Disclosure of Invention
The invention aims to provide a maintenance method suitable for in-situ chemical oxidation remediation of contaminated soil according to the defects of the prior art, the maintenance method monitors the pH value of the soil body in each maintenance monitoring unit in real time, knows the progress of oxidation reaction, and supplements an alkaline activator according to the monitoring result, thereby improving the removal efficiency of organic pollutants.
The purpose of the invention is realized by the following technical scheme:
a maintenance method suitable for in-situ chemical oxidation remediation of contaminated soil is characterized by comprising the following steps: dividing a plurality of grid-shaped maintenance monitoring units within the restoration range after the in-situ dosing and stirring are completed; in the maintenance process, monitoring the PH value of the soil body in each maintenance monitoring unit; setting medicine injection points at the center point and the four corner positions of the maintenance monitoring unit based on the PH value monitoring result in the maintenance monitoring unit, inserting medicine injection steel pipes, and adding the alkaline activator into the soil body with the corresponding depth through the medicine injection steel pipes; and the maintenance of the soil body in each maintenance monitoring unit is completed in sequence by repeating the steps.
The method for monitoring the PH value of the soil body in each maintenance monitoring unit comprises the following steps: sampling points are respectively arranged at the central point and four corner points of the maintenance monitoring unit, soil sampling test is carried out in each sampling point by taking 10-14 hours as sampling intervals, and the sampling interval depth in each sampling point is 0.8-1.2 m.
If the PH value monitoring data at the sampling point is less than 10, adding and supplementing an alkaline activator through the medicine injection steel pipe; and if the pH value monitoring data at the sampling point is between 10 and 12, adding and supplementing the alkali exciting agent.
The alkaline activator is sodium hydroxide solution.
The adding method of the alkaline exciting agent comprises the following steps: (1) pressing the medicine injection steel pipe uniformly provided with the medicine outlet holes to a first-stage depth in the medicine injection point; arranging a pipe sealing cover at the upper end of the drug injection steel pipe to enable the drug injection steel pipe to form a sealed cavity, pumping the alkaline activator into the sealed drug injection steel pipe, and adding the alkaline activator into soil in a first-stage depth range through the drug outlet holes; (2) disassembling the tube sealing cover, lengthening the medicine injection steel tube by using a connecting tube group, pressing the medicine injection steel tube to a second-stage depth in the medicine injection point, hermetically installing the disassembled tube sealing cover to the upper port of the connecting tube group, and pumping the alkaline activator into the medicine injection steel tube to perform feeding within the range of the second-stage depth; (3) and (3) performing reciprocating operation according to the step (2), and sequentially completing the injection repair within each level of depth range in the injection point by lengthening the injection steel pipe.
The front end of the medicine injection steel pipe is connected with a conical probe, and the diameter of the upper part of the conical probe is larger than that of the medicine injection steel pipe.
The sealing tube cover is provided with a medicine injection hole and an exhaust hole, the medicine injection hole is communicated with the booster pump and the medicine stirring barrel through a medicine conveying hose, and the booster pump is provided with a pressure controller and a flow control meter.
The connecting pipe group comprises at least one section of connecting steel pipe, and is adjacent to the connecting steel pipe, and a detachable threaded connection structure is adopted between the connecting steel pipes.
Before entering the maintenance process, the in-situ dosing and stirring method comprises the following steps: (1) dividing a construction area into a plurality of latticed restoration units on a plane, and dividing the construction area into an upper polluted soil layer and a lower polluted soil layer in depth; (2) a groove is formed in the surface of the repairing unit, and soil is irrigated and leached by surfactant solution along the groove so as to permeate deep polluted soil for solubilization; (3) excavating the upper polluted soil layer in the restoration unit by using an excavator, and spraying an alkaline activator while rotating and stirring the polluted soil in the lower polluted soil layer by using a stirring and spraying head on shallow in-situ stirring equipment to adjust the pH value to be between 10 and 12; (4) spraying an oxidation remediation agent to remediate the contaminated soil while rotating and stirring the contaminated soil in the lower contaminated soil layer by using the stirring and spraying head; (5) backfilling the upper polluted soil layer by using the excavator, repeating the steps (3) and (4), and finishing the adding and stirring of the alkaline exciting agent and the oxidation repairing agent in the upper polluted soil layer; (6) and (5) sequentially finishing in-situ dosing and stirring of the repair units according to the steps (3) to (5).
The invention has the advantages that: the maintenance method is simple and easy to operate, the oxidation reaction process is known by monitoring the pH value of the soil body in each maintenance monitoring unit in real time, and the alkaline exciting agent is added according to the monitoring result, so that the utilization rate of each agent is improved, and the removal efficiency of organic pollutants is improved.
Example (b): as shown in fig. 1 to 9, this embodiment specifically relates to a maintenance method suitable for in-situ chemical oxidation remediation of contaminated soil, which mainly relates to an in-situ chemical-adding stirring process and a subsequent maintenance process, and specifically includes the following steps:
[ in-situ adding drugs and stirring ] see fig. 1-6
(1) Before in-situ stirring, the construction area 5 of the field is cleaned by using the excavator 6, and meanwhile, surface soil is loosened, so that proper soil conditions are created for shallow in-situ stirring equipment to sink.
(2) As shown in fig. 5, the range of the construction area 5 is divided into a plurality of repair units 53 in a grid shape, in the present embodiment, each repair unit 53 has a specification of 4m × 4m, and a timber pile or lime is used as a division mark between the repair units 53.
(3) After a groove with the depth of 30cm is dug longitudinally and transversely in a repairing unit 53 to be constructed, a surfactant is irrigated and infiltrated into soil for solubilization, the surfactant is a negative nonionic surfactant with the concentration of 20 g/L, the adding amount of the surfactant is determined according to the using amount of an oxidation repairing medicament used later, in the embodiment, the adding amount of the surfactant is 10 mass percent of the using amount of the oxidation repairing medicament, after solubilization for a certain time, as shown in fig. 5, a polluted soil body in the repairing unit 53 is divided into an upper layer and a lower layer, namely an upper polluted soil layer 54 and a lower polluted soil layer 55, the thicknesses of the upper layer and the lower layer are both 0.5-1.0m, and the upper polluted soil layer 54 is dug and removed by using a digging machine 6.
(4) Then, moving the installed shallow in-situ stirring equipment to the position of a repair unit 53 to be constructed; shallow normal position agitated vessel main part in this embodiment is automobile body 1 for having the arm, install stirring injector head 4 at the front end of arm, arranged injection pipeline 3 along the arm extending direction, an end connection injection storage pumping device 2 of injection pipeline 3 is used for the pump sending to restore the medicament, another end connection stirring injector head 4 of injection pipeline 3, stirring injector head 4 can outwards spray the restoration medicament in its in-process of impressing the contaminated soil body and carrying out the stirring, so that restoration medicament and contaminated soil can fully contact in order to restore contaminated soil.
As shown in fig. 1 and 2, the vehicle body 1 is composed of four parts, namely a crawler-type traveling base 11, a frame 12, a mechanical arm and a power device 13, wherein: (a) the crawler-type traveling base 11 is used for driving the whole vehicle body 1 to move and travel, so that the vehicle can conveniently travel in different terrains and environments, and the working efficiency is improved; (b) the frame 12 is connected with the crawler-type traveling base 11 through a rotating mechanism, and the frame 12 can rotate for 360 degrees under the driving of the rotating mechanism; (c) the mechanical arm specifically comprises a first mechanical arm 14, a second mechanical arm 16 and a third mechanical arm 19, wherein one end of the first mechanical arm 14 is hinged and fixed on the frame 12, the other end of the first mechanical arm is rotatably connected with the second mechanical arm 16, and the second mechanical arm 16 and the third mechanical arm 19 form a coaxial arrangement through a front end connecting piece 18; a first hydraulic telescopic rod 15 is arranged on the first mechanical arm 14 and used for driving a second mechanical arm 16 to rotate, and a second hydraulic telescopic rod 17 is arranged on the second mechanical arm 16 and used for driving a front end connecting piece 18 and a third mechanical arm 19 to do telescopic motion; (d) the power device 13 is mounted and fixed on the frame 12, and is used for converting mechanical energy of the diesel engine into hydraulic energy and providing the hydraulic energy to each component on the vehicle body 1, and comprises a crawler-type walking base 11, a rotating mechanism under the frame 12, a first hydraulic telescopic rod 15, a second hydraulic telescopic rod 17 and a stirring and spraying head 4.
As shown in fig. 1 and 2, the injection storage pumping device 2 comprises a crawler-type traveling base 23, and a medicament storage bin 21 and a medicament storage bin 22 which are arranged on the crawler-type traveling base 23; the medicament storage bin 21 and the medicament storage bin 22 are connected to the vehicle body 1 through the medicament injection pipeline 3, different types of repairing medicaments can be stored in the medicament storage bin 21 and the medicament storage bin 22 and pumped outwards, the shape of the repairing medicaments can be cylindrical or rectangular, and the size of the volume of the repairing medicaments is determined according to the actual engineering situation; each medicament storage bin is correspondingly connected with a medicament injection pipeline 3, a medicament injection metering sensor 24, a flow control valve 25, a high-pressure pump 27 and a pressure controller 26 are sequentially installed at the interface position of the medicament injection pipeline 3 and the medicament storage bin 21/the medicament storage bin 22, wherein the medicament injection metering sensor 24 is used for detecting and controlling the medicament flow output outwards, the high-pressure pump 27 is used for pumping the medicament solution in the medicament storage bin 21/the medicament storage bin 22 and pumping outwards to provide certain injection pressure for the medicament, and the flow control valve 25 and the pressure controller 26 regulate the transmission speed of the medicament.
As shown in fig. 1 and 2, the drug injection pipeline 3 is composed of a flexible pipeline 31 and a drug injection pipe cavity 32, wherein the flexible pipeline 31 is made of corrosion-resistant flexible pipe material and is arranged along the extending direction of the first mechanical arm 14 and the second mechanical arm 16, and in order to enable the flexible pipeline 31 to rotate along with the first mechanical arm 14 and the second mechanical arm 16, certain redundancy is provided in length selection; the medicine injection tube cavity 32 is arranged along the axial direction of the third mechanical arm 19, one end part of the flexible pipeline 31 is connected with the medicine injection storage pumping device 2, the other end part of the flexible pipeline 31 is communicated with the medicine injection tube cavity 32, the medicine injection storage pumping device 2 is provided with the medicine storage bin 21 and the medicine storage bin 22 in the embodiment, the number of the flexible pipelines 31 is two, the flexible pipelines 31 connected to the medicine storage bins are converged and converged into the medicine injection tube cavity 32, and the flexible pipelines 31 convey the repairing medicines in the medicine injection storage pumping device 2 into the medicine injection tube cavity 32 and spray the repairing medicines outwards through the stirring and spraying head 4 at the end part of the flexible pipelines.
As shown in fig. 1, 2, 3 and 4, the mixing and spraying head 4 is disposed at the front end of the third mechanical arm 19, and is composed of a central chemical spraying head 42 and three groups of rotary tillage soil-cutting cutter discs 41 located outside the central chemical spraying head, and the three groups of rotary tillage soil-cutting cutter discs 41 are distributed in a Y shape on a plane; the central medicament injection head 42 is communicated with the medicament injection tube cavity 32 in the third mechanical arm 19, a medicament heating device 43 and a pressurizing device 44 are arranged at the joint, and the medicament heating device 43 can increase the medicament injection temperature before the medicament is injected into the soil body so as to improve the reaction efficiency; the direction of the medicament jet flow of the medicament injection head 42 points to the three groups of rotary tillage soil-cutting cutter discs 41 positioned at the outer side of the medicament injection head respectively; as shown in fig. 3, the rotary tillage soil cutting cutter head 41 of the present embodiment includes a cutter head 46 and a plurality of cutting blades 47 spaced along an outer edge portion thereof, the cutting blades 47 are fixed to the cutter head 46 via fastening bolts 48, and the rotary driving of the cutter head 46 is performed by a rotating device 45. In the process of cutting and stirring the soil body by the rotary tillage soil cutting cutter head 41, the agent injection head 42 can synchronously inject the remediation agent, so that the remediation agent and the polluted soil body can be fully mixed.
(5) As shown in fig. 1 and 5, after the shallow in-situ stirring apparatus is moved to the position of the repair unit 53 to be constructed, the second robot arm 16, the third robot arm 19 and the stir-spray head 4 thereon are maintained in a state of being vertically perpendicular to the ground.
(6) An oxidation remediation agent and an alkaline activator are configured according to the type and the pollution degree of the pollutants in the construction area 5 and are respectively added into an agent storage bin 21 and an agent storage bin 22 in the shallow in-situ stirring equipment; wherein:
the oxidation remediation agent adopts sodium persulfate solution (with the concentration of 400 g/L), the dosage of which is 1% -3% of the mass of the soil to be remediated, specifically, the dosage of which in a soil heavily polluted area is 3% of the mass of the soil to be remediated, and the dosage of which in a soil lightly polluted area is 1% -2% of the mass of the soil to be remediated;
the alkali activator adopts sodium hydroxide solution (with the concentration of 500 g/L), and the amount of the alkali activator is designed to be 20 percent (mass percentage) of the amount of the sodium hydroxide solution.
(7) As shown in fig. 1 to 6, the second hydraulic telescopic rod 17 on the second mechanical arm 16 is controlled to drive the third mechanical arm 19 to extend, so that the stirring and spraying head 4 is driven to press into the lower contaminated soil layer 55 while rotating and stirring, and in the pressing process, the stirring and spraying head 4 simultaneously sprays a sodium hydroxide solution outwards at a certain pressure to perform alkaline regulation on the lower contaminated soil layer 55; in addition, in the process of gradually lifting the stirring and spraying head 4, the sodium hydroxide solution is fully contacted with the soil through the high-speed rotation of the stirring and spraying head 4, so that the full uniform mixing is realized; repeatedly stirring and sinking, lifting while stirring, and uniformly stirring until the working area of the repair unit 53 of the square meter of 16 is completed; sampling, testing and repairing the pH value of the lower polluted soil layer 55 in the unit 53 to reach the pH value of 10-12; the first adding amount of the sodium hydroxide solution in the whole repairing unit 53 (including the upper polluted soil layer 54 and the lower polluted soil layer 55) is half of the designed using amount of the sodium hydroxide solution, namely, when the polluted soil in the whole repairing unit 53 is repaired for the first time, the adding amount of the sodium hydroxide solution accounts for 10% of the using amount of the sodium persulfate solution;
in the process of spraying the medicament, the high-pressure pump 27 pumps the sodium hydroxide solution out of the medicament storage bin 22, the sodium hydroxide solution is pumped to the medicament spraying head 42 of the stirring and spraying head 4 through the medicament injection pipeline 3, and under the action of pressure, the medicament solution is sprayed into the soil body from the medicament spraying head 42 at certain pressure to perform alkaline regulation on the soil body; during the delivery of the medicament, the injection metering sensor 24 is adjusted in real time to control the injection amount of the sodium hydroxide solution, while the delivery rate of the medicament is controlled by adjusting the flow control valve 25 and the pressure controller 26.
(8) As shown in fig. 1-6, the injection pipeline 3 of the sodium hydroxide solution is closed, and the injection pipeline 3 of the sodium persulfate solution is opened; and (5) repeating the step in the step (7), injecting a sodium persulfate solution into the lower polluted soil layer 55 in the repairing unit 53, uniformly mixing the sodium persulfate solution and the soil body by using the stirring and injecting head 4, and performing chemical reaction on the sodium persulfate solution and the polluted soil body to repair the polluted soil body.
(9) As shown in fig. 6, after completing the remediation of the lower contaminated soil layer 55 in the remediation unit 53, the excavator 6 is used to backfill the upper contaminated soil layer 54 into the remediation unit 53, and the above steps (7) and (8) are repeated to complete the remediation of the upper contaminated soil layer 54, i.e. the remediation work of the whole remediation unit 53 is completed;
(10) after the repair of the repair unit 53 is completed, the high-pressure pump 27 is turned off to stop pumping the medicine into the injection pipeline 3; then the second hydraulic telescopic rod 17 on the second mechanical arm 16 is controlled to contract so as to drive the third mechanical arm 19 and the stirring and spraying head 4 on the third mechanical arm to lift off the soil body;
(11) as shown in fig. 1 to 6, according to the steps (7) to (10), the operations of injecting and stirring the chemicals for the repairing units 53 are sequentially completed, and the contaminated soil after stirring is maintained in situ.
(maintenance process) see fig. 5, 7-9
(12) After the in-situ dosing and stirring work is finished, in-situ maintenance is carried out, a plurality of grid-shaped maintenance monitoring units are divided in the construction area 5, and in essence, the original dividing form of the repair unit 53 is adopted by each maintenance monitoring unit;
(13) respectively arranging PH value sampling points 52 at the central point and four corner positions of the repairing unit 53, and taking 12 hours as sampling time intervals to perform soil sampling test in each sampling point 52, wherein the depth of the sampling intervals in the sampling points 52 is 1 m;
(14) judging whether further medicine injection is needed or not according to the obtained PH value monitoring data; if the PH value of the soil body at the sampling point 52 is between 10 and 12, adding and supplementing the alkaline exciting agent is not carried out; if the PH value of the soil body at the sampling point 52 is less than 10, adding and supplementing the alkaline exciting agent;
(15) respectively arranging medicine injection points 51 at the central point and four corner positions of the repairing unit 53, inserting medicine injection steel pipes 72 into the medicine injection points 52 to supplement the alkali activator, wherein the alkali activator still uses sodium hydroxide solution in the maintenance process, the adding frequency of the alkali activator is preferably 2-3 times, and finally the pH value of the soil body is controlled to be about 11; the concrete pressing-in step of the injection steel pipe 72 and the concrete adding step of the alkaline activator are as follows:
15a) in each injection point 51, the depth of each stage which needs to be repaired by injection is determined, for example, in this embodiment, the first stage depth is 1m, the second stage depth is 2m, and the third stage depth is 3 m …, and the nth stage depth is n m;
15b) the preparation of the alkaline excitant solution is completed in the medicament stirring barrel 85, the medicament stirring barrel 85 is communicated with the liquid inlet of the booster pump 84 through the medicament conveying hose 81a, and meanwhile, the liquid outlet of the booster pump 84 is communicated with the medicament injection hole 75 on the tube sealing cover 74 through the medicament conveying hose 81b, so that the preparation work before medicament injection is completed;
15c) assembling the drug injection steel pipe 72, combining and connecting the conical probe 71 with the single-section drug injection steel pipe 72, uniformly distributing a plurality of drug outlet holes 79a on the wall surface of the drug injection steel pipe 72, arranging anti-blocking protective boots 79b on the wall surface of the upper edge part of each drug outlet hole 79a, and preventing the orifice from being blocked by the anti-blocking protective boots 79 b;
then, inserting the single-section injection steel pipe 2 and the conical probe 1 thereof into the first-stage depth of the soil body at each injection point 51 by using a pressing and pulling device, wherein the first-stage depth is selected to be 1m of the shallow part of the soil body in the embodiment; in the process of pressing soil into the soil body, the diameter of the upper part of the conical probe 71 is larger than that of the medicine injection steel pipe 72, so that the conical probe 71 forms a medicine injection well mouth with a larger well diameter, thereby preventing the soil body around the well wall from extruding to the pipe wall of the medicine injection steel pipe 72 and the medicine outlet hole 79a and playing a role of preventing blockage;
after the injection steel pipe 72 is inserted into position, the aforementioned tube sealing cap 74 is screwed to the upper end orifice of the injection steel pipe 72 by using the connecting thread 78; the tube sealing cover 74 seals the space in the drug injection steel tube 72 to form a sealed cavity, and simultaneously, under the action of the booster pump 84, the drug injection pressure and the medicament injection effect in the sealed cavity can be improved; wherein, a drug injection hole 75 is arranged at the center of the tube sealing cover 74, the drug injection hole 75 is communicated with the booster pump 84 through a drug delivery hose 81b, and a drug solution can be injected into the tube cavity of the drug injection steel tube 72; in addition, the tube sealing cover 74 is also provided with an exhaust hole 76 which can periodically exhaust the gas in the tube;
15d) starting a booster pump 84 to pump the alkaline activator solution in the agent stirring barrel 85 into the agent injection steel pipe 72 through the agent delivery hose 81 and the agent injection hole 75 at a certain agent injection pressure and agent injection flow rate; under the action of pump pressure, the alkaline activator solution is uniformly sprayed and injected into the soil body through each medicine outlet hole 79a of the medicine injection steel pipe 72, and the alkaline activator solution reacts with the sodium persulfate solution remained in the soil body, so that the utilization rate of the sodium persulfate solution at the first-stage depth is improved, and the removal efficiency of organic pollutants is improved;
15e) after the alkaline activator reacts in the soil body within the first-stage depth range for a period of time, the pipe sealing cover 74 is detached from the port of the drug injection steel pipe 72, the connecting pipe group 73 is installed at the upper port of the drug injection steel pipe 72 in a threaded fit manner, the connecting pipe group 73 at least comprises a section of connecting steel pipe 77, in the construction process, the number of sections of the connecting pipe group 73 is selected according to the depth of needed drug injection, in the embodiment, a section of connecting steel pipe 77 is actually installed at the upper port of the drug injection steel pipe 72, and the two end parts of the connecting steel pipe 77 are provided with connecting threads 78;
then, the tube sealing cap 74 detached before is screwed to the upper end of the connecting steel tube 77 again to seal the tube body to form a sealed cavity, and at the same time, the air in the cavity can be properly discharged through the air outlet 76; pressing the medicine injection steel pipe 72 to the underground second-stage depth position by using the pressing and pulling device again, repeating the medicine injection step in the step (15 d), and adding the alkaline exciting agent into the soil body within the second-stage depth range;
15f) repeating the steps (15 d) and (15 e), and sequentially completing the injection of the alkaline activator at each depth position (third-level depth, fourth-level depth, …) in each hole by connecting the long connecting tube group 73;
15g) after a period of time passes through the reaction, sampling and testing are carried out, and injection work is continuously carried out on the injection area which does not reach the repair target until the drug injection steel pipe 72 and the connecting pipe group 73 are pulled out after the repair target is completed.