FINAL REPORT Prospects for Remediation of 1 , 2 , 3-Trichloropropane by Natural and Engineered Abiotic Degradation Reactions SERDP Project ER-1457 AUGUST 2010 (original) (raw)
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Fate and remediation of 1, 2, 3-trichloropropane
2008
1,2,3-trichloropropane (TCP) has been used in a variety of chemical production processes, in agricultural chemicals, and as a solvent, resulting in point and nonpoint source contamination. The chemical properties, and the relatively few studies that have focused on the fate or remediation of TCP suggest that TCP-while very recalcitrant in general-can be degraded by biotic and abiotic processes under favorable conditions, including some of those employed for in situ chemical oxidation (ISCO) and in situ chemical reduction (ISCR). In general, TCP exhibits little or no reaction with mild reductants (including construction-grade Fe 0) but is dechlorinated by strong reductants (like palladized nano-Fe 0). Similarly, strong oxidants like activated peroxide or persulfate give favorable rates of degradation but a mild oxidant like permanganate does not. Aerobic and anaerobic biodegradation have been observed in laboratory studies, but the rates are comparatively slow, and definitive evidence for biodegradation in the field is still lacking.
Transformation and biodegradation of 1,2,3-trichloropropane (TCP)
Environmental Science and Pollution Research, 2012
Purpose 1,2,3-Trichloropropane (TCP) is a persistent groundwater pollutant and a suspected human carcinogen. It is also is an industrial chemical waste that has been formed in large amounts during epichlorohydrin manufacture. In view of the spread of TCP via groundwater and its toxicity, there is a need for cheap and efficient technologies for the cleanup of TCP-contaminated sites. In situ or on-site bioremediation of TCP is an option if biodegradation can be achieved and stimulated. This paper presents an overview of methods for the remediation of TCP-contaminated water with an emphasis on the possibilities of biodegradation. Conclusions Although TCP is a xenobiotic chlorinated compound of high chemical stability, a number of abiotic and biotic conversions have been demonstrated, including abiotic oxidative conversion in the presence of a strong oxidant and reductive conversion by zero-valent zinc. Biotransformations that have been observed include reductive dechlorination, monooxygenase-mediated cometabolism, and enzymatic hydrolysis. No natural organisms are known that can use TCP as a carbon source for growth under aerobic conditions, but anaerobically TCP may serve as electron acceptor. The application of biodegradation is hindered by low degradation rates and incomplete mineralization. Protein engineering and genetic modification can be used to obtain microorganisms with enhanced TCP degradation potential.
2010
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Remediation Journal, 2017
Laboratory and field demonstration studies were conducted to assess the efficacy of enhanced biological reduction of 1,2,3-trichloropropane (TCP) in groundwater. Laboratory studies evaluated the effects of pH and initial TCP concentrations on TCP reduction and the activity of a microbial inoculum containing Dehalogenimonas (Dhg). Laboratory results showed successful reduction at a pH of 5 to 9 with optimal reduction at 7 to 9 and at initial TCP concentrations ranging from 10 to over 10,000 micrograms per liter (g/L). Based on findings from the laboratory study, the effects of TCP concentration, geochemical conditions, and amendment concentration on bioremediation efficacy were investigated during a field demonstration at a site with relatively low initial concentrations of TCP (< 2 g/L). The field demonstration included injection of emulsified vegetable oil (EVO) and lactate as a carbon substrate for biostimulation, followed by bioaugmentation using the microbial inoculum containing Dhg. Post-injection performance monitoring demonstrated reduction of TCP to below laboratory detection limits (< 0.005 g/L) after an initial lag period of approximately six months following injections. TCP reduction was accompanied by generation of the degradation byproduct propene. A marginal increase in TCP concentrations, potentially due to an influx of upgradient aerobic groundwater containing TCP, was observed eight months after injections thereby demonstrating the sensitivity of this bioaugmentation application to changes in geochemical parameters. Despite this marginal increase, performance monitoring results indicate continued TCP biodegradation 15 months after implementation of the injection program. This demonstration suggests that enhanced biodegradation of TCP by combining biostimulation and bioaugmentation may be a promising solution to the challenges associated with remediation of TCP, even when present at low part per billion concentrations in groundwater.
Environmental Science & Technology, 2014
The anthropogenic compound 1,2,3-trichloropropane (TCP) has recently drawn attention as an emerging groundwater contaminant. No living organism, natural or engineered, is capable of the efficient aerobic utilization of this toxic industrial waste product. We describe a novel biotechnology for transforming TCP based on an immobilized synthetic pathway. The pathway is composed of three enzymes from two different microorganisms: engineered haloalkane dehalogenase from Rhodococcus rhodochrous NCIMB 13064, and haloalcohol dehalogenase and epoxide hydrolase from Agrobacterium radiobacter AD1. Together, they catalyze consecutive reactions converting toxic TCP to harmless glycerol. The pathway was immobilized in the form of purified enzymes or cell-free extracts, and its performance was tested in batch and continuous systems. Using a packed bed reactor filled with the immobilized biocatalysts, 52.6 mmol of TCP was continuously converted into glycerol within 2.5 months of operation. The efficiency of the TCP conversion to the intermediates was 97%, and the efficiency of conversion to the final product glycerol was 78% during the operational period. Immobilized biocatalysts are suitable for removing TCP from contaminated water up to a 10 mM solubility limit, which is an order of magnitude higher than the concentration tolerated by living microorganisms.
Site-specific pre-evaluation of bioremediation technologies for chloroethene degradation
International Journal of Environmental Science and Technology, 2013
Groundwater systems are important sources of water for drinking and irrigation purposes. Unfortunately, human activities have led to widespread groundwater contamination by chlorinated compounds such as tetrachloroethene (PCE). Chloroethenes are extremely harmful to humans and the environment due to their carcinogenic properties. Therefore, this study investigated the potential for bioremediating PCE-contaminated groundwater using laboratory-based biostimulation (BS) and biostimulationbioaugmentation (BS-BA) assays. This was carried out on groundwater samples obtained from a PCE-contaminated site which had been unsuccessfully treated using chemical oxidation. BS resulted in complete dechlorination by week 21 compared to controls which had only 30 % PCE degradation. BS also led to a approximately threefold increase in 16S rRNA gene copies compared to the controls. However, the major bacterial dechlorinating group, Dehalococcoides (Dhc), was undetectable in PCE-contaminated groundwater. This suggested that dechlorination in BS samples was due to indigenous non-Dhc dechlorinators. Application of the BS-BA strategy with Dhc as the augmenting organism resulted in complete dechlorination by week 17 with approximately twofold to threefold increase in 16S rRNA and Dhc gene abundance. Live/dead cell counts (LDCC) showed 70-80 % viability in both treatments indicating active growth of potential dechlorinators. The LDCC was strongly correlated with cell copy numbers (r [ 0.95) suggesting its potential use for low-cost monitoring of bioremediation. This study also shows the dechlorinating potential of indigenous non-Dhc groups can be successfully exploited for PCE decontamination while demonstrating the applicability of microbiological and chemical methodologies for preliminary site assessments prior to field-based studies.
Trichloroethylene (TCE) is found in all mediums of environment in varying concentrations. Over the past 25 years, many engineered systems have been devised for its complete and sustainable degradation. This study reviews the environmental factors that influence the TCE pollution in environment and its biological mineralization via engineered systems. Although at some polluted sites natural attenuation of TCE has been found to occur but generally the natural process is very slow. The use of nanoparticles and composites provides a comparatively novel approach for the treatment of TCE contaminated waters. Biological engineered systems have been found to degrade TCE on much faster rates and higher concentrations. To identify the appropriate microorganisms in any engineered system that can effectively provide a low-cost treatment option for TCE degradation is the pressing need at the moment. Adding a second distinct organic phase to the aqueous medium for degrading fast and high concentration of TCE is recommended. The organic phase, which do not mix with the aqueous phase and can be easily separated, discharged, and reuse, should be selected based on its insolubility, volatility, non-biodegradability by the selected microorganism and the cost of the overall engineered system. Biodegradation offers the potential of cost effective treatment of TCE, however, that engineered systems should effectively use the biodegradative metabolism that nature has evolved.
Biodegradation of Tetrachloroethene in Batch Experiment and PHREEQC Model; Kinetic Study
2021
Introduction Tetrachloroethylene (Cl2C=CCl2) with the systematic name tetrachloroethene or perchloroethylene (perc, PERC, or PCE) is a chlorocarbon and a colorless liquid sometimes called "dry-cleaning fluid". It is estimated that almost 85% (76.39%-99.69%) of tetrachloroethylene produced is released into the atmosphere (with a lifetime of about 2 months in the Southern Hemisphere and 5-6 months in the Northern Hemisphere); and about 10% (0.23%-23.2%) is in water, 0.06-7% is in soil and the remainder is in sediment and biota. Tetrachloroethylene is a typical soil pollutant. 1-3 The PCE cleanup from groundwater is more difficult than from oil spills, because of its mobility, high toxicity even in low concentrations, and its density. As a result, the current research is focused on in-place remediation of contaminants including bioremediation and biodegradation. 4,5 Degradation products observed in a laboratory include phosgene, trichloroacetyl chloride, hydrogen chloride, carbon dioxide, and carbon monoxide. The degradation products of tetrachloroethylene include trichloroethylene, dichloroethylene, vinyl chloride, ethylene, and ethane. The by-products of aerobic biodegradation of PCE include trichloroethylene, cis-1,2-dichloroethene, and vinyl chloride; while its full degradation converts it to ethene and dissolved hydrogen chloride in water. 6,7 Trichloroethylene (TCE) is used for cleaning grease from industrial instruments. As an abundant environmental pollutant in groundwater, in some places, TCE undergoes reductive dechlorination catalyzed by anaerobic bacteria and produces vinyl chloride, which is a potent human carcinogen. Since air stripping or dumping methods are not currently permittedfor removal of TCE, recent efforts for its removal from soil and water are focused on biological degradation and removal. 8 Recent researches have focused on in-place remediation of TCE from soil and groundwater instead of disposal or Abstract Introduction: Bioremediation and biodegradation are considered as environmental friendly techniques for contaminants' removal in polluted environment. In this study the removal and kinetics of Tetrachloroethene (PCE) and Trichloroethene (TCE) microbial degradation, their inhibitory effects and the rate of dehalogenation capacity at high concentration of PCE were investigated. Materials and Methods: Dechlorinating culture was provided by Bioclear B.V. from a PCE-contaminated site (Evenblij in Hoogeveen-The Netherlands). The batch apparatuses were placed in an orbital shaker at 150 rpm at room temperature. In all the 18 batches, 6 different concentrations of PCE were measured from 0.1 mM to 0.6 mM. The degradation rate of PCE, Trichloroethene (TCE), and cis-1,2-dichloroethene (cDCE) were determined by the PHREEQC model. Results: The results revealed that the final product was ethene and the rate of dechlorinating of PCE increased gradually. The degradation process started after 3 days in batch modes (0.1 mM). After 10 days, the dechlorination of PCE to TCE was obtained in a low concentration of PCE (0.1 mM). Also, the TCE concentration became close to zero after 10 days. However, the start point was longer than PCE and the rate of biodegradation of TCE was faster than PCE. PCE did not show any progress in the dechlorinating procedure at 13th and 14th batch series and none of the daughter products were observed. Conclusions: It should be concluded that there was no single organism that could dechlorinate PCE to ethene, directly. Therefore, the best consortium of microorganisms to dechlorinate PCE to ethene faster, with less production of VC as the most hazardous compound, should be studied.
Reviews in Environmental Science and Bio/Technology, 2013
Due to its toxicity and persistence in the environment, trichloroethylene (TCE) has become a major soil and groundwater contaminant in many countries. A group of aliphatic-and aromatic-degrading bacteria expressing nonspecific oxygenases have been reported to transform TCE through aerobic cometabolism in the presence of primary substrate such as methane, ammonia, propane, phenol, toluene or cumene. This paper reviews the fundamentals and results of TCE cometabolism from laboratory and field studies. The limitations associated with TCE
2013
Natural Attenuation (NA) in the case of groundwater contaminated with organic compounds relies mainly on intrinsic biodegradation processes. The aim of reliance on natural processes is to achieve site-specific cleanup objectives within reasonable time frames and costs. Such approach may be considered as a risk reduction/remedial option for groundwater contaminated with trichloroethene (TCE) and tetrachloroethene (PCE) in the vicinity of Nowa Deba waterworks. This case study presents implementation of the USEPA's guideline "Technical protocol for evaluating natural attenuation of chlorinated solvents in ground water" to asses intrinsic biodegradation potentials in contaminated groundwater in the case of Nowa Deba. Literature and field data collected from wells and piezometers were used to develop a conceptual model of contaminants' fate and transport from a source to a receptor. The intrinsic biodegradation was investigated basing on available analytical parameters (eg concentrations of oxygen, nitrates, chlorides, and pH, TOC and temperature) that are considered as indicators of TCE and PCE transformation. Preliminary screening was done by giving certain points for these parameters, and interpreted in order to asses intrinsic biodegradation potentials. The results indicate inadequate evidence for intrinsic biodegradation (reductive dehalogenation) of TCE and PCE, thus a limited potential for NA as a remedial/risk reduction option in the studied case, unless some measures for enhancement of TCE and PCE intrinsic biodegradation are applied.