Method for producing liquid fertilizer by using sludge hydrothermal carbonization liquid

Abstract

The invention belongs to the fields of fermentation engineering and sludge disposal and resource utilization, and relates to a method for producing a liquid fertilizer by using a sludge hydrothermal carbonization solution. The method comprises the following steps: by taking a sludge hydrothermal carbonization solution as a carbon source, carrying out aerobic fermentation treatment by adopting S.cerevisiae, thereby obtaining the product. By adopting the method, a seed germination test proves that the compound can be used as a liquid fertilizer raw material; the COD (Chemical Oxygen Demand) removal rate of the hydrothermal carbonization liquid treated by the saccharomycetes can reach 70%, and other pollutants in the hydrothermal carbonization liquid are degraded to a certain extent. According to the method, the hydrothermal carbonization liquid is used for replacing a traditional carbon source, so that the raw material cost is reduced, all waste water is utilized, the liquid fertilizer product can be efficiently produced, the problem of high pollution treatment cost of the conventional hydrothermal carbonization liquid is solved, and the fermentation liquid can be applied as the liquid fertilizer.

Description

Technical Field

[0001] The invention belongs to the field of fermentation engineering and sludge disposal and resource utilization, and relates to a method for producing liquid fertilizer by utilizing sludge hydrothermal carbonization liquid. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] The hydrothermal carbonization process has the advantages of low reaction temperature and adaptability to sludge with different water contents. It is a common technology in sludge treatment and resource utilization. The main product of sludge hydrothermal carbonization is sludge-based hydrothermal carbon, which is a potential fuel source. Hydrothermal carbonization liquid is a high-concentration organic wastewater produced by the hydrothermal carbonization process. It is rich in organic matter such as humic acid, protein, volatile fatty acids (such as acetic acid, propionic acid) and sugars. It also contains inorganic minerals such as N, P, and K. Therefore, hydrothermal carbonization liquid is a potential biomass energy resource. The liquid contains not only high-concentration organic pollutants, but also NH4 + PO4 3+ , Cl - , Ca 2+ and Na + The COD of sludge hydrothermal carbonization liquid is 35,000-50,000 mg / L. If it is not properly treated, it will cause potential environmental pollution risks. At the same time, the BOD5 of this waste liquid is 10,000-15,000 mg / L, and the BOD / COD ratio is 0.2-0.35. It is not suitable to directly use anaerobic treatment process. In addition, it also contains phenols, aromatic hydrocarbons and long-chain alkanes and other difficult-to-degrade substances, so it is difficult to treat with conventional biochemical methods.

[0004] At present, the utilization of sludge hydrothermal carbonization liquid has received little attention. In traditional hydrothermal carbonization processes, the liquid phase products of hydrothermal carbonization are often paid less attention than solid carbon materials. Although some studies have reported the use of sludge hydrothermal carbonization liquid to recover nitrogen and phosphorus resources and increase the combustion performance of hydrothermal carbon, such technologies usually require the consumption of alkali to adjust the pH and supplement soluble salts such as magnesium, nitrogen and phosphorus. Some researchers have reported the use of "physical and chemical coupling biochemical, biochemical-based" treatment technology for sludge carbonization liquid, but this technology has complex processes, increases the load of the biochemical stage, and does not recover nitrogen and phosphorus resources in the carbonization liquid. Some researchers have also evaporated and concentrated the sludge hydrothermal carbonization liquid and then supplemented it with macroelements and trace elements to prepare liquid fertilizer, but this technology has the disadvantages of high energy consumption and the need to supplement nitrogen, phosphorus, potassium and trace elements, and no fertilizer efficiency test has been conducted. Therefore, how to improve the treatment and utilization efficiency of sludge hydrothermal carbonization liquid, obtain high value-added products and reduce environmental risks is a key issue that needs to be solved urgently.

[0005] Liquid fertilizer, also known as liquid fertilizer, is a new chemical product containing one or more nutrient elements (such as N, P, K) required by crops, which can dissolve solid fertilizers in aqueous solution. Liquid fertilizer types include fertilizers in solution state such as ammonia, liquid ammonia, carbonized ammonia water and fertilizers containing suspensions of solid particles such as mixed aqueous solutions (or suspensions) containing nitrogen fertilizers, phosphate fertilizers and potash fertilizers. Liquid fertilizers, as one of the trends of the development of the fertilizer industry in the world today, have the sustainable advantages of ecological environmental protection in production, use and transportation, and are easy to achieve uniform mixing, good crop absorption, high fertilizer utilization rate and convenient fertilization during fertilization. However, the present invention has found that sludge hydrothermal carbonization liquid has a toxic effect on plants, and it is difficult to directly use it as liquid fertilizer. Summary of the invention

[0006] In order to solve the shortcomings of the prior art, the purpose of the present invention is to provide a method for producing liquid fertilizer using sludge hydrothermal carbonized liquid. The present invention replaces the traditional carbon source with hydrothermal carbonized liquid to ferment and prepare liquid fertilizer, which not only reduces the cost of raw materials, realizes full utilization of wastewater, and simplifies the process, but also can efficiently produce liquid fertilizer products, which not only solves the problem of high pollution treatment cost of conventional hydrothermal carbonized liquid, but also can use the fermentation liquid as liquid fertilizer.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] In a first aspect, a method for producing liquid fertilizer using sludge hydrothermal carbonized liquid is provided, wherein the sludge hydrothermal carbonized liquid is used as a carbon source and aerobic fermentation is performed using Saccharomyces cerevisiae.

[0009] The present invention has been found through research that after being treated with S. cerevisiae, the COD removal rate of the sludge hydrothermal carbonized liquid can reach 70%, other pollutants are also degraded to a certain extent, and the heavy metal content in the sludge hydrothermal carbonized liquid can be reduced, so that the sludge hydrothermal carbonized liquid after fermentation has the premise of being used as liquid fertilizer. The seed germination test proves that the sludge hydrothermal carbonized liquid after fermentation is non-toxic to plants and can be used as liquid fertilizer.

[0010] Aerobic fermentation in the present invention refers to fermentation under aerobic conditions. In some embodiments, after adding saccharomyces cerevisiae seed liquid and sterile hydrothermal carbonization liquid to the sterile fermentation medium, fermentation is carried out under aerobic conditions using sludge hydrothermal carbonization liquid as a carbon source. The present invention uses sludge hydrothermal carbonization liquid to replace the carbon source, which can not only reduce the cost of raw materials, but also expand the application field by utilizing sludge hydrothermal carbonization waste liquid.

[0011] Sterile sludge hydrothermal carbonized liquid can be obtained by sterilizing the sludge hydrothermal carbonized liquid at high temperature and high pressure.

[0012] The aerobic condition refers to the presence of oxygen in the microbial fermentation environment, and the aerobic condition can be obtained by conventional methods in the art, such as setting the shaker speed to ensure a certain amount of dissolved oxygen.

[0013] Except for using sludge hydrothermal carbonized liquid to replace conventional fermentation carbon source, other components except the fermentation medium (the carbon source content here can be zero) used in the present invention can be the same as other components except the carbon source in conventional culture medium for microbial fermentation.

[0014] Specifically, the brewer's yeast seed solution is prepared by inoculating brewer's yeast into a seed culture medium for fermentation. The inoculation amount of brewer's yeast inoculated into the seed culture medium is 4-8% of the volume of the seed culture medium, generally 6%.

[0015] More specifically, the seed culture medium is a glucose yeast peptone culture medium. The fermentation conditions of the microbial seed solution can be conventional fermentation conditions suitable for seed solution in the art.

[0016] In some embodiments, the temperature of aerobic fermentation is 28-35° C. Under this condition, the effect of fermentation to prepare liquid fertilizer is better.

[0017] In some embodiments, in aerobic fermentation, the inoculation amount of brewer's yeast is 5-7%. Under this condition, the effect of preparing liquid fertilizer by fermentation is better.

[0018] In some embodiments, during aerobic fermentation, the pH value of the treatment system is 6.5 to 9. Under such conditions, the effect of preparing liquid fertilizer by fermentation is better.

[0019] In some embodiments, during aerobic fermentation, the COD concentration in the sludge hydrothermal carbonization liquid is 46-54 g / L. The liquid fertilizer prepared by fermentation under such conditions has a higher fertilizer efficiency.

[0020] In some embodiments, the medium used in aerobic fermentation is a yeast fermentation medium. Specifically, the components of the yeast fermentation medium include: 9-11 g / L yeast powder, 18-22 g / L peptone, and 18-22 g / L glucose.

[0021] In a second aspect, a liquid fertilizer is obtained by the above method.

[0022] A third aspect provides an application of the liquid fertilizer in treating plant seed germination.

[0023] In some embodiments, the plant is lettuce.

[0024] The beneficial effects of the present invention are:

[0025] (1) The present invention replaces the traditional carbon source in the fermentation medium with the sludge hydrothermal carbonized liquid, and utilizes the aerobic proliferation characteristics of yeast to apply it as liquid fertilizer after aerobic fermentation, which significantly reduces the production cost and simplifies the production process.

[0026] (2) From the perspective of resource utilization, brewer's yeast uses sludge hydrothermal carbonized liquid as a substrate for aerobic fermentation culture. Its purpose is to utilize the organic matter, nitrogen, phosphorus and trace elements in the sludge carbonized liquid. After aerobic fermentation, it can meet the nutritional needs of plants and can be used as liquid fertilizer, thus realizing the resource utilization of sewage and reducing environmental risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0028] Figure 1 The OD value change curve (a) and pH change curve (b) of the fermentation liquid with the extension of time in Examples 1 to 6 of the present invention are shown.

[0029] Figure 2 The figures are the effects of different COD concentrations on microbial growth and conventional physical and chemical properties of sludge hydrothermal carbonized liquid in Examples 1 to 6 of the present invention; a is a graph showing the change in ammonia nitrogen concentration in sludge hydrothermal carbonized liquid at different COD concentrations before and after fermentation, b is a graph showing the change in phosphate concentration in sludge hydrothermal carbonized liquid at different COD concentrations before and after fermentation, c is a graph showing the change in COD concentration and COD removal rate in sludge hydrothermal carbonized liquid at different COD concentrations before and after fermentation, and d is a graph showing the removal rates of total nitrogen and total phosphorus in sludge hydrothermal carbonized liquid at different COD concentrations after fermentation.

[0030] Figure 3 The graphs are the distribution diagram of differentially expressed genes regulated by carbon sources (a) and the KEGG functional enrichment analysis diagram (b) of the present invention.

[0031] Figure 4 Figure 1 is a diagram for evaluating the phytotoxicity of the hydrothermal carbonized sludge before and after fermentation in Examples 1 to 6 of the present invention; a is a diagram for the relative germination rate, relative root length and seed germination index of the hydrothermal carbonized sludge with different COD concentrations before and after fermentation during the germination test; and b is a diagram for the germination test of the hydrothermal carbonized sludge with different COD concentrations before and after fermentation. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0033] The sludge used in the following examples comes from the dewatered sludge of a domestic sewage treatment plant in Shandong. The obtained sludge hydrothermal carbonization liquid is obtained at 180°C (sludge and deionized water are in a mass ratio of 1:10, and the hydrothermal reaction is carried out at 180°C for 4 hours). The component analysis data are shown in Table 1:

[0034] Table 1 Composition of sludge hydrothermal carbonization liquid

[0035]

[0036]

[0037] The growth of the strain was determined by measuring the optical density of the fermentation broth at a wavelength of 600 nm using a UV-visible spectrophotometer.

[0038] The ammonia nitrogen was determined by the "Determination of Ammonia Nitrogen in Water Quality - Nessler's Reagent Spectrophotometric Method" (HJ535-2009), the total nitrogen was determined by the "Determination of Total Nitrogen in Water Quality - Alkaline Potassium Persulfate Digestion Ultraviolet Spectrophotometric Method" (HJ636-2012), the phosphate and total phosphorus were determined by the "Determination of Total Phosphorus in Water Quality - Ammonium Molybdate Spectrophotometric Method" (GB11893-89), and the COD was determined by the "Determination of Chemical Oxygen Demand in Water Quality - Dichromate Method" (HJ828-2017).

[0039] The brewer's yeast used in the following examples were all purchased from Angel Yeast Co., Ltd.

[0040] Example 1

[0041] A method for generating liquid fertilizer using sludge hydrothermal carbonization liquid, the steps are as follows:

[0042] Step 1: Inoculate 100 mL of seed culture medium with brewer's yeast for fermentation to prepare a microbial seed solution. The fermentation process can be carried out in a shaker with a shaker speed of 180 rpm and a fermentation temperature set at 30°C.

[0043] Step 2: dilute the sterile sludge hydrothermal carbonized liquid with distilled water in proportion to a COD concentration of 10 g / L. Place 100 mL of the diluted sterile sludge hydrothermal carbonized liquid in a 250 mL conical flask and mix well to obtain a fermentation medium.

[0044] Step 3, inoculate the microbial seed liquid obtained in step 1 into the fermentation medium prepared in step 2 at a 6% inoculation rate, mix well, set the shaker speed to 180 rpm, set the fermentation temperature to 30°C, and ferment for 3 days to obtain a fermentation liquid.

[0045] Example 2

[0046] A method for generating liquid fertilizer using sludge hydrothermal carbonization liquid, the steps are as follows:

[0047] Step 1: Inoculate 100 mL of seed culture medium with brewer's yeast for fermentation to prepare a microbial seed solution. The fermentation process can be carried out in a shaker with a shaker speed of 180 rpm and a fermentation temperature set at 30°C.

[0048] Step 2: dilute the sterile sludge hydrothermal carbonized liquid with distilled water in proportion to a COD concentration of 20 g / L. Place 100 mL of the diluted sterile sludge hydrothermal carbonized liquid in a 250 mL conical flask and mix well to obtain a fermentation medium.

[0049] Step 3, inoculate the microbial seed liquid obtained in step 1 into the fermentation medium prepared in step 2 at a 6% inoculation rate, mix well, set the shaker speed to 180 rpm, set the fermentation temperature to 30°C, and ferment for 3 days to obtain a fermentation liquid.

[0050] Example 3

[0051] A method for generating liquid fertilizer using sludge hydrothermal carbonization liquid, the steps are as follows:

[0052] Step 1: Inoculate 100 mL of seed culture medium with brewer's yeast for fermentation to prepare a microbial seed solution. The fermentation process can be carried out in a shaker with a shaker speed of 180 rpm and a fermentation temperature set at 30°C.

[0053] Step 2: dilute the sterile sludge hydrothermal carbonized liquid with distilled water in proportion to a COD concentration of 30 g / L. Place 100 mL of the diluted sterile sludge hydrothermal carbonized liquid in a 250 mL conical flask and mix well to obtain a fermentation medium.

[0054] Step 3, inoculate the microbial seed liquid obtained in step 1 into the fermentation medium prepared in step 2 at a 6% inoculation rate, mix well, set the shaker speed to 180 rpm, set the fermentation temperature to 30°C, and ferment for 3 days to obtain a fermentation liquid.

[0055] Example 4

[0056] A method for generating liquid fertilizer using sludge hydrothermal carbonization liquid, the steps are as follows:

[0057] Step 1: Inoculate 100 mL of seed culture medium with brewer's yeast for fermentation to prepare a microbial seed solution. The fermentation process can be carried out in a shaker with a shaker speed of 180 rpm and a fermentation temperature set at 30°C.

[0058] Step 2: dilute the sterile sludge hydrothermal carbonized liquid with distilled water in proportion to a COD concentration of 40 g / L. Place 100 mL of the diluted sterile sludge hydrothermal carbonized liquid in a 250 mL conical flask and mix well to obtain a fermentation medium.

[0059] Step 3, inoculate the microbial seed liquid obtained in step 1 into the fermentation medium prepared in step 2 at a 6% inoculation rate, mix well, set the shaker speed to 180 rpm, set the fermentation temperature to 30°C, and ferment for 3 days to obtain a fermentation liquid.

[0060] Example 5

[0061] A method for generating liquid fertilizer using sludge hydrothermal carbonization liquid, the steps are as follows:

[0062] Step 1: Inoculate 100 mL of seed culture medium with brewer's yeast for fermentation to prepare a microbial seed solution. The fermentation process can be carried out in a shaker with a shaker speed of 180 rpm and a fermentation temperature set at 30°C.

[0063] Step 2: dilute the sterile sludge hydrothermal carbonized liquid with distilled water in proportion to a COD concentration of 50 g / L. Place 100 mL of the diluted sterile sludge hydrothermal carbonized liquid in a 250 mL conical flask and mix well to obtain a fermentation medium.

[0064] Step 3, inoculate the microbial seed liquid obtained in step 1 into the fermentation medium prepared in step 2 at a 6% inoculation rate, mix well, set the shaker speed to 180 rpm, set the fermentation temperature to 30°C, and ferment for 3 days to obtain a fermentation liquid.

[0065] Example 6

[0066] A method for generating liquid fertilizer using sludge hydrothermal carbonization liquid, the steps are as follows:

[0067] Step 1: Inoculate 100 mL of seed culture medium with brewer's yeast for fermentation to prepare a microbial seed solution. The fermentation process can be carried out in a shaker with a shaker speed of 180 rpm and a fermentation temperature set at 30°C.

[0068] Step 2: The COD concentration of the undiluted sterile hydrothermal carbonized liquid is 60 g / L. 100 mL of the sterile sludge hydrothermal carbonized liquid is placed in a 250 mL conical flask and mixed evenly to obtain a fermentation medium.

[0069] Step 3, inoculate the microbial seed liquid obtained in step 1 into the fermentation medium prepared in step 2 at a 6% inoculation rate, mix well, set the shaker speed to 180 rpm, set the fermentation temperature to 30°C, and ferment for 3 days to obtain a fermentation liquid.

[0070] from Figure 1 It can be seen that as the fermentation time increases, the microorganisms basically stop growing on the third day. When the COD concentration is 50g / L, the microorganisms grow well. The production strain can only achieve a good fermentation effect if it grows within the appropriate pH range. The pH value in the environment will directly affect the activity and structure of the cells. Figure 1 It can be seen that the pH range is between 6 and 9, which is within the normal growth range of yeast. This shows that under roughly the same pH trend, the COD concentration is different and the yeast shows different growth conditions.

[0071] Figure 2 It is the change of related substances in the hydrothermal carbonization liquid after fermentation under different COD concentrations. When the COD concentration is 50g / L, the COD removal rate is 70%, the ammonia nitrogen removal rate is 55%, the phosphate removal rate is 94%, the TN removal rate is 71%, and the TP removal rate is 98%. In addition to utilizing carbon-containing substances, brewer's yeast also utilizes nitrogen, phosphorus and other related substances. On the one hand, after high-temperature hydrothermal carbonization, the protein in the liquid is hydrolyzed to generate a large amount of NH4 + -N. As the yeast grows, part of the NH4 + -N participates as a nitrogen source, resulting in NH4 + -N concentration decreased. After 24 hours, as the yeast entered the stable phase, the NH4 + -N no longer participates in the reaction, and the concentration begins to stabilize. On the other hand, phosphorus in the hydrothermal carbonization solution is converted into PO4 by yeast during the reaction. 3- -P and exploited, PO4 3- -P is also consumed continuously with the reaction. After 24 hours, some other phosphorus-containing substances are converted into phosphate again, and then after 48 hours, the yeast enters the stable period, and the PO4 3- -P concentration tended to be stable, and yeast no longer absorbed a large amount, with the only exception being the 50g-COD / L group, where the concentration was still decreasing. However, under the condition of 10g-COD / L, yeast 3- -P absorption and utilization is low. This may indicate that in this environment, yeast is more sensitive to NH4 + -N utilization is greater than PO4 3- -P, the limited types of material utilization also led to poor aerobic fermentation of yeast. Therefore, COD concentration of 50g / L is the optimal COD concentration for brewer's yeast to use sludge hydrothermal carbon liquid as a carbon source.

[0072] The samples were taken after 12 hours of fermentation for transcriptome analysis, and the carbon source deficiency (COD concentration was 10 g / L) was used as the control group. The results are as follows Figure 3As shown. There were 2710 differentially expressed genes in the carbon source regulation process, of which 1291 were upregulated and 1419 were downregulated, indicating that changes in carbon source content had a significant regulatory effect on the gene expression of Saccharomyces cerevisiae. The differentially expressed genes involved more than 20 pathways, and several annotated signal pathways with a large number were meiosis, cell cycle, glycolysis, fatty acid degradation and pyruvate metabolism. The differential gene expression involved in the relevant signal pathways is shown in Table 2. Among them, the significant downregulation of genes in the meiosis process and cell cycle process indicated that insufficient carbon source content affected the cell growth and viability of Saccharomyces cerevisiae, as shown by related genes such as MEK1, SMC1, and IRR1. At the same time, in terms of energy acquisition pathways, glycolysis is the main way for microorganisms to metabolize sugar to obtain energy. When the concentration of external metabolites changes, cells reallocate limited enzyme resources through gene regulatory networks to adapt to the new stable state and increase flux. However, under the condition of insufficient carbon source content, the activities of pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH), the key enzymes in the ethanol production pathway, were significantly reduced, and their main genes (such as ADH2 and PDC6) were downregulated by 4.8 and 5.2 times, respectively. In addition, the significant downregulation of PFK1 and PFK2, the encoding genes of phosphofructokinase (PFK), the key rate-limiting enzyme of glycolysis, further indicated that glycolysis was inhibited; TDH1, TDH2, and TDH3 genes involved in glyceraldehyde-3-phosphate metabolism were downregulated by 3.3 to 5.5 times, respectively. In contrast, some genes in the fatty acid degradation pathway, such as ALD6, were upregulated by 2.4 times, indicating that this pathway may provide additional energy support for cells when the carbon source content is insufficient. The fatty acid degradation pathway generates acyl-CoA by hydrolyzing endogenous lipids (such as triacylglycerol) under the condition of carbon source deficiency. Five fatty acid transporters (FAT1, FAA1, FAA2, FAA3, and FAA4) in Saccharomyces cerevisiae are essential for the metabolism of long-chain fatty acids. Among them, the expression of FAA1, FAA2 and FAA4 was significantly downregulated, indicating that the transport of fatty acids in the plasma membrane may be inhibited. In pyruvate metabolism, pyruvate is an important intermediate metabolite and is closely related to energy consumption. Its key genes such as DLD2 and DLD3 are upregulated under the condition of insufficient carbon source, indicating that pyruvate is the main source of energy when carbon source is scarce.

[0073] Comprehensive analysis shows that Saccharomyces cerevisiae cells optimize resource allocation by dynamically regulating carbon metabolic pathways under stress conditions. For example, the initial stage of glycolysis may be moderately maintained to meet the necessary energy needs, while subsequent branches (such as the ethanol production pathway) are significantly limited. At the same time, fatty acid degradation may replenish energy by mobilizing endogenous lipid reserves. These mechanisms reflect the strategy of cells to flexibly allocate metabolism to maintain survival under conditions of limited resources. It can also be seen that when Saccharomyces cerevisiae uses sludge hydrothermal carbonization liquid as a carbon source to produce liquid fertilizer, it is not regulated by one or several genes, but requires the joint participation of multiple genes in multiple metabolic pathways and signal transduction pathways.

[0074] Table 2 Differential gene expression

[0075]

[0076] In order to further prove that the fermentation liquid obtained in step 3 of Examples 1 to 6 has practical agronomic application performance, a seed germination experiment was carried out.

[0077] Three groups of samples were set up, including hydrothermal carbonized liquid before fermentation (6 different COD concentrations), hydrothermal carbonized liquid after fermentation (6 different COD concentrations), and distilled water (blank control) as samples to evaluate whether the fermentation liquid as fertilizer has biological toxicity to seeds. The liquids except the blank control were diluted to 5% and shaken for 20 minutes before use.

[0078] Place a piece of filter paper of corresponding size in a 9 cm culture dish, evenly place 10 lettuce seeds with full grains of similar size, use a pipette to take 5.0 mL of the liquid in each sample and the blank control group in step 3, add them to different culture dishes, then place the culture dishes in a constant temperature climate incubator at (25±1)°C and 80% humidity, observe the water status in the culture dishes, and replenish the fermentation liquid fertilizer of the corresponding treatment group in time until germination is completed. Perform three parallel experiments for each group.

[0079] After germination, the root length and number of germination of all seeds in each group of culture dishes were measured, and the seed germination index (GI), relative root length and relative seed germination rate (GR) were calculated to prove that the fermentation liquid was non-toxic to plant growth. The average value and error value of each group were calculated to obtain Table 3 and Figure 4 data.

[0080] Table 3

[0081]

[0082] From Table 3 and Figure 4It can be seen that the GR and relative root length of the non-fermented treatment group were significantly lower than those of the control group, and the GI was lower than 70%, indicating that the sludge hydrothermal carbonized liquid before fermentation had a certain degree of phytotoxicity. It is generally believed that a GI greater than 70% can be considered that the fertilizer is basically non-toxic to seeds. In contrast, the GR, relative root length and GI of the fermented sludge hydrothermal carbonized liquid increased significantly. The GI of all fermentation treatment groups was higher than that of the original sludge hydrothermal carbonized liquid, and all values ​​were greater than 70%, indicating that the fermented sludge hydrothermal carbonized liquid at a concentration of 5% was harmless to plants. Compared with the control group, the increase in GI was related to the growth of root length, which may be due to the presence of NH4 in the liquid. + , P and K. It was further shown that the 50 g-COD / L fermented sludge hydrothermal carbonized liquid had the highest GR, root length and GI, and could be used as the best liquid fertilizer product.

[0083] It can be seen from the results of each embodiment that according to the method of the present invention, liquid fertilizer is generated using sludge hydrothermal carbonized liquid as raw material, and the nutrients in the hydrothermal carbonized liquid can be utilized, which can not only significantly reduce the COD of the sludge hydrothermal carbonized liquid and reduce its harm to environmental pollution, but also realize the resource utilization of wastewater and achieve the purpose of turning waste into treasure.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for producing liquid fertilizer using sludge hydrothermal carbonization liquid, characterized in that: The sludge hydrothermal carbonized liquid is used as the carbon source and aerobic fermentation is carried out using Saccharomyces cerevisiae.

2. The method for producing liquid fertilizer by utilizing sludge hydrothermal carbonization liquid as claimed in claim 1, characterized in that: After inoculating the brewer's yeast seed liquid and the sterile hydrothermal carbonized liquid into the sterile fermentation medium, the sludge hydrothermal carbonized liquid was used as the carbon source to carry out fermentation under aerobic conditions; Preferably, the brewer's yeast seed solution is prepared by inoculating brewer's yeast into a seed culture medium for fermentation; More preferably, the seed culture medium is glucose yeast peptone medium.

3. The method for producing liquid fertilizer by utilizing sludge hydrothermal carbonization liquid as claimed in claim 1, characterized in that: The temperature of aerobic fermentation is 28-35℃.

4. The method for producing liquid fertilizer by utilizing sludge hydrothermal carbonization liquid as claimed in claim 1, characterized in that: In aerobic fermentation, the inoculation amount of brewer's yeast is 5-7%.

5. The method for producing liquid fertilizer by utilizing sludge hydrothermal carbonization liquid as claimed in claim 1, characterized in that: During aerobic fermentation, the pH value of the treatment system is 6.5-9.

6. The method for producing liquid fertilizer using sludge hydrothermal carbonization liquid as claimed in claim 1, characterized in that: During aerobic fermentation, the COD concentration in the sludge hydrothermal carbonization liquid was 46-54 g / L.

7. The method for producing liquid fertilizer by utilizing sludge hydrothermal carbonization liquid as claimed in claim 1, characterized in that: In aerobic fermentation, the culture medium used is yeast fermentation culture medium; preferably, the components of the yeast fermentation culture medium include: yeast powder 9-11 g / L, peptone 18-22 g / L, glucose 18-22 g / L.

8. A liquid fertilizer, characterized in that: Obtained by the method described in any one of claims 1 to 7.

9. Use of the liquid fertilizer according to claim 8 in treating plant seed germination.

10. The use according to claim 9, characterized in that: The plant is lettuce.

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