Method for promoting co-fermentation of seaweed sludge to produce carbon source by utilizing microbial pretreatment

Abstract

The invention provides a method for promoting co-fermentation of seaweed sludge to produce a carbon source by utilizing microbial pretreatment. The method comprises the following steps: adding a microbial agent with protein degradation capability into the sludge; adding free nitrous acid and rhamnolipid into the sludge obtained in the step 1, and performing pretreatment in an anaerobic environment; mixing the pretreated sludge with seaweed, and carrying out seaweed and sludge co-fermentation to obtain supernate of a fermentation mixture; the method for promoting co-fermentation of the seaweed sludge by utilizing microbial pretreatment can be widely applied to treatment and recycling of the sludge, the treatment efficiency of the sludge can be improved, and the treatment cost of the sludge can be reduced. The prepared seaweed sludge fermentation liquor can be used as an external carbon source for sewage treatment, can provide sufficient nutrient substances for microorganisms, and effectively promotes denitrification and phosphorus-accumulating bacteria metabolism in the sewage treatment process, so that the sewage nitrogen and phosphorus removal effect is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of resource recycling, and in particular relates to a method for promoting the co-fermentation of seaweed sludge to produce carbon sources by utilizing microbial pretreatment. Background Art

[0002] With the rapid advancement of urbanization, the total amount of sewage has increased, and with it the production of sludge. As a byproduct of urban sewage treatment, sludge is a typical organic waste. Its treatment and disposal face severe challenges and are costly, accounting for up to 60% of the total cost of a sewage treatment plant.

[0003] Microorganisms play a key role in the sewage treatment process. They participate in sewage purification in the form of aggregates. However, microorganisms need to consume carbon sources, such as methanol, sodium acetate and other nutrients, during the metabolic process. The purchase of this part of carbon sources constitutes an important expense of the sewage treatment plant. At the same time, microorganisms will proliferate in large numbers when treating sewage. When the number is too large, some microbial aggregates (i.e. sludge) need to be discharged to maintain the normal operation of the system. If the sludge is directly piled up without treatment, it will emit a foul odor due to the corruption of the microorganisms in it, and because inorganic substances such as coagulants are added when treating sewage, its total amount is quite considerable.

[0004] At present, in order to achieve resource recycling, the research direction is mainly focused on converting sludge into carbon sources through anaerobic fermentation. Under specific temperature and pH conditions, anaerobic microorganisms in sludge can function, dissolving some substances in the sludge and converting them into carbon sources. However, this process has the problem of low efficiency. For example, out of one ton of sludge, only about one-tenth can be converted into an effective carbon source, which is difficult to meet the demand for carbon sources in sewage treatment plants, and the problem of handling and disposing of large amounts of sludge still needs to be solved urgently.

[0005] Therefore, seeking more efficient methods to improve the efficiency of sludge conversion into carbon sources and realize the resource utilization of sludge is of great significance for reducing sewage treatment costs and reducing environmental pollution.

[0006] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present invention, and therefore it may contain information that does not constitute the prior art known to those skilled in the art. Summary of the invention

[0007] In order to solve one or more of the above problems existing in the prior art, the present invention aims to provide a method for promoting the co-fermentation of seaweed sludge to produce carbon source by using microbial pretreatment and a seaweed sludge fermentation liquid.

[0008] The method for promoting the co-fermentation of seaweed sludge to produce carbon source by microbial pretreatment according to the present invention may include the following steps: Step 1: Add a microbial agent with the ability to degrade proteins to the sludge; Step 2: Add free nitrous acid and rhamnolipid to the sludge obtained in Step 1 and perform pretreatment in an anaerobic environment; Step 3: Mix the pretreated sludge with seaweed and perform co-fermentation of seaweed sludge to obtain the supernatant of the fermentation mixture, wherein the supernatant is the seaweed sludge fermentation broth.

[0009] According to an embodiment of the present invention, the microbial agent may be compounded from multiple microbial strains, wherein the microbial strains may include Vibrio diabolicus, Pseudomonas guguanensis, Thermobacillus, and Bacillus tequilensis.

[0010] According to an embodiment of the present invention, the proportion of the microbial concentration of Vibrio diabolicus in the microbial agent may be 30% to 95%.

[0011] According to an embodiment of the present invention, Vibrio diabolicus, Pseudomonas guguanensis, Thermobacillus, and Bacillus tequilensis may be compounded to form the microbial agent in a ratio of 3:3:3:1, 5:2.5:2:0.5, 7:1.5:1:0.5, 19:0.4:0.4:2, or 6:2:1.5:0.5.

[0012] According to an embodiment of the present invention, the concentration of the microbial agent is 10 5 cfu·m / L to 10 8 cfu·m / L.

[0013] According to an embodiment of the present invention, the volume ratio of the microbial agent to the sludge may be 1:500 to 1:2000.

[0014] According to an embodiment of the present invention, the water content of the seaweed is 85% to 99%, and in Step 3, the ratio of the VSS of the pretreated sludge to the VSS content of the seaweed may range from 0.5 to 3.0.

[0015] According to an embodiment of the present invention, the dosing concentration of free nitrous acid in the sludge obtained in Step 1 may be 0.3 mg / L to 1.2 mg / L, and the dosing amount of rhamnolipid in the sludge may be 0.02 g / gTSS to 0.1 g / gTSS.

[0016] According to an embodiment of the present invention, in step two, the temperature for the pretreatment of the sludge can be maintained at approximately 25°C.

[0017] According to an embodiment of the present invention, in step two, an anaerobic environment is obtained by introducing nitrogen. Among them, the stripping time for introducing nitrogen can be 3 min to 10 min, and the time for the pretreatment of the sludge can be 36 h to 48 h.

[0018] According to an embodiment of the present invention, in step three, the pH value of the fermentation tank can be controlled to be approximately 7.5, and the time for co-fermentation can be 10 days to 20 days.

[0019] According to an embodiment of the present invention, the seaweed sludge fermentation broth includes volatile fatty acids, and the volatile fatty acids include acetic acid and / or propionic acid.

[0020] According to an embodiment of the present invention, the method may further include separating the fermentation mixture produced by the co-fermentation of seaweed sludge using a centrifuge. The centrifugation speed of the centrifuge can be 4000 r / min, and the centrifugation time can be 8 min to 10 min.

[0021] According to an embodiment of the present invention, the sludge in step one can be obtained by the following method: taking the sludge from the primary sedimentation tank of a municipal wastewater treatment plant as the fermentation bottom sludge, standing and settling for 20 h to 24 h, and then discharging the upper liquid to obtain the sludge in step one.

[0022] The present invention also provides a seaweed sludge fermentation broth, which is prepared by a method of promoting the co-fermentation of seaweed sludge to produce carbon sources by using microbial pretreatment.

[0023] The present invention also provides an application of the seaweed sludge fermentation broth in wastewater treatment. The seaweed sludge fermentation broth is prepared by the above method of promoting the co-fermentation of seaweed sludge to produce carbon sources by using microbial pretreatment, and the seaweed sludge fermentation broth can be used as an external carbon source and input into the sewage for wastewater treatment.

[0024] Beneficial effects:

[0025] The method of promoting the co-fermentation of seaweed sludge to produce carbon sources by using microbial pretreatment of the present invention can be widely applied to the treatment and recycling of sludge, improve the biodegradability of sludge, and thus improve the carbon source conversion efficiency of sludge.

[0026] The seaweed sludge fermentation broth prepared by the present invention can be used as an external carbon source for wastewater treatment, improve the nitrogen and phosphorus removal effects of sewage, and at the same time can improve the sludge sedimentation performance, reduce the treatment cost and enhance the system stability. Description of the Drawings

[0027] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the embodiments of this specification. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0028] Figure 1 A line graph showing the change in ammonia nitrogen concentration over fermentation time during the anaerobic fermentation of Example Group A and Comparative Example Groups F1 and G;

[0029] Figure 2 A line graph showing the change in humic acid concentration over fermentation time during the anaerobic fermentation of Example Group A and Comparative Example Groups F1 and G. Detailed implementation manners

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention and the drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. It should be noted that, without conflict, the implementation manners and features in the implementation manners of the present invention can be combined, separated, interchanged, and / or rearranged. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0031] In addition, when the exemplary embodiments can be implemented differently, the specific process sequences can be executed in a different order than described. For example, two consecutive processes described can be executed substantially simultaneously or in an order opposite to the described order.

[0032] In addition, the terms used in this specification are for the purpose of describing specific embodiments and are not intended to be restrictive. As used herein, unless the context clearly indicates otherwise, the singular forms "a", "an", and "the" are also intended to include the plural forms. Furthermore, when the terms "comprise" and / or "include" and their variants are used in this specification, it indicates the presence of the stated features, wholes, steps, operations, components, assemblies, and / or their groups, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, components, assemblies, and / or their groups. It should also be noted that, as used herein, the terms "substantially", "about", and other similar terms are used as approximate terms rather than degree terms, so they are used to explain the inherent deviations of measured values, calculated values, and / or provided values that those of ordinary skill in the art will recognize.

[0033] In the field of sewage treatment, carbon source is a key factor affecting the treatment effect, and anaerobic fermentation of sludge has attracted much attention as a potential carbon source production pathway. At present, improving the conversion efficiency of sludge carbon source and reducing sludge discharge have become the core tasks to overcome the sludge treatment problem. During the anaerobic fermentation of sludge, although a certain amount of carbon source can be produced, there are still problems such as the efficiency needing to be improved.

[0034] Meanwhile, seaweeds are abundant in coastal areas, and seaweeds are rich in easily biodegradable components such as carbohydrates and have the potential to become low-cost fermentation substrates. Therefore, the synchronous treatment of seaweeds and sludge can be carried out to co-degrade organic matter and achieve the resource utilization of "treating waste with waste".

[0035] Therefore, the present invention proposes a method for promoting the co-fermentation of seaweed sludge to produce carbon source by microbial pretreatment.

[0036] According to an embodiment of the present invention, the method for promoting the co-fermentation of seaweed sludge to produce carbon source by microbial pretreatment includes: adding a microbial agent with the ability to degrade proteins to the sludge; adding free nitrous acid (FNA) and rhamnolipid (RL) to the sludge obtained in the first step, and pretreating the sludge in an anaerobic environment; mixing the pretreated sludge with seaweeds, and carrying out the co-fermentation of seaweed sludge to obtain the supernatant of the fermentation mixture, and the supernatant is the seaweed sludge fermentation broth. This seaweed sludge fermentation broth contains a large amount of volatile fatty acids and can be used as an external carbon source and input into sewage for sewage treatment.

[0037] In the method for promoting the co-fermentation of seaweed sludge to produce carbon source by microbial pretreatment of the present invention, the protease produced by adding a microbial agent with the ability to degrade proteins can catalyze the hydrolysis of proteins in the sludge, denature and rupture the microbial membrane proteins, release the organic matter wrapped inside the cells, and further promote the dissolution of substances such as proteins and polysaccharides in the anaerobic digestion of sludge, and enhance the activity of hydrolytic acidifying bacteria in the subsequent anaerobic fermentation process. On the other hand, using surfactants such as free nitrous acid (FNA) and rhamnolipid (RL) to jointly pretreat the sludge can effectively promote the hydrolysis and acid production efficiency of the sludge, inhibit the activity of methanogens, convert more macromolecular substances into soluble small molecular substances, and facilitate subsequent utilization as a carbon source. At the same time, this joint pretreatment method can also shorten the fermentation time by about 1 / 3, improve the biodegradability of the sludge and the yield of volatile fatty acids (VFAs).

[0038] The present invention realizes the joint and efficient fermentation of sludge and seaweeds by adding a microbial agent for sludge pretreatment, achieves the purpose of resource utilization and reduction, reduces environmental pollution, and at the same time produces a fermentation broth with highly valuable volatile fatty acids to supplement carbon source for sewage treatment, having significant economic and environmental benefits.

[0039] According to an embodiment of the present invention, the above-mentioned sludge is taken from the secondary sedimentation tank or the primary sedimentation tank of a sewage treatment plant, and the initial moisture content can be in the range of about 70% to 85% (mass ratio). Preferably, the initial moisture content of the sludge is about 80%.

[0040] According to an embodiment of the present invention, the microbial inoculant is composed of a plurality of microbial strains. The microbial strains may include Vibrio diabolicus, Pseudomonas guguanensis, Thermobacillus, and Bacillus tequilensis.

[0041] According to a preferred embodiment of the present invention, the proportion of the microbial concentration of Vibrio diabolicus in the mixed inoculant can be 30% to 95%. As the main strain for forming the microbial inoculant of the present invention, when its concentration proportion is in the range of 30% to 95%, the protein degradation ability of the microbial inoculant can be maximized.

[0042] According to a preferred embodiment of the present invention, Vibrio diabolicus, Pseudomonas guguanensis, Thermobacillus, and Bacillus tequilensis can be compounded in a ratio of 3:3:3:1, a ratio of 5:2.5:2:0.5, a ratio of 7:1.5:1:0.5, a ratio of 19:0.4:0.4:2, or a ratio of 6:2:1.5:0.5 to form a microbial inoculant.

[0043] The compounded microbial inoculant can efficiently degrade organic matters such as cellulose, polysaccharides, and proteins in seaweed and sludge. According to a preferred embodiment of the present invention, the concentration of the microbial inoculant in the sludge can be 10 5 cfu·m / L to 10 8 cfu·m / L. In addition, after determining the dosing concentration of the microbial inoculant in the sludge, it can be dosed at different volume ratios of the microbial inoculant to the sludge. According to a preferred embodiment of the present invention, the volume ratio of the dosed microbial inoculant to the sludge can be 1:500 to 1:2000. Additionally, in the present invention, the hydrolysis time for dosing the microbial inoculant can be 4 hours.

[0044] In addition, the dosing concentration of free nitrous acid in the sludge can be in the range of 0.3 mg / L to 1.2 mg / L, and the dosing dosage of rhamnolipid in the sludge is in the range of 0.02 g / gTSS to 0.1 g / gTSS. Preferably, the dosing dosage of free nitrous acid is 0.67 mg / L, and the dosing dosage of rhamnolipid is 0.04 g / gTSS.

[0045] According to an embodiment of the present invention, in the step of pretreating sludge, an anaerobic environment can be obtained by introducing nitrogen into the reactor. Among them, the stripping time for introducing nitrogen can be 3 min to 10 min, and the sludge pretreatment time can be 36 h to 48 h. Among them, the temperature for pretreating sludge can be maintained at about 25°C.

[0046] According to an embodiment of the present invention, the seaweed mixed with the sludge can be fresh seaweed, and the water content of the seaweed can be in the range of 85% to 99%, and the ratio of the VSS (volatile suspended solids) content of the sludge to the VSS content of the seaweed can be in the range of 0.5 to 3.0. For example, the VSS content range of the sludge can be 5.2 g / L to 24.6 g / L, and the VSS content range of the seaweed can be 1.7 g / L to 10.4 g / L.

[0047] According to an embodiment of the present invention, the co-fermentation of seaweed sludge can be carried out in a fermenter (such as an anaerobic fermentation reactor), and potassium bicarbonate with a dosing concentration of 200 mg / L can be used in the potassium bicarbonate buffer solution to control the pH value of the fermenter to about 7.5, and the co-fermentation time can be 10 days to 20 days.

[0048] After the sludge and seaweed are mixed, the sludge and seaweed in the fermenter or reaction tank can be shaken evenly by a water bath shaker. The rotation speed of the shaker can be 130 r / min to 150 r / min, and the water bath temperature is maintained at 25°C. That is, after the sludge and seaweed are mixed, the anaerobic fermentation reaction can be carried out while being placed in a water bath shaker.

[0049] According to an embodiment of the present invention, after the co-fermentation of seaweed sludge is completed, the fermentation mixture produced by the co-fermentation of seaweed sludge can be separated by a centrifuge. The centrifugation speed of the centrifuge can be 4000 r / min, and the centrifugation time can be 8 min to 10 min. Then, the supernatant separated is the seaweed sludge fermentation broth rich in VFAs.

[0050] Before centrifugal dewatering, the sludge at the bottom of the anaerobic acid production tank and the sedimentation tank is collected in the sludge storage tank, and then centrifugal dewatering is carried out with a centrifuge. After obtaining the supernatant, the remaining mud cake is transported out. According to an embodiment of the present invention, the water content of the dewatered mud cake is 40 to 60%, and compared with the initial sludge, about 20 to 40% of the sludge is converted into a carbon source and dissolved into the supernatant, and the sludge reduction and carbon source production effects are significant.

[0051] The present invention will be further described in detail below with specific embodiments, but the present invention is not limited to the following embodiments. The implementation conditions adopted in the embodiments can be further adjusted according to different requirements of specific use, and the implementation conditions not specified are the conventional conditions in the industry.

[0052] I. Experimental steps

[0053] The seaweeds used in the present invention were taken from the seaside of Maidao Park in Qingdao and directly utilized after salvage. The sludge was sourced from a sewage treatment plant in Qingdao and was added to the fermentation tank after static sedimentation.

[0054] The inventors completed the following seven groups of experiments. Among them, the examples and comparative experiments in the first to sixth groups of experiments all included the following implementation steps:

[0055] Step 1: Add a microbial inoculant with the ability to degrade proteins to the sludge with a water content of approximately 80%.

[0056] Step 2: After hydrolysis, add free nitrous acid and rhamnolipid. The dosage of free nitrous acid is 0.67 mg / L, and the dosage of rhamnolipid is 0.04 g / gTSS. Then, the sludge is anaerobically stirred in a completely sealed fermentation tank for 36 h, and the temperature is maintained at 25 °C.

[0057] Step 3: Mix the pretreated sludge with fresh seaweed, add KHCO3 with a concentration of 200 mg / L, adjust the pH to approximately 7.5, and conduct anaerobic co-fermentation for 20 d.

[0058] In addition, in the following first to sixth groups of experiments, by changing data such as the volume ratio of the microbial inoculant to the sludge, the concentration of the inoculant in the sludge, the VSS ratio of the sludge to the seaweed, the proportion of Vibrio diabolicus in the microbial inoculant, and different microbial strains.

[0059] II. Experimental Design and Variable Combinations

[0060] In the following experiments, in each table, the inventors only selectively listed some experimental data as examples. For example, in Table 1, the volume ratio of the inoculant to the sludge was listed as a variable for experimental groups A1 - A4, and only the values close to the middle value in the corresponding ranges were selected as examples for the inoculant concentration, the VSS ratio of the sludge to the seaweed, the proportion of Vibrio diabolicus, and the composition of other strains.

[0061] However, in fact, the inventors also selected various inoculant concentrations (i.e., other values in the range of 10 5 cfu·m / L to 10 8 cfu·m / L), various VSS ratios of the sludge to the seaweed (i.e., other values in the range of 0.5 - 3.0), different proportions of Vibrio diabolicus (other values in the range of 30% - 95%), and different proportional relationships of other strains (Pseudomonas vallida, Geobacillus stearothermophilus, and Bacillus tequilensis) as fixed quantities, and only conducted experiments with the volume ratio of the inoculant to the sludge as a variable. The results of these experimental data are similar to the results of the experimental data listed in Table 1. Therefore, due to the experimental data and results in Table 1 (such asFigure 1 and Figure 2 As shown, it can clearly express the influence of the change in the volume ratio of the bacterial agent to the sludge on the experimental results. Therefore, only these values are selected as examples and listed in Table 1. However, those skilled in the art should understand that other experimental results within the above range also conform to the experimental results in Table 1, that is, the description of the experimental results in Table 1 also applies to other data within the above range.

[0062] The situations of Tables 2 to 4 are similar to that of Table 1, so their detailed descriptions are omitted. In addition, in the experiment of the co-variation of multiple variables in Table 5, some experimental data of the partial endpoint values within the above range are further selected as examples and listed to further verify the rationality of the selected value range.

[0063] Table 6 shows the comparative examples of the above experimental examples. In each experimental group of the comparative examples, there is at least one data not within the above range of this application. Similar to Tables 1 to 5, Table 6 also only shows partial experimental data, that is, only shows the situations where some data are not within the above range of this application as examples of the comparative examples. However, those skilled in the art should understand that other experimental results not within the above range of this application also conform to the experimental results in Table 6.

[0064] 1. Volume ratio gradient group (other parameters fixed)

[0065] Table 1

[0066]

[0067] 2. Bacterial agent concentration gradient group (other parameters fixed)

[0068] Table 2

[0069]

[0070] 3. VSS ratio gradient group (other parameters fixed)

[0071] Table 3

[0072]

[0073]

[0074] 4. Proportion gradient group of Vibrio cholerae (other parameters fixed)

[0075] Table 4

[0076]

[0077] 5. Combined example group (co-verification of multiple variables)

[0078] Table 5

[0079]

[0080]

[0081] 6. Comparative example group

[0082] Table 6

[0083]

[0084]

[0085] 7. Comparative example group (missing key steps or components, other parameters are set according to Example A1)

[0086] Comparative example G1: Omit Step 1 (do not add microbial inoculant), and directly perform Step 2 and Step 3;

[0087] Comparative example G2: Lack of free nitrous acid in Step 2, and other operations remain unchanged;

[0088] Comparative example G3: Do not add seaweed in Step 3, and only perform sludge fermentation.

[0089] III. Effect verification and comparison

[0090] Figure 1 and Figure 2 respectively show the graphs of the changes in ammonia nitrogen content and humic acid content of the volume ratio gradient group (A1 - A4) and the comparative example G group with the change of fermentation time. The concentration levels of ammonia nitrogen and humic acid can, on the one hand, characterize the hydrolysis degree of sludge cells, and on the other hand, have an important impact on the subsequent acid production process.

[0091] From Figure 1 and Figure 2 it can be seen that when the volume ratio of the inoculant to the sludge changes, even if the concentration of the added inoculant is the same, the accumulation effects of ammonia nitrogen and humic acid are different. And when the volume ratio is larger, the initial density of the added inoculant is larger, which can thus promote sludge fermentation faster. Therefore, in Group A, the A1 experimental group produces ammonia nitrogen fastest and the most ammonia nitrogen, and the accumulation effect of humic acid in this experimental group is the best. However, when the volume ratio is greater than 1:500 (for example, when the volume ratio is 1:400 of the control group F1), due to the excessive initial density of the added inoculant, part of the inoculant may not be effectively utilized, resulting in a reduction in the accumulation of ammonia nitrogen and humic acid. When the volume ratio is less than 1:2000 (for example, when the volume ratio is 1:2100 of the control group F2), due to the too small initial density of the added inoculant, the low inoculant density will lead to a competitive disadvantage of the microbial population and a decrease in metabolic activity, resulting in a delay in fermentation start-up and a significant reduction in the production of ammonia nitrogen and humic acid. It shows that the volume ratio in the range of 1:500 - 1:2000 has the best promotion effect on fermentation.

[0092] Therefore, under the same volume ratio, compared with Group G and F1 and F2 of Comparative Example F, the accumulation effects of ammonia nitrogen and humic acid in Group A are significantly better. The highest ammonia nitrogen concentration can reach 27.8 mg / L, and the humic acid concentration can reach 225.5 mg / L. At the same time, the overall increase rate of ammonia nitrogen during the co-fermentation of seaweed and sludge is higher, and the peak value can be reached on the ninth day of fermentation, indicating that the overall effect of adding the necessary components FNA, RL and microbial agents and co-fermenting seaweed sludge is better.

[0093] In terms of the changes in ammonia nitrogen and humic acid contents among Group A, F1 and F2 of Comparative Example F, and Comparative Example G, the experimental results are visually presented in the form of a line graph to more clearly compare the dynamic changes of key indicators under different conditions. For the microbial agent concentration gradient group (Group B), VSS ratio gradient group (Group C), Vibrio diabolicus proportion gradient group (Group D), other comparative example groups, and combined example group (Group E), their fermentation effects are described in detail in words to show the effects of various variables on the fermentation process and products.

[0094] In the experiment of the microbial agent concentration gradient group (B1 - B4), as the microbial agent concentration increased from 10 5 cfu / mL to 10 8 cfu / mL, the ammonia nitrogen production and humic acid release showed a trend of first increasing and then slightly decreasing, and reached the maximum when the microbial agent concentration was 10 6 cfu / mL. When the microbial agent concentration was too low (Group F3, 10 4 cfu / mL), due to reasons such as weak microbial biomass and relatively insufficient nutrients, the fermentation effect was instead affected, resulting in no further increase or even a slight decrease in the ammonia nitrogen production and humic acid release. When the microbial agent concentration was too high (Group F4, 10 9 cfu / mL), due to intense competition among microorganisms, the normal decomposition and utilization processes of nitrogen-containing organic matter and humic acid were interfered, resulting in abnormal changes in the ammonia nitrogen content and the humic acid release being difficult to decline according to the normal trend. This result verifies that the microbial agent concentration in the range of 10 5 ~10 8 cfu / mL is better for promoting ammonia nitrogen production and humic acid decomposition during the co-fermentation of seaweed sludge.

[0095] For the VSS ratio gradient groups (C1 - C6), as the VSS ratio (sludge: seaweed) gradually increased from 0.5 to 3.0, the ammonia nitrogen production and humic acid release showed a trend of first increasing and then decreasing, and reached the maximum when the VSS ratio (sludge: seaweed) was 1.5. When the VSS ratio was too low (Group F5, 0.4), the relative content of seaweed was too high, and the nutrients available for microorganisms were unbalanced, resulting in low ammonia nitrogen production and humic acid release. When the VSS ratio was too high (Group F6, 3.5), the proportion of sludge relative to seaweed was too large, and the microbial nutrition was unbalanced, resulting in the change of ammonia nitrogen content deviating from the normal trend, and the decomposition and utilization of humic acid were disturbed, and the release amount changed abnormally. This result indicates that when the VSS ratio is in the range of 0.5 - 3.0, it can optimize the co-fermentation of seaweed sludge, increase the ammonia nitrogen production and humic acid release, and improve the fermentation efficiency.

[0096] In the experiment of the proportion gradient group of Vibrio diabolicus (D1 - D4), as the proportion of Vibrio diabolicus increased from 30% to 95%, the ammonia nitrogen production and humic acid release showed a trend of first rising and then falling. When the proportion of Vibrio diabolicus was too low (Group F7, 25%), its role in the microbial flora was not significant, and it could not fully play the promoting role in fermentation, resulting in low ammonia nitrogen production and humic acid release. When the proportion of Vibrio diabolicus was too high (Group F8, 100%), due to the lack of cooperation of other strains, the microbial community structure was unbalanced, the decomposition of nitrogen-containing organic matter in sludge was blocked, the ammonia nitrogen content increased slowly and was difficult to reach the normal peak, and the later conversion and utilization were also limited; the decomposition and utilization of humic acid were also ineffective, and the decline rate of humic acid release was much lower than the normal level, and high-efficiency fermentation could not be achieved as a whole. Control experimental groups F9, F10, F11 and F12 were set up to remove Pseudomonas kukanensis, Bacillus thermophilus, Bacillus tequilensis and Vibrio diabolicus respectively. During the experiment, the change of ammonia nitrogen content was abnormal, the rising speed in the early stage was unstable, and there was a downward trend in the later stage, and it could not be stabilized in a reasonable range, indicating that the decomposition and transformation process of nitrogen-containing organic matter was damaged. The release amount of humic acid was also affected, and the decline rate decreased significantly, and the fermentation effect was much worse than that of the normal experimental group, fully reflecting the serious negative effect of the absence of key strains on the co-fermentation of seaweed sludge. This result verifies the importance of maintaining the balance of the microbial flora and promoting the ammonia nitrogen production and humic acid decomposition in the co-fermentation process of seaweed sludge when the proportion of Vibrio diabolicus is in the range of 30% - 95% and the strains are reasonably matched.

[0097] The combined example groups (E1, E2, E3, E4, E5) carried out experiments within the specified ranges of multiple parameter combinations. All the E groups obtained relatively high ammonia nitrogen production and humic acid release. At the same time, the sedimentation performance of the sludge was significantly improved after treatment, and the fermentation products showed good performance in the actual sewage treatment application. The experiments of the E groups fully demonstrated that when the parameters were combined according to the numerical ranges of this application, the synergistic optimization of the co-fermentation of seaweed and sludge could be achieved, comprehensively improving the quality and performance of the fermentation products.

[0098] According to the method for promoting the co-fermentation of seaweed and sludge to produce carbon source by microbial pretreatment provided by the present invention, by co-fermenting seaweed with high organic matter content and sludge, the acid production efficiency of the fermentation system was significantly improved, and the biomass energy in the seaweed could be efficiently recovered. In addition, by directly applying the VFAs produced by fermentation to the sewage treatment plant, the sewage denitrification efficiency was improved, and the purpose of synchronous reduction and resource recovery of sludge and seaweed was realized.

[0099] According to the method for promoting the co-fermentation of seaweed and sludge to produce carbon source by microbial pretreatment of the present invention, by using the microbial pretreatment method and adding protease-producing microorganisms, the fermentation efficiency was improved. At the same time, the added FNA, as a green antibacterial agent, may be contained in the sewage itself, avoiding additional treatment costs and effectively shortening the fermentation time. In addition, the added RL can significantly reduce the surface tension of the sludge hydrolysate, and has the advantages of low toxicity and easy degradation in the environment. The combined action of FNA and RL enhances the activity of hydrolytic acidification bacteria while inhibiting the activity of methanogens, providing a large number of available substrates for the hydrolysis and fermentation process, and then increasing the accumulation of VFAs. The overall operation process is simple, cost-saving, and has good environmental and economic benefits.

[0100] The specific embodiments described above have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for promoting the co-fermentation of seaweed sludge to produce carbon source by microbial pretreatment, characterized in that: The following steps are involved: Step 1: Adding microbial agents capable of degrading protein into the sludge; Step 2: adding free nitrite and rhamnolipid to the sludge obtained in step 1, and pre-treating in an anaerobic environment; Step 3: Mix the pretreated sludge with seaweed to perform seaweed sludge co-fermentation to obtain the supernatant of the fermentation mixture. Wherein, the supernatant is seaweed sludge fermentation liquid.

2. The method according to claim 1, characterized in that The microbial agent is compounded from a plurality of microbial strains, wherein the microbial strains include Vibrio diabolicus, Pseudomonas guguanensis, Thermobacillus and Bacillus tequilensis.

3. The method according to claim 2, characterized in that The microbial concentration of the Vibrio diabolicus in the microbial agent is 30% to 95%.

4. The method according to claim 3, characterized in that The Vibrio divilus, the Pseudomonas guineensis, the thermophilic Bacillus and the Bacillus tequila are compounded in a ratio of 3:3:3:1, a ratio of 5:2.5:2:0.5, a ratio of 7:1.5:1:0.5, a ratio of 19:0.4:0.4:2 or a ratio of 6:2:1.5:0.5 to form the microbial agent.

5. The method according to any one of claims 2 to 4, characterized in that: The concentration of the microbial agent in the sludge is 10 5 cfu·m / L~10 8 cfu·m / L.

6. The method according to any one of claims 2 to 4, characterized in that: The volume ratio of the microbial agent to the sludge is 1:500 to 1:2000.

7. The method according to claim 1, characterized in that The water content of the seaweed is 85% to 99%, and in step three, the ratio of the VSS content of the pretreated sludge to the VSS content of the seaweed is in the range of 0.5 to 3.

0.

8. The method according to claim 1, characterized in that The free nitrite is added to the sludge obtained in step 1 at a concentration of 0.3 mg / L to 1.2 mg / L, and the rhamnolipid is added to the sludge at a dosage of 0.02 g / gTSS to 0.1 g / gTSS.

9. A seaweed sludge fermentation liquid, characterized in that: The seaweed sludge fermentation liquid is prepared by the method of promoting seaweed sludge co-fermentation to produce carbon source by using microbial pretreatment according to any one of claims 1 to 8.

10. Application of seaweed sludge fermentation liquid in sewage treatment, characterized in that: The seaweed sludge fermentation liquid is prepared by the method for promoting seaweed sludge co-fermentation to produce carbon source by microbial pretreatment according to any one of claims 1 to 9, and the seaweed sludge fermentation liquid can be added to sewage as an external carbon source for sewage treatment.

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