A method for recycling agricultural wastewater

Abstract

The present invention belongs to the technical field of wastewater treatment, and in particular, relates to a method for recycling agricultural wastewater. The method comprises: (1) mixing agricultural wastewater, waste biomass and microbial capsules in proportion and fermenting them uniformly, filtering to obtain primary filtered biomass and primary filtered wastewater; (2) mixing primary filtered biomass and inorganic salts in proportion, sintering to obtain coarse modified biochar, ball milling to obtain modified biochar; (3) passing the primary filtered wastewater into a microbial fuel cell for secondary degradation to obtain secondary filtered wastewater; (4) filtering the secondary filtered wastewater using modified biochar to prepare water for greening. The present invention not only promotes the recycling and reuse of agricultural wastewater, but also realizes the reuse of waste biomass, thereby achieving the dual benefits of environmental protection and energy utilization.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a method for recycling agricultural wastewater. Background Art

[0002] Among the published technical means, removing ammonia nitrogen through nitrification and denitrification processes is a common method, but this method is accompanied by high energy consumption and cost; aquaculture wastewater contains high concentrations of organic matter, nitrogen, phosphorus, suspended solids, heavy metals, antibiotics, microplastics and other components, making it difficult to carry out targeted recovery and treatment.

[0003] Biological treatment is a wastewater treatment method. Its principle is to use microorganisms to oxidize and decompose organic matter and some inorganic poisons (such as cyanide compounds and sulfides) in wastewater in the natural environment, and convert them into stable and harmless inorganic substances. However, given that biological methods require the preparation and cultivation of a large number of microorganisms, and that the microbial growth cycle is long, and that environmental conditions such as pH and temperature are high, the effectiveness of biological treatment methods may be affected to a certain extent during actual operation. In addition, the uncertainty and instability of wastewater quality also make it difficult for the microbial living environment to remain stable, which further affects the final effectiveness of wastewater treatment.

[0004] In addition, the amount of water used in urban greening is very large. At present, most urban greening irrigation uses recycled water and cooperates with water-saving irrigation to save water to avoid excessive consumption of water resources. In this regard, researchers have found that after proper treatment, agricultural wastewater is actually a kind of recycled water that is very suitable for greening irrigation, because agricultural wastewater contains not only pollutants, but also a certain amount of effective substances such as plant nutrients. Simply removing such substances is time-consuming and labor-intensive, with high costs and causing a certain waste of resources. If the pollutants are removed by proper treatment, the nutrients will be retained to a certain extent, and even some pollutants will be converted into effective ingredients that are beneficial to plant growth during the treatment process. Then it will be used for urban greening irrigation, which can not only achieve water recycling and reuse, reduce the amount of natural water, but also provide better conditions for the growth of urban greening plants.

[0005] In this regard, the present invention conducts in-depth research on the removal and transformation of agricultural wastewater. Summary of the invention

[0006] The technical solution of the present invention aims to provide a method for recycling agricultural wastewater in order to address the technical difficulties in the existing published technologies, such as the long growth cycle of microorganisms, excessively high environmental requirements, and incomplete treatment of pollutants by a single treatment method, as well as the current problems of poor recycled water effect and waste of natural water resources in urban greening water use.

[0007] The main purpose of the present invention is:

[0008] 1. Efficiently treat organic pollutants and heavy metals in agricultural wastewater;

[0009] 2. Improve the efficiency of agricultural wastewater treatment;

[0010] 3. Bring additional benefits in the process of wastewater treatment;

[0011] 4. During the recycling process, it can be effectively transformed into greening water that is beneficial to the growth of urban greening plants.

[0012] To achieve the above objectives, the present invention adopts the following technical solutions.

[0013] A method for recycling agricultural wastewater,

[0014] The method comprises:

[0015] (1) Mixing agricultural wastewater, waste biomass and microbial capsules in proportion and fermenting them uniformly, and filtering to obtain primary filtered biomass and primary filtered wastewater;

[0016] (2) mixing the primary filtered biomass and inorganic salt in proportion, sintering to obtain coarse modified biochar, and ball milling to obtain modified biochar;

[0017] (3) Passing the primary filtered wastewater into a microbial fuel cell for secondary degradation to produce secondary filtered wastewater;

[0018] (4) The secondary filtered wastewater is filtered using modified biochar to prepare water for greening.

[0019] As a preference,

[0020] The waste biomass in step (1) is agricultural waste;

[0021] The agricultural waste includes waste corn biomass and / or waste rice biomass and / or waste peanut biomass;

[0022] In step (1), the agricultural wastewater, waste biomass and microbial capsules are uniformly mixed in a mass ratio of (5-7):1.5:(0.1-0.3).

[0023] As a preference,

[0024] The microbial capsule in step (1) is prepared by the following method:

[0025] The licheniformis agent, sphingomonas agent, cladosporium agent and spore agent were mixed evenly according to the volume ratio of (3.3-3.7): (6.3-6.7): 1: (1.8-2.2), and the concentration of the bacterial agent was 4×10 11 ~6×10 11CFU / mL, the mixed bacterial agent and the sodium alginate solution with a concentration of 3-6 wt% were mixed in a volume ratio of 1: (1.5-2) to form a mixed bacterial solution, and then calcium salt was added, and the amount of calcium salt added was 30-35 wt% of the sodium alginate content in the sodium alginate solution. Subsequently, the mixed bacterial solution was mixed with 4.5-5.5 times the volume of liquid paraffin to form an oil-in-water emulsion, and a sedimentation agent was added and precipitated to obtain a microbial capsule;

[0026] The liquid paraffin contains 0.5-1.5 wt% of Span 80;

[0027] The precipitant is a 2-3 mol / L calcium chloride solution containing 0.8-1.2 wt% tween-80, and the precipitant is slowly added dropwise until the precipitate at the bottom of the solution no longer increases.

[0028] As a preference,

[0029] The fermentation process in step (1) is carried out at 20-40°C and the fermentation is continued for 96-144 hours.

[0030] As a preference,

[0031] The inorganic salt in step (2) is ferric chloride;

[0032] In step (2), the pre-filtered biomass and the inorganic salt are uniformly mixed in a mass ratio of 1: (1.2-1.4).

[0033] As a preference,

[0034] The sintering process in step (2) is carried out in a protective atmosphere at a temperature of 700 to 800° C. for 2 to 4 hours;

[0035] The ball milling in step (2) is to grind the coarse modified biochar into particles with a size of 80 to 100 meshes.

[0036] As a preference,

[0037] The method for constructing the microbial fuel cell in step (3) is as follows:

[0038] The battery is separated into an anode chamber and a cathode chamber by a proton exchange membrane, and the pre-filtered wastewater obtained in step (1) is added as an electrolyte into the anode chamber and the cathode chamber;

[0039] The anode chamber is provided with an anode electrode, which is a graphite plate with a surface uniformly covered with a positive electrode active material;

[0040] The positive electrode active material is composed of polyaniline, polythiophene and the modified biochar obtained in step (2), wherein the content of polyaniline is 25-35 wt%, the content of modified biochar is 6-8 wt%, and the balance is polythiophene. The total amount of the positive electrode active material is 22-30 wt% of the graphite plate;

[0041] The mixed microbial agent is added to the electrolyte in the anode chamber, the amount of the mixed microbial agent is 0.01-0.05 mL / mL of the electrolyte in the anode chamber, and the total bacterial concentration is 3×10 11 ~5×10 11 CFU / mL;

[0042] The concentration of sulfate-reducing bacteria in the mixed microbial agent is 18-22 wt %, the concentration of Shewanella putrefaciens is 28-32 wt %, and the balance is actinomycetes;

[0043] The cathode chamber is provided with a cathode electrode, and the cathode electrode substrate is formed by pressing the modified biochar obtained in step (2), and 2 to 4 wt% of HKUST-1 catalyst is loaded on the cathode electrode substrate.

[0044] As a preference,

[0045] When the secondary degradation in step (3) reaches an output current of the microbial fuel cell of ≤0.02 mA, the wastewater in the anode chamber and the cathode chamber is stopped and recovered, i.e., the secondary filtered wastewater.

[0046] As a preference,

[0047] The amount of modified biochar used in step (4) is 10-20 mg / L of primary filtered wastewater.

[0048] As a preference,

[0049] The greening water obtained in step (4) is used for urban greening irrigation and / or early irrigation after plant transplanting.

[0050] The biological treatment method of sewage is an artificial enhancement technology developed based on the principle of environmental self-purification. This technology aims to create a high-quality environment suitable for the rapid and large-scale reproduction of microorganisms, thereby strengthening their metabolic functions and accelerating the inorganic transformation process of organic matter to achieve efficient and rapid purification of wastewater. Biological treatment methods cover a variety of technical approaches, such as activated sludge method, biological pond method, anaerobic biological treatment method and contact oxidation method. This type of method not only has low operating costs, but also has significant advantages such as high pollutant removal efficiency, low energy consumption, safety and environmental protection, especially in the removal of organic pollutants.

[0051] For the technical solution of the present invention, the core lies in utilizing the interbacterial relationship formed between microbial colonies, and through the means of biological treatment, after in-depth scientific research, it is confirmed that the mixed strains show more excellent performance in degradation ability compared with single strains, and can degrade and remove organic pollutants or convert them into a small amount of nutrients that are effective for plants. Although it is difficult to meet the needs of agricultural growth, it is more than enough for simple urban greening irrigation. In particular, microbial strains with mycelium structure not only have a strong ability to degrade organic pollutants, but also their unique mycelium structure can promote the growth of other microorganisms and enhance their biological activity, thereby significantly improving the overall degradation efficiency. At the same time, sodium alginate is used in the technical solution of the present invention to prepare a microbial capsule with a sustained release effect. In the early stage when the mixed strain fails to reproduce in large quantities, it can effectively isolate the sulfide and organic acid present in the wastewater environment, allowing small molecules such as oxygen and inorganic salts to freely enter and metabolites in the capsule to be freely discharged, thereby achieving the purpose of immune isolation and ensuring the stock rate of the mixed strain in the wastewater environment.

[0052] In the technical solution of the present invention, the core mechanism of the degradation of the mixed strain is the enzymatic reaction, wherein the core degradation enzymes include hydrolases such as esterases, lipases, and peptidases, as well as oxidoreductases such as oxygenases and peroxidases. In order to ensure the smooth production of the degradation effect, the pheromones secreted by Bacillus licheniformis and Sphingomonas during the growth and reproduction process jointly construct a kind of amino acid information group, and the extracellular enzyme activates the free hydroxyl groups in the extracellular environment under the catalytic action of the information group, and obtains electrons from it for release, so that the geometric configuration of the carbon structure for the reaction is changed from a stable configuration to an extremely unstable tetrahedral intermediate, which collapses with the enzyme in the subsequent enzymolysis process, forming an acyl esterase complex to enter the intracellular acylation reaction, providing an external carbon source and nitrogen source for the growth of bacteria. In this catalytic process, water molecules can act as nucleophiles and carriers to accelerate the reaction. In the process of slow release, Cladosporium and Bacillus gradually begin to grow with the supplement of external carbon and nitrogen sources, and release signal molecules to the extracellular environment at the same time as the remaining two bacteria. In the initial stage, the concentration of signal molecules in the environment is maintained at a low level. These molecules help a single bacterial colony detect changes in the number of the same or other bacterial species in its surrounding environment and environmental conditions. As all bacterial colonies gradually release signal molecules, when the concentration accumulates to a preset threshold level, these signal molecules will be recognized by the corresponding receptors in the microorganisms. This recognition process will trigger the inhibition of growth and reproduction gene expression in the microbial community, thereby achieving synchronization of the behavior of all members in the community. In this way, the microbial community can perform complex physiological functions and behaviors that a single microbial individual cannot accomplish alone. And through precise microbial community synchronization technology, the growth of miscellaneous bacteria in the wastewater environment can be inhibited. The synchronized microbial flora can release specific signal molecules, which not only transmit complex growth instructions, but also accurately control the growth rate of the microbial colony, which not only prevents the bacteria in the wastewater environment from entering the decay period too quickly, thereby ensuring a longer growth period, but also inhibits the activity of biological enzymes in the bacteria, thereby hindering the synthesis of the growth protein of the bacteria, and finally achieving effective inhibition of the growth of the bacteria. When dealing with the bacteria in the wastewater, the microbial flora provided by the present invention first effectively blocks the communication of the flora by inhibiting the synthesis of the quorum sensing signal molecules of the bacteria, which mainly relies on the mixed flora to inhibit the activity of the key enzymes in the signal molecule synthesis pathway, and blocks the signal molecule synthesis process; secondly, the mixed flora can also degrade the synthesized quorum sensing signal molecules of the bacteria, further reducing its influence on the bacteria flora; finally, the mixed flora can synthesize the signal molecule analogs that competitively bind to the signal molecule receptor protein, or even preferentially bind, thereby hindering the binding of the bacteria signal molecule to the corresponding receptor protein, and achieving the purpose of blocking the communication of the bacteria flora.

[0053] In addition, the co-metabolism between signal molecules and organophosphorus has the effect of promoting the biodegradation of organic pollutants in wastewater, thereby achieving more efficient purification of wastewater. In traditional sewage biological treatment processes, biological phosphorus removal technology usually maintains its phosphorus removal efficiency in the range of only 30% to 40%. Therefore, it is difficult to meet the urban greening water use standards by using biological methods to treat phosphorus alone. In the technical solution of the present invention, different bacterial communities are uniformly dispatched by signal molecules to carry out a series of co-metabolism with pesticide residues represented by organophosphorus, which can completely degrade organic residues of pesticide residues. The mixed bacterial community uses organic residues as the only carbon source and energy source, and completely converts organic residues into water and carbon dioxide through the biological activities of the mixed bacterial community. In the degradation process of microorganisms in the co-metabolism mode, due to the limitations of the enzyme system and the negative impact of the toxic metabolites that may be produced on the growth environment, a single bacterial agent often requires the synergistic effect of multiple microorganisms to achieve the effect of complete degradation of pesticides. However, the mixed bacterial community provided by the present invention can not only produce co-metabolism with organic residues, but also adsorb and fix the metabolic residues on biomass without producing additional toxic metabolites.

[0054] In the technical solution of the present invention, the waste biomass introduced during microbial fermentation can produce a synergistic effect in the subsequent wastewater treatment process. Biomass, as an organic matter generated by photosynthesis, is significantly characterized by its renewability. Waste biomass refers to the waste generated in the production and consumption of biomass, covering multiple sources such as agricultural and forestry waste, wood waste, and urban solid waste. In the agricultural production process, the amount of waste biomass generated is quite considerable. However, in the past, the treatment methods for this type of waste, such as burial, dumping, and even direct burning, not only led to a huge waste of resources, but also caused unnecessary waste of land resources, and caused a series of problems such as air pollution. The present invention can not only provide a carrier for fixing metabolic waste for the mixed bacterial community through waste biomass, but also prepare the waste biomass into modified biochar through subsequent operating steps, which can perform the final decolorization and adsorption of wastewater. The modified biochar provided by the present invention has a higher specific surface area and a rich functional group structure, has excellent heavy metal adsorption capacity and good biocompatibility. The modified biochar has a porous structure and a large number of adsorption sites. These pores can significantly accommodate heavy metal ions, thereby effectively inhibiting their migration in the environment and reducing their biological effectiveness. The functional groups on the surface of the modified biochar, including carboxyl, phenolic hydroxyl and lactone groups, have the ability to undergo chemical reactions such as complexation and chelation with heavy metal ions. This characteristic effectively enhances the adsorption effect of biochar on heavy metals. In addition, with the addition of ferric chloride, the modified biochar has partial magnetism, which can cause some heavy metal ions to deposit on the surface of the biochar, and can also adsorb microorganisms in wastewater, and under the stimulation of microorganisms, the polysaccharide undergoes Maillard reaction, further enhancing the adsorption capacity of the biochar.

[0055] Another core of the technical solution of the present invention is that the present invention uses an optimized microbial battery. When compared with existing organic energy generation technologies, microbial fuel cells demonstrate their unique operational and functional advantages. First, it directly converts substrates into electrical energy, ensuring efficient energy conversion efficiency; second, unlike other bioenergy treatment methods, microbial fuel cells can operate stably under normal temperature conditions without the need for additional environmental condition control; finally, this technology has a natural advantage in waste gas treatment because the main waste gas it produces is carbon dioxide, which can be discharged without further treatment. During the operation of the microbial fuel cell, microorganisms simultaneously generate electrons and protons by decomposing oxidized fuels at the anode, and the electrons are then smoothly transferred to the cathode through an external circuit, while the protons migrate to the cathode through a proton exchange membrane; in the cathode area, electrons and protons are consumed and combined with oxygen to eventually generate water. Compared with traditional fuel cells, microbial fuel cells provide a stable power supply while demonstrating effective treatment capabilities for organic wastewater, and do not produce secondary pollution, and are significantly environmentally friendly. In the present invention, the microbial fuel cell is specially optimized, the anode is composed of organic polymer materials and modified biochar, the functional modification of the modified biochar particles can improve the conductivity and contact area of ​​the electrode, optimize the conductive performance of the anode, and provide catalytic activity for the anaerobic growth of microorganisms; the optimization of the microbial flora, using the more efficient biomineralization effect of the optimized microorganisms, in the anode environment of the microbial fuel cell, the electrogenic microorganisms anaerobically decompose the organic matter in the wastewater, the core mechanism of this biochemical process involves the loss and dehydrogenation of the electrons of the substrate, followed by a combination reaction with oxygen, and finally converted into carbon dioxide and water, in this process, the extracellular electrogenic bacteria play a vital role, they are specifically responsible for the effective removal of electrons from the microbial cells The electrons are transferred to the outside of the cell, and the redox reaction and the electron transfer process are expanded through the participation of extracellular electrogenic bacteria. They are no longer limited to the inside of a single cell, but are extended to the outside of the entire battery system, thereby significantly improving the energy conversion efficiency and utilization rate. The efficient biomineralization effect can expand the contact area of ​​the electrogenic microorganisms and provide more conductive pathways, thereby improving the microbial electricity generation effect. In the cathode chamber, the cathode material is the modified biochar prepared by the present invention and the HKUST-1 catalyst. Under the joint catalytic action of the two, the electrochemical reaction rate is enhanced and the current output is improved. The electrolyte is the primary filtered wastewater that has been biodegraded. The inorganic ion concentration in the wastewater is reduced through preliminary biodegradation, thereby improving the operation effect of the microbial fuel cell of the present invention.

[0056] In addition, in each of the above-mentioned treatment stages, in addition to the degradation and removal of organic pollutants and the adsorption and removal of heavy metal ions, other additional work is also carried out at the same time. The enzymatic degradation process of the mixed strain and the redox reaction process of the fuel cell actually transform some macromolecular organic matter into small molecular organic matter. Among them, some small molecular organic matter will be retained in the water, while inorganic phosphorus formed by the degradation of organic phosphorus pollutants is actually more easily absorbed by plants. This is not only a more effective recycling method for agricultural wastewater, but also retains and even transforms some effective substances while removing impurities. When these treated wastewaters are used for irrigation in urban greening, they can even improve the growth effect of urban greening plants and achieve sustainable utilization of resources.

[0057] The advantages of the present invention are: through rigorous technical integration, the combination of biodegradation and microbial fuel cells not only successfully solves the problem of agricultural wastewater treatment, but also achieves effective growth of energy. This method not only promotes the recycling and reuse of agricultural wastewater, but also realizes the reuse of waste biomass, thus achieving the dual benefits of environmental protection and energy utilization. DETAILED DESCRIPTION

[0058] The present invention is further described in detail below in conjunction with specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention involved in the following description are generally only embodiments of a part of the present invention, rather than all embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work should fall within the scope of protection of the present invention.

[0059] Unless otherwise specified, the raw materials used in the examples of the present invention are all commercially available or available to those skilled in the art; unless otherwise specified, the methods used in the examples of the present invention are all methods known to those skilled in the art.

[0060] Example 1: A method for recycling agricultural wastewater,

[0061] The method comprises:

[0062] (1) Bacillus licheniformis, Sphingomonas, Cladosporium and Bacillus were mixed evenly in a volume ratio of 3.3:6.3:1:1.8. The concentration of each bacterial agent used was 4×10 11CFU / mL, the concentration difference value is less than 5%. The mixed bacterial agent and sodium alginate aqueous solution (3 wt%) are mixed evenly at a volume ratio of 1:1.5 to form a mixed bacterial solution, and then calcium salt is added. The amount of calcium salt added is 30 wt% of the sodium alginate content in the sodium alginate aqueous solution. Subsequently, the mixed bacterial solution is mixed with 4.5 times the volume of liquid paraffin to form an oil-in-water emulsion, and a sedimentation agent is added and precipitated to obtain a microbial capsule;

[0063] The liquid paraffin contains 0.5 wt% of Span 80;

[0064] The above-mentioned sedimentation agent is a 2 mol / L calcium chloride solution containing 0.8 wt% tween-80, and the sedimentation agent is slowly added dropwise until the sediment at the bottom of the solution no longer increases;

[0065] (2) Agricultural wastewater, waste biomass and microbial capsules were mixed evenly in a mass ratio of 5:1.5:0.1, fermented at 25 °C for 144 h, and filtered to obtain primary filtered biomass and primary filtered wastewater, respectively;

[0066] The waste biomass is corn stalks and corn cobs;

[0067] (3) The primary filtered biomass and ferric chloride were mixed evenly in a mass ratio of 1:1.2, and sintered at 700 °C in a nitrogen atmosphere for 4 h to obtain a coarse modified biochar. The coarse modified biochar was ground to a particle size of 80 mesh by ball milling to obtain a modified biochar.

[0068] (4) Build a microbial fuel cell and pass the primary filtered wastewater into the microbial fuel cell for secondary degradation. When the output current of the microbial fuel cell is ≤0.02 mA, stop the process to obtain secondary filtered wastewater.

[0069] The microbial fuel cell construction method is as follows:

[0070] The battery is separated into an anode chamber and a cathode chamber by a proton exchange membrane, and the pre-filtered wastewater obtained in step (2) is added as an electrolyte into the anode chamber and the cathode chamber;

[0071] The anode chamber is provided with an anode electrode, which is a graphite plate with a surface uniformly covered with a positive electrode active material;

[0072] The positive electrode active material is composed of polyaniline, polythiophene and the modified biochar obtained in step (3), wherein the content of polyaniline is 30 wt%, the content of modified biochar is 7 wt%, and the balance is polythiophene. The total amount of the positive electrode active material is 27 wt% of the graphite plate;

[0073] The mixed microbial agent was added to the electrolyte in the anode chamber, the amount of the mixed microbial agent was 0.03 mL / mL of the electrolyte in the anode chamber, and the total bacterial concentration was 4×10 11 CFU / mL;

[0074] The concentration of sulfate-reducing bacteria in the mixed microbial agent is 20 wt %, the concentration of Shewanella putrefaciens is 30 wt %, and the balance is actinomycetes;

[0075] The cathode chamber is provided with a cathode electrode, the cathode electrode substrate is formed by pressing the modified biochar obtained in step (3), and a HKUST-1 catalyst accounting for 3 wt% of the cathode electrode substrate is loaded thereon;

[0076] (5) The secondary filtered wastewater was filtered using modified biochar at a rate of 1.5 m / h to prepare water for greening.

[0077] The performance of the greening water obtained in the example was tested, and the specific characterization results are as follows.

[0078] Water quality pH detection: refer to HJ 1147-2020 electrode method, at room temperature and pressure, the greening water prepared in the example is tested for pH (6.0-9.0)

[0079] Water quality turbidity detection (NTU): Referring to the surface water turbidity meter method in HJ 1075-2019, the greening water prepared in the example was tested on site.

[0080] Five-day biochemical oxygen demand detection (BOD5): With reference to HJ 505-2009 Determination of five-day biochemical oxygen demand (BOD5) of water quality, the greening water prepared in the embodiment was tested using the dilution and dilution inoculation method, and the BOD5 data of the greening water prepared in the embodiment was calculated according to the following formula.

[0081] Where:

[0082] ——Five-day biochemical oxygen demand mass concentration, mg / L;

[0083] ——Dissolved oxygen mass concentration of the inoculated water sample before cultivation, mg / L;

[0084] ——Dissolved oxygen mass concentration of the inoculated water sample after incubation, mg / L;

[0085] ——Dissolved oxygen mass concentration of blank sample before incubation, mg / L;

[0086] ——Dissolved oxygen mass concentration of blank sample after incubation, mg / L;

[0087] ——Inoculation dilution water or the proportion of dilution water in the culture medium;

[0088] ——The proportion of water used for greening in the culture medium.

[0089] Water quality ammonia nitrogen detection: With reference to HJ 535-2009 water quality ammonia nitrogen detection, the greening water prepared in the example was detected using Nessler's reagent spectrophotometry, and the mass concentration of ammonia nitrogen in the greening water prepared in the example was calculated according to the following formula.

[0090] Where:

[0091] ——Mass concentration of ammonia nitrogen in greening water, mg / L;

[0092] ——Detect the absorbance of water samples;

[0093] ——absorbance of blank sample;

[0094] a——intercept of the calibration curve;

[0095] b – the slope of the calibration curve;

[0096] V——test water sample volume, mL.

[0097] Sulfide detection of water quality: With reference to HJ / T 200-2005 sulfide detection of water quality, meteorological molecular absorption spectroscopy was used to detect the greening water prepared in the embodiment.

[0098] Water quality organic phosphorus detection: Referring to the water quality detection method of GB 11893-89, the greening water prepared in the embodiment was detected using ammonium molybdate spectrophotometry.

[0099] Water quality suspended matter detection: The greening water prepared in the embodiment is passed through a filter membrane with a pore size of 0.45 μm at a flow rate of 2 m / min. After the filtration is completed, the filter membrane and the filtered solids are moved into an oven, dried at a temperature of 105 °C for 1.5 h, cooled and weighed, and the suspended matter content in the water quality is calculated according to the following formula.

[0100] Where:

[0101] SS——suspended solids content in greening water, mg / L;

[0102] A——Mass of suspended matter and filter membrane after drying, g;

[0103] B——dry filter membrane mass, g;

[0104] V——The volume of water used for greening testing, mL.

[0105]

[0106] In addition, the heavy metal content in the greening water prepared in the example was detected by inductively coupled plasma mass spectrometry, and the specific characterization results are as follows.

[0107]

[0108] Meanwhile, no Escherichia coli was detected in the greening water prepared in the example, and the total concentration of coliform bacteria was ≤150 / mL.

[0109] The above test results show that the greening water obtained in this case fully meets the requirements of GB / T 25499-2010 for greening water and can be used directly as greening water. In addition, after the safety and effectiveness were verified in the laboratory, the special greening water was contacted with the municipal department for field verification, and comparative tests were carried out in some intersection flower beds.

[0110] The original flower bed had five planting areas, two of which were replaced with the greening water prepared in this example as the test area, and the other three maintained the original water quality as the control area. Greening irrigation was carried out according to the original irrigation plan, and the flower bed was planted with roses. After 42 days of irrigation, the number of roses blooming in the test area increased by about 11.3% compared with the number of roses blooming in the control area, which had a relatively obvious improvement effect, and the landscape flowers grew well. The soil test was qualified after irrigation, and there was no pollution or harm to the soil.

[0111] Example 2: A method for recycling agricultural wastewater,

[0112] The method comprises:

[0113] (1) Bacillus licheniformis, Sphingomonas, Cladosporium and Bacillus were mixed in a volume ratio of 3.5:6.5:1:2. The concentration of each bacterial agent was 5×10 11 CFU / mL, the concentration difference value is less than 5%. The mixed bacterial agent and sodium alginate aqueous solution (4 wt%) are mixed evenly at a volume ratio of 1:1.8 to form a mixed bacterial solution, and then calcium salt is added. The amount of calcium salt added is 33 wt% of the sodium alginate content in the sodium alginate solution. Subsequently, the mixed bacterial solution is mixed with 5 times the volume of liquid paraffin to form an oil-in-water emulsion, and a sedimentation agent is added and precipitated to obtain a microbial capsule;

[0114] The liquid paraffin contains 1.0 wt% of Span 80;

[0115] The above-mentioned sedimentation agent is a 2.5 mol / L calcium chloride solution containing 1.0 wt% tween-80, and the sedimentation agent is slowly added dropwise until the sediment at the bottom of the solution no longer increases;

[0116] (2) Agricultural wastewater, waste biomass and microbial capsules were mixed evenly in a mass ratio of 6:1.5:0.2, fermented at 25 °C for 120 h, and filtered to obtain primary filtered biomass and primary filtered wastewater, respectively;

[0117] The above-mentioned waste biomass is corn stalks and corn cobs.

[0118] (3) The primary filtered biomass and ferric chloride were mixed evenly in a mass ratio of 1:1.3, and sintered at 750 °C in a nitrogen atmosphere for 3 h to obtain a coarse modified biochar. The coarse modified biochar was ground to a particle size of 90 mesh by ball milling to obtain a modified biochar.

[0119] (4) Build a microbial fuel cell and pass the primary filtered wastewater into the microbial fuel cell for secondary degradation. When the output current of the microbial fuel cell is ≤0.02 mA, stop the process to obtain secondary filtered wastewater.

[0120] The microbial fuel cell construction method is as follows:

[0121] The battery is separated into an anode chamber and a cathode chamber by a proton exchange membrane, and the pre-filtered wastewater obtained in step (2) is added as an electrolyte into the anode chamber and the cathode chamber;

[0122] The anode chamber is provided with an anode electrode, which is a graphite plate with a surface uniformly covered with a positive electrode active material;

[0123] The positive electrode active material is composed of polyaniline, polythiophene and the modified biochar obtained in step (3), wherein the content of polyaniline is 25 wt%, the content of modified biochar is 6 wt%, and the balance is polythiophene. The total amount of the positive electrode active material is 22 wt% of the graphite plate;

[0124] The mixed microbial agent was added to the electrolyte in the anode chamber, the amount of the mixed microbial agent was 0.01 mL / mL of the electrolyte in the anode chamber, and the total bacterial concentration was 5×10 11 CFU / mL;

[0125] The concentration of sulfate-reducing bacteria in the mixed microbial agent is 18 wt %, the concentration of Shewanella putrefaciens is 28 wt %, and the balance is actinomycetes;

[0126] The cathode chamber is provided with a cathode electrode, the cathode electrode substrate is formed by pressing the modified biochar obtained in step (3), and a HKUST-1 catalyst accounting for 2 wt% of the cathode electrode substrate is loaded thereon;

[0127] (5) The secondary filtered wastewater is filtered using modified biochar at a rate of 15 mg / L of the secondary filtered wastewater to prepare water for greening.

[0128] Referring to the greening water detection method of Example 1, the same performance test was performed on the example, and the specific characterization results are as follows.

[0129]

[0130] Meanwhile, no Escherichia coli was detected in the greening water prepared in the example, and the total concentration of coliform bacteria was ≤150 / mL.

[0131] The above test results show that the greening water obtained in this case fully meets the requirements of GB / T 25499-2010 for greening water and can be used directly as greening water. In addition, after the safety and effectiveness were verified in the laboratory, the special greening water was contacted with the municipal department for field verification, and comparative tests were carried out in some intersection flower beds.

[0132] The original flower bed had 11 planting areas, of which 6 were replaced with the greening water prepared in this example as the test area, and the other 5 were kept with the original water quality as the control area. Greening irrigation was carried out according to the original irrigation plan, and the flower bed was planted with dianthus. After 45 days of irrigation, the number of dianthus flowers in the test area increased by about 12.2% compared with the number of dianthus flowers in the control area, which had a relatively obvious improvement effect, and the landscape flowers grew well. The soil test was qualified after irrigation, and there was no pollution or harm to the soil.

[0133] Embodiment 3: A method for recycling agricultural wastewater,

[0134] The method comprises:

[0135] (1) Bacillus licheniformis, Sphingomonas, Cladosporium and Bacillus were mixed in a volume ratio of 3.7:6.7:1:2.2. The concentration of each bacterial agent was 6×10 11 CFU / mL, the concentration difference value is less than 5%. The mixed bacterial agent and sodium alginate aqueous solution (6 wt%) are mixed evenly at a volume ratio of 1:2 to form a mixed bacterial solution, and then calcium salt is added. The amount of calcium salt added is 35 wt% of the sodium alginate content in the sodium alginate solution. Subsequently, the mixed bacterial solution is mixed with 4.5 times the volume of liquid paraffin to form an oil-in-water emulsion, and a sedimentation agent is added and precipitated to obtain a microbial capsule.

[0136] The liquid paraffin contains 1.5 wt% of Span 80;

[0137] The above-mentioned sedimentation agent is a 3 mol / L calcium chloride solution containing 1.2 wt% tween-80, and the sedimentation agent is slowly added dropwise until the sediment at the bottom of the solution no longer increases;

[0138] (2) Agricultural wastewater, waste biomass and microbial capsules were mixed evenly in a mass ratio of 7:1.5:0.3, fermented at 25 °C for 96 h, and filtered to obtain primary filtered biomass and primary filtered wastewater, respectively;

[0139] The above-mentioned waste biomass is corn stalks and corn cobs.

[0140] (3) The primary filtered biomass and ferric chloride were mixed evenly in a mass ratio of 1:1.4, and sintered at 800 °C in a nitrogen atmosphere for 2 h to obtain a coarse modified biochar. The coarse modified biochar was ground to a particle size of 100 mesh by ball milling to obtain a modified biochar.

[0141] (4) Building a microbial fuel cell, passing the primary filtered wastewater into the microbial fuel cell for secondary degradation, and stopping when the output current of the microbial fuel cell is no greater than ≤0.02 mA to obtain secondary filtered wastewater;

[0142] The microbial fuel cell construction method is as follows:

[0143] The battery is separated into an anode chamber and a cathode chamber by a proton exchange membrane, and the pre-filtered wastewater obtained in step (2) is added as an electrolyte into the anode chamber and the cathode chamber;

[0144] The anode chamber is provided with an anode electrode, which is a graphite plate with a surface uniformly covered with a positive electrode active material;

[0145] The positive electrode active material is composed of polyaniline, polythiophene and the modified biochar obtained in step (3), wherein the content of polyaniline is 35 wt%, the content of modified biochar is 8 wt%, and the balance is polythiophene. The total amount of the positive electrode active material is 30 wt% of the graphite plate;

[0146] The mixed microbial agent was added to the electrolyte in the anode chamber, the amount of the mixed microbial agent was 0.01 mL / mL of the electrolyte in the anode chamber, and the total bacterial concentration was 3×10 11 CFU / mL;

[0147] The concentration of sulfate-reducing bacteria in the mixed microbial agent is 22 wt %, the concentration of Shewanella putrefaciens is 32 wt %, and the balance is actinomycetes;

[0148] The cathode chamber is provided with a cathode electrode, the cathode electrode substrate is formed by pressing the modified biochar obtained in step (3), and a HKUST-1 catalyst accounting for 4 wt% of the cathode electrode substrate is loaded thereon;

[0149] (5) The secondary filtered wastewater is filtered using modified biochar at a rate of 20 mg / L of the secondary filtered wastewater to prepare water for greening.

[0150] Referring to the greening water detection method of Example 1, the same performance test was performed on the example, and the specific characterization results are as follows.

[0151]

[0152] Meanwhile, no Escherichia coli was detected in the greening water prepared in the example, and the total concentration of coliform bacteria was ≤150 / mL.

[0153] The above test results show that the greening water obtained in this case fully meets the requirements of GB / T 25499-2010 for greening water and can be used directly as greening water. In addition, after the safety and effectiveness were verified in the laboratory, the special greening water was contacted with the municipal department for field verification, and comparative tests were carried out in some intersection flower beds.

[0154] The original flower bed had six planting areas, three of which were replaced with the greening water prepared in this example as the test area, and the other three maintained the original water quality as the control area. Greening irrigation was carried out according to the original irrigation plan, and the flower beds were planted with landscape flowers of cosmos. After 45 days of irrigation, the number of cosmos flowers in the test area increased by about 10.9% compared with the number of cosmos flowers in the control area, which had a relatively obvious improvement effect, and the landscape flowers grew well. The soil test was qualified after irrigation, and there was no pollution or harm to the soil.

[0155] Example 4: A method for recycling agricultural wastewater,

[0156] The method comprises:

[0157] (1) Bacillus licheniformis, Sphingomonas, Cladosporium and Bacillus were mixed in a volume ratio of 3.5:6.5:1:2. The concentration of each bacterial agent was 5×10 11 CFU / mL, the concentration difference value is less than 5%. The mixed bacterial agent and sodium alginate aqueous solution (4 wt%) were mixed at a volume ratio of 1:1.8 to form a mixed bacterial solution, and then calcium salt was added. The amount of calcium salt added was 33 wt% of the sodium alginate content in the sodium alginate solution. Subsequently, the mixed bacterial solution was mixed with 4.5 times the volume of liquid paraffin to form an oil-in-water emulsion, and a sedimentation agent was added and precipitated to obtain a microbial capsule.

[0158] The liquid paraffin contains 1.0 wt% of Span 80;

[0159] The above-mentioned sedimentation agent is a 2.5 mol / L calcium chloride solution containing 1.0 wt% tween-80, and the sedimentation agent is slowly added dropwise until the sediment at the bottom of the solution no longer increases;

[0160] (2) Agricultural wastewater, waste biomass and microbial capsules were mixed evenly in a mass ratio of 6:1.5:0.2, fermented at 25 °C for 120 h, and filtered to obtain primary filtered biomass and primary filtered wastewater, respectively;

[0161] The above-mentioned waste biomass is rice straw and husk.

[0162] (3) The primary filtered biomass and ferric chloride were mixed evenly in a mass ratio of 1:1.3, and sintered at 750 °C in a nitrogen atmosphere for 3 h to obtain a coarse modified biochar. The coarse modified biochar was ground to a particle size of 90 mesh by ball milling to obtain a modified biochar.

[0163] (4) Build a microbial fuel cell and pass the primary filtered wastewater into the microbial fuel cell for secondary degradation. When the output current of the microbial fuel cell is ≤0.02 mA, stop the process to obtain secondary filtered wastewater.

[0164] The microbial fuel cell construction method is as follows:

[0165] The battery is separated into an anode chamber and a cathode chamber by a proton exchange membrane, and the pre-filtered wastewater obtained in step (2) is added as an electrolyte into the anode chamber and the cathode chamber;

[0166] The anode chamber is provided with an anode electrode, which is a graphite plate with a surface uniformly covered with a positive electrode active material;

[0167] The positive electrode active material is composed of polyaniline, polythiophene and the modified biochar obtained in step (3), wherein the content of polyaniline is 25 wt%, the content of modified biochar is 6 wt%, and the balance is polythiophene. The total amount of the positive electrode active material is 22 wt% of the graphite plate;

[0168] The mixed microbial agent was added to the electrolyte in the anode chamber, the amount of the mixed microbial agent was 0.01 mL / mL of the electrolyte in the anode chamber, and the total bacterial concentration was 5×10 11 CFU / mL;

[0169] The concentration of sulfate-reducing bacteria in the mixed microbial agent is 18 wt %, the concentration of Shewanella putrefaciens is 28 wt %, and the balance is actinomycetes;

[0170] The cathode chamber is provided with a cathode electrode, the cathode electrode substrate is formed by pressing the modified biochar obtained in step (3), and a HKUST-1 catalyst accounting for 2 wt% of the cathode electrode substrate is loaded thereon;

[0171] (5) The secondary filtered wastewater is filtered using modified biochar at a rate of 15 mg / L of the secondary filtered wastewater to prepare water for greening.

[0172] Referring to the greening water detection method of Example 1, the same performance test was performed on the example, and the specific characterization results are as follows.

[0173]

[0174] Meanwhile, no Escherichia coli was detected in the greening water prepared in the example, and the total concentration of coliform bacteria was ≤150 / mL.

[0175] The above test results show that the greening water obtained in this case fully meets the requirements of GB / T 25499-2010 for greening water and can be used directly as greening water. In addition, after the safety and effectiveness were verified in the laboratory, the special nutrient greening water was contacted with the municipal department for field verification, and a comparative test was conducted in the greening landscape layout area along the elevated road.

[0176] A total of 120 m long plants planted in the green landscape layout area along the elevated road were selected as experimental objects, of which 60 m was used as the experimental area and the remaining 60 m was used as the control area. There were 97 landscape roses in the experimental area and 101 landscape roses in the control area. The growth of the original roses in the experimental and control areas was basically the same. The irrigation water in the experimental area was replaced with the greening water prepared in this example, and the control area maintained the original water quality for irrigation, and greening irrigation was carried out according to the original irrigation plan. After 48 days of irrigation, the number of roses in the experimental area increased by about 8.6% compared with the number of roses in the control area, which had a relatively obvious improvement effect, and the landscape flowers grew well. The cultivation soil after irrigation was tested to be qualified, and there was no pollution or harm to the soil.

[0177] Example 5: A method for recycling agricultural wastewater,

[0178] The method comprises:

[0179] (1) Bacillus licheniformis, Sphingomonas, Cladosporium and Bacillus were mixed in a volume ratio of 3.5:6.5:1:2. The concentration of each bacterial agent was 5×10 11CFU / mL, the concentration difference value is less than 5%. The mixed bacterial agent and sodium alginate aqueous solution (4 wt%) are mixed evenly at a volume ratio of 1:1.8 to form a mixed bacterial solution, and then calcium salt is added. The amount of calcium salt added is 33 wt% of the sodium alginate content in the sodium alginate solution. Subsequently, the mixed bacterial solution is mixed with 4.5 times the volume of liquid paraffin to form an oil-in-water emulsion, and a sedimentation agent is added and precipitated to obtain a microbial capsule;

[0180] The liquid paraffin contains 1.0 wt% of Span 80;

[0181] The above-mentioned sedimentation agent is a 2.5 mol / L calcium chloride solution containing 1.0 wt% tween-80, and the sedimentation agent is slowly added dropwise until the sediment at the bottom of the solution no longer increases;

[0182] (2) Agricultural wastewater, waste biomass and microbial capsules were mixed evenly in a mass ratio of 6:1.5:0.2, fermented at 25 °C for 120 h, and filtered to obtain primary filtered biomass and primary filtered wastewater, respectively;

[0183] The above-mentioned waste biomass is peanut straw and pod shell.

[0184] (3) The primary filtered biomass and ferric chloride were mixed evenly in a mass ratio of 1:1.3, and sintered at 750 °C in a nitrogen atmosphere for 3 h to obtain a coarse modified biochar. The coarse modified biochar was ground to a particle size of 90 mesh by ball milling to obtain a modified biochar.

[0185] (4) Building a microbial fuel cell, passing the primary filtered wastewater into the microbial fuel cell for secondary degradation, and stopping when the output current of the microbial fuel cell is no greater than ≤0.02 mA to obtain secondary filtered wastewater;

[0186] The microbial fuel cell construction method is as follows:

[0187] The battery is separated into an anode chamber and a cathode chamber by a proton exchange membrane, and the pre-filtered wastewater obtained in step (2) is added as an electrolyte into the anode chamber and the cathode chamber;

[0188] The anode chamber is provided with an anode electrode, which is a graphite plate with a surface uniformly covered with a positive electrode active material;

[0189] The positive electrode active material is composed of polyaniline, polythiophene and the modified biochar obtained in step (3), wherein the content of polyaniline is 25 wt%, the content of modified biochar is 6 wt%, and the balance is polythiophene. The total amount of the positive electrode active material is 22 wt% of the graphite plate;

[0190] The mixed microbial agent was added to the electrolyte in the anode chamber, the amount of the mixed microbial agent was 0.01 mL / mL of the electrolyte in the anode chamber, and the total bacterial concentration was 5×10 11 CFU / mL;

[0191] The concentration of sulfate-reducing bacteria in the mixed microbial agent is 18 wt %, the concentration of Shewanella putrefaciens is 28 wt %, and the balance is actinomycetes;

[0192] The cathode chamber is provided with a cathode electrode, the cathode electrode substrate is formed by pressing the modified biochar obtained in step (3), and a HKUST-1 catalyst accounting for 2 wt% of the cathode electrode substrate is loaded thereon;

[0193] (5) The secondary filtered wastewater is filtered using modified biochar at a rate of 15 mg / L of the secondary filtered wastewater to prepare water for greening.

[0194] Referring to the greening water detection method of Example 1, the same performance test was performed on the example, and the specific characterization results are as follows.

[0195]

[0196] Meanwhile, no Escherichia coli was detected in the greening water prepared in the example, and the total concentration of coliform bacteria was ≤150 / mL.

[0197] The above test results show that the greening water obtained in this case fully meets the requirements of GB / T 25499-2010 for greening water and can be used directly as greening water. In addition, after the safety and effectiveness were verified in the laboratory, the special greening water was contacted with the municipal department for field verification, and comparative tests were carried out in some roadside green belts.

[0198] There were five heather shrubs in the original green belt, two of which were irrigated with the greening water prepared in this example as the test area, and the other three were kept with the original water quality as the control area, and the greening irrigation was carried out according to the original irrigation plan. After 45 days of irrigation, the number of heather flowers in the test area increased by about 26.7% compared with the number of heather flowers in the control area, which had a relatively obvious improvement effect, and the landscape flowers grew well. The soil test was qualified after irrigation, and there was no pollution or harm to the soil.

[0199] Comparative Example 1: A method for recycling agricultural wastewater. Its specific preparation method is the same as that of Example 1. The comparative example only changes the unique microbial agent component of the present invention, and uses an equal amount of Monosporus to replace Cladosporium to prepare greening water. The greening water prepared in the comparative example is subjected to partial performance testing in the same manner as in Example 1, and the characterization results are as follows.

[0200]

[0201] At the same time, a small amount of Escherichia coli was detected in the greening water prepared in the comparative example, and the total concentration of coliform bacteria was greater than 200 / mL.

[0202] Comparative Example 2: A method for recycling agricultural wastewater. Its specific preparation method is the same as that of Example 1. The comparative example only changes the unique microbial agent component of the present invention, and uses an equal amount of bifidobacterium amine to replace Sphingomonas to prepare greening water. The greening water prepared in the comparative example is subjected to partial performance testing in the same manner as in Example 1, and the characterization results are as follows.

[0203]

[0204] At the same time, a small amount of Escherichia coli was detected in the greening water prepared in the comparative example, and the total concentration of coliform bacteria was greater than 200 / mL.

[0205] Comparative Example 3: A method for recycling agricultural wastewater. Its specific preparation method is the same as that of Example 1. The comparative example only changes the unique microbial agent component of the present invention, and uses an equal amount of Bacillus subtilis instead of Bacillus to prepare greening water. The greening water prepared in the comparative example is subjected to partial performance testing in the same manner as in Example 1, and the characterization results are as follows.

[0206]

[0207] At the same time, a small amount of Escherichia coli was detected in the greening water prepared in the comparative example, and the total concentration of coliform bacteria was greater than 200 / mL.

[0208] Comprehensive analysis of the characterization results of the comparative examples shows that the pH value of the greening water prepared by the comparative examples varies greatly, which can reflect at a macroscopic level that the relationship between the bacterial communities in the comparative examples is not stable, especially for comparative example 3, which does not meet my country's urban greening water standards. A comprehensive comparison of the data of the embodiment with the data of the comparative examples shows that the most drastic data change is the content of organic matter in the treated water samples, and the comparative example data has increased significantly, which macroscopically reflects that the microbial community relationship constructed by the comparative examples cannot reflect high efficiency in the treatment of organic matter. In addition, the greening water treated by the comparative examples was found to contain Escherichia coli, which did not meet my country's urban greening water standards, proving that the use of microorganisms of the same genus cannot completely replace the solution provided by the present invention to achieve the expected antibacterial and sterilization effects.

[0209] Comparative Example 4: A method for recycling agricultural wastewater, wherein the specific preparation method is the same as that of Example 1, except that the microbial fuel cell unique to the present invention is not constructed and used, and a commercially available microbial fuel cell is used instead (the proton membrane is used to separate the anode chamber and the cathode chamber, the electrolyte is pre-filtered wastewater, the anode and the cathode are carbon cloth electrodes, the electrolyte in the anode chamber contains Shewanella, Geobacter and Klebsiella in a concentration ratio of 1:1:2, and the total bacterial concentration is the same as that in Example 1, both being 4×10 11 CFU / mL, run until the output current is ≤2 mA), and prepare the greening water. The greening water prepared in the comparative example is partially tested in the same way as in Example 1, and the characterization results are as follows.

[0210]

[0211] At the same time, the presence of Escherichia coli was not detected in the greening water prepared in the comparative example, and the total concentration of coliform bacteria was ≤150 / mL.

[0212] In addition, after the safety and effectiveness were verified in the laboratory, a plant cultivation experiment was conducted. Five roses were cultivated separately in the laboratory, and each rose was cultivated separately in a flowerpot. The irrigation water for two of them was replaced with the greening water prepared in this example as the test area, and the other three were maintained with normal urban greening water as the control area. After 42 days of irrigation, the roses in the test area bloomed earlier than those in the control area, with a relatively obvious improvement effect, but the flowering period ended prematurely. The soil in the test area was tested, and it was found that antagonistic bacteria existed in the soil, which caused the rose flowering period to end prematurely. If used in nature, it will cause the root growth of perennial plants to be hindered, affecting plant development.

[0213] Analyzing the above characterization results, the mass concentration of ammonia nitrogen and the sulfide content in the greening water prepared in the comparative example are significantly higher than the data in the embodiment. After further observation and analysis, it is concluded that due to the "passivation" of the internal bacterial flora of the microbial fuel cell during the esterase catalysis process, the fuel cell has defects in the treatment and degradation of organic matter, which may cause eutrophication of the water system in the natural environment at a macroscopic level.

[0214] Comparative Example 5: A method for recycling agricultural wastewater. Its specific preparation method is the same as that of Example 1, except that the comparative example does not add waste biomass and subsequent waste biomass processing (the biochar-related materials used in the remaining steps, such as modified biochar, are replaced with commercially available biochar materials), and prepares greening water. The greening water prepared in the comparative example is subjected to partial performance testing in the same manner as in Example 1, and the characterization results are as follows.

[0215]

[0216] Meanwhile, the presence of Escherichia coli was not detected in the greening water prepared in the comparative example.

[0217] Analyzing the above characterization results, in the greening water prepared by the comparative example, since no biomass is added during the fermentation process, the mixed bacterial community can only carry out mineralization reaction to reduce the content of organic matter in the wastewater. However, due to the lack of a suitable carrier as a storage point for metabolic waste and the subsequent decolorization and adsorption of wastewater by modified biochar, the heavy metal content in the greening water prepared by the comparative example obviously exceeds the standard and does not meet the standards for urban greening water in my country. In addition, the suspended particles in the greening water system prepared by the comparative example also increase significantly, and it cannot be used as urban greening water.

Claims

1. A method for recycling agricultural wastewater, characterized in that: The method comprises: (1) Mixing agricultural wastewater, waste biomass and microbial capsules in proportion and fermenting them uniformly, and filtering to obtain primary filtered biomass and primary filtered wastewater; (2) mixing the primary filtered biomass and inorganic salt in proportion, sintering to obtain coarse modified biochar, and ball milling to obtain modified biochar; (3) Passing the primary filtered wastewater into a microbial fuel cell for secondary degradation to produce secondary filtered wastewater; (4) Filtering the secondary filtered wastewater using modified biochar to prepare water for greening; The method for constructing the microbial fuel cell in step (3) is as follows: The battery is separated into an anode chamber and a cathode chamber by a proton exchange membrane, and the pre-filtered wastewater obtained in step (1) is added as an electrolyte into the anode chamber and the cathode chamber; The anode chamber is provided with an anode electrode, which is a graphite plate with a surface uniformly covered with a positive electrode active material; The positive electrode active material is composed of polyaniline, polythiophene and the modified biochar obtained in step (2), wherein the content of polyaniline is 25-35 wt%, the content of modified biochar is 6-8 wt%, and the balance is polythiophene. The total amount of the positive electrode active material is 22-30 wt% of the graphite plate; The mixed microbial agent is added to the electrolyte in the anode chamber, the amount of the mixed microbial agent is 0.01-0.05 mL / mL of the electrolyte in the anode chamber, and the total bacterial concentration is 3×10 11 ~5×10 11 CFU / mL; The concentration of sulfate-reducing bacteria in the mixed microbial agent is 18-22%, the concentration of Shewanella putrefaciens is 28-32wt%, and the balance is actinomycetes; The cathode chamber is provided with a cathode electrode, and the cathode electrode substrate is formed by pressing the modified biochar obtained in step (2), and 2 to 4 wt% of HKUST-1 catalyst is loaded on the cathode electrode substrate.

2. The method for recycling agricultural wastewater according to claim 1, characterized in that: The waste biomass in step (1) is agricultural waste; The agricultural waste includes waste corn biomass and / or waste rice biomass and / or waste peanut biomass; In step (1), the agricultural wastewater, waste biomass and microbial capsules are uniformly mixed in a mass ratio of (5-7):1.5:(0.1-0.3).

3. A method for recycling agricultural wastewater according to claim 1 or 2, characterized in that: The fermentation process in step (1) is carried out at 20-40°C and the fermentation is continued for 96-144 hours.

4. The method for recycling agricultural wastewater according to claim 1, characterized in that: The inorganic salt in step (2) is ferric chloride; In step (2), the pre-filtered biomass and the inorganic salt are uniformly mixed in a mass ratio of 1: (1.2-1.4).

5. A method for recycling agricultural wastewater according to claim 1 or 4, characterized in that: The sintering process in step (2) is carried out in a protective atmosphere at a temperature of 700 to 800° C. for 2 to 4 hours; The ball milling in step (2) is to grind the coarse modified biochar into particles with a size of 80 to 100 meshes.

6. The method for recycling agricultural wastewater according to claim 1, characterized in that: When the secondary degradation in step (3) reaches an output current of the microbial fuel cell of ≤0.02 mA, the wastewater in the anode chamber and the cathode chamber is stopped and recovered, i.e., the secondary filtered wastewater.

7. The method for recycling agricultural wastewater according to claim 1, characterized in that: The amount of modified biochar used in step (4) is 10-20 mg / L of primary filtered wastewater.

8. The method for recycling agricultural wastewater according to claim 1, characterized in that: The greening water obtained in step (4) is used for urban greening irrigation and / or early irrigation after plant transplanting.

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