Method for treating biogas slurry by using photosynthetic bacteria to obtain efficient seed soaking liquid

Abstract

The invention relates to the technical field of wastewater treatment and recycling, and discloses a method for treating biogas slurry by using photosynthetic bacteria to obtain an efficient seed soaking solution, which comprises the following steps: S1, taking out biogas slurry in a cow dung fermentation process, carrying out standing, filtering and centrifugal pretreatment on the biogas slurry, collecting, sealing at normal temperature, and storing in a shading manner; s2, sterilizing and diluting the biogas slurry treated in the step S1, then inoculating photosynthetic bacteria for domestication culture, and then collecting the photosynthetic bacteria maturely domesticated and cultured; and S3, adding the mature photosynthetic bacteria cultured in the S2 into the biogas slurry, controlling the adding proportion of the photosynthetic bacteria, the light-oxygen condition and the time, and reacting to obtain the efficient seed soaking liquid. According to the method for obtaining the efficient seed soaking liquid by treating the biogas slurry with the photosynthetic bacteria, the content of SMP (soluble microbial by-products) and humus in the biogas slurry is increased, the content of fulvic acid is reduced, effective nutritional ingredients of the biogas slurry are increased, inhibition of high-concentration carbon, nitrogen and phosphorus is relieved, the pollution hazard degree is reduced, and therefore seed germination is effectively promoted.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment and resource utilization, and in particular to a method for obtaining efficient seed soaking liquid by treating biogas slurry with photosynthetic bacteria. Background Art

[0002] Biogas slurry is rich in nutrients such as nitrogen, phosphorus and other organic matter. Therefore, it is often used as an organic liquid fertilizer for soaking seeds, irrigating roots or spraying leaves on crops in agricultural production. Biogas slurry can increase enzyme activity in seeds, promote embryonic cell division, and thus stimulate seed germination and seedling growth. However, some research results show that long-term direct application of biogas slurry not only fails to promote crop growth, but also has some defects, such as:

[0003] Excess nutrients in the directly sprayed biogas slurry will accumulate on the surface of seeds, which is detrimental to seed germination; at the same time, excess biogas slurry migrates to surface water and groundwater through surface runoff or soil infiltration, causing environmental pollution. Therefore, the biogas slurry needs to be treated secondary to reduce the pollution of carbon, nitrogen and phosphorus to the environment.

[0004] In view of the above problems, it is urgently necessary to carry out innovative designs based on the original biogas slurry treatment. Summary of the invention

[0005] The object of the present invention is to provide a method for obtaining efficient seed soaking solution by treating biogas slurry with photosynthetic bacteria, so as to solve the problem of environmental pollution caused by ultra-high concentrations of carbon, nitrogen and phosphorus in biogas slurry during direct spraying proposed in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for treating biogas slurry with photosynthetic bacteria to obtain efficient seed soaking solution, comprising S1. taking biogas slurry from the fermentation process of cow dung, pre-treating the biogas slurry by standing, filtering and centrifuging, collecting and storing the biogas slurry in a sealed manner at room temperature and in a light-shielded state, sterilizing and diluting the treated biogas slurry, then inoculating photosynthetic bacteria for culturing and domestication, and then collecting the photosynthetic bacteria that have been domesticated and cultured to maturity;

[0007] S2. Add the mature photosynthetic bacteria cultured in S1 to the biogas slurry, control the dosage ratio of photosynthetic bacteria, light-oxygen conditions and time, and after the reaction is completed, centrifuge and filter out the supernatant, and then detect the concentrations of carbon, nitrogen, phosphorus and dissolved organic matter in the supernatant;

[0008] S3. The supernatant prepared in S2 was used to dilute the seed soaking solution into different concentrations for mung bean seed germination experiments, among which the seed soaking solution with a diluted concentration of 75% had the best germination effect on mung bean seeds.

[0009] By adopting the above technical scheme, the biogas slurry can be effectively utilized and efficiently processed to prepare the corresponding seed soaking solution.

[0010] Preferably, the fermentation temperature in step S1 is 35-38° C., and the fermentation time is 60 days for normal gas production.

[0011] The above technical solution is adopted to facilitate the full fermentation of cow dung to obtain high-quality biogas slurry.

[0012] Preferably, the photosynthetic bacteria domestication implementation step in step S1 includes: rejuvenating the photosynthetic bacteria with a special culture medium, inoculating them into the diluted and sterilized original biogas slurry, and domesticating and culturing the photosynthetic bacteria with the biogas slurry culture medium to make the photosynthetic bacteria adapt to the growth environment of the biogas slurry.

[0013] The above technical solution is adopted to make the photosynthetic bacteria rejuvenate and adapt to the biogas slurry-based nutrient environment, thus providing conditions for the photosynthetic bacteria to grow advantageously in the biogas slurry.

[0014] Preferably, the bacterial species in the culture medium is a photosynthetic bacterial mother solution with Rhodopseudomonas palustris as the dominant bacteria.

[0015] The above technical solution is adopted to provide conditions for rapid growth of photosynthetic bacteria in biogas slurry.

[0016] Preferably, the Rhodopseudomonas palustris is a dark red liquid with a special odor, a biomass of 8 billion / mL, and is refrigerated in a refrigerator at 4°C.

[0017] By adopting the above technical scheme, dominant strains suitable for growth are selected for the photosynthetic bacteria inoculated in the culture medium.

[0018] Preferably, the optimal addition ratio of photosynthetic bacteria to biogas slurry in step S2 is F / M=3.

[0019] By adopting the above technical scheme, by controlling the adding ratio of photosynthetic bacteria and biogas slurry, it is convenient to obtain the output of the best quality seed soaking liquid with the minimum inoculation amount.

[0020] Preferably, the optimal photo-oxygen conditions for photosynthetic bacteria to degrade biogas slurry in step S2 are dark aerobic conditions.

[0021] By adopting the above technical solution, the biogas slurry degradation and the seed soaking liquid output are carried out under the optimal treatment conditions.

[0022] Preferably, the reaction temperature in step S2 is controlled at 37° C. and the reaction time is 15 days.

[0023] By adopting the above technical solution, the reaction of photosynthetic bacteria in the biogas slurry is controlled to proceed within the optimal temperature conditions and time range.

[0024] Preferably, the mung bean seed soaking liquid in step S3 is the supernatant produced after photosynthetic bacteria in biogas slurry are inoculated under dark aerobic conditions with F / M=3 as the mung bean seed soaking liquid.

[0025] Preferably, the mung bean seed soaking solution in step S3 is selected to have a dilution concentration of 75%, which has the best effect on the germination of mung bean seeds.

[0026] By adopting the above technical scheme and selecting dark aerobic conditions, the supernatant produced by photosynthetic bacteria degrading the biogas slurry has a significant effect on accelerating the germination of mung bean seeds.

[0027] Compared with the prior art, the beneficial effect of the present invention is that a method for obtaining a high-efficiency seed soaking solution by treating biogas slurry with photosynthetic bacteria is obtained.

[0028] After the photosynthetic bacteria degraded the biogas slurry, the SMP and humus contents in the biogas slurry were increased, the fulvic acid content was reduced, the effective nutrient components of the biogas slurry were improved, the inhibition of high concentrations of carbon, nitrogen and phosphorus was relieved, and the degree of pollution damage was reduced, thereby effectively promoting seed germination and providing a new way for the resource utilization of biogas slurry. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a diagram of activation and expansion culture of the special culture medium for photosynthetic bacteria of the present invention;

[0030] Figure 2 This is a diagram of activation and expansion culture of photosynthetic bacteria diluted and sterilized biogas slurry culture medium of the present invention;

[0031] Figure 3 This is a schematic diagram of the growth law of biogas slurry-based photosynthetic bacteria under light aerobic conditions of the present invention;

[0032] Figure 4 This is a schematic diagram of the growth law of biogas slurry-based photosynthetic bacteria under dark aerobic conditions of the present invention;

[0033] Figure 5 This is a schematic diagram of the growth law of biogas slurry-based photosynthetic bacteria under dark anaerobic conditions of the present invention;

[0034] Figure 6 This is a schematic diagram of the growth law of biogas slurry-based photosynthetic bacteria under light anaerobic conditions of the present invention;

[0035] Figure 7 The fluorescence spectra of DOM of photosynthetic bacteria treatment liquid under different light-oxygen conditions of the present invention;

[0036] Figure 8 Schematic diagram of COD removal rate of biogas slurry by photosynthetic bacteria under dark aerobic conditions of the present invention;

[0037] Fig. 9 It is a schematic diagram of the removal rate of ammonia nitrogen in biogas slurry by photosynthetic bacteria under dark aerobic conditions of the present invention;

[0038] Fig.10It is a schematic diagram of the removal rate of nitrite nitrogen in biogas slurry by photosynthetic bacteria under dark aerobic conditions of the present invention;

[0039] Fig.11 It is a schematic diagram of the removal rate of nitrate nitrogen in biogas slurry by photosynthetic bacteria under dark aerobic conditions of the present invention;

[0040] Fig.12 It is a schematic diagram of TP removal rate of biogas slurry by photosynthetic bacteria under dark aerobic conditions of the present invention;

[0041] Fig.13 This is a diagram showing the effects of soaking seeds with the biogas slurry stock solution and photosynthetic bacteria treatment solution on seed germination. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] See also Figure 1-13 , the present invention provides a technical solution: a method for obtaining efficient seed soaking solution by treating biogas slurry with photosynthetic bacteria;

[0044] Example

[0045] In this embodiment, the following steps are included:

[0046] S1. The biogas slurry is taken out from the cow dung fermentation process, and the biogas slurry is allowed to stand, filtered, and centrifuged for pretreatment. After collection, it is sealed and stored at room temperature and shaded. The treated biogas slurry is sterilized and diluted, and then photosynthetic bacteria are put into the culture, and then mature photosynthetic bacteria are collected;

[0047] In step S1, the fermentation temperature is 35-38°C, and the fermentation time is 60 days for normal gas production. The fully fermented biogas slurry is centrifuged and filtered, collected and stored in a 50L plastic barrel at room temperature in a sealed and light-shielded state. The water quality data indicators of the biogas slurry are shown in Table 1 below:

[0048] Table 1: Biogas slurry water quality indicators

[0049]

[0050] In the preparation process, photosynthetic bacteria are first activated and expanded using a special culture medium, and the bacterial solution in the logarithmic growth period is added to the sterilized and diluted biogas slurry to acclimate and culture the photosynthetic bacteria. Figure 1-2 As shown, mature photosynthetic bacteria are domesticated and cultured and collected for later use;

[0051] The photosynthetic bacteria domestication implementation step in step S1 includes: rejuvenating the photosynthetic bacteria with a special culture medium, inoculating it into the diluted and sterilized original biogas slurry, using the biogas slurry culture medium to domesticate and culture the photosynthetic bacteria, so that the photosynthetic bacteria adapt to the growth environment of the biogas slurry, the mother liquid used in the culture medium is selected as the dominant bacterial community of photosynthetic bacteria of Rhodopseudomonas palustris, the color of Rhodopseudomonas palustris is dark red liquid, has a special odor, and the biomass is 8 billion / mL, and is refrigerated in a refrigerator at 4°C;

[0052] The experimental reagents and instruments used in the above-mentioned steps of implementing the domestication of photosynthetic bacteria are shown in Tables 2 and 3 below:

[0053] Table 2 Experimental reagents

[0054]

[0055]

[0056] Table 3 Experimental instruments

[0057]

[0058] After the photosynthetic bacteria were domesticated, a light test was conducted in a biochemical culture under 60W incandescent light. The bottle mouth was sealed with plastic wrap under anaerobic conditions, and was not sealed under aerobic conditions. The dark experiment was conducted in a shaker. The conical flask was wrapped with tin foil and the bottle mouth was opened for dark aerobic; the conical flask and bottle mouth were wrapped with tin foil for dark anaerobic. The dissolved oxygen content was detected using a dissolved oxygen instrument. The dissolved oxygen under aerobic conditions was maintained between 2.0 and 4.0 mg / L, and the dissolved oxygen under anaerobic conditions was below 1.0 mg / L. The temperature was maintained at 37°C. The reaction vessel was a 500ml conical flask with an effective reaction volume of 300mL.

[0059] After precipitation, the upper bacterial liquid was taken for colorimetric determination at a wavelength of 660nm, and the OD 660 As an indicator of bacterial liquid concentration;

[0060] S2. Add the photosynthetic bacteria cultured in S1 to the biogas slurry, control the dosage ratio of photosynthetic bacteria, light-oxygen conditions and time, and after the reaction is completed, centrifuge and filter out the supernatant, and then detect the concentrations of carbon, nitrogen, phosphorus and dissolved organic matter in the supernatant;

[0061] Results of three-dimensional fluorescence analysis of the soaking solution: From Table 4 below, it can be seen that the content of fulvic acid in the original biogas slurry is relatively high. After being treated with dark aerobic photosynthetic bacteria, the content of fulvic acid in the soaking solution, which has an inhibitory effect on plant growth, is significantly reduced to 19.15%.

[0062] The content of tryptophan-like substances increased significantly, reaching 0.96%;

[0063] The content of soluble microbial byproducts also increased, reaching 2.83%;

[0064] Humic acid increased the most, reaching 76.74%;

[0065] In general, the protein substances in the biogas slurry, such as tryptophan and tyrosine, increased, while the content of soluble microbial byproducts and humic acid increased significantly, and the content of harmful component fulvic acid decreased, as shown in the attached figure of the specification. Figure 7 As shown;

[0066] Table 4: DOM content of seed soaking solution obtained from dark aerobic, F / M=3 conditions:

[0067]

[0068]

[0069] The optimal addition ratio of photosynthetic bacteria and biogas slurry in step S2 is F / M=3, the reaction temperature is controlled at 37°C, the reaction time is 15 days, and the optimal light-oxygen condition for photosynthetic bacteria to degrade biogas slurry is dark aerobic condition;

[0070] In this experiment, F / M is used to represent the inoculum of photosynthetic bacteria in the biogas slurry. F / M = COD / cell ratio, where COD refers to the organic carbon source in the biogas slurry, and its value is 2128 mg / L. M is the inoculum of photosynthetic bacteria (PSB), which are 1400 mg / L, 710 mg / L, 350 mg / L, and 212 mg / L, respectively. The F / M values ​​are 1.5, 3.0, 6.0, and 10.0, respectively.

[0071] They were cultured under four light-oxygen conditions for 15 days;

[0072] Samples were collected every 24 h for 15 consecutive days, and samples (10 mL each) were collected every day and centrifuged at 9000 rpm for 10 min to separate the supernatant and photosynthetic bacterial cells. Various water quality indicators were measured for the supernatant and used in the seed germination experiment;

[0073] Effect of photosynthetic bacteria on biogas slurry degradation: The initial COD of the original biogas slurry was 2128mg / L. After being degraded by photosynthetic bacteria, it dropped to the lowest level of 920.8mg / L on the 5th day, and the COD removal rate reached 56.4%. At the same time, the changes of ammonia nitrogen, nitrite nitrogen, nitrate nitrogen and TP in the biogas slurry were also measured. These indicators gradually decreased with the degradation time, reaching 122.3mg / L, 0.275mg / L, 3.08mg / L and 2.71mg / L respectively. Compared with the original biogas slurry, the highest removal rates can reach 42.9%, 32.43%, 20.56% and 25.01% respectively; comprehensive analysis of carbon source, nitrogen source and phosphorus source were reduced by 56.4%, 95.89% and 25.01% respectively, see the attached figure of the specification. Figure 8-12 As shown;

[0074] S3. The supernatant prepared in S2 was diluted into different concentrations of soaking solution for mung bean seed germination experiment;

[0075] The sample groups of the mung bean seed germination test soaking solution in the above step S3 are as shown in Table 5 below:

[0076] Table 5: Seed soaking solution samples

[0077]

[0078]

[0079] The above-mentioned dark aerobic and F / M=3 inoculation conditions that are most suitable for the growth of photosynthetic bacteria were selected to treat the biogas slurry with photosynthetic bacteria, and the supernatant was used as the seed soaking liquid for the mung bean seed germination experiment. The germination potential, germination index and vitality index were significantly (P<0.05) higher than those of the original biogas slurry and clean water seed soaking treatments. Compared with the germination rate of 23.5% of the original biogas slurry (S3) after dilution, the germination rate of the 75% photosynthetic bacteria treatment liquid (PS3) with the same concentration reached 94.0%, and its germination rate reached the maximum. The photosynthetic bacteria treatment liquid has a significant effect on accelerating the germination of mung bean seeds. The table of the germination potential, germination rate, germination index and vitality index of mung bean seeds is shown in the attached figure of the specification. Fig.13 As shown in Table 6 below:

[0080] Table 6: Mung bean seed germination potential, germination rate, germination index, vitality index

[0081]

[0082]

[0083] Different lowercase letters in the same column indicate significant differences (P<0.05), TW means soaking seeds in water;

[0084] The mung bean seed soaking liquid in step S3 is the supernatant produced after the photosynthetic bacteria treatment of the biogas slurry under the dark aerobic inoculation conditions of F / M=3 as the mung bean seed soaking liquid;

[0085] The supernatant under the best dark aerobic conditions was taken as the seed soaking solution, and the seed germination experiment was carried out after diluting it in different proportions, and compared with the soaking of seeds in different volume percentages of biogas slurry and clean water;

[0086] The experimental steps are as follows:

[0087] (1) Activation and expansion of photosynthetic bacteria

[0088] The activation, expansion and acclimatization of photosynthetic bacteria were carried out under anaerobic conditions. 660 The initial value is 0.213, according to the attached figure of the specification Figure 1 It can be seen that photosynthetic bacteria grow rapidly after being inoculated in the special culture medium. 0-4h is the adaptation period, 4-10h has reached the logarithmic growth period, the speed of entering the logarithmic growth period is fast, the growth stability period is long, 30-75h, and the decline period is after 75h.

[0089] Take the photosynthetic bacteria in the logarithmic phase with a high total number of viable bacteria as the inoculum and inoculate it into the diluted and sterilized biogas slurry culture medium to make the photosynthetic bacteria adapt to the growth environment of the biogas slurry. Figure 2 It can be seen that after the photosynthetic bacteria were inoculated into the sterilized diluted biogas slurry medium, they grew slowly within 0 to 10 hours, which was the adaptation period. This was due to the partial inhibition of the biogas slurry on the photosynthetic bacteria in the initial inoculation period.

[0090] The photosynthetic bacteria entered the rapid growth phase within 10 to 70 hours, and adapted to the growth environment of the biogas slurry base, and began to grow at a relatively fast speed; after 70 hours, it showed a downward trend and entered the decay phase, indicating that the photosynthetic bacteria could grow and reproduce well in the biogas slurry after being domesticated and cultured. The photosynthetic bacteria liquid in this rapid growth phase was used as the inoculum to carry out the biogas slurry degradation experiment under different light-oxygen conditions;

[0091] (2) Growth patterns of photosynthetic bacteria based on biogas slurry under different culture conditions

[0092] As shown in the attached figure of the specification Figure 3-6 As shown in the figure, after 15 days of biogas slurry-based culture experiment, the photosynthetic bacteria under four different light-oxygen conditions, with the increase of photosynthetic bacteria inoculation amount, F / M changes along 10.0, 6.0, 3.0, 1.5. The longitudinal comparison of photosynthetic bacteria biomass shows that it increases with the increase of inoculation amount under different light-oxygen conditions.

[0093] The drawings in the specification Figure 4 Under dark aerobic conditions, the amount of photosynthetic bacteria in the F / M=3 ratio reached its peak on the first day, and OD 660The value is 1.55, which is the maximum value;

[0094] This may be because the photosynthetic bacteria acclimated with biogas slurry can quickly adapt to the F / M=3 nutritional environment and reach the highest biomass quickly after being inoculated into biogas slurry under dark aerobic conditions. By comparing the growth of different photosynthetic bacteria inoculation amounts under four light-oxygen conditions, it can be concluded that the F / M=3 inoculation ratio is more conducive to the growth of photosynthetic bacteria in biogas slurry under dark aerobic conditions;

[0095] (3) Three-dimensional fluorescence characteristics of DOM in the supernatant of F / M=3 biogas slurry under different light-oxygen conditions

[0096] As shown in the attached figure of the specification Figure 7 As shown, tyrosine and tryptophan are both related to aromatic amino acids in proteins and belong to protein-like fluorescence peaks, while fulvic acid and humic acid are both produced by humic substances with complex molecular structures and belong to humic-like fluorescence peaks;

[0097] The drawings in the specification Figure 7 Zone I is tyrosine-like, zone II is tryptophan-like, zone III is fulvic acid, zone IV is soluble microbial byproducts, and zone V is humic acid;

[0098] Soluble microbial byproducts are organic substances released by microbial cells during biological wastewater treatment;

[0099] From the attached drawing Figure 7 It can be seen that the content of fulvic acid in the original biogas slurry is relatively high. After being treated with four different light-oxygen conditions, the content of fulvic acid is significantly reduced, and it is reduced to 19.15% under dark aerobic conditions;

[0100] The content of tyrosine-like substances increased slightly, and the content of tryptophan-like substances increased significantly under dark aerobic conditions, reaching 0.96%.

[0101] The contents of soluble microbial byproducts all increased, reaching the highest level of 2.83% under dark aerobic conditions;

[0102] The humic acid content increased, and it reached the maximum under dark anaerobic conditions, reaching 89.83%;

[0103] In general, under the four different light-oxygen treatment conditions of photosynthetic bacteria, the protein substances in the biogas slurry, such as tryptophan and tyrosine, increased, the content of soluble microbial byproducts and humic acid increased significantly, and the content of fulvic acid decreased;

[0104] Among them, the content of protein tryptophan and humus increased significantly under dark aerobic conditions. Humus plays a major role in plant growth, plant nutrition and soil fertility improvement, while protein is a high-value nutrient that also promotes plant growth.

[0105] Among them, fulvic acid has a high inhibitory and low promoting effect on plant growth, that is, the reduction of fulvic acid content helps to promote plant growth;

[0106] Based on the above analysis, the biogas slurry degradation experiment was carried out under dark aerobic conditions with a ratio of F / M=3, the carbon, nitrogen and phosphorus indicators of the treated liquid were tested, and the seed soaking liquid was prepared;

[0107] (4) Effect of photosynthetic bacteria on biogas slurry degradation under dark aerobic conditions with F / M=3

[0108] The dark aerobic conditions most suitable for photosynthetic bacteria growth were selected, and the photosynthetic bacteria with F / M=3 were inoculated to carry out the biogas slurry degradation experiment, as shown in the attached figure of the specification. Figure 8-12 As shown in the figure, the COD of the original biogas slurry with an initial COD of 2128 mg / L showed a downward trend after being degraded by photosynthetic bacteria, and dropped to the lowest level of 920.8 mg / L on the 5th day, with a COD removal rate of 56.4%. At the same time, the changes in ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, and TP in the biogas slurry were also measured. These indicators gradually decreased with the degradation time, and dropped to the lowest level around 12-14 days, reaching 122.3 mg / L, 0.275 mg / L, 3.08 mg / L, and 2.71 mg / L, respectively. The corresponding maximum removal rates can reach 42.9%, 32.43%, 20.56%, and 25.01%, respectively.

[0109] Compared with biogas slurry, its excessively high carbon, nitrogen and phosphorus indexes are reduced, the adaptability to plant growth is enhanced, and the potential threat of eutrophication to the environment is reduced;

[0110] (5) Seed soaking in treatment solution and mung bean seed germination

[0111] As shown in the attached figure of the specification Fig.13 As shown, S1-S4 are the seed soaking effects of 25%, 50%, 75%, and 100% volume percentage of the original biogas slurry after dilution with deionized water, respectively;

[0112] PS1-PS4 are the soaking effects of photosynthetic bacteria solution diluted with deionized water at 25%, 50%, 75%, and 100% volume percentages, respectively;

[0113] From the soaking photos, we can see that high concentration of biogas slurry will inhibit the growth of mung bean seeds. 100% biogas slurry directly causes mung bean seeds not to germinate. However, as the concentration of photosynthetic bacteria treatment solution increases, mung bean seeds show a good germination trend visible to the naked eye, and the effect is better than soaking in water.

[0114] In conjunction with the accompanying drawings Fig.13As shown in Table 6, compared with the control of soaking seeds in clear water, the germination potential, germination rate, germination index and vitality index under conditions S1-S4 were all reduced, especially the germination rate of seeds after S4 soaked with 100% biogas slurry was particularly low, almost inhibiting the germination of seeds, indicating that the higher the concentration of biogas slurry, the stronger the inhibitory effect on the germination of mung bean seeds;

[0115] When the seeds were soaked in photosynthetic bacteria treatment solution, under the conditions of PS1-PS4, the germination potential, germination index and vitality index of mung bean seeds changed significantly (P<0.05), which were higher than the original biogas slurry and clean water soaking treatments. Among them, the germination rate and germination index of the 75% photosynthetic bacteria treatment solution, i.e. PS3, reached the maximum.

[0116] It shows that compared with the original biogas slurry, soaking seeds in biogas slurry treated with photosynthetic bacteria can more effectively enhance the germination effect of mung bean seeds. The humus content in its DOM (dissolved organic matter) increased by 88.22%, and the carbon source, nitrogen source and phosphorus source decreased by 56.4%, 95.89% and 25.01% respectively. The effective nutrients in the biogas slurry, such as protein, were improved, the inhibition of high concentrations of carbon, nitrogen and phosphorus was relieved, and the degree of pollution hazard was reduced, thereby effectively promoting seed germination.

[0117] While embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for obtaining efficient seed soaking solution by treating biogas slurry with photosynthetic bacteria, It is characterized in that The following steps are involved: S1. The biogas slurry is taken out from the cow dung fermentation process, and the biogas slurry is allowed to stand, filtered, and centrifuged for pretreatment. After collection, it is sealed and stored at room temperature and shaded. The treated biogas slurry is sterilized and diluted, and then inoculated with photosynthetic bacteria, and then mature photosynthetic bacteria adapted to the biogas growth environment are collected and cultivated; S2. Add the mature photosynthetic bacteria cultured in S1 to the biogas slurry, control the dosage ratio of photosynthetic bacteria, light-oxygen conditions and time, and after the reaction is completed, centrifuge and filter out the supernatant, and then detect the concentrations of carbon, nitrogen, phosphorus and dissolved organic matter in the supernatant; S3. The supernatant prepared in S2 was used to dilute the seed soaking solution into different concentrations for mung bean seed germination experiments, among which the seed soaking solution with a diluted concentration of 75% had the best germination effect on mung bean seeds.

2. A method for obtaining efficient seed soaking solution by treating biogas slurry with photosynthetic bacteria according to claim 1, Features: During the fermentation process in step S1, the fermentation temperature is 35-38° C. and the fermentation time is 60 days for normal gas production.

3. A method for obtaining efficient seed soaking solution by treating biogas slurry with photosynthetic bacteria according to claim 1, Features: The photosynthetic bacteria domestication implementation step in step S1 includes: rejuvenating the photosynthetic bacteria with a special culture medium, inoculating them into the diluted and sterilized original biogas slurry, and domesticating and culturing the photosynthetic bacteria with the biogas slurry culture medium to make the photosynthetic bacteria adapt to the growth environment of the biogas slurry.

4. A method for obtaining efficient seed soaking solution by treating biogas slurry with photosynthetic bacteria according to claim 3, Features: The bacterial species in the culture medium is a photosynthetic bacterial mother liquid with Rhodopseudomonas palustris as the dominant bacterial group.

5. The method of claim 4 for obtaining efficient seed soaking solution by treating biogas slurry with photosynthetic bacteria, Features: The Rhodopseudomonas palustris is a dark red liquid with a special odor, a biomass of 8 billion / mL, and is refrigerated in a refrigerator at 4°C.

6. The method of claim 1 for obtaining efficient seed soaking solution by treating biogas slurry with photosynthetic bacteria, Features: The optimal addition ratio of photosynthetic bacteria to biogas slurry in step S2 is F / M=3, where F is COD mg / l of biogas slurry and M is inoculum amount of photosynthetic bacteria in mg / L.

7. The method of claim 1 for obtaining efficient seed soaking solution by treating biogas slurry with photosynthetic bacteria, Features: The reaction temperature in step S2 is controlled at 37° C. and the reaction time is 15 days.

8. The method of claim 1 for obtaining efficient seed soaking solution by treating biogas slurry with photosynthetic bacteria, Features: The best light-oxygen condition for photosynthetic bacteria to degrade biogas slurry in step S2 is dark aerobic condition.

9. The method of claim 1 for obtaining efficient seed soaking solution by treating biogas slurry with photosynthetic bacteria, Features: The mung bean seed soaking solution in step S3 is the supernatant obtained by treating biogas slurry with photosynthetic bacteria under the inoculation conditions of dark aerobic and F / M=3.

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