Method for producing acid and improving dehydration performance through anaerobic fermentation of paper waste and multisource organic waste

Abstract

The invention relates to a method for producing acid and improving dehydration performance through anaerobic fermentation of paper waste and multisource organic waste, which comprises the following steps: S1, settling multisource organic solid waste, removing supernatant, and adding into an anaerobic fermentation reactor; s2, crushing paper wastes, adding the crushed paper wastes into the anaerobic fermentation reactor in the step S1, and mixing the crushed paper wastes with the multi-source organic solid wastes; s3, removing oxygen in the anaerobic fermentation reactor, and performing sealed constant-temperature fermentation; and S4, product separation. Compared with the prior art, the method disclosed by the invention has the advantages that the reaction period is greatly shortened compared with the conventional anaerobic digestion method, and the organic acid in the generated supernate is more easily recycled than methane; by adding the paper wastes, the dehydration performance of the organic solid wastes can be improved, and the stability of the fermentation liquor can be adjusted; for paper wastes such as waste tissues and waste paper meal boxes which are difficult to directly recycle due to organic pollution, the method is an important way for realizing carbon reduction and recycling.

Description

Technical Field

[0001] The invention relates to the field of environmental protection and comprehensive resource utilization, and in particular to a method for producing acid and improving dehydration performance by anaerobic fermentation of paper waste in coordination with multi-source organic waste. Background Art

[0002] In the current field of environmental protection and resource recycling, the treatment and utilization of organic solid waste has received extensive attention. However, fermentation treatment of organic solid waste alone often faces challenges in operational stability. For example, due to the imbalance of carbon and nitrogen content in food waste, acid inhibition, ammonia inhibition and other unfavorable conditions often occur during the anaerobic digestion process. In order to solve this problem, in practice, the feed components are usually adjusted by co-fermentation with other materials to improve the stability and efficiency of the fermentation process.

[0003] As a common household waste, paper waste is an ideal choice for synergistic fermentation due to its good biodegradability. In daily life, some paper waste is widely used, but it is often polluted in various ways during use, which greatly reduces the value of their direct recycling.

[0004] In addition, the dehydration of the fermentation broth after the biological fermentation process is also one of the difficulties in current technical research. The fermentation broth usually contains a large amount of water and soluble organic matter, and the presence of these components greatly increases the difficulty and cost of subsequent treatment. The current methods for enhancing dehydration performance mainly focus on improving the physical treatment processes such as various chemical agents or ultrasound, such as CN117247220B, CN118702391A, etc., but the processing cost of such methods is relatively high. Summary of the invention

[0005] The purpose of the present invention is to find a new collection and disposal solution for multi-source organic waste in cities, to solve the current operational abnormalities such as acid-ammonia inhibition generated when organic solid waste produces acid, and the problem that the remaining fermentation liquid has a high moisture content and is difficult to handle. Thus, a method for anaerobic fermentation of paper waste in coordination with multi-source organic waste to produce acid and adjust dehydration performance is provided. By introducing paper waste for coordinated fermentation, the operational stability of the anaerobic fermentation reaction is improved by utilizing the simple elemental composition and good degradability of such waste; at the same time, the long fiber structure of such waste is utilized to adjust the properties of the fermentation liquid and improve the dehydration performance of the fermentation liquid.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] The technical solution of the present invention is to provide a method for producing acid and improving dehydration performance by anaerobic fermentation of paper waste in cooperation with multi-source organic waste, comprising the following steps:

[0008] S1, after settling, remove the supernatant from multi-source organic solid waste and add it to an anaerobic fermentation reactor;

[0009] S2, crushing the paper waste and adding it to the anaerobic fermentation reactor in step S1 to mix with multi-source organic solid waste;

[0010] S3, removing oxygen from the anaerobic fermentation reactor and sealing and fermenting at a constant temperature;

[0011] S4. Product separation.

[0012] In some specific embodiments, in step S1, the multi-source organic solid waste is selected from any one or more of food waste and residual sludge, and the concentration of the multi-source organic solid waste is 30-100 g / L.

[0013] In some specific embodiments, the concentration of the food waste is 50-100 g / L. Exemplarily, the food waste may be urban kitchen waste.

[0014] In some specific embodiments, the concentration of the excess sludge is 30-60 g / L. Exemplarily, the excess sludge can be taken from the secondary sedimentation tank of a municipal domestic sludge plant.

[0015] Exemplarily, in step S2, the paper waste is classified according to the product classification method of the China Paper Association, including newsprint, uncoated printing and writing paper, packaging paper, household paper, etc., but excluding coated paper, coated printing paper, corrugated paper and other special paper. According to the product classification, the paper waste includes waste paper towels, waste toilet paper, personal care paper, waste paper lunch boxes, waste paper cups and the like.

[0016] In some specific embodiments, in step S1, biogas slurry is further added to the anaerobic fermentation reactor as inoculant, and the ratio of the biogas slurry to the multi-source organic solid waste after removing the supernatant is: the dry weight ratio of the multi-source organic solid waste to the biogas slurry is: 3:1 to 2:1.

[0017] In some specific embodiments, in step S2, the paper waste is shredded to a diameter less than 5 mm.

[0018] In some specific embodiments, in step S2, the dry weight ratio of the paper waste to the multi-source organic solid waste is 1-3%.

[0019] In some specific embodiments, in step S3, the method for removing oxygen in the anaerobic fermentation reactor is to remove oxygen in the anaerobic fermentation reactor by blowing nitrogen, and the flow rate of nitrogen is 0.1-0.5 L / min, and the time is 10-30 min.

[0020] In some specific embodiments, in step S3, the temperature of the sealed constant temperature fermentation is 30-50°C, the time is 3-8 days, and the pH is 4.0-6.8.

[0021] In some specific embodiments, the time of constant temperature fermentation is 4 to 6 days.

[0022] In the present invention, the characteristics of paper waste itself are mainly used to adjust the properties of organic waste fermentation liquid. The basic principles are: (1) the cellulose contained in paper is used as the substrate of the fermentation reaction to supplement the carbon content in the substrate, adjust the carbon-nitrogen balance of the reaction system, and at the same time, the paper is partially converted into low-molecular organic acids through biological fermentation to achieve its resource effect; (2) the cellulose contained in paper is a natural organic polymer material, which can play the role of a partial flocculant in the fermentation process, adjust the structure of the fermentation liquid, and improve the dehydration performance of the fermentation liquid.

[0023] The total concentration of volatile fatty acids in the supernatant during the constant temperature anaerobic fermentation reaction was 20-80 mmol / L when the residual sludge was used as the substrate, and the total concentration was 120-200 mmol / L when the food waste was used as the substrate.

[0024] During the constant temperature anaerobic fermentation reaction, the concentration of dissolved organic carbon in the supernatant was 1000-2500 mg / L when residual sludge was used as substrate, and was 7000-10000 mg / L when food waste was used as substrate.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) Compared with the existing conventional anaerobic digestion method, the reaction cycle of the method of the present invention is greatly shortened. Generally, the hydraulic retention time of a complete anaerobic digestion process is 15 to 30 days, while the hydraulic retention time of the fermentation process of the method of the present invention is 3 to 8 days. The organic acid in the generated supernatant is easier to realize resource recovery than methane.

[0027] (2) The present invention can improve the dehydration performance of organic solid waste and adjust the stability of fermentation liquid by adding paper waste.

[0028] (3) The method of the present invention is an important way to achieve carbon reduction and resource utilization for paper wastes such as waste paper towels and waste paper lunch boxes that are difficult to directly recycle due to organic pollution.

[0029] (4) The present invention has developed a method for synchronously regulating the dehydration performance of paper waste and biomass waste by fermenting acid, which can not only improve the treatment efficiency of organic solid waste, but also promote the resource utilization of paper waste, while improving the dehydration performance of the fermentation liquid to facilitate further treatment of the fermentation liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1It is a schematic diagram of the process of the present invention.

[0031] Figure 2 The organic acid concentration and capillary water absorption time in Examples 1 to 4.

[0032] Figure 3 The types and concentrations of organic acids in Examples 1 to 4. DETAILED DESCRIPTION

[0033] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0034] In the following examples, unless otherwise specified, raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0035] Materials in the examples:

[0036] (1) Food waste: refers to food waste that is collected by the municipal solid waste collection and transportation system and then pre-processed by crushing and removing impurities.

[0037] (2) Residual sludge: taken from the secondary sedimentation tank of the urban domestic sewage treatment plant.

[0038] (3) Biogas slurry: taken from the anaerobic digestion plant of urban organic waste.

[0039] Embodiment 1:

[0040] like Figure 1 As shown, the supernatant was discarded after the residual sludge was settled in a 4°C environment for 24 hours, 1200mL (solid content 2.67%, initial pH 6.8) was taken and loaded into the fermenter, and 600mL of biogas slurry was added as inoculum (solid content 2.37%). Nitrogen was used to drive air into the reactor and aerated at 0.3L / min for 15min. After inflation, the reactor was sealed and the electromagnetic stirrer was set to a constant speed (60 rpm) to ensure mixing. The reactor retained two silicone tubes for subsequent feeding and discharging and an air bag for collecting the gas generated by the reactor. After the reactor was assembled, the reactor was placed in a water bath (38°C) for anaerobic digestion. During the operation, 450mL of feed was fed and discharged every day. The control group only added residual sludge, and the experimental group added soluble toilet paper waste (mechanically crushed to less than 5mm) at 1% of the dry weight of the sludge at the same time as the residual sludge, and 5 groups were parallel. A small amount of biogas is produced at the beginning of the fermentation process, and the acid production begins to stabilize after 4 days. The pH range during this period is 4.0-6.8. Figure 2As shown, the average total concentration of short-chain organic acids in the subsequent supernatant was 53.50 mmol / L. The difference with the control group shows that the conversion of paper into organic acids has a significant effect on the total acid concentration. After calculation, the conversion rate of the added paper into short-chain organic acids was 35.4% in terms of carbon element. At the same time, the capillary water absorption time of the fermentation broth was tested to be 38.25s, which was 42.1% less than that of the control group, thereby improving the dehydration performance of the fermentation broth. The types of short-chain organic acids converted from paper include lactic acid, valeric acid, isovaleric acid, butyric acid, isobutyric acid, propionic acid, and acetic acid. The concentrations of each are as shown in the figure. Figure 3 shown.

[0041] Embodiment 2:

[0042] After the residual sludge was settled in a 4°C environment for 24 hours, the supernatant was discarded, 1200 mL (solid content 2.67%, initial pH 6.8) was taken and loaded into the fermentation tank, and 600 mL of biogas slurry was added as inoculum (solid content 2.37%). Nitrogen was used to drive the air into the reactor and aerated at 0.3L / min for 15 minutes. After inflation, the reactor was sealed and the electromagnetic stirrer was set to a constant speed (60 rpm) to ensure mixing. The reactor retains two silicone tubes for subsequent feeding and discharging and an air bag for collecting the gas produced by the reactor. After the reactor was assembled, the reactor was placed in a water bath (50°C) for anaerobic digestion. During the operation, 450 mL of feed was fed and discharged every day. The control group only added residual sludge, and the experimental group added 1% of the dry weight of sludge with facial tissue waste (mechanically crushed to less than 5mm) at the same time as the residual sludge, and 5 groups were carried out in parallel. A small amount of biogas was produced in the early stage of the fermentation process, and the acid production began to stabilize after 4 days. The pH range during this period was 4.0-6.8. Figure 2 As shown, the average total concentration of short-chain organic acids in the subsequent supernatant was 57.69 mmol / L. The difference with the control group shows that the conversion of paper into organic acids was significantly effective. After calculation, the conversion rate of the added paper into short-chain organic acids was 40.7% in terms of carbon element. At the same time, the capillary water absorption time of the fermentation broth was tested to be 25.75s, which was 61.0% less than that of the control group, thereby improving the dehydration performance of the fermentation broth. The types of short-chain organic acids converted from paper include lactic acid, valeric acid, isovaleric acid, butyric acid, isobutyric acid, propionic acid, and acetic acid. The concentrations of each are as shown in Figure 3 shown.

[0043] Embodiment 3:

[0044] 1200mL of food waste slurry (solid content 8.13%, initial pH 4.6) was loaded into the fermentation tank, and 600mL of biogas slurry was added as inoculum (solid content 2.37%). Nitrogen was used to drive air out of the reactor and aerated at 0.3L / min for 15min. After inflation, the reactor was sealed and the electromagnetic stirrer was set to a constant speed (60 rpm) to ensure mixing. The reactor retained two silicone tubes for subsequent feeding and discharging and an air bag to collect the gas produced by the reactor. After the reactor was assembled, the reactor was placed in a water bath (38°C) for anaerobic digestion. During the operation, 450mL of feed was fed and discharged every day. Only residual sludge was added to the control group. At the same time as the residual sludge, 1% of the dry weight of sludge was added to the experimental group. Five groups were carried out in parallel. A small amount of biogas was produced in the early stage of the fermentation process. After 4 days, the acid production began to stabilize. The pH range during this period was 4.0-4.6. Figure 2 As shown, the average total concentration of short-chain organic acids in the subsequent supernatant was 155.9 mmol / L. The difference with the control group shows that the presence of paper increased the total acid production of the reactor. After calculation, the conversion rate of the added paper into short-chain organic acids was 8.83% in terms of carbon element. At the same time, the capillary water absorption time of the fermentation broth was tested to be 111.25s, which was 19.6% less than that of the control group, thereby improving the dehydration performance of the fermentation broth. The types of short-chain organic acids converted from paper include lactic acid, heptanoic acid, hexanoic acid, isohexanoic acid, valeric acid, isovaleric acid, butyric acid, isobutyric acid, propionic acid, and acetic acid. The concentrations of each are as shown in the figure. Figure 3 shown.

[0045] Embodiment 4:

[0046] 1200mL of food waste slurry (solid content 8.13%, initial pH 4.6) was loaded into the fermentation tank, and 600mL of biogas slurry was added as inoculum (solid content 2.37%). Nitrogen was used to drive air out of the reactor and aerated at 0.3L / min for 15min. After inflation, the reactor was sealed and the electromagnetic stirrer was set to a constant speed (60 rpm) to ensure mixing. The reactor retained two silicone tubes for subsequent feeding and discharging and an air bag to collect the gas produced by the reactor. After the reactor was assembled, the reactor was placed in a water bath (38°C) for anaerobic digestion. During the operation, 450mL of feed was fed and discharged every day. Only residual sludge was added to the control group. At the same time as the residual sludge, 1% of the dry weight of facial tissue waste (mechanically crushed to less than 5mm) was added to the experimental group. Five groups were carried out in parallel. A small amount of biogas was produced in the early stage of the fermentation process. After 4 days, the acid production began to stabilize. The pH range during this period was 4.0-4.6. Figure 2As shown, the average total concentration of short-chain organic acids in the subsequent supernatant was 153.3 mmol / L. The difference with the control group shows that the presence of paper increased the total acid production of the reactor. After calculation, the conversion rate of the added paper into short-chain organic acids was 9.51% in terms of carbon element. At the same time, the capillary water absorption time of the fermentation broth was tested to be 106.00s, which was 23.4% less than that of the control group, thereby improving the dehydration performance of the fermentation broth. The types of short-chain organic acids converted from paper include lactic acid, heptanoic acid, hexanoic acid, isohexanoic acid, valeric acid, isovaleric acid, butyric acid, isobutyric acid, propionic acid, and acetic acid. The concentrations of each are as shown in the figure. Figure 3 shown.

[0047] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for anaerobic fermentation of paper waste and multi-source organic waste to produce acid and improve dehydration performance, characterized in that: The steps include: S1, after settling, remove the supernatant from multi-source organic solid waste and add it to an anaerobic fermentation reactor; S2, crushing the paper waste and adding it to the anaerobic fermentation reactor in step S1 to mix with multi-source organic solid waste; S3, removing oxygen from the anaerobic fermentation reactor and sealing and fermenting at a constant temperature; S4. Product separation.

2. The method according to claim 1, characterized in that In step S1, the multi-source organic solid waste is selected from any one or more of food waste and residual sludge, and the concentration of the multi-source organic solid waste is 30-100 g / L.

3. The method according to claim 2, characterized in that The concentration of the food waste is 50-100 g / L.

4. The method according to claim 2, characterized in that: The concentration of the excess sludge is 30-60 g / L.

5. The method according to claim 1, characterized in that In step S1, biogas slurry is added into the anaerobic fermentation reactor as inoculant, and the ratio of the biogas slurry to the multi-source organic solid waste after the supernatant is as follows: the dry weight ratio of the multi-source organic solid waste to the biogas slurry is 3:1 to 2:

1.

6. The method according to claim 1, characterized in that In step S2, the paper waste is shredded to a diameter less than 5 mm.

7. The method according to claim 1, characterized in that In step S2, the dry weight ratio of the paper waste to the multi-source organic solid waste is 1-3%.

8. The method according to claim 1, characterized in that In step S3, the method for removing oxygen in the anaerobic fermentation reactor is to remove oxygen in the anaerobic fermentation reactor by blowing nitrogen, the flow rate of nitrogen is 0.1-0.5 L / min, and the time is 10-30 min.

9. The method according to claim 1, characterized in that: In step S3, the temperature of the sealed constant temperature fermentation is 30-50°C, the time is 3-8 days, and the pH is 4.0-6.

8.

10. The method according to claim 9, characterized in that The time for constant temperature fermentation is 4 to 6 days.

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