Pilot System to Remediate Contaminated Groundwater in Arid Regions: Challenges and Achievements

Abstract

Proximity of shallow groundwater systems to sources of contamination usually puts them before severe environmental threats. Pollutants that leak from gas stations, hazardous landfills, and industrial facilities could eventually reach the underneath shallow unconfined aquifers. If contaminated, the groundwater system, possibly, communicates pollutants to either nearby seashores or lower freshwater aquifers. This situation poses considerable risk to both human health and environment. This study discusses the development of a pilot groundwater remediation approach that could be utilized to restore contaminated shallow brackish aquifers. The study addresses different challenges encountered during field investigations and remediation system design stage. Examples of challenges are the limited information about aquifer's geology & hydrogeology, lack of knowledge about groundwater hydrodynamics, and optimization of contaminant removal process. In addition, high groundwater salinity and water hardness & turbidity are also additional challenges that could affect the remediation system performance. To eliminate the problem of limited information, geophysical survey was conducted to define the depth to water table. The survey revealed that the water table is about 15 – 16 m below ground surface. Based on this, several wells were drilled to describe aquifer's geology, collect water samples, install the remediation system, and monitor system's performance. Down-hole geological investigations indicated that the aquifer is composed mainly of weathered limestone with thin layers of marl. Hydrogeological tests showed that the estimated hydraulic conductivity and average groundwater velocity under natural gradient are 9.3 × 10^-6 m/s and 3.7 × 10^-6 m/s, respectively. Analytical modeling was utilized to estimate pumping rates and select the most appropriate operational ones based on aquifer's hydrodynamic attributes. Extraction / injection rates that will be used to optimally manage the circulation remediation system are between 2.5 and 8.0 gpm. In this study, Advanced Oxidation Technology (AOT) is assumed optimum to remove the target pollutant, which is Methyl Tertiary Butyl Ether (MTBE). Design and fabrication of the groundwater remediation system is based on an integrated approach that relates Circulation-AOT-GAC technologies. A Bench scale AOT system showed successful MTBE removal at around 95% from contaminated water that initially has CMTBE of 500 μg/l.

AAPG Datapages/Search and Discovery Article #90194 © 2014 International Conference & Exhibition, Istanbul, Turkey, September 14-17, 2014