CN111318561A

CN111318561A - Contaminated soil remediation method and system

Info

Publication number: CN111318561A
Application number: CN202010135005.0A
Authority: CN
Inventors: 王红; 林强
Original assignee: Nanjing Xiaoxiang Engineering Technology Co ltd
Current assignee: Weihai CONI Lihe Environmental Protection Technology Co.,Ltd.
Priority date: 2020-03-02
Filing date: 2020-03-02
Publication date: 2020-06-23
Anticipated expiration: 2040-03-02
Also published as: CN111318561B

Abstract

The invention relates to a method and a system for restoring polluted soil, in particular to a method and a system for restoring petroleum-polluted soil in situ, and belongs to the technical field of soil restoration. The method provided by the invention is suitable for in-situ leaching remediation treatment of the petroleum-polluted soil, and can be used for dividing the field into two parts by utilizing the heat source in the soil, wherein the heat of one part is transferred to the other part, so that the leaching effect can be improved, and the suction risk of personnel working caused by volatilization of organic matters in the field can be avoided.

Description

Contaminated soil remediation method and system

Technical Field

The invention relates to a method and a system for restoring polluted soil, in particular to a method and a system for restoring petroleum-polluted soil in situ, and belongs to the technical field of soil restoration.

Background

In recent years, with the continuous development of economy, the production and consumption of petroleum have been increasing. This directly leads to an increasing problem of petroleum-contaminated soil. In the large-scale exploitation, smelting, transportation, use and treatment processes of petroleum, accidents such as pollution, omission, blowout, oil pipeline leakage and the like frequently occur, and serious soil pollution is caused. Well-digging detection shows that many gas stations have the problem of oil leakage. The leakage of petroleum into soil and groundwater poses serious threats to ecological environment, food safety and human health, and becomes an important social and environmental problem in the field of environment. Therefore, the remediation of the petroleum-polluted soil and the restoration of the ecological function thereof are urgent.

The chemical repair mainly refers to chemical leaching repair, and can be subdivided into in-situ leaching repair and ex-situ leaching repair according to different repair methods. The ectopic leaching remediation is to dig out the polluted soil, clean the polluted soil in a laboratory, place the cleaned soil back for application, and discharge the cleaning waste liquid after treatment. The ex-situ leaching can control conditions such as temperature, pH and the like, the sea-dissolving cleaning effect of the surfactant can be exerted to the greatest extent, the washing is assisted by means of oscillation, radiation and the like, the residue of the surfactant is reduced by washing with clear water after the pollutants are basically removed, and the harm of secondary pollution is avoided. However, this method is only suitable for a small range of high concentration soil contamination, and the soil structure and organisms are destroyed destructively. The in-situ leaching does not need to dig out the polluted soil, the surfactant solution can be directly sprayed on the polluted site, the damage to the soil structure caused by digging, oscillation and the like is reduced, and the in-situ leaching method has the advantage of ex-situ leaching.

As can be seen from the above, the ex-situ leaching method is easier to control the temperature than in-situ leaching, and generally, the higher the temperature is, the easier the hydrocarbons and oils adsorbed in the soil can be removed, and the washing rate is improved. For in-situ leaching, although the construction procedures of soil excavation, backfilling and the like are avoided, the temperature during leaching is not easy to be controlled well, so that the removal efficiency is low.

On the other hand, when a polluted site such as petroleum and organic matter is constructed, once a building on the surface is removed, soil in a deep layer is exposed, so that adsorbed organic matter is volatilized to a certain extent, and although the volatilization amount is not high, for personnel working on the construction site, the potential health hazard caused by accumulation of toxic substances exposed to the volatilized organic matter still exists.

Disclosure of Invention

The first technical problem to be solved by the invention is as follows: when the in-situ leaching repair is carried out on the organic polluted site, the leaching temperature is not easy to control; moreover, the pollutants in the organic pollution site volatilize, so that health hidden troubles can be caused to constructors.

The second technical problem to be solved by the invention is as follows: the eluate is subjected to an advanced treatment and the components thereof are recovered.

The third technical problem to be solved by the invention is: when the leacheate is treated, the flux of the ultrafiltration membrane is reduced and membrane pores are blocked in the operation process.

The invention adopts the following technical scheme:

a method for restoring polluted soil, which is petroleum polluted soil, comprises the following steps:

step 1, firstly, respectively digging a first shaft, a second shaft and a third shaft on a polluted site, wherein the second shaft is positioned between the first shaft and the third shaft;

step 2, an evaporator is installed in the first access way, a condenser is installed in the second access way, an expansion valve and a compressor are installed on the site, and the evaporator, the expansion valve, the condenser and the compressor are connected in sequence to form a heat pump system;

step 3, starting a heat pump system, transferring a heat source in the first well to a second well, adding leacheate into the second well, installing a negative pressure suction pump in a third well, sucking underground water from the third well in a suction mode, and discharging the leacheate from the third well after the leacheate leachates soil;

step 4, arranging the operation position of a constructor in a field between the first shaft and the second shaft;

step 5, after the soil leaching operation is finished, interchanging the positions of an evaporator and a negative pressure suction pump, transferring a heat source in a third well to a second well, adding a leaching solution into the second well, installing the negative pressure suction pump in the first well, and performing underground water suction from the first well in a suction mode to discharge the leaching solution from the first well after the soil is leached by the leaching solution; and an operation position of a construction worker is set in a place between the second shaft and the third shaft.

In one embodiment, in the 4 th step, the operation position of the constructor is close to the first shaft.

In one embodiment, the leacheate comprises a base and a surfactant.

In one embodiment, the base is NaOH or KOH and the base is added in an amount such that the pH of the eluate is between 8 and 10.

In one embodiment, the surfactant concentration is 0.5 to 2 wt%.

In one embodiment, the oil content of the petroleum-contaminated soil is 5000-50000mg/Kg, and the pH value is 4.5-6.5.

In one embodiment, the leaching waste liquid obtained in the negative pressure suction pump is sequentially processed by the following steps:

s1, adding a flocculating agent into the leaching waste liquid for flocculation treatment;

s2, oxidizing the supernatant fluid after flocculation treatment in the S1;

s2, carrying out ultrafiltration treatment on the waste liquid after oxidation treatment in the S2;

s4, carrying out nanofiltration treatment on the ultrafiltration penetrating fluid obtained in the S3.

In one embodiment, in step S1, the flocculating agent used in the flocculation treatment is an inorganic flocculating agent or an organic flocculating agent.

In one embodiment, the inorganic flocculant is selected from polyaluminum chloride or ferric chloride; the organic flocculant is selected from polyacrylamide; the addition amount of the flocculant is 50-150 mg/L.

In one embodiment, the oxidation treatment is ozone oxidation, the adding amount of ozone is 100-500mg/L, the ozone reaction temperature is 30-60 ℃, and the ozone reaction time is 30-60 min.

In one embodiment, the ultrafiltration process uses a multichannel ceramic ultrafiltration membrane with an average pore size in the range of 50-200 nm; the ultrafiltration process requires the addition of a filter aid to the influent water, said filter aid being diatomaceous earth.

In one embodiment, the multichannel ceramic ultrafiltration membrane is described.

In one embodiment, the cross section of the multi-channel ceramic membrane is rectangular, an array formed by filtering channels is arranged in the multi-channel ceramic membrane, and the array is arranged according to the transverse direction and the longitudinal direction which are perpendicular to each other and rectangular;

at the end in the feed liquid outlet direction of the multi-channel ceramic membrane, a transverse particulate matter concentration identifier consisting of a transverse light source and a transverse receiver is arranged on the transverse edge of the rectangular section of the multi-channel ceramic membrane, the transverse light source is adjacent to the transverse receiver, the number of the transverse particulate matter concentration identifiers is multiple, the position of each transverse particulate matter concentration identifier in the transverse direction is matched with the position of each filtering channel in the transverse direction one by one, and the transverse receiver in each transverse particulate matter concentration identifier is used for receiving light rays emitted by the transverse light source after laser is reflected by particulate matters; meanwhile, a particle concentration identifier consisting of a longitudinal light source and a longitudinal receiver is arranged on the longitudinal edge of the rectangular section of the multi-channel ceramic membrane, the longitudinal light source is adjacent to the longitudinal receiver, the number of the longitudinal particle concentration identifiers is multiple, and the position of each longitudinal particle concentration identifier in the longitudinal direction is matched with the position of each filtering channel in the longitudinal direction one by one; the longitudinal receiver in each longitudinal particle concentration recognizer is used for receiving light rays emitted by the longitudinal light source after the laser light is reflected by the particles; the transverse light source, the transverse receiver, the longitudinal light source and the longitudinal receiver all protrude out of the end face of the multi-channel ceramic membrane in the direction of the feed liquid outlet;

further comprising: during filtering, a step of detecting blockage of a filtering channel of the multi-channel ceramic membrane in real time;

the real-time detection method comprises the following steps:

converting the optical signals obtained by the transverse receiver and the longitudinal receiver into particle concentrations;

judging the value of the particle concentration corresponding to each transverse receiver and each longitudinal receiver in real time;

when the particle concentration corresponding to a certain transverse receiver and a certain longitudinal receiver is smaller than a set threshold, judging that: the filtration channel is blocked at the same position in the transverse direction as the transverse receptacle and at the same position in the longitudinal direction as the longitudinal receptacle.

In one embodiment, a transverse rod body is arranged on one edge of the multichannel ceramic membrane at the end in the feed liquid inlet direction of the multichannel ceramic membrane, a vertical longitudinal rod body is further arranged on the transverse rod body, the longitudinal rod body can controllably move on the transverse rod body, a washing water nozzle is further arranged on the longitudinal rod body, the washing water nozzle can controllably move on the longitudinal rod body, the washing water nozzle is connected with an external water hose, and the washing water nozzle is used for spraying high-pressure washing water into the filtering channel; the transverse rod body and the longitudinal rod body are used for controlling the flushing water spray head to move to the position of the blocked filtering channel; one end of the external water hose is connected with the washing water nozzle, and the other end of the external water hose is connected with a washing water joint on the shell of the multi-channel ceramic membrane, and washing water is supplied to the multi-channel ceramic membrane through the outside of the multi-channel ceramic membrane;

the method also comprises the step of flushing the filtering channel: when the potential blockage or blockage of one filtering channel is detected, the washing water spray head is moved to the position of the filtering channel with the potential blockage or the blockage through the movement of the transverse rod body, the longitudinal rod body and the washing water spray head, and the blockage of the filter cake is washed by the washing water spray head.

In one embodiment, the permeate obtained from the nanofiltration treatment is reused as a leacheate after being supplemented with a surfactant.

A contaminated soil remediation system comprising:

a first hoistway, a second hoistway, and a third hoistway; and the second hoistway is located intermediate the first hoistway and the third hoistway;

an evaporator is installed in the first hoistway, a condenser is installed in the second hoistway, and an expansion valve and a compressor are arranged above the polluted soil; the evaporator, the expansion valve, the condenser and the compressor are connected in sequence to form a heat pump system;

further comprising: the leaching solution tank is used for filling leaching solution into the second well;

a negative pressure suction pump connected to the third well for pumping the leacheate from the third well;

a working area is formed between the first shaft and the second shaft, and a leaching area is formed between the second shaft and the third shaft;

the operating equipment of the constructor is arranged above the working area.

In one embodiment, further comprising: and the alkali adding tank and the surfactant adding tank are respectively connected with the leaching solution tank and are respectively used for adding alkali and surfactant into the leaching solution tank.

In one embodiment, further comprising:

the flocculation tank is connected with the negative pressure suction pump and is used for carrying out flocculation treatment on the leacheate obtained in the negative pressure suction pump;

the flocculating agent feeding tank is connected with the flocculation tank and is used for adding a flocculating agent into the flocculation tank;

the oxidation reaction tank is connected with the flocculation tank and is used for carrying out oxidation treatment on the clear liquid obtained in the flocculation tank;

the ultrafiltration membrane is connected with the oxidation reaction tank and is used for carrying out ultrafiltration treatment on the waste liquid obtained in the oxidation reaction tank;

and the nanofiltration membrane is connected to the permeation side of the ultrafiltration membrane and is used for performing nanofiltration treatment on the permeation liquid of the ultrafiltration membrane.

In one embodiment, the permeate side of the nanofiltration membrane is connected to a rinse tank.

In one embodiment, a filter aid adding tank is further connected to the feed liquid inlet of the ultrafiltration membrane and is used for adding the filter aid to waste liquid entering the ultrafiltration membrane.

In one embodiment, the ultrafiltration membrane is a multichannel ceramic membrane.

In one embodiment, the ceramic membrane is a multi-channel ceramic membrane.

Advantageous effects

The method provided by the invention is suitable for in-situ leaching remediation treatment of the petroleum-polluted soil, and can be used for dividing the field into two parts by utilizing the heat source in the soil, wherein the heat of one part is transferred to the other part, so that the leaching effect can be improved, and the suction risk of personnel working caused by volatilization of organic matters in the field can be avoided.

The method can also carry out advanced treatment on the leacheate, the COD index in the produced water is qualified, and simultaneously the alkali in the leacheate can be recycled. Meanwhile, during the deep treatment of the leacheate, the ultrafiltration membrane can stably run and is not easy to block a filtration channel.

Drawings

FIG. 1 is a schematic view of a repair system of the present invention.

Fig. 2 is a multi-channel ceramic membrane.

Fig. 3 is a schematic of filter cake formation in multi-channel ceramic membrane cross-flow filtration.

Fig. 4 is a particle force diagram in multi-channel ceramic membrane cross-flow filtration.

Fig. 5 is a structural view of a multi-channel ceramic membrane.

Fig. 6 is an outlet end structure of a multi-channel ceramic membrane tube.

Fig. 7 is an inlet end structure of a multi-channel ceramic membrane tube.

Wherein, 1, a first well; 2. a second hoistway; 3. a third hoistway; 4. an evaporator; 5. an expansion valve; 6. a condenser, 7, a compressor; 8. a leaching solution tank; 9. a working area; 10. leaching the area; 11. an alkali addition tank; 12. a surfactant adding tank; 13. a negative pressure suction pump; 14. a flocculation tank; 15. a flocculant adding tank; 16. an oxidation reaction tank; 17. adding a filter aid into a tank; 18. ultrafiltration membranes; 19. a nanofiltration membrane; 20. a multi-channel ceramic membrane; 21. a filtration channel; 22. a housing; 23. a material inlet; 24. a material outlet; 25. a permeate outlet; 26. a lateral light source; 27. a lateral receiver; 28. a longitudinal light source; 29. a longitudinal receptacle; 30. a longitudinal rod body; 31. a transverse rod body; 32. rinsing the water spray head; 33. is externally connected with a water hose.

Detailed Description

The technical repair method is mainly oriented to places containing petroleum pollutants, and the places mainly contain organic matters of oil and hydrocarbon and have certain volatility.

Firstly, as shown in fig. 1, the processing system of the present invention firstly drills three shafts, namely a first shaft 1, a second shaft 2 and a third shaft 3, on a contaminated site; an evaporator 4 is installed in a first well 1, a condenser 6 is installed in a second well 2, an expansion valve 5 and a compressor 7 are arranged above a field, and the evaporator 4, the expansion valve 5, the condenser 6 and the compressor 7 are sequentially connected to form a heat pump system; at the same time, the rinse solution tank 8 is connected to the second well 2 and the negative pressure suction pump 13 is connected to the third well 3. Thus, a working area 9 is formed between the first shaft 1 and the second shaft 2, and a rinsing area 10 is formed between the second shaft 2 and the third shaft 3.

During the repair treatment, the leacheate is continuously added into the second well 2 through the leacheate tank 8 to enable the leacheate to permeate into the ground, and meanwhile, the underground water (the leacheate) between the second well 2 and the third well 3 is pumped out from the third well 3 through the suction of the negative pressure suction pump 13, so that the petroleum pollutants in the leaching area 10 formed between the second well 2 and the third well 3 are taken away by the leacheate, and the purpose of washing the leaching area 10 is achieved.

Since higher temperatures are generally required when leaching organic contaminants, the oil wash rate can be increased. However, for in-situ leaching, the leaching temperature is not easy to control; meanwhile, because the working face is exposed after the polluted site is excavated, the volatilization of organic matters and hydrocarbons is caused, and the hidden trouble is generated to the health of constructors. Therefore, by further providing the first hoistway 1, in which the evaporator 4 is installed, the soil temperature in the working area 9 formed between the first hoistway 1 and the second hoistway 2 can be reduced by using the underground heat source from the address by the heat pump system formed by connecting the evaporator 4, the expansion valve 5, the condenser 6, and the compressor 7 in this order, and when the constructor performs the work, the constructor performs the remote operation on the working area 9 by performing the main operation, and can reduce the volatilization amount of organic matter in the area; meanwhile, as the heat source stored in the soil in the working area 9 is transferred to the second well 2, the effect of increasing the leaching temperature is achieved, so that the washing effect is improved. Because the heat source in the soil is transferred from one place to another place only by utilizing the heat pump system, the energy consumption is obviously reduced, and the external energy consumption is lower.

After the construction is finished, the evaporator 4 in the first access 1 is transferred and installed in the third well 3, and then the negative pressure suction pump 13 in the third well 3 is installed in the first well 1, so that the original leaching area 10 and the working area 9 are exchanged in position, and the constructor continues to perform construction on the address where the original leaching is finished and continues to perform in-situ leaching on the original region which is not leached.

The present invention is not particularly limited to the leacheate, and it is generally considered in the prior art that the leacheate containing alkali and surfactant has a good removal effect, so that alkali (such as NaOH) and surfactant can be added into the leacheate at the same time. After leaching, the leacheate extracted from the third well 3 mainly contains suspended silt and oil pollutants, the water quality of the leacheate is 5-20mg/L of oil, 50-400mg/L of COD and 20-80mg/L of SS under the common condition, and a part of COD and oil can be removed and most of particle suspended matters are removed through a flocculation mode. The flocculant can be an organic flocculant (such as polyacrylamide) or an inorganic flocculant (polyaluminium chloride, ferric chloride) and the like, and the adding amount can be controlled to be 50-150 mg/L. The surfactant used herein may be an anionic surfactant or a nonionic surfactant, and the concentration may be controlled to be 0.5 to 2wt%, and the concentration of the alkali may be controlled to make the pH of the eluate be 8 to 10.

After the flocculation treatment, through the oxidation treatment step, COD and oil in the water can be further reduced, and the COD and the oil are decomposed or degraded, so that the subsequent operation load of the ultrafiltration membrane is reduced; through subsequent treatment of the ultrafiltration membrane, the wastewater can be further treated, and most of oil pollutants can be removed. The permeated liquid after ultrafiltration is sent to a nanofiltration membrane for filtration treatment, and because the nanofiltration membrane can not intercept monovalent salt and can intercept organic matters with molecular weight of 200-1000, a small amount of organic matters can be intercepted, so that NaOH can permeate the nanofiltration membrane, the alkali liquor can be returned to the leaching process again, and the alkali liquor can be reused by supplementing corresponding surfactant.

Due to the oily components contained in the leacheate, the components can cause the membrane pores of the ultrafiltration membrane to be blocked and polluted during the ultrafiltration process, so that the flux is rapidly reduced and difficult to recover. In one embodiment, a filter aid can be added into the feed liquid entering the ultrafiltration membrane to form a cake layer on the surface of the ultrafiltration membrane, so that the ultrafiltration membrane is protected and the blockage of membrane pores is prevented. The filter aids used here may be conventional inorganic particles, for example diatomaceous earth.

The ultrafiltration membrane used herein may be a multi-channel ceramic membrane, whose basic configuration is shown in fig. 2, and is composed of a membrane tube and a plurality of filtration channels in the membrane tube, wherein the feed liquid is fed into the filtration channels and seeps out from the tube wall under the action of pressure to obtain a permeate, so that the feed liquid is filtered and purified. However, when a filter aid is used, in some cases, the filter cake formed by the filter aid in the filtration channel grows continuously, which leads to the problem of blockage of the filtration channel and thus to complete blockage and rejection of this filtration channel. The basic principle is shown in fig. 3 and 4:

the inside of the multi-channel ceramic membrane 20 is provided with a filtering channel 21, and after the feed liquid enters the filtering channel 21, a filter cake is formed on the inner wall of the filtering channel 21, generally, the thickness of the filter cake at the inlet end of the multi-channel ceramic membrane 20 is generally thinner, and the thickness of the filter cake at the outlet end is thicker; this phenomenon can be deduced by the formula of the thickness of the filter cake layer in the tube of the ceramic membrane cross-flow filtration (analysis of the thickness of the filter cake by the particle deposition model in cross-flow filtration, Yangzhi, Liwai, Mayan Mei, university of east Hua, journal of Nature's edition, Vol.34, No. 6):

as shown in fig. 4: wherein Δ L is the cake layer thickness; f1 is the force perpendicular to the membrane surface caused by osmosis; f2 is the force parallel to the membrane surface caused by the cross flow velocity; f3 is the rearward force caused by adhesion and friction; s is the specific surface area of the particle; c is the particle mass concentration; Δ t is the filtration time. In the filtering process, the inlet end of the raw material has larger flow, so the flow rate f2 is larger, and the formed filter cake layer formed by the particles in the filtered liquid is easily removed by the cross flow effect, so the thickness of the filter cake layer of the particles formed at the inlet end is not thicker; as filtration proceeds, permeate continues to pass from the surface of the ceramic membrane to the permeate side, and the flow rate in the membrane tubes decreases accordingly, resulting in a corresponding decrease in the K3 · f2 term in the formula, resulting in an increase in cake thickness Δ L, which can result in a cake layer that tends to form a thicker structure at the outlet end. In the case shown in fig. 3, an extreme case may occur where the filter cake blocks all the channels at the end of the filtration channel, resulting in the rejection of all channels.

When the multi-channel ceramic membrane 20 is installed in a ceramic membrane filtration apparatus, the structure thereof is shown in fig. 5:

the ceramic membrane filtering equipment comprises a shell 22, wherein a material inlet 23 and a material outlet 24 are respectively arranged at two ends of the shell 22, a multi-channel ceramic membrane 20 is arranged in the shell 22, filtering channels 21 at two ends of the multi-channel ceramic membrane 20 are respectively communicated with the material inlet 23 and the material outlet 24, and a penetrating fluid outlet 25 is also arranged on the shell 22; when filtering the waste water containing particulate matters, the waste water enters the multi-channel filtering channel 21 of the ceramic membrane 20 from the material inlet 23, and the filtered waste water seeps out from the periphery of the filtering channel 21 under the action of pressure and is finally discharged from the penetrating fluid outlet 25. Clogging is liable to occur in the filtration passage 21; the cause of blockage is generally related to three factors: particle concentration, filtration channel diameter, flow rate of wastewater on the surface of the filtration channel. The higher the concentration of the particulate matter, the more likely the clogging occurs; likewise, the cause of clogging is also related to the diameter of the filtration channel 21, the smaller the diameter, the more likely clogging occurs; for the flow rate of the wastewater, when the flow rate is higher, the water flow force for flushing away the filter cake blockage is stronger, the blockage is less likely to occur, and otherwise, the channel blockage is likely to occur.

In one embodiment, the structure of the multi-channel ceramic membrane 20 used in the present invention is shown in fig. 6, the cross section of the multi-channel ceramic membrane 20 is rectangular, an array of filter channels 21 is disposed in the multi-channel ceramic membrane 20, and the array is arranged in the transverse direction and the longitudinal direction of the rectangle, which are perpendicular to each other; at the end in the direction of the feed liquid outlet of the multi-channel ceramic membrane 20, a plurality of transverse particulate matter concentration identifiers composed of a transverse light source 26 and a transverse receiver 27 are arranged on the transverse edge of the rectangular cross section of the multi-channel ceramic membrane 20, the transverse light source 26 is adjacent to the transverse receiver 27, the transverse particulate matter concentration identifiers are in a plurality, the position of each transverse particulate matter concentration identifier in the transverse direction is paired with the position of each filtering channel 21 in the transverse direction one by one, and the transverse receiver 27 in each transverse particulate matter concentration identifier is used for receiving light rays of laser light emitted by the transverse light source 26 after being reflected by particulate matters; meanwhile, a particle concentration identifier consisting of a longitudinal light source 28 and a longitudinal receiver 29 is arranged on the longitudinal side of the rectangular section of the multi-channel ceramic membrane 20, the longitudinal light source 28 is adjacent to the longitudinal receiver 29, the number of the longitudinal particle concentration identifiers is multiple, and the position of each longitudinal particle concentration identifier in the longitudinal direction is matched with the position of each filtering channel 21 in the longitudinal direction one by one; the longitudinal receiver 29 in each longitudinal particle concentration identifier is used for receiving light rays emitted by the longitudinal light source 26 after the laser light is reflected by the particles;

the transverse light source 26, the transverse receiver 27, the longitudinal light source 28 and the longitudinal receiver 29 all protrude from the end face of the multi-channel ceramic membrane 25 in the direction of the feed liquid outlet;

the transverse light source 26 and the longitudinal light source 28 are used for emitting light, and the transverse receiver 27 and the longitudinal receiver 29 are used for receiving reflected light of the light refracted by the particles and obtaining light intensity;

the term "paired" in the context of the present invention, with respect to the light source, receiver and filter channel, means a match of the array positions in the horizontal and vertical directions in the rectangle, with the positions of the particle concentration identifier and filter channel both on the array in the rectangle.

In the filtering process, each pair of light source and receiver mutually performs laser emission and reception, and as waste water containing particulate matters flows in the filtering channel 21, the concentration change of the particulate matters in the material liquid can influence the light intensity obtained by the receiver, if slight blockage occurs or the blockage is formed in the filtering channel 21, the concentration of the particles flowing out is reduced, the refraction of rays emitted by the light source is reduced, and the light intensity obtained by the receiver is reduced, which means that the concentration of the particles is reduced; the light intensity is related to the particle concentration (the stronger the reflected light, the more particles; the weaker the reflected light, the less particles). In the device, the device further comprises a determination module which is used for converting the light intensity into corresponding particle concentration, and analyzing which channel in the multi-channel ceramic membrane is blocked according to the particle concentration corresponding to each particle concentration identifier. (ii) a

For the above specific implementation of the particle concentration detection process, reference may be made to the prior art documents, for example:

a main detection method for particles in water bodies for treating the buelitis is summarized in J, Guangdong chemical industry, 2010, 37(5):296-298.

Correlation study of particle detection technology in Wangzlongyu, Low turbidity Water [ D ]. 2008.

Chenweikang, afterglow, particle solution particle size and concentration differential polarization elastic scattering spectrum on-line analysis method [ J ] spectroscopy and spectrum analysis, 2016, v.36(03): 166-.

Through the above process, the particle concentration variation of all the filtering channels 21 corresponding to the longitudinal receivers 29 and the transverse line receivers 27 can be obtained, since the longitudinal receivers 29 correspond to the longitudinal filtering channels one by one, and the transverse receivers 27 correspond to the transverse filtering channels one by one, the particle concentration obtained by the transverse receivers 27 is set to be a1, a2, A3, … … An in turn, where n is the number of the filtering channels in the transverse direction, and the particle concentration obtained by the longitudinal receivers 29 is set to be B1, B2, B3, … … Bm in turn, where m is the number of the filtering channels in the longitudinal direction; if any one of the channels is blocked or has a potential blocking tendency, because the channel is in a rectangular array, the decrease of the particle concentration is determined on a certain transverse receiver and a certain longitudinal receiver at the same time, because the array arrangement of the transverse receiver and the certain longitudinal receiver is corresponding to the arrangement of the filtering channels, for example, the particle concentration after the conversion of the optical signals obtained by the 5 th transverse receiver and the 3 rd longitudinal receiver is decreased, and when the particle concentration is smaller than a set threshold value, the filtering channel with the 5 th transverse position and the 3 rd longitudinal position is blocked. Therefore, the plugging condition of the pore channels of the ceramic membrane filter can be directly positioned.

As shown in fig. 7, at the end of the multi-channel ceramic membrane 20 in the feed liquid inlet direction, a transverse rod 31 is disposed on one edge of the multi-channel ceramic membrane 20, a vertical longitudinal rod 30 is further disposed on the transverse rod 31, the longitudinal rod 30 can move controllably on the transverse rod 31, a washing water nozzle 32 is further disposed on the longitudinal rod 30, the washing water nozzle 32 can move controllably on the longitudinal rod 30, the washing water nozzle 32 is connected to an external water hose 33, and the washing water nozzle 32 is used for spraying high-pressure washing water into the filtering channel 21; the transverse rod 31 and the longitudinal rod 30 are used for controlling the washing water nozzle 32 to move to the position of the blocked filtering channel 21. As the previous steps, when a potential blockage or blockage of a certain filtering channel is detected, through the movement of the transverse rod body 31, the longitudinal rod body 30 and the washing water nozzle 32, washing liquid can be generated at the blockage position of the nozzle on a filter cake, so that the blockage is avoided; the external water hose 33 may be connected to the washing water shower head 32 at one end thereof and to a washing water joint formed in the casing of the multi-channel ceramic membrane 20 at the other end thereof, and may be supplied with washing water through the outside.

Based on the above method, the remediation system for contaminated soil provided by the invention is shown in fig. 1, and comprises:

a first hoistway 1, a second hoistway 2, and a third hoistway 3; and the second hoistway 2 is located intermediate the first hoistway 1 and the third hoistway 3;

an evaporator is installed in the first well 1, a condenser 6 is installed in the second well 2, and an expansion valve 5 and a compressor 7 are arranged above the polluted soil; the evaporator 4, the expansion valve 5, the condenser 6 and the compressor 7 are connected in sequence to form a heat pump system;

further comprising: a leaching solution tank 10 for filling leaching solution into the second hoistway 2;

a negative pressure suction pump 13 connected to the third well 3 for pumping the leacheate from the third well 3;

a working area 9 is formed between the first shaft 1 and the second shaft 2, and a rinsing area 10 is formed between the second shaft 2 and the third shaft 3;

the operating equipment of the constructor is located above the working area 9.

In one embodiment, further comprising: and the alkali adding tank 11 and the surfactant adding tank 12 are respectively connected to the leaching solution tank 10 and are respectively used for adding alkali and surfactant into the leaching solution tank 10.

In one embodiment, further comprising:

a flocculation tank 14 connected to the negative pressure suction pump 13 for performing flocculation treatment on the leacheate obtained in the negative pressure suction pump 13;

a flocculating agent adding tank 15 connected to the flocculation tank 14 and used for adding a flocculating agent into the flocculation tank 14;

an oxidation reaction tank 16 connected to the flocculation tank 14 for performing oxidation treatment on the clear liquid obtained in the flocculation tank 14;

an ultrafiltration membrane 18 connected to the oxidation reaction tank 16 for performing ultrafiltration treatment on the waste liquid obtained in the oxidation reaction tank 16;

and a nanofiltration membrane 19 connected to the permeate side of the ultrafiltration membrane 18 and used for performing nanofiltration treatment on the permeate of the ultrafiltration membrane 18.

In one embodiment, the permeate side of the nanofiltration membrane 19 is connected to the rinse tank 10.

In one embodiment, a filter aid adding tank 17 is further connected to the feed liquid inlet of the ultrafiltration membrane 18 for adding filter aid to the waste liquid entering the ultrafiltration membrane 18.

In one embodiment, the ultrafiltration membrane 18 is a multichannel ceramic membrane.

In one embodiment, the multichannel ceramic membrane 20 is described.

In the following examples, the oil washing rate of the soil was calculated as follows:

oil washing rate = (oil content in soil before washing-oil content in soil after washing)/oil content in soil before washing × 100%.

In the following embodiment, petroleum-contaminated site soil, which is brown in color and slightly oily in flavor, was used, oil content thereof was measured by gravimetric method at 26100mg/Kg, pH was measured at about 5.2, and soil was stored at 0 to 4 ℃ before the experiment in order to prevent evaporation.

Example 1

Preparing an leacheate, adding NaOH to enable the pH to be about 8.5, simultaneously adding sodium hexadecylbenzene sulfonate (with the concentration of 1 wt%) into a second well (with the depth of 2.5 m), simultaneously opening an account heat pump system, and transferring an underground heat source near the first well (with the depth of 2.5 m) into the second well to enable the temperature of the leacheate to be increased; pumping is carried out from a third shaft (with the depth of 2 m) to enable underground water to flow, the flow rate of the waste water after washing is about 12L/h, and the washing time is controlled at 100 h. When the initial temperature of the leaching solution in the second well is 20 ℃, the temperature is increased to 35 ℃ after the heat pump system works. The soil wash rates obtained after operation under heat pump on and off conditions were as follows:

it can be seen that the soil oil washing effect is improved after the heat source of the heat pump system is transferred.

The water quality of the leacheate obtained from the third well was as follows: oil content is 7.6mg/L, COD is 210mg/L, and SS is 30 mg/L; adding 75mg/L polyaluminium chloride into leacheate for flocculation, reacting the flocculated supernatant with 2.1mg/L oil, 104mg/L COD and 9mg/L SS for 60min at 45 ℃ under 200mg/L ozone to reduce the COD to 54mg/L and 0.8mg/L oil, filtering with a ceramic ultrafiltration membrane with an average pore size of 50mn, adding 500mg/L diatomite filter aid into the inlet water of the ultrafiltration membrane, reducing the COD of the produced water of the ultrafiltration membrane to 12mg/L, and detecting no oil, wherein the average running flux of the ultrafiltration membrane is 122L/m²h. After the nanofiltration membrane with the molecular weight cutoff of 400 is used for filtering, the COD in the permeation solution of the nanofiltration membrane is 1mg/L, the pH value is about 8.0, and the nanofiltration membrane can be recycled after being supplemented with a proper amount of surfactant and alkali.

Claims

1. A method for restoring polluted soil, wherein the polluted soil is petroleum polluted soil, and is characterized by comprising the following steps:

step 1, firstly, respectively drilling a first shaft (1), a second shaft (2) and a third shaft (3) on a polluted site, wherein the second shaft (2) is positioned in the middle of the first shaft (1) and the third shaft (3);

step 2, installing an evaporator (4) in the first access way (1), installing a condenser (6) in the second access way (2), installing an expansion valve (5) and a compressor (7) on the site, and connecting the evaporator (4), the expansion valve (5), the condenser (6) and the compressor (7) in sequence to form a heat pump system;

step 3, starting a heat pump system, transferring a heat source in the first well (1) to the second well (2), adding leacheate into the second well (2), installing a negative pressure suction pump (13) in the third well (3), sucking underground water from the third well (3) in a suction mode, and discharging the leacheate from the third well (3) after the leacheate leachates soil;

step 4, arranging the operation position of a constructor in a place between the first shaft (1) and the second shaft (2);

step 5, after the soil leaching operation is finished, the positions of an evaporator (4) and a negative pressure suction pump (13) are exchanged, a heat source in a third well (3) is transferred to a second well (2), the leaching solution is added into the second well (2), the negative pressure suction pump (13) is installed in the first well (1), underground water is sucked from the first well (1) in a suction mode, and the leaching solution is drained from the first well (1) after being leached for soil; and the operation position of the constructor is arranged at the place between the second shaft (2) and the third shaft (3).

2. The method for remediating contaminated soil as recited in claim 1, wherein in one embodiment, in the 4 th step, the operation position of the construction worker is close to the first hoistway (1);

in one embodiment, the leacheate comprises a base and a surfactant;

in one embodiment, the base is NaOH or KOH and the base is added in an amount such that the pH of the eluate is between 8 and 10;

in one embodiment, the surfactant concentration is 0.5 to 2 wt%.

3. The method as claimed in claim 1, wherein the oil content of the oil-contaminated soil is 5000-50000mg/Kg, and the pH value is 4.5-6.5;

in one embodiment, the leaching waste liquid obtained in the negative pressure suction pump (13) is sequentially processed by the following steps:

s2, oxidizing the supernatant fluid after flocculation treatment in the S1;

s4, carrying out nanofiltration treatment on the ultrafiltration penetrating fluid obtained in the S3;

in one embodiment, in step S1, the flocculating agent used in the flocculation treatment is an inorganic flocculating agent or an organic flocculating agent;

in one embodiment, the inorganic flocculant is selected from polyaluminum chloride or ferric chloride; the organic flocculant is selected from polyacrylamide; the addition amount of the flocculant is 50-150 mg/L;

in one embodiment, the oxidation treatment is ozone oxidation, the adding amount of ozone is 100-500mg/L, the ozone reaction temperature is 30-60 ℃, and the ozone reaction time is 30-60 min;

4. The method of remediating contaminated soil as recited in claim 1, wherein, in one embodiment, said multichannel ceramic ultrafiltration membrane (20);

in one embodiment, the cross section of the multi-channel ceramic membrane (20) is rectangular, an array formed by the filter channels (21) is arranged in the multi-channel ceramic membrane (20), and the array is arranged according to the transverse direction and the longitudinal direction which are perpendicular to each other and rectangular;

at the end in the feed liquid outlet direction of the multi-channel ceramic membrane (20), a transverse particulate matter concentration identifier composed of a transverse light source (26) and a transverse receiver (27) is arranged on the transverse edge of the rectangular section of the multi-channel ceramic membrane (20), the transverse light source (26) is adjacent to the transverse receiver (27), the number of the transverse particulate matter concentration identifiers is multiple, the position of each transverse particulate matter concentration identifier in the transverse direction is matched with the position of each filtering channel (21) in the transverse direction one by one, and the transverse receiver (27) in each transverse particulate matter concentration identifier is used for receiving light rays emitted by the transverse light source (26) after laser particulate matters are reflected; meanwhile, a particle concentration identifier consisting of a longitudinal light source (28) and a longitudinal receiver (29) is arranged on the longitudinal side of the rectangular section of the multi-channel ceramic membrane (20), the longitudinal light source (28) is adjacent to the longitudinal receiver (29), the number of the longitudinal particle concentration identifiers is multiple, and the position of each longitudinal particle concentration identifier in the longitudinal direction is matched with the position of each filtering channel (21) in the longitudinal direction one by one; the longitudinal receiver (29) in each longitudinal particle concentration identifier is used for receiving light rays emitted by the longitudinal light source (26) after the laser light is reflected by the particles; the transverse light source (26), the transverse receiver (27), the longitudinal light source (28) and the longitudinal receiver (29) all protrude out of the end face of the multi-channel ceramic membrane (25) in the direction of the feed liquid outlet;

further comprising: during filtering, the step of detecting the blockage of the filtering channel (21) of the multi-channel ceramic membrane in real time;

the real-time detection method comprises the following steps:

converting the optical signals obtained by the transverse receiver (27) and the longitudinal receiver (29) into particle concentrations;

real-time judging the particle concentration value corresponding to each transverse receiver (27) and each longitudinal receiver (29);

when the particle concentration corresponding to one transverse receiver (27) and one longitudinal receiver (29) is smaller than a set threshold value, judging that: the filter channel (21) is blocked in the same position in the transverse direction as the transverse receiver (27) and in the same position in the longitudinal direction as the longitudinal receiver (29).

5. A method for remediating contaminated soil according to claim 1, wherein, in one embodiment, at the end in the feed liquid inlet direction of the multi-channel ceramic membrane (20), a transverse rod (31) is provided at one edge of the multi-channel ceramic membrane (20), a vertical longitudinal rod (30) is further provided on the transverse rod (31), the longitudinal rod (30) is controllably movable on the transverse rod (31), a washing water nozzle (32) is further provided on the longitudinal rod (31), the washing water nozzle (32) is controllably movable on the longitudinal rod (30), the washing water nozzle (31) is connected with an external water hose (33), and the washing water nozzle (32) is used for spraying high-pressure washing water into the filter channel (21); the transverse rod body (31) and the longitudinal rod body (30) are used for controlling the washing water spray head (32) to move to the position of the blocked filtering channel (21); one end of an external water hose (33) is connected with the washing water spray head (31), and the other end is connected with a washing water joint on the shell (22) of the multi-channel ceramic membrane (20), and washing water is supplied to the multi-channel ceramic membrane (20) through the outside of the multi-channel ceramic membrane;

further comprising the step of flushing the filtration channel (21): when the potential blockage or blockage of one filtering channel (21) is detected, the flushing water spray head (32) is moved to the position of the filtering channel (21) with the potential blockage or the blockage through the movement of the transverse rod body (31), the longitudinal rod body (30) and the flushing water spray head (32), and the blockage of the filter cake is flushed by the flushing water spray head (32); further comprising the step of flushing the filtration channel (21): when a potential blockage or a blockage of one filter channel (21) is detected, the flushing water spray head (32) is moved to the position of the filter channel (21) where the potential blockage or the blockage occurs through the movement of the transverse rod body (31), the longitudinal rod body (30) and the flushing water spray head (32), and the blockage of the filter cake is flushed through the flushing water spray head (32).

6. The method of remediating contaminated soil as set forth in claim 1, wherein in one embodiment, the permeate obtained from the nanofiltration is reused as a leachate after being supplemented with a surfactant.

7. A contaminated soil remediation system, comprising:

a first hoistway (1), a second hoistway (2), and a third hoistway (3); and the second hoistway (2) is located intermediate the first hoistway (1) and the third hoistway (3);

an evaporator is installed in the first well (1), a condenser (6) is installed in the second well (2), and an expansion valve (5) and a compressor (7) are arranged above the polluted soil; the evaporator (4), the expansion valve (5), the condenser (6) and the compressor (7) are connected in sequence to form a heat pump system;

further comprising: a leaching solution tank (10) for filling leaching solution into the second hoistway (2);

a negative pressure suction pump (13) connected to the third well (3) for pumping the leacheate from the third well (3);

a working area (9) is formed between the first shaft (1) and the second shaft (2), and a rinsing area (10) is formed between the second shaft (2) and the third shaft (3);

the operating equipment of the constructor is arranged above the working area (9).

8. The contaminated soil remediation system of claim 7, further comprising, in one embodiment: an alkali adding tank (11) and a surfactant adding tank (12) which are respectively connected with the leaching solution tank (10) and are respectively used for adding alkali and surfactant into the leaching solution tank (10).

9. The contaminated soil remediation system of claim 7, further comprising, in one embodiment:

a flocculation tank (14) connected to the negative pressure suction pump (13) and used for carrying out flocculation treatment on the leacheate obtained in the negative pressure suction pump (13);

the flocculating agent adding tank (15) is connected to the flocculation tank (14) and is used for adding a flocculating agent into the flocculation tank (14);

an oxidation reaction tank (16) connected to the flocculation tank (14) and used for carrying out oxidation treatment on the clear liquid obtained in the flocculation tank (14);

an ultrafiltration membrane (18) connected to the oxidation reaction tank (16) and used for performing ultrafiltration treatment on the waste liquid obtained in the oxidation reaction tank (16);

and a nanofiltration membrane (19) connected to the permeation side of the ultrafiltration membrane (18) and used for performing nanofiltration treatment on the permeation liquid of the ultrafiltration membrane (18).

10. The contaminated soil remediation system of claim 7, wherein in one embodiment, the permeate side of the nanofiltration membrane (19) is connected to a rinse liquor tank (10);

in one embodiment, a feed liquid inlet of the ultrafiltration membrane (18) is also connected with a filter aid adding tank (17) for adding the filter aid into waste liquid entering the ultrafiltration membrane (18);

in one embodiment, the ultrafiltration membrane (18) is a multichannel ceramic membrane;

in one embodiment, the multichannel ceramic membrane (20) is described.