CN108101332B - Method and equipment for reducing sludge by compounding ultrasonic and ozone coupled with carrousel oxidation ditch - Google Patents
Method and equipment for reducing sludge by compounding ultrasonic and ozone coupled with carrousel oxidation ditch Download PDFInfo
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- CN108101332B CN108101332B CN201711362126.3A CN201711362126A CN108101332B CN 108101332 B CN108101332 B CN 108101332B CN 201711362126 A CN201711362126 A CN 201711362126A CN 108101332 B CN108101332 B CN 108101332B
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- C02F11/06—Treatment of sludge; Devices therefor by oxidation
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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Abstract
The invention provides a method for coupling with carrousel oxidation ditchAn ultrasonic ozone composite sludge reduction method and equipment thereof belong to the technical field of excess sludge treatment; the method comprises the following steps: 1) mixing excess sludge of the carrousel oxidation ditch with ozone to obtain a gas-liquid mixture; the amount of ozone is 0.01-0.1 gO3/gTSS; 2) the gas-liquid mixture is subjected to pressurization sludge reduction under ultrasonic treatment to obtain a reduced mixed solution; the ultrasonic frequency is 50-100 KHz, and the sound energy density of the ultrasonic is 0.2-0.3 w/ml; 3) and carrying out phosphorus recovery on the reduced mixed solution to obtain phosphorus recovery feed liquid, carrying out solid-liquid separation on the phosphorus recovery feed liquid to obtain supernatant, and refluxing the supernatant to a carrousel oxidation ditch. The method provided by the invention is simple to operate, low in cost and free of secondary pollution.
Description
Technical Field
The invention belongs to the technical field of excess sludge treatment, and particularly relates to an ultrasonic ozone composite sludge reduction method and equipment coupled with a carrousel oxidation ditch.
Background
The activated sludge process is a sewage treatment process, and has become the main process used by current sewage treatment plants due to the low cost, good effluent quality and wide application range. The carrousel oxidation ditch is one of the main implementation processes of the activated sludge sewage treatment technology, and is widely selected by domestic and foreign sewage treatment plants due to the strong denitrification capability, the low sludge yield coefficient, the small occupied area and the like. The carrousel oxidation ditch process structure mainly comprises a grating, an anaerobic zone, an oxidation ditch, a secondary sedimentation tank and the like, has higher removal efficiency of COD and ammonia nitrogen, and is a mature sewage treatment process in the prior art.
A large amount of excess sludge is produced during the wastewater treatment process of the carrousel oxidation ditch process. Because the composition of the excess sludge is very complex, the water content is high, and the excess sludge contains pollutants such as pathogenic bacteria and heavy metals, once the excess sludge is treated improperly, the excess sludge can cause secondary pollutionAnd (5) secondary pollution risk. In recent years, China has strengthened the construction of sewage treatment facilities, and the sewage treatment capacity is gradually enhanced, so that the amount of sludge produced is synchronously increased. At present, the conventional treatment method of excess sludge is to reduce the volume and water content of the excess sludge by means of concentration dehydration, sludge digestion and the like, and then to carry out final treatment in the modes of sanitary landfill, incineration, land utilization and the like. The concentration and dehydration only reduce the volume of the sludge and do not really realize the reduction of the sludge; the sludge digestion can realize the reduction of the residual sludge and simultaneously recover a part of methane, but the occupied area is large, the process is complex, the sludge digestion and recovery methane is generally used for large-scale sewage treatment plants, meanwhile, the sludge digestion and recovery methane is limited by conditions such as weather, process operation conditions and the like, the stability of the recovery process of the methane is poor, and the difficulty in realizing stable operation is high; the sludge landfill technology occupies a large amount of land resources, and has very high secondary pollution risk due to large amount of residual sludge and harmful substances such as pathogens, heavy metals and the like contained in the residual sludge; the incineration process needs to firstly realize sludge drying, consumes a large amount of energy, and the sludge incineration technology can possibly generate fly ash and SO2Secondary pollution is caused; the sludge biological treatment land utilization technology mainly utilizes organisms such as earthworms to reduce sludge, but the occupied area is large, and heavy metals, toxic and harmful substances in the sludge are possibly leaked to cause secondary pollution.
The traditional excess sludge reduction method has various defects, and under the current situation that the excess sludge amount is continuously increased, how to simply treat the excess sludge without secondary pollution, which is a problem to be solved urgently in the technical field of excess sludge treatment.
Disclosure of Invention
In view of the above, the present invention aims to provide an ultrasonic ozone composite sludge reduction method coupled to a carrousel oxidation ditch, which is simple in operation, low in cost and free from secondary pollution. In order to achieve the above object, the present invention provides the following technical solutions: an ultrasonic ozone composite sludge reduction method coupled with a carrousel oxidation ditch comprises the following steps: 1) mixing excess sludge of the carrousel oxidation ditch with ozone to obtain a gas-liquid mixture; of the ozoneThe amount of the surfactant is 0.01 to 0.1gO3/gTSS; 2) the gas-liquid mixture is subjected to pressurization sludge reduction under ultrasonic treatment to obtain a reduction mixed solution; the frequency of ultrasonic treatment is 50-100 KHz, and the acoustic energy density of ultrasonic treatment is 0.2-0.3 w/ml; 3) and carrying out phosphorus recovery on the reduced mixed solution to obtain a phosphorus recovery feed liquid, carrying out solid-liquid separation on a supernatant obtained from the phosphorus recovery feed liquid, and refluxing the supernatant to a carrousel oxidation ditch.
Preferably, the pressure in the pressurized sludge reduction process in the step 2) is 0.05-0.08 MPa, and the time in the pressurized sludge reduction process is 45-60 min.
Preferably, the pH value of the feed liquid in the pressurized sludge reduction process is 6-8.
Preferably, the phosphorus recovery is: and adding an alkalizer and a phosphorus recovery agent to the reduction mixed solution.
Preferably, the time for recovering the phosphorus is 20-30 min.
Preferably, 20-25% of the volume of the supernatant liquid flows back to the pre-anoxic zone; refluxing 50-60% of the volume of the mixture to an aerobic zone; 15-30% of the volume of the mixed gas is refluxed to an anoxic zone of the oxidation ditch.
The invention also provides equipment used by the method, which comprises a carrousel oxidation ditch system, and further comprises a residual sludge pump, an ultrasonic ozone composite reactor, a phosphorus recovery reactor and a phosphorus recovery separator which are sequentially connected with a residual sludge discharge port of the carrousel oxidation ditch system; the equipment also comprises an ozone generator, wherein an ozonized gas outlet of the ozone generator is connected with an inlet of the excess sludge pump through a pipeline; an ultrasonic generator is arranged in the ultrasonic ozone composite reactor, and an internal circulating pump ejector are arranged outside the ultrasonic ozone composite reactor; and the outlet of the supernatant of the phosphorus recovery separator is connected with the carrousel oxidation ditch system through a pipeline.
Preferably, the ultrasonic ozone composite reactor is a closed cylindrical reactor, and an inlet of the ultrasonic ozone composite reactor is connected with an outlet of the residual sludge pump through a pipeline.
Preferably, an ozone outlet of the ozone generator is respectively connected with an inlet of the internal circulation pump ejector and a feeding port of the excess sludge pump through pipelines.
Preferably, the height-diameter ratio of the ultrasonic ozone composite reactor is 1: 1-1: 0.6.
Preferably, the inside stainless steel screen cloth that sets up a plurality of load MnO of supersound ozone composite reactor, the aperture of stainless steel screen cloth is 100 ~ 120 meshes, and when the stainless steel screen cloth was a plurality of, the perpendicular interval of adjacent stainless steel screen cloth was 200 ~ 300 mm.
Preferably, the ultrasonic generators comprise a plurality of rod-type ultrasonic generators, the rod-type ultrasonic generators are arranged in the ultrasonic ozone composite reactor in a transversely and longitudinally staggered manner, and the ratio of the number of the ultrasonic rods arranged in the vertical direction to the number of the ultrasonic rods arranged in the horizontal direction is 2 (0.8-1.2).
The invention has the beneficial effects that: the ultrasonic ozone composite sludge reduction method coupled with the carrousel oxidation ditch is simple to operate, and in the sludge reduction process, a high-efficiency ozone hydration and ultrasonic combined cracking mode is adopted, so that the utilization rate of ozone is improved, the cell dissolving effect of sludge is enhanced, the high-efficiency reduction of activated sludge is realized, the economic cost in the sludge reduction process is reduced, and the economic applicability of the reduction technology is improved; meanwhile, aiming at the reduced mixed liquor with high contents of organic matters, nitrogen and phosphorus after the sludge reduction, phosphorus in the reduced mixed liquor is recovered by adopting a phosphorus recovery and branching backflow mode, and the supernatant containing nitrogen and organic matters flows back to the carrousel oxidation ditch, so that the nitrogen and phosphorus removal of the supernatant is realized. Compared with the conventional sludge reduction technology, the method has the advantages of simple process control, small occupied area, small influence on the conventional sewage treatment system, no risk of secondary pollution and the like by fully combining the conventional water treatment engineering, and has remarkable advantages on the reconstruction of the sludge treatment systems of medium and small sewage treatment plants and the conventional sewage treatment plants.
Drawings
FIG. 1 is a schematic flow diagram of a method for ultrasonic ozone composite sludge decrement coupled with a carrousel oxidation ditch.
Detailed Description
The invention provides an ultrasonic ozone composite sludge reduction method coupled with a carrousel oxidation ditch, which comprises the following steps: 1) mixing excess sludge of the carrousel oxidation ditch with ozone to obtain a gas-liquid mixture; the amount of ozone is 0.01-0.1 gO3/gTSS; 2) the gas-liquid mixture is subjected to pressurization sludge reduction under ultrasonic treatment to obtain a reduced mixed solution; the ultrasonic frequency is 50-100 KHz, and the sound energy density of the ultrasonic is 0.2-0.3 w/ml; 3) and carrying out phosphorus recovery on the reduced mixed solution to obtain phosphorus recovery feed liquid, carrying out solid-liquid separation on the phosphorus recovery feed liquid to obtain supernatant, and refluxing the supernatant to a carrousel oxidation ditch.
The excess sludge of the carrousel oxidation ditch is the excess sludge after the sewage treatment of the carrousel oxidation ditch in the field, the excess sludge comprises four parts, namely microorganisms, the oxidation residues of the microorganisms, organic matters and inorganic matters which are attached to the surface of activated sludge and are not degraded or difficult to degrade, and living microorganisms are taken as the main components. The excess sludge of the carrousel oxidation ditch is mixed with ozone to obtain a gas-liquid mixture. In the invention, the amount of ozone in the gas-liquid mixture is 0.01-0.1 gO3/gTSS, preferably 0.04 to 0.08gO3/gTSS; the ozone is preferably prepared by an ozone generator, the ozone is preferably present in the form of ozonized gas, and the concentration of the ozone in the ozonized gas is preferably 20-50 mg/L, and more preferably 30-40 mg/L.
The feeding and adding point of the sludge mixed liquid adopts a pre-pump adding mode to add ozone, an open impeller centrifugal pump is adopted, the ozonized gas is sucked into a feeding pipeline by utilizing the negative pressure formed before the pump when the centrifugal pump operates, and the negative pressure vacuum degree of the residual sludge and the ozone is preferably 0.1-0.25 Mpa, more preferably 0.15-0.2 Mpa; the ozone pressure in the mixing process is 0.05-0.1 Mpa, and more preferably 0.7-0.9 Mpa; the flow ratio of the ozone to the residual sludge in the pipeline is preferably 1-2: 1.
After a gas-liquid mixture is obtained, the gas-liquid mixture enters a pressurized sludge reduction reactor, and pressurized sludge reduction is carried out under ultrasonic treatment to obtain a reduced mixed solution. In the invention, the pressure in the pressurized sludge reduction process is preferably 0.05-0.08 MPa, and more preferably 0.06-0.07 MPa; the pH value of the feed liquid in the pressurized sludge reduction process is preferably 6-8, and more preferably 7; the time of the pressurized sludge reduction process is preferably 45-60 min, and more preferably 50-55 min.
In the invention, the pressurized sludge reduction is carried out in an ultrasonic treatment environment; the ultrasonic frequency is 50-100 KHz, preferably 60-90 KHz, and more preferably 70-80 KHz; the sound energy density of the ultrasonic is 0.2-0.3 w/ml, and the preferable sound energy density is 0.24-0.26 w/ml.
In the present invention, it is preferable to further add ozone to the gas-liquid mixture; the flow ratio of the ozone to the gas-liquid mixture is preferably 2-5: 1, and more preferably 3-4: 1. In the invention, the flow velocity of the gas-liquid mixture in the pressurized sludge reduction process is preferably 8-10 m/s, the gas-liquid mixture can flow upwards in a spiral manner, the contact time of ozone gas and the gas-liquid mixture is prolonged, and the reduction efficiency is improved. In the pressurized sludge reduction process, ozone and ultrasonic waves react simultaneously, on one hand, the ultrasonic cavitation effect of the ultrasonic waves is utilized to promote the disintegration of sludge flocs, on the other hand, the ultrasonic waves are utilized to enhance the dispersion of the ozone and catalyze the ozone to generate hydroxyl radicals, so that the reduction efficiency of the ozone on the sludge is promoted, and the ultrasonic ozone composite reduction of the residual sludge is realized.
After the reduced mixed liquid is obtained, the reduced mixed liquid is subjected to phosphorus recovery to obtain phosphorus recovery feed liquid. Adding an alkalizer and a phosphorus recovery agent into the phosphorus recovery process; the alkalizer is preferably NaOH, and the alkalizer is used for adjusting the pH value of the reduction mixed solution to 7.5-8.5; the addition amount of the alkalizer is based on the fact that the pH can be adjusted to 7.5-8.5. The phosphorus recovery agent is MgCl2The dosage of the phosphorus recovery agent is adjusted according to the content of P in the supernatant, and the content ratio of Mg in the phosphorus recovery agent to P in the reduction mixed liquid is preferably controlled to be 11 to 2: 1. In the invention, the time of the phosphorus recovery process is preferably 20-30 min.
After the phosphorus recovery feed liquid is obtained, the supernatant obtained by solid-liquid separation of the phosphorus recovery feed liquid is refluxed to the carrousel oxidation ditch. In the invention, the supernatant has the pollution characteristics of high COD, high ammonia nitrogen and high phosphorus, wherein the concentration of the COD, the ammonia nitrogen and the phosphorus is 3000-6000 mg/L, 600-800 mg/L and 80-150 mg/L, the COD in the supernatant mainly takes cytoplasm dissolved out in the reduction process as a main component, has good biodegradability and can be used as a preferential electron donor in the denitrification process. In the present invention, the solid-liquid separation method is preferably still standing precipitation; the time for standing and precipitating is preferably 2-4 h; and after standing and precipitating, the solid phase is recovered phosphorus, and the separated supernatant liquid flows back to the carrousel oxidation ditch to finish sludge reduction.
In the invention, by combining the pollutant property in the supernatant and the combination of the processes of pre-anaerobic denitrification, aerobic reaction, anoxic reaction and the like in the carrousel oxidation ditch, COD (chemical oxygen demand) and ammonia nitrogen in the supernatant respectively flow back to different efficient reaction zones in the oxidation ditch, and the reduction process is coupled with the water treatment process of the carrousel oxidation ditch to realize the nitrogen and phosphorus removal of the supernatant.
In the specific implementation process of the invention, 20-25% of the volume of the supernatant liquid flows back to the pre-anoxic zone; the preferred residence time is 8-12 h, and then the oxygen-deficient zone is entered. The DO in the anoxic zone is preferably controlled to be 0.05-0.1 mg/L, BOD: NOxPreferably 3-5: 1, and the alkalinity is preferably 150-200 mg/L (as CaCO)3Measured), the retention time is preferably 3-4 h, and the sludge load is preferably controlled to be 0.05-0.07 kgNO3/kgMLSS.d。
50-60% of the volume of the supernatant liquid returns to the aerobic zone, the residence time of the supernatant liquid in the aerobic zone is preferably 30-40 h, the sludge load of the aerobic zone is preferably controlled to be 0.05-0.12 kgBOD/kgMLSS.d, the concentration of the feed liquid in the aerobic zone is preferably 3.5-4.0 kgVSS/L, the DO is preferably 2-3 mg/L, and the pH is preferably 6-8.
In the invention, the supernatant is 15-30%The volume percent of the supernatant is refluxed to an anoxic zone of the oxidation ditch, the residence time of the supernatant in the anoxic zone is preferably 16-20 h, the DO of the anoxic zone is preferably controlled to be 0.1-0.3 mg/L, and the alkalinity of the anoxic zone is preferably 100-150 mg/L (as CaCO)3Meter), BOD of the anoxic zone: NO is BOD: NOxPreferably 2-3: 1; the sludge load of the anoxic zone is preferably 0.02-0.03 kgNO3/kgMLSS.d。
The invention also provides equipment used by the method, the equipment structure is shown in figure 1, and the equipment comprises a carrousel oxidation ditch system, and further comprises a residual sludge pump 5, an ultrasonic ozone composite reactor 7, a phosphorus recovery reactor 10 and a phosphorus recovery separator 13 which are sequentially connected with the discharge of the carrousel oxidation ditch system; an ultrasonic generator 20 is arranged in the ultrasonic ozone composite reactor; the device also comprises an ozone generator 6, wherein an ozone outlet of the ozone generator is connected with an inlet of the excess sludge pump 5 through a pipeline; the outlet of the supernatant of the phosphorus recovery separator 13 is connected with the carrousel oxidation ditch system through a pipeline.
In the invention, the carrousel oxidation ditch system only needs to adopt a conventional carrousel oxidation ditch system in the field, and has no other special requirements; in the specific implementation process of the invention, the carrousel oxidation ditch system comprises a water inlet, a pre-anoxic zone 1, a grid, a plug-flow type surface aerator 17, an oxidation ditch 2, a secondary sedimentation tank 3 and a return sludge pipeline 4 which are connected in sequence; the oxidation ditch 2 comprises an aerobic zone 18 and an anoxic zone 19. The carrousel oxidation ditch is used as a plug flow type reactor, sewage entering a sewage plant generally enters a pre-anoxic zone 1 and then enters an aerobic zone 18, surface aeration equipment is generally arranged in the aerobic zone 18 of the carrousel oxidation ditch to form the aerobic zone, dissolved oxygen is continuously metabolized and consumed by microorganisms along with the flowing of the sewage in the oxidation ditch, so that an anoxic zone 19 is formed at the rear end of the oxidation ditch, organic pollutants are continuously degraded in the aerobic zone and the anoxic zone of the oxidation ditch, ammonia nitrogen is nitrified in the aerobic zone to generate nitrate, and nitrogen generated by denitrification in the anoxic zone escapes, so that the removal of total nitrogen is realized.
The device is connected with the inlet of the excess sludge pump 5 and the inlet of the return sludge pipeline 4 at the outlet of a secondary sedimentation tank 3 of a carrousel oxidation ditch system respectively; the outlet of the sludge return line 4 is connected with the pre-anoxic zone 1 of the carrousel oxidation ditch system. In the invention, the outlet of the excess sludge pump 5 is connected with an ultrasonic ozone composite reactor 7; the residual sludge pump is used for mixing residual sludge and ozone and pumping the mixture into the ultrasonic ozone composite reactor; the residual sludge pump preferably adopts a centrifugal pump, more preferably adopts an open impeller centrifugal pump, and the working specific speed of the open impeller centrifugal pump is preferably 150-300. The residual sludge pump is also used for adding ozone, ozonized gas is sucked into the feed pipeline by utilizing negative pressure formed before the pump when the centrifugal pump operates, and the ozonized gas and the sludge mixed solution are pumped into the ultrasonic ozone composite reactor 7 after being fully mixed.
In the invention, the equipment also comprises an ultrasonic ozone composite reactor 7, wherein the inlet of the ultrasonic ozone composite reactor 7 is connected with the outlet of the excess sludge pump 5; an internal circulating pump 8 and an internal circulating ejector 9 are also arranged outside the ultrasonic ozone composite reactor 7; the inner circulating pump extracts the liquid at the upper part in the ultrasonic ozone composite reactor 7 and pumps the liquid into the inner circulating pump ejector 9, and the inner circulating pump ejector 9 is used for mixing the ozone and the liquid extracted from the ozone composite reactor 7 and then feeding the mixed liquid into the lower part of the ultrasonic ozone composite reactor 7. An ultrasonic generator 20 is arranged in the ultrasonic ozone composite reactor 7 in the invention; the ultrasonic generators 20 are preferably a plurality of rod-type ultrasonic generators, the rod-type ultrasonic generators are preferably arranged in the ultrasonic ozone composite reactor in a transversely and longitudinally staggered manner, and the ratio of the number of the ultrasonic rods arranged in the vertical direction to the number of the ultrasonic rods arranged in the horizontal direction in the invention is preferably 2: 0.8-1.2, and more preferably 2: 1; the ultrasonic generator 20 is used for providing an ultrasonic environment, ozonated gas and ultrasonic waves in the ultrasonic-ozone composite reactor 7 react simultaneously, on one hand, the ultrasonic supercavitation effect of the ultrasonic waves is utilized to promote the sludge floc disintegration, on the other hand, the ultrasonic waves are utilized to enhance the ozone dispersion, and the ozone is catalyzed to generate hydroxyl radicals, so that the sludge reduction efficiency of the ozone is promoted to be improved, and the ultrasonic-ozone composite reduction of the residual sludge is realized.
The ratio of the height to the diameter of the ultrasonic ozone composite reactor 7 is preferably 1: 1-1: 0.6; a plurality of stainless steel screens loaded with MnO are preferably arranged in the ultrasonic ozone composite reactor 7; the specific number of the stainless steel screens is determined according to the height and the size of the ultrasonic ozone composite reactor 7; the stainless steel screen is preferably arranged between 0.3-0.5 m above the bottom of the ultrasonic ozone composite reactor 7 and 0.3-0.5 m below the top of the ultrasonic ozone composite reactor. The aperture of the stainless steel screen is preferably 100-120 meshes, and the distance between the screens in the ultrasonic ozone composite reactor 7 is 200-300 mm. MnO loaded on the surface of the stainless steel screen can catalyze ozone to generate hydroxyl radicals, so that the progress of the sludge reduction reaction by the ozone is promoted, and meanwhile, the stainless steel screen can further disperse ozone gas to form small bubbles, so that the mass transfer of the ozone into a liquid phase is promoted.
In the invention, the equipment also comprises an ozone generator 6, and an ozone outlet of the ozone generator 6 is connected with an inlet of the excess sludge pump 5 through a pipeline; the ozone generator 6 is used for preparing and generating ozonized gas; in the invention, the outlet of the ozone generator 6 is preferably connected with the inlet of a circulating pump ejector 9 in the ultrasonic ozone composite reactor through a pipeline; ozone is mixed with a gas-liquid mixture entering the ultrasonic ozone composite reactor through the inner circulating pump ejector 9, so that secondary adding of ozone is realized.
In the invention, the equipment also comprises a phosphorus recovery reactor 10, and the phosphorus recovery reactor 10 does not need to adopt a reactor which is conventional in the field; the inlet of the phosphorus recovery reactor 10 is connected with the outlet of the ultrasonic ozone composite reactor 7 through a pipeline, and the outlet of the phosphorus recovery reactor 10 is connected with the phosphorus recovery separator 13 through a pipeline. In the invention, the phosphorus recovery reactor 10 is connected with an alkalizer doser 11 and a phosphorus recovery agent doser 12 through pipelines, and outlets of the alkalizer doser 11 and the phosphorus recovery agent doser 12 are respectively communicated with a medicine inlet of the phosphorus recovery reactor 10; the inlets of the alkalizer doser 11 and the phosphorus recovery agent doser 12 are arranged on the alkalizer doser and the phosphorus recovery agent doser, are only used for adding the alkalizer and the phosphorus recovery agent, and are not communicated with other pipelines.
The equipment of the invention also comprises a phosphorus recovery separator 13, wherein the inlet of the phosphorus recovery separator 13 is connected with the outlet of the phosphorus recovery reactor 10; the supernatant outlet of the phosphorus recovery separator 13 is arranged on the side wall of one end of the phosphorus recoverer close to the return pipeline; the supernatant outlet is respectively connected with a pre-anoxic zone 1 in a carrousel oxidation ditch system and an aerobic zone 18 and an anoxic zone 19 in an oxidation ditch 2 through pipelines. The phosphorus recovery separator 13 in the present invention is used for solid-liquid separation, and the feed liquid in the phosphorus recovery reactor is separated into the recovered solid phosphorus, and the supernatant is respectively refluxed to the pre-anoxic zone in the carrousel oxidation ditch system and the aerobic zone 18 and the anoxic zone 19 in the oxidation ditch 2 through pipelines.
In combination with the equipment, the flow of the ultrasonic ozone composite sludge reduction method coupled with the carrousel oxidation ditch is shown in figure 1, during operation, a part of sludge separated by the secondary sedimentation tank 3 is taken as return sludge and flows back to the pre-anoxic zone 1 through the sludge return pipeline 4 to be mixed with sewage in the pre-anoxic zone 1. The excess sludge firstly enters an ultrasonic ozone composite reactor 7 from a secondary sedimentation tank 3 through an excess sludge pump 5, an internal circulating pump 8 is arranged outside the ultrasonic ozone composite reactor 7, and ozone is further added through an internal circulating pump ejector 9 behind the internal circulating pump, so that the ozone addition is ensured to meet the design requirements, and the sludge reduction is realized. After the main reduction of the residual sludge is completed, the reduction mixed liquor enters a phosphorus recovery reactor 10, an alkalizer and a phosphorus recovery agent are added into the phosphorus recovery reactor 10 through an alkalizer adding device 11 and a phosphorus recovery agent adding device 12 for phosphorus recovery, feed liquor enters a phosphorus recovery separator 13, the recovered phosphorus can be used for resource comprehensive utilization as a phosphate fertilizer, and high-COD and high-ammonia-nitrogen supernatants after phosphorus recovery respectively enter an oxidation ditch pre-anoxic zone 1, an aerobic zone 18 and an anoxic zone 19 through pipelines 14, 15 and 16, so that the whole sludge reduction process is completed.
The method and the equipment for ultrasonic ozone composite sludge reduction coupled with the carrousel oxidation ditch provided by the invention are described in detail below with reference to the examples, but the method and the equipment are not to be construed as limiting the scope of the invention.
Example 1
Aiming at the excess sludge reduction process of a certain small sewage treatment plant, the excess sludge discharged from a secondary sedimentation tank firstly enters an ultrasonic composite ozone reactor, an ozone generator is started, the cell dissolution and reduction treatment of ultrasonic composite ozone are carried out, the ozone concentration is 20mg/L, the ozone adding amount is 0.01gO3/g TSS, and the ozone pressure is 0.05 Mpa. The feeding and adding point of the sludge mixed liquid adopts a mode of adding before a pump to add ozone, the vacuum degree before the pump is controlled to be 0.1Mpa, the adding point of the circulating ozone in the reactor adopts a mode of adding an ejector, and the flow ratio of the ozone gas to the mixed liquid in the pipeline is 1: 1.
The ozonized sludge reduction reactor adopts a closed cylindrical reactor, and is provided with a stainless steel screen loaded with MnO, the aperture of the screen is 100 meshes, and the distance between screens in the reactor is 200 mm. The pressure in the reaction tank is 0.05Mpa, the pH value is preferably 6, the retention time of the mixed liquid is controlled to be 45min, the mixed liquid of ozone enters tangentially, and the flow rate of the mixed liquid is 8 m/s. The reactor is internally provided with ultrasonic generators, the distribution of the sound fields is staggered, and the ratio of the number of the ultrasonic rods in the vertical direction to the number of the ultrasonic rods in the horizontal direction is 2: 1. The ultrasonic frequency is selected to be 50KHz, the sound energy density is 0.2w/ml, and the sludge reduction rate reaches 60 percent (calculated by MLVSS) through the ozone-ultrasonic combined sludge reduction process.
Coupling the reduced sludge mixed liquor subjected to ultrasonic ozone composite treatment with a carrousel oxidation ditch treatment process, enabling the reduced mixed liquor to enter a phosphorus recoverer, recovering a phosphate fertilizer by adding an alkalizer and a phosphorus removing agent, wherein the alkalizer is NaOH, adjusting the pH of the alkalizer to 7 by controlling the addition of the NaOH, the phosphorus removing agent is MgCl, and controlling the Mg: the proportion of P is: 1:1, controlling the reactor time of the supernatant in the phosphorus recoverer to be 20min, and allowing the mixed solution after reaction to enter a precipitator for 2 h. And the phosphate fertilizer is precipitated and recovered after precipitation in the precipitator. And recovering the supernatant after precipitation into a carrousel oxidation ditch. The supernatant fluid is refluxed by adopting a branching flow measuring mode, 20% returns to the pre-anoxic zone, the retention time is 8h, the DO in the anoxic zone is controlled to be 0.05mg/L, the alkalinity is 150mg/L (calculated by CaCO 3), the retention time is 3h, and the sludge load is 0.05kgNO3(ii)/kgMLSS.d; 50 percent of the sludge is returned to the aerobic zone, the retention time is 10 hours, DO is 2mg/L, the pH is 6, and the sludge load is 0.05 kgBOD/kgMLSS.d; 30 percent of the sludge is refluxed to the anoxic zone of the oxidation ditch and stays for 20 hours, the DO of the anoxic zone is controlled to be 0.3mg/L, and the sludge load is controlled to be 0.02kgNO3Kg MLSS.d. Alkalinity was 100mg/L (as CaCO 3).
In the implementation process, the sludge reduction efficiency reaches 60 percent (calculated by MLVSS), and COD, ammonia nitrogen and phosphorus released in the reduction process are effectively removed in the water treatment process, and the removal rates reach 85 percent, 90 percent and 92 percent respectively.
Example 2
Aiming at the excess sludge reduction process of a sewage treatment plant with the treatment scale of 50000 tons every day, the excess sludge discharged from the secondary sedimentation tank firstly enters an ultrasonic composite ozone reactor, and an ozone generator is started to carry out the cell dissolving and reducing treatment of ultrasonic composite ozone.
The feeding point of the sludge mixed liquid adopts a mode of feeding before a pump, and the feeding amount of ozone is ensured to reach 0.1gO3/g TSS by adopting a process of circulating in the reactor through a reflux process. The concentration of ozone generated by the ozone generator is 50mg/L, the ozone pressure is 0.1Mpa, the vacuum degree before pumping is 0.1Mpa, and the flow ratio of the ozone gas to the mixed liquid in the pipeline is 1: 1.
The ozonized sludge reduction reactor adopts a closed cylindrical reactor, and is provided with a stainless steel screen loaded with MnO, the aperture of the screen is 120 meshes, and the distance between screens in the reactor is 200 mm. The pressure in the reaction tank is 0.1Mpa, the pH value is 8, the retention time of the mixed liquid is controlled for 60min, the mixed liquid of ozone enters tangentially, and the flow rate of the mixed liquid is 8 m/s. The reactor is internally provided with ultrasonic generators, the distribution of the sound fields is staggered, and the ratio of the number of the ultrasonic rods in the vertical direction to the number of the ultrasonic rods in the horizontal direction is 2: 1. The ultrasonic frequency is selected to be 100KHz, the sound energy density is 0.3w/ml, and the sludge reduction rate reaches 90 percent (calculated by MLVSS) through the ozone-ultrasonic combined sludge reduction process.
Coupling the reduction sludge mixed liquor subjected to ultrasonic ozone composite treatment with a carrousel oxidation ditch treatment process, enabling the reduction mixed liquor to enter a phosphorus recoverer, recovering a phosphate fertilizer by adding an alkalizer and a phosphorus removing agent, wherein the alkalizer is NaOH, adjusting the pH of the mixture to 8.5 by controlling the addition of the NaOH, the phosphorus removing agent is MgCl, and controlling Mg: the proportion of P is: 2:1, controlling the reactor time of the supernatant in the phosphorus recoverer to be 30min, and allowing the mixed solution after reaction to enter a precipitator for 4 h. And the phosphate fertilizer is precipitated and recovered after precipitation in the precipitator. And recovering the supernatant after precipitation into a carrousel oxidation ditch.
Refluxing the supernatant by adopting a branching flow measuring mode, refluxing 25 percent of the supernatant to a pre-anoxic zone, keeping the supernatant for 12 hours, controlling DO of the anoxic zone to be 0.1mg/L, controlling alkalinity to be 200mg/L (calculated as CaCO 3), keeping the supernatant for 4 hours, and controlling sludge load to be 0.07kgNO3(ii)/kgMLSS.d; 60 percent of the sludge is returned to the aerobic zone, the retention time is 40 hours, DO is 3mg/L, the pH is 7, and the sludge load is 0.12 kgBOD/kgMLSS.d; 15 percent of the sludge is refluxed to the anoxic zone of the oxidation ditch and stays for 16 hours, the DO of the anoxic zone is controlled to be 0.1mg/L, and the sludge load is controlled to be 0.03kgNO3Kg MLSS.d, alkalinity of 100mg/L (calculated as CaCO 3).
In the implementation process, the sludge reduction efficiency reaches 90 percent (calculated by MLVSS), and COD, ammonia nitrogen and phosphorus released in the reduction process are effectively removed in the water treatment process, and the removal rates reach 90 percent, 95 percent and 95 percent respectively.
Example 3
Aiming at the excess sludge reduction process of a sewage treatment plant with treatment scale of 80000 tons per day, the excess sludge discharged from the secondary sedimentation tank firstly enters an ultrasonic composite ozone reactor, and an ozone generator is started to perform cell dissolving and reduction treatment on the ultrasonic composite ozone.
The feeding point of the sludge mixed liquid adopts a mode of feeding before a pump, and the feeding amount of ozone is ensured to reach 0.05gO3/g TSS by a process of internal circulation of the reactor through a reflux process. The concentration of ozone generated by the ozone generator is 30mg/L, the ozone pressure is 0.05Mpa, the vacuum degree before pumping is 0.2Mpa, and the flow ratio of the ozone gas to the mixed liquid in the pipeline is 1.5: 1.
The ozonized sludge reduction reactor adopts a closed cylindrical reactor, and is provided with a stainless steel screen loaded with MnO, the aperture of the screen is 110 meshes, and the screen space in the reactor is 240 mm. The pressure in the reaction tank is 0.06Mpa, the pH value is 7, the retention time of the mixed liquid is controlled for 50min, the mixed liquid of ozone enters tangentially, and the flow rate of the mixed liquid is 9 m/s. The reactor is internally provided with ultrasonic generators, the distribution of the sound fields is staggered, and the ratio of the number of the ultrasonic rods in the vertical direction to the number of the ultrasonic rods in the horizontal direction is 2: 1. The ultrasonic frequency is selected to be 60KHz, the sound energy density is 0.25w/ml, and the sludge reduction rate reaches 80 percent (calculated by MLVSS) through the ozone-ultrasonic combined sludge reduction process.
Coupling the reduction sludge mixed liquor subjected to ultrasonic ozone composite treatment with a carrousel oxidation ditch treatment process, enabling the reduction mixed liquor to enter a phosphorus recoverer, recovering a phosphate fertilizer by adding an alkalizer and a phosphorus removing agent, wherein the alkalizer is NaOH, adjusting the pH of the mixture to 8.0 by controlling the addition of the NaOH, the phosphorus removing agent is MgCl, and controlling Mg: the proportion of P is: and (3) controlling the time of the supernatant in the reactor of the phosphorus recoverer to be 25min at a ratio of 1.5:1, and allowing the mixed solution to enter a precipitator after reaction for 2.5 h. And the phosphate fertilizer is precipitated and recovered after precipitation in the precipitator. And recovering the supernatant after precipitation into a carrousel oxidation ditch.
Refluxing supernatant by adopting a branching flow measuring mode, refluxing 23 percent of supernatant to a pre-anoxic zone, keeping the supernatant for 12 hours, controlling DO in the anoxic zone to be 0.07mg/L, controlling alkalinity to be 200mg/L (calculated as CaCO 3), keeping the supernatant for 4 hours, and controlling sludge load to be 0.06kgNO3(ii)/kgMLSS.d; refluxing 55 percent of the sludge to the aerobic zone, keeping the sludge for 50 hours, wherein DO is 3mg/L, the sludge load is 0.08kgBOD/kgMLSS.d, and the pH is 7; 22 percent of the sludge is refluxed to the anoxic zone of the oxidation ditch and stays for 18 hours, the DO of the anoxic zone is controlled to be 0.1mg/L, and the sludge load is controlled to be 0.025kgNO3Kg MLSS.d, alkalinity of 100mg/L (calculated as CaCO 3).
In the implementation process, the sludge reduction efficiency reaches 80% (calculated by MLVSS), and COD, ammonia nitrogen and phosphorus released in the reduction process are effectively removed in the water treatment process, and the removal rates reach 86%, 93% and 90% respectively.
According to the embodiment, the ultrasonic ozone composite sludge reduction method coupled with the carrousel oxidation ditch provided by the invention is based on ozone sludge reduction, combines ultrasonic treatment, acts on the wall breaking of cells in the residual sludge, improves the cell lysis reduction efficiency of microorganisms in the residual activated sludge, inhibits the microorganisms from participating in the oxidation process of organic matters, reduces the adding amount of ozone and ultrasound, and reduces the energy consumption cost of sludge reduction; aiming at the reduction mixed liquor with high organic matter content, nitrogen and phosphorus content in the sludge reduction process, a phosphorus recovery and branching backflow mode is adopted, and the supernatant liquid flows back to the carrousel oxidation ditch to realize the nitrogen and phosphorus removal of the supernatant liquid, so that the risk of secondary pollution is avoided.
The method and the equipment provided by the invention can realize the reduction of the excess sludge and can also play a role in promoting the treatment efficiency of the in-situ sewage treatment system. The influence on the original sewage treatment system is small, and the improvement on the sludge treatment systems of medium and small sewage treatment plants and the existing sewage treatment plants has remarkable advantages.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (5)
1. An ultrasonic ozone composite sludge reduction method coupled with a carrousel oxidation ditch comprises the following steps:
1) mixing excess sludge of the carrousel oxidation ditch with ozone to obtain a gas-liquid mixture; the amount of the ozone is 0.04-0.08 gO 3/gTSS; the ozone exists in the form of ozonized gas, and the concentration of the ozone in the ozonized gas is 20-50 mg/L;
the negative pressure vacuum degree of the mixing of the residual sludge and the ozone is 0.1-0.25 Mpa, and the ozone pressure in the mixing process is 0.05-0.1 Mpa; the flow ratio of the ozone to the residual sludge in the pipeline is 1-2: 1;
2) the gas-liquid mixture is subjected to pressurization sludge reduction under ultrasonic treatment to obtain a reduction mixed solution; the frequency of ultrasonic treatment is 50-100 KHz, and the acoustic energy density of ultrasonic treatment is 0.2-0.3 w/ml;
3) recovering phosphorus from the reduced mixed solution; obtaining a phosphorus recovery feed liquid, carrying out solid-liquid separation on a supernatant obtained from the phosphorus recovery feed liquid, and refluxing the supernatant to a carrousel oxidation ditch; in the step 2), the pressure for reducing the pressurized sludge is 0.05-0.08 Mpa, and the time for reducing the pressurized sludge is 45-60 min; the pH value of the feed liquid in the pressurized sludge reduction is 6-8; refluxing 20-25% of the volume of the supernatant to the pre-anoxic zone; refluxing 50-60% of the volume of the mixture to an aerobic zone; refluxing 15-30% of the volume of the mixed solution to an anoxic zone of the oxidation ditch;
the phosphorus recovery is as follows: adding an alkalizer and a phosphorus recovery agent to the reduction mixed solution;
the recovery time of the phosphorus is 20-30 min;
the equipment used by the sludge reduction method comprises a carrousel oxidation ditch system, and further comprises an excess sludge pump, an ultrasonic ozone composite reactor, a phosphorus recovery reactor and a phosphorus recovery separator which are sequentially connected with an excess sludge discharge port of the carrousel oxidation ditch system;
the device also comprises an ozone generator, wherein an ozone outlet of the ozone generator is connected with an inlet of the excess sludge pump through a pipeline;
the ultrasonic ozone composite reactor is provided with an ultrasonic generator and is connected with an internal circulating pump and an internal circulating pump ejector through pipelines; an ozone outlet of the ozone generator is respectively connected with an inlet of the inner circulating pump ejector and an inlet of the excess sludge pump through pipelines;
and the outlet of the supernatant of the phosphorus recovery separator is connected with the carrousel oxidation ditch system through a pipeline.
2. The ultrasonic-ozone composite sludge reduction method according to claim 1, wherein the ultrasonic-ozone composite reactor is a closed cylindrical reactor, and a feed inlet of the ultrasonic-ozone composite reactor is connected with an outlet of a residual sludge pump through a pipeline.
3. The ultrasonic-ozone composite sludge reduction method according to claim 1, wherein the ultrasonic-ozone composite reactor has a height-diameter ratio of 1:1 to 1: 0.6.
4. The ultrasonic-ozone composite sludge reduction method according to claim 1, wherein a plurality of stainless steel screens loaded with MnO are arranged in the ultrasonic-ozone composite reactor, the aperture of each stainless steel screen is 100-120 meshes, and when a plurality of stainless steel screens are arranged, the vertical distance between adjacent stainless steel screens is 200-300 mm.
5. The ultrasonic-ozone composite sludge reduction method according to claim 1, wherein the ultrasonic generators comprise a plurality of rod-type ultrasonic generators, the rod-type ultrasonic generators are arranged in the ultrasonic-ozone composite reactor in a transversely-longitudinally staggered manner, and the ratio of the number of ultrasonic rods arranged in the vertical direction to the number of ultrasonic rods arranged in the horizontal direction is 2 (0.8-1.2).
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| CN112209596B (en) * | 2020-10-30 | 2022-12-16 | 张家港东艺超声有限公司 | Sludge dewatering device and method based on ultrasonic waves |
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| CN104085987A (en) * | 2014-07-10 | 2014-10-08 | 中国科学院生态环境研究中心 | Method and device for synchronously realizing sewage nitrogen and phosphorus removal, residual sludge reduction and phosphorus resource recovery |
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| CN103508617B (en) * | 2012-06-27 | 2015-08-19 | 中国石油化工股份有限公司 | The method of petrochemical industry reducing biological sludge and treatment unit thereof |
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| CN104085987A (en) * | 2014-07-10 | 2014-10-08 | 中国科学院生态环境研究中心 | Method and device for synchronously realizing sewage nitrogen and phosphorus removal, residual sludge reduction and phosphorus resource recovery |
| CN107473544A (en) * | 2017-09-26 | 2017-12-15 | 江苏阿拉丁环保科技有限公司 | A kind of sludge reduction equipment |
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