JP2002263700A - Sludge thickener and method of preparing flocculating agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably regulate a flocculating agent amount. SOLUTION: This equipment is provided with branch piping 6 for measurement of a small diameter which shunts a portion of separating water and the concentration of the residual fluctuation in the separating water flowing in the branch piping 6 for measurement is optically measured. A flocculating agent amount adjusting device 8 (1) increases the flocculating agent supply rate according to the number of revolutions exceeding the upper limit value among the measured values of a prescribed number of times, (2) decreases the flocculating agent supply rate according to the number of revolutions falling under the lower limit value among the measured values of the prescribed number of times, (3) decreases the flocculating agent supply rate if the dispersion of the measured values of the prescribed number of times is smaller than the threshold and (4) controls a flocculating agent supply pump P so as to maintain the flocculating agent supply rate of the previous time in the cases exclusive of the cases described above. Accordingly, the concentration of the thickened sludge can be stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sludge concentrating apparatus and a coagulant amount adjusting method, and more particularly, to a sludge concentrating apparatus and a coagulant amount adjusting method capable of stably adjusting a coagulant supply amount.

[0002]

2. Description of the Related Art A conventional sludge concentrator and a method for adjusting the amount of a flocculant are disclosed in, for example, Japanese Patent Publication No. 7-8325 and
No. 347599.

[0003] In the sludge concentrator and the method for adjusting the amount of flocculant disclosed in Japanese Patent Publication No. 7-8325, the amount of colloid charged in separated water flowing through a separated water drain pipe is measured, and the measured value becomes a predetermined optimum value. The supply amount of the flocculant is calculated as described above, and the supply amount of the flocculant is adjusted based on the calculation result.

[0004] In the sludge concentrating apparatus and the method for adjusting the amount of flocculant disclosed in Japanese Patent Application Laid-Open No. 11-347599, a measuring tank is provided in a separation water drainage channel, and the average absorbance and the standard deviation of the absorbance are measured in the measuring tank. The residual floc volume ratio is determined from the measurement result, and the coagulant supply amount is adjusted so that the amount of floc is minimized.

[0005]

SUMMARY OF THE INVENTION The above Japanese Patent Publication No. 7-832
In the sludge concentrating apparatus and the method for adjusting the amount of coagulant disclosed in Japanese Patent Publication No. 5 (1999), the colloidal charge of the separated water flowing through the separated water drain pipe is measured. However, in order to reduce drain resistance, the separated water drain pipe has an inner diameter. However, there is a problem that it is difficult to obtain a stable measurement result and that the supply amount of the flocculant cannot be adjusted stably.

[0006] Further, in the sludge concentrating apparatus and the coagulant amount adjusting method disclosed in the above-mentioned JP-A-11-347599,
Since the absorbance of the separated water is measured near the outlet in the measurement tank provided in the separation water channel, the residence time of the separated water in the measurement tank becomes longer, causing a time delay in the measured value and reagglomeration in the measurement tank. (The reaggregation can be prevented to some extent by a stirrer), so that it is difficult to obtain a stable measurement result, and it is not possible to stably adjust the supply amount of the flocculant.

Further, when the sludge concentration of raw water sludge is extremely low and most of the supplied coagulant is excessive,
Since a large amount of flocculant remains in the separated water, the flocculant is erroneously measured as a residual floc, so that there has been a problem that the supply amount of the flocculant cannot be adjusted stably.

Accordingly, an object of the present invention is to provide a sludge concentrating apparatus and a method for adjusting the amount of a flocculant which can stably adjust the amount of a flocculant supplied.

[0009]

According to a first aspect of the present invention, there is provided a mixed flocculation tank for supplying raw water sludge and a coagulant, mixing the two, and coagulating suspended components in the raw water sludge; A flocculant dissolving tank for storing the flocculant; a flocculant supply means for supplying the flocculant from the flocculant dissolving tank to the sludge concentration mixing tank; Sludge concentrating means for liquid separation, large-diameter separated water drainage pipe for draining separated water, and small-diameter branch pipe for measuring part of separated water to measure residual floc concentration in separated water And optical measuring means for optically measuring the residual floc concentration in the separated water flowing through the branch pipe for measurement, and controlling the flocculant supplying means in accordance with the measured residual floc concentration to adjust the supply amount of the flocculant. Means for controlling the amount of flocculant Providing sludge concentrating apparatus according to claim. The inner diameter of the separation water drain pipe is 50 mm or more, and the inner diameter of the branch pipe for measurement is 10 mm or less.

In the sludge concentrator according to the first aspect,
Provision of a small-diameter branch pipe for measuring a part of the separated water,
The residual floc concentration in the separated water flowing through the branch pipe for measurement was optically measured. For this reason, the variation due to the location was substantially eliminated, and the influence of the re-aggregation was also eliminated. Therefore, since a stable measurement result can be obtained,
It becomes possible to stably adjust the coagulant supply amount.

[0011] In a second aspect, the present invention provides a raw sludge and a flocculant supplied to a sludge flocculation and mixing tank, and the mixture is stirred and mixed to flocculate suspended components in the raw water sludge. In the flocculant amount adjusting method of controlling the supply amount of the flocculant supplied to the sludge flocculation mixing tank according to the measured value, When an appropriate upper limit value and lower limit value and an appropriate threshold value of the variance of the measured value are set, and a predetermined number of measured values are obtained, (1) the flocculant according to the number of times exceeding the upper limit value among the predetermined number of measured values. Increase the supply,
(2) The coagulant supply amount is reduced in accordance with the number of times below the lower limit among the predetermined number of measurement values, and (3) the coagulant supply amount is reduced if the dispersion of the predetermined number of measurement values is smaller than the threshold value. (4) A method for adjusting the amount of a coagulant characterized by maintaining the previous coagulant supply amount other than the above. Note that using a standard deviation instead of the variance is equivalent and is included in the scope of the present invention.

When an appropriate upper limit and lower limit of the absorbance and an appropriate threshold value of the variance of the measured value are set, the following behavior is predicted. (1) When the coagulant is insufficient with respect to the sludge concentration of the raw water sludge, the ratio of suspended components remaining in the separated water increases,
The probability that the absorbance rises above the upper limit increases. (2) When the flocculant is excessive with respect to the sludge concentration of the raw water sludge, the floc is formed excessively, and the ratio of suspended components remaining in the separated water is reduced. Therefore, the probability that the absorbance falls below the lower limit is high. Become. (3) When the flocculant is neither inadequate nor excessive with respect to the sludge concentration of the raw water sludge (when the amount is appropriate), the absorbance falls between the upper limit and the lower limit, and the flocculation varies. The probability that the variation of the measurement value becomes larger than the threshold value increases. (4) When the sludge concentration of the raw water sludge is extremely low and most of the supplied flocculant is excessive, a large amount of the flocculant remains in the separated water. Since there is no variation in the supply amount of the agent, the probability that the variation in the measured value becomes smaller than the threshold value increases.

In the coagulant amount adjusting method according to the second aspect, the coagulant supply amount is controlled as follows. (1) The coagulant supply amount is increased in accordance with the number of times exceeding the upper limit value among the predetermined number of measurement values. (2) The coagulant supply amount is reduced according to the number of times below the lower limit among the predetermined number of measured values. (3) If the variance (variation) of the predetermined number of measurement values is smaller than the threshold value, the coagulant supply amount is reduced. (4) Other than the above, the previous coagulant supply amount is maintained. Thereby, the amount of the coagulant can be suitably adjusted. In particular, the amount of coagulant can be reduced when most of the supplied coagulant is excessive because the sludge concentration of raw water sludge is extremely low. In addition, when the sludge concentration of the raw water sludge is about the usual level and the amount of the flocculant is appropriate, the amount of the flocculant can be maintained at the current level.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. Note that the present invention is not limited by this.

FIG. 1 is a configuration diagram of a sewage sludge concentrator 100 according to one embodiment of the present invention. The sludge concentrating apparatus 100 is provided with a raw water sludge and a coagulant, which are mixed to mix the two and coagulate suspended components in the raw water sludge.
A flocculant dissolving tank 2 for storing the flocculant; a flocculant supply pump P for supplying the flocculant from the flocculant dissolving tank 2 to the sludge concentration mixing tank 1; Sludge concentrator 3 for solid-liquid separation of sludge and separated water
A concentrated sludge discharge pipe 4 for discharging the concentrated sludge, a large-diameter separated water drain pipe 5 for discharging the separated water, and a part of the separated water for measuring the residual floc concentration in the separated water. The branch pipe for measurement 6 having a small diameter to be diverted, the turbidity meter 7 for measuring the concentration of residue floc in the separated water flowing through the branch pipe 6 for measurement, and the flocculant supply pump P according to the measured concentration of residue floc. A coagulant amount control device 8 for controlling and adjusting the supply amount of the coagulant.

Raw water sludge is sewage sludge obtained by treating sewage by an activated sludge method. The sludge concentration is between 0.5 and 1.7%.
The flocculant is a polymer flocculant. For example, a trade name “MX-
6144 "(manufactured by Hymo Corporation).

As the sludge concentrator 3, for example, trade name "Fine Screen" (manufactured by Suido Kiko Co., Ltd.) can be used. In this “fine screen”, concentrated sludge and separated water are separated into solid and liquid by a drum screen 31 having an opening of 0.75 mm in which a notch wire is wound in a cylindrical shape. Then, the concentrated sludge is dropped from the drum screen 31 to the screw 32, and is scraped out by the screw 32 to the concentrated sludge discharge pipe 4. Further, the separated water falls into the receiving tray 33 and is immediately discharged to the separated water drain pipe 5.

In order to reduce drainage resistance, the inner diameter of the separation water drainage pipe 5 is, for example, 10 cm. On the other hand, the inner diameter of the branch pipe 6 for measurement is, for example, 5 mm in conformity with the flow path diameter of the flow cell of the turbidity meter 7.

The branch pipe 6 for measurement is installed below the separated water drain pipe 5 so that the separated water can flow appropriately.

The turbidimeter 7 transmits the measurement light through the flow cell, measures the absorbance, and outputs an absorbance signal s.

The coagulant amount adjusting device 8 has two operation modes, an automatic control operation mode and a fixed supply operation mode. In the automatic control operation mode, the drive signal c is changed in accordance with the change in the absorbance signal s, the output of the coagulant supply pump P is changed, and the supply amount of the coagulant is changed. In the quantitative supply operation mode, the supply amount of the flocculant is kept constant regardless of the change in the absorbance signal s.

FIGS. 2 and 3 are flowcharts showing the coagulant amount adjusting process executed by the coagulant amount adjusting device 8 in the automatic operation mode. In step P0, the number of measurements is reset to zero.

In step P1, the process waits for 5 seconds. In Step P2, the absorbance of the separated water as an index of the residual floc concentration in the separated water is measured from the absorbance signal s and stored. In Step P3, the number of measurements is incremented by one. In step P4, steps P1 to P3 are
The process proceeds to Step P5 when measurement values for 24 times are obtained.

In step P5, if the number of times exceeding the upper limit value among the 24 measured values is 24, the process proceeds to step P6, and if not, the process proceeds to step P7. Step P6
Then, the coagulant supply amount is greatly increased (for example, increased by 20%). Then, the process returns to the step P0.

In step P7, if the number of times exceeding the upper limit value is 22 to 23 times out of the 24 measured values, step P8
If not, the process proceeds to Step P9. In Step P8, the coagulant supply amount is increased moderately (for example, increased by 10%).
Let it. Then, the process returns to the step P0.

In step P9, if the number of times exceeding the upper limit value is 20 to 21 times out of the 24 measured values, step P1
0, otherwise, to step P11 in FIG. In Step P10, the coagulant supply amount is slightly increased (for example, increased by 5%). Then, the process returns to the step P0.

In step P11, if the number of times below the lower limit of the 24 measured values is 24, the process proceeds to step P12, and if not, the process proceeds to step P13. In Step P12, the coagulant supply amount is greatly reduced (for example, reduced by 20%). Then, the process returns to the step P0.

In step P13, if the number of times that the value falls below the lower limit is 22 to 23 times out of the 24 measured values, step P
Proceed to Step P14, otherwise proceed to Step P15. In Step P14, the coagulant supply amount is reduced moderately (for example, 10
% Reduction). Then, the process returns to the step P0.

In step P15, if the number of times below the lower limit is 20 to 21 out of the 24 measured values, step P
Proceed to Step P16, otherwise proceed to Step P17. In Step P16, the coagulant supply amount is slightly reduced (for example, 5%
Decrease). Then, the process returns to the step P0.

In step P17, if the number of times slightly exceeding the lower limit value among the 24 measured values is 15 or more and the variance of the 24 measured values is smaller than the threshold value, the process proceeds to step P18. If not, the process proceeds to step P19. move on. In Step P18, the coagulant supply amount is slightly reduced (for example, 5%).
Let it. Then, the process returns to the step P0.

In Step P19, the coagulant supply amount is maintained at the current level. Then, the process returns to the step P0.

-Example-The residence time of raw water sludge in the mixing flocculation tank 1 was set to 2 minutes. As described with reference to FIGS. 2 and 3, the absorbance signal s is read every 5 seconds, the next flocculant supply amount is calculated based on the measured value every 24 times, and the drive signal c is changed every 2 minutes in accordance with it. Updated to. FIG. 4 shows the results of the implementation. In the automatic control operation mode, the supply rate of the coagulant is automatically adjusted, and even if the raw water sludge concentration changes, the concentrated sludge concentration is stable (the change is small). In the fixed supply operation mode, the supply rate of the flocculant is constant, and the concentration of the concentrated sludge fluctuates greatly with the fluctuation of the raw water sludge concentration.

[0033]

According to the sludge concentrating apparatus and the coagulant amount adjusting method of the present invention, since the coagulant supply amount can be adjusted stably, the concentrated sludge concentration can be stabilized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a sludge concentration apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the sludge concentration device of FIG.

FIG. 3 is a flowchart continued from FIG. 2;

FIG. 4 is a graph showing an execution result.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Admixing coagulation tank 2 Coagulant dissolution tank 3 Sludge concentrator 4 Condensed sludge discharge pipe 5 Separation water drainage pipe 6 Measurement branch pipe 7 Turbidity meter 8 Coagulant amount controller 31 Drum screen 32 Screw 33 Receiving tray 100 Sludge concentrator P Coagulant supply pump P

Continued on the front page (72) Inventor Kazuyuki Kisaka 5-48-16 Sakuragaoka, Setagaya-ku, Tokyo Inside Waterworks Kiko Co., Ltd. (72) Kazumasa Kasakura 5-48-16 Sakuraoka, Setagaya-ku, Tokyo Waterworks Kiko Co., Ltd. F term (reference) 4D059 AA05 BE12 BE57 CB06 CB09 CB18 CB19 CB20 CB27 DB11 EA20 EB11

Claims (2)

[Claims] 1. A mixing flocculation tank for supplying raw water sludge and a flocculant and mixing them to coagulate suspended components in the raw water sludge, a flocculant dissolving tank for storing the flocculant, and dissolving the flocculant. A coagulant supply means for supplying a coagulant from the tank to the sludge concentration mixing tank, a sludge concentrating means for solid-liquid separation of the concentrated sludge having flocculated suspended components by flocculation and separated water, and a drainage of separated water Large-diameter separated water drain pipe, a small-diameter branch pipe for measuring a part of the separated water to measure the residual floc concentration in the separated water, and a residual floc in the separated water flowing through the branch pipe for the measurement. An optical measuring means for optically measuring the concentration, and a flocculant amount controlling means for controlling the flocculant supplying means in accordance with the measured residual floc concentration and controlling the flocculant supply amount. Sludge concentrator. 2. A raw water sludge and a flocculant are supplied to a sludge flocculation mixing tank and mixed by stirring to flocculate suspended components in the raw water sludge, and then solid-liquid separated into concentrated sludge and separated water. In a flocculant amount adjusting method of measuring the residual floc concentration in water and controlling the supply amount of the flocculant to be supplied to the sludge flocculation mixing tank according to the measured value, an appropriate upper limit value and lower limit value of the residual floc concentration and An appropriate threshold value for the dispersion of the measured values is set, and every time a predetermined number of measurement values are obtained, (1) the coagulant supply amount is increased according to the number of times exceeding the upper limit among the predetermined number of measurement values, 2) The coagulant supply amount is reduced according to the number of times below the lower limit value among the predetermined number of measurement values. (3) If the dispersion of the predetermined number of measurement values is smaller than the threshold value, the coagulant supply amount is reduced. ,
(4) A method for adjusting the amount of a coagulant characterized by maintaining the previous supply amount of the coagulant other than the above.