DEVELOPMENT OF AN ENGINEERED TREATMENT SYSTEM FOR THE REMEDIATION OF BRINE-CONTAMINATED SOILS
Date
2023-05
Authors
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Publisher
University of Delaware
Abstract
Produced water is a highly concentrated brine produced during the extraction
of oil and natural gas from geological formations. When spilled, it threatens nearby
vegetation and groundwater. The current way of dealing with produced water spills is
to excavate the impacted soil and send it to a specialized landfill. This study is
concerned with the lab-scale development of an engineered system to remediate salt
contamination from produced water spills.
Evaporative flux is the process where water passes upward through soil as it
evaporates at the surface, carrying solutes with it. Crystallization modifiers are
compounds that alter the precipitation of minerals, delaying the onset of crystallization
and/or modifying crystal habit, until salts approach or emerge at the surface.
Evaporative flux and crystallization modifiers provide the basis for the design
evaluated herein, where a constant supply of treatment solution consisting of water
and crystallization modifier is supplied at the base of contaminated soil and transports
through soil via evaporative flux.
A remediation system was devised in the lab based upon these ideas, where a
Mariotte bottle which exerts a constant hydraulic head on the system is connected to a
beaker containing a 3cm depth of contaminated soil. To create a brine-contaminated
soil, a 3.8M salt solution saturates a loamy sand followed by oven drying. This
contaminated soil was passively flushed with treatment solution containing various
concentrations of a crystallization modifier for five days, before being dried and
analyzed by depth. The electrical conductivity of each depth layer of the soil column
was collected to understand where the salt was removed and where it remained. Lab-scale experiments show up to 96% removal using a 3mM potassium ferrocyanide
solution. Experiments testing the ideal dosage and application of crystallization
modifier, the potential use of fabrics to harvest salts, and the impact of using real
produced waters were evaluated to improve this system before it is repeated at pilot
scale.