Kitchen wastewater organic acid fertilizer and preparation method thereof

Abstract

The invention discloses kitchen wastewater organic acid fertilizer and a preparation method thereof, and belongs to the technical field of comprehensive utilization of resources. According to the kitchen wastewater organic acid fertilizer, kitchen wastewater serves as a raw material, VFAs fermentation liquor is produced through AnMBR under the condition that the pH ranges from 5 to 6, then the VFAs fermentation liquor is compounded with base fertilizer, and the preparation method of the kitchen wastewater organic acid fertilizer solves the problems that at present, kitchen wastewater treatment difficulty is large, the operation cost is high, the product value is low, and the yield is large; and the prepared organic acid fertilizer has an obvious improvement effect on crop growth and quality compared with a traditional fertilizer, and has an obvious improvement effect on soil nutrient effective components.

Description

Technical Field

[0001] The present invention relates to the technical field of comprehensive utilization of resources, and particularly relates to an organic acid fertilizer for kitchen waste wastewater and a preparation method thereof. Background Art

[0002] With the rapid development of the catering industry, the generation amount of kitchen waste is increasing day by day. After pretreatment and separation, a large amount of kitchen waste wastewater is generated. Such wastewater has the characteristics of high-concentration organic matter, high suspended solids and high nitrogen. On the one hand, it is difficult to treat it to meet the discharge standards, and if the treatment is not thorough, it is extremely easy to cause serious environmental pollution; on the other hand, the biodegradability of kitchen waste wastewater is good, and if only simple treatment is carried out, it will lead to serious waste of resources.

[0003] At present, anaerobic fermentation to produce biogas is the mainstream technology for treating kitchen waste wastewater. However, with the development of the times and the progress of technology, biogas production is no longer the best choice. The reasons are as follows: on the one hand, the economic value of biogas is relatively low and the production cost is high; on the other hand, if biogas is not properly treated, it will cause a greenhouse effect more serious than carbon dioxide.

[0004] The intermediate product of anaerobic fermentation of kitchen waste wastewater - volatile fatty acids (VFAs) can not only be used as a carbon source for sewage treatment, but also be an important precursor for many chemical syntheses. In addition, it can be further applied to the field of agricultural fertilizers. However, at present, the production of VFAs faces factors such as high cost, small output and unstable system. At the same time, the VFAs fermentation broth has not been effectively utilized. Summary of the Invention

[0005] Aiming at the above problems existing in the prior art, the purpose of the present invention is to provide a method for preparing an organic acid fertilizer by using kitchen waste wastewater. This method solves the problems of difficult treatment of kitchen waste wastewater, high operating cost, low product value and large output existing at present; and the prepared organic acid fertilizer has an obvious promoting effect on crop growth and quality compared with traditional fertilizers.

[0006] In order to achieve the above purpose, the following technical solutions are provided:

[0007] The first purpose of the present invention is to provide a preparation method of a VFAs fermentation broth of kitchen waste wastewater, and the method includes:

[0008] Using an AnMBR reactor device to treat kitchen waste wastewater. During the operation of the reactor, the inoculated sludge and the kitchen waste wastewater mixture in the digestion tank are filtered through the membrane module, and the effluent is the VFAs fermentation broth of kitchen waste wastewater; the temperature of the digestion tank is controlled at 36-38°C; the pH value is controlled at 5-6.

[0009] In one embodiment, the AnMBR reactor device includes:

[0010] A peristaltic pump (1) is used to input the kitchen wastewater and acid and alkali solution into the digestion tank;

[0011] Digestion tank (4), used for anaerobic digestion of food wastewater;

[0012] A circulation pump (8) for circulating the mixed liquid in the digester;

[0013] The membrane assembly (9) is used to filter the mud-water mixture in the digester to obtain fermentation liquid;

[0014] The peristaltic pump (1) inputs the kitchen wastewater into the digester through the first pipeline Q1, inputs the acid and alkali solution into the digester through the second pipeline Q2 according to the control of the pH controller (11), and returns the effluent to the digester through the third pipeline Q3; the tank body of the digester (4) is circulated through the circulation pump (8) and the fourth pipeline Q4, and the effluent is transported to the water outlet bucket through the membrane assembly (9).

[0015] In one embodiment, the working volume of the digester is 40-45L.

[0016] In one embodiment, the pH value of the digester is controlled to be 6.

[0017] In one embodiment, the AnMBR reactor uses an organic load of 3 kg·(m3·d) -1 Start up and gradually increase the organic load to a stable 15kg·(m3·d) -1 Fermentation is carried out.

[0018] In one embodiment, a stirrer (2) is provided in the water inlet bucket connected to the peristaltic pump, for uniformly inputting the kitchen wastewater into the digestion tank.

[0019] In one embodiment, the digestion tank body is provided with a temperature probe (6), a heating belt (3) and a cooling water system (5) for controlling the temperature of the digestion tank.

[0020] In one embodiment, a gas flow meter (7) is provided on the digestion tank body for monitoring gas production.

[0021] In one embodiment, the pH controller (11) on the digestion tank body is used to transport acid and alkali solutions into the digestion tank to maintain a stable pH value.

[0022] In one embodiment, a pressure gauge (10) is provided on the membrane assembly for detecting the pressure in the pipeline.

[0023] In one embodiment, the food waste wastewater is transported into a digestion tank filled with anaerobic sludge through a peristaltic pump and a first pipeline, and then the acid-base solution is transported into the digestion tube through the peristaltic pump and a second pipeline to adjust the pH to 5 and 6. The temperature in the digestion tank is controlled at 36 - 38 °C through a temperature control system, namely a temperature probe (6), a heating tape (3) and a cooling water system (5). The mud-water mixture in the digestion tank is fully reacted through a circulation pump and a fourth pipeline, and the mud-water mixture is filtered through a membrane module to finally obtain a VFAs fermentation broth.

[0024] In one embodiment, in the AnMBR reactor, when the pH is 5, the VFAs yield, energy production and COD recovery rate in the reactor are respectively stabilized at 0.28 g / g-COD, 3.8 kg / m 3 / d and 32.7%, and the COD VFAs / effluent COD ratio is 60%; when the pH is 6, the VFAs yield, energy production and COD recovery rate in the reactor are respectively stabilized at 0.35 g / g-COD, 4.7 kg / m 3 / d and 39.8%, and the COD VFAs / effluent COD ratio is 80%.

[0025] In one embodiment, the digestion tank is filled with inoculated sludge and food waste wastewater; both the inoculated sludge and the food waste wastewater are taken from a certain food waste treatment plant in Zhangjiagang, Jiangsu Province. The inoculated sludge is anaerobic sludge, and the inoculation amount is 40 - 45 L. Its specific properties are as follows: pH 7.87 ± 0.05, mixed liquor suspended solid concentration MLSS 35.45 ± 1.1 g / L, mixed liquor volatile suspended solid concentration MLVSS 20.24 ± 1.9 g / L.

[0026] In one embodiment, the membrane module (9) is made of polyvinylidene fluoride and contains 2 membrane tubes with a length of 50 cm and a diameter of 8 mm. The total area of the membrane tubes is 0.025 m 2 , and the molecular weight cut-off is 100 kDa.

[0027] In one embodiment, the membrane flux during the operation of the membrane module is 12 L·(m 2 ·h) -1 - to 26.7 L·(m 2 ·h) -1 . Whenever the membrane flux drops to about 12 L·(m 2 ·h) -1 , on-line membrane cleaning is carried out; the membrane pressure during the operation of the membrane module is 0.18 Mpa - 0.26 Mpa.

[0028] In one embodiment, the flow rate of the circulation pump is 1 m 3 ·h -1 .

[0029] The second object of the present invention is to provide a fermentation broth of VFAs from food waste wastewater obtained by the above-mentioned method.

[0030] In one embodiment, the content of VFAs in the fermentation broth of VFAs from food waste wastewater is 34.4 - 42.0 g acetic acid / L, and the COD is 56.4 - 66.8 g / L.

[0031] The third object of the present invention is to provide a method for preparing organic fertilizer based on the fermentation broth of VFAs from food waste wastewater, and the method includes:

[0032] Concentrating the obtained fermentation broth of VFAs from food waste wastewater in a FO forward osmosis device, and then compounding the concentrated fermentation broth of VFAs from food waste wastewater after treatment with a basal fertilizer or a microbial fertilizer, that's all.

[0033] The FO forward osmosis device includes a circulation pump (1), a membrane module (2), a temperature probe (3), a conductivity meter (4) and a real-time online conductivity controller (5);

[0034] Among them, the circulation pump (1) sucks and transports the liquid below the membrane module (2) to the bottom of the draw solution tank through the first pipeline Q1; sucks and transports the feed liquid from the bottom of the feed tank to the membrane module (2) through the second pipeline Q2; the real-time online conductivity controller (5) transports the high-concentration draw solution to the draw solution tank through the third pipeline Q3; the operation mode of the FO forward osmosis device is the AL-FS mode; the feed liquid is the fermentation broth of VFAs from food waste wastewater; and the draw solution tank contains the draw solution.

[0035] In one embodiment, the draw solution is any one of NH4H2PO4, (NH4)2HPO4, KH2PO4, NaCl and KCl solutions; preferably (NH4)2SO4 solution or KCl solution.

[0036] In one embodiment, the concentration of the draw solution in the draw solution tank is 0.5 - 4 mol / L; preferably 3 - 4 mol / L.

[0037] In one embodiment, the cross-flow rate of the FO forward osmosis device during operation is 6 - 14 cm / s; preferably 10 cm / s.

[0038] In one embodiment, the concentration volume multiple of the concentrated fermentation broth of VFAs from food waste wastewater is 2 - 6 times; preferably 3 - 5 times.

[0039] In one embodiment, the basal fertilizer is a basal fertilizer containing N, P, and K; further, the N-containing basal fertilizer is urea; the P-containing basal fertilizer is potassium dihydrogen phosphate; the K-containing basal fertilizer is potassium nitrate.

[0040] In one embodiment, the microbial fertilizer includes one or more of yeast fertilizer, lactic acid bacteria fertilizer, bacillus fertilizer, photosynthetic bacteria fertilizer, and actinomycetes fertilizer.

[0041] In one embodiment, the mass ratio of the concentrated fermentation liquid of VFAs from food waste wastewater to the base fertilizer or the microbial fertilizer in the compounding is 1-2:1; preferably 1:1.

[0042] The fourth object of the present invention is to provide an organic fertilizer formed based on the fermentation liquid of VFAs from food waste wastewater prepared by the above-mentioned method.

[0043] The fifth object of the present invention is to provide the application of the above-mentioned organic fertilizer formed based on the fermentation liquid of VFAs from food waste wastewater in agricultural production.

[0044] The sixth object of the present invention is to provide a method for improving the yield and quality of cherry radishes, and the method is to apply the above-mentioned organic fertilizer formed based on the fermentation liquid of VFAs from food waste wastewater to cherry radishes.

[0045] In one embodiment, the fertilization method is root fertilization.

[0046] In one embodiment, the organic fertilizer needs to be diluted before fertilization, and the dilution multiple is 200-800 times.

[0047] In one embodiment, the number of fertilizations is once every 3-5 days; the time is selected in the evening.

[0048] The seventh object of the present invention is to provide a method for improving soil nutrient availability, and the method is to apply the above-mentioned fermentation liquid of VFAs from food waste wastewater or the organic fertilizer formed based on the fermentation liquid of VFAs from food waste wastewater to the soil.

[0049] In one embodiment, the improvement of soil nutrient availability refers to increasing the content of organic phosphorus in the soil.

[0050] In one embodiment, the improvement of soil nutrient availability refers to increasing the activity of alkaline phosphatase in the soil and inhibiting the activity of catalase in the soil.

[0051] In one embodiment, the improvement of soil nutrient availability refers to adjusting the soil pH, removing soil heavy metals, optimizing the soil microbial community structure, providing a suitable living environment for beneficial microorganisms, and thus promoting the circulation and transformation of nutrients in the soil, so as to continuously improve soil fertility.

[0052] In one embodiment, the organic fertilizer needs to be diluted before fertilization, and the dilution multiple is 200-800 times; preferably 200 times.

[0053] The beneficial effects of the present invention are as follows:

[0054] (1) The present invention uses kitchen waste wastewater as a raw material to produce VFAs fermentation broth by AnMBR under the condition of pH 5-6, realizing the resource utilization of waste. In addition, in traditional continuous VFAs production systems, such as CSTR, there are problems such as poor solid-liquid separation effect, low microbial retention rate, low digestion efficiency, and turbidity of VFAs fermentation broth when treating kitchen waste wastewater. AnMBR is a fermentation system that combines anaerobic digestion and membrane filtration technologies, which can effectively retain microorganisms to maintain a high biomass concentration, thereby increasing the conversion rate of organic matter; at the same time, it can also achieve good solid-liquid separation and obtain high-quality VFAs fermentation broth. Finally, it can reach a VFAs concentration of 42 g acetic acid / L, a VFAs production rate of 0.35 g / g-inlet COD, a VFAs production capacity of 4.7 kg / m 3 / d, and a COD recovery efficiency of 38.8%. In addition, the acidic condition of pH 6 during the production process greatly reduces the amount of alkali used compared with the alkaline condition, and the amount of alkali used at its stability is only 0.081 g NaOH / g COD VFAs .

[0055] (2) The present invention concentrates the VFAs fermentation broth of kitchen waste wastewater by the forward osmosis process. Compared with traditional pressure-driven membrane processes (such as reverse osmosis), it has potential advantages such as low energy consumption and low pollution, and shows unique application value in multiple fields such as water treatment, food processing, pharmaceuticals, and energy. At the same time, using chemical fertilizers as the draw solution in the forward osmosis process, compared with traditional draw solutions, its cost is not only the lowest among all types of draw solutions, but also can generate a relatively high osmotic pressure. And the chemical fertilizer draw solution is used to concentrate the VFAs fermentation broth that can be planted, without worrying about the occurrence of reverse solute diffusion, and the diluted chemical fertilizer draw solution is easy to recover and can be re-injected into the farmland. Among them, (NH4)2SO4 has the strongest stability as the draw solution, and the reverse solute flux is the lowest, only 23.29 g / (m 2 ·h); and the degree of membrane fouling caused is relatively light. After online cleaning, the flux can be restored to the initial pure water flux of 16.39 L / (m 2 ·h). This process can finally concentrate the high-concentration VFAs fermentation broth of kitchen waste wastewater to 3.3 times.

[0056] (3) Compared with traditional organic fertilizers, the present invention is not only weakly acidic but also contains a large amount of VFAs. It can have many positive effects on soil and crop growth. When applied to the soil, VFAs can adjust the soil pH, remove soil heavy metals, optimize the soil microbial community structure, provide a suitable living environment for beneficial microorganisms, and thus promote the circulation and transformation of nutrients in the soil, continuously improving soil fertility. For crops, the nutrients decomposed by VFAs in the soil can be directly absorbed and utilized by plant roots and participate in the metabolic process in plants. For example, it stimulates root development, making the roots stronger and more developed, enhancing the root's ability to absorb water and minerals; it also promotes the growth of stems and leaves above the ground, improves the photosynthesis efficiency of leaves, and guarantees the yield and quality of crops. Finally, the application of the C-group fertilizer formulated with the VFAs fermentation broth and N, P, and K nutrients in the present invention has an obvious promoting effect on the agronomic traits and quality of crops, and the best effect is achieved when diluted 400 times. Among them, in soluble protein and soluble sugar, the effect of applying C 400 is significantly greater than that of other fertilizers, and their contents are 2.11 mg / g FW and 49.53 mg / g FW respectively. In addition, the content of vitamin C in the fruits of applying C 400 is 0.352 mg / g FW, only 0.01 mg / g FW lower than that of C 200 , and the nitrate content in the fruits is the lowest in the C-group, only 0.53 mg / g FW. In terms of soil nutrients and soil enzyme activities, the performance of various fertilizers varies greatly. Among them, the ammonium nitrogen content in the soil of applying D 200 is the highest, reaching 56.21 mg / g; the organic matter content in the soil of applying B 200 is the highest, reaching 4.36 g / kg. In addition, compared with the A-group fertilizer, the alkaline phosphatase activity in the soil of applying the fertilizer containing the VFAs fermentation broth is significantly increased, but the catalase activity is significantly decreased. Description of the Drawings

[0057] Figure 1 is the overall schematic diagram of the AnMBR reactor device of the present invention;

[0058] Figure 2 is the data graph of the operation process of the AnMBR reactor device of the present invention; (a) pH 5 reactor; (b) pH 6 reactor;

[0059] Figure 3 is the component data graph of the VFAs fermentation broth produced by the present invention using AnMBR; (a) pH 5 reactor; (b) pH 6 reactor;

[0060] Figure 4Efficiency data graph of producing VFAs fermentation broth by AnMBR of the present invention; (a) Reactor with pH 5; (b) Reactor with pH 6

[0061] Figure 5 Overall schematic diagram of the FO device of the present invention

[0062] Figure 6 Comparison data graph of various fertilizer extraction solutions of the present invention; (a) NH4H2PO4; (b) (NH4)2HPO4; (c) KH2PO4; (d) (NH4)2SO4; (e) KCl; (f) NaCl

[0063] Figure 7 Selection comparison graph of the optimal fertilizer extraction solution of the present invention; (a) KCl standard curve; (b) NaCl standard curve; (c) (NH4)2SO4 standard curve; (d) Reverse solute flux

[0064] Figure 8 Data graph of the concentration effect of VFAs fermentation broth with different membrane orientations of the FO device of the present invention; (a) Membrane orientation; (b) Concentration multiple

[0065] Figure 9 Data graph of the concentration effect of VFAs fermentation broth with different extraction solution concentrations of the FO device of the present invention; (a) Extraction solution concentration; (b) Concentration multiple

[0066] Figure 10 Data of the concentration effect of VFAs fermentation broth with different cross - flow rates of the FO device of the present invention; (a) Cross - flow rate; (b) Concentration multiple

[0067] Figure 11 Data graph of concentrating VFAs fermentation broth of food waste water with different concentration multiples by the FO device of the present invention; (a) Concentration multiple; (b) Quality of concentrated solution

[0068] Figure 12 Data graph of the influence of four fertilizers on the agronomic growth indexes of cherry radish; (a) Maximum leaf length; (b) Maximum leaf width; (c) Stem height; (d) Stem diameter; (e) Single fruit weight; (f) Number of leaves

[0069] Figure 13 Data graph of the influence of four fertilizers on the fruit quality of cherry radish

[0070] Figure 14 Data graph of the influence of four fertilizers on the nutrients in the tested soil

[0071] Figure 15 Influence of four fertilizers on the enzyme activity in the tested soil Detailed implementation mode

[0072] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope protected by the present invention. The following specific embodiments further describe the present invention.

[0073] The raw material sources involved in the present invention:

[0074] The inoculated sludge and the food waste wastewater are both taken from a certain food waste treatment plant in Zhangjiagang, Jiangsu Province. The inoculated sludge is taken from the anaerobic sludge in the AnMBR digestion tank, and the inoculation amount is 45L. Its specific properties are as follows: pH 7.87±0.05, MLSS 35.45±1.1g / L, MLVSS 20.24±1.9g / L.

[0075] The food waste wastewater is a slurry obtained by subjecting food waste to high-temperature cooking and three-phase separation. Its main properties are shown in Table 1.

[0076] Table 1 Properties of food waste wastewater

[0077]

[0078]

[0079] Example 1

[0080] A method for producing volatile fatty acids (VFAs) fermentation broth from food waste wastewater includes the following:

[0081] As Figure 1 Shown in the AnMBR device diagram, it includes a peristaltic pump (1), a stirrer (2), a heating belt (3), a digestion tank (4), a cooling water system (5), a temperature probe (6), a gas flow meter (7), a circulation pump (8), a membrane module (9), a pressure gauge (10) and a pH controller (11).

[0082] Among them, the peristaltic pump (1) inputs the food waste wastewater into the digestion tank through the first pipeline Q1, controls the input of acid-base solution into the digestion tank through the second pipeline Q2 according to the pH controller (11), and returns the effluent to the digestion tank through the third pipeline Q3; the tank body of the digestion tank (4) is circulated through the circulation pump (8) and the fourth pipeline Q4 and the effluent is transported to the effluent bucket through the membrane module (9).

[0083] By increasing the feed volume of the food waste wastewater, the organic loading rate (OLR) of the two reactors is gradually increased. The hydraulic retention time (Hydraulic Retention Time, HRT) can be calculated according to the feed volume and the reactor volume.

[0084] The entire operation process of the two reactors consists of 7 stages, as shown in Table 2. In the first stage, it is mainly the pH adjustment and reactor stabilization stage. The pH values of the two reactors are adjusted and stabilized at 5 and 6 respectively, and the temperature is controlled at 38 ± 1 °C. After judging that the final acid production amount of the load in each stage is stable, the load is slowly increased to start a new stage. In addition, the sludge retention time (SRT) of the reactor is calculated based on the sludge discharge amount. Since the initial MLSS of the food waste wastewater and sludge is relatively high, from day 1 to day 75, 1 L of sludge is discharged from the bottom of each reactor every day. Subsequently, from day 76 to day 120, the daily discharge amount is increased to 2 L. In addition, in order to keep the volume in the fermentation tank constant, the excess membrane effluent is returned to the reactor through a pump every day. When the membrane flux is lower than 12 L / (m 2 ·h), on-line membrane cleaning is carried out. The methods are as follows: first, clean with tap water for 30 min, then clean with 0.5% NaClO solution (10 L) for 60 min, immediately clean with 0.5% HCl solution (10 L) for 60 min, and finally clean with tap water for 30 min.

[0085] Table 2 AnMBR operating parameters

[0086]

[0087]

[0088] Figure 2 Shows the changes of VFAs with the pH 5 reactor and pH 6 reactor under different OLRs. In the first 10 days of stage I (HRT = 45 d, SRT = 45 d), the OLRs of the two reactors are both maintained at 3.0 kg-COD / (m 3 ·d), and the pH values are gradually reduced from 7.9 to 5 and 6 by real-time on-line hydrochloric acid adjustment. In the next 10 days of stage I, the pH values of the pH 5 reactor and pH 6 reactor are continuously maintained at 5 and 6 respectively, so that the microorganisms gradually adapt to the acidic environment. During this process, the VFAs in the effluent of pH 5 and 6 slowly increase from 0.35 g acetic acid / L to 10.3 g acetic acid / L and 8.7 g acetic acid / L, and the effluent COD slowly increases from 2.3 g / L to 14.6 g / L and 11.7 g / L. In the subsequent operation stage, when the OLR increases from 4.5 kg-COD / (m 3 ·d) (stage II, 10 d, HRT = 30 d) to 12.6 kg-COD / (m 3·d) (Stage VI, 20 d, HRT = 10.7 d), the VFAs in the effluents of the pH 5 reactor and the pH 6 reactor accumulated to 32.2 g acetic acid / L and 39.0 g acetic acid / L respectively, and the effluent COD were 64.2 g-COD / L and 62.4 g-COD / L respectively. When the OLR was increased to 15.0 kg-COD / (m 3 ·d) (Stage VII, 91 - 120 d, HRT = 9 d), the VFAs in the effluents of the pH 5 reactor and the pH 6 reactor were stabilized at 34.4 g acetic acid / L and 42.0 g acetic acid / L respectively, and the effluent COD were 66.8 g / L and 56.4 g / L respectively. Finally, the VFAs production of the pH 5 reactor was lower than that of the pH 6 reactor.

[0089] The components of the VFAs fermentation broth produced by treating food waste wastewater with AnMBR are as Figure 3 shown. During the whole operation process of the pH 5 reactor and the pH 6 reactor, the VFAs were mainly composed of acetic acid, propionic acid, butyric acid, valeric acid and caproic acid. In the pH 5 reactor, in the initial stage of fermentation (Stages I - III, 1 - 40 d), the contents of acetic acid and propionic acid decreased, while the contents of butyric acid, valeric acid and caproic acid increased. Especially, butyric acid showed an obvious accumulation phenomenon and became the main component in the IV - VI stages (41 - 90 d). However, in the VII stage (91 - 120 d), the content of butyric acid began to gradually decrease, while the content of acetic acid increased significantly. Finally, the VFAs in the effluent of the pH 5 reactor were mainly butyric acid and acetic acid, with the same proportion of 35.2% each. In the pH 6 reactor, propionic acid was the main component in the early stage of fermentation (Stages I - III, 1 - 40 d). Subsequently, in the middle stage of fermentation (Stages IV - VI, 41 - 90 d), the content of propionic acid decreased, while the contents of acetic acid, butyric acid, valeric acid and caproic acid increased. Especially in the VI stage (71 - 90 d), the contents of butyric acid and caproic acid increased significantly, and caproic acid was the main component. In the final stage of fermentation (Stage VII, 90 - 120 d), the contents of caproic acid and valeric acid decreased significantly, while the contents of acetic acid, propionic acid and butyric acid increased, especially the content of acetic acid increased to be the main component. Finally, acetic acid dominated in the VFAs in the effluent of the pH 6 reactor, with a proportion of 45.3%.

[0090] The performance of producing VFAs fermentation broth by treating food waste wastewater with AnMBR is as Figure 4 shown. In order to further evaluate the fermentation performance of VFAs, the changes of VFAs yield, energy production and COD recovery efficiency of the pH 5 and pH 6 reactors were calculated, and these indexes increased with the increase of organic loading rate (OLR). Finally, the VFAs yield, energy production and COD recovery rate in the pH 5 reactor were stabilized at 0.28 g / g-COD, 3.8 kg / m 3 / d and 32.7%; the VFAs yield, energy production and COD recovery rate in the pH 6 reactor were stably at 0.35 g / g-COD, 4.7 kg / m 3 / d and 39.8%. In addition, the COD VFAs / effluent COD ratios of the pH 5 reactor and the pH 6 reactor were 60% and 80% respectively, indicating that the VFAs purity of the effluent from the pH 6 reactor was higher than that of the pH 5 reactor. Therefore, compared with the pH 6 reactor, the fermentation efficiency of the pH 5 reactor was lower.

[0091] Example 2

[0092] A method for concentrating the VFAs fermentation broth of food waste wastewater prepared in Example 1 by a forward osmosis device, comprising the following:

[0093] As Figure 5 is a diagram of the FO forward osmosis device, specifically including a circulation pump (1), a membrane module (2), a temperature probe (3), a conductivity meter (4) and a real-time online conductivity controller (5). Among them, the circulation pump (1) sucks out the draw solution below the membrane module (2) through the first pipeline Q1 and transports it to the bottom of the draw solution tank; sucks out the feed solution from the bottom of the feed tank through the second pipeline Q2 and transports it into the membrane module (2); the real-time online conductivity controller (5) transports the high-concentration draw solution into the draw solution tank through the third pipeline Q3.

[0094] The VFAs fermentation broth of food waste used in this example was the effluent from the pH 6 reactor in Example 1, and its properties are shown in Table 3.

[0095] Table 3 Properties of VFAs Fermentation Broth of Food Waste Wastewater

[0096]

[0097] The specific implementation steps are as follows:

[0098] 1. Explore the performance and membrane flux recovery of different fertilizer draw solutions for forward osmosis concentration of VFAs fermentation broth of food waste wastewater

[0099] Select five kinds of chemical fertilizers, namely NH4H2PO4, (NH4)2HPO4, KH2PO4, (NH4)2SO4, and KCl, all with a concentration of 1 mol / L, and use them as the absorbents in comparison with the common NaCl solution. During the experiment, keep the temperature constant. The membrane operates in the AL-FS mode, and the cross-flow rate is set at 10 cm / s. Read the data every 15 minutes. The specific operation is as follows: First, measure the pure water flux (for 2 h) with the absorbent. After that, clean the two containers and then measure the membrane flux of the VFAs fermentation broth (for 4 h). Then, after physical on-line cleaning (run with pure water on both sides for 1 h and repeat three times), measure the pure water flux again. Finally, after chemical on-line cleaning (clean with 0.5% HCl + pure water cleaning and repeat three times), measure the pure water flux again to observe the membrane flux recovery situation.

[0100] The comparative result data of various chemical fertilizer absorbents are as Figure 6 shown. In the first two-hour pure water flux measurement stage, there are significant differences in the initial membrane fluxes of different chemical fertilizer absorbents. Among them, the initial membrane fluxes of NH4H2PO4 and (NH4)2HPO4 are the same, both being 8.47 L / (m 2 ·h). In contrast, the initial membrane fluxes of KH2PO4 and NaCl have relatively large increases, reaching 10.58 L / (m 2 ·h) and 14.81 L / (m 2 ·h) respectively. And the most prominent ones in terms of initial membrane flux are (NH4)2SO4 and KCl, reaching 16.39 L / (m 2 ·h) and 16.93 L / (m 2 ·h) respectively. During the two-hour pure water operation process, it can be found that due to the influence of reverse solute permeation, the membrane fluxes of NH4H2PO4, (NH4)2HPO4, KH2PO4, NaCl, and KCl all show a continuous decline. By the end of the operation, the decline rates of the membrane fluxes all exceed 18%. Relatively speaking, the membrane flux of (NH4)2SO4 only shows a small decline during this process, dropping from 16.39 L / (m 2 ·h) to 15.87 L / (m 2 ·h), with a decline rate of only 3%, showing very excellent stability.

[0101] In the stage of concentrating the VFAs fermentation broth, the initial membrane fluxes of the six absorbents have decreased significantly compared with the initial membrane fluxes of pure water. The highest initial membrane flux is that of (NH4)2SO4, reaching 8.47 L / (m 2 ·h). It is worth noting that KH2PO4, whose initial membrane flux was lower than that of NaCl and KCl in the pure water stage, instead has an initial membrane flux of 6.35 L / (m 2·h)) is higher than that of NaCl (3.22 L / (m 2 ·h)) and KCl (3.38 L / (m 2 ·h)). During the concentration process, a large amount of white precipitate appeared on the membrane surface of NH4H2PO4, (NH4)2HPO4, and KH2PO4, and the conductivity of the VFAs fermentation broth hardly changed. This may be due to the blockage of the membrane pores by the white precipitate, resulting in a decrease in the membrane flux and reverse solute flux. In contrast, for (NH4)2SO4, NaCl, and KCl, the conductivity of the VFAs fermentation broth increased from 32 mS / cm to 42 mS / cm, 48 mS / cm, and 53 mS / cm, respectively, during the operation. This indicates that the reverse solute diffusion of NaCl and KCl is relatively more serious than that of (NH4)2SO4, which is also one of the reasons for the decrease in the membrane flux. After the concentration stage ended, the membrane flux of (NH4)2SO4 decreased and stabilized at 4.75 L / (m 2 ·h), while the membrane fluxes of the other five draw solutions all decreased to below 2.0 L / (m 2 ·h).

[0102] In the subsequent membrane cleaning stage, after physical cleaning, the measured membrane fluxes of (NH4)2SO4, NaCl, and KCl could all be restored to the initial pure water flux level; for NH4H2PO4, (NH4)2HPO4, and KH2PO4, the recovery effect of the physical cleaning membrane flux was not obvious, while the membrane flux increased significantly after chemical cleaning, but it could not be completely restored to the initial flux.

[0103] Therefore, considering the pure water flux, the VFAs fermentation broth flux, the change value of conductivity, and the recovery of the membrane flux after cleaning, the current best choices as draw solutions are (NH4)2SO4 > KCl > NaCl in sequence. However, it is still necessary to further explore their operation stability to more deeply analyze the performance of the three draw solutions.

[0104] The selection of the best fertilizer draw solution is as Figure 7 shown. The standard curves of the reverse solute fluxes of KCl, NaCl, and (NH4)2SO4 drawn through experiments are as follows: (a) KCl: y = 0.76625x - 1.59831; (b) NaCl: y = 0.6894x - 2.4098; (c) (NH4)2SO4: y = 1.0067x - 4.5475, and the fitting degrees of all three reach above 0.999. These three standard curves are used in combination with the conductivity value to calculate the reverse solute flux. The reverse solute flux of KCl is the highest, reaching 171.69 g / (m 2 ·h), and its concentration multiple is the lowest, only 1.08 times; the reverse solute flux of the common draw solution NaCl is relatively low, at 115.76 g / (m 2·h), but its concentration multiple is similar to that of KCl; while the concentration multiple of (NH4)2SO4 is the highest, reaching 1.36 times, and the reverse solute flux is the lowest, only 23.29 g / (m 2 ·h), which is much lower than that of KCl and NaCl. In summary, among these three draw solutions, (NH4)2SO4 has the best stability and is most suitable as the draw solution for the forward osmosis concentration of VFAs fermentation broth.

[0105] 2. Explore the influence of different membrane operation modes on the forward osmosis concentration of food waste fermentation broth

[0106] Select the draw solution (NH4)2SO4 and operate it for 10 h in the AL-FS mode (the active layer faces the feed solution) and the AL-DS mode (the active layer faces the draw solution) respectively to calculate the membrane flux change and the concentration multiple.

[0107] The influence of different membrane orientations on the FO device for concentrating food waste VFAs fermentation broth is as Figure 8 shown. In the membrane flux change, the initial membrane flux of the AL-DS mode (9.52 L / (m 2 ·h)) is higher than that of the AL-FS mode (8.47 L / (m 2 ·h)). After running for one hour, the membrane flux of the AL-DS mode drops to 6.08 L / (m 2 ·h), which is lower than the membrane flux of the AL-FS mode, 6.35 L / (m 2 ·h); until the end of the operation, the membrane flux of the AL-DS mode is lower than that of the AL-FS mode. This indicates that the membrane flux under the AL-FS mode is relatively more stable than that under the AL-DS mode. At the same time, after the concentration is completed, it can also be seen that a concentration effect of 1.85 times is achieved under the AL-FS mode, while only 1.78 times of concentration is achieved under the AL-DS mode. Therefore, the AL-FS mode has better stability and concentration effect.

[0108] 3. Explore the influence of the draw solution concentration in different draw solution tanks on the forward osmosis concentration of food waste fermentation broth

[0109] Set five concentration gradients of 0.5 mol / L, 1.0 mol / L, 2.0 mol / L, 3.0 mol / L, and 4.0 mol / L for the (NH4)2SO4 draw solution, and conduct a 10 h concentration experiment in the AL-FS mode of operation to calculate the membrane flux change and the concentration multiple.

[0110] The influence of different draw solution concentrations on the FO device for concentrating food waste VFAs fermentation broth is as Figure 9 shown. From the trend in the figure, it can be seen that as the draw solution concentration increases, the initial membrane flux also increases. Especially when the draw solution concentration increases from 2 mol / L (the initial membrane flux is 10.58 L / (m2 · h)) rises to 3 mol / L (initial membrane flux 14.81 L / (m 2 · h)), the difference in the initial membrane fluxes of the two reaches the maximum. As the concentration time progresses, the membrane fluxes of both show a continuous decline. Until the end of the operation, it can be found that the membrane fluxes corresponding to the draw solutions with concentrations of 3 mol / L and 4 mol / L are both stable at 5.95 L / (m 2 · h), and the initial membrane flux of 3 mol / L (14.81 L / (m 2 · h)) and the initial membrane flux of 4 mol / L (16.93 L / (m 2 · h)) do not show an obvious gap. This indicates that the increase in the draw solution concentration does contribute to the increase in the initial membrane flux, but too high a draw solution concentration will not only reduce the concentration efficiency but also exacerbate membrane fouling. From the concentration multiple, it can also be seen that as the draw solution concentration increases, the concentration multiple also increases accordingly. However, when the concentration reaches 3 mol / L and 4 mol / L, the concentration multiples of the two are 2.45 and 2.48 respectively, which are almost the same.

[0111] 4. Explore the influence of different cross-flow rates on the forward osmosis concentration of food waste fermentation broth

[0112] Under the AL-FS mode of operation and a draw solution concentration of 3 mol / L of (NH4)2SO4, set three different cross-flow rates of 6 cm / s, 10 cm / s, and 14 cm / s, and run for 10 h to observe the changes in membrane flux and concentration multiple.

[0113] The influence of different cross-flow rates on the concentration of food waste VFAs fermentation broth by the FO device is as Figure 10 shown. When the cross-flow rate rises from 6 cm / s to 10 cm / s, the initial membrane flux increases by 4.23 L / (m 2 · h); while when the cross-flow rate rises from 10 cm / s to 14 cm / s, the increase in the initial membrane flux is significantly reduced, only rising by 2.11 L / (m 2 · h). When the operation ends, the membrane flux corresponding to a cross-flow rate of 14 cm / s (5.55 L / (m 2 · h)) is lower than the membrane flux corresponding to a cross-flow rate of 10 cm / s (5.95 L / (m 2 · h)). This indicates that increasing the cross-flow rate to 14 cm / s is not ideal and will increase energy consumption. From the concentration multiple, the concentration multiples obtained under the three cross-flow rates do not show a significant difference, and the highest concentration effect of 2.45 times is achieved when the cross-flow rate is 10 cm / s.

[0114] 5. Determine the optimal concentration multiple.

[0115] Under the operating mode of AL-FS and with (NH4)2SO4 at a concentration of 3 mol / L as the draw solution and a cross-flow rate of 10 cm / s, a long-term operation concentration experiment was carried out. Based on the volume concentration multiple, samples were taken when the volume concentration multiples were 2, 3, 4, 5, and 6 respectively to measure their COD in order to calculate the optimal actual concentration multiple.

[0116] The data of the FO device for concentrating the VFAs fermentation broth of food waste kitchen wastewater are as Figure 11 shown. As the concentration time progresses, the actual concentration multiple also gradually increases. The final actual concentration multiple (calculated based on COD) is 3.41 times, at which time the volume concentration multiple is 6, and the entire concentration process takes 10.5 h. Relatively speaking, when the actual concentration multiple is 3.35 times, the required concentration time is shortened to 9.25 h, and the volume concentration multiple is 5 at this time. This indicates that when the volume multiple increases from 5 times to 6 times, the concentration effect does not increase significantly. Therefore, the quality of the concentrated liquid after the volume is concentrated 5 times was analyzed, and it was found that the VFAs concentration was as high as 139.78 g acetic acid / L, which was concentrated 3.33 times. It is worth noting that the concentrations of NH4 + -N and TN were 22.34 g / L and 24.67 g / L respectively, which were concentrated 9.8 times and 9.34 times respectively. This may be due to the reverse solute diffusion of the selected (NH4)2SO4 draw solution, resulting in a relatively large increase in the concentration multiple. At the same time, the concentration of SO4 2- also reached 19.18 g / L, which is the main form for plants to absorb sulfur elements. The concentrations of Ca 2+ and Mg 2+ were both concentrated 3.4 times, and their concentrations reached 5.02 g / L and 0.58 g / L respectively. The concentration of K + changed little, only concentrated from 1.02 g / L to 1.18 g / L. This may be because K + underwent concentration polarization diffusion and migrated into the draw solution. In short, considering the time cost and concentration effect comprehensively, the optimal maximum volume concentration multiple is 5, and the actual concentration multiple is 3.3.

[0117] Example 3

[0118] The method for the fertilizer efficiency of applying the organic acid fertilizer prepared based on the concentrated VFAs fermentation broth of food waste kitchen wastewater to cherry radishes includes the following:

[0119] (1) Under the operating mode of AL-FS and with (NH4)2SO4 at a concentration of 3 mol / L as the draw solution and a cross-flow rate of 10 cm / s, the VFAs fermentation broth of food waste kitchen wastewater from the effluent of the pH 6 reactor in Example 1 was concentrated, and the actual concentration multiple was 3.3.

[0120] The specific water quality indicators of the obtained concentrated VFAs fermentation broth of food waste kitchen wastewater are shown in Table 4:

[0121] Table 4 Properties of Fermentation Broth of Concentrated Kitchen Waste VFAs

[0122]

[0123] (2) The cherry radish used was the Carol fruit-type cherry radish. After being seeded in a plug tray (50 holes, 54 cm × 28 cm × 0.6 mm) and raised in seedling, it was transplanted into a pot for cultivation. The upper diameter of the experimental pot was 15.7 cm, the height was 16.5 cm, and the soil filling amount was 2 kg without a bottom tray. The tested soil was garden soil, and its basic physical and chemical properties were as follows: pH 6.65, organic matter 1.85 g / kg, ammonium nitrogen 35.07 mg / kg, available phosphorus 9.06 mg / kg, and available potassium 214.05 mg / kg. The fertilizer configuration and planting method were as follows:

[0124] CK group: tap water;

[0125] Group A: 10.87 g of urea, 9.62 g of potassium dihydrogen phosphate, and 21.74 g of potassium nitrate were dissolved in 100 mL of tap water;

[0126] Group B: concentrated fermentation broth of kitchen waste VFAs;

[0127] Group C: 10.87 g of urea, 9.62 g of potassium dihydrogen phosphate, and 21.74 g of potassium nitrate were dissolved in 100 mL of concentrated fermentation broth of kitchen waste VFAs;

[0128] Group D: concentrated fermentation broth of kitchen waste VFAs and EM bacterial agent were configured at a ratio of 1:1 (the EM bacterial agent was commercially available).

[0129] The cherry radish seeds were raised by the plug tray seedling method. After the fourth to fifth true leaves appeared, they were transplanted into pots. During the planting period, fertilization was carried out once every five days, in the evening. The fertilization method was root fertilization, and the fertilization amount was 100 mL. Each group of fertilizers was diluted 200 times, 400 times, and 800 times before application. According to different fertilizers and different dilution multiples, they were CK group, Group A (A 200 、A 400 、A 800 ), Group B (B 200 、B 400 、B 800 ), Group C (C 200 、C 400 、C 800 ), and Group D (D 200 、D 400 、D 800 ), a total of 13 groups of experiments. Two parallel potted plants were added to each experiment, for a total of 39 pots. The planting lasted for 50 days to obtain the harvest.

[0130] The effects of different types of fertilizers on the agronomic traits of cherry radish are asFigure 12 As shown in the figure, from the perspective of Group A and Group B, both groups were treated with a single fertilizer. The growth rate of Group A in terms of maximum leaf length / width and stem height / thickness relative to Group CK was more than 60%, while the growth rate of Group B was only about 20%. 200 The maximum can be 5.6 times that of the CK group, and 1.1 times that of the B group. After analyzing and comparing the fertilizers in groups A and C, it was found that the addition of VFAs fermentation liquid to the C group fertilizer increased the maximum leaf length / width, stem height / thickness and single fruit weight of cherry radish by approximately 12.48%, 21.79%, 4.16%, 21.9% and 15.83%, respectively. Therefore, VFAs fermentation liquid also has a positive promoting effect on the growth of cherry radish. The effect of group D fertilizer is no different from that of group B fertilizer, but it is far inferior to group C fertilizer in terms of cherry radish growth indicators. In summary, the results show that N, P, and K are the main sources of nutrients absorbed by crops. VFAs fermentation liquid can effectively promote the growth and development of cherry radish, and microbial agents cannot provide sufficient nutrients for plants.

[0131] Effects of different types of fertilizers on the quality of cherry radish fruit Figure 13 As shown. In terms of soluble protein, single fertilization group A 200 The treatment reached the highest level of 1.76 mg / gFW; Group B with single fertilizer application 400 The treatment was 1.32mg / gFW, which increased by 36.17% compared with the CK group; the compound fertilization group C 400 The highest treatment was 2.11 mg / gFW, which was higher than that of A 200 Soluble sugar content, A 200 Fertilization was 40.19 mg / g FW, Group B 800 The highest is 43.11mg / gFW, which is higher than A 200 Increased by 7.27%. Group C 400 It ranks first with 49.53mg / gFW, compared with A 200 and B 800 They increased by 25.84% and 14.89% respectively. 800 The highest is 42.94 mg / gFW, which is higher than A 200 In terms of vitamin C content, the four groups of fertilizers were the highest when diluted 200 times. 200 、B 200 、C 200 and D 200 The vitamin C content in the treated fruits was 0.345mg / gFW, 0.318mg / gFW, 0.362mg / gFW and 0.305mg / gFW respectively. The single fertilization group A was higher than group B, and the combined fertilization group C was higher than group D. The differences within the groups were small, with the lowest C800 in group C being 0.341mg / gFW, which was lower than the highest in group A. 200Only 0.004 mg / g FW less, the overall impact of Group C on vitamin C is greater than other groups, and the N, P, K fertilizers added with VFAs fermentation broth have a promoting effect. In terms of nitrate content, the treatment groups containing VFAs fermentation broth are significantly higher than other groups. Among the single-fertilizer groups, Group B is much higher than Group A, and Group A 200 is up to 0.42 mg / g FW, similar to 0.38 mg / g FW of the CK group, Group B 200 reaches 0.79 mg / g FW, about twice that of the CK group. The nitrate content of the fruits in the compound-fertilizer group, Group D, is significantly higher than that of Group C, perhaps because the EM bacterial agent in Group D contains nitrifying bacteria that can convert ammonia nitrogen, and the concentrated fermentation broth contains a large amount of ammonia nitrogen. Group C 200 The highest nitrate content of the fruits under the treatment is 0.56 mg / g FW, lower than the national standard (less than 1.2 mg / g FW for root vegetables).

[0132] According to the above analysis, it can be found that applying the VFAs fermentation broth of food waste water has a promoting effect on the agronomic traits, soluble protein, soluble sugar, vitamin C and nitrate in the fruits of cherry radish. In addition, the increase in nitrate content is within the scope of the national standard. Moreover, adding nitrogen, phosphorus and potassium nutrient elements to the VFAs fermentation broth of food waste water can significantly increase the effect. Among them, the fertilizer in Group C shows the best performance, and the best dilution ratio is 400 times.

[0133] The effects of different types of fertilizers on the nutrients in the tested soil are as Figure 14 shown. In terms of ammonia nitrogen content, the average of Group A is 46.56 mg / g, Group B is 45.63 mg / g, and Group C is 45.3 mg / g, which are 21.97%, 19.53% and 18.66% higher than the CK group respectively. Group D 200 is up to 56.21 mg / g at most, 47.27% higher than the CK group. The concentrated VFAs fermentation broth helps the accumulation of ammonia nitrogen, and the effect is not much different from directly adding N element. In terms of available potassium content, A 200 directly adds K element, and the highest content is 309.09 mg / g. B 200 uses the VFAs fermentation broth for fertilization, and the content is 27,098 mg / g. C 200 is between A and B, being 296.67 mg / g. D 200 is 288.14 mg / g, greater than B 200 . In terms of available phosphorus content, the impacts on Group A and Group C are significant. Both Group A and Group C add phosphorus element externally. The available phosphorus content under the treatment of A 200 is 55.767 mg / L, greater than 53.161 mg / L of C 200 . The content under the treatment of Group B 200 is 14.683 mg / L, and that of Group D 200The treatment value is 14.969 mg / L, all of which are higher than that of CK, indicating that the VFAs fermentation broth can promote the available phosphorus content. Among the organic matter contents, the soil organic matter content with the application of VFAs fermentation broth is higher than that of other treatments, and the order is B > C > D > A > CK. The highest value in Group B 200 under treatment is 4.36 g / kg, higher than that of Group A 200 by 62.69%, higher than that of Group C 200 and Group D 200 by 31.33% and 62.08% respectively. Group C 200 and Group D 200 are increased by 23.88% and 3.73% respectively compared with Group A 200 . The VFAs fermentation broth has a significant promoting effect on the soil organic matter content.

[0134] In summary, different fertilizers and dilution multiples have different effects on the nutrient contents in the soil. The VFAs fermentation broth has a positive effect on the accumulation of ammonium nitrogen, available phosphorus, and organic matter.

[0135] The effects of different types of fertilizers on the enzyme activities in the tested soil are as Figure 15 shown. In terms of urease activity, there are significant differences between Group A and Group C, while there is no significant difference between Group B and Group D. The urease activity under Treatment A 200 is 0.126 mg / d / g, and that under Treatment C 200 is 0.128 mg / d / g, which are increased by 31.25% and 33.33% respectively compared with CK. The activities of Group B and Group D have a weak correlation with the dilution multiple, and the average values are 0.104 mg / d / g and 0.103 mg / d / g respectively. The key factor affecting the soil urease activity is mainly nitrogen element, and it has a small correlation with the VFAs fermentation broth. In terms of sucrase activity, the effects of Group A and Group B are relatively small, and the maximum activity is 1.55 mg / d / g for both, which is increased by 11.51% compared with CK. In the compound group, Treatment C 800 (1.72 mg / d / g) and Treatment D 800 (1.57 mg / d / g) have the greatest influence, which are increased by 23.74% and 12.94% respectively compared with CK. The sucrase activity in the soil treated with the fertilizer in Group C is significantly higher than that of other groups. The promotion effect of single nutrients on the soil sucrase activity is not significant, and the combination of multiple nutrients can effectively promote its activity. In terms of alkaline phosphatase activity, the effect of Group B with single application of VFAs fermentation broth is significant. The enzyme activity under Treatment B 200 reaches up to 2.8 μmol / d / g at most, which is 5.83 times that of the CK group. The enzyme activities under Treatments C 200 and D 200 in the compound fertilization group are 1.84 μmol / d / g and 1.45 μmol / d / g respectively, which are 3.83 times and 3.02 times that of the CK group respectively. In Group A without the addition of VFAs fermentation broth 200It was 0.87 μmol / d / g, which was 1.81 times the CK value. Applying the VFAs fermentation broth was beneficial to enhancing the activity of soil alkaline phosphatase. Among the activities of catalase, the activities of catalase in the soil of groups B, C, and D to which the VFAs fermentation broth was applied were significantly lower than those of group A without addition, and had little correlation with the dilution factor. The activity under treatment B was relatively the highest, being 13.87 μmol / d / g, showing a 17.34% increase compared to CK. 200 The activity under treatment A was up to 17.69 μmol / d / g at most, showing a 49.66% increase compared to CK, and was 27.54% higher than the enzyme activity under treatment B. Applying the VFAs fermentation broth inhibited the increase in the activity of soil catalase to a certain extent. 200 The activity under treatment A was up to 17.69 μmol / d / g at most, showing a 49.66% increase compared to CK, and was 27.54% higher than the enzyme activity under treatment B. Applying the VFAs fermentation broth inhibited the increase in the activity of soil catalase to a certain extent. 200 The activity under treatment A was up to 17.69 μmol / d / g at most, showing a 49.66% increase compared to CK, and was 27.54% higher than the enzyme activity under treatment B. Applying the VFAs fermentation broth inhibited the increase in the activity of soil catalase to a certain extent.

[0136] In summary, different fertilizers and dilution factors had different effects on soil enzyme activities. Nitrogen elements affected urease activity, and the combination of multiple nutrient elements promoted sucrase activity. Applying the VFAs fermentation broth enhanced alkaline phosphatase activity and inhibited catalase activity.

[0137] The embodiments provided above are not intended to limit the scope covered by the present invention, nor are the described steps intended to limit the order of their execution. Obvious improvements made by those skilled in the art to the present invention in combination with the existing common general knowledge also fall within the protection scope defined by the claims of the present invention.

Claims

1. A preparation method of fermentation broth of volatile fatty acids (VFAs) from kitchen and restaurant wastewater, characterized in that, The preparation method includes: Using an AnMBR reactor device to treat kitchen waste wastewater. During the operation of the reactor, the anaerobic sludge and the kitchen waste wastewater mixture in the digestion tank are filtered through a membrane module, and the effluent is the kitchen waste wastewater VFAs fermentation broth. The temperature of the digestion tank is controlled at 36 - 38 °C, and the pH value is controlled at 5 - 6.

2. The kitchen waste wastewater VFAs fermentation broth obtained by the preparation method according to Claim 1.

3. A method for preparing organic fertilizer from the VFAs fermentation broth of kitchen waste wastewater according to claim 2, characterized in that, The method includes: Concentrating the kitchen waste wastewater VFAs fermentation broth in a FO forward osmosis device, and then compounding the treated kitchen waste wastewater VFAs concentrated fermentation broth with a base fertilizer or a microbial fertilizer. The FO forward osmosis device includes a circulation pump (1), a membrane module (2), a temperature probe (3), a conductivity meter (4), and a real-time online conductivity controller (5). Among them, the circulation pump (1) sucks and transports the liquid below the membrane module (2) to the bottom of the draw solution tank through the first pipeline Q1, and sucks and transports the raw material liquid from the bottom of the raw material tank to the membrane module (2) through the second pipeline Q2. The real-time online conductivity controller (5) transports the high-concentration draw solution to the draw solution tank through the third pipeline Q3. The operation mode of the FO forward osmosis device is the AL-FS mode. The raw material liquid is the kitchen waste wastewater VFAs fermentation broth, and the draw solution tank contains the draw solution.

4. The method according to claim 3, characterized in that The draw solution is any one of the solutions of NH4H2PO4, (NH4)2HPO4, KH2PO4, NaCl, and KCl.

5. The method according to claim 3, wherein The concentration of the draw solution in the draw solution tank is 0.5 - 4 mol / L.

6. The organic fertilizer formed based on the kitchen waste wastewater VFAs fermentation broth obtained by the method according to any one of Claims 3 - 5.

7. The application of the organic fertilizer formed based on the kitchen waste wastewater VFAs fermentation broth according to Claim 6 in agricultural production.

8. A method for improving the yield and quality of cherry radish, characterized in that, The method is to apply the organic fertilizer formed based on the kitchen waste wastewater VFAs fermentation broth according to Claim 6 to cherry radishes.

9. The method according to claim 8, wherein The fertilization method is root fertilization.

10. A method for improving soil nutrient availability, characterized in that, The method is to apply the kitchen waste wastewater VFAs fermentation broth according to Claim 2 or the organic fertilizer formed based on the kitchen waste wastewater VFAs fermentation broth according to Claim 6 to the soil.

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