JP2023142677A - Device and method for monitoring flocculation state of wastewater - Google Patents

Abstract

To provide a monitoring device capable of accurately monitoring the flocculation state of wastewater over a long time period using a simple mechanism.SOLUTION: A monitoring device provided herein is for monitoring the flocculation state of wastewater drawn from a downstream side of or directly from a flocculation mixing tank of a flocculation device. The monitoring device comprises an optical measurement device 3 for acquiring optical measurements of the wastewater, and a numerical analysis device 5 configured to numerically analyze the optical measurements and output numerical analysis values. The optical measurement device 3 comprises a nozzle 30 for allowing wastewater to flow downward to the atmosphere, and an optical sensor 35 configured to irradiate the wastewater flowing down from the nozzle 30 with light to acquire optical measurements.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a monitoring device and method for monitoring the state of coagulation of wastewater.

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. For example, an appropriate amount of flocculant to be injected into wastewater such as sludge is determined based on the properties of the wastewater. 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 an appropriate value is determined based on a numerical analysis value calculated from the obtained optical measurement value. A flocculation method is described that determines the flocculant injection rate.

In this agglomeration method, in order to obtain optical measurements, a pair of transparent windows are provided in the pipe through which the stock solution discharged from the stirrer flows, and the optical measuring device is directed toward one of the transparent windows. It is equipped with a light projector that emits light and a photodetector that receives light coming out of the other transparent window. The pair of transparent windows function as measurement windows (light transmitting portions) of the optical measurement device.

In addition, in the flocculant injection control method described in Patent Document 2, the flocs flowing in the stock solution supply pipe connected to the dehydrator are photographed with a television camera, which is an optical measuring device, and the flocs 1 Accumulate the analysis area for each piece. Next, the floc formation status is obtained by comparing the obtained analysis area with a predetermined reference area, and the flocculant injection rate is controlled based on the floc formation status obtained. Also in the method described in Patent Document 2, an autopsy window for imaging by a television camera is provided in the stock solution supply pipe. This autopsy window also functions as a measurement window (light transmission section) of the optical measurement device.

International Publication No. 2016/6419 Japanese Patent Application Publication No. 2005-7338

Piping equipped with a pair of transparent windows or a light-transmitting part of an optical measuring device, such as a coroner's window, contains flocs formed by mixing with a flocculant in a stirrer, and flocs used to form flocs. Sewage containing foreign substances such as excess coagulant that was not present flows. Therefore, the light transmitting portion may be contaminated with foreign matter, and in this case, it becomes difficult for the optical measurement device to obtain accurate optical measurement values. Therefore, it is necessary to periodically clean the light transmitting section.

In order to clean the light transmitting part, the optical measuring device must be stopped, which increases the burden on the workers, so the frequency of cleaning the light transmitting part is an important issue. Further, if the optical measuring device is provided with a mechanism that can automatically clean the light transmitting portion in order to reduce the burden on the operator, the optical measuring device becomes complicated and costs increase.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a monitoring device and a monitoring method that can accurately monitor the coagulation state of wastewater over a long period of time using a simple mechanism.

In one embodiment, there is provided a monitoring device that monitors the flocculation state of wastewater drawn from the downstream side of a coagulation mixing tank of a coagulation device or directly drawn from the coagulation mixing tank, the monitoring device including an optical system that measures an optical measurement value of the wastewater. and a numerical analysis device that numerically analyzes the optical measurement value and outputs the numerical analysis value, and the optical measurement device includes a nozzle that causes the wastewater to flow downward into the atmosphere. and an optical sensor that irradiates light onto the wastewater flowing down from the nozzle to obtain an optical measurement value.

In one aspect, the monitoring device further includes a determination device that determines whether the flocculation state of the wastewater is good or bad based on the numerical analysis value.
In one aspect, the monitoring device further includes a return line that returns the wastewater flowing down from the nozzle to the coagulation mixing tank.

In one aspect, the nozzle includes a nozzle body in which the wastewater flow path is formed, and a discharge part connected to a tip of the wastewater flow path and in which the wastewater discharge flow path is formed, and the The discharge channel has a diameter smaller than the diameter of said channel.
In one embodiment, the diameter of the discharge channel is in the range of 5 to 30 mm.
In one aspect, the optical sensor is disposed near the discharge port of the nozzle, and irradiates light onto the wastewater immediately after being discharged from the nozzle.

In one aspect, there is provided a monitoring method for monitoring the flocculation state of wastewater drawn from the downstream side of a coagulation mixing tank of a coagulation device or directly drawn from the coagulation mixing tank, the method comprising: directing the wastewater downward from a nozzle into the atmosphere; A monitoring method is provided in which wastewater is allowed to flow down, irradiates light from an optical sensor onto the flowed wastewater to obtain an optical measurement value, and numerically analyzes the optical measurement value to obtain a numerical analysis value.

The optical measurement device can obtain optical measurement values using a simple mechanism such as directly irradiating light onto wastewater flowing down from a nozzle. That is, there is no light transmitting part contaminated by foreign matter in the wastewater in the sensing zone of the optical sensor. As a result, the cleaning work traditionally required to obtain proper optical measurements is eliminated, allowing optical measurement devices to obtain optical measurements stably over long periods of time, and numerical analysis devices can stably output accurate numerical analysis values over a long period of time. Therefore, the state of sewage coagulation can be monitored stably over a long period of time in real time.

FIG. 1 is a schematic diagram showing an example of a sewage treatment apparatus in which an optical measuring device according to an embodiment is arranged. FIG. 2 is a schematic diagram showing the configuration of the optical measuring device shown in FIG. 1. FIG. 3 is an enlarged view schematically showing the vicinity of the nozzle shown in FIG. 2. FIG. Figure 4(a) shows an example of measuring the intensity of transmitted light when flocs are not formed in the stock solution 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 the stock solution is shown to ensure that this is appropriate. FIG. 5 is a table showing the experimental results.

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 device in which a monitoring device according to an embodiment is arranged. The sewage treatment equipment shown in Figure 1 includes a flocculation device for treating sewage (sludge) discharged from wastewater treatment facilities, water treatment facilities, etc., and a flocculation device that squeezes the sewage discharged from the stirring tank of the flocculation device and filters it. It is equipped with a dehydrator that separates liquid and cake. A monitoring device that monitors the flocculation state of wastewater, which will be described later, is placed between the flocculation device and the dehydrator. This monitoring device includes an optical measurement device for obtaining optical measurement values of wastewater, and numerically analyzes the optical measurement values obtained by the optical measurement device to determine the properties of wastewater (e.g., color tone, turbidity, etc.). and a numerical analysis device that calculates and outputs numerical analysis values indicating (transparency, concentration of suspended solids, and aggregation state of suspended solids).

The numerical analysis value calculated and output by the numerical analysis device is, for example, informed to an operator of the flocculation device, and helps the operator to determine and/or change the injection rate of the flocculant. In one embodiment, the numerical analysis values calculated and output by the numerical analysis device are communicated to, for example, a dehydrator operator to assist the operator in determining and/or changing the operating conditions of the dehydrator. In one embodiment, the monitoring device may include a control device that automatically changes the injection rate of the flocculant based on the numerical analysis value calculated and output by the numerical analysis device; The dehydrator may include a control device that changes the operating conditions of the dehydrator based on the numerical analysis values obtained.

In the following, wastewater equipped with a coagulation device that processes a stock solution containing suspended solids, which is an example of wastewater, and a dehydrator that removes liquid components from the stock solution (in particular, the stock solution containing flocs) discharged from the coagulation device. A processing device will be described as an example of a facility in which a monitoring device is provided. However, the monitoring device according to this embodiment may be placed in a wastewater treatment device having another configuration. 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 agglomeration device shown in FIG. 1 is equipped with a stock solution storage tank 10 and an agitator 1, and the agitator 1 of the aggregation device is connected to a dehydrator through a discharge pipe 28 through which the stock solution discharged from the agitator 1 flows. It is connected to a screw press 60, which is an example. The discharge pipe extends from the stirring tank 2 of the flocculation device to the screw press (dehydrator) 60.

In this embodiment, the stock solution storage tank 10, the stirrer 1, and the screw press 60 are connected in series in this order. The monitoring device, which will be described later, has an optical measuring device 3 that irradiates the stock solution discharged from the stirrer 1 with light to obtain an optical measurement value. It is connected to a branch line 77 that has branched off. A portion of the wastewater flowing through the discharge pipe 28 is supplied to the optical measuring device 3 via a branch line 77.

The stock solution storage tank 10 stores stock solution (sewage) containing suspended substances. The stirrer 1 includes a stirring tank 2 to which a stock solution containing suspended substances is supplied, stirring blades 8 that stir the stock solution containing suspended substances, and a motor 9 as a drive device that rotates the stirring blades 8. A supply pipe 18 extending from the stock solution storage tank 10 is connected to the stirring tank 2 of the stirrer 1, and the supply pipe 18 is connected to a supply pipe 18 for supplying the stock solution stored in the stock solution 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, a line mixer may be used as the agitator 1. A line mixer is a mixer built into piping. The advantage of the line mixer is that the mixer is sealed, so if you have two pumps, one for the stock solution upstream of the line mixer and the pump for the flocculant, you can send the stock solution downstream 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.

The rotational speed of the stirring blades 8 depends on the type of stock solution containing suspended substances (e.g., wastewater, sludge, etc.), the properties of the stock solution (e.g., SS (Suspended Solids) concentration, viscosity, etc.), and the type of flocculant (e.g., The speed is adjusted within the range of 10 to 1200 min ^-1 based on the amount of flocculant (inorganic flocculant, organic flocculant, polymer flocculant, etc.). Preferably, the rotational speed of the stirring blades 8 ranges from 10 to 300 min ⁻¹ . The flocculant to be injected into the stock solution containing suspended matter 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 a stock solution containing suspended matter 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 this flocculation device, a stock solution containing suspended matter is supplied from a stock solution storage tank 10 to a stirring 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 rotational speed in the range of 10 to 1200 min ⁻¹ to mix the stock solution and the flocculant, thereby forming a floc of suspended matter. 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 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.

Next, a monitoring device for monitoring the state of coagulation of wastewater will be described. In this embodiment, the monitoring device includes an optical measurement device 3 that irradiates light onto wastewater to obtain optical measurement values, and a numerical analysis device 5 that numerically analyzes the optical measurement values obtained by the optical measurement device. and a control device 6 to which the numerical analysis value calculated by the numerical analysis device 5 is sent. The optical measurement device 3 is a device for irradiating the stock solution containing flocs formed by the stirrer 1 with light 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 the stock solution containing flocs. The optical measuring device 3 may be a device capable of measuring transmittance, scattered light intensity, diffracted light intensity, diffracted/scattered light intensity, absorbance, reflected light intensity, and the like.

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. The numerical analysis device 5 outputs the calculated numerical analysis value to the control device 6. The control device 6 functions, for example, as a determination device that determines the quality of the flocculation state of wastewater based on the received numerical analysis value.

FIG. 2 is a schematic diagram showing the configuration of the optical measuring device shown in FIG. 1. FIG. 3 is an enlarged view schematically showing the vicinity of the nozzle shown in FIG. 2. FIG. As shown in FIG. 2, the optical measuring device 3 includes a nozzle 30 connected to the end of the branch line 77 and a saucer (liquid receiving part) 32 connected to the end of the return line 78. The nozzle 30 is a component that causes the stock solution flowing through the branch line 77 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 tray 32 is a component for receiving the stock solution flowing down from the nozzle 30, and has a funnel shape in the illustrated example.

As shown, the monitoring device has a return line 78 for returning the wastewater that has passed through the optical measuring device 3 to (the stirring tank 2 of) the flocculating device. Since the return line 78 returns the waste water to the stirring tank 2, the surrounding environment is prevented from being contaminated by the waste water used for optical measurements. In one embodiment, the return line 78 may be omitted and the wastewater that has passed through the optical measurement device 3 may be discharged to a gutter and to a disposal facility such as a collection tank.

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 saucer 32, through which the stock solution flows down. Therefore, the stock solution flows down from the nozzle 30 into the atmosphere.

The optical measurement device 3 further includes an optical sensor 35 that irradiates the stock solution flowing down from the nozzle 30 with light to obtain an optical measurement value. In this embodiment, the optical sensor 35 includes a light source (light projector) 35a that irradiates light toward the stock solution, and a photodetector (light receiver) 35b that detects the light coming out of the stock solution. 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 stock solution 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.

The numerical analysis value calculated by the numerical analysis device 5 is sent to the control device 6. For example, the control device 6 displays the received numerical analysis value on a display (not shown), and the displayed numerical analysis value is used for operating the flocculation device and/or the dehydrator. The numerical analysis value is used, for example, to determine whether the state of coagulation of wastewater is good or bad. In one embodiment, the numerical analysis value may be used by an operator to determine and/or change the injection rate of flocculant supplied to the stirring tank 2, or may be used by an operator to determine the operating conditions of the screw press 60. (e.g., the rotational speed of the screw). In one embodiment, the control device 6 may determine whether the state of flocculation of wastewater is good or bad based on numerical analysis values, determine an appropriate injection rate of the flocculant, or determine the appropriate injection rate of the screw press 60. Operating conditions may also be determined.

In the monitoring device, the data logger 50, the numerical analysis device 5, and the control device (determination 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 a stock solution containing suspended matter 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 the stock solution 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 the stock solution is shown to ensure that this is appropriate. 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. 4(a), if no flocs are formed in the stock solution, 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, if flocs are formed in the undiluted solution, suspended substances 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.

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.

In this embodiment, the optical sensor 35 can obtain optical measurement values using a simple mechanism such as directly irradiating light onto the raw solution (sewage) flowing down from the nozzle 30. That is, there are no members in the sensing zone of the optical sensor 35 that are contaminated by foreign substances such as flocs formed by mixing with the flocculant in the stirrer and surplus flocculant not used to form the flocs. As a result, the cleaning work conventionally required to obtain appropriate optical measurement values is not required, so the optical sensor 35 can stably obtain optical measurement values for a long period of time, and the numerical analysis device 5 can stably output accurate numerical analysis values over a long period of time. Therefore, the monitoring device can stably monitor the coagulation state of wastewater over a long period of time in real time.

In order for the optical sensor 35 to obtain appropriate optical measurements, it is preferable that the stock solution flowing down from the nozzle 30 is rectified (ie, laminar flow). In order to effectively rectify the stock solution, the nozzle 30 according to this embodiment includes a nozzle body 30a extending in the vertical direction and a discharge part 30b connected to the tip of the nozzle body 30a. The end of the nozzle body 30a is connected to a branch line 77. The nozzle body 30a has a flow path 30c for the stock solution formed therein. The discharge part 30b has a discharge passage 30d formed therein, and the discharge passage 30d is connected to the passage 30c of the nozzle body 30a. The center axis of the discharge flow path 30d coincides with the center axis of the flow path 30c.

When viewed in a cross section perpendicular to the central axis of the nozzle 30, the flow path 30c and the discharge flow path 30d have a circular cross-sectional shape. Furthermore, the discharge flow path 30d has a diameter d2 smaller than the diameter d1 of the flow path 30c. That is, the discharge part 30b functions as a diameter reducing part with respect to the nozzle main body 30a.

According to the experiments conducted by the inventors, the nozzle 30 composed of the nozzle body 30a and the discharge part 30b has a lower cost than the nozzle 30 composed only of the nozzle body 30a (that is, the discharge part 30b is omitted). It was found that the rectifying effect of the undiluted solution was dramatically improved. Therefore, the nozzle 30 is preferably composed of a nozzle body 30a and a discharge part 30b that functions as a diameter-reducing part with respect to the nozzle body 30a.

Furthermore, according to experiments conducted by the inventors, the rectifying effect of the stock solution is highest when the cross-sectional shape of the discharge flow path 30d (that is, the cross-sectional shape perpendicular to the central axis of the discharge flow path 30d) is circular. I understand. It was also found that even if the length L in the longitudinal direction of the discharge portion 30b, which corresponds to the length of the discharge channel 30d, is short, the rectification effect of the stock solution flowing down from the nozzle 30 is not significantly affected. For example, it was found that even if the length L in the longitudinal direction of the discharge portion 30b was 3 cm, the stock solution flowing down from the nozzle 30 was rectified.

The flow rate of the stock solution flowing through the nozzle 30 also affects the rectification effect of the stock solution. Generally, the larger the flow rate of the stock solution flowing through the discharge portion 30b of the nozzle 30, the better the rectification effect of the stock solution. That is, it is preferable to increase the flow rate of the concentrate flowing through the discharge part 30b by reducing the inner diameter of the discharge part 30b (the diameter of the discharge flow path 30d), thereby improving the rectification effect of the concentrate. Therefore, by using PVC piping with a nominal diameter of 13A (inner diameter 13 mm), which is the smallest among commercially available PVC piping, for the discharge portion 30b, it is possible to provide a nozzle 30 with a high rectification effect at low cost.

Note that if the inner diameter of the discharge section 30b is made too small, the discharge section 30b may be clogged with flocs depending on the properties (size, shape, viscosity, etc.) of the flocs formed in the stock solution. Therefore, the inner diameter of the discharge portion 30b should be selected with consideration not only to the flow rate of the stock solution but also to the properties of the flocs. For example, the inner diameter of the discharge portion 30b may be 5 mm or more, or 10 mm or more. Generally, the diameter of the formed flocs is often in the range of several mm to more than 10 mm, so it is preferable that the inner diameter of the discharge portion 30b is 13 mm or more. In commercially available PVC piping, in addition to piping with a nominal diameter of 13A, piping with a nominal diameter of 16A, 20A, 25A, or 30A can be suitably used.

The stock solution immediately after being discharged from the nozzle 30 is the most rectified. Therefore, as shown in FIGS. 2 and 3, it is preferable to arrange the optical sensor 35 near the discharge port of the nozzle 30. In this case, the optical sensor 35 can obtain an optical measurement value by irradiating light onto the stock solution immediately after being discharged from the nozzle 30.

As shown in FIG. 2, the optical measuring device 3 may include a box 38 surrounding the nozzle 30 and the receiving tray 32. The stock solution discharged from the nozzle 30 flows down in the atmosphere until it reaches the receiving tray 32. The box 38 prevents the odor of the stock solution from spreading to the surroundings. Furthermore, in the embodiment shown in FIG. 2, the box 38 encloses not only the nozzle 30 and the saucer 32, but also the optical sensor 35. According to such a configuration, disturbances such as natural light and wind that affect optical measurement values can be excluded.

The wastewater supplied from the flocculation device to the screw press 60 via the discharge pipe 28 is squeezed by the screw press and separated into a filtrate and a cake. The screw press 60 shown in FIG. 1 includes a cylindrical screen casing (filtration tube) 61, and is arranged concentrically within the screen casing 61 to transfer wastewater as a liquid in a predetermined direction. A screw (not shown) for transferring to D, a rotation mechanism (not shown) for rotating the screw, a filtrate receiver 68 for collecting the filtrate that has passed through the screen casing 61, and a filtrate receiver 68 connected to the filtrate receiver 68. A drain line 69 is provided.

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 disposed below the screen casing 61 and discharged from the screw press via a drain line 69.

In this embodiment, the above-mentioned numerical analysis values are used for the operation of the screw press 60. For example, the operator can determine and/or change the rotational speed of the screw based on numerical analysis values. In one embodiment, the numerical analysis values may be input to the controller of the screw press 60, and the controller may automatically control the rotational speed of the screw to obtain a cake with the appropriate moisture content. In this case, the control device 6 described above may be used as a control device for the screw press 60.

The control device 6 shown in FIG. 1 may automatically control the injection rate of the flocculant supplied to the flocculation device based on the acquired numerical analysis value. Below, a method for the control device 6 to automatically control the injection rate of the flocculant will be explained.

As shown in FIG. 1, the control device 6 is connected to the flocculant injection device 4. As mentioned above, 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 and obtains 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.

From at least one numerical analysis value obtained by injecting a flocculant into the stock solution, stirring the stock solution, acquiring an optical measurement value, and performing a numerical analysis based on the optical measurement value at least once, the control device 6 , determine the proper injection rate of flocculant. That is, the control device 6 injects a flocculant into a stock solution containing suspended solids, stirs the stock solution to form flocs of suspended solids, performs optical measurement on the stirred stock solution, and determines the resultant solution. 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.

The inventors measured optical measurements by varying the injection rate of the flocculant and the flow rate of the stock solution discharged from the nozzle 30, numerically analyzed the obtained optical measurements, and calculated the obtained numerical values. An experiment was conducted to confirm whether there is a correlation between analytical values and visual judgment of floc quality. In the experiment, a predetermined flocculant was injected into a plurality of sludges at a plurality of injection rates, and then each sludge into which the flocculant had been injected was stirred for a predetermined period of time by setting the rotational speed of the stirring blade to 1080 min ^-1 . Next, light is irradiated from the light source 35a of the optical sensor 35 to the agitated sludge flowing down from the nozzle 30, which is composed of a nozzle body 30a having an inner diameter of 20 mm and a discharge part 30b having an inner diameter of 13 mm. Target measurements were obtained. Furthermore, the obtained optical measurements were numerically analyzed to determine an appropriate flocculant injection rate. The flow rate of sludge was set at 1.47 L/min.

FIG. 5 is a table showing the experimental results. As shown in Fig. 5, multiple numerical analysis values, which are the average value, variance, and number of optical measurements above a predetermined threshold of optical measurements, were obtained when the flocculant injection rate was 2.5%. It was found that the maximum value is . This was consistent with the flocculant injection rate that was determined to be a good floc by visual inspection. Therefore, it has been found that it is possible to automatically determine the quality of flocs from the optical measurement values obtained by the optical measurement device 3 according to the embodiment described above.

For example, when the dispersion is a numerically analyzed value, the control device can determine that the agglomeration state is good if the dispersion is a numerical value of 17.4 or more. Similarly, the operator can judge whether the aggregation state is good or bad from the numerical analysis value displayed on the display of the control device.

As shown in FIG. 2, the optical measurement device 3 may include a dilution line 55 that supplies a diluent to the stirred stock solution, if necessary. The dilution line 55 is connected to the branch line 77 and supplies a diluent to the stock solution after stirring and before optical measurement. A diluent supply valve (not shown) is disposed in the dilution line 55, and the control device 6 operates the opening/closing operation of the diluent supply valve as necessary to supply the diluent to the stock solution after stirring. Control.

The purpose of supplying the diluent to the stirred stock solution is to reduce the concentration of suspended matter and/or the concentration of flocs contained in the stirred stock solution. For stock solutions 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 measuring device 3 measures the transmitted light intensity of a stock solution 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 stock solution 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 is transmitted 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. As the diluent, pure water, tap water, industrial water, ground water, treated water from various wastewater treatments, seawater, etc. can be used.

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 Stock solution storage tank 11 Flocculant storage tank 14 Dehydrator 18 Supply source pipe 26 Flocculant supply piping 28 Discharge piping 30 Nozzle 32 Receiver (liquid receiving part)
35 Optical sensor 35a Light source (light projector)
35b Photodetector (light receiving section)
38 Box 50 Data logger 55 Dilution line 60 Screw press (dehydrator)
61 Screen casing (filtration cylinder)
68 Filtrate receiver 69 Drain line 77 Branch line

Claims (7)

A monitoring device for monitoring the flocculation state of sewage drawn from the downstream side of a coagulation mixing tank of a coagulation device or directly drawn from the coagulation mixing tank, comprising:
an optical measurement device that measures an optical measurement value of the wastewater;
A numerical analysis device that numerically analyzes the optical measurement value and outputs a numerical analysis value,
The optical measuring device includes:
a nozzle that directs wastewater downward into the atmosphere;
A monitoring device comprising: an optical sensor that irradiates light onto the wastewater flowing down from the nozzle to obtain an optical measurement value. The monitoring device according to claim 1, further comprising a determination device that determines whether the coagulation state of the wastewater is good or bad based on the numerical analysis value. The monitoring device according to claim 1 or 2, further comprising a return line that returns the wastewater flowing down from the nozzle to the coagulation mixing tank. The nozzle is
a nozzle body in which the wastewater flow path is formed;
a discharge part connected to the tip of the wastewater flow path and in which the wastewater discharge flow path is formed;
The monitoring device according to any one of claims 1 to 3, wherein the discharge flow path has a smaller diameter than the diameter of the flow path. The monitoring device according to claim 4, wherein the diameter of the discharge channel is in the range of 5 to 30 mm. The monitoring device according to any one of claims 1 to 5, wherein the optical sensor is disposed near a discharge port of the nozzle and irradiates light to the wastewater immediately after being discharged from the nozzle. A monitoring method for monitoring the flocculation state of sewage drawn from the downstream side of a coagulation mixing tank of a coagulation device or directly drawn from the coagulation mixing tank, the method comprising:
Sewage flows downward from the nozzle into the atmosphere,
irradiating the flowing wastewater with light from an optical sensor to obtain an optical measurement value;
A monitoring method comprising numerically analyzing the optical measurement value to obtain a numerical analysis value.

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