Kitchen waste anaerobic biogas slurry treatment system based on enhanced pretreatment

Abstract

A kitchen waste anaerobic biogas slurry treatment system based on enhanced pretreatment comprises a pretreatment system, a biochemical treatment system and a sludge dewatering system, and the sludge dewatering system comprises a sludge storage tank and a centrifugal dehydrator which are connected together. The biochemical treatment system is formed by sequentially connecting a first-stage A tank, a first-stage O tank, a second-stage A tank, a second-stage O tank, an external ultrafiltration membrane tank and a water outlet tank, and the external ultrafiltration membrane tank is respectively connected with the first-stage A tank and the sludge storage tank; the pretreatment system is formed by sequentially connecting an adjusting tank, a rotary grate, an air floatation oil separation tank, a membrane grate, an aeration biological adsorption tank, a sedimentation tank and a microfilter, and the air floatation oil separation tank, the membrane grate, the sedimentation tank and the microfilter are respectively connected with the sludge storage tank. The invention can realize efficient removal of suspended matters in biogas slurry and strict control of the particle size of the suspended matters in biochemical treatment inlet water, thereby ensuring the microbial activity of the system, improving the operation stability of the system and ensuring stable and up-to-standard discharge of the outlet water.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to an anaerobic digester system for kitchen waste based on enhanced pretreatment. Background Technology

[0002] Food waste is often partially utilized through wet anaerobic fermentation. However, the biogas slurry formed after solid-liquid separation of the fermentation residue still contains high concentrations of suspended solids, grease, ammonia nitrogen, fibrous substances such as chili seeds, and other contaminants, making direct biological treatment difficult to achieve discharge standards. Food waste anaerobic fermentation biogas slurry requires strict pretreatment before biological treatment. Currently, biogas slurry pretreatment commonly employs methods such as coagulation, flotation, and high-load aeration to remove suspended solids and grease. However, due to the high concentration of colloidal particles and limited removal of fibrous impurities in the biogas slurry, controlling the properties of the biogas slurry entering the subsequent biological treatment stage is difficult, increasing the risk of effluent exceeding standards.

[0003] Chinese patent CN 114133115 A discloses a food waste biogas slurry treatment system, including a pre-coagulation flotation tank, a primary A tank, a primary O tank, a secondary A tank, a secondary O tank, a secondary sedimentation tank, and a post-coagulation flotation tank. This patent only uses coagulation and flotation to remove suspended solids and grease before biochemical treatment. It lacks specific design for addressing suspended solids and fibrous debris in the anaerobic biogas slurry from food waste, resulting in high suspended solids levels after pretreatment and the disadvantage of capsaicin inhibiting microbial growth.

[0004] Chinese patent CN 110092536 A discloses a combined treatment process for anaerobic digestion slurry from food waste, including a pretreatment system, a high-efficiency biological denitrification system, and an MBR treatment system. The pretreatment system uses an equalization tank and a coagulation-flotation tank to remove suspended solids and grease from the slurry; the high-efficiency biological denitrification system uses a high-load aeration tank and an anaerobic ammonia oxidation tank to remove ammonia nitrogen; and the MBR treatment system uses a two-stage AO tank and an internal ultrafiltration membrane tank to further remove pollutants such as COD. While this patent adds a high-load aeration tank to enhance the removal of suspended solids and supplements the anaerobic ammonia oxidation tank to improve nitrogen removal efficiency, the lack of necessary particle size control technology between the various stages poses a risk of abnormal microbial growth.

[0005] In conclusion, it is necessary to further improve the existing anaerobic digestate treatment process for kitchen waste to achieve long-term stable operation of the system. Summary of the Invention

[0006] The purpose of this invention is to propose an anaerobic digester system for kitchen waste based on enhanced pretreatment. This system, through a pretreatment system, a biochemical treatment system, and a sludge dewatering system, can achieve efficient removal of suspended solids from the digester, strictly control the particle size of suspended solids in the biochemical treatment influent, thereby ensuring the activity of microorganisms in the system, improving the stability of system operation, and ensuring that the effluent meets the discharge standards.

[0007] As conceived above, the present invention adopts the following technical solution: an anaerobic digester system for treating kitchen waste based on enhanced pretreatment, comprising a pretreatment system, a biochemical treatment system, and a sludge dewatering system. The sludge dewatering system includes a sludge storage tank and a centrifugal dewatering machine connected together. The biochemical treatment system is composed of a primary A tank, a primary O tank, a secondary A tank, a secondary O tank, an external ultrafiltration membrane tank, and an effluent tank connected in sequence. The external ultrafiltration membrane tank is connected to the primary A tank and the sludge storage tank respectively. The pretreatment system comprises an equalization tank, a rotating bar screen, an air flotation oil separator, a membrane bar screen, an aerated biological adsorption tank, a sedimentation tank, and a microfilter. The equalization tank, rotating bar screen, air flotation oil separator, membrane bar screen, aerated biological adsorption tank, sedimentation tank, and microfilter are connected in sequence. The air flotation oil separator, membrane bar screen, sedimentation tank, and microfilter are connected to the sludge storage tank respectively.

[0008] Preferably, the wastewater generated by the centrifugal dewatering machine is connected to the equalization tank via a pump and pipeline.

[0009] Preferably, the dissolved air flotation tank is used as the oil-water separator.

[0010] Preferably, the aerated biological adsorption tank adopts a rectangular reinforced concrete structure, with a designed retention time of 24 hours, an effective water depth of 8 meters, and an aerator installed inside the tank.

[0011] Preferably, the sedimentation tank is a radial flow sedimentation tank.

[0012] Preferably, the microfilter is a disc microfilter.

[0013] Preferably, the external ultrafiltration membrane is a cross-flow filter ultrafiltration membrane.

[0014] Preferably, a mixer is installed in the primary A tank and the secondary A tank.

[0015] Preferably, jet aerators are installed in the primary O pool and the secondary O pool.

[0016] Preferably, the sludge storage tank and the centrifugal dewatering machine are connected by a screw pump and pipelines.

[0017] The present invention has the following advantages:

[0018] 1. This invention can effectively reduce the amount of impurities entering the system, avoid the adverse effects of impurities on subsequent pumps, pipelines and membranes, prevent pump damage, reduce pipeline wear, reduce membrane puncture damage, and thus improve the stability of system operation.

[0019] 2. This invention combines physical and chemical processes with filtration methods, which complement each other. The physical and chemical processes significantly reduce particulate matter in the water, while the filtration methods strictly control the size of particulate matter entering the next stage. Through strict two-stage control, it ensures that the influent of each stage of treatment meets the process requirements, thus guaranteeing the stable and efficient operation of each stage. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the process principle of the present invention.

[0021] Attached diagram labeling: Solid line - sewage pipe, dashed line - sludge pipe. Detailed Implementation

[0022] like Figure 1 As shown, the present invention provides an anaerobic digester system for kitchen waste based on enhanced pretreatment, including a pretreatment system, a biochemical treatment system and a sludge dewatering system.

[0023] 1. The sludge dewatering system includes a sludge storage tank and a centrifugal dewatering machine, which are connected by a screw pump and pipelines.

[0024] The sludge storage tank has dimensions of 5 m × 5 m × 5 m, an effective water depth of 3.5 m, and a hydraulic retention time of 24 h. The sludge storage tank is equipped with a mixer for mixing and stirring the sludge.

[0025] The centrifugal dewatering machine is used to separate the incoming sludge into mud and water. The separated sludge cake is transported off-site for centralized treatment, while the separated wastewater is sent to a regulating tank for reprocessing. The centrifugal dewatering machine can dewater the sludge to a moisture content of about 80%, and then transport it off-site for landfill or incineration.

[0026] II. The pretreatment system includes an equalization tank, a rotating bar screen, an air flotation oil separator, a membrane bar screen, an aerated biological adsorption tank, a sedimentation tank, and a microfilter. The equalization tank is connected to the rotating bar screen via a water pump and a pipeline. The rotating bar screen is connected to the air flotation oil separator via a water pump and a pipeline. The air flotation oil separator is connected to the membrane bar screen via a pipeline. The membrane bar screen is connected to the aerated biological adsorption tank via a water pump and a pipeline. The aerated biological adsorption tank is connected to the sedimentation tank via an overflow hole. The sedimentation tank is connected to the microfilter via a water pump and a pipeline.

[0027] The equalization tank is used to balance the water quality and quantity of anaerobic digestate from kitchen waste, buffer instantaneous load shocks, and adjust the time differences between the solid-liquid separation section and the digestate treatment section of the digestion residue. The retention time in the equalization tank is 5-7 days.

[0028] The rotating bar removes large impurities with a particle size greater than 10mm, improving the uniformity of suspended solids in the influent of the air flotation oil separator.

[0029] The air flotation oil separator has two parallel sets of equipment, each with a non-metallic chain plate scraper for scraping off the air flotation scum. The single cell size is 7m×1.5m×1.8m, the effective water depth is 1.3m, the hydraulic retention time is 1.6h, and the generated air flotation oil separator scum is sent to the sludge storage tank through pumps and pipelines.

[0030] The aerated biological adsorption tank adopts a rectangular reinforced concrete structure with a designed retention time of 24 hours and an effective water depth of 8 meters. Aerators are installed within the tank to cultivate aerobic biological sludge through aeration, thereby degrading and adsorbing organic matter to remove suspended solids (SS) and carbon dioxide (COD). The aerated biological adsorption tank must not exceed 10% for ammonia nitrogen removal and ensure an effluent COD removal rate of not less than 30%. To control sludge age and prevent nitrification within the aeration tank, the sludge concentration (MLSS) in the aerated biological adsorption tank must not exceed 8 g / L. The effluent from the aerated biological adsorption tank enters the sedimentation tank by gravity. Due to the strong aeration and agitation effect of the aerated biological adsorption tank, the sludge-water mixture in the effluent requires a relatively long retention time for sedimentation and sludge-water separation.

[0031] The sedimentation tank is a radial-flow vertical-flow sedimentation tank with a designed surface hydraulic load of 0.75m. 3 / (m 2 The SS removal rate is not less than 50%, and the sludge generated in the sedimentation tank is sent to the sludge storage tank through pumps and pipelines.

[0032] The microfilter is a disc filter cloth microfilter, and the backwash water it produces is connected to the sludge storage tank through a pipeline.

[0033] The microfilter and sedimentation tank are connected in series after the aerated biological adsorption tank for mud-water separation, ensuring that the COD and SS of the pretreatment system effluent meet the requirements of the two-stage AO influent, and ensuring that the system effluent meets the standards.

[0034] III. The biochemical treatment system comprises a primary A tank, a primary O tank, a secondary A tank, a secondary O tank, an external ultrafiltration membrane tank, and an effluent tank connected sequentially. The primary A tank and the primary O tank are connected via flow holes, the primary O tank and the secondary A tank are connected via flow holes, the secondary A tank and the secondary O tank are connected via flow holes, and the secondary O tank and the external ultrafiltration membrane system are connected via an ultrafiltration inlet pump and pipeline.

[0035] The primary A tank has dimensions of 9×12×10m, an effective water depth of 8m, a water temperature ≤35℃, MLSS of 12000 mg / L, a denitrification rate of 0.043 kg NO3-N / (kg MLSS·d), a hydraulic retention time of 4.1d, and a sludge production coefficient of 0.21 kg VSS / kg COD. The primary A tank is equipped with a mixer with a mixing intensity of 8w / m³. 3 The wastewater in the primary A tank is in an anaerobic environment. Under the action of a carbon source, nitrates are converted into nitrogen gas through denitrification and discharged from the system, thereby removing total nitrogen. The wastewater after the reaction enters the primary O tank.

[0036] The primary O-tank measures 9 m × 26 m × 10 m, with an effective water depth of 8 m, a water temperature ≤ 35℃, MLSS 12000 mg / L, aerobic sludge age of 25 days, an air-to-water ratio of 670:1, an internal recirculation ratio of 16, and a hydraulic retention time of 9.36 days. A jet aerator is installed in the primary O-tank to meet the air-to-water ratio requirements. The mixed liquor from the primary O-tank is returned to the primary A-tank via a recirculation pump and pipeline at a recirculation ratio of 1600%. Under the aerobic environment of the primary O-tank, organic matter in the wastewater undergoes degradation while ammonia nitrogen is oxidized to nitrate nitrogen. The wastewater from the primary O-tank after the reaction proceeds enters the secondary A-tank.

[0037] The secondary A tank has dimensions of 4.3 m × 6 m × 10 m, an effective water depth of 8 m, a water temperature ≤ 35℃, MLSS 12000 mg / L, a denitrification rate of 0.043 kg NO3-N / (kgMLSS·d), and a hydraulic retention time of 1.0 d. The secondary A tank is equipped with the aforementioned agitator, with a stirring intensity of 8 W / m². 3 In the secondary A tank, the wastewater is in an anaerobic environment. Under the action of a carbon source, nitrates are converted into nitrogen gas through denitrification and discharged from the system, thereby further removing total nitrogen. The wastewater after the reaction enters the secondary O tank.

[0038] The secondary O-tank measures 4.3 m × 6 m × 10 m, with an effective water depth of 8 m, a water temperature ≤ 35℃, MLSS 12000 mg / L, aerobic sludge age of 25 days, and a hydraulic retention time of 1.0 day. A jet aerator is installed in the secondary O-tank to meet the required air-to-water ratio. The mixed liquor from the secondary O-tank is returned to the secondary A-tank via an ultrafiltration influent pump and pipeline, with a return ratio of 900%. In the aerobic environment of the secondary O-tank, organic matter in the wastewater undergoes degradation, while ammonia nitrogen is oxidized to nitrate nitrogen. The mixed liquor is then returned to the secondary A-tank via a second mixed liquor return pump for denitrification. The wastewater after reaction in the secondary O-tank enters an external ultrafiltration membrane.

[0039] The external ultrafiltration membrane is a PVDF tubular ultrafiltration membrane with a designed membrane flux of 55 L / (m²).2 (h) The external ultrafiltration membrane is a cross-flow filter ultrafiltration membrane. The ultrafiltration feed pump provides a flow rate of 3.5~5 m / s to the mixed liquor (sludge), creating a turbulent flow state in the tubular membrane and preventing sludge deposition on the membrane surface. A portion of the mixed liquor, excluding the permeate, is returned to the primary A tank, and a portion is discharged as sludge. The sludge generated by the external ultrafiltration membrane is connected to a sludge storage tank via a pipeline.

[0040] The effluent from the outlet pool meets the standards and is discharged into the municipal pipe network.

[0041] The present invention also includes a control device, which is controlled by a PLC and is used to control the operation of the anaerobic digester system for food waste.

[0042] The above embodiments are merely conventional implementations of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept or principle of the present invention, and these modifications and improvements all fall within the protection scope of the present invention.

Claims

1. A kitchen waste anaerobic sludge treatment system based on enhanced pretreatment, comprising a pretreatment system, a biochemical treatment system and a sludge dewatering system, wherein the sludge dewatering system comprises a sludge storage tank and a centrifugal dewatering machine connected together, the biochemical treatment system is composed of a primary A tank, a primary O tank, a secondary A tank, a secondary O tank, an external ultrafiltration membrane tank and an effluent tank connected in sequence, and the external ultrafiltration membrane tank is connected with the primary A tank and the sludge storage tank respectively, characterized in that, The pretreatment system comprises a regulating tank, a turning bar screen, a gas float oil separation tank, a membrane screen, a biological aerated adsorption tank, a sedimentation tank and a micro filter, which are connected in sequence, and the gas float oil separation tank, the membrane screen, the sedimentation tank and the micro filter are connected with a sludge storage tank respectively.

2. The kitchen waste anaerobic slurry treatment system based on the reinforced pretreatment according to claim 1, characterized in that: The centrifugal dewaterer is connected with the regulating tank through a pump and a pipeline.

3. The kitchen waste anaerobic slurry treatment system based on the reinforced pretreatment according to claim 1, characterized in that: The gas float oil separation tank adopts a dissolved air floatation tank.

4. The kitchen waste anaerobic slurry treatment system based on the reinforced pretreatment according to claim 1, characterized in that: The biological aerated adsorption tank adopts a rectangular reinforced concrete structure, and is designed with a residence time of 24 h, an effective water depth of 8 m, and an aerator arranged in the tank.

5. The kitchen waste anaerobic slurry treatment system based on the reinforced pretreatment according to claim 1, characterized in that: The sedimentation tank adopts a radial flow sedimentation tank.

6. The kitchen waste anaerobic slurry treatment system based on the reinforced pretreatment according to claim 1, characterized in that: The micro filter adopts a disc micro filter.

7. The kitchen waste anaerobic slurry treatment system based on the reinforced pretreatment according to claim 1, characterized in that: The external ultrafiltration membrane tank adopts a cross-flow filter ultrafiltration membrane.

8. The kitchen waste anaerobic slurry treatment system based on the reinforced pretreatment according to claim 1, characterized in that: Stirring machines are arranged in the primary A tank and the secondary A tank.

9. The kitchen waste anaerobic slurry treatment system based on the reinforced pretreatment according to claim 1, characterized in that: Jet aerators are arranged in the primary O tank and the secondary O tank.

10. The kitchen waste anaerobic slurry treatment system based on the reinforced pretreatment according to claim 1, characterized in that: The sludge storage tank and the centrifugal dewaterer are connected through a screw pump and a pipeline.

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