CN104550206A

CN104550206A - Method for degrading polycyclic aromatic hydrocarbon and polychlorocarbon pollutants in soil

Info

Publication number: CN104550206A
Application number: CN201310472290.5A
Authority: CN
Inventors: 曹惠忠; 李卓坪
Original assignee: Nanjing Kesheng Environmental Protection Technology Co Ltd
Current assignee: Nanjing Kesheng Environmental Protection Technology Co Ltd
Priority date: 2013-10-11
Filing date: 2013-10-11
Publication date: 2015-04-29

Abstract

The invention relates to a technology for polluted soil restoration. Pollutants in soil mainly comprise polycyclic aromatic hydrocarbons and polychlorocarbons. In a biological-chemical-biological treatment restoration order, the pollutants are degraded under suitable conditions.

Description

A kind of method of polycyclic aromatic hydrocarbons and polychlorocarbon pollutant in soil of degrading

Technical field

The present invention relates generally to the recovery technique containing the soil of organic solid pollutant, deposit, mud and mud, and organic solid pollutant comprises polycyclic aromatic hydrocarbons material, polychlorocarbon class material.This process is usually directed to aerobic bioreactor degraded, chemical oxidation, again microorganism aerobic digest three processing steps.

Background technology

Soil is very complicated heterogeneous system, after pollutant enters soil, is reduced the concentration of pollutant by effects such as dilution, diffusion and migrations; Change the form of pollutant and toxicity by acid-base reaction or redox reaction etc., or there is absorption or cohesion and by fixing at colloid surface in pollutant, or by biological or microbial degradation, absorption and conversion.Thus soil has certain receiving and buffer capacity to external contaminant, and soil pollution is often not easily intuitively found.Polycyclic aromatic hydrocarbon (PAHs) and polychlorocarbon, as Polychlorinated biphenyls (PCBs), are modal organic pollutions, are present in contaminated soil, deposit, mud and mud.PCBs possesses the characteristics such as refractory organics, bio-toxicity, bioconcentration and Long-distance Migrating.PCBs, after entered environment, affects by various factors, in different media, a series of conversion can occur, and finally enters in soil, and the health of the mankind and other biological in serious threat.And PAHs is mainly derived from the accessory substance of organic imperfect combustion or Pintsch process, there is potential teratogenesis.Carcinogenicity and genotoxicity.This two organic pollution all has extremely low water-soluble, is difficult in the environment eliminate.

The current recovery technique for the soil containing this two classes SOLID ORGANIC pollutant is primarily of peripheral doses, chemical redemption and biological prosthetic three classes.Peripheral doses is security landfill and high temperature incineration mainly, be applicable to high pollution soil, but it is costly, and has the risk of secondary pollution to environment, and practical application is very limited.

For the reparation of these two kinds of SOLID ORGANIC pollutants in soil, domestic commonly have chemical oxidization method and chemical reduction method.Oxidant can be added in soil, as ozone, hydrogen peroxide, potassium permanganate or Fenton reagent etc., make itself and pollutant generation chemical reaction and realize purifying the object of soil.But due to the SOLID ORGANIC pollutant distribution in soil and heterogeneity, pollutant itself is insoluble solid, as added chemical surfactant, especially itself has toxicity, can pollute again to soil.Therefore, chemical oxidative decomposition can not obtain desired result for the repair of soil.

Biological prosthetic is utilize the biological function such as absorption, metabolism, degraded to environmental pollutants, accelerates the process removing polluter in environment, can be divided into microorganism remediation, phytoremediation and combine d bioremediation.Microorganism remediation can utilize indigenous flora, by providing oxygen or adding nutrient source, the capacity of decomposition of the flora strengthened, or directly to dropping into Inoculating microbes in contaminated environment to strengthen repair, though but indigenous flora decomposes potentiality comparatively greatly, because geobiont is complicated, be difficult to regulation and control, the external source engineering bacteria dropped in addition is difficult to again continue to maintain high activity in soil, also receives certain restriction in actual applications.And planting plants is to assimilate pollutant, the solid organic matters action effect for slightly solubility is not remarkable, and the whole cycle is longer.

Summary of the invention

Invention broadly provides the technical method of polycyclic aromatic hydrocarbons and polychlorocarbon pollutant in soil of effectively degrading.After utilizing the technology process, the amount of contaminant degradation is greater than 90%.

Contaminated soil, deposit, mud, mud etc., the organic solid pollutant wherein contained mainly polycyclic aromatic hydrocarbons and polychlorocarbon class, as Polychlorinated biphenyls.The process of repairing utilizes biological-chemical-biological continuous print processing procedure exactly, can reach the object of degradable organic pollutant.So-called " degraded " is exactly that pollutant PBCs and PAHs is changed into harmless form, all might not produce carbon dioxide.As everyone knows, the steps necessary of the degraded of alkyl class organic compound is exactly biodegradation, also can increase the solubility of PAHs.Therefore, the first step is exactly biological treatment process, and Alcaligenes eutrophus can be selected to belong to and pseudomonad, and in this step, pH value scope is 4.0-6.0, and best pH value is 5.0.Although have bibliographical information Alcaligenes and pseudomonad, be under the environment of 7.5 at pH value, can the PCBs that degrades to greatest extent.But find in experiment, slightly reduce pH value, although have a certain impact to the degraded of organic pollution, pH value, in the scope of 4.0-6.0, is conducive to next step chemical treatment step.

After the biological aerobic of the first step or anaerobic digestion organic pollution, its product can enter next step chemical oxidative decomposition step.In this process, temperature is about 20 DEG C-40 DEG C, application Fenton reagent.The system that Fenton reagent is made up of ferrous ion (Fe2+) and hydrogen peroxide (H2O2), be that catalyst hydrogen peroxide carries out chemical oxidation with ferrous ion, it can generate the hydroxyl radical free radical of strong oxidizing property, generate organic free radical with hardly degraded organic substance in aqueous and make it structural deterioration, final oxidation Decomposition.

Experiment also confirms, the hydrocarbons produced after chemical treatment, is more easily degraded again by biology.Therefore, the 3rd step that the organic pollution in soil is repaired, utilizes microorganism to carry out second time aerobic or anaerobic digestion exactly.And the carbon dioxide produced in chemical oxidation of gold and a small amount of ethanol are also conducive to the complete of bio-digestion.

SOLID ORGANIC pollutant through bio-digestion, chemical oxidative decomposition and bio-digestion again, the resolution ratio nearly 99% of PBCs and PAHs.

caption

Figure 1 shows that the principle schematic of this invention;

Fig. 2-6 is that application alcaligenes are to the degradation experiment result of Polychlorinated biphenyls;

Fig. 7-10 is that application pseudomonas is to the degradation experiment result of Polychlorinated biphenyls;

Figure 11-12 is that application alcaligenes and pseudomonas combine bacterium liquid to the degradation experiment result of Polychlorinated biphenyls.

Detailed description of the invention

As shown in Figure 1, be the principle schematic of this invention.First contaminated soil need inject a certain amount of water, and stirs into mud, is mud or waters mud etc., directly can drops in treatment pond and stir if pending.Adding phosphate buffer regulates pH value to 4.0-6.0, and preferably pH value is 5.0.Also need in addition to add a certain amount of yeast extract, using the nutrient source as microorganism.The microorganism added is the mixture of alcaligenes and pseudomonas.Through biological respinse after a while, pH value can raise slightly, but generally its pH value, not higher than 5.5, now without the need to regulating pH value, can add Fenton reagent directly in reactant, and after adding Fenton reagent, the pH value of slurry mixture can slightly reduce.If but now pH value, higher than 5.5, need add dilute hydrochloric acid and regulate about pH value to 5.2.Through the chemical oxidation reaction stage after a while, then enter into the biological respinse stage, this elementary reaction time is generally long, sustainable 4 weeks-8 weeks.Through this process, organic pollution is decomposed removal, is finally purified soil.

Carry out experiment, detect alcaligenes, pseudomonad to the degradation of Polychlorinated biphenyls.Under the condition of pH value 7.0, the OD value that the alkali bacillus added belongs to is 1.0, and two other is tested at ordinary times, and the OD value of the pseudomonad added is respectively 0.2 and 1.0.As shown in Figure 2, through the biodegradation process of nearly month, add separately alkali bacillus genus or pseudomonad that OD value is 1, the mineralising reactivity difference of chlordiphenyl was little, close to 20% for its result.If but the OD value of the pseudomonad added is down to 0.2, the mineralising reactivity of chlordiphenyl is less than 10%.Based on this result, apply higher OD value to a certain extent, the degradation rate that organic solid is polluted can be strengthened.

Therefore, improve the OD value of bacterial strain in biodegradation process, and the amalgamation oxidation reaction stage, find that the degradation rate of some organic pollutions strengthens greatly.Be about the condition of 5.0 at pH value under, select Bacillus alcaligenes OD value to be 2.0 and 4.0, purified treatment dichloro-benzidine is after 26 days, add Fenton reagent (hydrogen peroxide containing 4%), overall reaction 106 days, the results are shown in Figure 3, finds that the purifying rate of dichloro-benzidine is up to 94% and 98%.Apply same bacterial strain, same bacterial strain OD value, other conditions are all constant, process tetrachloro biphenyl, result as shown in Figure 4, when the OD value of discovery application Bacillus alcaligenes is 2.0, the purifying rate of tetrachloro biphenyl is 92%, and when bacterial strain OD is 4.0, under the condition of purifying rate higher than 95%PH value 5.0, biological degradation rate is all higher than 40%.Still apply the Bacillus alcaligenes of different OD value, under the condition of pH value 7.0-7.5, decomposing, purifying process dichloro-benzidine, after 26 days, adds Fenton reagent (hydrogen peroxide containing 4%), overall reaction 106 days.The results are shown in Figure 5, find that the purifying rate of dichloro-benzidine is respectively 74% and 82%.Under same experiment condition, purified treatment tetrachloro biphenyl, the results are shown in Figure 6, finds that speech rate is all lower than 45%.

Fig. 7 to Figure 10 is the result of application pseudomonad.The OD value of pseudomonad selects 2.0 and 4.0 respectively, to be about under the condition of 5.0 decomposing organic pollutant 26 days, to add Fenton reagent afterwards and carrying out oxidation Decomposition, whole process lasts 106 days at pH value.As shown in Figure 7, OD most 4.0 time, purified treatment DCBP higher than 95%, the effect basic simlarity of this and Bacillus alcaligenes.But under identical condition, purified treatment tetrachloro biphenyl, can find from Fig. 8, the biological decomposition stage, resolution ratio just comparatively Bacillus alcaligenes reduce nearly half, less than 25%, through the reaction of 106 days, the purifying rate of tetrachloro biphenyl is less than 85%.Decompose in the reaction of DCBP and tetrachloro biphenyl, when other conditions are constant, only change the pH value of reaction system, make pH value within the scope of 7.0-7.5, find the OD value of pseudomonad, impact for whole course of reaction is also little, and in the bio-degradation reactions process of 26 days started, as shown in Figure 9 and Figure 10, biological decomposition rate is all lower than 20%, and through 106 days, the degradation rate of DCBP and tetrachloro biphenyl was respectively lower than 60% and 80%.As can be seen here, under the condition of pH value 5.0, pseudomonad for the resolution ratio of DCBP and the action effect of Bacillus alcaligenes similar, but poor to the decomposition of tetrachloro biphenyl; And under the condition of pH value 7.0-7.5, comparatively Bacillus alcaligenes is good to the effect of tetrachloro biphenyl for pseudomonad.Therefore, test below, even in process implementing, two kinds of strain-combined application should be adopted, reach best biodegradation effect.

But for soil remediation, although bacterial strain, suitable reaction condition that application is suitable, utilize microbial degradation and chemical oxidation two processes, most PBCs pollutant can be degraded removal, and the history trimestral time is obviously long, and is not suitable for practical application.If Reaction time shorten, use in conjunction pseudomonad and Bacillus alcaligenes, under being about the condition of 5.0, last the course of reaction of 21 days altogether at PH, and as shown in figure 11, by different process, the degradation rate of PCB also has obvious difference to result.As shown in figure 11, through the purified treatment of 21 days, three process of biodegradation-chemical oxidation-biodegradation set, best results; And the degradation rate of simple biodegradation or chemical oxidation is only 60% and 29%.

In laboratory conditions, get the mud sample that 2.5L water content is 20%, the PCB content detected wherein is 175ppm.Be under the condition of 5.0 at pH value, add pseudomonad and Bacillus alcaligenes mixed bacteria liquid that OD value is 2.0, under room temperature 25 DEG C of-30 DEG C of conditions, bio-degradation reactions 4 days, finds that pH value rises to 5.6.Add Fenton reagent (2% hydrogen peroxide) afterwards, detecting pH value has and slightly declines, and is 5.47, now, falls into watery hydrochloric acid adjustment pH value to 5.2.Through the chemical oxidation stage of 8 days, afterwards continued biological degradation process.Whole repair process continues 60 days.Result as shown in figure 12, to be decomposed removal to whole course of reaction by, the PCB of nearly 99%.Further analysis finds, to secondary biological oxidation, the clearance rate of PCB is higher than 90%.

Claims

1. the technical method of the polycyclic aromatic hydrocarbons (PAH) in repairing polluted soil, deposit, mud, mud and polychlorocarbon class material, the order of biological-chemical-biology is adopted to administer step: first to utilize microorganism aerobic or anaerobic digestion effect, protopepsia decomposing pollutant; Then in pollutant, add Fenton reagent, mix in 10 DEG C of-100 DEG C of temperature ranges, accelerating oxidation decomposition reaction; Finally enter secondary microbial digestion catabolic phase.

2. the bacterial strain of twice microbial digestion stage application according to claim 1 is alcaligenes, pseudomonad.

3. the step of bio-digestion first according to claim 1, the pH value of reaction system is within the scope of 4.0-6.0.

4. the step of microbial decomposition first according to claim 1, the OD value of microorganism is within the scope of 1.0-4.0.

5., in Fenton reagent according to claim 1, the ratio of hydrogen peroxide is 0.5%-5%; Per hour, add the Fenton reagent of 1g-300g in every kilogram of pollutant.