CN106424129B

CN106424129B - Method for repairing 2,2 ', 4, 4' -tetrabromobisphenol contaminated soil

Info

Publication number: CN106424129B
Application number: CN201610894681.XA
Authority: CN
Inventors: 陈耀宁; 陈艳容; 黎媛萍; 曾光明; 马騻; 袁兴中; 晏铭; 伍艳馨; 张嘉超
Original assignee: Hunan University
Current assignee: Hunan University
Priority date: 2016-10-13
Filing date: 2016-10-13
Publication date: 2019-12-06
Anticipated expiration: 2036-10-13
Also published as: CN106424129A

Abstract

The invention discloses a method for restoring 2,2 ', 4, 4' -tetrabromobisphenol polluted soil, which comprises the following steps: mixing agricultural solid waste with 2,2 ', 4, 4' -tetrabromobisphenol polluted soil to obtain a compost raw material; adding fatty alcohol-polyoxyethylene ether into the composting raw material, inoculating Rhodococcus RAH1 strain, and composting to complete the remediation of the 2,2 ', 4, 4' -tetrabromobisphenol-contaminated soil. According to the invention, the agricultural solid waste is utilized to repair the 2,2 ', 4, 4' -tetrabromobisphenol-contaminated soil, so that the potential of indigenous microorganisms in the soil is excited, the indigenous microorganisms are propagated in a large amount in a short time, and the activity of the microorganisms is greatly increased; and the strain RHA1 is inoculated, so that the capacity of degrading pollutants is greatly improved, and the strain has the advantages of simple operation and maintenance, low operation cost, small environmental risk and the like.

Description

Method for repairing 2,2 ', 4, 4' -tetrabromobisphenol contaminated soil

Technical Field

The invention relates to the technical field of soil remediation, in particular to a method for remediating 2,2 ', 4, 4' -tetrabromobisphenol-contaminated soil.

Background

Polybrominated diphenyl ethers (PBDEs) are a class of Persistent Organic Pollutants (POPs) that are ubiquitous in the environment. The european union in 2006 clearly limited the use of PBDEs in electronic products by resolution due to greater environmental hazards. In the 5 th month of 2009, PBDEs seriously harmed human health and natural environment, and the "stockholm convention" increased it into convention. Researches show that the PBDEs have large relative molecular mass, low vapor pressure, low water solubility and high Kow (octanol-water distribution coefficient) value, and are easy to adsorb and accumulate in soil, such as PBDEs with high concentration in the soil are detected in places such as Yangtze delta in China. PBDEs has a total of 209 monomeric compounds. Among them, 2 ', 4, 4' -tetrabromobiphenyl ether (BDE-47) is a PBDEs which is widely detected and has larger biological toxicity, and researches show that BDE-47 and metabolites thereof can cause abnormal development of the nervous system, and the risk of children who often contact BDE-47 to have attention deficit hyperactivity disorder symptoms is greatly increased.

At present, the methods for removing 2,2 ', 4, 4' -tetrabromobisphenol in soil are few in types, common photodegradation methods are adopted, and the method mainly comprises the steps of leaching the 2,2 ', 4, 4' -tetrabromobisphenol in the soil by using an organic solvent and the like, and irradiating ultraviolet light on leacheate so as to achieve the purpose of degrading the 2,2 ', 4, 4' -tetrabromobisphenol. However, the method is high in cost, and the physical and chemical properties of the soil are affected in the leaching process, so that the application range is limited. Compared with the traditional physical and chemical remediation method, the bioremediation method has the advantages of low cost, small environmental risk, difficult generation of secondary pollution, easy management and operation and the like, is widely concerned, plays an increasingly important role in engineering practice of remediation of polluted soil, and shows good development prospect. But is limited by the number and activity of microorganisms in soil and 2,2 ', 4, 4' -tetrabromobisphenol is less hydrophilic, so that it is difficult to efficiently degrade 2,2 ', 4, 4' -tetrabromobisphenol in soil using biotechnology.

Generally, surfactants such as fatty alcohol-polyoxyethylene ether and the like can effectively solubilize insoluble organic pollutants in soil, and are widely applied to soil remediation practices. Meanwhile, the method for treating the refractory organic matters in the soil by using the compost is generally considered to be an effective method, so that how to use the composting technology to increase the bioavailability of the BDE-47 and improve the removal efficiency of the BDE-47 in the polluted soil and further develop a method for effectively and biologically removing the BDE-47 in the soil is a research direction of researchers in the field.

Disclosure of Invention

The invention aims to solve the technical problems of overcoming the defects of traditional physical and chemical remediation of 2,2 ', 4, 4' -tetrabromobisphenol ether (BDE-47) polluted soil, providing a method for remedying BDE-47 polluted soil with low environmental risk and convenient management and operation, not only effectively removing BDE-47 in soil, but also effectively improving the utilization rate of agricultural waste and reducing agricultural waste pollution by utilizing agricultural solid waste compost; meanwhile, the repairing method is simple to operate, convenient to manage and maintain, low in environmental risk and stable in repairing effect, and is used for repairing the BDE-47 polluted soil.

In order to solve the technical problem, the method for repairing the soil polluted by the 2,2 ', 4, 4' -tetrabromobisphenol is provided, and comprises the following steps:

S1, mixing the agricultural solid waste with the soil polluted by 2,2 ', 4, 4' -tetrabromobisphenol to obtain a composting raw material;

s2, adding fatty alcohol-polyoxyethylene ether into the composting raw materials, inoculating Rhodococcus RAH1 bacterial strain, and composting to finish the restoration of 2,2 ', 4, 4' -tetrabromobisphenol-contaminated soil.

Preferably, in the above method, the step S2 specifically includes:

S2-1, preparing a fatty alcohol-polyoxyethylene ether solution, and mixing the fatty alcohol-polyoxyethylene ether solution and the composting raw material to obtain a mixture;

S2-2, activating RAH1 bacteria to prepare a bacterial suspension, and adding the bacterial suspension into the mixture obtained in the step S2-1;

S2-3, adjusting the water content to 45% -60%, and composting.

In the method, the concentration of the fatty alcohol-polyoxyethylene ether solution is preferably 10g/L to 20 g/L.

in the above method, preferably, in step S2-2, the concentration of the bacterial suspension is 1 × 106CFU/mL to 1 × 107CFU/mL, and the addition amount of the bacterial suspension is 3% to 5% of the dry weight of the mixture.

In the above method, preferably, in the step S1, the agricultural solid waste includes straw, vegetable leaves and bran.

In the above method, preferably, in the step S1, the mass ratio of the 2,2 ', 4, 4' -tetrabromobiphenyl ether polluted soil to the straws, the vegetable leaves and the bran is (8-20) to (7-13) to (3-5) to (1-3).

In the method, the carbon-nitrogen ratio of the composting raw materials is preferably 20-30: 1.

in the above method, preferably, the addition amount of the fatty alcohol-polyoxyethylene ether in the step S2 is 0.1g/kg to 0.5 g/kg.

In the above method, preferably, the compost is aerobic compost; the composting time is 45-90 days; the composting temperature is 20-70 ℃.

in the method, preferably, in the composting process, the moisture content of the composting raw material is controlled to be 55-60% in the 1 st-30 th day of the composting, and the moisture content of the composting raw material is controlled to be 45-55% after the 31 st day of the composting.

Compared with the prior art, the invention has the advantages that:

(1) The invention provides a method for restoring soil polluted by 2,2 ', 4, 4' -tetrabromobisphenol, which is characterized in that agricultural solid waste is mixed with the soil polluted by 2,2 ', 4, 4' -tetrabromobisphenol, and the potential of indigenous microorganisms in the soil is excited in the composting process of restoring the soil polluted by the 2,2 ', 4, 4' -tetrabromobisphenol by utilizing the agricultural solid waste, so that the indigenous microorganisms can be greatly reproduced in a short time, and the activity of the microorganisms is greatly improved. And inoculates Rhodococcus sp.RHA1 strain with better degradation capability to 2,2 ', 4, 4' -tetrabromobisphenol ether, so that the capability of degrading pollutants is greatly improved. The method overcomes the defects that physicochemical properties of soil are damaged by physical and chemical remediation, the soil function is reduced, secondary pollution is easy to generate and the like, has the advantages of simple operation and maintenance, low operation cost, small environmental risk and the like, and can quickly and effectively degrade the BDE-47 in the soil.

(2) according to the invention, the fatty alcohol-polyoxyethylene ether is added in the composting process, so that the 2,2 ', 4, 4' -tetrabromobisphenol ether is dissolved in the water phase, and the problems that the common bioremediation cannot be utilized and decomposed by microorganisms due to the fact that the 2,2 ', 4, 4' -tetrabromobisphenol ether is insoluble in water, and the remediation effect is poor are solved.

(3) The invention provides a method for repairing soil polluted by 2,2 ', 4, 4' -tetrabromobiphenyl ether, which comprises the following steps of mixing the soil polluted by the 2,2 ', 4, 4' -tetrabromobiphenyl ether, straws, vegetable leaves and bran according to the mass ratio of (8-20) to (7-13) to (3-5) to (1-3). Wherein the straws provide a carbon source, the bran mainly provides a nitrogen source, and the vegetable leaves provide easily degradable organic matters and soil for microorganism. The mass ratio of the four components is (8-20): (7-13): (3-5): (1-3), so that the carbon-nitrogen ratio can be properly provided, and the composting can be smoothly carried out. If the C/N is exceeded, the C/N is too high, so that the carbon element which can be consumed is more, the nitrogen nutrient is relatively lack, the growth of most microorganisms is limited, and the degradation of organic matters is slow. If the C/N is low, the carbon consumption is low, the composting temperature is low, the high temperature period is short, the decomposition period is delayed, and nitrogen is relatively excessive, so that nitrogen is changed into ammonia nitrogen and is volatilized. Resulting in offensive odor and substantial loss of nitrogen element from the compost.

(4) The invention provides a method for restoring 2,2 ', 4, 4' -tetrabromobisphenol polluted soil, wherein the water content of compost raw materials is controlled to be 55-60% at 1 d-30 d of compost, which is beneficial to the growth of microorganisms. Excessive moisture in the early stage of composting, reduces free porosity, influences air diffusion, easily causes an anaerobic state, and simultaneously causes a percolate treatment problem; when the water content is lower than 40%, the microbial activity is reduced, and the composting temperature is reduced.

Drawings

in order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.

FIG. 1 is a broken-line scattergram showing the residual rate of 2,2 ', 4, 4' -tetrabromobisphenol in compost and natural conditions as a function of time.

FIG. 2 is a graph showing the temperature change of the compost in example 1 and comparative example 2 of the present invention during composting.

Detailed Description

The invention is further described below with reference to the drawings and specific preferred embodiments of the description, without thereby limiting the scope of protection of the invention.

examples

The materials and equipment used in the following examples are commercially available.

Example 1

The invention relates to a method for restoring 2,2 ', 4, 4' -tetrabromobisphenol (BDE-47) polluted soil, which comprises the following steps:

(1) pretreatment of raw materials: respectively air-drying and crushing the straws and the vegetable leaves into the lengths of about 1-1.5 cm. Taking soil with BDE-47 content of 0.384mg/kg (dry weight), crushing and sieving by a 10-mesh sieve.

(2) Preparing compost raw materials: mixing the pretreated soil, the straws, the vegetable leaves and the bran according to the mass ratio of 15: 11: 3: 2 to obtain compost raw materials, wherein the carbon-nitrogen ratio of the compost raw materials is 25: 1.

(3) Dissolving fatty alcohol-polyoxyethylene ether (AEO-9) in water to prepare a fatty alcohol-polyoxyethylene ether solution with the concentration of 10 g/L. And adding the fatty alcohol-polyoxyethylene ether solution into the compost raw material (the initial concentration of the fatty alcohol-polyoxyethylene ether in the added compost raw material is about 0.35g/kg dry weight), and adjusting the water content to 58% to obtain the mixed soil.

(4) the RHA1 strain was activated to prepare a suspension of 5X 106 CFU/mL. And (3) adding the bacterial suspension into the mixed soil in the step (3) (the adding amount of the bacterial suspension is 5 percent of the dry weight of the mixed soil), and then performing composting treatment. In the composting process, the moisture content of the composting raw materials is controlled to be 55% -60% in the earlier stage of composting (namely 1 st-30 th day of composting), 1-15 th day, the compost is turned over every three days for oxygen supply, 15-30 th day, and every 10 th day for oxygen supply, and the temperature is automatically increased due to the adoption of strip-pile composting. So that the composting temperature can be prevented from being overhigh by adopting the modes of adding water, turning and the like, and the temperature is generally 40-50 ℃. And controlling the water content of the compost raw materials to be 45-50% in the later composting period (namely 31-75 d of composting). Turning the compost every 10 days at 30-50 days in the composting process; turning the pile once every 20 days at 50 d-75 d, wherein the temperature is 20-30 ℃. The stack is denoted as stack A.

Comparative example 1

a method for restoring BDE-47 polluted soil comprises the steps of screening BDE-47 polluted soil, and composting for 75d in a natural state, wherein the pile is marked as a pile body B.

Comparative example 2

the soil contaminated with 2,2 ', 4, 4' -tetrabromobisphenol (BDE-47) was remediated according to the method of example 1 without inoculation with the strain RHA1 and the remaining steps were identical to those of example 1 and marked as pile C.

During the 75d processing, the BDE-47 residual rate in the stack A, B, C was examined separately for changes over time, and the results of the residual rate are shown in Table 1 and FIG. 1.

Table 1: table of BDE-47 residual rate in pile as a function of time

FIG. 1 is a graph of degradation trend. From the results of table 1 and fig. 1, it can be seen that: the removal efficiency of BDE-47 by composting was significantly better than that of BDE-47 in the natural state and better than that of a pile not inoculated with Rhodococcus RAH1 strain (the residual rate of initial BDE-47 in FIG. 1 was more than 100% which is an error caused by the determination of BDE-47 by the internal standard method). Under the condition that the initial concentrations are almost the same (the initial concentrations of the detected stacks A and B are 0.185mg/kg and 0.183mg/kg respectively, dry weight), the residual rate of the BDE-47 in a natural state still reaches 96.88 percent after 75 d; the residual rate of the strain without being inoculated with RAH1 is 60.2 percent, while the residual rate of BDE-47 after composting for 75d is only 50.8 percent, the removal rate is 16.4 times of that of the strain in the natural state at the same time, and the removal effect is good.

The temperature change of the stacks a and C during composting 75d was examined, and the results were shown in table 2 and fig. 2.

table 2: temperature change table of compost pile

The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make many possible variations and modifications to the disclosed embodiments, or equivalent modifications, without departing from the spirit and scope of the invention, using the methods and techniques disclosed above. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention.

Claims

1. A method for remediating 2,2 ', 4, 4' -tetrabromobisphenol contaminated soil, comprising the steps of:

S2, adding fatty alcohol-polyoxyethylene ether into the composting raw materials, inoculating Rhodococcus RAH1 bacterial strain, and composting to finish the restoration of 2,2 ', 4, 4' -tetrabromobisphenol-contaminated soil; the addition amount of the fatty alcohol-polyoxyethylene ether is 0.1 g/kg-0.5 g/kg; in the composting process, controlling the water content of the composting raw material to be 55-60% at 1 st-30 th days of composting, and controlling the water content of the composting raw material to be 45-55% after 31 th day of composting;

The step of S2 is specifically:

S2-1, preparing a fatty alcohol-polyoxyethylene ether solution, and mixing the fatty alcohol-polyoxyethylene ether solution and the composting raw material to obtain a mixture; the concentration of the fatty alcohol-polyoxyethylene ether solution is 10 g/L-20 g/L;

S2-2, activating RAH1 bacteria to prepare a bacterial suspension, and adding the bacterial suspension into the mixture in the step S2-1; the concentration of the bacterial suspension is 1 × 106 CFU/mL-1 × 107CFU/mL, and the addition amount of the bacterial suspension is 3% -5% of the dry weight of the mixture;

s2-3, adjusting the water content to 45% -60%, and composting.

2. The method of claim 1, wherein in the step of S1, the agricultural solid waste comprises straw, vegetable leaves and bran.

3. The method according to claim 2, wherein in the step S1, the mass ratio of the 2,2 ', 4, 4' -tetrabromobiphenyl ether polluted soil to the straws, the vegetable leaves and the bran is (8-20) to (7-13) to (3-5) to (1-3).

4. The method according to claim 1, wherein the carbon-nitrogen ratio of the composting raw material is 20-30: 1.

5. The method of claim 1, wherein the composting is aerobic composting; the composting time is 45-90 days; the composting temperature is 20-70 ℃.