An algal bio-disc system and a method for treating aquaculture tail water and harvesting microalgae using the system

Abstract

The application discloses an algae biological rotating disc system and a method for treating aquaculture tail water and collecting microalgae by using the system. The algae biological rotating disc system comprises a reaction tank body, a rotating disc assembly and a collecting device, the rotating disc assembly is arranged in the reaction tank body, the rotating disc assembly comprises a rotatable rotating shaft and a rotating disc fixed on the rotating shaft, the rotating shaft is arranged through the reaction tank body, so that the rotating disc assembly rotates relative to the reaction tank body, the rotating disc comprises a disc piece and a carrier layer, the disc piece is provided with a supporting surface, the carrier layer is detachably fixed on the supporting surface, and the surface water contact angle of the carrier layer is greater than 90 degrees; and the collecting device comprises a scraper or a scraper knife and a collecting container for collecting algal sludge. The application can collect algal sludge with a water content of 70% to 85% and a microalgae purity of greater than or equal to 80% by using aquaculture tail water as a culture medium to produce microalgae biomass, and can be used for protein feed, bait or biodiesel raw material, and can simultaneously realize sewage purification.

Description

Technical Field

[0001] This invention relates to the field of microalgae cultivation and wastewater treatment technology, specifically to an algae rotating disc system and a method for treating aquaculture wastewater and harvesting microalgae using this system. Background Technology

[0002] The Algal Rotating Biological Contactor (ARBC) is a typical semi-submerged, rotating attachment culture system. Due to its simple structure, low energy consumption, small footprint, and ease of maintenance, it shows promising application prospects in wastewater treatment and microalgae cultivation. The core structure of the ARBC consists of a series of parallel discs, partially submerged in a nutrient-rich liquid. Driven by a motor, the discs rotate slowly, causing the microalgae attached to the discs to periodically undergo alternating "submersion-exposure" cycles, thus enhancing the mass transfer efficiency of CO2 and O2.

[0003] Existing algal biodisc technologies mainly fall into two categories: one targets wastewater treatment, utilizing an algal-microbe symbiotic system to remove pollutants such as COD, nitrogen, and phosphorus; the other targets microalgal biomass production, using artificial culture media (such as BG11 and M8-a) for pure cultivation. In recent years, some studies have attempted to combine the two, recovering microalgal biomass while treating wastewater. However, existing technologies have the following shortcomings:

[0004] (1) Low harvesting efficiency and high water content of algae sludge: Existing algae bioreactors generally use mechanical brushes or scrapers to scrape the algae film into the reactor water. After the algae sludge falls to the bottom of the tank, it is discharged after sedimentation. The water content is as high as 95% or more, resulting in high energy consumption and high cost for subsequent treatment. At the same time, the harvested algae sludge contains a large amount of suspended solids in the reactor, and the purity of microalgae is low, making it difficult to use directly as a high-value feed ingredient. For example, Li et al. (Li et al., Aquaculture, 2026, 611: 743036) reported an algae and bacteria bioreactor system with automatic harvesting using mechanical brushes. Its carrier is hydrophilic canvas. During harvesting, the algae sludge falls to the bottom of the tank with a high water content and needs to be settled and dehydrated before it can be used.

[0005] (2) Inconvenient replacement and maintenance of the carrier: The existing algal biological rotating discs are mostly rigid structures, and the carrier and the disc are fixed together. When it is necessary to change the algal species or deal with system pollution, the entire disc needs to be replaced, which is costly and complicated to operate.

[0006] Furthermore, existing technologies primarily focus on improving pollutant removal efficiency or simply cultivating algae, neglecting key indicators that constrain the economics of microalgae biomass, such as the moisture content, purity, and suitability for direct resource utilization of the harvested algae sludge. For example, while CN117003371A mentions recyclable microalgae, its core innovation lies in constructing a layered algae-bacteria structure using 3D bioprinting to improve wastewater treatment efficiency and achieve carbon reduction, without providing a specific technical solution for obtaining low-moisture-content, high-purity algae sludge. Therefore, there is an urgent need to propose an algae bio-rotating disc system and its operation method oriented towards the direct harvesting of high-quality algae sludge. Summary of the Invention

[0007] To overcome the problems of high water content in algal sludge harvesting, inconvenient carrier maintenance, and low resource utilization efficiency in existing technologies, this invention provides an algal bio-rotating disc system and a method for treating aquaculture wastewater and harvesting microalgae using this system. The method proposed in this invention uses aquaculture wastewater as a culture medium for microalgal biomass production, and can harvest algal sludge with a water content of 70%~85% and a microalgae purity of ≥80%, which can be used for protein feed, bait, or biodiesel feed, while simultaneously achieving wastewater purification, thus realizing the organic unity of high-value algal biomass production and wastewater purification.

[0008] The first objective of this invention is to provide an algae bioreactor system, comprising a reaction tank, a rotating disc assembly, and a harvesting device for scraping algae film. The rotating disc assembly is disposed within the reaction tank and includes a rotatable shaft and a rotating disc fixed on the shaft. The shaft extends through the reaction tank, allowing the rotating disc assembly to rotate relative to the reaction tank. The rotating disc includes a disc plate and a carrier layer. A support surface is provided on the disc plate, and the carrier layer is detachably fixed to the support surface. The surface water contact angle of the carrier layer is >90°. The harvesting device includes a scraper or blade for scraping algae film and a collection container for collecting algae sludge.

[0009] Preferably, the carrier layer is made of polyester fiber with a water contact angle of 100°~110° and a surface zeta potential of -20~(-10) mV. The carrier layer is a hydrophobic flexible sheet material. The polyester fiber material proposed in this invention has strong hydrophobicity (water contact angle 105°) and a negative surface charge (zeta potential -15.40 mV). This hydrophobic material has a strong hydrophobic interaction with microalgal cells, which is beneficial for the rapid initial attachment of microalgae, and the resulting algal film is stable and not easily detached. This invention applies this hydrophobic carrier to an algal biodisc system and designs a matching dry harvesting process and a detachable fixing structure based on its hydrophobic characteristics, thereby achieving synergistic optimization of wastewater resource utilization and high-value algal sludge production.

[0010] More preferably, the polyester fiber is polyethylene terephthalate fiber, and the length of the polyethylene terephthalate fiber is 11~14 mm or 5~8 mm.

[0011] The polyester fiber material proposed in this invention exhibits strong hydrophobicity (water contact angle 105°), which generates strong Lewis acid-base interactions, driving microalgae to rapidly attach within 24 hours (attachment rate ≥95%) and maintaining the clarity of the reactor water (OD680 ≤ 0.05). This characteristic provides a prerequisite for subsequent dry harvesting: due to the minimal amount of suspended algae, pre-harvest drainage will not cause algal sludge pollution.

[0012] Preferably, the detachable method is selected from one or more of Velcro, snaps, pressure strips, and clamps. The carrier layer is fixed to the support surface by a detachable connection. The detachable connection method allows the carrier layer to be replaced without removing the disk.

[0013] The detachable fixing structure proposed in this invention is compatible with the material properties of the hydrophobic carrier: the polyester fiber carrier has a smooth, flexible surface, is resistant to water immersion, and is resistant to biodegradation, allowing for easy peeling and reattaching via Velcro or other detachable methods. While other flexible carriers (such as canvas) can also be made detachable, canvas, being a natural fiber material, is prone to biodegradation and decay after long-term immersion in wastewater, resulting in a short lifespan, frequent replacements, and increased maintenance costs. Using 3D-printed hydrogel membranes is expensive; the microalgae are embedded within the gel, requiring the hydrogel to be dissolved before harvesting to extract the algal cells. Furthermore, the carrier cannot retain algal cells after each harvest, necessitating the re-preparation of hydrogel and re-encapsulation of microalgae, making continuous cultivation difficult and resulting in complex and costly operations. Therefore, this invention chooses a polyester fiber carrier combined with a detachable fixing structure, based on a comprehensive consideration of material durability, harvesting convenience, and economy. Meanwhile, the hydrophobic surface of the polyester fiber carrier allows algae to mainly adhere to the surface rather than easily penetrate into the pores or inside the fibers like hydrophilic carriers (such as canvas). When scraping, the algal membrane is easy to peel off, and the remaining bottom layer of algae is uniform, which is conducive to rapid recovery.

[0014] Preferably, the turntable assembly has a plurality of turntables connected by a rotating shaft, and the ratio of the spacing between adjacent discs to the disc diameter is 1:3.25 to 1:5.20.

[0015] More preferably, the ratio of the spacing between adjacent disks to the disk diameter is 1:3.5 to 1:4.5.

[0016] In a further preferred embodiment, the ratio of the spacing between adjacent disks to the disk diameter is 1:4.

[0017] Preferably, the immersion rate of the turntable in the reaction tank is 30% to 50%.

[0018] The harvesting device proposed in this invention is used to contact the surface of the carrier layer in the harvesting state and scrape off the algal film; the harvesting tool is configured such that the scraped algal mud falls directly into or is introduced into the collection container without contacting the water in the reaction tank.

[0019] The second objective of this invention is to provide the application of the aforementioned algal rotating disc system in treating aquaculture wastewater and harvesting microalgae.

[0020] A third objective of this invention is to provide a method for treating aquaculture wastewater and harvesting microalgae using the aforementioned algae-rotating disc system, comprising the following steps:

[0021] S1. Inoculate microalgae onto the surface of the carrier layer, introduce aquaculture wastewater into the reaction tank, and operate the turntable assembly under light conditions to allow microalgae to form an algal film on the surface of the carrier layer.

[0022] S2. According to the preset harvesting frequency, stop the water intake and drain part or all of the water in the reaction tank, so that the carrier layer is exposed above the liquid surface.

[0023] S3. Use a scraper or scraper to contact the surface of the carrier layer and scrape off the algal film. The scraped algal mud is directly received by the collection container. The scraped algal mud does not come into contact with the water in the reaction tank during the entire harvesting process.

[0024] S4. After harvesting, retain the bottom algae seed layer on the surface of the carrier layer, restore the water level in the inlet and reaction tank, and continue operation.

[0025] The method proposed in this invention combines drainage, dry scraping, and preservation of the seed source layer: ① Due to the extremely low amount of suspended algae, there are no impurities remaining in the reactor after drainage, and the purity of the scraped algal sludge is as high as 80% or more; ② Drainage completely exposes the carrier layer, preventing water film from mixing into the algal sludge, and reducing the water content of the algal sludge to 70%~85% (far lower than the 95% or more of the prior art); ③ Preserving the bottom algal seed layer allows the system to restore photosynthetic activity within 5 days without the need for re-inoculation.

[0026] Preferably, the microalgae described in step S1 completes attachment within 24 hours after inoculation, with an attachment rate ≥95% on the carrier layer surface and an OD680 ≤0.05 in the water within the reaction tank; and / or, the algal film does not detach naturally without external scraping and can only be peeled off by applying mechanical force with a scraper or scraper during harvesting; and / or, the harvesting frequency described in step S2 is 5-7 days. The microalgae is Chlorella vulgaris.

[0027] Preferably, the water content of the harvested algal mud in step S3 is 70%~85%, and the purity of microalgae in the algal mud is ≥80%.

[0028] Preferably, the thickness of the bottom algal seed layer in step S4 is 0.5~2.0 mm.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. The present invention significantly improves the quality of algal mud, with a harvested algal mud moisture content of 70-85%, microalgae purity ≥80%, and rich in high-value compounds such as protein or oil, which can be directly used as protein feed or biodiesel feed without the need for a high-energy-consuming dehydration step.

[0031] 2. The method proposed in this invention achieves the treatment effect simultaneously, purifying wastewater while obtaining high-quality algae sludge, with high DO in the effluent, which can be reused without aeration.

[0032] 3. The algae biological rotating disc system proposed in this invention is easy to maintain, the carrier is detachable and replaceable, and the cost is low; the algae membrane is not easy to fall off and recovers quickly after harvesting.

[0033] In summary, the present invention proposes a method for producing microalgae biomass using aquaculture wastewater as a culture medium through an algae rotating disc system, while simultaneously treating wastewater. By optimizing the disc spacing, hydraulic retention time, and harvesting frequency, algae mud with a moisture content of 70%~85% and a microalgae purity of ≥80% can be obtained. This mud can be used as protein feed, bait, or biodiesel feed, while simultaneously achieving the effect of purifying aquaculture wastewater. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of the algal bio-rotating disk proposed in this invention;

[0035] Figure 2 This is a schematic diagram of a single turntable structure;

[0036] Explanation of reference numerals in the attached figures:

[0037] 1. Reaction tank; 2. Rotating shaft; 3. Turntable; 301. Disc; 302. Carrier layer; 4. Drive motor; 5. Inlet; 6. Outlet; 7. Drain; 8. Clamping plate; 9. Scraper; 10. Collection container;

[0038] Figure 3 The yield and productivity of algal biofilm under different turntable spacings in Example 2 are shown, where a is the yield and productivity based on the surface area of ​​the carrier material; and b is the yield and productivity based on the floor area.

[0039] Figure 4 The yield and productivity of algal biofilm under different HRTs in Example 2 are shown, where a is the yield and productivity based on the surface area of ​​the carrier material; and b is the yield and productivity based on the floor area.

[0040] Figure 5The yield and productivity of algal biofilm at different harvesting frequencies in Example 2 are shown, where a is the yield and productivity based on the surface area of ​​the carrier material; and b is the yield and productivity based on the land area.

[0041] Figure 6 The carrier material after multiple harvests of algal biofilm in Example 3;

[0042] Figure 7 The figures show the time-varying parameters of the algal biofilm on each rotating disk in Example 3, where a is the maximum photon yield (F). v / F m b is the energy loss photon yield (F0 / F) m c is the electron transport photon yield (ET0 / ABS); d is the photosynthetic electron transport efficiency (ET0 / TR0). Detailed Implementation

[0043] The following embodiments are further illustrations of the present invention, but not limitations thereof.

[0044] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention. Unless otherwise specified, the experimental materials and reagents used herein are commercially available products conventionally available in this technical field.

[0045] like Figure 1-2 As shown, the algae bioreactor system includes a reaction tank 1, a rotating disk assembly, a drive motor 4, and a harvesting device. The rotating disk assembly is located inside the reaction tank 1 and includes a rotatable shaft 2 and a rotating disk 3 fixed on the shaft. The shaft 2 extends through the reaction tank 1. The drive motor 4 drives the shaft 2 to rotate the rotating disk assembly relative to the reaction tank 1. The rotating disk 3 includes a disc 301 and a carrier layer 302. A support surface is provided on the disc 301, and the carrier layer 302 is detachably fixed to the support surface. The surface water contact angle of the carrier layer 302 is >90°. The harvesting device includes a scraper 9 or blade for scraping algae film and a collection container 10 for collecting algae sludge.

[0046] The carrier layer is made of hydrophobic flexible sheet material. In the following embodiments, polyester fiber is preferred, with a water contact angle of 100°~110° and a surface zeta potential of -20~(-10) mV.

[0047] The turntable assembly comprises several turntables 3 connected by a rotating shaft 2. The ratio of the spacing between adjacent discs 301 to their diameter is 1:3.25 to 1:5.20. The immersion rate of the turntables 3 in the reaction tank is 30% to 50%. In the following preferred embodiments, the ratio of the spacing between adjacent discs 301 to their diameter is 1:3.5 to 1:4.5, and the spacing between adjacent discs 301 is 5 to 8 cm. More preferably, the ratio of the spacing between adjacent discs 301 to their diameter is 1:4, and the spacing between adjacent discs 301 is 6.5 cm.

[0048] In the preferred embodiment described below, the reaction tank 1 has dimensions of 35 cm × 35 cm × 17.5 cm and an effective volume of 12 L. A rotating shaft 2 runs through the entire reaction tank 1 and is driven to rotate by a drive motor 4 via a transmission system. A disc 301, with an outer diameter of 26 cm and a thickness of 2 mm, is made of plexiglass and is fixed to the rotating shaft 2. The liquid level in the reaction tank 1 is controlled to ensure that the disc 301 (rotating disc 3) is 40% submerged.

[0049] In the preferred embodiment described below, the carrier layer 302 is made of polyester fiber, specifically polyethylene terephthalate fiber. The length of the polyethylene terephthalate fiber is 11-14 mm or 5-8 mm, the thickness is 0.6 mm, the water contact angle is 105°, the zeta potential is -15.40 mV, and it exhibits strong hydrophobicity. The carrier layer is detachably fixed to the support surface of the disk 301 using Velcro. The hook side of the Velcro is fixed to the support surface, and the rough side is fixed to the back of the carrier layer. When the carrier layer needs to be replaced, it is peeled off from the support surface, a new carrier layer is installed, and then pressed and attached. The support surface is reusable, and the disk does not need to be replaced. The detachable connection method proposed in this invention is not limited to Velcro; it can also be achieved using snaps, pressure strips, clamps, etc. In the preferred embodiment described below, the carrier layer 302 is fixed to the support surface of the disk 301 using clamp 8. When the carrier layer needs to be replaced, it is peeled off from the support surface, a new carrier layer is installed, and then fixed using clamp 8.

[0050] In this invention, the specific form of the harvesting device is not limited, as long as it can achieve contact with the carrier layer surface, scrape off the algal film, and directly collect the scraped algal sludge without it falling into the reactor water. As an example, the tool for scraping the algal film can be a handheld scraper or scraper blade, which the operator places in contact with the disc surface, and the scraped algal sludge falls directly into a pre-placed collection container. The harvesting tool can also be a scraper or scraper blade mounted on a support, moved into the working position during harvesting, and removed after harvesting. Alternatively, the tool can be an automatic scraper or scraper blade device integrated with the rotary disc assembly, which separates from or detaches from the carrier layer in the non-harvesting state, and automatically extends to contact the carrier layer in the harvesting state. Regardless of the form used, the scraped algal sludge does not contact the reactor water during the harvesting process.

[0051] In the preferred embodiment described below, the harvesting device employs a handheld scraper 9 and a collection container 10. In the non-harvesting state, the harvesting device is separated from the turntable assembly, does not contact the surface of the carrier layer 302, and does not affect the normal rotation of the turntable 3. In the harvesting state, the operator brings the scraper 9 into contact with the surface of the carrier layer 302, while the turntable 3 rotates at a speed lower than the normal operating speed (or pauses rotation). The scraper 9 scrapes off the algal film from the surface of the carrier layer 302, and the scraped algal sludge falls directly into the collection container 10. Throughout the harvesting process, the scraped algal sludge does not come into contact with the reactor water. After harvesting is completed, the harvesting device is moved out of its operating position, and the reactor is restored to normal operation.

[0052] The method for treating aquaculture wastewater and harvesting microalgae using the above-mentioned algal rotating disc system includes the following steps:

[0053] S1. Aquaculture wastewater is introduced into the reaction tank through inlet 5, and microalgae are inoculated into the wastewater. The rotating disk assembly is operated under light conditions to allow the microalgae to stably attach to the surface of the carrier layer 302 and form an algal film.

[0054] S2. According to the preset harvesting frequency (5~7 days), stop the water intake and discharge part or all of the water in the reaction tank through the drain outlet 7, so that the carrier layer 302 is exposed above the liquid surface.

[0055] S3. Use a scraper 8 or a scraper to contact the surface of the carrier layer 302 to scrape off the algal film. The scraped algal mud is directly received by the collection container 10. The scraped algal mud does not come into contact with the water in the reaction tank during the entire harvesting process.

[0056] S4. After harvesting, retain the bottom algal seed layer (0.5~2.0 mm) on the surface of carrier layer 302, restore the water level at inlet 5 and the liquid level in the reaction tank, and continue operation.

[0057] Example 1

[0058] A method for treating aquaculture wastewater and harvesting microalgae includes the following steps:

[0059] S1, Film Formation Stage

[0060] Add BG11 medium to the reaction tank, inoculate with Chlorella vulgaris, and the initial OD... 680 =2.0. The hydrophobic carrier layer used in this embodiment is polyethylene terephthalate fiber (water contact angle >90°) with a length of 11-14 mm and a thickness of 0.6 mm, which has a strong hydrophobic interaction with the microalgal cells. This hydrophobic carrier enables the microalgae to complete attachment within 24 hours after inoculation, with an attachment rate exceeding 95%, and the water in the reaction tank changes from initial green turbidity to clear and transparent (OD). 680(Value below 0.05). Subsequently, the algal film continued to grow on the surface of the carrier layer. During nearly four months of continuous operation and multiple harvests, the algal film only peeled off during active scraping, without any natural detachment due to hydraulic shear or disc rotation. Based on these characteristics, this embodiment adopts a dry harvesting method, where the scraped algal film is directly received by the collection container without contacting the reactor water. This harvesting method ensures that the scraped algal film contains almost no suspended solids, and the harvesting operation does not affect the effluent quality, avoiding secondary pollution caused by natural detachment of the algal film or algal sludge falling into the water during harvesting, as is common in traditional technologies.

[0061] S2, Wastewater Acclimation and Continuous Operation

[0062] After the biofilm stabilized, the influent was gradually replaced with aquaculture wastewater (1 / 4 replaced daily), and after complete replacement with aquaculture wastewater on the 9th day, continuous influent was introduced. The aquaculture wastewater used in the experiment had the following water quality indicators: COD 75 mg / L, NH4+... + -N 4 mg / L, NO3 - -N 20 mg / L, PO4 3- -P 4 mg / L. Hydraulic retention time (HRT) was controlled at 24 h, with a light-dark cycle of 14 h:10 h.

[0063] S3, Harvesting Operations

[0064] When the preset harvesting frequency is reached (5 days in this embodiment), the water intake is stopped, and some or all of the water in the reaction tank is drained, so that the carrier layer is completely exposed above the liquid surface. This prevents the water film in the submerged area at the bottom of the carrier layer from mixing with algal mud during scraping, ensuring the dry harvesting effect and obtaining a lower moisture content in the algal mud.

[0065] Subsequently, a tool for scraping the algal film, such as a handheld scraper, is brought into contact with the surface of the carrier layer exposed above the liquid level to scrape off the algal film. The scraped algal sludge is directly collected by a collection container. Throughout the entire harvesting process, the scraped algal sludge never comes into contact with the reactor water. After harvesting, the bottom algal seed layer (approximately 0.5–2.0 mm thick) on the surface of the carrier layer is retained, the influent and reaction tank levels are restored, and operation continues. Because there are very few suspended algal cells in the water, the harvesting operation does not affect the effluent quality, and operation can continue without additional treatment.

[0066] This embodiment uses clamps for fixing and a hand scraper for harvesting, but it is not limited to this method. Figure 2 This is just one example.

[0067] Example 2: Optimization of Operating Parameters

[0068] (1) Platter spacing optimization: The platter spacing was set to 5 cm, 6.5 cm, and 8 cm, with other conditions the same as in Example 1. The results are as follows: Figure 3As shown, the algal biofilm yield is highest when the distance between adjacent discs is 6.5 cm (disc diameter / distance between adjacent discs ≈ 4).

[0069] (2) Hydraulic Retention Time (HRT) Optimization: HRTs were set to 12 h, 24 h, and 48 h, with other conditions the same as in Example 1. Results are as follows: Figure 4 As shown, the algal biofilm yield was highest when the HRT was 24 h.

[0070] (3) Harvesting frequency optimization: The harvesting frequencies were set to 1 day, 3 days, 5 days, 7 days, and 9 days, with other conditions the same as in Example 1. The results are as follows: Figure 5 As shown, the biomass yield is highest when the harvesting frequency is 5 days.

[0071] Example 3: Treatment Efficiency and Algae Sludge Quality

[0072] Under optimal operating conditions (disc spacing 6.5 cm, HRT 24 h, harvesting frequency 5 days / time), other treatment steps were the same as in Example 1, and the system's removal effect on pollutants is shown in Table 1:

[0073] Table 1 Pollutant Removal Efficiency

[0074] During operation, the water pH is maintained at 7-8 and DO is maintained at 7-8 mg / L. The effluent has a high DO content and can be reused without further oxygenation.

[0075] The harvested algal sludge is collected directly in a collection container without contacting the reactor water. The water content of the harvested algal sludge is 70%–85%, far lower than that of traditional techniques (>95%). Metagenomic sequencing analysis shows that microalgae account for as much as 81.88% of all microorganisms in the algal sludge (microalgae purity), maintaining a high microalgae cultivation advantage.

[0076] The harvested algal mud contained 29.31% carbohydrates, 42.29% protein, and 19.79% oil, respectively. The high protein content (42.29%) indicates that the algal mud can be used as a high-quality raw material for protein feed or bio-fertilizer. The fatty acid composition was predominantly C16-C18 (99.12%), with methyl hexadecanoate (C16:0) accounting for 31.88%, which can significantly improve the cetane number of biodiesel and demonstrates good biodiesel conversion potential.

[0077] The carrier layer remained structurally intact and undamaged during nearly four months of continuous cultivation and repeated harvesting. Figure 6 This verified the stability and durability of the carrier material. The photosynthetic activity parameters of the algal biofilm (F0 / F...) m F v / F mET0 / TR0, ET0 / ABS) remain stable during long-term culture. Figure 7 This indicates that the bottom algal seed layer retained after harvesting has good activity recovery ability.

[0078] The above description of the embodiments is only for the purpose of helping to understand the technical solution and core idea of ​​the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. An algal rotating disc system, characterized in that, The invention includes a reaction tank, a turntable assembly, and a harvesting device for scraping algal film. The turntable assembly is disposed within the reaction tank and includes a rotatable shaft and a turntable fixed on the shaft. The shaft extends through the reaction tank, allowing the turntable assembly to rotate relative to the reaction tank. The turntable includes a disc and a carrier layer. A support surface is provided on the disc, and the carrier layer is detachably fixed to the support surface. The surface water contact angle of the carrier layer is >90°. The harvesting device includes a scraper or blade for scraping algal film and a collection container for collecting algal sludge.

2. The algal rotating disc system according to claim 1, characterized in that, The carrier layer is made of polyester fiber, with a water contact angle of 100°~110° and a surface zeta potential of -20~(-10) mV.

3. The algal rotating disc system according to claim 2, characterized in that, The polyester fiber is polyethylene terephthalate fiber.

4. The algal rotating disc system according to claim 1 or 2, characterized in that, The detachable method is selected from one or more of Velcro, buckles, pressure strips, and clamps; and / or, the turntable assembly has a plurality of turntables, which are connected by a rotating shaft, and the ratio of the spacing between adjacent discs to the disc diameter is 1:3.25 to 1:5.

20.

5. The algal rotating disc system according to claim 1 or 2, characterized in that, The immersion rate of the rotating disk in the reaction tank is 30% to 50%.

6. The application of the algae rotating disc system according to claim 1 or 2 in treating aquaculture wastewater and harvesting microalgae.

7. A method for treating aquaculture wastewater and harvesting microalgae using the algae-biological rotating disc system as described in claim 1 or 2, characterized in that, Includes the following steps: S1. Inoculate microalgae onto the surface of the carrier layer, introduce aquaculture wastewater into the reaction tank, and operate the turntable assembly under light conditions to form an algal film on the surface of the carrier layer. S2. According to the preset harvesting frequency, stop the water intake and drain part or all of the water in the reaction tank, so that the carrier layer is exposed above the liquid surface. S3. Use a scraper or scraper to contact the surface of the carrier layer and scrape off the algal film. The scraped algal mud is directly received by the collection container. The scraped algal mud does not come into contact with the water in the reaction tank during the entire harvesting process. S4. After harvesting, retain the bottom algae seed layer on the surface of the carrier layer, restore the water level in the inlet and reaction tank, and continue operation.

8. The method according to claim 7, characterized in that, The microalgae described in step S1 complete attachment within 24 hours after inoculation, with an attachment rate of ≥95% on the surface of the carrier layer and an OD680 of ≤0.05 in the water of the reaction tank; and / or, the algal film does not fall off naturally without external scraping and can only be peeled off by applying mechanical force with a scraper or scraper during harvesting; and / or, the harvesting frequency described in step S2 is 5 to 7 days.

9. The method according to claim 7, characterized in that, The water content of the harvested algal mud in step S3 is 70%~85%, and the purity of microalgae in the algal mud is ≥80%.

10. The method according to claim 7, characterized in that, The thickness of the bottom algal seed layer mentioned in step S4 is 0.5~2.0 mm.

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