JP6164941B2 - Muddy water treatment system and muddy water treatment method - Google Patents

Description

  The present invention relates to a muddy water treatment system and a muddy water treatment method for treating muddy water containing oil produced by civil engineering work.

  In Patent Document 1, a mud pipe that connects one end to a mud water generation source, a pH adjuster tank that injects a pH adjuster into the mud pipe, and a waste mud disposed at a subsequent stage of the pH adjuster tank. It is equipped with an ozone generator that injects ozone into the pipe, and removes wastewater generated by removing harmful substances while circulating the muddy water while maintaining the physical properties of the muddy water and circulating the muddy water or treating sludge. A muddy water treatment system that can be discharged to an external level is described.

  In Patent Document 2, a high-efficiency solid-liquid separation and filtration tank filled with a floating filter medium that performs filtration on the inflowing raw water, and activated sludge for filtered water that has passed through the high-efficiency solid-liquid separation and filtration tank. A water treatment system having a membrane separation activated sludge means for performing the biological treatment and membrane filtration treatment used is described.

  Further, Patent Document 3 includes a cylindrical container for storing a liquid to be stirred, and a nozzle disposed at a certain depth from the liquid level in the cylindrical container, and a flow rate higher than a certain level from the nozzle. A stirrer that stirs a liquid in a cylindrical container without using a mechanical drive source such as a propeller is described. In this stirring device, one using ozone as a gas is used for wastewater treatment in a food factory or the like.

JP 2011-161405 A JP 2013-046905 A Japanese Patent No. 4195782

  When releasing turbid water generated by civil works such as tunnel excavation, it is required to purify the turbid water with high purity for environmental protection. In a conventional turbid water treatment system using a membrane filtration treatment, turbid water can be purified until the turbidity is about SS = 10 to 20 ppm. Here, SS (Suspended Solids) is the total amount of suspended suspended matter that is not dissolved in water and causes turbidity. However, in order for treated water that has been treated with turbid water to satisfy river discharge standards, the turbid water must be purified to a higher purity with a turbidity of about SS = 1 to 2 ppm.

  Generally, since muddy water generated by excavation of a tunnel contains oil, it is assumed that muddy water treatment system treats raw water mixed with oil. However, during the membrane filtration treatment, the filter membrane may be clogged by the oil, and the performance of the membrane filtration device may be significantly reduced. For this reason, if the muddy water to be treated contains oil, the turbidity cannot be lowered to about SS = 1 to 2 ppm simply by passing the muddy water through the membrane filtration device.

  Then, this invention aims at providing the muddy water treatment system and muddy water treatment method which can purify the muddy water containing the oil which arises by civil engineering to high purity whose amount of suspended suspended solids (SS) is about 1-2 ppm. To do.

  The turbid water treatment system according to the present invention includes an oil content treatment unit that decomposes oil contained in turbid water by reacting turbid water generated by civil engineering work with an oxidizing reactive gas, and treated water treated by the oil content treatment unit. It has a coagulation process part which coagulates and removes the suspended | floating matter contained, and a membrane filtration process part which lets the treated water processed by the coagulation process part pass through a filtration membrane.

  In the muddy water treatment system according to the present invention, it is preferable to further include a pH adjusting unit that measures the pH of muddy water before being treated by the oil component treatment unit and adjusts the pH of muddy water when the muddy water is strongly alkaline. The oil content processing unit has a container for storing turbid water and a jet port arranged upward in the container, and swirls the turbid water in the container by jetting reactive gas from the jet port, and is contained in the turbid water. It is preferable that the oil component is decomposed by reacting with a reactive gas.

  In the turbid water treatment system according to the present invention, the oil content treatment unit ejects the reactive gas and the ejection time so as to decompose the oil contained in the turbid water until the n-hexane extract substance in the turbid water becomes 10 mg / L or less. Is preferably adjusted. Moreover, it is preferable that an oil content processing part uses ozone gas as a reactive gas.

  The method for treating turbid water according to the present invention comprises reacting turbid water generated by civil engineering work with a reactive gas having an oxidizing action to decompose oil contained in turbid water, and treating water treated by the oil treating step. A coagulation treatment step for coagulating and removing the suspended matter contained therein, and a membrane filtration treatment step for passing the treated water treated in the coagulation treatment step through the filtration membrane.

  ADVANTAGE OF THE INVENTION According to this invention, the muddy water processing system and muddy water processing method which can purify the muddy water containing the oil produced by civil engineering to high purity whose suspended suspended solids amount (SS) is about 1-2 ppm can be provided.

It is a figure for demonstrating the excavation construction of a tunnel. It is the top view and sectional drawing of the muddy water processing system. It is a figure for demonstrating adhesion of the oil component to a filtration membrane. 2 is a cross-sectional view of an ozone treatment tank 30. FIG. 3 is a cutaway perspective view of a ceramic membrane element 51. FIG. It is a flowchart of the muddy water process by the muddy water treatment system.

  Hereinafter, a muddy water treatment system and a muddy water treatment method according to the present invention will be described in detail with reference to the accompanying drawings. However, it should be noted that the technical scope of the present invention is not limited to these embodiments, but extends to the invention described in the claims and equivalents thereof.

  In the following, the muddy water treatment caused by tunnel excavation work will be described as an example. However, the following muddy water treatment system and muddy water treatment method are applicable not only to tunnel construction, but also to muddy water treatment that occurs in civil works that excavate the ground or rock and use concrete.

  FIG. 1 is a diagram for explaining tunnel excavation work. During excavation work, the tunnel 100 is dug with the excavator 101 or the like. The peripheral wall 102 of the tunnel 100 is reinforced with concrete by spraying cement or the like. At this time, spring water 103 from the ground may accumulate inside the tunnel 100. This spring 103 is pumped out by pumps 104, 105 and the like. The spring water 103 is collected in the storage tank 108 together with the washing water for concrete, the washing water for the mixer truck 106, the rain water 107 collected outside the tunnel, and the like. Then, the muddy water collected in the storage tank 108 is purified to the river discharge water level by the muddy water treatment system 1 and discharged into the river 109.

The turbid water flowing into the turbid water treatment system 1 has, for example, a water amount of about 30 m ³ / h, an average turbidity SS of about 1700 to 3000 ppm, a pH of over 7.5, and contains a low concentration of oil. The turbid water treatment system 1 is almost neutral with, for example, an amount of water of about 30 m ³ / h which is the same as the inflow, an average turbidity SS of about 1 to 2 ppm, and a pH of 5.8 to 8.6. The n-hexane extract material is treated and discharged to 5 ppm or less. Here, the n-hexane extract substance is an index indicating the oil content contained in the muddy water. Hereinafter, the n-hexane extract material is referred to as “n-Hex”. The treated water to be discharged shall satisfy the river discharge standards established by local governments.

  2A and 2B are a plan view and a cross-sectional view of the muddy water treatment system 1, respectively. The muddy water treatment system 1 includes a raw water tank 10, a sand settling tank 20, an ozone treatment tank 30, a mixing tank 40, a membrane filtration device 50, and a discharge tank 60 as main components. The entire muddy water treatment system 1 is controlled by a control unit (not shown) installed in the vicinity of the facility of this system. The turbid water treatment system 1 decomposes the oil contained in the turbid water in the ozone treatment tank 30 (oil content treatment), aggregates the suspended matter contained in the turbid water in the mixing tank 40 (aggregation treatment), and treats the treated water with the membrane filtration device 50. The turbid water is treated mainly in three stages of passing through a filtration membrane (membrane filtration treatment).

  First, the reason why the oil component treatment is performed as the pretreatment of the flocculation treatment and the membrane filtration treatment in the turbid water treatment system 1 will be described. In the membrane filtration process of the membrane filtration device 50, when a ceramic membrane described later is used as the filtration membrane, high performance is obtained. When a ceramic membrane is used as the filtration membrane, it has been experimentally known that when turbid water containing an oil component of n-Hex = 800 mg / L is subjected to membrane filtration treatment, the turbidity is reduced to about SS = 3 mg / L. That is, when oil content is contained in turbid water, even if a high performance ceramic membrane is used, turbidity cannot be lowered to the target SS = 1 to 2 ppm only by membrane filtration treatment.

  In addition, the experimental result that the turbidity of n-Hex = 800 mg / L turbid water can be lowered to SS = 3 mg / L by membrane filtration treatment is the case where turbid water containing this concentration of oil temporarily flows. . When such turbid water containing a high concentration of oil is treated continuously for a long time, the oil adheres to the pore wall of the filtration membrane, and even if the membrane filtration treatment is performed, the performance of SS = 3 mg / L cannot be realized. is expected.

  FIG. 3 is a diagram for explaining the adhesion of oil to the filtration membrane. In FIG. 3, it is assumed that turbid water flows through the filtration membrane 150 in the direction of the arrow in the figure. In general, oil droplets 151 in muddy water are larger than the membrane pore diameter of the filtration membrane 150, and are thus captured on the membrane surface of the filtration membrane 150. However, if the inflow of oil droplets 151 continues, an oil film 152 is formed on the surface of the filtration membrane 150. When the oil film 152 adheres, the filtration film 150 is clogged, and turbid water cannot be filtered. Further, the membrane pressure difference at which the oil component is mixed into the membrane-filtered treated water is about 100 kPa, and when the membrane operating pressure of the membrane filtration treatment exceeds this limit, the oil membrane 152 is deformed and the oil droplets 153 are filtered. 150 is transmitted. Then, there exists a possibility that oil may mix in the treated water membrane-filtered.

  For this reason, when turbid water with high oil content is directly subjected to membrane filtration, in order to ensure the quality of the treated water, the membrane pressure difference of the operation membrane is suppressed to about 30 kPa, or the membrane is backwashed frequently. It is necessary to clean the turbid water treatment system, and the amount of treatment of the turbid water treatment system is reduced. Moreover, unless the oil component is decomposed before the membrane filtration treatment, the turbidity of the final treated water is reduced only to about SS = 3 mg / L. Therefore, in the turbid water treatment system 1, in order to lower the turbidity to a higher purity of about SS = 1 to 2 ppm, the oil content in the turbid water is decomposed in the preceding ozone treatment tank 30.

  Next, with reference to FIG. 2 (A) and FIG. 2 (B), each component of the muddy water treatment system 1 is demonstrated.

  In the raw water tank 10, turbid water collected at a construction site such as tunnel excavation is received and stored. In the raw water tank 10, a water level gauge and a pump (both not shown) are installed. The muddy water is sent to the next settling tank 20 by the pump. The control unit of the muddy water treatment system 1 controls the water level of the raw water tank 10 using the water level gauge.

  In the sand settling tank 20, large sand and soil contained in muddy water are settling. The sand settling tank 20 is particularly necessary when the turbidity of the muddy water to be treated is high. The sand settling tank 20 is provided with a quantitative transfer pump (not shown) for sending muddy water to the next ozone treatment tank 30. A constant amount of turbid water per unit time is sent to the ozone treatment tank 30 by this fixed transfer pump.

  The ozone generator 35 is a device for generating ozone to be supplied to the ozone treatment tank 30. For example, the ozone generator 35 compresses air by an air compressor, generates concentrated oxygen gas from the compressed air by a PSA (Pressure Swing Adsorption) method, and further applies a high voltage using a discharge unit or the like to concentrate oxygen gas. Ozone is generated from.

  In the ozone treatment tank 30, the muddy water is swirled by jetting ozone gas into the muddy water to be treated stored in the tank, and the oil contained in the muddy water is reacted with the ozone gas and decomposed (oil treatment). The ozone treatment tank 30 is an example of an oil component treatment unit. The ozone treatment tank 30 performs a so-called swirling jet type ozone treatment using, for example, a stirrer described in Japanese Patent No. 4195782.

  4A and 4B are cross-sectional views of the ozone treatment tank 30. FIG. As shown in FIG. 4A, the ozone treatment tank 30 includes a cylindrical container 31 that stores muddy water to be treated, and an ozone gas ejection port 32 that is disposed so as to protrude upward from the bottom surface of the cylindrical container 31. And a muddy water outlet 33. The inner diameter of the cylindrical container 31 is D, and the depth from the turbid water level to the tip of the spout 32 is H1. The muddy water is appropriately discharged from the discharge port 33 so that the height of the liquid level in the cylindrical container 31 is kept constant.

As described in Japanese Patent No. 4195782, the ratio H1 / D of the depth H1 of the jet port 32 to the inner diameter D of the cylindrical container 31 is in the range of about 0.3 to about 1, and the flow rate is constant. When the gas satisfying the condition is ejected from the ejection port 32, the muddy water in the cylindrical container 31 turns in the direction of the arrow A, for example, as shown in FIG. Here, the certain condition is that the flow rate Q of the gas to be ejected is equal to or higher than the flow rate satisfying ρQ ² / (σD ³ ) = 10 ⁻⁵ and is equal to or lower than the flow rate at which bubbles do not blow through the liquid surface. Where ρ is the density of turbid water and σ is the surface tension of turbid water. When the turbid water above the spout 32 is swung in the direction of arrow A, the turbid water below the spout 32 is swung in the direction of arrow B in the opposite direction according to the law of conservation of angular momentum.

  Thus, in the ozone treatment tank 30, the swirling of the jet flow is generated by ejecting ozone gas. Accordingly, in the ozone treatment tank 30, turbid water in the tank is agitated without using a mechanical drive source such as a propeller. In the ozone treatment tank 30, the turbid water in the tank is thus stirred, and the ozone gas is dispersed in the turbid water as fine bubbles, so that ozone and turbid water can be efficiently removed compared to a method in which ozone gas is simply injected from the bottom of the tank. React. Then, the oil in muddy water is decomposed by the strong oxidizing power of ozone. The amount of ozone gas ejected from the ozone generator 35 and the ejection time are controlled by the control unit of the turbid water treatment system 1 so that the concentration of oil in the turbid water is sufficiently reduced (for example, the numerical value of n-Hex is 10 mg / L or less). Controlled by

  Thus, the process which produces a swirling jet by ejecting ozone gas and reacts ozone and muddy water is called swirling jet type ozone treatment. According to the swirling jet type ozone treatment, it becomes possible to remove the oil content in the muddy water more efficiently than the method of removing the oil content of the muddy water in the raw water tank 10 using an oil mat or an oil skimmer.

  In addition to the ability to decompose oil, swirling jet ozone treatment has various advantages such as less sludge generation and excellent deodorizing and decoloring effects. For these reasons, it is preferable to use ozone gas, which is a reactive gas having an oxidizing action, as the gas ejected during the oil treatment.

  Regarding the performance of the swirling jet type ozone treatment, it has been experimentally known that muddy water containing an oil component of n-Hex = 870 mg / L can be treated until the oil content becomes n-Hex = 3.3 mg / L. The swirling jet ozone treatment has so far been used only for sewage treatment at food factories, etc., but the results of this experiment show that it is effective as an oil treatment when treating turbid water generated by tunnel excavation. I can say that. If the n-Hex value of turbid water is reduced to, for example, 10 mg / L or less in the preceding ozone treatment tank 30, the turbidity can be reduced to about SS = 1 to 2 ppm by the subsequent membrane filtration device 50. become.

  The swirling jet ozone treatment can be used if the pH of the turbid water is about 5 to 11. However, turbid water generated by tunnel excavation and the like includes, for example, concrete washing water and the like, and thus generally shows alkalinity and tends to have a high pH. Therefore, a pH adjusting unit 34 is provided in the previous stage of the ozone treatment tank 30, and before the swirling jet type ozone treatment is performed at the stage of the sand settling tank 20, the pH of the muddy water is adjusted to 5 to 11 by the pH adjusting unit 34. It is preferable to adjust to the extent.

  The pH adjusting unit 34 has a pH meter, and determines the pH of the turbid water fed to the ozone treatment tank 30 with the pH meter. When the muddy water is strongly alkaline having a pH of 11 or more, the pH adjusting unit 34 injects a pH adjusting agent into the muddy water and neutralizes the muddy water so that the pH is less than 11.

  In the mixing tank 40, the treated water treated in the ozone treatment tank 30 is stored. The mixing tank 40 includes a pH adjusting tank 41, a first mixing tank 42, and a second mixing tank 43, and a stirrer is installed in each tank. In the mixing tank 40, the pH adjusting agent and the flocculant are poured into the muddy water, and the mixture is stirred and mixed to agglomerate and remove the suspended matter contained in the muddy water (aggregation treatment). The mixing tank 40 is an example of an aggregation processing unit.

  In the pH adjusting tank 41, the pH adjusting agent is poured into the muddy water from the ozone treatment tank 30 and stirred with a stirrer, so that the pH of the muddy water is approximately 7 neutral. Since turbid water generated by excavation of a tunnel or the like tends to be alkaline, for example, dilute sulfuric acid is used as a pH adjuster. The dilute sulfuric acid is stored in a dilute sulfuric acid storage tank 44 provided alongside the mixing tank 40 and is injected into the pH adjustment tank 41 via a pump. A pH meter (not shown) is installed in the pH adjustment tank 41. The control unit of the turbid water treatment system 1 monitors the pH of the turbid water using this pH meter, and controls the injection amount of the pH adjusting agent.

  In the 1st mixing tank 42 and the 2nd mixing tank 43, a flocculant is further inject | poured into the muddy water neutralized by the pH adjustment tank 41, and it stirs with a stirrer, and a suspended | floating matter is aggregated. And the suspended matter is removed from muddy water by settling the aggregated suspended matter. As the flocculant, for example, PAC (polyaluminum chloride) is used. The PAC is stored in a coagulant storage tank 45 provided in the mixing tank 40, and is injected into the first mixing tank 42 via a pump.

  The second mixing tank 43 has a volume about twice that of the first mixing tank 42, for example. In addition, for example, the stirring speed in the second mixing tank 43 is about ½ of the stirring speed of the first mixing tank 42. In this way, a relatively large suspended matter is settled in the first mixing tank 42, and a smaller suspended matter is settled in the second mixing tank 43. Thus, in the mixing tank 40, the suspended matter in muddy water is more effectively removed by making the tank which performs a coagulation process into two steps.

  The turbidity of the treated water after the coagulation treatment in the mixing tank 40 is such that the turbidity of the treated water finally discharged to the river or the like is about SS = 1 to 2 ppm. It is set in consideration of the performance of the membrane filtration treatment. For example, when a membrane filtration process using a ceramic membrane is performed in the membrane filtration device 50 as described later, it is preferable to reduce the turbidity to about SS = 100 ppm by the mixing tank 40. The control unit of the turbid water treatment system 1 adjusts the injection amount of the flocculant and the residence time of the turbid water in the first mixing tank 42 and the second mixing tank 43 in accordance with the target decrease in turbidity in the mixing tank 40. Control.

  A water level meter (not shown) is also installed in the mixing tank 40, and the control unit of the muddy water treatment system 1 controls the water level of the mixing tank 40 using the water level gauge. The treated water after the aggregation treatment in the second mixing tank 43 is sent to the membrane filtration device 50 by the transfer pump 46.

  The membrane filtration device 50 reduces the turbidity of the treated water to about SS = 1 to 2 ppm by passing the treated water treated by the mixing tank 40 through the filtration membrane (membrane filtration treatment). The membrane filtration device 50 is an example of a membrane filtration processing unit. The membrane filtration device 50 has a filter membrane in which many ceramic membrane elements 51 described below are arranged.

  FIG. 5 is a cutaway perspective view of the ceramic membrane element 51. Each ceramic membrane element 51 is, for example, a cylindrical porous block having a diameter of 180 mm obtained by integrally sintering 2000 cylindrical membranes having an inner diameter of 2.5 mm. FIG. 5 schematically shows this porous block. Inside the ceramic membrane element 51, a membrane filtration cell 52, a water collection cell 53, and a water collection slit 54 are formed.

  The membrane filtration cell 52 is a tubular cavity extending along the axial direction of the ceramic membrane element 51, into which water to be treated flows. A separation membrane for membrane filtration is formed on the inner surface of the membrane filtration cell 52. The water that has flowed into the membrane filtration cell 52 passes through this separation membrane, is separated from the suspended matter, and is subjected to membrane filtration.

  The water collection cell 53 is a tubular cavity extending along the axial direction of the ceramic membrane element 51, but is not directly connected to the membrane filtration cell 52. Into the water collection cell 53, treated water that has been soaked into the ceramic membrane element 51 from the membrane filtration cell 52 and passed through the separation membrane flows.

  The water collection slit 54 is a part that connects the water collection cells 53 to each other. The membrane filtrate flowing into the water collection cell 53 flows out to the outer peripheral surface of the ceramic membrane element 51 through the water collection slit 54. Thus, the membrane filtrate flowing out from the ceramic membrane element 51 is further fed to the discharge tank 60.

  Usually, when a membrane filtration device is used, maintenance work such as detection, repair and replacement of a damaged membrane or a deteriorated membrane is required. However, a ceramic filter membrane such as the ceramic membrane element 51 has high strength and high corrosion resistance and is not deteriorated due to chemical deterioration or heat and pressure. Can be used for a period. For this reason, there is an advantage that maintenance work is reduced by using the ceramic membrane element 51 as a filtration membrane. Therefore, in the membrane filtration apparatus 50, it is preferable to use a ceramic filtration membrane.

  However, if the n-hexane extractable material can be reduced to a sufficiently low value of, for example, n-Hex = 10 mg / L by the oil treatment in the ozone treatment tank 30, the filtration membrane is not necessarily a ceramic membrane. . Further, even when the turbidity of the turbid water can be reduced to a sufficiently low value of, for example, SS = 10 ppm by the coagulation treatment in the mixing tank 40, the filtration membrane is not necessarily a ceramic membrane. In general, since a ceramic membrane is expensive, if high performance is not required for the membrane filtration treatment by the membrane filtration device 50, another filtration membrane may be employed in order to reduce costs.

  Even if the separation membrane of the ceramic membrane element 51 is clogged with foreign matter or the like, the clogging can be removed by washing. When washing the ceramic membrane element 51, water is allowed to flow in the opposite direction to that in the normal membrane filtration treatment (back washing step), and foreign matter is peeled off by applying compressed air (blow step). Thereby, the foreign matter clogged in the separation membrane of the ceramic membrane element 51 is removed.

  The reservoir tank 55 stores compressed air for backwashing the ceramic membrane of the ceramic membrane element 51 and for driving an automatic valve of the membrane filtration device 50. The air compressor 56 is a device for generating compressed air stored in the reservoir tank 55, and is attached to the reservoir tank 55.

  In the discharge tank 60, the treated water subjected to the membrane filtration process by the membrane filtration device 50 is stored. The discharge tank 60 is provided with a turbidity meter and a pH meter, and the turbidity and pH of the treated water are measured by the turbidity meter and the pH meter before the discharge. For example, if the average turbidity SS is about 1 to 2 ppm and the pH is almost neutral at 5.8 to 8.6, the control unit of the turbid water treatment system 1 satisfies the river discharge standard. The treated water is discharged from the discharge tank 60 to the river.

  The discharge tank 60 is also provided with a return pump (not shown). When the treated water does not satisfy the conditions of SS = 1 to 2 ppm and pH = 5.8 to 8.6, the control unit of the muddy water treatment system 1 determines that the treated water does not satisfy the river discharge standard. The treated water is returned to the mixing tank 40 by this return pump. In the mixing tank 40, the pH adjusting agent and the flocculant are injected again into the returned treated water.

  FIG. 6 is a flowchart of muddy water treatment by the muddy water treatment system 1. First, turbid water generated by excavating a tunnel and flowing into the turbid water treatment system 1 is stored in the raw water tank 10 (S10). The muddy water is pumped from the raw water tank 10 to the next sand settling tank 20 by a pump, where large sand and soil contained in the muddy water are settled (S20). Next, the muddy water is sent from the sand settling tank 20 to the ozone treatment tank 30.

  In that case, the pH meter provided in the front | former stage of the ozone treatment tank 30 measures the pH of the muddy water sent. If the measured pH is 11 or more and the turbid water is strongly alkaline (Yes in S22), a pH adjusting agent is injected into the turbid water and the pH of the turbid water is adjusted so that the pH is less than 11 (S24). ). On the other hand, when the measured pH is less than 11 and the turbid water is not strongly alkaline (No in S22), the pH adjustment is not performed and the process proceeds to the next swirling jet ozone treatment (S30).

  In the ozone treatment tank 30, ozone gas is jetted by the ozone generator 35, and swirling jet type ozone treatment (oil content treatment) is performed (S30). That is, turbid water is swirled by ozone gas, and oil contained in the turbid water is reacted with ozone gas to be decomposed. Next, the muddy water is fed from the ozone treatment tank 30 to the mixing tank 40.

  In the mixing tank 40, a pH adjusting agent and an aggregating agent are injected, and agitation is performed by aggregating and removing suspended matters contained in the turbid water by stirring and mixing (S40). In S40, first, in the pH adjustment tank 41, a pH adjusting agent is injected into the turbid water from the ozone treatment tank 30, and the turbid water is neutralized to a neutral pH of about 7 by stirring with a stirrer (S42). . Subsequently, in the first mixing tank 42 and the second mixing tank 43, a flocculant is further injected into the turbid water neutralized in the pH adjustment tank 41, and the suspended matter is aggregated by stirring with a stirrer (S44). . The treated water after the coagulation treatment in the second mixing tank 43 is sent to the membrane filtration device 50.

  In the membrane filtration device 50, the turbidity of the treated water is reduced to about SS = 1 to 2 ppm by passing the treated treated water through the filtration membrane (membrane filtration treatment) (S50). The treated water that has passed through the membrane filtration device 50 is further fed to the discharge tank 60. In the discharge tank 60, the turbidity and pH of the treated water subjected to membrane filtration are measured by a turbidimeter and a pH meter. If the measured pH and turbidity do not satisfy the conditions of pH = 5.8 to 8.6 and SS = 1 to 2 ppm (No in S62), the river discharge standard is not satisfied. The mixture is returned to the mixing tank 40. That is, in this case, the muddy water treatment returns to S40. On the other hand, when the measured pH and turbidity satisfy the conditions of pH = 5.8 to 8.6 and SS = 1 to 2 ppm (Yes in S62), the treated water is regarded as satisfying the river discharge standard. Discharge into rivers. This completes the muddy water treatment by the muddy water treatment system 1.

  As described above, the muddy water treatment system 1 decomposes the oil contained in the muddy water in the ozone treatment tank 30 (oil treatment), and aggregates the suspended matter contained in the muddy water in the mixing tank 40 (coagulation treatment). The turbid water containing oil components generated by civil engineering work such as tunnel excavation is mainly processed in three stages of passing the treated water through the filtration membrane by the filtration device 50 (membrane filtration treatment). In particular, if the numerical value of n-Hex of turbid water is reduced to, for example, 10 mg / L or less in the ozone treatment tank 30, the membrane filtration device 50 can reduce the turbidity to about SS = 1 to 2 ppm. .

DESCRIPTION OF SYMBOLS 1 Turbid water treatment system 10 Raw water tank 20 Sand settling tank 30 Ozone treatment tank 40 Mixing tank 50 Membrane filtration device 60 Discharge tank

Claims (5)

An oil content processing unit for reacting muddy water generated by civil engineering work with a reactive gas having an oxidizing action, and decomposing oil contained in the muddy water;
A coagulation treatment unit for coagulating and removing suspended matter contained in the treated water treated by the oil content treatment unit;
A membrane filtration treatment section for passing treated water treated by the aggregation treatment section through a filtration membrane;
I have a,
The oil content processing unit has a container for storing the muddy water, and a jet port arranged upward in the container, and swirls the muddy water in the container by jetting the reactive gas from the jet port. A turbid water treatment system , wherein oil contained in the turbid water is decomposed by reacting with the reactive gas .   The turbid water treatment system according to claim 1, further comprising a pH adjusting unit that measures pH of turbid water before being treated by the oil content treatment unit and adjusts the pH of the turbid water when the turbid water is strongly alkaline. The said oil content process part adjusts the ejection amount and the ejection time of the said reactive gas so that the oil content contained in the said muddy water may be decomposed | disassembled until the n-hexane extract substance in the said muddy water becomes 10 mg / L or less. Item 3. A muddy water treatment system according to item 1 or 2 . The muddy water treatment system according to any one of claims 1 to 3 , wherein the oil component treatment unit uses ozone gas as the reactive gas. An oil treatment step for reacting turbid water generated by civil engineering work with a reactive gas having an oxidizing action to decompose oil contained in the turbid water;
A coagulation treatment step for coagulating and removing suspended matters contained in the treated water treated by the oil content treatment step;
A membrane filtration treatment step of passing the treated water treated by the aggregation treatment step through a filtration membrane;
I have a,
In the oil treatment step, the turbid water in a container storing the turbid water is swirled by ejecting the reactive gas from a jet port arranged upward in the container, and the oil contained in the turbid water is reacted with the reaction. A method for treating turbid water, which decomposes by reacting with a reactive gas .

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