CN101704615B - Method for reducing sludge by adopting ultrasound-magnetic field coupling to disrupt sludge - Google Patents

Abstract

The invention belongs to the field of solid waste treatment, and relates to a method for reducing sludge by using ultrasonic-magnetic field coupling to crack sludge. Separation of mud and water; the ultrasonic-magnetic field processing unit uses ultrasonic waves with a frequency of 16-200kHz, a sound energy density of 0.1-1.0W/mL, and a magnetic field with a magnetic field strength of 300-20000Gs, and the synergistic time is more than 1min to break the remaining sludge; The anaerobic digestion unit is anaerobic digestion of sludge in the digestion tank; the sludge dehydration unit uses centrifugal dehydration for solid-liquid separation. This method greatly reduces the energy consumption of sludge cracking, and the sludge weight is reduced by more than 80% during aerobic digestion of cracked sludge; during anaerobic digestion, the digestion time is shortened by more than 60%, the biogas production is increased by more than 35%, and the sludge weight is reduced by 30% %above. The method has obvious economic benefits and has the value of popularization and application.

Description

Ultrasonic-magnetic field coupling cracks sludge to reduce sludge

technical field

The invention belongs to the field of solid waste treatment, and relates to a method of synergistically cracking sludge by ultrasonic technology and magnetic field technology, and the sludge after cracking is returned to an aerobic biochemical tank or flows into an anaerobic digestion tank, thereby realizing sludge reduction method.

Background technique

With the development of industry and urbanization, a large amount of sewage (including domestic sewage and industrial wastewater) is discharged into the water body, causing huge pollution. Using the activated sludge process to treat sewage will produce a large amount of residual sludge while treating the sewage. It is estimated that the sewage discharge in 2010 will reach 4.40×10 ¹⁰ m ³ /d, and the amount of dry sludge generated will be 44.54 million tons. In 2020, the sewage discharge will reach 5.36×10 ¹⁰ m ³ /d, and the amount of dry sludge generated is expected to It is 45.42 million tons. Although the generation of excess sludge is usually less than 1% of the volume of treated wastewater, its treatment costs generally account for 25%-40% of the total operating costs of sewage treatment plants, even as high as 60%.

The composition of the remaining sludge is complex. It is an aggregate composed of bacteria gelatin formed by various microorganisms and the organic and inorganic substances adsorbed. In addition to containing a large amount of water (up to more than 99%), it also contains refractory organic substances, heavy metals, A small amount of pathogenic microorganisms (pathogenic bacteria, pathogens, parasites, harmful insect eggs, etc.), as well as general organic matter and plant nutrients (N, P, K), etc., will occupy a large amount of land if they are stacked arbitrarily without treatment. resources, and are perishable and smelly, and leachate is easy to pollute soil and groundwater, as well as surface water bodies such as rivers, lakes, and oceans, causing serious secondary pollution to the environment.

Traditional sludge treatment and disposal methods mainly include agricultural composting, landfill, and incineration. These three types of sludge treatment and disposal methods have their own defects. For example, the remaining sludge contains harmful substances such as heavy metals. Farmland may affect people's health due to the accumulation of harmful substances. Therefore, European and American countries have set strict standards for sludge farming. Because the sludge is still bulky even after being concentrated and dehydrated, if it is disposed of in a landfill, it will take up a lot of land and cost a lot of transportation costs, and the environment around the landfill will also deteriorate. In many countries and regions, people firmly oppose it. New landfill. Incineration was once very popular, but it is expensive and has smoke pollution problems. In addition, incineration consumes a lot of energy. Even if the technology is improved and heat energy is recovered in the incineration process, it still cannot greatly reduce energy consumption.

Sludge treatment and disposal methods have brought a heavy burden to sewage treatment due to their respective problems. Sludge treatment and disposal has developed from being only a unit of sewage treatment in the past to an important link that sewage treatment plants have to give priority to. After the harmless and resourceful stages, reduction has become the primary principle of sludge treatment. Reduction is based on the existing activated sludge treatment system, through physical, chemical, biological and other means to reduce the sludge yield, and reduce the amount of sludge discharged from the entire activated sludge system. At present, the main sludge reduction methods are: decoupling technology, high-concentration dissolved oxygen method, dissolving cell method, micro-animals to reduce the amount of biological sludge, etc. Among them, the dissolving cell method is to lyse the growing organisms, and then Participate in the metabolic process as a microbial substrate, thereby reducing the amount of sludge produced. This method is easy to implement in existing sewage treatment plants. It is only necessary to add a lysis system to the sludge treatment pipeline, which is easier to implement. Commonly used lysis treatment methods include adding ozone and ultrasonic treatment. Dosing ozone will increase the operating cost of the system and have a certain corrosion effect on the equipment. The ozone lysis process may also produce other organic pollutants. Ultrasonic treatment is a physical lysis method, and there is no problem of ozone lysis. Therefore, using ultrasonic treatment to treat excess sludge is a sludge reduction technology route with broad development prospects.

Ultrasonic cracking of sludge is to use ultrasonic waves to generate cavitation (mechanical effect, thermal effect, sonochemical effect, etc.) As a substrate for microbial growth, thereby reducing the sludge production of the system. However, due to the high energy consumption and high operating cost of ultrasonic treatment, it has not been applied in actual engineering.

Contents of the invention

The purpose of the present invention is to solve the problem of high energy consumption in ultrasonic treatment of sludge, and propose a method for economically and effectively treating sludge and realizing industrial application of ultrasonic-magnetic field coupling to crack sludge and reduce sludge.

The object of the present invention is achieved in this way: the excess sludge is mainly in the reactor equipped with ultrasonic and magnetic field devices, and the ultrasonic cavitation effect generated by ultrasonic waves and the magnetochemical effect generated by magnetic fields are organically combined to greatly strengthen the ultrasonic Cracks the effect of sludge. Because the mechanism of ultrasonic cracking sludge is to generate strong shock waves, high temperature and high pressure, accompanied by the generation of strong oxidants such as OH free radicals, which destroy the structure of sludge flocs and microbial cell walls in sludge, release intracellular substances, and become difficult Degraded solid substances are soluble substances that are easily degraded. Under the action of a magnetic field, it can effectively reduce the recombination of OH and H, increase the concentration of OH, and change the physical and chemical structure of sludge particles, thereby greatly improving the ability of ultrasonic cracking sludge. The magnetic field is generated by a permanent strong magnet, which does not consume energy and does not add any chemicals. Compared with the single ultrasonic sludge cracking process, the energy consumption is reduced by more than 30%, which greatly reduces the operating cost.

The method for decomposing sludge with ultrasonic-magnetic field coupling of the present invention to reduce sludge, the steps include:

(1) Aerobic biochemical unit: In the aerobic biochemical pool, the organic pollutants in the wastewater are removed through the aerobic digestion of microorganisms, so that the water quality is purified.

(2) Sedimentation unit: The wastewater after biochemical reaction is separated from mud and water in the sedimentation tank, and the effluent is discharged up to the standard. The sludge is divided into two parts, one part is returned to the aerobic biochemical tank as return sludge, and the microbial biomass in the biochemical tank is increased. Part of it enters the ultrasonic-magnetic field treatment device as excess sludge to be cracked.

(3) Ultrasonic-magnetic field treatment unit: Under the combined action of ultrasonic waves and magnetic fields, the microbial cells in the sludge are cracked, and intracellular substances are released, which are returned to the aerobic biochemical pool to be directly used by organisms to achieve reduction, or Enter the anaerobic digestion tank for anaerobic digestion to achieve reduction.

(4) Anaerobic digestion unit: The remaining sludge after ultrasonic-magnetic coupling cracking is anaerobically digested under the action of anaerobic and facultative bacteria in the digestion tank, and the organic compounds in the sludge are converted into methane, carbon dioxide and water , to reduce sludge.

(5) Sludge dehydration unit: The sludge stabilized by anaerobic digestion is separated from solid and liquid through a centrifugal dehydration device, the mud cake is transported outside for disposal, and the supernatant is returned to the aerobic biochemical tank for treatment.

The method of the present invention using ultrasonic-magnetic field coupling to crack sludge to reduce sludge has the following advantages and effects:

(1) Low energy consumption and low operating costs during the sludge cracking process;

(2) Cracked sludge can be directly used by aerobic microorganisms to produce recessive growth and reduce sludge;

(3) The efficiency of sludge anaerobic digestion is improved and the digestion time is shortened;

(4) Significantly increase the amount of biogas generated;

(5) reduce the residual sludge of the whole sewage treatment system;

The method of using ultrasonic-magnetic field coupling to decompose sludge to reduce sludge is an economical and effective sludge reduction technology, which can be popularized and used in water treatment process.

Description of drawings

Fig. 1 is a flow chart of the method for decomposing sludge by ultrasonic-magnetic field coupling to reduce sludge according to the present invention.

Detailed ways

The method for decomposing sludge with ultrasonic-magnetic field to reduce sludge volume of the present invention comprises an aerobic biochemical unit, a sedimentation unit, an ultrasonic-magnetic field treatment unit, anaerobic digestion unit and a sludge dehydration unit.

The aerobic biochemical unit concentrates the sludge in the wastewater aerobic biochemical pool, and transforms the organic pollutants in the wastewater into small molecular substances through the action of microorganisms in the sludge. Air is introduced into the sewage by means of aeration or stirring to increase the oxygen content in the waste water, so that the aerobic bacteria in the sludge can multiply and accelerate the degradation of organic pollutants.

The sedimentation unit is to separate the sludge and water from the biochemically treated wastewater in the sedimentation tank. After 1-2 hours of precipitation, the supernatant can reach the standard discharge. After sedimentation, part of the sludge is return sludge, which is returned to the aerobic biochemical unit to supplement the microbial biomass in the biochemical tank and improve the efficiency of wastewater treatment. Usually, the sludge return ratio (that is, the ratio of the return sludge to the influent volume) is 50-400%; the other part is the remaining sludge, which enters the ultrasonic-magnetic field treatment unit for cracking.

The ultrasonic-magnetic field processing unit utilizes the synergistic effect of ultrasonic waves and magnetic fields to decompose sludge. The frequency range of ultrasonic waves is 16-200kHz, the sound energy density is 0.1-1.0W/mL, and the action time is more than 1min. The tiny bubble nuclei in the sludge liquid are intensified under the action of ultrasonic waves, showing the growth of bubble nuclei , Oscillation, contraction and bursting and a series of dynamic processes. Instantaneous high temperature (up to 5000°C), high pressure (up to 500bar) and micro-jet with strong impact will be generated in the tiny environment where the bubbles are broken, and a large number of strong oxidants such as OH free radicals will be generated. Under these actions, the cell wall is crushed, the cell ruptures, and the intracellular material is released. This provides favorable conditions for aerobic decomposition or anaerobic digestion of sludge, increases the reaction rate and reduces the reaction time. At the same time, a magnetic field is applied, the magnetic field strength is 300-20000Gs, the chemical effect of the magnetic field is used to change the physical and chemical structure of the sludge particles, prevent or reduce the recombination of OH and H free radical pairs generated by ultrasonic cavitation, and strengthen the ultrasonic cracking of sludge The effect of ultrasonic treatment reduces the energy consumption of ultrasonic treatment, and the dissolution rate of sludge SCOD (dissolved chemical oxygen demand) reaches more than 70%.

The sludge cracked by the ultrasonic-magnetic field treatment unit can have two destinations. One destination is to enter the aerobic biochemical tank through reflux. After the sludge cracked by the ultrasonic-magnetic field, the floc structure is destroyed, and the microbial cell wall is broken. The intracellular substances are released to provide a substrate for the invisible growth of microorganisms, reducing the amount of residual sludge discharged from the system by more than 80%. Another destination is to flow into the anaerobic digestion tank. After the sludge is cracked by the ultrasonic-magnetic field, the intracellular substances released by the microbial cells provide a carbon source for the anaerobic digestion reaction, and the easily degradable dissolved substances increase, overcoming the pollution. The limiting factor of the anaerobic digestion reaction of mud can speed up the digestion process, effectively shorten the digestion residence time, reduce the volume of the sludge digester, shorten the digestion residence time by more than 60%, reduce the volume of the sludge digester by more than 60%, and reduce the biogas per unit time The output is increased by more than 35%, and the digested sludge is reduced by more than 30%.

The anaerobic digestion unit uses facultative bacteria and anaerobic bacteria to anaerobically digest the remaining sludge flowing out of the sedimentation tank, decomposes the organic matter in the sludge, converts the organic matter into non-polluting small molecular substances, and recovers biogas , Realize sludge reduction and recycling. The present invention adopts the anaerobic digestion method, and the sludge contains effective microorganisms required for digestion, so no additional addition is required, and only the microorganisms need to be cultivated and domesticated in an anoxic or hypoxic environment.

The sludge dewatering unit uses a centrifugal dehydrator to separate mud and water. According to the density difference between the sludge particles and water, a centrifugal force difference is generated in the centrifugal dehydrator to separate the sludge particles from the water to achieve the purpose of dehydration. The supernatant returns to the aerobic biochemical tank through the pipeline, and the dehydrated mud cake It has been stabilized and can be applied to farmland as organic fertilizer.

Claims (5)

1. make the method for sludge reduction with ultrasonic-magnetic field coupling breaking sludge, its step comprises:

(1) aerobic biochemical unit: in the aerobic biochemical pond, the organic pollutant by in the aerobic sigestion removal waste water of microorganism is purified water quality;

(2) precipitation unit: in settling tank, carry out mud-water separation through the waste water behind the biochemical reaction, the water outlet qualified discharge, mud is divided into two portions, and a part is back to the aerobic biochemical pond as returned sluge, increase microbial biomass in the biochemistry pool, return sludge ratio is 50-400%; Another part enters ultrasonic-magnetic field treatment device and cracks as excess sludge;

(3) ultrasonic-magnetic field treatment unit: mud is under the combined action in ultrasonic wave and magnetic field, microorganism cells is cracked in the mud, discharge intracellular organic matter, be back to the aerobic biochemical pond and directly utilized the realization minimizing, perhaps enter anaerobic digestor and carry out anaerobic digestion realization minimizing by biology;

(4) anaerobic digestion unit: carry out anaerobic digestion under the effect of the excess sludge after ultrasonic-magnetic field coupling cracks anerobe and amphimicrobe in digester, the organic compound in the mud changes methane, carbonic acid gas and water into, makes sludge reduction;

(5) sludge dewatering unit: the mud through the anaerobic digestion stabilization carries out solid-liquid separation by centrifugal dehumidifier, and the mud cake outward transport is disposed, and supernatant liquor is back to the aerobic biochemical pond and handles.

2. usefulness according to claim 1 is ultrasonic-and magnetic field coupling breaking sludge makes the method for mud decrement, it is characterized in that hyperacoustic optimal selection scope ultrasonic frequency is 20-100kHz, acoustic density is 0.1-0.6W/mL, magneticstrength is 400-10000Gs, and ultrasonic-magnetic field synergy time is more than 2min.

3. usefulness according to claim 1 is ultrasonic-and magnetic field coupling breaking sludge makes the method for mud decrement, it is characterized in that adopting any mode in various electromechanical type or the mechanical type to produce ultrasonic wave.

4. usefulness according to claim 1 is ultrasonic-and magnetic field coupling breaking sludge makes the method for mud decrement, it is characterized in that magnetic field is stabilizing magnetic field, adopts permanent strong magnet to produce.

5. usefulness according to claim 1 is ultrasonic-and magnetic field coupling breaking sludge makes the method for mud decrement, it is characterized in that breaking sludge is back to the aerobic biochemical pond and is directly utilized by biology and realize that minimizing is that ultrasonic-magnetic field treatment device is connected with the aerobic biochemical pond, breaking sludge enters anaerobic digestor, and to carry out anaerobic digestion realization minimizing be that ultrasonic-magnetic field treatment device is connected with anaerobic digestor.

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