Nitrate addition to groundwater impacted by ethanol-blended fuel accelerates ethanol removal and mitigates the associated metabolic flux dilution and inhibition of BTEX biodegradation

A comparison of two controlled ethanol-blended fuel releases under monitored natural attenuation (MNA) versus nitrate biostimulation (NB) illustrates the potential benefits of augmenting the electron acceptor pool with nitrate to accelerate ethanol removal and thus mitigate its inhibitory effects on BTEX biodegradation. Groundwater concentrations of ethanol and BTEX were measured 2 m downgradient of the source zones. In both field experiments, initial source-zone BTEX concentrations represented less than 5% of the dissolved total organic carbon (TOC) associated with the release, and measurable BTEX degradation occurred only after the ethanol fraction in the multicomponent substrate mixture decreased sharply. However, ethanol removal was faster in the nitrate amended plot (1.4 years) than under natural attenuation conditions (3.0 years), which led to faster BTEX degradation. This reflects, in part, that an abundant substrate (ethanol) can dilute the metabolic flux of target pollutants (BTEX) whose biodegradation rate eventually increases with its relative abundance after ethanol is preferentially consumed. The fate and transport of ethanol and benzene were accurately simulated in both releases using RT3D with our general substrate interaction module (GSIM) that considers metabolic flux dilution. Since source zone benzene concentrations are relatively low compared to those of ethanol (or its degradation byproduct, acetate), our simulations imply that the initial focus of cleanup efforts (after free-product recovery) should be to stimulate the degradation of ethanol (e.g., by nitrate addition) to decrease its fraction in the mixture and speed up BTEX biodegradation.Petróleo Brasileiro S/A — PETROBRASCoordination of Improvement of Higher Education Personnel (CAPES)National Council for Scientific and Technological Development (CNPq

Avaliação da eficiência de impermeabilização de bacias de contenção em áreas petrolíferas

Este livro é resultado de um estudo pioneiro realizado pela UFSC e pela UFBA em parceria com a Petrobras/Cenpes e com a Transpetro e compreende uma densa investigação tanto de campo como de laboratório sobre os fenômenos que afetam a infiltração de diferentes tipos de derivados de petróleo em solos de terminais de armazenamento de combustíveis em diversas regiões do Brasil. O estudo demonstrou que a permeabilidade do solo à água pode diferir em várias ordens de grandeza quando comparado à dos hidrocarbonetos de petróleo, sugerindo uma nova abordagem para a avaliação da permeabilidade de bacias de contenção com vistas à proteção do meio ambiente

Enhanced degradation of monoaromatic hydrocarbons in sandy aquifer materials by microbial inoculation using biologically active carbon reactors.

A technique using biologically active carbon reactors for seeding the subsurface with adapted microbes was proposed and tested to enhance the degradation of monoaromatic hydrocarbons in aquifer materials. Biodegradation experiments with indigenous and adapted microorganisms from a non-contaminated aquifer solids and sorption studies under abiotic conditions were developed to determine the reasons for the lag phase prior to the onset of biodegradation. It was concluded that enhanced rates of degradation could be obtained when the number of adapted microbes seeded to the soil matrix was increased above 10\sp5 cells/g of soil. Under these conditions, immediate degradation of benzene, toluene and xylene (added as single carbon sources) was observed at concentrations ranging from 25 $\mu$g/l to 9 mg/l. The use of BAC adsorbers was demonstrated to be an efficient technique for growth, acclimation, and enrichment of adapted microbes for subsequent inoculation into sandy aquifer materials. Empty bed BAC reactor contact times of less than one minute were sufficient for microorganisms to degrade BTX compounds and to produce a continuous mass of adapted microbes in effluent streams for inoculation. A lag period preceding onset of measurable biodegradation of the monoaromatic hydrocarbons was observed in batch and column experiments. This lag period varied according to the initial number of adapted microbes present, suggesting that this phase was primarily dependent on the presence of an initial biomass of microorganisms significant enough to accomplish measurable degradation of the target compound. The Monod-with-growth model adequately described the aerobic degradation of BTX compounds for concentrations ranging from 25 $\mu$g/l to 3.5 mg/l. The bioremediation model used to simulate column experiments under oxygen limiting conditions described the data well. The model agreed with the laboratory estimations that the number of xylene degraders originally present in Kalkaska, MI solids was approximately one order of magnitude smaller than the number of benzene degraders.Ph.D.Environmental EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/103060/1/9303723.pdfDescription of 9303723.pdf : Restricted to UM users only