Remediation Of DDT-contaminated Soil Research Articles

Dichlorodiphenyltrichloroethane (DDT) degradation by Streptomyces sp. isolated from DDT contaminated soil

Bioaccumulation, toxicity and long-range transport of persistent organic pollutants (POPs) is a threat to soil and other ecosystems, therefore removal of such pollutants from soil is required. This study thus aimed to isolate and identify bacteria capable of biodegrading a persistent organic pollutant; dichlorodiphenyltrichloroethane (DDT) from a former DDT production unit. The soil was sampled, transported to Japan through standard protocols and bacteria were isolated and assayed for dichlorodiphenyldichloroethane (DDD) and dichlorodiphenyldichloroethylene (DDE) degradation. The concentration of DDTs in a composite soil sample was 0.7 mg kg−1. Twenty-four bacterial strains were isolated from DDT-contaminated soil, and one of them, strain 885, showed degradation of DDT but could not degrade DDE after 14 days of incubation. This strain also showed significant degradation of 15.6 µM DDD (degradation rate 55.9%) after 28 days incubation. Further metabolites of DDT including 2,2-bis(p-chlorophenyl) ethanol (DDOH) and 4,4-dichlorobenzophenone (DBP) were detected from a 14-day incubation culture with DDD as initial substrate. Strain 885 also showed degradation of metabolites of DDT including those of DDOH, and DBP. In conclusion, strain 885 successfully degraded DDT; therefore, it can be used for remediation of DDT-contaminated soil.

Pilot-scale Installation for Remediation of DDT-contaminated Soil

ABSTRACTAn effective remediation method of DDT-contaminated soil was developed. The preliminary results of investigations on a laboratory scale were exploited to scale up the technology into pilot scale. The approach for soil remediation was based on the utilization of hydroxyl radicals that were generated from water aerosol and ozone in a fluidized bed reactor. During the remediation procedure the level of soil contamination was reduced by 80%. The procedure was successfully scaled up; no degradation products were detected and the total organic carbon was preserved.

A Novel Method for Degradation of DDT in Contaminated Soil

A novel method for remediation of DDT contaminated soil based on advanced oxidation processes including reactions with hydroxyl radicals and ozone has been developed. On the basis of the conducted experiments the authors concluded that ozone did not degrade DDT in soil. Analysis of degradation products that were formed during exposure to a stream of gaseous ozone indicated that hydroxyl radicals might play a key role in degradation of this compound. In the modified fluidized bed reactor where hydroxyl radicals could be generated from ozone and water vapor, reduction of over 90% of DDT residue level has been achieved. Authors proposed a pathway of DDT degradation, under the influence of hydroxyl radicals and ozone. As a result of this research, an effective method for remediation of DDT-contaminated soil has been proposed.

Studies on Remediation of DDT-Contaminated Soil and Dechlorination of DDT

A practical and efficient disposal method for 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT)-contained soil is reported. The treatment process was a combination technique: first to extract DDT in the soil, and then to hydrogenate the extract containing DDT. 4, 4'-DDT was effectively extracted in the soil and hydrodechlorinated in this treatment process. Additionally, solvent media and extracting time for DDT removal were investigated. An efficient heterogeneous catalytic method was also developed by comparing the rates of dechlorination of DDT over two different catalysts in organic-aqueous heterogeneous system. Compared to Raney Ni, Pd/C is a more efficient catalyst in disposing DDT. (C) 2012 Selection and/or peer-review under responsibility of Basel Convention Coordinating Centre for Asia and the Pacific and National Center of Solid Waste Management, Ministry of Environmental Protection of China.

Effects of Soil Oxygen Conditions and Soil pH on Remediation of DDT-contaminated Soil by Laccase from White Rot Fungi

High residues of DDT in agricultural soils are of concern because they present serious threats to food security and human health. This article focuses on remediation of DDT-contaminated soil using laccase under different soil oxygen and soil pH conditions. The laboratory experiment results showed significant effects of soil oxygen conditions and soil pH on remediation of DDT-contaminated soil by laccase at the end of a 25-d incubation period. This study found the positive correlation between the concentration of oxygen in soil and the degradation of DDT by laccase. The residue of DDTs in soil under the atmosphere of oxygen decreased by 28.1% compared with the atmosphere of nitrogen at the end of the incubation with laccase. A similar pattern was observed in the remediation of DDT-contaminated soil by laccase under different flooding conditions, the higher the concentrations of oxygen in soil, the lower the residues of four DDT components and DDTs in soils. The residue of DDTs in the nonflooding soil declined by 16.7% compared to the flooded soil at the end of the incubation. The residues of DDTs in soils treated with laccase were lower in the pH range 2.5–4.5.

Remediation of DDT contaminated soil by using laccase in different application ways

Remediation of DDT contaminated soil by using laccase in different application ways

Development of a Two-Phase Cosolvent Washing-Fungal Biosorption Process for the Remediation of DDT-Contaminated Soil

A bench scale, two-phase soil washing-biosorption process was developed for the remediation of p,p′-DDT-contaminated soil (containing 990 and 7750 mg kg-1 of p,p′-DDT). Removal of p,p′-DDT from contaminated soil was achieved by washing the soil with low molecular weight primary alcohols (ethanol or 1-propanol). An improved efficiency of p,p′-DDT removal was observed with increasing C-chain length of the cosolvent and by increasing the cosolvent volume fraction. When 40 or 80% 1-propanol were used, greater than 93% of p,p′-DDT was desorbed from the respective soils. p,p′-DDT was partitioned from the cosolvent solutions using biomass of Cladosporium sp. strain AJR318,501 as the sorptivematrix. When studies were conducted using a cosolvent-recycling regime (with 80% 1-propanol) greater than 95% of p,p′-DDT was removed from Soil A (990 mg kg-1p,p′-DDT) and Soil B (7750 mg kg-1p,p′-DDT) with the majority of the desorbed organochlorine repartitioning onto the fungal biomass. Less than 2.4 μg mL-1p,p′-DDT was detected in the cosolvent wash solution of Soil A after 80 hr: potentially the cosolvent could be further reused to treat other soil. A higher concentration of p,p′-DDT was detected in the cosolvent wash solution of soil B after 120 hr (13.3 μg mL-1) indicating that the p,p′-DDT sorption sites on the fungal biomass were fully saturated.

In situ Remediation of DDT-contaminated Soil Using a Two-Phase Cosolvent Flushing-Fungal Biosorption Process

The effectiveness of cosolvent soil flushing and fungal biosorption for the remediation of p,p′-DDT-contaminated soil was evaluated usingpacked soil columns in order to simulate an in situ soil flushing technique. Greater than 95% of p,p′-DDT (940 mg kg-1) was desorbed from the soil by flushing with 40 or 80% 1-propanol. Increasing the cosolvent volume fraction increased the rate of p,p′-DDT removal from the soil, however, the extent of p,p′-DDT removal was not enhanced. A further enhancement in therate of p,p′-DDT removal was achieved by increasing the cosolventflow rate from 6 ml hr-1 to 12 ml hr-1 (pore water velocity from 18.9 to 37.8 cm hr-1). The desorbed p,p′-DDT was removed from cosolvent wash solutions by partitioning onto fungal biomass. Biosorption of p,p′-DDT resulted in low concentrations of the organochlorine (3.3 μg ml-1) remaining in thecosolvent effluent indicating that the cosolvent could be reused for further p,p′-DDT desorption. Using this technique, between 53 and 95 pore volumes were required to reduce p,p′-DDT concentrationsfrom 990 mg kg-1 to below Australian and New Zealand Environmentaland Conservation Council (ANZECC) guidelines (50 mg kg-1).