A green and low-carbon method for the classification, collection, and treatment of municipal sludge.

Abstract

A green and low-carbon method for classifying, collecting, and treating municipal sludge includes the following steps: Step 1: Collecting municipal sludge according to its composition and source, temporarily storing it in sealed containers, and affixing labels containing parameters such as sludge source, composition, and physicochemical properties to obtain sludge from grit chambers, primary sedimentation tanks, secondary sedimentation tanks, and physicochemical treatment tanks; Step 2: Screening the grit chamber sludge, treating the oversize as construction waste, and then filtering the undersize. The filter cake is sent to a brick-making machine or used as backfill, while the filtrate is sent to a wastewater treatment unit; Step 3: Mixing, conditioning, and dewatering the sludge from the primary and secondary sedimentation tanks, and then sending it to a fermentation system for anaerobic or aerobic fermentation to obtain fermented compost. The fermented compost is then used as organic fertilizer or mixed with different nutrients and granulated to produce compound fertilizer products. This invention can effectively solve the problems of high difficulty and high cost in treating mixed sludge in current wastewater treatment plants, and realize the resource utilization of sludge.

Description

Technical Field

[0001] This invention relates to the field of sludge treatment technology, and in particular to a green and low-carbon method for the classification, collection and treatment of municipal sludge. Background Technology

[0002] Wastewater treatment processes generate tens of millions of tons of wet sludge annually (estimated at 80% moisture content), and this figure is increasing by 10% each year. The contradiction between the continuously rising amount of sludge generated during municipal wastewater treatment and insufficient treatment capacity is becoming increasingly prominent, posing a severe challenge to municipal sludge disposal and management.

[0003] Wastewater treatment sludge can be categorized into grit chamber sludge, primary sedimentation tank sludge, secondary sedimentation tank sludge, and physicochemical treatment sludge based on its source. The conventional practice in wastewater treatment plants is to mix these sludges and outsource their disposal. Disposal methods include landfill and pyrolysis. Landfilling requires a large land area, incurs high sludge dewatering costs, easily pollutes groundwater, and does not fundamentally eliminate the polluting properties of the sludge. Pyrolysis involves complex reaction conditions, is constrained by the properties of the sludge itself, has poor equipment adaptability, and is extremely difficult to control. However, the composition of sludge varies greatly depending on its source. For example, grit chamber sludge mainly consists of inorganic sand and gravel, while primary and secondary sedimentation tank sludge mainly consists of organic matter, and physicochemical treatment sludge mainly consists of heavy metals. Mixing these sludges for disposal not only wastes resources but also increases the difficulty and cost of treatment. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a green and low-carbon method for the classified collection and treatment of municipal sludge. This method can effectively solve the problems of high difficulty and high cost in treating mixed sludge in sewage treatment plants, and can also realize the resource utilization of sludge.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a green and low-carbon method for the classification, collection, and treatment of municipal sewage sludge, comprising the following steps: Step 1: Collect municipal sludge generated from each treatment section of the wastewater treatment plant according to its composition and source, temporarily store it in a sealed container, and attach a label containing parameters such as the source, composition, and physicochemical properties of the sludge to obtain sludge from the grit chamber, sludge from the primary sedimentation tank and the secondary sedimentation tank, and sludge from the physicochemical treatment tank. Step 2: Screen the sludge in the grit chamber. The material over the screen is treated as construction waste, and the material under the screen is filtered. The filter cake is sent to the brick-making machine to make bricks or used as backfill soil, and the filtrate is sent to the sewage treatment unit for treatment. Step 3: Mix the sludge from the primary sedimentation tank and the secondary sedimentation tank, condition and dewater it, and then send it into the fermentation system for anaerobic or aerobic fermentation to obtain fermented cooked material. Then, the fermented cooked material can be used as organic fertilizer or mixed with different nutrients to granulate and produce compound fertilizer products. Step 4: After pre-treating the sludge from the physicochemical treatment pond, it is either landfilled or incinerated.

[0006] Furthermore, the conditioning process involves slowly adding sawdust or crushed straw to the sludge and then mixing it at high speed to control the moisture content of the mixed sludge to below 60%.

[0007] Furthermore, the fermentation system adopts mesophilic anaerobic fermentation at 42~45℃ or aerobic fermentation with forced ventilation by a fan.

[0008] Furthermore, the nutrients added in the manufacture of compound fertilizers are at least one of nitrogen, phosphorus, and potassium.

[0009] Furthermore, the aerobic fermentation time is 10-20 days.

[0010] Furthermore, the pretreatment method used for landfill disposal is stabilization and solidification.

[0011] Furthermore, the pretreatment method for the waste sent to the incineration system is drying.

[0012] In summary, the beneficial effects of this invention are as follows: The green and low-carbon municipal sludge classification, collection, and treatment method of this invention classifies and collects sludge from different sources in sewage treatment plants, and adopts corresponding comprehensive utilization methods based on the sludge composition. This solves the sludge pollution problem while obtaining corresponding products, and greatly reduces the difficulty and cost of sludge treatment. It is preliminarily estimated that compared with landfill, it saves 80% of land area; compared with pyrolysis, it saves more than 60% of energy and reduces exhaust emissions by more than 80%.

[0013] Currently, municipal sludge is mainly treated by drying, incineration, and landfilling. Due to its complex composition, high treatment costs, and significant environmental pollution and safety hazards, other treatment methods are scarce. The green and low-carbon municipal sludge classification, collection, and treatment method of this invention classifies, treats, and utilizes sludge from the source. It is technically and economically reasonable, low-carbon and environmentally friendly, and highly applicable, representing a future direction for sustainable development. Attached Figure Description

[0014] Figure 1 This is a process flow diagram of the green and low-carbon municipal sludge classification, collection, and treatment method of the present invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] Please see Figure 1 This invention provides a green and low-carbon method for the classification, collection, and treatment of municipal sewage sludge, comprising the following steps: Step 1: Collect municipal sludge generated from each treatment section of the wastewater treatment plant according to its composition and source, temporarily store it in a sealed container, and attach a label containing parameters such as the source, composition, and physicochemical properties of the sludge to obtain sludge from the grit chamber, sludge from the primary sedimentation tank and the secondary sedimentation tank, and sludge from the physicochemical treatment tank. Step 2: Screen the sludge in the grit chamber. The material over the screen is treated as construction waste, and the material under the screen is filtered. The filter cake is sent to the brick-making machine to make bricks or used as backfill soil, and the filtrate is sent to the sewage treatment unit for treatment. Step 3: Mix the sludge from the primary sedimentation tank and the secondary sedimentation tank, condition and dewater it, and then send it into the fermentation system for anaerobic or aerobic fermentation. Then, use the fermented material as organic fertilizer or add different nutrients to mix and granulate to produce compound fertilizer products. Step 4: After pretreatment, the sludge from the physicochemical treatment pond is either utilized, sent to a landfill, or dried and then incinerated.

[0017] In step 3, the sludge from the primary and secondary sedimentation tanks is mixed with sawdust or straw powder and conditioned until the moisture content is no higher than 60%. After reaching a temperature of 42-45℃, it is fed into a fermentation system for anaerobic fermentation or aerobic fermentation with forced ventilation. The fermented material is then used as organic fertilizer or granulated with different nutrients to produce compound fertilizer. Specifically, in step 3, the conditioning involves slowly adding sawdust or crushed straw to the sludge and mixing it at high speed to control the moisture content of the mixed sludge to below 60%. The fermentation system uses mesophilic anaerobic fermentation at 42-45℃ or aerobic fermentation with forced ventilation. The nutrients added to the compound fertilizer are at least one of nitrogen, phosphorus, and potassium. The aerobic fermentation time is 10-20 days.

[0018] Furthermore, in step 4, the pretreatment method used for disposal in the landfill is stabilization and solidification, and the pretreatment method used for disposal in the incineration system is drying.

[0019] Specifically, municipal sludge is the sludge produced during the municipal wastewater treatment process. In the municipal wastewater treatment process: The principle of step 2 is as follows: The sludge in the sedimentation tank is produced during the pretreatment of municipal sewage. Its main components are large particles of sand and gravel, small particles of soil, and a small amount of plastic, wood, and metal. During the screening process, the large particles of sand and gravel, and the small amount of plastic, wood, and metal cannot pass through the screen and are retained as the oversize. The small particles of soil pass through the screen and become the undersize. The large particles of sand and gravel, and the small amount of plastic, wood, and metal are sent to the construction waste treatment plant for comprehensive utilization. The small particles of soil are filtered and then sent to a brick-making machine for brick making or used as backfill soil. After granular sand and gravel, along with small amounts of plastic, wood, and metal, enter the construction waste integrated treatment plant, the raw materials first need to undergo preliminary screening to remove unusable plastics, wood, and metal. Then, the raw materials undergo multi-stage crushing to break large pieces of sand and gravel into the required particle size range, followed by screening to obtain aggregates of different particle sizes. Finally, the aggregates are washed to remove surface soil, yielding commercial-grade construction aggregates. The sludge from the primary and secondary sedimentation tanks is then mixed, conditioned, dewatered, and sent to the fermentation system for anaerobic or aerobic fermentation.

[0020] The principle of step 3 is as follows: The sludge produced in the primary and secondary sedimentation tanks is rich in organic matter, which serves as the raw material for fermentation. Step 3 uses sawdust and straw to condition the sludge, primarily to adjust the ratio of elements such as C and N and the moisture content in the sludge to achieve optimal living conditions for microorganisms, thereby obtaining a good fermentation effect. In the fermentation material, C and N are the two most important elements. C provides energy for microorganisms, while N participates in building the microbial cell structure. Since the carbon-to-nitrogen ratio of microorganisms is generally around 5:1, assimilating 5 parts carbon requires 1 part nitrogen to form its own cell body, and absorbing and utilizing 1 part nitrogen requires consuming 5 parts organic carbon for energy, microorganisms need to consume 25 parts organic carbon to absorb and utilize 1 part nitrogen. Therefore, the most suitable carbon-to-nitrogen ratio for aerobic fermentation of the material should be between 25:1 and 31:1. When it is too low, the material pile tends to accumulate "partially oxidized" organic matter rather than further decomposing and transforming it into humus, thus hindering the normal process of aerobic fermentation. Fermentation is further divided into aerobic fermentation and anaerobic fermentation. Aerobic fermentation is the process by which microorganisms decompose organic matter in an oxygen-rich environment. Its main fermentation products are humic substances, carbon dioxide, and water. Its main reaction equation is: [C, H, O, N, S, P] + O 2 →CO2+NO 3- +SO4 2- + Simple organic matter (organic fertilizer) + Proliferated microorganisms + Heat. Anaerobic fermentation is the process by which microorganisms decompose organic matter under anaerobic conditions. Its main fermentation products are humus and biogas. Its main process can be divided into the following four steps: (1) Hydrolysis stage: Due to their large molecular size, macromolecular organic matter cannot directly pass through the cell wall of anaerobic bacteria. It needs to be decomposed into small molecules by extracellular enzymes outside the microorganism. These small molecules after decomposition can pass through the cell wall and enter the cell for the next step of decomposition.

[0021] (2) Acidification stage: The above-mentioned small molecule organic matter enters the cell and is transformed into simpler compounds and distributed outside the cell. The main product of this stage is volatile fatty acids (VFA), and some alcohols, lactic acid, carbon dioxide, hydrogen, ammonia, hydrogen sulfide and other products are also produced.

[0022] (3) Acetic acid production stage: In this stage, the products of the previous step are further converted into acetic acid, carbonic acid, hydrogen and new cellular substances.

[0023] (4) Methanogenic stage: In this stage, acetic acid, hydrogen, carbonic acid, formic acid and methanol are converted into methane, carbon dioxide and new cellular material.

[0024] Humus obtained from aerobic and anaerobic fermentation is an important active substance that constitutes soil fertility. It can be used directly as organic fertilizer or mixed with active substances such as nitrogen, phosphorus, and potassium to make compound fertilizer.

[0025] The principle of step 4 is as follows: The sludge produced during the physicochemical treatment of municipal wastewater contains a large amount of heavy metals and organic matter, and cannot be directly fermented and utilized like the sludge from primary and secondary sedimentation tanks. The treatment process of this invention involves stabilizing and solidifying this type of sludge. After passing the leaching test, the solidified body is either landfilled or dried and dehydrated before being sent to an incineration system for harmless and volume-reducing treatment. The incineration residue is then stabilized and solidified before being landfilled. Stabilization and solidification are actually two processes: stabilization and solidification. Stabilization uses chemical agents, such as sodium sulfide, to convert free heavy metal ions in the sludge into sulfide precipitates, preventing them from being released into the environment as free metal ions and polluting it. Solidification uses a solidifying agent, such as cement, to solidify the stabilized sludge. The solidified body is then subjected to a leaching test. If the heavy metal ion content of the leachate meets the standards, it is landfilled; if not, it is crushed again and then subjected to stabilization and solidification treatment until the standards are met.

[0026] This invention presents a green and low-carbon municipal sludge classification, collection, and treatment method. It classifies and treats municipal sludge at the source, reducing the volume of sludge containing heavy metals and other harmful substances. Traditional incineration processes generate large amounts of harmful flue gas, which, although treated to meet emission standards, still pose significant environmental risks. Landfilling, due to the high water content of the sludge, easily leads to secondary pollution from leachate. This invention provides a refined classification and treatment process that is gentle, produces virtually no secondary pollution, and is highly environmentally adaptable. Based on engineering experience, the equipment investment for a 50t / d sludge incineration line and drying equipment is approximately 30-40 million RMB, while the 50t / d sludge treatment line of this invention costs approximately 12 million RMB.

[0027] The green and low-carbon municipal sludge classification, collection, and treatment method of this invention only requires stabilizing and solidifying the municipal sludge through physical and chemical treatment before placing it in a landfill, which can significantly reduce landfill volume. The treatment method of this invention operates under mild process conditions, requires no additional energy input, and generates no secondary waste gas. Compared with pyrolysis, it can save a significant amount of natural gas and flue gas treatment agents, reducing waste gas emissions.

[0028] The green and low-carbon municipal sludge classification, collection, and treatment method of the present invention classifies and collects sludge from different sources in sewage treatment plants, and adopts corresponding comprehensive utilization methods according to the sludge composition. This method not only solves the sludge pollution problem but also obtains corresponding products, and greatly reduces the difficulty and cost of sludge treatment. It is estimated that compared with landfill, it saves 80% of land area; compared with pyrolysis, it saves more than 60% of energy and reduces exhaust emissions by more than 80%.

[0029] Currently, municipal sludge is mainly treated by drying, incineration, and landfilling. Due to its complex composition, high treatment costs, and significant environmental pollution and safety hazards, other treatment methods are scarce. The green and low-carbon municipal sludge classification, collection, and treatment method of this invention classifies, treats, and utilizes sludge from the source. It is technically and economically reasonable, low-carbon and environmentally friendly, and highly applicable, representing a future direction for sustainable development.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A green low-carbon municipal sludge classification collection and treatment method, characterized in that, Includes the following steps: Step 1: Collect municipal sludge generated from each treatment section of the wastewater treatment plant according to its composition and source, temporarily store it in a sealed container, and attach a label containing parameters such as the source, composition, and physicochemical properties of the sludge to obtain sludge from the grit chamber, sludge from the primary sedimentation tank and the secondary sedimentation tank, and sludge from the physicochemical treatment tank. Step 2: Screen the sludge in the grit chamber. The material over the screen is treated as construction waste, and the material under the screen is filtered. The filter cake is sent to the brick-making machine to make bricks or used as backfill soil, and the filtrate is sent to the sewage treatment unit for treatment. Step 3: Mix the sludge from the primary sedimentation tank and the secondary sedimentation tank, condition and dewater it, and then send it into the fermentation system for anaerobic or aerobic fermentation to obtain fermented cooked material. Then, the fermented cooked material can be used as organic fertilizer or mixed with different nutrients to granulate and produce compound fertilizer products. Step 4: After pre-treating the sludge from the physicochemical treatment pond, it is either landfilled or incinerated.

2. The green low-carbon municipal sludge classified collection and treatment method according to claim 1, characterized in that, In step 3, the conditioning involves slowly adding sawdust or crushed straw to the sludge and mixing it at high speed to control the moisture content of the mixed sludge to within 60%.

3. The green low-carbon municipal sludge classified collection and treatment method according to claim 1, characterized in that, In step 3, the fermentation system adopts mesophilic anaerobic fermentation at 42~45℃ or forced ventilation fermentation by a fan.

4. The green low-carbon municipal sludge classified collection and treatment method according to claim 1, characterized in that, In step 3, the nutrients added to the compound fertilizer are at least one of nitrogen, phosphorus, and potassium.

5. The green low-carbon municipal sludge classified collection and treatment method according to claim 1, characterized in that, In step 3, the aerobic fermentation time is 10-20 days.

6. The green low-carbon municipal sludge classified collection and treatment method according to claim 1, characterized in that, In step 4, the pretreatment method used for landfill disposal is stabilization and solidification.

7. The green and low-carbon municipal sludge classification, collection, and treatment method according to claim 1, characterized in that, In step 4, the pretreatment method for sending the waste into the incineration system is drying.

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