JP4505772B2 - Coagulant injection control method for water purification plant - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control apparatus for a water purification plant coagulation process in which impurities in raw water are aggregated and agglomerated as floc in order to separate impurities in raw water by precipitation and filtration.
[0002]
[Prior art]
FIG. 11 shows an example of a conventional agglomeration process. In the figure, the raw water of the water purification plant flows into the mixing basin 2 after passing through the landing well 1. In the mixing basin 2, the flocculant is injected from the flocculant injection means 3 and is rapidly stirred by a stirrer (not shown) to form micro flocs. Colloidal particles, suspended matter in the raw water, suspended from the flocs. Adsorb turbid substances and microorganisms. As the flocculant, aluminum salt sulfate and PAC (polyaluminum chloride: hereinafter referred to as pack) are used, and suspensions and impurities contained in tap water raw water are removed from water-insoluble aluminum hydroxide. Flock to settle.
[0003]
Next, flocs are grown in the floc formation pond 5 by slow stirring with a stirrer (not shown), and solid components are precipitated in the sedimentation basin 6 for solid-liquid separation. Accordingly, it is necessary that a floc having an appropriate size and density is formed at the outlet of the flock formation pond 5 (inlet of the precipitation pond 6). The injection amount of the pack is adjusted so that the degree becomes an appropriate value.
[0004]
In addition, 7 is a flow meter that measures the amount of water flowing into the landing well 1, 8 is a treated water turbidity detection value and a treated water turbidity set value from a turbidimeter 9 as a turbidity sensor. The coagulant injection rate calculation control means 4 outputs the coagulant injection rate by adjusting the two so as to coincide with each other, and 4 is a pack injection control means. Here, the injection rate of the pack into the raw water is influenced by the strength of the agitator in the mixing basin and the strength of the agitator in the sedimentation basin, but these are fixed and controlled.
[0005]
[Problems to be solved by the invention]
It is important that the flocculant is injected in an appropriate amount according to the quality and quantity of the suspension. The balance of the sum is lost and the agglomeration effect becomes worse. In particular, when the amount of injection is excessive, the aggregation is worsened and the quality of the purified water is lowered, and the economic burden is increased.
[0006]
As described above, the injection rate is calculated by the flocculant injection rate calculation control means 8, and the pack is injected into the mixing basin 2 according to the turbidity measured at the landing well 1 by the pack injection control means 4 and the measured value of the flow meter 7. The amount of injection is adjusted according to the turbidity measured by the turbidimeter 9 in the vicinity of the outlet of the sedimentation basin 6, but it takes time to reach the vicinity of the outlet of the sedimentation basin after injecting the pack (for example, about 4 hours). Therefore, when the raw water turbidity changes suddenly as at the start of rainfall, stable and accurate control is impossible.
[0007]
The present invention has been made to solve the above-mentioned problems, and the object of the present invention is to provide a water purification plant that can perform stable and accurate control even when a sudden fluctuation occurs in the raw water turbidity. The object is to provide a drug injection control device.
[0008]
[Means for Solving the Problems]
In order to solve such problems, the flocculant injection control method of the water purification plant of the present invention,
In claim 1, the flocculant is injected into the raw water that has flowed into the mixing pond through the landing well and stirred to form micro flocs, and the micro flocs are grown in the subsequent floc forming ponds. In the coagulant injection control method of the water purification plant that coagulates the solid components and separates into solid and liquid in the subsequent sedimentation pond, the injection rate of the coagulant for injecting the coagulant into the mixing pond is calculated by the following formula: A feature of the water treatment plant flocculant injection control method.
[{(Basic value of injection rate−actual injection rate at present) + (a: basic amount of correction for alkalinity of raw water in landing well, b: basic value of correction amount for pH of raw water in landing well, c: basic amount of correction for PH of raw water in landing well] Basic correction value for raw water temperature in water well, d: Basic correction value for sudden change in raw water turbidity in landing well, e: Basic correction value for deviation between turbidity of sedimentation basin and management target value a correction amount basic value of at least one of a to e)} × predetermined constant × manual correction value provided according to low , medium, and high turbidity] + actual injection rate at the present time.
However,
Injection rate basic value: A value obtained by calculating the pack injection rate results for turbidity conducted in the past by statistical analysis (correlation).
Manual correction value: A value manually input by the operator via the terminal of the coagulant injection rate calculation means. (The coefficient currently set by the operator according to the difference between the solid-liquid separation process in the sedimentation basin and the control target value (the sedimentation basin outlet turbidity setting value))
Low, medium, high turbidity: When the turbidity is rising and falling, a predetermined upper and lower limit area that varies depending on the individual circumstances of the water treatment plant is defined and rising. When the turbidity is lower than the lower limit value, low turbidity, when the turbidity is in the same or higher range as the lower limit value, and when lower than the upper limit value, medium turbidity, when the turbidity is equal to or higher than the upper limit value When the turbidity is lower than the upper limit value, the turbidity is in the region where the turbidity is the same as or higher than the upper limit value. When in the region, the medium turbidity is determined as low turbidity when the turbidity is lower than the lower limit.
[0009]
In Claim 2, in the flocculant injection control method of the water purification plant of Claim 1,
The correction amount basic value for alkalinity of the raw water in the reservoir well is alkalinity without basic amount correction at 26 or less (zero ppm), such that 8 (ppm) in 40 6.0,50 above relationship Is graphed and obtained based on this graph .
[0010]
In claim 3, in the flocculant injection control method of the water purification plant according to claim 1,
The basic value of the correction amount for the raw water pH at the receiving well is graphed based on a relationship such that the pH is zero (ppm) when the pH is 7.3 or less and 8 (ppm) when the pH is 8.5 or more. It is characterized by that.
[0011]
In claim 4, in the flocculant injection control method of the water purification plant according to claim 1,
Correction amount basic value for the water temperature of the raw water in the reservoir well has water temperature graph the relationship such that zero (ppm) in 6 (ppm) 15 ° C. or higher at 12.5 ° C. or less, Ru determined based on the graph It is characterized by that.
[0012]
In Claim 5, in the flocculant injection control method of the water purification plant of Claim 1,
Correction amount basic value for the turbidity sudden change of the raw water in the reservoir well is turbidity sudden change before and after the difference is zero at 1 or less (ppm), graphed such that 3 (ppm) relationship is 4.2 or more, this characterized in that the so that calculated based on the graph.
[0013]
In Claim 6, in the flocculant injection control method of the water purification plant of Claim 1,
The correction amount basic value for the deviation between the turbidity of the settling basin and the turbidity of the management target value is calculated using at least one of the intermediate turbidity of the settling basin and the outlet turbidity.
[0014]
In claim 7, in the flocculant injection control method of the water purification plant according to claim 1,
The sudden change in turbidity of the raw water in the landing well is characterized in that a difference between a moving average in minutes and a moving average in hours is obtained and the direction of change in turbidity is judged from the difference .
[0015]
In claim 8, in the flocculant injection control method of the water purification plant according to claim 1,
The correction amount basic value for the deviation between the turbidity of the settling basin and the turbidity of the management target value is the deviation from the management target value (settling basin outlet turbidity setting value) set by the operator when using intermediate turbidity The relationship is such that 0 (ppm) when the value is 0.1 or less and 5 (ppm) when the value is 1.0 or more is graphed and obtained based on this graph.
In Claim 9, in the flocculant injection control method of the water purification plant according to claim 1,
The correction amount basic value for the deviation between the turbidity of the settling basin and the turbidity of the management target value is the deviation from the management target value (settling basin outlet turbidity setting value) set by the operator when the turbidity at the outlet is used. The relationship is such that 0 (ppm) is 0 to 0.1 and 3 (ppm) is 1.0 or more, and the relationship is obtained based on this graph .
[0018]
In claim 10 , in the flocculant injection control method of the water purification plant according to claim 1 ,
The manual correction value determined by the operator is in the range of 0.0 to 1.0 .
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
As described above, in the water purification treatment, it is essential to remove the suspended matter in the inflow raw water by coagulating and precipitating by injecting the flocculant. The phenomenon in which flocs are generated when a flocculant is mixed in the suspended substance is based on the following principle.
[0020]
That is, there are many suspended particles of about several μm in the raw water. Most of these fine particles are negatively charged and repel each other due to mutual charge to form a stable dispersion system. In this state, they do not settle. When a negatively charged flocculant is added to such a negatively charged system to neutralize the suspended particles, the electric repulsive force between the particles is reduced and the particles can be contacted with each other. Aggregates and settles.
[0021]
FIG. 1 shows an example of the embodiment of the present invention. The same elements as those in the conventional example shown in FIG. A turbidimeter 9a is also provided in the middle of the outlet, and at least one of the output values of the conventional turbidimeter 9 provided at the outlet is used, and the flocculant is injected according to the change in water quality. The amount is controlled.
[0022]
First, the relationship between the basic injection rate of the pack and the turbidity used in the flocculant injection control method of the present invention will be described.
FIG. 2 shows the relationship between turbidity and the basic injection rate (ppm) of the pack. As the turbidity increases, the injection rate of the pack also increases, and at the turbidity 240, the injection rate of the pack reaches 80 (ppm). ing. This relationship is obtained by calculating the injection rate of the pack with respect to the turbidity by calculating the past injection result by statistical analysis (correlation).
[0023]
FIG. 3 (a) shows the turbidity change with respect to the elapsed time indicated by the turbidimeter (not shown) provided in the landing well 1 shown in FIG. 1, the dotted line is in minutes (for example, 5 minutes), and the solid line is in time. It is the result measured at intervals (for example, 2 hours).
FIG. 3B shows a state in which only the large value is left by combining the results shown in FIG. 3A, and the turbidity values shown in FIG. In order to correct the difference, the pack injection rate is determined based on the synthesized turbidity.
[0024]
FIG. 4 shows the relationship between the alkalinity measured in the landing well 1 shown in FIG. 1 and the basic value of the correction amount. In this embodiment, the alkalinity of about 26 is set to the basic value of correction amount 0 (ppm), and the alkalinity is 30. The relationship is 2.0 (ppm), 6.0 (ppm) when the alkalinity is 40, and 8 (ppm) when the alkalinity is 50 or more. Based on this graph, the correction amount corresponding to each alkalinity Use basic value.
[0025]
And this correction amount basic value is multiplied by a predetermined constant provided according to low, medium, and high turbidity according to the standard determined by the raw water quality or the water purification plant, and the operator further processes the solid separation in the settling tank 6 A correction value is determined by adding a coefficient A (0.00 to 3.00 ppm) set according to the above.
The coefficient A is a value determined by initial tuning, subsequent operation results, periodic laboratory analysis, or the like.
FIG. 5 is a diagram showing a concept for selecting low, medium and high turbidity when the turbidity (TU) of raw water flowing into the landing well 1 is directed upward and downward. A constant is selected according to the turbidity of the upper and lower limit values. In addition, a concrete numerical value changes with the circumstances of each water purification plant.
[0026]
FIG. 6 is a diagram showing the relationship between the PH measured in the landing well 1 shown in FIG. 1 and the correction amount basic value. In this embodiment, PH 7.3 or less is a correction amount of 0 (ppm), and the relationship of 4.5 (ppm) at PH8 and 8.0 (ppm) at PH 8.5 is graphed. Based on the above, a correction amount basic value for each PH is determined. In this case as well, a factor B (0.00 to 3.00) set by the operator according to the treatment status is further multiplied by a predetermined constant set according to the low, medium and high turbidity according to the standard determined by the raw water quality or the water purification plant. ppm) is added to determine the correction value.
[0027]
FIG. 7 is a diagram showing the relationship between the water temperature measured at the landing well 1 shown in FIG. 1 and the correction amount basic value. In this embodiment, the relationship is such that the basic value of correction amount is 6 (ppm) when the water temperature is 12.5 ° C. or lower, and 0 (ppm) when the water temperature is 15 ° C. or higher. Based on this graph, the basic value of correction amount for each water temperature is plotted. Is decided. In this case as well, the coefficient C (0.00 to 3.00) set by the operator according to the treatment status is further multiplied by a predetermined constant set according to the low, medium and high turbidity according to the standard determined by the raw water quality or the water purification plant. ppm) is added to determine the correction value.
[0028]
FIG. 8 is a diagram showing the relationship between the turbidity change (turbidity difference) and the correction amount basic value when the turbidity changes suddenly in the landing well 1 shown in FIG.
FIGS. 9A and 9B are diagrams showing the concept of turbidity difference. In this figure, in order to catch a sudden increase in raw water turbidity, the difference between the 5-minute moving average (dotted line) and the N-hour moving average (solid line) of turbidity is obtained. In the figure, (a) the figure shows a 5-minute moving average and N-hour moving average superimposed, and (b) the figure shows the difference in turbidity at each time, and the direction of the change in turbidity is determined from the difference. to decide.
[0029]
Returning to FIG. 8, in this example, the relationship between the turbidity difference of 1.0 or less and the correction amount basic value of 0 (ppm), and the difference of 4.2 or more to 3.0 (ppm) is graphed. Based on this graph, a correction amount basic value for each difference is determined.
Also in this case, the operator multiplies predetermined constants set according to the low, medium and high turbidity according to the standards determined by the raw water quality or the water purification plant, and the operator sets the solid separation in the sedimentation basin 6 according to the processing status of solid separation. The correction value is determined by adding the coefficient D (0.00 to 3.00 ppm) to be performed.
[0030]
FIG. 10 is a management target value (set value) based on the basic value of the injection rate calculated by statistical analysis of the turbidity measured at the middle and outlet of the settling basin 6 shown in FIG. In this embodiment, the deviation from the control target value (set value) when measured with a turbidimeter provided in the middle of the settling basin is 0.1 or less. The relationship between the basic value of correction amount 0 (ppm) and 5 (ppm) when the deviation is 1.0 or more is graphed, and the control target value when measured with a turbidimeter installed at the outlet of the sedimentation tank When the deviation from (set value) is 0.1 or less, the correction amount basic value is 0 (ppm), and when the deviation is 1.0 or more, the relationship is 3 (ppm). A correction amount basic value for each deviation is determined.
In this case as well, a coefficient E (0.00 to 3.00) set by the operator according to the treatment situation is further multiplied by a predetermined constant set according to the low, medium and high turbidity according to the standards determined by the raw water quality or the water purification plant. ppm) is added to determine the correction value. The sedimentation tank turbidity correction may be performed using at least one of the middle and the outlet.
[0031]
In summary, the pack injection rate (ppm) is
[{(Basic value of injection rate−actual injection rate at present) + (a: basic amount of correction for alkalinity of raw water in landing well, b: basic value of correction amount for PH of raw water in landing well, c: basic amount of landing of well] Correction value basic value for raw water temperature in d, d: correction value basic value for sudden change in turbidity of raw water in landing well, e: correction value basic value for deviation between turbidity of sedimentation basin and management target value a ~ At least one correction amount basic value among e)} x predetermined constant provided according to low , medium, high turbidity x manual correction value] + actual injection rate at the present time.
However,
Injection rate basic value: A value obtained by calculating the pack injection rate results for turbidity conducted in the past by statistical analysis (correlation).
Manual correction value: A value manually input by the operator via the terminal of the coagulant injection rate calculation means. (The coefficient currently set by the operator according to the difference between the solid-liquid separation process in the sedimentation basin and the control target value (the sedimentation basin outlet turbidity setting value))
Low, medium, high turbidity: When the turbidity is rising and falling, a predetermined upper and lower limit area that varies depending on the individual circumstances of the water treatment plant is defined and rising. When the turbidity is lower than the lower limit value, low turbidity, when the turbidity is in the same or higher range as the lower limit value, and when lower than the upper limit value, medium turbidity, when the turbidity is equal to or higher than the upper limit value When the turbidity is lower than the upper limit value, the turbidity is in the region where the turbidity is the same as or higher than the upper limit value. When in the region, the medium turbidity is determined as low turbidity when the turbidity is lower than the lower limit.
It becomes.
[0032]
The calculation of the pack injection rate is performed by the coagulant injection calculation control device 8, and the pack injection amount calculated here is output to the pack injection control means 4, and the pack is injected based on the signal transmitted from here. .
【The invention's effect】
As is clear from the above description, the following effects can be expected according to the present invention. According to the invention of claim 12 wherein, rapid fluctuations in the raw water turbidity as at rainfall starts becomes possible to quickly stable control even when produced.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an example of an embodiment of an apparatus used in a flocculant injection control method for a water purification plant of the present invention.
FIG. 2 is a graph showing the relationship between turbidity and basic injection rate (ppm) of a pack.
FIG. 3 is a diagram showing a change in turbidity with respect to an elapsed time of a turbidimeter provided in a landing well.
FIG. 4 is a diagram showing a relationship between alkalinity measured at a landing well and a basic value of correction amount.
FIG. 5 is a diagram showing a concept for selecting low, medium, and high turbidity when turbidity (TU) flowing into a landing well is directed upward and downward.
FIG. 6 is a diagram showing a relationship between PH measured at a landing well and a basic value of correction amount.
FIG. 7 is a diagram showing a relationship between a water temperature measured at a landing well and a basic value of correction amount.
FIG. 8 is a diagram showing a relationship between a turbidity change (turbidity difference) and a correction amount basic value when the turbidity suddenly changes in a landing well.
FIG. 9 is a diagram showing the concept of turbidity difference.
FIG. 10 shows the deviation between the turbidity measured at the middle and outlet of the settling basin 6 and the target value based on the injection rate basic value calculated by statistical analysis of the past turbidity, and the basic value of the correction amount. It is a figure which shows the relationship.
FIG. 11 is a block diagram showing a control device of a conventional flocculant injection method for a water purification plant.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Landing well 2 Mixing pond 3 Flocculant (pack) injection means 4 Pack injection control means 5 Flock formation pond 6 Sedimentation basin 7 Flow meter 8 Flocculant injection control means 9 Turbidimeter

Claims (10)

A micro floc is formed by injecting and stirring the flocculant into the raw water flowing into the mixing pond through the landing well, and the micro floc grows in the subsequent floc forming pond to agglomerate solid components in the raw water. In the flocculant injection control method of the water purification plant for solid-liquid separation in the subsequent settling pond, the injection rate of the flocculant for injecting the flocculant into the mixing pond is calculated by the following formula: Flocculant injection control method.
[{(Basic value of injection rate−actual injection rate at present) + (a: basic amount of correction for alkalinity of raw water in landing well, b: basic value of correction amount for pH of raw water in landing well, c: basic amount of correction for PH of raw water in landing well] Basic correction value for raw water temperature in water well, d: Basic correction value for sudden change in raw water turbidity in landing well, e: Basic correction value for deviation between turbidity of sedimentation basin and management target value a correction amount basic value of at least one of a to e)} × predetermined constant × manual correction value provided according to low, medium, and high turbidity] + actual injection rate at the present time.
However,
Injection rate basic value: Statistical analysis of the pack injection rate performance against turbidity was carried out in the past value determined by calculating Ri by the (correlation).
Manual correction value: A value manually input by the operator via the terminal of the coagulant injection rate calculation means. (The coefficient set by the operator according to the difference between the solid-liquid separation processing status in the sedimentation basin and the control target value (sedimentation basin outlet turbidity setting value)).
Low, medium, high turbidity: When the turbidity is rising and falling, a predetermined upper and lower limit area that varies depending on the individual circumstances of the water treatment plant is defined and rising. When the turbidity is lower than the lower limit value, low turbidity, when the turbidity is in the same or higher range as the lower limit value, and when lower than the upper limit value, medium turbidity, when the turbidity is equal to or higher than the upper limit value When the turbidity is lower than the upper limit value, the turbidity is in the region where the turbidity is the same as or higher than the upper limit value. When in the region, the medium turbidity is determined as low turbidity when the turbidity is lower than the lower limit.   The correction amount basic value for the alkalinity of the raw water in the landing well is such that the basic amount correction is not performed when the alkalinity is 26 or less (zero ppm), 6.0 at 40, and 8 (ppm) at 50 or more. The flocculant injection control method for a water purification plant according to claim 1, characterized in that the graph is obtained based on the graph.   The basic value of the correction amount for the pH of the raw water in the landing well is obtained by graphing a relationship in which the pH is zero (ppm) when the pH is 7.3 or less and 8 (ppm) when the pH is 8.5 or more. The flocculant injection control method for a water purification plant according to claim 1.   The correction amount basic value for the raw water temperature in the receiving well is graphed based on a relationship such that the water temperature is 6 (ppm) when the water temperature is 12.5 ° C. or lower and zero (ppm) when the water temperature is 15 ° C. or higher. The flocculant injection control method for a water purification plant according to claim 1.   The correction amount basic value for the sudden turbidity change of the raw water in the landing well is graphed in such a relationship that the difference before and after the turbidity sudden change is 1 (zero) when it is 1 or less, and 3 (ppm) when it is 4.2 or more. The flocculant injection control method for a water purification plant according to claim 1, characterized in that it is obtained based on a graph. The correction amount basic value for the deviation between the turbidity of the settling basin and the turbidity of the management target value is calculated using at least one of the intermediate turbidity and the outlet turbidity of the settling basin. The water purification plant flocculant injection control method described.   The sudden change in turbidity of the raw water in the landing well is characterized in that a difference between a moving average in minutes and a moving average in hours is obtained, and the direction of change in turbidity is determined from the difference. Item 8. A method for controlling flocculant injection in a water purification plant according to Item 1.   The correction amount basic value for the deviation between the turbidity of the settling basin and the turbidity of the management target value is the deviation from the management target value (settling basin outlet turbidity setting value) set by the operator when using intermediate turbidity The water purification plant agglomeration according to claim 6, wherein the relationship is 0 (ppm) when the water content is 0.1 or less and 5 (ppm) when the water content is 1.0 or more, and is determined based on the graph. Agent injection control method.   The correction amount basic value for the deviation between the turbidity of the settling basin and the turbidity of the management target value is the deviation from the management target value (settling basin outlet turbidity setting value) set by the operator when the turbidity at the outlet is used. The water purification plant according to claim 6, wherein the relationship is 0 (ppm) when 0 is 0.1, and 3 (ppm) when 1.0 or more, and is calculated based on the graph. Flocculant injection control method. Manual correction value claim 1 filtration plant coagulant injection control method, wherein a is in the range of 0.0 to 1.0 for the operator to determine.

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