A Haematococcus pluvialis-MBR coupled biogas slurry purification device and method

Abstract

The present invention belongs to the technical field of Haematococcus pluvialis cultivation, and discloses a Haematococcus pluvialis-MBR coupled biogas slurry purification device and method. The device includes a biogas slurry water inlet barrel, an MBR membrane treatment device, a water storage device and a Haematococcus pluvialis cultivation device. The present invention uses organic matter and nutrients such as nitrogen, phosphorus, potassium, and trace elements in the biogas slurry as essential elements for the growth of Haematococcus pluvialis, reduces the addition of exogenous nutrients in the cultivation of Haematococcus pluvialis, reduces the cultivation cost, and Haematococcus pluvialis can deeply treat wastewater to achieve the purpose of purification treatment, while producing a high-added product astaxanthin, thereby improving economic benefits. Haematococcus pluvialis uses CO2 to photosynthesize in the water body to release O2, reducing external oxygen supply, thereby reducing the consumption of electrical energy. At the same time, by virtue of the characteristics of Haematococcus pluvialis's fast photosynthetic rate and the accumulation of biomass by fixing CO2, CO2 emissions are reduced and the greenhouse effect is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of Haematococcus pluvialis cultivation, and in particular to a Haematococcus pluvialis-MBR coupled biogas slurry purification device and method. Background Art

[0002] Currently, there are two main types of astaxanthin on the market: synthetic astaxanthin and natural astaxanthin. Astaxanthin has strong antioxidant activity and is the most powerful antioxidant substance discovered so far. The functional structure of synthetic astaxanthin is difficult to control, and the use of some chemicals in the synthesis process causes problems such as low safety. Therefore, it is only allowed to be used in animal feed additives and is restricted in the fields of food, cosmetics and medicine. There are three main sources of natural astaxanthin: (1) crustaceans, such as shrimp, crab, fish, etc.; (2) some fungi and bacteria, such as Phaffia rhodozyma, gene-edited Escherichia coli, etc.; (3) microalgae, such as Haematococcus pluvialis (more than 5% dry weight), Botryococcus braunii (0.01% dry weight), and Chloromonas nivalis (0.04% dry weight). Natural astaxanthin has good stability and high safety. It has been proven to be non-toxic and harmless to humans through animal toxicology experiments and human experiments. Therefore, natural astaxanthin is widely used in food, animal feed, cosmetics and medicine.

[0003] The cost of pure culture of astaxanthin from Haematococcus pluvialis is high, currently estimated at $7,000 per kilogram, while the market price of synthetic astaxanthin is $2,000, with a production cost of $1,000 per kilogram. A suitable geographical location facilitates efficient cultivation of microalgae, potentially reducing the production cost of astaxanthin from Haematococcus pluvialis to $1,800 per kilogram. Wastewater treatment is fundamental to water reuse and plays a vital role in ecosystem protection. Microalgae can remove nutrients and organic matter during their growth and product accumulation, making them a candidate for environmentally friendly water treatment. This also opens new avenues for the synergistic accumulation of bioproducts by microalgae and wastewater treatment, in line with emerging trends in future wastewater treatment.

[0004] Currently, the prior art discloses a patented "one-step" technology for Haematococcus pluvialis. The entire production process, including the growth of green cells, the transformation of motile cells into immotile spores, and the accumulation of astaxanthin in the spores, is completed in an open culture tank. This utilizes a less expensive open tank system, rather than an expensive closed system, reducing investment and production costs and creating favorable conditions for large-scale industrial production. However, the open system in this technology is susceptible to contamination. Haematococcus pluvialis, as an environmentally sensitive algae, is susceptible to biotic and abiotic factors such as microorganisms, light, temperature, and weather, resulting in low yields or even culture failure. Furthermore, pollution control costs are unavoidable. Chinese patent application CN103589643B discloses a culture medium for Haematococcus pluvialis, which focuses on improving the traditional culture medium formula for photosynthetic autotrophic cultivation of Haematococcus pluvialis. It can significantly promote the growth of Haematococcus pluvialis, allowing Haematococcus pluvialis to quickly enter the exponential growth phase, reach a high growth density in a short period of time, and maintain its dominant position in the population, thereby helping to minimize the probability of contamination by foreign bacteria, algae, and protozoa during field expansion cultivation, shorten the growth cycle, and increase the success rate of cultivation. This technical solution and existing culture technology both use formulated culture medium for the production of Haematococcus pluvialis, ignoring the high cost of pure culture. Although the selected ingredients such as 3-IBA and 6-BA greatly promote the division and growth of Haematococcus pluvialis, they also increase the cultivation cost. Therefore, reducing the cultivation cost can effectively improve the production value of Haematococcus pluvialis. In addition, technical research has found that Haematococcus pluvialis achieves high biomass, efficient nutrient removal, and high lipid accumulation in domestic secondary effluent. The maximum algae weight was 207 mg / L, and the maximum population growth rate was 1.16×10 4 cells mL -1 d -1 The maximum algal biomass productivity was 27.8 mg / L -1 d -1 Although the nitrogen-phosphorus ratio of the secondary effluent was as high as 15:1, after the stabilization period, the microalgae removed 93.8% of nitrogen and 97.8% of phosphorus, respectively. In addition, as nutrients in the secondary effluent were consumed, the lipid content of Haematococcus pluvialis increased by 43%. The lipid accumulation rate also reached a maximum of 12.0 mg / L. -1 d -1. Compared with other microalgae reported in the literature, Haematococcus pluvialis is superior to most other microalgae in producing biomass, removing nutrients and accumulating oil in domestic secondary sewage. However, the wastewater selected by this technical solution has lower organic matter, nitrogen and phosphorus than other wastewaters, so it can be directly diluted for microalgae cultivation. The small-scale experiments have not verified the feasibility of scale-up, and the safety assessment of algae powder has not been conducted. Although the study confirmed that Haematococcus pluvialis can be used as a wastewater treatment and microalgae biofuel coupling system based on microalgae cultivation, it is not suitable for the treatment of high-concentration and highly polluted wastewater.

[0005] Therefore, how to provide a low-cost microalgae-wastewater purification coupling treatment method suitable for high-concentration, highly polluted wastewater is of great value for the low-cost cultivation of Haematococcus pluvialis and the subsequent extraction of natural astaxanthin. Summary of the Invention

[0006] The object of the present invention is to provide a Haematococcus pluvialis-MBR coupled biogas slurry purification device and method to solve the above-mentioned problems existing in the cultivation of Haematococcus pluvialis provided by the prior art.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a Haematococcus pluvialis-MBR coupled biogas slurry purification device, which includes a biogas slurry water inlet barrel, an MBR membrane treatment device, a water storage device and a Haematococcus pluvialis cultivation device;

[0009] The biogas slurry inlet bucket is connected to the MBR membrane treatment device through a water inlet pipe;

[0010] The MBR membrane treatment device is connected to the water storage device through a water outlet pipe;

[0011] The outlet water of the water storage device enters the Haematococcus pluvialis cultivation device.

[0012] Preferably, in the above-mentioned Haematococcus pluvialis-MBR coupled biogas slurry purification device, the MBR membrane treatment device includes a hollow fiber membrane module, an aerobic sedimentation tank, a clear water tank, an aeration device, and a filtration device;

[0013] The hollow fiber membrane assembly is composed of a plurality of hollow fiber ultrafiltration membranes arranged in parallel;

[0014] The aeration device is composed of two parallel hollow tubes, each of which is provided with air outlets, and the air flow meter is used to control the air flow.

[0015] Preferably, in the above-mentioned Haematococcus pluvialis-MBR coupled biogas slurry purification device, the filtration device includes a water pump, a water outlet pipe, and a flow meter; the water pump is connected to the water outlet pipe and the hollow fiber membrane assembly, and the water pump is connected to the hollow fiber membrane assembly to discharge the biogas in the aerobic sedimentation tank into the clear water tank, and then pumped into the water storage device through the water pump.

[0016] Preferably, in the above-mentioned Haematococcus pluvialis-MBR coupled biogas slurry purification device, the water storage device includes an ultraviolet sterilization lamp and a water storage barrel.

[0017] Preferably, in the above-mentioned Haematococcus pluvialis-MBR coupled biogas slurry purification device, the Haematococcus pluvialis cultivation device includes a conical flask.

[0018] The present invention also provides a method for purifying Haematococcus pluvialis-MBR coupled biogas slurry using the above-mentioned Haematococcus pluvialis-MBR coupled biogas slurry purification device, comprising the following steps:

[0019] The biogas in the biogas inlet tank enters the MBR membrane treatment device through the water inlet pipe. In the MBR membrane treatment device, the biogas enters the aerobic sedimentation tank for aerobic treatment, and the dissolved oxygen content of aeration is controlled at 6.0 mg / L. Then, the biogas is subjected to a sedimentation treatment for 3 hours, and the hydraulic retention time is 48 hours. The biogas is then discharged into the clear water tank through the suction filtration device to obtain the biogas treated by the MBR membrane treatment device.

[0020] The biogas slurry treated by the MBR membrane treatment device enters the outlet pipe through a water pump and then enters the water storage device; after being sterilized by the ultraviolet sterilization lamp of the water storage device, the pH is adjusted to obtain effluent; the effluent is passed into the Haematococcus pluvialis culture device to culture Haematococcus pluvialis.

[0021] Preferably, in the above-mentioned Haematococcus pluvialis-MBR coupled biogas slurry purification method, the flow rate of the introduced air is 20 to 30 L / min;

[0022] The aeration time in the aerobic sedimentation tank is 3 hours, and the sedimentation time is 3 hours.

[0023] Preferably, in the above-mentioned Haematococcus pluvialis-MBR coupled biogas slurry purification method, the pH of the effluent is 7; and the time of the ultraviolet sterilization is 30 to 40 minutes.

[0024] Preferably, in the above-mentioned method for coupling biogas slurry purification with Haematococcus pluvialis and MBR, the cultivation of Haematococcus pluvialis is divided into two stages: the first stage of cultivation is green stage cultivation, and the second stage of cultivation is red stage cultivation;

[0025] The temperature of the green stage culture is 23-25°C, the light intensity is 2500Lx, and the light-dark ratio is 12h:12h;

[0026] The temperature of the red phase culture is 30° C., the light intensity is 6500 Lx, and the light is continuous.

[0027] It can be seen from the above technical solutions that compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The Haematococcus pluvialis-MBR coupled biogas slurry purification process of the present invention uses organic matter and nutrients such as nitrogen, phosphorus, potassium, and trace elements in the biogas slurry as essential elements for the growth of Haematococcus pluvialis, thereby reducing the addition of exogenous nutrients to the culture of Haematococcus pluvialis and reducing the culture cost. In addition, the Haematococcus pluvialis can deeply treat the wastewater to achieve the purpose of purification, while producing a high-added product astaxanthin, thereby improving economic benefits.

[0029] (2) The method of the present invention can reduce the cost of achieving standard treatment. Traditional wastewater treatment processes consume a lot of energy, mainly due to the consumption of electricity caused by aeration. Haematococcus pluvialis uses CO2 to photosynthesize in water to release O2, reducing external oxygen supply and thus reducing electricity consumption. At the same time, by leveraging the characteristics of Haematococcus pluvialis's rapid photosynthesis rate and the ability to fix CO2 and accumulate biomass, CO2 emissions can be reduced, thereby reducing the greenhouse effect.

[0030] (3) The present invention utilizes biogas slurry to cultivate Haematococcus pluvialis, reducing land absorption, lowering the nutrient and heavy metal content in infiltrating water, and alleviating biogas slurry contamination of groundwater and surface runoff. The wastewater is deeply treated. MBR, as a high-standard wastewater treatment process, combined with deep treatment of Haematococcus pluvialis, brings wastewater up to standard, conforming to the concept of a green ecological cycle and reducing pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for describing the embodiments or the prior art.

[0032] Figure 1 Schematic diagram of the Haematococcus pluvialis-MBR coupled biogas slurry purification device of the present invention;

[0033] Figure 2 This is a rear view of the Haematococcus pluvialis-MBR coupled biogas slurry purification device of the present invention;

[0034] Figure 3 The changes of dry weight of Haematococcus pluvialis when culturing Haematococcus pluvialis on different culture media;

[0035] Figure 4 The final dry weight of Haematococcus pluvialis after the green stage culture and the red stage culture when Haematococcus pluvialis was cultured on different culture media;

[0036] Figure 5The pH changes of effluent when Haematococcus pluvialis is cultivated in different culture media;

[0037] Figure 6 NO3 in the water when culturing Haematococcus pluvialis in different culture media - -N、NH4 + -N changes;

[0038] Figure 7 NO3 in the water when culturing Haematococcus pluvialis in different culture media - -N、NH4 + -N removal rate;

[0039] Figure 8 The changes in chlorophyll concentration in Haematococcus pluvialis during the green phase culture;

[0040] Figure 9 The changes of carotenoid concentration in Haematococcus pluvialis during green stage culture;

[0041] Figure 10 The changes in chlorophyll concentration in Haematococcus pluvialis during the red phase culture;

[0042] Figure 11 The changes of carotenoid concentration in Haematococcus pluvialis during red phase culture;

[0043] Figure 12 To determine the yield and content of astaxanthin in Haematococcus pluvialis cultured in different culture media. DETAILED DESCRIPTION

[0044] The present invention provides a Haematococcus pluvialis-MBR coupled biogas slurry purification device, which includes a biogas slurry water inlet barrel, an MBR membrane treatment device, a water storage device and a Haematococcus pluvialis cultivation device;

[0045] The biogas slurry inlet bucket is connected to the MBR membrane treatment device through a water inlet pipe;

[0046] The MBR membrane treatment device is connected to the water storage device through a water outlet pipe;

[0047] The outlet water of the water storage device enters the Haematococcus pluvialis cultivation device.

[0048] In the present invention, the MBR membrane treatment device includes a hollow fiber membrane module, an aerobic sedimentation tank, a clear water tank, an aeration device, and a filtration device;

[0049] The hollow fiber membrane assembly is composed of a plurality of hollow fiber ultrafiltration membranes arranged in parallel;

[0050] The aeration device is composed of two parallel hollow tubes, each of which is provided with air outlets, and the air flow meter is used to control the air flow.

[0051] In the present invention, the filtration device includes a water pump; the water pump, an outlet pipe, and a flow meter; the water pump is connected to the outlet pipe and the hollow fiber membrane assembly, and the water pump is connected to the hollow fiber membrane assembly to discharge the biogas slurry in the aerobic sedimentation tank into the clear water tank, and then pumped into the water storage device through the water pump.

[0052] In the present invention, the water storage device includes an ultraviolet sterilization lamp and a water storage barrel.

[0053] In the present invention, the Haematococcus pluvialis culture device comprises a conical flask.

[0054] The present invention also provides a method for purifying Haematococcus pluvialis-MBR coupled biogas slurry using the above-mentioned Haematococcus pluvialis-MBR coupled biogas slurry purification device, comprising the following steps:

[0055] The biogas in the biogas inlet tank enters the MBR membrane treatment device through the water inlet pipe. In the MBR membrane treatment device, the biogas enters the aerobic sedimentation tank for aerobic treatment and digestion treatment under the action of microorganisms. The microorganisms decompose macromolecular organic matter into small molecular substances. Under the action of nitrifying bacteria and denitrifying bacteria, ammonia nitrogen is converted into nitrite nitrogen. Part of the nitrite nitrogen is denitrified to form N2 and escapes, while most of it is converted into nitrate nitrogen through aerobic digestion. The dissolved oxygen content of aeration is controlled at 6.0 mg / L, and then a sedimentation treatment is carried out for 3 hours, and the hydraulic retention time is 48 hours. The biogas slurry is then discharged into the clear water tank through the suction filtration device to obtain the biogas slurry treated by the MBR membrane treatment device;

[0056] The biogas slurry treated by the MBR membrane treatment device enters the outlet pipe through a water pump and then enters the water storage device; after being sterilized by the ultraviolet sterilization lamp of the water storage device, the pH is adjusted to obtain effluent; the effluent is passed into the Haematococcus pluvialis culture device to culture Haematococcus pluvialis.

[0057] In the present invention, the flow rate of the introduced air is preferably 20 to 30 L / min, more preferably 22 to 27 L / min, and more preferably 25 L / min;

[0058] The aeration time in the aerobic sedimentation tank is 3 hours, the sedimentation time is 3 hours, and the hydraulic retention time is 48 hours.

[0059] In the present invention, the pH of the effluent is preferably 7; the UV sterilization time is preferably 30 to 40 minutes, more preferably 32 to 36 minutes, and even more preferably 33 minutes.

[0060] In the present invention, the culture solution for culturing Haematococcus pluvialis is effluent diluted with sterile distilled water; the volume concentration of the effluent in the culture solution is preferably 50%.

[0061] In the present invention, the cultivation of Haematococcus pluvialis is divided into two stages: the first stage is the green stage, and the second stage is the red stage.

[0062] The temperature of the green stage culture is preferably 23-25°C, the light intensity is preferably 2500Lx, and the light-dark ratio is preferably 12h:12h;

[0063] The temperature of the red phase culture is preferably 30°C, and the light intensity is preferably 6500 Lx, with continuous light.

[0064] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0065] Example 1

[0066] Use Figure 1 and Figure 2 The method for purifying biogas slurry by coupling Haematococcus pluvialis with MBR is shown, comprising the following steps:

[0067] (1) The pig farm biogas in the biogas inlet barrel enters the MBR membrane treatment device through the water inlet pipe. In the MBR membrane treatment device, the biogas enters the aerobic sedimentation tank, undergoes aerobic treatment, and is digested under the action of microorganisms. The microorganisms decompose macromolecular organic matter into small molecular substances. Under the action of nitrifying bacteria and denitrifying bacteria, ammonia nitrogen is converted into nitrite nitrogen. Part of the nitrite nitrogen is denitrified to form N2 and escapes. Most of it is converted into nitrate nitrogen through aerobic digestion; the inlet pH is controlled at around 7.5, and the dissolved oxygen content during aeration is controlled at 6.0 mg / L. In order to reduce energy consumption, a 3-hour sedimentation treatment is carried out, and the hydraulic retention time is 48 hours; finally, the digestate is discharged into the clear water tank through a suction filtration device;

[0068] The performance parameters of the MBR membrane treatment device are shown in Table 1;

[0069] Table 1 Performance parameters of MBR membrane treatment device

[0070]

[0071] The operating conditions of the MBR membrane treatment unit are shown in Table 2;

[0072] Table 2 Operating conditions of MBR membrane treatment device

[0073]

[0074]

[0075] (2) The biogas slurry treated by the MBR membrane treatment device enters the outlet pipe through the pump and then enters the water storage device; the pH is adjusted to 7.0, filtered with a 0.22 μm membrane, and then sterilized by ultraviolet sterilization lamp in the water storage device for 30 minutes to obtain the effluent;

[0076] (3) The effluent was diluted with sterile distilled water to a 50% dilution culture solution (labeled as 50% EFF), and passed into a Haematococcus pluvialis culture device (250 mL conical flask). Haematococcus pluvialis was inoculated into the conical flask at 15% v / v and cultured in the green phase at a temperature of 24°C, a light intensity of 2500 Lx, and a light-dark ratio of 12 h:12 h.

[0077] After the green stage cultivation, the culture was transferred to high temperature and high light stress, and the red stage stress culture was carried out at a temperature of 30℃, a light intensity of 6500Lx and continuous light to stimulate the accumulation of astaxanthin in Haematococcus pluvialis.

[0078] Comparative Example 1

[0079] This comparative example uses Figure 1 and Figure 2 The method for purifying biogas slurry by coupling Haematococcus pluvialis with MBR is described in detail in Example 1, except that in step (3), the effluent (undiluted) is used as the culture medium (labeled as EFF) to culture Haematococcus pluvialis.

[0080] Comparative Example 2

[0081] In this comparative example, commercially available BG11 culture medium (labeled as BG11) was used to culture Haematococcus pluvialis. For the specific culture method, see Example 1.

[0082] The biomass changes of Haematococcus pluvialis when cultured in different culture media (50% EFF in Example 1, EFF in Comparative Example 1, BG11 in Comparative Example 2) are as follows: Figures 3-4 As shown. Figures 3-4 Green vegetative cells began to grow well on the one-fold diluted MBR effluent (50% EFF). Among the MBR cultures, after four days, the 50% EFF culture had the highest cell growth rate, at 0.245 g / day, similar to that of the pure BG11 culture. By the end of the green phase, biomass concentrations in BG11, 50% EFF, and EFF were 1.78, 1.88, and 1.31 g / L, respectively. These biomass concentration changes indicate that the MBR effluent can provide the necessary growth elements for Haematococcus pluvialis to divide and grow, maintaining its normal growth cycle.

[0083] The removal efficiency of nutrients in biogas slurry by the cultivation of Haematococcus pluvialis is shown in Table 3 and Figures 5-7 As shown in Table 3 and Figures 5-7It can be seen that the pH shows an overall trend of first rising, then falling and tending to be stable. However, under pure culture conditions, the pH changes and fluctuates greatly. In 50% EFF, the culture of Haematococcus pluvialis can remove 97.44% of NO3 - -N and 86.85% of TP, ammonia nitrogen was completely removed, and COD showed an upward trend. The concentrations of Ca, S, Fe, Mn, Pb, Cu, Cr, and Zn metal ions in the system also decreased, and Hg and Se were not detected. In EFF, the culture of Haematococcus pluvialis can remove 52.68% of NO3 - -N, 34% NH4 + -N and 71.95% TP, COD and metal ion changes were similar to those of 50% EFF. However, as the culture process progressed, NH4 + -N initially showed an upward trend but subsequently declined. This is likely because the oxygen produced during the cultivation of Haematococcus pluvialis was utilized by aerobic bacteria, which denitrified nitrate nitrogen to form ammonia nitrogen. The changes in water quality indicate that Haematococcus pluvialis can utilize nutrients in the wastewater for cell division and growth, and the effluent can be used as a culture medium for Haematococcus pluvialis.

[0084] Table 3 Changes in water quality of biogas slurry (influent) and effluent (p<0.05)

[0085]

[0086]

[0087] The concentration changes of chlorophyll and carotenoids in Haematococcus pluvialis during the green and red phases of culture are shown in Figure 2. Figures 8-11 As shown. Figures 8-9 As shown in the figure, the chlorophyll content gradually increases with the increase of biomass concentration. At the same time, with the consumption of nutrients, the concentration of carotenoids also gradually increases. Astaxanthin is a type of carotenoid, the increase in carotenoid concentration indicates that astaxanthin is gradually accumulating. The microscopic examination results prove that the green period has ended and the Haematococcus pluvialis cells have entered the non-motile cyst spore stage from the swimming stage. Chlorophyll not only plays an important role in absorbing light energy, but also transmits light energy through the photosynthetic electron transport chain. Figures 10-11 As shown, after entering the stress period (red phase culture), as the stress time increases, carotenoids rapidly accumulate, accompanied by chlorophyll degradation. Chlorophyll can be degraded into phytol, which is ultimately oxidized into various isoprenoid compounds. Isoprene pyrophosphate can serve as a substrate for astaxanthin synthesis. Therefore, it is speculated that chlorophyll degradation products may be used to synthesize astaxanthin through certain pathways.

[0088] Astaxanthin accumulation is triggered by high light and high temperature, and then accelerated during the induction process without adding any substances to the culture medium. The astaxanthin content and yield of Haematococcus pluvialis cultured in different culture media (50% EFF in Example 1, EFF in Comparative Example 1, and BG11 in Comparative Example 2) are shown in Figure 2. Figure 12 As shown. Figure 12 Microscopic observation confirmed that green vegetative cells transformed into red cyst cells during the induction process. During this period, the biomass of the induced cells also increased from 1.78, 1.88, and 1.31 g / L to 3.16 g / L, 2.63 g / L, and 1.54 g / L in BG11, 50% EFF, and EFF media, respectively. Astaxanthin concentrations reached 9.28 mg / L, 10.96 mg / L, and 3.41 mg / L, respectively. Astaxanthin contents were 2.99 mg / g, 4.18 mg / g, and 2.21 mg / g, respectively. Based on the entire growth and induction cycle, among the wastewater cultures, 50% EFF medium had the highest astaxanthin production, with the highest cell growth rate and biomass concentration. The astaxanthin production and content in the BG11 pure culture were slightly lower than those in the 50% EFF culture, possibly because BG11 is not the optimal medium for the growth of Haematococcus pluvialis. The use of half-diluted MBR effluent (50% EFF) can meet the basic growth of Haematococcus pluvialis and the accumulation of astaxanthin. Therefore, the production of astaxanthin-rich Haematococcus pluvialis from inorganic waste has high economic value.

[0089] The results of the safety assessment of algae powder are shown in Table 4. Haematococcus pluvialis enriches heavy metal ions in the environment through biosorption, which has a positive significance for the remediation of environmental heavy metals. Metal ions at baseline concentrations significantly promote the growth of Haematococcus pluvialis, and too high or too low concentrations will limit the cultivation of Haematococcus pluvialis. Heavy metals are important monitoring indicators when Haematococcus pluvialis biomass is used. The concentrations of As, Hg, Cd, and Pb in algae powder were determined. The results in Table 4 show that the concentrations of the four heavy metal ions in Haematococcus pluvialis biomass are all within the allowable content range stipulated by the EU food safety regulations. The results for Escherichia coli and Staphylococcus aureus were negative, indicating that the Haematococcus pluvialis cultured in the effluent from the pig farm biogas wastewater treatment is safe and meets the requirements for use as food, feed, etc.

[0090] Table 4 Safety assessment results of algae powder

[0091]

[0092]

[0093] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A Haematococcus pluvialis-MBR coupled biogas slurry purification device, characterized in that: The device includes a biogas slurry inlet tank, an MBR membrane treatment device, a water storage device and a Haematococcus pluvialis cultivation device; The biogas slurry inlet bucket is connected to the MBR membrane treatment device through a water inlet pipe; The MBR membrane treatment device is connected to the water storage device through a water outlet pipe; The water outlet of the water storage device enters the Haematococcus pluvialis cultivation device; The MBR membrane treatment device includes a hollow fiber membrane module, an aerobic sedimentation tank, a clear water tank, an aeration device, and a filtration device; The hollow fiber membrane assembly is composed of a plurality of hollow fiber ultrafiltration membranes arranged in parallel; The aeration device is composed of two parallel hollow tubes, each of which is provided with air outlets, and the air flow meter is used to control the air flow.

2. A Haematococcus pluvialis-MBR coupled biogas slurry purification device according to claim 1, characterized in that, The filtration device includes a water pump, a water outlet pipe, and a flow meter; the water pump is connected to the water outlet pipe and the hollow fiber membrane assembly. The water pump is connected to the hollow fiber membrane assembly to discharge the biogas slurry in the aerobic sedimentation tank into the clear water tank, and then pumped into the water storage device through the water pump.

3. A Haematococcus pluvialis-MBR coupled biogas slurry purification device according to claim 1 or 2, characterized in that, The water storage device comprises an ultraviolet sterilization lamp and a water storage barrel.

4. A Haematococcus pluvialis-MBR coupled biogas slurry purification device according to claim 3, characterized in that: The Haematococcus pluvialis culture device comprises a conical flask.

5. A method for purifying Haematococcus pluvialis-MBR coupled biogas slurry using a Haematococcus pluvialis-MBR coupled biogas slurry purification device according to any one of claims 1 to 4, characterized in that: The following steps are involved: The biogas in the biogas inlet tank enters the MBR membrane treatment device through the water inlet pipe. In the MBR membrane treatment device, the biogas enters the aerobic sedimentation tank for aerobic treatment, and the dissolved oxygen content of aeration is controlled at 6.0 mg / L. Then, the biogas is subjected to a sedimentation treatment for 3 hours, and the hydraulic retention time is 48 hours. The biogas is then discharged into the clear water tank through the suction filtration device to obtain the biogas treated by the MBR membrane treatment device. The biogas slurry treated by the MBR membrane treatment device enters the outlet pipe through a water pump and then enters the water storage device; after being sterilized by the ultraviolet sterilization lamp of the water storage device, the pH is adjusted to obtain effluent; the effluent is passed into the Haematococcus pluvialis culture device to culture Haematococcus pluvialis.

6. The method for purification of biogas slurry by coupling Haematococcus pluvialis with MBR according to claim 5, characterized in that: The flow rate of the air is 20-30 L / min; The aeration time in the aerobic sedimentation tank is 3 hours, and the sedimentation time is 3 hours.

7. The method for purification of biogas slurry by coupling Haematococcus pluvialis with MBR according to claim 6, characterized in that: The pH of the effluent is 7; and the UV sterilization time is 30 to 40 minutes.

8. The method for purification of biogas slurry by coupling Haematococcus pluvialis with MBR according to claim 6 or 7, characterized in that: The cultivation of Haematococcus pluvialis is divided into two stages: the first stage is the green stage, and the second stage is the red stage. The temperature of the green stage culture is 23-25°C, the light intensity is 2500Lx, and the light-dark ratio is 12h:12h; The temperature of the red phase culture is 30° C., the light intensity is 6500 Lx, and the light is continuous.

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