Chlamydomonas reinhardtii granular sludge and cultivation method and application thereof

Abstract

The present application belongs to the technical field of sewage treatment, and in particular to a granular sludge of Chlamydomonas reinhardtii, a cultivation method and an application thereof; the cultivation method of the granular sludge of Chlamydomonas reinhardtii provided in the present application can cultivate the granular sludge to obtain a granular sludge with an average particle size of nearly 0.5 mm, SVI5 and SVI 30 The ratio is close to 1, and the Chlamydomonas reinhardtii granular sludge can be completely precipitated within 1 minute. The structure of the cultivated Chlamydomonas reinhardtii granular sludge is dense and rich in voids, which is conducive to the pollutants in the sewage to enter the internal reaction of the particles faster, promote the generation of high-value resources such as protein and reduce N2O emissions; on the one hand, the ability of Chlamydomonas reinhardtii to utilize resources such as nitrogen in sewage to generate high-value resources and reduce N2O emissions is improved, and on the other hand, it is convenient to collect the Chlamydomonas reinhardtii granular sludge, improves the effect of sewage treatment, and thus solves the technical problem of poor sewage treatment effect in the prior art.

Description

Technical Field

[0001] The present application belongs to the technical field of sewage treatment, and in particular relates to a Chlamydomonas reinhardtii granular sludge and a cultivation method and application thereof. Background Art

[0002] carbon dioxide( ), nitrous oxide (N 2 O), methane ( ) and CFCs are the main greenhouse gases in the atmosphere. The carbon emissions from greenhouse gas emissions into the atmosphere will consume or reduce stratospheric ozone, causing the atmospheric temperature to rise. Nitrous oxide (N 2 O) has a much greater warming effect than CO2 ( ), and nitrous oxide (N 2 O) has a very long life in the atmosphere, so controlling nitrous oxide (N 2 O) emissions help mitigate the greenhouse effect and reduce carbon emissions.

[0003] Carbon emissions from the sewage treatment industry are an important part of the carbon emissions process of the whole society. At present, the mainstream sewage treatment processes are mainly sewage treatment processes such as sequencing batch sludge process (SBR), oxidation ditch and anaerobic-anoxic-aerobic process (A2 / O). In the sewage treatment process such as sequencing batch sludge process (SBR), bacteria in the activated sludge remove organic matter, nitrogen, phosphorus and other pollutants in the sewage through biochemical reactions such as nitrification and denitrification. The incomplete nitrification and denitrification reactions of bacteria can easily lead to nitrous oxide (N 2 O) into the atmosphere, causing carbon emissions and also causing a waste of resources such as nitrogen. Algae have the ability to assimilate and absorb nitrogen and other elements and convert them into biomass, which not only reduces nitrous oxide (N 2 O) emissions, and improve the utilization rate of nitrogen. Chlamydomonas reinhardtii belongs to the Chlorophyta, Volvoxales, Chlamydomonas, and grows rapidly. 4 + -N assimilation and enrichment efficiency is higher than that of NO 3 - -N and urea, is an edible natural algae, rich in protein, dietary fiber and other high-value substances. Therefore, using Chlamydomonas reinhardtii for sewage treatment can reduce nitrous oxide (N 2 O) discharge, achieving water purification requirements and recovering high-value organic matter.

[0004] In addition to utilizing nitrogen and other resources in sewage to generate high-value resources, on the other hand, Chlamydomonas reinhardtii has poor sedimentation properties and poor mud-water separation, and is easily discharged from the outlet, which reduces the effectiveness of sewage treatment. Summary of the invention

[0005] In view of this, the present application provides a Chlamydomonas reinhardtii granular sludge and a cultivation method and application thereof, which are used to solve the technical problem of poor sewage treatment effect in the prior art.

[0006] In a first aspect, the present application provides a method for culturing Chlamydomonas reinhardtii granular sludge, the culturing method comprising the steps of:

[0007] Step S1, inoculating Chlamydomonas reinhardtii into a culture medium for activation to obtain activated Chlamydomonas reinhardtii;

[0008] Step S2, performing step-by-step propagation and cultivation on the activated Chlamydomonas reinhardtii to obtain Chlamydomonas reinhardtii after expanded culture;

[0009] Step S3, the expanded cultured Chlamydomonas reinhardtii and the sludge are mixed and inoculated into a closed sequencing batch reactor, and the microalgae are granulated and cultured in a cycle of water inlet-anaerobic-aeration-sedimentation-drainage-standing to obtain Chlamydomonas reinhardtii granular sludge;

[0010] In step S3, the time of the aeration phase is gradually prolonged, and the time of the sedimentation phase is gradually shortened.

[0011] Preferably, in step S3, the microalgae granulation culture time is 48 days;

[0012] During the 1st to 5th day of microalgae granulation culture, the aeration phase lasted 190 min and the sedimentation phase lasted 30 min;

[0013] When the microalgae pellet culture was carried out for 6 to 10 days, the aeration phase lasted for 215 min and the sedimentation phase lasted for 5 min;

[0014] During the 11th to 48th day of microalgae granulation culture, the aeration phase lasted for 220 minutes and the sedimentation phase lasted for 1 minute.

[0015] Preferably, in the microalgae granulation culture, the water intake stage lasts for 6 to 8 minutes;

[0016] The duration of the anaerobic phase is 110-130 min;

[0017] The duration of the aeration phase is 110-220 min;

[0018] The precipitation stage lasts from 1 to 30 min;

[0019] The drainage phase lasts for 6 to 8 minutes;

[0020] The resting phase lasts for 5 to 6 minutes.

[0021] Preferably, in the microalgae granulation culture, the time of one cycle is 6 hours.

[0022] Preferably, in the microalgae granular culture, the air rise velocity in the aeration stage is 1.0-1.5 cm / s.

[0023] Preferably, in the microalgae granular culture, the hydraulic retention time is 12 h, the volume exchange ratio is 50%, and the light intensity is 6000 lux.

[0024] Preferably, in step S1, the culture medium used for activation is TAP culture medium, the temperature is 25±1°C, the light intensity is 1500-2500 lux, the light-dark ratio is 12 h:12 h, and the time is 1 day.

[0025] Preferably, in step S2, the culture medium used in the first stage of the stepwise propagation culture is TAP culture medium, the temperature is 25±1°C, the light intensity is 1500-2500 lux, the light-dark ratio is 12 h:12 h, and the time is 10 d;

[0026] The culture medium used in the second stage of the stepwise propagation culture is TAP culture medium, the temperature is 25±1°C, the light intensity is 1500-2500 lux, and the time is 7 days.

[0027] A second aspect of the present application provides a Chlamydomonas reinhardtii granular sludge obtained by culturing using the culturing method described in the first aspect.

[0028] The third aspect of the present application provides the use of the cultivation method described in the first aspect or the Chlamydomonas reinhardtii granular sludge described in the second aspect in sewage treatment.

[0029] In summary, the present application provides a Chlamydomonas reinhardtii granular sludge and a cultivation method and application. The present application provides a Chlamydomonas reinhardtii granular sludge cultivation method, which first inoculates the purchased Chlamydomonas reinhardtii into a TAP culture medium for activation and step-by-step propagation and cultivation to obtain the Chlamydomonas reinhardtii after expanded culture, and then mixes the Chlamydomonas reinhardtii sludge and inoculates it into a closed sequencing batch reactor for microalgae granular culture. The microalgae granular culture is carried out with a cycle of water inlet-anaerobic-aeration-sedimentation-drainage-standing to obtain the Chlamydomonas reinhardtii granular sludge; the Chlamydomonas reinhardtii granular sludge obtained by culture has a dense structure and is rich in voids, which are conducive to mass transfer. Pollutants in sewage can enter the interior of the particles faster, promoting the generation of high-value biomass, and the Chlamydomonas reinhardtii granular sludge can be precipitated quickly, realizing the generation and collection of high-value biomass in the sewage treatment process, thereby solving the technical problem of poor sewage treatment effect in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 A schematic diagram of the structure of a device used in a method for culturing Chlamydomonas reinhardtii granular sludge provided in Example 1 of the present application;

[0032] Figure 2 The Chlamydomonas reinhardtii granular sludge culture method provided in Example 1 of the present application is cultured for 0 days;

[0033] Figure 3 The Chlamydomonas reinhardtii granular sludge cultured for 24 days by the Chlamydomonas reinhardtii granular sludge culture method provided in Example 1 of the present application;

[0034] Figure 4 The Chlamydomonas reinhardtii granular sludge cultured for 48 days according to the Chlamydomonas reinhardtii granular sludge culture method provided in Example 1 of the present application;

[0035] Figure 5 Electron microscopic image (50 times) of the surface of Chlamydomonas reinhardtii granular sludge culture method provided in Example 1 of the present application after 48 days of culture;

[0036] Figure 6 Electron microscope image (300 times) of the second position of the surface of Chlamydomonas reinhardtii granular sludge culture method provided in Example 1 of the present application after 48 days of culture;

[0037] Figure 7 Electron microscope image (300 times) of the third position of the surface of Chlamydomonas reinhardtii granular sludge culture method provided in Example 1 of the present application after 48 days of culture;

[0038] Figure 8 Electron microscopic image (50 times) of the cross section of the Chlamydomonas reinhardtii granular sludge culture method provided in Example 1 of the present application after 48 days of culture;

[0039] Fig. 9 Electron microscope image (300 times) of the second position of the cross section after 48 days of cultivation of the Chlamydomonas reinhardtii granular sludge cultivation method provided in Example 1 of the present application;

[0040] Fig.10 Electron microscope image (300 times) of the third position of the cross section after 48 days of cultivation of the Chlamydomonas reinhardtii granular sludge cultivation method provided in Example 1 of the present application;

[0041] Fig.11This is the energy spectrum of the Chlamydomonas reinhardtii granular sludge culture method provided in Example 1 of the present application after 48 days of culture;

[0042] Fig.12 A graph showing the change in particle size of Chlamydomonas reinhardtii granular sludge over time during the culturing process for 0 to 48 days of the Chlamydomonas reinhardtii granular sludge culturing method provided in Example 1 of the present application;

[0043] Fig.13 A graph showing the change in chlorophyll content in Chlamydomonas reinhardtii granular sludge over time during the 0-48 day cultivation process of the Chlamydomonas reinhardtii granular sludge cultivation method provided in Example 1 of the present application;

[0044] Fig.14 A graph showing changes in extracellular polymers (EPS) in Chlamydomonas reinhardtii granular sludge over treatment time during the 0-48 day culturing process of the Chlamydomonas reinhardtii granular sludge culturing method provided in Example 1 of the present application;

[0045] Fig.15 Distribution map of eukaryotic species at the family level during the 0-48 day cultivation process of the Chlamydomonas reinhardtii granular sludge cultivation method provided in Example 1 of the present application;

[0046] Fig.16 During the 0-48 days of culturing the Chlamydomonas reinhardtii granular sludge culture method provided in Example 1 of the present application, nitrous oxide (N 2 O) Graph showing the change of emission with culture time;

[0047] Fig.17 A graph showing the change in the suspended solids concentration (MLSS) of the Chlamydomonas reinhardtii granular sludge during the culturing process of Chlamydomonas reinhardtii granular sludge provided in Example 1 of the present application over the culturing time during the culturing period of 0 to 48 days, simulating the domestic sewage treatment process;

[0048] Fig.18 A graph showing changes in the sludge volume index (SVI) of the Chlamydomonas reinhardtii granular sludge during the 0-48 day culturing process of the Chlamydomonas reinhardtii granular sludge in the simulated domestic sewage treatment process as a function of the culturing time during the culturing process of the Chlamydomonas reinhardtii granular sludge provided in Example 1 of the present application;

[0049] Fig.19 A graph showing the change of chemical oxygen demand (COD) with culture time during the 0-48 day culture process of the Chlamydomonas reinhardtii granular sludge culture method provided in Example 1 of the present application, during the simulated domestic sewage treatment process;

[0050] Fig. 20 A graph showing the change of total phosphorus (TP) with culture time during the 0-48 day culture process of the Chlamydomonas reinhardtii granular sludge culture method provided in Example 1 of the present application, during the simulated domestic sewage treatment process;

[0051] Fig.21 During the 0-48 days of culturing of Chlamydomonas reinhardtii granular sludge provided in Example 1 of the present application, ammonia nitrogen (NH 4 + -N), nitrite nitrogen (NO 2 - -N), nitrate nitrogen (NO 3 - -N) Graph showing changes over culture time;

[0052] Fig. 22 This is a graph showing the change in total nitrogen (TN) over culture time during the 0-48 day culture process of the Chlamydomonas reinhardtii granular sludge culture method provided in Example 1 of the present application, simulating the treatment of domestic sewage. DETAILED DESCRIPTION

[0053] The present application provides a Chlamydomonas reinhardtii granular sludge and a cultivation method and application thereof, which are used to solve the technical problem of poor sewage treatment effect in the prior art.

[0054] The technical solution of the present application will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0055] In view of the defect that the current sewage treatment effect is not good, the present application provides a method for culturing Chlamydomonas reinhardtii granular sludge, the culturing method comprising: firstly inoculating Chlamydomonas reinhardtii (FACHB-2217) purchased from the freshwater algae seed bank of the National Aquatic Biological Germplasm Resource Bank into TAP culture medium for activation and step-by-step propagation and culture to obtain Chlamydomonas reinhardtii after expanded culture; then mixing Chlamydomonas reinhardtii and flocculent sludge obtained from a sewage treatment plant and inoculating into a closed sequencing batch reactor for microalgae granular culture, the microalgae granular culture is carried out with a cycle of water inlet-anaerobic-aeration-sedimentation-drainage-standing, the culture time is 48 days in total, and Chlamydomonas reinhardtii granular sludge can be obtained.

[0056] In the microalgae granular culture, since the time of the aeration stage and the sedimentation stage is controlled, the time of the aeration stage is gradually extended, and the time of the sedimentation stage is gradually shortened; this allows the gradually extended aeration time to provide stronger hydraulic shear force during the aeration process, and makes it more difficult to precipitate; this allows the microalgae granular sludge with poor sedimentation to be discharged during the drainage stage due to the short time and the microalgae granular sludge with excellent sedimentation performance to be quickly deposited in the sequencing batch reactor, which is conducive to the convenient collection of Chlamydomonas reinhardtii granular sludge and the production of high-value biomass; and the Chlamydomonas reinhardtii granular sludge obtained by the culture method provided in the present application uses filamentous microalgae as the skeleton, and the cocci, Chlamydomonas, diatoms and bacteria are firmly attached to it through extracellular polymers, and Chlamydomonas reinhardtii occupies a dominant position, forming a dense and void-rich Chlamydomonas reinhardtii granular sludge; the voids in the Chlamydomonas reinhardtii granular sludge are conducive to mass transfer, and pollutants in the sewage can enter the particles faster, accelerate the reaction rate, and reduce N 2 O release, promote the increase of chlorophyll and protein (PN) content, and increase the production of high-value substances such as protein and dietary fiber; this shows that the Chlamydomonas reinhardtii granular sludge provided by the present application can achieve efficient nitrogen and phosphorus removal to generate high-value resources and reduce N 2 O release improves the ability of Chlamydomonas reinhardtii to utilize nitrogen and other resources in sewage to generate high-value resources; and it can quickly precipitate, making it convenient to collect Chlamydomonas reinhardtii granular sludge, which can be used as high-value biomass, improving the effect of sewage treatment, thereby overcoming the current defect of poor sewage treatment effect.

[0057] Preferably, in the method for cultivating Chlamydomonas reinhardtii granular sludge provided in the present application, the time of the aeration phase of the microalgae granular culture is gradually extended, and the time of the sedimentation phase is gradually shortened. Specifically, when the microalgae granular culture is 1 to 5 days, the time of the aeration phase is 190 min, and the time of the sedimentation phase is 30 min; when it is 6 to 10 days, the time of the aeration phase is 215 min, and the time of the sedimentation phase is 5 min;

[0058] During the 11-48 days, the aeration phase lasted for 220 min and the sedimentation phase lasted for 1 min. By gradually extending the aeration phase and shortening the sedimentation phase to the above-specified time during the 48-day culture period, the average particle size of the collected particles was close to 0.5 mm and could be precipitated within 1 min. SVI 5 With SVI 30 The Chlamydomonas reinhardtii granular sludge with a ratio close to 1 further promotes the generation and collection of high-value biomass and improves the effect of sewage treatment.

[0059] At the same time, in the method for cultivating Chlamydomonas reinhardtii granular sludge provided in the present application, a cycle time of microalgae granular cultivation is controlled at 6 hours, and the gas rise rate in the aeration stage is 1.0-1.5 cm / s.

[0060] The Chlamydomonas reinhardtii granular sludge provided in this application will be specifically described below in combination with embodiments and experimental examples.

[0061] Example 1

[0062] Example 1 of the present application provides a method for culturing Chlamydomonas reinhardtii granular sludge, the culturing method comprising: a step of activating Chlamydomonas reinhardtii, a step of expanding the culture of Chlamydomonas reinhardtii, and a step of granulating microalgae.

[0063] The activation steps of Chlamydomonas reinhardtii include: adding TAP medium to a 50 mL conical flask, sealing it with a breathable membrane, and sterilizing it in an autoclave at 121 °C for 30 min. Chlamydomonas reinhardtii (FACHB-2217) purchased from the freshwater algae seed bank of the National Aquatic Biological Germplasm Resource Bank was inoculated into the sterilized TAP medium in a clean bench. Cultivate in a constant temperature incubator, shake the conical flask several times a day, and control the constant temperature incubator parameters as follows: temperature 25±1 °C; light intensity 2000 lux; light-dark ratio 12h:12 h, and obtain activated Chlamydomonas reinhardtii.

[0064] The steps for expanding the culture of Chlamydomonas reinhardtii include:

[0065] In the first stage, activated Chlamydomonas reinhardtii was inoculated into a 500 mL conical flask with TAP medium and cultured for 10 days. The biomass and NH in the culture medium were sampled every other day. 4 + -N concentration, repeated twice, the volume ratio of Chlamydomonas reinhardtii and TAP medium was 1:5;

[0066] In the second stage, the Chlamydomonas reinhardtii cultured in 500 mL of culture medium in the first stage was added to a 1 L conical flask and cultured in a light incubator for 7 days to obtain the expanded cultured Chlamydomonas reinhardtii. The volume ratio of Chlamydomonas reinhardtii to TAP culture medium was 1:5.

[0067] The steps of microalgae granulation culture include:

[0068] The expanded cultured Chlamydomonas reinhardtii was centrifuged at 3000 rpm for 10 min, the supernatant was discarded and mixed with flocculent sludge obtained from an actual sewage treatment plant and inoculated into a closed sequencing batch reactor. Figure 1As shown in the figure, the main reactor of the closed sequencing batch reactor has an inner diameter of 10 cm and a height of 65 cm. The liquid level is 38-39 cm during operation and the working volume is 3 L. The water inlet is located at the lower side, the water outlet is located in the middle of the side, and the exhaust port is located at the upper side. The length, width and height of the water outlet bucket are 30*30*40 cm, half of which is sealed and half of which is open. There is a 35 cm long baffle in the middle to separate the water outlet liquid. The airtightness is ensured by the outlet liquid, and the open port can be drained out regularly. In addition to the outlet pipe, the closed area is connected to an air bag with a hose to balance the air pressure. The exhaust port is also connected to an air bag, which is connected to an air pump to achieve cyclic aeration, and a gas flow meter is used to monitor the aeration intensity. The top of the reactor is closed, and a circular hole with a diameter of 3 cm is opened and plugged with a rubber stopper to ensure air tightness. Two glass tubes are inserted in the middle, one for collecting gas samples on the top of the reactor, and the other for collecting water samples and mud samples in the reactor. The outer end of the glass tube is connected to a latex tube and clamped with a water stop clamp to ensure air tightness. Water inlet and outlet are achieved through a peristaltic pump, and lighting is achieved through an LED.

[0069] The influent of the closed sequencing batch reactor was simulated urban domestic sewage, with a volume exchange ratio of 50%, a controlled hydraulic retention time of 12 h, a light intensity of 6000 lux, and a cycle of influent-anaerobic-aeration-sedimentation-drainage-standing for 6 hours. The microalgae granular culture was carried out for 48 days to obtain Chlamydomonas reinhardtii granular sludge. In the microalgae granular culture, at 1 to 5 days, the time of the influent stage was 7 min, the time of the anaerobic stage was 120 min, the time of the aeration stage was 190 min, the time of the sedimentation stage was 30 min, the time of the drainage stage was 7 min, and the time of the standing stage was 6 min; at 6 to 10 days, the time of the influent stage was 7 min, the time of the anaerobic stage was 120 min, the time of the aeration stage was 215 min, the time of the sedimentation stage was 5 min, the time of the drainage stage was 7 min, and the time of the standing stage was 6 min; at 11 to 48 days, the time of the influent stage was 7 min, the time of the anaerobic stage was 120 min, the time of the aeration stage was 220 min, the time of the min, the sedimentation stage time is 1 min, the drainage stage time is 7 min, and the static stage time is 5 min.

[0070] In this embodiment, the TAP culture medium used is configured according to Table 1-2, and the simulated urban domestic sewage is configured according to Table 3-4.

[0071] Table 1: TAP medium

[0072]

[0073] Table 2: Components 1 to 3 in TAP medium

[0074]

[0075] Table 3: Composition of simulated urban domestic sewage

[0076]

[0077] Table 4: Trace elements in Table 3

[0078]

[0079] Experimental Example 1

[0080] Experimental Example 1 of the present application is a method for cultivating Chlamydomonas reinhardtii granular sludge provided in Example 1, and the structural characterization of Chlamydomonas reinhardtii granular sludge during the microalgae granulation culture process, as well as the removal of pollutants, the generation of valuable resources, and the production of nitrous oxide (N 2 O) Emission test results.

[0081] Among them, the structural characterization of Chlamydomonas reinhardtii granular sludge during microalgae granulation culture is as follows Figure 2-12 As shown, from Figure 2~Figure 4 and Fig.12 It can be seen that as the culture time increases from 0 to 24 days, the sludge gradually granulates, but there are still many fungal flocs around it; then as the culture time increases from 24 to 48 days, the particle size of the granular sludge gradually increases, and the particle size of the granular sludge is concentrated in 250-500 μm and 250-500 μm; the average particle size increases to 497.88 μm; and the microstructure and composition of the Chlamydomonas reinhardtii granular sludge after 48 days of culture are as follows Figure 5-Figure 11 As shown, from Figure 5~Figure 7 The surface shown and Figure 8~Figure 10 The 50-300 times electron microscope images of the cross section shown in the figure show that the microalgae and bacteria in the particles are closely combined. After 48 days of cultivation, the Chlamydomonas reinhardtii granular sludge uses filamentous microalgae as the skeleton, and the coccophora, Chlamydomonas, diatoms and bacteria are firmly attached to it through extracellular polymers to form dense and porous particles. These voids are conducive to mass transfer. Pollutants in sewage can enter the particles faster and accelerate the removal rate. The energy spectrum and analysis results of the Chlamydomonas reinhardtii granular sludge after 48 days of cultivation are shown in Figure 1. Fig.11 As shown in Table 5, Fig.11 From the results of energy spectrum analysis shown in Table 5, it can be seen that the main component of the Chlamydomonas reinhardtii granular sludge is carbon, which has the highest content and a specific gravity of 53.85%, followed by oxygen, nitrogen and iron, which have specific gravity of 31.20%, 6.69% and 4.15% respectively; carbon is an important component of organic matter, which indicates that the organic matter content in the Chlamydomonas reinhardtii granular sludge is extremely high and has strong biological activity;

[0082] Table 5: Fig.11 The analysis results of the energy spectrum shown

[0083]

[0084] The increase in valuable resources in Chlamydomonas reinhardtii granular sludge during microalgae granulation culture Figure 13~Figure 14 shown; from Fig.13 The results show that with the extension of culture time, the contents of chlorophyll a (chl-a), chlorophyll b (chl-b) and chlorophyll c (chl-c) all increased, and the increase of chlorophyll a (chl-a) was greater; the contents of chlorophyll a (chl-a), chlorophyll b (chl-b) and chlorophyll c (chl-c) all increased, resulting in the total chlorophyll content of sludge being 0.97 mg / g-VSS after 12 days of microalgae granulation culture; after 24 days, the total chlorophyll content increased to 1.78 mg / g-VSS; after 36 days, it increased to 4.94 mg / g-VSS, and after 48 days, it increased to 5.99 mg / g-VSS, indicating that the microalgae granulation culture process is conducive to promoting the increase of chlorophyll content; and the content of polysaccharides (PS) and proteins (PN) also gradually increased with the extension of microalgae granulation culture time; Fig.14 As shown, after 12 days of cultivation, the total PN content reached 25.04 mg / g-VSS, and PN / PS reached 0.62; after 24 days of cultivation, the total PN content reached 45.41 mg / g-VSS, and PN / PS reached 0.77; after 36 days of cultivation, the total PN content reached 63.12 mg / g-VSS, and PN / PS reached 1.19; after 48 days of cultivation, the total PN content reached 74.66 mg / g-VSS, and PN / PS reached 1.04. The increase in PN improves the hydrophobicity of Chlamydomonas reinhardtii granular sludge, which is more conducive to granule formation. PS plays the role of a binder in the granulation process and is an important reason for the formation of a stable granule structure. This shows that the present application promotes the increase of PS content by extending the culture time from 36 days to 48 days, which is conducive to the formation of Chlamydomonas reinhardtii granules with a stable structure, and with the extension of the culture time, the extracellular polymers also undergo a transformation from dissolved EPS loosely bound EPS (LB-EPS) to tightly bound EPS (TB-EPS).

[0085] After 48 days of microalgae pellet culture, the eukaryotic species composition of Chlamydomonas reinhardtii pellets at the family level is shown in the figure. Fig.15 As shown, from Fig.15 It can be seen that the proportion of Chlamydomonadaceae is 18.39%, indicating that Chlamydomonas reinhardtii occupies a dominant position in the cultured Chlamydomonas reinhardtii granular sludge. The high proportion of Chlamydomonas reinhardtii is conducive to promoting the production of high-value substances and reducing nitrous oxide (N 2 O) emission.

[0086] N in the process of microalgae granulation culture 2 O changes with time Fig.16 As shown, N 2 O release factor through influent NH 4 + -N is calculated; when just cultured, N 2 The O release factor is 0.0042 kg N 2 ON / kg N, with the extension of culture time, N 2 The O release factor decreased significantly and could be reduced to 0.0004 kg N 2 ON / kg N; significantly lower than the current full-scale sewage treatment plant N 2 The O release factor is 0.0100~0.0240 kg N 2 ON / kg N, artificial wetland N 2 The O release factor is 0.0021~0.0320 kgN 2 ON / kg N, full-scale SBR wastewater treatment plant N 2 The O release factor is 0.0560 kg N 2 ON / kg N level; and the energy consumption of the microalgae granulation culture process provided in the present application is similar to the average electricity consumption of a sewage treatment plant.

[0087] The sedimentation test results during microalgae granulation culture are as follows: Figure 17-18 As shown, from Fig.17 It can be seen that with the extension of the culture time, the suspended solid concentration (MLSS) did not change much and increased slightly; Fig.18 It can be seen that the sludge index SVI of the mixed liquid at the outlet of the aeration tank after 30 minutes of static sedimentation can be reduced with the extension of the culture time. After 12 days of culture, the SVI can be significantly reduced to 60.8 mL / g, and the sedimentation is improved; and with the extension of the culture time, the SVI 5 With SVI 30 The ratio increased from 0.91 to 1.0, indicating that the formation and sedimentation of Chlamydomonas reinhardtii granular sludge were improved.

[0088] Chemical oxygen demand (COD), total phosphorus (TP), and ammonia nitrogen (NH 4 + -N), nitrite nitrogen (NO 2 - -N), nitrate nitrogen (NO 3 - -N) changes over time such as Figure 19 to Figure 22 shown; from Fig.19It can be seen that during the operation, the COD removal efficiency (COD Removal Efficiency) is above 80%, and the average effluent COD concentration (Efflluent COD) is 23.7 mg / L, which meets the Class A standard of the pollutant discharge standard for urban sewage treatment plants. Fig. 20 It can be seen that at the beginning of the microalgae granulation culture process, the total phosphorus removal efficiency (TP Removal Efficiency) varies greatly, but with the extension of the culture time, the TP removal efficiency can be maintained above 50%, and can reach a maximum of about 95%. The effluent TP concentration (Efflluent TP) is lower than 0.5 mg / L, meeting the Class A standard specified in the pollutant discharge standard for urban sewage treatment plants.

[0089] And from Fig.21 It can be seen that the effluent ammonia nitrogen (Efflluent NH 4 + -N), nitrite nitrogen (Efflluent NO 2 - -N) concentrations were relatively low, ranging from 0 to 1.56 mg / L and 0.03 to 0.77 mg / L; while the effluent nitrate nitrogen (Efflluent NO 3 - -N) concentration can be reduced to 10~15mg / L with the extension of culture time; while the influent NH 4 + -N) and the concentration of ammonia nitrogen remained stable, and the removal rate of ammonia nitrogen (NH 4 + -N RemovalEfficiency) can be close to 100%; and since the effluent is mainly nitrate nitrogen (Efflluent NO 3 - -N), nitrate nitrogen (Efflluent NO 3 - -N) factor has a greater impact on total nitrogen (TN), which makes Fig. 22 The change rates of total nitrogen (TN) and nitrate nitrogen (Efflluent NO 3 - -N), the concentration of effluent total nitrogen (TN Concentration) is about 10~15 mg / L, and the removal efficiency of effluent total nitrogen (TN Removal Efficiency) can be close to 75%.

[0090] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for cultivating Chlamydomonas reinhardtii granular sludge, It is characterized in that Includes steps: Step S1, inoculating Chlamydomonas reinhardtii into a culture medium for activation to obtain activated Chlamydomonas reinhardtii; Step S2, performing step-by-step propagation and cultivation on the activated Chlamydomonas reinhardtii to obtain Chlamydomonas reinhardtii after expanded culture; Step S3, inoculating the expanded cultured Chlamydomonas reinhardtii and the sludge into a closed sequencing batch reactor, and performing microalgae granulation culture with a cycle of water inlet-anaerobic-aeration-sedimentation-drainage-standing to obtain Chlamydomonas reinhardtii granular sludge; In the microalgae granulation culture, the water inlet stage lasts for 6 to 8 minutes, and the water inlet is simulated urban domestic sewage; The duration of the anaerobic stage is 110-130 min; The duration of the aeration phase is 110-220 min; The precipitation stage lasts from 1 to 30 min; The drainage phase lasts for 6 to 8 minutes; The resting phase lasts for 5 to 6 minutes; In step S3, the microalgae granulation culture time is 48 days; During the 1st to 5th day of microalgae granulation culture, the aeration phase lasted 190 min and the sedimentation phase lasted 30 min; When the microalgae pellet culture was carried out for 6 to 10 days, the aeration phase lasted for 215 min and the sedimentation phase lasted for 5 min; During the 11th to 48th day of microalgae granulation culture, the aeration phase lasted 220 min and the sedimentation phase lasted 1 min; The components of simulated urban domestic sewage are as follows: 300 mg CH 3 COONa, 30mgNH 4 Cl, 3mgKH 2 PO 4 、40 mgCaCl 2 ·2H 2 O, 75mgMgSO 4 7H 2 O, 25 mgFeSO 4 7H 2 O and 1 mL of trace elements; Each 1000mL trace elements include: 2.86gH 3 BO 3 , 0.39gNaMoO 4 ·2H 2 O, 1.86 gMnCl 2 ·4H 2 O, 0.08gCuSO 4 ·5H 2 O, 0.22gZnSO 4 7H 2 O and 0.05 gCo(NO 3 ) 2 6H 2 O.

2. The method for culturing Chlamydomonas reinhardtii granular sludge according to claim 1, It is characterized in that In the microalgae granulation culture, one cycle lasts for 6 hours.

3. The method for culturing Chlamydomonas reinhardtii granular sludge according to claim 1, It is characterized in that In the microalgae granulation culture, the gas rise velocity in the aeration stage is 1.0-1.5 cm / s.

4. The method for culturing Chlamydomonas reinhardtii granular sludge according to claim 1, It is characterized in that In the microalgae granulation culture, the hydraulic retention time is 12 h, the volume exchange ratio is 50%, and the light intensity is 6000 lux.

5. The method for culturing Chlamydomonas reinhardtii granular sludge according to claim 1, It is characterized in that In step S1, the activation medium used is TAP medium, the temperature is 25±1°C, the light intensity is 1500-2500 lux, the light-dark ratio is 12 h:12 h, and the time is 1 day.

6. The method for culturing Chlamydomonas reinhardtii granular sludge according to claim 1, It is characterized in that In step S2, the culture medium used in the first stage of the step-by-step propagation culture is TAP culture medium, the temperature is 25±1°C, the light intensity is 1500-2500 lux, the light-dark ratio is 12 h:12 h, and the time is 10 d; The culture medium used in the second stage of the stepwise propagation culture is TAP culture medium, the temperature is 25±1°C, the light intensity is 1500-2500 lux, and the time is 7 days.

7. A Chlamydomonas reinhardtii granular sludge, It is characterized in that The method is described in any one of claims 1 to 6.

8. Use of the culturing method according to any one of claims 1 to 6 or the Chlamydomonas reinhardtii granular sludge according to claim 7 in sewage treatment.

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