CN108971221B

CN108971221B - Method for restoring nitrobenzene contaminated soil

Info

Publication number: CN108971221B
Application number: CN201810750372.4A
Authority: CN
Inventors: 吕正勇; 朱湖地; 秦森; 苗竹; 李淑彩; 范吉强; 宋登慧; 郭明达
Original assignee: Beijing Geoenviron Engineering and Technology Inc
Current assignee: Beijing Geoenviron Engineering and Technology Inc
Priority date: 2018-07-10
Filing date: 2018-07-10
Publication date: 2020-08-21
Anticipated expiration: 2038-07-10
Also published as: CN108971221A

Abstract

The invention relates to the technical field of polluted soil remediation, in particular to a method for remediating nitrobenzene polluted soil. The method comprises the following steps: after in-situ leaching, performing in-situ remediation by using functional flora obtained by indigenous microorganism culture; the culture solution used by the indigenous microorganisms comprises an inducing substrate, wherein the inducing substrate comprises one or two combinations of phenol and catechol. The method has the advantages that the in-situ leaching is used in cooperation with the indigenous microorganisms to reinforce and repair the nitrobenzene contaminated soil, the removal effect is obvious, the method can take effect quickly, is stable and durable, long-term continuous addition is not needed, the process is reasonable, the cost is low, the method is easy to popularize and implement, and the environmental benefit, the economic benefit and the social benefit are good.

Description

Method for restoring nitrobenzene contaminated soil

Technical Field

The invention relates to the technical field of polluted soil remediation, in particular to a method for remediating nitrobenzene polluted soil.

Background

Nitrobenzene substances are important chemical raw materials and are widely applied to the fields of national defense, printing and dyeing, plastics, pesticides, medicines and the like. With the acceleration of the industrialization process, more and more nitrobenzene substances enter soil and underground water along with industrial wastewater and waste residues. Nitrobenzene compounds can be absorbed by the human body through the skin and respiratory tract, causing poisoning and even death, and pose serious threats to human health and ecological environment, and various compounds of the nitrobenzene class have been prioritized as pollutants for control by the united states Environmental Protection Agency (EPA). At present, the restoration method of nitrobenzene-polluted soil mainly comprises chemical reduction, chemical oxidation, thermal desorption, soil leaching, biochemical treatment and the like. However, due to the existence of the inert group nitro group, the single repair method generally has limited treatment effect or excessively high treatment cost, so the composite process becomes a hot point for the research of scholars at home and abroad. For example, Chinese patent CN104511476A discloses a zero-valent iron reduction-chemical oxidation combined process, and the removal rate of chloronitrobenzene in soil reaches 88.3-95.8%. Chinese patent CN103624074B discloses a repair method combining solubilization with Fenton oxidation by a mixed surfactant, which is suitable for repairing high-concentration chloronitrobenzene.

However, the traditional physical and chemical methods have high treatment cost, are easy to generate secondary pollution and have incomplete degradation on certain intermediate products. Compared with the prior art, the biochemical method has the advantages of economy, high efficiency, thorough treatment, no secondary pollution and the like, and has remarkable advantages in remediation of nitrobenzene-polluted soil.

The biological strengthening is an important technology in the field of soil bioremediation, and a certain kind of harmful substances or a certain kind of harmful substances are removed by adding dominant strains screened from the nature or high-efficiency strains generated by a gene combination technology into soil. So far, the research focus at home and abroad is to find or construct efficient degradation strains, and prepare a biological agent for soil remediation by using single strains or the combination of the single strains and the complex of the single strains. The existing mature biological microbial inoculum products at home and abroad are put into the market, but similar products are exogenous strains, the strain composition is single, the adaptability to specific soil environment is poor, the strain is difficult to become dominant strains in soil and needs to be continuously added for a long time, in addition, the separation and construction difficulty of high-efficiency strains is large, the research and development period is long, so that most microbial inoculum products are expensive, the operation cost is high, and the adding of the exogenous strains can cause the biological safety problem due to the overlapping with the ecological niche of indigenous strains. In addition, only about 1% of strains in the nature can be separated by means of the current biotechnology, and most of strains cannot be separated, so that the huge potential of indigenous microorganisms in the ecological environment for degrading pollutants is not fully exploited.

The single bioremediation method also has significant limitations, such as long remediation periods, limited ability to treat high concentrations of contaminants, and the like.

In view of the above, the present invention is particularly proposed.

Disclosure of Invention

The invention aims to provide a method for restoring nitrobenzene-polluted soil, which uses in-situ leaching in cooperation with indigenous microorganisms to reinforce and restore the nitrobenzene-polluted soil, has obvious removal effect, can quickly take effect, is stable and durable, does not need to be continuously added for a long time, has reasonable process, low cost, is easy to popularize and implement, and has good environmental benefit, economic benefit and social benefit.

In order to achieve the above purpose of the present invention, the following technical solutions are adopted:

a method for remediating nitrobenzene-contaminated soil, comprising: after in-situ leaching, performing in-situ remediation by using functional flora obtained by indigenous microorganism culture; the culture solution used by the indigenous microorganisms comprises an inducing substrate, wherein the inducing substrate comprises one or two combinations of phenol and catechol.

Compared with the prior art, the invention has the beneficial effects that:

(1) the method for repairing the nitrobenzene polluted soil has the advantages of wide applicable pollutant concentration range, obvious pollutant removal effect and high pollutant removal rate of more than 99 percent for various concentration levels;

(2) according to the invention, the functional flora is constructed by utilizing indigenous microorganisms, the concentration of effective strains is high, the adaptability is strong, the effect can be quickly achieved and the stability is durable after the functional flora is injected into a polluted soil environment, the biosafety problem is avoided, the functional flora does not need to be continuously added for a long time, and the operation cost is low;

(3) the leaching and biological enhancement processes are organically combined, on one hand, the soil leaching is carried out firstly, the concentration of the pollutants is greatly reduced, and the problems of long repairing period and poor removing effect caused by directly adopting biological repair for high-concentration pollutants are avoided, on the other hand, the biological enhancement solves the problem that the leaching process cannot completely remove low-concentration pollutants, and the leaching agent remained in the soil can be thoroughly degraded, so that secondary pollution is avoided;

(4) in summary, the invention takes leaching and biological enhancement technology as the core, and fully combines technical principles and ideas such as microbial domestication and co-metabolism, and creatively provides a set of method for enhancing remediation of nitrobenzene contaminated soil by in-situ leaching in cooperation with indigenous microorganisms.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

FIG. 1 is a process flow diagram in one embodiment of the present invention.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

The invention relates to a method for repairing nitrobenzene contaminated soil, which comprises the following steps: after in-situ leaching, performing in-situ remediation by using functional flora obtained by indigenous microorganism culture; the culture solution used by the indigenous microorganisms comprises an inducing substrate, wherein the inducing substrate comprises one or two combinations of phenol and catechol.

Aiming at the defects in the prior art, the invention organically combines a biological strengthening technology and an in-situ leaching technology, fully utilizes indigenous microorganism resources of nitrobenzene polluted soil, and provides a method for strengthening and repairing the nitrobenzene polluted soil by using the in-situ leaching and the indigenous microorganisms. The method has good effect of removing nitrobenzene pollutants, the leaching process has obvious effect of removing high-concentration nitrobenzene pollutants, the construction of the biological strengthening functional flora is based on indigenous microorganisms in the original site, the adaptability is strong, the biological strengthening functional flora can quickly take effect and is stable and durable after being added, long-term continuous addition is not needed, the defects of single strains and exogenous strains are overcome, the low-concentration pollutants after the leaching treatment are thoroughly removed, and the leaching agent residual in soil can be effectively removed. The invention has reasonable process, low cost, easy popularization and implementation and good environmental, economic and social benefits.

The inducing substrate is one or the combination of phenol and catechol in any proportion. Phenol is easier to biodegrade compared with nitrobenzene substances, and can generate enzyme required for thoroughly mineralizing benzene rings in the aerobic biodegradation process of phenol, catechol is an important intermediate product in the phenol degradation process and also an important substrate for generating the enzyme, so that phenol and catechol are added as induction substrates, an enzyme system for degrading the nitrobenzene substances is favorably and rapidly formed, and the bioaugmentation process is accelerated.

In some embodiments, the culture fluid further comprises a basal culture fluid, a co-metabolic substrate, and a contaminant in the nitrobenzene-contaminated soil.

In some embodiments, the soil sample containing the indigenous microorganisms is taken from at least three of the nitrobenzene-contaminated soils that differ in degree of contamination.

And (3) equally and uniformly sampling the soil at the high, medium and low pollution points in the nitrobenzene pollution field to be restored, wherein the mixed soil sample is the soil sample containing the indigenous microorganisms without being strengthened.

The sampling points are selected mainly because in the soil polluted by nitrobenzene substances for a long time, indigenous microorganisms with certain tolerance and degradation capability to pollutants exist in the soil, the soil is easy to be intensively cultured, and the functional flora constructed based on the indigenous microorganisms acts on the original soil environment, so that the soil is strong in adaptability, can quickly take effect and form dominant bacteria, does not need to be continuously added for a long time, and does not have the problem of biological safety.

In some embodiments, the inoculation is performed after the culture solution is prepared.

In some embodiments, the soil sample is inoculated into the culture medium to obtain a seed culture;

adding an induction substrate, a co-metabolism substrate and pollutants in nitrobenzene polluted soil in the culture solution before inoculation, wherein the initial addition amount of corresponding components meets the requirements that the final concentration is 25-100 mg/L, 50-200 mg/L and 5-25 mg/L respectively;

performing the culture on the strain, wherein the culture comprises primary culture and secondary culture;

the primary culture is continuous culture for 3-5 periods, after each period is finished, pollutants in the induction substrate, the co-metabolism substrate and the nitrobenzene polluted soil are respectively supplemented, and the supplement amount of corresponding components is 1.8-2.2 times of the initial addition amount;

removing 10-50% volume of upper layer culture solution of the culture solution after the primary culture before the secondary culture, supplementing a new basic culture solution to the original volume, and respectively supplementing pollutants in the induction substrate, the co-metabolism substrate and the nitrobenzene polluted soil, wherein the supplement amount of corresponding components is 3.6-4.4 times of the initial addition amount;

the culture time of the secondary culture is 15-30 d, multiple periods are cultured, after each period is finished, pollutants in soil polluted by induction substrates, co-metabolism substrates and nitrobenzene are respectively supplemented, the supplement amount of corresponding components is 3.6-4.4 times of the initial addition amount, and the degradation rate of the induction substrates by the culture solution in the last period is not lower than 200mg/L per day;

and after the last period of the secondary culture is finished, obtaining the strain containing the functional flora.

The flora culture is carried out by adopting a mode of increasing the concentration of a substrate in a gradient way, and the aim is to eliminate the mixed bacteria which cannot adapt to the high-concentration nitrobenzene substances, so that the strains which can tolerate and degrade the high-concentration nitrobenzene substances become dominant flora, the adaptability and the processing capacity of the strains are improved, and a large amount of enrichment is carried out in a secondary culture stage.

In some embodiments, the initial amount of induction substrate added to the culture broth can also be a final concentration of 30mg/L, 50mg/L, 60mg/L, 80mg/L, 90mg/L, etc.; the final concentration of the initial addition amount of the co-metabolic substrate can also be 80mg/L, 100mg/L, 120mg/L, 150mg/L, 180mg/L and the like; the final concentration of the initial addition amount of the pollutants in the nitrobenzene-contaminated soil can also be 8mg/L, 10mg/L, 12mg/L, 15mg/L, 18mg/L, 20mg/L, 23mg/L and the like.

In some embodiments, the culture endpoint of each cycle other than the last cycle of the secondary culture during the culturing is a greater than 90% induction substrate removal rate in the culture fluid.

In the first-stage culture, when the removal rate of the induction substrate reaches more than 90%, the first-stage culture is a period, the induction substrate, the co-metabolism substrate and pollutants in the nitrobenzene polluted soil are supplemented, the supplementation amount is 1.8-2.2 times of the inoculation amount (the results are basically consistent in the range), the supplementation amount of each period is the same, and the first-stage culture is continuously cultured for 3-5 periods; in some embodiments, there may also be 4 cycles of incubation.

In the secondary culture, when the removal rate of the induction substrate reaches more than 90%, the culture medium is a cycle, the induction substrate, the co-metabolism substrate and the pollutants in the nitrobenzene-polluted soil are supplemented, the supplement amount is 3.6-4.4 times of the inoculation amount (the result is basically consistent within the range), the supplement amount in each cycle is the same, and the culture medium is cultured for 15-30 d (in some embodiments, the culture time can be 18d, 20d, 25d, 28d and the like) until the rate of the culture medium for degrading the induction substrate is not lower than 200mg/L per day (in some embodiments, the rate can be 250mg/L, 300mg/L, 350mg/L, 380mg/L and the like). In this case, the functional bacterial flora was successfully constructed.

The index of the removal rate detection is the content of the induction substrate, namely the content of phenol and catechol, because the detection of total phenol can adopt a chemical method, the data is timely, the detection of the nitrobenzene substances has higher requirements on equipment, and corresponding conditions are not easy to meet on site, so the detection data has certain hysteresis, the reduction of the content of the total phenol has correlation with the degradation of the nitrobenzene substances, and the culture process is monitored by detecting the content of the induction substrate. If the field has the detection condition of the nitrobenzene substances, the culture process is preferably controlled by detecting the degradation effect of the nitrobenzene substances.

In some embodiments, the method further comprises the step of stopping aeration and standing for 2 hours after the primary culture and before the secondary culture, so as to better separate the supernatant of the culture solution after the primary culture, and to better discard 10-50% of the volume of the supernatant of the culture solution after the primary culture before the secondary culture is completed.

In some embodiments, the culture conditions are water dissolved oxygen of 2-4 mg/L and temperature of 15-37 ℃.

The first-stage culture and the second-stage culture can be carried out in a culture container with an aeration facility, and the dissolved oxygen in water can be maintained at 2-4 mg/L through aeration; in some embodiments, the amount of dissolved oxygen in the water may also be 2.5mg/L, 3mg/L, 3.5mg/L, and the like.

In some embodiments, the soil sample is inoculated in an amount of 2-10 g/L based on the dry mass of the soil sample.

Inoculating a soil sample of indigenous microorganisms into a culture container, wherein the inoculation amount of the soil sample is 2-10 g/L based on the dry mass of the soil sample; in some embodiments, the amount of inoculation may also be 3g/L, 5g/L, 7g/L, 9g/L, and the like.

The construction of the functional flora is completed by preparing culture solution, inoculating, primary culturing and secondary culturing.

In some embodiments, the construction process of the functional flora is performed in an open environment, and operations such as sterilization and the like are not needed, so that special equipment such as a fermentation tank and the like is not needed, the culture container only adopts a common water tank and aeration equipment, and the equipment cost is low.

The advantage of the integral culture of the indigenous microorganism flora is that functional strains which cannot be separately cultured by the traditional biotechnology can also grow along with the advantage of the culture process of the flora, thereby exerting the processing capacity of the indigenous microorganisms to the maximum extent and reducing the cost of strain culture.

In some embodiments, the co-metabolic substrates comprise one or more of ethanol, glucose, sodium acetate, sodium lactate, sodium succinate.

The nitro group in the nitrobenzene substances is an inert group, the biodegradability is poor, and the addition of the co-metabolism substrate is beneficial to the degradation of the nitrobenzene substances by the flora.

In some embodiments, the basal medium comprises: 0.1-1% w/v of basic inorganic salt culture medium, 0.1-1% w/v of inorganic carrier, 0.005-0.1% w/v of Tween 80 and water.

Mixing the above components to obtain basic culture solution. The surfactant Tween 80 has the functions of increasing the water solubility of nitrobenzene pollutants, reducing the surface tension, increasing the contact of microorganisms and the pollutants and promoting the absorption and degradation of biological cells to the pollutants. In some embodiments, the base medium can also be 0.5% w/v base mineral salts medium, 0.5% w/v inorganic carrier, 0.05% w/v tween 80, water; 0.3% w/v of basic inorganic salt culture medium, 0.8% w/v of inorganic carrier, 0.01% w/v of Tween 80, water and the like.

In some embodiments, the above ingredients are mixed uniformly in a culture vessel with aeration means.

In some embodiments, the basal mineral salts medium comprises: in parts by weight, NH₄NO₃8 to 12 portions of K₂HPO₄4 to 6 parts of KH₂PO₄4 to 6 portions of CaCl₂0.8-1.2 parts of NaCl, 1.8-2.2 parts of MgSO₄0.8 to 1.2 parts of MnSO₄0.05 to 0.15 part of FeSO₄0.05 to 0.15 portion.

Mixing the above components to obtain basic inorganic salt culture medium. The culture medium provides nitrogen, phosphorus and trace elements required by the enrichment culture of indigenous strains. In some embodiments, the base mineral salts medium can also be NH₄NO₃10 parts of, K₂HPO₄5 portions of KH₂PO₄5 parts of CaCl₂1 part, NaCl 2 parts, MgSO₄1 part of MnSO₄0.1 part of FeSO₄0.1 part, and the like.

In some embodiments, the inorganic support is one or more of zeolite powder, diatomaceous earth, activated carbon, calcium carbonate.

The existence of the inorganic carrier can provide a place for the attachment and growth of microorganisms, thereby improving the flora concentration.

In some embodiments, the pH of the culture medium is 6 to 8.

The pH value is adjusted to 6-8, so that the method is more suitable for the survival, propagation and enhancement of microorganisms. In some embodiments, the pH may also be 6.5, 7, 7.5, etc.

In some embodiments, the in situ eluted eluent is a composition of tween 80 and n-butanol in any ratio.

In some embodiments, the eluting agent is used in an amount of 5 to 20 times the pore volume of the soil in the contaminated area.

In some embodiments, the eluting agent has a mass concentration of 3-30 g/L.

In some embodiments, the eluent is injected upstream of the contaminated area through an injection well.

Injecting the composite eluting agent with the concentration of 3-30 g/L into the upstream of the polluted area through an injection well in an amount which is 5-20 times of the pore volume of the polluted area, extracting the underground water at the downstream by using an extraction well, collecting the underground water on the ground, treating the underground water according to a conventional method, and continuously extracting the underground water with the volume which is 1-2 times of the pore volume of the polluted area after the injection is finished.

Wherein the compound eluting agent is the combination of Tween 80 and n-butanol in any proportion. The surfactant and the alcohol substance are used as the eluting agent, the eluting effect on the nitrobenzene pollutants is good, the pollutants in the soil can be reduced by at least more than 80%, and the concentration of the pollutants entering the subsequent biodegradation stage is reduced. Meanwhile, the surfactant Tween 80 remained in the soil can increase the water solubility of nitrobenzene pollutants, increase the contact of microorganisms and the pollutants and promote the absorption and degradation of biological cells to the pollutants. In some embodiments, the eluent is 10g/L tween 80 and 5g/L n-butanol, 10g/L tween 80 and 20g/L n-butanol, 2g/L tween 80 and 1g/L n-butanol, and the like; the using amount is 8, 10, 15, 18 times of the pore volume of the soil in the polluted area, and the like.

In some embodiments, the in situ remediation method comprises mixing a culture solution containing the functional flora with a nutrient solution and adding the mixture to the contaminated soil.

In some embodiments, the nutrient solution comprises: according to each liter of the culture solution, 500-1000 mg of easily degradable carbon source, 50-100 mg of urea and 15-30 mg of KH₂PO₄(ii) a The easily degradable carbon source comprises one or more of ethanol, glucose and sodium acetate.

In some embodiments, the nutrient solution may also be: 800mg of readily degradable carbon source, 80mg of urea and 20mg of KH₂PO₄(ii) a 600mg of readily degradable carbon source, 90mg of urea, 25mg of KH₂PO₄(ii) a 900mg of readily degradable carbon source, 60mg of urea and 28mg of KH₂PO₄And the like.

In some embodiments, the volume of the additive is 1-2 times of the pore volume of the soil in the polluted area.

In some embodiments, the culture solution and nutrient solution of the functional flora are injected upstream of the contaminated area through an injection well.

After the functional flora is constructed, firstly detecting the content of nitrobenzene substances in the culture solution, adding a compound nutrient solution into the functional flora after the nitrobenzene substances are completely degraded, and uniformly stirring; injecting the bacterial liquid obtained in the step A into the upstream of the polluted area through an injection well, wherein the injection volume is 1-2 times of the pore volume of the polluted area; and operation and maintenance are carried out during the period: and (4) performing low-speed low-flow air injection by using an air injection well, and sampling every week to detect the concentration of the pollutants until the remediation target is reached.

The addition of the nutrient solution can supplement carbon, nitrogen and phosphorus in the soil environment, so that functional flora injected into the soil can quickly colonize and take effect.

Functional flora and the compound nutrient solution only need to be added once, and do not need to be supplemented continuously in the later period. After the microbial community is added, the low-concentration nitrobenzene pollutants after the leaching treatment can be further removed, and the Tween 80 and the n-butanol remained in the soil can be thoroughly degraded, so that the secondary pollution is eliminated.

In some embodiments, the nitrobenzene-contaminated soil comprises one or more of nitrobenzene soil, nitrochlorobenzene soil, nitrophenol soil, nitroaniline-contaminated soil.

The soil can be a single pollutant or a composite pollutant, and the remediation method can have a good remediation effect.

In some embodiments, the leaching and biological enhancement technology is taken as a core, technical principles and ideas such as surfactant solubilization, microbial domestication, co-metabolism and the like are fully combined, a set of method for enhancing remediation of nitrobenzene contaminated soil by using in-situ leaching and indigenous microorganisms is creatively provided, and the method is reasonable in design of each process step, simple to operate, low in cost and easy to popularize and implement.

Example 1

And (3) restoring soil of a certain nitrobenzene-polluted land.

In an old site of a chemical plant, the soil overproof pollutant is nitrobenzene, and the polluted soil volume is 2400m³The maximum pollution concentration is 465mg/kg, the soil remediation is carried out by adopting the process, and the specific implementation conditions are as follows:

equivalent soil samples are collected at point positions with the site pollution concentrations of 400mg/kg, 260mg/kg and 120mg/kg respectively, and 2t is collected in total.

With an effective volume of 1000m³The water pool is provided with an aeration facility as a culture container according to NH₄NO₃10 parts of, K₂HPO₄5 portions of KH₂PO₄5 parts of CaCl₂1 part, NaCl 2 parts, MgSO₄1 part of MnSO₄0.1 part of FeSO₄Weighing 1t of basic inorganic salt culture medium according to 0.1 part, putting into a water tank, adding water until the effective volume is completely dissolved, adding 1t of inorganic carrier zeolite powder, adding 50kg of Tween 80, starting aeration, and uniformly mixing to obtain the culture solution.

Adding 60kg of phenol, 100kg of glucose and 18kg of nitrobenzene into the culture solution, adjusting the pH to 7.5, and uniformly putting the collected 2t of indigenous microorganism samples into a water pool.

And (3) carrying out aeration culture on the inoculated culture solution, controlling DO to be 3mg/L, controlling the temperature to be natural, detecting the total phenol content in the culture solution every 24h in spring during the culture period and at the average temperature of 22 ℃, supplementing 120kg of phenol, 200kg of glucose and 36kg of nitrobenzene when the total phenol content in the culture solution is reduced to be below 6mg/L, continuing the culture, supplementing again when the total phenol content is reduced to be below 12mg/L, and carrying out the culture for 4 periods.

Stopping aeration, standing for 2h, and mixing to obtain a mixture with a diameter of 300m³Pumping supernatant liquor to water treatment equipment for treatment, discharging the supernatant liquor through a nano tube, newly configuring a 300m3 culture solution, simultaneously supplementing 240kg of phenol, 400kg of glucose and 72kg of nitrobenzene, continuing aeration culture, supplementing the culture solution again when the total phenol is reduced to below 24mg/L, continuously culturing for 20 days, and finishing the construction of functional flora when the phenol reduction rate of the culture solution reaches 300 mg/(L.d).

The porosity of the soil at the site is 0.36, namely the pore volume is 864m 3. The eluent is 10g/L Tween 80 and 5g/L n-butanol, the eluent is injected into the upstream of the polluted area through an injection well, the injection amount is 4320m3, meanwhile, an extraction well is adopted at the downstream to extract underground water, the underground water is collected on the ground and then treated according to a conventional method, and extraction 864m is continuously carried out after the injection is finished³Ground water.

And (4) sampling the washed soil to determine the nitrobenzene content, wherein the highest pollution concentration is 35 mg/L.

Before the functional flora is injected, the content of nitrobenzene in the culture solution is measured to be 0.1mg/L, and a compound nutrient solution is added into the functional flora, wherein the nutrient solution comprises the following components in parts by weight: 500kg of glucose, 80kg of urea and KH₂PO₄430kg, and the aeration is started for a short time to mix evenly.

Injecting the bacterial liquid into the upstream of the polluted area through an injection well, wherein the injection amount is 1000m³. After injection, adopting an air injection well for low-speed low-flow air injection, sampling every week to detect the concentration of pollutants, and after 3 months, reducing the concentration of nitrobenzene to below 1mg/kg, and completing restoration.

Example 2

Restoring soil of a certain nitrochlorobenzene polluted land.

The accident of nitrochlorobenzene leakage occurs in a certain land, the nitrochlorobenzene concentration in the soil still reaches over 1300mg/L after the pretreatment, and the polluted soil volume is 300m³The soil remediation is carried out by adopting the process, and the specific implementation conditions are as follows:

equivalent soil samples are collected at point positions with the pollution concentrations of 1300mg/kg, 800mg/kg and 450mg/kg respectively, and 2t is collected totally.

With an effective volume of 200m³The water pool is provided with an aeration facility as a culture container according to NH₄NO₃8 parts of, K₂HPO₄6 parts of KH₂PO₄4 portion of CaCl₂1.2 parts of NaCl, 1.5 parts of MgSO₄1.2 parts of MnSO₄0.05 part of FeSO₄0.15 part of basic inorganic salt culture medium is weighed according to the proportion of 2t, the basic inorganic salt culture medium is put into a water tank and added with water until the effective volume is completely dissolved, 1t of inorganic carrier zeolite powder and 1t of active carbon are added respectively, 200kg of Tween 80 is added, aeration is started, and the culture solution is obtained after uniform mixing.

Adding 10kg of phenol and catechol respectively, 20kg of ethanol and sodium succinate respectively and 5kg of nitrochlorobenzene into the culture solution, adjusting the pH value to 6, and uniformly putting 2t of the collected indigenous microorganism samples into a water tank.

And (3) carrying out aeration culture on the inoculated culture solution, controlling DO to be 4mg/L, controlling the temperature to be natural, detecting the total phenol content in the culture solution every 24h in summer at an average air temperature of 32 ℃, supplementing 20kg of phenol and pyrocatechol, 40kg of ethanol and sodium succinate and 10kg of nitrochlorobenzene when the total phenol content in the culture solution is reduced to be below 10mg/L, continuing the culture, supplementing again when the total phenol content is reduced to be below 20mg/L, and carrying out the culture for 5 periods.

Stopping aeration, standing for 2h, and mixing with water to obtain a mixture of 100m³Pumping supernatant liquor to water treatment equipment for treatment, discharging the supernatant liquor through a nano tube, and newly configuring the water treatment equipment into a 100m tank³And (3) simultaneously supplementing 40kg of phenol and 40kg of catechol, 80kg of ethanol and 80kg of sodium succinate and 20kg of nitrochlorobenzene to the culture solution, continuing aeration culture, supplementing the culture solution again when the total phenol is reduced to be below 40mg/L, continuously culturing for 30 days, and finishing the construction of the functional flora when the phenol reducing rate of the culture solution reaches 350 mg/(L.d).

The porosity of the soil in the field is 0.33, namely the pore volume is 100m³. The eluent is 10g/L Tween 80 and 20g/L n-butanol, and is injected into the upstream of the polluted area through injection well at an injection amount of 2000m³Meanwhile, an extraction well is adopted at the downstream to extract underground water, the underground water is collected on the ground and then treated according to a conventional method, and extraction is continued for 200m after injection is finished³Ground water.

And (4) sampling the washed soil to determine the content of nitrochlorobenzene, wherein the highest pollution concentration is 78 mg/L.

Before the functional flora is injected, the content of nitrochlorobenzene in the culture solution is measured to be 0.5mg/L, and a composite nutrient solution is added into the functional flora, wherein the nutrient solution comprises the following components in parts by weight: 200kg of ethanol, 20kg of urea and KH₂PO₄4kg, and aerating and mixing uniformly for a short time.

Injecting the bacterial liquid into the upstream of the polluted area through an injection well, wherein the injection amount is 200m³. After injection, adopting an air injection well for low-speed low-flow air injection, sampling every week to detect the concentration of pollutants, and after 5 months, reducing the concentration of nitrochlorobenzene to be below 2mg/kg, thus completing restoration.

Example 3

Restoring soil of a certain nitrophenol and nitroaniline compound polluted land.

In an old site of a chemical plant, soil is polluted by nitrophenol and nitroaniline in a composite way, the maximum pollution concentration reaches 628mg/L, and the polluted soil volume is about 1000m³The soil remediation is carried out by adopting the process, and the specific implementation conditions are as follows:

equivalent soil samples are collected at point positions with the site pollution concentrations of 600mg/kg, 350mg/kg and 120mg/kg respectively, and 1.6t is collected in total.

With an effective volume of 400m³The water pool is provided with an aeration facility as a culture container according to NH₄NO₃12 parts of, K₂HPO₄4 parts of KH₂PO₄6 portions of CaCl₂0.8 part, NaCl 2.5 parts, MgSO₄0.8 part of MnSO₄0.15 part of FeSO₄Weighing 2t of basic inorganic salt culture medium according to 0.05 part, putting into a water tank, adding water until the effective volume is completely dissolved, adding 2t of inorganic carrier diatomite, adding 160kg of Tween 80, starting aeration, and uniformly mixing to obtain the culture solution.

10kg of catechol, 20kg of sodium acetate and 1kg of nitrophenol and nitroaniline are added into the culture solution, the pH value is adjusted to 8, and 1.6t of the collected indigenous microorganism samples are uniformly put into a water tank.

And (3) carrying out aeration culture on the inoculated culture solution, controlling DO to be 2mg/L, controlling the temperature to be natural, detecting the total phenol content in the culture solution every 24h in autumn during the culture period, supplementing 20kg of pyrocatechol, 40kg of sodium acetate and 2kg of nitrophenol and nitroaniline when the total phenol content in the culture solution is reduced to be below 2.5mg/L, continuing the culture, supplementing again when the total phenol content is reduced to be below 5mg/L, and carrying out the culture for 3 periods.

Stopping aeration, standing for 2h, and mixing 40m³Pumping supernatant liquor to water treatment equipment for treatment, discharging the supernatant liquor through a nano tube, and newly configuring the nano tube at 40m³And (3) simultaneously supplementing 40kg of catechol, 80kg of sodium acetate, 4kg of nitrophenol and nitroaniline into the culture solution, continuing aeration culture, supplementing the culture solution once the total phenol is reduced to below 10mg/L, continuously culturing for 15 days, and completing the construction of the functional flora, wherein the phenol reducing rate of the culture solution reaches 380 mg/(L.d).

The porosity of the soil in the field is 0.4, namely the pore volume is 400m³. The eluent is 2g/L Tween 80 and 1g/L n-butanol, and is injected into the upstream of the polluted area via injection well at 3200m³Meanwhile, an extraction well is adopted at the downstream to extract underground water, the underground water is collected on the ground and then treated according to a conventional method, and the extraction is continued for 600m after the injection is finished³Ground water.

And (4) sampling the washed soil to determine the content of nitrophenol and nitroaniline, wherein the highest pollution concentration is 45 mg/L.

Before the functional flora is injected, the content of nitrophenol and nitroaniline in the culture solution is measured to be 0.2mg/L, and the composite nutrient solution is added into the functional flora, wherein the components and the adding amount of the nutrient solution are as follows: 160kg of glucose, 160kg of sodium acetate, 20kg of urea and KH₂PO₄6kg, and the aeration is started for a short time to mix evenly.

Injecting the bacterial liquid into the upstream of the polluted area through an injection well, wherein the injection amount is 400m³. After injection, adopting an air injection well for low-speed low-flow air injection, sampling every week to detect the concentration of pollutants, and after 2 months, reducing the concentrations of nitrophenol and nitroaniline to be below 0.5mg/kg, thus completing the restoration.

Experimental example 1

Repair time and effect.

Comparative example 1 was set up based on example 3, the construction of functional flora was completed by culturing for only one cycle, and the contaminant concentration was measured after 2 months in the same manner as in example 3.

The results of the remediation time of the nitrobenzene-contaminated soil and the concentration of the corresponding nitrobenzene contaminant after the remediation is completed in the examples are shown in Table 1. As can be seen from Table 1, the method of the embodiment has good repairing effect on the nitrobenzene contaminated soil within 5 months, and can be reduced to below 2mg/kg, wherein the embodiment of the embodiment 3 can reduce the concentration of the pollutants to 0.5mg/kg within 2 months. Comparative example 1 in the experiment, the concentration of the contaminant after the indigenous microorganisms are enhanced is 31 mg/kg. In contrast, comparison of comparative example 1 and example 3 shows that the concentration of contaminants after two months of indigenous microbial fortification was 30mg/kg, which is about 60 times that of example 3. As is clear from comparison between comparative example 1 and example 3, the repair effect is poor when only one cycle of cultivation is performed.

TABLE 1 remediation Effect on Nitrobenzene contaminants

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for restoring nitrobenzene contaminated soil is characterized by comprising the following steps: after in-situ leaching, performing in-situ remediation by using functional flora obtained by indigenous microorganism culture;

the culture solution used by the indigenous microorganisms comprises an induction substrate, wherein the induction substrate comprises one or two combinations of phenol and catechol;

inoculating the soil sample into the culture solution to obtain a strain;

after the last period of the secondary culture is finished, obtaining a strain containing the functional flora;

during the culturing, the culture endpoint of each cycle except the last cycle of the secondary culture is the culture substrate removal rate in the culture solution exceeding 90%.

2. The method for remediating nitrobenzene-contaminated soil as recited in claim 1, wherein the culture medium further comprises a basal culture medium, a co-metabolic substrate, and contaminants in the nitrobenzene-contaminated soil.

3. The method for remediating nitrobenzene-contaminated soil as recited in claim 2, wherein the soil sample containing said indigenous microorganisms is taken from at least three of said nitrobenzene-contaminated soils having different degrees of contamination.

4. The method for remediating nitrobenzene contaminated soil as claimed in claim 1, wherein the culturing conditions are water dissolved oxygen of 2-4 mg/L and temperature of 15-37 ℃.

5. The method for remediating nitrobenzene-contaminated soil according to claim 1, wherein the inoculation amount of the soil sample is 2-10 g/L based on the dry mass of the soil sample.

6. The method for remediating nitrobenzene-contaminated soil as recited in any one of claims 2 to 5, wherein the co-metabolic substrates comprise one or more of ethanol, glucose, sodium acetate, sodium lactate, and sodium succinate.

7. The method for remediating nitrobenzene-contaminated soil as recited in claim 2, wherein the basal medium comprises: 0.1-1% w/v of basic inorganic salt culture medium, 0.1-1% w/v of inorganic carrier, 0.005-0.1% w/v of Tween 80 and water.

8. The method for remediating nitrobenzene-contaminated soil as recited in claim 7, wherein the basic mineral salt medium comprises: in parts by weight, NH₄NO₃8 to 12 parts of K₂HPO₄4 to 6 parts of KH₂PO₄4 to 6 portions of CaCl₂0.8-1.2 parts of NaCl, 1.8-2.2 parts of MgSO₄0.8 to 1.2 parts of MnSO₄0.05 to 0.15 part of FeSO₄0.05 to 0.15 portion.

9. The method for remediating nitrobenzene contaminated soil as recited in claim 7, wherein the inorganic carrier is one or more of zeolite powder, diatomaceous earth, activated carbon, and calcium carbonate.

10. The method for remediating nitrobenzene-contaminated soil as recited in claim 7, wherein the pH of the culture solution is 6 to 8.

11. The method for remediating nitrobenzene contaminated soil as recited in claim 1, wherein the in situ eluted eluent is a combination of tween 80 and n-butanol in any ratio.

12. The method for remediating nitrobenzene-contaminated soil as recited in claim 11, wherein the amount of the eluting agent is 5 to 20 times the pore volume of the soil in the contaminated area.

13. The method for remediating nitrobenzene-contaminated soil as recited in claim 11, wherein the eluting agent has a mass concentration of 3 to 30 g/L.

14. The method for remediating nitrobenzene-contaminated soil as recited in claim 11, wherein the eluent is injected into the contaminated area upstream from the injection well.

15. The method for remediating nitrobenzene-contaminated soil as recited in any one of claims 1 to 5 or 7 to 14, wherein the in situ remediation method comprises adding a mixed culture containing the functional flora and a nutrient solution to the contaminated soil.

16. The method for remediating nitrobenzene contaminated soil as recited in claim 15, wherein the volume of the added nitrobenzene is 1 to 2 times the pore volume of the soil in the contaminated area.

17. The method for remediating nitrobenzene-contaminated soil as recited in claim 16, wherein the nutrient solution and the culture solution of the functional flora are injected into the contaminated area upstream through an injection well.

18. The method for remediating nitrobenzene-contaminated soil as recited in claim 15, wherein the nutrient solution comprises: according to each liter of the culture solution, 500-1000 mg of easily degradable carbon source, 50-100 mg of urea and 15-30 mg of KH₂PO₄(ii) a The easily degradable carbon source comprises one or more of ethanol, glucose and sodium acetate.

19. The method for remediating nitrobenzene-contaminated soil as recited in any one of claims 1 to 5 or 7 to 14, wherein the nitrobenzene-contaminated soil comprises one or more of nitrobenzene soil, nitrochlorobenzene soil, nitrophenol soil, and nitroaniline-contaminated soil.