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M.M. Lorah

Publications and source records attributed to M.M. Lorah.

7 recordsLinked to original sources
USGS2005

Development and composition of a mixed culture for bioremediation of chlorinated ethenes and ethanes

Microbial organisms capable of dechlorinating 1,1,2,2 tetrachloroethane (TeCA) and its chlorinated ethane and ethylene daughter products were enriched in surface sediments collected from the West Branch Canal Creek wetland area, leading to the formation of two mixed cultures using slightly different enrichment methods. Both WBC-1 and WBC-2 were capable of rapid and complete reductive dechlorination of TeCA and its daughter products (1,1,2-trichloroethane, 1,2-dichloroethane, trichloroethylene, 1,2-dichloroethylene, and vinyl chloride) to ethylene, and addition of either culture to wetland sediment and to engineered peat/compost mixtures resulted in significant enhancement of dechlorination. However, the WBC-2 culture supported better sustained activity and was more readily scaled up for application in bioaugmentation treatments, whereas dechlorination activity was gradually lost in WBC-1. The microbial composition of WBC-1 and WBC-2 were determined by cloning and sequencing 500 base pairs of the 16S rDNA gene and the methyl co-reductase. Methanogens identified in the consortia were members of the Order Methanomicrobiales, which includes acetoclastic methanogens. This is an abstract of a paper presented at the Proceedings of the 8th International In Situ and On-Site Bioremediation Symposium (Baltimore, MD 6/6-9/2005).

Conference Paper↗
USGS2005

Physiological characterization of a broad spectrum reductively dechlorinating consortium

A wetland sediment-derived microbial consortium (WBC-2) was developed by the US Geological Survey and propagated in vitro to large quantities by SiREM Laboratory for potential use in bioaugmentation applications. On the basis of bench-scale tests, the consortium could completely dechlorinate 1,1,2,2-tetrachloroethylene, tetrachloroethylene, trichloroethylene, 1,1,2-trichloroethane, cis- and trans-1,2-dichoroethylene, 1,1-dichloroethylene, 1,2-dichloroethane, and vinyl chloride in culture medium. Batch microcosms were carried out under anaerobic conditions in culture medium with neutral pH and with pH adjusted from acidic (pH 4, 5, and 6) to alkaline (pH 8 and 9). To evaluate oxygen sensitivity of WBC-2, an aliquot was removed from an anaerobic culture vessel and poured into smaller containers on the bench top where a series of oxygen exposures were applied to the culture by bubbling ambient air through the culture at a rate of ??? 100 mL/min. Chlorinated methanes tended to inhibit activity of a wide range of microorganisms. Although toxicity effects from CT addition were observed with WBC-2 in liquid culture at 3 mg/L concentration, WBC-2 in the columns could maintain degradation of CT and chloroform (CF) and of the chlorinated ethanes and ethylenes at CT and CF concentrations of 10 and 20 mg/L, respectively. This is an abstract of a paper presented at the Proceedings of the 8th International In Situ and On-Site Bioremediation Symposium (Baltimore, MD 6/6-9/2005).

Conference Paper↗
USGS2005

In situ treatability testing of reductive dechlorination in wetland sediments

In situ treatability testing was conducted in the discharge wetlands along West Branch Canal Creek at Aberdeen Proving Ground, MD. The potential for stimulating reductive dechlorination of 1,1,2,2-tetrachloroethane, tetrachloroethylene, trichloroethylene, and carbon tetrachloride in areas of preferential discharge or seeps was evaluated. Geological Survey that degrades chlorinated ethanes and ethylenes was tested using MICRO-Trac??? devices. At seep 3-4W, results of the C and BA MICRO-Trac??? treatments showed essentially no biodegradation of chlorinated solvents occurring under natural and bioaugmented conditions. Results of geochemical samples at this site indicated predominantly iron- and sulfate-reducing conditions consistent with the rapid discharge rates previously measured. The biostimulated treatment showed stimulation of methanogenic conditions and partial degradation of the parent chlorinated VOC to intermediate chlorinated compounds. The bioaugmented and bistimulated treatment showed the highest production of methane, the highest removal of parent compounds and intermediate daughter products, and the highest production of the non-chlorinated end product ethylene. This is an abstract of a paper presented at the proceedings of the 8th International In Situ and On-Site Bioremediation Symposium (Baltimore, MD 6/6-9/2005).

Conference Paper↗
USGS2004

Degradation of 1,1,2,2-tetrachloroethane and accumulation of vinyl chloride in wetland sediment microcosms and in situ porewater: Biogeochemical controls and associations with microbial communities

The biodegradation pathways of 1,1,2,2-tetrachloroethane (TeCA) and 1,1,2-trichloroethane (112TCA) and the associated microbial communities in anaerobic wetland sediments were evaluated using concurrent geochemical and genetic analyses over time in laboratory microcosm experiments. Experimental results were compared to in situ porewater data in the wetland to better understand the factors controlling daughter product distributions in a chlorinated solvent plume discharging to a freshwater tidal wetland at Aberdeen Proving Ground, Maryland. Microcosms constructed with wetland sediment from two sites showed little difference in the initial degradation steps of TeCA, which included simultaneous hydrogenolysis to 112TCA and dichloroelimination to 1,2-dichloroethene (12DCE). The microcosms from the two sites showed a substantial difference, however, in the relative dominance of subsequent dichloroelimination of 112TCA. A greater dominance of 112TCA dichloroelimination in microcosms constructed with sediment that was initially iron-reducing and subsequently simultaneously iron-reducing and methanogenic caused approximately twice as much vinyl chloride (VC) production as microcosms constructed with sediment that was methanogenic only throughout the incubation. The microcosms with higher VC production also showed substantially more rapid VC degradation. Field measurements of redox-sensitive constituents, TeCA, and its anaerobic degradation products along flowpaths in the wetland porewater also showed greater production and degradation of VC with concurrent methanogenesis and iron reduction. Molecular fingerprinting indicated that bacterial species [represented by a peak at a fragment size of 198 base pairs (bp) by MnlI digest] are associated with VC production from 112TCA dichloroelimination, whereas methanogens (190 and 307 bp) from the Methanococcales or Methanobacteriales family are associated with VC production from 12DCE hydrogenolysis. Acetate-utilizing methanogens (acetotrophs) appear to be involved in the biodegradation of VC. The relative abundance of Methanosarcinaceae, the only methanogen group with acetotrophic members, doubled in microcosms in which degradation of VC was observed. In addition, molecular analyses using primers specific for known dehalorespiring bacteria in the Dehalococcoides and Desulfuromonas groups showed the presence of these bacteria in microcosm slurry from the site that showed the highest VC production and degradation. Determination of biogeochemical controls and microbial consortia involved in TeCA degradation is leading to a better understanding of the heterogeneity in biodegradation rates and daughter product distribution in the wetland, improving capabilities for developing remediation and monitoring plans.

Journal of Contaminant Hydrology↗
USGS2001

Biodegradation of trichloroethylene and its anaerobic daughter products in freshwater wetland sediments

Laboratory microcosms were prepared under methanogenic, sulfate-reducing, and aerobic conditions using sediment and groundwater from a freshwater wetland that is a discharge area for a trichloroethylene (TCE) to evaluate potential biodegradation rates of TCE and its anaerobic daughter products (cis-1,2-dichloroethylene, trans-1,2-dichloroethylene, and vinyl chloride (VC)). Anaerobic degradation of TCE was about an order of magnitude faster under methanogenic conditions than under sulfate-reducing conditions. Both 12DCE and VC were found under sulfate-reducing conditions in the microcosms containing the wetland sediment, but their production, especially for VC, was substantially slower than under methanogenic conditions. Methane concentrations remained approximately constant (when losses in the formalin-amended controls are considered) in the microcosms amended with TCE and increased in the microcosms amended with the 12DCE isomers and VC during the first 18-25 days of incubation. The most rapid decrease in concentrations of TCE, cis-12DCE, trans-12DCE, and VC was found after aerobic methane-oxidizing conditions were definitely established.

Bioremediation Journal↗
USGS2000

Biotic and abiotic degradation of 1,1,2,2-tetrachloroethane in wetland sediments: Geochemical and microbial community analyses

Additional microcosm experiments with the wetland sediment and groundwater at the Aberdeen Proving Ground, MD, site was presented to assist in elucidating the conditions under which these potentially competing biotic and abiotic degradation reactions for 1,1,2,2-tetrachloroethane (PCA) occur in the environment and to evaluate potential seasonal changes in degradation reactions. PCA concentration decreased to below detection within 21 days in the March 1999 experiment, while PCA was still present at day 35 in the July 1999 experiment. Compared to March 1999 experiment, peak concentrations of all daughter products except trichloroethylene (TCE) were delayed in the July 1999 experiment. The relative intensity of the peaks was directly related to the biomass present for each fragment length (bp, base pair). The relative intensities were lower in sediment collected in August 1999 than in March 1999, especially in the bp size range of ??? 160??-240??. These microbial community analyses, along with the geochemical analyses of the microcosms, provide evidence that abiotic production of TCE from PCA degradation is more significant under conditions of low bacterial biomass in the wetland sediments.

Conference Paper↗