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Subsurface microorganisms can use many different electron acceptors to yield energy for metabolism and growth through dissimilatory pathways. The reductive processes can be impacted by toxic species introduced by human activities. The research mainly focused on two conditions: the co-occurrence of nitrate and antibiotics in soil and groundwater; the co-occurrence of sulfate and biocides in hydraulically fractured shale. The first condition causes the activities of nitrate reducing bacteria to be severely impacted by excessive antibiotics discharged into soil/groundwater by human. Prior research mostly evaluated the impact of antibiotics on nitrate biotransformation in batch microcosms, resulting in a knowledge gap between spatial heterogeneity and concentration gradients of antibiotics present in soil/groundwater and bacteria response. To address this gap, a microfluidic gradient chamber was used to create concentration gradients of the antibiotic polymyxin b, and the growth, migration and nitrate reduction activity of Shewanella oneidensis was monitored and analyzed; complementary batch experiments were also performed to support the microfluidic experiments. Results show that S. oneidensis migrated to bactericidal regions for nutrients without developing antibiotic resistance, with motility being the key factor in a spatially heterogenous environment. The migration was inhibited by acutely lethal concentration of antibiotics. The second condition has been extensively studied in batch microcosms and inferred from limited field observations, primarily motivated from the concerns that sulfate reducing bacteria promote bioclogging and biosouring in oil and gas reservoirs. However, few studies have quantified biomass growth and activity in shale fractures due to the complexity of studying processes at this scale, resulting in a knowledge gap regarding the ability of microbes to colonize shale fracture surfaces and clog these oil and gas flow conduits. To address this gap, a shale-based microfluidic flow cell reactor was inoculated with a field culture dominated by dissimilatory sulfate-reducing bacteria (DSRB), followed by incubation and biocide injection. Microscopic images and effluent samples were analyzed to assess biofilm growth and biocide inhibition, with a numerical model developed to quantify sulfate reduction rates. The results indicate that biomass grows as biofilms on shale surfaces with little mass transfer limitations, and that accurate quantification of sulfate reduction rates depends on quantifying this biomass. The results also indicate that while biocides eliminated microbial activity in shale fractures, they do little to remove biomass and open up shale fractures. The findings of the study are an important contribution to our understanding of the impacts of toxic species on microbial accepting reductive processes in subsurface environments and will help decisions on the use and control of toxic species including antibiotics and biocides for human health and environmental protection
Selected Proceedings of the 1st IWA World Water Congress, held in Paris, France, 3-7 July 2000. The World Water Congress held in Paris in July 2000 was the first under the banner of the International Water Association, formed by the merger of the International Association on Water Quality and the International Water Services Association. The success of the merger was reflected in the unprecedented degree of interest and participation in the Congress, with nearly two-and-a-half thousand delegates attending for 450 oral presentations, 750 poster presentations and 4 workshops and seminars. From the large number of oral presentations, 41 have been selected for this issue. The first five highlight the work of the IWA Task Group that is devising the River Water Quality Model No 1; three papers set out key aspects of the model as it reaches its final form and two case studies show how the model can be implemented. Other papers selected cover the topics of: stormwater management; water resources management and protection including diffuse pollution; river basin management and organization; environmental restoration; and environmental engineering education. With authors who rank among the world's leading experts in these fields, tackling some of the most prominent contemporary problems, these proceedings are an essential compilation of the latest advances relating to the management of impacts on the water environment.
Provides a detailed background of the technologies available for the bioremediation of contaminated soil & ground water. Prepared for scientists, consultants, regulatory personnel, & others who are associated in some way with the restoration of soil & ground water at hazardous waste sites. Also provides insights to emerging technologies which are at the research level of formation, ranging from theoretical concepts, through bench scale inquiries, to limited field-scale investigations. 95 tables & figures.
In situ bioremediationâ€"the use of microorganisms for on-site removal of contaminantsâ€"is potentially cheaper, faster, and safer than conventional cleanup methods. But in situ bioremediation is also clouded in uncertainty, controversy, and mistrust. This volume from the National Research Council provides direction for decisionmakers and offers detailed and readable explanations of: the processes involved in in situ bioremediation, circumstances in which it is best used, and methods of measurement, field testing, and modeling to evaluate the results of bioremediation projects. Bioremediation experts representing academic research, field practice, regulation, and industry provide accessible information and case examples; they explore how in situ bioremediation works, how it has developed since its first commercial use in 1972, and what research and education efforts are recommended for the future. The volume includes a series of perspective papers. The book will be immediately useful to policymakers, regulators, bioremediation practitioners and purchasers, environmental groups, concerned citizens, faculty, and students.