CN110627213A - A method for efficiently treating high-ammonia nitrogen wastewater by microalgae photofermentation - Google Patents

Abstract

The invention discloses a method for efficiently treating high-ammonia-nitrogen wastewater by microalgae photofermentation, comprising the following steps: S1, activating and culturing seed liquid: inoculating microalgae cells on the culture medium for activation, and then obtaining logarithmic stage seed liquid; S2, photofermentation culture: Put the prepared high-ammonia-nitrogen wastewater into a photofermentation tank, inoculate the seed liquid obtained from S1 after sterilization for cultivation, and carry out feeding in several stages of cultivation in the fermenter; Ammonium ions are depleted, microalgal biomass is harvested and purified water is obtained. The method of the present invention realizes the production of high-protein microalgae biomass while efficiently removing ammonia nitrogen in wastewater, effectively reduces the cost of wastewater treatment, realizes the comprehensive development and utilization of wastewater resources, and is suitable for wastewater rich in ammonia nitrogen in industrial and agricultural fields High-quality water purification and co-production of high-protein biomass have dual values of economy and environmental protection.

Description

A method for efficiently treating high-ammonia nitrogen wastewater by microalgae photofermentation

technical field

The invention belongs to the technical field of high-ammonia-nitrogen wastewater treatment, and in particular relates to a method for efficiently treating high-ammonia-nitrogen wastewater by microalgae photofermentation.

Background technique

The source of high ammonia nitrogen wastewater is mainly agriculture (animal husbandry), industrial wastewater (including chemical industry, biogas, brewing, fermentation, food, slaughtering and other industries), the NH ₄ ⁺ content in wastewater is as high as 300-10000mg/L, if it is discharged into Rivers will cause great pollution to the environment. The traditional treatment technology has obvious shortcomings in cost, energy consumption and effect, and the country's environmental protection requirements are becoming increasingly stringent. The government emphasizes the need to take the path of ecological priority and green development. Therefore, it is urgent to develop a new technical system for centralized treatment of high ammonia nitrogen wastewater.

At present, there are four main methods for treating high ammonia nitrogen wastewater, namely air stripping method, ion exchange method, wet oxidation method, and biological method. The most common method is the stripping method, whose reaction principle is the movement of chemical equilibrium. The waste water is continuously stirred in the pipeline mixer and a large amount of lye is added and heated. At this time, NH ₄ ⁺ generates NH ₃ and H ₂ O under high-temperature alkaline conditions. , the chemical balance is constantly shifting to the right, and NH ₃ is blown into the strong acid absorption system by the fan through the fluidized stripping tower to achieve the purpose of recycling. The stripping method has a good effect on the removal of ammonia nitrogen, and the equipment operation is relatively simple. It has a huge application market in the treatment of industrialized high-concentration ammonia nitrogen wastewater. During the stable operation of the factory equipment, the stripping efficiency of ammonia nitrogen is greatly affected by the pH value and temperature, and a large amount of strong alkali is consumed, so the energy consumption and material consumption cost are high. In addition, ammonia gas will escape during the stripping process, which will easily pollute the environment.

Therefore, it is urgent to develop a high-ammonia-nitrogen wastewater treatment method with high efficiency, low energy consumption cost, environmental protection and resource utilization.

Contents of the invention

In order to solve the above-mentioned technical problems existing in the prior art, the present invention provides a method for efficiently treating high-ammonia-nitrogen wastewater by microalgae photofermentation. Produce chlorella biomass to achieve a win-win situation in water cycle and resource utilization.

Technical purpose of the present invention is achieved through the following technical solutions:

The invention provides a method for efficiently treating high-ammonia-nitrogen wastewater by microalgae photofermentation, comprising the following steps:

S1, seed solution activation culture: inoculate microalgae cells on the medium for activation, and then obtain logarithmic seed solution through high-density culture;

S2, photo-fermentation culture: put the prepared high-ammonia-nitrogen waste water into a photo-fermentation tank, inoculate the seed liquid obtained from S1 after sterilization, and carry out cultivation in several stages of the fermentation tank; when the ammonium ion consumption in the fermentation tank As far as possible (reduced to below 200mg/L), the microalgae biomass is harvested and purified water is obtained. The formulation here is to make each component of the nitrogen-free medium in the fermentation broth reach a predetermined concentration by adding the nitrogen-free medium mother liquor. Preferably, when the salinity of the high ammonia nitrogen wastewater is higher than 15‰, it is necessary to pre-dilute the salinity of the high ammonia nitrogen wastewater to 15‰, and then prepare it.

Preferably, the selected microalgae in the present invention is Chlorella pyrenoidosa; preferably, the Chlorella pyrenoidosa is Chlorella pyrenoidosa or domesticated Chlorella pyrenoidosa.

Specifically, the S2 photofermentation culture of the present invention comprises the following steps:

Stir the high-ammonia-nitrogen wastewater and nitrogen-free medium into a light fermenter, sterilize and cool, add S1 to obtain seed liquid inoculation and culture, and wait until the ammonium ion in the fermenter is reduced to below 200 mg/L, take out part of the fermentation liquid, and put Put the same volume of waste water medium into the fermenter to continue culturing; the initial inoculated cell density is 5×10 ⁷ -3×10 ⁸ cfu/mL, the pH of the fermenter is controlled to be 6.5-7.0, and the glucose concentration is 1-20g/L; Preferably, when the salinity of the wastewater is higher than 15‰, it is necessary to pre-dilute the salinity of the high ammonia nitrogen wastewater to below 15‰, and then mix it with the nitrogen-free medium.

More specifically, the photofermentation culture also includes the following culture conditions: external LED lighting system (white light), light intensity of 200-2500 μmols ^-1 m ^-2 , ventilation rate of 100-500 L/h, rotation speed of 100-400 r /min, the waste water renewal rate is 20%-80% (v/v).

Preferably, the nitrogen-free medium of the present invention is a nitrogen-free Basal medium; the content of each component of the nitrogen-free Basal medium formula is: MgSO ₄ 7H ₂ O is 1,000 mg/L, EDTA is 500 mg/L, K ₂ HPO ₄ is 1,250 mg/L, CaCl ₂ is 111 mg/L, FeSO4 7H ₂ O is 4.98 mg/L, H ₃ BO ₃ is 114.2 mg/L, MnCl ₂ 4H ₂ O is 1.42 mg/L, NaMoO ₄ ·2H ₂ O is 1.19 mg/L, ZnSO ₄ ·7H ₂ O is 8.82 mg/L, Co(NO ₃ ) ₂ ·6H ₂ O is 0.49 mg/L, CuSO ₄ ·5H ₂ O is 1.57 mg/L L, the pH value is 6.1.

Specifically, the fermentation culture described in the present invention is a two-stage culture:

S21. After diluting the high-ammonia-nitrogen waste water, add the nitrogen-free medium mother solution (reaching the concentration of each component in Table 1, without sugar) and mix evenly, put it into a fermenter, sterilize and cool it, and insert the seed solution obtained in S1 to start culturing , the initial inoculated cell density of microalgae was 5×10 ⁷ -1×10 ⁸ cfu/mL, the glucose concentration was maintained at 5-10 g/L, the light intensity was 200-2500 μmols ^-1 m ^-2 , and the pH value of the fermenter was controlled at 6.5- 7.0, ventilation volume is 100-500L/h, speed is 100-400r/min;

S22. When the concentration of ammonium ion is lower than 200 mg/L, the fermented liquid with a total volume of 28.0-33.3% of the fermented liquid is released into the concentration tank, and the microalgae are harvested to obtain biomass;

S23. Add the original wastewater to the mother liquor of the nitrogen-free medium and mix it to form a wastewater medium, sterilize and cool it, then add it to a photofermentation tank to reach the total volume of the fermentation liquid before feeding, and continue to cultivate until the ammonium ion concentration is lower than 200mg /L, harvesting microalgae; preferably, the addition amount of the mother liquid of the nitrogen-free medium is: the concentration of each component of the nitrogen-free medium is half of the original formula.

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

As another embodiment of the present invention, the fermentor culture is a three-stage culture: the operation according to S22-S23 is repeated twice. Wherein the light intensity is 200-2500μmols ^-1 m ^-2 , the pH value of the fermenter is 6.5-7.0, the glucose concentration is 5-10g/L, the ventilation rate is 100-500L/h, and the rotation speed is 100-400r/min; preferably Specifically, the added amount of the nitrogen-free medium mother solution is: the concentration of each component of the nitrogen-free medium is three-quarters of the original formula.

As another embodiment of the present invention, the fermentor culture is a four-stage culture: repeat the operation according to S22-S23 for 3 times. The light intensity is 200-2500μmol s ^-1 m ^-2 , the pH value of the fermenter is controlled at 6.5-7.0, the concentration of glucose is 5-10g/L, the ventilation rate is 100-500L/h, and the rotation speed is 100-400r/min ; Preferably, the addition amount of the nitrogen-free medium mother solution is: the concentration of each component of the nitrogen-free medium is the original formula concentration.

Specifically, the composition of high ammonia nitrogen wastewater in the present invention is as follows: NH ₄ ⁺ content is 600-10,000 mg/L, salinity is 5‰-60‰, rare earth element content is 0-10 mg/L, PO ₄ ^3- 0-300mg/L, pH 6-8.

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

The beneficial effect that the present invention can reach by adopting above-mentioned technical scheme is:

Chlorella pyrenoidosa is rich in protein and natural pigments, and has a variety of nutritional modes. During the cultivation process, it has a strong tolerance to stress environments such as high temperature, high light, high salt, and high ammonium. It can use simple components in wastewater to synthesize its own cell components, so as to realize the recycling and utilization of nutrients in wastewater. Quality Chlorella Biomass Joint Produce. The method is not only environmentally friendly, has low energy consumption, but also can recycle and utilize the nutrient elements in the waste water and co-produce chlorella biomass, so as to realize the win-win situation of water circulation and resource utilization.

Description of drawings

Fig. 1 shows the time-varying graph of light intensity, pH, rotating speed and air flow during the two-stage cultivation process of the fermenter.

Figure 2a shows the change of NH ₄ ⁺ content with time during the two-stage culture of the fermenter; Figure 2b shows the change of PO ₄ ^3- content with time during the two-stage culture of the fermenter; Figure 2c shows the change of biological Figure 2d shows the change of chlorophyll fluorescence over time during the two-stage culture of the fermenter.

Fig. 3a shows the two-stage culture process of the fermenter, and the change diagram of protein in Chlorella pyrenoidosa with time; Fig. 3b shows the change diagram of the pigment content with time during the two-stage culture process of the fermenter.

Fig. 4 shows the three-stage cultivation process of the fermenter, and the variation curves of light intensity, pH, rotational speed and ventilation volume during the cultivation process.

Figure 5a shows the three-stage cultivation of the fermenter, and the NH ₄ ⁺ content change curve during the cultivation process; Fig. 5b shows the three-stage cultivation of the fermenter, and the biomass dry weight change curve with time during the cultivation process; Fig. 5c shows the three-stage cultivation of the fermenter, the cultivation The time-varying curve of PO ₄ ^3- content during the process; Figure 5d shows the three-stage culture of the fermenter, and the time-varying curve of chlorophyll fluorescence during the culture process.

Fig. 6a shows the change of protein content in Chlorella pyrenoidosa over time during the three-stage culture of the fermenter; Fig. 6b shows the change of pigment content in Chlorella pyrenoidosa over time during the three-stage culture of the fermenter.

Figure 7a shows the four-stage culture of the fermenter, and the NH ₄ ⁺ content change curve during the culture process; Figure 7b shows the four-stage culture of the fermenter, the time-varying curve of PO ₄ ^3- content during the culture process; Figure 7c shows the four-stage culture of the fermenter, The change curve of biomass dry weight with time during the culture process; Figure 7d shows the four-stage culture of the fermenter, and the change curve of chlorophyll fluorescence with time during the culture process.

Fig. 8a shows the change of protein content in Chlorella pyrenoidosa over time during the four-stage culture of the fermenter; Fig. 8b shows the change of pigment content in Chlorella pyrenoidosa over time during the four-stage culture of the fermenter.

Figure 9a shows the graph of the change of biomass over time in the three-stage culture process of the fermentor under different inoculated cell densities; Figure 9b shows the graph of the change of ammonium root concentration with time in the three-stage culture of the fermentor under different inoculated cell densities; Figure 9c shows At different inoculated cell densities, the glucose concentration changes with time during the three-stage culture of the fermenter.

Fig. 10a shows the change diagram of cell number over time in the three-stage culture process of the fermentor under different glucose initial concentrations; Fig. 10b shows the change diagram of the relative concentration of ammonium root with time in the three-stage culture process of the fermentor under different glucose initial concentrations; Figure 10c shows the change of chlorophyll fluorescence over time during the three-stage culture of the fermenter under different initial concentrations of glucose; Figure 10d shows the change of dry weight of biomass over time during the three-stage culture of the fermenter under different initial concentrations of glucose.

Fig. 11 shows the change of glucose concentration with time during the three-stage cultivation process of the fermenter under different initial concentrations of glucose.

Detailed ways

Below in conjunction with accompanying drawing, technical scheme of the present invention is described further:

Definition of professional terms:

1. High-density culture: refers to inoculation of algae cells into the medium for activation, and cultivation until the dry weight of algae cells is greater than 20g/L.

2. Wastewater renewal rate refers to the fact that after the algae cells are cultured in the fermenter, when the ammonium ions are exhausted (less than 200mg/L), part of the fermentation liquid in the fermenter is taken out, and the volume of waste water culture medium corresponding to the released fermentation liquid is (Original wastewater and nitrogen-free medium are configured in proportion) into the fermenter to continue cultivation.

1. High renewal culture in fermenter

1.1 Activation of algal species and preparation of seed solution

Transfer the C. pyrenoidosa species preserved in the laboratory to the slant of basal medium containing 10g/L glucose for cultivation. The cultivation temperature is 30°C and the light is 100μmol m ^-2 s ^-1 , and observe the growth of Chlorella pyrenoidosa.

Use an inoculation loop to inoculate a single algal colony of Chlorella pyrenoidosa into nitrogen-free basal medium containing 10 g/L glucose, in a constant temperature shaking shaker with a temperature of 30 °C and a light of 100 μmol m ^-2 s ^-1 , Cultivate for 3-6 days and use as seed liquid. The composition of the nitrogen-free basal medium (pH 6.1) described therein is shown in Table 1 below (in mg/L):

Table 1 Composition list of nitrogen-free basal medium (pH 6.1)

1.2 High density culture

Prepare basal medium, add nitrogen source to maintain the concentration of sodium nitrate at 3.75g/L, stir and mix well, adjust the pH value to 6.1, and finally add glucose at a final concentration of 50g/L. Divide into 250mL Erlenmeyer flasks, the liquid volume is 100mL, seal with parafilm, place in an autoclave, and sterilize at 115°C for 20min. After sterilization, take out the shaker flask and cool to room temperature.

The seed liquid of Chlorella pyrenoidosa in the logarithmic growth phase was inoculated into the above-mentioned culture medium. The culture conditions were as follows: the rotation speed was 150r/min, the temperature was 30°C, and the light source was positive white LED hard light strips placed side by side in series. The intensity was 150±10 μmol m ^-2 s ^-1 , and the culture time was 6 days.

1.3 Fermentation tank culture

Please refer to Examples 1-3 for specific cultivation conditions.

2. Test method

2.1 Determination of biomass

Biomass was measured using the differential method. Three replicates were set for each sample, the average value was taken and the standard deviation was calculated.

2.2 Determination of NH ₄ ⁺ , PO ₄ ^3- content in wastewater

Use Italy HANNA HI83200 multi-parameter water quality analyzer to measure. Select an appropriate range, dilute the sample to be tested to the measurement range, and add the corresponding reagents to the cuvette according to the instrument instructions for measurement and reading. After the reading is finished, the reading multiplied by the dilution factor is the content of NH ₄ ⁺ and PO ₄ ^3- in the medium.

2.3 Determination of protein content

The protein was determined by the Kjeldahl method; the instrument used was a semi-automatic Kjeldahl analyzer from FOSS Company.

2.4 Determination of pigment content

Accurately weigh 20 mg of freeze-dried algae powder and crush it with ceramic beads, then extract with 90% acetone until the ceramic beads and algae powder are white. Dilute the supernatant to 10mL, take an appropriate amount of sample and dilute to a suitable multiple, use 90% acetone solution as a blank, measure the absorbance of the sample at 470nm, 646nm, and 663nm in a UV-visible spectrophotometer, and bring the results into the empirical formula calculate:

C _a =12.21×A ₆₆₃ -2.81×A ₆₄₆

C _b =20.13×A ₆₄₆ -5.03×A ₆₆₃

C _t =(1000×A ₄₇₀ -3.27×C _a -104×C _b )/198

Among them, C _a refers to chlorophyll a, C _b refers to chlorophyll b, C _t refers to total carotenoids, and the unit is μg/mL.

Three, embodiment 1～3 fermentation tank culture

Embodiment 1 fermentor two-stage cultivation

2.1 High-density culture: the method is the same as Section 1.2 of the first part

2.2 Two-stage culture in fermenter

(1) Take 1.1L of high ammonia nitrogen wastewater and mix with 2.2L of dilution water, add Basal medium mother liquor (without nitrogen) to reach the concentration of each component in Table 1 (sugar-free). Put it into a 5L glass fermenter (the total volume of fermented liquid in the fermenter is 3.5L), sterilize at 115°C for 20 minutes, take it out after sterilization and cool to room temperature, add sterilized glucose mother liquor to make the final concentration of bacterial grapes reach 10g/L, and then insert Part 2.1 The obtained seed solution. Make the initial inoculated cell density of Chlorella pyrenoidosa be 1×10 ⁸ cfu/mL, pass feeding bottle every 12 hours (3‰ defoaming agent, 3mol/L hydrochloric acid, 4mol/L hydrochloric acid, 4mol/L L of sodium hydroxide, 600g/L of glucose) added glucose to 10g/L, the pH control range in the fermenter was 7.0, and the gradient adjustment of light intensity, rotation speed, and ventilation was shown in Figure 1.

(2), until the ammonium ion concentration is lower than 200mg/L (complete consumption), release the fermented liquid with a total volume of the fermenter of 1L (28.0% of the total liquid volume of the fermenter), and centrifugally collect microalgae to obtain algae mud.

Add 1.1L of raw wastewater to the mother liquor of Basal medium to reach one-half of the concentration of each component in Table 1 (no nitrogen, no sugar, phosphorus element is supplemented separately, Table 1), mix well, sterilize and cool, then add light fermentation In the tank, reach the culture volume before discharging, continue to cultivate until the ammonium ion concentration is lower than 200mg/L, and harvest microalgae.

2.3 Test method: The method is the same as the test method in the second part above

2.4 Result analysis

Table 2 shows the results of the removal rate and average absorption of NH ₄ ⁺ in different culture stages in the two-stage culture in Example 1. As shown in Figure 1, the result analysis shows that in the two-stage culture, appropriately reducing the amount of medium added (the concentration in Table 1 is halved) and setting the initial pH value to 7.0 will help to improve the average NH ₄ ⁺ absorption rate to 500 (mg/L/d) or more. During the cultivation process, at 0-24h, set the light intensity, rotational speed, and air flow to 743μmols ^-1 m ^-2 , 200r/min, and 300L/h respectively; at 36h, respectively increase to 1117.6μmols ^-1 m ^-2 , 250r/min, 400L/h; at 60h, they increased to 1490μmols ^-1 m ^-2 , 300r/min, 500L/h respectively; at 72h, the light intensity increased to 2238.6μmols ^-1 m ^-2 , the speed and The ventilation rate was maintained at 300r/min and 500L/h. See Figure 1 for detailed conditions and curve changes during cultivation.

Table 2 The removal rate and average absorption of NH ₄ ⁺ in different culture stages in the two-stage culture

The calculated removal rate and average consumption of NH ₄ ⁺ in the two-stage fermentation are shown in Table 2. The removal rates of NH ₄ ⁺ in the two culture stages are 94.8% and 100%, respectively, which can realize the complete absorption of NH ₄ ⁺ . The average consumption rate of NH ₄ ⁺ in the first stage is slightly higher than that in the second stage, which may be due to the limitation of nutrient salts in the medium in the second stage. Studies have shown that iron is one of the essential nutrients for chlorophyll synthesis, supplementing half of Basal culture The content of FeSO ₄ ·7H ₂ O is only 24.9 mg/L, which may be insufficient for the growth of cells, resulting in a decrease in the average consumption rate of NH ₄ ⁺ . Combining Figures 2a-2d and 3a-3b, it can be seen that the growth of protein and pigment is the fastest in the first stage during the whole culture process. At this time, the content of nitrogen source in the medium is rich, which is conducive to the accumulation of nitrogenous substances. When cultured for 36 hours, the protein content reached 40.8%, and then increased slightly, and the highest content was 43.4% at the end of the culture, which indicated that the fed-batch culture was conducive to the rapid attainment of the effluent standard, and the output of algae flour had a high protein content. The total chlorophyll began to decrease at 84 hours, which may be due to the high cell concentration and insufficient nitrogen supply in the medium.

Embodiment 2 fermentor three-stage cultivation

3.1 High-density cultivation: the method is the same as that in section 1.2 of the first part, and the cultivation steps of the first two stages of fermentor cultivation are the same as in Example 1.

3.2 Three-stage cultivation in fermenter

(1) After the ammonium ion concentration is lower than 200mg/L (complete consumption), the fermentation broth in the 1L fermenter is released into the concentration tank, and the microalgae are collected by centrifugation to obtain the algae mud.

(2) Take 1.1L of high ammonia nitrogen wastewater and mix with 2.2L of dilution water, add Basal medium mother solution (without nitrogen) to reach 3/4 of the concentration of each component in Table 1 (no sugar, phosphorus element supplemented separately) . Pack into a 5L glass fermenter (total liquid volume of the fermenter is 3.5L), stir and mix well after sterilization, pour into the fermenter to continue culturing.

Repeat steps (2)-(3) once. The initial inoculum of Chlorella pyrenoidosa was 1×10 ⁸ cfu/mL, glucose was added continuously, and every 12 hours passed through the feeding bottle (3‰ defoaming agent and 3mol/L hydrochloric acid were prepared respectively in the four types of feeding tanks). , the sodium hydroxide of 4mol/L, the glucose of 600g/L) add glucose to 10g/L. The pH value in the fermenter was controlled to be 6.5, and the light intensity, rotational speed, and ventilation were adjusted in gradients as shown in Figure 4. The waste water renewal rate was maintained at 28%, and the other conditions were controlled with 2.2 in Example 1.

3.3 Test method: the method is the same as the test method in the second part above

3.4 Result analysis

Table 3 shows the results of the removal rate and average absorption of NH ₄ ⁺ in different culture stages in the three-stage culture in this example. As shown in Figure 4, during the whole cultivation process, from 0 to 24 hours, the light intensity, rotational speed and air flow were set to 743μmols ^{- 1} m ^-2 , 200r/min and 200L/h respectively; μmols ^-1 m ^-2 , 250r/min, 250L/h; at 60h, increased to 1490μmols ^-1 m ^-2 , 300r/min, 300L/h; at 72h, light intensity increased to 2238.6 μmols ^-1 m ^-2 , the rotation speed and ventilation volume are maintained at 350r/min and 350L/h.

Result analysis shows: prolong cultivating time, change the addition amount of culture medium (two-stage culture medium addition amount is the 1/2th of table 1 full formula to three-stage cultivation adds three-quarters of full formula), can keep the first The average absorption rate of NH ₄ ⁺ reached over 660 (mg/L/d) during the stage. See Figure 4 for detailed conditions and curve changes during cultivation.

Table 3 The removal rate and average absorption of NH ₄ ⁺ in different culture stages in the three-stage culture

After calculation, the removal rate and average consumption of NH ₄ ⁺ in the three stages of cultivation are shown in Table 3. Combining with Figure 5a-5d and Figure 6a-6b, it can be seen that compared with the two-stage cultivation, the pH during the cultivation period was changed value, the average consumption rate of NH ₄ ⁺ in the first stage was 58.7mg/L/d higher than that of the two-stage culture, indicating that the constant pH value set at 6.5 is more suitable for the growth of Chlorella pyrenoidosa, and when feeding in the later stage, the culture The amount of substrate added, the average consumption rate of NH ₄ ⁺ in the third stage reached 689 mg/L/d, which was significantly better than that in the first two culture stages. At the end of the cultivation, the maximum values were reached, which were 52.3% and 4.3%, respectively, which were 9% and 5.7% higher than the highest values of the two-stage cultivation, probably because at the end of the cultivation, the NH ₄ ⁺ content in the medium was 494mg/L, nitrogen Sufficient sources are conducive to the accumulation of protein and pigment. Nitrogen supplementation in the medium can effectively increase the protein content in Chlorella cells. In addition, the addition of Basal medium was increased during the feeding process, and the presence of various trace elements would increase the growth rate of Chlorella pyrenoidosa, thereby promoting its absorption of nitrogen.

Embodiment 3 fermentor four-stage culture

4.1 High-density culture: the method is the same as Section 1.2 of the first part

4.2 Four stages of fermenter

The cultivation steps of the first two stages of fermentor cultivation are the same as in Example 1.

(1) After the ammonium ion concentration is lower than 200mg/L (consumed), release 1L of fermented liquid into the concentration tank, collect microalgae by ultrafiltration to obtain algae mud.

(2), get 1.1L of ammonium-rich industrial waste water and add Basal medium mother liquor (no nitrogen, no sugar, phosphorus element is supplemented separately, the concentration of each component of the nitrogen-free medium is as shown in Table 1) to configure the waste water medium, Stir and mix evenly after sterilization, pour into the fermenter, reach the culture volume before discharging, continue to cultivate until the concentration of ammonium ion is lower than 200mg/L, and harvest microalgae.

Repeat the above steps (2)-(3) twice. The initial inoculum of Chlorella pyrenoidosa was 1×10 ⁸ cfu/mL, glucose was added continuously, and every 12 hours passed through the feeding bottle (3‰ defoaming agent and 3mol/L hydrochloric acid were prepared respectively in the four types of feeding tanks). , the sodium hydroxide of 4 mol/L, the glucose of 600g/L) add glucose to 10g/L. The pH value in the fermenter was set at a constant value of 6.5, and the light intensity, rotational speed, and ventilation rate were set at constant values, which were 1117.4 μmol s ^-1 m ^-2 , 200 r/min, and 300 L/h, respectively. Other condition control and method are the same as 2.2 of embodiment 1.

4.3 Test method: the method is the same as the test method in the second part above

4.4 Result analysis

Table 4 The removal rate and average absorption of NH ₄ ⁺ in different culture stages in the four-stage culture

After calculation, the removal rate and average consumption of NH ₄ ⁺ in the four stages of cultivation are shown in Table 4. Combining with Figure 7a-7d and Figure 8a-8b, it can be seen that the average consumption rate of NH ₄ ⁺ in the four stages of culture basically shows a gradually increasing trend, reaching a maximum of 1021mg/L/d in the fourth stage , which are 1.67, 1.68 and 14.8 times the highest value of the first three batches of fermenters, respectively, further confirming the effectiveness of seed liquid acclimation. The protein content in microalgae reached a maximum value of 56.7% at the 36th hour of culture, and then fluctuated around 50%, and the corresponding total pigment content was basically stable at 3.7%, which was increased compared with the previous experimental culture, which proved that calcium and iron in the medium were supplemented. , magnesium and other nutrients are beneficial to the absorption of NH ₄ ⁺ and the accumulation of pigments.

4. Effect comparison examples 1 to 10

1. Effect of inoculation cell density on ammonia nitrogen assimilation rate

Put 100mL of Basal medium into a 250mL Erlenmeyer flask, inoculate Chlorella pyrenoidosa, and culture continuously for 6 days in a constant temperature shaker at 30°C, light intensity 100μmol m ^-2 s ^-1 , 150r/m as the seed solution (according to the Part 1.2 high-density culture was carried out).

Then transferred to the ammonium-rich industrial wastewater medium diluted 2 times with distilled water, and the inoculated cell densities were 1×10 ⁶ , 5×10 ⁶ , 1×10 ⁷ , 5×10 ⁷ , 1×10 ⁸ cfu/mL ( Followed by comparative examples 1-5) The three-stage culture of the fermenter The culture steps and culture conditions are the same as in Example 3. Regarding the control examples 1-5, the changes of biomass, ammonium root and glucose concentration under different inoculated cell densities are shown in Figures 9a-9c.

It can be seen from Figures 9a-9c that Chlorella grows at five inoculated cell densities, and the growth rate of Chlorella at 1×10 ⁸ cfu/mL (Control Example 5) is the fastest, and the dry weight concentration reaches the highest on the 6th day The value of ammonium root was 27.3g/L, while the ammonium root concentration was lower than 200mg/L on the 6th day, and the average consumption rate of ammonium root was also the highest, reaching 171.1mg/L/d (Table 5), which was significantly higher than other conditions (P<0.05) .

Table 5. Ammonium root removal rate, consumption and average consumption rate under different seeding cell densities

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

Put 100 mL of Basal medium into a 250 mL Erlenmeyer flask, inoculate Chlorella pyrenoidosa, and culture continuously for 6 days at 30°C, light intensity 100 μmol m ^-2 s ^-1 , 150 r/m constant temperature shaker as seed solution. Then transfer it to the wastewater medium composed of ammonium-rich industrial wastewater diluted 2 times with distilled water and supplemented with Basal culture, and the inoculation density is 1×10 ⁸ cfu/mL. The initial concentration of glucose was set to 10g/L, 20g/L, 30g/L, 40g/L, and 50g/L (in order of comparison examples 6-10 ⁾ . Cultivate for 5 days under the condition of rotating speed 150r/m.

From Figures 10a to 10d and Figure 11, it can be seen that Chlorella pyrenoidosa grew at five initial concentrations of glucose, and the growth rate was the fastest at 10g/L, reaching the highest value of 19.3g/L at 108h. On the 4.5th day, it decreased to the lowest, and the average consumption rate was also the highest (222.9mg/L/d) (Table 6), which was significantly higher than other conditions (P<0.05).

Table 6. Ammonium root removal rate, consumption and average consumption rate under different glucose initial concentrations

5. Processing capacity, operating cost and benefit analysis

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

Four-stage method and three-batch feeding process are adopted: in the first stage, 1/3 of the 7.5 tons of waste water culture medium is the original waste water, that is, 2.5 tons. The ammonium root in the original wastewater is calculated as 5000mg/L, and the ammonium root is 1667mg/L after being diluted twice. According to the calculation of the process parameters, it is estimated that it will take 30 hours (excluding operating time) for the ammonium root to drop to within 100mg/L, that is, every 120 hours (5 days) It can treat 2.5 tons of raw wastewater × 4 = 10 tons, and can co-produce the dry weight of algae powder 32kg/T × 7.5 × 4 = 960kg.

The total energy consumption of the 10-ton pilot plant is 65Kw, calculated on the basis of 24 hours per day, industrial electricity consumption is 4.0 yuan/kwh, the subtotal electricity fee is 6240 yuan/day; industrial water consumption is 2.0 yuan/ton, 5 tons per day is 10 yuan; labor costs per person per day 200 yuan, according to two people, three shifts, subtotal 1200 yuan / day. Other raw materials are 500 yuan/day. The total operating cost is 7950 yuan/day. A total of 10 tons of waste water will be treated in 4 batches in 5 days, total: 7950×5=39750 yuan, 3975 yuan/ton of waste water.

Output 960 kilograms of algae flour (containing 95% of dry matter) every 5 days, converted into algae pulp by 20% dry matter content is 4560 kg, converted into 91200 kg of concentrate by 1% dry matter content. Current market price: feed grade algae powder 50 yuan/kg, algae pulp 45 yuan/kg, concentrate 40 yuan/kg. Estimated sales revenue: 48,000 yuan for algal powder, 205,200 yuan for algal pulp, and 3.648 million yuan for concentrated liquid. It can be seen that the cost of wastewater treatment can be recovered by selling feed-grade algae powder, and 20% gross profit can also be realized. If the algae pulp is sold, a gross profit of 416% can be realized; if the concentrate is sold, a gross profit of 90.8 times can be realized. The economic benefits are very considerable.

Through the above data analysis, it can be seen that the present invention provides a method for treating high-ammonia-nitrogen wastewater by microalgae photofermentation, which can realize the accumulation of microalgae biomass while purifying the wastewater quality, effectively reducing the treatment cost of wastewater, and achieving The comprehensive development and utilization of resources has the dual value of economy and environmental protection. It is suitable for the purification and treatment of wastewater in large, medium and small chemical plants, and is very suitable for promotion in large-scale enterprises with high production of ammonium-rich wastewater.

The present invention is not limited to the above-mentioned embodiments, if the various changes or modifications of the present invention do not depart from the spirit and scope of the present invention, if these changes and modifications belong to the claims of the present invention and the equivalent technical scope, then the present invention is also These modifications and variations are intended to be included.

Claims (10)

1. A method for highly efficient treatment of high ammonia nitrogen wastewater by microalgae photofermentation, characterized in that, comprising the steps: S1, seed solution activation culture: inoculate microalgae cells on the medium for activation, and then obtain logarithmic seed solution through high-density culture; S2, photo-fermentation culture: put the prepared high-ammonia-nitrogen waste water into a photo-fermentation tank, inoculate the seed liquid obtained from S1 after sterilization, and carry out cultivation in several stages of the fermentation tank; when the ammonium ion consumption in the fermentation tank exhausted, the microalgal biomass is harvested and purified water is obtained. 2. The method according to claim 1, wherein the selected microalgae is Chlorella; preferably, said Chlorella is Chlorella pyrenoidosa or domesticated Chlorella pyrenoidosa; preferably , S2 fermenter several stages of cultivation are two-stage cultivation in fermentor, three-stage cultivation in fermentor, or four-stage cultivation in fermentor; preferably, when the wastewater salinity is higher than 15‰, the high ammonia nitrogen The salinity of the waste water is diluted to 15‰, and then adjusted. 3. according to the described method of claim 1 and 2, it is characterized in that, S2 fermentor cultivation comprises the following steps: Stir the high-ammonia-nitrogen waste water and nitrogen-free medium and put it into the fermenter, sterilize and cool it, add S1 to obtain seed liquid inoculation and culture, supplement the sterilized carbon and phosphorus source mother liquid, and wait until the ammonium ion in the fermenter is reduced to 200mg Below /L, take out part of the fermentation broth, put the same volume of waste water medium into the fermenter to continue culturing; the initial inoculated cell density is 5×10 ⁷ -3×10 ⁸ cfu/mL, and the pH of the fermenter is controlled to be 6.5-7.0 , the glucose concentration is 1-20g/L. 4. The method according to claim 3, characterized in that, the fermentor cultivation further comprises the following cultivation conditions: the light intensity is 200-2500 μmols ^-1 m ^-2 , the ventilation rate is 100-500 L/h, and the rotation speed is 100 -400r/min, the waste water renewal rate is 20%-80%. 5. The method according to claim 4, wherein the nitrogen-free medium is nitrogen-free Basal medium; the content of each component of the nitrogen-free Basal medium formula is: MgSO ₄ 7H ₂ O is 1,000 mg/L, EDTA 500mg/L, K ₂ HPO ₄ 1,250mg/L, CaCl ₂ 111mg/L, FeSO ₄ 7H ₂ O 4.98mg/L, H ₃ BO ₃ 114.2mg/L, MnCl ₂ 4H ₂ O 1.42 mg/L, NaMoO ₄ 2H ₂ O 1.19 mg/L, ZnSO ₄ 7H ₂ O 8.82 mg/L, Co(NO ₃ ) ₂ 6H ₂ O 0.49 mg/L , CuSO ₄ ·5H ₂ O is 1.57 mg/L, and the pH value is 6.1. 6. method according to claim 5, is characterized in that, described fermentor is cultivated as two-stage cultivation: S21. After diluting the high-ammonia-nitrogen wastewater, add the nitrogen-free medium mother liquid and mix evenly, put it into a fermenter, sterilize and cool it, insert the seed liquid obtained in S1 to start culturing, and the initial inoculated cell density of microalgae is 5×10 ⁷ - 1×10 ⁸ cfu/mL, the glucose concentration is kept at 5-10g/L, the light intensity is 200-2500μmols ^-1 m ^-2 , the pH value of the fermenter is controlled at 6.5-7.0, the ventilation rate is 100-500L/h, and the rotation speed is 100-400r/min; S22. When the concentration of ammonium ion is lower than 200 mg/L, the fermented liquid with a total volume of 28.0-33.3% of the fermented liquid is released into the concentration tank, and the microalgae are harvested to obtain biomass; S23. Add the original wastewater to the mother liquor of the nitrogen-free medium and mix it to form a wastewater medium, sterilize and cool it, then add it to a photofermentation tank to reach the total volume of the fermentation liquid before feeding, and continue to cultivate until the ammonium ion concentration is lower than 200mg /L, harvesting microalgae; preferably, the addition amount of the mother liquid of the nitrogen-free medium is: the concentration of each component of the nitrogen-free medium is half of the original formula. 7. The method according to claim 6, characterized in that, adding the glucose mother liquor in S21 is before inserting the seed liquor obtained in S1; the glucose mother liquor is sterilized glucose mother liquor. 8. The method according to claim 7, characterized in that the cultivation in the fermenter is a three-stage cultivation: repeat the operation twice according to S22-S23; wherein the light intensity is 200-2500 μmols ⁻¹ m ⁻² , the fermentor The pH value is 6.5-7.0, the glucose concentration is 5-10g/L, the ventilation rate is 100-500L/h, and the rotation speed is 100-400r/min; preferably, the addition amount of the nitrogen-free medium mother liquor is: nitrogen-free The concentration of each component of the medium is three quarters of the original formula. 9. The method according to claim 8, characterized in that the fermentor cultivation is a four-stage cultivation: repeat the operation 3 times according to S22-S23; wherein the light intensity is 200-2500μmol s ^-1 m ^-2 , the fermentor The control pH value is 6.5-7.0, the concentration of glucose is 5-10g/L, the ventilation rate is 100-500L/h, and the rotation speed is 100-400r/min; preferably, the addition amount of the nitrogen-free medium mother liquor is: The concentration of each component of the nitrogen-free medium is the concentration of the original formula. 10. The method according to claim 1 or 2, the composition of the high ammonia nitrogen wastewater is as follows: NH ₄ ⁺ content is 600-10,000mg/L, salinity is 5‰-60‰, and the content of rare earth elements is 0-10mg /L, PO ₄ ^3- content is 0-300mg/L, pH value 6-8; preferably, the glucose concentration in the medium for high-density culture is 30-60g/L, and the sodium nitrate concentration is 2.5-5.0g /L, the range of initial pH value is between 5.5-6.5.