JPS6242799Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention removes solids present in wastewater (hereinafter simply referred to as wastewater) after microbial treatment of wastewater such as activated sludge using a particle group with a specific gravity lighter than water as a material, and the solids that are captured by the material. The present invention relates to a device that regenerates layers by treating solids in wastewater without using washing water. Generally, when over-separating solids in wastewater,
A layer is formed using a group of particles such as sand and anthracite that have a specific gravity greater than the specific gravity of the wastewater, and the wastewater is passed downward, upward, or horizontally to capture and remove solids within the layer. are doing. In such cases, when the pressure loss increases due to solids trapped in the bed, the supply of wastewater to the bed and the outflow of treated water from the bed are stopped, and water or air and water are allowed to flow in from the bottom of the bed. This causes the bed to expand and particles to collide and mix, thereby discharging trapped solids and cleaning the bed. The cleaning wastewater produced by this cleaning operation requires separate treatment equipment or the like to remove solids contained in the cleaning wastewater. These equipment costs can be so large that they account for approximately 50% of the total cost of the filtration equipment, and when considering the treatment of washing wastewater, including the disposal of the solids contained in the wastewater, the cost of water treatment is much lower. occupied a large proportion of the top. In particular, this trend showed that the smaller the water treatment capacity, the more limited the treatment and disposal methods, and the more significant the cost increase. Generally, microbial treatment such as activated sludge method and
Solids present in wastewater that has been treated using a sprinkler bed or rotating disk method can be separated by simple sedimentation in a sedimentation tank, or in some cases, a coagulant can be added to separate the solids by coagulation. After these treatments, the wastewater is fed to a general filtration device to remove fine solids remaining in the wastewater. The solids trapped in the layer by this method are contained in the wastewater generated by cleaning the layer by the method described above, and the wastewater containing these solids is subject to the sedimentation described above. Although it is easy to separate solids and wastewater by returning them to a tank, the amount of sludge generated does not decrease, and generally accounts for 40 to 80% of the amount of BOD flowing into the microbial treatment equipment. It is said to be equivalent to In order to dispose of such sludge separately, it is necessary to install new equipment. Furthermore, since these sludges are mainly composed of organic solids, they have a poor concentration rate compared to inorganic solids, resulting in large sludge volumes, and are compressible, making dewatering extremely difficult. It had the following drawbacks. As a method for solving the above-mentioned problems, the applicant of the present invention previously proposed the method of JP-A No. 56-33013 (hereinafter referred to as the prior invention). That is, particles having a specific gravity smaller than the specific gravity of the waste water are used as the material, and the upper end opening of the draft tube is located below the upper surface of the layer formed by the particles floating and formed by the water-permeable retaining plate provided at the upper part of the filtration device. When the wastewater is passed through the filtration device and the pressure loss in the bed becomes large, the flow of wastewater is stopped and air is blown out from below the draft tube to create a circulation flow in the bed and remove the solids in the wastewater. He proposed a method to remove the object. However, in the prior invention, the circulating flow does not pass water through the holding plate, so in large equipment, the entire layer does not expand uniformly, resulting in a shot pass, and the circulating flow occurs only near the draft tube, making it impossible to effectively clean the layer. There are cases. In addition, since the floating particles circulate through the draft tube, the air introduced into the draft tube creates a pressure difference in this area while passing through the buoyant particle layer and the holding plate. Requires large back pressure. Furthermore, floating particles may block the clearance between the holding plate and the upper end of the draft tube, which may prevent particles from circulating through the draft tube, or may cause uneven flow or shot passes in the circulating water. Therefore, in the prior invention, it was not always possible to effectively clean the layer in some cases. In addition, in the prior invention, the main purpose is to expand the buoyant particle layer that has been formed and peel off the solid matter attached to the particles by colliding with each other. This method involves sedimentation and separation, followed by extraction. Therefore, after stopping the blowing of air, it is necessary for the separated solids to settle and separate at the bottom of the device by allowing the device to stand still for a predetermined period of time, and then to be extracted from the device, and the discharged solids must be treated separately. It was necessary to do it. The inventors of the present invention conducted various studies to further improve the above-mentioned problems, and as a result, they discovered an excellent device that does not have these problems. In other words, the present invention places the drainage inlet at the bottom of the device.
An outlet for the treated water is provided at the top of the device, and a water-permeable retaining plate made of particles having a specific gravity smaller than the specific gravity of the waste water and preventing the particles from floating or flowing out is provided at the top of the device. A nozzle that includes vertical draft tubes each having an opening with an upper end protruding above the holding plate and a lower end protruding below the layer formed by the particle group, and air is ejected upward below the draft tube. The present invention provides an apparatus for removing solid matter from microbially treated water. The device of the present invention not only filters wastewater containing solids that has been treated with microorganisms, but also removes solids in the layer without using washing water when the pressure loss in the layer becomes large. By regenerating the layer and subjecting the organic solids in the solids to aerobic digestion, the amount of solids discharged is greatly reduced. The device of the present invention uses particles having a specific gravity smaller than the specific gravity of wastewater as a material, and the particles float to a layer formed under a water-permeable retaining plate provided at the top of the device, with the upper end being higher than the retaining plate. The waste water is passed in an upward flow from the lower part of the filtration device, which is equipped with draft tubes that protrude upward and have draft tubes whose lower ends protrude below the layer and open respectively, to filter the solid content in the waste water, and the treated water is passed through the device. When the pressure loss in the layer increases due to the solids extracted from the upper part and trapped in the layer, the flow of wastewater is stopped and the liquid level in the layer is maintained near the upper end of the draft tube, and the liquid level is kept below the draft tube. Air is ejected from the tube to form a circular flow of upward flow of water due to the rise of air bubbles in the tube and downward flow of water in the layer, thereby expanding the layer and removing the solids trapped within the layer. This is an apparatus for removing solids from microbial-treated water, which performs removal and cleaning of solids attached to the surface of particles, and reduces organic solids by aerobic digestion using dissolved oxygen. That is, a layer is formed using the device of the present invention, and wastewater that has been subjected to microbial treatment is passed through the layer in an upward flow to overseparate the solids in the wastewater, and the solids trapped in the layer are By introducing air into the draft tube installed in the filtration device to create a downward flow in the bed and expand the bed, without introducing new water for washing when the specified pressure loss is reached due to the material. The method is characterized in that solids trapped in the bed are removed, and organic solids among the solids are subjected to aerobic digestion to reduce the amount of sludge generated. In order to pass through the solid matter present in the wastewater in the device of this invention, particles lighter than water are placed under the water-permeable retaining plate made of grids, perforations, wire mesh, etc. under the water surface in the device. This layer is used to form a layer, and the wastewater is passed through this layer in an upward flow.
In this case, the particles are brought close to each other by buoyancy and form a layer under the holding plate, resulting in excessive separation of solids in the waste water. In addition, since the wastewater contains microorganisms, a microbial film is formed on the surface of the material particles over time, and residual BOD can be treated by dissolved oxygen in the wastewater. At the same time, the cells of the organic solids trapped within the layer are reduced due to basic biological metabolism, and the increase in pressure loss within the layer becomes gradual, allowing for long-term overtreatment. Cleaning of the bed becomes necessary when the pressure drop within the bed increases with continued overtreatment. In general, in conventional cleaning methods, these fluids are introduced into the bottom of the bed, either alone or in combination with air, to expand the material and cause particles to collide with each other to remove solids trapped in the bed. It was peeled off and discharged with washing water. This resulted in a large amount of cleaning wastewater, which needed to be treated. In the device of the present invention, air is introduced into the filter device under the draft tube to create an upward flow in the draft tube and a downward flow in the layer section, thereby forming a circulating flow of water in the device. , the bed is expanded by a downward flow from the top to the bottom of the bed without using new wash water, and solids trapped in the bed are released;
The system also removes solid matter adhering to the particle surface, and by introducing air, a liquid with a high dissolved oxygen concentration is circulated within the device to remove organic solids from the solid matter. The sludge is aerobically digested in the equipment, greatly reducing the amount of sludge generated. When the aerobic digestion of the sludge is completed, the supply of air into the draft tube is stopped to stop the circulating flow, and the solids remaining in the circulating flow are allowed to settle to the bottom of the device, allowing the circulating flow to continue. The material particles, which had expanded due to the heat, float again and form a layer under the water-permeable retaining plate installed above. The solid matter that has settled and accumulated at the bottom is extracted from the device using a pump or the like as appropriate and returned to the microbial treatment device, which is a pretreatment device. In some cases, it may be extracted and stored in a sludge tank or the like outside the system. As is clear from the above explanation, in the device of the present invention, solid matter is trapped in the layer, and when cleaning the layer, the treated water outlet is stopped, and when the water level reaches near the upper end of the draft tube, the inflow from the drain inlet is stopped. All you have to do is stop the air flow and start feeding air into the draft tube inside the device, and there is no need for water for washing during washing in the conventional filtering device, and there is no need for incidental equipment to treat the washing water. come. At the same time, the captured solids are reduced through aerobic digestion, so the amount of sludge is also reduced. Particles used to form the layer in the present invention are suitable if they have an apparent specific gravity of 1.0 or less and do not absorb water even if they exist in water. Natural materials such as perlite and shirasu balloons, which are generally used as lightweight aggregates, and artificial materials such as plastics and foamed plastics with a specific gravity of 1.0 or less are used. Among these, foamed plastics are most desirable as they allow arbitrary selection of specific gravity, shape, uniformity coefficient, etc. In particular, it is possible to arbitrarily change the specific gravity of foamed plastics by adding one or more inorganic substances such as calcium carbonate, barium sulfate, and magnesium oxide as fillers during their manufacture, and they also have good microbial adhesion. It is extremely desirable because it has high particle strength, can be used semi-permanently, and is inexpensive. For filter layers that use particles with a specific gravity of 1.0 or more, a water-permeable retaining plate is provided at the bottom of the filter layer, so if solid matter becomes trapped in the filter layer and the pressure loss becomes large, the wastewater will flow to other parts. As a result, the flow velocity locally increases and the materials forming the layer move, making it easy for trapped solids to flow out, leading to deterioration in the quality of treated water. This does not happen with particles with a specific gravity of 1.0 or less because a water-permeable retaining plate is provided on the top.
The representative diameter of the particles used in this device is preferably in the range of 1 to 20 mm, taking into account the formation of a microbial film on the surface. The device of the present invention must have an inlet for wastewater at the bottom of the device, an outlet for treated water at the top of the device, and a filtration device using buoyant particles as a layer with a draft tube having an air inlet. The upper end of this draft tube is located above the water-permeable retaining plate that prevents the layer from floating and near the water level of the drainage inlet.The opening at the lower end of the draft tube is located at least 1/3 of the layer thickness from the bottom layer during over-operation. Preferably located at the bottom. It is desirable that the air supply position be provided directly below the opening at the lower end of the draft tube. Further, the area of the draft tube used is equivalent to 1/100 to 1/3 of the cross-sectional area of the layer. It is necessary that the amount of air introduced is such that the buoyant particles do not expand too much and the particles do not flow into the draft tube from the lower end of the draft tube. Next, in order to efficiently remove solids from wastewater, the device of the present invention is equipped with a plurality of the above-mentioned filtration devices.
While the above group is being overtreated, the remaining group is being washed and aerobically digested, and solids in the wastewater can be continuously removed by alternating between the two operations. . For example, 3
Two of these units are connected in series for overtreatment, and the remaining unit is used for layer cleaning and aerobic digestion to continuously treat wastewater and perform filtration. If the pressure loss of the equipment on the upstream side increases, it will be switched from over-operation to cleaning and aerobic digestion, while other equipment that has finished cleaning and aerobic digestion will be switched to the subsequent filtration equipment and continuously operated. Solids can be removed from wastewater. In addition, after microbial treatment of wastewater is performed by the microbial treatment device in the first stage using a device that combines a microbial treatment device such as activated sludge treatment and the filtration device of the present invention, the treated water is treated to remove the solids contained therein. The solid content can be filtered by directly passing it through a subsequent filtration device without performing sedimentation separation. Further, a microbial treatment device is installed in the first stage and two or more filtration devices of the present invention are installed in the second stage, and the waste water is produced by connecting the outlet of the treated water discharged from the first stage microbial treatment device and the waste water intake of the second stage filtration device. After the wastewater is subjected to microbial treatment by the first-stage microbial treatment device using the treatment device, the treated water is directly passed through at least one of the second-stage filtration devices without performing sedimentation separation of solids contained therein. When the pressure drop in the bed increases due to the solids trapped in the bed, the waste water to the filter device is switched to flow to the remaining filter device, and the filtration continues. At the same time, air is blown into the draft tube of the above-mentioned filtration device, which has stopped the inflow and outflow, to clean the layer to remove and peel off the solids trapped in the layer, and to aerobically digest the organic solids. After completing this treatment, the device is used again for over-operation, and thus the wastewater can be continuously treated by sequentially or alternately switching the filtration device to filtration, bed washing, and aerobic digestion treatment. ,
As a result, it is possible to omit the sedimentation and separation device for solid matter provided in general microbial treatment, thereby saving land for wastewater treatment equipment and making the equipment more compact. Next, the present invention will be explained based on the drawings.
FIG. 1 illustrates overoperation in the apparatus for removing solids from wastewater according to the present invention. FIG. 2 shows the layer cleaning and aerobic digestion operations of the present invention. Moreover, FIG. 3 shows the situation when the residual solid content is sedimented and separated after the cleaning and aerobic digestion operations are completed, and the settled sludge is returned to the microbial treatment device which is a pretreatment device. In the over-operation shown in Fig. 1, waste water is caused to flow into the filter device through the waste water inlet 1 using the water level difference from the microbial treatment device provided as a pre-treatment device, and the packed bed 7 of buoyant particles is raised. The treated water is extracted from the treated water outlet 2 while being passed in a countercurrent flow. As the wastewater flows through the packed bed 7, solids present in the wastewater are captured and removed within the bed. As the solids in the wastewater are captured in the layer, the pressure loss in the layer increases, and the water level gradually rises until it reaches the top of the draft tube.
Then, when the water level in the device reaches the vicinity of the upper end of the draft tube, the inflow from the drain inlet 1 is stopped. Thereafter, as shown in FIG. 2, air is introduced into the draft tube from the air inflow pipe 3 provided at the bottom of the draft tube 5, and the layer cleaning operation is started. The air introduced from the nozzle of the air inflow pipe 3 rises in the draft tube 5, causing an air lift phenomenon, and flows in the draft tube 5 in an upward flow and in the outer layer part in a downward flow. Form a circulating flow of water. The layer is expanded by the downward flow flowing through the layer, and solids trapped within the layer are removed.
In addition, solid matter adhering to the particle surface is peeled off due to the collision between the particles. At the same time, organic solids attached to the particles and organic components present in the circulating water are aerobically digested using dissolved oxygen in the water, thereby reducing organic sludge. After the aerobic treatment is sufficiently completed, as shown in Figure 3, the inflow of air from the air inflow pipe 3 is stopped, the particles are floated again to form a layer, and the remaining solids are sent to the bottom of the device. Let it settle.
The sludge settled at the bottom is returned to the microbial treatment device installed as a pretreatment device or taken out of the system through the sludge extraction pipe 4 using a pump or the like. Thereafter, the outflow of treated water from the treated water outlet 2 and the inflow of waste water from the drainage inlet 1 are restarted, respectively, and normal over-operation is started. FIG. 4 is a diagram showing an example of an integrated device that combines a microbial treatment device and the filtration device of the present invention. The center of the figure is a square-shaped microbial treatment device, and the ones on the left and right are square-shaped filtration devices. The wastewater is led to the microbial treatment device No. 11, where it is subjected to aerobic oxidation treatment by active microorganisms, and the treated wastewater is sent to the wastewater inlet No. 1.
The water is introduced into the filtration device on the right side, flows upward through the packed bed 7 of floating particles, and is extracted from the treated water outlet 2. As the waste water flows through this layer 7, solids present in the waste water are trapped within the layer and removed. As the solids in the wastewater are captured in the layer, the pressure loss in the layer increases, and the water level at the drain inlet gradually rises until it reaches near the water level of the microbial treatment device, when the treated water outlet 2 is stopped, and then When the water level in the filtration device becomes the same as the water level in the microbial treatment device, the inflow from the waste water inlet 1 is stopped and cleaning and aerobic digestion are performed (as shown on the left side of FIG. 4). In other words, the filtration device on the left is in the process of cleaning and aerobic digestion, with the waste water inlet 1 and the treated water outlet 2 closed, and air being fed through the air inlet pipe 3 provided at the bottom of the draft tube 5. A cleaning operation is being carried out on the layer. The air introduced from the air supply pipe flows upward in the draft tube 5.
In addition, a circulating flow of water flowing downward through the outer layer is formed, which expands the layer and removes the solids trapped within the layer and peels off the solids attached to the particles. Organic solids are aerobically digested using dissolved oxygen in wastewater to reduce organic sludge. After the above-mentioned cleaning and aerobic digestion processes are sufficiently completed, the supply of air from the air supply pipe 3 is stopped, and the particles are floated again to form a layer, and the remaining solid content is allowed to settle to the bottom of the device. let The sludge settled at the bottom is returned to the central microbial treatment device or other treatment device through the sludge extraction pipe 4 using a pump or the like. This post-treated water outlet 2
The outflow of the treated water and the inflow of wastewater from the wastewater inlet 1 are restarted to carry out the filtration again. As described above,
The solid components contained in the wastewater treated with the microbial treatment equipment are not separated by the sedimentation separation tank, but are directly guided to the filtration tank for overtreatment. Cleaning and aerobic digestion are performed at the same time, and solids in wastewater can be continuously treated by alternately switching between the two treatments. Next, examples of the present invention will be described, but these examples do not limit the present invention. Company A cafeteria wastewater was pretreated using a microbial treatment device using granular carriers, and then the wastewater was treated using the filtration device shown in FIG.
The main device dimensions and experimental conditions used in this experiment are as follows. Microbial treatment equipment 370mmW x 550mmL x 600mmD Reaction section volume 60 370mmW x 400mmL x 420mmD Carrier particles used Foamed polypropylene particles added with 20wt% calcium carbonate 3.5mmφ x 4.0mmL Particle density 0.82g/cm ³ Amount used 26 Draft tube 50mmW x 370mmL x 500mmD Inflow air amount 60N/min Filtration device 100mmφ×3500mmH Bed volume 11.5 100mmφ×1500mmH Carrier particles used Properties are the same amount as the carrier particles used in the microbial treatment device 11.5 Draft tube 25mmφ×3000mmH Water flow rate Average 23.6/hr The above microbial treatment device Table 1 shows the properties of the wastewater (super raw water) obtained by treating wastewater using the filtration device and the treated water treated by the filtration device of the present invention. After 284 hours had passed since the filtration device started operating, when the differential pressure in the superlayer reached 87 cmAq, the filtration was stopped and air at 3.1N/min was sent to the draft tube of the filtration device to clean the layer and perform aerobic digestion. I did it.
Table 2 shows the change in water quality within the apparatus over time in this case. It can be seen that SS and COD are reduced to about 1/4 after 284 hours of circulation. After 284 hours, the properties of the liquid in the apparatus after standing for 2 hours are shown in Table 3. The amount of solid matter deposited at the bottom of the device was approximately 1.4.

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【table】 [Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of over-operation of the over-operation device used in the present invention. FIG. 2 is an explanatory diagram of the cleaning and aerobic digestion operations of the filtration apparatus used in the present invention. FIG. 3 is an explanatory diagram of the situation when the settled sludge after completion of the cleaning and aerobic digestion operations of the filtration device used in the present invention is returned to the microbial treatment device which is the pretreatment device. FIG. 4 is an explanatory diagram of an apparatus in which a microbial treatment apparatus and a filtration apparatus are combined and integrated. 1... Drainage inlet; 2... Treated water outlet; 3... Air introduction pipe; 4... Sludge withdrawal pipe; 5... Draft tube; 6... Water-permeable retaining plate; 7... Layer; 11
...Wastewater inlet.

Claims (1)

[Scope of utility model registration request] An inlet for wastewater is provided at the bottom of the device, an outlet for treated water is provided at the top of the device, and a water-permeable retaining plate made of particles having a specific gravity smaller than the specific gravity of the wastewater is installed at the top of the device to prevent the particles from floating or flowing out. the holding plate has an upper end protruding above the retaining plate;
Vertical draft tubes each having an opening with their lower ends protruding below the layer formed by the particle groups are provided, and solids in the microbially treated water are removed by having nozzles below the draft tubes for blowing air upward. device to do.