A biological treatment method for ammonia-nitrogen wastewater
By optically modifying corn stalks and treating them with carbon-ytterbium-doped cerium dioxide polyhedra, the problems of low photosynthetic efficiency and poor ammonia nitrogen wastewater treatment efficiency of traditional biomass carriers have been solved, achieving efficient ammonia nitrogen wastewater treatment and resource utilization.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- LIANSHENG XIAMEN COLOR PRINTING CO LTD
- Filing Date
- 2025-08-04
- Publication Date
- 2026-08-04
AI Technical Summary
Traditional biomass carriers have low photosynthetic efficiency for microalgae growth, and existing ammonia nitrogen wastewater treatment methods are inefficient, costly, and difficult to effectively remove ammonia nitrogen and heavy metals from wastewater.
By optically modifying corn stalks to enable them to refract and reflect light, and combining ytterbium-doped cerium dioxide polyhedra and cellulose nanocrystals, a composite optical dispersion was prepared for vacuum impregnation of corn stalks to prepare microbially modified straw husks, which were then co-treated with microalgae to treat ammonia nitrogen wastewater.
It improves light transmission in wastewater, enhances the growth and activity of microalgae, increases the treatment efficiency of ammonia nitrogen wastewater, and effectively adsorbs heavy metals, achieving efficient treatment and resource utilization.
Smart Images
Figure CN120573867B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of water treatment technology, and particularly relates to a biological treatment method for ammonia nitrogen wastewater. Background Technology
[0002] In the metallurgical process of non-ferrous metals, ammonia or ammonium salts are often used as leaching agents, precipitants or neutralizing agents, which leads to the generation of a large amount of ammonia nitrogen wastewater. In addition to high concentrations of ammonia nitrogen, this type of wastewater also contains one or more heavy metals, and has relatively low organic matter content and poor biodegradability.
[0003] The main methods for treating ammonia nitrogen wastewater include physicochemical methods and biological methods. Physicochemical methods mainly include stripping, chemical precipitation, adsorption, and ion exchange. Among them, stripping is easily affected by conditions such as temperature, pH, and gas-liquid ratio, while chemical precipitation requires a large amount of chemicals and is constrained by the cost of the chemicals. Adsorption has good removal effect and is simple to operate, but the adsorbent is easily saturated and needs to be replaced regularly, resulting in higher costs. Ion exchange requires a large amount of resin, is difficult to regenerate, and is also costly.
[0004] Compared to physicochemical methods for treating ammonia nitrogen wastewater, biological methods utilize microorganisms such as bacteria and microalgae to absorb and harmlessly transform ammonia nitrogen in the wastewater. These methods offer stable ammonia nitrogen removal, low cost, and minimal secondary pollution. While microalgae are more widely available, have greater resource recovery potential, and are more environmentally friendly than bacteria, their treatment efficiency for ammonia nitrogen wastewater is relatively low. Therefore, it is often necessary to add biomass carriers to the ammonia nitrogen wastewater to adsorb microalgae and provide them with organic carbon, promoting microalgae growth and improving treatment efficiency. However, biomass carriers often suffer from poor light transmittance; their small size or excessive quantity can block light, affecting the photosynthetic efficiency of microalgae. Therefore, traditional biomass carriers have limited effectiveness in promoting microalgae growth. Summary of the Invention
[0005] To address the aforementioned technical deficiencies, this invention presents a biological treatment method for ammonia nitrogen wastewater. By optically modifying the surface of corn stalks, the method enables them to fully refract and reflect light, significantly enhancing light transmission in the wastewater. This prevents the corn stalks from blocking light due to their small size and large quantity, thereby providing more adsorption area and organic carbon for microalgae, promoting their growth and activity, and ultimately achieving efficient treatment of ammonia nitrogen wastewater.
[0006] A biological treatment method for ammonia nitrogen wastewater includes the following steps: S1: Preparation of ytterbium-doped cerium dioxide polyhedra Cerium nitrate hexahydrate and ytterbium nitrate pentahydrate were mixed and dissolved in deionized water, then NaOH solution was added, and the mixture was transferred to a hydrothermal reactor for hydrothermal reaction. After filtration and drying, ytterbium-doped cerium dioxide polyhedra were obtained. The ytterbium-doped cerium dioxide polyhedra were placed in CO2 gas and heated at 800-850℃ to obtain carbon ytterbium-doped cerium dioxide polyhedra. S2: Preparation of composite optical dispersion Microcrystalline cellulose was hydrolyzed in concentrated sulfuric acid aqueous solution, then deionized water was added to separate the layers. The lower layer suspension was taken and centrifuged. After separating and removing the upper transparent solution, deionized water was added and centrifuged and washed. Then, dialysis was performed to obtain a cellulose nanocrystal suspension. Carbon ytterbium-doped cerium dioxide polyhedra were ultrasonically dispersed in the cellulose nanocrystal suspension to obtain a composite optical dispersion. S3: Treatment and Modification of Corn Stalks Corn stalks are dried, peeled, and granulated to obtain corn stalk pellets and stalk skin. The corn stalk pellets are immersed in a composite optical dispersion solution for vacuum impregnation, filtered, and dried to obtain optically modified straw. The stalk skin is sterilized and mixed with a bacterial solution obtained from Bacillus parasiticus culture. The mixture is then cross-linked in a sodium alginate and CaCl2 system to obtain microbially modified stalk skin. S4: Domestication of Microalgae and Treatment of Ammonia Nitrogen Wastewater Microbial-modified straw husks were used to adsorb and remove heavy metals from ammonia nitrogen wastewater, resulting in pretreated ammonia nitrogen wastewater. The wastewater was then diluted to different concentrations and subjected to gradient acclimation of natural microalgae under light and aeration. After acclimation, the pretreated ammonia nitrogen wastewater was continuously biologically treated in a microbial treatment tank, and the ammonia nitrogen content of the effluent was recorded.
[0007] Furthermore, the preparation of the carbon-ytterbium-doped cerium dioxide polyhedron in step S1 specifically includes the following steps: S1.1: Add 8-10 parts by weight of cerium nitrate hexahydrate and 0.8-1.2 parts by weight of ytterbium nitrate pentahydrate to 100-120 parts by weight of deionized water, and stir until cerium nitrate hexahydrate and ytterbium nitrate pentahydrate are completely dissolved to obtain a mixed nitrate solution. Dissolve 1.5-2 parts by weight of sodium hydroxide in 200-250 parts by weight of deionized water to obtain a NaOH solution. Slowly add the NaOH solution to the mixed nitrate solution and stir for 25-30 minutes. Then transfer it to a polytetrafluoroethylene hydrothermal reactor and keep it at 100-105℃ for 24-30 hours to obtain a reaction suspension. After cooling to room temperature, filter the suspension. Take the filter cake and wash it 3-4 times with deionized water. Then dry it in an oven at 80-85℃ to constant weight to obtain ytterbium-doped cerium dioxide polyhedra. S1.2: Place the ytterbium-doped cerium dioxide polyhedron in a tube furnace and continuously introduce CO2 gas with a purity of 99.5%. At the same time, control the gas pressure inside the furnace to 0.08-0.1 MPa through the exhaust valve. Then, heat the furnace to 800-850℃ at a heating rate of 10-12℃ / min, hold the temperature for 1-1.5 hours, and then stop heating. After cooling the furnace to room temperature, stop introducing CO2 gas to obtain carbon ytterbium-doped cerium dioxide polyhedron.
[0008] Furthermore, the preparation of the composite optical dispersion in step S2 specifically includes the following steps: S2.1: Place a 60-65% sulfuric acid aqueous solution in a container, then heat it in a constant temperature water bath to 45-50℃, keep it at the temperature, add 10-12wt% microcrystalline cellulose of sulfuric acid aqueous solution, stir for 1-1.5 hours at 350-400 rpm, add 10-15 times the amount of deionized water, let it stand for 10-12 hours to obtain a layered solution; S2.2: Discard the supernatant of the layered solution, take the lower suspension and centrifuge at 6000-8000 rpm for 10-15 minutes to separate and remove the supernatant transparent solution. Then add an equal volume of deionized water to the supernatant transparent solution and stir well. Repeat the centrifugation and washing operation to remove the supernatant transparent solution 2-3 times. Take the precipitate after centrifugation and put it into a dialysis bag. Then dialyze it in deionized water for 70-75 hours, changing the deionized water every 8-10 hours. Then ultrasonically disperse the suspension in the dialysis bag at a frequency of 25-30 kHz for 10-15 minutes, and then perform rotary evaporation until the concentration of cellulose nanocrystals is 3.5-4 wt%, to obtain a cellulose nanocrystal suspension. S2.3: Place the cellulose nanocrystal suspension in a container, add 1-1.5 wt% of carbon ytterbium-doped cerium dioxide polyhedra, and then ultrasonically disperse at a frequency of 35-40 kHz for 15-20 minutes to obtain a composite optical dispersion.
[0009] Furthermore, step S3, the treatment and modification of corn stalks, specifically includes the following steps: S3.1: Take corn stalks with a diameter of 2-3cm, dry them, then peel off the smooth outer skin and slice them to obtain stalk slices and stalk skin with a thickness of 0.4-0.5cm. Then cut the stalk slices into 8 equal weight portions along the axis through the center to obtain corn stalk pellets. S3.2: Immerse 4-6 parts by weight of corn stalk particles in 50-70 parts by weight of composite optical dispersion, then transfer to a vacuum impregnation tank and impregnate under vacuum conditions of 300-500 Pa for 15-20 minutes, then filter, and place the filter cake in an oven at 60-65℃ to dry to obtain optically modified straw. S3.3: Inoculate Bacillus paramycoides into LB liquid medium at an inoculum of 2-3% and culture at a constant temperature and shaking at 30-32℃ and 150-200rpm until OD600=1-1.2 to obtain bacterial solution. Sterilize the straw husks from step S3.1 and mix them with the bacterial solution at a solid-liquid ratio of 1:(40-45)g / mL. Then continue to culture at a constant temperature and shaking at 30-32℃ and 150-200rpm for 12-15 hours. Then add an equal volume of sodium alginate solution with a concentration of 4-5% and mix well to obtain a mixture. Add the mixture dropwise to an equal volume of CaCl2 solution with a concentration of 2-3% using a syringe. Let it stand at 4-5℃ for 10-12 hours, filter and store at low temperature to obtain microbially modified straw husks.
[0010] Furthermore, step S4, the domestication of microalgae and the treatment of ammonia nitrogen wastewater, specifically includes the following steps: S4.1: Pass the ammonia nitrogen wastewater into the pretreatment tank, add microbially modified straw husks, the material-to-liquid ratio of microbially modified straw husks to ammonia nitrogen wastewater is (2-3):1000, stir for 30-40 minutes, filter to remove filter residue to obtain pretreated ammonia nitrogen wastewater; S4.2: Dilute the pretreated ammonia nitrogen wastewater to an ammonia nitrogen concentration of 215-230 mg / L, then transfer it to a microbial treatment tank. Add 8-10 wt% natural microalgae and 50-55 wt% optically modified straw. Set the daily light time to 24 hours, with artificial lighting throughout the day. The aeration type is CO2 gas with a concentration of 1-2%, and the ventilation rate is 0.1-0.15 vvm. Measure the ammonia nitrogen concentration of the wastewater in the microbial treatment tank every 4 hours. When the ammonia nitrogen concentration drops below 35 mg / L, drain the wastewater. Then dilute the same volume of pretreated ammonia nitrogen wastewater to an ammonia nitrogen concentration of 300-320 mg / L and add it to the microbial treatment tank. Perform the same lighting and aeration conditions, continuously feeding and effluent for 10-15 hours. S4.3: Dilute the pretreated ammonia nitrogen wastewater to an ammonia nitrogen concentration of 412 mg / L and add it to the microbial treatment tank. Under the same conditions of light and aeration, with a hydraulic retention time of 4 days, the pretreated ammonia nitrogen wastewater is continuously treated for 20 days. During this period, the ammonia nitrogen content in the effluent of the microbial treatment tank is continuously recorded.
[0011] Furthermore, in step S2.2, the retention capacity of the dialysis bag is 8000-10000 Da.
[0012] Furthermore, the LB culture medium in step S3.3 consists of 10-15 g / L peptone, 10-15 g / L sodium chloride, 5-7 g / L yeast extract, and 1000 mL of ultrapure water.
[0013] Furthermore, the natural microalgae in step S4.2 were collected from waters near the ammonia nitrogen wastewater treatment plant, mainly belonging to the Chlorella family.
[0014] The beneficial effects are as follows: 1. This invention obtains a composite optical dispersion by mixing and ultrasonically dispersing cerium dioxide polyhedra with cellulose nanocrystal suspension. Then, corn stalks cut into small particles are vacuum impregnated with the composite optical dispersion and dried to obtain optically modified straw as a carrier. At this time, the surface of the corn stalks is loaded with cerium dioxide polyhedra coated with cellulose nanocrystal membrane. When light shines on the surface of the cellulose nanocrystal membrane, due to the difference in internal refractive index, the light undergoes a series of refractions and reflections and finally converges on the surface. This can greatly enhance the transmission of light in wastewater, optically modified straw carrier and microalgae system, avoid excessive carrier amount from blocking light in the subsequent microbial pool, and add small-sized and large-quantity carriers without affecting microalgae growth. This increases the contact area between the carrier and wastewater and microalgae, releases more small-molecule organic carbon, promotes the growth and activity of microalgae, and thus achieves efficient treatment of ammonia nitrogen wastewater.
[0015] 2. This invention, by doping cerium dioxide polyhedra with carbon ytterbium, not only increases the refractive index of cerium dioxide polyhedra but also allows them to absorb ultraviolet light and convert it into near-infrared light, thereby improving the utilization of light by microalgae, promoting their growth, and increasing the treatment efficiency of ammonia nitrogen wastewater.
[0016] 3. This invention separates hydrophobic straw husks and hydrophilic straw. Optically modified straw is prepared using the hydrophilic straw, which can better support hydrophilic microalgae. The hydrophobic straw husks are then immobilized by loading *Bacillus paramyophyte* with a hydrophobic outer membrane and cross-linking with sodium alginate and CaCl2, resulting in microbially modified straw husks. This modified straw husks can effectively adsorb heavy metals in ammonia nitrogen wastewater, preventing them from affecting microalgae growth. This achieves efficient wastewater treatment and effective utilization of waste biomass resources. Attached Figure Description
[0017] Figure 1 This is a flowchart of the biological treatment method for ammonia nitrogen wastewater used in an embodiment of the present invention. Detailed Implementation
[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0019] Example 1 A biological treatment method for ammonia nitrogen wastewater, such as Figure 1 As shown, the specific steps include: S1: Preparation of ytterbium-doped cerium dioxide polyhedra S1.1: Add 8 parts by weight of cerium nitrate hexahydrate and 0.8 parts by weight of ytterbium nitrate pentahydrate to 100 parts by weight of deionized water, and stir until cerium nitrate hexahydrate and ytterbium nitrate pentahydrate are completely dissolved to obtain a mixed nitrate solution. Dissolve 1.5 parts by weight of sodium hydroxide in 200 parts by weight of deionized water to obtain a NaOH solution. Slowly add the NaOH solution to the mixed nitrate solution and stir for 25 minutes. Then transfer it to a polytetrafluoroethylene hydrothermal reactor and keep it at 100°C for 24 hours to obtain a reaction suspension. After cooling to room temperature, filter it. Take the filter cake and wash it three times with deionized water. Then place it in an 80°C oven and dry it to constant weight to obtain ytterbium-doped cerium dioxide polyhedra. S1.2: The ytterbium-doped cerium dioxide polyhedron is placed in a tube furnace, and CO2 gas with a purity of 99.5% is continuously introduced. At the same time, the gas pressure inside the furnace is controlled to be 0.08 MPa through the exhaust valve. Then, the temperature is raised to 800℃ at a heating rate of 10℃ / min. After holding at this temperature for 1 hour, the heating is stopped. After the furnace is cooled to room temperature, the CO2 gas is stopped, and carbon ytterbium-doped cerium dioxide polyhedron is obtained.
[0020] S2: Preparation of composite optical dispersion S2.1: Place a 60% sulfuric acid aqueous solution in a container, then heat it to 45°C in a constant temperature water bath, keep it at the temperature, add 10wt% microcrystalline cellulose of sulfuric acid aqueous solution, stir at 350rpm for 1 hour, add 10 times the amount of deionized water, let it stand for 10 hours, and obtain a layered solution. S2.2: Discard the supernatant of the layered solution, take the lower suspension and centrifuge at 6000 rpm for 10 minutes to separate and remove the upper transparent solution. Then add an equal volume of deionized water to the upper transparent solution and stir well. Repeat the centrifugation and washing operation to remove the upper transparent solution twice. Take the precipitate after centrifugation and put it into a dialysis bag with a cutoff of 8000 Da. Then dialyze in deionized water for 70 hours, changing the deionized water every 8 hours. Then the suspension in the dialysis bag is ultrasonically dispersed at a frequency of 25 kHz for 10 minutes and then rotary evaporated until the concentration of cellulose nanocrystals is 3.5 wt%, to obtain a cellulose nanocrystal suspension. S2.3: Place the cellulose nanocrystal suspension in a container, add 1 wt% of carbon ytterbium-doped cerium dioxide polyhedrons, and then ultrasonically disperse at a frequency of 35 kHz for 15 minutes to obtain a composite optical dispersion.
[0021] S3: Treatment and Modification of Corn Stalks S3.1: Take corn stalks with a diameter of 2cm, dry them, then peel off the smooth outer skin and slice them to obtain stalk slices and stalk skin with a thickness of 0.4cm. Then cut the stalk slices into 8 equal weight portions along the axis through the center to obtain corn stalk granules. S3.2: Immerse 4 parts by weight of corn stalk particles in 50 parts by weight of composite optical dispersion, then transfer to a vacuum impregnation tank and impregnate under vacuum conditions of 300 Pa for 15 minutes, then filter, take the filter cake and dry it in an oven at 60℃ to obtain optically modified straw. S3.3: Bacillus paramycoides was inoculated into LB liquid medium at an inoculum of 2%. The LB medium consisted of 10 g / L peptone, 10 g / L sodium chloride, 5 g / L yeast extract, and 1000 mL of ultrapure water. The medium was cultured at 30°C and 150 rpm under constant temperature shaking until OD600=1 to obtain a bacterial solution. The sterilized straw husks from step S3.1 were mixed with the bacterial solution at a solid-liquid ratio of 1:40 g / mL. The mixture was then cultured at 30°C and 150 rpm under constant temperature shaking for 12 hours. An equal volume of 4% sodium alginate solution was then added and mixed thoroughly to obtain a mixed solution. The mixed solution was then added dropwise to an equal volume of 2% CaCl2 solution using a syringe. The mixture was allowed to stand at 4°C for 10 hours, filtered, and stored at low temperature to obtain microbially modified straw husks.
[0022] S4: Domestication of Microalgae and Treatment of Ammonia Nitrogen Wastewater S4.1: Ammonia nitrogen wastewater is fed into a pretreatment tank, and microbially modified straw husks are added. The ratio of microbially modified straw husks to ammonia nitrogen wastewater is 2:1000. The mixture is stirred for 30 minutes, and the filter residue is removed by filtration to obtain pretreated ammonia nitrogen wastewater. S4.2: Dilute the pretreated ammonia nitrogen wastewater to an ammonia nitrogen concentration of 215 mg / L, then transfer it to a microbial treatment tank. Add 8 wt% natural microalgae and 50 wt% optically modified straw. The natural microalgae are collected from waters near the ammonia nitrogen wastewater treatment plant and are mainly Chlorella. Set the daily light time to 24 hours and provide artificial light throughout the day. The aeration type is 1% CO2 gas with an aeration rate of 0.1 vvm. Measure the ammonia nitrogen concentration of the wastewater in the microbial treatment tank every 4 hours. When the ammonia nitrogen concentration drops below 35 mg / L, drain the wastewater. Dilute the same volume of pretreated ammonia nitrogen wastewater to an ammonia nitrogen concentration of 300 mg / L and add it to the microbial treatment tank. Perform the same lighting and aeration conditions, continuously feeding and effluent for 10 hours. S4.3: Dilute the pretreated ammonia nitrogen wastewater to an ammonia nitrogen concentration of 412 mg / L and add it to the microbial treatment tank. Under the same conditions of light and aeration, with a hydraulic retention time of 4 days, the pretreated ammonia nitrogen wastewater is continuously treated for 20 days. During this period, the ammonia nitrogen content in the effluent of the microbial treatment tank is continuously recorded.
[0023] Example 2 A biological treatment method for ammonia nitrogen wastewater, such as Figure 1 As shown, the specific steps include: S1: Preparation of ytterbium-doped cerium dioxide polyhedra S1.1: Add 10 parts by weight of cerium nitrate hexahydrate and 1.2 parts by weight of ytterbium nitrate pentahydrate to 120 parts by weight of deionized water, and stir until cerium nitrate hexahydrate and ytterbium nitrate pentahydrate are completely dissolved to obtain a mixed nitrate solution. Dissolve 2 parts by weight of sodium hydroxide in 250 parts by weight of deionized water to obtain a NaOH solution. Slowly add the NaOH solution to the mixed nitrate solution and stir for 25 minutes. Then transfer it to a polytetrafluoroethylene hydrothermal reactor and keep it at 100°C for 24 hours to obtain a reaction suspension. After cooling to room temperature, filter it. Take the filter cake and wash it three times with deionized water. Then place it in an 80°C oven and dry it to constant weight to obtain ytterbium-doped cerium dioxide polyhedra. S1.2: The ytterbium-doped cerium dioxide polyhedron is placed in a tube furnace, and CO2 gas with a purity of 99.5% is continuously introduced. At the same time, the gas pressure inside the furnace is controlled to be 0.08 MPa through the exhaust valve. Then, the temperature is raised to 800℃ at a heating rate of 10℃ / min. After holding at this temperature for 1 hour, the heating is stopped. After the furnace is cooled to room temperature, the CO2 gas is stopped, and carbon ytterbium-doped cerium dioxide polyhedron is obtained.
[0024] S2: Preparation of composite optical dispersion S2.1: Place a 60% sulfuric acid aqueous solution in a container, then heat it to 45°C in a constant temperature water bath, keep it at the temperature, add 12wt% microcrystalline cellulose of sulfuric acid aqueous solution, stir for 1 hour at 350 rpm, add 10 times the amount of deionized water, let it stand for 10 hours, and obtain a layered solution. S2.2: Discard the supernatant of the layered solution, take the lower suspension and centrifuge at 6000 rpm for 10 minutes to separate and remove the upper transparent solution. Then add an equal volume of deionized water to the upper transparent solution and stir well. Repeat the centrifugation and washing operation to remove the upper transparent solution twice. Take the precipitate after centrifugation and put it into a dialysis bag with a cutoff of 8000 Da. Then dialyze in deionized water for 70 hours, changing the deionized water every 8 hours. Then the suspension in the dialysis bag is ultrasonically dispersed at a frequency of 25 kHz for 10 minutes and then rotary evaporated until the concentration of cellulose nanocrystals is 4 wt%, to obtain a cellulose nanocrystal suspension. S2.3: Place the cellulose nanocrystal suspension in a container, add 1.5 wt% of carbon ytterbium-doped cerium dioxide polyhedra, and then ultrasonically disperse at a frequency of 35 kHz for 15 minutes to obtain a composite optical dispersion.
[0025] S3: Treatment and Modification of Corn Stalks S3.1: Take corn stalks with a diameter of 2cm, dry them, then peel off the smooth outer skin and slice them to obtain stalk slices and stalk skin with a thickness of 0.4cm. Then cut the stalk slices into 8 equal weight portions along the axis through the center to obtain corn stalk granules. S3.2: Immerse 6 parts by weight of corn stalk particles in 70 parts by weight of composite optical dispersion, then transfer to a vacuum impregnation tank and impregnate under vacuum conditions of 300 Pa for 15 minutes, then filter, take the filter cake and dry it in an oven at 60℃ to obtain optically modified straw. S3.3: Bacillus paramycoides was inoculated into LB liquid medium at an inoculum of 2%. The LB medium consisted of 10 g / L peptone, 10 g / L sodium chloride, 5 g / L yeast extract, and 1000 mL of ultrapure water. The medium was cultured at 30°C and 150 rpm under constant temperature shaking until OD600 = 1 to obtain the bacterial solution. The sterilized straw husk from step S3.1 was mixed with the bacterial solution at a solid-liquid ratio of 1:45 g / mL. The mixture was then cultured at 30°C and 150 rpm under constant temperature shaking for 12 hours. An equal volume of 5% sodium alginate solution was then added and mixed thoroughly to obtain the mixture. The mixture was then added dropwise to an equal volume of 3% CaCl2 solution using a syringe. The mixture was allowed to stand at 4°C for 10 hours, filtered, and stored at low temperature to obtain the microbially modified straw husk.
[0026] S4: Domestication of Microalgae and Treatment of Ammonia Nitrogen Wastewater S4.1: Ammonia nitrogen wastewater is fed into a pretreatment tank, and microbially modified straw husks are added. The ratio of microbially modified straw husks to ammonia nitrogen wastewater is 3:1000. The mixture is stirred for 30 minutes, and the filter residue is removed by filtration to obtain pretreated ammonia nitrogen wastewater. S4.2: Dilute the pretreated ammonia nitrogen wastewater to an ammonia nitrogen concentration of 215 mg / L, then transfer it to a microbial treatment tank. Add 10 wt% natural microalgae and 55 wt% optically modified straw. The natural microalgae are collected from waters near the ammonia nitrogen wastewater treatment plant and are mainly Chlorella. Set the daily light time to 24 hours, with artificial lighting throughout the day. The aeration type is 1% CO2 gas with an aeration rate of 0.1 vvm. Measure the ammonia nitrogen concentration of the wastewater in the microbial treatment tank every 4 hours. When the ammonia nitrogen concentration drops below 35 mg / L, drain the wastewater. Dilute the same volume of pretreated ammonia nitrogen wastewater to an ammonia nitrogen concentration of 300 mg / L and add it to the microbial treatment tank. Perform the same lighting and aeration conditions, continuously feeding and effluent for 10 hours. S4.3: Dilute the pretreated ammonia nitrogen wastewater to an ammonia nitrogen concentration of 412 mg / L and add it to the microbial treatment tank. Under the same conditions of light and aeration, with a hydraulic retention time of 4 days, the pretreated ammonia nitrogen wastewater is continuously treated for 20 days. During this period, the ammonia nitrogen content in the effluent of the microbial treatment tank is continuously recorded.
[0027] Example 3 A biological treatment method for ammonia nitrogen wastewater, such as Figure 1 As shown, the specific steps include: S1: Preparation of ytterbium-doped cerium dioxide polyhedra S1.1: Add 8 parts by weight of cerium nitrate hexahydrate and 0.8 parts by weight of ytterbium nitrate pentahydrate to 100 parts by weight of deionized water, and stir until cerium nitrate hexahydrate and ytterbium nitrate pentahydrate are completely dissolved to obtain a mixed nitrate solution. Dissolve 1.5 parts by weight of sodium hydroxide in 200 parts by weight of deionized water to obtain a NaOH solution. Slowly add the NaOH solution to the mixed nitrate solution and stir for 30 minutes. Then transfer it to a polytetrafluoroethylene hydrothermal reactor and keep it at 105°C for 30 hours to obtain a reaction suspension. After cooling to room temperature, filter it. Take the filter cake and wash it 4 times with deionized water. Then place it in an oven at 85°C and dry it to constant weight to obtain ytterbium-doped cerium dioxide polyhedra. S1.2: The ytterbium-doped cerium dioxide polyhedron is placed in a tube furnace, and CO2 gas with a purity of 99.5% is continuously introduced. At the same time, the gas pressure inside the furnace is controlled to be 0.1 MPa through the exhaust valve. Then, the temperature is raised to 850°C at a heating rate of 12°C / min. After holding at this temperature for 1.5 hours, the heating is stopped. After the furnace is cooled to room temperature, the CO2 gas is stopped, and carbon ytterbium-doped cerium dioxide polyhedron is obtained.
[0028] S2: Preparation of composite optical dispersion S2.1: Place a 65% sulfuric acid aqueous solution in a container, then heat it to 50°C in a constant temperature water bath, keep it at the temperature, add 10wt% microcrystalline cellulose of sulfuric acid aqueous solution, stir at 400rpm for 1.5 hours, add 15 times the amount of deionized water, let it stand for 12 hours, and obtain a layered solution. S2.2: Discard the supernatant of the layered solution, take the lower suspension and centrifuge at 8000 rpm for 15 minutes to separate and remove the upper transparent solution. Then add an equal volume of deionized water to the upper transparent solution and stir well. Repeat the centrifugation and washing operation to remove the upper transparent solution three times. Take the precipitate after centrifugation and put it into a dialysis bag with a cutoff of 8000 Da. Then dialyze in deionized water for 75 hours, changing the deionized water every 10 hours. Then the suspension in the dialysis bag is ultrasonically dispersed at a frequency of 30 kHz for 15 minutes and then rotary evaporated until the concentration of cellulose nanocrystals is 4 wt%, to obtain a cellulose nanocrystal suspension. S2.3: Place the cellulose nanocrystal suspension in a container, add 1 wt% of carbon ytterbium-doped cerium dioxide polyhedrons, and then ultrasonically disperse at a frequency of 40 kHz for 20 minutes to obtain a composite optical dispersion.
[0029] S3: Treatment and Modification of Corn Stalks S3.1: Take corn stalks with a diameter of 3cm, dry them, then peel off the smooth outer skin and slice them to obtain stalk slices and stalk skin with a thickness of 0.5cm. Then cut the stalk slices into 8 equal weight portions along the axis through the center to obtain corn stalk granules. S3.2: Immerse 4 parts by weight of corn stalk particles in 50 parts by weight of composite optical dispersion, then transfer to a vacuum impregnation tank and impregnate under vacuum conditions of 500 Pa for 20 minutes. Then filter, take the filter cake and dry it in an oven at 65℃ to obtain optically modified straw. S3.3: Bacillus paramycoides was inoculated into LB liquid medium at an inoculum of 3%. The LB medium consisted of 15 g / L peptone, 15 g / L sodium chloride, 7 g / L yeast extract, and 1000 mL of ultrapure water. The medium was cultured at 32°C and 200 rpm under constant temperature shaking until OD600 = 1.2 to obtain the bacterial solution. The sterilized straw husks from step S3.1 were mixed with the bacterial solution at a solid-liquid ratio of 1:40 g / mL. The mixture was then cultured at 32°C and 200 rpm under constant temperature shaking for 15 hours. An equal volume of 5% sodium alginate solution was then added and mixed thoroughly to obtain the mixture. The mixture was then added dropwise to an equal volume of 3% CaCl2 solution using a syringe. The mixture was allowed to stand at 5°C for 12 hours, filtered, and stored at low temperature to obtain the microbially modified straw husks.
[0030] S4: Domestication of Microalgae and Treatment of Ammonia Nitrogen Wastewater S4.1: Ammonia nitrogen wastewater is fed into a pretreatment tank, and microbially modified straw husks are added. The ratio of microbially modified straw husks to ammonia nitrogen wastewater is 2:1000. The mixture is stirred for 40 minutes, and the filter residue is removed by filtration to obtain pretreated ammonia nitrogen wastewater. S4.2: Dilute the pretreated ammonia nitrogen wastewater to an ammonia nitrogen concentration of 230 mg / L, then transfer it to a microbial treatment tank. Add 8 wt% natural microalgae and 50 wt% optically modified straw. The natural microalgae are collected from waters near the ammonia nitrogen wastewater treatment plant and are mainly Chlorella. Set the daily light time to 24 hours, with artificial lighting throughout the day. The aeration type is 2% CO2 gas with an aeration rate of 0.15 vvm. Measure the ammonia nitrogen concentration of the wastewater in the microbial treatment tank every 4 hours. When the ammonia nitrogen concentration drops below 35 mg / L, discharge the wastewater. Then dilute the same volume of pretreated ammonia nitrogen wastewater to an ammonia nitrogen concentration of 320 mg / L and add it to the microbial treatment tank. Perform the same lighting and aeration conditions, continuously feeding and effluent for 15 hours. S4.3: Dilute the pretreated ammonia nitrogen wastewater to an ammonia nitrogen concentration of 412 mg / L and add it to the microbial treatment tank. Under the same conditions of light and aeration, with a hydraulic retention time of 4 days, the pretreated ammonia nitrogen wastewater is continuously treated for 20 days. During this period, the ammonia nitrogen content in the effluent of the microbial treatment tank is continuously recorded.
[0031] Comparative Example 1: The difference from Example 1 is that the optically modified straw in step S4.2 is replaced with corn straw pellets in step S3.1, while the rest of the specific implementation remains the same.
[0032] Comparative Example 2: The difference from Example 1 is that ytterbium pentahydrate was not added in step S1.1, carbon-doped cerium dioxide polyhedra were prepared in step S1.2, and the carbon-ytterbium-doped cerium dioxide polyhedra in step S2.3 were replaced with carbon-doped cerium dioxide polyhedra of equal mass. The other specific implementation methods remain unchanged.
[0033] Comparative Example 3: The difference from Example 1 is that Comparative Example 3 removes step S1.2 and replaces the carbon ytterbium-doped cerium dioxide polyhedron in step S2.3 with ytterbium-doped cerium dioxide polyhedrons of equal mass, while the rest of the specific implementation remains unchanged.
[0034] Experiment 1: The average ammonia nitrogen content in the effluent recorded over 20 days in steps S4.3 of Examples 1-3 and Comparative Examples 1-3 was calculated, and the ammonia nitrogen removal rate was also calculated. The data were compiled into a table, as shown in Table 1.
[0035] Table 1: Average ammonia nitrogen content in effluent over 20 days and ammonia nitrogen removal rate in wastewater
[0036] As shown by the data in Table 1 for Examples 1-3, Examples 1-3 can effectively remove ammonia nitrogen from wastewater. Furthermore, the data from Comparative Example 1 shows that when corn stalk particles are not optically modified, adding 55 wt% corn stalk particles to wastewater significantly increases the ammonia nitrogen content in the effluent and significantly decreases the ammonia nitrogen removal rate compared to Example 1. This demonstrates that optical modification of corn stalk particles can introduce small-sized and numerous carriers without affecting microalgae growth, thereby increasing the contact area between the carrier and wastewater and microalgae, releasing more small-molecule organic carbon, promoting the growth and activity of microalgae, and thus achieving efficient treatment of ammonia nitrogen wastewater. As shown in Comparative Examples 2-3 in Table 1, carbon and ytterbium doping of cerium dioxide can increase the refractive index of cerium dioxide polyhedra, thereby improving the utilization of light by microalgae, better promoting the growth of microalgae, and improving the treatment efficiency of ammonia nitrogen wastewater.
[0037] Experiment 2: Take 200 mg of the microbially modified straw husks prepared in Examples 1-3, and prepare 3 groups of heavy metal solutions, each group containing 3 100 mL heavy metal solutions with a Cu concentration of 100 mg / L. 2+ 100 mg / L Cr 2+ 100 mg / L Zn 2+ and 100 mg / L Ni 2+ Microbial modified straw husks prepared in Examples 1-3 were added to each group of heavy metal solutions. The solutions were shaken and adsorbed at 25℃ and 180r / min for 3 hours. The metal ion concentration N1 in the metal solutions after adsorption equilibrium was measured after filtration. The heavy metal removal rate of each sample after metal solution adsorption treatment was calculated as follows: heavy metal removal rate = (100-N1) / 100×100%. Each group of experiments was conducted in three parallel experiments. The average value of the heavy metal removal rate was taken. The data were recorded and compiled into a table, as shown in Table 2.
[0038] Table 2: Removal rate of heavy metals by microbially modified straw husks
[0039] As can be seen from the removal rates of heavy metals by the microbially modified straw husks prepared in Examples 1-3 in Table 2, the microbially modified straw husks have a good adsorption effect on heavy metals. They can effectively adsorb heavy metals in ammonia nitrogen wastewater, prevent them from affecting the growth of microalgae, and achieve efficient wastewater treatment and effective utilization of waste biomass resources.
[0040] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.
Claims
1. A biological treatment method for ammonia nitrogen wastewater, characterized in that, Includes the following steps: S1: Preparation of ytterbium-doped cerium dioxide polyhedra Cerium nitrate hexahydrate and ytterbium nitrate pentahydrate were mixed and dissolved in deionized water, then NaOH solution was added, and the mixture was transferred to a hydrothermal reactor for hydrothermal reaction. After filtration and drying, ytterbium-doped cerium dioxide polyhedra were obtained. The ytterbium-doped cerium dioxide polyhedra were placed in a tube furnace, and CO2 gas was continuously introduced. The mixture was heated at 800-850℃ and then cooled to room temperature with the furnace. The CO2 gas was then stopped to obtain carbon ytterbium-doped cerium dioxide polyhedra. S2: Preparation of composite optical dispersion Microcrystalline cellulose was hydrolyzed in concentrated sulfuric acid aqueous solution, then deionized water was added to separate the layers. The lower layer suspension was taken and centrifuged. After separating and removing the upper transparent solution, deionized water was added and centrifuged and washed. Then, dialysis was performed to obtain a cellulose nanocrystal suspension. Carbon ytterbium-doped cerium dioxide polyhedra were ultrasonically dispersed in the cellulose nanocrystal suspension to obtain a composite optical dispersion. S3: Treatment and Modification of Corn Stalks Corn stalks are dried, peeled, and granulated to obtain corn stalk pellets and stalk skin. The corn stalk pellets are immersed in a composite optical dispersion solution for vacuum impregnation, filtered, and dried to obtain optically modified straw. The stalk skin is sterilized and mixed with a bacterial solution obtained from Bacillus parasiticus culture. The mixture is then cross-linked in a sodium alginate and CaCl2 system to obtain microbially modified stalk skin. S4: Domestication of Microalgae and Treatment of Ammonia Nitrogen Wastewater Microbial-modified straw husks were used to adsorb and remove heavy metals from ammonia nitrogen wastewater, resulting in pretreated ammonia nitrogen wastewater. This pretreated wastewater was then diluted to different concentrations. The lower concentration of the pretreated ammonia nitrogen wastewater was transferred to a microbial treatment tank, where natural microalgae and optically modified straw were added. The natural microalgae were acclimated under light and aeration. After wastewater discharge, a higher concentration of the pretreated ammonia nitrogen wastewater was added again to acclimate the natural microalgae. After acclimation, the pretreated ammonia nitrogen wastewater was continuously biologically treated in the microbial treatment tank, and the ammonia nitrogen content of the effluent was recorded.
2. The biological treatment method for ammonia nitrogen wastewater according to claim 1, characterized in that, Step S1, the preparation of carbon ytterbium-doped cerium dioxide polyhedra, specifically includes the following steps: S1.1: Add 8-10 parts by weight of cerium nitrate hexahydrate and 0.8-1.2 parts by weight of ytterbium nitrate pentahydrate to 100-120 parts by weight of deionized water, and stir until cerium nitrate hexahydrate and ytterbium nitrate pentahydrate are completely dissolved to obtain a mixed nitrate solution. Dissolve 1.5-2 parts by weight of sodium hydroxide in 200-250 parts by weight of deionized water to obtain a NaOH solution. Slowly add the NaOH solution to the mixed nitrate solution and stir for 25-30 minutes. Then transfer it to a polytetrafluoroethylene hydrothermal reactor and keep it at 100-105℃ for 24-30 hours to obtain a reaction suspension. After cooling to room temperature, filter the suspension. Take the filter cake and wash it 3-4 times with deionized water. Then dry it in an oven at 80-85℃ to constant weight to obtain ytterbium-doped cerium dioxide polyhedra. S1.2: Place the ytterbium-doped cerium dioxide polyhedron in a tube furnace and continuously introduce CO2 gas with a purity of 99.5%. At the same time, control the gas pressure inside the furnace to 0.08-0.1 MPa through the exhaust valve. Then, heat the furnace to 800-850℃ at a heating rate of 10-12℃ / min, hold the temperature for 1-1.5 hours, and then stop heating. After cooling the furnace to room temperature, stop introducing CO2 gas to obtain carbon ytterbium-doped cerium dioxide polyhedron.
3. The biological treatment method for ammonia nitrogen wastewater according to claim 2, characterized in that, The preparation of the composite optical dispersion in step S2 specifically includes the following steps: S2.1: Place a 60-65% sulfuric acid aqueous solution in a container, then heat it in a constant temperature water bath to 45-50℃, keep it at the temperature, add 10-12wt% microcrystalline cellulose of sulfuric acid aqueous solution, stir for 1-1.5 hours at 350-400 rpm, add 10-15 times the amount of deionized water, let it stand for 10-12 hours to obtain a layered solution; S2.2: Discard the supernatant of the layered solution, take the lower suspension and centrifuge at 6000-8000 rpm for 10-15 minutes to separate and remove the supernatant transparent solution. Then add an equal volume of deionized water to the supernatant transparent solution and stir well. Repeat the centrifugation and washing operation to remove the supernatant transparent solution 2-3 times. Take the precipitate after centrifugation and put it into a dialysis bag. Then dialyze it in deionized water for 70-75 hours, changing the deionized water every 8-10 hours. Then ultrasonically disperse the suspension in the dialysis bag at a frequency of 25-30 kHz for 10-15 minutes, and then perform rotary evaporation until the concentration of cellulose nanocrystals is 3.5-4 wt%, to obtain a cellulose nanocrystal suspension. S2.3: Place the cellulose nanocrystal suspension in a container, add 1-1.5 wt% of carbon ytterbium-doped cerium dioxide polyhedra, and then ultrasonically disperse at a frequency of 35-40 kHz for 15-20 minutes to obtain a composite optical dispersion.
4. The biological treatment method for ammonia nitrogen wastewater according to claim 3, characterized in that, Step S3, the treatment and modification of corn stalks, specifically includes the following steps: S3.1: Take corn stalks with a diameter of 2-3cm, dry them, then peel off the smooth outer skin and slice them to obtain stalk slices and stalk skin with a thickness of 0.4-0.5cm. Then cut the stalk slices into 8 equal weight portions along the axis through the center to obtain corn stalk pellets. S3.2: Immerse 4-6 parts by weight of corn stalk particles in 50-70 parts by weight of composite optical dispersion, then transfer to a vacuum impregnation tank and impregnate under vacuum conditions of 300-500 Pa for 15-20 minutes, then filter, and place the filter cake in an oven at 60-65℃ to dry to obtain optically modified straw. S3.3: Inoculate Bacillus paramycoides into LB liquid medium at an inoculum of 2-3% and culture at a constant temperature and shaking at 30-32℃ and 150-200rpm until OD600=1-1.2 to obtain bacterial solution. Sterilize the straw husks from step S3.1 and mix them with the bacterial solution at a solid-liquid ratio of 1:(40-45)g / mL. Then continue to culture at a constant temperature and shaking at 30-32℃ and 150-200rpm for 12-15 hours. Then add an equal volume of sodium alginate solution with a concentration of 4-5% and mix well to obtain a mixture. Add the mixture dropwise to an equal volume of CaCl2 solution with a concentration of 2-3% using a syringe. Let it stand at 4-5℃ for 10-12 hours, filter and store at low temperature to obtain microbially modified straw husks.
5. The biological treatment method for ammonia nitrogen wastewater according to claim 2, characterized in that, Step S4, the domestication of microalgae and the treatment of ammonia nitrogen wastewater, specifically includes the following steps: S4.1: Pass the ammonia nitrogen wastewater into the pretreatment tank, add microbially modified straw husks, the material-to-liquid ratio of microbially modified straw husks to ammonia nitrogen wastewater is (2-3):1000, stir for 30-40 minutes, filter to remove filter residue to obtain pretreated ammonia nitrogen wastewater; S4.2: Dilute the pretreated ammonia nitrogen wastewater to an ammonia nitrogen concentration of 215-230 mg / L, then transfer it to a microbial treatment tank. Add 8-10 wt% natural microalgae and 50-55 wt% optically modified straw. Set the daily light time to 24 hours, with artificial lighting throughout the day. The aeration type is CO2 gas with a concentration of 1-2%, and the ventilation rate is 0.1-0.15 vvm. Measure the ammonia nitrogen concentration of the wastewater in the microbial treatment tank every 4 hours. When the ammonia nitrogen concentration drops below 35 mg / L, drain the wastewater. Then dilute the same volume of pretreated ammonia nitrogen wastewater to an ammonia nitrogen concentration of 300-320 mg / L and add it to the microbial treatment tank. Perform the same lighting and aeration conditions, continuously feeding and effluent for 10-15 hours. S4.3: Dilute the pretreated ammonia nitrogen wastewater to an ammonia nitrogen concentration of 412 mg / L and add it to the microbial treatment tank. Under the same conditions of light and aeration, with a hydraulic retention time of 4 days, the pretreated ammonia nitrogen wastewater is continuously treated for 20 days. During this period, the ammonia nitrogen content in the effluent of the microbial treatment tank is continuously recorded.
6. The biological treatment method for ammonia nitrogen wastewater according to claim 3, characterized in that, In step S2.2, the retention capacity of the dialysis bag is 8000-10000 Da.
7. The biological treatment method for ammonia nitrogen wastewater according to claim 4, characterized in that, The LB medium in step S3.3 consists of 10-15 g / L peptone, 10-15 g / L sodium chloride, 5-7 g / L yeast extract, and 1000 mL of ultrapure water.
8. The biological treatment method for ammonia nitrogen wastewater according to claim 5, characterized in that, The natural microalgae in step S4.2 were collected from waters near the ammonia nitrogen wastewater treatment plant, and mainly belong to the Chlorella family.