A circulating multi-process sewage plant odor treatment process

Abstract

This invention discloses a circulating, multi-stage odor treatment process for wastewater treatment plants, specifically relating to the field of chemical and environmental waste gas treatment technology. It includes a waste gas collection system, a pretreatment system, a purification system, and an emission system connected in sequence. The waste gas collection system uses micro-negative pressure suction technology to collect waste gas, which is then treated by a multi-stage coalescing coarse granulator to remove oil, gas, and aerosols. The pretreatment system uses a multi-tube cyclone scrubbing tower combined with alkaline solution addition to remove acidic pollutants and water-soluble substances. The purification system utilizes a three-layer combined biological filter tower with a layered structure to degrade pollutants, supplemented by a security filter to handle conditions exceeding emission standards. The emission system achieves compliant emissions through an induced draft fan and a chimney. This process integrates multiple processes, efficiently treating oil, gas, acidic gases, VOCs, and odorous substances in waste gas. It has advantages such as low operating costs, energy saving, environmental protection, and no secondary pollution, making it suitable for wastewater treatment plant waste gas treatment.

Description

Technical Field

[0001] This invention relates to the field of chemical environmental waste gas treatment technology, and more specifically, to a circulating multi-process odor treatment process for wastewater treatment plants. Background Technology

[0002] With national development and accelerated urbanization, wastewater treatment plants, as a core component of municipal infrastructure and the petrochemical industry, are increasingly facing odor pollution problems. Odors are complex in composition and characterized by low threshold emissions and high toxicity, not only polluting the atmosphere but also threatening the health of nearby residents. In recent years, with the continuous strengthening of national and local environmental protection policies, existing odor control facilities have become unable to meet new environmental requirements.

[0003] The existing odor treatment processes in wastewater treatment plants have the following core pain points:

[0004] Traditional coalescing degreasing relies solely on physical interception, which cannot handle viscous oil mist and trace amounts of organic oil, easily leading to clogging of subsequent equipment;

[0005] Chemical washing relies on a single vortex / spray, resulting in low gas-liquid mass transfer efficiency and incomplete removal of acidic pollutants.

[0006] Biofilters have a weak ability to degrade recalcitrant VOCs such as benzene series compounds, and the activity of microorganisms is easily affected by fluctuations in operating conditions.

[0007] Security filters use conventional filter media and regeneration methods, resulting in low adsorption capacity, short lifespan, and limited emergency response capabilities.

[0008] 5) The entire process lacks intelligent collaborative control, resulting in high energy and reagent consumption.

[0009] Furthermore, the existing technology CN212017359U discloses a complete set of equipment for treating odorous gases in a biodiesel production workshop, which only achieves basic physical-chemical-biological combined use and does not solve the above-mentioned pain points.

[0010] Conventional applications of coarse-grained agglomeration (such as those in Lu Yuyun's literature) involve only physical separation and lack catalytic function; conventional security filters lack efficient adsorption and regeneration designs.

[0011] Therefore, a circulating multi-stage odor treatment process for wastewater treatment plants is proposed. Summary of the Invention

[0012] In order to overcome the above-mentioned defects of the prior art, the present invention provides a circulating multi-stage odor treatment process for sewage treatment plants to solve the problems mentioned in the background art.

[0013] To achieve the above objectives, the present invention provides the following technical solution: a circulating multi-process odor treatment process for wastewater treatment plants, comprising an intelligent negative pressure exhaust gas collection system, a catalytic coalescence pretreatment system, a purification system, and a MOFs regeneration and emission system connected in sequence, wherein each system is linked together through a PLC intelligent control system;

[0014] The intelligent negative pressure exhaust gas collection system 1 is equipped with a multi-channel H2S / VOCs online monitoring instrument and branch pipe electric regulating valves to dynamically adjust the negative pressure of the branch pipes according to the odor concentration in the sewage tank.

[0015] The negative pressure in the high-concentration pool is maintained at -80 to -100 Pa, the negative pressure in the medium-concentration pool is maintained at -60 to -80 Pa, and the negative pressure in the low-concentration pool is maintained at -50 to -60 Pa.

[0016] The catalytic coalescence pretreatment system includes a multi-stage coalescence coarsener, an ultrasonically enhanced multi-tube cyclone scrubbing tower, a cyclone circulation pump, and an intelligent alkali dosing unit. The inlet and outlet of the cyclone circulation pump are connected to the bottom and top of the ultrasonically enhanced multi-tube cyclone scrubbing tower via pipelines, respectively. The alkali tank is connected to the ultrasonically enhanced multi-tube cyclone scrubbing tower via an alkali metering pump. The multi-stage coalescence coarsener is filled with nano-SiO2 / TiO2 oleophilic and hydrophobic-catalytic composite coating packing. The packing pore size is distributed in a gradient of 50-80μm, 80-120μm, and 120-150μm. It is equipped with an oil mist concentration sensor to link the 1-3 stages of coalescence switching. The ultrasonically enhanced multi-tube cyclone scrubbing tower is equipped with a 20-40kHz high-frequency ultrasonic generator.

[0017] The purification system includes a three-layer combined biofilter tower, a circulating water tank, an intelligent biological circulating water pump, a demister, and a MOFs regeneration security filter. The three-layer combined biofilter tower includes a lower biological trickling filter layer, a middle biofilm layer, and an upper biological filter layer. The MOFs regeneration security filter uses composite gradient filter media, consisting of a mesoporous MOFs layer, an activated carbon fiber layer, and a nano-TiO2 / modified molecular sieve layer, and is regenerated using low-temperature plasma and hot nitrogen gas.

[0018] The MOFs regeneration emission system includes an induced draft fan, a chimney, and an intelligent switching device that automatically switches between direct discharge and security filtration paths based on VOCs / H2S concentrations.

[0019] Preferably, the first section of the multi-stage coalescing coarsener, i.e. the pipeline at the top of the pool, is equipped with 0.3-0.5MPa high-pressure water mist flushing, and the second section, i.e. the pipeline before the treatment facility, is equipped with 50-60℃ hot air purging.

[0020] Preferably, the intelligent alkali solution dosing unit includes an alkali solution tank and two variable frequency alkali solution metering pumps, which dynamically adjust the dosage of 10%-20% NaOH solution according to online pH monitoring data to maintain the pH of the circulating washing solution at 8.0-9.0.

[0021] Preferably, the lower layer of the three-layer combined biological filter tower is filled with polyurethane sponge packing and inoculated with Pseudomonas spp., the upper layer is filled with a mixture of humus and volcanic rock packing and inoculated with Actinomycetes spp., and a microbial nutrient agent with N:P=10:1 is added to the circulating water tank, wherein the volume ratio of humus to volcanic rock in the mixture of humus and volcanic rock packing is 1:1.

[0022] Preferably, the mesoporous MOFs layer of the MOFs co-regenerated security filter is UiO-66-NH2 with a thickness of 5-7cm. During regeneration, it is treated with 100-150W low-temperature plasma and 60-80℃ hot nitrogen gas in a synergistic manner, and the regeneration time is 2-3h.

[0023] The technical effects and advantages of this invention are as follows:

[0024] The exhaust gas collection system uses micro-negative pressure suction to ensure effective collection of odorous gases from the sewage treatment plant, and prevents large-scale volatilization of oil and gas in the pool.

[0025] By properly configuring coalescing oil separators on the collection ducts, oil and aerosols can be effectively removed, reducing the load on subsequent treatment equipment and improving the overall efficiency and economy of the waste gas treatment system.

[0026] Multi-tube cyclone pretreatment removes water-soluble pollutants such as NH3 and H2S from waste gas through water spraying; at the same time, water mist spraying also has a cooling effect, preventing sudden high-temperature waste gas from entering the three-layer combined biological filter tower, affecting the growth of microorganisms, and ensuring the normal operation of the biochemical system.

[0027] This process uses physical and biological methods to treat waste gas from wastewater treatment plants, achieving efficient multi-stage purification, low operating costs, energy saving, environmental protection, and no secondary pollution. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the process of the present invention.

[0029] The attached diagram is labeled as follows: 1. Intelligent negative pressure exhaust gas collection system; 2. Catalytic coalescence pretreatment system; 3. Purification system; 4. MOFs regeneration and emission system; 201. Multi-stage coalescence coarsener; 202. Ultrasonic enhanced multi-tube cyclone scrubber; 203. Cyclone circulation pump; 204. Alkali tank; 205. Alkali metering pump; 301. Three-layer combined biological filter tower; 302. Circulating water tank; 303. Intelligent biological circulating water pump; 304. Demister; 305. Security filter; 401. Exhaust fan; 402. Chimney. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0031] Example 1

[0032] As attached Figure 1 The odor treatment process of a circulating multi-process wastewater treatment plant shown includes an intelligent negative pressure exhaust gas collection system 1, a catalytic coalescence pretreatment system 2, a purification system 3, and a MOFs regeneration and emission system 4 connected in sequence. Each system is linked together through a PLC intelligent control system.

[0033] The intelligent negative pressure exhaust gas collection system 1 is equipped with a multi-channel H2S / VOCs online monitoring instrument and branch pipe electric regulating valves to dynamically adjust the negative pressure of the branch pipes according to the odor concentration in the sewage tank.

[0034] The negative pressure in the high-concentration pool is maintained at -80 to -100 Pa, the negative pressure in the medium-concentration pool is maintained at -60 to -80 Pa, and the negative pressure in the low-concentration pool is maintained at -50 to -60 Pa.

[0035] The catalytic coalescence pretreatment system 2 includes a multi-stage coalescence coarsener 201, an ultrasonically enhanced multi-tube cyclone scrubbing tower 202, a cyclone circulation pump 203, and an intelligent alkali dosing unit. The inlet and outlet of the cyclone circulation pump 203 are connected to the bottom and top of the ultrasonically enhanced multi-tube cyclone scrubbing tower 202 respectively through pipelines. The alkali tank 204 is connected to the ultrasonically enhanced multi-tube cyclone scrubbing tower 202 through an alkali metering pump 205. The multi-stage coalescence coarsener 201 is filled with nano-SiO2 / TiO2 oleophilic and hydrophobic-catalytic composite coating packing. The pore size of the packing is distributed in a gradient of 50-80μm, 80-120μm, and 120-150μm. It is equipped with an oil mist concentration sensor to link the 1-3 stages of coalescence switching. The ultrasonically enhanced multi-tube cyclone scrubbing tower 202 is equipped with a 20-40kHz high-frequency ultrasonic generator.

[0036] The purification system 3 includes a three-layer combined biofilter tower 301, a circulating water tank 302, an intelligent biological circulating water pump 303, a demister 304, and a MOFs regeneration security filter 305. The three-layer combined biofilter tower 301 includes a lower biological trickling filter layer, a middle biofilm layer, and an upper biological filter layer. The MOFs regeneration security filter 305 uses composite gradient filter media, consisting of a mesoporous MOFs layer, an activated carbon fiber layer, and a nano-TiO2 / modified molecular sieve layer, and is regenerated by low-temperature plasma and hot nitrogen.

[0037] The MOFs regeneration emission system 4 includes an induced draft fan 401, a chimney 402, and a cross-line intelligent switching device that automatically switches between direct discharge and security filtration paths based on VOCs / H2S concentrations.

[0038] In practice, by configuring a multi-channel H2S / VOCs online monitoring instrument and a branch pipe electric regulating valve, the odor concentration in the sewage tank is adjusted according to the following: high concentration: H2S > 50 mg / m³ 3 Or VOCs > 200 mg / m³ 3 Medium concentration: H2S 20-50 mg / m³ 3 Or VOCs 100-200mg / m³ 3 Low concentration: H2S < 20 mg / m³ 3 Or VOCs < 100 mg / m³ 3 It dynamically matches different negative pressure values ​​(-80 to -100Pa, -60 to -80Pa, -50 to -60Pa), and precisely couples concentration and negative pressure to avoid the problem of incomplete collection of high concentration or energy waste of low concentration caused by a single negative pressure. This improves the odor collection rate of high concentration tank and reduces energy consumption of low concentration tank.

[0039] The multi-stage coalescing coarsener 201 uses a nano-SiO2 / TiO2 oleophilic-hydrophobic-catalytic composite coating packing with a coating thickness of 50-100nm. It physically intercepts oil and gas through its oleophilic and hydrophobic properties, and initially degrades 10%-15% of organic oil through TiO2 photocatalysis. The packing is distributed in gradients of 50-80μm, 80-120μm, and 120-150μm, and is linked to the 1-3 stages of coalescing switching with the oil mist concentration sensor to achieve precise interception of small particles and efficient capture of large particles. The ultrasonically enhanced multi-tube cyclone scrubbing tower 202 uses 20-40kHz high-frequency ultrasound to destroy the gas-liquid interfacial tension, enhance the mass transfer efficiency of acidic pollutants (H2S, SO2) and scrubbing liquid, and make up for the deficiency of insufficient gas-liquid contact in traditional cyclone scrubbing. In this way, the oil and gas removal rate and the acidic pollutant removal rate are improved, and the initial degradation of organic oil reduces the load on subsequent biological treatment.

[0040] The three-layer combined biofilter 301 uses a lower biological trickling filter layer (polyurethane sponge packing and Pseudomonas spp.) to degrade water-soluble pollutants (such as NH3), a middle biofilm layer to biodegrade recalcitrant VOCs such as benzene series compounds, and an upper biological filter layer (humus volcanic rock packing and Actinomycetes spp.) to treat olefin pollutants. The MOFs regenerable security filter 305 uses mesoporous UiO-66-NH2 as its core filter media, utilizing its high specific surface area (>1000m²). 2 It has a specific pore size structure (0.5-1.2nm) and can efficiently adsorb residual VOCs. The adsorption capacity can be restored by low temperature plasma and hot nitrogen regeneration.

[0041] The cross-line intelligent switching device is linked with the VOCs / H2S online monitoring instrument, automatically selecting the emission path based on the concentration of purified gas, i.e., under normal operating conditions, VOCs ≤ 40 mg / m³. 3 H2S ≤ 5 mg / m³ 3时 Direct discharge, VOCs exceeding the standard in operating conditions > 40mg / m³ 3 Or H2S > 5 mg / m³ 3 It switches to the MOFs security filtering path in a timely manner, forming a dual guarantee of routine processing and emergency backup.

[0042] The PLC intelligent control system collects key parameters of each system in real time, including negative pressure, oil mist concentration, pH value, and VOCs concentration. Through preset algorithms, it synchronously adjusts the negative pressure of the collection system, the number of coalescing sections, the ultrasonic power of the scrubbing tower, the spraying frequency of the biological filter tower, and the discharge path, realizing unattended operation and adaptive adjustment throughout the entire process. This enhances the system's resistance to shock loads and enables it to cope with fluctuations in odor concentration in wastewater treatment plants, such as sudden increases in VOCs concentration caused by sudden changes in influent load.

[0043] The first stage of the multi-stage coalescing coarsener 201, namely the pipeline at the top of the pool, is equipped with 0.3-0.5MPa high-pressure water mist flushing, and the second stage, namely the pipeline before the treatment facility, is equipped with 50-60℃ hot air purging.

[0044] In practical implementation, the multi-stage coalescing coarsener 201 is equipped with two targeted cleaning devices. The first stage (top pipe) is equipped with 0.3-0.5MPa high-pressure water mist flushing, which uses high-pressure water flow to remove sticky oil stains adhering to the surface of the packing material, avoiding pore blockage caused by oil stain accumulation. The second stage (pipe before the treatment facility) is equipped with 50-60℃ hot air purging, which uses the softening effect of hot air on the oil film and the turbulence of airflow to clean the tiny oil droplets remaining deep in the packing material, ensuring unobstructed coalescence channels. In this way, the combined cleaning of pressurized water mist and hot air extends the packing material blockage cycle, reduces the frequency of packing material replacement, and lowers operation and maintenance costs.

[0045] Furthermore, by controlling the flow rates of the branch pipes and main pipes (12-15 m / s for branch pipes and 18-22 m / s for main pipes) and the network pressure, and by fine-tuning the opening of the terminal valves, the micro-negative pressure in the wastewater tank is stabilized in the range of -50 Pa to -100 Pa. This ensures that odorous gases are effectively extracted and prevented from escaping, while also preventing excessive negative pressure from causing a large amount of oil and gas to evaporate in the tank, thus reducing the subsequent treatment load. This keeps the network pressure fluctuation range within ±5 Pa, avoiding the odor escape problem caused by sudden pressure changes in traditional negative pressure systems, and ensuring that the odor gas collection rate is stabilized at over 98%.

[0046] The intelligent alkali solution dosing unit includes an alkali solution tank 204 and two variable frequency alkali solution metering pumps 205. It dynamically adjusts the dosage of 10%-20% NaOH solution based on online pH monitoring data to maintain the pH of the circulating washing solution at 8.0-9.0.

[0047] In practice, the alkali solution dosing unit consists of an alkali solution tank 204 and two variable frequency alkali solution metering pumps 205. The pH value of the circulating washing liquid is collected in real time by an online pH monitor. When the pH is < 8.0, the variable frequency pump automatically increases the amount of alkali solution, i.e., 10%-20% NaOH solution. When the pH is > 9.0, the dosage is reduced to achieve on-demand dosing. This avoids the waste of excessive alkali solution or incomplete removal of acidic pollutants caused by traditional fixed dosing, thereby reducing the consumption of NaOH solution and avoiding secondary pollution caused by excessive alkali solution. At the same time, it also avoids the washing liquid pH being too high and affecting subsequent biological treatment.

[0048] The first coalescing facility is vertically installed on the exhaust gas extraction pipe at the top of the pool. It uses packing material to physically intercept large-diameter oil and gas particles (>120μm). The condensed oil (glue) droplets fall freely to the pool surface by gravity, reducing the amount of oil entering the main pipeline. The second coalescing facility is installed in the pipeline before the treatment facility. It uses gradient pore size packing material to capture small and medium-diameter oil and gas particles (50-120μm). The collected condensed oil droplets are discharged into the wastewater pool through the bottom drain pipe, achieving graded interception and source recovery, thereby avoiding the inactivation of microorganisms caused by oil adhering to the surface of the biofilter packing material.

[0049] The lower layer of the three-layer combined biological filter tower 301 is filled with polyurethane sponge packing and inoculated with Pseudomonas spp., and the upper layer is filled with a mixture of humus and volcanic rock packing and inoculated with Actinomycetes spp. The circulating water tank 302 is filled with microbial nutrients with an N:P ratio of 10:1. The volume ratio of humus to volcanic rock in the mixture of humus and volcanic rock packing is 1:1.

[0050] In practice, the lower bio-trickling filter layer is filled with polyurethane sponge packing (porosity 85%-90%) and inoculated with Pseudomonas spp. (functional bacteria that efficiently degrade H2S). A humid environment is maintained through continuous spraying to ensure microbial activity. The biofilm in the middle biofilm layer can degrade benzene compounds that are difficult to degrade. The upper biofilter layer is filled with a mixture of humus and volcanic rock packing (volume ratio 1:1) and inoculated with Actinomycetes spp. (degrades olefin VOCs). Intermittent spraying is controlled by a gas humidity detector (stopping when humidity is 60%-70% and starting when humidity is <60%) to avoid anaerobic problems caused by continuous spraying. Microbial nutrients with an N:P ratio of 10:1 are added to the circulating water tank 302 to supplement the nitrogen and phosphorus required for microbial metabolism and maintain the stability of the microbial community.

[0051] The multi-tube cyclone scrubbing tower 202 is a honeycomb tube packed tower. After the exhaust gas enters from the bottom of the tower, it forms multiple swirls in the packing layer, which form swirl shear and reverse contact with the water film sprayed in the opposite direction at the top, increasing the gas-liquid contact area. The cyclone circulation pump 203 realizes the recycling of the scrubbing liquid, and the alkali metering pump 205 dynamically adds alkali to adjust the pH and enhance the absorption of acidic pollutants.

[0052] The mesoporous MOFs layer of the MOFs co-regenerated security filter 305 is UiO-66-NH2 with a thickness of 5-7cm. During regeneration, it is treated with 100-150W low-temperature plasma and 60-80℃ hot nitrogen gas in a synergistic manner, and the regeneration time is 2-3h.

[0053] In practical implementation, the mesoporous MOFs layer of the MOFs regenerated security filter 305 uses UiO-66-NH2 material (5-7cm thick), whose Zr-O cluster structure and amino functional groups have a strong adsorption capacity for VOCs (such as benzene and toluene). During regeneration, 100-150W low-temperature plasma is used to decompose the adsorbed organic pollutants (CO2 and H2O), and 60-80℃ hot nitrogen is used to purge the degradation products to restore the pore channels, achieving in-situ regeneration without the need to replace the filter media. The middle activated carbon fiber layer further adsorbs residual VOCs, and the lower nano-TiO2 / modified molecular sieve layer catalytically oxidizes the remaining H2S, i.e., converts it into S and H2O, forming a dual deep treatment of adsorption and catalysis.

[0054] The three-layer combined biological filter tower 301 is equipped with a demister 304 at the top, which intercepts water mist through baffles to prevent water mist from carrying biofilm fragments into subsequent pipelines, causing pipeline corrosion or filter media blockage.

[0055] The specific principle of this embodiment is as follows:

[0056] The odor concentration of each sewage tank is collected in real time by a multi-channel H2S / VOCs online monitoring instrument and the data is transmitted to the PLC control system.

[0057] Based on the concentration classification results, the PLC controls the opening of the branch pipe electric regulating valve to maintain the negative pressure of the high concentration tank at -80 to -100 Pa, the medium concentration tank at -60 to -80 Pa, and the low concentration tank at -50 to -60 Pa. At the same time, it adjusts the main pipe pressure balancing valve to compensate for pipeline resistance loss and ensure that the negative pressure of the entire system is stable within ±5 Pa.

[0058] The waste gas enters the first multi-stage coalescing coarsener 201 through the top pipe of the pool, which traps large-diameter oil and gas particles (>120μm), and the condensed oil droplets drip back into the water pool; the remaining waste gas enters the second coalescer (the pipe before the treatment facility), which captures medium and small-diameter oil and gas particles (50-120μm), and the condensed oil droplets are discharged into the sewage pool through the drain pipe; a cleaning procedure is initiated every 30 days: the first stage is flushed with 0.3-0.5MPa high-pressure water mist for 10 minutes, and the second stage is purged with 50-60℃ hot air for 15 minutes to prevent the packing material from clogging;

[0059] After oil removal, the exhaust gas enters the ultrasonic-enhanced multi-tube cyclone scrubbing tower 202, the 20-40kHz high-frequency ultrasonic generator is turned on, and the cyclone circulation pump 203 is started at the same time, so that the scrubbing liquid is sprayed counterclockwise from the top of the tower, forming a composite mass transfer environment of cyclone, water film and ultrasound.

[0060] The pH online monitoring instrument collects the pH value of the washing solution in real time. The PLC controls two variable frequency alkaline metering pumps 205: when pH < 8.0, the dosage of 10%-20% NaOH solution is increased to 0.5-1.0 L / h; when pH > 9.0, the dosage is reduced to 0.1-0.3 L / h to maintain the pH stable at 8.0-9.0.

[0061] After pretreatment, the H2S removal rate in the exhaust gas reached 99%, and the residual oil and gas content was <5mg / m³. 3 It then enters the subsequent purification system;

[0062] The pretreated waste gas enters from the bottom of the three-layer combined biological filter tower 301:

[0063] Lower biological trickling filter layer: Start the intelligent biological circulating water pump 303 for continuous spraying, with a spray volume of 1-2m³. 3 / h, Pseudomonas spp. degrades NH3 in waste gas;

[0064] Middle biofilm layer: biofilm oxidative decomposition of benzene series compounds and intermediate products;

[0065] Upper biofilter layer: Intermittent spraying controlled by a gas humidity detector, spraying for 3 minutes when humidity is <60%, with an interval of 30 minutes, where actinomycetes degrade olefin VOCs;

[0066] The circulating water tank 302 is replenished with microbial nutrients with an N:P ratio of 10:1 every 7 days, at a dosage of 50-100 mL, to maintain the activity of the microbial community.

[0067] The purified exhaust gas passes through the tower top demister 304 to remove water mist, and then enters the front end of the MOFs regeneration security filter 305.

[0068] VOCs / H2S online monitoring instrument detects the concentration of exhaust gas after demisting:

[0069] Under normal operating conditions (VOCs≤40mg / m³) 3 H2S ≤ 5 mg / m³ 3 PLC-controlled intelligent switching device for cross-line switching: exhaust gas directly enters the induced draft fan 401 and is discharged through the chimney 402;

[0070] Excessive operating conditions (VOCs > 40 mg / m³) 3 Or H2S > 5 mg / m³ 3 ): Switch to MOFs security filtration path, the exhaust gas sequentially passes through the UiO-66-NH2 layer to adsorb VOCs, the activated carbon fiber layer for secondary adsorption, and the nano TiO2 / modified molecular sieve layer for catalytic oxidation of H2S, and then enters the exhaust fan 401 for discharge.

[0071] When the pressure difference of the MOF filter media exceeds 5 kPa, indicating adsorption saturation, the PLC automatically starts the regeneration program: 100-150W low-temperature plasma operation for 1 hour, simultaneously introducing 60-80℃ hot nitrogen gas at a flow rate of 5-10 m³ / h. 3 Purging for 2 hours ( / h) allows the adsorption capacity of the regenerated filter media to recover.

[0072] Example 2

[0073] As attached Figure 1 The odor treatment process of a circulating multi-stage wastewater treatment plant shown includes an intelligent negative pressure exhaust gas collection system 1, a catalytic coalescence pretreatment system 2, a purification system 3, and a MOFs regeneration and emission system 4 connected in sequence.

[0074] The catalytic coalescence pretreatment system 2 includes a multi-stage coalescing coarsener 201, an ultrasonically enhanced multi-tube cyclone scrubbing tower 202, a cyclone circulation pump 203, an alkali tank 204, and an alkali metering pump 205. The inlet and outlet of the cyclone circulation pump 203 are connected to the bottom and top of the ultrasonically enhanced multi-tube cyclone scrubbing tower 202 respectively through pipelines. The alkali tank 204 is connected to the ultrasonically enhanced multi-tube cyclone scrubbing tower 202 through the alkali metering pump 205. The multi-stage coalescing coarsener 201 is equipped with coalescing packing with a nano-scale oleophilic and hydrophobic coating. The coalescing packing is used for the graded capture of oil and gas and aerosols of different particle sizes through a specific pore size gradient distribution.

[0075] The purification system 3 includes a three-layer combined biological filter tower 301, a circulating water tank 302, an intelligent biological circulating water pump 303, a demister 304, and a security filter 305. The security filter 305 uses composite gradient filter media, which consists of an upper activated carbon fiber layer, a middle modified molecular sieve layer, and a lower nano metal oxide catalytic layer. The filter media is periodically activated in situ through an automatic regeneration device.

[0076] MOFs regenerated emission system 4 includes an induced draft fan 401 and a chimney 402;

[0077] The ultrasonic-enhanced multi-tube cyclone scrubbing tower 202 is connected to the three-layer combined biological filter tower 301, the demister 304, the security filter 305, and the induced draft fan 401. The circulating water tank 302 is connected to the three-layer combined biological filter tower 301 through the intelligent biological circulating water pump 303. The induced draft fan 401 is connected to the chimney 402 through the pipe.

[0078] The intelligent negative pressure exhaust gas collection system 1 is connected to the ultrasonic enhanced multi-tube cyclone scrubbing tower 202 through the multi-stage coalescing coarsener 201;

[0079] The catalytic coalescence pretreatment system 2 is connected to the security filter 305 of the purification system 3 through a three-layer combined biofilter 301 and a demister 304;

[0080] The induced draft fan 401 of the MOFs regeneration emission system 4 is connected to the security filter 305 and the chimney 402 pipe respectively.

[0081] In practical implementation, the intelligent negative pressure exhaust gas collection system 1 absorbs and collects exhaust gas from the wastewater tank through micro-negative pressure, and removes oil and gas and aerosols through a multi-stage coalescing coarsener 201; the catalytic coalescing pretreatment system 2 utilizes the swirling, water film and spraying effects of the ultrasonic-enhanced multi-tube cyclone scrubbing tower 202, combined with the addition of alkaline solution to remove acidic pollutants and water-soluble substances; the purification system 3 removes VOCs and other recalcitrant pollutants through the biodegradation effect of the three-layer combined biological filter tower 301, and then further treats them through the demister 304 and the security filter 305; the MOFs regeneration emission system 4 discharges the qualified exhaust gas from the chimney 402 through the induced draft fan 401; integrating multiple processes of "physical oil removal → chemical washing → biodegradation → emergency filtration", it realizes the full-process treatment of oil, gas, acidic gases, VOCs and malodorous substances in the exhaust gas.

[0082] The intelligent negative pressure exhaust gas collection system 1 adopts micro negative pressure suction technology. By controlling the flow rate of the branch pipe and the main pipe, as well as the pipeline pressure, the system ensures the pressure balance of the intelligent negative pressure exhaust gas collection system 1. By controlling the opening of the terminal valve, the system maintains a micro negative pressure state in the wastewater pool, keeping the micro negative pressure in the wastewater pool between -50Pa and -100Pa, ensuring the effective collection of odorous gases, and preventing a large amount of oil and gas from evaporating in the pool.

[0083] The multi-stage coalescing coarsener 201 uses coalescing packing with a nano-level oleophilic and hydrophobic coating. The packing pore size is distributed in a gradient of 50-100μm. The first coalescing facility is vertically installed on the exhaust gas suction pipe at the top of the pool, and the second facility is installed in the pipe before entering the exhaust gas treatment facility. The collected condensed oil droplets are discharged into the sewage pool through the bottom drain pipe.

[0084] The security filter 305 has a composite gradient filter media inside, consisting of an upper 5-8cm thick activated carbon fiber layer, a middle 10-15cm thick modified molecular sieve layer, and a lower 3-5cm thick nano metal oxide catalytic layer. It is equipped with an automatic regeneration device that can periodically reactivate the filter media in situ.

[0085] Specifically, the nanoscale oleophilic and hydrophobic coating enhances the adsorption capacity for oil, gas, and aerosols, while the pore size gradient distribution of 50-100 μm can specifically capture oil droplets and aerosol particles of different sizes. Small-diameter oil droplets are intercepted when passing through the packing material with smaller pore sizes, while large-diameter oil droplets are captured at the packing material with larger pore sizes, thus improving oil removal efficiency through staged capture.

[0086] The upper activated carbon fiber layer utilizes its abundant porous structure to adsorb VOCs and other organic compounds in the waste gas; the middle modified molecular sieve layer further removes specific pollutants through its selective adsorption performance; the lower nano-metal oxide catalytic layer can catalytically oxidize and decompose residual pollutants, achieving deep purification. The automatic regeneration device can restore the adsorption and catalytic performance of the filter media through heating, purging, and other methods.

[0087] The exhaust gas is first collected by the intelligent negative pressure exhaust gas collection system 1 and then enters the catalytic coalescence pretreatment system 2. The multi-stage coalescence coarsener 201 removes oil and gas and aerosols, and the ultrasonically enhanced multi-tube cyclone scrubber 202, combined with the addition of alkaline solution, removes acidic pollutants and water-soluble substances. Then it enters the purification system 3. The three-layer combined biological filter tower 301 removes pollutants through biodegradation, the demister 304 removes water mist, and the security filter 305 performs deep treatment. Finally, the MOFs regeneration emission system 4 discharges the qualified exhaust gas.

[0088] Compared to traditional coalescence degreasing methods, the multi-stage coalescing coarsener 201 with a nano-level oleophilic and hydrophobic coating and a pore size gradient distribution can remove oil, gas and aerosols more efficiently, reduce the load on subsequent processing equipment, and improve the overall processing efficiency.

[0089] The composite gradient filter media of the security filter 305 combines adsorption and catalytic oxidation, significantly improving the removal rate of pollutants such as VOCs and H2S. Especially when the inlet concentration exceeds the standard, it can ensure that the exhaust gas meets the emission standards, making up for the shortcomings of traditional processes in emergency treatment.

[0090] Furthermore, the automatic regeneration device of the security filter 305 extends the service life of the filter media, reduces the frequency of filter media replacement, and lowers operating costs. Simultaneously, the coordinated operation of all systems reduces energy and chemical consumption while ensuring treatment effectiveness.

[0091] This process can effectively handle wastewater treatment plant exhaust gases of different concentrations and compositions, and has good treatment effects on oil and gas, acidic gases, VOCs and malodorous substances. It is suitable for exhaust gas treatment scenarios in various wastewater treatment plants.

[0092] The multi-stage coalescing coarsener 201 includes two coalescing facilities:

[0093] The first exhaust gas extraction pipe is vertically installed at the top of the pool to intercept oil and gas and aerosols, and the condensed oil and aerosol droplets drip freely onto the pool surface.

[0094] The second pipeline, located before the exhaust gas treatment facility, collects condensed oil droplets which are then discharged into the wastewater tank through a bottom drain pipe.

[0095] In practice, the negative pressure in the wastewater tank is maintained between -50Pa and -100Pa by adjusting the flow rate of the branch pipes and main pipes, as well as the network pressure, and the pressure is dynamically balanced at the end valves; and two-stage coalescence oil removal is utilized.

[0096] The first coalescer is vertically installed on the pipe at the top of the pool to intercept large oil and gas particles, and the condensed oil droplets drip back into the water pool.

[0097] The second coalescer is installed in the pipeline before the treatment facility to further remove small oil and gas particles, and the condensate is discharged into the wastewater tank for treatment.

[0098] This allows for precise micro-negative pressure, ensuring effective collection of odorous gases while preventing excessive evaporation of oil and gas in the pool due to excessive negative pressure. Staged oil removal reduces the oil content in the exhaust gas, lowers the load on subsequent scrubbing towers and biofilters, and extends the service life of the equipment.

[0099] The ultrasonically enhanced multi-tube cyclone scrubbing tower 202 of the catalytic coalescence pretreatment system 2 is a honeycomb tube packed tower, employing a composite process of "multi-tube cyclone + water film + spray scrubbing".

[0100] The exhaust gas enters from the bottom of the tower and forms multiple swirling streams in the packing layer, which fully contact and transfer mass with the water film sprayed counterclockwise from the top.

[0101] The cyclone circulation pump 203 connects the bottom and top of the tower to realize the circulation of the washing liquid;

[0102] The alkali tank 204 adds alkali solution into the tower through the alkali metering pump 205, and dynamically adjusts the pH value of the circulating washing liquid to enhance the removal of acidic pollutants.

[0103] In practice, the exhaust gas enters from the bottom of the tower and forms multiple swirling streams in the honeycomb packing layer, which come into full contact with the water film sprayed in the opposite direction at the top of the tower, removing pollutants through inertial collision, dissolution and mass transfer.

[0104] Circulating washing and alkali addition: The cyclone circulation pump 203 drives the washing liquid to circulate, and the alkali metering pump 205 dynamically adds alkali according to the acid concentration of the waste gas, adjusting the pH value to enhance the absorption of acidic gases such as H2S and SO2.

[0105] This utilizes a composite process of "cyclone + water film + spray" to increase the gas-liquid contact area, improving the washing efficiency by more than 30% compared to traditional spray towers; dynamic pH adjustment increases the removal rate of acidic pollutants to over 90%, while reducing reagent waste.

[0106] The three-layer combined biofilter tower 301 adopts a layered structure of "bio-trickling filter layer + biofilter layer":

[0107] The lower layer is a biological trickling filter layer, which is continuously sprayed by the intelligent biological circulating water pump 303;

[0108] The upper layer is a biological filter layer, which is intermittently sprayed by a gas humidity detector;

[0109] The two layers share a circulating water tank 302, and the exfoliated biological strains can be cross-inoculated to form a biodiversity degradation environment;

[0110] A 304 demister is installed at the top of the tower to reduce water mist from being discharged with the purified gas.

[0111] In practice, the lower biological drip filter layer is continuously sprayed to maintain the activity of microorganisms, which mainly degrade water-soluble pollutants such as NH3; the upper biological filter layer is sprayed intermittently, controlled by a gas humidity detector, to form an alternating aerobic and microaerobic environment, which is suitable for degrading insoluble pollutants such as benzene series compounds; the two layers share a circulating water tank 302, and the shed bacteria are cross-inoculated to form a diverse microbial community similar to a wetland; the tower top demister 304 removes gaseous water mist to avoid subsequent pipeline corrosion.

[0112] This allows for targeted treatment of different pollutants through a stratified process, achieving a benzene series removal rate of over 95%, which is 50% more efficient than a single biological filter. The biodiversity enhancement system's ability to withstand shock loads and adapt to fluctuations in waste gas composition is improved. Intermittent spraying reduces energy consumption, saving 20%-30% of water compared to continuous spraying.

[0113] The purification system 3 is equipped with a dry chemical security filtration process:

[0114] Under normal operating conditions, the exhaust gas is treated by the three-layer combined biological filter tower 301 and then discharged directly through the induced draft fan 401.

[0115] When the intake gas concentration exceeds the standard, the exhaust gas undergoes chemical adsorption filtration through the security filter 305 to ensure that VOCs and H2S are discharged in compliance with standards.

[0116] In practice, after the exhaust gas is treated by the biological filter tower to meet the standards, it is directly discharged through the induced draft fan 401.

[0117] When the intake concentration exceeds the design value, the exhaust gas passes through the dry chemical filter media of the security filter 305, such as activated carbon and alkaline oxides, to adsorb the remaining VOCs and H2S, ensuring compliance with standards.

[0118] By using security filtration as a redundancy guarantee for biological treatment, it can cope with sudden high concentrations of exhaust gas, such as in the event of equipment failure, and avoid the risk of exceeding emission standards; the chemical filter media has a long service life and is only used in emergency situations, reducing daily operating costs.

[0119] A cross-line switching device is installed between the induced draft fan 401 and the chimney 402 of the MOFs regeneration emission system 4, which is used to automatically switch between direct discharge and security filtration paths according to the concentration of purified gas.

[0120] In practice, a cross-line switching device is installed between the induced draft fan 401 and the chimney 402. Through online monitoring instruments, such as VOCs sensors, the concentration of purified gas is judged in real time, and the direct discharge or security filtration path is automatically switched. This enables intelligent switching, reduces manual intervention, improves system response speed, avoids operational errors that may be caused by traditional manual switching, and ensures emission stability.

[0121] Two alkali metering pumps 205 and one alkali tank 204 together form an alkali dosing system, which is used to control the pH value of the circulating washing liquid by adding alkali through the two alkali metering pumps 205.

[0122] In practice, the dosing system, consisting of two alkali metering pumps 205 and an alkali tank 204, automatically starts and stops the pumps based on the online pH monitoring data of the circulating washing liquid to adjust the alkali dosage and maintain the pH value in the high-efficiency absorption range of 7.5-9.0.

[0123] The dual-pump redundancy design improves system reliability, with one pump in use and one on standby. At the same time, two alkali metering pumps 205 can be used in conjunction to improve the accuracy of alkali addition, avoid the decrease in treatment efficiency caused by single pump failure, and ensure that the acid gas removal efficiency is stable at over 92% by precise pH control, while reducing secondary pollution caused by excessive alkali addition.

[0124] The entire process of waste gas treatment is as follows:

[0125] Micro-negative pressure collection → two-stage coalescence coarse oil removal → multi-tube cyclone washing (alkaline solution pH adjustment) → bio-trickling filtration + filtration synergistic degradation → demisting → security filtration (emergency) → emission in compliance with standards.

[0126] Through progressive processing at each stage, a complete technology chain is formed: "coarse separation → fine washing → biodegradation → safety guarantee".

[0127] The comprehensive removal rates for non-methane total hydrocarbons, hydrogen sulfide, and odor concentration are over 90%, 95%, and 90%, respectively, which are superior to traditional single processes, such as activated carbon adsorption, which only achieves a hydrogen sulfide removal rate of 60%-70%.

[0128] In a specific embodiment, the waste gas treatment capacity of a certain wastewater treatment plant is 6000 Nm³. 3 The gas composition is mainly non-methane total hydrocarbons, hydrogen sulfide, and has a high concentration of odor. The exhaust gas in the covered sewage tank first passes through a coalescing coarse particle remover installed vertically on the exhaust gas extraction pipe at the top of the tank to remove oil and aerosols. The condensed oil (gel) droplets drip freely into the tank. Next, it enters a multi-stage coalescing coarse particle remover 201 installed on the main exhaust gas pipe before entering the exhaust gas treatment facility to further remove oil and aerosols. The collected condensed oil droplets are discharged into the sewage tank through the drain pipe at the bottom of the coalescing coarse particle remover and then enter the sewage treatment system for treatment.

[0129] After initial removal of oil and gas, the waste gas enters a multi-tube cyclone pretreatment system. Water spraying removes water-soluble pollutants such as NH3 and H2S. The waste gas enters the processor from the bottom, forming multiple gas swirls in the packing material in the middle section, increasing the gas-water contact surface. Nozzles at the top spray water in a counter-current direction onto the airflow, forming a downward-flowing water film on the packing wall and facilitating mass transfer with the airflow. The combined effect of these mechanisms ensures sufficient contact between the waste gas and water mist / film within the ultrasonic-enhanced multi-tube cyclone scrubber 202, resulting in washing and cooling of the waste gas. The condensed oil, aerosols, and water-soluble pollutants are discharged into the wastewater treatment system with the sprayed water. The pretreated waste gas then enters a three-layer combined biological filter 301. The ultrasonic-enhanced multi-tube cyclone scrubber 202 is connected to an alkali dosing system. When the concentration of acidic gases in the waste gas is high, alkali is added to control the pH of the circulating scrubbing liquid, thereby improving the removal rate of acidic substances.

[0130] The exhaust gas passes through a biological packing layer consisting of a bio-trickling filter layer and a bio-filter layer from bottom to top. The spraying of the upper and lower bio-filter layers is controlled by a gas humidity detector installed at the bottom of the water collector, which signals the opening and closing of the spray water control valves. When the humidity of the exhaust gas is lower than the set value, the spray water control valve of the lower bio-trickling filter layer is closed, and the spray water control valve of the upper bio-filter layer is opened. After continuous operation for a set time or when the humidity exceeds the set value, the spray water control valve of the upper bio-filter layer is closed, and the spray water control valve of the lower bio-trickling filter layer is opened. Different pollutants in the exhaust gas come into contact with the dominant bacteria attached to the biofilm growing on the surface of the porous bio-filter media. Through the metabolic action of microorganisms, the pollutants in the exhaust gas are effectively degraded, especially difficult-to-degrade pollutants such as benzene, toluene, and xylene. Meanwhile, because the spray water from both biological filtration and bio-trickling filtration is collected in a single pool, the sloughed microbial strains from the upper and lower layers can be alternately inoculated, creating a biodiversity in the three-layer combined biological filter tower 301 that differs from any single filter layer. This forms an environment composed of multiple dominant microbial species, similar to the biodiversity of tropical rainforests and constructed wetlands. A demister 304 is installed at the top of the three-layer combined biological filter tower 301 to reduce water mist emissions with the treated gas. An intelligent biological circulating water pump 303 supplies spray water to the three-layer combined biological filter tower 301. The effluent from the bio-trickling filter flows by gravity to the circulating water tank 302 for water intake by the intelligent biological circulating water pump 303, replenishment of the biochemical system, and addition of microbial nutrient agents. Simultaneously, the pH value of the spray water is monitored and adjusted to ensure that microorganisms grow and reproduce in a suitable acidic or alkaline environment.

[0131] To ensure that exhaust gases still meet emission standards even under abnormal production conditions or when inlet gas concentrations exceed design values, a dry chemical filter media security filter 305 is added after the biological treatment process. This filter media removes excess VOCs and H2S. Under normal circumstances, exhaust gases are directly discharged through chimney 402 via induced draft fan 401 after biological treatment. In cases of abnormal production conditions or when inlet gas concentrations exceed design values, the gases bypass the biological treatment process and are treated by the dry chemical filter media security filter 305 before being discharged through chimney 402 via induced draft fan 401.

[0132] After treatment, the total non-methane hydrocarbons in the exhaust gas are ≤60mg / m³. 3 Odor concentration ≤1500, hydrogen sulfide ≤10mg / m³ 3 .

[0133] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A circulating, multi-stage odor treatment process for wastewater treatment plants, characterized in that, It includes an intelligent negative pressure exhaust gas collection system (1), a catalytic coalescence pretreatment system (2), a purification system (3), and a MOFs regeneration and emission system (4) connected in sequence. Each system is linked together through a PLC intelligent control system. The intelligent negative pressure exhaust gas collection system (1) is equipped with a multi-channel H2S / VOCs online monitoring instrument and a branch pipe electric regulating valve to dynamically adjust the negative pressure of the branch pipe according to the odor concentration of the sewage tank: The negative pressure in the high-concentration pool is maintained at -80 to -100 Pa, the negative pressure in the medium-concentration pool is maintained at -60 to -80 Pa, and the negative pressure in the low-concentration pool is maintained at -50 to -60 Pa. The catalytic coalescence pretreatment system (2) includes a multi-stage coalescence coarsener (201), an ultrasonically enhanced multi-tube cyclone scrubbing tower (202), a cyclone circulation pump (203), and an intelligent alkali addition unit. The inlet and outlet of the cyclone circulation pump (203) are connected to the bottom and top of the ultrasonically enhanced multi-tube cyclone scrubbing tower (202) through pipelines, respectively. The intelligent alkali addition unit is connected to the ultrasonically enhanced multi-tube cyclone scrubbing tower (202). The multi-stage coalescence coarsener (201) is filled with nano-SiO2 / TiO2 oleophilic and hydrophobic-catalytic composite coating packing. The packing pore size is distributed in a gradient of 50-80μm, 80-120μm, and 120-150μm. It is equipped with an oil mist concentration sensor to link the 1-3 stage coalescence switching. The ultrasonically enhanced multi-tube cyclone scrubbing tower (202) is equipped with a 20-40kHz high-frequency ultrasonic generator. The purification system (3) includes a three-layer combined biofilter tower (301), a circulating water tank (302), an intelligent biological circulating water pump (303), a demister (304), and a MOFs regeneration security filter (305). The three-layer combined biofilter tower (301) includes a lower biological trickling filter layer, a middle biofilm layer, and an upper biological filter layer. The MOFs regeneration security filter (305) uses composite gradient filter media, consisting of a mesoporous MOFs layer, an activated carbon fiber layer, and a nano-TiO2 / modified molecular sieve layer, and is regenerated by low-temperature plasma and hot nitrogen. The MOFs regeneration emission system (4) includes an induced draft fan (401), a chimney (402), and a cross-line intelligent switching device that automatically switches between direct discharge and security filtration paths based on VOCs / H2S concentration.

2. The odor treatment process for a circulating multi-stage wastewater treatment plant according to claim 1, characterized in that, The first section of the multi-stage coalescing coarsener (201), namely the top pipeline of the pool, is equipped with 0.3-0.5MPa high-pressure water mist flushing, and the second section, namely the pipeline before the treatment facility, is equipped with 50-60℃ hot air purging.

3. The odor treatment process for a circulating multi-stage wastewater treatment plant according to claim 1, characterized in that, The intelligent alkali solution dosing unit includes an alkali solution tank (204) and two variable frequency alkali solution metering pumps (205). It dynamically adjusts the dosage of 10%-20% NaOH solution according to the pH online monitoring data to maintain the pH of the circulating washing liquid at 8.0-9.

0.

4. The odor treatment process for a circulating multi-stage wastewater treatment plant according to claim 1, characterized in that, The lower layer of the three-layer combined biological filter tower (301) is filled with polyurethane sponge packing and inoculated with Pseudomonas spp., and the upper layer is filled with a mixture of humus and volcanic rock packing and inoculated with Actinomycetes spp. The circulating water tank (302) is filled with microbial nutrients with N:P=10:1, wherein the volume ratio of humus to volcanic rock in the mixture of humus and volcanic rock packing is 1:

1.

5. The odor treatment process for a circulating multi-stage wastewater treatment plant according to claim 1, characterized in that, The mesoporous MOFs layer of the MOFs regenerated security filter (305) is UiO-66-NH2 with a thickness of 5-7cm. During regeneration, it is treated with 100-150W low-temperature plasma and 60-80℃ hot nitrogen gas in synergy, and the regeneration time is 2-3h.

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