Ms. Dworatzek is a Senior Manager of SiREM. SiREM maintains state-of-the-art biotreatability, molecular testing and microbial culture development facilities, and currently manages maintenance and culturing of KB-1Â® and KB-1Â® Plus, dehalorespiring microbial cultures that have been widely used in field demonstrations to improve the rate and extent of bioremediation of chlorinated solvents in groundwater (e.g., tetrachloroethene (PCE) and trichloroethene (TCE) dechlorination to ethene). She provides technical oversight for field application of KB-1Â® and KB-1Â® Plus and also provides technical oversight for the development of new bioaugmentation cultures including 1,4-dioxane, 1,2,3-trichloroprpane, benzene, toluene and xylene.
1,4-Dioxane Bioremediation: Lessons Learned in the Laboratory
Results from enhanced in situ bioremediation (EISB) bench-scale and field trials for 1,4-dioxane treatment have often varied widely and consistent and effective application approaches for in situ treatment have yet to be developed. A key tool in developing field approach(es) is to use bench-scale treatability testing to identify conditions where EISB can be compatible with remediation success or alternatively when it may be unlikely to succeed. Bench-scale testing is a rigorous means to assess treatment amendments, improve analytical methodologies and provide standardized results for comparison between sites. Additionally, bench-scale tests can be used to simulate and test field approaches for EISB, so that effective bioaugmentation protocols can be developed. It is important that both successful and unsuccessful trials be presented so that technology performance can be better understood.
Specific challenges associated with evaluating EISB for 1,4-dioxane remediation include: analysis (low site concentrations and specialty analytical methods); inhibitory effects by co-contaminants; and the fact that bioaugmentation using metabolic 1,4-dioxane degrading organisms has yet to be successfully demonstrated in the field. Bench-scale batch microcosm and column tests were completed to: i) develop consistent protocols to evaluate aerobic EISB for 1,4-dioxane; ii) confirm the effectiveness of several potential bioaugmentation cultures; and iii) identify the conditions and treatments associated with successful outcomes, as well those that were ineffective or negatively affected outcomes. Results from bench-scale studies for EISB will be presented, including studies testing bioaugmentation with aerobic metabolic 1,4-dioxane degrading populations or biostimulation of co-metabolic populations.
Bioaugmentation Approaches for Anaerobic BTEX Remediation
Degradation of benzene, toluene, ethylbenzene and xylene (BTEX) typically occurs with faster degradation kinetics under aerobic conditions than in anaerobic systems. Nevertheless, where aerobic bioremediation approaches are not feasible, anaerobic approaches may be more suitable to address benzene contamination including deep anaerobic aquifer systems where oxygen application would be challenging and expensive.
Over the past 15 years, anaerobic enrichment cultures that are capable of complete degradation of benzene, toluene, o-xylene to carbon dioxide and methane (if methanogenic) have been developed at the University of Toronto, and have recently been thoroughly characterized using next-generation sequencing technologies. This characterization has helped identify the organisms responsible for benzene, toluene and xylene degradation (Luo et al, 2015).
SiREM and University of Toronto are collaborating on a project with objectives including scale up of an anaerobic benzene bioaugmentation culture from research to commercial volumes, demonstrating its effectiveness in laboratory treatability studies and ultimately testing the culture in field pilot trials. The culture has been used in three laboratory treatability studies to evaluate its performance to remediate a variety of hydrocarbon contaminated materials from field sites. The growth of the augmented benzene degrading microbes was also tracked by quantitative polymerase chain reactions to establish correspondence between the growth of these organisms and biodegradation activity. Information to be developed from this testing includes cell density requirements, degradation rates and the range of geochemical conditions required for optimal performance, which will be used to design future field pilot trials. Results from laboratory studies will be used to validate molecular biomarkers which will be used for monitoring in situ biodegradation activity, facilitating site management and bioaugmentation for accelerated remediation of benzene in anoxic groundwater.
This presentation will present results of laboratory treatability studies and discuss lessons learned as we move towards field application of these promising anaerobic BTEX bioaugmentation cultures.