CN110697968A

CN110697968A - Pulse current and permeable reactive barrier co-processing method for removing pollution in soil and underground water

Info

Publication number: CN110697968A
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 Kang Heng Environmental Restoration Co Ltd
Current assignee: Shanghai Kang Heng Environmental Restoration Co Ltd
Priority date: 2019-10-17
Filing date: 2019-10-17
Publication date: 2020-01-17
Anticipated expiration: 2039-10-17
Also published as: CN110697968B

Abstract

The invention is suitable for the technical field of pollution treatment of soil and underground water thereof. Relates to a pulse current and permeable reactive barrier co-processing method for removing the pollution in soil and underground water, which comprises a pulse current pollutant removal technology and a permeable reactive barrier pollutant removal technology. Pulse current is introduced into a polluted area by using a pulse generating device, the purpose of separating pollutants from soil particles is achieved through the change of the anode and the cathode, and the pollutants are transferred in soil and underground water media. A continuous or discontinuous permeable reactive wall is arranged between the electrodes of the pulse current, and a reactive medium is filled in the permeable reactive wall according to the pollution type to react with the pollutants in the migration process, so that the pollutants are blocked, fixed or degraded. The invention can enhance the mobility of pollutants in soil and underground water by means of pulse current, and greatly improves the reaction efficiency between the pollutants and the permeable reactive barrier.

Description

Pulse current and permeable reactive barrier co-processing method for removing pollution in soil and underground water

Technical Field

The invention belongs to the technical field of soil and underground water pollution remediation control and environmental protection engineering, and relates to a method for cooperatively treating pollutants by two technologies of pulse current and permeable reactive barrier.

Background

The total pollution types of the soil environment are mainly organic and inorganic pollution, and the specific gravity of the composite pollution is small. The soil pollution brings great environmental risk to urban development, the pollutant is naturally removed for a long time, so that the land cannot be developed, and a large amount of manpower and materials are also input into the country to repair the polluted soil.

The main pollutants of the underground water condition are soluble total solids, sulfate, fluoride, chloride and the like, and the phenomenon that heavy metals exceed standards exists.

Permeable reactive barrier technology is a pollution treatment system that achieves environmental pollution abatement goals and installs specific reactive media in a contaminated site. The permeable reactive barrier is installed in the migration path of the contaminant to form a blocking effect. The pollutants react with the reaction medium inside the permeable reactor wall when passing through the permeable reactor wall, so that the pollutants are converted into substances which are not polluted by the environment. A large number of research and engineering cases prove that the permeable reactor wall can effectively remove heavy metals and organic matters. 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 used in the removal of water and groundwater pollution. Due to the fact that the horizontal migration capacity of pollutants in soil is poor, the practical application and popularization of the permeable reactive barrier in the field of soil pollutant removal are influenced.

The electrochemical restoration technology is a restoration technology which is simultaneously suitable for soil and underground water. The purpose of pollution treatment is achieved by generating an oxidation effect around the electrode. The technology is mostly used in combination with other technologies at present, the aim of reducing cost or improving the repairing effect is achieved, and the repairing effect is limited. Because the traditional electrochemical restoration technology cannot generate an oxidation effect on the whole polluted site, and meanwhile, the electrodes with the same polarity for a long time easily cause the soil around the electrodes to be over-acidic or alkaline.

Disclosure of Invention

The invention aims at solving all the problems of the prior art and provides a pulse current and permeable reactive barrier co-processing method which is low in cost and wide in application range.

In order to achieve the aim of solving the defects of 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 Cheng-brand double-pulse power supply (GKPD numerical control type).

Pulse current is generated by a pulse generator, the voltage of the output current is 6-20V, and the switching period of the positive electrode and the negative electrode of the pulse current is 100 ms.

The used electrode is deformed steel bar with the diameter of at least 10mm, is buried in a polluted site and then is connected with a pulse generator, and 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 quartz sand layer, fine sand layer, reaction layer, fine sand layer, quartz sand layer in proper order. The reaction medium in the reaction layer is determined by the contaminants of the contaminated site.

And a mesh grid is arranged between each layer of the permeable reactive barrier for separation.

The thickness of the quartz sand layer and the fine sand layer is 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 50 cm.

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

The invention has the following innovation and beneficial effects:

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

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

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

The pulse current which is generated and led in by the pulse generator has the voltage of 6-20V and belongs to 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 is avoided, and the soil near the electrodes is excessively acidified.

The pulse current generated by the pulse generator is utilized to achieve the moving and mixing effect of the underground water and the ions. The pollutants are separated from the soil particles through the back-and-forth movement of the water, and the migration effect that the pollutants horizontally move back and forth between the electrodes is achieved, so that the condition that the permeable reactive barrier is used 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 view of an installation structure of a pulse current and permeable reactive barrier co-processing method for removing pollution in soil and groundwater according to the present invention.

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

Detailed Description

Referring to fig. 1, a deformed steel electrode 1 having a diameter of not less than 10mm is buried in contaminated soil and groundwater. The deformed steel electrode 1 is connected with the pulse generator 6. The permeable reactive barrier is arranged in the middle of the deformed steel 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 not less than 50 cm. Under the action of the pulse current, pollutants in soil and underground water horizontally move between the two deformed steel electrodes 1 in a migration path 5 mode. When the pollutants pass through the permeable reactive barrier, the reactants arranged in the reactive layer 4 react to convert the pollutants into pollutants which are acceptable in the natural environment and are free of pollutants.

Referring to fig. 2, which is a structural view of the permeable reactive barrier of the present invention, the permeable reactive barrier is composed of a quartz sand layer 2, a fine sand layer 3 and a reactive layer 4, each of which is partitioned by a mesh grid 1. The thickness of the quartz sand layer 2 and the fine sand layer 3 is 5-10cm, wherein the grain diameter of the quartz sand is 0.5-1.0mm, and the grain diameter of the fine sand is less than 0.25 mm. The reaction layer 4 has a thickness of not less than 50 cm.

In the present embodiment, referring to fig. 1, a pulsed current and permeable reactive barrier co-processing method for removing pollution in soil and groundwater is provided, which uses a current leading-in device, wherein the current leading-in device is composed of a power supply 6 and two electrodes 1. The electrode 1 adopts a threaded steel bar, and the power supply 6 adopts a pulse generator to generate pulse current.

Referring to fig. 1, in the reactive layer 4 of the permeable reactive barrier, 1: zero-valent iron and quartz sand are added in proportion of 1, a power supply device 6 generates 6-20V pulse current, and the current enters an electrode 1. Soil 5 polluted by chromium element is added between the permeable reactive barrier 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 a period, and the positive and negative electrodes of the two electrodes 1 are changed in the period of 100 ms. Pollutants in the pollution pattern migrate back and forth in the two electrodes 1 and repeatedly pass through the reaction layer 4, so that the aim of removing heavy metal chromium from soil is fulfilled.

In this case, referring to fig. 1, a pulsed current and permeable reactive wall co-processing method for removing contamination in soil and groundwater has the following steps:

preparing the polluted soil with chromium pollution, wherein the chromium pollution concentration is 50 mg/kg.

Burying 2 electrodes 1 into contaminated soil 5, wherein the electrodes 1 are twisted steel bars, the buried depth is to the bottom of the soil, a pulse power generator is connected with the electrodes 1, a permeable reactive barrier is inserted between the two electrodes 1, the permeable reactive barrier is composed 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 not less than 50cm, and 1 is added into the reactive layer 4 in the permeable reactor 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.

The experimental results of this case are:

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

The pulse current and permeable reactive barrier co-processing method for removing the pollution in the soil and the underground water in the embodiment has the advantages of short repair period, low cost and safe construction, and is not easy to cause secondary pollution.

The characteristic of the embodiment is that

The pulse generator switches the positive electrode and the negative electrode of the electrode 1 in a period of 100ms, avoids the polarization phenomenon around the electrode after long-time electrification, and 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, so that the pollutant removal effect is improved.

Claims

1. A pulse current and permeable reactive barrier co-processing method for removing pollution in soil and underground water is characterized in that,

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

after being separated from 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; pollutants in soil and groundwater are removed by adsorption, precipitation, chemical sedimentation or biodegradation of reactive materials.

2. The method of claim 1, wherein the pulse current installation step comprises:

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

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

(3) the spacing of each electrode is controlled to be 3-5 m;

(4) the cross section of the electrode between the same poles is not less than 20mm²The cables are connected in sequence and connected with the pulse generating device.

3. The method for the cooperative treatment of the pulse current and the permeable reactive barrier for the decontamination of the soil and the groundwater according to claim 1, wherein the step of the pulse current treatment comprises:

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

(2) installing a pulse generator in the polluted site, and outputting pulse current to the electrodes to generate an electric field of the pulse current 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 m, and the voltage between the electrodes is controlled to be 2-4V/m.

4. The method of claim 1, wherein the permeable reactive barrier treating step comprises:

(1) a continuous reactor wall structure is used. Embedding a polluted medium in parallel with the electrode to ensure that the polluted medium is vertical to a pollutant migration path;

(2) the permeable reactive barrier adopts a 5-layer design, and comprises a quartz sand layer, a fine sand layer, a reactive layer, a fine sand layer and a quartz sand layer in sequence in the migration direction of pollutants;

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

(4) the top of the reaction layer is provided with an opening for replacing reaction substances;

(5) each layer of the permeable reactive barrier is separated by a mesh grid;

(6) the reaction layer is provided with a reaction medium for removing corresponding pollutants and is used for removing the pollutants in the underground water and the soil.