JP3827228B2 - Polluted water treatment method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for treating polluted water that separates and removes pollutants in polluted water, and more particularly, to a method for treating polluted water that flows into a treatment facility in a large amount from a combined sewer during rainfall.
[0002]
[Prior art]
There are two types of sewerage: a sewer sewer that is configured to drain rainwater and sewage to the treatment facility using separate pipes, and a combined sewer that supplies water to the treatment equipment using the same pipe. The combined sewer system has been adopted by local governments mainly in large cities from the late Meiji period to the early Showa era, as the sewerage system has only one system, is easy to construct, and is inexpensive. Currently widely used. In this combined sewer, a large amount of contaminated water mixed with sewage and rainwater may flow into the treatment facility during rainy weather, and the treatment facility will allow the normal treatment route capacity in addition to the normal treatment route during such rain. A separate treatment path is provided in which the excess amount of contaminated water is drawn into a separate path from the normal treatment path and discharged by a simple process such as an untreated or coarse screen or a sedimentation process. (Hereinafter, the polluted water that is drawn into another processing path when it exceeds the allowable capacity of the normal processing path is called overflow water.)
[0003]
One of the reasons why the overflow water is treated only by simple treatment as described above is because the overflow water contains a large amount of solids such as earth and sand, so it is highly turbid and flows in a large amount at once. This is because clogging occurs with a fine screen, and processing with a long storage time cannot be performed quantitatively. However, with simple processing, fine solids such as fine plastic pieces and dendritic pieces cannot be removed, and these are discharged as they are. In addition, harmful substances caused by domestic sewage and the like are also released. However, such pollutants such as fine solids or harmful substances should be removed in consideration of the environment such as rivers, lakes, and marine areas in the vicinity or downstream, and a removal process is actually required.
[0004]
Therefore, in recent years, eddy currents that separate solids and liquids by collecting the water to be treated into cylindrical water tanks and generating eddy currents in the water tanks to collect solids in the lower direction of the center of the water tank. An attempt has been made to use a solid-liquid separator (also referred to as a swirl). In addition, a flocculant is added to agglomerate the pollutant before the overflow water flows into the vortex solid-liquid separator. Since the treatment method using such a vortex type solid-liquid separation device separates the solid and liquid by using the vortex flow, it can be processed without hindering the flow of the water to be treated. Things can be removed in a short time.
[Patent Literature]
Special table flat 10-504227
JP2002-18210
[0005]
[Problems to be solved by the invention]
However, in the conventional treatment method using the vortex type solid-liquid separation apparatus as described above, such pollution is caused even though the pollution degree of overflow water changes every moment depending on the amount of rainfall and the inflow of domestic wastewater. There was no technology to cope with changes in temperature and flow rate. Therefore, the following bad effects have occurred. That is, even when a flocculant is added, the flocculant is excessively added at a certain point and discharged while the additive remains. There has been a situation where it is released without being removed. In addition, the vortex type solid-liquid separation device needs to remove the collected solids out of the water tank, but if it is not removed outside the water tank at an appropriate time, the floc formed by the addition of the flocculant is caused by the eddy current. It may collapse and be released without removing fine solids and harmful substances.
[0006]
Therefore, the main problem of the present invention is to establish a technique for processing in response to the change in the pollution level described above, and to effectively and effectively remove pollutants from a polluted water having a high pollution level such as overflow water in a short time. The object is to provide a method for treating polluted water that can be separated and removed.
[0007]
[Means for Solving the Problems]
The present invention that has solved the above-described problems and the effects thereof are as follows.
<Invention of Claim 1>
The first solid-liquid separation means for removing contaminants from the contaminated water, the addition of a flocculant to agglomerate the pollutants in the treated water by adding a flocculant to the water to be treated treated by the first solid-liquid separation means Means for removing polluted water in the polluted water through the second solid-liquid separation means for separating the treated water treated by the flocculant adding means into a clarified portion and a solid content in this order Because
At least the second solid-liquid separation means feeds the water to be treated into the cylindrical water tank along the tangential direction of the water tank, generates a vortex in the water tank, and causes the solid content to enter the lower center of the water tank. A vortex-type solid-liquid separator that collects and collects the collected solids outside the water tank and separates them into solid and liquid, and
Measure the turbidity and flow rate of the treated water treated by the first solid-liquid separation means, and determine the addition amount of the flocculant in the flocculant addition means according to this measured value,
Further, the solid content is intermittently withdrawn from the cylindrical water tank, and the amount of withdrawal and the frequency of withdrawal are determined by the first solid-liquid separation means and the water to be treated flowing into the flocculant addition means. A method for treating polluted water that is determined according to the measured value of the degree and flow rate.
[0008]
<Invention of Claim 2>
In the vortex-type solid-liquid separator, a cylindrical screen is disposed vertically in a cylindrical water tank, and water to be treated is fed into the cylindrical screen along the tangential direction of the screen. 2. The polluted water according to claim 1, wherein the solid content is collected at the center lower part of the water tank while generating a vortex flow through the screen and sending out the clarified content to the outside of the water tank, and the collected solid content is drawn out of the water tank. Processing method.
[0010]
(Function and effect)
By removing the contaminants by the first solid-liquid separation means, the flocculant and the aggregation time necessary for the aggregation of the contaminants are unnecessary in the subsequent flocculant addition means, and the amount of the flocculant added is reduced. As a result, the coagulation effect of the pollutants is increased. Further, by removing impurities, the burden of removing impurities in the second solid-liquid separation means is reduced, and it is possible to design a solid-liquid separation means suitable for the aggregated contaminants.
[0011]
On the other hand, by measuring the turbidity and flow rate of the water to be treated treated by the first solid-liquid separation means, and determining the addition amount of the flocculant in the flocculant addition means according to this measured value, The cost caused by the addition of the flocculant is reduced, and the unreacted flocculant is prevented from being discharged. Furthermore, since the amount of the flocculant added is small, the contaminants are not removed.
[0012]
On the other hand, since at least the second solid-liquid separation means is a vortex-type solid-liquid separation device, it is preferable to remove harmful substances that have been aggregated by a flocculant and become a flock, which is difficult to capture with a screen device of a bar screen. Can be removed.
[0013]
Here, the solid-liquid separation device used for the solid-liquid separation means assumes that the cylindrical screen is arranged vertically in the cylindrical water tank, and when the vortex is generated in the screen, the clarified portion passes through the screen. Since it is sent out of the tank and becomes a configuration, the clarified component and the solid component are separated in a shorter time. In particular, when a vortex type solid-liquid fractionation device in which a cylindrical screen is arranged in the second solid-liquid means, flocs formed by adding a flocculant are difficult to collapse, and removal of harmful substances, etc. Increases efficiency.
[0014]
On the other hand, in the vortex type solid-liquid separator, the solid content is concentrated according to time to some extent. If the solid content is intermittently extracted from the water tank, the concentrated solid content can be taken out. In the present invention, the amount of withdrawal and the frequency of withdrawal are determined according to the measured values of the turbidity and flow rate of the water to be treated which is treated by the first solid-liquid separation means and flows into the flocculant addition means. Since it is determined, the solid content can be extracted at the time of the most concentrated time or at a time close thereto.
[0015]
As a result, even if the pollution level and flow rate of the polluted water changes, the treatment corresponding to the change is surely performed, and it is possible to reliably reduce harmful substances in the polluted water such as overflow water. It becomes.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Next, the method for treating overflow water will be described in detail below as an embodiment of the present invention.
In the present embodiment, as shown in FIG. 1, the overflow water is processed through the first solid-liquid separation means 1, the flocculant addition means 2, and the second solid-liquid separation means 3 in this order. Then, at least the second solid-liquid separation means 2 feeds the water to be treated into the cylindrical water tank along the tangential direction of the water tank, generates a vortex in the water tank, and removes the solid content of the water tank. The liquid is separated from the clarified portion and the solid content by collecting at the center lower part, and the clarified portion is sent out of the water tank, and the collected solid content is drawn out of the water tank by opening and closing the extraction valve provided at the lower part of the water tank and pump means. A vortex-type solid-liquid separator (also called swirl) is used. Of course, a vortex solid-liquid separation device may be used as the first solid-liquid separation means.
[0017]
Hereinafter, the first solid-liquid separation means, the flocculant addition means, and the second solid-liquid separation means will be described in detail.
(First solid-liquid separation means)
The first solid-liquid separation means 1 separates and removes impurities such as gravel such as plastic pieces and tree branch pieces contained in the overflow water. A method for guiding the overflow water to the first solid-liquid separation means 1 is not particularly limited. It may be guided using a conventionally known pump means, or may be guided by natural flow, for example, by providing an inclination in piping or pipes of processing equipment.
[0018]
The first solid-liquid separation means 1 is not particularly limited as long as it is a solid-liquid separation apparatus capable of removing impurities, but overflow water is generated about 60 times a year, and the weather is irregular. Therefore, a solid-liquid separation device with a low maintenance cost such as a maintenance cost is preferable. Examples of such a suitable separation device include a vortex solid-liquid separation device and a bar screen. The vortex type solid-liquid separator is more desirable than the bar screen because it can remove small impurities such as gravel and earth and sand to some extent.
[0019]
When a vortex type solid-liquid separator is used as the first solid-liquid separator 1, it is preferable to efficiently extract the collected solid content outside the cylindrical water tank. In the vortex type solid-liquid separator, the extraction of the solid content is performed by opening and closing the extraction valve provided in the lower part of the water tank or by operating a suction pump connected thereto. Further, in the vortex type solid-liquid separator, the solid matter is collected at the lower center of the water to be treated in the cylindrical water tank for a certain period of time according to the swirling time. As for the solid content, if the turbidity is high, the solid content is collected quickly, and even if the flow rate is large, the solid content is collected quickly. For this reason, it can grasp | ascertain from the turbidity and flow volume of the overflow water which flows into a solid-liquid separation means. Therefore, a conventionally known turbidity meter and flow meter are provided in the middle of the pipe culvert and pipe for guiding the overflow water to the first solid-liquid separation means 1, and the turbidity and flow rate are measured. If the frequency (the number of times of opening / closing of the on-off valve per unit time) and the amount of drawing once (the amount of opening of the on-off valve per time and the amount of solid content determined by the suction capacity of the suction pump) are controlled, it will be efficient Solids can be extracted. Specifically, as shown in FIG. 3, a multiplication value of the measured value of turbidity and the measured value of flow rate is calculated as a judgment value, and the operation of the on-off valve and the suction pump is controlled according to this judgment value. To do. For example, when the opening time of one extraction valve is set to X seconds and the determination value is 8000 or more, the control opens the extraction valve three times in 30 minutes and operates the suction pump. If so, open the extraction valve three times in 40 minutes and operate the suction pump. If it is 4000-6000, open the extraction valve three times in 54 minutes and operate the suction pump. If it is 2000-4000, If the drawing valve is opened twice in 60 minutes and the suction pump is operated, and less than 2000, the drawing valve is opened twice in 180 minutes and the suction pump is operated. Of course, the above numerical values are merely examples, and actual specific judgment values and the corresponding drawing frequency are appropriately changed according to the suction capacity of the suction pump used, the throughput of the vortex solid-liquid separator, and the like. In this way, if the control of the step-by-step drawing frequency according to the multiplication value (judgment value) is performed, even if the amount of solids and the flow rate of the overflow water flowing into the first solid-liquid separation means change, the change depends on the change. Optimum removal of impurities is made.
[0020]
(About coagulant addition means)
As described above, in the first solid-liquid separation means 1, if the contaminants in the overflow water are removed, then the flocculant addition means 2 leads to the addition of the flocculant and the pollutants in the overflow water and the second Flocks are formed by agglomerating fine solids that could not be removed by the solid-liquid separation means 1. The method for introducing the water to be treated to the flocculant adding means 2 is not particularly limited. What is necessary is just to guide | lead using a conventionally well-known pump means.
[0021]
As the flocculant addition means 2, a flocculant addition facility composed of a medicine pump 20 and a flocculent tank 21 can be used. Other conventional coagulant addition equipment or addition equipment such as a flocculant addition equipment using a rapid mixing water tank instead of the coagulation tank, a flocculant addition equipment provided with a flock formation tank in addition to a coagulation tank, or a static mixer are used. be able to.
[0022]
The type of the flocculant can be appropriately selected from conventionally known flocculants such as inorganic flocculants and polymer flocculants. Specific examples include PAC, sulfate band, polyiron, ferrous sulfate, ferric chloride, cationic polymer, amphoteric polymer, and anionic polymer. These may be used alone or in combination. Considering that the second solid-liquid separation means 2 is an eddy current solid-liquid separation device, PAC and cationic polymer are particularly suitable.
[0023]
The amount of flocculant added is the turbidity of the treated water treated by the first solid-liquid separation means, the turbidity of COD, BOD, TOC, TOD, etc., and the flow rate of the treated water flowing into the flocculant adding means. Determine from. As shown in FIG. 1, the flow rate and the turbidity are measured in the middle of pipes and pipes for introducing the water to be treated to the coagulant adding means 2, a conventionally known flow meter 4, a turbidimeter, a COD meter, a BOD meter, What is necessary is just to provide and measure the turbidity meter 5 such as a TOC meter, a TOD meter or the like. The degree of contamination does not have to be measured for all measurement items listed here, but may be measured from at least one of the measurement items listed above. Moreover, a measurement technique and a measurement apparatus can be based on a conventionally known technique.
[0024]
The addition amount control of the flocculant is, for example, a control to change the discharge amount of the drug injection pump if the flocculant addition means is configured to add the flocculant to the aggregation tank using the drug injection pump. This can be done by providing a valve in the middle of the feed pipe for sending the coagulant from the chemical injection pump to the coagulation tank and controlling the degree of opening of the valve. In the control, for example, a measuring device is provided in the middle of the pipe rod that guides the treated water from which the contaminants have been removed by the first solid-liquid separation means to the coagulation tank, and the multiplication value of the flow rate flowing in and the pollution degree is calculated. The calculated value is a calculated value of the measured value of the flow rate and the measured value of the turbidity, a calculated value of the measured value of the flow rate and the COD value, a measured value of the flow rate, the measured value of the turbidity and the measured value of the COD value, etc. It can be selected appropriately. And the control which changes the discharge amount of a chemical injection pump etc. continuously or in steps according to this calculated value is performed. The relationship between the actual specific judgment value and the discharge amount of the chemical injection pump corresponding thereto is appropriately changed according to the capacity of the coagulation tank used. If the additive amount control according to the multiplication value (judgment value) is performed in this way, even if the solids amount or flow rate of the overflow water changes, the optimum flocculant addition amount corresponding to the change can be obtained. This eliminates the situation where an excessive flocculant is added, or because the amount of flocculant added is small, the pollutant is not agglomerated.
[0025]
(About the second solid-liquid separation means)
If the flocculant is added by the flocculant adding means 2 to aggregate the pollutants and flocs are formed, then the flocculant aggregated in the flocculant adding means 2 is led to the second solid-liquid separation means 3. The solid matter remaining in the water to be treated is separated and removed. In the present invention, the second solid-liquid separation means 2 uses a vortex solid-liquid separation device. The vortex type solid-liquid separation device feeds water to be treated into the cylindrical water tank along the tangential direction of the water tank, generates a vortex flow in the water tank, and collects solids at the lower center of the water tank. The collected solid content can be extracted out of the water tank and separated into solid and liquid. More preferably, in the vortex type solid-liquid separator, as shown in FIGS. 3 and 4, a cylindrical screen 31 is disposed vertically in a cylindrical water tank 30, and the cylindrical screen 31 is covered with the cylindrical screen 31. The treated water is of a type that feeds along the tangential direction of the screen 31. The vortex type solid-liquid separation device shown in FIGS. 3 and 4 generates a vortex in the screen 31 and sends the clarified portion out of the tank through the screen 31 while collecting the solid content in the central lower part 30D of the water tank. The collected solid content is drawn out of the water tank. Therefore, there is an advantage that the floc formed by the addition of the flocculant is difficult to disintegrate and the time until the solid content is collected is fast. If such a vortex type solid-liquid separation device having the cylindrical screen 31 is used, the screen of the cylindrical screen has a predetermined angle in the inner and outer directions of the screen 31 as shown in FIG. The cylindrical inner opening Mi of the eye is directed in a direction that does not oppose the flow direction of the inner Si vortex Fi of the screen 31, and the cylindrical outer opening Mo is the flow direction of the inner Si vortex Fi of the screen 31. It is desirable that the screen 31 is oriented so as to generate a flow opposite to the above. Furthermore, as shown in the drawing, it is desirable that the surface A facing the vortex flow Fi of the screen 31 is formed as an arc surface. The screen 31 has a vortex flow Fi generated in the inner Si and a flow Fo opposite in the flow direction on the outer side So of the screen 31, and can effectively send clear water to the outside of the tank. Is difficult to adhere to the screen, and is also excellent in preventing flocs from collapsing.
[0026]
Regarding the extraction of the solid content, it is desirable to perform intermittently by opening and closing the extraction valve provided in the lower part of the water tank or by operating the suction pump connected thereto. As described in the column, it is desirable to do this also in the second solid-liquid separation means. What is characteristic about the extraction of the solid content in the second solid-liquid separation means is that, in the second solid-liquid separation means, the extraction frequency and the like are measured values of turbidity and flow rate of the overflow water flowing into the solid-liquid separation means. It is preferable to determine not by the flow rate but by the pollution level and flow rate flowing into the coagulant adding means in the preceding stage. This is because, after passing through the flocculant addition means, it is difficult to accurately measure turbidity because it is a mixture of clarified and floc. This is because the separation device cannot separate and remove, and even if it is measured, the process according to the measured value cannot be performed. On the other hand, the amount of flocs that are generally solidified in proportion to the amount of flocculant added can be grasped in accordance with the flow rate and pollution level of the water to be treated flowing into the flocculant addition means, and the drawing amount based on this It is possible to pull out more effectively if it is determined. In addition, if a measuring device or the like that is used to determine the amount of flocculant added is used, there is no need to provide a separate measuring instrument to determine the drawing frequency in the second solid-liquid separation means, thereby reducing costs. Also become. Further, since it is possible to grasp such flocking, control based on TOC and COD as well as turbidity can be performed.
[0027]
A specific example of the control is shown in FIG. 6 together with the control of the chemical injection pump of the flocculant means. First, as described in the flocculant addition means, a multiplication value of the flow rate and the turbidity is calculated. Then, the multiplication value is used as a judgment value, and the discharge amount of the chemical injection pump and the opening / closing of the extraction valve are controlled according to the judgment value. For example, when the opening time of one extraction valve is set to X seconds and the determination value is 8000 or more, the discharge amount of the chemical injection pump is set to 100% and the extraction valve is set to 30 minutes. Open the suction pump three times and operate the suction pump. If the above judgment value is 6000 to 8000, the discharge amount of the medicinal pump is set to 80% and the extraction valve is opened three times in 40 minutes and the suction pump is operated. If the judgment value is 4000 to 6000, the discharge amount of the chemical injection pump is set to 60%, the extraction valve is opened three times in 54 minutes and the suction pump is operated. If the judgment value is 2000 to 4000, When the discharge amount of the medicinal pump is 40%, the extraction valve is opened twice in 60 minutes and the suction pump is operated. If the above judgment value is less than 2000, the discharge amount of the medicinal pump is 20%. As well as, to operate the suction pump is opened twice pull valve 180 minutes. The numerical value is an example, and the actual specific judgment value and the number of extractions corresponding thereto are appropriately changed according to the suction capacity of the suction pump used, the throughput of the vortex-type solid-liquid separator, and the like. Thus, if the discharge amount of the chemical injection pump and the control of the extraction valve are controlled according to the multiplication value (judgment value), the change of the pollutant in the overflow water, and further the removal of contaminants after the first solid-liquid separation means Even if there is a change in the rate or the like, the second solid-liquid separation means suitably separates and removes the contaminants of the water to be treated without being affected by the influence.
[0028]
(Other)
The clarified water separated through each of the above treatments is discharged to the outside of the conventional treatment system, or sent to other treatment facilities without being discharged as necessary, and then subjected to other treatments. To be released. On the other hand, the collected solid content is treated according to conventional techniques such as dewatering as sludge.
[0029]
In addition, although the said embodiment described the example of the treatment of the overflow water from the combined sewer at the time of raining, the treatment object in the treatment method of the present invention is not limited to the overflow water alone, the diversion type Covers all polluted water that contains pollutants, such as sewage, rainwater, river water, industrial wastewater, etc., sent from the sewer to the sewage treatment facility and whose pollution level changes with time and conditions.
[0030]
【The invention's effect】
As described above in detail, according to the present invention, there is provided a treatment method capable of treating, in a short time and effectively, polluted water whose flow rate and pollution degree change every moment, such as overflow water.
[Brief description of the drawings]
FIG. 1 is a flowchart showing an outline of a method for treating overflow water according to the present embodiment.
FIG. 2 is a diagram showing an example of the relationship between the turbidity and flow rate of overflow water and the extraction frequency in the first vortex type solid-liquid separator.
FIG. 3 is a perspective view showing an outline of a vortex solid-liquid separator.
FIG. 4 is a cross-sectional view showing an outline of the vortex type solid-liquid separator.
FIG. 5 is a partially enlarged sectional view of the screen.
FIG. 6 is a diagram showing an example of the relationship between the turbidity and flow rate of overflow water and the extraction frequency in the second vortex solid-liquid separator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... 1st solid-liquid separation means, 2 ... Coagulant addition means, 3 ... 2nd solid-liquid separation means, 4 ... Flowmeter, 5 ... Pollution meter, 20 ... Coagulant addition apparatus, 21 ... Coagulation tank, 30 ... Cylindrical water tank, 31 ... Cylindrical screen, Fi ... Eddy current inside cylindrical screen, Fo ... Eddy current outside cylindrical screen, Si ... Inside cylindrical screen, So ... Outside cylindrical screen, Mo ... Outside cylindrical Opening, Mi ... Cylindrical inner opening.

Claims (2)

The first solid-liquid separation means for removing contaminants from the contaminated water, and the addition of a flocculant for aggregating the pollutants in the treated water by adding a flocculant to the water to be treated treated by the first solid-liquid separation means Means for removing polluted water in the polluted water through the second solid-liquid separating means for separating the treated water treated by the flocculant adding means into a clarified portion and a solid content in this order. Because
At least the second solid-liquid separation means feeds the water to be treated into a cylindrical water tank along the tangential direction of the water tank, generates a vortex in the water tank, and causes a solid content to enter the lower center of the water tank. A vortex-type solid-liquid separator that collects and collects the collected solids outside the water tank and separates them into solid and liquid, and
Measure the turbidity and flow rate of the water to be treated treated by the first solid-liquid separation means, and determine the addition amount of the flocculant in the flocculant addition means according to this measured value,
Further, the solid content is intermittently withdrawn from the cylindrical water tank, and the amount of withdrawal and the frequency of withdrawal are determined by the first solid-liquid separation means and the water to be treated flowing into the coagulant adding means. A method for treating polluted water that is determined according to the measured value of the degree and flow rate. In the vortex-type solid-liquid separator, a cylindrical screen is disposed vertically in a cylindrical water tank, and water to be treated is fed into the cylindrical screen along the tangential direction of the screen. 2. The polluted water according to claim 1, wherein the solid content is collected at the center lower part of the water tank while generating a vortex flow through the screen and sending out the clear content to the outside of the water tank, and the collected solid content is drawn out of the water tank. Processing method.

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