System and method for treating LNAPL polluted underground water

Abstract

A system for treating LNAPL polluted underground water comprises a dissolved phase treatment space, a first LNAPL phase separation space and a treated underground water space, the first LNAPL phase separation space and the treated underground water space are arranged on the two sides of the dissolved phase treatment space respectively, and filter material spaces are arranged on the sides, opposite to the dissolved phase treatment space, of the first LNAPL phase separation space and the treated underground water space. The filter material space, the first LNAPL phase separation space, the dissolved phase treatment space and the treated underground water space are communicated through sieve plates; the partition plate area is used for preventing LNAPL phase pollutants floating above a water layer of the first LNAPL phase separation space from flowing to the dissolved phase treatment space; the first combined sieve plate is arranged to block floating LNAPL phase pollutants, and the LNAPL phase extraction module is arranged to extract the floating LNAPL phase, so that the amount of the floating LNAPL phase entering a dissolved phase treatment space is reduced, and the service life of an active filler in the dissolved phase treatment space is prolonged.

Description

Technical Field

[0001] The present invention relates to the field of remediation and risk control of contaminated groundwater in sites, and specifically to a system and method for treating LNAPL-contaminated groundwater. Background Art

[0002] Light Non-Aqueous Phase Liquid (LNAPL) refers to a liquid that is insoluble in water and has a density less than that of water. Most LNAPLs are petroleum-based; during oil exploration, storage, transportation, and processing, leakage incidents are inevitable. Oil leaked on the ground surface or underground pipelines will penetrate the soil and contaminate groundwater under the action of its own gravity, capillary force, surface water, or rainwater leaching, thus causing a larger area of pollution. Moreover, most LNAPL pollutants can directly affect human health, and some substances even have "carcinogenic, teratogenic, and mutagenic effects".

[0003] Currently, the main ex-situ treatment technologies for LNAPL pollution are: pumping and treatment technology. In practical engineering applications, when using this technology, extraction wells and above-ground treatment systems need to be built at the site where the contaminated groundwater is located. However, the precise extraction effect of this technology on pollutants is not good, and it will extract groundwater together, resulting in a relatively high disposal cost. Moreover, the setting of extraction wells is also a major problem.

[0004] In-situ treatment technologies for LNAPL pollution include: recirculation well technology, in-situ bioremediation technology, in-situ heat treatment technology, biosparging technology, in-situ chemical oxidation technology, and permeable reactive barrier technology. Among the above technologies, the permeable reactive barrier technology is considered the most cost-effective technology for reducing, intercepting, and remediating pollutants in groundwater. This technology is to construct a wall composed of reactive filler materials downstream of the contaminated groundwater. The key point of this technology is to construct a wall in the underground aquifer, and this wall is composed of reactive materials. When water flows through this wall, the pollutants carried in the groundwater will react with the reactive materials in the wall, reducing the concentration of pollutants in the water, thereby remediating the groundwater.

[0005] In traditional permeable reactive barrier technology, contaminated groundwater is usually directly introduced into the reactive filler wall to treat dissolved pollutants in the groundwater; however, when treating relatively severe LNAPL pollution, the free phase will penetrate the upper filler layer, resulting in a reduced service life of the reactive filler and frequent replacement of the filler, leading to an increase in disposal costs. Therefore, it is necessary to improve the permeable reactive barrier technology so that it can treat contaminated groundwater for a long time, avoid upper layer penetration, and extend the service life of the reactive filler. Summary of the Invention

[0006] The present invention aims to provide a system for treating LNAPL - contaminated groundwater to improve the permeable reactive barrier technology, thereby extending the service life of the active packing material.

[0007] To solve the above - mentioned technical problems, the specific solution adopted by the present invention is as follows:

[0008] A system for treating LNAPL - contaminated groundwater, comprising a dissolved - phase treatment space, a first LNAPL - phase separation space and a treated - groundwater space respectively arranged on both sides of the dissolved - phase treatment space. Filter - material spaces are provided on the sides of the first LNAPL - phase separation space and the treated - groundwater space that are opposite to the dissolved - phase treatment space. The filter - material space, the first LNAPL - phase separation space, the dissolved - phase treatment space and the treated - groundwater space are all connected through sieve plates. The sieve plate at the connection between the first LNAPL - phase separation space and the dissolved - phase treatment space adopts a first combined sieve plate. The first combined sieve plate is provided with a sieve - hole area and a partition area located above the sieve - hole area. The partition area is used to block the flow of LNAPL - phase pollutants floating above the water layer in the first LNAPL - phase separation space into the dissolved - phase treatment space.

[0009] An LNAPL - phase extraction module is provided on the first LNAPL - phase separation space. The LNAPL - phase extraction module includes a first oil - water interface sensor and an LNAPL - phase extraction metering pump arranged in the first LNAPL - phase separation space. The LNAPL - phase extraction metering pump is connected to an LNAPL - phase collection barrel, and the LNAPL - phase collection barrel is used to collect the LNAPL - phase pollutants extracted by the LNAPL - phase extraction metering pump from the first LNAPL - phase separation space.

[0010] An LNAPL - phase transfer pump is provided on the LNAPL - phase collection barrel for pumping out the LNAPL - phase pollutants in the LNAPL - phase collection barrel.

[0011] A water - replenishing module is provided on the treated - groundwater space for replenishing water to the first LNAPL - phase separation space. The water - replenishing module includes a water - replenishing metering pump. The water inlet of the water pipe of the water - replenishing metering pump is located at the bottom of the treated - groundwater space, and the water outlet of the water pipe of the water - replenishing metering pump is located at the bottom of the first LNAPL - phase separation space.

[0012] A second LNAPL - phase separation space is provided between the first LNAPL - phase separation space and the dissolved - phase treatment space. A second combined sieve plate is provided between the second LNAPL - phase separation space and the dissolved - phase treatment space, and the second combined sieve plate has the same structure as the first combined sieve plate.

[0013] A second oil - water interface sensor is provided in the second LNAPL - phase separation space, and the second oil - water interface sensor is arranged 5 - 30 cm below the partition area.

[0014] The first oil-water interface sensor, the second oil-water interface sensor, the make-up water metering pump, and the LNAPL phase extraction metering pump are all connected to the computer control system by signals.

[0015] The height of the baffle area is 30 - 40 cm.

[0016] The first oil-water interface sensor is arranged 5 - 30 cm below the baffle area.

[0017] The dissolved phase treatment space is a packing layer, and the packing in the packing layer is adsorptive activated packing or microbial degradation type material.

[0018] The adsorptive activated packing is activated carbon, molecular sieve, or fly ash.

[0019] A method for treating LNAPL-contaminated groundwater. For the system for treating LNAPL-contaminated groundwater, the specific method is as follows: Install the system for treating LNAPL-contaminated groundwater downstream of the pollution plume, make the first LNAPL phase separation space located in the upstream direction of the groundwater flow direction, enable the LNAPL-phase contaminated groundwater to pass through the filter media space, the first LNAPL phase separation space, the dissolved phase treatment space, the treated groundwater space, and the filter media space in sequence, and extract the LNAPL-phase pollutants blocked by the baffle area.

[0020] The LNAPL-phase pollutants located in the first LNAPL phase separation space are pumped into the LNAPL phase collection bucket by the LNAPL phase extraction metering pump, and the LNAPL-phase pollutants in the LNAPL phase collection bucket are sent to the waste treatment site for centralized treatment by the LNAPL phase transfer pump.

[0021] The treated groundwater space is supplemented into the first LNAPL phase separation space by the make-up water metering pump to prevent the groundwater in the dissolved phase treatment space from flowing back when the LNAPL-phase pollutants are extracted.

[0022] Due to the adoption of the above technical solutions, the present invention has the following beneficial effects: By setting the first combined sieve plate to block the floating LNAPL-phase pollutants, by setting the LNAPL phase extraction module to extract and treat the floating LNAPL phase, reducing its entry into the dissolved phase treatment space, thereby prolonging the service life of the activated packing in the dissolved phase treatment space; By setting the make-up water module to supplement the water in the treated groundwater space into the first LNAPL phase separation space to prevent the groundwater in the dissolved phase treatment space from flowing back; By setting the second LNAPL phase separation space beside the first LNAPL phase separation space to work instead of the first oil-water interface sensor when the first oil-water interface sensor fails. Description of the Drawings

[0023] Figure 1 Schematic diagram of the structure of Embodiment 1 of the present invention;

[0024] Figure 2 Schematic diagram of the structure of Embodiment 2 of the present invention;

[0025] Figure 3 Schematic diagram of the structure of the first combined sieve plate and the second combined sieve plate of the present invention;

[0026] Figure 4 Schematic diagram of the sieve plate structure adopted in the prior art;

[0027] 1. Filter material space; 2. First oil-water interface sensor; 3. Signal transmitter; 4. Computer control system; 5. Make-up water metering pump; 6. LNAPL phase extraction metering pump; 7. LNAPL phase collection bucket; 8. LNAPL phase transfer pump; 9. First LNAPL phase separation space; 10. First combined sieve plate; 11. Dissolved phase treatment space; 12. Treated groundwater space; 14. Second oil-water interface sensor; 15. Second signal transmitter; 16. Second LNAPL phase separation space; 17. Second combined sieve plate; 18. Partition area; 19. Sieve hole area. Detailed implementation manners

[0028] The usage method of the present invention is briefly described through the following two embodiments:

[0029] Embodiment 1:

[0030] As Figure 1 shown, the arrangement order of each space is arranged in sequence along the flow direction of the contaminated groundwater, which are: filter material space 1, first LNAPL phase separation space 9, dissolved phase treatment space 11, treated groundwater space 12 and filter material space 1. Each space is connected through a sieve plate. After the contaminated groundwater is filtered through the filter material space 1, it enters the first LNAPL phase separation space 9. Since the density of the LNAPL phase pollutant is less than the density of water, the pollutant in the first LNAPL phase separation space 9 will float. The sieve plate at the connection between the first LNAPL phase separation space 9 and the dissolved phase treatment space 11 adopts the first combined sieve plate 10.

[0031] As Figure 3As shown, the structure of the first combined sieve plate 10 is a plate-like structure. The first combined sieve plate 10 is respectively provided with a sieve hole area 19 and a partition area 18. The partition area 18 is located above the sieve hole area 19. The height of the partition area 18 is 10 - 60 cm. The partition area 18 is mainly used to isolate the LNAPL-phase pollutants floating above the water surface. The partition area 18 can effectively reduce the entry of LNAPL pollutants into the dissolved-phase disposal space 11. The sieve hole area 19 below the partition area 18 is mainly used for the contaminated groundwater to pass through the sieve hole area 19 and enter the dissolved-phase disposal space 11. In this way, by reducing the entry of LNAPL-phase pollutants into the dissolved-phase disposal space 11, the service life of the packing in the dissolved-phase disposal space 11 can be effectively extended.

[0032] An LNAPL-phase extraction module is provided on the first LNAPL-phase separation space 9. The LNAPL-phase extraction module includes a first oil-water interface sensor 2 and an LNAPL-phase extraction metering pump 6 provided in the first LNAPL-phase separation space 9. The LNAPL-phase extraction metering pump 6 is signal-connected to the computer control system 4. The LNAPL-phase extraction metering pump 6 is mainly controlled by the computer control system 4. The end of the water inlet pipe of the LNAPL-phase extraction metering pump 6 is located in the first LNAPL-phase separation space 9 and is 2 - 10 cm higher than the first oil-water interface sensor 2. The water outlet pipe of the LNAPL-phase extraction metering pump 6 is connected to the LNAPL-phase collection bucket 7. The LNAPL-phase collection bucket 7 is used to collect the LNAPL-phase pollutants extracted by the LNAPL-phase extraction metering pump 6 from the first LNAPL-phase separation space 9. An LNAPL-phase transfer pump 8 is also provided on the LNAPL-phase collection bucket 7. The LNAPL-phase transfer pump 8 is mainly used to transport the LNAPL-phase pollutants in the LNAPL-phase collection bucket 7 to the waste treatment site for disposal. The top end face of the first combined sieve plate is higher than the liquid level in the first LNAPL-phase separation space 9. The first oil-water interface sensor 2 is arranged 5 - 30 cm below the partition area 18. When the LNAPL-phase pollutants accumulate too much and exceed the partition area 18, the first oil-water interface sensor 2 will detect it in the first time. A first signal transmitter 3 is provided on the first oil-water interface sensor 2 to transmit the signal to the computer control system 4, and the computer control system 4 starts the LNAPL-phase extraction metering pump 6 to work.

[0033] A water replenishing module for replenishing water to the first LNAPL phase separation space 9 is provided on the treated groundwater space 12. The water replenishing module includes a water replenishing metering pump 5. The water replenishing metering pump 5 is signal-connected to the computer control system 4 and is controlled by the computer control system 4. When the LNAPL phase extraction metering pump 6 extracts a certain amount of LNAPL phase pollutants, the computer control system 4 will control the water replenishing metering pump 5 to replenish the corresponding water to the first LNAPL phase separation space 9. This water is extracted from the treated groundwater space 12. Therefore, by replenishing this water, the working intensity of the dissolved phase treatment space 11 can be reduced. The water inlet of the water pipe of the water replenishing metering pump 5 is located at the bottom of the treated groundwater space 12 and is 10-20 cm away from the bottom. The water outlet of the water pipe of the water replenishing metering pump 5 is located at the bottom inside the first LNAPL phase separation space 9 and is away from the bottom.

[0034] The dissolved phase treatment space 11 is a packing layer, and the packing in the packing layer is adsorbent activated packing or microbial degradation type material. The adsorbent activated packing is activated carbon, molecular sieve or fly ash. The activated packing can use a single one of activated carbon, molecular sieve or fly ash, or can use a variety of composite packings. The microbial degradation type material can be specific degradation bacteria screened and mutagenized for characteristic pollutants.

[0035] The specific usage method of Example 1 is briefly described as follows:

[0036] Install the system for treating LNAPL-polluted groundwater downstream of the pollution plume, so that the first LNAPL phase separation space 9 is located upstream in the direction of groundwater flow. The groundwater polluted by the LNAPL phase first passes through the filter media space 1. The polluted water filtered through the filter media space 1 enters the first LNAPL phase separation space 9. Since the density of the LNAPL phase itself is less than that of water, the LNAPL phase pollutants in the first LNAPL phase separation space 9 will float above the water layer. When the LNAPL phase pollutants contact the first oil-water interface sensor 2, the first oil-water interface sensor 2 transmits the signal to the computer control system 4 through the first signal transmitter 3. The polluted water below the LNAPL phase pollutants will enter the dissolved phase treatment space 11 through the sieve hole area 19 on the first combined sieve plate 10, while the LANPL phase pollutants floating above the sieve hole area 19 will be evacuated by the computer control system 4 sending an instruction to the LNAPL phase extraction metering pump 6. Thus, the filtration pressure of the dissolved phase treatment space 11 can be reduced. The LNAPL phase pollutants extracted from the first LNAPL phase separation space 9 will enter the LNAPL phase collection bucket 7 and be stored in the LNAPL phase collection bucket 7 and then sent to the waste treatment site for centralized treatment of the LNAPL phase. The polluted water passing through the dissolved phase treatment space 11 enters the treated groundwater space 12 and can be discharged after being filtered through the adjacent filter media space 1.

[0037] After treatment, the groundwater space 12 continuously replenishes the first LNAPL phase separation space 9 through the water replenishment module to control the water level in the first LNAPL phase separation space 9, thereby preventing the groundwater in the dissolved phase treatment space 11 from flowing back. The water replenishment metering pump 5 is controlled by the computer control system 4. When the LNAPL phase extraction metering pump 6 extracts a certain volume of LNAPL phase pollutants, the computer control system 4 will synchronously control the water replenishment metering pump 5 to replenish the corresponding volume of water into the first LNAPL phase separation space 9.

[0038] Embodiment 2:

[0039] As Figure 2 shown, different from Embodiment 1, a second LNAPL phase separation space 16 is provided between the first LNAPL phase separation space 9 and the dissolved phase treatment space 11. The first LNAPL phase separation space 9 and the second LNAPL phase separation space 16 are separated by the first combined sieve plate 10; the second LNAPL phase separation space 16 and the dissolved phase treatment space 11 are separated by the second combined sieve plate 17, and the first combined sieve plate 10 and the second combined sieve plate 17 have the same structure. The second LNAPL phase separation space 16 is equipped with a second oil-water interface sensor 14, which has the same structure as the first oil-water interface sensor 2. The second oil-water interface sensor 14 in the second LNAPL phase separation space is connected to the computer control system 4 through the second signal transmitter 15; at the same time, the second LNAPL phase separation space 16 is provided with a water extraction pipeline connected to the LNAPL phase extraction metering pump 6; the installation positions of the second oil-water interface sensor 14, the extraction pipeline and the delivery pipeline of the water replenishment module in the second LNAPL phase separation space 16 are the same as those in the first LNAPL phase separation space 9.

[0040] The specific usage method of Embodiment 2 is briefly described as follows:

[0041] When designed according to Embodiment 2, when LNAPL phase pollution occurs, the LNAPL-polluted groundwater first passes through the filter media space 1. The filter media space 1 filters the sediment in the polluted groundwater and at the same time plays a role in dispersing the water flow. Subsequently, the LNAPL-polluted groundwater enters the first LNAPL phase separation space 9. In the polluted groundwater in the first LNAPL phase separation space 9, due to the relatively low density of the LNAPL phase, stratification occurs. When the lower layer of the LNAPL phase reaches the detection surface of the first oil-water interface sensor 2, the first oil-water interface sensor 2 sends a signal to the computer control system 4 through the first signal transmitter 3. The computer control system 4 issues control instructions to the LNAPL phase extraction metering pump 6 and the makeup water metering pump 5. The LNAPL phase extraction metering pump 6 extracts the LNAPL pollutants to the LNAPL phase collection bucket 7, and the makeup water metering pump 5 simultaneously extracts the treated groundwater with the same volume as the LNAPL phase extraction metering pump 6 from the treated groundwater space 12 and injects it into the first LNAPL phase separation space 9 to maintain the liquid level height of the first LNAPL phase separation space 9. The pollutants entering the LNAPL phase collection bucket 7 are sent to the waste treatment site for centralized disposal under the action of the LNAPL phase transfer pump 8.

[0042] When a large amount of LNAPL phase leaks or the first oil-water interface sensor 2 in the first LNAPL phase separation space 9 fails, the LNAPL phase enters the second LNAPL phase separation space 16. When the lower layer of the LNAPL phase reaches the detection surface of the second oil-water interface sensor 14, the second oil-water interface sensor 14 sends a signal to the second signal transmitter 15, and at the same time the information is transmitted to the computer control system 4. The computer control system 4 issues control instructions to the LNAPL phase extraction metering pump 6 and the makeup water metering pump 5. The LNAPL phase extraction metering pump 6 extracts the LNAPL pollutants into the LNAPL phase collection bucket 7, and the makeup water metering pump 5 simultaneously extracts the treated groundwater with the same volume as the LNAPL phase extraction metering pump 6 from the treated groundwater space 12 and injects it into the second LNAPL phase separation space 16 to maintain the liquid level height of the second LNAPL phase separation space 16.

[0043] In the second LNAPL phase separation space 16, the water body dissolved in the groundwater in the lower part enters the dissolved phase treatment space 11. Under the action of the composite material composed of the adsorbent activated carbon and specific degradation bacteria, the pollutants dissolved in the water are treated. The treated groundwater passes through the treated groundwater space 12 and the filter media in sequence, and the groundwater passing through the filter media can meet the standards for discharge.

Claims

1. A system for treating LNAPL - contaminated groundwater, comprising a dissolved - phase treatment space (11), a first LNAPL - phase separation space (9) and a treated - groundwater space (12) respectively arranged on two sides of the dissolved - phase treatment space (11). A filter - media space (1) is provided on the side of the first LNAPL - phase separation space (9) and the treated - groundwater space (12) that is opposite to the dissolved - phase treatment space (11). The filter - media space (1), the first LNAPL - phase separation space (9), the dissolved - phase treatment space (11) and the treated - groundwater space (12) are all connected through sieve plates. It is characterized in that: The sieve plate at the connection between the first LNAPL phase separation space (9) and the dissolved phase treatment space (11) adopts a first combined sieve plate (10). The first combined sieve plate (10) is provided with a sieve hole area (19) and a partition area (18) located above the sieve hole area (19). The partition area (18) is used to block the flow of LNAPL phase pollutants floating above the water layer in the first LNAPL phase separation space (9) to the dissolved phase treatment space (11).

2. The system for treating LNAPL-contaminated groundwater according to claim 1, characterized in that: An LNAPL phase extraction module is provided on the first LNAPL phase separation space (9). The LNAPL phase extraction module includes a first oil-water interface sensor (2) and an LNAPL phase extraction metering pump (6) arranged in the first LNAPL phase separation space (9). The LNAPL phase extraction metering pump (6) is connected to an LNAPL phase collection bucket (7). The LNAPL phase collection bucket (7) is used to collect the LNAPL phase pollutants extracted by the LNAPL phase extraction metering pump (6) from the first LNAPL phase separation space (9).

3. The system for treating LNAPL-contaminated groundwater according to claim 2, characterized in that: An LNAPL phase transfer pump (8) is provided on the LNAPL phase collection bucket (7) for extracting the LNAPL phase pollutants in the LNAPL phase collection bucket (7).

4. The system for treating LNAPL-contaminated groundwater according to claim 2, characterized in that: A water replenishment module is provided on the treated groundwater space (12) for replenishing water to the first LNAPL phase separation space (9). The water replenishment module includes a water replenishment metering pump (5). The water inlet of the water pipe of the water replenishment metering pump (5) is located at the bottom of the treated groundwater space (12), and the water outlet of the water pipe of the water replenishment metering pump (5) is located at the bottom in the first LNAPL phase separation space (9).

5. The system for treating LNAPL-contaminated groundwater according to claim 4, characterized in that: A second LNAPL phase separation space (16) is provided between the first LNAPL phase separation space (9) and the dissolved phase treatment space (11). A second combined sieve plate (17) is provided between the second LNAPL phase separation space (16) and the dissolved phase treatment space (11). The second combined sieve plate (17) has the same structure as the first combined sieve plate (10).

6. The system for treating LNAPL-contaminated groundwater according to claim 5, characterized in that: A second oil-water interface sensor (14) is provided in the second LNAPL phase separation space (16). The second oil-water interface sensor (14) is arranged 5 - 30 cm below the partition area (18).

7. The system for treating LNAPL-contaminated groundwater according to claim 6, characterized in that: The first oil-water interface sensor (2), the second oil-water interface sensor (14), the water replenishment metering pump (5), and the LNAPL phase extraction metering pump (6) are all signal-connected to the computer control system (4).

8. The system for treating LNAPL-contaminated groundwater according to claim 1, characterized in that: The height of the partition area (18) is 30 - 40 cm.

9. The system for treating LNAPL-contaminated groundwater according to claim 1, characterized in that: The first oil-water interface sensor (2) is arranged 5 - 30 cm below the partition area (18).

10. The system for treating LNAPL-contaminated groundwater according to claim 1, characterized in that: The dissolved phase treatment space (11) is a packing layer, and the packing in the packing layer is adsorptive activated packing or microbial degradation type material.

11. The system for treating LNAPL-contaminated groundwater according to claim 10, characterized in that: The adsorptive activated packing is activated carbon, molecular sieve, or fly ash.

12. A method for treating LNAPL-contaminated groundwater, characterized in that: Adopt the system for treating LNAPL - contaminated groundwater according to any one of claims 1 to 11. The specific method is as follows: Install the system for treating LNAPL - contaminated groundwater downstream of the pollution plume, so that the first LNAPL phase separation space (9) is located in the upstream direction of the groundwater flow direction, and make the groundwater contaminated by the LNAPL phase sequentially pass through the filter media space (1), the first LNAPL phase separation space (9), the dissolved - phase treatment space (11), the treated - groundwater space (12) and the filter media space (1), and extract the LNAPL - phase pollutants blocked by the baffle area (18).

13. The method for treating LNAPL-contaminated groundwater according to claim 12, wherein: Extract the LNAPL - phase pollutants in the first LNAPL phase separation space (9) into the LNAPL - phase collection barrel (7) through the LNAPL - phase extraction metering pump (6), and send the LNAPL - phase pollutants in the LNAPL - phase collection barrel (7) to the waste treatment site for centralized treatment by the LNAPL - phase transfer pump (8).

14. The method for treating LNAPL-contaminated groundwater according to claim 12, characterized in that: Supplement the treated - groundwater space (12) into the first LNAPL phase separation space (9) through the makeup water metering pump (5) to prevent the groundwater in the dissolved - phase treatment space (11) from flowing back when the LNAPL - phase pollutants are extracted.

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