Microalgae bioreactor and sewage treatment method

Abstract

The invention relates to a microalgae bioreactor and a sewage treatment method. The microalgae bioreactor comprises a shell, a filter bed, an LED light source and a spraying device, a water outlet and a reflux inlet are formed in the lower part of the shell; the filter bed is made of a porous material and is arranged in the shell; the number of the LED light sources is at least one, and the LED light sources are arranged outside and / or inside the shell; the spraying device is arranged above the filter bed; a water inlet connected with a sewage inlet pipeline is formed in the spraying device; the water inlet is also connected with the reflux inlet through a reflux pipeline. According to the microalgae bioreactor disclosed by the invention, nitrogen and phosphorus substances in sewage are effectively removed by utilizing a microalgae biological membrane, and the effect of recycling nitrogen and phosphorus nutrient elements is realized.

Description

Technical Field

[0001] This invention belongs to the field of biological wastewater treatment, and in particular relates to a method for treating wastewater using a microalgae bioreactor. Background Technology

[0002] Since the British engineers Ardern and Lockett first proposed the activated sludge process in 1914, marking the beginning of modern wastewater treatment technology, traditional wastewater treatment processes centered on activated sludge treatment, through aerobic and anaerobic processes, superficially remove nitrogen and phosphorus from wastewater, but in reality, they harbor secondary pollution. For example, during nitrification, some NO is converted to nitrate nitrogen. x NO emitted into the atmosphere x As a greenhouse gas, phosphorus also contributes to environmental problems such as acid rain and photochemical smog. After being absorbed and accumulated by microorganisms, phosphorus is released back into the environment with sludge, potentially causing eutrophication and preventing the effective utilization of phosphorus. Furthermore, traditional biological methods for nitrogen and phosphorus removal suffer from high energy consumption, high costs, unstable treatment effects, and low nitrogen and phosphorus recovery rates.

[0003] The principle of biological filters for wastewater treatment began to be applied in the 1950s. They use a bed of packed material made of soil or rock to filter wastewater, utilizing microorganisms to degrade organic matter. With the development of packing bed materials, filter beds have achieved higher specific surface areas, lower costs, and higher durability, leading to a wider range of applications for biological filters.

[0004] The most commonly used method for treating domestic sewage is the activated sludge process. Stable operation of this method requires a relatively stable balance between the amount of activated sludge and the influent flow. However, domestic sewage in mining areas mainly originates from employee shower wastewater, living area wastewater, and toilet flushing wastewater, resulting in significant fluctuations in water quality and quantity, and low organic matter concentrations. Therefore, the traditional activated sludge process is generally unstable and has poor treatment efficiency.

[0005] Microalgae are characterized by rapid growth and short life cycles. Their absorption and utilization of nitrogen and phosphorus in water bodies is a crucial part of the nutrient cycle. Microalgae remove nitrogen from the water by absorbing nitrogen sources in different forms, such as ammonium salts and nitrates, and synthesize it into amino acids, proteins, and other substances necessary for growth. Phosphorus, as a limiting element for microalgae growth, plays a vital role in cell synthesis and metabolism. Microalgae can adsorb phosphorus from the water onto their cell surface and transfer it into the cell interior for storage and metabolism, thus removing phosphorus from wastewater. Therefore, microalgae can be used to effectively remove nitrogen and phosphorus from wastewater. Summary of the Invention

[0006] The purpose of this invention is to provide a microalgae bioreactor and a method for treating wastewater, which effectively removes nitrogen and phosphorus from wastewater by utilizing microalgae biofilms, thereby achieving the effect of recovering and utilizing nitrogen and phosphorus nutrients.

[0007] To achieve one aspect of the above-mentioned objectives, the present invention adopts the following technical solution:

[0008] A microalgae bioreactor, comprising a shell, a filter bed, an LED light source, and a spraying device;

[0009] The lower part of the shell is provided with a water outlet and a return outlet;

[0010] The filter bed is made of porous material and is disposed inside the housing;

[0011] The number of LED light sources is at least one, and they are disposed on the outside and / or inside the housing;

[0012] The spraying device is positioned above the filter bed; the spraying device is provided with an inlet connected to the sewage inlet pipe, and the inlet is also connected to the return outlet via a return pipe.

[0013] In some embodiments, the housing is a transparent housing.

[0014] Furthermore, multiple LED light sources are evenly arranged around the transparent shell, and at least one LED light source is provided inside the transparent shell.

[0015] In some embodiments, the filter bed is made of a transparent porous material. Preferably, multiple filter beds are disposed within the microalgae bioreactor, and the multiple filter beds are uniformly distributed within the shell.

[0016] To achieve another aspect of the above-mentioned objective, the present invention also provides a method for treating domestic sewage, the method using a microalgae bioreactor as described above;

[0017] The method includes the following steps:

[0018] S1. Cultivate microalgae to obtain algal solution;

[0019] S2. The algal solution is sprayed onto the surface of the filter bed through a spraying device. After the algal solution flows through the filter bed, it flows out from the return port and is introduced into the inlet through the return pipe to circulate back to the spraying device for spraying. The algal solution is sprayed in a circulating manner until a microalgal biofilm is formed on the surface of the filter bed.

[0020] S3. Pre-treat the wastewater to remove large particulate impurities to obtain pre-treated wastewater;

[0021] S4. The pretreated wastewater is introduced into the spraying device through the inlet and sprayed onto the surface of the filter bed. After contacting the microalgae biofilm, it is circulated back to the spraying device through the return pipe for continuous spraying until the water quality reaches the predetermined standard and is then discharged from the outlet.

[0022] S5. Optionally, remove microalgae from the discharged water.

[0023] In some embodiments, the algal solution is circulated and sprayed for 48-72 hours to form a microalgal biofilm.

[0024] In some embodiments, the microalgae are green algae, preferably Chlorella or Scenedesmus.

[0025] In some embodiments, the amount of water in the microalgae bioreactor does not exceed 1 / 5 of the total reactor capacity.

[0026] In some embodiments, the pretreatment of the wastewater also includes anaerobic conversion of recalcitrant organic matter into smaller molecule organic matter.

[0027] In some embodiments, the wastewater is nitrogen- and phosphorus-rich domestic sewage, preferably domestic sewage from mining areas.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1) This invention uses microalgae biofilm to treat wastewater such as domestic sewage from mining areas, and can treat wastewater in batches according to the volume. Compared with traditional methods, this invention does not produce a large amount of sludge that requires subsequent treatment, and the microalgae cultivated during the wastewater treatment process can be used as fertilizer for subsequent applications.

[0030] 2) The filter bed is made of porous material, which increases the specific surface area of ​​the filter bed and can provide more attachment area for microalgae, thereby improving the treatment efficiency;

[0031] 3) Wastewater is sprayed onto the filter bed surface by a spraying device, allowing it to come into contact with CO2 in the air without the need for aeration. Attached Figure Description

[0032] Figure 1 This is a cross-sectional view of a microalgae bioreactor according to an embodiment of the present invention.

[0033] Figure 2 This is a schematic diagram of a method for treating wastewater using a microalgae bioreactor according to an embodiment of the present invention. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 should fall within the scope of protection of the present invention.

[0035] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to these ranges or values, such as values ​​±10% of the endpoint values. For numerical ranges, endpoint values ​​of various ranges, endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Without conflict, the embodiments and features described in this application can be combined with each other.

[0036] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0037] Furthermore, it should be understood in the description of this application that the terms "above", "below", "top", "bottom", "side", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0038] In one aspect, the present invention provides a microalgae bioreactor. For example... Figure 1 As shown, the microalgae bioreactor 001 includes a shell 1, a filter bed 2, an LED light source 3, and a spray device 4. The lower part of the shell 1 is provided with an outlet 11 and a return port 12; the filter bed 2 is made of porous material and is disposed inside the shell 1; the LED light source 3 is disposed outside and / or inside the shell 1; the spray device 4 is disposed above the filter bed 2; the spray device 4 is provided with an inlet 41 connected to a sewage inlet pipe, and the inlet 41 is also connected to the return port 12 through a return pipe.

[0039] Although not specifically stated, it should be understood that valves may be appropriately installed on the pipes connected to the microalgae bioreactor. For example, valves may be installed on the wastewater inlet pipe and the return pipe respectively to ensure normal flow and circulation of water.

[0040] The lower part of the housing 1 is provided with an outlet 11 and a return outlet 12. The outlet 11 can be located on the lower part of the side wall or the bottom of the housing 1; the outlet 12 can also be located on the lower part of the side wall or the bottom of the housing 1. In a specific embodiment, the outlet 11 is located at the bottom of the housing 1, and the outlet 12 is located on the lower part of the side wall of the housing 1.

[0041] The filter bed 2 provides a surface for microalgae to attach and grow, thereby forming a microalgal biofilm on the surface of the filter bed 2. The filter bed 2 is made of a porous material to increase the surface area available for microalgae to attach and grow. There are no particular limitations on the material used to prepare the filter bed 2, the pore size, etc. In a preferred embodiment, the filter bed 2 is made of a transparent porous material, such as a 3D-printed porous transparent resin. Preferably, the microalgae bioreactor 001 may have one filter bed 2; alternatively, it may have multiple filter beds 2, which are uniformly distributed within the shell 1.

[0042] LED light sources 3 are used to provide the light source required for microalgae growth, and the number and arrangement of the LED light sources 3 can be appropriately set according to the size, shape, or other requirements of the microalgae bioreactor 001. In one embodiment, the shell 1 is a transparent shell made of transparent material, and multiple LED light sources 3 are evenly arranged around the periphery of the shell 1, with at least one LED light source 3 installed inside the shell 1. By installing LED light sources 3 both inside and outside the shell 1, sufficient and uniform light for microalgae growth inside the reactor can be ensured. For example, when there are multiple filter beds 2 in the microalgae bioreactor 001, multiple LED light sources 3 can be arranged between the multiple filter beds 2 to ensure that the light source evenly illuminates the microalgae biofilm attached to the filter beds.

[0043] The spraying device 4 only needs to be able to uniformly spray algae solution or wastewater to be treated onto the surface of the filter bed 2, and its structure is not particularly limited. In one embodiment, the spraying device 4 is a pipe with several nozzles. In another embodiment, the spraying device 4 is a pipe with small water outlet holes at the bottom. The shape of the pipe is not particularly limited, for example, it can be annular, square, or multiple pipes arranged side by side.

[0044] In another aspect, the present invention provides a method for treating wastewater, the method using the above-described microalgae bioreactor;

[0045] The method includes the following steps:

[0046] S1. Cultivate microalgae to obtain algal solution;

[0047] S2. The algal solution is sprayed onto the surface of the filter bed through a spraying device. After the algal solution flows through the filter bed, it flows out from the return port and is introduced into the inlet through the return pipe to circulate back to the spraying device for spraying. The algal solution is sprayed in a circulating manner until a microalgal biofilm is formed on the surface of the filter bed.

[0048] S3. Pre-treat the wastewater to remove large particulate impurities to obtain pre-treated wastewater;

[0049] S4. The pretreated wastewater is introduced into the spraying device through the inlet and sprayed onto the surface of the filter bed. After contacting the microalgae biofilm, it is circulated back to the spraying device through the return pipe for continuous spraying until the water quality reaches the predetermined standard and is discharged from the outlet.

[0050] The method may also optionally include the following steps:

[0051] S5. Remove microalgae from the discharged water.

[0052] In one embodiment, microalgae suspended in the discharged water are removed by sedimentation.

[0053] In this invention, the large particulate impurities include, but are not limited to, silt, suspended matter, etc., which can be easily removed by methods such as sedimentation and filtration.

[0054] Furthermore, the predetermined standard can be appropriately set according to actual applications, without any particular limitations. In one embodiment, the predetermined standard is an industry-related wastewater discharge standard or a reclaimed water reuse standard.

[0055] In this invention, the algal culture method can be any microalgae culture method known in the art. For example, microalgae can be cultured in a conventional photobioreactor (e.g., column, pipeline, etc.) using BG11 medium, wherein the components of the BG11 medium include:

[0056] Sodium nitrate 1.3-1.5 g / L, dipotassium hydrogen phosphate 0.032-0.048 g / L, magnesium sulfate heptahydrate 0.06-0.09 g / L, calcium chloride dihydrate 0.029-0.043 g / L, sodium carbonate 0.018-0.022 g / L, citric acid 0.005-0.007 g / L, ferric ammonium citrate 0.005-0.007 g / L, EDTA 0.0009-0.0011 g / L, trace element solution A 51 mL / L. The components of the trace element solution A5 are: boric acid 2.29-3.43 g / L, manganese chloride dihydrate 1.45-2.17 g / L, zinc sulfate heptahydrate 0.178-0.266 g / L, sodium molybdate 0.312-0.468 g / L, copper sulfate pentahydrate 0.063-0.095 g / L, and cobalt nitrate hexahydrate 0.039-0.059 g / L.

[0057] In one embodiment, the algal solution is circulated and sprayed for 48-72 hours to form a microalgal biofilm.

[0058] In one embodiment, the microalgae is a green algae, which can be a green algae known in the art, such as Chlorella or Scenedesmus.

[0059] The microalgae bioreactor of the present invention treats wastewater in batches, and the amount of wastewater treated in each batch is not particularly limited and can be adjusted appropriately according to actual needs. In a preferred embodiment, the amount of water in the microalgae bioreactor does not exceed 1 / 5 of the total reactor capacity.

[0060] In one embodiment, the pretreatment of the wastewater further includes anaerobic conversion of recalcitrant organic matter into smaller molecule organic matter.

[0061] In one embodiment, the wastewater is nitrogen- and phosphorus-rich domestic sewage, preferably domestic sewage from a mining area.

[0062] In one embodiment of the method of the present invention, a step of periodically cleaning the microalgae biofilm may also be included. When the microalgae biofilm gradually thickens to the point of clogging the water flow, the microalgae biofilm is rinsed clean, and the algal solution is collected from the drain outlet for downstream use, and the microalgae bioreactor is disinfected, for example, using a 100-200 ppm sodium hypochlorite solution.

[0063] Combination Figure 1 and Figure 2The method according to an embodiment of the present invention will be described. Microalgae are cultured in a culture medium to obtain algal solution. The algal solution is sprayed onto the surface of a filter bed 2 through a spray device 4. After flowing through the filter bed 2, the algal solution flows out from the return port 12 and enters the inlet 41 through a return pipe, circulating back to the spray device 4 and spraying onto the surface of the filter bed 2 again. This circulation continues until a microalgal biofilm forms on the surface of the filter bed 2, thus completing the biofilm formation. Wastewater is discharged into a primary sedimentation tank for pretreatment to remove large particulate impurities and anaerobically convert recalcitrant organic matter into smaller organic molecules. The pretreated wastewater is introduced into the spray device 4 through the wastewater inlet pipe via the inlet 41 and sprayed onto the surface of the filter bed 2 where the microalgal biofilm has formed. The wastewater contacts the microalgal biofilm, allowing the microalgae to absorb nitrogen and phosphorus in the water. The wastewater is then circulated back to the spray device 4 through the return pipe for further circulation spraying until the water quality meets the predetermined discharge standards and is discharged from the outlet. The discharged water is then fed into a secondary sedimentation tank for sedimentation to remove any small amount of suspended microalgae before being discharged. Fresh pretreated wastewater is injected into the microalgae bioreactor 001 to continue wastewater treatment. When the microalgae biofilm gradually thickens and clogs the water flow, the microalgae biofilm is cleaned periodically.

[0064] The present invention will be further illustrated below with reference to embodiments / comparative examples.

[0065] Example

[0066] Use such as Figure 1 The microalgae bioreactor 001 shown includes a transparent shell 1, a filter bed 2, an LED light source 3, and a spray device 4. The transparent shell 1 has an outlet 11 at its bottom and a return port 12 on its lower side wall. The filter bed 2 is made of transparent porous resin using 3D printing technology and is located inside the transparent shell 1. Six LED light sources 3 are arranged around the periphery of the transparent shell 1, and one is located at the center inside the transparent shell 1. The spray device 4 is a pipe with nozzles, located above the filter bed 2. The spray device 4 has an inlet 41 connected to a wastewater inlet pipe, and the inlet 41 is also connected to the return port 12 via a return pipe.

[0067] Application example:

[0068] A self-isolated *Scenedesmus* sp. strain was selected and cultured in a 5L Erlenmeyer flask (working volume 4L) using 1% CO2 and BG11 medium. After 6 days, the *Scenedesmus* concentration reached 3.5 g / L (dry weight), yielding the algal solution. A 30L microalgae bioreactor was used, with a transparent porous resin material fabricated using 3D printing technology as the filter bed. The algal solution was sprayed onto the filter bed material through a pipe with nozzles, and a microalgae biofilm formed on the filter bed after 48 hours. After the microalgae biofilm forms, the spraying of algal solution is stopped. The pipes are then cleaned, and artificially prepared wastewater is introduced, containing COD 300 mg / L (sodium acetate), ammonia nitrogen 50 mg / L, and phosphorus 10 mg P / L. The wastewater flowing through the filter bed is circulated back into the spraying device via a return pipe, spraying it onto the filter bed. After 96 hours, the effluent quality of the microalgae bioreactor is tested. The COD in the effluent is consistently below 60 mg / L, ammonia nitrogen below 8 mg / L, and phosphorus below 1 mg / L. The effluent is then passed into a secondary sedimentation tank to remove suspended microalgae, and wastewater is reintroduced into the microalgae bioreactor for the next batch of wastewater treatment.

Claims

1. A microalgae bioreactor, characterized in that, The microalgae bioreactor includes a shell, a filter bed, an LED light source, and a spray device; The lower part of the shell is provided with a water outlet and a return outlet; The filter bed is made of porous material and is disposed inside the housing; The number of LED light sources is at least one, and they are disposed on the outside and / or inside the housing; The spraying device is positioned above the filter bed; the spraying device is provided with an inlet connected to the sewage inlet pipe, and the inlet is also connected to the return outlet via a return pipe.

2. The microalgae bioreactor according to claim 1, characterized in that, The housing is a transparent housing; and / or Multiple LED light sources are evenly arranged around the outer periphery of the transparent shell, and at least one LED light source is provided inside the transparent shell.

3. The microalgae bioreactor according to claim 1, characterized in that, The filter bed is made of a transparent porous material; preferably, the microalgae bioreactor is provided with multiple filter beds, which are evenly distributed within the shell.

4. The microalgae bioreactor according to any one of claims 1 to 3, characterized in that, The spraying device is a pipe with several nozzles.

5. A method for treating wastewater, characterized in that, The method uses the microalgae bioreactor as described in any one of claims 1 to 4; The method includes the following steps: Cultivating microalgae to obtain algal solution; The algal solution is sprayed onto the surface of the filter bed through a spraying device. After flowing through the filter bed, the algal solution flows out from the return port and is introduced into the inlet through the return pipe to circulate back to the spraying device for spraying. The algal solution is circulated and sprayed until a microalgal biofilm is formed on the surface of the filter bed. Wastewater is pretreated to remove large particulate impurities, resulting in pretreated wastewater. The pretreated wastewater is introduced into the spraying device through the inlet and sprayed onto the surface of the filter bed. After contacting the microalgae biofilm, it is circulated back to the spraying device through the return pipe for continuous spraying until the water quality reaches the predetermined standard and is then discharged from the outlet. Optionally, microalgae in the discharged water can be removed.

6. The method according to claim 5, characterized in that, The algal solution is circulated and sprayed for 48-72 hours to form a microalgal biofilm.

7. The method according to claim 5, characterized in that, The microalgae are green algae, preferably Chlorella or Scenedesmus.

8. The method according to claim 5, characterized in that, The amount of water in the microalgae bioreactor does not exceed 1 / 5 of the total reactor capacity.

9. The method according to any one of claims 5 to 8, characterized in that, The pretreatment of the wastewater also includes anaerobic conversion of recalcitrant organic matter into small molecule organic matter.

10. The method according to claim 9, characterized in that, The wastewater is domestic sewage rich in nitrogen and phosphorus, preferably domestic sewage from mining areas.

Images