8 to 7.8, after 7 days of cultivation, a continuous and uniform green algal film formed on the surface of the immobilized carrier material 1. After scraping and dry weight determination, the microalgal biomass yield per unit carrier area was 16.8 g / (m²·d), and the concentration of suspended algal cells in the culture medium was less than 0.15 g / L. Compared with the same area and light conditions for shallow suspension culture, the volume of culture medium used for circulation in this embodiment was reduced by about 72%. Compared with direct drip supply from the outer surface, the algal cell shedding rate was reduced by about 45% within 24 hours after inoculation in this embodiment.

[0053] Example 2

[0054] Spirulina was cultured using the reactor of this invention.

[0055] The bottom circular structure of the reactor has a diameter D of 3.0m, the top circular flat structure 4 has a diameter d of 0.40m, d / D is about 0.13, close to 1 / 7.5, the semi-arch height is 0.9m, when the immobilized carrier material (1) adopts a composite layer of burlap and non-woven fabric, the outer side is a burlap attachment layer, the inner side is a non-woven fabric water-retaining layer, the perforated stainless steel support structure 2 has a thickness of 1.5mm, a pore diameter of 3mm, an opening rate of 25%, and the interlayer flow channel (3) has a spacing of 5mm; In this embodiment, Zygium culture medium was used, and the Spirulina seed culture was concentrated to 2.0 g dry weight / L. During the inoculation stage, a low-flow intermittent sandwich immersion solution was used, and the solution was uniformly coated once on the outer surface of the carrier. After 24 hours of film formation, a sandwich immersion solution of 0.10 to 0.20 L / (min·m² carrier area) was used. The culture temperature was controlled at 28 to 32℃, and the pH was controlled at 9.5 to 10.2. After 6 days of culture, the microalgal biomass yield per unit carrier area was 18.5 g / (m²·d), the algal film thickness was relatively uniform, and the dry weight difference between the top, middle and bottom sampling areas was less than 18%.

[0056] Example 3

[0057] The reactor of this invention is used to treat simulated aquaculture wastewater.

[0058] The culture medium was prepared aquaculture wastewater with an initial ammonia nitrogen concentration of 18.0 mg / L and a total phosphorus concentration of 2.5 mg / L. The inoculated algae were a mixed species of Chlorella and Scenedesmus. The immobilization carrier material 1 was non-woven fabric. The bottom circular structure of the reactor had a diameter of 1.5 m, the top circular flat structure 4 had a diameter of 0.22 m, the interlayer flow channels 3 had a spacing of 3 mm, and the circulating liquid volume was 10 L. During the cultivation process, air containing 1% carbon dioxide was added according to the pH value. The interlayer liquid supply intensity was 0.10 L / (min·m² carrier area). After 8 days of continuous operation, the ammonia nitrogen removal rate was 82%, the total phosphorus removal rate was 76%, the dry weight of the harvested immobilized algal film was 14.2 g / (m²·d), and the concentration of suspended algal cells in the circulating liquid was less than 0.20 g / L.

[0059] Example 4

[0060] Sensor placement and feedback control training.

[0061] Using the reactor structure of Example 1, a level sensor, a temperature sensor, and a pH sensor are installed in the funnel-shaped liquid collection tank 7. A conductivity sensor and a dissolved oxygen sensor are installed on the pipeline between the bottom drain port 8 and the circulation pump 9. A nutrient sensor is installed on the reflux pipe 10 near the liquid distributor 5. Carrier surface humidity sensors are installed on the top adjacent area, middle area, and bottom edge area of ​​the outer surface of the immobilized carrier material 1. All sensors are connected to a controller, which is connected to the circulation pump 9. In this example, the controller sets the lower limit of carrier surface humidity to 55% and the upper limit to 90%. The minimum safe liquid level in the funnel-shaped liquid collection tank 7 is 20% of the effective height of the tank, and the upper limit of the culture medium temperature is 32°C. When the detected value of any carrier surface humidity sensor is lower than 55%, the controller starts the circulation pump 9 and operates at 0.12... The liquid supply is L / (min·m² carrier area). When all humidity detection points are above 90%, the controller stops the liquid supply for 10 to 30 minutes. When the temperature is above 32°C, the controller increases the liquid supply frequency to promote evaporative cooling and liquid replacement. When the liquid level is below the minimum safe level, the controller immediately stops the circulation pump 9 and issues a liquid replenishment alarm. After 7 days of operation, compared with the fixed pulse cycle liquid supply, the sensor feedback liquid supply reduces the humidity difference between the top, middle and bottom of the carrier, and the regional difference in algal film dry weight is reduced from about 20% to about 12%. The microalgal biomass yield per unit carrier area is increased to 17.6 g / (m²·d). This embodiment shows that the sensor setting position directly corresponds to the circulating liquid status, the liquid supply inlet status, the collection tank liquid level and the algal film surface wetness status, which can provide feedback basis for the start and stop of the circulation pump 9, the flow rate and the pulse liquid supply cycle.

[0062] Comparative Example 1: The same semi-arched structure, the same immobilized carrier material, and the same culture conditions as in Example 1 were used, but the interlayer flow channel 3 was removed, so that the culture medium flowed directly from the top through the outer surface of the immobilized carrier material 1.

[0063] After 7 days of cultivation, a clear scouring zone appeared in the initial liquid distribution area at the top, and the algal film was thicker in the lower area. The dry weight difference between the top, middle and bottom sampling areas reached 42%, the microalgal biomass yield per unit carrier area was 12.1 g / (m²·d), and the concentration of suspended algal cells in the circulating liquid was about 0.42 g / L.

[0064] Comparative Example 2: An inverted V-shaped adherent culture structure was adopted, and external surface spraying was used for liquid supply. The culture medium, algal species, and light conditions were the same as in Example 1.

[0065] After 7 days of cultivation, the algal film at the top of the inverted V and in the area directly affected by the spray was relatively thin, while the algal film accumulated in the bottom confluence area. The microalgal biomass yield per unit carrier area was 13.0 g / (m²·d), and the average daily evaporation water replenishment was about 1.6 times that of Example 1 of this invention.

[0066] Comparative Example 3: A rotating carrier membrane culture structure was used, with the carrier periodically immersed in the culture medium. The culture medium, algae species, and light conditions were the same as in Example 1.

[0067] After 7 days of cultivation, local algal membranes detached during the carrier rotation process, the concentration of suspended algal cells in the culture medium reached 0.55 g / L, and the microalgal biomass yield per unit carrier area was 13.7 g / (m²·d).

[0068] Microalgae were cultured using the sandwich-type semi-arched immobilized microalgae membrane reactors and methods described in Examples 1 to 3 of this invention, and compared with the control culture methods of Comparative Examples 1 to 3. The comparison of key performance parameters such as culture cycle, biomass yield per unit carrier area, and concentration of suspended algae in the circulating liquid is shown in Table 1. Table 1 Comparison of culture results between the embodiments of the present invention and the comparative examples:

[0069] As shown in Table 1, the results of Examples 1 to 3 and Comparative Examples 1 to 3 indicate that the present invention, through the combined design of a semi-arched gentle slope configuration, back-side wetting of the interlayer flow channel, perforated stainless steel support structure for air and liquid permeability, and bottom funnel-shaped liquid collection and circulation, can reduce the amount of culture medium used while reducing algal film erosion and shedding, improving algal film thickness distribution, and increasing the stability of immobilized microalgal film culture and yield per unit carrier area.

[0070] The data in Table 1 above are exemplary culture results conducted according to the structural design of this invention and under the same light, temperature and culture medium conditions. They are used to illustrate the technical effects of this invention and are not intended to limit the scope of protection of this invention under different algal species, different scales and different operating conditions.

[0071] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A sandwich-wetting semi-arched immobilized microalgae membrane reactor, characterized in that, It includes a support base (11), a semi-arched culture body, a liquid distributor (5), a liquid distribution port (6), a funnel-shaped liquid collection tank (7), a bottom drain port (8), a circulation pump (9), and a return pipe (10). The semi-arched culture body is fixedly installed above the support base (11). The semi-arched culture body includes an immobilized carrier material (1) on the outer side, a perforated stainless steel support structure (2) on the inner side, and a sandwich flow channel (3) between the immobilized carrier material (1) and the perforated stainless steel support structure (2). The bottom of the semi-arched culture body is a circular or nearly circular support area, and the top is provided with a top circular flat structure (4). The liquid distributor (5) is located at the top circular flat structure (4), and the liquid distributor (5) is provided with a liquid distribution port (6), which is connected to the interlayer flow channel (3). The funnel-shaped liquid collection tank (7) is located below the semi-arched culture body. The bottom of the funnel-shaped liquid collection tank (7) is provided with a bottom drain port (8). The bottom drain port (8) is connected to the liquid distributor (5) via the circulation pump (9) and the return pipe (10) in sequence, so that the culture medium enters the interlayer flow channel (3) from the liquid distributor (5) through the liquid distribution port (6) and flows from top to bottom along the semi-arched arc surface, wetting the immobilized carrier material (1) from the back side.

2. The sandwich-wetting semi-arched immobilized microalgae membrane reactor according to claim 1, characterized in that: The semi-arched culture body is an axisymmetric structure. The diameter of the top circular flat structure (4) is 1 / 5 to 1 / 10 of the diameter of the bottom circular structure of the semi-arched culture body. The height of the semi-arched culture body is 0.2 to 0.6 times the diameter of the bottom circular structure.

3. The sandwich-wetting semi-arched immobilized microalgae membrane reactor according to claim 1, characterized in that: The immobilization carrier material (1) is selected from one or more of nylon cloth, linen, cotton cloth, non-woven fabric, filter cloth, polyester fiber cloth, polypropylene fiber cloth, sponge layer, fiber felt or modified hydrophilic fabric. The immobilization carrier material (1) is fixed to the outside of the perforated stainless steel support structure (2) by means of pressure strip, buckle, cable tie, edge clamp, detachable ring pressure frame or corrosion resistant adhesive. The immobilized carrier material (1) is a composite carrier structure. The composite carrier structure includes an outer microalgae attachment layer, a middle water-retaining capillary layer and an inner liquid-conducting contact layer arranged sequentially from the outside to the inside. The outer microalgae attachment layer is used to provide a surface for microalgae cell attachment, and the inner liquid-conducting contact layer is in contact with the interlayer flow channel (3).

4. The sandwich-wetting semi-arched immobilized microalgae membrane reactor according to claim 1, characterized in that: The perforated stainless steel support structure (2) is a perforated stainless steel plate, stainless steel mesh plate, stainless steel perforated plate or stainless steel wire mesh composite plate. The thickness of the perforated stainless steel support structure (2) is 0.3mm to 5mm, the hole diameter is 0.2mm to 10mm, and the opening rate is 5% to 50%. The perforated stainless steel support structure (2) and the immobilized carrier material (1) define the interlayer flow channel (3), the spacing of the interlayer flow channel (3) is 0.2 mm to 20 mm, and the interlayer flow channel (3) is provided with one or more of the following: liquid guiding mesh, capillary liquid guiding layer, spacer protrusions, microgrooves, hydrophilic fiber layer or partition flow blocking element.

5. The sandwich-wetting semi-arched immobilized microalgae membrane reactor according to claim 1, characterized in that: The liquid distributor (5) is an annular distribution pipe, a circular disc distributor, a perforated annular pipe, a radial branch pipe, or an annular groove distributor. The liquid distribution port (6) is a small hole, a short pipe, a slit, a drip tip, or a microporous liquid distribution device. Multiple liquid distribution ports (6) are evenly arranged along the circumference of the top circular flat layer structure (4).

6. The sandwich-wetting semi-arched immobilized microalgae membrane reactor according to claim 1, characterized in that: The upper edge of the funnel-shaped liquid collection tank (7) corresponds to the bottom circular area of ​​the semi-arched culture body. The funnel-shaped liquid collection tank (7) gradually shrinks from the periphery to the center to the bottom drain port (8), which is used to collect the culture solution flowing out from the bottom of the interlayer channel (3) and the culture solution dripping through the holes of the perforated stainless steel support structure (2).

7. The sandwich-wetting semi-arched immobilized microalgae membrane reactor according to claim 1, characterized in that: It also includes one or more of the following: pH sensor, temperature sensor, liquid level sensor, conductivity sensor, dissolved oxygen sensor, nutrient salt sensor, carrier surface humidity sensor or controller. When the reactor also includes the controller, the controller is connected to the circulating pump (9) and is used to adjust the start / stop, flow rate or pulse supply cycle of the circulating pump (9) according to the detection signal.

8. The sandwich-wetting semi-arched immobilized microalgae membrane reactor according to claim 1, characterized in that: It also includes one or more of the following: scraping components, flexible scrapers, backflushing pipelines, carrier disassembly components, or carrier clamping components, used to harvest microalgae after the immobilized microalgae film reaches the target thickness, and to retain a portion of the residual algae film as seed film for the next round of cultivation.

9. A method for cultivating microalgae in a sandwich-wetting semi-arched immobilized microalgae membrane reactor, applied to the sandwich-wetting semi-arched immobilized microalgae membrane reactor as described in any one of claims 1-8, characterized in that: Includes the following steps: S1, the immobilized carrier material (1) is installed on the outside of the perforated stainless steel support structure (2), and the sandwich flow channel (3) is formed between the two. S2, add culture medium to the funnel-shaped liquid collection tank (7) or the matching liquid storage container; S3, start the circulation pump (9) so that the culture medium enters the liquid distributor (5) through the return pipe (10) and enters the interlayer flow channel (3) through the liquid distribution port (6). S4, the microalgae seed liquid is inoculated onto the outer surface of the immobilized carrier material (1), or the microalgae cells are inoculated by back-side wetting through the interlayer channel (3) so that the microalgae cells attach to the immobilized carrier material (1). S5, low flow or intermittent interlayer immersion solution is used in the early stage of membrane formation, and continuous or pulsed interlayer immersion solution is used in the growth period, so that microalgae form an immobilized microalgae membrane on the surface of the immobilized carrier material (1). S6. When the immobilized microalgae film reaches the target thickness or target biomass, microalgae are harvested by scraping, flexible scraping, increasing the liquid supply flow rate for rinsing, backwashing, or disassembling the immobilized carrier material (1).

10. The method for cultivating microalgae in a sandwich-wetting semi-arched immobilized microalgae membrane reactor according to claim 9, characterized in that: In the early stage of film formation, the supply intensity of the culture medium is lower than that in the growth period. The intermittent supply method is adopted in the early stage of film formation. After running for 1 to 10 minutes, it is stopped for 5 to 60 minutes. After the immobilized microalgal film is continuously formed, the supply method is adjusted to continuous supply or pulse supply. At the time of harvest, 5% to 30% of the residual algal film is retained as the seed film for the next round of culture. The microalgae are selected from one or more of Chlorella, Scenedesmus, Spirulina, Dunaliella, Haematococcus pluvialis, diatoms, Euglena, or mixed microalgae species. The culture medium is selected from one of BG11 medium, Z medium, F / 2 medium, SM medium, D1 medium, aquaculture tailwater, agricultural wastewater, food processing wastewater, secondary effluent of domestic sewage, or industrial wastewater that has been adjusted with nutrients. During the cultivation process, the flow rate or supply cycle of the circulating pump (9) is adjusted according to the pH value, temperature, liquid level, conductivity, dissolved oxygen, nutrient salt concentration or carrier surface humidity signal. When the microalgae is Chlorella or Scenedesmus, the pH of the culture medium is controlled between 6.0 and 8.

5. When the microalgae is Spirulina, the pH of the culture medium is controlled between 8.5 and 11.0.

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