A sludge fermentation method for municipal wastewater treatment

Abstract

This application relates to the technical field of wastewater treatment, specifically disclosing a sludge fermentation method for municipal wastewater treatment, comprising the following steps: mixing sludge, fermentation compound agent, pest control compound agent, and water evenly and stirring for 15-18 hours, followed by filtration to obtain fermented sludge; the pest control compound agent includes bactericides, insecticides, and heavy metal removal agents, wherein the bactericides include a hyperbranched polyester bactericide and penicillin in a weight ratio of (2.5-3):(1.2-1.5), and the fermentation compound agent includes *Trichoderma reesei*, *Candida*, *Aspergillus*, cellulase, and pectinase. The method of this application can be used to treat municipal wastewater, and has the advantages of reducing the harmful content of fermented sludge, realizing sludge recycling and reuse, and having a simple procedure.

Description

Technical Field

[0001] This application relates to the technical field of wastewater treatment, specifically to a sludge fermentation method for municipal wastewater treatment. Background Technology

[0002] With the increase in urban population, the discharge of municipal sewage is increasing daily, and the amount of sludge produced in sewage is also increasing rapidly. Tests have shown that the sludge in municipal sewage contains a large amount of water, as well as a certain amount of pathogens, parasites (eggs), heavy metals, and organic pollutants. Therefore, the sludge often emits a foul odor after it decomposes, and it must be properly treated to minimize the possibility of secondary pollution.

[0003] The most common initial method for sludge treatment was landfilling. However, sludge transportation and landfill construction costs are high, and as landfilling progresses, researchers have found that the leakage of harmful components may pollute urban groundwater. Furthermore, landfill capacity is limited, and finding suitable landfill sites is difficult in many urban areas with saturated land use. At this point, some researchers proposed that sludge contains various vitamins and minerals, which are essential nutrients for plant growth. By fermenting the sludge, it can be used as fertilizer and soil conditioner in farmland and woodlands, turning sludge into a valuable resource. Due to its scalability and reuse value, sludge fermentation (composting) has gradually become one of the most popular sludge treatment methods.

[0004] In existing sludge fermentation methods, pesticides are typically added to the sludge first to condition it and remove pathogens, parasites (eggs), and heavy metals. Then, bacteria and enzymes are added to ferment the vitamins and minerals in the sludge. However, existing pesticides inhibit the biological activity of bacteria and enzymes. To ensure effective fermentation, the amount of pesticides used must be minimized. This results in the current fermentation methods not completely removing pathogens, parasites (eggs), and heavy metals, leaving room for further reduction in the harmful substance content of the treated sludge. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides a sludge fermentation method for municipal wastewater treatment.

[0006] This application provides a sludge fermentation method for municipal wastewater treatment, which adopts the following technical solution:

[0007] A sludge fermentation method for municipal wastewater treatment includes the following steps: mixing sludge, fermentation compound agent, pest control compound agent and water evenly and stirring for 15-18 hours, and then filtering to obtain fermented sludge; the pest control compound agent includes bactericide, insecticide and heavy metal removal agent, the bactericide includes hyperbranched polyester bactericide and penicillin in a weight ratio of (2.5-3):(1.2-1.5), and the fermentation compound agent includes Trichoderma reesei, Candida albicans, Aspergillus, cellulase and pectinase.

[0008] By adopting the above technical solution, this application first utilizes the extremely high bactericidal ability of the hyperbranched polyester bactericide in the bactericide to efficiently inactivate harmful bacteria such as Staphylococcus aureus, Micrococcus luteus, Escherichia coli, Pseudomonas schrenckii, and Aeromonas hydrophila in the sludge. Then, it utilizes the highly selective bactericidal ability of penicillin to further inactivate the remaining bacteria in the sludge. Furthermore, penicillin does not have the ability to inactivate the fermentation compound agent used in this application. Therefore, the bactericide provided by this application can significantly inactivate harmful bacteria in the sludge and reduce the content of harmful substances in the fermented sludge with almost no impact on the activity of the fermentation compound agent.

[0009] This application also utilizes the insecticide in the pest control compound to inactivate parasites (eggs) in the sludge, and uses a heavy metal removal agent to wash away heavy metals in the sludge. Therefore, the pest control compound can effectively reduce the content of pathogens, parasites (eggs) and heavy metals in the sludge, thereby reducing the content of harmful substances in the fermented sludge, making the fermented sludge more suitable for fertilization, soil improvement and other uses.

[0010] Secondly, this application utilizes fungi such as Trichoderma reesei, Candida albicans, and Aspergillus to exert a synergistic effect, assisting in sludge fermentation and thus accelerating the fermentation rate. Furthermore, the application uses cellulase and pectinase in combination with the above three fungi, which not only enhances the biological activity of the fungi but also has a better removal effect on vitamins, lignin, pectin, and other organic matter in the sludge. Therefore, the fermentation compound can improve the fermentation rate of sludge and accelerate the fermentation process.

[0011] In summary, this application utilizes a certain amount of fermentation compound agent to rapidly assist the fermentation of vitamins and minerals in sludge, generating fermented fertilizer that is beneficial to crop growth and helps improve soil. At the same time, the pest control compound agent in this application does not affect the biological activity of fungi in the fermentation compound agent, and there is no need to reduce the amount of pest control compound agent to ensure normal fermentation. Therefore, this application can add sufficient amount of pest control compound agent without affecting sludge fermentation, and carry out normal pest control, effectively reducing the content of harmful substances in fermented sludge.

[0012] Preferably, the hyperbranched polyester bactericide is modified using the following steps:

[0013] 1. Hyperbranched polyester, catalyst and 4-chlorobutyryl chloride are dispersed in an organic solvent and mixed evenly. The mixture is then reacted for 20-22 hours, solidified, dissolved and dried to obtain an intermediate product. The weight ratio of hyperbranched polyester to 4-chlorobutyryl chloride is (15-18):(30-35).

[0014] 2. The intermediate product and the quaternary ammonium salt in a weight ratio of (10-12):(50-60) are dispersed in an organic solvent, mixed evenly, and reacted at 80-85℃ for 75-80h until solidification occurs. After drying, the quaternary ammonium salt modified hyperbranched polyester bactericide is obtained.

[0015] By adopting the above technical solution, this application first uses 4-chlorobutyryl chloride in a certain weight ratio to carry out a chlorination reaction with hyperbranched polyester, providing active sites brought by chloride ions to the hyperbranched polyester, and obtaining an intermediate product. Then, a certain amount of quaternary ammonium salt is added to the intermediate product, and a quaternization reaction occurs at the active sites, finally obtaining a quaternary ammonium salt modified hyperbranched polyester bactericide. Compared with the unmodified hyperbranched polyester bactericide, the quaternary ammonium salt modified hyperbranched polyester bactericide has higher adsorption capacity and more efficient cell membrane destruction force. During the sterilization and inactivation process, it can adsorb more and faster on the cell membrane of the bacterial community and destroy the cell membrane more rapidly, so that the bacterial community is quickly inactivated. The quaternary ammonium salt modified hyperbranched polyester bactericide significantly improves the bactericidal ability of the bactericide and further reduces the content of harmful substances in fermentation sludge.

[0016] Preferably, in step II, the quaternary ammonium salt is octyl dimethyl tertiary amine.

[0017] By adopting the above technical solution, this application uses octyl dimethyl tertiary amine to quaternize and modify hyperbranched polyester bactericide. Compared with other quaternary ammonium salts, octyl dimethyl tertiary amine has a shorter hydrophobic chain length, which means it has smaller water solubility and molecular volume. It can be more uniformly dispersed in the reaction system and enter the cell membrane of the bacterial community more quickly, further improving the bactericidal ability of the hyperbranched polyester bactericide and reducing the content of harmful substances in fermentation sludge.

[0018] Preferably, the weight ratio of the sludge, fermentation compound agent, pest control compound agent and water is (100-120):(3-4):(1.5-2.0):(50-60).

[0019] By adopting the above technical solution, this application adds a certain amount of fermentation compound agent and pest control compound agent to the sludge. Since the pest control compound agent of this application does not reduce the biological activity of the fermentation compound agent, the dosage of the pest control compound agent in this application can effectively reduce the content of harmful substances in the fermentation sludge without affecting the biological activity of the fermentation compound agent or generating additional raw material costs.

[0020] Preferably, during the fermentation process, a stabilizer is added at a dosage of 15-18 wt% of the fermentation compound agent, and mixed evenly with sludge, fermentation compound agent, pest control compound agent and water.

[0021] By adopting the above technical solution, this application utilizes stabilizers to improve the thermal and structural stability of Trichoderma reesei, Candida albicans, and Aspergillus, making the biological activity of the microbial community more stable, thereby making the auxiliary fermentation ability of the fermentation compound more stable and further accelerating the fermentation process of sludge.

[0022] Preferably, the stabilizer is isomaltooligosaccharide.

[0023] By adopting the above technical solution, this application utilizes isomaltooligosaccharide as a stabilizer. Compared with other stabilizers, it has higher fungal selectivity, which can effectively maintain the thermal and structural stability of fungi such as Trichoderma reesei, Candida albicans, and Aspergillus without affecting them, while not hindering the process of fungicide inactivating harmful bacteria such as Staphylococcus aureus, Micrococcus luteus, Escherichia coli, Pseudomonas schrenckii, and Aeromonas hydrophila.

[0024] Preferably, the weight ratio of the bactericide, insecticide and heavy metal remover is (12-15):(10-11):(55-60).

[0025] By adopting the above technical solution, this application combines a certain ratio of bactericide, insecticide and heavy metal remover, giving full play to the synergistic effect among the three, and effectively reducing the content of harmful substances in fermentation sludge without affecting the biological activity of the fermentation compound.

[0026] Preferably, the insecticide comprises ivermectin and pyridostigmine in a weight ratio of (2-2.2):(5-6).

[0027] Parasites (eggs) in sludge can be broadly classified into several categories, including nematodes, tapeworms, trematodes, and arthropods. By adopting the above-mentioned technical solutions, this application utilizes ivermectin to achieve highly efficient and selective inactivation of nematodes (eggs) and arthropods in sludge, and also utilizes pyridostigmine to achieve highly efficient and selective inactivation of tapeworms (eggs) and trematodes (eggs) in sludge. The synergistic use of the two can effectively inactivate parasites (eggs) in sludge and significantly reduce the content of harmful substances in fermented sludge.

[0028] Preferably, the heavy metal removal agent includes oxalic acid, citric acid, and water.

[0029] Preferably, in the heavy metal removal agent, the concentration of oxalic acid is 6-9 wt% and the concentration of citric acid is 20-25 wt%.

[0030] By adopting the above technical solution, this application disperses a certain amount of oxalic acid and citric acid in water to obtain a heavy metal removal agent. Oxalic acid and citric acid exhibit a synergistic effect, providing an acid radical ion to bind with metal ions, effectively removing heavy metals (lead, mercury, iron, copper, and zinc, etc.) from the water in the sludge, while not being excessively acidic, thus not negatively affecting the biological activity of the fermentation compound, bactericide, and insecticide, effectively reducing the content of harmful substances in the fermentation sludge. Experimental data demonstrates that the heavy metal removal agent with an oxalic acid concentration of 8.4 wt% and a citric acid concentration of 21.5 wt% possesses optimal heavy metal removal capacity while ensuring that the biological activity of the fermentation compound, bactericide, and insecticide is not negatively affected.

[0031] In summary, this application has the following beneficial technical effects:

[0032] 1. The sludge fermentation method for municipal wastewater treatment provided in this application can effectively reduce the content of harmful substances in fermented sludge without affecting sludge fermentation, and can realize the recycling and reuse of sludge;

[0033] 2. The sludge fermentation method for municipal sewage treatment provided in this application has simple steps, readily available raw materials, and a wide range of applications and high feasibility. Detailed Implementation

[0034] Material source

[0035] Unless otherwise specified, all raw materials used in this application are commercially available products, specifically:

[0036] The hyperbranched polyester bactericide was purchased from Guangdong Yunxing Biotechnology Co., Ltd.

[0037] Dodecyl chloride pyridine was purchased from Hubei Chengfeng Chemical Co., Ltd.

[0038] 4-Chlorobutyryl chloride was purchased from Shandong Xiya Chemical Co., Ltd.

[0039] Dimethylformamide was purchased from Jinan Xinchaorui Chemical Co., Ltd.

[0040] Acetone was purchased from Shanghai Aladdin Chemical Reagent Co., Ltd.

[0041] Hexadecyl dimethyl tertiary amine, tetradecyl dimethyl tertiary amine, dodecyl dimethyl tertiary amine, decyl dimethyl tertiary amine and octyl dimethyl tertiary amine were all purchased from Shandong Guohua Chemical Co., Ltd.

[0042] Oxalic acid was purchased from Weifang Chenyang Chemical Co., Ltd.

[0043] Citric acid was purchased from Henan Mingzhixin Chemical Products Co., Ltd.

[0044] Trichoderma reesei was purchased from Shanghai Biotechnology Center, model number NRCC2906;

[0045] Candida albicans was purchased from Wuhan Kemike Biomedical Technology Co., Ltd., with approximately 1.5 × 10⁻⁶ viable cells per unit. 10 -2.0×10 10 The Aspergillus was purchased from Jinan Chenyu Environmental Protection Technology Co., Ltd.

[0046] The cellulase was purchased from Jiangsu Haoxin Biotechnology Co., Ltd., and its enzyme activity was 100,000 U / g.

[0047] Pectinase was purchased from Anhui Weimao Biotechnology Co., Ltd., with an enzyme activity of 30,000 U / g.

[0048] The penicillin was purchased from Guangzhou Mingteng Biotechnology Co., Ltd.

[0049] Ivermectin was purchased from Sichuan Weikeqi Biotechnology Co., Ltd., with the molecular formula C. 48 H 74 O 14 ;

[0050] Silylpyridine was purchased from Wuhan Zhongchang Guoyan Standard Technology Co., Ltd., with the molecular formula C. 19 H 24 N2O2;

[0051] Isomaltooligosaccharide was purchased from the official flagship store of Yujian Kangyuan, model number IMO900;

[0052] Trehalose was purchased from the official Qinuo Liangpu store, model number JSLP-HZ-1;

[0053] The fructooligosaccharides were purchased from Henan Beicheng Food Co., Ltd., with an effective content of 95%.

[0054] Glycerin was purchased from Guangzhou Haozhao Chemical Co., Ltd.

[0055] Chitosan was purchased from Wuhan Baixing Biotechnology Co., Ltd.

[0056] Thiazidin insecticide was purchased from Shandong Guohua Chemical Co., Ltd.

[0057] Potassium ferrate bactericide was purchased from Henan Mingzhixin Chemical Products Co., Ltd.

[0058] The heavy metal chelating agent was purchased from Gongyi Hongyuan Environmental Protection Technology Co., Ltd.

[0059] Lactobacillus plantarum was purchased from Shandong Pingju Biotechnology Co., Ltd.

[0060] The metallophilic thermophilic bacillus was purchased from Shanghai Yansheng Industrial Co., Ltd.

[0061] Preparation Example 1.1

[0062] A method for preparing a quaternary ammonium salt modified hyperbranched polyester bactericide includes the following steps:

[0063] I. Disperse 15 kg of hyperbranched polyester bactericide, 1.2 kg of dodecyl chloropyridine and 35 kg of 4-chlorobutyryl chloride in 50 L of dimethylformamide, mix them evenly, and then react for 22 h. Pour the mixture obtained after the reaction into deionized water to precipitate solid, filter to obtain a solid substance, pour the solid substance into acetone to dissolve, pour the dissolved substance into deionized water to precipitate solid again, until no more solid is precipitated, dry the obtained solid substance, and then obtain the intermediate product.

[0064] II. Disperse 10 kg of intermediate product and 60 kg of hexadecyl dimethyl tertiary amine in 55 L of dimethylformamide, mix thoroughly, and react at 85 °C for 75 h. Pour the mixture obtained after the reaction into deionized water to precipitate solid, filter to obtain a solid substance, dissolve the solid substance in acetone, pour the dissolved substance into deionized water again to precipitate solid, until no more solid is precipitated, dry the obtained solid substance, and then obtain the quaternary ammonium salt modified hyperbranched polyester bactericide.

[0065] Preparation Example 1.2

[0066] A method for preparing a quaternary ammonium salt modified hyperbranched polyester bactericide includes the following steps:

[0067] I. Disperse 18 kg of hyperbranched polyester bactericide, 1.0 kg of dodecyl chloropyridine, and 30 kg of 4-chlorobutyryl chloride in 50 L of dimethylformamide, mix thoroughly, and react for 20 h. Pour the resulting mixture into deionized water to solidify, filter to obtain a solid substance, dissolve the solid substance in acetone, and then pour the dissolved substance into deionized water to solidify again.

[0068] After the solid no longer precipitates, the obtained solid material is dried to obtain the intermediate product;

[0069] II. Disperse 12 kg of intermediate product and 50 kg of hexadecyl dimethyl tertiary amine in 50 L of dimethylformamide, mix them evenly, and react at 80 °C for 80 h. Pour the mixture obtained after the reaction into deionized water to precipitate solid, filter to obtain a solid substance, pour the solid substance into acetone to dissolve, pour the dissolved substance into deionized water to precipitate solid again, until no more solid is precipitated, dry the obtained solid substance, and then obtain the quaternary ammonium salt modified hyperbranched polyester bactericide.

[0070] Preparation Example 2.1

[0071] The preparation method of the quaternary ammonium salt modified hyperbranched polyester bactericide differs from that of Preparation Example 1.1 in that: hexadecyl dimethyl tertiary amine in step II is replaced with tetradecyl dimethyl tertiary amine, while the rest is the same as that of Preparation Example 1.1.

[0072] Preparation Example 2.2

[0073] The preparation method of the quaternary ammonium salt modified hyperbranched polyester bactericide differs from that of Preparation Example 1.1 in that: hexadecyl dimethyl tertiary amine in step II is replaced with dodecyl dimethyl tertiary amine, while the rest is the same as in Preparation Example 1.1.

[0074] Preparation Example 2.3

[0075] The preparation method of the quaternary ammonium salt modified hyperbranched polyester bactericide differs from that of Preparation Example 1.1 in that: hexadecyl dimethyl tertiary amine in step II is replaced with decyl dimethyl tertiary amine, while the rest is the same as in Preparation Example 1.1.

[0076] Preparation Example 2.4

[0077] The preparation method of the quaternary ammonium salt modified hyperbranched polyester bactericide differs from that of Preparation Example 1.1 in that: hexadecyl dimethyl tertiary amine in step II is replaced with octyl dimethyl tertiary amine, while the rest is the same as that of Preparation Example 1.1.

[0078] Preparation Example 3.1

[0079] The preparation method of the heavy metal removal agent includes the following steps:

[0080] A heavy metal removal agent with an oxalic acid concentration of 6 wt% and a citric acid concentration of 25 wt% was obtained by mixing 6 kg of oxalic acid, 25 kg of citric acid and 69 kg of water evenly.

[0081] Preparation Example 3.2

[0082] The preparation method of the heavy metal removal agent includes the following steps:

[0083] A heavy metal removal agent with an oxalic acid concentration of 9 wt% and a citric acid concentration of 20 wt% was obtained by mixing 9 kg of oxalic acid, 20 kg of citric acid and 71 kg of water evenly.

[0084] Preparation Example 3.3

[0085] The preparation method of the heavy metal removal agent includes the following steps:

[0086] A heavy metal removal agent with an oxalic acid concentration of 8.4 wt% and a citric acid concentration of 21.5 wt% was obtained by mixing 8.4 kg of oxalic acid, 21.5 kg of citric acid and 70.1 kg of water evenly.

[0087] Preparation Example 3.4

[0088] The preparation method of the heavy metal removal agent includes the following steps:

[0089] A heavy metal removal agent with an oxalic acid concentration of 2 wt% and a citric acid concentration of 10 wt% was obtained by mixing 2 kg of oxalic acid, 10 kg of citric acid and 88 kg of water evenly.

[0090] Preparation Example 3.5

[0091] The preparation method of the heavy metal removal agent includes the following steps:

[0092] A heavy metal removal agent with an oxalic acid concentration of 15 wt% and a citric acid concentration of 30 wt% was obtained by mixing 15 kg of oxalic acid, 30 kg of citric acid and 55 kg of water evenly.

[0093] Example 1.1

[0094] A sludge fermentation method for municipal wastewater treatment includes the following steps:

[0095] 1000 kg of sludge, 40 kg of fermentation compound agent, 15 kg of pest control compound agent and 600 kg of water are mixed evenly and stirred for 15 hours. The resulting mixture is then filtered to obtain fermented sludge.

[0096] The fermentation compound agent includes 7.5 kg of Trichoderma reesei, 11 kg of Candida albicans, 3.5 kg of Aspergillus, 9 kg of cellulase and 9 kg of pectinase;

[0097] The pesticide compound includes 2.3 kg of fungicide (1.4 kg of hyperbranched polyester fungicide and 0.9 kg of penicillin), 2.1 kg of insecticide (0.53 kg of ivermectin and 1.57 kg of pyridostigmine) and 10.6 kg of the heavy metal removal agent prepared in Preparation Example 3.1.

[0098] Example 1.2

[0099] A sludge fermentation method for municipal wastewater treatment includes the following steps:

[0100] 1200 kg of sludge, 30 kg of fermentation compound agent, 20 kg of pest control compound agent and 500 kg of water were mixed evenly and stirred for 18 hours. The resulting mixture was then filtered to obtain fermented sludge.

[0101] The fermentation compound agent includes 5.5 kg of Trichoderma reesei, 9 kg of Candida albicans, 1.5 kg of Aspergillus, 7 kg of cellulase and 7 kg of pectinase;

[0102] The pesticide compound formulation includes 3.5 kg of fungicide (2.5 kg of hyperbranched polyester fungicide and 1.0 kg of penicillin), 2.4 kg of insecticide (0.73 kg of ivermectin and 1.67 kg of pyridostigmine) and 14.1 kg of the heavy metal removal agent prepared in Preparation Example 3.2.

[0103] Examples 2.1-2.2

[0104] A sludge fermentation method for municipal wastewater treatment differs from Example 1.1 in that the hyperbranched polyester bactericide is replaced with the quaternary ammonium salt modified hyperbranched polyester bactericide prepared in Examples 1.1-1.2, while the rest is the same as in Example 1.1.

[0105] Examples 3.1-3.4

[0106] A sludge fermentation method for municipal wastewater treatment differs from Example 2.1 in that the hyperbranched polyester bactericide is replaced with the quaternary ammonium salt modified hyperbranched polyester bactericide prepared in Examples 2.1-2.4, while the rest is the same as in Example 2.1.

[0107] Example 4.1

[0108] A sludge fermentation method for municipal wastewater treatment differs from Example 1.1 in that the heavy metal removal agent prepared in Preparation Example 3.1 is replaced with the heavy metal removal agent prepared in Preparation Example 3.3, while the rest is the same as in Example 1.1.

[0109] Examples 4.2-4.3

[0110] A sludge fermentation method for municipal wastewater treatment differs from Example 1.1 in that the heavy metal removal agent prepared in Preparation Example 3.1 is replaced with the heavy metal removal agent prepared in Preparation Examples 3.4-3.5, while the rest is the same as in Example 1.1.

[0111] Example 5.1

[0112] A sludge fermentation method for municipal wastewater treatment differs from Example 1.1 in that ivermectin is removed, and the amount of pyrazinol used is 2.1 kg, while the rest is the same as in Example 1.1.

[0113] Example 5.2

[0114] A sludge fermentation method for municipal wastewater treatment differs from Example 1.1 in that: pyridostigmine is removed, and the amount of ivermectin used is 2.1 kg; otherwise, it is the same as in Example 1.1.

[0115] Example 6.1

[0116] A sludge fermentation method for municipal wastewater treatment includes the following steps:

[0117] 1000 kg of sludge, 40 kg of fermentation compound agent, 15 kg of pest control compound agent, 6 kg of isomaltooligosaccharide and 600 kg of water were mixed evenly and stirred for 15 hours. The resulting mixture was then filtered to obtain fermented sludge.

[0118] The fermentation compound agent includes 7.5 kg of Trichoderma reesei, 11 kg of Candida albicans, 3.5 kg of Aspergillus, 9 kg of cellulase and 9 kg of pectinase;

[0119] The pesticide compound includes 2.3 kg of fungicide (1.4 kg of hyperbranched polyester fungicide and 0.9 kg of penicillin), 2.1 kg of insecticide (0.53 kg of ivermectin and 1.57 kg of pyridostigmine) and 10.6 kg of the heavy metal removal agent prepared in Preparation Example 3.1.

[0120] Example 6.2

[0121] A sludge fermentation method for municipal wastewater treatment includes the following steps:

[0122] 1000 kg of sludge, 40 kg of fermentation compound agent, 15 kg of pest control compound agent, 7.2 kg of isomaltooligosaccharide and 600 kg of water were mixed evenly and stirred for 15 hours. The resulting mixture was then filtered to obtain fermented sludge.

[0123] The fermentation compound agent includes 7.5 kg of Trichoderma reesei, 11 kg of Candida albicans, 3.5 kg of Aspergillus, 9 kg of cellulase and 9 kg of pectinase;

[0124] The pesticide compound includes 2.3 kg of fungicide (1.4 kg of hyperbranched polyester fungicide and 0.9 kg of penicillin), 2.1 kg of insecticide (0.53 kg of ivermectin and 1.57 kg of pyridostigmine) and 10.6 kg of the heavy metal removal agent prepared in Preparation Example 3.1.

[0125] Example 7.1

[0126] A sludge fermentation method for municipal wastewater treatment differs from Example 6.1 in that isomaltooligosaccharide is replaced with trehalose, while all other aspects are the same as in Example 6.1.

[0127] Example 7.2

[0128] A sludge fermentation method for municipal wastewater treatment differs from Example 6.1 in that isomaltooligosaccharide is replaced with fructooligosaccharide, while the rest is the same as in Example 6.1.

[0129] Example 7.3

[0130] A sludge fermentation method for municipal wastewater treatment differs from Example 6.1 in that isomaltooligosaccharide is replaced with glycerol, while all other aspects are the same as in Example 6.1.

[0131] Example 7.4

[0132] A sludge fermentation method for municipal wastewater treatment differs from Example 6.1 in that isomaltooligosaccharide is replaced with chitosan, while the rest is the same as in Example 6.1.

[0133] Example 8.1

[0134] A sludge fermentation method for municipal wastewater treatment differs from Example 1.1 in that the amount of the pesticide compound is 10 kg, including 1.3 kg of bactericide (0.81 kg of hyperbranched polyester bactericide and 0.49 kg of penicillin), 1.1 kg of insecticide (0.275 kg of ivermectin and 0.825 kg of pyridostigmine) and 7.6 kg of the heavy metal removal agent prepared in Preparation Example 3.1. The rest is the same as in Example 1.1.

[0135] Example 8.2

[0136] A sludge fermentation method for municipal wastewater treatment differs from Example 1.1 in that the amount of the pesticide compound is 20 kg, including 3.3 kg of bactericide (2.06 kg of hyperbranched polyester bactericide and 1.24 kg of penicillin), 3.1 kg of insecticide (0.78 kg of ivermectin and 2.32 kg of pyridostigmine) and 13.6 kg of the heavy metal removal agent prepared in Example 3.1. The rest is the same as in Example 1.1.

[0137] Comparative Example 1.1

[0138] 1. Mix 1000kg sludge, 2kg thiamethoxam insecticide, 2kg potassium ferrate bactericide, 15kg heavy metal chelating agent and 300kg water evenly and stir for 10 hours. Filter the mixture to obtain sludge to be fermented.

[0139] 2. Mix all the sludge to be fermented with 20 kg of Lactobacillus plantarum and 20 kg of metallophilic thermophilic bacteria, and let stand for 20 hours to obtain fermented sludge.

[0140] Comparative Example 1.2

[0141] The difference from Example 1.1 is that 40 kg of fermentation compound agent is replaced with 20 kg of Lactobacillus plantarum and 20 kg of metallophilic thermophilic bacteria, while the rest is the same as in Example 1.1.

[0142] Comparative Example 1.3

[0143] The difference from Example 1.1 is that 15 kg of the pesticide compound agent is replaced with 2.3 kg of potassium ferrate fungicide, 2.1 kg of thiamethoxam insecticide and 10.6 kg of heavy metal chelating agent, while the rest is the same as in Example 1.1.

[0144] Comparative Example 2.1

[0145] The difference from Example 1.1 is that Trichoderma reesei, Candida albicans and Aspergillus are removed, the amount of cellulase used is 20 kg, the amount of pectinase used is 20 kg, and the rest are the same as in Example 1.1.

[0146] Comparative Example 2.2

[0147] The difference from Example 1.1 is that cellulase and pectinase are removed, the amount of Trichoderma reesei is 13.5 kg, the amount of Candida albicans is 14 kg, and the amount of Aspergillus is 6.5 kg, while the rest are the same as in Example 1.1.

[0148] Comparative Example 3.1

[0149] The difference from Example 1.1 is that the fungicide is removed, the amount of insecticide used is 3.0 kg (0.75 kg ivermectin and 2.25 kg pyridostigmine), and the amount of heavy metal removal agent prepared in Example 3.1 is 12 kg. All other aspects are the same as in Example 1.1.

[0150] Comparative Example 3.2

[0151] The difference from Example 1.1 is that the insecticide is removed, the amount of fungicide used is 3.0 kg (1.875 kg of hyperbranched polyester fungicide and 1.125 kg of penicillin), the amount of heavy metal removal agent prepared in Example 3.1 is 12 kg, and the rest is the same as in Example 1.1.

[0152] Performance testing

[0153] The sterilization rate, insecticidal rate, heavy metal removal effect, and fermentation effect of the fermented sludge obtained in Examples 1.1-8.2 and Comparative Examples 1.1-3.2 were determined, specifically as follows:

[0154] 1. The viable counts of Staphylococcus aureus, Micrococcus luteus, Escherichia coli, Pseudomonas schlegelii, and Aeromonas hydrophila were determined using the plate count method and recorded as N1, N2, N3, N4, and N5, respectively. Untreated sludge was used as a control group and the same test was performed. The original bacterial counts were recorded as N. 10 N 20 N 30 N 40 N 50 Total sterilization rate = {[(N 10 -N1) / N10 ]+[(N 20 -N2) / N 20 ]+[(N 30 -N3) / N 30 ]+[(N 40 -N4) / N 40 ]+[(N 50 -N5) / N 50 ]}×100% / 5, and record the results in Table 1;

[0155] 2. Determine the total insecticidal rate (nematodes, tapeworms, trematodes, and arthropods) according to the method in 1, and record the results in Table 1;

[0156] 3. The heavy metal removal rate before and after sludge fermentation was determined by atomic absorption spectrometry. The heavy metal removal rate was calculated as follows: (heavy metal content in sludge before fermentation - heavy metal content in sludge after fermentation) × 100% / heavy metal content in sludge before fermentation. The results are recorded in Table 1.

[0157] 4. The total nutrient content (various vitamins and minerals, etc.) in fermented sludge was determined according to the "Comparative Study of Fertilizer Nutrient Rapid Tester and Conventional Method for Determining Nutrient Content [J]. Chinese Horticulture Abstracts, 2014, 30(9):209-211." and the results are recorded in Table 1.

[0158] Table 1

[0159]

[0160]

[0161] Analyze the data in Table 1:

[0162] Examples 1.1-1.2 show that the total sterilization rate can reach 98.956-98.962%, the total insecticidal rate can reach 98.23-98.25%, the heavy metal removal rate can reach 98.34-98.38%, and the total nutrient content can reach 8.19-8.26%. This demonstrates that this application effectively reduces the content of harmful substances in fermented sludge by utilizing the auxiliary fermentation ability of the fermentation compound, the pest control ability of the pest control compound, and the synergistic effect between the two, without affecting the sludge fermentation.

[0163] The total sterilization rates of Examples 2.1-3.4 are all higher than those of Example 1.1, by approximately 0.37-0.9%, demonstrating that the quaternized modified hyperbranched polyester bactericide prepared in this application has a stronger bactericidal ability compared to the unmodified hyperbranched polyester bactericide, further reducing the content of harmful substances in fermentation sludge. Among them, the total sterilization rates of Examples 3.1-3.4 are all higher than those of Example 2.1, and the total sterilization rate increases sequentially, demonstrating that this application uses octyl dimethyl tertiary amine to perform quaternization modification treatment on the hyperbranched polyester bactericide. By utilizing the shorter hydrophobic chain length of octyl dimethyl tertiary amine, the bactericidal ability of the hyperbranched polyester bactericide is further improved.

[0164] The heavy metal removal rate of Example 4.1 is higher than that of Example 1.1, while the heavy metal removal rate of Example 4.2 is lower than that of Example 1.1. Although the heavy metal removal rate of Example 4.3 is higher than that of Example 1.1, the total sterilization rate, total insecticidal rate and total nutrient content are all much lower than those of Example 1.1. This proves that by controlling the concentration of acidic substances in the heavy metal removal agent, this application can improve the heavy metal removal rate to the optimal level while ensuring that the biological activity of the fermentation compound, bactericide and insecticide is not negatively affected.

[0165] The total insecticidal rate of Examples 5.1-5.2 was lower than that of Example 1.1, proving that this application fully utilizes the synergistic effect between ivermectin and pyridostigmine, effectively inactivating parasites (eggs) in sludge and reducing the content of harmful substances in fermented sludge;

[0166] The total nutrient content of Examples 6.1-7.4 is higher than that of Example 1.1, proving that the present application utilizes stabilizers to enhance the biological activity of the microbial community and further accelerate the fermentation process of the sludge;

[0167] The total nutrient content of Examples 7.1-7.4 was not significantly different from that of Example 6.1, but the total bactericidal rate was lower than that of Example 6.1. This proves that the use of isomaltooligosaccharide as a stabilizer in this application can effectively maintain the thermal and structural stability of fungi such as Trichoderma reesei, Candida albicans, and Aspergillus without hindering the inactivation of harmful bacteria such as Staphylococcus aureus, Micrococcus luteus, Escherichia coli, Pseudomonas schrenckii, and Aeromonas hydrophila.

[0168] The total sterilization rate, total insecticidal rate, and heavy metal removal rate of Example 8.1 are all lower than those of Example 1.1, and the total nutrient content is not significantly different from that of Example 1.1. Similarly, the total sterilization rate, total insecticidal rate, heavy metal removal rate, and total nutrient content of Example 8.2 are not significantly different from those of Example 1.1. Even with increased dosage, the pest control compound agent in this application does not affect the biological activity of the fermentation compound agent, nor does it significantly improve the pest control effect. This proves that the dosage of the pest control compound agent in this application can effectively reduce the content of harmful substances in the fermentation sludge without affecting the biological activity of the fermentation compound agent or incurring additional raw material costs.

[0169] The total sterilization rate, total insecticidal rate, and heavy metal removal rate of Comparative Example 1.1 were all much lower than those of Example 1.1, and the total nutrient content was not significantly different from that of Example 1.1, proving that the sludge fermentation method provided in this application can effectively reduce the content of harmful substances in fermented sludge without affecting sludge fermentation.

[0170] The total nutrient content of Comparative Example 1.2 was much lower than that of Example 1.1, and the total sterilization rate, total insecticidal rate and heavy metal removal rate of Comparative Example 1.3 were all much lower than those of Example 1.1. This proves that the synergistic effect between the fermentation compound agent and the pest control compound agent fully utilized in this application effectively reduced the content of harmful substances in the fermented sludge without affecting the sludge fermentation.

[0171] The total nutrient content of Comparative Examples 2.1-2.2 was much lower than that of Example 1.1, proving that this application fully utilizes the synergistic effect between fungi such as Trichoderma reesei, Candida albicans, and Aspergillus and enzymes such as cellulase and pectinase, effectively improving the fermentation speed of sludge and accelerating the fermentation process;

[0172] The overall sterilization rates of Comparative Examples 3.1-3.2 were all lower than those of Example 1.1, proving that this application fully utilizes the synergistic effect between hyperbranched polyester bactericide and penicillin, effectively inactivating harmful bacteria in sludge and reducing the content of harmful substances in fermented sludge.

[0173] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A sludge fermentation method for municipal wastewater treatment, characterized in that: Includes the following steps: Sludge, fermentation compound, pest control compound and water are mixed evenly in a weight ratio of (100-120):(3-4):(1.5-2.0):(50-60) and stirred for 15-18 hours. After filtration, fermented sludge is obtained. The pest control compound includes bactericide, insecticide and heavy metal removal agent in a weight ratio of (12-15):(10-11):(55-60). The bactericide includes hyperbranched polyester bactericide and penicillin in a weight ratio of (2.5-3):(1.2-1.5). The fermentation compound includes Trichoderma reesei, Candida albicans, Aspergillus, cellulase and pectinase. During the fermentation process, a stabilizer is added at a dosage of 15-18 wt% of the fermentation compound agent and mixed evenly with sludge, fermentation compound agent, pest control compound agent and water. The stabilizer is isomaltooligosaccharide.

2. The sludge fermentation method for municipal wastewater treatment according to claim 1, characterized in that: The hyperbranched polyester bactericide is modified using the following steps: I. Disperse hyperbranched polyester, catalyst and 4-chlorobutyryl chloride in an organic solvent and mix them evenly. Then react for 20-22 hours, solidify, dissolve and dry to obtain intermediate product. The weight ratio of hyperbranched polyester to 4-chlorobutyryl chloride is (15-18):(30-35). II. Disperse the intermediate product and quaternary ammonium salt in an organic solvent at a weight ratio of (10-12):(50-60). After mixing evenly, react at 80-85℃ for 75-80 hours until solidification. After drying, obtain the quaternary ammonium salt modified hyperbranched polyester bactericide.

3. The sludge fermentation method for municipal wastewater treatment according to claim 2, characterized in that: In step II, the quaternary ammonium salt is octyl dimethyl tertiary amine.

4. The sludge fermentation method for municipal wastewater treatment according to claim 1, characterized in that: The insecticide comprises ivermectin and pyridostigmine in a weight ratio of (2-2.2):(5-6).

5. The sludge fermentation method for municipal wastewater treatment according to claim 1, characterized in that: The heavy metal removal agent includes oxalic acid, citric acid, and water.

6. The sludge fermentation method for municipal wastewater treatment according to claim 5, characterized in that: The heavy metal removal agent contains oxalic acid at a concentration of 6-9 wt% and citric acid at a concentration of 20-25 wt%.

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