A low-cost, high-efficiency biological composite carbon source for wastewater treatment and its preparation method

Abstract

This application discloses a low-cost, high-efficiency bio-composite carbon source for wastewater treatment and its preparation method, belonging to the field of wastewater treatment technology. By weight, the bio-composite carbon source comprises: 100 parts vegetable waste fermentation broth, 30-40 parts water, 15-25 parts pear peel fermentation broth, 8-10 parts functional matrix, 6-10 parts sodium acetate, 7-10 parts potassium formate, 3-5 parts carbohydrate compounds, and 0.2-0.4 parts biological enzymes. The vegetable waste fermentation broth and pear peel fermentation broth are the effective components of this bio-composite carbon source, which can significantly reduce the preparation cost. Furthermore, the surface modification treatment of the composite carrier using a first mixed liquid can improve the physical structural stability of the functional matrix. In addition, the oxidized functional matrix can play an auxiliary role in wastewater treatment, improving the wastewater treatment effect.

Description

Technical Field

[0001] This application relates to a low-cost, high-efficiency biological composite carbon source for wastewater treatment and its preparation method, belonging to the field of wastewater treatment technology. Background Technology

[0002] In recent years, eutrophication of water bodies has become increasingly serious. If there is insufficient carbon source in wastewater treatment plants, the effluent quality will be difficult to meet discharge standards. In order to achieve efficient wastewater treatment, an external composite carbon source is usually used. The core function of the composite carbon source is to provide electron donors for denitrifying microorganisms in wastewater treatment, helping them to reduce nitrates to nitrogen gas and achieve efficient removal of total nitrogen.

[0003] However, some chemically-based composite carbon sources may have drawbacks such as inhibiting microbial growth during use and polluting the environment after disposal. Therefore, current research focuses on bio-based composite carbon sources. Bio-based composite carbon sources use biomass as the core source and are mainly produced through bioconversion or refining of renewable resources such as animal and plant residues and organic waste. Compared with ordinary chemically-based composite carbon sources, their components are natural and completely biodegradable, with no risk of secondary pollution. They can precisely match the nutritional needs of microbial communities, promote the rapid reproduction of denitrifying heterotrophic bacteria, and significantly improve the total nitrogen removal efficiency.

[0004] In existing technologies, to achieve slow release of carbon sources, microbial attachment, and promotion of synergistic metabolism among microbial communities, it is often necessary to introduce a carrier. The carrier serves several purposes: First, it can adsorb and bond organic components in the bio-composite carbon source, utilizing its porous structure to regulate the carbon source release rhythm, matching the "carbon demand curve" of biochemical reactions such as denitrification, maintaining a stable carbon-to-nitrogen ratio in the water, and improving denitrification efficiency. Second, it facilitates the attachment of functional organisms (such as denitrifying bacteria and polyphosphate-accumulating bacteria) to form a dense biofilm, enhancing the microbial community's resistance to hydraulic shocks, preventing the community from being lost with the effluent, and enabling the rapid formation of a dominant microbial community within the system, thus shortening the sludge acclimatization cycle. Third, its porous structure can create a "aerobic-anoxic-anaerobic" micro-gradient, providing a suitable living environment for different functional microorganisms, promoting synergistic effects among microbial communities, and adsorbing harmful substances in the water (such as heavy metal ions and toxic organic matter), reducing their inhibitory effect on functional microorganisms.

[0005] For example, patent CN119219213A discloses a biocomposite carbon source consisting of a carrier with metakaolin as the main component, mixed with brewer's waste yeast liquid, biodiesel byproducts, and enzyme preparations. This source exhibits advantages such as long-lasting effect, high denitrification rate, and high denitrification performance. Another example is patent CN118771613A, which discloses a composite carbon source consisting of a functional filler (made from a composite carrier, polyvinyl alcohol, and sodium alginate) and plant extracts. This source demonstrates good carbon release rate performance and excellent denitrification performance. However, current carriers still have the following problems that need to be addressed:

[0006] 1. The physical structure is easily damaged, affecting the water treatment effect.

[0007] On the one hand, the carrier is prone to wear and breakage under aeration, stirring, and hydraulic flushing conditions, which in turn produces fine particulate matter and affects the slow release efficiency of the carbon source. On the other hand, in current water treatment, the carrier needs to be placed in a microbial and acidic / alkaline environment for a long time, which will cause pore collapse and loss of carbon source loading and microbial attachment ability.

[0008] 2. It relies solely on its own structure to promote the function of bio-complex carbon sources, without any additional auxiliary effects.

[0009] Current carriers rely solely on their surface sites or porous structures to facilitate the attachment of biocomposite carbon sources, offering no additional auxiliary benefits for wastewater treatment. Consequently, their ability to improve the treatment capacity of biocomposite carbon sources is limited. Furthermore, with prolonged use, undegraded macromolecular organic matter accumulates within the pores, triggering anaerobic putrefaction, producing toxic substances such as hydrogen sulfide, inhibiting microbial activity, and ultimately leading to a decline in treatment effectiveness.

[0010] Therefore, in order to further improve the treatment effect of sewage, it is necessary to develop a biological composite carbon source containing a novel functional carrier to solve the above problems. Summary of the Invention

[0011] To address the aforementioned issues, a low-cost, high-efficiency bio-composite carbon source for wastewater treatment is provided. This bio-composite carbon source uses vegetable waste fermentation liquid and pear peel fermentation liquid as effective components, which can significantly reduce the preparation cost of the bio-composite carbon source. Furthermore, the surface modification treatment of the composite carrier using a first mixed liquid can improve the physical structural stability of the functional matrix. In addition, the oxidized functional matrix can play an auxiliary role in wastewater treatment, thereby improving the wastewater treatment effect.

[0012] According to one aspect of this application, a low-cost, high-efficiency biological composite carbon source for wastewater treatment is provided, comprising, by weight: 100 parts vegetable waste fermentation liquid, 30-40 parts water, 15-25 parts pear peel fermentation liquid, 8-10 parts functional base material, 6-10 parts sodium acetate, 7-10 parts potassium formate, 3-5 parts carbohydrate compounds, and 0.2-0.4 parts biological enzymes;

[0013] The preparation method of the vegetable waste fermentation liquid is as follows:

[0014] After crushing the vegetable waste, add it to 10-15 times the amount of water, then add a microbial agent and ferment for at least 12 hours. Filter to obtain the final product. The amount of microbial agent added is 0.2-0.5 wt% of the total weight of the vegetable waste. The microbial agent includes Lactobacillus rhamnosus and Weizmannii coagulans.

[0015] The preparation method of the functional base material is as follows:

[0016] S1: Phytic acid and epoxy olefin compounds are reacted to obtain intermediate A. Intermediate A, N-vinylimidazole and initiator are added to a solvent and polymerized to obtain the first mixture.

[0017] S2: Add the composite carrier formed by chitin and bentonite to the first mixture, and continue stirring at the temperature for 2-3 hours to obtain the second mixture;

[0018] S3: Add N,N-dimethylacrylamide, accounting for 5-10 wt% of phytic acid, to the second mixture, and continue the reaction at this temperature for at least 0.5 h. After oxidation treatment, filter and dry to obtain the functional base material.

[0019] The bio-composite carbon source of this application uses vegetable waste fermentation liquid, water, pear peel fermentation liquid, sodium acetate, potassium formate, sugar compounds, and biological enzymes as effective components. Firstly, it achieves a hierarchical carbon source supply. Sodium acetate and potassium formate are fast-acting carbon sources, while vegetable waste fermentation liquid and pear peel fermentation liquid provide medium- to slow-release carbon supply. The biological enzymes continue to catalyze the degradation of macromolecular organic matter in the two fermentation liquids into smaller carbon sources during use, improving carbon source utilization. Therefore, the above setup forms a gradient carbon supply mode, improving denitrification efficiency and stabilizing denitrification. Secondly, the vegetable waste fermentation liquid and pear peel fermentation liquid contain amino acids, vitamins, and trace elements (such as iron, manganese, and zinc), which are microbial growth-promoting factors that can optimize the microbial community structure and improve microbial activity. Thirdly, the separate fermentation of vegetable waste and pear peels to obtain fermentation liquids enables the resource utilization of waste, reduces production costs, and the carbon source does not contain toxic organic matter, heavy metals, or other harmful components, avoiding secondary pollution of water bodies.

[0020] The functional matrix prepared from the bio-composite carbon source in this application has the following functions:

[0021] 1. Improve the strength of functional matrix materials and enhance their resistance to breakage and degradation.

[0022] In the first mixture, a prepolymer is formed through intermediates A and N-vinylimidazolium polymers, which then crosslinks under the action of N,N-dimethylacrylamide to form a three-dimensional network polymer network. Combined with the rigid support of the chitin-bentonite composite carrier, the mechanical strength of the functional matrix is ​​significantly improved. It is less prone to breakage and wear under aeration, stirring, and hydraulic scouring conditions, solving the problem of carbon source loss caused by the fragility of traditional carriers. Furthermore, the phosphate ester and imidazole functional groups in the polymer endow the functional matrix with acid and alkali resistance and resistance to microbial degradation. Combined with the layered barrier structure of bentonite, this prevents structural collapse of the carrier after long-term immersion in the wastewater treatment system, extending its service life.

[0023] 2. Enhanced adsorption enables efficient loading and precise controlled release of carbon sources.

[0024] The composite carrier has a high specific surface area and abundant hierarchical channels. With polymer modification, it can form stable bonds with organic acids, sugars, and fermentation broth components in the biocomposite carbon source, achieving efficient and uniform loading of the carbon source and preventing rapid dissolution and loss. Therefore, the combination of pore structure and surface functional groups can realize gradient carbon supply and improve the utilization rate of carbon source.

[0025] 3. Rich in functional groups and with excellent biocompatibility, enhancing microbial attachment and community synergy.

[0026] The phosphate ester groups, imidazole groups, amine oxides, amino groups, and glucose groups of chitin on the surface of the functional matrix are all affinity sites for microorganisms. They can adsorb functional microorganisms such as denitrifying bacteria and polyphosphate-accumulating bacteria through electrostatic interactions, promoting the rapid formation of biofilms. Moreover, chitin, as a natural biological macromolecule, can provide growth-promoting factors for microorganisms, enhance the activity and proliferation rate of the microbial community, shorten the system acclimatization cycle, adapt to the metabolic needs of different functional microbial communities, promote synergistic effects among microbial communities, and optimize the system's nitrogen and phosphorus removal efficiency.

[0027] 4. Strong resistance to contamination, reducing the risk of scaling and clogging.

[0028] The polyphosphate groups in phytic acid molecules have the ability to chelate metal ions, forming stable chelates with calcium and magnesium ions in water, preventing them from depositing on the carrier surface to form carbonate scale and preventing pore blockage. At the same time, the hydrophilic-hydrophobic balance of the polymer skeleton can reduce the adsorption and accumulation of macromolecular organic matter on the carrier surface, reducing the risk of anaerobic putrefaction.

[0029] 5. Synergistically promotes denitrification and improves total nitrogen removal efficiency.

[0030] The oxidation in step S3 forms amine oxide groups, whose oxygen atoms possess certain redox activity. These groups can act as electron transport mediators, participating in the respiratory metabolism of microorganisms, accelerating the efficiency of the intracellular electron transport chain, and promoting the reduction of nitrate nitrogen to nitrogen gas by denitrifying bacteria. Furthermore, amine oxide groups can regulate the distribution of dissolved oxygen in the water, creating localized hypoxic microregions on the carrier surface, thus providing favorable conditions for denitrification. Simultaneously, unlike strong oxidants, they do not destroy microbial activity and can synergistically work with biological carbon sources to improve total nitrogen removal rates.

[0031] Optionally, the molar ratio of phytic acid, epoxy olefin compound and N-vinylimidazole is 1:(1-1.2):(2-3).

[0032] Phytic acid's phosphate group ring-opens with the epoxy group of an epoxy olefin to obtain intermediate A. This constraint ensures that all phytic acid participates in the reaction, and each phytic acid molecule contains a double bond. This prevents cross-linking of the prepolymer in the first mixture, extending the chain length of the prepolymer in the first mixture, thus controlling the proportion of phytic acid in the final polymer. The amount of N-vinylimidazole added determines the number of imidazole rings and also the number of amine oxide groups, thereby affecting the wastewater treatment effect. The above molar ratio can control the number of functional groups in the polymer, resulting in optimal mechanical strength of the functional matrix, best carbon source utilization, and optimal denitrification effect.

[0033] Optionally, the reaction temperature of the phytic acid and the epoxy olefin compound is 30-50°C, and the reaction time is 4-6 hours.

[0034] The reaction temperature of intermediate A and N-vinylimidazole is 65-75°C, and the reaction time is at least 4 hours.

[0035] The above reaction conditions can ensure the formation of intermediate A, the smooth polymerization of intermediate A and N-vinylimidazole to form a prepolymer, and improve production efficiency.

[0036] Optionally, the epoxy olefin compound is selected from at least one of 3,4-epoxy-1-butene, 1,2-epoxy-5-hexene, 1,2-epoxy-7-octene, and 1,2-epoxy-9-decene.

[0037] Optionally, the epoxy olefin compound is selected from 1,2-epoxy-5-hexene and 1,2-epoxy-9-decene in a molar ratio of 1:(1-3).

[0038] In epoxy olefin compounds, the epoxy groups react with phytic acid, and the double bond groups polymerize with the double bonds of N-vinylimidazolium. Therefore, the structure of epoxy olefin compounds determines the position between the phytic acid groups and the prepolymer backbone. When 1,2-epoxy-5-hexene and 1,2-epoxy-9-decene are used in the above molar ratio of 1:(1-3), the distance between phytic acid and the prepolymer backbone can be moderate, which can improve the reactivity of the remaining phosphate groups on phytic acid. Furthermore, two distances can exist between phytic acid and the prepolymer backbone to improve the slow release capacity of the biocomposite carbon source.

[0039] Optionally, the amount of the composite carrier added is 8-12 times the weight of phytic acid, and the preparation method of the composite carrier is as follows:

[0040] Add bentonite completely to a chitin solution with a concentration of 10-15 wt%, mix and stir at 30-50℃ for 2-3 hours, filter and dry to obtain the final product.

[0041] The composite carrier uses bentonite as a matrix. Chitosan can improve the biocompatibility of the composite carrier and facilitate its binding with the prepolymer in the first mixture.

[0042] Optionally, the oxidant used in step S3 is selected from a 30% hydrogen peroxide solution, the amount of hydrogen peroxide solution added is 15-25 times the weight of N-vinylimidazole, and the oxidation treatment time is 1.5-3 hours.

[0043] In step S3, after the addition of N,N-dimethylacrylamide, the prepolymer crosslinks to form a three-dimensional network structure, thereby modifying the composite carrier. The subsequent oxidation treatment can oxidize the tertiary amine groups on N-vinylimidazole to obtain amine oxide groups, which can retain the polymer compatibility of N-vinylimidazole, while endowing the functional matrix with zwitterionic properties, surface activity and microbial affinity, so that the amine oxide can play an additional auxiliary role and significantly improve the processing capacity of the biocomposite carbon source.

[0044] Optionally, the microbial agent is selected from Lactobacillus rhamnosus and Weizmannella coagulans in a weight ratio of 1:(0.5-0.8).

[0045] Using *Lactobacillus rhamnosus* and *Weizmannii coagulans* in the aforementioned weight ratio to ferment vegetable waste enables the graded degradation of different components in the waste. *Lactobacillus rhamnosus* excels at decomposing large polysaccharides such as pectin and cellulose, generating monosaccharides such as glucose and fructose, as well as small organic acids (lactic acid and acetic acid). *Weizmannii coagulans* further converts some monosaccharides into medium-chain organic acids such as propionic acid and butyric acid. The final fermentation broth has a gradient carbon source structure, allowing for slow release. Furthermore, the amino acids, vitamins, trace elements, and extracellular polysaccharides produced after fermentation enhance the activity of functional microorganisms and improve treatment efficiency.

[0046] Optionally, the fermentation temperature of the vegetable waste fermentation liquid is 30-50℃.

[0047] The above fermentation conditions can improve the fermentation efficiency of vegetable waste, shorten the fermentation time, and increase the content of organic matter, thus enabling a stable supply of carbon source.

[0048] The vegetable waste in this application can be the waste from leafy vegetables.

[0049] Specifically, in the preparation of vegetable waste fermentation liquid, the fermentation temperature is 35-37℃.

[0050] Optionally, the weight ratio of the fermented pear peel broth to the functional base material is (1.5-2):1.

[0051] The fermented broth from pear peels can adhere to the interior and surface of the functional substrate. Therefore, the above-mentioned weight ratio setting can increase the adhesion amount of the fermented broth from pear peels, thereby improving the treatment effect of the bio-composite carbon source.

[0052] Optionally, the preparation method of the pear peel fermentation broth is as follows:

[0053] After crushing the pear peel, soak it in a 0.5-1.0 wt% citric acid solution for 1 hour. Rinse until neutral, then add it to 10-15 times its volume of water. Add pectinase and cellulase and enzymatically hydrolyze at 45-50℃ for 3-5 hours. The amount of pectinase added is 0.5-1.0 wt% of the pear peel, and the amount of cellulase added is 1.0-1.5 wt% of the pear peel. Finally, add *Lactobacillus rhamnosus* and *Weizmannii coagulans* and ferment at 30-50℃ for 8-10 hours. Filter to obtain the final product. The amount of *Lactobacillus rhamnosus* added is 1.0-2.0 wt% of the pear peel, and the amount of *Weizmannii coagulans* added is 0.8-1.5 wt% of the pear peel.

[0054] The peel of the pear fruit in this application is first soaked in citric acid to destroy its internal structure, which facilitates subsequent enzymatic hydrolysis and fermentation. Enzymatic hydrolysis first destroys the cell wall structure of the peel, so that it can release more polysaccharides, organic acids and other usable carbon sources during fermentation, thereby improving the treatment capacity of biological composite carbon source for sewage.

[0055] Optionally, the bioenzyme includes at least one of yeast cell wall breaking enzyme, pectin lyase, alkaline protease, and aminopeptidase.

[0056] The bioenzyme of this application can target and degrade macromolecular organic matter, improve carbon source utilization, and enhance microbial affinity. In particular, aminopeptidase can progressively cleave amino acid residues at the amino terminus of peptides, further degrading peptides produced by alkaline protease hydrolysis into free amino acids, completely eliminating the degradation bottleneck of peptides. The degraded amino acids can serve as signaling molecules to directionally induce gene expression in functional microorganisms such as denitrifying bacteria, promote the synthesis of their metabolic enzyme systems, and enhance denitrification function. At the same time, amino acids can regulate the osmotic pressure within microbial cells, enhancing the strain's tolerance to high-salt environments.

[0057] Optionally, the carbohydrate compound includes sucrose, glucose, and fructose.

[0058] According to another aspect of this application, a method for preparing a low-cost, high-efficiency biological composite carbon source for wastewater treatment as described in any of the above claims is provided, comprising the following steps:

[0059] (1) Preparation of functional substrate and fermentation broth of pear peel, and preparation of fermentation broth of vegetable waste using microbial agents;

[0060] (2) The functional base material and vegetable waste fermentation liquid are mixed and treated at 20-50℃ to obtain the first treatment liquid;

[0061] (3) Add pear peel fermentation liquid to the first treatment liquid and treat it at 30-40℃ to obtain the second treatment liquid;

[0062] (4) Add water, sodium acetate, potassium formate, sugar compounds and biological enzymes to the second treatment solution, and stir evenly at a constant temperature to obtain the final product.

[0063] The preparation method described in this application enables efficient composite synthesis of bio-based carbon sources, thereby improving production efficiency.

[0064] Optionally, the temperature in step (4) is 30-50℃ and the stirring time is 10-30min.

[0065] Optionally, the processing time for step (2) is 2-4 hours; the processing time for step (3) is 1-3 hours.

[0066] The beneficial effects of this application include, but are not limited to:

[0067] 1. The biological composite carbon source according to this application can realize hierarchical carbon source supply, form a gradient carbon supply mode, improve denitrification efficiency and stabilize denitrification, optimize the microbial community structure to improve microbial activity, and realize the resource utilization of waste to reduce production costs.

[0068] 2. The bio-composite carbon source of this application has high mechanical strength of functional matrix to reduce the probability of breakage and degradation, and enhance adsorption, so as to achieve efficient loading and precise slow release of carbon source, strengthen microbial attachment and synergy of microbial community, and optimize the system's nitrogen and phosphorus removal efficiency.

[0069] 3. According to the bio-composite carbon source of this application, the functional matrix has strong anti-pollution ability, reduces the risk of scaling and clogging, reduces the adsorption and accumulation of macromolecular organic matter on the carrier surface, and reduces the risk of anaerobic putrefaction.

[0070] 4. The biological composite carbon source according to this application can participate in the respiratory and metabolic processes of microorganisms, synergistically promote denitrification, create favorable conditions for denitrification reaction, and improve the total nitrogen removal effect. Detailed Implementation

[0071] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0072] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application were all purchased commercially.

[0073] Unless otherwise specified, the methods used in the embodiments and comparative examples of this application are conventional methods in the prior art.

[0074] Example 1

[0075] This embodiment relates to a low-cost, high-efficiency biological composite carbon source for wastewater treatment, which, by weight, comprises: 100 parts vegetable waste fermentation liquid, 30 parts water, 15 parts pear peel fermentation liquid, 8 parts functional base material, 6 parts sodium acetate, 7 parts potassium formate, 3 parts carbohydrate compound, and 0.2 parts biological enzyme, wherein the biological enzyme is yeast cell wall breaking enzyme.

[0076] The preparation method of a bio-composite carbon source includes the following steps:

[0077] (1) Preparation of functional substrate and fermentation broth of pear peel, and preparation of fermentation broth of vegetable waste using microbial agents;

[0078] The preparation method of functional base material is as follows:

[0079] S1: Phytic acid and an epoxy olefin compound were reacted at 30°C for 6 hours to obtain intermediate A. Intermediate A, N-vinylimidazole, and the initiator azobisisobutyronitrile were added to a solvent and polymerized at 75°C for 4 hours to obtain the first mixture. The molar ratio of phytic acid, epoxy olefin compound, and N-vinylimidazole was 1:1:2. The epoxy olefin compound was 3,4-epoxy-1-butene, and the amount of azobisisobutyronitrile added was 1.5 wt% of the weight of N-vinylimidazole.

[0080] S2: Add a composite carrier formed by chitin and bentonite to the first mixture, and continue stirring at the same temperature for 2 hours to obtain a second mixture. The amount of composite carrier added is 8 times the weight of phytic acid. The preparation method of the composite carrier is as follows: add bentonite completely into a chitin solution with a concentration of 15wt%, mix and stir at 30°C for 3 hours, filter and dry to obtain the final product.

[0081] S3: Add N,N-dimethylacrylamide, which accounts for 5 wt% of phytic acid, to the second mixture and continue the reaction at this temperature for 2 hours. Then add 30% hydrogen peroxide solution, which is 15 times the weight of N-vinylimidazole. After oxidation treatment for 3 hours, filter and dry to obtain the functional base material.

[0082] The preparation method of vegetable waste fermentation liquid is as follows:

[0083] After crushing the vegetable waste, add it to 10 times the amount of water, then add the bacterial agent and ferment at 35℃ for 15 hours. Filter to obtain the final product. The amount of bacterial agent added accounts for 0.2 wt% of the total weight of the vegetable waste. The bacterial agent is Lactobacillus rhamnosus and Weizmannella coagulans in a weight ratio of 1:0.8.

[0084] The preparation method of pear peel fermentation broth is as follows:

[0085] After crushing the pear peel, soak it in a 0.5wt% citric acid solution for 1 hour. Rinse until neutral, then add 10 times its volume of water. Add pectinase and cellulase and enzymatically hydrolyze at 45℃ for 5 hours. The amount of pectinase added is 0.5wt% of the pear peel, and the amount of cellulase added is 1.5wt% of the pear peel. Finally, add Lactobacillus rhamnosus and Weizmannii coagulans and ferment at 30℃ for 10 hours. Filter to obtain the final product. The amount of Lactobacillus rhamnosus added is 1.0wt% of the pear peel, and the amount of Weizmannii coagulans added is 1.5wt% of the pear peel.

[0086] (2) The functional base material and vegetable waste fermentation liquid were mixed and treated at 20°C for 4 hours to obtain the first treatment liquid;

[0087] (3) Add pear peel fermentation liquid to the first treatment liquid and treat at 30°C for 3 hours to obtain the second treatment liquid;

[0088] (4) Add water, sodium acetate, potassium formate, sugar compounds and biological enzymes to the second treatment solution, and stir at a constant temperature of 50°C for 10 minutes to obtain the solution.

[0089] Example 2

[0090] This embodiment relates to a low-cost, high-efficiency biological composite carbon source for wastewater treatment, which, by weight, comprises: 100 parts vegetable waste fermentation liquid, 40 parts water, 25 parts pear peel fermentation liquid, 10 parts functional base material, 10 parts sodium acetate, 10 parts potassium formate, 5 parts carbohydrate compounds, and 0.4 parts biological enzymes, wherein the biological enzymes are pectin lyase and alkaline protease in a weight ratio of 1:1.

[0091] The preparation method of a bio-composite carbon source includes the following steps:

[0092] (1) Preparation of functional substrate and fermentation broth of pear peel, and preparation of fermentation broth of vegetable waste using microbial agents;

[0093] The preparation method of functional base material is as follows:

[0094] S1: Phytic acid and epoxy olefins were reacted at 50°C for 4 hours to obtain intermediate A. Intermediate A, N-vinylimidazole, and initiator azobisisobutyronitrile were added to a solvent and polymerized at 65°C for 8 hours to obtain the first mixture. The molar ratio of phytic acid, epoxy olefins, and N-vinylimidazole was 1:1.2:3. The epoxy olefins were selected from 1,2-epoxy-5-hexene and 1,2-epoxy-9-decene in a molar ratio of 1:1. The amount of azobisisobutyronitrile added was 1.5 wt% of the weight of N-vinylimidazole.

[0095] S2: Add a composite carrier formed by chitin and bentonite to the first mixture, and continue stirring at the same temperature for 3 hours to obtain a second mixture. The amount of composite carrier added is 12 times the weight of phytic acid. The preparation method of the composite carrier is as follows: add bentonite completely into a chitin solution with a concentration of 10wt%, mix and stir at 50°C for 2 hours, filter and dry to obtain the final product.

[0096] S3: Add N,N-dimethylacrylamide, which accounts for 10 wt% of phytic acid, to the second mixture and continue the reaction at this temperature for 0.5 h. Then add 30% hydrogen peroxide solution, which is 25 times the weight of N-vinylimidazole. After oxidation treatment for 1.5 h, filter and dry to obtain the functional base material.

[0097] The preparation method of vegetable waste fermentation liquid is as follows:

[0098] After crushing the vegetable waste, add it to 15 times the amount of water, then add the bacterial agent and ferment at 37℃ for 12 hours. Filter to obtain the final product. The amount of bacterial agent added accounts for 0.5 wt% of the total weight of the vegetable waste. The bacterial agent is Lactobacillus rhamnosus and Weizmannella coagulans in a weight ratio of 1:0.5.

[0099] The preparation method of pear peel fermentation broth is as follows:

[0100] After crushing the pear peel, soak it in a 1.0 wt% citric acid solution for 1 hour. Rinse until neutral, then add 15 times its volume of water. Add pectinase and cellulase and enzymatically hydrolyze at 50°C for 3 hours. The amount of pectinase and cellulase added is 1.0 wt% of the pear peel. Finally, add *Lactobacillus rhamnosus* and *Weizmannii coagulans*, and ferment at 50°C for 8 hours. Filter to obtain the final product. The amount of *Lactobacillus rhamnosus* added is 2.0 wt% of the pear peel, and the amount of *Weizmannii coagulans* added is 0.8 wt% of the pear peel.

[0101] (2) The functional base material and vegetable waste fermentation liquid were mixed and treated at 50°C for 2 hours to obtain the first treatment liquid;

[0102] (3) Add pear peel fermentation liquid to the first treatment liquid and treat at 40°C for 1 hour to obtain the second treatment liquid;

[0103] (4) Add water, sodium acetate, potassium formate, sugar compounds and biological enzymes to the second treatment solution, and stir at a constant temperature of 30°C for 30 minutes to obtain the solution.

[0104] Example 3

[0105] This embodiment relates to a low-cost, high-efficiency biological composite carbon source for wastewater treatment, which, by weight, comprises: 100 parts vegetable waste fermentation liquid, 35 parts water, 20 parts pear peel fermentation liquid, 10 parts functional base material, 8 parts sodium acetate, 8 parts potassium formate, 4 parts carbohydrate compounds, and 0.3 parts biological enzymes, wherein the biological enzymes are alkaline protease and aminopeptidase in a weight ratio of 1:1.

[0106] The preparation method of a bio-composite carbon source includes the following steps:

[0107] (1) Preparation of functional substrate and fermentation broth of pear peel, and preparation of fermentation broth of vegetable waste using microbial agents;

[0108] The preparation method of functional base material is as follows:

[0109] S1: Phytic acid and epoxy olefins were reacted at 40°C for 5 hours to obtain intermediate A. Intermediate A, N-vinylimidazole, and initiator azobisisobutyronitrile were added to a solvent and polymerized at 70°C for 6 hours to obtain the first mixture. The molar ratio of phytic acid, epoxy olefins, and N-vinylimidazole was 1:1.2:2. The epoxy olefins were selected from 1,2-epoxy-5-hexene and 1,2-epoxy-9-decene in a molar ratio of 1:3. The amount of azobisisobutyronitrile added was 1.5 wt% of the weight of N-vinylimidazole.

[0110] S2: Add a composite carrier formed by chitin and bentonite to the first mixture, and continue stirring at the same temperature for 3 hours to obtain a second mixture. The amount of composite carrier added is 10 times the weight of phytic acid. The preparation method of the composite carrier is as follows: add bentonite completely into a chitin solution with a concentration of 15wt%, mix and stir at 40℃ for 3 hours, filter and dry to obtain the final product.

[0111] S3: Add N,N-dimethylacrylamide, which accounts for 8 wt% of phytic acid, to the second mixture and continue the reaction at this temperature for 1 hour. Then add 30% hydrogen peroxide solution, which is 20 times the weight of N-vinylimidazole. After oxidation treatment for 2 hours, filter and dry to obtain the functional base material.

[0112] The preparation method of vegetable waste fermentation liquid is as follows:

[0113] After crushing the vegetable waste, add it to 15 times the amount of water, then add the bacterial agent and ferment at 37℃ for 12 hours. Filter to obtain the final product. The amount of bacterial agent added accounts for 0.4 wt% of the total weight of the vegetable waste. The bacterial agent is Lactobacillus rhamnosus and Weizmannella coagulans in a weight ratio of 1:0.6.

[0114] The preparation method of pear peel fermentation broth is as follows:

[0115] After crushing the pear peel, soak it in a 0.8wt% citric acid solution for 1 hour. Rinse until neutral, then add 15 times its volume of water. Add pectinase and cellulase and enzymatically hydrolyze at 50℃ for 4 hours. The amount of pectinase added is 0.8wt% of the pear peel, and the amount of cellulase added is 1.2wt% of the pear peel. Finally, add Lactobacillus rhamnosus and Weizmannii coagulans, and ferment at 40℃ for 10 hours. Filter to obtain the final product. The amount of Lactobacillus rhamnosus added is 1.5wt% of the pear peel, and the amount of Weizmannii coagulans added is 1.3wt% of the pear peel.

[0116] (2) The functional base material and vegetable waste fermentation liquid were mixed and treated at 40°C for 3 hours to obtain the first treatment liquid;

[0117] (3) Add pear peel fermentation liquid to the first treatment liquid and treat at 35°C for 1.5 h to obtain the second treatment liquid;

[0118] (4) Add water, sodium acetate, potassium formate, sugar compounds and biological enzymes to the second treatment solution, and stir at a constant temperature of 40°C for 30 minutes to obtain the solution.

[0119] Example 4

[0120] The difference between this embodiment and Embodiment 3 is that the molar ratio of phytic acid and epoxy olefin compounds in step S1 is 1:2.

[0121] Example 5

[0122] The difference between this embodiment and Embodiment 3 is that the molar ratio of phytic acid and N-vinylimidazole in step S1 is 1:4.

[0123] Example 6

[0124] The difference between this embodiment and Embodiment 3 is that in step S1, 1,2-epoxy-7-octene is used in the same molar amount to replace 1,2-epoxy-5-hexene and 1,2-epoxy-9-decene in a molar ratio of 1:3.

[0125] Example 7

[0126] The difference between this embodiment and Embodiment 3 is that the concentration of the chitin solution in the preparation of the composite carrier is 5 wt%.

[0127] Example 8

[0128] The difference between this embodiment and Embodiment 3 is that the amount of hydrogen peroxide solution added in step S3 is 10 times the weight of N-vinylimidazole.

[0129] Comparative Example 1

[0130] The difference between this comparative example and Example 3 is that phytic acid is not added in step S1; instead, epoxy olefins and N-vinylimidazole are polymerized directly to obtain the first mixture.

[0131] Comparative Example 2

[0132] The difference between this comparative example and Example 3 is that N,N-dimethylallylamine is used instead of N-vinylimidazole.

[0133] Comparative Example 3

[0134] The difference between this comparative example and Example 3 is that step S3 does not involve oxidation treatment, and the N,N-dimethylacrylamide is filtered and dried immediately after the reaction is complete.

[0135] Comparative Example 4

[0136] The difference between this comparative example and Example 3 is that no pear peel fermentation liquid was added.

[0137] Comparative Example 5

[0138] The difference between this comparative example and Example 3 is that Lactobacillus plantarum is used instead of Lactobacillus rhamnosus.

[0139] Test Example 1

[0140] Wastewater from the same wastewater treatment plant is first added to a sedimentation tank. Under the action of a coagulant, flocs are separated and removed. Then, the wastewater enters an aerated biological filter for carbonization and nitrification. The effluent from the aerated biological filter then enters a denitrification filter. In the denitrification filter, a biological composite carbon source prepared according to the embodiments and comparative examples of this application is added to carry out the denitrification reaction. The amount of biological composite carbon source added is 300 g / L of wastewater to remove total nitrogen from the water. The effluent from the denitrification filter then sequentially enters a sand filter and a catalytic oxidation tank to finally obtain purified water.

[0141] The total phosphorus content, chemical oxygen demand (COD), total nitrogen content, and ammonia nitrogen content in the purified water of each embodiment or comparative example were tested, and the test results are shown in Table 1.

[0142] Table 1

[0143]

[0144] Test Example 2

[0145] The composite biocarbon source prepared in the above examples and comparative examples was stirred at 50°C and 1500 r / min for 4 h to simulate the impact process of water treatment. Then, the same test was performed on the same wastewater to be treated using the method of Test Example 1 to detect the change rate of total nitrogen content and the change rate of total phosphorus content. The test results are shown in Table 2.

[0146] The total nitrogen content change rate is calculated as [(N2-N1) / N1]×100%, where N1 is the total nitrogen content in the water after direct denitrification using the composite biological carbon source, and N2 is the total nitrogen content in the water after denitrification using the composite biological carbon source after stirring at 1500 r / min for 4 hours. The total phosphorus content change rate is calculated as [(P2-P1) / P1]×100%, where P1 is the total phosphorus content in the water after direct denitrification using the composite biological carbon source, and P2 is the total phosphorus content in the water after denitrification using the composite biological carbon source after stirring at 1500 r / min for 4 hours. A lower total nitrogen content change rate indicates a more stable mechanical structure and a longer service life for the biological composite carbon source of this application.

[0147] Table 2

[0148]

[0149] As can be seen from the above test examples, the biological composite carbon source of this application can continuously and efficiently provide carbon source, improve the treatment capacity of sewage, and has good water impact resistance, and can maintain high denitrification and dephosphorization effect during long-term use.

[0150] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A low-cost, high-efficiency biological composite carbon source for wastewater treatment, characterized in that, By weight, it includes: 100 parts vegetable waste fermentation liquid, 30-40 parts water, 15-25 parts pear peel fermentation liquid, 8-10 parts functional base material, 6-10 parts sodium acetate, 7-10 parts potassium formate, 3-5 parts carbohydrate compounds, and 0.2-0.4 parts biological enzymes. The preparation method of the vegetable waste fermentation liquid is as follows: After crushing the vegetable waste, add it to 10-15 times the amount of water, then add a microbial agent and ferment for at least 12 hours. Filter to obtain the final product. The amount of microbial agent added is 0.2-0.5 wt% of the total weight of the vegetable waste. The microbial agent includes Lactobacillus rhamnosus and Weizmannii coagulans. The preparation method of the functional base material is as follows: S1: Phytic acid and epoxy olefin compounds are reacted at 30-50℃ for 4-6h to obtain intermediate A. Intermediate A, N-vinylimidazolium and initiator are added to a solvent and polymerized at 65-75℃ for at least 4h to obtain the first mixture. S2: Add the composite carrier formed by chitin and bentonite to the first mixture, and continue to stir at 65-75℃ for 2-3 hours to obtain the second mixture; S3: Add N,N-dimethylacrylamide, accounting for 5-10 wt% of phytic acid, to the second mixture, and continue to react at 65-75℃ for at least 0.5 h. After oxidation treatment, filter and dry to obtain the functional base material.

2. The low-cost, high-efficiency biological composite carbon source for wastewater treatment according to claim 1, characterized in that, The molar ratio of phytic acid, epoxy olefins and N-vinylimidazole is 1:(1-1.2):(2-3).

3. The low-cost, high-efficiency biological composite carbon source for wastewater treatment according to claim 1, characterized in that, The epoxyene compound is selected from at least one of 3,4-epoxy-1-butene, 1,2-epoxy-5-hexene, 1,2-epoxy-7-octene, and 1,2-epoxy-9-decene.

4. The low-cost, high-efficiency biological composite carbon source for wastewater treatment according to claim 1, characterized in that, The epoxy olefin compounds are selected from 1,2-epoxy-5-hexene and 1,2-epoxy-9-decene in a molar ratio of 1:(1-3).

5. The low-cost, high-efficiency biological composite carbon source for wastewater treatment according to claim 1, characterized in that, The amount of the composite carrier added is 8-12 times the weight of phytic acid, and the preparation method of the composite carrier is as follows: Add bentonite completely to a chitin solution with a concentration of 10-15 wt%, mix and stir at 30-50℃ for 2-3 hours, filter and dry to obtain the final product.

6. The low-cost, high-efficiency biological composite carbon source for wastewater treatment according to claim 1, characterized in that, In step S3, the oxidant for oxidation treatment is selected from a 30% hydrogen peroxide solution. The amount of hydrogen peroxide solution added is 15-25 times the weight of N-vinylimidazole, and the oxidation treatment time is 1.5-3 hours.

7. The method for preparing a low-cost, high-efficiency biological composite carbon source for wastewater treatment according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Preparation of functional substrate and fermentation broth of pear peel, and preparation of fermentation broth of vegetable waste using microbial agents; (2) The functional base material and vegetable waste fermentation liquid are mixed and treated at 20-50℃ to obtain the first treatment liquid; (3) Add pear peel fermentation liquid to the first treatment liquid and treat it at 30-40℃ to obtain the second treatment liquid; (4) Add water, sodium acetate, potassium formate, sugar compounds and biological enzymes to the second treatment solution, and stir evenly at a constant temperature to obtain the final product.

8. The method for preparing a low-cost, high-efficiency biological composite carbon source for wastewater treatment according to claim 7, characterized in that, The temperature in step (4) is 30-50℃ and the stirring time is 10-30min.

9. The method for preparing a low-cost, high-efficiency biological composite carbon source for wastewater treatment according to claim 7, characterized in that, The processing time for step (2) is 2-4 hours; The processing time for step (3) is 1-3 hours.

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