CN110526414B

CN110526414B - Use method of membrane-photobioreactor

Info

Publication number: CN110526414B
Application number: CN201910930998.8A
Authority: CN
Inventors: 李晨; 高锋; 杨紫嫣; 杨红丽
Original assignee: Zhejiang Ocean University ZJOU
Current assignee: Zhejiang Ocean University ZJOU
Priority date: 2019-09-29
Filing date: 2019-09-29
Publication date: 2022-01-11
Anticipated expiration: 2039-09-29
Also published as: CN110526414A

Abstract

The invention provides a membrane-photobioreactor for purifying phenol-containing wastewater and a use method thereof, belonging to the technical field of wastewater treatment. The use method of the membrane-photobioreactor comprises the steps of inoculating microalgae in a logarithmic growth phase into the membrane-photobioreactor; supplying phenol-containing wastewater into the reactor, culturing microalgae, and purifying the phenol-containing wastewater; and discharging the purified water out of the reactor through an ultrafiltration membrane component and a suction pump. The application method is simple and feasible, the operation condition is good, and the nitrogen, phosphorus and phenol in the phenol-containing wastewater are efficiently removed.

Description

Use method of membrane-photobioreactor

Technical Field

The invention belongs to the technical field of wastewater treatment, and particularly relates to a membrane-photobioreactor for purifying phenol-containing wastewater and a using method thereof.

Background

With the rapid development of economy, the social productivity is continuously improved, and the discharge amount of industrial sewage is increased sharply. Organic polluted wastewater generated in chemical industries such as coking, oil refining, plastics, paper making, textile, ceramics and the like contains a large amount of phenol. Phenol can enter human body through contacting skin or respiratory system, and has high toxicity, no easy degradation, and harm to human health. For example, drinking phenol-contaminated water for a long time can cause chronic toxic reaction, and digestive tract symptoms such as dizziness, headache, rash, decreased appetite, emesis, diarrhea, etc. appear. At present, the main means for treating the phenol-containing wastewater comprises biological treatment methods such as an activated sludge method, an enzyme treatment technology and an immobilized microorganism technology. Physical methods such as adsorption, liquid membrane, solvent extraction. Chemical methods such as oxidation, precipitation, photocatalysis. Compared with biological methods, physical methods and chemical methods have the disadvantages of high cost, secondary pollution, uneconomical treatment at low concentration and the like. The biochemical method has low cost and small secondary pollution in wastewater treatment, so the method is always a hot point of research.

Microalgae are increasingly used for the removal of organic substances, such as aromatic compounds, steroid compounds, pesticides, oil pollutants, etc., due to their large adsorption and biodegradation capabilities. During the growth and propagation of microalgae, organic compounds in water can be used as assimilated carbon sources, nitrogen sources and sulfur sources to enrich and absorb, so that the microalgae can degrade various organic compounds such as pesticides, hydrocarbons, polycyclic aromatic hydrocarbons, metal organic matters and the like. Since Oswald et al proposed the use of microalgae to treat wastewater in the fifties of the twentieth century, microalgae resources have been utilized in many areas such as water purification, water quality monitoring, medical care, biological feed, and the like. Later, the students research and discover that chlorella, scenedesmus, crescent moon algae, Platymonas, Ochrostis, Sphingomonas vaginalis, Nostoc and Oscillatoria can degrade phenolic compounds, and carry out related mechanism and application research. At present, people develop researches on various algae bioreactors to realize high yield of microalgae and high efficiency of wastewater treatment, but most of the treatment systems have complex structures and high operation difficulty, and are difficult to achieve ideal wastewater treatment effects.

Disclosure of Invention

An object of the present invention is to provide a membrane-photobioreactor for purifying phenol-containing wastewater, which can completely intercept microalgae cells, can continuously culture microalgae using phenol-containing wastewater, and can effectively remove phenol in phenol-containing wastewater.

The technical scheme adopted by the invention for realizing the purpose is as follows: the membrane-photobioreactor for purifying the phenol-containing wastewater is internally provided with an ultrafiltration membrane component and utilizes the phenol-containing wastewater to continuously culture microalgae. The arrangement of the ultrafiltration membrane component in the membrane-photobioreactor can realize complete interception of microalgae cells, realize continuous water inlet and outlet operation of phenol-containing wastewater and avoid loss of the microalgae cells; in addition, the continuously fed phenol-containing wastewater provides sufficient nutrient salts required for growth for the growth of the microalgae in the reactor, so that the microalgae in the reactor is more efficiently cultured compared with batch culture, and the concentration of the microalgae in the reactor is enriched to a level far higher than that of the batch culture, thereby effectively removing phenol in the phenol-containing wastewater.

According to one embodiment of the present invention, the ultrafiltration membrane module is made of polyvinylidene fluoride, and the membrane pore size is 0.01 μm.

According to one embodiment of the present invention, the phenol-containing wastewater is a wastewater having a phenol concentration of less than 300 mg/L. The phenol with lower concentration can be used as an organic carbon source for heterotrophic growth of the microalgae, thereby promoting the rapid growth of the microalgae. In contrast, when the phenol concentration in the wastewater is high, the growth of microalgae is obviously inhibited.

According to one embodiment of the invention, illumination is provided at 1-3cm of the surface of the membrane-photobioreactor, and the illumination is provided by 2-5 LED lamps with power of 9W.

The second purpose of the invention is to provide a using method of the membrane-photobioreactor, which has good operating condition and realizes the efficient removal of nitrogen, phosphorus and phenol in the phenol-containing wastewater, and comprises the following steps,

culturing microalgae to logarithmic growth phase;

inoculating microalgae in logarithmic growth phase into a membrane-photobioreactor;

supplying phenol-containing wastewater into the reactor, culturing microalgae, and purifying the phenol-containing wastewater;

and discharging the purified water out of the reactor through an ultrafiltration membrane component and a suction pump.

According to an embodiment of the present invention, the microalgae is selected from at least 1 of chlorella, scenedesmus, nostoc, and crescent algae.

According to one embodiment of the invention, the inoculation concentration of the microalgae is 0.1-0.5 g/L.

According to one embodiment of the present invention, the phenol-containing wastewater is a wastewater having a phenol concentration of less than 300 mg/L.

According to one embodiment of the present invention, the inflow and outflow rates are equal.

According to one embodiment of the invention, the hydraulic retention time in the membrane-photobioreactor is 2-3d, and the microalgae solid retention time is 10-40 d.

Compared with the prior art, the invention has the beneficial effects that: the arrangement of the ultrafiltration membrane component in the membrane-photobioreactor can realize complete interception of microalgae cells, realize continuous water inlet and outlet operation of phenol-containing wastewater and avoid loss of the microalgae cells; in addition, the continuously fed phenol-containing wastewater provides sufficient nutrient salts required for growth for the growth of the microalgae in the reactor, and the growth of the microalgae is utilized to realize more efficient culture compared with batch culture, and the concentration of the microalgae in the reactor is enriched to a level far higher than that of the batch culture, so that the phenol in the phenol-containing wastewater is effectively removed. The membrane-photobioreactor provided by the invention utilizes phenol-containing wastewater to continuously culture microalgae, is simple and feasible in use method and good in operation condition, and realizes efficient removal of nitrogen, phosphorus and phenol in the phenol-containing wastewater.

The invention adopts the technical scheme to provide the membrane-photobioreactor for purifying the phenol-containing wastewater and the use method thereof, which make up the defects of the prior art, and have reasonable design and convenient operation.

Drawings

FIG. 1 is a schematic view showing the overall structure of a membrane-photobioreactor according to the present invention in example 1 of the present invention;

FIG. 2 is a graph showing the growth of Chlorella in wastewater containing phenol at various concentrations according to example 1 of the present invention;

FIG. 3 shows the removal rate of TIN and TIP in the batch culture process of example 1;

FIG. 4 is a graph showing the relative enzyme activity of Chlorella in wastewater of various phenol concentrations in example 1 of the present invention;

FIG. 5 is a graph showing the change of the chlorella concentration in the MPBR reactor with the culture time during the continuous culture in experimental example 1 of the present invention;

FIG. 6 is a graph showing the changes of phenol, TIN and TIP concentrations in effluent of an MPBR reactor with respect to the culture time during the continuous culture in test example 1 of the present invention;

FIG. 7 is a graph showing the growth of chlorella in waste water containing phenol at various concentrations obtained in example 8 of the present invention in test example 2.

Detailed Description

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It is not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

These examples are provided only for more specifically illustrating the present invention, and it is apparent to those skilled in the art that the scope of the present invention is not limited to these examples according to the gist of the present invention.

FIG. 1 is a schematic view showing the overall structure of the membrane-photobioreactor according to the present invention. The invention provides a Membrane-photobioreactor (MPBR) for purifying phenolic wastewater, which mainly comprises a phenolic wastewater tank 1, a water inlet valve 2, a pH meter 3, a flow meter 4, a water outlet valve 5, a Membrane-photobioreactor 6, an air outlet 61, an ultrafiltration Membrane assembly 62, concentrated microalgae liquid harvesting 7, an air compressor 8, an air flow meter 9, a gas distributor 10 and the like. The phenolic wastewater tank 1 is connected with the membrane-photobioreactor 6 through the water inlet valve 2, the bottom of the phenolic wastewater tank 1 is higher than the top of the membrane-photobioreactor 6, so that phenolic wastewater can be conveniently introduced into the membrane-photobioreactor 6 by self gravity without pumping, and degradation treatment and algae-water separation processes of the algae-membrane reactor are guaranteed to be completed under the condition of low energy consumption. The main body of the membrane-photobioreactor 6 is a cylindrical organic glass container with a volume of 3 liters. The membrane-photobioreactor 6 is characterized in that illumination is arranged at the position 1-3cm away from the surface of the membrane-photobioreactor, and the illumination is provided by 2-5 LED lamps with power of 9W. An ultrafiltration membrane component 62 is arranged in the membrane-photobioreactor 6, the membrane-photobioreactor 6 utilizes the wastewater containing phenol to continuously culture microalgae, after the microalgae and the wastewater containing phenol react for a period of time, a suction filtration pump is started, the wastewater after the reaction is separated from the microalgae in the membrane-photobioreactor 6 through the ultrafiltration membrane component 62 immersed in the wastewater, and the water after membrane filtration is pumped into a storage tank. The bottom of the membrane-photobioreactor 6 is provided with 1 gas distributor 10 which is connected with an air compressor 8 for aeration, and the sprayed bubbles play roles of uniformly stirring and supplementing dissolved oxygen so as to meet the requirement of oxygen required by the growth of microalgae on one hand, and wash membrane components in the membrane-photobioreactor 6 in the rising process on the other hand, so that the pollution of the membrane is relieved. The arrangement of the ultrafiltration membrane component in the membrane-photobioreactor can realize complete interception of microalgae cells, realize continuous water inlet and outlet operation of phenol-containing wastewater and avoid loss of the microalgae cells; in addition, the continuously fed phenol-containing wastewater provides sufficient nutrient salts required for growth for the growth of the microalgae in the reactor, so that the microalgae in the reactor is more efficiently cultured compared with batch culture, and the concentration of the microalgae in the reactor is enriched to a level far higher than that of the batch culture, thereby effectively removing phenol in the phenol-containing wastewater.

In one embodiment of the present invention, the ultrafiltration membrane module is made of polyvinylidene fluoride, and the membrane pore diameter is 0.01 μm.

In one embodiment of the invention, the phenol-containing wastewater is wastewater with a phenol concentration of less than 300 mg/L. The phenol with lower concentration can be used as an organic carbon source for heterotrophic growth of the microalgae, thereby promoting the rapid growth of the microalgae. In contrast, when the phenol concentration in the wastewater is high, the growth of microalgae is obviously inhibited. More preferably, the phenol-containing waste water is waste water having a phenol concentration of 100 mg/L. The phenol of 100mg/L in the wastewater does not produce inhibition effect on the chlorella, and the phenol is used as an organic carbon source to promote the heterotrophic growth of the chlorella, when the concentration reaches more than 300mg/L, the growth of the chlorella is obviously inhibited, and the absorption and removal effect on nitrogen and phosphorus is influenced.

An embodiment of the present invention provides a method for using the above membrane-photobioreactor, comprising,

culturing microalgae to logarithmic growth phase;

In one embodiment of the present invention, the microalgae is at least 1 selected from anabaena flos-aquae, scenedesmus, spirulina platensis, and chlorella.

In one embodiment of the invention, the inoculation concentration of the microalgae is 0.1-0.5 g/L.

The phenol-containing wastewater is wastewater with the phenol concentration less than 300 mg/L.

In one embodiment of the invention, the inflow and outflow are equal.

In one embodiment of the invention, the hydraulic retention time in the membrane-photobioreactor is 2-3d, and the microalgae solid retention time is 10-40 d. Further preferably, the hydraulic retention time of the membrane-photobioreactor is 3d, and the microalgae solid retention time is 20 d. When the operation parameters of the membrane-photobioreactor are controlled to be 3d of hydraulic retention time and 20d of microalgae solid retention time, the operation condition of the membrane-photobioreactor is good, the removal rate of phenol and phosphorus is highest, and meanwhile, nitrogen also has a good treatment effect, so that nitrogen, phosphorus and phenol in the phenol-containing wastewater are efficiently removed.

In one embodiment of the present invention, a method for using the above membrane-photobioreactor comprises,

centrifuging and collecting Chlorella in logarithmic growth phase at 6000rpm for 15min, and inoculating to a membrane-photobioreactor at concentration of 0.1-0.5 g/L;

after inoculation is finished, phenol-containing wastewater is continuously supplied into the reactor, and the concentration of inlet phenol is controlled to be 100 mg/L;

discharging purified water out of the reactor through an ultrafiltration membrane component and a suction filtration pump, wherein the water inlet flow and the water outlet flow are equal, the Hydraulic Retention Time (HRT) in the reactor is controlled to be 2.0-3.0d, the continuous culture is divided into four stages, the chlorella is grown to a stable stage in the first stage, and the chlorella is grown to the reactor in the second, third and fourth stages every dayHarvesting the algae liquid in the reactor to ensure that the retention time (SRT) of the microalgae solid in the reactor is 10-40 days, and the light intensity on the surface of the reactor is 180 mu mol m^-2s^-1Light: the dark is 12:12, the air flow is controlled at 0.5L/min, and the temperature is kept at 25 +/-2 ℃.

The invention is further illustrated by the following examples. It is to be understood that the examples are for illustrative purposes only and are not intended to limit the scope and spirit of the present invention.

Example 1:

growth status of Chlorella under different phenol concentrations

The algae is Chlorella preserved in laboratory. Chlorella species were inoculated into Erlenmeyer flasks containing modified BG11 medium prepared in seawater and pre-cultured in a light incubator. The main parameter for adjusting the illumination incubator is that the illumination intensity is 90 mu mol m^-2 s^-1Light: dark-12: 12 at a temperature of 25 ℃. The algal cells were cultured to a logarithmic growth phase for use.

The microalgae cells in the logarithmic growth phase are inoculated in a photobioreactor containing 1.5 liters of phenol-containing wastewater, the main body of the photobioreactor is a cylindrical organic glass container, and the volume of the photobioreactor is 3 liters. The illumination of the reactor was provided by 3 LED lamps with power of 9W and placed at a distance of 2cm from the reactor surface. At the bottom of the reactor, 1 gas distributor was installed, connected to an air compressor for aeration, and used for stirring in the reactor. The maximum light intensity at the reactor surface was 180. mu. mol m during the entire experimental period^-2s^-1The air flow rate was controlled at 0.5L/min. All reactors were placed in a chamber maintained at a temperature of 25. + -. 2 ℃. The concentrations of phenol in the batch cultures were 0, 100, 300, 500 and 700mg/l, respectively. The contents of the components other than phenol in the simulated wastewater are shown in Table 1. The microalgae concentration in the reactor is periodically measured in the experimental process, and meanwhile, water quality indexes such as phenol concentration and the like are analyzed and measured. Finally, the activities of superoxide dismutase (SOD), Catalase (CAT) and Ascorbate Peroxidase (APX) of the microalgae were determined at the end of the batch culture test.

TABLE 1 simulated wastewater Components Table

Medicine and food additive	Concentration of	Medicine and food additive	Concentration of
				NH₄Cl	154.3mg/l	MnCl·4H₂O	1.81mg/l
KH₂PO₄	22mg/l	ZnSO₄·7H₂O	0.22mg/l
				NaHCO₃	125mg/l	FeSO₄·7H₂O	4.99mg/l
CaCl₂	2.5mg/l	(NH₄)₆MoO₂₄·7H₂O	0.4mg/l
				MgSO₄·7H₂O	27.5mg/l	NaCl	20g/l
H₃BO₃	2.86mg/l

The effect of different phenol concentrations on chlorella biomass accumulation is shown in figure 2, in the batch culture process, phenol with different concentrations in the wastewater has different effects on the growth of the seawater chlorella, when the phenol concentration in the wastewater is lower, such as 100mg/L, the phenol in the wastewater can obviously promote the growth of the chlorella, and the finally obtained microalgae concentration reaches 1.6 times of that of a control group (the phenol concentration is 0 mg/L). This indicates that lower concentrations of phenol can be used as an organic carbon source for heterotrophic growth of microalgae, thereby promoting rapid growth of microalgae. In contrast, when the phenol concentration in the wastewater is high, the growth of microalgae is obviously inhibited. As shown in FIG. 2, the microalgae biomass at day 13 in the experimental groups with phenol concentrations of 300, 500 and 700mg/L were 62%, 32% and 24% of the control group, respectively. The microalgae concentration tends to rise again, which may be because the chlorella gradually adapts to the environment with high concentration of phenol after a period of cultivation, i.e. is acclimatized, so that the microalgae concentration rises to some extent.

The measured removal rates of Total Inorganic Nitrogen (TIN) and Total Inorganic Phosphorus (TIP) in the wastewater after the batch culture are shown in FIG. 3, and it can be seen from the figure that the wastewater with the phenol concentration of 100mg/L has the best nitrogen and phosphorus removal effect, and the removal rates of TIN and TIP are the highest among several samples, which is mainly benefited from the higher microalgae growth amount in the wastewater with the phenol concentration of 100mg/L (FIG. 2). Therefore, the phenol with lower concentration in the wastewater can promote the growth of the chlorella, thereby simultaneously improving the removal efficiency of nitrogen and phosphorus nutrition in the wastewater.

All aerobic organisms have a relatively well-established set of antioxidant systems, which are closely related to their ability to resist adversity stress. In the case of chlorella, the APX and CAT activities both react to different degrees to the increase of phenol concentration, while the change of SOD activity is not obvious. Therefore, the change of APX and CAT activities in chlorella is a preferable biological index indicating that the phenol concentration is enhanced ideally. The activity changes of three antioxidant enzymes of chlorella under different phenol concentration treatments are shown in fig. 4. The Catalase (CAT) enzyme activity of microalgae in phenol-containing wastewater was increased relative to the control group. The activity of superoxide dismutase (SOD) enzyme of the microalgae is kept relatively stable in phenol wastewater with different concentrations, and no obvious ascending and descending change is shown. The Ascorbyl Peroxidase (APX) enzyme activities of the microalgae in the phenol-containing wastewater were all lower than those of the control, especially at phenol concentrations of 100, 300 and 500 mg/L.

The results show that 100mg/L of phenol in the wastewater does not have an inhibition effect on the chlorella and can be used as an organic carbon source to promote the heterotrophic growth of the chlorella, when the concentration of the phenol reaches 300mg/L or more, the growth of the chlorella is obviously inhibited, and the nitrogen and phosphorus removal capability of the system is reduced. As the phenol concentration in the wastewater increases, the antioxidant system in the plant body starts to function, and the activity changes of Ascorbate Peroxidase (APX) and Catalase (CAT) prove to be the preferable biological indexes indicating that the phenol inhibition effect is ideal. Then, the chlorella was continuously cultured in a membrane-photobioreactor using wastewater having a phenol concentration of 100 mg/L.

Example 2:

a membrane-photobioreactor for purifying phenol-containing wastewater mainly comprises a phenol-containing wastewater tank 1, a water inlet valve 2, a pH meter 3, a flow meter 4, a water outlet valve 5, a membrane-photobioreactor 6, an air outlet 61, an ultrafiltration membrane component 62, concentrated microalgae liquid harvesting 7, an air compressor 8, an air flow meter 9, a gas distributor 10 and the like. The phenolic wastewater tank 1 is connected with the membrane-photobioreactor 6 through a water inlet valve 2, and the bottom of the phenolic wastewater tank 1 is higher than the top of the membrane-photobioreactor 6. The main body of the membrane-photobioreactor 6 is a cylindrical organic glass container with a volume of 3 liters. The membrane-photobioreactor 6 is provided with illumination at 2cm from the surface of the membrane-photobioreactor, and the illumination is provided by 3 LED lamps with power of 9W. The bottom of the membrane-photobioreactor 6 is provided with 1 gas distributor 10 which is connected with an air compressor 8 for aeration and plays a role in stirring in the membrane-photobioreactor 6. An ultrafiltration membrane component 62 is arranged in the membrane-photobioreactor 6, the material of the ultrafiltration membrane component is polyvinylidene fluoride, the membrane aperture is 0.01 mu m, and the membrane-photobioreactor 6 utilizes phenol-containing wastewater to continuously culture microalgae. The phenol-containing wastewater is wastewater with the phenol concentration of 100 mg/L.

A method for using the membrane-photobioreactor comprises the following steps,

1) inoculating Chlorella strain into conical flask containing modified BG11 culture medium prepared from seawater, pre-culturing in light incubator with illumination intensity of 90 μmol m as main parameter^-2s^-1Light: dark-12: 12, culturing the algae cells to a logarithmic growth phase at the temperature of 25 ℃ for later use;

2) centrifuging and collecting Chlorella in logarithmic growth phase (6000rpm,15min), inoculating into two groups of membrane-photobioreactor, wherein the inoculation concentration is 0.23 g/L;

3) after the completion of the inoculation, phenol-containing wastewater (the composition of which is shown in Table 1) was continuously supplied into the reactor, and the concentration of inlet phenol was controlled at 100 mg/L;

4) discharging purified water out of the reactor through an ultrafiltration membrane component and a suction filtration pump, wherein the water inlet flow and the water outlet flow are equal, the Hydraulic Retention Time (HRT) in the reactor is controlled to be 2.0d, the continuous culture is divided into four stages, the chlorella is grown to a stable period in the first stage, the chlorella liquid in the reactor is harvested in the second, third and fourth stages every day, the Solid Retention Time (SRT) of the chlorella in the reactor is 20d, and the light intensity on the surface of the reactor is 180 mu mol m^-2s^-1Controlling the air flow at 0.5L/min, the temperature at 25 +/-2 ℃ and the pH at 7.0, and simultaneously carrying out microalgae concentration and inlet and outlet water quality in the reactor every dayAnd (4) analyzing and measuring.

Example 3:

the difference from example 2 is that HRT was controlled to be 3.0d and SRT was controlled to be 20 d.

Example 4:

the difference from example 2 is that HRT was controlled to be 2.0d and SRT was controlled to be 10 d.

Example 5:

the difference from example 2 is that HRT was controlled to be 2.0d and SRT was controlled to be 40 d.

Example 6:

the difference from example 2 is that HRT was controlled to be 3.0d and SRT was controlled to be 10 d.

Example 7:

the difference from example 2 is that HRT was controlled to be 3.0d and SRT was controlled to be 40 d.

Example 8:

when the concentration of phenol in the phenol-containing wastewater is higher, the growth and biodegradation activities of chlorella are inhibited, and the chlorella reaches the death phase earlier than normal algae cells, and in order to improve the tolerance and degradation capability of microalgae to phenol in the phenol-containing wastewater, and further improve the working efficiency of an MPBR reactor, the difference from the example 2 is that the chlorella cultured in the step 1) of the embodiment contains 4.6 mu g/L dipotassium glycyrrhizinate and 2.0 mu g/L D-mannitol. The existence of dipotassium glycyrrhizinate and D-mannitol in the BG11 culture medium can improve the content of chlorophyll a in chlorella, thereby improving the adaptability enhancement of the chlorella to phenol-containing wastewater, increasing the growth rate and the removal capability of phenol, and simultaneously improving the removal rate of nitrogen and phosphorus in the phenol-containing wastewater.

Comparative example 1:

the difference from example 8 is that BG11 medium for acclimatized chlorella does not contain dipotassium glycyrrhizinate.

Comparative example 2:

the difference from example 8 is that BG11 medium for domesticated chlorella does not contain D-mannitol.

Test example 1:

1. growth of Chlorella in continuous culture

The ultrafiltration membrane component in the MPBR can realize the complete interception of microalgae cells in the reactor, thereby promoting the reactor to continuously culture microalgae in a continuous water inlet and outlet mode. In examples 2 to 7, the change of the chlorella concentration in the MPBR reactor with the culture time during the continuous culture using phenol-containing wastewater as the culture medium is shown in fig. 5 (in the figure, the 1 st to 11 th days are the start-up period, and the 12 th to 35 th days are the steady operation period, in which the SRT is 40d for 12 to 19 days, 20d for 20 to 28 days, and 10d for 29 to 35 days). From FIG. 5, it can be seen that when the HRT of the MPBR reactor is controlled to be 2d and 3d, the continuously fed phenol-containing wastewater provides sufficient nutrient salts for the growth of the microalgae in the reactor, and 100mg/L phenol in the wastewater can provide an organic carbon source for the heterotrophic growth of the microalgae. During the starting period of the first 11 days, the chlorella in the reactor all realize rapid growth, and the concentrations at the end of the rapid growth reach 0.67g/L and 0.69g/L respectively (figure 5). And then the operation of the MPBR enters a stable operation stage, in order to realize stable long-term operation, the chlorella in the reactor needs to be harvested at a certain speed, continuous culture is carried out in three stages, and the corresponding Solid Retention Time (SRT) of the chlorella is respectively 40d, 20d and 10 d. As shown in FIG. 5, the concentration of Chlorella in the first two-stage reactor was maintained at a high level, and when the SRT was adjusted to 10 days, the concentration of microalgae in the reactor gradually decreased, indicating that the harvesting rate of microalgae in the reactor exceeded the growth rate of microalgae.

2. Efficiency of chlorella in removing phenol, nitrogen and phosphorus in continuous culture process

Examples 2-7 the efficiency of removing phenol and nitrogen and phosphorus from chlorella during continuous cultivation is shown in fig. 6 (in the figure, days 1-11 are start-up period, days 12-35 are steady operation period, where SRT 40d for days 12-19, 20d for days 28, and 10d for days 29-35), and table 2. as can be seen from fig. 6, the concentrations of phenol and nitrogen and phosphorus in the effluent of the MPBR reactor are gradually reduced in the start-up period of the MPBR reactor, because the concentration of microalgae in the reactor is limited at the beginning of cultivation, the pollutant removal capacity of the reactor is limited. As the culture proceeded, it is understood from FIG. 6 that the concentration of microalgae in the reactor gradually increased and the ability to absorb and remove phenol and nitrogen and phosphorus also increased.

After the start-up phase is completed, the operation of the MPBR enters a stable operation phase, and the SRT of the reactor is controlled at 40d, 20d and 10d in sequence. It can be seen from the data in table 2 that, when the operation parameters of the reactor are controlled to HRT 3d and SRT 20d, the operation conditions of the system are better, the removal rate of phenol and phosphorus is the highest, and the nitrogen achieves better treatment effect.

In a word, continuous water inlet and outlet culture of chlorella can be realized in the MPBR through the filtering action of the membrane module, the obtained microalgae biomass is far larger than batch culture, and in the aspect of pollutant treatment, when the operating parameters of the reactor are controlled to be HRT (Rockwell temperature) 3d and SRT (SRT) 20d, the efficient removal of nitrogen, phosphorus and phenol in wastewater is realized.

TABLE 2 Effect of MPBR reactor operation under different HRT and SRT conditions

Test example 2:

1. adaptability of chlorella to phenol

The chlorella obtained in example 8 was subjected to a batch culture process under the conditions of example 1, and the effect of different phenol concentrations on the biomass accumulation of the chlorella of example 8 is shown in fig. 7, and it can be seen that when the phenol concentration in the wastewater is 300mg/L, the phenol present in the wastewater can also significantly promote the growth of the chlorella, which is significantly higher than the phenol concentration of 100mg/L in the wastewater of example 1. The results show that the pellet obtained by the culture in example 8 shows a strong adaptability to phenol-containing wastewater without being acclimated.

2. The chlorella removes nitrogen, phosphorus and phenol in the wastewater

The nitrogen and phosphorus removal rate of the wastewater by the chlorella is shown in table 3, and the data in table 3 show that the removal rate of phenol, phosphorus and nitrogen is highest in example 8, which indicates that the content of chlorophyll a in the chlorella can be increased by the presence of dipotassium glycyrrhizinate and D-mannitol in a BG11 culture medium, so that the adaptability of the chlorella to the phenol-containing wastewater is improved, and the removal capacity of phenol, nitrogen and phosphorus in the phenol-containing wastewater is improved.

TABLE 2 Effect of MPBR reactor operation under different HRT and SRT conditions

Index (I)	Example 2	Example 8	Comparative example 1	Comparative example 2
					TIN removal (%)	69.51±8.66	78.87±5.42	68.55±3.47	70.26±4.57
TIN removal Rate (mg/L/d)	13.73±1.71	19.23±1.83	13.63±1.52	14.1±1.04
					TIP removal Rate (%)	94.42±4.53	97.64±6.14	93.89±5.21	94.09±4.99
TIP removal Rate (mg/L/d)	2.20±0.11	3.13±0.18	2.31±0.24	2.12±0.33
					Phenol removal rate (%)	97.06±1.83	99.2±1.24	96.44±1.92	97.31±1.54
Phenol removal Rate (mg/L/d)	48.53±0.91	52.37±0.51	47.97±0.84	47.78±0.65

Conventional techniques in the above embodiments are known to those skilled in the art, and therefore, will not be described in detail herein.

The above embodiments are merely illustrative, and not restrictive, and those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention, and the protection scope of the present invention should be defined by the claims.

Claims

1. A method of using a membrane-photobioreactor, comprising: comprises the steps of (a) preparing a mixture of a plurality of raw materials,

culturing microalgae to logarithmic growth phase; the microalgae is selected from chlorella; the microalgae are pre-cultured in an illumination incubatorThe main parameter for adjusting the illumination incubator is illumination intensity of 90 mu mol.m^-2s^-1Light: dark-12: 12, the temperature is 25 ℃;

inoculating microalgae in logarithmic growth phase into a membrane-photobioreactor; the inoculation concentration of the microalgae is 0.23 g/L;

supplying phenol-containing wastewater into the reactor, culturing microalgae, and purifying the phenol-containing wastewater; the phenol-containing wastewater is wastewater with the phenol concentration of 100 mg/L;

discharging the purified water out of the reactor through an ultrafiltration membrane component and a suction pump; the hydraulic retention time in the reactor is controlled to be 2.0d, the continuous culture is divided into four stages, the first stage enables the chlorella to grow to a stable period, the second, third and fourth stages harvest the algae liquid in the reactor every day, the microalgae solid retention time of the chlorella in the reactor is 20d, and the light intensity on the surface of the reactor is 180 mu mol.m^-2s^-1Controlling the air flow at 0.5L/min, keeping the temperature at 25 +/-2 ℃ and the pH value at 7.0;

the microalgae culture adopts an improved BG11 culture medium prepared from seawater, and the BG11 culture medium contains 4.6 mug/L dipotassium glycyrrhizinate and 2.0 mug/L D-mannitol.

2. Use according to claim 1, characterized in that: the water inlet flow and the water outlet flow are equal.