JP2023142676A - Measuring system and measuring method - Google Patents

Abstract

To provide a measuring system that can stabilize the state of dilution of dirty water to which a diluent is supplied to precisely acquire an optical measured value.SOLUTION: A measuring system 60 comprises: a transfer pipe for measurement 28 through which dirty water flows; a dilution line 55 that is connected with the transfer pipe for measurement 28 and supplies a diluent to the dirty water; a mixing channel 40 that is arranged on the transfer pipe for measurement 28 to mix the dirty water with the diluent; and an optical measuring device 3 that acquires an optical measured value of the dirty water mixed with the diluent. The mixing channel 40 has a bent part 40a that changes the direction of flow of the dirty water to which the diluent is supplied.SELECTED DRAWING: Figure 2

Description

The present invention relates to a measurement system and method for obtaining optical measurements of wastewater mixed with a diluent.

In order to properly manage the operation of sewage treatment in various facilities such as wastewater treatment facilities and water treatment facilities, it is necessary to check the properties of sewage (e.g., color, turbidity, transparency, concentration of suspended solids, and flocculation of suspended solids). condition) must be accurately understood. Therefore, conventionally, optical measurement values are obtained using an optical measuring device, and numerical analysis values indicating the properties of wastewater are calculated from the optical measurement values. For example, Patent Document 1 discloses that an optical measurement value of sewage discharged from a stirrer is obtained using an optical measurement device, and a flocculant is determined based on a numerical analysis value calculated from the obtained optical measurement value. A flocculation method is described to determine the appropriate injection rate for.

In wastewater with a high concentration of suspended solids or flocs formed by mixing with flocculants, for example, when measuring transmitted light intensity as an optical measurement value, the transmitted light intensity measured by an optical measuring device is The light intensity becomes almost constant, and it may not be possible to determine the appropriate injection rate of the flocculant. Therefore, by diluting the wastewater discharged from the stirrer with a diluent and increasing the gap between flocs in the wastewater, we can measure the optical measurement value when flocs are present and the optical measurement when no flocs are present. What is being done is to create a difference between the values.

International Publication No. 2016/6419

However, when the diluent is supplied to piping through which sewage flows, the sewage and the diluent are not sufficiently mixed, and the diluted state of the sewage may not be stable. As a result, the concentration of suspended solids or the concentration of flocs contained in the wastewater to be measured may not be stable, and optical measurement values may not be accurately obtained.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a measurement system and a measurement method that can stabilize the diluted state of wastewater supplied with a diluent and accurately obtain optical measurement values.

In one embodiment, a measurement transfer pipe through which wastewater flows, a dilution line connected to the measurement transfer pipe and supplying a diluent to the wastewater, and a dilution line connected to the measurement transfer pipe to supply the wastewater and the diluent and an optical measurement device that obtains an optical measurement value of the sewage mixed with the diluent, the mixing flow path is configured to mix the sewage to which the diluent has been supplied. A measurement system is provided having a bend that changes the direction of flow.
In one aspect, the mixing flow path is arranged downstream of a connection point between the dilution line and the measurement transfer pipe.
In one embodiment, the mixing channel is an L-shaped pipe.
In one embodiment, the outlet of the mixing channel faces downward.
In one aspect, the inner diameter of the mixing channel is the same as the inner diameter of the measurement transfer pipe.

In one embodiment, a dilution step of supplying a diluent to wastewater, a mixing step of mixing the wastewater and the diluent through a mixing flow path, and obtaining an optical measurement value of the wastewater mixed with the diluent. an optical measurement step, and the mixing flow path has a bending part that changes the flow direction of the wastewater supplied with the diluent.

The measurement system includes a mixing channel connected to a measurement transfer pipe. By mixing the wastewater to be measured and the diluent, the mixing channel can stabilize the diluted state of the wastewater and accurately obtain optical measurement values.

FIG. 1 is a schematic diagram showing an example of a sewage treatment apparatus equipped with a measurement system according to an embodiment. FIG. 2 is a schematic diagram showing the configuration of the measurement system shown in FIG. 1. FIG. 3 is an enlarged view schematically showing one embodiment of the mixing channel shown in FIG. 2. Figure 4(a) shows an example of measuring the intensity of transmitted light when flocs are not formed in wastewater due to an inappropriate injection rate of the flocculant, and Figure 4(b) shows an example of measuring the intensity of transmitted light when the flocculant injection rate is not appropriate. An example of measuring the intensity of transmitted light when flocs are formed in wastewater is shown below. FIG. 5 is a schematic diagram showing another example of a sewage treatment apparatus in which the measurement system shown in FIG. 2 is arranged.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic diagram showing an example of a sewage treatment apparatus equipped with a measurement system according to an embodiment. The sewage treatment device shown in FIG. 1 is a coagulation device for treating sewage discharged from a wastewater treatment facility, a water purification treatment facility, or the like. The measurement system described below obtains optical measurement values for calculating numerical analysis values indicating the properties of wastewater (e.g., color tone, turbidity, transparency, concentration of suspended solids, and state of agglomeration of suspended solids). used for In this embodiment, an appropriate injection rate of the flocculant is determined based on numerical analysis values obtained by numerically analyzing optical measurement values.

In the following, a flocculation device for treating wastewater containing suspended solids, which is an example of wastewater, will be described as an example of equipment equipped with a measurement system. However, the measurement system according to this embodiment may be placed in other equipment that processes wastewater. For example, the sewage to be treated may be sludge discharged from a wastewater treatment facility, water treatment facility, etc., wastewater from a wastewater treatment facility, raw water from a water treatment facility, or the like. The sludge may be either organic sludge or inorganic sludge.

Examples of organic sludge include organic sludge generated in sewage treatment, human waste treatment, and wastewater treatment in various industries. More specifically, examples of organic sludge include primary sedimentation tank sludge, surplus sludge, anaerobic digestion sludge, aerobic digestion sludge, human waste sludge, septic tank sludge, digestion and desorption liquid, and coagulated sedimentation sludge. can. Organic sludge may contain inorganic substances.

Examples of inorganic sludge include inorganic sludge generated in water purification, construction wastewater treatment, and wastewater treatment in various industries. Here, the sludge generated in water purification treatment refers to sludge discharged from settling tanks, sludge ponds, thickening tanks, etc. in water purification facilities. Inorganic sludge may contain organic matter.

Examples of wastewater in wastewater treatment facilities include wastewater from various industries such as sewage, food industry, drinking water industry, chemical industry, and machinery industry. Examples of raw water in water treatment facilities include river water, lake water, and groundwater.

Furthermore, the wastewater to be treated may be water prepared in the process of treatment such as wastewater treatment or water purification treatment. Examples of wastewater in wastewater treatment include pH-adjusted wastewater, wastewater in which an inorganic flocculant is injected, wastewater in which an organic coagulant is injected, and wastewater in which a metal chelating agent is injected. Furthermore, examples of wastewater used in water purification include raw water whose pH has been adjusted, raw water which has been injected with an inorganic flocculant, and the like.

The flocculation device shown in FIG. 1 has a configuration in which a wastewater storage tank 10, an agitator 1, and a measurement system 60 are connected in series in this order. The wastewater storage tank 10 stores wastewater containing suspended solids. The stirrer 1 includes a stirring tank 2 to which sewage containing suspended solids is supplied, stirring blades 8 that stir the sewage containing suspended solids, and a motor 9 as a drive device that rotates the stirring blades 8. A supply source pipe 18 extending from the sewage storage tank 10 is connected to the stirring tank 2 of the agitator 1, and the supply source pipe 18 is connected to a supply pipe 18 that supplies the sewage stored in the sewage storage tank 10 to the stirring tank 2 at a predetermined flow rate. A device 7 is arranged. The supply device 7 is, for example, a pump or a valve or a combination of a pump and a valve. In one embodiment, the flocculation device does not include the sewage storage tank 10, and the sewage may be supplied by branching into the supply source pipe 18 from an existing sewage pipe through which the sewage flows.

In one embodiment, a line mixer may be used as the agitator 1. A line mixer is a mixer built into piping. The advantage of a line mixer is that since the mixer is sealed, sewage can be sent downstream of the line mixer with two pumps, a sewage pump and a coagulant pump upstream of the line mixer. be. On the other hand, in the case of the stirrer 1 in which the stirring blades 8 are installed in the stirring tank 2, the upper part of the stirring tank is open, so in order to send the liquid downstream of the stirrer, it is necessary to In addition to the pump and the flocculant pump, another pump or pump-equivalent equipment is required. Therefore, it is common practice to send liquid downstream using height differences without installing a pump.

In this embodiment, the stirrer 1 is configured as a high-speed stirrer that performs high-speed stirring with the rotational speed of the stirring blades 8 set at 300 to 5000 min ^-1 . By this high-speed stirring, the flocculant is instantly dispersed in the wastewater, and the flocculant is efficiently and uniformly mixed with the wastewater. As a result, suspended matter contained in wastewater can be efficiently aggregated.

In the agitator 1, it is important to rotate the agitating blades 8 at a rotational speed of 300 to 5000 min ^-1 to agitate the wastewater containing suspended solids into which the flocculant has been injected at a high speed. Preferably, the rotational speed of the stirring blade 8 is 300 to 2000 min ^-1 . More preferably, the rotational speed of the stirring blade 8 is 400 to 1500 min ^-1 . More preferably, the rotational speed of the stirring blade 8 is 500 to 1200 min ⁻¹ .

When such high-speed stirring is performed, high stress is applied to the wastewater into which the flocculant has been injected, so if the flocculant is not injected at an appropriate injection rate, the flocs will be destroyed before they grow. Therefore, unless the flocculant is injected at an appropriate injection rate, flocs will not grow properly. In this embodiment, a control device, which will be described later, acquires an optical measurement value from an optical measurement device 3 provided in a measurement system 60, and further uses the optical measurement value to confirm that the flocs are growing appropriately. Judgment is made from numerical analysis values obtained through numerical analysis. Thereby, the appropriate injection rate of the flocculant can be determined with high accuracy. As a result, the amount of coagulant used can be reduced. Furthermore, the injection rate of the flocculant can be appropriately controlled without the operator's experience or intuition. Furthermore, even if the properties of sewage containing suspended solids (for example, the concentration of suspended solids in sewage) change, the injection rate of the flocculant can be appropriately controlled.

The rotational speed of the stirring blades 8 depends on the type of wastewater containing suspended solids (e.g., wastewater, sludge, etc.), the properties of the wastewater (e.g., SS (Suspended Solids) concentration, viscosity, etc.), and the type of flocculant (e.g., The speed is adjusted at 300 to 5000 min ^-1 based on the amount of flocculant (inorganic flocculant, organic flocculant, polymer flocculant, etc.). The flocculant to be injected into the wastewater containing suspended solids may be injected into the stirring tank 2 or into the supply source pipe 18 arranged upstream of the stirring tank 2.

In this embodiment, a flocculant storage tank 11 for storing a flocculant is provided, and a flocculant supply pipe 26 extending from the flocculant storage tank 11 is connected to the stirring tank 2 . A flocculant injection device 4 is arranged in the flocculant supply pipe 26 . The flocculant injection device 4 is a device that injects a flocculant into wastewater containing suspended solids at a predetermined injection rate. The flocculant injection device 4 is, for example, a pump, a valve, or a combination of a pump and a valve. In one embodiment, the flocculant may not be provided with the flocculant storage tank 11, and the flocculant may be supplied by branching from the existing flocculant piping through which the flocculant flows to the flocculant supply piping 26.

In this flocculation device, sewage containing suspended solids is supplied from a sewage storage tank 10 to an agitation tank 2 by a supply device 7. The flocculant is supplied to the stirring tank 2 by the flocculant injection device 4. In the stirring tank 2, the stirring blades 8 are rotated at a high speed of 300 to 5000 min ^-1 to mix the waste water and the flocculant, thereby forming flocs of suspended solids. Note that depending on the injection rate of the flocculant, flocs of suspended matter may not be formed. That is, in the stirrer 1, the stirring blades 8 are rotated at high speed in order to form flocs of suspended solids, but depending on the injection rate of the flocculant, flocs of suspended solids may not be formed.

The measurement system 60 includes an optical measurement device 3, a measurement transfer pipe 28 that sends waste water from the stirrer 1 to the optical measurement device 3, a dilution line 55 that supplies a dilution liquid to the waste water, and a dilution line 55 that connects the waste water and the dilution liquid. It is provided with a mixing channel 40 for mixing and a measuring discharge pipe 29 for discharging wastewater measured by the optical measuring device 3. The measurement transfer pipe 28 is connected to the stirring tank 2 and the optical measurement device 3. The wastewater discharged from the stirrer 1 is transferred to the optical measurement device 3 through the measurement transfer piping 28. The measuring discharge pipe 29 is connected to the optical measuring device 3 . The waste water discharged from the optical measurement device 3 is discharged through the measurement discharge pipe 29.

The optical measurement device 3 is a device for irradiating light onto the wastewater containing flocs formed by the stirrer 1 to obtain an optical measurement value. In this embodiment, the optical measuring device 3 is a device that can measure the intensity of transmitted light coming out of wastewater containing flocs. The optical measurement device 3 may be a device capable of measuring transmittance, intensity of diffracted light, absorbance, intensity of reflected light, and the like.

The dilution line 55 is connected to the measurement transfer pipe 28, and supplies the diluted liquid to the wastewater after stirring and before optical measurement. The dilution line 55 includes a diluent storage tank 52 that stores a diluted liquid, and a diluted liquid supply device 53 that supplies the diluted liquid stored in the diluted liquid storage tank 52 to the wastewater stirred by the stirrer 1 at a predetermined flow rate. A diluent supply pipe 57 extending from the diluent storage tank 52 is connected to the measurement transfer pipe 28 at a position between the stirrer 1 and the optical measuring device 3 . The diluent supply device 53 is arranged in the diluent supply pipe 57.

The diluent supply device 53 is a device that supplies a diluent to the wastewater stirred by the stirrer 1 at a predetermined flow rate before the wastewater is supplied to the optical measuring device 3 . The diluent supply device 53 is, for example, a pump, a valve, or a combination of a pump and a valve. The wastewater supplied with the diluent is supplied to the optical measurement device 3 through a mixing channel 40 connected to the measurement transfer piping 28 . As the diluent, pure water, tap water, industrial water, ground water, treated water from various wastewater treatments, seawater, etc. can be used. In one embodiment, the dilution line 55 does not include the diluent storage tank 52, and the diluent is supplied by using an existing pipe as the diluent supply piping 57 through which tap water, treated water, etc. flows at a predetermined pressure. Good too.

The mixing channel 40 is a structure for mixing wastewater and diluent. The wastewater mixed with the diluent through the mixing flow path 40 is supplied to the optical measurement device 3, where the optical measurement device 3 performs optical measurement.

FIG. 2 is a schematic diagram showing the configuration of the measurement system 60 shown in FIG. 1. As shown in FIG. 2, the measurement transfer pipe 28 includes a primary transfer pipe 28A connected to the inlet of the mixing flow path 40 and a secondary transfer pipe 28B connected to the outlet of the mixing flow path 40. The mixing channel 40 is arranged downstream of the connection point 55a between the dilution line 55 and the measurement transfer pipe 28. That is, the dilution line 55 is connected to the primary transfer pipe 28A at the connection point 55a. In one embodiment, the measurement transfer pipe 28 does not have the secondary transfer pipe 28B, and the outlet of the mixing channel 40 may be connected to the optical measurement device 3.

FIG. 3 is an enlarged view schematically showing one embodiment of the mixing channel 40 shown in FIG. 2. FIG. The mixing channel 40 is an L-shaped tube having a bent portion 40a. A cross section perpendicular to the central axis of the mixing channel 40 has a circular shape. In one embodiment, the cross section of the mixing channel 40 may have a shape other than circular (eg, square, rectangular). The mixing channel 40 is configured to change the flow direction of the wastewater mixed with the diluent at the bent portion 40a. An inlet 40b of the mixing flow path 40 faces in the horizontal direction, and an upstream portion 40d located upstream of the bent portion 40a of the mixing flow path 40 extends in the horizontal direction. An outlet 40c of the mixing channel 40 faces downward, and a downstream portion 40e located downstream of the bent portion 40a of the mixing channel 40 extends in the vertical direction.

In this embodiment, the bending part 40a of the mixing flow path 40 is bent at a right angle, but the bending angle of the bending part 40a is not limited to this embodiment, and in one embodiment, the bending angle of the bending part 40a is It may be within the range of 45 degrees to 135 degrees. Further, in this embodiment, the downstream portion 40e of the mixing channel 40 downstream of the bent portion 40a extends in the vertical direction, but in other embodiments, the downstream portion 40e of the mixing channel 40 extends horizontally. It may extend in the direction. That is, the mixing flow path 40 may change the flow direction of the wastewater supplied with the diluent within a horizontal plane. In yet another embodiment, the mixing flow path 40 may have a plurality of bent portions 40a and may be configured to change the flow direction of the wastewater supplied with the diluent multiple times.

The mixing channel 40 can mix the sewage and the diluted liquid by changing the flow direction of the sewage to which the diluted liquid is supplied by the bending part 40a and creating a turbulent flow of the sewage. Therefore, the diluted state of the sewage sent to the optical measurement device 3 is stabilized, and the optical measurement device 3 can accurately obtain the optical measurement value of the sewage. In particular, the entire interior of the mixing channel 40 is hollow, and a structure (for example, a baffle plate, etc.) for mixing the wastewater and the diluent does not need to be present in the mixing channel 40. Therefore, the mixing channel 40 is less likely to be clogged with flocs, dirt, etc. contained in the wastewater.

The inner diameter d1 of the inlet 40b and upstream portion 40d located upstream of the bent portion 40a is the same as the inner diameter d2 of the outlet 40c and downstream portion 40e located downstream of the bent portion 40a. Further, the inner diameter d3 of the bent portion 40a is the same as or larger than the inner diameter d1 of the inlet 40b and the inner diameter d2 of the outlet 40c. The inner diameters d1 and d2 of the mixing channel 40 are the same as the inner diameters of the measurement transfer pipe 28, that is, the inner diameter d4 of the primary transfer pipe 28A and the inner diameter d5 of the secondary transfer pipe 28B. By making the internal diameters of the measuring transfer pipe 28 and the mixing channel 40 the same, it is possible to prevent flocs and dirt contained in the wastewater from clogging the mixing channel 40.

Returning to FIG. 2, the optical measurement device 3 includes a nozzle 30 connected to the end of the secondary transfer pipe 28B, and a saucer (liquid receiving part) 32 connected to the tip of the measurement discharge pipe 29. . The nozzle 30 is a structure that causes the dirty water mixed with the diluent flowing through the secondary transfer pipe 28B to flow downward, and has a cylindrical shape. The tray 32 is arranged below the nozzle 30 and spaced apart from the nozzle 30. The receiving tray 32 is a structure for receiving wastewater flowing down from the nozzle 30, and has a funnel shape in the illustrated example.

In this embodiment, the nozzle 30 and the tray 32 are arranged along the vertical direction, and the central axis of the nozzle 30 coincides with the central axis of the tray 32. An open space is formed between the nozzle 30 and the tray 32, through which the wastewater flows. Therefore, the waste water flows down from the nozzle 30 into the atmosphere.

The optical measurement device 3 further includes an optical sensor 35 that irradiates light onto the wastewater mixed with the diluent flowing down from the nozzle 30 to obtain an optical measurement value. In this embodiment, the optical sensor 35 includes a light source (light projector) 35a that irradiates light toward wastewater, and a photodetector (light receiver) 35b that detects light coming out of the wastewater. This is an optical sensor that measures the intensity of transmitted light that has reached the detector 35b. The light emitted from the light source 35a and transmitted through the wastewater containing flocs is detected by the photodetector 35b. This transmitted light intensity is measured for a predetermined period of time, and the measured transmitted light intensity is used as an optical measurement value.

Examples of the light source 35a include various lamps (mercury lamp, xenon lamp, krypton lamp, metal halide lamp, halogen lamp, etc.), various lasers (solid laser, semiconductor laser, liquid laser, gas laser, etc.), various LEDs, etc. . The light source 35a is preferably an LED, because an LED is a light source that can emit relatively high-intensity light among commercially available optical sensors. Examples of the photodetector 35b include a CCD, a photodiode, a phototransistor, a photomultiplier tube, a photoconductive element, an infrared optical sensor, a CMOS, and the like. In any case, a commercially available product can be used as the optical sensor 35.

The measurement of transmitted light intensity, which is an optical measurement value, is carried out once or multiple times while changing the injection rate of the flocculant, thereby obtaining at least one optical measurement value. Note that the transmitted light intensity detected by the photodetector 35b is accumulated in the data logger 50 and then sent to the numerical analysis device 5, which will be described later. The numerical analysis value calculated by the numerical analysis device 5 is sent to the control device 6, and the control device 6 determines an appropriate injection rate of the flocculant based on the numerical analysis value. The data logger 50, the numerical analysis device 5, and the control device 6 may be provided separately. Alternatively, the data logger 50 and the numerical analysis device 5 may be incorporated into a control device 6 configured as one computer or one programmable logic controller (for example, a sequencer).

Next, with reference to FIGS. 4(a) and 4(b), an example of measuring the intensity of transmitted light of wastewater containing suspended solids using the optical measuring device 3 will be described. Figure 4(a) shows an example of measuring the intensity of transmitted light when flocs are not formed in wastewater due to an inappropriate injection rate of the flocculant, and Figure 4(b) shows an example of measuring the intensity of transmitted light when the flocculant injection rate is not appropriate. An example of measuring the intensity of transmitted light when flocs are formed in wastewater is shown below. In FIGS. 4(a) and 4(b), the horizontal axis represents measurement time, and the vertical axis represents transmitted light intensity.

As shown in FIG. 4A, if no flocs are formed in the wastewater, the light emitted from the light source 35a is blocked by suspended matter and hardly reaches the photodetector 35b. As a result, the measured transmitted light intensity remains at a low value as the measurement time passes. On the other hand, when flocs are formed in wastewater, suspended solids are aggregated as flocs. Therefore, as shown in FIG. 4(b), during the measurement of the transmitted light intensity, there is a time when the light emitted from the light source 35a is blocked by the flocks and does not reach the photodetector 35b, and a time when the light emitted from the light source 35a does not reach the photodetector 35b from the gap between the flocks. 35b. As a result, multiple peaks of transmitted light intensity are measured. These multiple peaks are used in the numerical analysis process described later.

The purpose of supplying the diluted liquid to the stirred wastewater through the dilution line 55 is to reduce the concentration of suspended matter and/or the concentration of flocs contained in the stirred wastewater. In wastewater with a high concentration of suspended solids, there is no difference between optical measurements when flocs are formed and optical measurements when no flocs are formed, making it difficult to determine the flocculant injection rate. There are cases where For example, when the optical measurement device 3 measures the transmitted light intensity of wastewater with a high concentration of suspended solids, even if the flocculant injection rate is appropriate and flocs are formed, there are almost no gaps between the flocs. , as shown in FIG. 4(a), the transmitted light intensity may become almost constant. On the other hand, when the stirred wastewater is diluted with a diluent, the gaps between the flocs can be increased, so light passes through the gaps between the flocs, and as shown in Figure 4(b), the light passes through the flocs. Multiple peaks of light intensity are measured. As a result, a difference occurs between the transmitted light intensity when flocs are formed and the transmitted light intensity when no flocs are formed, and an appropriate injection rate can be determined.

Returning to FIG. 1, a numerical analysis device 5 is electrically connected to the optical measurement device 3, and a control device 6 is connected to the numerical analysis device 5. The numerical analysis device 5 may be incorporated into the control device 6. Further, the control device 6 is connected to the flocculant injection device 4.

The optical measurement values obtained from the optical measurement device 3 are sent to the numerical analysis device 5. The numerical analysis device 5 numerically analyzes the optical measurement value to obtain a numerical analysis value. The obtained numerical analysis value is sent to the control device 6. The control device 6 determines an appropriate injection rate of the flocculant based on the numerical analysis value.

Examples of numerical analysis values include the average value, dispersion, standard deviation, peak area, and peak height of optically measured values. The dispersion of optical measurement values is a value obtained by statistically analyzing optical measurement values, and is an amount indicating the degree of dispersion of the distribution of optical measurement values obtained during a predetermined measurement time. Standard deviation is the positive value of the square root of the variance. The peak area is calculated using a curve drawn by plotting the optical measurement values obtained during a given measurement time on a graph where the vertical axis represents the optical measurement value and the horizontal axis represents the measurement time, and the reference This is the area of the region surrounded by a line (for example, a baseline). The peak area corresponds to, for example, the area of the hatched region in FIG. 4(b). The peak height is the peak height of a curve drawn by plotting the optical measurements obtained during a given measurement time on a graph where the vertical axis represents the optical measurement value and the horizontal axis represents the measurement time. is the height from the horizontal axis.

The number of optical measurement values greater than or equal to a certain threshold value or the number of optical measurement values less than or equal to a certain threshold value may be used as the numerical analysis value. The numerical analysis device 5 may calculate SS concentration, turbidity, chromaticity, floc particle size, etc. from the optical measurement values, and use these as numerical analysis values. Here, the floc particle size means the diameter of the floc when the floc is spherical. When the flocs are not spherical, the floc particle size means the Stokes diameter or the particle size measured by various measuring methods. The floc particle size may be the average particle size of the flocs. Examples of the average particle diameter include an arithmetic mean diameter, a maximum diameter, and a median diameter. Further, the average particle size may be based on number, mass, or volume.

As a method for calculating SS concentration and turbidity from optically measured values, a known method such as a transmitted light measurement method can be used. As a method for calculating chromaticity from optical measurement values, a known method such as a transmitted light measurement method can be used. As a method for calculating the floc particle size from the optical measurement value, a known method such as a laser diffraction/scattering method or a method of analyzing an image taken with a camera can be used. The floc particle size may be an average floc particle size or a particle size distribution of floc particle sizes. A commercially available measuring device that can perform optical measurements and calculate SS concentration, turbidity, chromaticity, floc particle size, etc. from the obtained optical measurements can be used.

The control device 6 controls at least one of the following: injecting a flocculant into the wastewater, stirring the wastewater (high-speed stirring), obtaining an optical measurement value, and performing numerical analysis based on the optical measurement value at least once. Determine the appropriate injection rate of flocculant from the numerical analysis values. That is, the control device 6 injects a flocculant into wastewater containing suspended solids, stirs the wastewater to cause the suspended solids to form flocs, performs optical measurement on the stirred wastewater, and measures the obtained wastewater. The obtained optical measurement values are numerically analyzed to obtain numerical analysis values. Furthermore, the control device 6 determines whether the injection rate of the flocculant is appropriate based on the obtained numerical analysis value, and if the injection rate is not appropriate, changes the injection rate of the flocculant and stirs again. , optical measurements, and numerical analysis to determine the appropriate injection rate. Note that depending on the injection rate of the flocculant, flocs of suspended matter may not be formed.

As a method for determining an appropriate flocculant injection rate, a plurality of preset injection rates may be used. The control device 6 injects a flocculant into wastewater containing suspended solids at a preset injection rate, stirs the wastewater in order to form flocs of suspended solids, and performs optical imaging on the stirred wastewater. Measurement is carried out, and the obtained measured values are numerically analyzed to obtain numerical analysis values. This is repeated for each of a plurality of preset injection rates. The control device 6 compares a plurality of numerical analysis values obtained at each of a plurality of preset injection rates. In one embodiment, the injection rate at which the maximum or minimum value is obtained is determined as the appropriate injection rate. In other embodiments, the average value of the injection rate at which the largest numerical analysis value was obtained and the injection rate at which the second largest numerical analysis value was obtained may be used as the appropriate injection rate, or the appropriate injection rate may be the smallest numerical analysis value. The appropriate injection rate may be the average value of the injection rate at which the value is obtained and the injection rate at which the second smallest numerical analysis value is obtained.

In yet another embodiment, the control device 6 displays a plurality of numerical analysis values at a plurality of preset injection rates on a graph in which the vertical axis represents the numerical analysis value and the horizontal axis represents the injection rate of the flocculant. The appropriate injection rate of the flocculant may be determined based on the approximate expression obtained by plotting the plot and calculating the approximate expression showing the relationship between the plurality of injection rates and the plurality of numerical analysis values. For example, the injection rate at which the peak value of the numerical analysis value is obtained can be calculated from an approximate formula, and the obtained injection rate can be used as the appropriate injection rate of the flocculant.

The configuration of the optical measurement device 3 of the measurement system 60 is not limited to this embodiment, as long as it can obtain a measurement value for determining an appropriate injection rate of the flocculant. For example, in one embodiment, the optical measurement device 3 is provided with a pair of transparent windows in the secondary transfer pipe 28B through which the wastewater discharged from the stirrer 1 flows, instead of the nozzle 30, and the optical sensor 35 is provided with a pair of transparent windows. Accordingly, the optical measurement value may be obtained by emitting light toward one transparent window and detecting the light coming out from the other transparent window.

FIG. 5 is a schematic diagram showing another example of a wastewater treatment apparatus in which the measurement system 60 shown in FIG. 2 is arranged. The sewage treatment apparatus shown in FIG. 5 is a screw press (dehydrator) that squeezes a liquid-containing substance such as sludge and separates the liquid-containing substance into a filtrate and a cake.

The screw press shown in FIG. 5 includes a cylindrical screen casing (filtration cylinder) 61, and is arranged concentrically within the screen casing 61, and is configured to move sludge (sewage) as a liquid content into a predetermined range. A screw (not shown) that transfers in the transfer direction D, a rotation mechanism (not shown) that rotates the screw, a filtrate receiver 68 that collects the filtrate that has passed through the screen casing 61, and is connected to the filtrate receiver 68. and a measurement transfer pipe 28.

The screen casing 61 is formed from a screen (perforated plate) such as punched metal. The sludge introduced into the screen casing 61 is transferred within the screen casing 61 by rotation of the screw. As the sludge is transferred through the screen casing 61, it is compressed and dewatered. The filtrate that has passed through the screen of the screen casing 61 is collected by a filtrate receiver 68 arranged below the screen casing 61.

In this embodiment, the measurement transfer pipe 28 of the measurement system 60 is connected to a filtrate receiver 68 and is configured to obtain an optical measurement value of the filtrate (sewage) collected by the measurement system 60. There is. The filtrate flowing through the measurement transfer pipe 28 is supplied with a diluent through a dilution line 55, and the filtrate (sewage) and diluted liquid are mixed through a mixing channel 40. The optical measurement device 3 acquires optical measurement values of the filtrate mixed with the diluent. The obtained optical measurements are sent to a control device (not shown) of the screw press, and the control device controls the operation of the screw press based on the sent optical measurements. For example, the controller controls the rotational speed of the screw based on the optical measurements obtained in order to obtain a cake with the appropriate moisture content.

The embodiments described above have been described to enable those skilled in the art to carry out the invention. Various modifications of the above embodiment can be naturally made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Therefore, the invention is not limited to the described embodiments, but is to be construed in the broadest scope according to the spirit defined by the claims.

1 Stirrer 2 Stirring tank 3 Optical measurement device 4 Flocculant injection device 5 Numerical analysis device 6 Control device 7 Supply device 8 Stirring blades 9 Motor 10 Sewage storage tank 11 Flocculant storage tank 18 Supply source pipe 26 Flocculant supply piping 28 For measurement Transfer piping 28A Primary side transfer piping 28B Secondary side transfer piping 29 Measurement discharge piping 30 Nozzle 32 Receiver (liquid receiving part)
35 Optical sensor 35a Light source (light projector)
35b Photodetector (light receiving section)
40 Mixing channel 50 Data logger 52 Diluent storage tank 53 Diluent supply device 55 Dilution line 57 Diluent supply piping 60 Measurement system 61 Screen casing (filtration cylinder)
68 Filtrate receiver

Claims (6)

A measurement transfer pipe through which wastewater flows,
a dilution line connected to the measurement transfer piping and supplying a diluent to the wastewater;
a mixing flow path connected to the measurement transfer pipe and mixing the wastewater and the diluent;
an optical measurement device that obtains an optical measurement value of the wastewater mixed with the diluent,
The measurement system, wherein the mixing flow path has a bent portion that changes the flow direction of the wastewater to which the diluent is supplied. The measurement system according to claim 1, wherein the mixing flow path is arranged downstream of a connection point between the dilution line and the measurement transfer piping. The measurement system according to claim 1 or 2, wherein the mixing flow path is an L-shaped pipe. 4. The measurement system according to claim 3, wherein the outlet of the mixing channel is directed downward. The measurement system according to any one of claims 1 to 4, wherein an inner diameter of the mixing flow path is the same as an inner diameter of the measurement transfer pipe. a dilution step of supplying a diluent to the wastewater;
a mixing step of mixing the wastewater and the diluted liquid through a mixing channel;
an optical measurement step of obtaining an optical measurement value of the wastewater mixed with the diluent,
The measuring method, wherein the mixing flow path has a bent portion that changes the flow direction of the wastewater to which the diluent is supplied.

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