Drainage neutralization method

Abstract

To propose a wastewater neutralization method and a wastewater treatment system that can reduce the environmental load associated with tunnel construction.SOLUTION: A wastewater neutralization method for neutralizing construction wastewater W0 using a wastewater treatment system 1 equipped with a neutralization tank 2 for neutralizing the construction wastewater W0 discharged from a tunnel T and gas supply means 3 connected to the neutralization tank 2 comprises steps for recovering exhaust gas G0 from the tunnel T, collecting the construction wastewater W0 associated with tunnel construction, extracting carbon dioxide gas G1 from the exhaust gas G0, supplying the construction wastewater W0 and the carbon dioxide gas G1 to the neutralization tank 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for neutralizing wastewater. By law Regarding. [Background technology]

[0002] During mountain tunnel construction (including NATM), groundwater may flow into the tunnel shaft, resulting in spring water. Spring water is often discharged from the tunnel shaft as turbid water containing sediment and other materials. The turbid water discharged from the tunnel is generally discharged into a river or other such location after the slurry has been removed using a turbid water treatment device and made harmless. At this time, turbid water that has become alkaline due to the inclusion of minerals from the ground and shotcrete must be neutralized. Furthermore, when shotcrete, lining concrete, etc. are manufactured in a concrete plant within the construction yard, alkaline wastewater (washing wastewater) discharged from the cleaning of the equipment, piping, etc. within the concrete plant must be neutralized. For example, Patent Document 1 discloses a turbid water treatment device that neutralizes alkaline turbid water and removes slurry from the turbid water. Note that turbid water is generally neutralized by supplying carbon dioxide gas (liquefied carbon dioxide) to the turbid water in a neutralization tank. Patent Document 2 discloses a pH reduction method in which exhaust gas emitted from a vehicle is supplied to alkaline raw water, and the carbon dioxide contained in the exhaust gas reacts with the alkaline components in the raw water to neutralize it. The pH reduction method of Patent Document 2 aims to reduce carbon dioxide emissions, which are said to be a cause of global warming, and also makes it possible to neutralize alkaline raw water. Note that although the pH reduction method of Patent Document 2 uses exhaust gas emitted from parked vehicles to neutralize the raw water, it does not use exhaust gas emitted from vehicles in operation (driving). During tunnel construction, a large amount of carbon dioxide is emitted from inside the tunnel due to the large number of construction machines and vehicles operating inside the tunnel. If the amount of carbon dioxide emitted during tunnel construction can be reduced, the environmental impact associated with tunnel construction can be reduced. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-080267 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-165694 Summary of the Invention [Problem to be solved by the invention]

[0004] This invention is a method for neutralizing wastewater that can reduce the environmental load associated with tunnel construction. The law The task is to make a proposal. [Means for solving the problem]

[0005] The wastewater neutralization method of the present invention for solving the above problems comprises: With the tunnel construction, Recovering exhaust gas from inside the tunnel The exhaust gas is then transported to an exhaust gas plant equipped with carbon dioxide extraction means outside the tunnel. and The aforementioned Due to tunnel construction The gas was discharged from inside and outside the tunnel. Collecting construction wastewater Construction wastewater collection The process and In the exhaust gas plant Extracting carbon dioxide from the exhaust gas Carbon dioxide extraction and supplying the carbon dioxide gas and the construction wastewater to a neutralization tank for neutralizing the construction wastewater. Gas supply In the wastewater neutralization method of the present invention, when a step of extracting carbon dioxide gas from the exhaust gas is included, the carbon dioxide gas may be supplied to the neutralization tank.

[0006] Such wastewater neutralization method By lawThis means that construction wastewater discharged during tunnel construction (for example, groundwater flowing into the tunnel shaft from the tunnel excavation surface, or cleaning wastewater discharged from a concrete plant in a construction yard) can be neutralized using exhaust gas recovered from inside the tunnel shaft. In other words, the carbon dioxide in the exhaust gas reacts with the alkaline components in the construction wastewater, neutralizing the construction wastewater. This neutralizes the construction wastewater to a state that can be discharged, reduces the amount of carbon dioxide emissions associated with tunnel construction, and reduces the environmental burden. In addition, this method is efficient because exhaust gas is recovered from the tunnel shaft, which is a closed space. Furthermore, the carbon dioxide (carbon dioxide) used in the neutralization process is extracted from the exhaust gas, eliminating or reducing the cost and effort of purchasing liquefied carbon dioxide. In addition, , charcoal Since the effort required to produce acid gas can be eliminated, carbon dioxide emissions associated with transporting carbon dioxide gas can be reduced.

[0007] If a soundproof door is installed at the tunnel entrance, the exhaust gas duct and the air supply duct that supplies air from outside the tunnel into the tunnel are passed through the soundproof door. By shielding the tunnel entrance with a soundproof door, exhaust gas can be collected more efficiently. Furthermore, if the neutralization tank further includes a pH measuring means for measuring the pH of the construction wastewater after neutralization treatment and a gas supply means for supplying liquefied carbon dioxide gas to the neutralization tank, it is possible to reliably neutralize the construction wastewater by supplying liquefied carbon dioxide gas when the neutralization is incomplete by supplying exhaust gas alone. [Effects of the Invention]

[0008] The method for neutralizing wastewater according to the present invention By law Therefore, by utilizing the exhaust gas generated during tunnel construction, it is possible to efficiently neutralize construction wastewater and reduce carbon dioxide emissions, thereby reducing the environmental burden associated with tunnel construction. [Brief explanation of the drawings]

[0009] [Figure 1]1 is a schematic diagram showing an overview of a wastewater treatment system according to an embodiment of the present invention. [Figure 2] 1 is a flowchart showing a method for neutralizing wastewater. DETAILED DESCRIPTION OF THE INVENTION

[0010] In this embodiment, a method for neutralizing wastewater that efficiently neutralizes construction wastewater generated during tunnel construction will be described. The method for neutralizing wastewater is performed using a wastewater treatment system. FIG. 1 shows an overview of the wastewater treatment system 1. As shown in FIG. 1, the wastewater treatment system 1 includes a neutralization tank 2 and a gas supply means 3. The neutralization tank 2 neutralizes the construction wastewater W0 discharged from the tunnel T and the concrete plant 7. The neutralization tank 2 constitutes part of a wastewater treatment facility installed on the outskirts of the tunnel T. Carbon dioxide (carbon dioxide G1) sent from the exhaust gas plant 31 is used to neutralize the construction wastewater W0. Carbon dioxide G1 and a polymer flocculant are supplied to the neutralization tank 2 along with the construction wastewater W0. The construction wastewater (mixed water) mixed with the carbon dioxide G1 and the polymer flocculant in the neutralization tank 2 is sent to a settling tank 22 and separated into treated water and flocs. The neutralized treated water W1 can be discharged into a nearby river, or it can be sent to the concrete plant 7 to be used as mixing water for concrete, or it can be used on the construction site as washing water for construction vehicles, for example.

[0011] The gas supply means 3 includes an exhaust gas plant 31 , a gas delivery pipe 32 and an exhaust gas duct 33 . The exhaust gas plant 31 temporarily stores the exhaust gas G0 from inside the tunnel T that is transported via an exhaust gas duct 33. The exhaust gas plant 31 of this embodiment is equipped with a carbon dioxide gas extraction means 34 that extracts carbon dioxide gas G1 from the exhaust gas G0. The extracted carbon dioxide gas G1 is transported to the neutralization tank 2 via a gas transport pipe 32. The gas transport pipe 32 is a pipeline that leads from the exhaust gas plant 31 to the neutralization tank 2. The carbon dioxide gas G1 extracted from the exhaust gas G0 in the carbon dioxide gas extraction means 34 of the exhaust gas plant 31 is transported to the neutralization tank 2 via the gas transport pipe 32. The carbon dioxide gas G1 transported via the gas transport pipe 32 is supplied to the neutralization tank 2. The exhaust gas duct 33 is a pipe extending from the tunnel T to the exhaust gas plant 31, and guides the exhaust gas G0 inside the tunnel T to the exhaust gas plant 31. In this embodiment, a soundproof door 4 is provided at the entrance of the tunnel T, and the exhaust gas duct 33 passes through this soundproof door 4 and opens at its end inside the tunnel T. The air supply duct 5 is a pipe extending from a blower 51 installed outside the tunnel T to the vicinity of the working face K, and passes through the soundproof door 4, similar to the exhaust gas duct 33. In this embodiment, the exhaust gas duct 33 and the air supply duct 5 are made of cylindrical members having the same inner diameter (internal area).

[0012] The wastewater neutralization method of this embodiment is shown in Figure 2. As shown in Figure 2, the wastewater neutralization method of this embodiment includes an exhaust gas recovery step S1, a construction wastewater recovery step S2, a carbon dioxide gas extraction step S3, and a gas aeration step S4. The exhaust gas recovery process S1 is a process of recovering exhaust gas G0 from inside tunnel T. The exhaust gas duct 33 is used to recover exhaust gas G0 from inside tunnel T. The exhaust gas duct 33 transports the air inside tunnel T, including exhaust gas G0 emitted from heavy machinery, construction vehicles, etc. operating inside tunnel T, to exhaust gas plant 31.

[0013] The construction wastewater recovery process S2 is a process of recovering construction wastewater W0 resulting from tunnel construction. The construction wastewater W0 is transported from tunnel T to the neutralization tank 2 via a waterway 21 extending from tunnel T. The waterway 21 guides the construction wastewater W0 collected inside the tunnel T to the neutralization tank 2. The construction wastewater W0 may be transported inside tunnel T by gravity flow, or may be pumped. The construction wastewater W0 is sent to the neutralization tank 2.

[0014] The carbon dioxide extraction step S3 is a step of extracting carbon dioxide G1 from the recovered exhaust gas G0. The exhaust gas G0 is transported to the exhaust gas plant 31 via an exhaust gas duct 33 and then transported to a carbon dioxide extraction means 34. The carbon dioxide extraction means 34 extracts the carbon dioxide G1 from the exhaust gas G0. Methods for extracting the carbon dioxide G1 from the exhaust gas G0 include, for example, a carbon dioxide separation and capture technology using a membrane separation method and a carbon dioxide absorption and release system using layer separation. The carbon dioxide separation and capture technology using a membrane separation method involves passing the exhaust gas G0 through a CO2 separation membrane module equipped with a high-performance CO2 selective permeable membrane (molecular gate membrane) to capture the CO2 that has passed through the CO2 separation membrane module. The carbon dioxide absorption and release system also involves bringing the exhaust gas G0 into contact with an amine compound (adsorbent liquid or solid absorbent) to adsorb the CO2 in the exhaust gas G0 onto the amine compound, and then heating the amine compound to capture a high concentration of CO2.

[0015] The gas supply process S4 is a process of supplying carbon dioxide G1 together with the construction wastewater W0 into the neutralization tank 2. When the carbon dioxide G1 is sent into the neutralization tank 2 together with the construction wastewater W0, the construction wastewater W0 and the carbon dioxide G0 are mixed, and the alkali content in the construction wastewater W0 is neutralized by the carbon dioxide G1. The neutralized construction wastewater W0 (mixed water W2) is sent to the settling tank 22 and separated into treated water W1 and flocs. In this embodiment, a pH measurement means 6 is provided to measure the pH of the treated water W1, making it possible to check the neutralization status of the treated water W1. If the neutralization of the treated water W1 is determined to be incomplete, the neutralization process is repeated in the neutralization tank 2. In this embodiment, a gas supply means 61 is further provided to supply liquefied carbon dioxide to the neutralization tank 2. This makes it possible to supply liquefied carbon dioxide to the neutralization tank 2 if the neutralization of the construction wastewater W0 is incomplete when only the exhaust gas G0 (carbon dioxide G1 extracted from the exhaust gas G0) is supplied.

[0016] According to the wastewater neutralization method of this embodiment, construction wastewater W0 discharged during tunnel construction can be neutralized using exhaust gas G0 recovered from inside tunnel T. Carbon dioxide gas (carbon dioxide) G1 extracted from the exhaust gas G0 reacts with the alkaline components in the construction wastewater W0 to neutralize the construction wastewater W0. Therefore, it is possible to neutralize the construction wastewater W0 to a state where it can be discharged, reduce carbon dioxide emissions associated with tunnel construction, and reduce the environmental burden. In addition, since the exhaust gas G0 is collected from inside the tunnel T, which is a space closed off by the soundproof door 4, the exhaust gas G0 emitted from operating heavy machinery, etc. can be efficiently collected and effectively utilized.

[0017] In addition, since the exhaust gas G0 (carbon dioxide G1 extracted from the exhaust gas G0) is used as the carbon dioxide (carbon dioxide G1) used in the neutralization treatment of the construction wastewater W0, the cost and effort of purchasing liquefied carbon dioxide can be eliminated or reduced. , charcoal Since the effort of producing acid gas G1 can be omitted, the amount of carbon dioxide emissions associated with the transportation of carbon dioxide gas G1 can be reduced. In this embodiment, the pH of the construction wastewater W0 in the neutralization tank 2 is measured by the pH measurement means 6, so the construction wastewater W0 is not discharged in an incompletely neutralized state. Furthermore, since the gas supply means 61 is provided, even if the construction wastewater W0 is not completely neutralized by supplying only the exhaust gas G0, it can be reliably neutralized by supplying liquefied carbon dioxide gas.

[0018] Here, the amount G1 of carbon dioxide (CO2) contained in the exhaust gas recovered from inside the tunnel T can be calculated using Equation 1. In this embodiment, the coefficients in Equation 1 are calculated using the values ​​shown in Table 1. If the fuel consumption in the tunnel construction is 467 L and the values ​​in Table 1 are applied to Equation 1, the amount of carbon dioxide recovered per day will be 45 kg to 75 kg. Formula 1: G1 (kg) = fuel consumption (L) of all heavy machinery (including vehicles) x percentage of CO2 contained in diesel vehicle exhaust gas (%) x exhaust gas production per 1 L of diesel fuel (m 3 / L) × density of gaseous CO2 (kg / m 3 )

[0019] [Table 1]

[0020] In addition, the carbon dioxide consumption Gc required to neutralize construction wastewater can be calculated using Equation 2. Formula 2: Gc (kg / day) = Amount of construction wastewater (m 3 ) × theoretical amount of carbon dioxide gas injected (44 kg / m when pH = 14) 3 ) × Neutralizer safety factor × 10 -(14-工事排水の最大pH)

[0021] According to formula 2, when treating construction wastewater with a pH of 11.0 to 11.4, the required amount is 91 to 568 m per day. 3 The safety factor of the neutralizer is set at 3 to 4.5. Here, the capacity of the construction wastewater neutralization treatment is 20 to 30 m3 / h(480~720m 3 Therefore, it is possible to treat most of the construction wastewater generated by tunnel construction using the exhaust gas recovered from Tunnel T.

[0022] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and each of the above-described components can be modified as appropriate within the scope of the invention. For example, in the above embodiment, the carbon dioxide gas G1 extracted in the exhaust gas plant 31 (carbon dioxide gas extraction means 34) is supplied to the neutralization tank 2, but the exhaust gas G0 may be supplied directly to the neutralization tank 2. In this case, the carbon dioxide gas extraction means 34 can be omitted, thereby simplifying the exhaust gas plant 31. Furthermore, when the exhaust gas G0 is supplied to the neutralization tank 2, the exhaust gas plant 31 may be omitted by connecting the exhaust gas duct 33 to the neutralization tank 2. Moreover, the gas supply means 61 may be provided as needed. [Explanation of symbols]

[0023] 1. Wastewater treatment system 2 Neutralization tank 3 Gas supply means 31 Exhaust Gas Plant 32 Gas transmission pipe 33 Exhaust gas duct 34 Carbon dioxide extraction means 4. Soundproof doors 5 Air supply duct 51 Blower 6 pH measurement methods 61 Gas supply means A. Air G0 Exhaust gas G1 Carbon dioxide T-Tunnel W0 Construction drainage W1 treated water

Claims

[Claim 1] An exhaust gas recovery process for recovering exhaust gas from inside a tunnel during tunnel construction and transporting the exhaust gas to an exhaust gas plant equipped with a carbon dioxide gas extraction means outside the tunnel; A construction wastewater recovery process for recovering construction wastewater discharged from inside and outside the tunnel due to the tunnel construction; a carbon dioxide extraction step of extracting carbon dioxide from the exhaust gas in the exhaust gas plant; A wastewater neutralization method characterized by comprising a gas supplying step of supplying the carbon dioxide gas and the construction wastewater to a neutralization tank that performs neutralization treatment of the construction wastewater.

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