Biological filtration system and cleaning method thereof

Abstract

To provide a biological filtration device equipped with a mechanism for reducing excessive cleaning and insufficient cleaning, and a cleaning method thereof.SOLUTION: A biological filtration device includes a treatment tank, a biological filtration layer arranged inside the treatment tank, a water level sensor that acquires a water level of water to be treated inside the treatment tank, and a control unit that acquires an output of the water level sensor, in which the water level sensor obtains a first water level that is higher by a predetermined distance from a preset reference water level, and a second water level that is higher by a predetermined distance from the first water level, and the control unit measures a first time until the water to be treated reaches the first water level from the reference water level, and a second time until the water reaches the second water level from the first water level, based on the output of the water level sensor, and changes a cleaning pattern of the biological filtration layer depending on a result of comparing the first time and the second time.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] One embodiment of the present invention relates to a biological filtration device and a cleaning method thereof.

Background Art

[0002] Conventionally, as a filtration device used for purification treatment of feces and urine, household wastewater, etc., a biological filtration device that utilizes microorganisms for decomposition of organic substances is known. Usually, such a biological filtration device has a filtration layer formed by filling a filter medium in a treatment tank, and the wastewater is purified by passing through this filtration layer. For example, in the biological filtration device described in Patent Document 1, sludge containing aerobic or anaerobic microorganisms is attached to the filtration layer. Therefore, the above biological filtration device can simultaneously perform the decomposition treatment of organic pollutants and the separation treatment of suspended substances (referred to as SS) by supplying wastewater into the filtration layer.

[0003] In the filtration device having the above-described configuration, as the purification treatment continues, a part of the pollutants and suspended substances gradually adhere to the inside of the filtration layer, and the treatment capacity as the filtration layer decreases. Therefore, in order to maintain the treatment capacity of the filtration layer, regular cleaning of the filter medium is necessary. Therefore, in the biological filtration device described in Patent Document 1, a cleaning process called backwashing is performed on the filtration layer, and a process for periodically improving the treatment capacity of the filtration layer is performed. Here, backwashing is a cleaning method in which air (air), water, or air and water are supplied in a direction opposite to the direction in which the water to be treated flows, and the filter media are mixed with air or water to remove a part of the pollutants and suspended substances adhering to the filter media.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The biological filtration system described above typically requires daily cleaning because the filter chamber is not very large. For example, a timer is used to manage the cleaning interval, and cleaning is performed regularly at predetermined times. However, conventionally, cleaning is performed periodically based on time management without monitoring the condition of the filter chamber, which has the problem of not being able to detect if cleaning is excessive or insufficient.

[0006] Therefore, normally, measures were taken to prevent insufficient cleaning by setting shorter intervals between cleaning processes or longer cleaning times. However, setting the cleaning time too high risked washing away microorganisms attached to the filter media, which would actually reduce the processing capacity.

[0007] This invention has been made in view of the above-mentioned problems, and one of its objectives is to provide a biological filtration device and a cleaning method thereof equipped with a mechanism for reducing excessive and insufficient cleaning. [Means for solving the problem]

[0008] A biological filtration apparatus according to one embodiment of the present invention comprises a treatment tank, a biological filtration layer disposed inside the treatment tank, a water level sensor for acquiring the water level of the water to be treated inside the treatment tank, and a control unit for acquiring the output of the water level sensor. The water level sensor acquires a first water level that is a predetermined distance higher than a preset reference water level, and a second water level that is a predetermined distance higher than the first water level. Based on the output of the water level sensor, the control unit measures a first time until the water to be treated reaches the first water level from the reference water level, and a second time until the water to be treated reaches the second water level from the first water level, and changes the cleaning pattern of the biological filtration layer according to the result of comparing the first time and the second time.

[0009] The water level sensor may further acquire a third water level that is higher than the second water level. When the control unit detects that the water to be treated has reached the third water level, it may execute a control to forcibly wash the biological filtration layer.

[0010] The control unit may select a first cleaning pattern in which, if the first time is longer than the second time, cleaning of the biological filtration layer is performed on the condition that the water to be treated reaches the third water level, or if the first time and the second time are equal, it may select a second cleaning pattern in which cleaning of the biological filtration layer is performed at a preset cleaning interval.

[0011] If, while the control unit is selecting the second washing pattern, the water to be treated reaches the third water level a predetermined number of times consecutively, the washing interval may be shortened.

[0012] If the control unit does not detect that the water to be treated has reached the first water level while it is selecting the second washing pattern, it may lengthen the washing interval.

[0013] The cleaning of the biological filtration layer may be performed by supplying air, water, or air and water into the biological filtration layer in the opposite direction to the direction of flow of the water being treated during the filtration process.

[0014] If, after comparing the average value of the first time obtained from multiple past measurements with the first time, the cleaning period of the biological filtration layer may be shortened by a predetermined period. Conversely, if, after comparing the average value with the first time, the first time is shorter than the average value, the cleaning period of the biological filtration layer may be extended by a predetermined period.

[0015] A cleaning method for a biological filtration apparatus according to one embodiment of the present invention is a cleaning method for a biological filtration apparatus including a biological filtration layer disposed inside a treatment tank, wherein a first time is measured until the water to be treated reaches a first water level that is a predetermined distance higher than a preset reference water level, a second time is measured until the water to be treated reaches a second water level that is a predetermined distance higher than the first water level, and the cleaning pattern of the biological filtration layer is changed according to the result of comparing the first time and the second time.

[0016] As a result of comparing the first time and the second time, if the first time is longer than the second time, a first cleaning pattern may be selected in which the cleaning of the biological filtration layer is performed on the condition that the water to be treated reaches a third water level higher than the second water level. If the first time and the second time are equal, a second cleaning pattern may be selected in which the cleaning of the biological filtration layer is performed at a preset cleaning interval. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic diagram showing the configuration of a biological filtration system in one embodiment of the present invention. [Figure 2] This is a flowchart illustrating an example of the cleaning process in one embodiment of the present invention. [Figure 3] This is a diagram illustrating the processing cycle in one embodiment of the present invention. [Figure 4] This figure illustrates a first washing pattern in one embodiment of the present invention. [Figure 5] This figure illustrates a second washing pattern in one embodiment of the present invention. [Figure 6] This is a schematic diagram showing the configuration of a biological filtration system in one embodiment of the present invention. [Modes for carrying out the invention]

[0018] Embodiments of the present invention will be described below with reference to the drawings. However, the present invention can be implemented in various forms without departing from its essence, and is not to be interpreted as being limited to the embodiments described below. In order to make the explanation clearer, the drawings may schematically represent the size, width, thickness, shape, etc. of each part compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention. In this specification and in each drawing, elements having the same function as those described with respect to previously shown drawings are denoted by the same reference numerals, and redundant explanations may be omitted.

[0019] (First Embodiment) [Configuration of Biological Filter Device] FIG. 1 is a schematic diagram showing the configuration of a biological filter device 100 according to an embodiment of the present invention. The biological filter device 100 of the present embodiment is a purification device that removes SS (suspended solids) and organic pollutants from treated water (raw water) using a filter medium to which aerobic microorganisms are attached. In the present embodiment, the treated water is supplied from above the biological filter layer 120, and the treated water is purified by a downward flow.

[0020] The biological filter device 100 includes a treatment tank 110, a biological filter layer 120, a water level sensor 130, and a control unit 140. However, the configuration of the biological filter device 100 shown in FIG. 1 is an example, and other elements may be added. In the present embodiment, the biological filter device 100 will be described, but as a purification system, various purification devices other than the biological filter device 100 may be provided. For example, one or more anaerobic filter bed devices may be provided in front of the biological filter device 100.

[0021] The treatment tank 110 is a cylindrical housing formed of a steel plate or a synthetic resin. The treatment tank 110 corresponds to the outer frame of the biological filter device 100 of the present embodiment. Inside the treatment tank 110, the biological filter layer 120 is disposed.

[0022] The biological filter layer 120 is responsible for removing SS by the filter medium and decomposing and removing organic pollutants by aerobic microorganisms. As the filter medium, it is preferable to use a member (carrier) having a large surface area so that many microorganisms can inhabit. As the filter medium, for example, rocks, molten slag, ceramics, plastics, etc. can be used. In the present embodiment, a filter medium combining filtered sand and crushed anthracite is used, but it is not limited to this example. As the microorganisms to be attached to the filter medium, aerobic microorganisms are used. Aerobic microorganisms have the property of decomposing organic substances and decomposing ammonia to nitrates. What kind of microorganisms to use may be determined according to the use of the biological filter device 100 and the contents of the treated water.

[0023] In this embodiment, the biological filtration layer 120 includes an upper filtration layer 121 and a lower filtration layer 122. In the upper filtration layer 121, mainly dissolved organic matter and suspended solids (SS) are decomposed and removed. In the lower filtration layer 122, mainly ammoniacal nitrogen is decomposed and removed. As described above, in this embodiment, the purification treatment is performed in a downward flow, so by dividing the roles of the purification treatment between the upper filtration layer 121 and the lower filtration layer 122, the water to be treated can be purified efficiently. However, the configuration of the biological filtration layer 120 is not limited to this example, and it may be a single-layer configuration or a multi-layer configuration of three or more layers.

[0024] Inside the treatment tank 110, below the biological filtration layer 120, a cleaning assistance area 125 is provided for supplying air and cleaning water. The cleaning assistance area 125 is used to supply air and water from outside the treatment tank 110 when performing the cleaning treatment of the biological filtration layer 120, which will be described later. In this embodiment, the biological filtration device 100 uses a filter material with a specific gravity greater than water, so the entire filter material settles. Therefore, although not shown in the illustration, in this embodiment, a mesh partition member is installed inside the treatment tank 110 to partition the inside of the treatment tank 110 and form the cleaning assistance area 125.

[0025] The water level sensor 130 has the function of acquiring the water level of the water to be treated inside the treatment tank 110. In this embodiment, an example using a contact-type water level sensor with multiple terminals is shown. When the water level inside the treatment tank 110 rises, the water to be treated comes into contact with each terminal. Therefore, by knowing the position of the tip of each terminal, the water level reached by the water to be treated can be acquired.

[0026] However, the water level sensor 130 is not limited to a contact-type water level sensor; a non-contact type water level sensor using an ultrasonic sensor (distance sensor) or the like can also be used. In this case, by periodically emitting ultrasonic waves toward the surface of the water to be treated, changes in the water level can be acquired in near real-time.

[0027] In this embodiment, the water level sensor 130 acquires the first water level (water level A), the second water level (water level B), and the third water level (water level C) as shown in Figure 1. The first water level indicates a water level that is a predetermined distance H higher than the reference water level. Here, the reference water level is a preset water level, which is shown as water level R in Figure 1. The reference water level indicates the initial water level when the biological filtration device 100 starts operation, and is at the same height as the bottom of the highest part of the treated water pipe 12, which will be described later.

[0028] The second water level is a water level that is a predetermined distance H higher than the first water level. In other words, in this embodiment, the height from the reference water level to the first water level is set to be equal to the height from the first water level to the second water level. However, the predetermined distance H is not limited to being perfectly equal, and may include an error within a range that can be considered substantially equal. For example, the predetermined distance H may be set to allow an error of ±5%.

[0029] The third water level is higher than the second water level and determines the upper limit of the water to be treated. Specifically, it is set at a position lower than the bottom of the raw water supply pipe 11, which will be described later. In this embodiment, when the water level of the water to be treated rises to the third water level, the process is forcibly switched to the washing process in order to avoid overflow of the water to be treated.

[0030] In this embodiment, the predetermined distance H is set to 300 mm and the distance between the second and third water levels is set to 100 mm, but the example is not limited to this. That is, the positions of the first, second, and third water levels can be appropriately determined according to the height of the treatment tank 110, the position of the bottom of the raw water supply pipe 11, the position of the bottom of the treated water pipe 12, etc.

[0031] The control unit 140 has functions for controlling various aspects of the biological filtration device 100. Although not shown in the figures, the control unit 140 has an arithmetic processing unit and a memory unit, and stores various programs and parameters required for controlling the biological filtration device 100 in the memory unit. For example, the memory unit of the control unit 140 stores a program for determining the cleaning pattern of the biological filtration layer 120, which will be described later. The arithmetic processing unit of the control unit 140 determines the cleaning pattern of the biological filtration device 100 by executing this program. In this embodiment, an example is shown in which wireless communication is used for communication between the control unit 140 and other elements, but it is not limited to this example, and wired communication may also be used.

[0032] The treated water, purified inside the treatment tank 110, is stored in the treated water tank 150. The treated water tank 150 is a storage tank for temporarily storing the treated water. When the treated water tank 150 has accumulated a predetermined amount of treated water or more, it is transported to an external facility.

[0033] Next, the peripheral elements of the biological filtration system 100 described above will be explained. A raw water supply pipe 11 is connected to the upper part of the treatment tank 110. An automatic valve 21 is located in the middle of the raw water supply pipe 11. The automatic valve 21 is a control valve controlled by the control unit 140 and operated by an actuator. For example, the automatic valve 21 may be an electromagnetic valve. The water to be treated supplied from the raw water supply pipe 11 to the inside of the treatment tank 110 is adjusted in flow rate and limited by the automatic valve 21.

[0034] A treated water pipe 12 is connected to the lower part of the treatment tank 110 (specifically, the cleaning assistance area 125). An automatic valve 22 is positioned along the treated water pipe 12. The automatic valve 22, like the automatic valve 21, is a control valve controlled by the control unit 140. The water to be treated, transferred from the treatment tank 110 by the treated water pipe 12, has its flow rate adjusted and supply restricted by the automatic valve 22.

[0035] The water flushing pipe 13 is connected at one end to the bottom of the treated water tank 150, and at the other end to the treated water pipe 12 via a pump 31 and a check valve 23. The pump 31 is responsible for drawing treated water from the treated water tank 150 and sending the treated water as flushing water to the flushing auxiliary area 125 of the treated tank 110 via the check valve 23. The check valve 23 is provided to prevent backflow from the treated tank 110 to the treated water tank 150.

[0036] The air irrigation pipe 14 has one end open to the air and the other end connected to the treated water pipe 12 via a pump 32 and a check valve 24. The pump 32 is responsible for supplying irrigation air to the irrigation assistance area 125 of the treatment tank 110 via the check valve 24. The check valve 24 is provided to prevent backflow of treated water from the treatment tank 110.

[0037] The drain pipe 15 is a drainage pipe for removing water from inside the treatment tank 110. An automatic valve 25 is located upstream of the drain pipe 15. An automatic valve 26 is also located between the treated water pipe 12, the water flushing pipe 13, and the air flushing pipe 14 and the drain pipe 15. Both automatic valves 25 and 26 are control valves, similar to the automatic valve 21, and are controlled by the control unit 140.

[0038] [Cleaning process for the biological filtration layer] Next, the cleaning process of the biological filtration layer 120 in the biological filtration device 100 of this embodiment will be explained with reference to Figures 1 and 2.

[0039] Figure 2 is a flowchart showing an example of a cleaning process in one embodiment of the present invention. The cleaning process shown in Figure 2 is executed by the control unit 140 when, for example, during the operation of the biological filtration device 100, clogging occurs in the biological filtration layer 120, the water level inside the treatment tank 110 gradually rises, and the water level of the water to be treated reaches the third water level (water level C).

[0040] First, a draining process is performed to remove water from the treatment tank 110 (S201). Specifically, automatic valves 21 and 22 are closed and automatic valves 25 and 26 are opened, and the water inside the treatment tank 110 is discharged through the drain pipe 15. The draining process continues until the water level of the water to be treated reaches the first water level (water level A).

[0041] When it is detected that the water level of the water to be treated has reached the first water level, a primary air washing treatment is then performed (S202). Prior to the primary washing treatment, the automatic valve 25 is left open and the automatic valve 26 is closed. Then, the pump 32 is activated to supply air to the washing assistance area 125 of the treatment tank 110. The air supplied to the inside of the treatment tank 110 passes through the biological filtration layer 120 while stirring the filter media and is discharged through the drain pipe 15. In this embodiment, since the treatment tank 110 is a sealed type, the air is discharged through the drain pipe 15, but if the treatment tank 110 is an open type (for example, a type with an open top), the automatic valve 25 may be closed.

[0042] The primary washing process agitates the filter media, causing friction between the media to detach sludge such as suspended solids (SS) adhering to the surface of the media. It also breaks down solidified sludge into smaller pieces, making it easier to discharge in subsequent processes. This primary washing process is continued for a predetermined time.

[0043] Once the primary cleaning process is complete, a secondary cleaning process using air and water is performed (S203). The secondary cleaning process is carried out by operating pump 31 in addition to pump 32. Specifically, pump 31 supplies a portion of the treated water stored in the treated water tank 150 to the cleaning assistance area 125 of the treated tank 110 via the water cleaning pipe 13. As a result, both air and treated water are supplied to the cleaning assistance area 125, and the air and water pass through the biological filtration layer 120.

[0044] As the water passes through the biological filtration layer 120, the air and water agitate the filter media and carry the detached sludge upwards with the water flow. The secondary washing treatment continues until the washing water level exceeds the third water level.

[0045] When it is detected that the water level of the washing water has reached the third water level, a tertiary washing treatment with water is then performed (S204). The tertiary washing treatment is performed by stopping the pump 32. That is, when the pump 32 stops and the supply of air stops, only treated water is supplied to the washing assistance area 125. The tertiary washing treatment continues for a predetermined time, during which time the sludge and other materials that have been removed from the biological filtration layer 120 by the primary and secondary washing treatments are discharged to the outside through the drain pipe 15.

[0046] Once the tertiary washing process is complete, the rinsing process is performed (S205). Prior to the rinsing process, the automatic valve 25 is closed and the automatic valve 26 is opened, and the pump 31 is stopped. In other words, during the rinsing process, the washing water remaining inside the treatment tank 110 is discharged while rinsing the biological filtration layer 120. The rinsing process continues until the washing water level reaches the first water level (water level A).

[0047] When it is detected that the washing water level has reached the first water level, the final step is to perform a filtration preparation treatment (S206). In the filtration preparation treatment, with automatic valves 21 and 22 open, the water to be treated is supplied to the biological filtration layer 120 for a predetermined time to prepare for the next purification treatment (filtration treatment).

[0048] After each of the above steps, the cleaning process of the biological filtration device 100 (specifically, the biological filtration layer 120) is performed. However, the cleaning process shown in Figure 2 is merely an example and is not limited to this example.

[0049] The biological filtration device 100 of this embodiment has a function to optimize the cleaning process by varying the timing of the cleaning process and the setting time for each step based on the output of the water level sensor 130. The optimization of the cleaning process will be described below.

[0050] Figure 3 is a diagram illustrating the processing cycle in one embodiment of the present invention. Specifically, Figure 3 shows the processing cycle from the start of operation of the biological filtration device 100 to the second cycle. As shown in Figure 3, one processing cycle includes a filtration step and a washing step. The specific washing process in the washing step is as described using Figures 1 and 2.

[0051] At the start of the treatment cycle, i.e., at the start of the filtration process, the water level inside the treatment tank 110 is the reference water level (water level R). As the filtration process progresses, the water level of the water to be treated gradually rises. Specifically, the water level of the water to be treated rises exponentially (curvilinearly) to approximately the first water level (water level A). At this time, the time it takes for the water to be treated to reach the first water level from the reference water level is defined as the first time T1.

[0052] Subsequently, as the filtration process continues, the water level of the treated water rises linearly (in a straight line) to the second water level (water level B). At this time, the time it takes for the treated water to reach the second water level from the first water level is defined as the second time T2.

[0053] As the filtration process progresses, the water level of the treated water rises linearly until it reaches the third water level (water level C). In the example shown in Figure 3, when the water level (water surface) of the treated water reaches the third water level, the process is forcibly switched from the filtration process to the washing process. At this time, the time it takes for the treated water to rise from the reference water level to the third water level is defined as the third time T3. Once the process switches to the washing process, the washing process of the biological filtration device 100 is performed according to the process flow shown in Figure 2.

[0054] By repeating the above treatment cycle, the raw water is continuously purified by biological filtration. However, as the biological filtration progresses, the time required for the water level to rise gradually changes due to the deterioration of the biological filtration layer 120 (for example, clogging). Here, we will explain the change in the time required for the water level to rise using Figures 4 and 5.

[0055] Figure 4 is a diagram illustrating a first cleaning pattern in one embodiment of the present invention. Figure 5 is a diagram illustrating a second cleaning pattern in one embodiment of the present invention. The graphs shown in Figures 4 and 5 correspond to one processing cycle shown in Figure 3. For example, Figure 4 corresponds to the first processing cycle, and Figure 5 corresponds to the tenth processing cycle.

[0056] As shown in Figure 4, in the initial treatment cycle, the water level of the treated water changes exponentially from the reference water level to the first water level. In the initial treatment cycle, there are not enough microorganisms of sufficient quantity and quality in the biological filtration layer 120, so the capture of suspended solids (SS) in the surface layer becomes the dominant cause of clogging. At this time, fine SS is captured in the inner layer of the biological filtration layer 120, which causes clogging in the inner layer. Subsequently, as the growth of microorganisms in the biological filtration layer 120 progresses, the assimilation and solubilization of SS in the surface layer by the microorganisms progresses, and the capture of SS in the inner layer of the biological filtration layer 120 also increases. As a result, clogging in the inner layer gradually increases over time, which manifests as an exponential rise in the water level.

[0057] Subsequently, the water level of the treated water changes linearly once it exceeds the first water level. Here, as mentioned above, the distance between the first water level and the second water level (distance H in Figure 1) is equal to the distance between the reference water level and the first water level. Therefore, as shown in Figure 4, the first time T1, which is the time it takes for the treated water to reach the first water level from the reference water level, is longer than the second time T2, which is the time it takes for the treated water to reach the second water level from the first water level.

[0058] In this embodiment, the control unit 140 of the biological filtration device 100 measures the first time T1 and the second time T2 based on the output of the water level sensor 130, and determines the relative magnitude of the first time T1 and the second time T2 by comparing them. As a result, as shown in Figure 4, if the second time is shorter than the first time, the control unit 140 triggers the cleaning process of the biological filtration layer 120 when the water to be treated reaches the third water level (water level C). This cleaning pattern, in which the cleaning of the biological filtration layer 120 is performed on the condition that the water to be treated reaches the third water level, is called the "first cleaning pattern".

[0059] In the initial treatment cycle shown in Figure 4, microorganisms are actively multiplying in the biological filtration layer 120. Therefore, it is desirable to prioritize the reproduction of organisms and avoid performing the washing process as much as possible. For this reason, in this embodiment, if it is determined that the first time is longer than the second time, the control unit 140 executes control to select a first washing pattern that waits for the water level of the treated water to rise to the third water level before proceeding to the washing process.

[0060] On the other hand, as the treatment cycle is repeated and the proliferation of microorganisms in the biological filtration layer 120 progresses, and their quantity and quality stabilize, the filtration process reaches equilibrium in the inner layer of the biological filtration layer 120. In other words, a series of cycles is formed in which the inner layer is blocked by microorganisms, SS is assimilated or solubilized by microorganisms, and microbial proliferation is repeated, and the change in the water level of the treated water from the reference water level to the first water level becomes linear. As a result, as shown in Figure 5, the water level of the treated water changes linearly from the reference water level to the second water level, so the first time T1 and the second time T2 become equal. In other words, the fact that the first time T1 and the second time T2 are equal means that the proliferation of microorganisms has stabilized.

[0061] Therefore, as shown in Figure 5, when the first time and the second time are equal, the control unit 140 proceeds to the cleaning process of the biological filtration layer 120 at a preset cleaning interval without waiting for the treated water to reach the third water level. That is, the cleaning process of the biological filtration layer 120 is executed on the condition that a preset time (for example, 24 hours) has been reached since the start of operation. This cleaning pattern in which the biological filtration layer 120 is cleaned at a preset cleaning interval is called the "second cleaning pattern". Note that "the first time and the second time are equal" is not limited to cases where they are exactly equal, but may include errors within a range that can be considered substantially equal. For example, it may be acceptable if the difference between the first time and the second time falls within a range of ±5%.

[0062] As described above, the biological filtration device 100 of this embodiment measures the first time it takes for the water to be treated to reach a first water level from a reference water level, and the second time it takes to reach a second water level from the first water level. Based on the comparison result of these two measurements, it performs control to change the cleaning pattern of the biological filtration layer 120. This optimizes the cleaning pattern of the biological filtration layer 120, reducing excessive or insufficient cleaning and achieving efficient purification. Thus, this embodiment provides a biological filtration device 100 and a cleaning method therefor that are equipped with a mechanism to reduce excessive and insufficient cleaning.

[0063] (Second Embodiment) In the first embodiment, the first time it takes for the treated water to reach a first water level from a reference water level and the second time it takes to reach a second water level from the first water level are measured, and if the first time and the second time are equal, the process proceeds to the cleaning step of the biological filtration layer 120 at a preset cleaning interval (i.e., the second cleaning pattern is selected). At this time, the preset cleaning interval can be adjusted when certain conditions are met.

[0064] For example, when the control unit 140 has selected the second cleaning pattern (i.e., is executing a processing cycle with the second cleaning pattern), if the water level of the water to be treated reaches the third level three times in a row before proceeding to the cleaning process, the preset cleaning interval (e.g., 24 hours) may be shortened by one hour. The fact that the water level of the water to be treated reaches the third level before proceeding to the cleaning process indicates a high probability that the cleaning interval is too long. Therefore, as described above, it is effective to change the parameters to shorten the cleaning interval when the water level of the water to be treated reaches the third level consecutively.

[0065] When performing the control described above, the number of consecutive times the treated water reaches the third water level before the parameter is changed is not limited to three; it can be determined as appropriate. Also, in the example above, the predetermined washing interval was shortened by one hour, but the extent to which it is shortened can be determined as appropriate based on the operating conditions of the biological filtration system 100, etc.

[0066] Furthermore, when the control unit 140 has selected the second washing pattern, if it is not detected that the water to be treated has reached the first water level before proceeding to the washing process, the preset washing interval (for example, 24 hours) may be changed to be one hour longer. If the water level of the water to be treated does not reach the first water level before proceeding to the washing process, it is highly likely that the washing interval is too short. Therefore, as described above, if it is not detected that the water to be treated has reached the first water level, it is effective to change the parameter to lengthen the washing interval. In this case as well, the amount to which the preset washing interval should be lengthened should be determined appropriately based on the operating status of the biological filtration device 100, etc.

[0067] (Third embodiment) In this embodiment, we describe an example in which each parameter of the washing process is changed based on the time (first time T1) required for the water level of the water to be treated to change from a reference water level to a first water level.

[0068] In this embodiment, first, the average value D1 obtained from multiple past measurements is calculated for the first time period T1 described above. For example, the control unit 140 calculates the average value for the past seven first time period T1 measurements. Then, the control unit 140 compares the first time period T1 with the average value D1 to determine the relationship between the first time period T1 and the average value D1.

[0069] If the judgment shows that the first hour T1 is greater than or equal to the average value D1 (D1 ≤ T1), it can be determined that there is excessive washing because the rate of water level rise to the first water level is slower than the past average value. Therefore, the processing periods for the "primary treatment" and "tertiary treatment" explained using Figure 2 are shortened by a predetermined period. For example, the parameters can be changed to shorten the processing periods for the "primary treatment" and "tertiary treatment" by 1 minute.

[0070] Furthermore, if the judgment results show that the first time T1 is shorter than the average value D1 (D1 > T1), it can be determined that the water level is rising to the first level faster than the past average value, indicating insufficient cleaning. Therefore, the processing periods for the "primary treatment" and "tertiary treatment" explained using Figure 2 are extended by a predetermined period. For example, the parameters can be changed to extend the processing periods for the "primary treatment" and "tertiary treatment" by 1 minute.

[0071] As described above, by monitoring the behavior of water level changes from the reference water level to the first water level, it becomes possible to optimize each parameter of the cleaning process and execute the cleaning process efficiently.

[0072] (Fourth Embodiment) In this embodiment, we will describe an example of its application to a biological filtration system that performs purification treatment using an upward flow.

[0073] Figure 6 is a schematic diagram showing the configuration of a biological filtration device 100a in one embodiment of the present invention. In this embodiment, the water to be treated is supplied from below the biological filtration layer 120a, and the water to be treated is purified by an upward flow.

[0074] The biological filtration system 100a includes a treatment tank 110a, a biological filtration layer 120a, a water level sensor 130a, and a control unit (not shown). For the sake of clarity, the piping connected to the biological filtration system 100a is not shown in the illustration, but the use of treated water in the washing process and the supply of air, water, or air and water from below the biological filtration layer 120a for washing are the same as in the first embodiment. Although not shown in the illustration, similar to the first embodiment, pumps and automatic valves are arranged in each pipe connected to the biological filtration system 100a, and each is controlled by the control unit of the biological filtration system 100a.

[0075] In the biological filtration apparatus 100a of this embodiment, the treatment tank 110a is divided into two spaces by a partition member 111a. Specifically, the treatment tank 110a includes a reaction tank 111b and a raw water supply layer 111c. A biological filtration layer 120a is located in the reaction tank 111b, where the water to be treated is purified. Raw water (water to be treated) is supplied to the raw water supply layer 111c from above. The supplied raw water is supplied to the reaction tank 111b via the raw water supply layer 111c and passes through the biological filtration layer 120a in an upward flow. The treated water that has been purified after passing through the biological filtration layer 120a is stored in the treated water tank 150a.

[0076] In this embodiment, a biological filtration system 100a that performs purification treatment using an upward flow is used to monitor the water level of the water to be treated in the raw water supply tank 111c. In this embodiment, a water level sensor 130a is placed above the raw water supply tank 111c to acquire the water level of the water to be treated. The water level sensor 130a in this embodiment can acquire the water level of the water to be treated by measuring the position of the water surface of the water to be treated using an ultrasonic sensor.

[0077] As described above, in the biological filtration system 100a that performs purification treatment using an upward flow, the water level of the water to be treated is obtained by measuring the position of the water surface of the water to be treated located upstream of the biological filtration layer 120a. As a result, in the biological filtration system 100a of this embodiment, as in the first embodiment, control is performed to change the washing pattern of the biological filtration layer 120a based on the output of the water level sensor 130a.

[0078] The embodiments of the present invention can be combined as appropriate, insofar as they do not contradict each other. Based on the embodiments described above, any additions, deletions, or design changes made by those skilled in the art, or additions, omissions, or changes in processes, are also included within the scope of the present invention, as long as they retain the essence of the invention.

[0079] Furthermore, any effects or benefits other than those brought about by the embodiments described above, if they are clear from the description herein or easily predictable to a person skilled in the art, are naturally considered to be brought about by the present invention. [Explanation of Symbols]

[0080] 11…Raw water supply pipe, 12…Treated water pipe, 13…Water washing pipe, 14…Air washing pipe, 15…Drain pipe, 21, 22…Automatic valves, 23, 24…Check valves, 25, 26…Automatic valves, 31, 32…Pumps, 100, 100a…Filtration device, 110, 110a…Treatment tank, 111a…Partition member, 111b…Reaction tank, 111c…Raw water supply layer, 120, 120a, 121, 122…Filtration layer, 125…Washing assistance area, 130, 130a…Water level sensor, 140…Control unit, 150, 150a…Treated water tank

Claims

1. Processing tank and A biological filtration layer is placed inside the aforementioned treatment tank, A water level sensor that acquires the water level of the water to be treated inside the treatment tank, A control unit that acquires the output of the water level sensor, Equipped with, The water level sensor acquires a first water level that is a predetermined distance higher than a preset reference water level, and a second water level that is a predetermined distance higher than the first water level. The control unit measures, based on the output of the water level sensor, the first time it takes for the water to be treated to reach the first water level from the reference water level, and the second time it takes for the water to reach the second water level from the first water level, and changes the cleaning pattern of the biological filtration layer according to the result of comparing the first time and the second time.

2. The water level sensor further acquires a third water level that is higher than the second water level, The biological filtration apparatus according to claim 1, wherein the control unit, upon detecting that the water to be treated has reached the third water level, executes a control to forcibly wash the biological filtration layer.

3. The biological filtration apparatus according to claim 2, wherein the control unit selects a first cleaning pattern that performs cleaning of the biological filtration layer on the condition that the water to be treated reaches the third water level when the first time is longer than the second time, and selects a second cleaning pattern that performs cleaning of the biological filtration layer at a preset cleaning interval when the first time and the second time are equal.

4. The biological filtration apparatus according to claim 3, wherein the control unit shortens the washing interval if the water to be treated reaches the third water level a predetermined number of times consecutively while the second washing pattern is being selected.

5. The biological filtration apparatus according to claim 3 or 4, wherein the control unit lengthens the washing interval if it does not detect that the water to be treated has reached the first water level while the second washing pattern is being selected.

6. The biological filtration apparatus according to any one of claims 1 to 5, wherein the cleaning of the biological filtration layer is performed by supplying air, water, or air and water into the biological filtration layer in the opposite direction to the direction of flow of the water to be treated during the filtration process.

7. The biological filtration apparatus according to claim 6, wherein, as a result of comparing the first time with the average value of the first time obtained from multiple past measurements, if the first time is equal to or greater than the average value, the cleaning period of the biological filtration layer is shortened by a predetermined period.

8. The biological filtration apparatus according to claim 7, wherein, as a result of comparing the average value with the first time, if the first time is shorter than the average value, the cleaning period of the biological filtration layer is extended by a predetermined period.

9. A method for cleaning a biological filtration system that includes a biological filtration layer located inside a treatment tank, The first time is measured until the treated water reaches a first water level that is a predetermined distance higher than the pre-set reference water level. The second time is measured until the water to be treated reaches a second water level that is a predetermined distance higher than the first water level. A method for cleaning a biological filtration apparatus, comprising changing the cleaning pattern of the biological filtration layer according to the result of comparing the first time and the second time.

10. A method for cleaning a biological filtration apparatus according to claim 9, wherein, as a result of comparing the first time and the second time, if the first time is longer than the second time, a first cleaning pattern is selected in which the cleaning of the biological filtration layer is performed on the condition that the water to be treated reaches a third water level higher than the second water level, and if the first time and the second time are equal, a second cleaning pattern is selected in which the cleaning of the biological filtration layer is performed at a preset cleaning interval.

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