CN106040735B

CN106040735B - Heavily-polluted site Cu in-situ and ex-situ coupling detoxification method

Info

Publication number: CN106040735B
Application number: CN201610370393.4A
Authority: CN
Inventors: 张大磊; 李瑞栋; 王欣玉
Original assignee: Qingdao University of Technology
Current assignee: Qingdao University of Technology
Priority date: 2016-05-30
Filing date: 2016-05-30
Publication date: 2020-12-15
Anticipated expiration: 2036-05-30
Also published as: CN106040735A

Abstract

The invention adopts a Cu in-situ and ex-situ coupling detoxification method for a heavily polluted site, sludge, a carbon source and ferrous sulfate are prepared into a medicament to be applied to Cu-containing soil, and then a special construction and maintenance mode is adopted to enable a reduction ecological microbial inoculum to gradually permeate underground to reduce Cu in deep polluted soil. The method can be used for repairing the Cu-containing site with higher pollution depth at low cost and high efficiency, and simultaneously treats waste with waste to treat sludge.

Description

Heavily-polluted site Cu in-situ and ex-situ coupling detoxification method

Technical Field

The invention provides a method for treating Cu-polluted soil, which is characterized in that sludge, a carbon source and sulfate are prepared into a medicament to be applied to the Cu-contained soil, and then a special maintenance mode is adopted, so that Cu can be efficiently fixed, and secondary pollution of the sulfate is avoided, and the method belongs to the field of environmental protection.

Background

Due to the random discharge of mining and metallurgical waste water, a large amount of soil is polluted by Cu. Current methods of treating copper-containing soils have drawbacks. The high-temperature melting method has high cost and large energy consumption. The biological method has long reaction period and is easy to cause secondary pollution of external biological agents. The curing method has unstable effect, and the curing agent is easy to cause secondary pollution to soil. Patent No. 201510056406.6 describes a method for solidifying soil containing heavy metals, but this method uses a large amount of materials and is relatively expensive, and on the other hand, the solidification effect is unstable, for example, calcium oxide added is liable to carbonation under natural conditions, so that the alkaline solidification effect is reduced.

Disclosure of Invention

Aiming at the defects of the prior art, the invention adopts a Cu in-situ and ex-situ coupling detoxification method for a heavily polluted site, prepares sludge, a carbon source and sulfate into a medicament to be applied to Cu-containing soil, and then adopts a special construction and maintenance mode to enable a reduction ecological microbial inoculum to gradually permeate underground to reduce the Cu in the deep polluted soil. The method can be used for repairing the Cu-containing site with higher pollution depth at low cost and high efficiency, and simultaneously treats waste with waste to treat sludge. Which comprises the following steps:

(1) mixing sodium sulfate, sludge or carbon source solution according to a certain proportion, enabling the dry sludge content of the mixed solution to be 0.1-20%, the solid content to be 0.5-25%, the organic carbon content to be 0.5-25%, and the mass ratio of SO 4/organic carbon to be (0-1): 1, and reacting the mixed solution for 0-5 days to obtain a Cu soil remediation agent;

(2) excavating 1-10m of soil on the surface layer of the Cu-containing field, then paving a geomembrane with meshes at the bottom of the excavated field, and paving impermeable materials around the excavated field to build a semi-closed storage yard;

(3) crushing the soil in the step (2) to be less than 10mm, paving the crushed soil on a semi-closed storage yard, and then spraying and mixing the medicament in the step (1), wherein the mixing ratio is that the mass ratio of the Cu-containing soil to the medicament is 1 (0.1-0.8);

(4) during the stockpiling period, the water content of the soil is kept within the range of 5-60% within 5-100 days in the initial stage, so that biochemical reaction can be carried out, and sulfate reducing bacteria are propagated in a large amount in the field; spraying the soil remediation agent or the carbon source solution in the step (1) to the site every 1-200 days, wherein the ratio of accumulated organic carbon in the agent or the carbon source solution sprayed for several times to the total Cu content of the whole site is not lower than 0.5: 1; the average rainfall of the field per year is required to be more than 200mm, and if the average rainfall is not enough, the ground is supplemented by adopting a surface water spraying mode, so that the medicine can continuously seep to the lower layer.

In the above steps, the sludge is anaerobic sludge generated by a sewage treatment anaerobic process, and part of facultative sludge can be added; the carbon source solution can be a solution containing alcohol, sugar, protein and starch, can also be a solution of organic solid waste, can also be industrial and municipal organic wastewater, and the sodium sulfate can be replaced by other sulfates; the water sprayed on the surface can be replaced by organic solution, and the organic carbon content of the organic solution is 10-1000 mg/L; the material of the geomembrane paved with meshes in the step (2) can be a material which is difficult to biodegrade or a biodegradable material; the equivalent diameter of small holes in the mesh geomembrane is 1-100mm, and the distance between the holes is 0.01-10 m.

According to the method, through special ecological agent addition and special field maintenance, a flora mainly comprising sulfate reducing bacteria is promoted to be formed in a large field, the flora can effectively fix Cu by utilizing a carbon source, and simultaneously fully utilize sulfate to convert the sulfate into sulfide, and can convert the Cu into more stable Cu sulfide precipitate while effectively fixing the Cu.

Compared with the traditional Cu-containing soil treatment method, the method has the following advantages:

1. sulfate reducing bacteria in the sludge microbial inoculum reduce sulfate to generate sulfide, so that Cu can be more effectively fixed;

2. the cultured sulfate reducing flora is indigenous flora, has strong natural tolerance, is easy to propagate on site in a large scale, can permanently and effectively fix Cu, and does not cause ecological problems;

3. the reduced Cu and sulfide of a metabolic product of sulfate reducing bacteria form a Cu sulfide precipitate, so that the Cu in the soil is more stable and is obviously superior to other biochemical processes;

4. the method uses the sludge and the organic waste as main raw materials, so that the cost is greatly reduced;

5. the method adopts in-situ remediation for the deep soil, avoids excavation of the deep soil and greatly reduces the cost.

The specific implementation example is as follows:

example 1:

(1) mixing sodium sulfate, sludge or carbon source solution according to a certain proportion, enabling the dry sludge content of the mixed solution to be 0.1-5%, the solid content to be 0.5-5%, the organic carbon content to be 0.5-5% and the mass ratio of SO 4/organic carbon to be 0.7: 1, and reacting the mixed solution for 2 days to obtain a Cu soil remediation agent;

(2) excavating 10m soil on the surface layer of the Cu-containing field, then paving a geomembrane with meshes at the bottom of the excavated field, and paving impermeable materials around the excavated field to build a semi-closed storage yard;

(3) crushing the soil in the step (2) to be less than 5mm, then mixing the soil with the medicament in the step (1) in a mass ratio of the Cu-containing soil to the medicament of 1:0.5, and then placing the mixture in a semi-closed storage yard in the step (2) for closed storage;

(4) during the stockpiling period, the water content of the soil is kept within the range of 5-60% within 20 days in the initial stage, so that biochemical reaction can be carried out, and a large amount of sulfate reducing bacteria are propagated in the field; sprinkling the soil remediation agent or the carbon source solution in the step (1) to the site every 2 days for the initial 100 days, wherein the number of days at intervals in the later period exceeds 20 days, and the ratio of the accumulated organic carbon in the agent or the carbon source solution sprayed for several times to the total Cu content of the whole site is not lower than 0.5: 1; the average rainfall of the field is 500mm each year by natural rainfall and artificial spraying. After the engineering is carried out for 2 years, the Cu content of the soil with the depth of more than 20 meters is lower than 2mg/kg, and the Cu content of underground water is lower than 0.1 mg/L.

Example 2:

(1) mixing sodium sulfate, sludge or carbon source solution according to a certain proportion, enabling the dry sludge content of the mixed solution to be 5-15%, the solid content to be 5-15%, the organic carbon content to be 5-15% and the mass ratio of SO 4/organic carbon to be 0.5:1, and reacting the mixed solution for 1 day to obtain a Cu soil remediation agent;

(2) excavating soil with the surface layer of 5m of the Cu-containing field, then paving a geomembrane with meshes at the bottom of the excavated field, and paving impermeable materials at the periphery of the excavated field to build a semi-closed storage yard;

(4) during the stockpiling period, the water content of the soil is kept within the range of 5-60% within 20 days in the initial stage, so that biochemical reaction can be carried out, and a large amount of sulfate reducing bacteria are propagated in the field; sprinkling the soil remediation agent or the carbon source solution in the step (1) to the site every 2 days for the initial 100 days, wherein the number of days at intervals in the later period exceeds 20 days, and the ratio of the accumulated organic carbon in the agent or the carbon source solution sprayed for several times to the total Cu content of the whole site is not lower than 0.5: 1; the average rainfall of the field is 500mm each year by natural rainfall and artificial spraying. After the engineering is carried out for 1 year, the Cu content of the soil with the depth of more than 40 meters is less than 2mg/kg, and the Cu content of underground water is less than 0.1 mg/L.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions.

Claims

1. A Cu in-situ and ex-situ coupling detoxification method for a heavily polluted site is characterized by comprising the following steps:

(1) mixing sodium sulfate, sludge and a carbon source solution according to a certain proportion, enabling the dry sludge content of the mixed solution to be 0.1-20%, the solid content to be 0.5-25%, the organic carbon content to be 0.5-25%, and the mass ratio of SO 4/organic carbon to be 1: 1, and reacting the mixed solution for 0-5 days to obtain a Cu soil remediation agent;

(3) crushing the soil in the step (2) to be less than 10mm, paving the crushed soil on a semi-closed storage yard, spraying and mixing the medicament in the step (1) according to the mass ratio of the Cu-containing soil to the medicament of 1 (0.1-0.8), and then placing the mixture on the semi-closed storage yard in the step (2) for closed storage;

(4) during the stockpiling period, keeping the water content of the soil within the range of 5-60% within 5-100 days in the initial period, simultaneously sprinkling the soil remediation agent or the carbon source solution in the step (1) to the site every 1-200 days, and sprinkling the agent or the carbon source solution for a plurality of times, wherein the ratio of the accumulated organic carbon in the agent or the carbon source solution to the total Cu content of the whole site is not lower than 0.5: 1; the average rainfall of the field per year is required to be more than 200mm, and if the average rainfall is not enough, the ground is supplemented by adopting a surface water spraying mode, so that the medicine can continuously seep to the lower layer.

2. The in-situ and ex-situ coupling detoxification method for heavily polluted site Cu as claimed in claim 1, wherein the sludge is anaerobic sludge generated by anaerobic process of sewage treatment, and optionally some facultative sludge.

3. The in-situ and ex-situ coupling detoxification method for Cu in heavily polluted sites as claimed in claim 1, wherein the carbon source solution can be a solution containing alcohol, sugar, protein, starch, an organic solid waste solution, an industrial and municipal organic wastewater, and the sodium sulfate can be replaced by other sulfate.

4. The in situ and ex situ coupling detoxification method for heavily polluted site Cu as claimed in claim 1, wherein the water sprayed on the surface of the heavily polluted site Cu is replaced by an organic solution, and the organic carbon content of the organic solution is 10-1000 mg/L.

5. The Cu in-situ and ex-situ coupling detoxification method for the heavily polluted site as claimed in claim 1, wherein the geomembrane material laid with meshes in the step (2) can be a nonbiodegradable material or a biodegradable material; the equivalent diameter of small holes in the mesh geomembrane is 1-100mm, and the distance between the holes is 0.01-10 m.