Measurement System

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

[Technical Field]

[0001] The present invention relates to a measurement system for obtaining optical measurements of wastewater mixed with a diluent. Mu Regarding. [Background technology]

[0002] In order to properly manage the operation of wastewater treatment at various facilities such as wastewater treatment plants and water purification plants, it is necessary to accurately understand the properties of wastewater (e.g., color tone, turbidity, transparency, concentration of suspended solids, and state of aggregation of suspended solids). Therefore, optical measurement values ​​have traditionally been obtained using optical measurement devices, and numerical analysis values ​​indicating the properties of wastewater are calculated from the optical measurement values. For example, Patent Document 1 describes a flocculation method in which optical measurement values ​​of wastewater discharged from a mixer are obtained using an optical measurement device, and an appropriate injection rate of flocculant is determined based on numerical analysis values ​​calculated from the obtained optical measurement values.

[0003] In wastewater with a high concentration of suspended solids or flocs formed by mixing with a coagulant, for example, when measuring the transmitted light intensity as an optical measurement value, the transmitted light intensity measured by the optical measuring device becomes almost constant, and it may be impossible to determine an appropriate injection rate of the coagulant. Therefore, the wastewater discharged from the mixer is diluted with a diluent to increase the gaps between the flocs in the wastewater, thereby generating a difference between the optical measurement value when flocs are present and the optical measurement value when flocs are not present. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2016 / 6419 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when a diluent is supplied to a pipe through which wastewater flows, the wastewater and the diluent may not be mixed sufficiently, resulting in an unstable dilution of the wastewater. As a result, the concentration of suspended solids or flocs contained in the wastewater to be measured may not be stable, making it impossible to obtain accurate optical measurements.

[0006] Therefore, the present invention provides a measurement system that stabilizes the dilution state of the wastewater to which the dilution solution is supplied, and can accurately obtain optical measurement values. M The purpose is to provide. [Means for solving the problem]

[0007] In one aspect, a measurement system is provided that includes a measurement transfer pipe through which wastewater flows, a dilution line connected to the measurement transfer pipe and supplying a diluting liquid to the wastewater, a mixing flow path connected to the measurement transfer pipe and mixing the wastewater and the diluting liquid, and an optical measurement device that obtains optical measurement values ​​of the wastewater mixed with the diluting liquid, wherein the mixing flow path has a bend that changes the flow direction of the wastewater to which the diluting liquid has been supplied. In one embodiment, the mixing channel is disposed downstream of a connection point between the dilution line and the measurement transfer pipe. In one embodiment, the mixing channel is an L-shaped tube. In one embodiment, the outlet of the mixing channel faces downward. In one embodiment, the inner diameter of the mixing channel is the same as the inner diameter of the measurement transfer pipe.

[0008] In one aspect, a measurement method is provided that includes a dilution process of supplying a diluting solution to wastewater, a mixing process of mixing the wastewater and the diluting solution using a mixing flow path, and an optical measurement process of obtaining optical measurement values ​​of the wastewater mixed with the diluting solution, wherein the mixing flow path has a bent portion that changes the flow direction of the wastewater to which the diluting solution has been supplied. [Effects of the Invention]

[0009] The measurement system includes a mixing flow path connected to a measurement transfer pipe, which mixes the wastewater to be measured with a diluting solution, stabilizing the dilution state of the wastewater and enabling accurate optical measurements to be obtained. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing an example of a wastewater treatment device equipped with a measurement system according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the configuration of the measurement system shown in FIG. [Figure 3] FIG. 3 is an enlarged view schematically illustrating one embodiment of the mixing channel shown in FIG. [Figure 4] Figure 4(a) shows an example of the measurement of transmitted light intensity when flocs are not formed in the wastewater because the coagulant injection rate is inappropriate, and Figure 4(b) shows an example of the measurement of transmitted light intensity when flocs are formed in the wastewater because the coagulant injection rate is appropriate. [Figure 5] FIG. 5 is a schematic diagram showing another example of a sewage treatment device in which the measurement system shown in FIG. 2 is arranged. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an example of a wastewater treatment device equipped with a measurement system according to one embodiment. The wastewater treatment device shown in FIG. 1 is a flocculation device for treating wastewater discharged from a wastewater treatment facility, a water purification facility, or the like. The measurement system, which will be described later, is used to acquire optical measurement values ​​for calculating numerical analysis values ​​indicating the properties of the wastewater (e.g., color tone, turbidity, transparency, concentration of suspended solids, and flocculation state of suspended solids). In this embodiment, an appropriate injection rate of flocculant is determined based on the numerical analysis values ​​obtained by numerically analyzing the optical measurement values.

[0012] In the following, a flocculation device that treats 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 installed in other equipment that treats wastewater. For example, the wastewater to be treated may be sludge discharged from a wastewater treatment facility or a water purification facility, wastewater from a wastewater treatment facility, raw water from a water purification facility, etc. The sludge may be either organic sludge or inorganic sludge.

[0013] 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, excess sludge, anaerobic digestion sludge, aerobic digestion sludge, human waste sludge, septic tank sludge, digestion supernatant, coagulation sedimentation sludge, etc. The organic sludge may contain inorganic substances.

[0014] Examples of inorganic sludge include inorganic sludge generated in water purification treatment, wastewater treatment in construction work, wastewater treatment in various industries, etc. Here, sludge generated in water purification treatment refers to sludge discharged from settling tanks, sludge basins, thickening tanks, etc. in water purification treatment facilities. Inorganic sludge may contain organic matter.

[0015] Examples of wastewater for 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 for water purification facilities include river water, lake water, and groundwater.

[0016] Furthermore, the wastewater to be treated may be water prepared during processes such as wastewater treatment and water purification. Examples of wastewater from wastewater treatment include wastewater with an adjusted pH, wastewater injected with an inorganic coagulant, wastewater injected with an organic coagulant, and wastewater injected with a metal chelating agent. Examples of wastewater from water purification treatment include raw water with an adjusted pH, raw water injected with an inorganic coagulant, and the like.

[0017] The flocculation apparatus 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. Wastewater containing suspended solids is stored in the wastewater storage tank 10. The agitator 1 includes an agitation tank 2 to which the wastewater containing suspended solids is supplied, an agitator blade 8 that agitates the wastewater containing suspended solids, and a motor 9 that serves as a drive device for rotating the agitator blade 8. A supply pipe 18 extending from the wastewater storage tank 10 is connected to the agitation tank 2 of the agitator 1. The supply pipe 18 is provided with a supply device 7 that supplies the wastewater stored in the wastewater storage tank 10 to the agitation tank 2 at a predetermined flow rate. The supply device 7 is, for example, a pump, a valve, or a combination of a pump and a valve. In one embodiment, the flocculation apparatus does not include the wastewater storage tank 10, and wastewater may be supplied by branching off from an existing wastewater pipe through which wastewater flows to the supply pipe 18.

[0018] In one embodiment, a line mixer may be used as the agitator 1. A line mixer is a mixer incorporated into a pipe. The advantage of a line mixer is that, because the mixer is sealed, two pumps, a sewage pump and a coagulant pump upstream of the line mixer, are sufficient to send sewage downstream of the line mixer. On the other hand, in the case of an agitator 1 with an impeller 8 installed in a mixing tank 2, the top of the mixing tank is open, so in order to send liquid downstream of the agitator, in addition to the sewage pump and the coagulant pump upstream of the agitator, another pump or equipment equivalent to a pump is required. For this reason, it is common to send liquid downstream using a height difference without installing a pump.

[0019] In this embodiment, the agitator 1 has a rotation speed of the agitating blade 8 of 300 to 5000 min -1 This high-speed agitator instantly disperses the coagulant in the wastewater, allowing it to be efficiently and uniformly mixed with the wastewater. As a result, suspended solids contained in the wastewater are efficiently coagulated.

[0020] In the agitator 1, the agitator blade 8 is rotated at a speed of 300 to 5000 min -1It is important to rotate the impeller 8 at a rotation speed of 300 to 2000 min to rapidly agitate the wastewater containing suspended solids to which the coagulant has been injected. Preferably, the rotation speed of the impeller 8 is 300 to 2000 min -1 More preferably, the rotation speed of the stirring blade 8 is 400 to 1500 min -1 More preferably, the rotation speed of the stirring blade 8 is 500 to 1200 min -1 is.

[0021] Such high-speed mixing places high stress on the wastewater to which the coagulant has been injected. Therefore, if the coagulant is not injected at an appropriate injection rate, the flocs will be destroyed before they can grow. Therefore, if the coagulant is not injected at an appropriate injection rate, the flocs will not grow properly. In this embodiment, a control device (described later) acquires optical measurements from the optical measurement device 3 installed in the measurement system 60 and determines whether the flocs are growing properly based on numerical analysis values ​​obtained by numerically analyzing the optical measurements. This allows the appropriate coagulant injection rate to be determined with high accuracy. As a result, the amount of coagulant used can be reduced. Furthermore, the coagulant injection rate can be appropriately controlled without the operator's experience or intuition. Furthermore, the coagulant injection rate can be appropriately controlled even if the properties of the wastewater containing suspended solids (e.g., the concentration of suspended solids in the wastewater) change.

[0022] The rotation speed of the agitator blade 8 is set to 300 to 5000 min , depending 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., inorganic flocculant, organic coagulant, polymer flocculant, etc.). -1 The flocculant to be injected into the wastewater containing suspended solids may be injected into the mixing tank 2, or may be injected into the supply pipe 18 located upstream of the mixing tank 2.

[0023] In this embodiment, a flocculant storage tank 11 is provided for storing a flocculant, and a flocculant supply pipe 26 extending from the flocculant storage tank 11 is connected to the agitation tank 2. A flocculant injector 4 is disposed in the flocculant supply pipe 26. The flocculant injector 4 is a device that injects a flocculant into wastewater containing suspended solids at a predetermined injection rate. The flocculant injector 4 is, for example, a pump, a valve, or a combination of a pump and a valve. In one embodiment, the flocculation device does not need to be provided with the flocculant storage tank 11, and the flocculant may be supplied by branching off from an existing flocculant pipe through which the flocculant flows to the flocculant supply pipe 26.

[0024] In this flocculation device, wastewater containing suspended solids is supplied from a wastewater storage tank 10 to an agitation tank 2 by a supply device 7. A flocculant is supplied to the agitation tank 2 by a flocculant injector 4. In the agitation tank 2, the rotation speed of the agitation blades 8 is set to 300 to 5000 min -1 The wastewater and the coagulant are mixed at a high speed, which forms flocs of suspended matter. However, depending on the injection rate of the coagulant, flocs of suspended matter may not be formed. That is, in the mixer 1, the mixing blades 8 are rotated at a high speed to form flocs of suspended matter, but depending on the injection rate of the coagulant, flocs of suspended matter may not be formed.

[0025] The measurement system 60 includes an optical measurement device 3, a measurement transfer pipe 28 that transports wastewater from the agitator 1 to the optical measurement device 3, a dilution line 55 that supplies a diluent to the wastewater, a mixing flow path 40 that mixes the wastewater and the diluent, and a measurement discharge pipe 29 that discharges the wastewater measured by the optical measurement device 3. The measurement transfer pipe 28 is connected to the agitation tank 2 and the optical measurement device 3. The wastewater discharged from the agitator 1 is transferred through the measurement transfer pipe 28 to the optical measurement device 3. The measurement discharge pipe 29 is connected to the optical measurement device 3. The wastewater discharged from the optical measurement device 3 is discharged through the measurement discharge pipe 29.

[0026] The optical measurement device 3 is a device for irradiating light onto wastewater containing flocs formed by the agitator 1 to obtain optical measurement values. In this embodiment, the optical measurement device 3 is a device capable of measuring the intensity of transmitted light emerging from the wastewater containing flocs. The optical measurement device 3 may also be a device capable of measuring transmittance, intensity of diffracted light, absorbance, intensity of reflected light, etc.

[0027] The dilution line 55 is connected to the measurement transfer piping 28 and supplies the diluent to the wastewater after stirring but before optical measurement. The dilution line 55 includes a diluent storage tank 52 that stores the diluent, and a diluent supply device 53 that supplies the diluent stored in the diluent storage tank 52 at a predetermined flow rate to the wastewater stirred by the agitator 1. A diluent supply piping 57 extending from the diluent storage tank 52 is connected to the measurement transfer piping 28 at a position between the agitator 1 and the optical measurement device 3. The diluent supply device 53 is disposed in the diluent supply piping 57.

[0028] The diluent supply device 53 supplies a diluent to the wastewater stirred by the agitator 1 at a predetermined flow rate before the wastewater is supplied to the optical measurement 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 to which the diluent has been supplied passes through a mixing flow path 40 connected to the measurement transfer pipe 28 and is supplied to the optical measurement device 3. The diluent may be pure water, tap water, industrial water, groundwater, treated water from various wastewater treatment processes, seawater, or the like. In one embodiment, the diluent may be supplied to the diluent line 55 by using an existing pipe through which tap water, treated water, or the like flows at a predetermined pressure as the diluent supply pipe 57, without including the diluent storage tank 52.

[0029] The mixing flow path 40 is a structure for mixing the wastewater and the diluent. The wastewater mixed with the diluent by the mixing flow path 40 is supplied to the optical measurement device 3, where optical measurement is performed.

[0030] 2 is a schematic diagram showing the configuration of the measurement system 60 shown in FIG. 2. As shown in FIG. 2, the measurement transfer pipe 28 includes a primary transfer pipe 28A connected to the inlet of the mixing channel 40 and a secondary transfer pipe 28B connected to the outlet of the mixing channel 40. The mixing channel 40 is disposed downstream of a 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 include the secondary transfer pipe 28B, and the outlet of the mixing channel 40 may be connected to the optical measurement device 3.

[0031] FIG. 3 is an enlarged view schematically illustrating one embodiment of the mixing flow channel 40 shown in FIG. 2. The mixing flow channel 40 is an L-shaped pipe having a bent portion 40a. A cross section perpendicular to the central axis of the mixing flow channel 40 is circular. In one embodiment, the cross section of the mixing flow channel 40 may have a shape other than circular (e.g., square or rectangular). The mixing flow channel 40 is configured to change the flow direction of the wastewater mixed with the dilution liquid at the bent portion 40a. The inlet 40b of the mixing flow channel 40 faces horizontally, and the upstream portion 40d, which is upstream of the bent portion 40a of the mixing flow channel 40, extends horizontally. The outlet 40c of the mixing flow channel 40 faces downward, and the downstream portion 40e, which is downstream of the bent portion 40a of the mixing flow channel 40, extends vertically.

[0032] In this embodiment, the bent portion 40a of the mixing flow channel 40 is bent at a right angle, but the bend angle of the bent portion 40a is not limited to this embodiment. In one embodiment, the bend angle of the bent portion 40a may be within a range of 45 degrees to 135 degrees. In addition, in this embodiment, the downstream portion 40e of the mixing flow channel 40, which is downstream of the bent portion 40a, extends vertically. However, in other embodiments, the downstream portion 40e of the mixing flow channel 40 may extend horizontally. That is, the mixing flow channel 40 may change the flow direction of the wastewater to which the diluent has been supplied in a horizontal plane. In still other embodiments, the mixing flow channel 40 may have multiple bent portions 40a, so that the flow direction of the wastewater to which the diluent has been supplied is changed multiple times.

[0033] The mixing flow channel 40 changes the flow direction of the wastewater to which the diluent has been supplied by the bent portion 40a, generating turbulence in the wastewater, thereby mixing the wastewater and the diluent. Therefore, the dilution state of the wastewater sent to the optical measurement device 3 is stable, and the optical measurement device 3 can accurately obtain optical measurements of the wastewater. In particular, the entire interior of the mixing flow channel 40 is hollow, and a structure (such as a baffle) for mixing the wastewater and the diluent does not need to be present within the mixing flow channel 40. Therefore, flocs and debris contained in the wastewater are less likely to clog the mixing flow channel 40.

[0034] The inner diameter d1 of the inlet 40b and the upstream portion 40d, which are located upstream of the bent portion 40a, is the same as the inner diameter d2 of the outlet 40c and the downstream portion 40e, which are located downstream of the bent portion 40a. Furthermore, 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, i.e., the inner diameter d4 of the primary transfer pipe 28A and the inner diameter d5 of the secondary transfer pipe 28B. By making the inner diameters of the measurement transfer pipe 28 and the mixing channel 40 the same, clogging of the mixing channel 40 with flocs and debris contained in the wastewater can be prevented.

[0035] Returning to Figure 2, the optical measurement device 3 includes a nozzle 30 connected to the end of the secondary transfer piping 28B, and a receptacle (liquid receiving portion) 32 connected to the tip of the measurement discharge piping 29. The nozzle 30 is a structure that causes the wastewater mixed with the diluent that has flowed through the secondary transfer piping 28B to flow downward, and has a cylindrical shape. The receptacle 32 is disposed below the nozzle 30 at a distance from the nozzle 30. The receptacle 32 is a structure that receives the wastewater that has flowed down from the nozzle 30, and in the illustrated example, has a funnel shape.

[0036] In this embodiment, the nozzle 30 and the tray 32 are arranged vertically, and the central axis of the nozzle 30 coincides with the central axis of the tray 32. An open space through which the wastewater flows is formed between the nozzle 30 and the tray 32. Therefore, the wastewater flows from the nozzle 30 into the atmosphere.

[0037] The optical measurement device 3 further includes an optical sensor 35 that irradiates light onto the wastewater mixed with the dilution liquid flowing down from the nozzle 30 to obtain an optical measurement value. In this embodiment, the optical sensor 35 is an optical sensor that includes a light source (light-emitting unit) 35a that irradiates light onto the wastewater and a photodetector (light-receiving unit) 35b that detects light emerging from the wastewater, and measures the intensity of transmitted light that reaches the photodetector 35b. The light irradiated from the light source 35a and transmitted through the wastewater containing flocs is detected by the photodetector 35b. The intensity of this transmitted light is measured for a predetermined time, and the measured intensity of transmitted light is used as the optical measurement value.

[0038] Examples of the light source 35a include various lamps (mercury lamps, xenon lamps, krypton lamps, metal halide lamps, halogen lamps, etc.), various lasers (solid-state lasers, semiconductor lasers, liquid lasers, gas lasers, etc.), various LEDs, etc. Among commercially available optical sensors, LEDs are light sources that can emit relatively high-intensity light, so the light source 35a is preferably an LED. Examples of the photodetector 35b include a CCD, a photodiode, a phototransistor, a photomultiplier tube, a photoconductive element, an infrared optical sensor, a CMOS, etc. In any case, commercially available products can be used as the optical sensor 35.

[0039] The transmitted light intensity, which is an optical measurement value, is measured once or multiple times while changing the coagulant injection rate, thereby obtaining at least one optical measurement value. The transmitted light intensity detected by the photodetector 35b is stored 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, which determines the appropriate coagulant injection rate based on the numerical analysis value. The data logger 50, the numerical analysis device 5, and the control device 6 may each be provided separately. Alternatively, the data logger 50 and the numerical analysis device 5 may be incorporated into the control device 6, which is configured as a single computer or a single programmable logic controller (e.g., a sequencer).

[0040] Next, with reference to Figures 4(a) and 4(b), an example of measuring the transmitted light intensity of wastewater containing suspended solids using the optical measurement device 3 will be described. Figure 4(a) shows an example of measuring the transmitted light intensity when flocs are not formed in the wastewater because the coagulant injection rate is inappropriate, and Figure 4(b) shows an example of measuring the transmitted light intensity when flocs are formed in the wastewater because the coagulant injection rate is appropriate. In Figures 4(a) and 4(b), the horizontal axis represents measurement time, and the vertical axis represents transmitted light intensity.

[0041] As shown in FIG. 4(a), if flocs are not formed in the wastewater, the light irradiated from the light source 35a is blocked by the suspended matter and hardly reaches the photodetector 35b. As a result, the measured transmitted light intensity remains low over time. On the other hand, if flocs are formed in the wastewater, the suspended matter is aggregated as flocs. Therefore, as shown in FIG. 4(b), during the measurement of the transmitted light intensity, there are times when the light irradiated from the light source 35a is blocked by the flocs and does not reach the photodetector 35b, and times when the light reaches the photodetector 35b through gaps in the flocs. As a result, multiple peaks of the transmitted light intensity are measured. These multiple peaks are used in the numerical analysis process described below.

[0042] The purpose of supplying diluent to the stirred wastewater through the dilution line 55 is to reduce the concentration of suspended solids and / or flocs in the stirred wastewater. In wastewater with a high concentration of suspended solids, there is no difference between the optical measurements when flocs are formed and when they are not formed, which can make it difficult to determine the coagulant injection rate. 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 coagulant injection rate is appropriate and flocs are formed, there may be almost no gaps between the flocs, resulting in a nearly constant transmitted light intensity, as shown in Figure 4(a). In contrast, when the stirred wastewater is diluted with diluent, the gaps between the flocs can be increased, allowing light to pass through the gaps between the flocs, resulting in multiple peaks in the transmitted light intensity, as shown in Figure 4(b). As a result, a difference occurs between the transmitted light intensity when flocs are formed and when they are not formed, allowing the appropriate injection rate to be determined.

[0043] Returning to FIG. 1 , the optical measurement device 3 is electrically connected to a numerical analysis device 5, which is connected to a control device 6. The numerical analysis device 5 may be incorporated into the control device 6. The control device 6 is also connected to the coagulant injector 4.

[0044] The optical measurement values ​​obtained from the optical measurement device 3 are sent to the numerical analysis device 5. The numerical analysis device 5 performs numerical analysis on the optical measurement values ​​to obtain numerical analysis values. The obtained numerical analysis values ​​are sent to the control device 6. The control device 6 determines an appropriate injection rate of the coagulant based on the numerical analysis values.

[0045] Examples of numerical analysis values ​​include the mean value, variance, standard deviation, peak area, and peak height of optical measurements. The variance of optical measurements is a value obtained by statistically analyzing optical measurements and indicates the degree of dispersion in the distribution of optical measurements obtained over a specified measurement time. The standard deviation is the positive value of the square root of the variance. The peak area is the area enclosed by a curve drawn by plotting optical measurements obtained over a specified measurement time on a graph whose vertical axis represents optical measurements and whose horizontal axis represents measurement time, and a reference line (e.g., baseline). For example, the peak area corresponds to the area of ​​the hatched region in Figure 4(b). The peak height is the height from the horizontal axis of the peak of the curve drawn by plotting optical measurements obtained over a specified measurement time on a graph whose vertical axis represents optical measurements and whose horizontal axis represents measurement time.

[0046] The number of optical measurement values ​​equal to or greater than a certain threshold value, or the number of optical measurement values ​​equal to or less than a certain threshold value, may be used as the numerical analysis value. The numerical analysis device 5 may calculate the SS concentration, turbidity, chromaticity, floc particle size, etc. from the optical measurement values, and use these as the numerical analysis value. Here, the floc particle size means the diameter of the floc if the floc is spherical. If the floc is not spherical, the floc particle size means the Stokes diameter or a particle size measured by various measurement methods. The floc particle size may be the average particle size of the floc. Examples of the average particle size include the arithmetic mean diameter, the most common diameter, and the median diameter. The average particle size may be based on the number, mass, or volume.

[0047] Known methods such as transmitted light measurement can be used to calculate SS concentration and turbidity from optically measured values. Known methods such as transmitted light measurement can be used to calculate chromaticity from optically measured values. Known methods such as laser diffraction / scattering and image analysis of images taken with a camera can be used to calculate floc particle size from optically measured values. The floc particle size may be the average floc particle size or the particle size distribution of floc particle sizes. Commercially available measuring devices can be used to perform optical measurements and calculate SS concentration, turbidity, chromaticity, floc particle size, etc. from the obtained optical measured values.

[0048] The control device 6 determines an appropriate coagulant injection rate from at least one numerical analysis value obtained by injecting a coagulant into the wastewater, stirring the wastewater (high-speed stirring), acquiring optical measurements, and performing numerical analysis based on the optical measurements at least once. Specifically, the control device 6 injects a coagulant into the wastewater containing suspended solids, stirs the wastewater to form flocs of the suspended solids, performs optical measurements on the stirred wastewater, and numerically analyzes the acquired optical measurements to obtain a numerical analysis value. Furthermore, the control device 6 determines whether the coagulant injection rate is appropriate based on the acquired numerical analysis value. If the injection rate is inappropriate, the control device 6 changes the coagulant injection rate and repeats the stirring, optical measurements, and numerical analysis again to determine an appropriate injection rate. Note that depending on the coagulant injection rate, flocs of suspended solids may not be formed.

[0049] A method for determining an appropriate coagulant injection rate may use multiple preset injection rates. The control device 6 injects coagulant into wastewater containing suspended solids at a preset injection rate, agitates the wastewater to form flocs of the suspended solids, performs optical measurements on the agitated wastewater, and numerically analyzes the obtained measurements to obtain a numerical analysis value. This process is repeated for each of the multiple preset injection rates. The control device 6 compares the multiple numerical analysis values ​​obtained for each of the multiple preset injection rates. In one embodiment, the injection rate that yields the maximum or minimum value is determined as the appropriate injection rate. In another embodiment, the appropriate injection rate may be the average of the injection rate that yields the largest and the second largest numerical analysis value, or the average of the injection rate that yields the smallest and the second smallest numerical analysis value.

[0050] In yet another embodiment, the control device 6 may plot multiple numerical analysis values ​​at multiple preset injection rates on a graph whose vertical axis represents the numerical analysis value and whose horizontal axis represents the injection rate of the flocculant, calculate an approximate expression showing the relationship between the multiple injection rates and the multiple numerical analysis values, and determine an appropriate injection rate of the flocculant based on the obtained approximate expression. For example, the injection rate at which the peak value of the numerical analysis value is obtained may be calculated from the approximate expression, and the obtained injection rate may be set as the appropriate injection rate of the flocculant.

[0051] The configuration of the optical measurement device 3 of the measurement system 60 is not limited to this embodiment as long as it can acquire measurements for determining an appropriate injection rate of flocculant. For example, in one embodiment, the optical measurement device 3 may be configured such that, instead of the nozzle 30, a pair of transparent windows are provided in the secondary transfer pipe 28B through which the wastewater discharged from the agitator 1 flows, and the optical sensor 35 irradiates light toward one of the transparent windows and detects the light emerging from the other transparent window to acquire optical measurements.

[0052] Fig. 5 is a schematic diagram showing another example of a wastewater treatment device in which the measurement system 60 shown in Fig. 2 is arranged. The wastewater treatment device shown in Fig. 5 is a screw press (dehydrator) that squeezes liquid-containing material such as sludge to separate the liquid-containing material into filtrate and cake.

[0053] The screw press shown in Figure 5 includes a cylindrical screen casing (filter tube) 61, a screw (not shown) arranged concentrically with the screen casing 61 within the screen casing 61 to transport sludge (wastewater), which is a liquid-containing substance, in a predetermined transport direction D, a rotation mechanism (not shown) to rotate the screw, a filtrate receiver 68 to collect the filtrate that has passed through the screen casing 61, and a measurement transfer pipe 28 connected to the filtrate receiver 68.

[0054] The screen casing 61 is formed from a screen (perforated plate) such as punched metal. The sludge fed into the screen casing 61 is transported inside the screen casing 61 by the rotation of the screw. The sludge is squeezed and dehydrated as it is transported inside the screen casing 61. The filtrate that passes through the screen of the screen casing 61 is collected in a filtrate receiver 68 arranged below the screen casing 61.

[0055] In this embodiment, the measurement transfer pipe 28 of the measurement system 60 is connected to a filtrate receiver 68 and is configured to acquire optical measurement values ​​of the filtrate (wastewater) collected by the measurement system 60. A diluent is supplied to the filtrate flowing through the measurement transfer pipe 28 via a dilution line 55, and the filtrate (wastewater) and the diluent are mixed through a mixing flow path 40. The optical measurement device 3 acquires optical measurement values ​​of the filtrate mixed with the diluent. The acquired optical measurement values ​​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 measurement values. For example, the control device controls the screw rotation speed based on the acquired optical measurement values ​​in order to obtain a cake with an appropriate moisture content.

[0056] The above-described embodiments have been described for the purpose of enabling a person of ordinary skill in the art to practice the present invention. Various modifications of the above-described embodiments would naturally be possible for a person skilled in the art, and the technical concept of the present invention may also be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical concept defined by the claims. [Explanation of symbols]

[0057] 1. Mixer 2 Mixing tank 3 Optical measuring device 4 Coagulant injection device 5. Numerical analysis equipment 6. Control device 7 Feeding device 8 Mixing blades 9 motors 10 Sewage storage tank 11 Coagulant storage tank 18 Source pipe 26 Coagulant supply piping 28 Measurement transfer piping 28A Primary side transfer piping 28B Secondary side transfer piping 29 Discharge piping for measurement 30 nozzles 32 Receptacle (liquid receiving part) 35 Optical Sensor 35a Light source (light projector) 35b Photodetector (light receiving part) 40 Mixing channel 50 Data Logger 52 Dilution liquid storage tank 53 Dilution liquid supply device 55 Dilution Line 57 Diluted liquid supply piping 60 Measurement System 61 Screen casing (filter tube) 68 Filtrate receiver

Claims

[Claim 1] A measurement transfer pipe through which wastewater containing flocs of suspended matter formed by a coagulant flows; a dilution line connected to the measurement transfer pipe for supplying a dilution solution to the wastewater; a mixing flow path connected to the measurement transfer pipe for mixing the wastewater and the dilution liquid; an optical measurement device for obtaining optical measurements of the wastewater mixed with the dilution liquid; The mixing flow path has a bent portion that changes the flow direction of the wastewater to which the dilution liquid is supplied and generates turbulence in the wastewater, thereby mixing the wastewater and the dilution liquid, The entire interior of the mixing channel is hollow, the mixing channel is an L-shaped pipe, the measurement transfer pipe includes a primary transfer pipe connected to an inlet of the L-shaped pipe and a secondary transfer pipe connected to an outlet of the L-shaped pipe; A measurement system, wherein the inner diameter of the inlet of the L-shaped pipe and the inner diameter of the outlet of the L-shaped pipe are the same as the inner diameter of the primary transfer piping and the inner diameter of the secondary transfer piping.

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