CN111659729A

CN111659729A - Method for restoring chromium-polluted soil by Shewanella

Info

Publication number: CN111659729A
Application number: CN202010457365.2A
Authority: CN
Inventors: 邹德勋; 郑旭升; 郭荣欣; 刘研萍
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2020-05-27
Filing date: 2020-05-27
Publication date: 2020-09-15

Abstract

A method for restoring chromium-contaminated soil by Shewanella relates to the field of soil restoration, and comprises the steps of fully mixing Shewanella with chromium-contaminated soil to restore the chromium-contaminated soil, wherein the cell density of the added Shewanella is (2-3) × 10⁹Per mL; the Shewanella is a mature strain cultured for 24 hours in an LB culture medium at the temperature of 30 ℃ and under the condition of 180rpm according to the inoculation amount of 5 percent by volume; the repairing process is carried out under anaerobic condition, the repairing time is 80 days, and the temperature is 30 +/-1 ℃. The Shewanella in the method also has a certain repairing effect on the hexavalent chromium polluted soil with different concentrations, and other substances except a bacterial solution are not required to be added in the repairing process, so that a new green and environment-friendly method is provided for repairing the high-concentration hexavalent chromium polluted soil.

Description

Method for restoring chromium-polluted soil by Shewanella

Technical Field

The invention relates to the field of soil remediation, in particular to application of Shewanella in remediation of chromium-contaminated soil.

Background

Soil is a material foundation for sustainable development of economy and society and human survival, but according to survey bulletin of national soil pollution conditions issued by the ministry of environmental protection and the ministry of national soil resources in 2014, 16.1% of soil in China is polluted, wherein inorganic pollutants account for 82.8%, and the point standard exceeding rate of chromium pollution is 1.1%. Hexavalent chromium has carcinogenic, teratogenic, mutagenic effects, and is a serious health hazard to humans and other living beings.

In the production activities of human beings, chromium salt industries such as printing and dyeing, metallurgy, electroplating, tanning and the like can cause chromium pollution to soil, the concentration of hexavalent chromium in some seriously polluted plots can even reach more than 3000mg/kg, and the harm to human bodies and the environment is great. For the soil with a high pollution degree, the remediation method is mostly a physical method or a chemical method. The physical remediation method is mainly to add some materials to the soil to reduce the cr (vi) concentration by adsorption or solidification. However, the use of this method requires a large amount of capital and is costly. The chemical remediation method mainly comprises the step of adding some agents with reducing effect into soil to reduce Cr (VI) into Cr (III). However, the method introduces new pollutants into the soil, and is easy to cause problems of secondary pollution and the like.

The microbial remediation method has the advantages of low cost, no need of spending a large amount of capital, relatively convenient management and operation, no secondary pollution and environmental protection. Patent 1: the research shows that the method for restoring the soil polluted by deep mercury and chromium by using the anaerobic sulfate reducing bacteria and the iron-based material can reduce the concentration of Cr (VI) in the soil from 1287.61mg/kg to 50.92 mg/kg. Document 1: [1] SU C, LI L, YANG Z, et al, Cr (VI) reduction in chromium-associated soil under aerobic condition [ J ] Transactions of non-ferrous Metals Society of China,2019, 29(6): 1304-1311. for contaminated soil with Cr (VI) concentration of 1521.9mg/kg, the Cr (VI) concentration can be reduced to 199.2mg/kg by the life activity of indigenous microorganisms.

However, for contaminated soil with Cr (VI) concentration exceeding 3000mg/kg, methods related to microbial remediation have been rarely reported.

Disclosure of Invention

Aiming at the problems, the invention aims to provide a method for restoring chromium-polluted soil by using Shewanella, and the Shewanella in the method has a certain restoring effect on hexavalent chromium-polluted soil with different concentrations, and other substances except a bacterial solution are not required to be added in the restoring process, so that a novel green and environment-friendly method is provided for restoring the high-concentration hexavalent chromium-polluted soil.

The purpose of the invention is realized by the following technical scheme:

a method for restoring chromium-contaminated soil by Shewanella comprises the following steps:

the Shewanella bacterium liquid and the high-concentration chromium-polluted soil are uniformly mixed, so that the chromium-polluted soil can be repaired.

Further, the cell density of the Shewanella added in the repairing process is (2-3) × 10⁹one/mL.

Further, the repair process needs to be performed in an anaerobic environment.

Further, the repairing process needs to be carried out for 80 days at the temperature of 30 +/-1 ℃.

Furthermore, the concentration of hexavalent chromium in the chromium-polluted soil is between 300mg/kg and 4600mg/kg, the water content is between 30 percent and 60 percent, and the pH value is between 5 and 9.

Further, the Shewanella is a mature strain obtained by inoculating 5% of Shewanella in LB medium (tryptone 10g/L, sodium chloride 10g/L, yeast extract 5g/L, and water in balance, pH 7.0) at 30 ℃ for 24 hours at 180 rpm.

Compared with the existing repair technology, the invention has the advantages that:

(1) the invention can not introduce new pollutants in the repairing process, avoids secondary pollution and is a green and environment-friendly repairing method.

(2) The Shewanella used in the invention is not applied to the chromium-polluted soil remediation, has a certain remediation effect on the high-concentration chromium-polluted soil (the concentration of Cr (VI)) is more than 3000mg/kg, and provides a new remediation method for the high-concentration chromium-polluted soil.

(3) The Shewanella used in the invention can be directly purchased, is simple and easy to obtain and has lower cost.

Drawings

Fig. 1 is a graph showing the results of the tests obtained.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to specific embodiments and the accompanying drawings.

Example 1

Samples with the depth of 20-100cm are obtained from a site polluted by certain chromium of the complex fertilizer and the silver, and after the samples are air-dried and sieved (60 meshes), the soil property and the content of hexavalent chromium are measured, and the results are shown in table 1.

Culture of Shewanella: the strains used in this example were Shewanella alga, Shewanella pultracins and Shewanella oneidensis, wherein S.alga was purchased from China general microbiological culture Collection center (CGMCC) and numbered 1.8754; two additional strains of bacteria were purchased from the China center for type culture Collection, and numbered AB 2013239 and AB 2013238 in that order. The medium used was LB medium (tryptone 10g/L, sodium chloride 10g/L, yeast extract 5g/L, pH 7.0). 5 percent of the inoculation ratio is cultured in a constant temperature incubator for 24 hours at 30 ℃ and 180rpm for standby.

Repairing hexavalent chromium contaminated soil: the test is divided into A, B, C, D groups, wherein the group A is added with S.alga, the group B is added with S.putrefeaciens, the group C is added with S.oneidensis, and the group D is added with deionized water with the same volume.

100g of the 1 st group of soil is respectively placed in 4 anaerobic bags and numbered, 5mL of Shewanella bacteria liquid and a blank culture medium are sequentially added, the water content is adjusted to 30%, and the bag opening is sealed after air is exhausted. The anaerobic bag is placed in a constant temperature incubator at 30 ℃ for a repair test, samples are taken on days 7,14, 21, 35 and 52 to determine the leaching concentration of hexavalent chromium in the soil through a solid waste toxicity leaching Test (TCLP), and the total hexavalent chromium concentration of the soil is determined after the test on day 80 is finished. The test results obtained are shown in fig. 1 and table 2.

TABLE 1 soil Properties used in the examples

TABLE 2 Cr (VI) contaminated soil remediation Effect

Example 2

Culture of Shewanella: strain used in this example was s.alga, and other culture conditions were the same as in example 1.

Repairing the high-concentration hexavalent chromium polluted soil: the test is divided into A, B, C three groups, the test soil used in group A is group 1, and the concentration of hexavalent chromium is lower. The test soil used in the group B and the test soil used in the group C are respectively the group 2 and the group 3, and the concentration of hexavalent chromium is higher. The other experimental procedures were the same as in example 1, and the total hexavalent chromium concentration of the soil was measured after the test was finished on the 80 th day, and the test results obtained are shown in table 3.

TABLE 3 repairing effect of Cr (VI) contaminated soil

In conclusion, the Shewanella has a high repairing effect on the soil with low Cr (VI) concentration, the highest removing efficiency can reach 92.63%, and the Shewanella has a certain repairing effect on the soil polluted by high Cr (VI) concentration, and the highest removing efficiency can reach 27.48%. Therefore, the Shewanella has wide application prospect in the remediation of chromium-contaminated soil.

Claims

1. The method for restoring chromium-contaminated soil by using Shewanella is characterized by comprising the following steps of: the Shewanella and the chromium-polluted soil are fully mixed to realize the restoration of the chromium-polluted soil;

the cell density of the Shewanella added is (2-3) × 10⁹Per mL; the Shewanella is a mature strain cultured for 24 hours in an LB culture medium at the temperature of 30 ℃ and under the condition of 180rpm according to the inoculation amount of 5 percent by volume;

the repairing process is carried out under anaerobic condition, the repairing time is 80 days, and the temperature is 30 +/-1 ℃.

2. The method of Shewanella remediation of chromium-contaminated soil of claim 1, wherein the concentration of hexavalent chromium in the contaminated soil is between 300mg/kg and 4500 mg/kg.

3. The method for remediating chromium-contaminated soil with Shewanella as claimed in claim 1, wherein the contaminated soil has a water content of 30% to 60% and a pH of 5-9.