JPH0660890B2 - Suspended substance aggregation state determination device - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an apparatus for determining the state of aggregation of suspended substances for determining the state of aggregation of suspended substances in a suspension.

[Background of the Invention]

In the activated sludge process and the purified water treatment process of wastewater, the quality of the flocculation or sedimentation of the suspension flocs is closely related to the treated water quality. For this reason, the measurement of the flocculating property or sedimentation property of the suspension flocs is very important for the operational control of the process. The method for measuring these is to settle the suspended matter flocs in the suspension, and to optically detect the boundary between the flocculated suspended matter flocs and the separated liquid. A method for measuring flocculation or sedimentation of flocs or a suspension is introduced into a thin tube, and the optical turbidity of the agglomerated and non-aggregated agglomerates, especially non-aggregated agglomerates, is detected in the capillary and based on the detected value. There is known a method for discriminating the cohesiveness of a suspended substance in a suspension. However, in any of the methods, the boundary detection value or the turbidity detection value of the non-aggregated lump is determined by detecting the turbidity of the suspension by using the light transmittance or the scattering degree, and the cohesiveness is determined from the turbidity. This is a method for making a distinction, and is not a method for directly measuring the agglomeration state of suspended solids, and it is unavoidable that it lacks accuracy.

Further, in these methods, since an optical measuring means is used, an error occurs due to a stain on the wall surface of the detecting portion. Furthermore, it takes time for the aggregate to settle or for the aggregation-sedimentation reaction to proceed sufficiently. For this reason, it was not possible to judge the state of the activated sludge process or the water purification process and promptly reflect it in the coagulant injection control.

On the other hand, in the sludge treatment process, the concentrated sludge is dehydrated in the case of the direct dehydration system and the digested sludge is dehydrated in the case of the anaerobic digestion system. In the dehydration treatment, after the inorganic coagulant or the organic polymer coagulant is injected into the sludge, the aggregated sludge mass is formed by stirring, and the dehydration treatment in the dehydrator is effectively performed. As the inorganic coagulant, ferric chloride, ferrous sulfate, slaked lime, etc. are used. Further, as the organic polymer coagulant, polyacrylamide, polyvinyl pyridine hydrochloride,
Examples include sodium polyacrylate, water-soluble aniline resin hydrochloride and polyethyleneimine.

The coagulant is injected in proportion to the liquid flow rate of sludge or the solid flow rate. However, in reality, the required amount of coagulant is not always proportional to the flow rate of treated solid matter, and a predetermined coagulation effect cannot be obtained due to factors such as changes in sludge properties. Therefore, the amount of the injected coagulant is excessive or insufficient. If the coagulant injection amount is less than the proper amount, coagulation does not occur. On the other hand, if the coagulant is injected more than necessary, not only is it expensive to waste the expensive coagulant, it is also uneconomical. The phenomenon of redispersion of aggregates occurs. Therefore, the water content of the dehydrated sludge does not decrease, the amount of dehydrated sludge increases, and the dehydration time also increases.

In recent years, the capillary suction time CS has been used as a direct determination method for the aggregation effect.
A method for measuring T (Cpillary Suction Time) has been proposed. The CST is defined as the time in which a cylinder is placed in close contact with paper, sludge is put in from the top of the cylinder, and a predetermined amount of water is absorbed from the sludge onto the paper. Therefore, the CST measurement requires an operation of sampling sludge and supplying it to the cylinder, and the coagulation effect cannot be determined online.

On the other hand, a method of measuring the particle size of a suspended substance using ultrasonic waves is known in, for example, Japanese Patent Publication No. 48-6388. However, the particle size and the agglomerated state do not always match, and the agglomerated state cannot be accurately measured only by measuring the particle size.

[Object of the Invention]

An object of the present invention is to provide an apparatus for determining an agglomeration state of a suspended substance, which can accurately measure the agglomeration state of suspended particles in a suspension online.

[Outline of Invention]

The feature of the present invention is that it receives a pulse signal generated by a pulse oscillating circuit, generates ultrasonic waves, propagates in a suspension, receives a reflected wave reflected from a suspended substance, and converts it into an electric signal. An ultrasonic wave transmitting / receiving means, an agglomeration state judging circuit for taking in a signal received by the ultrasonic wave transmitting / receiving means and judging an agglomeration state of a suspended substance, and a pulse oscillation circuit and an agglomeration state judging circuit for 0.1 to 0.1 times in a constant cycle. A timing setting circuit for applying a frequency signal of 5 KHz, wherein the aggregation state determination circuit outputs a control signal based on the frequency signal, and the frequency signal is input to the timing control circuit. From the above, an ON control signal is output with a time delay to remove the influence of the ultrasonic transmission wave, and the reception signal received by the ultrasonic transmission / reception means is captured by turning on for a certain period of time. The analog switch, an integration circuit that integrates the ultrasonic reception signal captured by turning on the analog switch and is reset at regular intervals by a reset signal output from the timing control circuit, and the integration circuit is reset. A sample and hold circuit that holds the magnitude of the integrated signal immediately before
And an average value circuit for calculating an average value of the hold signals held by the sample hold circuit per unit time and outputting it as an aggregation determination signal. The signal level of ultrasonic waves is the amount of reflected waves.

Example of Invention

 FIG. 1 shows an embodiment of the present invention.

In FIG. 1, a mixing tank 10 contains a suspension 11 containing a suspended substance 12. An ultrasonic wave transmitter / receiver 20 is attached to the side wall of the mixing tank 10. As shown in FIG. 3, the ultrasonic wave transmitter / receiver 20 has a flange 101 and O-rings 102, 1
It is fixed by the flange 106 attached to the mixing tank 10 via 03. The ultrasonic wave transmitter / receiver 20 is a pulse oscillation circuit 3
The pulse signal is applied from 2. The ultrasonic wave transmitter / receiver 20 generates ultrasonic waves when a pulse signal is applied, propagates in the suspension, and receives the reflected waves from the suspended substance 12 and the opposing side wall. The pulse oscillator circuit 32 generates a pulse signal in synchronization with the frequency signal generated by the timing setting circuit 31. The timing setting circuit 31 generates a frequency signal (timing signal) S _T of 0.1 to 5 KHz. The timing signal S _T is also applied to the aggregation state determination circuit 40. The reception signal of the ultrasonic wave transmitter / receiver 20 is input to the detection circuit 34 after being amplified by the amplifier 33. The received signal (video signal) S ₀₁ detected by the detection circuit 34 is the aggregation state determination circuit 4
Added to 0.

FIG. 2 shows a detailed configuration diagram of the aggregation state determination circuit 40.

In FIG. 2, the timing control circuit 401 outputs various control signals S _{T1 to} S _T4 based on the timing signal S _T. The analog switch 402 is turned on for a certain period of time T ₁ by the ON control signal S _T1 and receives the received signal S _01, and the signal S
Output as ₀₂ . The integrating circuit 403 integrates the received signal S ₀₂ and resets it at a constant cycle by the reset signal S _T2 . The sample hold circuit 404 holds the magnitude of the integrated signal S ₀₃ immediately before the reset of the integrating circuit 403. The average value circuit 405 calculates the average value of the hold signal S ₀₄ per unit time and adds this average value to the display device 406 as the aggregation determination signal S ₀₅ .

Next, the operation will be described with reference to the waveform charts shown in FIGS.

The timing setting circuit 31 outputs the timing signal S at a constant cycle.
Generate _T. The pulse oscillation circuit 32 uses the timing signal S
_A pulse signal is generated in a cycle of _T and applied to the ultrasonic wave transmitter / receiver 20. The ultrasonic wave transmitter / receiver 20 transmits an ultrasonic wave into the suspension 11 when a pulse signal is applied. Among the ultrasonic waves propagated through the suspension 11, a part of the ultrasonic waves hitting the suspended substance 12 are transmitted, part of the ultrasonic waves is absorbed, and the other is reflected. The ultrasonic wave reflected from the suspended substance 12 is received by the ultrasonic wave transmitter / receiver 20 and converted into an electric signal. Received signal is amplifier 33
It is amplified by and input to the detection circuit 34. The detection circuit 34 outputs a video signal (received signal) S ₀₁ as shown in FIG. The received signal S ₀₁ is input to the analog switch 402. The timing control circuit 401 outputs the ON control signal S _T1 for a certain time T ₁ after Δt time from the input of the timing signal S _T. The analog switch 402 takes time T ₁
Just turn it on. The reason why the analog switch 402 is turned on is delayed from the timing signal S _T by the time Δt is to eliminate the influence of the transmission wave (leak wave). Further, the time T ₁ is determined so that the reflected wave from the opposing side wall surface of the mixing tank 10 is not input to the integrating circuit 403. Specifically, assuming that the inner diameter of the mixing tank 10 is L and the sound velocity in the suspension is v, the time t _{1 for the} ultrasonic wave to propagate from the ultrasonic wave transmitter / receiver 20 to the opposing side wall surface is represented by the following equation.

t ₁ = L / v (1) The time t ₂ until the ultrasonic wave reflected from the opposed side wall surface reaches the ultrasonic wave transmitter / receiver 20 and is received is as follows.

t ₂ = 2L / v (2) Therefore, the maximum time t _max of the time T ₁ is limited by the following equation.

t _max <2 L / v (3) The reception signal S ₀₂ obtained from the analog switch 402 is as shown in FIG. The integrating circuit 403 receives the received signal S _02.
An integrated signal S ₀₃ obtained by integrating is output. The timing control circuit 401 gives a hold command signal S _T3 to the sample hold circuit 404 in synchronization with the fall of the ON control signal S _T1 . The sample hold circuit 404 holds the hold command signal S
The value of the integrated signal S ₀₃ at the time when _T3 is given is taken in and held. The timing control circuit 401 gives a reset signal S _T2 to the integrator circuit 403 for resetting after a time required for performing the sample hold. Such an operation is repeated every time the timing setting circuit 31 generates the timing signal S _T. When this operation is performed a predetermined number of times, the timing control circuit 401 gives the average value circuit 405 a calculation start command signal S _T4 . When the average value circuit 405 is supplied with the signal S _T4 , it calculates the hold value S ₀₄ during one cycle of the signal S _T4 , that is, the average value S ₀₅ of the magnitude of the received signal S ₀₂ , as shown in FIG. FIG. 5 shows 3 of the timing signal S _T.
An example is shown in which the cycle is one cycle of the average value calculation.
In practical use, it is desirable to set 10 cycles or more of the timing signal S _T as one cycle of the average value calculation. The average value S ₀₅ is input to the display device 406 as an aggregation determination signal. If the magnitude of the aggregation determination signal S ₀₅ , that is, the level of the reflected wave from the suspended substance 12 is small, it is determined that the aggregation is performed well,
If the level of the signal S ₀₅ is large, it is determined that the aggregation is not sufficient.

As described above, the present invention determines the aggregation state based on the integrated value of the reflected wave from the suspended substance, in other words, the reflected wave amount. The reason why the aggregation state can be determined by the amount of reflected waves from the suspended substance will be explained based on the experimental results.

In the sludge dewatering process of an urban sewage treatment plant, the sludge before injecting the coagulant is collected and the ratio of the coagulant injection amount to the sludge suspended solids amount, that is, the coagulant injection rate is changed to determine the coagulation effect according to the present invention and CST. The value was measured.

FIG. 6 shows the change in CST with respect to the coagulant injection rate. The CST decreases as the coagulant injection rate increases, and reaches the minimum value when the injection rate is about 0.6%. Injection rate is 0.6%
It shows that the dehydration is the best.

On the other hand, in the present invention, the ultrasonic transducer 20 has a frequency of 0.5M.
The experiment was conducted by setting the frequency Hz, the time T ₁ to 60 μs, the frequency of the timing signal S _T to 1 KHz, and the period of one cycle of the average value calculation to 0.1 seconds. The changes in the video signal S ₀₁ and the integrated signal S ₀₃ with respect to the drug injection rate in this experiment are as shown in FIGS. 8 (a) to (f). The drug injection rate in FIGS. 8 (a) to (f) is 0,
It is 0.121, 0.220, 0.382, 0.578, 0.839%.

FIG. 7 shows the change in the aggregation effect determination value with respect to the coagulant injection rate according to the experimental results of the present invention.

As is clear from comparison between FIG. 6 and FIG. 7, the aggregation effect determination value according to the present invention has the same pattern as the logarithmic value of CST. Therefore, it can be seen that the quality of the aggregation effect can be determined based on the magnitude of the amount of reflection from the suspended substance.

As described above, the present invention discriminates the aggregation state based on the reflected wave amount of the suspended substance. Although this phenomenon is not clear, the present inventors consider it as the following reason.

A schematic diagram of sludge aggregation is shown in FIG. The fine particles 61 of sludge before aggregation are dispersed in a suspension in a colloidal form, and have a large amount of surface-adhered water 62 and pore water 63. When the coagulant 64 is injected, the coagulant 64 separates the adhered water from the surface of the fine sludge particles 61 and binds the particles 61 to each other to form a coagulated mass or a block 65. At the same time, the pore water 63 is removed from between the sludge particles 61. For this reason, the water content outside the block 65 increases, and the water content easily escapes from the sludge. Thus, in the sludge agglomeration, not only the particle size of the sludge particles increases, but also the properties (density and acoustic characteristics) of the sludge particles themselves change. In addition, since the sludge flocks are easily broken by stirring, the coagulant 64 becomes particles 61
The power to connect each other is weak. This means that the structure of the sludge block 65 is a flexible structure. Therefore, it is considered that the ultrasonic wave hitting the sludge flocks 65 causes a resonance phenomenon and absorbs ultrasonic energy when the wavelength thereof is close to the sludge flocks 65.

The following experiment was conducted to verify the validity of this inference. The ultrasonic waves that hit the sludge particles 61 are as shown in FIG.
Reflects, absorbs and transmits. Since the absorption amount of ultrasonic waves cannot be directly measured, the absorption amount was measured by simultaneously measuring the reflection amount and the transmission amount. The results are shown in Table 1.

As shown in Table 1, the amount of reflection and the amount of transmission after aggregation were smaller than those before aggregation. From this, it can be seen that the amount of ultrasonic waves absorbed by the sludge block 65 increased. When the particle size distribution of the sludge flocs 65 after coagulation was measured, the result was as shown in FIG. 11, and the majority of the flocs having particle sizes of 2 to 3 mm. When the frequency is 0.5MHz, the wavelength is 2.97mm
And is almost the same as the floc particle size. This is
This is consistent with the inference that sludge particles absorb ultrasonic waves when they become flocked.

〔The invention's effect〕

As described above, according to the present invention, the aggregating property of suspended substance particles in a suspension can be measured online,
It can be used for monitoring or controlling the process for controlling the agglomeration state or effect of suspended matter, and can improve the process performance of the process.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a detailed configuration diagram of an agglomeration state determination circuit, FIG. 3 is an attachment configuration diagram of ultrasonic transducers, and FIGS. 4 and 5 are operations. Waveforms for explanation, FIGS. 6 and 7 are characteristic diagrams of experimental results, FIG. 8 is a signal waveform diagram obtained in the experiment, FIG. 9 is a schematic diagram of aggregation, and FIG. 10 is absorption of ultrasonic waves. Fig. 11 is a schematic diagram for explaining the degree, and Fig. 11 is a characteristic diagram for measuring the particle size distribution of flock. 10 ... Mixing tank, 20 ... Ultrasonic transmitter / receiver, 30 ... Ultrasonic transceiver, 40 ... Aggregation effect discrimination circuit, 401 ...
Timing control circuit, 402 ... Analog switch, 4
03 ... integrator circuit, 404 ... sample hold circuit,
405 ... Average value circuit, 406 ... Display device.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shunsuke Nokita 4026 Kujimachi, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hitachi Co., Ltd. (72) Inventor Mikio Yoda 5-2-1 Omikacho, Hitachi City, Ibaraki Prefecture Incorporated company Hitachi Ltd. Omika factory (72) Inventor Yuji Yamazawa 4-6 Kanda Surugadai, Chiyoda-ku, Tokyo Inside Hitachi Ltd. (56) Reference JP 49-74995 (JP, A) JP 52 -148193 (JP, A)

Claims (1)

[Claims] 1. An ultrasonic wave transmitting / receiving means for receiving a pulse signal generated by a pulse oscillating circuit, generating ultrasonic waves, propagating in a suspension, receiving a reflected wave reflected from a suspended substance, and converting the reflected wave into an electric signal. An agglomeration state determination circuit that takes in a signal received by the ultrasonic transmission / reception means and determines the agglomeration state of a suspended substance, and a frequency signal of 0.1 to 5 KHz at a constant cycle in the pulse oscillation circuit and the agglomeration state determination circuit And a timing setting circuit that applies a timing control circuit that outputs a control signal based on the frequency signal, and an ultrasonic wave after the frequency signal is input to the timing control circuit. An analog switch that outputs an ON control signal with a time delay for removing the influence of a transmission wave, turns on for a certain period of time, and captures a reception signal received by the ultrasonic transmission / reception means. , An integrating circuit which integrates the ultrasonic reception signal taken in by turning on the analog switch and is reset at regular intervals by a reset signal output from the timing control circuit, and an integrating circuit immediately before the integrating circuit is reset. A sample and hold circuit that holds the magnitude of the integrated signal,
An average value circuit for calculating an average value of the hold signals held by the sample and hold circuit per unit time and outputting the average value as an aggregation determination signal.