Dechlorination

The performance and removal mechanisms of a hybrid constructed wetland (HCW) followed by a willow planted filter (WPF) were evaluated for the treatment of a leachate contaminated by wood pole preservatives (pentachlorophenol (PCP) and chromated copper arsenate) to reach the storm sewer discharge limits. The HCW aimed to dechlorinate the PCP and polychlorodibenzo-p-dioxins/polychlorodibenzofuran (PCDD/F) and to remove metals by adsorption and precipitation. The HCW was efficient in removing PCP (>98.6%), oil, arsenic (99...

Chlorates are present in the brine stream purged from chlor-alkali plants. Tests were conducted using activated carbon from coconut shell, coal or palm kernel shell to adsorb chlorate. The results show varying levels of adsorption with reduction ranging between 1.3 g/L and 1.8 g/L. This was higher than the chlorate generation rate of that plant, recorded at 1.22 g/L, indicating that chlorate can be adequately removed by adsorption using activated carbon. Coconut based activated carbon exhibited the best adsorption of chlorate of the three types of activated carbon tested...

Since 1972, the French departments of Guadeloupe and Martinique have intensively used organochlorinated pesticides such as chlordecone (CLD) and hexachlorocyclohexane (HCH) isomers to prevent the proliferation of banana weevil (Cosmopolite sordidus). These molecules are stable in the environment, leading to a continuous contamination of soils, water, and food chain in the banana-producing areas. In these polluted areas, water treatment plants are equipped with activated carbon (AC) filters. In order to improve treatment of CLD-contaminated waters by AC, CLD adsorption and desorption kinetic studies are carried out using different ACs produced from sugar cane bagasse as adsorbents and subsequent CLD degradation is performed using reduced vitamin B12 (VB12)...

Characterizing properties of the rock matrix that control retention and release of chlorinated solvents is essential in evaluating the extent of contamination and the application of remediation technologies in fractured rock. Core samples from seven closely spaced boreholes in a mudstone subject to trichloroethene (TCE) contamination were analyzed using Mercury Intrusion Porosimetry to investigate porosity and pore size distribution as a function of mudstone characteristics, and depth and lateral extent in the aquifer; organic carbon content was also evaluated to identify the potential for adsorption...

Results from a lab-scale investigation of a combined in/out ultrafiltration and powdered activated carbon adsorption (PAC/UF) for removal of diclofenac (c0=5 mg/L) are presented. The efficiency of the process was compared for single pulse and continuous carbon dosing (PAC dose 5 mg/L) in dechlorinated tap water under fluxes of 87 and 135 L/(m(2)·h). For higher flux conditions it was observed that single pulse dosing has an advantage over continuous dosing procedure when comparing cycle average removal efficiency...

A laterally π-extended dithia[6]helicene 1, representing an interesting saddle-helix hybrid molecule containing an unusual heptagon, has been synthesized by MoCl5-mediated oxidative stitching of tetrakis(thienylphenyl)naphthalene precursor 2 involving reactive-site capping by chlorination, and subsequent Pd-mediated dechlorination of tetrachlorinated intermediate 1-Cl4. Highly distorted, wide helical structures of dithia[6]helicenes (1 and 1-Cl4) were clarified by single crystal X-ray diffraction analyses, where heterochiral slipped π-π stacking was displayed in one-dimensional fashion...

The in vitro biochemical characterization revealed that iron/2-oxoglutarate (Fe/2OG)-dependent aliphatic halogenase WelO5* in Hapalosiphon welwitschii IC-52-3 has an enhanced substrate specificity towards 12-epi-hapalindole C (1) in comparison to WelO5 in H. welwitschii UTEX B1830. This allowed us to define the origin of the varied chlorinated versus dechlorinated alkaloid structural diversity between the two welwitindolinone producers. Furthermore, this study, along with the recent characterization of the AmbO5 protein, collectively confirmed the presence of a signature sequence motif in the C-terminus of this newly discovered halogenase enzyme family that confers substrate promiscuity and specificity...

2, 4-dichlorophenol (2, 4-DCP) is considered to be a highly toxic, mutagenic, and possibly carcinogenic pollutant. This study is focused on the electrochemical oxidation of 2, 4-DCP on nanostructured 3D-porous Ti/Sb-SnO2-Gr anodes, with the aim of presenting a comprehensive elucidation of mineralization process through the investigation of influential kinetics, the reactivity of hydroxyl radical's and analysis of intermediates. High efficiency was achieved at pH of 3 using Na2SO4 electrolytes at a current density of 30 mA cm(-2)...

Concentrations and spatial distribution pattern of organohalogen flame retardants were investigated in the riverine surface sediments from Taizhou, an intensive e-waste recycling region in China. The analytes were syn- and anti- Dechlorane Plus (DP), Dechloranes 602, 603, and 604, a DP monoadduct, two dechlorinated DPs and 8 congeners of polybrominated diphenyl ethers (PBDEs). The concentrations of Σ8PBDEs, ΣDP, ΣDec600s, and ΣDP-degradates ranged from <100 to 172,000, 100 to 55,000, not detectable (nd) to 1600, and nd to 2800 pg/g dry weight, respectively...

Biomolecular and hydrochemical tools were used to evaluate natural attenuation of chlorinated ethenes in a Quaternary alluvial aquifer located close to a historical source of large-scale tetrachloroethylene (PCE) contamination. Distinct stratification of redox zones was observed, despite the aquifer's small thickness (2.8 m). The uppermost zone of the target aquifer was characterised by oxygen- and nitrate-reducing conditions, with mixed iron- to sulphate-reducing conditions dominant in the lower zone, along with indications of methanogenesis...

Bioremediation at chlorinated solvent sites often leads to groundwater acidification due to electron donor fermentation and enhanced dechlorination activity. The microbial reductive dechlorination process is robust at circumneutral pH, but activity declines at groundwater pH values below pH 6.0. Consistent with this observation, the activity of tetrachloroethene (PCE) dechlorinating cultures declined at pH 6.0 and was not sustained in pH 5.5 medium, with one notable exception. Sulfurospirillum multivorans dechlorinated PCE to cis-1,2-dichloroethene (cDCE) in pH 5...

In this study, samples were taken from different types of municipal waste incineration plants in the Pearl River Delta, China. Analyzing the distributive characters of elements and dioxin congeners in fly ash, the method of washing-ball milling was utilized to remove chloride and degrade dioxin in fly ash. The results showed that more than 90% of particles were in the range of 1∼50μm and most of dioxin and metals existed in 0.030∼0.075mm of particles. K, Na, Cl and Br in fly ash could be removed by washing efficiently, however dioxin and other metals remained in the solid phase...

DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane) is one of the pesticides that are hazardous for the environment and human health. Effective environmental-friendly treatment using co-cultures of fungi and bacteria is needed. In this study, the bacteria Bacillus subtilis at various volumes of 1, 3, 5, 7, and 10 mL (1 mL ≈ 6.7 × 10(8) CFU) were mixed into 10 mL of the brown-rot fungus Fomitopsis pinicola culture for degrading DDT during a 7-days incubation period. DDT was degraded by approximately 42% by F...

The constant use of chemical insecticides for Aedes aegypti control has caused resistance in the mosquito populations. Thus, the objective of this study was to analyze the larvicidal potential of extracts and fractions of plants on A. aegypti larvae. The analysis included sixty one extracts and twenty five fractions of fifty botanical species at concentrations of 0.25; 0.12; 0.06 to 0.03 mg mL-1; 4 replications and one negative control of dechlorinate water and 1% DMSO; and a positive control with rotenone...

Sulfate-rich biochemical effluent of landfill leachate (BEL) resulting from aged refuse bioreactor was employed to wash municipal solid waste incineration (MSWI) fly ash. The dechlorination ability of BEL was found to be nearly equivalent to redistilled water (RW), and concentrations of lead (Pb) and zinc (Zn) in washing solution resulting from BEL washing process were lower than that of RW washing process, Fourier transform infrared (FTIR) analysis indicated that the formation of calcium sulfate and hydroxides in fly ash after BEL washing, and their entrapping function could significantly inhibit the leaching of Pb and Zn...

We report herein the purification of a chloroform (CF)-reducing enzyme, TmrA, from the membrane fraction of a strict anaerobe Dehalobacter sp. strain UNSWDHB to apparent homogeneity with an approximate 23-fold increase in relative purity compared to crude lysate. The membrane fraction obtained by ultracentrifugation was solubilized in Triton X-100 in the presence of glycerol, followed by purification by anion exchange chromatography. The molecular mass of the purified TmrA was determined to be 44.5 kDa by SDS-PAGE and MALDI-TOF/TOF...

In this study, bioelectrochemical-upflow anaerobic sludge blanket (BES-UASB) system was developed for treatment of 2,4-dichloronitrobenzen (DClNB) containing wastewater to investigate the effect of external voltage with different supplying modes. Results showed that 2,4-dichloroaniline (DClAN) was under detection limit in R1 (applied with intermittent voltage) and R2 (applied with continuous voltage) when the DClNB loading increased from 25 to 100gm(3)d(-1) (hydraulic retention time (HRT) was decreased from 24 to 6h) while sudden accumulation of DClAN (1...

Nanoscale zerovalent iron (NZVI) is a promising remediation agent for volatile organic compound (VOC) contamination in saturated sub-surfaces, but is rarely applied to the vadose zone as there are not enough water molecules in the unsaturated zone to participate in reductive dechlorination. In this study, we evaluated the possibility of using foam as a carrying vehicle to emplace NZVI in unsaturated porous media followed by the application of low frequency-electromagnetic field (LF-EMF) to enhance VOC volatilization in laboratory batch reactors...

A novel laboratory-scale bioelectrode and anaerobic sludge coupled system was established for the enhancement of p-chloronitrobenzenes (p-ClNB) reductive transformation with addition of magnetite nanoparticles. In this coupled system, the bioelectrodes were supplied with a voltage of 0.8 V and the amount of magnetite nanoparticles was set at 7.4 mL/400 mL. Results showed that high p-ClNB transformation rate of 0.284 h(-1) and high p-chloroaniline (p-ClAn) dechlorination rate of 0.082 h(-1) were achieved in the coupled system at p-ClNB initial concentration of 30 mg L(-1), and p-ClAn is one of the reductive products of p-ClNB...

We have developed and characterized a bacterial consortium that reductively dechlorinates trichloroethene to ethene. Quantitative PCR analysis for the 16S rRNA and reductive dehalogenase genes showed that the consortium is highly enriched with Dehalococcoides spp. that have two vinyl chloride reductive dehalogenase genes, bvcA and vcrA, and a trichloroethene reductive dehalogenase gene, tceA. The metagenome analysis of the consortium by the next generation sequencer SOLiD 3 Plus suggests that a Dehalococcoides sp...