Method for preparing liquid fertilizer by black water oxidation fermentation

Abstract

The invention discloses a method for preparing a liquid fertilizer through black water oxidation fermentation, and relates to the field of black water recycling. The invention aims to solve the technical problems of low conversion efficiency and poor product stability in current black water resource utilization. The method comprises black water pretreatment; performing oxidative fermentation to obtain fermentation liquor; and adding nano diatomite, concentrating, sterilizing and cooling. According to the invention, the dual goals of efficient black water treatment and high-value liquid fertilizer production are realized. The method has the advantages that microbial metabolism regulation and control are precise, energy consumption is minimized, products are recycled, and the development requirements of circular economy and green agriculture are met. The prepared liquid fertilizer is used for farmland production.

Description

Technical Field

[0001] The present invention relates to the field of black water resource utilization. Background Art

[0002] Fermentation of blackwater (such as livestock and poultry manure and domestic sewage) to produce liquid fertilizer is an important area of agricultural waste resource utilization. Existing technologies primarily utilize microbial fermentation to decompose organic matter, converting it into liquid fertilizer containing nitrogen, phosphorus, potassium, and humic acid. However, these technologies present several challenges: traditional bacterial strains are easily inactivated by high concentrations of organic matter, high temperatures, or acidic environments; fermentation cycles can take as long as 10-15 days; and these processes are poorly adapted to complex blackwater sources (such as livestock wastewater containing antibiotics or disinfectants). Reliance on manual adjustments to temperature, pH, and aeration levels, coupled with a lack of real-time monitoring and automated control, can lead to uneven fermentation or even failure. Liquid fertilizers are prone to stratification, bloating, or crystallization, resulting in a short storage life of typically less than six months. They also have a high moisture content (greater than 90%), increasing transportation costs. Incompletely decomposed liquid fertilizers may harbor pathogens or parasite eggs, posing a risk of seedling burn if applied directly. Summary of the Invention

[0003] In order to solve the technical problems of low conversion efficiency and poor product stability in the current black water resource utilization, the present invention provides a method for preparing liquid fertilizer by utilizing black water oxidation fermentation.

[0004] A method for preparing liquid fertilizer by using black water oxidation fermentation is specifically carried out according to the following steps:

[0005] 1. Filter the black water and pass it into the sedimentation tank for solid-liquid separation. Collect the liquid part and sterilize it. Then test the carbon-nitrogen ratio and adjust the carbon-nitrogen ratio to 15-25 and the pH to 5.5-6.

[0006] 2. Add biochar to the black water treated in step 1, then add ferrate, control the temperature to 30-35°C, stir for 10-12 hours, and filter to recover the biochar;

[0007] The filtered liquid is pumped into an aerobic reactor, and phosphate-solubilizing bacteria, nitrifying bacteria, and Bacillus subtilis are added in a volume ratio of 2:1:2. Micro-nano aeration is used to control the DO value to 2.0-3.0 mg / L, the pH is maintained at 4.0-4.5, and the temperature is 35-40°C. The reaction is carried out for 70-80 hours to obtain a fermentation mixture.

[0008] 3. Add nano-diatomaceous earth to the fermentation mixture obtained in step 2, stir evenly, and then introduce it into a vacuum evaporator for concentration, followed by sterilization, cooling, and filling into a sealed container to complete the preparation of liquid fertilizer.

[0009] Furthermore, the COD value of the liquid portion collected in step 1 is 8000~15000 mg / L.

[0010] Furthermore, in step 1, if the carbon-nitrogen ratio is detected to be greater than 25, urea or ammonium sulfate is added to adjust the carbon-nitrogen ratio to 20-25; if the carbon-nitrogen ratio is detected to be less than 15, molasses or glucose is added to adjust the carbon-nitrogen ratio to 15-20.

[0011] Furthermore, the amount of biochar added in step 2 is 5-10% of the mass of the black water, and the particle size is less than 1 mm;

[0012] The biochar is straw, coconut shell or wood, and is formed by pyrolysis.

[0013] Furthermore, the ferrate in step 2 is potassium ferrate or sodium ferrate, and the concentration of ferrate in the black water after addition is controlled to be 3-4 mmol / L.

[0014] Furthermore, in step 2, the stirring speed is controlled to be 100-300 rpm.

[0015] Furthermore, in step 2, the total dosage of phosphate-solubilizing bacteria, nitrifying bacteria and Bacillus subtilis is 2% of the volume of the hydrolyzate.

[0016] Furthermore, in step three, the particle size of the nano-diatomaceous earth is 100 nm, and the amount added is 0.5-1.0% of the mass of the fermentation mixture.

[0017] Furthermore, in step three, the pressure of the vacuum evaporator is controlled to be -0.08 MPa and the temperature is controlled to be 44-46°C.

[0018] Furthermore, step three adopts pasteurization, controls the temperature to 65° C., and sterilizes for 30 minutes.

[0019] Beneficial effects of the present invention:

[0020] The present invention first combines biochar with a ferrate carbon material to degrade refractory organic matter in blackwater. Biochar's surface contains numerous reducing functional groups, such as phenolic hydroxyl groups and carbonyl groups, and these functional groups have low reactivity with ferrate, allowing for the slow generation of intermediate-valent iron. Therefore, biochar activation of ferrate is a sustainable process, continuously generating highly reactive intermediate iron to degrade pollutants and improve organic matter removal efficiency. Furthermore, because biochar has excellent adsorption and electron transfer capabilities, after organic pollutants and ferrate are adsorbed on the carbon material's surface, the biochar can act as a bridge for electron transfer, enhancing the electron transfer process between the organic pollutants and ferrate, thereby further enhancing ferrate degradation of pollutants. Furthermore, ferrate oxidation of the biochar's surface functional groups generates responsive carbon free radicals, which further oxidize organic pollutants. Furthermore, the biochar's adsorption removes toxic and harmful pollutants and precursors of disinfection byproducts during the reaction, thereby reducing byproduct formation.

[0021] During the fermentation phase, the present invention further ferments the black water using a microbial synergistic metabolism method, accelerating the conversion of organic matter. Phosphate-solubilizing bacteria, nitrifying bacteria, and Bacillus subtilis, under micro-nano aeration conditions, further convert small-molecule acids into humic acid and amino acids, while simultaneously inhibiting the growth of putrefactive bacteria and enhancing humification efficiency. The addition of nano-diatomaceous earth in the present invention extends the suspension stability of the liquid fertilizer to 12 months, enhancing product stability.

[0022] This invention achieves the dual goals of efficient blackwater treatment and high-value liquid fertilizer production. Its advantages include precise regulation of microbial metabolism, minimized energy consumption, and product resource utilization, meeting the development needs of a circular economy and green agriculture.

[0023] The liquid fertilizer prepared by the invention is used for farmland production. DETAILED DESCRIPTION

[0024] Specific embodiment 1: This embodiment is a method for preparing liquid fertilizer by using black water oxidation fermentation, which is specifically carried out in the following steps:

[0025] 1. Filter the black water and pass it into the sedimentation tank for solid-liquid separation. Collect the liquid part and sterilize it. Then test the carbon-nitrogen ratio and adjust the carbon-nitrogen ratio to 15-25 and the pH to 5.5-6.

[0026] 2. Add biochar to the black water treated in step 1, then add ferrate, control the temperature to 30-35°C, stir for 10-12 hours, and filter to recover the biochar;

[0027] The filtered liquid is pumped into an aerobic reactor, and phosphate-solubilizing bacteria, nitrifying bacteria, and Bacillus subtilis are added in a volume ratio of 2:1:2. Micro-nano aeration is used to control the DO value to 2.0-3.0 mg / L, the pH is maintained at 4.0-4.5, and the temperature is 35-40°C. The reaction is carried out for 70-80 hours to obtain a fermentation mixture.

[0028] 3. Add nano-diatomaceous earth to the fermentation mixture obtained in step 2, stir evenly, and then introduce it into a vacuum evaporator for concentration, followed by sterilization, cooling, and filling into a sealed container to complete the preparation of liquid fertilizer.

[0029] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that the COD value of the collected liquid portion in step 1 is 8000-15000 mg / L. Other aspects are the same as specific embodiment 1.

[0030] Specific embodiment three: This embodiment differs from specific embodiments one or two in that, in step one, if the detected carbon-nitrogen ratio is greater than 25, urea or ammonium sulfate is added to adjust the carbon-nitrogen ratio to 20-25; if the detected carbon-nitrogen ratio is less than 15, molasses or glucose is added to adjust the carbon-nitrogen ratio to 15-20. Other steps are the same as specific embodiments one or two.

[0031] Specific embodiment 4: This embodiment differs from any one of specific embodiments 1 to 3 in that: the amount of biochar added in step 2 is 5-10% of the mass of the black water, and the particle size is less than 1 mm;

[0032] The biochar is straw, coconut shell or wood, and is formed by pyrolysis. Other embodiments are the same as those in the first to third embodiments.

[0033] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the ferrate in step 2 is potassium ferrate or sodium ferrate, and the concentration of ferrate in the black water after addition is controlled to be 3-4 mmol / L. Other aspects are the same as specific embodiments 1 to 4.

[0034] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that the stirring speed is controlled to be 100-300 rpm in step 2. The rest is the same as specific embodiments 1 to 5.

[0035] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that the total dosage of phosphate-solubilizing bacteria, nitrifying bacteria, and Bacillus subtilis in step 2 is 2% of the volume of the hydrolyzed solution. Other aspects are the same as specific embodiments 1 to 6.

[0036] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the particle size of the nano-diatomaceous earth in step 3 is 100 nm and the amount added is 0.5-1.0% of the mass of the fermentation mixture. Other aspects are the same as specific embodiments 1 to 7.

[0037] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that: in step 3, the pressure of the vacuum evaporator is controlled to be -0.08 MPa and the temperature is controlled to be 44-46° C. The rest is the same as specific embodiments 1 to 8.

[0038] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 39 in that step 3 uses pasteurization, with the temperature controlled at 65° C. and the sterilization time is 30 minutes. The rest is the same as specific embodiments 1 to 9.

[0039] The content of the present invention is not limited to the content of the above-mentioned embodiments. The combination of one or more specific embodiments can also achieve the purpose of the invention.

[0040] Example:

[0041] A method for preparing liquid fertilizer by using black water oxidation fermentation is specifically carried out according to the following steps:

[0042] First, filter the black water (domestic sewage from the sewage treatment plant) through a screen to remove large particles of impurities, pass it into a sedimentation tank for solid-liquid separation, collect the liquid part with a COD of 10500 mg / L, then sterilize it, and then test the carbon-nitrogen ratio (C / N) to be greater than 25. Add ammonium sulfate to adjust the carbon-nitrogen ratio to 22 and adjust the pH to 5.5-6.

[0043] 2. Add biochar (biochar formed by pyrolysis of wood) to the black water treated in step 1, and then add sodium ferrate. After addition, the concentration of ferrate in the black water is 4 mmol / L. Control the temperature at 30-35°C, stir for 10-12 hours, and filter to recover the biochar.

[0044] The filtered liquid is pumped into an aerobic reactor, and phosphate-solubilizing bacteria, nitrifying bacteria, and Bacillus subtilis are added in a volume ratio of 2:1:2. Micro-nano aeration is used to control the DO value to 2.0-3.0 mg / L, the pH is maintained at 4.0-4.5, and the temperature is 35-40°C. The reaction is carried out for 70-80 hours to obtain a fermentation mixture.

[0045] 3. Add nano-diatomaceous earth to the fermentation mixture obtained in step 2 in an amount of 0.8% by mass of the fermentation mixture, stir evenly, and then introduce it into a vacuum evaporator, control the pressure to -0.08MPa and the temperature to 45°C, carry out concentration treatment, and then sterilize, control the temperature to 65°C, sterilize for 30min, cool, and fill it into a closed container to complete the preparation of liquid fertilizer.

[0046] The phosphate-solubilizing bacteria, nitrifying bacteria and Bacillus subtilis are all commercially available strains.

[0047] The liquid fertilizer prepared in this example was tested: the final COD of the liquid fertilizer was 3500 mg / L, the total nitrogen was ≥1.2%, the total phosphorus was ≥0.8%, and the humic acid was ≥0.5%.

[0048] Microbiological safety: Escherichia coli was not detected (GB 20287-2006 standard).

[0049] Storage conditions: Store away from light at room temperature (5-25°C). Shelf life is 12 months.

[0050] The invention adds nano-diatomaceous earth to extend the suspension stability of liquid fertilizer to 12 months, and enhances product stability; vacuum low-temperature concentration technology reduces the moisture content from 90% to 70%, and reduces transportation costs by 50%.

[0051] The prepared liquid fertilizer was applied to wheat fields (diluted 10 times), and the soil organic matter increased by 0.5%, and the heavy metal residue was 50% lower than the national standard limit.

Claims

1. A method for preparing liquid fertilizer by utilizing black water oxidation fermentation, characterized in that The method is specifically carried out in the following steps:

1. Filter the black water and pass it into the sedimentation tank for solid-liquid separation. Collect the liquid part and sterilize it. Then test the carbon-nitrogen ratio and adjust the carbon-nitrogen ratio to 15-25 and the pH to 5.5-6.

2. Add biochar to the black water treated in step 1, then add ferrate, control the temperature to 30-35°C, stir for 10-12 hours, and filter to recover the biochar; The filtered liquid is pumped into an aerobic reactor, and phosphate-solubilizing bacteria, nitrifying bacteria, and Bacillus subtilis are added in a volume ratio of 2:1:

2. Micro-nano aeration is used to control the DO value to 2.0-3.0 mg / L, the pH is maintained at 4.0-4.5, and the temperature is 35-40°C. The reaction is carried out for 70-80 hours to obtain a fermentation mixture.

3. Add nano-diatomaceous earth to the fermentation mixture obtained in step 2, stir evenly, and then introduce it into a vacuum evaporator for concentration, followed by sterilization, cooling, and filling into a sealed container to complete the preparation of liquid fertilizer.

2. The method for preparing liquid fertilizer by utilizing black water oxidation and fermentation according to claim 1, characterized in that The COD value of the liquid portion collected in step 1 is 8000~15000 mg / L.

3. The method for preparing liquid fertilizer by utilizing black water oxidation and fermentation according to claim 1, characterized in that Step 1: If the carbon-nitrogen ratio is greater than 25, add urea or ammonium sulfate to adjust the carbon-nitrogen ratio to 20-25; If the detected carbon-nitrogen ratio is less than 15, add molasses or glucose to adjust the carbon-nitrogen ratio to 15-20.

4. The method for preparing liquid fertilizer by utilizing black water oxidation and fermentation according to claim 1, characterized in that The amount of biochar added in step 2 is 5-10% of the mass of black water, and the particle size is less than 1mm; The biochar is straw, coconut shell or wood, and is formed by pyrolysis.

5. The method for preparing liquid fertilizer by utilizing black water oxidation and fermentation according to claim 1, characterized in that The ferrate in step 2 is potassium ferrate or sodium ferrate, The concentration of ferrate in black water after addition is controlled to be 3~4mmol / L.

6. The method for preparing liquid fertilizer by utilizing black water oxidation and fermentation according to claim 1, characterized in that Step 2: Control the stirring speed to 100~300rpm.

7. The method for preparing liquid fertilizer by utilizing black water oxidation and fermentation according to claim 1, characterized in that In step 2, the total dosage of phosphate-solubilizing bacteria, nitrifying bacteria and Bacillus subtilis is 2% of the volume of the hydrolyzate.

8. The method for preparing liquid fertilizer by utilizing black water oxidation and fermentation according to claim 1, characterized in that Step 3: The particle size of nano-diatomaceous earth is 100 nm, and the amount added is 0.5-1.0% of the mass of the fermentation mixture.

9. The method for preparing liquid fertilizer by utilizing black water oxidation and fermentation according to claim 1, characterized in that Step 3: Control the pressure of the vacuum evaporator to -0.08 MPa and the temperature to 44~46°C.

10. The method for preparing liquid fertilizer by utilizing black water oxidation and fermentation according to claim 1, characterized in that Step three is pasteurization, controlling the temperature at 65°C and sterilizing for 30 minutes.