Municipal sludge micro-nano ozone pretreatment dehydration reduction method

Abstract

The invention discloses a micro-nano ozone pretreatment, dehydration and reduction method for municipal sludge. The micro-nano ozone pretreatment, dehydration and reduction method for municipal sludge comprises the following steps: S1, preparing high-purity ozone gas; s2, preparing ozone micro-nano bubbles from the obtained high-purity ozone gas; s3, dispersing the ozone micro-nano bubbles into the sludge to obtain wall-broken sludge; and S4, dehydrating the wall-broken sludge to obtain dehydrated sludge. Compared with the prior art, the micro-nano ozone pretreatment dehydration reduction method for the municipal sludge has an effective dehydration reduction effect on the sludge, and has economic and environment-friendly effects at the same time.

Description

Technical Field

[0001] This invention relates to the field of urban sewage sludge treatment and dewatering, and particularly to a method for dewatering and reducing municipal sewage sludge through micro-nano ozone pretreatment. Background Technology

[0002] Urban wastewater treatment plants generate large quantities of sludge, with a moisture content of approximately 80% (by weight). This high moisture content results in bulky sludge and poses significant disposal challenges. Traditional mechanical dewatering (centrifuges, belt filter presses, etc.) typically produces a filter cake with about 20% dry matter (≈80% moisture), which still requires further drying or stabilization for safe disposal. Furthermore, sludge with a moisture content of ~80% exhibits poor stability, high transport volume, and contains recalcitrant organic matter, pathogens, and other contaminants. Drying sludge to <50% moisture (i.e., >50% solids) can significantly reduce its volume and weight, making it easier to handle and facilitating processes such as incineration or land application. However, achieving this level of dryness usually requires energy-intensive thermal drying or complex chemical conditioning, increasing treatment costs. Traditional sludge reduction and stabilization methods have limitations. For example, anaerobic digestion is widely used to stabilize sludge and reduce its mass through biodegradation, but it is slow (retention >30 days) and still leaves a significant amount of water in the digested sludge. Therefore, existing research has developed mechanical and chemical pretreatment methods to accelerate sludge decomposition: for example, using ultrasound, hot water hydrolysis, acid or alkaline hydrolysis, and chemical oxidants to destroy microbial cells to release bound water and improve dewatering. However, existing technologies have drawbacks such as high energy consumption and susceptibility to corrosion, and there is an urgent need for innovative technologies to effectively break down sludge structure and release water in a short process.

[0003] Ozone has been incorporated into sludge treatment in existing technologies, but each method has its limitations. A 2010 Chinese patent (CN101708937A) focuses on ozone pretreatment to accelerate anaerobic digestion; ozone is primarily used to improve digestibility rather than directly maximizing dewatering. The digested sludge still requires conventional dewatering. Another recent method (CN109574446A) combines ozone with chemical modifiers: first, ozone is used to moderately break down the sludge, then a coagulant is added to rebuild flocs, and finally, a hydrophobic polyurethane additive is introduced to create a "water release channel" before dewatering. This multi-step chemical approach has achieved significant improvements in dewatering. However, this method relies on added chemicals (coagulants, polymers), increasing process complexity and cost. Other advanced dewatering technologies include adding electrolytes and applying electric fields (such as US Patent 4,655,932) or multi-stage chemical reactions (acids, peroxides, alkalis) to disrupt the sludge structure. For example, an industrial sludge treatment method combining acid / alkali and hydrogen peroxide oxidation can reduce moisture content to ~60%, but still exceeds the target of 50%, and involves hazardous reagents.

[0004] Therefore, how to provide a micro-nano ozone pretreatment method for municipal sludge to dewater and reduce its volume, so as to achieve effective dewatering and volume reduction of sludge under economical and environmentally friendly conditions, is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of the problems existing in the prior art, the technical problem to be solved by the present invention is to provide a method for dewatering and reducing municipal sludge by micro-nano ozone pretreatment, so as to achieve the technical effect of effective dewatering and reducing sludge under economic and environmentally friendly conditions. This is a technical problem that urgently needs to be solved by those skilled in the art.

[0006] To achieve the above objectives, the present invention provides a method for pretreatment, dehydration, and volume reduction of municipal sludge using micro-nano ozone. The method includes: S1, preparing high-purity ozone gas; S2, forming ozone micro-nano bubbles from the obtained high-purity ozone gas; S3, dispersing the ozone micro-nano bubbles into the sludge to obtain cell-wall-broken sludge; and S4, dehydrating the cell-wall-broken sludge to obtain dehydrated sludge.

[0007] In the first aspect, the high-purity ozone gas is prepared by an ozone generator.

[0008] In the first aspect, the high-purity ozone gas obtained is processed into ozone micro-nano bubbles in a micro-nano ozone dispersion device.

[0009] In the first aspect, the micro / nano ozone dispersion device is used to generate ozone micro / nano bubbles using the high-purity ozone gas; the ozone micro / nano bubbles include ozone bubbles ranging from micrometer to nanometer in size.

[0010] In the first aspect, the micro / nano ozone dispersion device includes a micro / nano injector or a micro / nano porous diffuser.

[0011] In the first aspect, the process of dispersing ozone micro-nano bubbles into sludge to obtain cell-wall-broken sludge is carried out in an ozone cell-wall-broken reactor.

[0012] In the first aspect, the ozone cell-breaking reactor is used to increase the contact between the sludge and the ozone micro-nano bubbles, so that the sludge and the ozone micro-nano bubbles are tightly bound together.

[0013] In the first aspect, the ozone cell disrupting reactor includes a piston flow tube reactor or a multi-stage reactor system; the multi-stage reactor system includes several piston flow tube reactors used in series.

[0014] In the first aspect, the dewatering is carried out in an integrated dewatering device; the integrated dewatering device is used for dewatering the cell-wall-breaking sludge.

[0015] In the first aspect, the ozone generator, the micro-nano ozone dispersion device, the ozone cell-breaking reactor, and the integrated dehydration device are all connected to the control system.

[0016] Beneficial effects: This invention discloses a method for dewatering and reducing the volume of municipal sludge through micro-nano ozone pretreatment. It combines ozone treatment with mechanical dewatering using ozone micro-nano bubbles to maximize the removal of water from the sludge, achieving dewatering and volume reduction. By preparing high-purity ozone gas and dispersing it into the sludge as ozone micro-nano bubbles, the contact between the sludge and the ozone micro-nano bubbles is increased, allowing the thickened sludge to bind tightly with the ozone micro-nano bubbles, improving the utilization rate of the ozone gas and making it more economical. The ozone gas releases bound water as free water, leading to the oxidation and disruption of microbial cells and flocculation structures in the sludge. Specifically, the ozone micro-nano bubbles break down cell walls and extracellular polymer networks, releasing bound water as free water. This facilitates the release of free water during subsequent dewatering, improving dewatering capacity and enabling the solid content of the subsequently dewatered sludge to reach 50%, effectively... This process achieves sludge reduction. In obtaining broken-cell sludge, ozone gas is used as the primary decomposition agent, eliminating the need for chemical adjustments to improve dewatering through the addition of iron or polymers. Ozone micro-nano bubbles maximize dewatering efficiency. The ozone micro-nano bubbles create a high interfacial area between the ozone gas and the biomass of the sludge, ensuring the powerful oxidizing effect of ozone gas is evenly distributed throughout the sludge matrix. This allows for more thorough oxidation and cell disruption of microbial cells and flocculation structures, further enhancing the sludge's dewatering capacity. The broken-cell sludge obtained after ozone disruption has its flocculated structure largely broken down into smaller fragments, with most of the interstitial or biologically bound water becoming free water. This results in a higher settling velocity, producing more filtrate during filtration and improving the dewatering rate of the broken-cell sludge. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of a municipal sludge micro-nano ozone pretreatment dewatering and volume reduction method according to the present invention.

[0019] Figure 2 This is a connection diagram of the main devices in a municipal sludge micro-nano ozone pretreatment dewatering and volume reduction method according to the present invention. Detailed Implementation

[0020] The technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments in this specification are within the scope of protection of this invention.

[0021] Example 1 like Figures 1-2 As shown in the figure, this embodiment provides a method for pretreatment, dehydration, and volume reduction of municipal sludge using micro-nano ozone. The method includes: S1, preparing high-purity ozone gas; S2, forming ozone micro-nano bubbles from the obtained high-purity ozone gas; S3, dispersing the ozone micro-nano bubbles into the sludge to obtain cell-wall-broken sludge; and S4, dehydrating the cell-wall-broken sludge to obtain dehydrated sludge.

[0022] This invention discloses a method for dewatering and reducing the volume of municipal sludge through micro-nano ozone pretreatment. It combines ozone treatment with mechanical dewatering using ozone micro-nano bubbles to maximize the removal of water from the sludge, achieving dewatering and volume reduction. By preparing high-purity ozone gas and dispersing it into the sludge as ozone micro-nano bubbles, the contact between the sludge and the ozone micro-nano bubbles is increased, allowing the thickened sludge to bind tightly with the ozone micro-nano bubbles, improving the utilization rate of the ozone gas and making it more economical. The ozone gas releases bound water as free water, leading to the oxidation and disruption of microbial cells and flocculation structures in the sludge. Specifically, the ozone micro-nano bubbles break down cell walls and extracellular polymer networks, releasing bound water as free water. This facilitates the release of free water during subsequent dewatering, improving dewatering capacity and enabling the solid content of the subsequently dewatered sludge to reach 50%, effectively... This process achieves sludge reduction. In obtaining broken-cell sludge, ozone gas is used as the primary decomposition agent, eliminating the need for chemical adjustments to improve dewatering through the addition of iron or polymers. Ozone micro-nano bubbles maximize dewatering efficiency. The ozone micro-nano bubbles create a high interfacial area between the ozone gas and the biomass of the sludge, ensuring the powerful oxidizing effect of ozone gas is evenly distributed throughout the sludge matrix. This allows for more thorough oxidation and cell disruption of microbial cells and flocculation structures, further enhancing the sludge's dewatering capacity. The broken-cell sludge obtained after ozone disruption has its flocculated structure largely broken down into smaller fragments, with most of the interstitial or biologically bound water becoming free water. This results in a higher settling velocity, producing more filtrate during filtration and improving the dewatering rate of the broken-cell sludge.

[0023] In some possible implementations, the high-purity ozone gas is prepared by an ozone generator.

[0024] Specifically, the ozone generator supplies high-purity ozone gas. The ozone generator includes an oxygen-fed ozone generator, which produces ozone at a concentration of 5-10% by weight. The oxygen-fed ozone generator can be a corona discharge type or a plasma type. During the dispersion of ozone gas into the sludge in the form of ozone micro-nano bubbles, it can be pure gas, air-carrying gas, or a mixture of air and oxygen-carrying gas. Ozone is highly reactive; therefore, the ozone generator should be located near the ozone cell disruptor to minimize transport time and ozone decay. The ozone dosage is controlled based on the sludge flow rate and characteristics.

[0025] In some possible implementations, the high-purity ozone gas is used to generate ozone micro-nano bubbles in a micro-nano ozone dispersion device; the micro-nano ozone dispersion device is used to generate ozone micro-nano bubbles through the high-purity ozone gas; the ozone micro-nano bubbles include ozone bubbles ranging from micrometer to nanometer in size; the micro-nano ozone dispersion device includes a micro-nano injector or a micro-nano porous diffuser.

[0026] Specifically, micro-nano injectors include specially designed nozzles or Venturi injectors; Venturi injectors can draw ozone gas into a high-speed sludge circulation flow, breaking the gas into tiny bubbles; for micro-nano porous diffusers. For example, ceramic or metal diffusers with microporous structures in the micrometer or submicrometer range can be placed in a contact tank to emit micro / nanobubbles. Ozone micro / nanobubbles can improve the contact efficiency between ozone gas and sludge. Tiny ozone bubbles have a very high surface area to volume ratio, and if they are nanoscale, they can remain suspended due to Brownian motion. The micro / nanobubbles of ozone increase the mass transfer of ozone gas into the sludge, and even generate local hydroxyl radicals during ozone decomposition, thereby intensifying the oxidation of organic solids. In addition, microbubbles have a longer residence time in the liquid, and larger bubbles can make more thorough contact, effectively improving the utilization rate and oxidation efficiency of ozone dispersed in the sludge. Ozone micro / nanobubbles dissolve rapidly into the sludge water and collide directly with sludge particles and microorganisms, ensuring that ozone reacts where needed and ensuring the effective utilization of ozone. At the same time, the bubbles also generate gentle mixing and turbulence at the microscale, which helps ozone gas penetrate into the flocs and makes the flocs break more thoroughly.

[0027] In some possible implementations, the dispersion of ozone micro-nano bubbles into sludge to obtain cell-wall-broken sludge is carried out in an ozone cell-wall-broken reactor; the ozone cell-wall-broken reactor is used to increase the contact between the sludge and the ozone micro-nano bubbles, so that the sludge and the ozone micro-nano bubbles are tightly bound together; the ozone cell-wall-broken reactor includes a piston flow tube reactor or a multi-stage reactor system; the multi-stage reactor system includes several piston flow tube reactors used in series.

[0028] Specifically, an ozone cell-wall breaking reactor is a reactor where sludge and ozone interact. It can be customized into multi-stage reactor systems for batch or continuous sludge processing. In an ozone cell-wall breaking reactor, for example, when it is a reciprocating flow tube reactor, including pipes or serpentine channels, sludge flows through it while ozone gas is injected at multiple points or continuously along the flow path, ensuring that each sludge particle comes into contact with ozone. When several reciprocating flow tube reactors are used in series, sludge passes through continuous chambers, with ozone injected at each stage. Several reciprocating flow tube reactors in series can be used for staged treatment, such as two stages: the first stage uses a lower ozone dosage to break down the floc structure, and the second stage uses a higher ozone dosage to deeply oxidize the cell contents. Ozone gas attacks the cell walls of microorganisms in sludge and extracellular polymeric substances bound to water in the sludge. When ozone microbubbles diffuse into the sludge, ozone oxidizes organic molecules and disrupts cell membranes, causing leakage of cell fluid and bound water, releasing free water. Simultaneously, ozone breaks down large flocs into smaller particles. Furthermore, ozone converts some organic matter in the sludge into smaller, more biodegradable compounds, and even converts them into carbon dioxide and water in partial oxidation, thereby reducing sludge mass and volume. In an ozone cell-breaking reactor, the ozone dosage and contact time are controlled to break down microbial cell walls and oxidize extracellular biopolymers, but without completely mineralizing the sludge. For example, an effective ozone dosage can be 0.5g~10g per kilogram of total solids. For sludge that is more resistant to oxidation and has good cell wall breaking properties, higher dosages of ozone can be used. The contact time between ozone and sludge can range from a few seconds to a few minutes. Ozone attacks easily accessible areas, and the microbubble effect continuously renews the interface. Shorter contact times between ozone and sludge solids also have an effect. For example, ozone is almost instantly consumed when it comes into contact with sludge solids, but longer contact times or multiple contacts will increase the degree of oxidation. The cell wall-breaking sludge obtained in the ozone cell wall-breaking reactor is a more "loose" slurry before dewatering, making it easier for water to separate from solids, and the dewatering rate can be increased by three times.

[0029] In some possible implementations, the dewatering is carried out in an integrated dewatering device; the integrated dewatering device is used to dewater the cell-wall-broken sludge.

[0030] Specifically, integrated dewatering units encompass any conventional mechanical dewatering system, such as belt filter presses, box filter presses, screw filter presses, centrifuges, and simpler gravity-drained beds for batch processing. These units are used to dewater cell-wound sludge, removing free water before the sludge matrix recombines, thus improving dewatering efficiency. For example, untreated waste sludge may be dewatered to 80% moisture content in a centrifuge, while cell-wound sludge can be dewatered to less than 50% moisture content under similar conditions. Because most of the gel-like, viscous biopolymers that trap water in the cell-wound sludge are destroyed by ozone, the dewatered sludge treated by the integrated dewatering unit has more porosity, allowing for further drying by evaporating remaining water at lower energy levels. The filtrate from the dewatering process of the broken sludge is rich in organic matter released by ozone and can be sent back to the source of the wastewater treatment plant or to the anaerobic digester for further treatment. Simultaneously, multiple ozone cell-breaking reactors and multiple integrated dewatering devices can be used in parallel to handle a large volume of sludge. This invention also includes an ozone gas destroyer and a sludge thickening device. The ozone gas destroyer is used to capture the ozone gas released into the air by this invention and decomposes the ozone gas into oxygen through a catalyst, avoiding any impact on the air. The sludge thickening device is used to pre-treat the sludge before it enters the ozone cell-breaking reactor, ensuring that the sludge entering the reactor has a sufficiently high solids content, for example, 2% to 5%, for effective treatment. This is because ozone oxidation of highly diluted sludge is not cost-effective, and sludge with very low water content may be difficult to pump. Therefore, sludge with a solids content in the range of 2% to 8% is preferred for ozone oxidation, with a solids content in the range of 2% to 5% being better.

[0031] In some possible implementations, the ozone generator, the micro / nano ozone dispersion device, the ozone cell-breaking reactor, and the integrated dehydration device are all connected to the control system.

[0032] Specifically, the control system is used to control the ozone generator to produce ozone gas, and to control the micro-nano ozone dispersion device to convert ozone gas into ozone micro-nano bubbles. It is also used to control the amount of ozone added to the ozone cell-breaking reactor, the ozone residence time, and the mixing of ozone with sludge. Furthermore, it is used to control the integrated dewatering device to dewater the cell-breaking sludge.

[0033] In summary, the municipal sludge micro-nano ozone pretreatment dewatering and volume reduction method of the present invention has the following advantages: 1. The present invention does not improve the dewatering situation through chemical adjustment, such as adding iron or polymers, which has good economic and environmental benefits; instead, it uses ozone gas to be converted into ozone micro-nano bubbles and mixed with sludge, improving the utilization rate of ozone gas, which is more economical. At the same time, the ozone micro-nano bubbles break the cell walls and extracellular polymer networks, and the ozone gas releases the bound water into free water, improving the dewatering capacity and effectively achieving sludge volume reduction treatment; 2. The municipal sludge micro-nano ozone pretreatment dewatering and volume reduction method of the present invention can make sludge treatment run continuously, which has good economic benefits; 3. The present invention does not require a large amount of fuel or energy input to evaporate water. It mainly works at ambient temperature, and the electrical energy is only used for ozone generation and mechanical equipment, which can save energy; 4. The solid content of the dewatered sludge obtained by the present invention can reach 50%, the sludge is relatively stable and has low humidity, which can shorten or eliminate downstream processes such as drying or composting, and at the same time, it is conducive to more effective incineration through energy recovery or use as fuel supplementation, which has economic benefits.

[0034] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A municipal sludge micro-nano ozone pretreatment dewatering reduction method, characterized in that, The municipal sludge micro-nano ozone pretreatment dewatering and reduction method comprises the following steps: S1, preparing high-purity ozone gas; S2, preparing ozone micro-nano bubbles from the high-purity ozone gas; S3, dispersing the ozone micro-nano bubbles into sludge to obtain broken-wall sludge; S4, dewatering the broken-wall sludge to obtain dewatered sludge.

2. The municipal sludge micro-nano ozone pretreatment dewatering and reduction method according to claim 1, characterized in that: The high-purity ozone gas is prepared by an ozone generator.

3. The municipal sludge micro-nano ozone pretreatment dewatering and reduction method according to claim 2, characterized in that: The preparation of ozone micro-nano bubbles from the high-purity ozone gas is performed in a micro-nano ozone dispersion device.

4. The municipal sludge micro-nano ozone pretreatment dewatering and reduction method according to claim 3, characterized in that: The micro-nano ozone dispersion device is used to generate ozone micro-nano bubbles from the high-purity ozone gas; the ozone micro-nano bubbles include micro-sized to nano-sized ozone bubbles.

5. The municipal sludge micro-nano ozone pretreatment dewatering and reduction method according to claim 4, characterized in that: The micro-nano ozone dispersion device includes a micro-nano sprayer or a micro-nano porous diffuser.

6. The municipal sludge micro-nano ozone pretreatment dewatering and reduction method according to claim 5, characterized in that: The dispersion of the ozone micro-nano bubbles into sludge to obtain broken-wall sludge is performed in an ozone broken-wall reactor.

7. A municipal sludge micro-nano ozone pretreatment dewatering and reduction method according to claim 6, characterized in that: The ozone broken-wall reactor is used to increase the contact between the sludge and the ozone micro-nano bubbles, so that the sludge and the ozone micro-nano bubbles are closely combined.

8. A municipal sludge micro-nano ozone pretreatment dewatering and reduction method according to claim 7, characterized in that: The ozone broken-wall reactor includes a plug flow tubular reactor or a multi-stage reactor system; the multi-stage reactor system includes a plurality of plug flow tubular reactors used in series.

9. The municipal sludge micro-nano ozone pretreatment dewatering and reduction method according to claim 8, characterized in that: The dewatering is performed in an integrated dewatering device; the integrated dewatering device is used to dewater the broken-wall sludge.

10. The municipal sludge micro-nano ozone pretreatment dewatering and reduction method according to claim 9, characterized in that: The ozone generator, the micro-nano ozone dispersion device, the ozone broken-wall reactor and the integrated dewatering device are connected with a control system.

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