JP4270174B2 - Aggregation apparatus and aggregation method - Google Patents

Description

  The present invention relates to a waste water treatment using natural water as a raw material, a waste water treatment for treating factory wastewater or sewage, etc., by adding an inorganic flocculant and a chlorinated chemical to the raw water, thereby suspending the suspended matter in the raw water, colloidal components Further, the present invention relates to a coagulation apparatus and a coagulation method for coagulating and coarsening organic substances.

  In water treatment using natural water as raw material and wastewater treatment for treating industrial wastewater or sewage, a flocculant is added to the raw water to condense and coarsen suspended substances, colloidal components and organic substances in the raw water. After that, solid-liquid separation is performed by precipitation, flotation, filtration, membrane filtration or the like.

  The agglomeration treatment is for increasing the solid-liquid separation efficiency such as precipitation, flotation, filtration, membrane filtration and the like located in the latter stage, and as the aggregating agent, generally an inorganic aggregating agent such as aluminum salt or iron salt is used. In many cases, a polymer flocculant is used in combination as an agglomeration aid for further coarsening the particles coagulated with the inorganic flocculant.

  In addition, it is known that the addition of a chlorine-based chemical agent such as sodium hypochlorite or chlorine together with an inorganic flocculant to raw water improves the aggregation state (however, the addition of a chlorine-based chemical improves the aggregation state. The mechanism of improvement has not been elucidated).

  Thus, when adding an inorganic flocculant and a chlorine chemical | medical agent together to raw | natural water, the chlorine chemical | medical agent is controlled so that the free residual chlorine density | concentration in treated water may become fixed.

In Japanese Patent No. 3205450, the aggregation floc particle size in the stirring tank and the ultraviolet absorbance of the soluble organic substance are measured, and the amount of flocculant added is controlled based on these results. There has been proposed a chemical injection device that determines the number of rotations of the agitator in the agitation tank. This device detects the concentration of soluble organic matter in the agitation tank, that is, the concentration of soluble organic matter in the coagulating liquid to which the coagulant is added and is stirred, and this is added together with the detected value of the particle size of the coagulation floc. On the other hand, the agitation strength is set based on the particle size of the agglomerated floc, but it cannot be said that a sufficiently satisfactory agglomeration result has been obtained, and further improvement is desired. It is rare.
Japanese Patent No. 3205450

  When the quality of the raw water is good, the effect of using a chlorine-based chemical in combination with the inorganic flocculant may not be so high. Therefore, in the addition method in which the chlorine-based chemical is added so that the free residual chlorine concentration becomes constant as described above, if the quality of the raw water is good, the chlorine-based chemical is unnecessarily added. This can result in increased drug costs.

  Further, when a chlorinated chemical is added when the dissolved organic matter concentration in the raw water is high, the trihalomethane concentration in the treated water may be increased.

  The present invention solves such a problem, and when adding an inorganic flocculant and a chlorine-based chemical to raw water and aggregating the raw water, an appropriate amount of the chlorine-based chemical should be added according to the quality of the raw water. It is an object of the present invention to provide an aggregating apparatus and method that can be used.

The flocculating apparatus of the present invention (Claim 1) measures the absorbance of 200 to 700 nm of raw water, a flocculant adding means for adding a flocculant to raw water, a chlorinated chemical adding means for adding a chlorinated chemical to raw water, and raw water. and the absorbance measurement unit, a Ru agglomerator name and a chlorine-based agent addition amount control means for controlling the addition amount of the salt Motokei agent adding means based on a measured value of absorbance measurement unit, the salt Motokei agent The addition amount control means does not add the chlorine-based chemical when the absorbance is smaller than the first threshold value a, and the residual chlorine when the absorbance is between the first threshold value a and the second threshold value b (where a <b). The chlorinated chemical is added so that the concentration becomes a target value, and when the absorbance is larger than the second threshold value b, the chlorinated chemical is controlled not to be added .

  According to a second aspect of the present invention, there is provided the aggregating apparatus according to the first aspect, wherein the absorbance measuring means is capable of measuring an ultraviolet absorbance at 200 to 490 nm and a visible absorbance at 500 to 700 nm of raw water, and the absorbance measuring means measures the absorbance. And a flocculant addition amount control means for controlling the flocculant addition amount by the flocculant addition means based on the difference between the ultraviolet absorbance and the visible absorbance.

A flocculating apparatus according to a third aspect is the flocculating apparatus according to the first aspect, wherein the flocculating agent is configured to be added in the flocculating tank or before the flocculating tank. And a flocculant addition amount control means for controlling the flocculant addition amount of the flocculant addition means based on the detection value of the aggregation state detection sensor.

According to a fourth aspect of the present invention, there is provided the coagulation apparatus according to the second aspect, wherein the coagulant is added in the coagulation tank or before the coagulation tank, and an aggregation state detection sensor for detecting the aggregation state in the coagulation tank is installed. The flocculant addition amount control means controls the flocculant addition amount of the flocculant addition means based on the absorbance difference measured by the absorbance measurement means and the detection value of the aggregation state detection sensor. It is characterized by being.
Agglomeration apparatus according to claim 5, in any one of claims 1 to 4, wherein the chlorine-based agents amount control means, a <c 1 between a and _{b <c 2 <...... <c} n <N threshold values of the relationship <b are set, a target value of residual chlorine concentration is set between a to c ₁ , c _{1 to} c ₂ ,..., C _{n to} b, and this target value is set. The amount of chlorinated drug added is controlled based on the above.
The flocculation apparatus according to claim 6 is a flocculation method in which an inorganic flocculant and a chlorine-based chemical are added to raw water, and the absorbance of raw water is measured at 200 to 700 nm, and chlorine is added to the raw water based on the measured value. In the aggregation method for controlling the amount of addition of the systemic drug, when the absorbance is smaller than the first threshold value a, the chlorine-based drug is not added, and the absorbances are the first threshold value a and the second threshold value b (where a <b ) Is added so that the residual chlorine concentration becomes a target value, and when the absorbance is larger than the second threshold value b, the chlorine-based agent is not added.
The aggregation method according to claim 7 is the aggregation method according to claim 6, wherein n threshold values of a <c ₁ <c ₂ <... <C _n <b are set between a and b. A target value of residual chlorine concentration is set between c ₁ , c _{1 to} c ₂ ,..., c _{n to} b, and the addition amount of the chlorinated chemical is controlled based on the target value. .

An aggregating method according to claim 8 is the method according to claim 6 or 7 , wherein the aggregating agent is added to the aggregating tank or upstream of the aggregating tank, the aggregating state in the aggregating tank is detected, and The addition amount of the flocculant to the raw water is controlled based on the detected value of the aggregation state.

The aggregation method according to claim 9 is the aggregation method according to claim 8 , based on the detected value of the aggregation state and the difference between the ultraviolet absorbance at 200 to 490 nm and the visible absorbance at 500 to 700 nm of the raw water. It is characterized by controlling the additive amount.

  In the coagulation method of adding an inorganic flocculant and a chlorinated chemical to raw water, when the absorbance of at least one wavelength at 200 to 700 nm of raw water is measured and the amount of chlorinated chemical added is controlled based on this measured value, chlorine Appropriate amount of system drug added. That is, when the quality of the raw water is good, the amount of chlorinated chemical added is reduced, and the generation of trihalomethane is reduced when the concentration of organic substances in the raw water is high.

  In addition, according to the present invention, the organic matter concentration of the agglomerated treated water is sufficiently low, so that when the agglomerated treated water is further subjected to membrane filtration treatment, it is also recognized that the membrane contamination is suppressed and high membrane filtration performance is maintained. It was.

  In the present invention, it is preferable to control the amount of the inorganic flocculant added based on the difference between the ultraviolet absorbance and the visible absorbance of the raw water.

That is, when examining the aggregation characteristics of natural water, the inhibitor concentration calculated from the result of measuring the ultraviolet absorbance at a wavelength of 200 nm to 490 nm and the visible absorbance at a wavelength of 500 nm to 700 nm, respectively, of natural water, There is a correlation between the optimum amount of flocculant added determined from the time required to filter a certain amount of sample water using a 45 μm membrane filter (hereinafter referred to as KMF value), and the inhibitor concentration It was found that there is a correlation between the absorbance in the ultraviolet region and the visible region as shown in the following equation. Therefore, the optimum amount of the flocculant added can be estimated by measuring the absorbance of the ultraviolet part and the visible part respectively by one wavelength or more.
(Inhibitor concentration) = [(Total organic matter)-(Turbidity substance)]
= A × [(UV absorbance)-(visible absorbance)]

  In order to control the addition amount of the flocculant based on the ultraviolet absorbance and the visible absorbance, for example, a jar test is performed in advance to determine the relationship between the difference between the ultraviolet absorbance and the visible absorbance and the optimum addition amount of the flocculant. The amount of flocculant added is controlled based on this relationship.

  In the present invention, as described above, not only the concentration of an inhibitory substance such as an organic substance in raw water that causes aggregation inhibition is detected by absorbance measurement, but also the aggregation state in the coagulation tank is detected, and the detected value of the amount of the inhibitory substance is detected. By controlling the addition amount of the flocculant based on the detected value of the agglomeration state, a very good agglomeration treatment can be performed. In addition, you may control the addition amount of a coagulant | flocculant based only on the detection result of the aggregation state in a coagulation tank.

  As the agglomeration state detection sensor, a light blocking fine particle sensor, a light scattering fine particle sensor, or the like that detects the clarity between the agglomerated particles of the liquid in the agglomeration tank can be used.

  Embodiments of the aggregating apparatus and the aggregating method of the present invention will be described below in detail with reference to the drawings.

Figure 1 is a system diagram showing an embodiment of a coagulating sedimentation apparatus including a flocculation apparatus of the present invention.

  In FIG. 1, reference numeral 1 denotes a raw water tank, which includes an absorbance sensor 11. Reference numeral 2 denotes a coagulation agitation tank, which includes an agitator 12 and an aggregation state detection sensor 13. A chlorinated chemical is supplied from the storage tank 6 to the agglomeration stirring tank 2 via a chemical injection pump 15. 3 is a settling tank. Reference numeral 4 denotes a flocculant storage tank, which includes a chemical injection pump 14. Reference numeral 5 denotes a control device to which the detection value of the absorbance sensor 11 and the detection value of the aggregation state detection sensor 13 are inputted, and the stirring intensity control signal of the stirrer 12 and the rotation of the chemical injection pump 14 and the chlorine-based chemical chemical injection pump 15. A number control signal is output.

  The raw water is introduced into the raw water tank 1, and the absorbance at 200 to 700 nm is measured by the absorbance sensor 11. This measured value is input to the control device 5. In this embodiment, the addition amount of the chlorinated drug is controlled based on the absorbance.

  The absorbance sensor 11 may be an immersion type or a badge type.

  The addition amount of the chlorine-based chemical is controlled by the control device 5 based on the absorbance of the absorbance sensor 11 in the ultraviolet region of 200 to 700 nm, preferably 230 to 400 nm. Thus, by controlling the addition amount of the chlorinated drug based on the absorbance in the ultraviolet region of 200 to 700 nm, particularly 230 to 400 nm, wasteful addition of the chlorinated drug when the raw water quality is good is suppressed, The production of trihalomethane when the organic matter concentration of raw water is high is suppressed. The reason for this is considered to be because the absorbance described above correlates with the concentration of organic substances in water.

Is the control added system of chlorine agent based on the absorbance, a <b consists of two thresholds a relationship determined in advance to b,
When the absorbance is smaller than a, no chlorinated chemical is added;
When the absorbance is a to b, add a chlorinated chemical so that the residual chlorine concentration becomes the target value;
Do not add chlorinated drugs when absorbance is greater than b;
Threshold system, such as a control. It should be noted that n threshold values of a <c ₁ <c ₂ ... <C _n <b are set between a and b, and a to c ₁ , c _{1 to} c ₂ ,. it may set a target value of each residual chlorine concentration between c n _~b.

  These threshold values are values determined in advance from the time required to filter a certain amount of sample water using a 0.45 μm membrane filter and the measurement of trihalomethane concentration, and need not be adjusted for each raw water.

  The raw water in the raw water tank 1 is then introduced into the coagulation stirring tank 2. In the flocculation agitation tank 2, the raw water is agglomerated by adding the flocculating agent in the flocculating agent storage tank 4 by the chemical injection pump 14, adding a chlorinated chemical by the chemical injection pump 15, and stirring it by the agitator 12. . The amount of the flocculant added is controlled based on the detection result of the absorbance sensor 11.

Generally, the organic matter concentration in the raw water is proportional to the difference between the ultraviolet absorbance and the visible absorbance, so that the flocculant addition amount is calculated by multiplying the ultraviolet absorbance and the visible absorbance by a coefficient, Based on this, the amount of flocculant added can be controlled.
Addition amount of flocculant = A × [(UV absorbance)-(visible absorbance)]

  The ultraviolet absorbance is 200 to 490 nm, particularly 230 to 300 nm, such as 260 nm, and the visible absorbance is 500 to 700 nm, particularly 600 to 700 nm, such as 660 nm.

  A is a coefficient determined in advance from a KMF value measured by a jar test using raw water, and it is not always necessary to adjust A for each raw water.

  In place of the flocculant addition amount control proportional to the absorbance difference, control based on the absorbance difference threshold may be used. The method of controlling the addition of the flocculant by this threshold is the same as the case of the addition control of the chlorinated drug by the above threshold.

  The aggregation state in the aggregation stirring tank 2 is detected by the aggregation state detection sensor 13, and the detection result is input to the control device 5. The agglomeration state detection sensor 13 includes a device and a sensor for detecting the turbidity of a supernatant obtained by transferring the liquid in the agglomeration stirring tank 2 to another sedimentation tank and allowing it to settle for a certain period of time, or the zeta potential of aggregated or agglomerated particles. Although a device and a sensor for detecting the flow potential can also be used, a light blocking fine particle sensor or a light scattering fine particle sensor for detecting the clarity between particles condensed or aggregated in the aggregation stirring tank 2 is preferable. Used.

  The stirring intensity of the stirrer 12 in the aggregation stirring tank 2 is controlled based on the detection value of the absorbance sensor 11. That is, for example, the control device 5 compares the input detection value of the absorbance sensor 11 with a preset reference value, and if this detection value exceeds the reference value, the agitation intensity is increased so that it is below the reference value. If so, control is performed to reduce the stirring intensity.

  The stirring strength of the agglomeration stirring tank 2 can be controlled by controlling the number of rotations of the stirrer 12 with a rotation control device attached to the drive motor of the stirrer 12. In addition to the stirrer 12, a circulation line including a circulation pump that pumps and circulates the liquid in the flocculation agitation tank 2 and agitation is provided, and the liquid in the flocculation agitation tank 2 is taken out. It is possible to control the stirring intensity by controlling the operation of the circulation pump and / or the stirring element by returning after stirring. Moreover, stirring intensity can also be controlled using these together.

  Note that the amount of the flocculant added to the aggregation stirring tank 2 may be controlled based on the detection value of the aggregation state detection sensor 13. That is, for example, in the control device 5, the input detection value of the aggregation state detection sensor 13 may be substituted into a preset formula for determining the addition amount of the coagulant, and the chemical injection control may be performed based on the calculation result.

  Further, the addition amount of the flocculant may be controlled based on both the detection value of the aggregation state detection sensor 13 and the detection value of the absorbance sensor 11.

  In order to control the addition amount of the flocculant to the aggregation stirring tank 2 based on the detection value of the absorbance sensor 11 and the detection value of the aggregation state detection sensor 13, for example, the control device 5 uses the input absorbance sensor 11. The detected value is substituted into a predetermined determination formula for the amount of flocculant added, and the number of revolutions of the medicinal pump 14 is controlled based on the calculation result. Correct the rotation speed.

  The agglomerated water that has been agglomerated by adding and aggregating the aggregating agent in the agitation agitation tank 2 is introduced into the precipitation tank 3 to coagulate and aggregated particles are settled and separated, and the supernatant water is taken out as treated water. .

  FIG. 1 shows an example of an embodiment of the present invention, and the present invention is not limited to the illustrated one as long as the gist of the present invention is not exceeded. The chlorinated chemical is preferably added to the raw water tank 1 as shown in FIG.

  Further, in FIG. 1, the flocculant is added to the flocculent stirring tank 2, but the flocculant may be injected into the raw water introduction pipe to the flocculent stirring tank 2. Furthermore, although the precipitation tank 3 is shown in FIG. 1 as the solid-liquid separation means of the coagulated treated water, the present invention is not limited to the precipitation tank, but various solid-liquid separation means such as a flotation tank, a filtration apparatus, and a membrane filtration apparatus. It can be effectively applied as an aggregation means in the previous stage. In the present invention, stirring may not be performed.

  Although illustration is omitted, in the present invention, a pH sensor is provided in the agglomeration agitation tank 2, and acid and alkali are poured into the agglomeration agitation tank 2 so that the pH in the agglomeration agitation tank 2 is about 5.0 to 7.0. Also good.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

Example 1
In the agglomeration / precipitation / sand filtration / UF membrane filtration facility using the river A where organic matter contamination progressed as a water source, the agglomeration precipitation treatment according to the present invention was performed using the agglomeration precipitation apparatus shown in FIG. For sand filtration, a column in which 600 mm of filtration sand having an effective diameter of 0.45 mm was laminated was used. The coagulation agitation tank is a square rapid agitation tank with a paddle type agitator (60 rpm, 5 kW) having an effective capacity of 300 m ³ , the raw water amount is 30 m ³ / h, and the residence time of the rapid agitation tank is 6 minutes. It was.

  Chlorine was used as the chlorinated drug. The amount of chlorine added was controlled based on the absorbance of the raw water at 260 nm for ultraviolet light. That is, the absorbance is 0.1 [abs. / 50 mm] and 0.5 [abs. / 50 mm], chlorine is not added, and 0.1 to 0.5 [abs. / 50 mm], chlorine was added so that the residual chlorine concentration was 0.5 mg / L. This threshold was determined in advance by performing a jar test.

  Polyaluminum chloride (PAC) was used as the flocculant. The amount of PAC added was controlled based on the difference between the ultraviolet absorbance at 260 nm and the visible absorbance at 660 nm. The arithmetic expression for controlling the PAC addition amount was obtained in advance from the result of the jar test using the A river water. Further, the pH of the coagulation agitation tank was automatically adjusted independently by a pH adjusting means (not shown) so as to be 6.5.

  As the absorbance sensor, an S :: CAN sensor (S :: CAN MESSTECHNIK GMBH (Austria), cell width 35 mm) capable of scanning the ultraviolet to visible light region in the vicinity of a wavelength of 200 nm to 700 nm was used.

Comparative Example 1
The same control as in Example 1 was performed except that the chlorine injection amount was not controlled by measuring the absorbance. The chlorine injection amount was adjusted so that the free residual chlorine concentration was maintained at 0.5 mg / L.

Comparative Example 2
The same control as in Example 1 was performed except that chlorine injection itself was not performed.

[Comparison between Examples and Comparative Examples]
Water was passed for 2 weeks each when the water quality fluctuated due to fine weather and rainy weather from 11 to December. In addition, in order to use the same raw | natural water, the structure in an Example and the structure in a comparative example were performed in parallel. Table 1 shows the raw water DOC, the PAC addition concentration, the coagulation sedimentation treated water KMF value, and the ΔP increase rate of the UF membrane during the water flow test. The KMF value is obtained by adding the first 500 mL filtration time and the subsequent 500 mL filtration time when filtration is performed at a vacuum suction pressure of 500 mmHg using a membrane filter having a diameter of 47 mm.

  In Example 1, compared with Comparative Example 2, the KMF value and the ΔP increase rate were low.

  The trihalomethane concentration in Comparative Example 1 sometimes became excessive as compared with the Example.

It is a systematic diagram which shows embodiment of the coagulation sedimentation apparatus provided with the coagulation apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Raw water tank 2 Aggregation stirring tank 3 Precipitation tank 4 Coagulant storage tank 5 Control apparatus 11 Absorbance sensor 12 Stirrer 13 Aggregation state detection sensor 14,15 Chemical injection pump

Claims (9)

A flocculant addition means for adding the flocculant to the raw water;
A chlorinated chemical addition means for adding a chlorinated chemical to raw water;
An absorbance measuring means for measuring the absorbance of raw water at 200 to 700 nm;
A Do that agglutination device and a chlorine-based agent addition amount control means for controlling the addition amount of the salt Motokei agent adding means based on a measured value of absorbance measurement means,
The chlorinated drug addition amount control means includes:
When the absorbance is smaller than the first threshold a, the chlorinated drug is not added,
When the absorbance is between the first threshold value a and the second threshold value b (where a <b), a chlorine-based chemical is added so that the residual chlorine concentration becomes a target value,
An aggregating apparatus characterized in that when the absorbance is larger than a second threshold value b, the chlorinated chemical is controlled not to be added. In claim 1, the absorbance measuring means can measure the ultraviolet absorbance of raw water 200-490nm and the visible absorbance of 500-700nm,
An aggregating apparatus comprising a flocculant addition amount control means for controlling a flocculant addition amount by the flocculant addition means based on a difference between an ultraviolet absorbance and a visible absorbance measured by the absorbance measuring means. . In claim 1,
The flocculant is configured to be added in the agglomeration tank or upstream thereof,
An aggregation state detection sensor for detecting the aggregation state in the aggregation tank is installed,
An aggregating apparatus comprising an aggregating agent addition amount control unit for controlling an aggregating agent addition amount of the aggregating agent addition unit based on a detection value of the aggregation state detection sensor. In claim 2,
The flocculant is configured to be added in the agglomeration tank or upstream thereof,
An aggregation state detection sensor for detecting the aggregation state in the aggregation tank is installed,
The flocculant addition amount control means controls the flocculant addition amount of the flocculant addition means based on the absorbance difference measured by the absorbance measurement means and the detection value of the aggregation state detection sensor. Agglomeration equipment. 5. The chlorinated drug addition amount control means according to claim 1, wherein: a <c ₁ <C ₂ <…… <c _n N threshold values of the relationship <b are set, and a to c ₁ , C ₁ ~ C ₂ ............ c _n A coagulating apparatus characterized in that a target value of residual chlorine concentration is set between ˜b and the amount of chlorinated chemical added is controlled based on this target value. In the coagulation method of coagulating by adding an inorganic coagulant and a chlorine-based chemical to raw water,
The absorbance of 200~700nm of the raw water is measured, a chlorine amount that controls the agglutination method of the agent to the raw water on the basis of the measured values,
When the absorbance is smaller than the first threshold a, the chlorinated drug is not added,
When the absorbance is between the first threshold value a and the second threshold value b (where a <b), a chlorine-based chemical is added so that the residual chlorine concentration becomes a target value,
An aggregating method, wherein the chlorine-based chemical is not added when the absorbance is larger than a second threshold value b. In claim 6, n threshold values of a <c ₁ <c ₂ <... <C _n <b are set between a and b, and a to c ₁ and c _{1 to} c _{2 are set.} A coagulation method characterized in that a target value of residual chlorine concentration is set between each of c _{n to} b, and the addition amount of the chlorine-based chemical is controlled based on the target value. The method according to claim 6 or 7 , wherein the flocculant is added on the flocculant tank or on the upstream side thereof.
Detecting the agglomeration state in the agglomeration tank;
A coagulation method characterized by controlling the amount of coagulant added to the raw water based on the detected value of the coagulation state. In claim 8, the detection value of the aggregated state, on the basis of the difference between the visible portion absorbance ultraviolet absorbance and 500~700nm of 200~490nm of the raw water, to control the flocculant amount to the raw water Aggregation method characterized.

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