Wastewater neutralization equipment and wastewater neutralization method utilizing an oil trap

Abstract

To provide a wastewater neutralization treatment facility and a wastewater neutralization treatment method using an oil trap which can stably perform neutralization control even when wastewater is flowing and includes various foreign matter, rainwater, etc.SOLUTION: While an oil content is caused to rise to a surface for separation from wastewater which flows in an oil trap tank 12, a required time which the wastewater takes to reach an outflow side pH meter 37 from a supply position of a neutralizer is used to determine a relation between a pH value of an inflow side pH meter 35, a supply amount of the neutralizer, and a pH value of the outflow side pH meter 37 at that point of time when the neutralizer is supplied to the wastewater according to each pH value of the inflow side pH meter 35 and the outflow side pH meter 37. The pH value of the inflow side pH meter 35 of the wastewater flowing in the oil trap tank 12 and the pH value of the outflow side pH meter 37 of the wastewater with the neutralizer supplied thereto in a supply amount obtained from the relation, when getting outside a preset pH range, correction of multiplication of the supply amount of the neutralizer according to the relation by a correction coefficient α is performed so as to get inside the pH range and then the neutralizer in a supply amount obtained by the correction is supplied to the wastewater in the oil trap tank 12.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to, for example, wastewater neutralization treatment equipment and a wastewater neutralization treatment method that utilize an oil trap that floats oil from wastewater discharged from facilities such as factories and separates water and oil.

Background Art

[0002] The most common method for neutralizing factory wastewater is batch treatment. Specifically, a dedicated neutralization treatment tank for wastewater is provided, and a neutralizing agent (neutralizing chemical) is added to the wastewater in this neutralization treatment tank and stirred, and then discharged after reaching a predetermined pH. However, such batch treatment requires a large-scale neutralization treatment tank and a large capital investment in equipment. On the other hand, factories are equipped with oil traps to recover oil before discharging wastewater, and there is a wastewater treatment system that utilizes this oil trap to continuously adjust the pH without blocking the factory wastewater and then discharge it.

[0003] As a wastewater treatment system using the above-described oil trap, for example, Patent Document 1 discloses a technique of utilizing an existing oil trap and injecting a neutralizing agent into continuously flowing wastewater. As a result, neutralization treatment can be carried out without a large capital investment in equipment, which is very effective in terms of efficiency and economy. Specifically, in Patent Document 1, the pH value on the inflow side (inflow side pH value) of the oil trap tank and the flow rate of the wastewater flowing through the oil trap tank are measured, and the necessary neutralizing agent is supplied to complete neutralization before the wastewater flows out of the oil trap tank. Also, the pH value of the wastewater (outflow side pH value) as a result of supplying the neutralizing agent is used to correct the supply amount of the above-described neutralizing agent.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] However, the wastewater flowing into the oil trap tank contains various foreign matter and rainwater, and the composition of the sample wastewater used to determine the calibration curve for calculating the amount of neutralizing agent to supply differs from that of the actual wastewater flowing through the tank, causing the required amount of neutralizing agent to fluctuate. Therefore, even if the pH value on the inlet side of the oil trap tank and the flow rate of the wastewater are measured and the amount of neutralizing agent required to neutralize the wastewater is supplied, it may not be possible to adjust the pH to the target value. It might also be thought that the pH value after supplying the neutralizing agent could be used for correction, but as mentioned above, accurate tracking may not be possible with flowing wastewater, and therefore, it may not be possible to accurately correct the neutralization of wastewater containing various foreign matter and rainwater.

[0006] This invention has been made in view of the above circumstances, and aims to provide a wastewater neutralization treatment facility and wastewater neutralization treatment method that utilize an oil trap, which can stably perform neutralization control even with flowing wastewater, and even with wastewater containing various foreign matter, rainwater, etc. [Means for solving the problem]

[0007] A wastewater neutralization treatment facility utilizing an oil trap according to the first invention in line with the aforementioned purpose comprises an oil trap tank through which wastewater flows in and out continuously, and an oil trap capable of flotation and separation of oil from wastewater flowing in the oil trap tank from the inlet side to the outlet side, The oil trap tank comprises an inlet pH meter for measuring the pH value of the inlet side of the wastewater and an outlet pH meter for measuring the pH value of the outlet side, A control means for determining the amount of neutralizing agent to be supplied to the wastewater flowing through the oil trap tank, using the pH values ​​of the inlet-side pH meter and the outlet-side pH meter, In a wastewater neutralization treatment facility utilizing an oil trap, the facility includes a neutralizing agent supply means that supplies the amount of the neutralizing agent determined by the control means to the wastewater, The control means is Using the time required for the wastewater from the oil trap tank to reach the outflow-side pH meter from the neutralizing agent supply position, the relationship between the pH value of the inflow-side pH meter, the amount of neutralizing agent supplied, and the pH value of the outflow-side pH meter of the wastewater to which the supplied amount of neutralizing agent has been supplied is determined in advance. When the pH value of the wastewater flowing through the oil trap tank, measured by the inlet side pH meter, and the amount of the neutralizing agent supplied, are found to be outside a preset pH range, a correction is performed by multiplying the amount of the neutralizing agent supplied by the relationship by a correction coefficient α so that the pH falls within that range.

[0008] In the wastewater neutralization treatment equipment utilizing an oil trap according to the first invention, the correction coefficient α can be determined by the following formula. α = {(X1 - R) / (X1 - X2)} Here, X1 is the pH value of the inlet pH meter of the wastewater flowing through the oil trap tank, X2 is the pH value of the outlet pH meter of the wastewater flowing through the oil trap tank to which the neutralizing agent has been supplied, and R is a predetermined value within a set pH range.

[0009] In the wastewater neutralization treatment equipment utilizing an oil trap according to the first invention, when the supply amount of the neutralizing agent is corrected multiple times, it is preferable to multiply the correction coefficient α from the previous correction by a new correction coefficient to obtain the correction coefficient α for the current correction.

[0010] In the wastewater neutralization treatment equipment utilizing an oil trap according to the first invention, a limit value β is set in advance in the control means, and if the correction coefficient α is less than or equal to the limit value β, the correction coefficient α is used as is, and if the correction coefficient α exceeds the limit value β, the limit value β is set as the correction coefficient α.

[0011] A wastewater neutralization treatment method utilizing an oil trap according to the second invention in line with the above objective uses an oil trap equipped with an oil trap tank in which wastewater flows in and out continuously, and separates oil from the wastewater flowing in the oil trap tank from the inlet side to the outlet side, and when supplying a neutralizing agent to the wastewater according to the pH values ​​of the inlet side pH meter and the outlet side pH meter provided on the inlet side and outlet side of the oil trap tank, Using the time required for the wastewater from the oil trap tank to reach the outflow-side pH meter from the neutralizing agent supply position, the relationship between the pH value of the inflow-side pH meter, the amount of neutralizing agent supplied, and the pH value of the outflow-side pH meter of the wastewater to which the supplied amount of neutralizing agent has been supplied is determined in advance. Conditional on the fact that the pH value of the outflow side pH meter of the wastewater flowing through the oil trap tank, after the supply amount of the neutralizing agent obtained from the relationship between the pH value of the inflow side pH meter of the wastewater flowing through the oil trap tank and the supply amount of the neutralizing agent, falls outside a preset pH range, a correction is made by multiplying the supply amount of the neutralizing agent in the relationship by a correction coefficient α so that it falls within the pH range, and then the corrected supply amount of the neutralizing agent is supplied to the wastewater of the oil trap tank.

[0012] In the wastewater neutralization treatment method utilizing an oil trap according to the second invention, the correction coefficient α can be determined by the following formula. α = {(X1 - R) / (X1 - X2)} Here, X1 is the pH value of the inlet pH meter of the wastewater flowing through the oil trap tank, X2 is the pH value of the outlet pH meter of the wastewater flowing through the oil trap tank to which the neutralizing agent has been supplied, and R is a predetermined value within a set pH range.

[0013] In the wastewater neutralization treatment method utilizing an oil trap according to the second invention, when the supply amount of the neutralizing agent is corrected multiple times, it is preferable to multiply the correction coefficient α from the previous correction by a new correction coefficient to obtain the correction coefficient α for the current correction.

[0014] In the wastewater neutralization treatment method using the oil trap according to the second invention, when the correction coefficient α is less than or equal to a preset limit value β, the correction coefficient α is used as it is, and when the correction coefficient α exceeds the limit value β, it is preferable to set the limit value β as the correction coefficient α.

Advantages of the Invention

[0015] The wastewater neutralization treatment equipment and method using the oil trap according to the present invention use the required time from when the wastewater in the oil trap tank flows out from the supply position of the neutralizing agent to reach the outflow side pH meter to obtain in advance the relationship among the pH value of the inflow side pH meter, the supply amount of the neutralizing agent, and the pH value of the outflow side pH meter of the wastewater to which the supply amount of this neutralizing agent is supplied. Therefore, it is possible to accurately grasp the degree of change in the pH value of the outflow side pH meter due to the supply of the neutralizing agent and accurately track the flow of wastewater in the oil trap tank. When the pH value of the outflow side pH meter of the wastewater flowing through the oil trap tank to which the neutralizing agent is supplied deviates from the preset pH range, correction is performed by multiplying the supply amount of the neutralizing agent in the above relationship by the correction coefficient α so that it falls within this pH range. Therefore, based on the above relationship, correction corresponding to wastewater with fluctuating properties can be performed. Therefore, even for flowing wastewater and wastewater whose properties fluctuate due to various foreign substances, rainwater, etc., neutralization control can be stably implemented.

Brief Description of the Drawings

[0016] [Figure 1] It is an explanatory diagram of wastewater neutralization treatment equipment using an oil trap according to an embodiment of the present invention. ]> [Figure 2] It is an explanatory diagram of a wastewater neutralization treatment method using an oil trap according to an embodiment of the present invention. [Figure 3] It is an explanatory diagram of a wastewater neutralization treatment method using the same oil trap. [Figure 4] It is an explanatory diagram of a wastewater neutralization treatment method using an oil trap according to an embodiment.

Modes for Carrying Out the Invention

[0017] Next, while referring to the attached drawings, embodiments embodying the present invention will be described to facilitate understanding of the present invention. As shown in FIG. 1, a drainage neutralization treatment facility (hereinafter, also simply referred to as a drainage neutralization treatment facility) 10 utilizing an oil trap according to an embodiment of the present invention has, for example, an oil trap 11 capable of separating oil components from drainage discharged from a factory, and this oil trap 11 is provided with a pH adjustment function. This will be described in detail below.

[0018] The oil trap 11 includes an oil trap tank 12. The oil trap tank 12 is a tank in which the inflow and outflow of drainage are continuously performed, and the oil trap 11 separates oil components from the drainage flowing from the inflow side (upstream side) to the outflow side (downstream side) of the oil trap tank 12 (in FIG. 1, flowing from the left side to the right side). An auxiliary tank 13 is attached to the outflow side of the oil trap tank 12, and the drainage (treated water) after oil separation flowing out of the oil trap tank 12 is discharged into the sea via the auxiliary tank 13. The length (distance) in the flow direction of the drainage in this oil trap tank 12 is, for example, about several meters to several tens of meters.

[0019] A plurality of partition plates 14 and 15 are provided at a position in the middle of the flow direction of the drainage in the oil trap tank 12. One of these partition plates 14 is arranged on the liquid surface (bath surface) side of the drainage in the oil trap tank 12, and the other partition plate 15 is arranged on the bottom side of the oil trap tank 12. The partition plate 14 and the partition plate 15 are alternately arranged with a gap in the flow direction of the oil trap tank 12 (so that the flow becomes zigzag). The upper end of the partition plate 14 on the liquid surface side protrudes from the liquid surface and is configured to be able to block the floating oil. The oil on the liquid surface blocked by the partition plate 14 is recovered by a suction pump (not shown).

[0020] At the inflow side of the oil trap tank 12 (upstream of the partition plates 14 and 15), a water intake and a water discharge of a drainage circulation path 16 are provided. The drainage circulation channel 16 is composed of piping, and a suction pump 17 installed at the intake port on the intake side end (upstream end) of the drainage circulation channel 16 draws a portion of the wastewater from the oil trap tank 12 into the drainage circulation channel 16. This drawn-in wastewater is then returned to the oil trap tank 12 through the discharge port on the drainage side end (downstream end) of the drainage circulation channel 16. The suction pump 17 is located upstream of the discharge port. Furthermore, the drainage circulation path 16 is sequentially equipped with an on-off valve 18, a check valve 19, a circulation flow meter 20, and an on-off valve 21, from the water intake to the discharge port.

[0021] The suction pump 17 is a submersible pump placed in the drainage of the oil trap tank 12. Although there may be only one suction pump 17, it is preferable to have multiple suction pumps 17 spaced apart in the width direction of the oil trap tank 12 (in the direction perpendicular to the direction of drainage flow). The depth of the water intake port of this water intake pump 17 is set below the upper layer (oil suspension area) of the wastewater in the oil trap tank 12, and above the bottom of the oil trap tank 12. As a result, the water intake pump 17 can take in the wastewater from the oil trap tank 12 into the drainage circulation path 16 without sucking up the oil that has risen to the surface in the oil trap tank 12 (avoiding the sucking up of oil contained in the wastewater), and while suppressing the sucking up of the sludge accumulated at the bottom of the oil trap tank 12. Furthermore, although the outlet of the drainage circulation path 16 is set above the liquid level of the drainage in the oil trap tank 12, it may also be submerged in the drainage in the oil trap tank 12. While there may be only one outlet, it is preferable to provide multiple outlets spaced apart in the width direction of the oil trap tank 12.

[0022] The drainage circulation path 16 is provided with supply ports for two neutralizing agent supply means 22 and 23. One neutralizing agent supply means 22 supplies liquid sulfuric acid (an example of a neutralizing agent) to the alkaline wastewater in the wastewater circulation path 16, while the other neutralizing agent supply means 23 supplies liquid caustic soda (an example of a neutralizing agent) to the acidic wastewater in the wastewater circulation path 16. Thus, the only difference between the neutralizing agent supply means 22 and the neutralizing agent supply means 23 is the type of neutralizing agent (chemical solution) used, and their configurations are substantially the same. Therefore, the reference numerals for the components of the neutralizing agent supply means 23 are simply the same as those for the components of the neutralizing agent supply means 22, with the numeral "a" added, and the explanation is omitted.

[0023] The neutralizing agent supply means 22 includes a tank 24 capable of storing sulfuric acid and a chemical input passage 25 that connects the tank 24 to the drainage circulation passage 16. The sulfuric acid stored in tank 24 is adjusted to a concentration of approximately 5-15%, and the caustic soda stored in tank 24a is also adjusted to a concentration of approximately 5-15%, but these concentrations can be changed as needed. Reference numeral 26 denotes a water level gauge installed in tank 24. The chemical supply channel 25 is composed of piping and is connected to the drainage circulation channel 16 between a check valve 19 and a circulation flow meter 20 installed in the drainage circulation channel 16.

[0024] In the chemical input passage 25, a transfer pump 27, an input flow meter 28, a back pressure valve 29, an electric valve 30, and a check valve 31 are sequentially installed from the tank 24 side to the drainage circulation passage 16 side. Reference numeral 32 denotes a maintenance passage for returning sulfuric acid to the tank 24 and circulating it to prevent solidification of the sulfuric acid, and reference numeral 33 denotes an electric valve installed in this passage 32. The chemical supply channel 25 is constantly filled with sulfuric acid. This allows for the rapid supply of sulfuric acid to the wastewater taken into the wastewater circulation channel 16, even if the pH value of the wastewater changes rapidly. However, the sulfuric acid does not need to be kept in the chemical supply channel 25 if necessary (for example, depending on the length of the chemical supply channel).

[0025] The drainage circulation path 16 is equipped with a static mixer (an example of a mixing means) 34 that mixes the wastewater in the drainage circulation path 16 with sulfuric acid (or caustic soda, hereinafter the same) supplied to the wastewater. The static mixer 34 is a conventionally known stationary mixer without a drive unit, and is installed between the circulation flow meter 20 and the on-off valve 21 of the drain circulation passage 16 (downstream from the sulfuric acid supply port of the chemical input passage 25). Furthermore, if the wastewater in the drainage circulation path 16 can be mixed with sulfuric acid, a mixer other than the static mixer described above, such as a mixer equipped with a drive unit, can also be used.

[0026] With the above configuration, sulfuric acid can be supplied to and mixed with the wastewater taken into the drainage circulation path 16. However, the amount of wastewater taken into the drainage circulation path 16 is preferably 3 to 10% (preferably with a lower limit of 5% and an upper limit of 8%) of the minimum amount of wastewater flowing into the oil trap tank 12. Here, if the amount of wastewater taken in by the wastewater circulation path 16 is less than 3% of the minimum inflow, the amount of wastewater taken in will be small, and when the wastewater mixed with sulfuric acid is returned to the oil trap tank 12, the diffusion efficiency of sulfuric acid into the wastewater in the oil trap tank 12 tends to decrease. On the other hand, if the amount of wastewater taken in by the wastewater circulation path 16 is more than 10% of the minimum inflow, the amount of wastewater taken in will be large, and when the wastewater mixed with sulfuric acid is returned to the oil trap tank 12, the flow of wastewater in the oil trap tank 12 tends to be disturbed. Normally, a constant flow rate is taken from the water supply, within the range of 3-10% of the minimum inflow.

[0027] In the oil trap 11, as wastewater flows from the inlet side to the outlet side of the oil trap tank 12, it is necessary to ensure a laminar flow region of the wastewater required for oil-water separation in order to separate the oil from the wastewater by flotation. For this reason, as described above, by providing an intake and outlet for the wastewater circulation channel 16 for adjusting the pH of the wastewater on the inlet side of the oil trap tank 12, even if the wastewater mixed with the neutralizing agent flows back into the oil trap tank 12, the region (distance) required for laminar flow of the wastewater within the oil trap tank 12 can be secured, and the oil-water separation function of the oil trap tank 12 can be maintained. Furthermore, by mixing the wastewater taken into the wastewater circulation channel 16 with the neutralizing agent and returning this mixture to the oil trap tank 12, the neutralizing agent diffuses into the wastewater in two stages. Therefore, even with an extremely small amount of required chemical solution, the neutralizing agent can be diffused and the neutralization reaction of the wastewater can proceed without directly stirring the contents of the oil trap tank 12. Therefore, the separation of oil from wastewater and the adjustment of the wastewater's pH can be carried out continuously and economically without damming the wastewater (without performing batch processing).

[0028] The oil trap tank 12 is equipped with three pH meters: an inlet pH meter 35, a monitoring pH meter 36, and an outlet pH meter 37. The inlet-side pH meter 35 is installed on the inlet side of the oil trap tank 12 (upstream of the suction pump 17 located at the water intake of the drainage circulation path 16) and is capable of measuring the pH value of the wastewater flowing into the oil trap tank 12. The monitoring pH meter 36 is installed downstream of the partition plates 14 and 15 and is used to monitor (as a reference value) the pH value of the wastewater flowing through the oil trap tank 12. The outflow-side pH meter 37 is installed on the outflow side of the oil trap tank 12 (downstream from the pH meter 36) and is capable of measuring (monitoring) the pH value of the wastewater discharged from the oil trap tank 12.

[0029] As described above, the inlet pH meter 35, monitoring pH meter 36, and outlet pH meter 37 were sequentially installed at three locations in the oil trap tank 12. However, it is sufficient for them to be installed at least on the inlet and outlet (downstream) sides of the oil trap tank 12, and they may be installed at four or more locations as needed. The number of pH meters installed at each location may be one or two or more. A weir-type flow meter 38 capable of measuring the flow rate of wastewater flowing through the oil trap tank 12 (outflow end of the oil trap tank 12) is installed at the outlet location of the wastewater from the oil trap tank 12 (outflow end of the oil trap tank 12). Of course, it is also possible to use a flow meter other than a weir-type flow meter, as long as it can measure the flow rate of the wastewater.

[0030] Each of the three inlet-side pH meters 35, monitoring pH meter 36, and outlet-side pH meter 37 and weir-type flow meter 38 described above is equipped with indicators 39 to 42, and the values ​​of each of these indicators 39 to 42 (the pH value and flow rate of the wastewater) are transmitted to a calculation processing means (an example of a control means) 43. The flow rates measured by the circulation flow meter 20 and the input flow meters 28 and 28a are also transmitted to this calculation processing means 43. The arithmetic processing means 43 is a computer that uses the transmitted data described above to perform the following processes according to a pre-set program, calculates the amount of sulfuric acid or caustic soda to be supplied to the drainage circulation path 16, and controls the operation of each transfer pump 27, 27a. The computer is a conventionally known one equipped with RAM, CPU, ROM, I / O, and a bus connecting these elements, but is not limited to this.

[0031] The calculation processing means 43 includes a chemical solution output determination SEQ unit, a reference magnification determination SEQ unit, and a chemical solution gain determination SEQ unit. The chemical solution output determination SEQ unit receives input from the wastewater flow rate measured by the weir-type flow meter 38 (flow rate on indicator 42) and the pH value measured by the inlet-side pH meter 35 of the oil trap tank 12 (pH value on indicator 39). Furthermore, the chemical output determination SEQ unit records reference data for determining the amount of sulfuric acid or caustic soda (i.e., neutralizing agent) to be supplied to neutralize the wastewater in the oil trap tank 12.

[0032] While standard data exists for sulfuric acid and caustic soda separately, their basic composition is the same, so they will be explained together as neutralizing agents below. This reference data was determined in advance by using the time required for the wastewater from the oil trap tank 12 to reach the outflow side pH meter 37 from the neutralizing agent supply location (i.e., the outlet of the wastewater circulation path 16) (the time required for neutralization to proceed), and determining the relationship between the pH value of the inflow side pH meter 35, the amount of neutralizing agent supplied, and the pH value of the outflow side pH meter 37 of the wastewater to which this amount of neutralizing agent has been supplied. Here, the time required for the neutralizing agent to reach the outflow pH meter 37 from the supply location can be calculated by determining the flow velocity of the wastewater from the flow rate of the wastewater measured by the weir-type flow meter 38 and the inner cross-sectional area of ​​the oil trap tank 12 in a direction perpendicular to the direction of wastewater flow.

[0033] Furthermore, the relationship between the pH value of the inlet pH meter 35, the amount of neutralizing agent supplied, and the pH value of the outlet pH meter 37 of the wastewater to which this amount of neutralizing agent has been supplied can be determined as follows. For the wastewater flowing through the oil trap tank 12 (typical (primarily flowing) wastewater), the pH value of the wastewater at the inlet side pH meter 35, the amount of neutralizing agent supplied to this wastewater (flow rate from the input flow meters 28 and 28a), and the pH value of the wastewater at the outlet side pH meter 37 where this amount of neutralizing agent was supplied are measured. Then, by plotting the pH value on the horizontal axis (X axis) and the amount of neutralizing agent supplied on the vertical axis (Y axis), the relationship shown in Figure 2, i.e., the reference calibration curve y (set input amount of neutralizing agent: a linear function in this case), is obtained. This calibration curve y includes the time required as a variable, but it is also possible to obtain calibration curve y for each time required.

[0034] The calibration curve y described above can also be obtained using the past operating records of the oil trap tank 12. Furthermore, the calibration curve y described above can also be obtained by pre-sampling the wastewater to be discharged into the oil trap tank 12 (without actually discharging wastewater into the oil trap tank 12). In this case, the pH value of the sampled wastewater (corresponding to the pH value of the inlet pH meter 35), the amount of neutralizing agent supplied to this wastewater, and the pH value of the wastewater after this amount of neutralizing agent has been supplied (corresponding to the pH value of the outlet pH meter 37) are measured. Note that the pH value of the wastewater after the neutralizing agent has been supplied can also be calculated from the pH value of the sampled wastewater and the amount of neutralizing agent supplied. Furthermore, the supply quantity of the neutralizing agent may be represented by a large number of point data points instead of a calibration curve.

[0035] Using the calibration curve y described above, the amount of neutralizing agent required to neutralize the wastewater in the oil trap tank 12 is calculated from the flow rate (measured value) of the weir-type flow meter 38 and the pH value (measured value) of the inlet-side pH meter 35 of the wastewater actually flowing through the oil trap tank 12. Here, the neutralization of the wastewater must be carried out so that the pH value of the outflow side pH meter 37 satisfies the environmental standards for discharge into the sea and falls within a predetermined pH range. Specifically, the environmental standard is a pH value of, for example, 5 to 9, and the predetermined pH range is, for example, 6.6 to 7.8, but this value may be changed depending on the situation and is not particularly limited.

[0036] The amount of neutralizing agent supplied, calculated by this chemical solution output determination SEQ unit, is output to the standard magnification determination SEQ unit. The reference magnification determination SEQ unit receives the pH value (actual value) measured by the inlet-side pH meter 35 mentioned above, and the pH value (pH value of indicator 40) measured by the pH meter 36 located downstream of the partition plates 14 and 15, respectively. The chemical solution gain determination SEQ unit receives the pH value measured by the inlet pH meter 35 and the respective flow rates measured by the circulation flow meter 20 and the input flow meters 28 and 28a, respectively, and outputs these to the reference magnification determination SEQ unit.

[0037] Then, the operation of the transfer pumps 27 and 27a is controlled via the reference magnification determination SEQ unit so that the amount of neutralizing agent calculated by the chemical solution output determination SEQ unit can be supplied. Here, if the pH value (actual value) of the outflow side pH meter 37 of the wastewater flowing through the oil trap tank 12 to which the amount of neutralizing agent calculated by the chemical output determination SEQ unit has been supplied is within the aforementioned preset pH range, then the above-mentioned amount of neutralizing agent is supplied to the wastewater. However, wastewater contains various foreign substances and rainwater, and the composition of the sample wastewater used to determine the calibration curve y may differ from that of the wastewater that actually flows. For this reason, even if the amount of neutralizing agent calculated by the chemical output determination SEQ unit is supplied, the pH value of the outflow side pH meter 37 of the wastewater flowing through the oil trap tank 12 may fall outside the aforementioned preset pH range.

[0038] Therefore, in this case, a correction is made by multiplying the supply amount of neutralizing agent obtained from the calibration curve y by a correction coefficient α so that the pH value of the outflow side pH meter 37 falls within the above-mentioned pH range. Specifically, it is preferable to determine the correction coefficient α using equation (1). α = {(X1 - R) / (X1 - X2)} ... (1) Here, X1 is the pH value (actual value) of the inlet side pH meter 35 of the wastewater flowing through the oil trap tank 12, X2 is the pH value (actual value) of the outlet side pH meter 37 of the wastewater flowing through the oil trap tank 12 to which the supply amount of neutralizing agent obtained from the calibration curve y has been supplied, and R is a predetermined value within the aforementioned preset pH range. For this predetermined value within the pH range, for example, if the pH value of the wastewater exceeds the aforementioned 7.8, 7.8 (upper limit) is used, and if the pH value of the wastewater is less than the aforementioned 6.6, 6.6 (lower limit) is used, thereby preventing excessive use of the neutralizing agent (allowing for economical neutralization control), but any pH value within the pH range may also be used.

[0039] The contents of the above formula will be explained with reference to Figure 2. If the pH value of the inlet pH meter 35 is, for example, X1, then to make the pH value of the outlet pH meter 37 7.8 (ΔpH=X1-7.8), the amount of neutralizing agent supplied must be y1, according to the calibration curve y. However, for the reasons mentioned above, the pH value of the outlet pH meter 37 may become X2 (ΔpH'=X1-X2), and may not reach 7.8. This means that the amount of neutralizing agent supplied is insufficient. Therefore, it is necessary to increase the supply of neutralizing agent to the wastewater, that is, to increase the slope of calibration curve y starting from a pH value of 7.8, and correct it so that it becomes calibration curve Y (as a result, the calibration curve becomes one in which the line with slope {y1 / (X1-X2)} has been shifted in parallel). This correction amount is the correction coefficient α. Y = α × y ... (2)

[0040] Furthermore, when wastewater is continuously flowed into the oil trap tank 12, the amount of neutralizing agent supplied may be corrected multiple times. In this case, it is preferable to use the correction coefficient α obtained by multiplying the correction coefficient α from the previous correction by the new correction coefficient. Specifically, if the new correction coefficient is α', the relationship between the calibration curve y before correction and the calibration curve Y after correction will be as shown in equation (3) using equation (2) above. Y = α × α' × y ... (3) In equation (3), the current correction coefficient α is obtained by multiplying the current correction coefficient α by the new correction coefficient α'. This allows for a correction that takes into account the previous correction coefficient α. The new correction coefficient α' can be calculated using the same method as the calculation of the correction coefficient α described above (using equation (1)). The timing for performing this correction of the supply amount of the neutralizing agent multiple times is not limited to, for example, every set time interval (e.g., every few tens of seconds to several tens of minutes) or whenever the type of wastewater changes.

[0041] When performing this correction, if the value of the correction coefficient α is large, the supply of the neutralizing agent will be excessive, resulting in an overcompensation state. This will cause large fluctuations in the pH value of the outflow side pH meter 37, which may lead to a hunting phenomenon where the supply of the neutralizing agent fluctuates wildly. Therefore, to prevent this, the following control is performed. A limit value β is pre-set in the calculation processing means 43. Then, if the correction coefficient α is less than or equal to the limit value β, the correction coefficient α is used, and if the correction coefficient α is greater than the limit value β, the limit value β is used as the correction coefficient α. The value of this limit value β is preferably 1.05 or more, more preferably 1.1 or more, and preferably 1.5 or less, more preferably 1.3 or less (for example, around 1.2).

[0042] Here, we will explain the case where the calculated correction coefficient α (target magnification) exceeds the limit value β, referring to Figure 3. First, at the first correction period, the calculated correction coefficient α exceeded the limit value β, so the limit value (magnification limit) β was used as the correction coefficient α. This operation was repeated at the second and third correction periods until the correction coefficient α reached the target magnification. Therefore, no correction was performed at the fourth correction period. At this time, each time a correction was made, the correction coefficient α was obtained by multiplying it by the limit value β, as shown in equation (3) above. Note that the limit value β set for each correction period is the same, but it may be a different value. Also, although this explanation describes the case where the number of corrections to reach the target magnification is 3, it may be 2 or even 4 or more depending on the calculated correction coefficient α. In this way, by gradually increasing the supply of the neutralizing agent, fluctuations in the pH value of the outflow side pH meter 37 can be reduced, thus preventing the hunting phenomenon caused by drastic fluctuations in the supply of the neutralizing agent.

[0043] Next, a wastewater neutralization treatment method utilizing an oil trap according to one embodiment of the present invention will be described with reference to Figure 1. Wastewater generated at the factory is treated in a wastewater neutralization treatment facility 10. After removing oil and adjusting the pH of the wastewater, it is discharged into the sea. A detailed explanation follows.

[0044] In the oil trap 11 of the wastewater neutralization treatment facility 10, wastewater flows continuously into and out of the oil trap tank 12. If the wastewater contains oil, the oil will float and separate from the wastewater as it flows from the inlet side to the outlet side of the oil trap tank 12. This floating oil is blocked by the partition plate 14 on the liquid surface side and is then collected by a suction pump.

[0045] Furthermore, the pH value of the wastewater flowing into the oil trap tank 12 is measured at each point by the inlet side pH meter 35, the monitoring pH meter 36, and the outlet side pH meter 37, and the flow rate is measured by the weir-type flow meter 38. The measured pH value and flow rate are transmitted sequentially to the calculation processing unit 43. Furthermore, if the wastewater becomes alkaline due to the influence of rainwater, for example, or acidic due to a factory malfunction (for example, equipment damage or chemical leakage), a portion of the wastewater in the oil trap tank 12 is continuously drawn into the wastewater circulation path 16 by the suction pump 17.

[0046] The suction pump 17 only needs to be operated intermittently when the pH value measured by the pH meter shows alkaline or acidic. However, it may also be operated continuously regardless of fluctuations in the pH value to continuously draw wastewater into the drainage circulation path 16. In this case, the depth position of the water intake port of the water intake pump 17 is set below the upper layer (oil suspension area) of the wastewater in the oil trap tank 12, and above the bottom of the oil trap tank 12, thereby suppressing the intrusion of oil and other substances into the wastewater circulation path 16. Furthermore, it is preferable that the amount of wastewater taken in by the wastewater circulation path 16 be 3 to 10% of the minimum inflow amount of wastewater into the oil trap tank 12.

[0047] Here, the case in which the calculation processing means 43 determines that the wastewater is alkaline based on the pH value measured by the pH meter 35 will be explained below. In the chemical solution output determination SEQ unit of the calculation processing means 43, the amount of sulfuric acid required to neutralize the wastewater in the oil trap tank 12 (hereinafter also referred to as the sulfuric acid amount) is calculated from the wastewater flow rate measured by the weir-type flow meter 38 (flow rate of indicator 42) and the pH value measured by the pH meter 35 on the inlet side of the oil trap tank 12 (pH value of indicator 39). This calculated sulfuric acid amount is output to the reference magnification determination SEQ unit.

[0048] The reference magnification determination SEQ unit then controls the operation of the transfer pump 27 so that the amount of sulfuric acid calculated by the chemical output determination SEQ unit can be supplied to the drainage circulation path 16. The operation of the transfer pump 27 is based on the flow rates measured by the circulation flow meter 20 and the input flow meter 28, which are transmitted to the chemical gain determination SEQ unit of the calculation processing means 43. At this time, the transfer pump 27a that supplies caustic soda is stopped. Here, if the pH value (actual value) of the outflow side pH meter 37 of the wastewater flowing through the oil trap tank 12 to which the above-mentioned amount of sulfuric acid has been supplied is within the preset pH range, the operation of the transfer pump 27 is controlled so that the above-mentioned amount of sulfuric acid can be supplied to the wastewater circulation path 16.

[0049] On the other hand, if the pH value (actual value) of the outflow-side pH meter 37 of the wastewater flowing through the oil trap tank 12 to which the above-mentioned amount of sulfuric acid is supplied falls outside the preset pH range, the amount of sulfuric acid supplied (amount of sulfuric acid supplied obtained from calibration curve y) calculated by the chemical output determination SEQ unit is corrected by multiplying it by the correction coefficient α so that the pH value of the outflow-side pH meter 37 falls within the above-mentioned pH range, and the operation of the transfer pump 27 is controlled so that this corrected amount of sulfuric acid can be supplied to the wastewater circulation path 16. This correction coefficient α is preferably determined using equation (1) as described above. Furthermore, when the amount of neutralizing agent supplied is corrected multiple times, it is preferable to multiply the previous correction coefficient α by a new correction coefficient α' to obtain the correction coefficient α. In addition, it is preferable to set a limit value β in the calculation processing means 43 in advance to gradually increase the amount of neutralizing agent supplied.

[0050] Since sulfuric acid is constantly filled in the chemical input passage 25 of the neutralizing agent supply means 22, even if the pH value of the wastewater changes rapidly, for example, sulfuric acid can be quickly supplied to the wastewater taken into the wastewater circulation passage 16. Furthermore, since the amount of sulfuric acid supplied from the neutralizing agent supply means 22 is the amount necessary to neutralize the wastewater in the oil trap tank 12, the alkaline wastewater taken into the wastewater circulation path 16 becomes acidic due to the supplied sulfuric acid.

[0051] The wastewater in the aforementioned wastewater circulation channel 16 and the sulfuric acid supplied to this wastewater are mixed by the static mixer 34, and then returned to the oil trap tank 12 from the outlet of the wastewater circulation channel 16. In this way, by adjusting the pH of the wastewater on the inlet side of the oil trap tank 12, the distance necessary for laminar flow formation within the oil trap tank 12 can be secured, and appropriate sulfuric acid can be added without hindering the oil-water separation function inherent to the oil trap 11.

[0052] Furthermore, by returning the wastewater mixed with sulfuric acid by the static mixer 34 to the oil trap tank 12 from the outlet of the wastewater circulation path 16, and flowing this wastewater from the upstream side to the downstream side of the oil trap tank 12, the neutralization reaction proceeds as the wastewater moves through the oil trap tank 12, enabling continuous neutralization treatment within the wastewater flow. At this time, the oil-water separation function is not affected.

[0053] Then, the treated wastewater, from which the oil has been separated and the pH has been adjusted, is discharged into the sea via the auxiliary tank 13. Although the method described above describes the case where the calculation processing means 43 determines that the wastewater is alkaline, if the calculation processing means 43 determines that the wastewater is acidic, the neutralizing agent supply means 23 is used to supply caustic soda to the wastewater circulation path 16 in the same manner as described above. [Examples]

[0054] Next, we will describe examples taken to confirm the effects and benefits of the present invention. The results of neutralizing wastewater using the wastewater neutralization equipment and wastewater neutralization method utilizing the oil trap of the present invention will be explained with reference to Figure 4. Figure 4 shows the changes in the flow rate of wastewater flowing through the oil trap tank, the pH value of the pH meter on the inlet side of the wastewater, a correction coefficient for correcting the amount of sulfuric acid supplied to the wastewater, the amount of sulfuric acid supplied calculated using this correction coefficient, and the pH value of the pH meter on the outlet side of the wastewater to which this amount of sulfuric acid was supplied. For the sake of explanation, the left vertical axis of the graph shows the pH value, and the right vertical axis shows the correction coefficient, and only the behavior of the wastewater flow rate and the amount of sulfuric acid supplied is illustrated.

[0055] As shown in Figure 4, the flow rate of wastewater flowing through the oil trap tank is not constant but fluctuates. In other words, the time required for the wastewater from the oil trap tank to reach the outflow pH meter from the sulfuric acid supply point varies. First, the pH value of the wastewater flowing through the oil trap tank was measured using an inlet-side pH meter. Since it was outside the aforementioned preset pH range (pH was above 8), the operation of the transfer pump was controlled so that the amount of sulfuric acid calculated by the chemical output determination SEQ unit could be supplied to the wastewater circulation path. Next, when the pH value of the wastewater to which this sulfuric acid was supplied was measured using an outflow pH meter, the pH value decreased slightly, but it was outside the preset pH range mentioned above (pH above 8).

[0056] Therefore, to ensure that the pH value of the outflow-side pH meter falls within the aforementioned pH range, the amount of sulfuric acid supplied, calculated by the chemical output determination SEQ unit, is corrected by multiplying it by a correction coefficient α. The operation of the transfer pump is then controlled so that this corrected amount of sulfuric acid is supplied to the wastewater circulation path. As shown in Figure 4, by correcting the sulfuric acid supply amount four times and gradually increasing the sulfuric acid supply amount, fluctuations in the pH value of the outflow side pH meter were reduced, preventing the hunting phenomenon caused by drastic fluctuations in the neutralizing agent supply amount, while lowering the pH value of the outflow side pH meter to the pH range described above. Although this description explains an example where correction was performed multiple times, if, for example, the pH value of the pH meter on the wastewater inlet side is only slightly outside the preset pH range described above, one correction may suffice.

[0057] Based on the above, by using the wastewater neutralization equipment and wastewater neutralization method utilizing the oil trap of the present invention, neutralization control can be stably performed even with flowing wastewater, and even with wastewater containing various foreign substances and rainwater.

[0058] Although the present invention has been described above with reference to embodiments, the present invention is not limited in any way to the configurations described in the embodiments described above, and includes other embodiments and modifications that can be considered within the scope of the matters described in the claims. For example, the scope of the present invention also includes cases where some or all of the above embodiments and modifications are combined to constitute a wastewater neutralization treatment facility and wastewater neutralization treatment method utilizing the oil trap of the present invention. Furthermore, the scope of the present invention is not limited to the installation of a new wastewater neutralization treatment facility utilizing an oil trap. For example, it also applies to cases where an existing oil trap used in a conventional factory is fitted with an inlet-side pH meter, an outlet-side pH meter, a control means, and a neutralizing agent supply means to constitute a wastewater neutralization treatment facility utilizing an oil trap according to the present invention.

[0059] Furthermore, while the above embodiment described a case where a wastewater neutralization treatment facility is installed in a factory, the facility is not particularly limited as long as it discharges wastewater that contains oil and requires pH adjustment. Furthermore, in the above embodiment, the wastewater neutralization treatment equipment is equipped with two systems, acid and alkali, as neutralizing agent supply means, making the wastewater neutralization treatment equipment capable of handling a wide range of pH changes. However, if the wastewater fluctuates between acidic and alkaline, only one of the acid or alkali systems may be used. Note that the acidic neutralizing agent is not limited to sulfuric acid as described above, but may also be hydrochloric acid, for example. Similarly, the alkaline neutralizing agent is not limited to caustic soda as described above. [Explanation of Symbols]

[0060] 10: Wastewater neutralization treatment equipment utilizing an oil trap, 11: Oil trap, 12: Oil trap tank, 13: Auxiliary tank, 14, 15: Partition plate, 16: Wastewater circulation path, 17: Suction pump, 18: On / off valve, 19: Check valve, 20: Circulation flow meter, 21: On / off valve, 22, 23: Neutralizing agent supply means, 24, 24a: Tank, 25, 25a: Chemical input path, 26, 26a: Water level meter, 2 7, 27a: Transfer pump, 28, 28a: Inlet flow meter, 29, 29a: Back pressure valve, 30, 30a: Motorized valve, 31, 31a: Check valve, 32, 32a: Flow path, 33, 33a: Motorized valve, 34: Static mixer (mixing means), 35: Inlet pH meter, 36: Monitoring pH meter, 37: Outlet pH meter, 38: Weir-type flow meter, 39-42: Indicator, 43: Calculation processing means (control means)

Claims

1. An oil trap is provided, which has an oil trap tank through which wastewater flows in and out continuously, and which is capable of separating oil from wastewater flowing from the inlet side to the outlet side within the oil trap tank. The oil trap tank comprises an inlet pH meter for measuring the pH value on the inlet side of the wastewater and an outlet pH meter for measuring the pH value on the outlet side, A control means for determining the amount of neutralizing agent to be supplied to the wastewater flowing through the oil trap tank, using the pH values ​​of the inlet-side pH meter and the outlet-side pH meter, In a wastewater neutralization treatment facility utilizing an oil trap, the facility includes a neutralizing agent supply means that supplies the amount of the neutralizing agent determined by the control means to the wastewater, The control means is Using the time required for the wastewater from the oil trap tank to reach the outflow-side pH meter from the neutralizing agent supply position, the relationship between the pH value of the inflow-side pH meter, the amount of neutralizing agent supplied, and the pH value of the outflow-side pH meter of the wastewater to which the supplied amount of neutralizing agent has been supplied is determined in advance. A wastewater neutralization treatment system utilizing an oil trap, characterized in that, when the pH value of the wastewater flowing through the oil trap tank, obtained from the relationship between the pH value of the inlet side pH meter and the amount of the neutralizing agent supplied, falls outside a preset pH range, a correction is made by multiplying the amount of the neutralizing agent supplied in the relationship by a correction coefficient α so that it falls within the preset pH range.

2. A wastewater neutralization treatment facility utilizing an oil trap as described in claim 1, characterized in that the correction coefficient α is determined by the following formula. α={(G) １ -R) / (+ １ -+ ２ )} Here, X １ X is the pH value of the inlet side pH meter of the wastewater flowing through the oil trap tank, X ２ R is the pH value measured by a pH meter on the outlet side of the wastewater flowing through the oil trap tank to which the neutralizing agent has been supplied, and R is a predetermined value within a set pH range.

3. A wastewater neutralization treatment facility utilizing an oil trap according to claim 1 or 2, characterized in that when the supply amount of the neutralizing agent is corrected multiple times, the correction coefficient α for the current correction is obtained by multiplying the correction coefficient α from the previous correction by a new correction coefficient.

4. A wastewater neutralization treatment facility utilizing an oil trap according to claim 1 or 2, wherein a limit value β is set in advance in the control means, and if the correction coefficient α is less than or equal to the limit value β, the correction coefficient α is used as is, and if the correction coefficient α exceeds the limit value β, the limit value β is set as the correction coefficient α.

5. Using an oil trap equipped with an oil trap tank in which wastewater flows in and out continuously, oil is separated from the wastewater flowing from the inlet side to the outlet side within the oil trap tank, and a neutralizing agent is supplied to the wastewater according to the pH values ​​of the inlet side pH meter and the outlet side pH meter installed on the inlet side of the oil trap tank, Using the time required for the wastewater from the oil trap tank to reach the outflow-side pH meter from the neutralizing agent supply position, the relationship between the pH value of the inflow-side pH meter, the amount of neutralizing agent supplied, and the pH value of the outflow-side pH meter of the wastewater to which the supplied amount of neutralizing agent has been supplied is determined in advance. A wastewater neutralization treatment method utilizing an oil trap, characterized in that, provided that the pH value of the wastewater flowing through the oil trap tank, to which the supply amount of the neutralizing agent obtained from the relationship between the pH value of the inlet side pH meter of the wastewater flowing through the oil trap tank has been supplied, falls outside a preset pH range, a correction is performed by multiplying the supply amount of the neutralizing agent in the relationship by a correction coefficient α so that it falls within the pH range, and then the corrected supply amount of the neutralizing agent is supplied to the wastewater in the oil trap tank.

6. A wastewater neutralization treatment method utilizing an oil trap as described in claim 5, characterized in that the correction coefficient α is determined by the following formula. α={(G) １ -R) / (+ １ -+ ２ )} Here, X １ is the pH value of the inflow side pH meter of the drainage flowing through the oil trap tank, and X ２ is the pH value of the outflow side pH meter of the drainage flowing through the oil trap tank to which a neutralizing agent is supplied, and R is a predetermined value within a preset pH range.

7. A wastewater neutralization treatment method utilizing an oil trap according to claim 5 or 6, characterized in that when the supply amount of the neutralizing agent is corrected multiple times, the correction coefficient α for the current correction is obtained by multiplying the correction coefficient α from the previous correction by a new correction coefficient.

8. A wastewater neutralization treatment method utilizing an oil trap according to claim 5 or 6, characterized in that if the correction coefficient α is less than or equal to a preset limit value β, the correction coefficient α is used as is, and if the correction coefficient α exceeds the limit value β, the limit value β is set as the correction coefficient α.

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