CN110627213A

CN110627213A - Method for efficiently treating high-ammonia-nitrogen wastewater by microalgae photo-fermentation method

Info

Publication number: CN110627213A
Application number: CN201910496358.0A
Authority: CN
Inventors: 魏东; 余宗苡; 王庆科
Original assignee: Guangzhou Algae Energy Biotechnology Co Ltd; South China University of Technology SCUT
Current assignee: Zaoeng Rare Biotechnology Research And Development Guangzhou Co ltd; South China University of Technology SCUT
Priority date: 2019-06-10
Filing date: 2019-06-10
Publication date: 2019-12-31
Anticipated expiration: 2039-06-10
Also published as: CN110627213B

Abstract

The invention discloses a method for efficiently treating high-ammonia nitrogen wastewater by a microalgae photo-fermentation method, which comprises the following steps: s1, activating and culturing a seed solution: inoculating microalgae cells to a culture medium for activation, and then carrying out high-density culture to obtain logarithmic phase seed liquid; s2, light fermentation culture: placing the blended high ammonia-nitrogen wastewater into a light fermentation tank, sterilizing, inoculating the seed solution obtained from S1 for culture, and supplementing materials in a plurality of stages of culture in the fermentation tank; and collecting microalgae biomass and obtaining purified water after ammonium ions in the fermentation tank are exhausted. The method disclosed by the invention can be used for efficiently removing ammonia nitrogen in the wastewater, realizing the production of the high-protein microalgae biomass, effectively reducing the wastewater treatment cost, realizing the comprehensive development and utilization of wastewater resource, being suitable for purifying the water rich in ammonia nitrogen wastewater in the industrial and agricultural fields and co-producing the high-protein biomass, and having economic and environmental-protection values.

Description

Method for efficiently treating high-ammonia-nitrogen wastewater by microalgae photo-fermentation method

Technical Field

The invention belongs to the technical field of high ammonia nitrogen sewage treatment, and particularly relates to a method for efficiently treating high ammonia nitrogen wastewater by a microalgae photo-fermentation method.

Background

The high ammonia nitrogen wastewater is mainly from agriculture (livestock breeding industry), industrial wastewater (including chemical industry, biogas, brewing, fermentation, food, slaughtering and other industries), and NH in wastewater₄ ⁺The content is as high as 300-10000mg/L, and if the waste water is discharged into rivers, the waste water can cause great pollution to the environment. The traditional treatment technology has obvious defects in cost, energy consumption and effect, the national environmental protection requirements are increasingly strict, and governments emphasize the way of ecological priority and green development. Therefore, the centralized treatment of high ammonia nitrogen wastewater urgently needs to develop a new technical system.

At present, the methods for treating the high ammonia nitrogen wastewater mainly comprise four types, namely a stripping method, an ion exchange method, a wet oxidation method and a biological method. The most common method is the blow-off method, the reaction principle is the movement of chemical equilibrium, wastewater is continuously stirred in a pipeline mixer, a large amount of alkali liquor is added and heated, and NH is generated at the moment₄ ⁺Formation of NH under alkaline conditions at elevated temperatures₃And H₂O, chemical equilibrium constantly moving to the right, NH₃The strong acid is blown into the strong acid absorption system by a fan through the fluidization stripping tower, thereby achieving the purpose of recycling. The stripping method has good ammonia nitrogen removal effect, relatively simple equipment operation and huge application market in industrial high-concentration ammonia nitrogen wastewater treatment. In the stable operation process of factory equipment, the ammonia nitrogen stripping efficiency is greatly influenced by the pH value and the temperature, and a large amount of strong base is consumed, so the energy consumption and material consumption cost are very high. In addition, ammonia escapes in the stripping process, so that the environment is easily polluted.

Therefore, a high-ammonia nitrogen wastewater treatment method which is efficient, low in energy consumption and cost, environment-friendly and capable of realizing resource utilization is urgently needed to be developed.

Disclosure of Invention

In order to solve the technical problems in the prior art, the invention provides a method for efficiently treating high-ammonia nitrogen wastewater by a microalgae photo-fermentation method, which is environment-friendly and low in energy consumption, can recycle nutrient elements in the wastewater and co-produce chlorella biomass, and realizes win-win of water circulation and resource utilization.

The technical purpose of the invention is realized by the following technical scheme:

the invention provides a method for efficiently treating high-ammonia nitrogen wastewater by a microalgae photo-fermentation method, which comprises the following steps:

s1, activating and culturing a seed solution: inoculating microalgae cells to a culture medium for activation, and then carrying out high-density culture to obtain logarithmic phase seed liquid;

s2, light fermentation culture: placing the blended high ammonia-nitrogen wastewater into a light fermentation tank, sterilizing, inoculating the seed solution obtained from S1 for culture, and supplementing materials in a plurality of stages of culture in the fermentation tank; and (4) harvesting the microalgae biomass and obtaining purified water after the ammonium ions in the fermentation tank are exhausted (reduced to below 200 mg/L). The formulation is carried out by adding the nitrogen-free medium mother liquor to make each component of the nitrogen-free medium in the fermentation liquor reach a predetermined concentration. Preferably, when the salinity of the high ammonia nitrogen wastewater is higher than 15 per mill, the salinity of the high ammonia nitrogen wastewater needs to be diluted to 15 per mill in advance, and then blending is performed.

Preferably, the microalgae selected in the present invention is chlorella; preferably, the chlorella is chlorella pyrenoidosa or chlorella pyrenoidosa obtained by domestication.

Specifically, the S2 light fermentation culture method comprises the following steps:

uniformly stirring the high ammonia-nitrogen wastewater and a nitrogen-free culture medium, introducing into a fermentation tank, sterilizing, cooling, adding S1 to obtain a seed solution, inoculating and culturing, taking out part of fermentation liquor when ammonium root ions in the fermentation tank are reduced to below 200mg/L, and pumping the same volume of wastewater culture medium into the fermentation tank for continuous culture; wherein the initial seeding cell density is 5X 10⁷-3×10⁸cfu/mL, controlling the pH value of the fermentation tank to be 6.5-7.0, and controlling the glucose concentration to be 1-20 g/L; preferably, when the salinity of the wastewater is higher than 15 per thousand, the salinity of the high ammonia nitrogen wastewater needs to be diluted to be lower than 15 per thousand in advance, and then the high ammonia nitrogen wastewater is stirred uniformly with the nitrogen-free culture medium.

More specifically, the light fermentation culture also comprises the following culture conditions: the external LED lighting system (white light) has the illumination intensity of 200-^-1m^-2The ventilation amount is 100-500L/h, the rotation speed is 100-400r/min, and the wastewater renewal rate is 20-80% (v/v).

Preferably, the nitrogen-free medium of the present invention is a nitrogen-free Basal medium; the nitrogen-free Basal medium comprises the following components in percentage by weight: MgSO (MgSO)₄·7H₂O is 1,000mg/L, EDTA and 500mg/L, K₂HPO₄Is 1,250mg/L, CaCl₂Is 111mg/L, FeSO4 & 7H₂O is 4.98mg/L, H₃BO₃Is 114.2mg/L, MnCl₂·4H₂O is 1.42mg/L, NaMoO₄·2H₂O is 1.19mg/L, ZnSO₄·7H₂O is 8.82mg/L, Co (NO)₃)₂·6H₂O is 0.49mg/L, CuSO₄·5H₂O is 1.57mg/L, and the pH value is 6.1.

Specifically, the fermentation culture of the invention is a two-stage culture:

s21, diluting the high ammonia nitrogen wastewater, adding a nitrogen-free culture medium mother solution (reaching the concentration of each component in the table 1, and being sugar-free) and uniformly mixing, filling the mixture into a fermentation tank, sterilizing, cooling, inoculating the seed solution obtained in the S1, and starting to culture, wherein the cell density of the microalgae initial inoculation is 5 multiplied by 10⁷-1×10⁸cfu/mL, glucose concentration maintained at 5-10g/L, illumination intensity of 200-^-1m^-2The pH value of the fermentation tank is controlled to be 6.5-7.0, the ventilation volume is 100-;

s22, when the concentration of ammonium ions is lower than 200mg/L, releasing fermentation liquor with the total volume of 28.0-33.3% of the fermentation liquor into a concentration tank, and harvesting microalgae to obtain biomass;

s23, adding the raw wastewater into the mother solution of the nitrogen-free culture medium, mixing uniformly to prepare a wastewater culture medium, sterilizing, cooling, adding into a light fermentation tank to reach the total volume of the fermentation solution before discharging, continuously culturing until the concentration of ammonium ions is lower than 200mg/L, and harvesting microalgae; preferably, the addition amount of the nitrogen-free culture medium mother liquor is as follows: the concentration of each component of the nitrogen-free culture medium is one half of the original formula.

Preferably, the addition of the S21 glucose mother liquor is before inoculating the seed liquor obtained in S1; the glucose mother liquor is sterilized glucose mother liquor.

As another embodiment of the present invention, the fermenter culture is a three-stage culture: the procedure was repeated 2 times in accordance with S22-S23. Wherein the illumination intensity is 200-^-1m^-2The pH value of the fermentation tank is 6.5-7.0, the glucose concentration is 5-10g/L, the ventilation amount is 100-; preferably, the addition amount of the nitrogen-free culture medium mother liquor is as follows: the concentration of each component of the nitrogen-free culture medium is three-fourths of the original formula.

As another embodiment of the present invention, the fermenter culture is a four-stage culture: the procedure was repeated 3 times in accordance with S22-S23. Wherein the illumination intensity is 200-^-1m^-2The pH value of the fermentation tank is controlled to be 6.5-7.0, the concentration of the glucose is 5-10g/L, the ventilation amount is 100-; preferably, the addition amount of the nitrogen-free culture medium mother liquor is as follows: the concentration of each component of the nitrogen-free culture medium is the original formula concentration.

Specifically, the high ammonia nitrogen wastewater comprises the following components: NH (NH)₄ ⁺10,000mg/L of 600-000, 5-60 per mill of salinity, 0-10mg/L of rare earth element, PO₄ ^3-The content is 0-300mg/L, and the pH value is 6-8.

More specifically, the concentration of glucose in the culture medium for high-density culture is 30-60g/L, the concentration of sodium nitrate is 2.5-5.0g/L, and the initial pH value is in the range of 5.5-6.5.

The invention adopts the technical scheme to achieve the following beneficial effects:

chlorella pyrenoidosa (Chlorella pyrenoidosa) is rich in protein and natural pigment, and has various nutrition modes. The method has the advantages that the method has super-strong tolerance capability to stress environments such as high temperature, high light, high salt, high ammonium and the like in the culture process, and can synthesize self cell components by using simple components in the wastewater, so that the recovery and utilization of nutrient elements in the wastewater and the joint output of high-quality chlorella biomass are realized. The method is environment-friendly and low in energy consumption, can recycle the nutrient elements in the wastewater and co-produce chlorella biomass, and realizes win-win of water circulation and resource utilization.

Drawings

FIG. 1 is a graph showing the change of illumination intensity, pH, rotation speed and aeration amount with time in a two-stage cultivation process in a fermenter.

FIG. 2a shows NH during two-stage cultivation in a fermenter₄ ⁺Graph of content versus time; FIG. 2b shows PO during two-stage cultivation in a fermenter₄ ^3-Graph of content versus time; FIG. 2c is a graph showing the dry weight of biomass as a function of time during a two-stage cultivation in a fermenter; FIG. 2d is a graph showing the change of chlorophyll fluorescence with time during two-stage cultivation in a fermenter.

FIG. 3a is a graph showing the time course of the protein in Chlorella pyrenoidosa during a two-stage cultivation in a fermenter; FIG. 3b is a graph showing the change of pigment content with time in the two-stage cultivation in the fermenter.

FIG. 4 shows the three-stage cultivation process in a fermenter, in which the change curves of the intensity of illumination, pH, rotation speed and aeration rate are plotted.

FIG. 5a shows a three-stage cultivation in a fermenter with NH being present during the cultivation₄ ⁺A content variation curve; FIG. 5b shows a three-stage cultivation in a fermenter with a course of the dry weight of the biomass as a function of time during the cultivation; FIG. 5c shows a three-stage cultivation in a fermenter with PO being present₄ ^3-Curve of content over time; FIG. 5d shows a three-stage cultivation in a fermenter, during which the chlorophyll fluorescence varies with time.

FIG. 6a is a graph showing the change of protein content in Chlorella pyrenoidosa with time during a three-stage cultivation in a fermenter; FIG. 6b is a graph showing the change of the pigment content in Chlorella pyrenoidosa with time during the three-stage cultivation in the fermenter.

FIG. 7a shows a four-stage fermenter culture with NH being present₄ ⁺A content variation curve; FIG. 7b shows four-stage cultivation in a fermenter with PO present₄ ^3-Curve of content over time; FIG. 7c shows a four-stage fermenter culture during which the dry weight of the biomass is plotted against time; FIG. 7d shows a four-stage cultivation in a fermenter,chlorophyll fluorescence curves over time during culture.

FIG. 8a is a graph showing the change with time of the protein content in Chlorella pyrenoidosa during the four-stage cultivation in the fermenter; FIG. 8b is a graph showing the change of the pigment content in Chlorella pyrenoidosa with time during the four-stage cultivation in the fermenter.

FIG. 9a is a graph showing the biomass as a function of time during three stages of cultivation in a fermenter at different cell densities for inoculation; FIG. 9b is a graph showing the ammonium concentration over time during three stages of culture in a fermentor at different inoculated cell densities; FIG. 9c is a graph showing the glucose concentration during three stages of culture in a fermentor as a function of time for different seeded cell densities.

FIG. 10a is a graph showing the change in the number of cells with time during three stages of culture in a fermentor at different initial concentrations of glucose; FIG. 10b is a graph showing the relative ammonium concentration during three stages of cultivation in a fermenter over time for different initial concentrations of glucose; FIG. 10c is a graph showing chlorophyll fluorescence with time during three stages of culture in a fermentor at different initial concentrations of glucose; FIG. 10d is a graph showing the change in dry weight of biomass with time during three stages of cultivation in a fermenter at different initial concentrations of glucose.

FIG. 11 is a graph showing the change of glucose concentration with time in the three-stage cultivation process in the fermenter under different initial glucose concentrations.

Detailed Description

The technical scheme of the invention is further explained by combining the accompanying drawings as follows:

professional wording defines:

1. high-density culture: the method is characterized in that algae cells are inoculated into a culture medium for activation and cultured until the dry weight of the algae cells is more than 20 g/L.

2. The wastewater renewal rate refers to that after the algae cells are cultured in the fermentation tank, part of fermentation liquor in the fermentation tank is taken out after ammonium ions are exhausted (less than 200mg/L), and wastewater culture medium (the original wastewater and the nitrogen-free culture medium are proportionally prepared) with the volume corresponding to the discharged fermentation liquor is pumped into the fermentation tank for continuous culture.

First, high renewal culture of fermentation tank

1.1 algal seed activation and seed liquid preparation

Transferring the strain of Chlorella pyrenoidosa (C. pyrenoidosa) stored in laboratory to the slant of basal medium containing 10g/L glucose, culturing at 30 deg.C under 100 μmol m illumination^-2s^-1And observing the growth condition of the chlorella pyrenoidosa.

Inoculating Chlorella pyrenoidosa single colony with inoculating loop into nitrogen-free basal medium containing 10g/L glucose at 30 deg.C under illumination of 100 μmol m^-2s^-1Culturing for 3-6 days in the constant-temperature shaking table to be used as seed liquid. Wherein the composition of said nitrogen-free basal medium (pH 6.1) is shown in Table 1 below (in mg/L):

TABLE 1 composition of nitrogen-free basal medium (pH 6.1)

1.2 high Density culture

Preparing basal culture medium, adding nitrogen source to maintain the concentration of sodium nitrate at 3.75g/L, stirring and mixing uniformly, adjusting the pH value to 6.1, and finally adding glucose according to the final concentration of 50 g/L. Subpackaging into 250mL conical bottles with liquid loading of 100mL, sealing with sealing film, placing into autoclave, and sterilizing at 115 deg.C for 20 min. After the sterilization is finished, the shake flask is taken out and cooled to the room temperature.

Inoculating the chlorella pyrenoidosa seed solution in the logarithmic growth phase into the culture medium under the culture conditions that: the rotating speed is 150r/min, the temperature is 30 ℃, the light source adopts the LED hard lamp strips of positive white light to be connected in series and arranged side by side, and the illumination intensity is 150 +/-10 mu mol m^-2s^-1The culture time was 6 days.

1.3 fermenter culture

See examples 1-3 for specific culture conditions.

Second, testing method

2.1 determination of Biomass

The biomass is determined by differential method. 3 replicates were set for each sample, averaged and the standard deviation calculated.

2.2 NH in wastewater₄ ⁺、PO₄ ^3-Determination of the content

The measurements were performed using a multi-parameter water quality analyzer, HANNA HI83200, italy. And selecting a proper range, diluting the sample to be detected to the measuring range, adding corresponding reagents into the cuvette according to the instrument instruction, measuring and reading. After the reading is finished, the reading is multiplied by the dilution factor to obtain NH in the culture medium₄ ⁺、PO₄ ^3-The content of (a).

2.3 protein content determination

The protein is measured by adopting a Kjeldahl method; the instrument used was a semi-automatic kjeldahl apparatus from FOSS corporation.

2.4 measurement of pigment content

20mg of freeze-dried algae powder is accurately weighed, crushed by ceramic beads and extracted by 90% acetone until the ceramic beads and the algae powder are white. Diluting the supernatant to 10mL with constant volume, taking a proper amount of sample to dilute to a proper time, taking 90% acetone solution as a blank, respectively measuring the absorbance of the sample under 470nm, 646nm and 663nm in an ultraviolet visible spectrophotometer, and substituting the result into an empirical formula for calculation:

C_a＝12.21×A₆₆₃－2.81×A₆₄₆

C_b＝20.13×A₆₄₆－5.03×A₆₆₃

C_t＝(1000×A₄₇₀－3.27×C_a－104×C_b)/198

wherein C is_aIs chlorophyll a, C_bIs chlorophyll b, C_tRefers to total carotenoids in units of μ g/mL.

Third, example 1-3 fermenter culture

Example 1Two-stage cultivation in fermenter

2.1 high-density culture: the method is as in section 1.2 of the first part

2.2 two-stage cultivation in fermenter

(1) And uniformly mixing 1.1L of high ammonia nitrogen wastewater with 2.2L of dilution water, and adding Basal medium mother liquor (without adding nitrogen) to reach the concentration (sugar-free) of each component in the table 1. Loading into 5L glass fermentation tank (total volume of fermentation broth is 3.5L), sterilizing at 115 deg.C for 20min, cooling to room temperature, adding sterilized glucose mother liquor to make final concentration of grape reach 10g/L, and inoculating 2.1 part of the obtained seed solution. The initial inoculation cell density of the chlorella pyrenoidosa is 1 multiplied by 10⁸cfu/mL, glucose was added to 10g/L through a feeding bottle (3 ‰ antifoam, 3mol/L hydrochloric acid, 4mol/L sodium hydroxide, 600g/L glucose were prepared in four types of feeding tanks, respectively) every 12h, pH in the fermentation tank was controlled within 7.0, and gradient-adjusted light intensity, rotation speed, and ventilation were as shown in FIG. 1.

(2) And when the ammonium ion concentration is lower than 200mg/L (after the ammonium ion is consumed), discharging fermentation liquor with the total volume of 1L (the total volume of the fermentation tank liquid is 28.0 percent) of the fermentation tank, and centrifugally harvesting the microalgae to obtain the algae mud.

Adding 1.1L of raw wastewater into basic culture medium mother liquor to reach one half of the concentration of each component in the table 1 (no nitrogen or sugar is added, phosphorus is independently supplemented, table 1) and mixing uniformly, sterilizing, cooling, adding into a light fermentation tank to reach the culture volume before discharging, continuously culturing until the concentration of ammonium ions is lower than 200mg/L, and collecting microalgae.

2.3 test methods: method and the second part of the test method

2.4 analysis of results

In example 1, NH at different stages of two-stage culture₄ ⁺The results of the removal rate and the average absorption amount are shown in Table 2. As shown in FIG. 1, the results of the analysis showed that the initial pH of 7.0 was set to appropriately reduce the amount of the medium added (halving the concentration in Table 1) in the two-stage culture, contributing to the increase in NH₄ ⁺The average absorption rate reaches more than 500 (mg/L/d). During the culture, setting the illumination intensity, rotation speed and ventilation amount to 743 μmols at 0-24h^-1m^-2200r/min and 300L/h; at 36h, respectively to 1117.6 μmols^-1m^-2250r/min and 400L/h; at 60h, the temperature is respectively increased to 1490 mu mols^-1m^-2300r/min and 500L/h; at 72h, the intensity increased to 2238.6 μmol^s-1m^-2The rotation speed and ventilation rate are maintained at 300r/min and 500L/h, and the detailed conditions and curve changes in culture are shown in figure 1.

TABLE 2 NH stages of different cultures in two-stage cultures₄ ⁺Removal rate and average absorption amount of

Calculating to obtain NH in the two-stage fermentation₄ ⁺The removal rate and average consumption of (2) are shown in Table 2, two incubation periods NH₄ ⁺The removal rates of the catalyst are respectively 94.8 percent and 100 percent, and NH can be realized₄ ⁺Is completely absorbed. NH (NH)₄ ⁺The average consumption rate of (1) was slightly higher in the first phase than in the second phase, probably due to the limitation of nutrient salts in the medium in the second phase, studies have shown that iron is one of the essential nutrients for chlorophyll synthesis, supplementing half of the Basal medium, FeSO₄·7H₂The content of O is only 24.9 mg/L, and the supply to the growth of cells is possibly insufficient, so that NH is generated₄ ⁺The average consumption rate of (a) decreases. As can be seen from FIGS. 2a to 2d and FIGS. 3a to 3b, the protein and pigment grow fastest in the first stage during the whole culture process, and the nitrogen source content in the culture medium is rich, which is beneficial to the accumulation of nitrogen-containing substances. When the culture is carried out for 36 hours, the protein content reaches 40.8 percent, the later growth amplitude is not large, the highest content is 43.4 percent after the culture is finished, which indicates that the supplemented culture is favorable for the effluent to quickly reach the standard, and the protein content of the produced algae powder is high. Total chlorophyll began to decline upon incubation for 84h, probably due to too high a cell concentration and insufficient supply of nitrogen source in the medium at this time.

Example 2 three-stage cultivation in fermenter

3.1 high-density culture: the procedure is the same as in section 1.2 of the first section, and the procedure of the first two stages of fermenter culture is the same as in example 1.

3.2 three-stage cultivation in fermenter

(1) And after the ammonium ion concentration is lower than 200mg/L (consumption is finished), discharging fermentation liquor in the 1L fermentation tank into a concentration tank, and centrifugally collecting microalgae to obtain algae mud.

(2) And uniformly mixing 1.1L of high ammonia nitrogen wastewater with 2.2L of dilution water, and adding basic culture medium mother liquor (without adding nitrogen) to reach three-quarters of the concentration of each component in the table 1 (without sugar, and with phosphorus element being supplemented independently). Loading into 5L glass fermentation tank (total volume of fermentation tank liquid is 3.5L), sterilizing, stirring, mixing, and culturing.

Repeating the steps (2) to (3) once. The initial inoculation amount of Chlorella pyrenoidosa is 1 × 10⁸cfu/mL, continuously adding glucose, and adding glucose to 10g/L through a feeding bottle (3 per mill of antifoaming agent, 3mol/L hydrochloric acid, 4mol/L sodium hydroxide and 600g/L glucose are respectively prepared in four types of feeding tanks) every 12 h. The pH value in the fermentation tank was controlled to 6.5, and the light intensity, the rotation speed and the ventilation were adjusted in a gradient manner as shown in FIG. 4. The wastewater turnover rate was maintained at 28%, and the other conditions were controlled to 2.2 of example 1.

3.3 test methods: the method is the same as the second part test method

3.4 analysis of results

In this example, NH at different stages of the three-stage culture₄ ⁺The results of the removal rate and the average absorption amount are shown in Table 3. As shown in FIG. 4, the light intensity, rotation speed and ventilation were set to 743. mu. mols for 0-24h during the whole culture process^- ¹m^-2200r/min and 200L/h; at 36h, respectively to 1117.6 μmols^-1m^-2250r/min and 250L/h; at 60h, the temperature is respectively increased to 1490 mu mols^-1m^-2300r/min and 300L/h; at 72h, the intensity increased to 2238.6 μmols^-1m^-2The rotating speed and the ventilation volume are maintained at 350r/min and 350L/h.

Analysis of the results shows that: the first stage NH was maintained by increasing the culture time and varying the amount of medium added (two-stage medium addition was one-half of the full formula in Table 1 to three-quarters of the full formula for three-stage culture addition)₄ ⁺The average absorption rate reaches more than 660 (mg/L/d). Detailed conditions andthe curve change in culture is shown in FIG. 4.

TABLE 3 NH of different stages of cultivation in the three stages of cultivation₄ ⁺Removal rate and average absorption amount of

Calculated NH in the three stages of the cultivation₄ ⁺The removal rate and the average consumption amount of (A) are shown in Table 3, and as can be seen from FIGS. 5a to 5d and FIGS. 6a to 6b, the pH value during the culture period, first stage NH, was changed as compared with the two-stage culture₄ ⁺The average consumption rate of the culture medium is improved by 58.7mg/L/d compared with that of the culture medium in the two stages, the constant pH value is set to be 6.5, the culture medium is more suitable for the growth of the chlorella pyrenoidosa, the addition amount of the culture medium is increased during the later stage of feeding, and NH in the third stage₄ ⁺The average consumption rate of 689 mg/L/d is obviously better than that of the former two culture stages, the protein content and total pigment in the inoculated chlorella pyrenoidosa are continuously increased and reach maximum values of 52.3 percent and 4.3 percent respectively after the culture is finished, and the maximum values are respectively 9 percent and 5.7 percent higher than the maximum values of the two-stage culture, probably because NH in the culture medium is completely cultured₄ ⁺The content is 494mg/L, and the nitrogen source is sufficient, which is beneficial to the accumulation of protein and pigment. The compensation of nitrogen element in the culture medium can effectively improve the protein content in chlorella cells. In addition, the addition amount of the basic culture medium is increased in the feeding process, and the growth rate of the chlorella pyrenoidosa can be improved due to the existence of various trace elements, so that the absorption of nitrogen elements is promoted.

EXAMPLE 3 four-stage cultivation in fermenter

4.1 high-density culture: the method is the same as that of section 1.2 of the first part

4.2 four stages of fermenter

The procedure of the first two stages of the fermenter culture was the same as in example 1.

(1) And after the ammonium ion concentration is lower than 200mg/L (consumption is finished), discharging 1L of fermentation liquor into a concentration tank, and performing ultrafiltration to collect microalgae to obtain algae mud.

(2) Adding 1.1L of ammonium-rich industrial wastewater into Basal culture medium mother liquor (nitrogen is not added, sugar is not added, phosphorus is supplemented independently, the concentrations of all components of a nitrogen-free culture medium are shown in table 1) to prepare a wastewater culture medium, stirring and uniformly mixing the wastewater culture medium after sterilization, pumping the mixture into a fermentation tank to reach the culture volume before discharging, continuously culturing until the concentration of ammonium ions is lower than 200mg/L, and harvesting microalgae.

Repeating the steps (2) - (3) twice. The initial inoculation amount of Chlorella pyrenoidosa is 1 × 10⁸cfu/mL, continuously adding glucose, and adding glucose to 10g/L through a feeding bottle (3 per mill of antifoaming agent, 3mol/L hydrochloric acid, 4mol/L sodium hydroxide and 600g/L glucose are respectively prepared in four types of feeding tanks) every 12 h. The pH value in the fermentation tank was set to be a constant value of 6.5, and the light intensity, the rotation speed and the aeration rate were set to be constant values of 1117.4. mu. mol s^-1m^-2200r/min and 300L/h. Other conditions and methods were the same as 2.2 of example 1.

4.3 test methods: the method is the same as the second part test method

4.4 analysis of results

TABLE 4 NH of different stages of cultivation in the four stages of cultivation₄ ⁺Removal rate and average absorption amount of

Calculated NH in four stages of culture₄ ⁺The removal rate and average consumption of (D) are shown in Table 4. As can be seen from FIGS. 7a to 7d and FIGS. 8a to 8b, NH was present in the four-stage culture₄ ⁺The average consumption rate of the fermentation tanks is basically in a gradually increasing trend, the highest value of the average consumption rate of the fermentation tanks reaches 1021mg/L/d in the fourth stage, and the average consumption rate of the fermentation tanks is respectively 1.67 times, 1.68 times and 14.8 times of the highest value of the previous three batches of fermentation tanks, and the effectiveness of the domestication of the seed liquid is further verified. The protein content in the microalgae reaches the maximum value of 56.7% in the 36 th hour of culture, and then fluctuates around 50%, and the corresponding total pigment content is basically stabilized at 3.7%, so that the total pigment content is increased compared with that in the earlier experimental culture, and the supplement of nutrient elements such as calcium, iron, magnesium and the like in the culture medium is proved to be beneficial to NH₄ ⁺Absorption and accumulation of pigments.

Fourth, effects of comparative examples 1 to 10

1. Influence of inoculated cell density on ammonia nitrogen assimilation rate

Placing 100mL Basal medium in 250mL triangular flask, inoculating Chlorella pyrenoidosa, and culturing at 30 deg.C under light intensity of 100 μmol m^-2s^-1The seed solution (which had been carried out according to the first 1.2 high-density cultivation) was continuously cultured for 6 days in a constant temperature shaker at 150 rpm.

Then transferring the culture medium into an ammonium-rich industrial wastewater culture medium diluted by 2 times by distilled water, and respectively inoculating the culture medium with the cell density of 1 multiplied by 10⁶、 5×10⁶、1×10⁷、5×10⁷、1×10⁸cfu/mL (comparative examples 1 to 5 in this order) the three-stage culture procedure in the fermenter was the same as in example 3. Comparative examples 1 to 5 show that the changes in biomass, ammonium radical and glucose concentration at different cell densities for inoculation are shown in FIGS. 9a to 9 c.

As can be seen in FIGS. 9a-9c, Chlorella grew at five cell densities of inoculation, 1X 10⁸The growth rate of chlorella was the fastest at cfu/mL (comparative example 5), the dry weight concentration reached the highest value of 27.3g/L at day 6, the ammonium root concentration was lower than 200mg/L at day 6, the average consumption rate of ammonium root was also the highest, and reached 171.1mg/L/d (Table 5), which is significantly higher than other conditions (P < 0.05).

TABLE 5 ammonium radical removal, consumption and average consumption rates at different seeded cell densities

2. Influence of initial concentration of glucose on ammonia nitrogen assimilation rate

Placing 100mL Basal medium in 250mL triangular flask, inoculating Chlorella pyrenoidosa, and culturing at 30 deg.C under light intensity of 100 μmol m^-2s^-1And continuously culturing in a constant-temperature shaking table of 150r/m for 6 days to obtain seed liquid. Then transferring the wastewater into a wastewater culture medium formed by adding 2 times of ammonium-rich industrial wastewater diluted by distilled water into basic culture medium, and inoculating the wastewater with the inoculation density of 1 multiplied by 10⁸cfu/mL. The initial concentration settings of glucose were 10g/L, 20g/L, 30g/L, 40g/L, 50g/L, respectivelyg/L (in turn, comparative examples 6 to 10), illumination intensity of 150. + -. 10. mu. mol/m at 30 ℃²Culturing for 5 days at a rotation speed of 150 r/m.

As can be seen from FIGS. 10a to 10d and FIG. 11, Chlorella pyrenoidosa grows at five initial glucose concentrations, the growth rate is fastest at 10g/L, the maximum value is 19.3g/L at 108h, the ammonium concentration is minimized at 4.5 days, and the average consumption rate is also highest (222.9mg/L/d) (Table 6), which is significantly higher than other conditions (P < 0.05).

TABLE 6 ammonium radical removal, consumption and average consumption rates at different initial glucose concentrations

Fifthly, analyzing processing capacity, operation cost and benefit

Taking a 10-ton production tank as an example, the working volume is 70 percent, namely 7.5 tons of wastewater culture medium;

adopts a four-stage method and a three-batch material supplementing process: in the first stage, 7.5 tons of wastewater in the culture medium make up 1/3, i.e., 2.5 tons of raw wastewater. The ammonium radical in the original wastewater is calculated according to 5000mg/L, the ammonium radical is 1667mg/L after 2 times of dilution, and calculated according to process parameters, 30 hours (without operation time) is expected to be required when the ammonium radical is reduced to be within 100mg/L, namely 2.5 tons of multiplied by 4 of the original wastewater can be processed by 10 tons every 120 hours (5 days), and the dry weight of the coproduced algae powder is 32kg/T multiplied by 7.5 multiplied by 4 is 960 kg.

The total energy consumption of a 10-ton pilot plant is 65Kw, the total energy consumption is calculated according to 24 hours and 4.0 yuan/degree of industrial electricity every day, and the small electric charge is 6240 yuan/day; 2.0 yuan/ton of industrial water, 5 tons of industrial water per day and 10 yuan; the labor cost is 200 yuan per person per day, and the labor cost is 1200 yuan per day according to two or three shifts. The other raw materials are counted for 500 yuan/day. The total running cost is 7950 yuan/day. The amount of wastewater treated in 4 batches in 5 days is 10 tons, and the total amount is as follows: 7950X 5 to 39750 yuan, 3975 yuan per ton of wastewater.

960kg of algae powder (containing 95% dry matter) is produced every 5 days, 4560 kg of algae slurry is obtained according to the conversion of 20% dry matter content, and 91200 kg of concentrated solution is obtained according to the conversion of 1% dry matter content. The current market price is as follows: 50 yuan/kg of feed-grade algae powder, 45 yuan/kg of algae pulp and 40 yuan/kg of concentrated solution. Expected sales revenue: 4.8 ten thousand yuan algae powder, 20.52 ten thousand yuan algae slurry and 364.8 ten thousand yuan concentrated solution. Therefore, the wastewater treatment cost can be recovered by selling the feed-grade algae powder, and 20% of gross profit can be realized. If the algae pulp is sold, 416% of gross profit can be realized; if the concentrated solution is sold, 90.8 times of gross profit can be realized. The economic benefit is very considerable.

Through the data analysis, the invention provides a method for treating high ammonia nitrogen wastewater by using a microalgae photo-fermentation method, which can realize microalgae biomass accumulation while purifying wastewater quality, effectively reduce the wastewater treatment cost, realize comprehensive development and utilization of resources, have economic and environmental-friendly double values, are suitable for wastewater quality purification treatment of large and medium-sized chemical plants, and are very suitable for popularization in large-scale enterprises with high-yield ammonium-rich wastewater.

The present invention is not limited to the above-described embodiments, and various changes and modifications of the present invention are intended to be included within the scope of the claims and the equivalent technology of the present invention if they do not depart from the spirit and scope of the present invention.

Claims

1. A method for efficiently treating high ammonia nitrogen wastewater by a microalgae photo-fermentation method is characterized by comprising the following steps:

s2, light fermentation culture: placing the blended high ammonia-nitrogen wastewater into a light fermentation tank, sterilizing, inoculating the seed solution obtained from S1 for culture, and supplementing materials in a plurality of stages of culture in the fermentation tank; and collecting microalgae biomass and obtaining purified water after ammonium ions in the fermentation tank are exhausted.

2. The method of claim 1, wherein the selected microalgae is chlorella; preferably, the chlorella is chlorella pyrenoidosa or chlorella pyrenoidosa obtained by domestication; preferably, the several-stage cultivation in the S2 fermenter is two-stage cultivation in the fermenter, three-stage cultivation in the fermenter, or four-stage cultivation in the fermenter; preferably, when the salinity of the wastewater is higher than 15 per thousand, the salinity of the high ammonia nitrogen wastewater needs to be diluted to 15 per thousand in advance, and then blending is carried out.

3. The method according to claim 1 or 2, characterized in that the S2 fermenter culture comprises the following steps:

uniformly stirring the high ammonia-nitrogen wastewater and a nitrogen-free culture medium, then putting the mixture into a fermentation tank, sterilizing, cooling, adding S1 to obtain a seed solution, inoculating and culturing, supplementing sterilized carbon and phosphorus source mother solution, taking out part of fermentation liquor when ammonium ions in a light fermentation tank are reduced to be below 200mg/L, and putting the same volume of wastewater culture medium into the fermentation tank for continuous culture; wherein the initial seeding cell density is 5X 10⁷-3×10⁸cfu/mL, the pH value of the fermentation tank is controlled to be 6.5-7.0, and the glucose concentration is 1-20 g/L.

4. The method of claim 3, wherein the fermentor culture further comprises the following culture conditions: the illumination intensity is 200-^-1m^-2The ventilation amount is 100-500L/h, the rotation speed is 100-400r/min, and the wastewater renewal rate is 20-80%.

5. The method according to claim 4, wherein the nitrogen-free medium is nitrogen-free Basal medium; the nitrogen-free Basal medium comprises the following components in percentage by weight: MgSO (MgSO)₄·7H₂O is 1,000mg/L, EDTA and 500mg/L, K₂HPO₄Is 1,250mg/L, CaCl₂Is 111mg/L, FeSO₄·7H₂O is 4.98mg/L, H₃BO₃Is 114.2mg/L, MnCl₂·4H₂O is 1.42mg/L, NaMoO₄·2H₂O is 1.19mg/L, ZnSO₄·7H₂O is 8.82mg/L, Co (NO)₃)₂·6H₂O is 0.49mg/L, CuSO₄·5H₂O is 1.57mg/L, and the pH value is 6.1.

6. The method of claim 5, wherein the fermentor culture is a two-stage culture:

s21, diluting the high ammonia nitrogen wastewater, adding the nitrogen-free culture medium mother liquor, mixing uniformly, filling the mixture into a fermentation tank, sterilizing, cooling, inoculating the seed liquor obtained in S1, and starting to culture, wherein the cell density of the microalgae initial inoculation is 5 multiplied by 10⁷-1×10⁸cfu/mL, glucose concentration maintained at 5-10g/L, illumination intensity of 200-^-1m^-2The pH value of the fermentation tank is controlled to be 6.5-7.0, the ventilation volume is 100-;

7. The method of claim 6, wherein the addition of the S21 glucose mother liquor is prior to inoculating the seed liquor obtained in S1; the glucose mother liquor is sterilized glucose mother liquor.

8. The method of claim 7, wherein the fermentor culture is a three-stage culture: repeating the operation according to S22-S23 for 2 times; wherein the illumination intensity is 200-^-1m^-2The pH value of the fermentation tank is 6.5-7.0, the glucose concentration is 5-10g/L, the ventilation amount is 100-; preferably, the addition amount of the nitrogen-free culture medium mother liquor is as follows: the concentration of each component of the nitrogen-free culture medium is three-fourths of the original formula.

9. The method of claim 8, wherein the fermentor culture is a four-stage culture: repeating the operation according to S22-S23 for 3 times; wherein the illumination intensity is 200-^-1m^-2The pH value of the fermentation tank is controlled to be 6.5-7.0, the concentration of the glucose is 5-10g/L, the ventilation amount is 100-; preferably, the addition amount of the nitrogen-free culture medium mother liquor is as follows: the concentration of each component of the nitrogen-free culture medium is the original formula concentration.

10. The method according to claim 1 or 2, wherein the high ammonia nitrogen wastewater comprises the following components: NH (NH)₄ ⁺10,000mg/L of 600-000, 5-60 per mill of salinity, 0-10mg/L of rare earth element, PO₄ ^3-The content is 0-300mg/L, and the pH value is 6-8; preferably, the concentration of glucose in the culture medium of the high-density culture is 30-60g/L, the concentration of sodium nitrate is 2.5-5.0g/L, and the initial pH value ranges from 5.5-6.5.