Method for preparing hydroponic plant nutrient solution from biogas slurry and nutrient solution
阅读说明：本技术 一种沼液制备水培植物营养液的方法及营养液 (Method for preparing hydroponic plant nutrient solution from biogas slurry and nutrient solution ) 是由 马武生 王如平 鲍家泽 王万华 潘其泉 马玉银 李霖 于 2021-09-14 设计创作，主要内容包括：本发明公开了一种沼液制备水培植物营养液的方法及营养液,沼液制备水培植物营养液的方法包括,将沼液通过滤网过滤、高压匀浆；调节料液pH至弱酸性；选用β-FeOOH作为催化剂、Al-(2)O-(3)作为载体,进行催化臭氧氧化；采用100kDa超滤膜分离料液,超滤后获得水培植物营养液。本发明采用高压匀浆-催化臭氧氧化-超滤的组合工艺,可有效分解沼渣中的固形物、破解大分子DOM,提高NH-(4)～(+)-N的硝化效率,同时起到消毒杀菌,达到肥料卫生学指标。该方法具有养分成分损失低、工艺难度小和生产成本相对较低等优点。(The invention discloses a method for preparing a hydroponic plant nutrient solution from biogas slurry and the nutrient solution, wherein the method for preparing the hydroponic plant nutrient solution from the biogas slurry comprises the steps of filtering the biogas slurry through a filter screen and homogenizing the biogas slurry at high pressure; adjusting the pH value of the feed liquid to subacidity; selecting beta-FeOOH as catalyst and Al 2 O 3 As a carrier, carrying out catalytic ozone oxidation; separating the feed liquid by adopting a 100kDa ultrafiltration membrane, and ultrafiltering to obtain the hydroponic plant nutrient solution. The invention adopts a combined process of high-pressure homogenization, catalytic ozonation and ultrafiltration, can effectively decompose solid matters in biogas residues, break macromolecular DOM and improve NH 4 + The nitrification efficiency of N and the disinfection and sterilization are achieved at the same time, and the indexes of fertilizer hygiene are achieved. The method comprisesLow nutrient component loss, small process difficulty, relatively low production cost and the like.)
1. A method for preparing a hydroponic plant nutrient solution from biogas slurry is characterized by comprising the following steps: comprises the steps of (a) preparing a mixture of a plurality of raw materials,
filtering the biogas slurry through a filter screen, and homogenizing at high pressure;
adjusting the pH value of the feed liquid to subacidity;
selecting beta-FeOOH as catalyst and Al2O3As a carrier, carrying out catalytic ozone oxidation;
separating the feed liquid by adopting a 100kDa ultrafiltration membrane, and ultrafiltering to obtain the hydroponic plant nutrient solution.
2. The method for preparing the hydroponic plant nutrient solution by using the biogas slurry as claimed in claim 1, wherein the method comprises the following steps: the biogas slurry is filtered by a filter screen, and the aperture of the filter screen is 100 mu m.
3. The method for preparing the hydroponic plant nutrient solution by using the biogas slurry as claimed in claim 1 or 2, wherein the method comprises the following steps: the high-pressure homogenate comprises single homogenate or multiple circulating homogenate, and the pressure is 40-60 MPa.
4. The method for preparing the hydroponic plant nutrient solution by using the biogas slurry as claimed in claim 3, wherein the method comprises the following steps: the high pressure homogenization was performed with a single homogenization at a homogenization pressure of 40 MPa.
5. The preparation method of the method for preparing the hydroponic plant nutrient solution by using the biogas slurry as claimed in any one of claims 1, 2 and 4, wherein the method comprises the following steps: and before high-pressure homogenization, adjusting the pH of the feed liquid to 10 by using a NaOH concentrated solution.
6. The preparation method of the method for preparing the hydroponic plant nutrient solution by using the biogas slurry as claimed in claim 5, is characterized in that: and adjusting the pH of the feed liquid to weak acidity, and adjusting the pH to 5-6.6.
7. The preparation method of the method for preparing the hydroponic plant nutrient solution by using the biogas slurry as claimed in any one of claims 1, 2, 4 and 6, wherein the method comprises the following steps: the catalytic ozonation, O31.9mg/L, beta-FeOOH/Al2O3The concentration was 1.7g/L and the reaction time was 60 min.
8. The preparation method of the method for preparing the hydroponic plant nutrient solution by using the biogas slurry as claimed in claim 7, is characterized in that: and separating the feed liquid by using a 100kDa ultrafiltration membrane, and selecting 40-80 kPa as the working pressure of the 100kDa ultrafiltration membrane for separating the feed liquid.
9. The nutrient solution obtained by the method for preparing the hydroponic plant nutrient solution from the biogas slurry as described in any one of claims 1 to 8, wherein the method comprises the following steps: among the nutrient solutions, TN>800mg/L，NO3 --N>600mg/L，DOC>1200mg C/L, fulvic acids>160mg C/L, soluble phosphorus>40mg/L, germination index>80％。
Technical Field
The invention belongs to the technical field of biogas slurry resource utilization, and particularly relates to a method for preparing a hydroponic plant nutrient solution from biogas slurry and the nutrient solution.
Background
The total yield and total dosage of the chemical fertilizer in China are the first in the world, but the application of the chemical fertilizer has many unreasonable and unscientific problems, thereby causing waste of chemical fertilizer resources and increasing the agricultural cost. If the nitrogen fertilizer sprayed exceeds the nitrogen amount required by crops, the amino fertilizer finally enters the aquatic environment through runoff, and nitrogen compounds produced by human and animal metabolism also enter the water body in the main forms of sewage and excrement respectively. This increases the ammonia concentration in the aqueous environment. In existing wastewater treatment systems, ammonia is typically removed by nitrification and denitrification and is ultimately converted to harmless gaseous N2. However, this method requires a large amount of energy, and nitrification by aeration alone occupies about 50% of the total energy of a sewage treatment plant and 60% of the operation cost of wastewater treatment. In addition, in the nitrification-denitrification process, since various chemical substances must act as electron donors, a large amount of chemical agents needs to be consumed. Thus, a sustainable ammonia supply and an efficient ammonia removal mechanism are very important. Therefore, in wastewater treatment, ammonia recovery is more valuable than ammonia removal, especially in view of the high energy consumption and high cost issues faced by traditional ammonia removal processes. Ammonia recovery not only supplements fertilizer production, but also promotes sustainable and better resource management.
Anaerobic digestion is the most widely used technology for harmlessness, reduction, minimization and recycling of excrement. Biogas slurry is a major byproduct of this process. The solid components (biogas residues) in the biogas slurry contain rich organic matters (lignin, long-chain carbohydrate, macromolecular protein and other refractory organic matters), phosphorus, potassium and other nutrient elements. Liquid fraction (in order to)Hereinafter referred to as biogas slurry) contains nitrogen at a high concentration and dissolved organic matter (DOC), such as polysaccharides, humic acid, crude protein, amino acids, nucleic acids, etc., and growth factors (vitamins, fulvic acid, gibberellin, etc.) required by various plants. To a certain extent, the biogas slurry can be used as a nutrient solution for the growth of farmland plants. However, the nitrogen source in biogas slurry exists mainly in the form of ammonia/ammonium, and contains a large amount of water-soluble organic matter (DOM) which is a complex mixture containing both small molecular substances and various macromolecular substances. Albeit ammonium Nitrogen (NH)4 +-N) and nitrate Nitrogen (NO)3 -N) are good nitrogen sources for the growth and development of crops, but NH4 +-N is better used in summer when plant photosynthesis is fast or when plant is in nitrogen deficiency, and NO is better3 --N can be used under any conditions. Application of NO in soilless culture production3 -The effect of-N is much greater than that of NH4 +-N. Most of the current nutrient solution formulations use nitrate as the primary nitrogen source. The reason is that the physiological alkalinity caused by the nitrate is weak and slow, and the plant has certain resistance capability and is easy to control manually; and NH4 +The physiological acidity caused by-N is strong and rapid, the plant itself is difficult to resist, and manual control is difficult. Therefore, when the nutrient solution is prepared, the safe nitrate nitrogen source is mainly used, and the proper proportion is kept. Research shows that NH4 +-N and NO3 -The elongation of the root system is more favorable when the-N ratio is 1: 6. In addition, high concentrations of ammonia/ammonium tend to volatilize resulting in nitrogen loss. The high molecular weight DOM in biogas slurry also causes uncertainty in bioavailability and biosafety. Studies have shown that the high bioavailability of DOM occurs mostly at low molecular weights, with the high molecular weight protein components being poorly utilized by the organism. When the high molecular weight components of the biogas slurry are directly used as hydroponic plant nutrient solution or discharged into soil, longer decomposition time is needed, and few biological effective organic components are obtained through microbial metabolism. Besides, the biogas slurry also contains various pathogenic microorganisms (salmonella, escherichia coli, clostridium and the like) which are easy to cause public health problems. Therefore, the biogas slurry is necessary to be reasonably treated and disposed。
In recent years, the invention of yao and the like discloses a green ammonia water recovery system based on anaerobic fermentation and membrane distillation, and ammonia is directly obtained from agricultural organic wastewater. But the high energy consumption results in a great reduction in economic performance. The invention discloses a biogas slurry biotrickling ammonia nitrogen nitration treatment device adopting a micro-foam filler. The method converts ammonium nitrogen in the biogas slurry into nitrate nitrogen through the nitrification of microorganisms. Although it is considered to be an effective mineralization method by microbial metabolism, part of the organic nutrients can be retained in the biogas slurry. However, the nitrification of ammonia nitrogen and the decomposition of biogas slurry require a long time, and a large amount of DOM and energy are consumed. The invention discloses a manufacturing method for producing a high-efficiency flush fertilizer by utilizing biogas slurry by utilizing ozone deodorization and biological aerobic fermentation technologies, such as Sterland and the like, and aims to remove odor factors and reducing substances in the biogas slurry and add a large amount of nutrient elements in subsequent compounding. The method has the defects of high-level nutrient loss, high process difficulty, high cost and the like.
Disclosure of Invention
This section is for the purpose of summarizing some aspects of embodiments of the invention and to briefly introduce some preferred embodiments. In this section, as well as in the abstract and the title of the invention of this application, simplifications or omissions may be made to avoid obscuring the purpose of the section, the abstract and the title, and such simplifications or omissions are not intended to limit the scope of the invention.
In view of the above and/or the problems in the prior art, the present invention is provided, which is based on the relevant data of the digested waste (biogas slurry and biogas residue), adopts the combined process of high pressure homogenization, catalytic ozonation and membrane separation, can effectively decompose the solid in the biogas residue, break down macromolecular DOM, and improve NH4 +The nitrification efficiency of N and the disinfection and sterilization are achieved at the same time, and the indexes of fertilizer hygiene are achieved.
In order to solve the technical problems, the invention provides the following technical scheme: a method for preparing a hydroponic plant nutrient solution from biogas slurry comprises,
filtering the biogas slurry through a filter screen, and homogenizing at high pressure;
adjusting the pH value of the feed liquid to subacidity;
selecting beta-FeOOH as catalyst and Al2O3As a carrier, carrying out catalytic ozone oxidation;
separating the feed liquid by adopting a 100kDa ultrafiltration membrane, and ultrafiltering to obtain the hydroponic plant nutrient solution.
As a preferred scheme of the method for preparing the hydroponic plant nutrient solution by using the biogas slurry, the method comprises the following steps: the biogas slurry is filtered by a filter screen, and the aperture of the filter screen is 100 mu m.
As a preferred scheme of the method for preparing the hydroponic plant nutrient solution by using the biogas slurry, the method comprises the following steps: the high-pressure homogenate comprises single homogenate or multiple circulating homogenate, and the pressure is 40-60 MPa.
As a preferred scheme of the method for preparing the hydroponic plant nutrient solution by using the biogas slurry, the method comprises the following steps: the high pressure homogenization was performed with a single homogenization at a homogenization pressure of 40 MPa.
As a preferred scheme of the method for preparing the hydroponic plant nutrient solution by using the biogas slurry, the method comprises the following steps: and before high-pressure homogenization, adjusting the pH of the feed liquid to 10 by using a NaOH concentrated solution.
As a preferred scheme of the method for preparing the hydroponic plant nutrient solution by using the biogas slurry, the method comprises the following steps: and adjusting the pH of the feed liquid to weak acidity, and adjusting the pH to 5-6.6.
As a preferred scheme of the method for preparing the hydroponic plant nutrient solution by using the biogas slurry, the method comprises the following steps: the catalytic ozonation, O31.9mg/L, beta-FeOOH/Al2O3The concentration was 1.7g/L and the reaction time was 60 min.
As a preferred scheme of the method for preparing the hydroponic plant nutrient solution by using the biogas slurry, the method comprises the following steps: and separating the feed liquid by using a 100kDa ultrafiltration membrane, and selecting 40-80 kPa as the working pressure of the 100kDa ultrafiltration membrane for separating the feed liquid.
Another object of the invention is to provide a nutrient solution obtained by the method for preparing the hydroponic plant nutrient solution by using the biogas slurry, wherein TN in the nutrient solution>800mg/L，NO3 —N>600mg/L，DOC>1200mg C/L, fulvic acids>160mg C/L, soluble phosphorus>40mg/L, germination index>80％。
Compared with the prior art, the invention has the following beneficial effects:
the invention adopts a combined process of high-pressure homogenization, catalytic ozonation and ultrafiltration, can effectively decompose solid matters in biogas residues, break macromolecular DOM and improve NH4 +The nitrification efficiency of N and the disinfection and sterilization are achieved at the same time, and the indexes of fertilizer hygiene are achieved. The method has the advantages of low nutrient component loss, small process difficulty, relatively low production cost and the like.
The hydroponic plant nutrient solution prepared by the invention has higher concentration, TN>800mg/L，NO3 --N of about 600mg/L, DOC of about 1200mg C/L, fulvic acids>160mg C/L, soluble phosphorus>40mg/L, germination index>80 percent. The number of faecal coliform and salmonella were not detected. And can be further concentrated for convenient transportation.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise. Wherein:
FIG. 1 is a graph showing the effect of high pressure homogenization conditions of the present invention on DOC and aromatic proteins.
FIG. 2 is an FTIR spectrum of DOM of a biogas slurry sample under different high pressure homogenization conditions according to the present invention. Wherein, (a) before high pressure homogenization treatment; (b) homogenizing at 30 MPa; (c) homogenizing at 40 MPa; (d) homogenizing at 50 MPa; (e) p-40 MPa, secondary homogenization.
FIG. 3 is a DOC treated with the combination of NaOH + high pressure homogenization of the present invention.
FIG. 4 shows the effect of the reaction time of the catalytic ozonation of the feed liquid on the main indexes.
FIG. 5 is a photograph of rice seedlings in a hydroponic test according to the present invention.
FIG. 6 is a photograph of rice seedlings cultured for 15 days in the hydroponic test of the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, specific embodiments thereof are described in detail below with reference to examples of the specification.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, but the present invention may be practiced in other ways than those specifically described and will be readily apparent to those of ordinary skill in the art without departing from the spirit of the present invention, and therefore the present invention is not limited to the specific embodiments disclosed below.
Furthermore, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
Example 1
(1) Filtering with a screen: the biogas slurry passes through a 100-micron filter screen to remove insoluble solid particles.
(2) High-pressure homogenization: homogenizing at 50 MPa.
(3) And (3) pH adjustment: the pH sensor and the PLC are used for realizing the automatic control of the pH, and the pH of the feed liquid is adjusted to be 5.6 before the catalytic ozonation.
(4) Catalyzing ozone oxidation: beta-FeOOH is selected as a catalyst, Al2O3As a carrier. Obtaining a preferred condition, O, using a BBD model31.9mg/L, beta-FeOOH/Al2O3The concentration is 1.7g/L, and the reaction time is 60 min.
(5) And (3) ultrafiltration: selecting an ultrafiltration membrane with 40-80 kPa as the working pressure of the separation feed liquid of the 100kDa, and obtaining the hydroponic plant nutrient solution after ultrafiltration. The performance index is shown in Table 2.
Example 2
(1) Filtering with a screen: the biogas slurry passes through a 100-micron filter screen to remove insoluble solid particles.
(2) High-pressure homogenization: homogenizing twice at 40 MPa.
(3) And (3) pH adjustment: the pH sensor and the PLC are used for realizing the automatic control of the pH, and the pH of the feed liquid is adjusted to be 5.6 before the catalytic ozonation.
(4) Catalyzing ozone oxidation: beta-FeOOH is selected as a catalyst, Al2O3As a carrier. Obtaining a preferred condition, O, using a BBD model31.9mg/L, beta-FeOOH/Al2O3The concentration is 1.7g/L, and the reaction time is 60 min.
(5) And (3) ultrafiltration: 40 kPa-80 kPa is selected as the working pressure of the ultrafiltration membrane of 100kDa for separating feed liquid. And (3) obtaining the hydroponic plant nutrient solution 2 after ultrafiltration. The performance index is shown in Table 2.
Example 3
(1) Filtering with a screen: the biogas slurry passes through a 100-micron filter screen to remove insoluble solid particles.
(2) High-pressure homogenization: homogenizing twice at 40 MPa.
(3) And (3) pH adjustment: the pH sensor and the PLC are used for realizing the automatic control of the pH, and the pH of the feed liquid is adjusted to be 6.6 before the catalytic ozonation.
(4) Catalyzing ozone oxidation: beta-FeOOH is selected as a catalyst, Al2O3As a carrier. Obtaining a preferred condition, O, using a BBD model3Is 2.3mg/L, beta-FeOOH/Al2O3The concentration is 1.4g/L, and the reaction time is 50 min.
(5) And (3) ultrafiltration: 40 kPa-80 kPa is selected as the working pressure of the ultrafiltration membrane of 100kDa for separating feed liquid. And (3) ultrafiltering to obtain the hydroponic plant nutrient solution 3. The performance index is shown in Table 2.
Example 4
(1) Filtering with a screen: the biogas slurry passes through a 100-micron filter screen to remove insoluble solid particles.
(2) And (3) pH adjustment: NaOH concentrated solution is adopted to adjust the pH value of the feed liquid to be approximately equal to 10, and automatic control is realized through a pH sensor and a PLC.
(3) High-pressure homogenization: homogenizing at 40 MPa.
(4) And (3) pH adjustment: the pH sensor and the PLC are used for realizing the automatic control of the pH, and the pH of the feed liquid is adjusted to be 5.6 before the catalytic ozonation.
(5) Catalyzing ozone oxidation: beta-FeOOH is selected as a catalyst, Al2O3As a carrier. Obtaining by selecting BBD modelPreferred condition, O31.9mg/L, beta-FeOOH/Al2O3The concentration is 1.7g/L, and the reaction time is 50 min.
(6) And (3) ultrafiltration: 40 kPa-80 kPa is selected as the working pressure of the ultrafiltration membrane of 100kDa for separating feed liquid. And when the pressure is higher than 80kPa, backwashing for 30min by adopting 100ppm (ten-thousandth) sodium hypochlorite, and cleaning the ultrafiltration membrane. And (4) obtaining the hydroponic plant nutrient solution after ultrafiltration. The performance index is shown in Table 2.
Example 5
(1) Filtering with a screen: the biogas slurry passes through a 100-micron filter screen to remove insoluble solid particles.
(2) And (3) pH adjustment: NaOH concentrated solution is adopted to adjust the pH value of the feed liquid to be approximately equal to 10, and automatic control is realized through a pH sensor and a PLC.
(3) High-pressure homogenization: homogenizing at 40 MPa.
(4) And (3) pH adjustment: the pH sensor and the PLC are used for realizing the automatic control of the pH, and the pH of the feed liquid is adjusted to be 6.6 before the catalytic ozonation.
(5) Catalyzing ozone oxidation: beta-FeOOH is selected as a catalyst, Al2O3As a carrier. Obtaining a preferred condition, O, using a BBD model3Is 2.3mg/L, beta-FeOOH/Al2O3The concentration is 1.4g/L, and the reaction time is 50 min.
(6) And (3) ultrafiltration: 40 kPa-80 kPa is selected as the working pressure of the ultrafiltration membrane of 100kDa for separating feed liquid. And when the pressure is higher than 80kPa, backwashing for 30min by adopting 100ppm (ten-thousandth) sodium hypochlorite, and cleaning the ultrafiltration membrane. And (5) obtaining the hydroponic plant nutrient solution after ultrafiltration. The performance index is shown in Table 2.
Example 6
(1) Filtering with a screen: the biogas slurry passes through a 100-micron filter screen to remove insoluble solid particles.
(2) And (3) pH adjustment: NaOH concentrated solution is adopted to adjust the pH value of the feed liquid to be approximately equal to 10, and automatic control is realized through a pH sensor and a PLC.
(3) High-pressure homogenization: homogenizing at 40 MPa.
(4) And (3) pH adjustment: the pH sensor and the PLC are used for realizing the automatic control of the pH, and the pH of the feed liquid is adjusted to be 6.6 before the catalytic ozonation.
(5) Catalyzing ozone oxidation: beta-FeOOH is selected asAs catalyst, Al2O3As a carrier. Obtaining a preferred condition, O, using a BBD model3Is 2.3mg/L, beta-FeOOH/Al2O3The concentration is 1.4g/L, and the reaction time is 60 min.
(6) And (3) ultrafiltration: 40 kPa-80 kPa is selected as the working pressure of the ultrafiltration membrane of 100kDa for separating feed liquid. And when the pressure is higher than 80kPa, backwashing for 30min by adopting 100ppm (ten-thousandth) sodium hypochlorite, and cleaning the ultrafiltration membrane. And (5) obtaining the hydroponic plant nutrient solution 6 after ultrafiltration.
The performance of the hydroponic plant nutrient solution obtained in the embodiment 1-6 is measured, and the measuring method is as follows:
(1) by K2Cr2O7Determination of Total Organic Carbon (TOC) by oxidation-spectrophotometry; h2SO4-H2O2Digestion and Kjeldahl determination of Total Nitrogen (TN), Nyquist reagent spectrophotometry of ammonia nitrogen, ultraviolet spectrophotometry of nitrate nitrogen. The total phosphorus is measured by ammonium molybdate spectrophotometry, and the soluble phosphorus is measured by 0.45 mu m filter membrane spectrophotometry.
(2) Analyzing and Dissolving Organic Matter (DOM) components by Fourier transform infrared spectroscopy (FTIR), wherein the wavelength range is 4000-400 cm-1The resolution is 4cm-1, and n is 10. And (3) analyzing different types of DOM (document object model) in the homogenized biogas slurry and the feed liquid after catalytic ozonation by using a three-dimensional fluorescence excitation-emission matrix (3D-EEM) spectrum. Wherein the emission wavelength (EM) is 200-900 nm, and the excitation wavelength (EX) is 200-900 nm. The percentage of DOM was calculated based on the numerical method of DOM under EEM of Zhou et al. It is defined as the following five regions: aromatic protein I (EX: 220-250 nm; EM: 280-330 nm); aromatic protein II (EX: 220-250 nm; EM: 330-380 nm); fulvic acid-like (EX: 220-250 nm; EM: 380-550 nm); a soluble microbial by-product sample (EX: 250-450 nm; EM: 280-380 nm); humic acid-like acids (EX: 250 to 450 nm; EM: 380 to 550 nm).
(3) And (3) determining the phytotoxicity: the invention belongs to the technical field of soilless culture of plants, and the Germination Index (GI) of seeds comprehensively reflects the phytotoxicity of a nutrient solution. Plant seeds at high content of macromolecular DOM and NH4 +-N nutrient solution is inhibited from growing and contains high content of small moleculesDOM and NO3 -The growth in the-N nutrient solution is promoted. 2.0mL of each feed solution was diluted 5-fold with 8mL of distilled water and transferred to a sterilized petri dish lined with filter paper. 20 seeds of Brassica chinensis (Brassica chinensis L.) were placed uniformly on filter paper and incubated for 72h at 25 ℃ in a dark room. Ultrapure water was used as a control. Growth of primary root>5mm is taken as a germination standard to count the germination number, and the GI is calculated by combining the root length: GI (%) ═ 100 × (Gt × Lt)/(Gc × Lc). In the formula, Gt and Gc are the germination rates of a treatment group and a control group respectively,%; lt and Lc are the lengths of the treated roots and the control roots, respectively, in mm.
(4) And (3) hygiene index detection: faecal Coliform (FC) is one of the important indexes for judging the safe utilization of sludge land. The salmonella is an important pathogenic bacterium causing food poisoning and is homologous with faecal coliform. The method has positive significance for judging the pollution degree of the product and whether the product meets the standard. 5mL of fresh sample was added to 45mL of sterile physiological saline (0.85%, w/v), shaken at 200rpm on a shaker for 30min, allowed to stand, and subjected to gradient dilution. The faecal coliform group (FC) is determined by a lauryl sulfate tryptone broth (LST) multi-tube fermentation method, the existence of the faecal coliform group is confirmed by primary fermentation (36 ℃, 48h) and a relapse fermentation test (44.5 ℃, 24h), and the most probable number (MPN/mL) of the FC in each milliliter of samples is calculated according to the number of positive tubes in which the FC exists, namely MPN index multiplied by dilution factor/mL. The salmonella detection was modified on the basis of the method described by Hassen et al: weighing 5g of fresh sample, placing the fresh sample in 45mL of GN enrichment medium, fully homogenizing, then performing dilution gradient by using the GN enrichment medium, setting 3 times for each dilution degree, and culturing at 37 ℃ for 18-24 h. Transferring 1mL of the cultured sample mixture into 9mL of sodium sulfolane brilliant green (TTB) enrichment solution, and culturing at 42 ℃ for 18-24 h. Meanwhile, another 1mL of the suspension was inoculated into 9mL of Selenite Cystine (SC) enrichment medium and cultured at 36 ℃ for 18-24 h. And respectively taking the bacterial liquid of each tube and streaking and inoculating the bacterial liquid to a bismuth sulfite agar (BS) plate (cultured for 40-48 h at 36 ℃) and a Xylose Lysine Deoxycholate (XLD) agar plate (cultured for 18-24 h at 36 ℃). More than 2 suspicious colonies (positive results) are picked from 2 selective agar plates respectively and inoculated to a trisaccharide iron agar (TSI) slant and a lysine decarboxylase culture medium (LIA), the TSI reaction is yellow on the bottom of the slant, and the possibility of salmonella can be eliminated if the LIA reaction is negative. And determining the maximum possible concentration of the salmonella in the nutrient solution according to the biochemical identification result.
The performance indexes of the hydroponic plant nutrient solutions obtained in examples 1 to 6 are shown in table 1.
TABLE 1
Example 7
This example 7 is essentially the same as example 5, except for the pressure of the high pressure homogenate, the number of cycles, and the results of the test are shown in FIG. 1.
As can be seen from fig. 1, when the homogenization pressure is higher than 50MPa and 40MPa, respectively, there is no significant increase in DOC and aromatic proteins for both single and double homogenations, indicating that there is a limit point for improving DOM macromolecule fragmentation/degradation under the high pressure homogenization pretreatment operating conditions. Considering energy consumption, the pressure should be 50MPa for one homogenate or 40MPa for two homogenates.
FTIR spectrograms of DOM before and after biogas slurry sample treatment show similar vibration bands, which shows that similar components exist in the DOM of the biogas slurry before and after high-pressure homogenization treatment, and the result is shown in figure 2. The wave number of the untreated biogas slurry DOM is 3400cm-1、1647cm-1、1540cm-1And 1124cm-1There is a vibration peak. 3400cm-1Nearby strong absorption band due to intermolecular O-H stretching, 1647cm-1Protein fraction C ═ O stretch (amide I), 1540cm-1The nearby main absorption band is amide II, representing the bending vibration of the amide N-H group and the stretching vibration of the C-N group in the protein component. 1124cm-1It is due to stretching of the polysaccharide component C-C or C-O. The result shows that the main components of DOM in the original biogas slurry are protein and polysaccharide substances.
FTIR spectrum of HPH-treated DOM at 2930cm-1Has a unique appearanceDue to aliphatic C-H stretching in the lipid component, indicating that some lipid component is released due to the high pressure homogenization treatment sludge disintegration. Thus, the major components of DOM in the treated feed are proteins, polysaccharides and lipids. Furthermore, although the amount of various dissolved organic species (e.g., protein and polysaccharide concentrations) increases with increasing homogenization pressure or number of homogenization cycles, no significant bands appear or disappear in the DOM spectrum of the treated feed.
By three-dimensional fluorescence spectrum analysis, two protein-like peaks are shown at excitation/emission wavelengths (Ex/Em) of 225/330-340 nm and 275/310-335 nm. Deducing that protein-like substances in the original biogas slurry and the treated feed liquid DOM are dominant fluorescent organic matters. After high-pressure homogenization treatment, the protein-like substances in DOM are changed, aromatic structural compounds are released, and the DOC intensity ratio (B/A) of the peak value B to the peak value A is increased, which shows that the proportion of the treated tryptophan protein substances is increased.
Example 8
This example 8 is essentially the same as example 5 except that the amount of NaOH added prior to high pressure homogenization was different and the results are shown in figure 3.
As can be seen from FIG. 3, the bacterial cell walls can be weakened by the alkaline pretreatment and then the cells can be more efficiently destroyed by the high pressure homogenization treatment. The adding amount of NaOH in the feed liquid is 2-6 g/L, and the reaction lasts for 2 hours. Then, at different pressures, a single homogenization treatment was performed. The results are shown in FIG. 3. The combination of alkali and high pressure homogenization breaks down cells more efficiently than a single homogenate, and the combination can achieve higher DOC. The DOC gradually rises with the rise of the pressure and the addition of NaOH, but the DOC gradually rises under the homogeneous pressure of more than 40 MPa. The increase of the amount of added NaOH can effectively promote the cell wall rupture, but the high amount of added NaOH causes the pH of the feed liquid to rise, resulting in NH3Volatilization loss is caused, the next ozone oxidation treatment is not facilitated, and the salt content of the feed liquid is increased by adding acid for neutralization. Furthermore, high NaOH may cause maillard reactions that brown free amino compounds and reducing sugars or carbonyl compounds.
The combination of NaOH pretreatment and high pressure homogenization showed a significant increase in energy efficiency compared to the high pressure homogenization treatment alone. Therefore, the high-pressure homogenization process adopts alkali pretreatment (the dosage of NaOH is 4g/L) for 2h reaction, and single homogenization treatment is carried out under the homogenization pressure of 40MPa, so that the release of relatively excellent DOC is realized.
Example 9
This example 9 is substantially the same as example 5 except that it is carried out only to step (1), only to step (3) and only to step (5). The performance indexes of the obtained hydroponic plant nutrient solution are shown in table 2.
TABLE 2
As can be seen from Table 2, NH was generated after 60min of catalytic ozonation4 +N and Kjeldahl nitrogen were reduced from 757mg/L and 1201mg/L to 107mg/L and 462mg/L, respectively, while NO was present3 -N increased from 104mg/L to 619 mg/L. Meanwhile, partial TOC is oxidized and decomposed, the content is reduced from 2478mg C/L to 2020mg C/L, and the DOC is increased by 17.9 percent. Indicating that 18.5% carbon loss was incurred during the catalytic ozonation process. Meanwhile, macromolecular DOM is decomposed, the content of soluble organic matters is increased, and the bioavailability of feed liquid is improved. This is also illustrated by the significant increase in fulvic acid and aromatic protein content. The feed liquid before catalytic ozone oxidation treatment has the highest biological toxicity (GI ═ 32.4%), and after catalytic ozone oxidation, GI ═ 77.8%. This is mainly because biotoxicity is closely and positively correlated with DOM concentration, and macromolecular DOM has biotoxicity higher than small-molecular DOM. In addition, high-concentration ammonia nitrogen has higher toxicity to the germination rate.
In addition, no fecal coliform bacteria and salmonella are detected in the feed liquid after the catalytic ozonation treatment, and the reduction is probably the comprehensive result of high-pressure homogenization and ozonation. Hygiene tests show that escherichia coli and salmonella generally exist in anaerobic digestate, various pathogenic bacteria contained in pig manure cannot be thoroughly killed by mesophilic anaerobic digestion, certain environmental risks can be caused by direct application, and the necessity of secondary hygienization treatment of the anaerobic digestate is highlighted.
Example 10
This example 10 is substantially the same as example 5 except that the ozone concentration (a), the active catalyst concentration (B), and the ph (c) of catalytic ozone are different. Through the analysis of variance of the secondary response model, the square value reflects the interaction influence strength of the three factors. The interaction of pH with the active catalyst concentration is strongest (BC ═ 3.80), the second interaction of ozone concentration with the active catalyst concentration (AC ═ 0.79), and the weakest interaction of ozone concentration with pH. Influencing NO3 -The factor for increasing N is in turn the ozone concentration>Active catalyst concentration>The pH value. Thus, increase of NO3 --N optimal parameter values are: o is31.9mg/L, pH 5.6, beta-FeOOH/Al2O3The concentration was 1.7 g/L. However, based on Germination Index (GI) results, O was shown3The interaction with catalyst concentration is strongest (AC ═ 3.48), followed by the interaction of ozone concentration with pH (AB ═ 2.02), and finally by the interaction of pH with active catalyst concentration. The factors affecting DOC are in turn: concentration of ozone>Active catalyst concentration>The pH value. Therefore, the optimal parameter values based on GI are: o is3The concentration is 2.3mg/L, the pH is 6.6, and the beta-FeOOH/Al2O3The concentration was 1.4 g/L. Cause NO3 -The factors that-Noptimal differs from GI optimal are manifold. Researches suggest that biological stimulants such as humic acid, fulvic acid and amino acid have promotion effects on seed germination and seedling growth, and high-concentration ammonia nitrogen has biological toxicity on seed germination. In addition, the increase of organic matters (micromolecular DOM, high-aromaticity components, humic acid and the like) with higher stability is beneficial to the improvement of the germination rate.
Example 11
This example 11 is substantially the same as example 5 except that the reaction time of catalytic ozone is different, and the change of the indexes such as TOC, TN and the like and the oxidation time are shown in FIG. 4.
Research shows that carbon in the reaction system is continuously catalyzedOzonized and mineralized to CO2. The new process not only needs to improve the bioavailability of organic nitrogen and phosphorus components, but also needs to reduce the loss of organic carbon. As can be seen from FIG. 4, the earliest crossover point in the catalytic ozonation process was 48min (FIG. 4a), where the TOC was 2061mg C/L and FA was 158mg C/L. TN and NO3 -The N content also substantially follows this characteristic (FIG. 4b), i.e.crossover occurs before and after 50 min. These results indicate that catalytic ozonation promotes DOC mineralization decomposition, produces small-molecule DOM, and biologically active ingredients increase. Simultaneous generation of NO3 -N, the biological toxicity of the feed liquid is reduced. But from FA and NO3 -The change of-N indicates that at 50min, FA still has a larger lifting space, while NH4 +the-N content was still high (188 mg/L). FA can effectively activate the activities of protease, peptidase and acid phosphatase in the seed germination process, improve the germination index and activity index of seeds, enhance the activity of nitrate reductase of seedlings and promote the absorption of nitrogen. It is known that the extension of the oxidation time is advantageous for the improvement of germination index and the growth of seedlings. This was verified from germination index data and hydroponic experimental results. Therefore, the reaction time is preferably 60 min.
Example 12
This example 12 is substantially the same as example 5 except that the pressure of ultrafiltration is different and the test results are shown in Table 3.
TABLE 3
As can be seen from Table 3, the change in pressure did not significantly affect the permeability and purity of the nutrient elements or growth factors such as nitrogen, soluble phosphorus, aromatic proteins, fulvic acid, etc., and the membrane flux at 40kPa to 80kPa was close to that at 20 min. However, the effect on DOC yield was large, and the membrane flux of DOC at 40kPa was only 71.6% at 80 kPa. This is mainly due to the entrapment of the macromolecule by the membrane at lower working pressures. 40 kPa-80 kPa is selected as the working pressure of the separation sample liquid of the ultrafiltration membrane with 100 kDa.
Hydroponic culture test
The influence of the nutrient solution prepared under different conditions on the growth of rice seedlings is researched. Selecting rice seeds with full grains and no obvious difference in character and size, soaking the rice seeds in 1% lime water for 12h to kill ova and germs, washing the rice seeds with deionized water for multiple times, placing the rice seeds in a glass plate, and germinating in the dark at 20 ℃. When the seedling grows to above 5cm above ground, selecting strong seedling with uniform height, and washing root system with tap water. The prepared feed liquid was diluted 5 times and used as a nutrient solution, and 50mL of hydroponic solution was taken for testing. The root system of 1/3 is kept bare air, and water is changed once every 3 d. Meanwhile, the commercial soilless culture nutrient solution is used as a control group. And observing the growth characters of the rice, and further judging the bioavailability and the biotoxicity of the hydroponic plant nutrient solution.
The rice seedlings are shown in FIG. 5. The commercial soilless culture nutrient solution (control), the original biogas slurry, the feed solution after catalytic ozone oxidation and the feed solution after membrane filtration are respectively cultured, and the culture is carried out for 15 days as shown in figure 6. As can be seen from the figure, after the catalytic ozonation, the biological effectiveness of the biogas slurry is obviously improved, and the biological toxicity is obviously reduced. And the macromolecular DOM is further effectively separated after membrane filtration, and the obtained nutrient solution can directly provide nutrient elements and mineral substances required by the growth of the plants.
It should be noted that the above-mentioned embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.