Filler for repairing chlorinated hydrocarbon pollution and method for repairing chlorinated hydrocarbon polluted underground water by using filler

Abstract

The invention discloses a filler for repairing chlorinated hydrocarbon pollution and a method for repairing chlorinated hydrocarbon polluted underground water by using the filler. The filler is prepared from the following components in percentage by mass: 65-85% of coarse sand, 1-10% of magnetite, 1-5% of groundwater polluted by chlorinated hydrocarbon, 1-5% of wheat bran, 1-5% of coarse gypsum, 1-5% of ferrous sulfate and 1-5% of limestone. The raw materials of the filler are industrial finished products, are low in price and are suitable for actual site repair. The method for repairing chlorohydrocarbon polluted underground water through biogeochemical conversion by using the filler does not need high temperature and high pressure, and the reaction condition is mild. The used filler and emulsified vegetable oil have the advantages of high safety and environmental friendliness, and do not cause secondary pollution to the underground environment. The generation and accumulation of incomplete dechlorination intermediate products can be obviously reduced, so that the chlorinated hydrocarbon can be completely dechlorinated.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of fillers for repairing chlorinated hydrocarbon pollution and its method for repairing chlorinated hydrocarbon pollution groundwater, belong to soil and groundwater remediation field. BACKGROUND

[0002] Chlorinated hydrocarbon is commonly used chemical raw material and organic solvent, is common groundwater characteristic pollutant. Most chlorinated hydrocarbons have the characteristics of low viscosity, high density, low water solubility, strong hydrophobicity, migrate to aquifer bottom under gravity and form persistent pollution, high control difficulty, high cost. In recent years, due to industrial enterprise relocation or closure, part of chlorinated hydrocarbon contaminated sites have been generated, which threatens human health and causes environmental pollution. Chlorinated hydrocarbon contaminated soil and groundwater has become a research hotspot of pollution prevention and control.

[0003] At present, for aquifer chlorinated hydrocarbon pollution, mainly adopts extraction treatment method, due to low viscosity of chlorinated hydrocarbon, strong hydrophobicity, poor fluidity, difficult to completely extract, easy to remain in soil and groundwater. If in-situ chemical oxidation method is used, there are problems of producing toxic intermediate products and secondary pollution. In-situ biogeochemical transformation can repair chlorinated hydrocarbon contaminated groundwater in-situ, with lower cost, and no toxic intermediate products and secondary pollution. SUMMARY

[0004] The purpose of the present application is to provide a filler for repairing chlorinated hydrocarbon pollution and its specific application method.

[0005] Technical scheme: The filler for repairing chlorinated hydrocarbon pollution prepared by the present application is prepared from the following ingredients and mass fraction: coarse sand 65% to 85%, magnetite 1% to 10%, root protection 1% to 5%, wheat bran 1% to 5%, coarse gypsum 1% to 5%, ferrous sulfate 1% to 5%, and limestone 1% to 5%.

[0006] Further, the filler for repairing chlorinated hydrocarbon pollution is prepared from the following ingredients and mass fraction: coarse sand 80% to 85%, magnetite 5% to 10%, root protection 1% to 5%, wheat bran 1% to 5%, coarse gypsum 1% to 5%, ferrous sulfate 1% to 5%, and limestone 1% to 5%.

[0007] The method for repairing chlorinated hydrocarbon contaminated groundwater by biogeochemical transformation according to the present application comprises the following steps:

[0008] (1) In the chlorinated hydrocarbon contaminated groundwater area, dig a pit to the corresponding pollution depth, backfill with the filler of claim 1 to form a filler layer, lay a gravel layer on the upper part of the filler layer, embed the backflow branch pipe in the gravel layer, cover the geotextile on the upper part of the gravel layer, and then cover the soil to the ground level; construct a groundwater extraction well downstream of the chlorinated hydrocarbon contaminated area and place a submersible pump in the well, and construct a groundwater injection well upstream;

[0009] (2) Mix sodium dodecyl sulfate, soybean oil and water thoroughly to prepare emulsified vegetable oil; inject the emulsified vegetable oil into the filler layer to make the filler layer in an anaerobic environment;

[0010] (3) Groundwater is extracted through the groundwater extraction well, part of which is injected into the groundwater injection well upstream to enhance the flow of groundwater; part of which enters the filler area for remediation.

[0011] The thickness of the filler layer in step (1) is 20-30 cm, the pipe diameter of the backflow branch pipe is 50-100 cm, the backflow branch pipe is obliquely downwardly perforated at intervals of 30-40 cm, and the hole diameter is 5-10 mm.

[0012] The pipe diameter of the groundwater extraction well in step (1) is DN200 mm, and the pipe diameter of the groundwater injection well is DN100 mm.

[0013] The groundwater extraction well in step (1) is connected to the groundwater injection well through the groundwater extraction main pipe and the groundwater extraction branch pipe 6; the groundwater extraction well is also connected to the filler layer through the groundwater extraction main pipe and the backflow main pipe.

[0014] The mass fraction of sodium dodecyl sulfate and soybean oil in step (2) is mixed in equal proportion, and the mass fraction of the mixture in the emulsified vegetable oil is 1-2%.

[0015] The injection amount of the emulsified vegetable oil in step (2) is half of the porosity of the filler layer.

[0016] During the remediation of groundwater, the dissolved oxygen in the groundwater is detected every 3-5 days, and when the dissolved oxygen concentration rises, the emulsified vegetable oil is supplemented in time.

[0017] The chlorinated hydrocarbon contaminated groundwater includes one or more of chloroform, dichloromethane and chloroethylene pollution.

[0018] Beneficial effects: Compared with the prior art, the present application has the following remarkable advantages: the filler raw material of the present application is an industrialized product with low price, and is suitable for actual site repair. The method for repairing chlorinated hydrocarbon contaminated groundwater by using the filler and the biogeochemical transformation has no need for high temperature and high pressure, and the reaction conditions are mild. The filler and the emulsified vegetable oil component used are safe and environmentally friendly, and will not cause secondary pollution to the underground environment. The generation and accumulation of non-complete dechlorination intermediates can be significantly reduced, and the chlorinated hydrocarbon can be completely dechlorinated. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The present application is a schematic diagram of a biogeochemical transformation system for repairing chlorinated hydrocarbon contaminated groundwater. DETAILED DESCRIPTION

[0020] The technical solutions of the present application will be further described below in combination with the drawings.

[0021] Example 1: Establishment of a method for repairing chlorinated hydrocarbon contaminated groundwater by biogeochemical transformation

[0022] (1) A pit is dug to the corresponding pollution depth in the chlorinated hydrocarbon contaminated groundwater area, and the pit is backfilled with the filler to form a filler layer 3. A gravel layer is laid on the upper part of the filler layer, and a backflow branch pipe 9 is laid in the gravel layer. A geotextile 10 is laid on the upper part of the gravel layer, and soil is covered to the ground level. A groundwater extraction well 1 is constructed downstream of the chlorinated hydrocarbon contaminated area, and a submersible pump is placed in the well. A groundwater injection well 2 is constructed upstream. A water injection control valve 8 is also provided on the groundwater extraction branch pipe 6;

[0023] The groundwater extraction main pipe 4 is also connected to the backflow branch pipe 9 through a backflow main pipe 5. A backflow pipe control valve 7 is provided at the upper end of the backflow main pipe 5, and an emulsified vegetable oil main pipe 12 is connected to the backflow main pipe 5 below the backflow pipe control valve 7. An emulsified vegetable oil control valve 13 is provided at the front end of the emulsified vegetable oil main pipe 12;

[0024] The thickness of the filler layer is 20-30 cm. The backflow pipe laid in the gravel layer has a pipe diameter of 50-100 cm, and is obliquely downwardly perforated at intervals of 30-40 cm with a hole diameter of 5-10 mm.

[0025] (2) Preparation of emulsified vegetable oil in a reactor: mix sodium dodecyl sulfate and soybean oil in a certain ratio, and then mix the mixture with water thoroughly. Sodium dodecyl sulfate is an anionic surfactant that can resist alkalinity.

[0026] The emulsified vegetable oil is delivered to the emulsified vegetable oil main pipe 12 by gravity flow. At this time, the emulsified vegetable oil control valve 13 is opened, and the backflow pipe control valve 7 is closed. The emulsified vegetable oil is injected into the filler layer 3 through the emulsified vegetable oil main pipe 12 and the backflow branch pipe 9, so that the filler layer is in an anaerobic environment.

[0027] The mixture of sodium lauryl sulfate and soybean oil accounts for 1-2% of the mass of the emulsified vegetable oil;

[0028] The filler porosity ranges from 20% to 25%, and the amount of emulsified vegetable oil injected is half the porosity of the filler layer;

[0029] (3) Groundwater is extracted through the groundwater extraction well. After some groundwater is extracted, it is injected into the upstream groundwater injection well through the groundwater extraction main pipe 4 and the groundwater extraction branch pipe 6 to enhance the flow of groundwater. After some groundwater is extracted, it enters the filling area for repair through the groundwater extraction main pipe 4, the return main pipe 5 and the return branch pipe 9. At this time, the water injection control valve 8 is closed, the emulsified vegetable oil control valve 13 is closed and the return pipe control valve 7 is opened.

[0030] During groundwater remediation, dissolved oxygen levels in the groundwater are monitored every 3-5 days. When the dissolved oxygen concentration rises, emulsified vegetable oil is added promptly.

[0031] Example 2

[0032] The following describes the implementation of the present invention on a groundwater site contaminated with chlorinated hydrocarbons. The contaminated area was divided into three zones, and the contamination level in each zone was tested to be no more than 10%. Subsequently, different ratios of remediation agents were used as comparative examples to implement the project and calculate the removal rate of chlorinated hydrocarbons.

[0033] (1) The groundwater contaminated area with chlorinated hydrocarbons is 5m × 5m, with a contamination depth of 4m. Coarse sand, magnetite, root protection, wheat bran, coarse gypsum, ferrous sulfate, and limestone are mixed. The mass fraction of the above filler is: coarse sand 85%, magnetite 5%, root protection 3%, wheat bran 3%, coarse gypsum 1%, ferrous sulfate 1%, and limestone 2%. A 30cm thick layer of gravel is laid on top of the filler, with return drainage branch pipes buried in the middle of the gravel. The main return drainage pipe is DN80mm, and the branch pipes are DN50mm. Based on the porosity of the filler area being 20%, the emulsified vegetable oil injection volume is approximately half the porosity, which is 10m³. 3 Sodium dodecyl sulfate and soybean oil each accounted for 1% of the total mass, with the remainder being water. The injection flow rate of the emulsified vegetable oil was 100 L / h. The groundwater extraction well diameter was DN200 mm, and the groundwater injection well diameter was DN100 mm. The groundwater extraction flow rate was 200 L / h, the groundwater injection flow rate was 80 L / h, and the main refluxing flow rate was 80 L / h. After 60 days of remediation, the removal rates of chloroform, dichloromethane, and vinyl chloride concentrations in the groundwater are shown in the table below.

[0034] Table 1 Removal rate of chlorinated hydrocarbons in groundwater

[0035]

[0036] (2) The groundwater contaminated area with chlorinated hydrocarbons is 5m × 5m, with a contamination depth of 4m. Coarse sand, magnetite, root protection, wheat bran, coarse gypsum, ferrous sulfate, and limestone are mixed. The mass fraction of the above filler is: coarse sand 81%, magnetite 5%, root protection 3%, wheat bran 3%, coarse gypsum 1%, ferrous sulfate 5%, and limestone 2%. A 30cm thick layer of gravel is laid on top of the filler, with return drainage branch pipes buried in the middle of the gravel. The main return drainage pipe is DN80mm, and the branch pipes are DN50mm. Based on the porosity of the filler area being 20%, the emulsified vegetable oil injection volume is approximately half the porosity, which is 10m³. 3 Sodium dodecyl sulfate and soybean oil each accounted for 1% of the total mass, with the remainder being water. The injection flow rate of the emulsified vegetable oil was 100 L / h. The groundwater extraction well diameter was DN200 mm, and the groundwater injection well diameter was DN100 mm. The groundwater extraction flow rate was 200 L / h, the groundwater injection flow rate was 80 L / h, and the main refluxing flow rate was 80 L / h. After 60 days of remediation, the removal rates of chloroform, dichloromethane, and vinyl chloride concentrations in the groundwater are shown in the table below.

[0037] Table 2 Removal rate of chlorinated hydrocarbons in groundwater

[0038]

[0039] Compared with the results of (1), it is shown that increasing the content of ferrous sulfate can increase the content of ferrous sulfide, which can effectively increase the removal rate of chlorinated hydrocarbons.

[0040] (3) The groundwater contaminated area with chlorinated hydrocarbons is 5m × 5m, with a contamination depth of 4m. Coarse sand, magnetite, root protection, wheat bran, coarse gypsum, ferrous sulfate, and limestone are mixed. The mass fraction of the above filler is: coarse sand 80%, magnetite 10%, root protection 3%, wheat bran 3%, coarse gypsum 1%, ferrous sulfate 1%, and limestone 2%. A 30cm thick layer of gravel is laid on top of the filler, with return drainage branch pipes buried in the middle of the gravel. The main return drainage pipe is DN80mm, and the branch pipes are DN50mm. Based on the porosity of the filler area being 20%, the emulsified vegetable oil injection volume is approximately half the porosity, which is 10m³. 3 Sodium dodecyl sulfate and soybean oil each accounted for 1% of the total mass, with the remainder being water. The injection flow rate of the emulsified vegetable oil was 100 L / h. Submersible pumps were installed, with a groundwater extraction well diameter of DN200 mm and a groundwater injection well diameter of DN100 mm. The groundwater extraction flow rate was 200 L / h, the groundwater injection flow rate was 80 L / h, and the main flow rate of the biological reactor backflow was 80 L / h. After 60 days of remediation, the removal rates of chloroform, dichloromethane, and vinyl chloride concentrations in the groundwater are shown in the table below.

[0041] Table 3 Removal rate of chlorinated hydrocarbons in groundwater

[0042]

[0043] Compared with the results of (1), it is shown that increasing the content of magnetite can increase the formation rate of ferrous sulfide, a strongly reducing iron mineral, and can effectively increase the removal rate of chlorinated hydrocarbons.

[0044] (4) The groundwater contaminated area with chlorinated hydrocarbons is 5m × 5m, with a contamination depth of 4m. Coarse sand, magnetite, root protection, wheat bran, coarse gypsum, ferrous sulfate, and limestone are mixed. The mass fraction of the above filler is: coarse sand 94%, magnetite 1%, root protection 1%, wheat bran 1%, coarse gypsum 1%, ferrous sulfate 1%, and limestone 1%. A 30cm thick layer of gravel is laid on top of the filler, with return drainage branch pipes buried in the middle of the gravel. The main return drainage pipe is DN80mm, and the branch pipes are DN50mm. Based on the porosity of the filler area being 20%, the emulsified vegetable oil injection volume is approximately half the porosity, which is 10m³. 3 Sodium dodecyl sulfate and soybean oil each accounted for 1% of the total mass, with the remainder being water. The injection flow rate of the emulsified vegetable oil was 100 L / h. The groundwater extraction well diameter was DN200 mm, and the groundwater injection well diameter was DN100 mm. The groundwater extraction flow rate was 200 L / h, the groundwater injection flow rate was 80 L / h, and the main flow rate of the biological reactor backflow was 80 L / h. After 60 days of remediation, the removal rates of chloroform, dichloromethane, and vinyl chloride concentrations in the groundwater are shown in the table below.

[0045] Table 4. Removal rate of chlorinated hydrocarbons in groundwater

[0046]

[0047] Compared with the results of (1), it is shown that reducing the content of magnetite, root protection, wheat bran, crude gypsum, ferrous sulfate and limestone reduces the formation rate of ferrous sulfide iron mineral and significantly reduces the removal rate of chlorinated hydrocarbons.

Claims

1. A packing material for remediating chlorinated hydrocarbon contamination, characterized in that, The filler is formulated from the following components and mass fractions: 65%–85% coarse sand, 1%–10% magnetite, 1%–5% root protection, 1%–5% wheat bran, 1%–5% coarse gypsum, 1%–5% ferrous sulfate, and 1%–5% limestone.

2. A method for biogeochemical transformation and remediation of chlorinated hydrocarbon-contaminated groundwater, characterized in that, The method includes the following steps: (1) In the area of ​​groundwater contaminated by chlorinated hydrocarbons, a pit is dug to the corresponding contamination depth, and the filler material described in claim 1 is used to backfill to form a filler layer. A gravel layer is laid on top of the filler layer, and a return-leakage branch pipe is buried in the gravel layer. Geotextile is covered on top of the gravel layer, and then soil is covered to be level with the ground. A groundwater extraction well is constructed downstream of the chlorinated hydrocarbon contaminated area and a submersible pump is placed in the well. A groundwater injection well is constructed upstream. (2) Thoroughly mix sodium dodecyl sulfate, soybean oil and water to prepare emulsified vegetable oil; inject the emulsified vegetable oil into the filler layer so that the filler layer is in an anaerobic environment; (3) Groundwater is extracted through groundwater extraction wells, and some groundwater is injected into the upstream groundwater injection wells to enhance the flow of groundwater; some groundwater enters the filler area for repair.

3. The method for biogeochemical transformation and remediation of chlorinated hydrocarbon-contaminated groundwater according to claim 2, characterized in that, The thickness of the packing layer in step (1) is 20-30cm, the diameter of the return shower branch pipe is 50-100cm, and the return shower branch pipe has holes at intervals of 30-40cm that are angled downwards with a diameter of 5-10mm.

4. The method for biogeochemical transformation and remediation of chlorinated hydrocarbon-contaminated groundwater according to claim 2, characterized in that, The groundwater extraction well in step (1) has a diameter of DN200mm, and the groundwater injection well has a diameter of DN100mm.

5. The method for biogeochemical transformation and remediation of chlorinated hydrocarbon-contaminated groundwater according to claim 2, characterized in that, The groundwater extraction well mentioned in step (1) is connected to the groundwater injection well through the groundwater extraction main pipe and the groundwater extraction branch pipe 6; the groundwater extraction well is also connected to the filler layer through the groundwater extraction main pipe and the return water main pipe.

6. The method for biogeochemical transformation and remediation of chlorinated hydrocarbon-contaminated groundwater according to claim 2, characterized in that, In step (2), sodium dodecyl sulfate and soybean oil are mixed in equal mass fractions, and the mass percentage of the mixture in the emulsified vegetable oil is 1-2%.

7. The method for biogeochemical transformation and remediation of chlorinated hydrocarbon-contaminated groundwater according to claim 2, characterized in that, The amount of emulsified vegetable oil injected in step (2) is half the porosity of the filler layer.

8. The method for biogeochemical transformation and remediation of chlorinated hydrocarbon-contaminated groundwater according to claim 2, characterized in that, During groundwater remediation, dissolved oxygen levels in the groundwater are monitored every 3-5 days. When the dissolved oxygen concentration rises, emulsified vegetable oil is added promptly.

9. The method for biogeochemical transformation and remediation of chlorinated hydrocarbon-contaminated groundwater according to claim 2, characterized in that, The chlorinated hydrocarbon-contaminated groundwater includes one or more of the following: chloroform, dichloromethane, and vinyl chloride.

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