At many sites, sulfate reducing bacteria have been demonstrated to be a dominant factor in the natural anaerobic biodegradation of petroleum hydrocarbons dissolved in groundwater. There are many benefits of providing sulfate as a terminal electron acceptor to the subsurface environment. As anaerobic conditions naturally prevail under petroleum- impacted sites, there is less acclimation time necessary for microbial populations, thus sulfate enhancement stimulates processes that are already occurring. The high solubility and stability of sulfate solutions relative to traditional electron acceptors allows for improved subsurface delivery and coverage, and higher concentrations of sulfate (as compared to oxygen) can be added to groundwater due to its high solubility. The lower energy reactions of sulfate reduction require less nutrient supplementation and produces less biomass and secondary precipitates, which can plug an aquifer. There is less non- target demand on sulfate when compared to oxygen, which provides better utilization efficiencies. Case studies that demonstrate the benefits of enhancing the sulfate concentrations in groundwater to stimulate the biodegradation of petroleum contaminants under field conditions are presented.
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