Watering and biological filtration methods

Abstract

To provide a water sprinkling biofiltration method that enhances removal effect of organic substances and suspended matters in water to be treated while saving an energy cost.SOLUTION: A water sprinkling biofiltration apparatus 100 includes a filter bed 104 filled with a filter material 103, a sprinkling unit 108 of water to be treated arranged above the filter bed, and an outflow unit 136 of treated water arranged below the filter bed. A storage unit 105 is installed for storing the water to be treated that is sprinkled from the sprinkling unit and flows down in the filter bed toward the lower part of and below the filter bed. A section of the filter bed that is not immersed with water in the storage unit is a water-sprinkled filter bed 106 in which the water to be treated sprinkled from the sprinkling unit flows down. A section of the filter bed that is immersed with water in the storage unit is a biofiltration unit 107. Air circulating means 109 is installed for circulating air into the water-sprinkled filter bed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a trickling and biological filtration method used to remove organic matter and suspended solids from water to be treated, for example in sewage treatment plants. [Background technology]

[0002] A trickling filter bed type water treatment device has a water tank with a filter media layer filled with filter media, and the water to be treated is trickled over the filter media layer from above. As the water passes through the filter media layer, organic matter and suspended solids contained in the water to be treated are removed by the decomposition of organic matter by microorganisms attached to the surface of the filter media in the filter media layer and by the capture of floating suspended solids by the filter media layer.

[0003] Trickling filter type water treatment equipment is an energy-saving type of water treatment equipment that does not require aeration, but the quality of the treated water is roughly the same as that of the activated sludge method, leaving room for further improvement in treatability.

[0004] In order to address this problem, Patent Document 1 below discloses a water treatment device that treats water to be treated, which has: a trickling filter bed tank equipped with a sprinkling means for the water to be treated, a filter media layer, an outlet for primary treated water, and a gas inlet; a biological treatment tank equipped with an inlet for primary treated water, an outlet for secondary treated water, a supply means for oxygen-containing gas, and a gas outlet; and a connecting member between the gas inlet of the trickling filter bed tank and the gas outlet of the biological treatment tank; and has a region inside the filter media layer where the flow direction of the water to be treated passing through the filter media layer is countercurrent to the flow direction of the gas discharged from the biological treatment tank and flowing into the trickling filter bed tank. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2018-69183 Summary of the Invention [Problem to be solved by the invention]

[0006] According to the method described in Patent Document 1, it is believed that organic matter in the treated water can be more effectively decomposed and removed by passing the water that has passed through the trickling filter tank further through a biological treatment tank where aeration is performed.

[0007] However, there is a problem in that the decomposition of organic matter by aeration in the biological treatment tank requires high energy costs.

[0008] Therefore, an object of the present invention is to provide a trickling and biological filtration method that can reduce energy costs while increasing the effect of removing organic matter and suspended solids from the water to be treated. [Means for solving the problem]

[0009] In order to achieve the above object, the trickling and biological filtration method of the present invention comprises the steps of: A filter bed filled with a filter medium; A water sprinkler unit for the water to be treated arranged above the filter bed; and a treated water outlet located below the filter bed, A storage section is provided below and below the filter bed, in which the water to be treated sprayed from the spray section flows down through the filter bed and accumulates therein, A portion of the filter bed that is not immersed in the water of the storage portion forms a trickling filter bed through which the water to be treated sprinkled from the sprinkling portion flows down, The portion of the filter bed that is immersed in the water of the storage portion forms a biological filtration portion, An air circulation means for circulating air inside the trickling filter is provided, A water sprinkling and biological filtration device is used, in which an aeration means is provided under the biological filtration section and an outlet for washing wastewater is provided under the filter bed, A normal operation in which the water to be treated is sprinkled from the sprinkling section to the upper part of the trickling filter while air is circulated through the trickling filter by the air circulation means, the water to be treated passes through the trickling filter and the biological filtration section, and is retained in the storage section for a predetermined time, and then is taken out from the outflow section; aeration cleaning including a water filling step in which the treated water outlet and the washing wastewater outlet are closed, the air circulation means is stopped, and the filter bed is filled with water until the entire filter bed is submerged, an aeration cleaning step in which air is supplied from the aeration means to flow-clean the filter media packed in the filter bed, and a drainage step in which the washing wastewater outlet is opened and the washing wastewater is drained, is alternately performed at a predetermined timing; During the aeration cleaning step, the aeration amount is adjusted so that the filter media located in the biological filtration section is dispersed throughout the entire filter bed with the biofilm attached to its surface. Effect of the Invention

[0010] According to the present invention, the lower part of the filter bed is immersed in the water of the storage section to provide a biological filtration section, so that the dissolved oxygen contained in the water that has passed through the trickling filter bed is utilized to decompose organic matter and nitrify ammonia by microorganisms in the biological filtration section. The biological filtration section also enhances the effect of removing suspended solids (hereinafter abbreviated as "SS"). Therefore, since decomposition of organic matter, nitrification of ammonia, and removal of SS are performed in both the trickling filter bed and the biological filtration section, more purified treated water can be obtained.

[0011] During the aeration cleaning, the water filling step, the aeration cleaning step, and the drainage step are performed to remove excess sludge adhering to the filter media and maintain the treatment performance. At this time, a biofilm of microorganisms that decompose organic matter such as proteins and microorganisms that nitrify ammonia produced by protein decomposition is formed on the filter media in the biological filtration section. This filter media is spread over the entire filter bed by adjusting the aeration volume of the flow cleaning. This appropriately reduces the amount of excess biofilm in the biological filtration section while increasing the amount of biofilm in the trickling filter bed, thereby promoting the decomposition of organic matter and the nitrification of ammonia in the entire filter bed. During this flow cleaning, the old biofilm in the filter bed can also be discharged.

[0012] In addition, by adjusting the washing conditions to a weaker flow rate as in this method, compared to conventional washing methods that only aimed to remove excess biofilm, it is possible to reduce the electricity costs for aeration. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing a water sprinkling and biological filtration device applied to one embodiment of a water sprinkling and biological filtration method according to the present invention. [Diagram 2] FIG. 2 is an explanatory diagram showing a cleaning step in one embodiment of the trickling and biological filtration method according to the present invention. [Diagram 3] 1 is a schematic diagram showing a water trickling and biological filtration device applied to another embodiment of the water trickling and biological filtration method according to the present invention. FIG. [Figure 4] 1 is a schematic diagram showing an embodiment of a sewage treatment device to which a trickling and biological filtration device according to the present invention is applied. [Diagram 5] FIG. 2 is an explanatory diagram showing a schematic configuration of a sewage treatment device used in a test example. [Figure 6] 1 is a graph showing the daily change in sludge adhesion rate in a test example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLES

[0014] Hereinafter, an embodiment of a water trickling and biological filtration method according to the present invention will be described with reference to the drawings.

[0015] FIG. 1 shows a water sprinkling / biological filtration device applied to one embodiment of the water sprinkling / biological filtration method according to the present invention. This water sprinkling / biological filtration device 100 has a filtration tank 101 into which water to be treated is sprinkled from above. A perforated plate 102 is arranged at the bottom of the filtration tank 101, and a number of filter media 103 are layered on the perforated plate 102 to form a filter bed 104. The filter media 103 is not particularly limited, but may be made of, for example, resin such as polyurethane or polypropylene, ceramics, stone, or the like. As a preferred example, resin formed into a cylindrical shape with both ends open may be used.

[0016] A reservoir 105 for water that has passed through a filter bed 104 is provided at the bottom of the filtration tank 101. The lower portion of the filter bed 104 is immersed in the water of the reservoir 105, and the filter bed 104 is divided into a trickling filter bed 106 that is not immersed in water, and a biological filtration section 107 that is immersed in water.

[0017] A sprinkling section 108 consisting of, for example, a number of sprinkling pipes extending radially from the rotation axis is disposed above the filtration tank 101, so that the water to be treated is sprinkled onto the upper surface of the trickling filter bed 106. A supply pipe 135 for the water to be treated is connected to the sprinkling section 108, and a flowmeter 137 is attached midway along the supply pipe 135 so that the amount of water to be treated supplied can be measured over time.

[0018] An air circulation means 109 is provided below the trickling filter bed 106, which draws out the air inside the filtration tank 101 and circulates outside air through the trickling filter bed 106. Therefore, air circulates inside the trickling filter bed 106, and the air comes into contact with the water to be treated passing through the trickling filter bed 106, thereby increasing the dissolved oxygen concentration of the water to be treated.

[0019] The storage unit 105 is connected to an adjustment tank 111 via a communication unit 110. The water level in the storage unit 105 and the water level in the adjustment tank 111 are the same according to Pascal's principle. Therefore, even if the water level in either tank changes, the water is moved so that they eventually reach the same water level.

[0020] A first pump 112 is provided in the adjustment tank 111, and the treated water is sent to the next treatment process by the first pump 112. In addition, a level gauge 113 for measuring the height of the water surface is attached to the adjustment tank 111, and the measured water surface height is transmitted to a control device 114.

[0021] The control device 114 determines the water level of the filtration tank 101 based on the water level measured by the level gauge 113, and when the water level of the filtration tank 101 falls outside a predetermined range, it sends an operation signal to the first pump 112 to control the outflow of water from the adjustment tank 111, thereby controlling the water level of the filtration tank 101 to be maintained within the predetermined range. The height direction length of the biological filtration section 107 is set according to the water level of the filtration tank 101.

[0022] The water sprinkler / biological filtration device 100 has a blower 120. An aeration pipe 122 is connected to the blower 120 via a valve 121, and the aeration pipe 122 is inserted into the lowest part of the biological filtration section 107 of the filtration tank 101 and arranged above the porous plate 102. The aeration pipe 122 may be arranged below or below the biological filtration section 107, and may be arranged below the porous plate 102, for example. In this embodiment, the blower 120, the valve 121, and the aeration pipe 122 constitute the aeration means of the present invention. When organisms such as microorganisms or flies or suspended particles adhere to the filter media 103 in the filter bed 104, causing an increase in the resistance of the water to be treated to pass through, the communication part 110 is closed by a valve or partition plate (not shown), water is stored in the filtration tank 101 so that the filter media 103 in the trickling filter bed 106 is also immersed in the water, and the blower 120 is operated to spray air from the aeration pipe 122, thereby agitating and cleaning the filter media 103.

[0023] A discharge pipe 136 for discharging water from the storage section 105 is connected to the bottom of the filtration tank 101, and the water from the storage section 105 can be discharged by a second pump 115 connected to the discharge pipe 136. Washing wastewater containing sludge peeled off from the surface of the filter medium 103 by agitation washing can be taken out through the discharge pipe 136 by the second pump 115. The part of the bottom of the filtration tank 101 to which the discharge pipe 136 is connected forms the outflow section for the washing wastewater in the present invention. The outflow section for the washing wastewater is not limited to the bottom of the filtration tank 101, but may be located below the filter bed 104.

[0024] In addition, a return path 117 is connected to the middle of discharge pipe 136 via three-way valve 116, and the tip of return path 117 is connected to supply pipe 135, so that the water in storage section 105 can be circulated to spray section 108 via return path 117 and supply pipe 135. In this embodiment, three-way valve 116 and return path 117 constitute the circulation means of the present invention.

[0025] A dissolved oxygen meter 118 is attached to the storage section 105 of the filtration tank 101, so that the dissolved oxygen concentration of the water in the storage section 105 can be measured. The dissolved oxygen concentration measured by the dissolved oxygen meter 118 is sent to the circulation amount control device 119, and when the dissolved oxygen concentration of the water in the storage section 105 becomes lower than a predetermined value, the circulation amount control device 119 sends a signal to the second pump 115 and the three-way valve 116 to send the water in the storage section 105 to the trickling section 108 through the return line 117, so that the water is circulated to the trickling filter bed 106. It is preferable that the dissolved oxygen meter 118 is attached, but there is no problem if it is not attached. By carrying out an experiment in which the circulation rate is changed in advance, the relationship between the circulation rate and the dissolved oxygen concentration (DO) can be obtained, and the circulation rate can be set based on the result.

[0026] On the other hand, the aforementioned control device 114 is also connected to the blower 120, the valve 121, the second pump 115, and the three-way valve 116, and also serves as a cleaning control device that controls not only the water level in the filtration tank 101 but also the cleaning operation of the filter media 103.

[0027] Next, an embodiment of the sprinkling and biological filtration method for water to be treated of the present invention using this sprinkling and biological filtration device 100 will be described.

[0028] In the present invention, the water to be treated may be, for example, water to be treated in a sewage treatment facility and containing organic matter and suspended solids. Examples of the water to be treated include, but are not limited to, effluent from a primary sedimentation tank in a sewage treatment facility and water obtained by passing inflowing sewage through a pre-filtration device.

[0029] The water to be treated is sprayed onto the upper surface of the trickling filter bed 106 from the spray section 108, and flows down through the gaps in the filter media 103 of the trickling filter bed 106. At this time, an air flow is generated by the air circulation means 109 that flows through the gaps in the filter media 103 of the trickling filter bed 106, and the water to be treated comes into contact with this air flow, increasing the dissolved oxygen concentration. The water to be treated then comes into contact with the surface of the filter media 103, where the microbial layer adhering to the surface of the filter media 103 decomposes organic matter and nitrifies ammonia, while filtering out and removing the suspended solids (SS) contained in the water.

[0030] The water to be treated that has passed through the trickling filter bed 106 then passes through the biological filtration section 107 immersed in the water of the storage section 105. More microorganisms are attached to the filter media 103 of the biological filtration section 107 than to the filter media 103 of the trickling filter bed 106, and the decomposition of organic matter and the nitrification of ammonia are more effectively carried out by utilizing the increased dissolved oxygen in the water when it passes through the trickling filter bed 106. In addition, the microorganisms attached to the surface of the filter media 103 of the biological filtration section 107 also enhance the SS removal effect.

[0031] In addition, because the biological filtration section 107 is immersed in the water of the storage section 105, the passing speed of the water to be treated is reduced, and the water to be treated is retained for a predetermined time in the storage section 105. This allows the decomposition of organic matter by microorganisms and the nitrification of ammonia to proceed over time, and also serves as a buffer tank when the inflow of the water to be treated supplied from the water spray section 108 fluctuates.

[0032] The length of the trickling filter bed 106 in the height direction of the filter bed 104 and the length of the biological filtration section 107 are not particularly limited, but when the overall length of the filter bed 104 in the height direction is taken as 10, it is preferable that the length of the trickling filter bed 106: the length of the biological filtration section 107 = 5 to 9.5: 0.5 to 5, and more preferably 8 to 9.5: 0.5 to 2. By setting the ratio within the above ranges, it is possible to obtain good organic matter decomposition, ammonia nitrification, and SS removal in both the trickling filter bed 106 and the biological filtration section 107.

[0033] In this embodiment, the water level of the adjustment tank 111 (which will be the same as the water level of the filtration tank 101) is measured by a level gauge 113, and when this water level falls outside a specified range, a water level control device 114 sends an operation signal to the first pump 112 to control the amount of water flowing out of the adjustment tank 111, thereby controlling the water level of the filtration tank 101 to be maintained within a specified range, so that the vertical length of the biological filtration section 107 can always be kept within a preferred range.

[0034] In addition, the increased dissolved oxygen when the treated water passes through the trickling filter bed 106 is used by the microorganisms attached to the filter medium 103 of the trickling filter bed 106 and the surface of the filter medium 103 of the biological filtration section 107 to decompose organic matter and nitrify ammonia. However, if there is a shortage of dissolved oxygen, the decomposition of organic matter and the nitrification of ammonia in the biological filtration section 107 will be weakened.

[0035] Therefore, in this embodiment, the dissolved oxygen concentration of the water in the storage section 105 is measured by the dissolved oxygen meter 118, and the measured value is sent to the circulation amount control device 119. When the dissolved oxygen concentration of the water in the storage section 105 falls below a predetermined value, the circulation amount control device 119 sends a signal to the second pump 115 and the three-way valve 116 to send the water in the storage section 105 to the trickling section 108 through the return line 117, and circulates it to the trickling filter bed 106. By increasing the circulation amount of the water in the storage section 105, some of the water passes through the trickling filter bed 106 multiple times, and the time that the water is in contact with the air flow circulating through the trickling filter bed 106 is extended, and the dissolved oxygen concentration of the water in the storage section 105 can be increased.

[0036] On the other hand, when the filtration operation is continued by passing the water to be treated through the trickling filter bed 106 and the biological filtration section 107, the microorganisms and SS attached to the surface of the filter media 103 of the trickling filter bed 106 and the filter media 103 of the biological filtration section 107 become sludge and accumulate. There is an appropriate range for this sludge adhesion rate, and if sludge adheres excessively, the treatment performance decreases, the pressure loss of the water to be treated increases, and the filtration efficiency decreases. In addition, fly larvae and eggs may adhere to the filter media 103 of the trickling filter bed 106 and emit a foul odor. For this reason, it is necessary to wash the filter media 103 at a predetermined timing.

[0037] In that case, the following washing procedure is carried out, which will be explained with reference to Figures 1 and 2.

[0038] STEP 1 in Fig. 2 shows a state during normal operation. When starting a cleaning operation in this state, as shown in STEP 2, the discharge pipe 136 is closed, and the air circulation means 109 is stopped and closed. Then, water is sprayed from the spray unit 108 to raise the water level stored in the storage unit 105 (water filling step). The water level in the preparation tank 11 also rises together with the water level in the storage unit 105.

[0039] At this time, the control device 114 can calculate the volume of water filled in the filter bed 104 and the adjustment tank 111 from the change in water level measured by the level meter 113 and the flow rate of the water to be treated measured by the flow meter 137. Then, the volume of water filled in the filtration tank 101 can be calculated by subtracting the volume of water filled in the adjustment tank 111 from the volume of water filled in both.

[0040] In this case, when the water to be treated is supplied from a state in which the biological filtration section 107 is submerged, it is possible to calculate the volume of water filled in the trickling filter bed 106. Furthermore, by opening the three-way valve 116 and operating the second pump 115 at the start of the cleaning operation to once discharge all the stored water and then supply the water to be treated from the trickling section 108, it is possible to calculate the volume of water filled in the entire filter bed 104, the volume of water filled in the biological filtration section 107, and the volume of water filled in the trickling filter bed 106.

[0041] The above volume corresponds to the volume of the space excluding the filter medium 103 and the part of the filter medium 103 to which the organisms are attached. The void ratio (VRo) can be calculated from the volume of this space and the volume of the filter tank 101 in that part.

[0042] The filled water is discharged as washing wastewater, but it is preferable that the amount of water discharged is small. For this reason, a structure may be adopted in which, for example, a pipe or the like having a smaller volume than the adjustment tank 111 is connected to the storage unit 105 for measuring the water depth, a level gauge 113 is inserted into the pipe, and a valve is provided at the connection unit 110. In this case, the flow path connecting the filter bed 104 and the adjustment tank 111 is blocked, and water is filled into the filter bed 104 and the parallel pipe.

[0043] Then, by determining the porosity (VRo1) in the initial state in a similar manner to the above, it is possible to determine the reduced porosity (VRo1-VRo) relative to the initial porosity (VRo1). This reduced porosity (VRo1-VRo) corresponds to the porosity reduced by the amount of biofouling Bm in that space, and is defined as the biofouling rate (%). The method for measuring the biofouling rate is described in detail in Japanese Patent No. 6545857, so please refer to this document.

[0044] In other words, when the water to be treated is supplied from a submerged state of the biological filtration section 107, the bioattachment rate (%) of the trickling filter bed 106 can be calculated by calculating the volume of water filled in the trickling filter bed 106, and by discharging all the stored water once and then supplying the water to be treated from the trickling section 108, the bioattachment rate (%) of the entire filter bed 104, the bioattachment rate (%) of the biological filtration section 107, and the bioattachment rate (%) of the trickling filter bed 106 can be calculated.

[0045] Then, as shown in STEP 2, when the filter bed 104 is completely submerged, the water spray from the water spray unit 108 is stopped.

[0046] Next, as shown in STEP 3, the aeration operation is started (aeration cleaning process). The aeration operation is performed by opening the valve 121, operating the blower 120, and blowing air from the aeration pipe 122. This agitates the filter medium 103, and removes the microbial film attached to the surface of the filter medium 103, organisms such as fly eggs and larvae, and suspended solids attached to the filter medium.

[0047] However, the microorganisms attached to the surface of the filter media are necessary for biological treatment such as decomposing organic matter in the treated water and nitrifying ammonia when normal operation is resumed, so if too many are removed, the purification action of the microorganisms will be impaired.

[0048] Therefore, in the present invention, the cleaning control device 142 controls the aeration conditions (aeration volume and aeration time) according to the bioadhesion rate calculated in STEP 2. That is, when the bioadhesion rate is high, the aeration conditions are strengthened, and when the bioadhesion rate is low, the aeration conditions are weakened. This allows the cleaning operation to be performed so that the bioadhesion rate on the surface of the filter medium 103 is optimal.

[0049] The aeration volume per unit area of ​​the filtration tank 101 in plan view is not particularly limited, but is preferably 0.25 m 3 / (m 2 min) or more than 1.5m 3 / (m 2 0.25m 3 / (m 2 min) or more than 0.5m 3 / (m 2 It is more preferable that the time is 100 s to 300 s.

[0050] The aeration time is not particularly limited, but is preferably 0.5 to 20 minutes, and more preferably 0.5 to 5 minutes.

[0051] It is preferable to control the aeration conditions so that the rate of bioadhesion remaining on the surface of the filter medium 103 after aeration cleaning is maintained within a range of preferably 5% to 25%, and more preferably 10% to 20%.

[0052] After the aeration and mixing operation is performed under the specified conditions, the blower 120 is stopped in STEP 4 to end the aeration and mixing operation. At this time, the filter media 103 in the trickling filter bed 106 and the filter media 103 in the biological filtration section 107 are mixed together, and each filter media 103 is generally dispersed. As a result, the filter media 103 in the biological filtration section 107, which has a relatively abundant microbial layer attached thereto, is also dispersed into the trickling filter bed 106, making it possible to enrich the microorganisms in the trickling filter bed 106.

[0053] Then, when the washing operation is completed, in STEP 5, the three-way valve 116 opens in the discharge direction, the pump 115 operates, and the washing wastewater is discharged (drainage process). When all the washing wastewater has been discharged, the three-way valve 116 closes, the process returns to STEP 1 again, and water sprinkling begins from the water sprinkling unit 108, and normal operation begins.

[0054] Thus, according to the trickling and biological filtration method of the present invention, in the aeration cleaning step (STEP 3), the filter media 103 in the biological filtration section 107 is also diffused into the trickling filter bed 106, so that the amount of biofilm in the trickling filter bed 106 increases while the amount of excess biofilm in the biological filtration section 107 is appropriately reduced, and organic matter decomposition and ammonia nitrification can be promoted in the entire filter bed 104. During this flow cleaning, the waste biofilm in the filter bed can also be discharged.

[0055] In addition, by measuring the amount of bioadhesion (Bm) on the filter medium 103 and adjusting the aeration amount in the aeration cleaning process based on this amount of bioadhesion (Bm), the amount of biofilm remaining on the surface of the filter medium 103 can be adjusted more accurately.

[0056] The amount of bioadhesion (Bm) can be calculated from the void fraction (VRo) of the filter bed, and the bioadhesion rate can be calculated by the difference from the initial void fraction (VRo1). Therefore, the aeration and mixing conditions can be controlled according to this bioadhesion rate.

[0057] Another embodiment of the water trickling and biological filtration device for carrying out the present invention is shown in Fig. 3. Note that the same reference numerals are used to designate parts that are substantially the same as those in the embodiment of Fig. 1, and the description thereof will be omitted.

[0058] In this trickling / biological filtration device 100a, the aeration means is different from that of the above embodiment. That is, an air supply pipe 126 connected to a blower 120 is branched into a first branch pipe 127 and a second branch pipe 128. The first branch pipe 127 is connected to a first aeration pipe 130 via a first valve 129, and the first aeration pipe 130 is inserted into the storage section 105 and disposed below the biological filtration section 107. The first aeration pipe 130 may be disposed below or below the biological filtration section 107, and may be disposed below the porous plate 102, for example. The second branch pipe 128 is connected to a second aeration pipe 132 via a second valve 131, and the second aeration pipe 132 is inserted and disposed below the trickling filter bed 106 in the filtration tank 101.

[0059] In this embodiment, the adjustment tank 111 and the level gauge 113 are not provided, and instead, three water level detection devices are installed. That is, a first water level detection device 140 is installed below or below the biological filtration section 107, a second water level detection device 141 is installed below or below the trickling filter bed 106, and a third water level detection device 142 is installed above or above the trickling filter bed 106, and these are connected to the control device 114. The control device 114 is also connected to the blower 120, the first valve 129, and the second valve 131.

[0060] Therefore, during the cleaning operation of the filter medium 103, if all the stored water is discharged once before the water to be treated is supplied, the water level will rise, and the porosity of the biological filtration section 107 and the porosity of the trickling filter bed 106 can be calculated using the calculation method described above from the time it takes for the water level to pass the first water level detection device 140, the second water level detection device 141, and the third water level detection device 142, and the flow rate of the flow meter 137 during that time, and the respective biological attachment rates (Bm) can be calculated by the difference from the initial porosity (VRo1).

[0061] In this way, by storing water in the filtration tank 101 so that the filter media 103 in the trickling filter bed 106 is submerged, the second valve 131 is closed, the first valve 129 is opened, and aeration is performed only through the first aeration pipe 130, the filter media 103 in the entire filter bed 104 can be agitated. Furthermore, by closing the first valve 129, opening the second valve 131, and aeration is performed only through the second aeration pipe 132, only the filter media 103 in the trickling filter bed 106 can be agitated. Furthermore, by opening both the first valve 129 and the second valve 131 and aeration is performed through both the first aeration pipe 130 and the second aeration pipe 132, the filter media 103 in the trickling filter bed 106 can be agitated more strongly than the filter media 103 in the biological filtration section 107.

[0062] In this embodiment, the above aeration conditions can be adjusted based on the bioattachment rate (Bm) of the biological filtration section 107 and the bioattachment rate (Bm) of the trickling filter bed 106, which are obtained by the above-mentioned method. That is, the cleaning effect of each filter medium 103 can be adjusted according to the bioattachment rate (Bm) of sludge, fly larvae, and eggs of the filter medium 103 of the trickling filter bed 106 and the bioattachment rate (Bm) of sludge of the biological filtration section 107. For example, it is preferable to clean the filter medium 103 of the biological filtration section 107 so that the sludge of microorganisms and the like that has adhered to it remains to some extent, because this will allow the decomposition of organic matter and the nitrification of ammonia to start up quickly when the operation is resumed. On the other hand, the filter medium 103 of the trickling filter bed 106 may have not only sludge but also fly larvae and eggs attached thereto, and may need to be cleaned more strongly than the filter medium 103 of the biological filtration section 107. Therefore, by adjusting the cleaning strength of the filter media 103 in the trickling filter bed 106 and the cleaning strength of the filter media 103 in the biological filtration section 107, each filter media 103 can be maintained in an appropriate state.

[0063] For example, during the aeration cleaning process, first the first valve 129 is closed and the second valve 131 is opened, and aeration is performed only through the second aeration pipe 132, thereby stirring only the filter material 103 in the trickling filter bed 106, thereby removing sludge, fly larvae, eggs, etc. adhering to the filter material 103 in the trickling filter bed 106, and then the second valve 131 is closed and the first valve 129 is opened, and aeration is performed only through the first aeration pipe 130, thereby stirring and cleaning the filter material 103 in the entire filter bed 104, cleaning the filter material 103 in the biological filtration section 107, and diffusing the filter material 103 in the biological filtration section 107 into the trickling filter bed 106.

[0064] An embodiment of a sewage treatment device for carrying out the trickling and biological filtration method of the present invention is shown in Fig. 4. Note that parts that are substantially the same as those in the embodiment of Fig. 1 are given the same reference numerals and their explanations will be omitted.

[0065] This sewage treatment device 200 includes a first solid-liquid separation device 210, a trickling / biological filtration device 100, and a second solid-liquid separation device 220. The first solid-liquid separation device 210 is a pre-stage filtration device for removing SS from the water to be treated that flows out of, for example, a final settling tank in a sewage treatment facility. This first solid-liquid separation device 210 includes a water to be treated inlet 211 and a filtration tank 212 having a filter layer 213. The water to be treated that flows in from the water to be treated inlet 211 flows down through the water to be treated inlet 211 and enters the filtration tank 212, passes from the bottom to the top of the filter layer 213 and is filtered, and then is sent to the next trickling / biological filtration device 100 by overflow. For example, a floating filter material can be used as the filter layer 213.

[0066] Although the trickling / biological filtration device 100 is not particularly limited, in this embodiment, a plurality of filtration tanks 101 are arranged side by side in a biological treatment tank 133. Each filtration tank 101 is provided with a trickling filter bed 106, a filter bed 104 having a biological filtration section 107, and a storage section 105 that keeps the biological filtration section 107 submerged. A trickling section 108 is arranged above the trickling filter bed 106 of each filtration tank 101. Although not shown, the storage section 105 of each filtration tank 101 is provided with a pipe and a valve that connect to the biological treatment tank 133, allowing each filtration tank 101 to be washed. The treated water that has passed through the trickling filter bed 106 and the biological filtration section 107 is stored in the common biological treatment tank 133. A first pump 112 is provided in the biological treatment tank 133, and is configured to send the water that has passed through the trickling filter bed 106 and the biological filtration section 107 to a second solid-liquid separation device 220. In addition, a third pump 134 is provided in the biological treatment tank 133, and is configured to return a portion of the water that has passed through the trickling filter bed 106 and the biological filtration section 107 and is stored in the biological treatment tank 133 to the trickling section 108 via a return line 117, thereby enabling circulation.

[0067] The second solid-liquid separation device 220 comprises a filtration tank 221 and a filter media layer 222, and the water treated in the trickle / biological filtration device 100 is introduced from below the filtration tank 221 and passed from bottom to top through the filter media layer 222, thereby further removing remaining SS and purifying the water.

[0068] Next, an embodiment of a sewage treatment method according to the present invention using the sewage treatment device 200 will be described.

[0069] For example, the inflow sewage of a sewage treatment plant is treated as the water to be treated. This water is introduced into the water to be treated inlet passage 211 of the first solid-liquid separation device 210, allowed to flow below the filtration tank 212, and passed from bottom to top through the filter media layer 213, thereby removing the SS contained in the water to be treated.

[0070] Next, the water to be treated that has been treated in the first solid-liquid separator 210 is sprinkled onto the trickling filter bed 106 from the trickling section 108 of the trickling / biological filtration device 100, passed through the trickling filter bed 106, and then passed through the biological filtration section 107 immersed in the water of the storage section 105. As a result, as described above, decomposition of organic matter and nitrification of ammonia by microorganisms attached to the surfaces of the filter media 103 of the trickling filter bed 106 and the filter media 103 of the biological filtration section 107, and further removal of SS contained in the water to be treated are performed. In addition, in the above-mentioned embodiment, the dissolved oxygen concentration of the water in the storage section 105 is measured, and when the dissolved oxygen concentration is insufficient, the water in the storage section 105 is circulated to the trickling section 108 by the third pump 134 to maintain the activity of the microorganisms in the biological filtration section 107.

[0071] Furthermore, the treated water is sent to the second solid-liquid separation device 220 by the first pump 112, and filtered by passing it from bottom to top through the filter layer 222, thereby more thoroughly removing remaining SS and discharging the water.

[0072] In the above embodiment, the first solid-liquid separator 210 serves to remove large SS, and is not limited to an upward filtration device using a floating filter medium as shown in this embodiment, but may be a settling tank such as a primary settling tank. The second solid-liquid separator 220 serves to remove fine SS remaining after treatment in the trickling / biological filtration device 100, and is not limited to an upward filtration device as shown in this embodiment, but may be a settling tank such as a final settling tank.

[0073] In addition, if the organic matter and SS in the water to be treated are reduced to an acceptable level by the treatment in the trickling and biological filtration device 100, it is possible to directly discharge the water treated in the trickling and biological filtration device 100 without providing the second solid-liquid separation device 220. This can reduce the equipment cost.

[0074] Although not explained here, in this embodiment as well, the trickle / biological filtration device 100 is provided with an aeration means and a cleaning control means, and the cleaning operation of the filter medium as described above is performed periodically. EXAMPLES

[0075] The following test was carried out using the sewage treatment device 200 shown in Fig. 5. This sewage treatment device 200 is an experimental reproduction of the sewage treatment device 200 shown in Fig. 4. Therefore, the same reference numerals will be used for the parts common to Fig. 4, and the description thereof will be omitted.

[0076] The first storage tank 214 is a tank into which the water to be treated is introduced, and the water to be treated is sent to the first solid-liquid separation device 210 via the fourth pump 215. The first solid-liquid separation device 210 has a filter layer 213, and the water to be treated passes through the filter layer 213 from bottom to top and is filtered. The second storage tank 216 is a tank in which the water to be treated that has passed through the first solid-liquid separation device 210 is stored, and a portion of the water to be treated stored here is sent to the sprinkling and biological filtration device 100, which is an embodiment of the present invention, by the sixth pump 218. Also, a portion of the water to be treated stored in the second storage tank 216 is sent to the conventional sprinkling filtration device 300 by the seventh pump 219.

[0077] In the trickling / biological filtration system 100, the water to be treated introduced by the sixth pump 218 is trickled onto the trickling filter bed 106, and is treated by passing through the trickling filter bed 106 and the biological filtration section 107 in the manner described above. The water thus treated is sent to the second solid-liquid separation device 220 by the second pump 115, and further passes from bottom to top through the filter media layer 222 of the second solid-liquid separation device 220, and is discharged under gravity flow.

[0078] In the trickling filtration device 300, the water to be treated introduced by the seventh pump 219 is trickled onto a trickling filter bed 304 consisting of a porous plate 303 filled with a large number of filter media 303, passes through the trickling filter bed 304 from top to bottom, and is removed by the ninth pump 315.

[0079] Although not shown in the figures, both the trickling / biological filtration system 100 and the trickling filtration system 300 are provided with an aeration means consisting of the blower 120, valve 121, and aeration pipe 122 shown in Figure 1, and the filter media 103, 303 are periodically cleaned by aeration.

[0080] Table 1 below shows the sizes and operating conditions of the filtration tank 101 and the filtration tank 301 in the trickling and biological filtration apparatus 100 and the trickling filtration apparatus 300. Note that the trickling filter bed method in Table 1 refers to filtration using the filtration tank 301 of the trickling filtration apparatus 300 (Comparative Example), and the trickling and biological filtration method refers to filtration using the filtration tank 101 of the trickling and biological filtration apparatus 100 (Example). Note that the experiments were performed using actual sewage, so the amount of inflowing water to be treated and the SS concentration change daily due to rainfall, etc.

[0081] [Table 1]

[0082] A test to evaluate the treatment performance of the water to be treated was carried out under the above conditions. Figure 6 shows the measurement results of the biofouling rate on the filter bed.

[0083] FIG. 6 shows the change in the biofouling rate of the filter bed, with "trickling filter bed method, overall" showing the biofouling rate (sludge adhesion rate) in the trickling filtration device 300 (comparative example), "trickling and biological filtration method, trickling filter bed" showing the biofouling rate of the trickling filter bed 106 in the trickling and biological filtration device 100 (example), "trickling and biological filtration method, biological filtration section" showing the biofouling rate in the biological filtration section 107 in the trickling and biological filtration device 100 (example), and "trickling and biological filtration method, overall" showing the biofouling rate of the entire filter bed 104 in the trickling and biological filtration device 100 (example).

[0084] As shown in Figure 6, the rate of biofouling increases especially in the biological filter section as operation continues. In this way, it has been experimentally confirmed that in the trickling and biological filtration method, the rate of biofouling increases faster in the biological filter section than in the trickling filter bed. [Explanation of symbols]

[0085] 100 Watering and biological filtration equipment 101 Filtration tank 102 Perforated plate 103 Filter media 104 Filter Bed 105 Storage section 106 Trickling filter 107 Biological filtration section 108 Watering section 109 Air circulation means 110 Communication part 111 Adjustment tank 112 First Pump 113 Level Gauge 114 Control device 115 Second Pump 116 Three-way valve 117 Return Route 118 Dissolved oxygen meter 119 Circulation volume control device 120 Blower 121 Valve 122 Aeration pipe 123 Drain pipe 124 Telescopic tube 125 Outlet 126 Air pipe 127 First Branch Pipe 128 Second Branch Pipe 129 First valve 130 First aeration pipe 131 Second valve 132 Second aeration pipe 133 Biological treatment tank 134 3rd Pump 135 Supply pipe 136 Discharge pipe 137 Flow meter 140 First water surface detection device 141 Second water surface detection device 142 Third water surface detection device 200 Sewage treatment equipment 211 Treated water inlet 212 Filtration tank 213 Filter layer 214 1st storage tank 215 4th Pump 216 2nd storage tank 217 5th Pump 218 6th Pump 219 7th Pump 220 Second solid-liquid separator 221 Filtration tank 222 Filter layer

Claims

1. A filter bed filled with a filter medium; A water sprinkler unit for the water to be treated arranged above the filter bed; and a treated water outlet located below the filter bed, A storage section is provided below and below the filter bed, in which the water to be treated sprayed from the spray section flows down through the filter bed and accumulates therein, A portion of the filter bed that is not immersed in the water of the storage portion forms a trickling filter bed through which the water to be treated sprinkled from the sprinkling portion flows down, The portion of the filter bed that is immersed in the water of the storage portion forms a biological filtration portion, An air circulation means for circulating air inside the trickling filter is provided, An aeration means is provided below the biological filtration section, and an outflow port for washing wastewater is provided below the filter bed, A trickling and biological filtration device having an aeration means provided under the trickling filter is used, A normal operation in which the water to be treated is sprinkled from the sprinkling section to the upper part of the trickling filter while air is circulated through the trickling filter by the air circulation means, the water to be treated passes through the trickling filter and the biological filtration section, and is retained in the storage section for a predetermined time, and then is taken out from the outflow section; aeration cleaning comprising a water filling step in which the treated water outlet and the cleaning wastewater outlet are closed, the air circulation means is stopped, and water is filled until the entire filter bed is submerged; an aeration cleaning step in which an aeration means arranged below the biological filtration section and an aeration means arranged below the trickling filter bed are selectively or simultaneously operated to supply air to flow-clean the filter media filled in the filter bed; and a drainage step in which the cleaning wastewater outlet is opened and the cleaning wastewater is drained, are alternately performed at a predetermined timing; A water spraying and biological filtration method, characterized in that during the aeration cleaning process, the aeration volume is adjusted so that the filter material located in the biological filtration section is dispersed throughout the entire filter bed with the biological film attached to its surface.

2. The method for water trickling and biological filtration according to claim 1, further comprising measuring the amount of biological adhesion (Bm) to the filter media in at least one of the trickling filter bed and the biological filtration section, and adjusting the amount of aeration in the aeration cleaning process based on the amount of biological adhesion (Bm).

3. The trickling and biological filtration method according to claim 2, wherein the porosity (VRo) of at least one of the trickling filter bed and the biological filtration section is measured, and the amount of attached organisms (Bm) is calculated based on the porosity.

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