4 / 2023-09-30 00:22:46

In Situ and Ex Situ Bioremediation for an Aquifer Contaminated with Hydrocarbons in La Guacamaya Industrial Zone – Carabobo State, Venezuela. Case: El Prado Fuel Service Station

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The work is focused on testing a new bioremediation method in an aquifer contaminated with hydrocarbons, located in La Guacamaya Industrial Zone, Carabobo state, Venezuela. The contamination was caused by fuel leaks from underground tanks sited in the area of El Prado fuel service station (EPFSS). It is placed in a zone that shares boundaries between residential and industrial uses. Ex situ remediation proposal will be developed to laboratory scale. For soil treatment, two coupled bioreactors are proposed consisting of a Soil-Slurry Sequencing Batch Reactor (SS-SBR) and Upflow Anaerobic Filter separated in three phases (UAF-3SS). These coupled bioreactors will treat soils containing hydrocarbons sorbed in concentrations upper to international regulations allowing the occurrence of mass transfer processes to the air (volatilization) present in soil empty spaces in the vadose zone and groundwater (sorption-desorption) in the saturated zone. For groundwater treatment, bioreactors involve SBR-UAF-3SS. Each bioreactor was experimentally tested, demonstrating satisfactory performance in Chemical Oxygen Demand (COD) removal from industrial wastewater containing inhibitory substances (46-98%). In-situ remediation proposal will be tested in pilot scale in the subsoil within EPFSS in order to compare the kinetic coefficients of indigenous microbial performance with ex situ bioremediation treatment, by implementing air sparging system in the saturated zone and soil vapor extraction system in the unsaturated zone. Both systems will be installed in two soil cross sections  in the area of EPFSS comprising fifteen monitoring wells where the highest Benzene, Toluene, Ethylbenzene and Xylenes (mixed) and Total Petroleum Hydrocarbons concentrations were determined in strata comprising the interface between the saturated and unsaturated zones at depths between 3 and 8 m below ground surface. It is recommended the implementation of ex situ proposal due to two main aspects, there is a heavy metal such as lead throughout the area of the station that can cause inhibition of autochthonous biomass to biodegrade hydrocarbons, causing significant restrictions for in situ bioremediation. Likewise, there are multilayer soils containing clay materials both in the vadose zone and in the depths of the saturated zone that significantly restrict the injection of air into the clay-sand interface that separates the unsaturated zone from the saturated zone, where the highest contamination by hydrocarbons occurs, as well as the difficulty of transporting the volatile organic compounds vapor-phase flux in the multiple strata of the vadose zone.