CN110697968B

CN110697968B - Pulse current and permeable reactive barrier cooperative treatment method for removing pollution in soil and underground water

Info

Publication number: CN110697968B
Application number: CN201910986573.9A
Authority: CN
Inventors: 王森; 朱晓平; 王湘徽; 王欢; 王加华; 胡佳晨; 余湛; 郑阳; 张章; 刘继东
Original assignee: Shanghai Sus Environment Restoration Co ltd
Current assignee: Shanghai Sus Environment Restoration Co ltd
Priority date: 2019-10-17
Filing date: 2019-10-17
Publication date: 2023-05-12
Anticipated expiration: 2039-10-17
Also published as: CN110697968A

Abstract

The invention is suitable for the technical field of pollution treatment of soil and groundwater thereof. Relates to a pulsed current and permeable reactive barrier cooperative treatment method for removing pollution in soil and underground water, which comprises pulsed current pollutant removal technology and permeable reactive barrier pollutant removal technology. The pulse generator is used to introduce pulse current into the polluted area, and the purpose of separating pollutant from soil particles is achieved through the change of anode and cathode, and the pollutant is migrated in soil and underground water medium. A continuous or discontinuous permeable reactive barrier is positioned between the electrodes of the pulsed current, in which the reactive medium is filled according to the type of contaminant, and reacts with the contaminant during migration, so that the contaminant is trapped, immobilized or degraded. The invention can strengthen the mobility of the pollutants in the soil and the groundwater by means of pulse current, and greatly improves the reaction efficiency between the pollutants and the permeable reaction wall.

Description

Pulse current and permeable reactive barrier cooperative treatment method for removing pollution in soil and underground water

Technical Field

The invention belongs to the technical fields of soil and groundwater pollution restoration control and environmental protection engineering, and relates to a method for cooperatively treating pollutants by using two technologies of pulse current and permeable reactive barrier.

Background

The general pollution types of the soil environment are mainly organic and inorganic pollution, and the proportion of the combined pollution is small. Soil pollution brings great environmental risks to urban development, and a long time is required for removing pollutants naturally, so that the land cannot be developed, and a large amount of manpower and materials are put into China to repair the polluted soil.

The main pollutants in the groundwater are soluble total solids, sulfate, fluoride, chloride and the like, and the phenomenon of exceeding heavy metals exists.

Permeable reactive barrier technology is a pollution treatment system that achieves environmental pollution abatement goals by installing a specific reaction medium in a contaminated site. The permeable reactive barrier is mounted in the path of migration of the contaminant, creating a blocking effect. The contaminants react with the reaction medium inside the permeable reactor wall as they pass through it, converting the contaminants into environmentally non-contaminating substances. Numerous research and engineering cases have demonstrated that permeable reactor walls are effective in removing heavy metals and organics. The type of contaminants removed and the effectiveness of the removal depend primarily on the reactants disposed in the permeable reactive barrier. Permeable reactive barrier technology is commonly used in the removal of water pollution and groundwater pollution. The practical application and popularization of the permeable reactive barrier in the field of soil pollutant removal are affected by the poor horizontal migration capability of pollutants in the soil.

The electrochemical repair technology is a repair technology which is simultaneously applicable to soil and underground water. The purpose of pollution control is achieved by generating an oxidation effect around the electrode. The technology is mostly used for being combined with other technologies at present, the purposes of reducing cost or improving the repairing effect are achieved, and the repairing effect is limited. Because the traditional electrochemical repair technology cannot generate oxidation effect on the whole pollution field, and meanwhile, the electrodes with the same polarity for a long time easily cause that soil around the electrodes is too acidic or alkaline.

Disclosure of Invention

The invention aims at solving the problems of the prior art and provides a pulse current and permeable reactive barrier cooperative treatment method with low cost and wide application range.

In order to achieve the aim of solving the defects in the prior art, the invention adopts the following scheme:

the pulse generator can use a mature double-pulse power supply product, and the double-pulse power supply used in the method is a Shenzhen hong brand double-pulse power supply (GKPD numerical control type).

The pulse generator is used for generating pulse current, the output current voltage is 6-20V, and the positive-negative electrode conversion period of the pulse current is 100ms.

The electrodes used are screw-thread steel with the diameter of at least 10mm, and are connected with a pulse generator after being buried in a polluted site, so that pulse current is led into the polluted site.

A continuous permeable reactive barrier is disposed between the positive and negative electrodes. The reaction wall is divided into 5 layers, and the structure is a quartz sand layer, a fine sand layer, a reaction layer, a fine sand layer and a quartz sand layer in sequence. The reaction medium in the reaction layer is determined by the contaminants contaminating the site.

A reticular grid is arranged between each two layers of permeable reactive barrier for separation.

The thickness of the quartz sand layer and the thickness of the fine sand layer are set to be 5-10cm, wherein the particle size of the quartz sand is 0.5-1.0mm, the particle size of the fine sand is less than 0.25mm, and the thickness of the reaction layer is not less than 50cm.

The top of the reaction layer is provided with an opening for changing the reaction substance.

The innovation and beneficial effects of the invention are as follows:

the pulse current and the permeable reactor wall are jointly acted on the polluted site to achieve the repairing effect.

The invention uses a pulse generator to generate pulse current, and the pulse current is led into a polluted site through a spiral steel electrode.

The deformed steel bar electrode has a larger surface area in contact with the soil and is more firmly in contact with the soil than other electrodes.

The pulse current generated by the pulse generator is 6-20V, which belongs to the safe construction voltage. The positive and negative poles of the pulse current are changed in a period of 100ms, so that the situation that the electrodes are in the same polarity for a long time and the soil near the electrodes is excessively acid-alkalized is avoided.

The movement and mixing effect of the groundwater and ions are achieved by using the pulse current generated by the pulse generator. The pollutant is separated from the soil particles through the back and forth movement of the moisture, and the migration effect of the pollutant which horizontally moves back and forth between the electrodes is achieved at the same time, so that the condition of using the permeable reaction wall in the soil is met. The migration rate is increased in the groundwater environment, the repairing effect of the permeable reactive barrier is improved, and the repairing time is shortened.

Drawings

FIG. 1 is a schematic diagram of the installation structure of a pulsed current and permeable reactive barrier co-treatment method for removing contaminants from soil and groundwater according to the present invention.

FIG. 2 is a schematic diagram of a permeable reactive barrier according to the invention.

Detailed Description

Referring to fig. 1, a deformed steel bar electrode 1 having a diameter of not less than 10mm is buried in contaminated soil and groundwater. The deformed steel bar electrode 1 and the pulser 6 are connected. The permeable reactive barrier is arranged in the middle of the deformed steel bar electrode 1. The permeable reactive barrier consists of a quartz sand layer 2 with the thickness of 5-10cm, a fine sand layer 3 and a reactive layer 4 with the thickness of not less than 50cm. Under the action of the pulse current, the pollutants in the soil and the groundwater move horizontally between the two screw-thread steel electrodes 1 in a migration way 5. The pollutants react with the reactants arranged in the reaction layer 4 when passing through the permeable reaction wall, and are converted into pollutants which are acceptable in natural environment.

Referring to fig. 2, a permeable reactive barrier according to the invention is shown as a structure of a permeable reactive barrier consisting of a layer of quartz sand 2, a layer of fine sand 3 and a reactive layer 4, each of which is separated by a mesh grid 1. The thickness of the quartz sand layer 2 and the fine sand layer 3 is 5-10cm, wherein the particle size of the quartz sand is 0.5-1.0mm, and the particle size of the fine sand is less than 0.25mm. The thickness of the reaction layer 4 is not less than 50cm.

In this embodiment, referring to fig. 1, a pulsed current and permeable reactive barrier co-treatment method for removing soil and groundwater pollution uses a current introduction device consisting of a power source 6 and two electrodes 1. The electrode 1 adopts a screw reinforcement, and the power supply 6 adopts a pulse generator to generate pulse current.

Referring to fig. 1, in the reaction layer 4 of the permeable reactive barrier, one 1: zero-valent iron and quartz sand are added in proportion 1, a power supply device 6 generates pulse current of 6-20V, and the current enters the electrode 1. Soil 5 polluted by chromium element is added between the gram-osmotic reaction wall and the electrode. The power supply means 6 ensure a voltage gradient of 2-4V/m in the contaminated soil 5. The switching of the positive and negative electrodes of the pulse current takes 100ms as one period, and the positive and negative electrodes of the two electrodes 1 are switched at 100ms period. The pollutants in the pollution map migrate back and forth in the two electrodes 1 and repeatedly pass through the reaction layer 4, so that the purpose of removing the heavy metal chromium from the soil is achieved.

In this case, referring to fig. 1, a pulsed current and permeable reactive barrier co-treatment method for soil and groundwater contamination removal has the steps of:

the contaminated soil with chromium contamination was prepared with a chromium contamination concentration of 50mg/kg.

2 electrodes 1 are buried in polluted soil 5, the electrodes 1 are screw-thread steel bars, the buried depth reaches the bottom of the soil, a pulse power generator is connected with the electrodes 1, a permeable reaction wall is inserted between the two electrodes 1, the permeable reaction wall consists of a quartz sand layer 2 with the thickness of 5-10cm, a fine sand layer 3 and a reaction layer 4 with the thickness of not less than 50cm, and 1 is added in the reaction layer 4 in the permeable reaction wall: 1 proportion of zero-valent iron and quartz sand. The pulse current 6 generates pulse current to maintain the voltage gradient in the polluted soil 5 at 2-4V/m, and the electrifying time is 7 days.

Experimental results of this case:

the chromium concentration in the restored soil is 15mg/kg, the removal rate is 70%, and the excellent pollutant removal effect is achieved.

The pulse current and permeable reactive barrier cooperative treatment method for removing the pollution in the soil and the groundwater in the embodiment has the advantages of short restoration period, low cost and safe construction, and is not easy to cause secondary pollution.

The embodiment is characterized in that

The pulse generator takes 100ms as a period to switch the anode and the cathode of the electrode 1, so that the polarization phenomenon around the electrode after long-time energization is avoided, meanwhile, pollutants are migrated back and forth in the two electrode limits 1 and repeatedly pass through the reaction layer 4 in the permeable reaction wall, and the pollutant removal effect is improved.

Claims

1. A pulsed current and permeable reactive barrier cooperative treatment method for removing pollution in soil and groundwater is characterized in that,

the pulse current is used for separating pollutants from soil particles and enhancing the mobility of the pollutants;

after separating from the soil, the pollutants move between the positive electrode and the negative electrode under the action of pulse current; the pollutants pass through the continuous permeable reactive barrier in the flowing process; removing pollutants in soil and groundwater by means of adsorption, precipitation, chemical sedimentation or biodegradation of the reaction materials;

the pulse current mounting step comprises the following steps:

(1) The pulse electrode takes a deformed steel bar with the diameter not smaller than 10mm as an electrode;

(2) The pulse electrode is embedded in the polluted soil and the underground water medium; the length of the electrode is equal to the pollution depth;

(3) The interval of each electrode is controlled to be 3-5 meters;

(4) The cross section of the electrode between homopolar is not less than 20mm ² Is connected in turn with the pulse generating device.

2. A pulsed electric current and permeable reactive barrier co-treatment method for removing soil and groundwater contamination according to claim 1, wherein the pulsed electric current treatment step comprises:

(1) A switching power supply with PFC function is arranged in a polluted site and is used for converting direct current and alternating current;

(2) A pulse generator is arranged in the polluted site and is used for outputting pulse current to the electrode, and an electric field of the pulse current is generated in the polluted site;

(3) The switching of the positive electrode and the negative electrode of the pulse current takes 100ms as a period;

(4) The voltage of the pulse current generated by the pulse generator is controlled to be 6-20V;

(5) The electrode spacing is 3 meters, and the inter-electrode voltage is controlled to be 2-4V/m.

3. A pulsed electric current and permeable reactive barrier co-treatment method for removing contaminants from soil and groundwater according to claim 1, wherein the permeable reactive barrier treatment step comprises:

(1) Adopting a continuous reactor wall structure, burying a pollution medium in parallel with the electrode, and ensuring the vertical pollutant migration path;

(2) The permeable reactive barrier adopts a 5-layer design, and adopts a quartz sand layer, a fine sand layer, a reactive layer, a fine sand layer and a quartz sand layer in turn in the pollutant migration direction;

(3) The thickness of the quartz sand layer and the thickness of the fine sand layer are set to be 5-10cm, and the thickness of the reaction layer is not less than 50cm;

(4) An opening is arranged at the top of the reaction layer and used for replacing the reaction substances;

(5) The layers of the permeable reactive barrier are separated by a reticular grid;

(6) The reaction medium for removing the corresponding pollutants is arranged in the reaction layer and is used for removing the pollutants in the underground water and the soil.