Hybrid Solution to Remediate Groundwater Contaminated by Petroleum-Hydrocarbons
Authors: Alahmari M. M. , Humam A. A. , Zefzafy I. M. , Sanchez-Huerta C. , Hong P. -Y , Zhang S. 
Published: March 2024

Abstract
Groundwater contamination by petroleum-hydrocarbons is a serious environmental problem. Crude oil is a complex mixture of hydrocarbons with serious environmental and health risks. Thus, remediation of groundwater from petroleum hydrocarbon contamination is an emerging priority. Current approaches to remediate hydrocarbon contamination include physical and chemical methods. However, most of these approaches have a limited application for in-situ groundwater remediation. This study aims to develop a sustainable hybrid solution for efficient restoration of groundwater polluted by crude oil, providing a source of high-quality groundwater stream. Hybrid solution compromises in-situ addition of biosurfactant followed by a flow through electrochemical reactor installed in the groundwater well.
The proposed hybrid solution comprises a two-stage process evaluated through lab-scale experiments treating crude oil that was mixed with synthetic water, mimicking groundwater contamination by petroleum-hydrocarbons.
For biosurfactant optimization, glass flasks containing synthetic groundwater and crude oil were supplemented with biosurfactant BS, and C added at the three surfactants: oil (S:O) ratios 1:5, 1:10, and 1:50. Two temperature (25-35 °C) conditions were analyzed to simulate groundwater environment. The change in the crude oil layer thickness total petroleum hydrocarbon concentration (TPH) was continuously monitored for 60 days. Electron Oxidation was carried out where Boron-dopped diamond (BDD) anode and titanium cathode plates, were fitted into a 1 L reactor containing groundwater, crude oil and biosurfactant. Kinetic analysis at three constant currents (20, 30 and 40 mA/cm2) was performed. Samples were collected at regular intervals along 120 min to determine changes in TPH, COD and pH.
The performance of biosurfactant BS and C in reducing the thickness of crude oil layer was influenced by different parameters including temperature, and S:O ratio. The increase in temperature further allowed higher effectiveness. For surfactant C, higher concentration of biosurfactant per unit of crude oil increased oil dispersion, the optimal S:O ratio of 1:5 allowed a maximal reduction of the crude oil layer of 27%. Biosurfactant BS, in contrast, presented optimal performance at ratio of 1:10 with a 30% reduction of the crude oil layer. Boron-doped diamond anode demonstrated high potential to oxidize TPH. The increased applied current from 20 to 40 mA enhanced the oxidation of COD and hydrocarbons (TPH ∼15-34%) along 120 min reaction. Addition of biosurfactant C resulted favorable COD and TPH oxidation. The proposed solution included adding biosurfactants followed by oxidation in a flow-through electrochemical reactor. Boron-doped diamond anode provided high electrochemical oxidation of COD and TPH, with an improved removal achieved when increasing the applied current from 20 to 40 mA and supplementing with biosurfactant C. The study provides a novel insight into enhanced bioremediation mechanism which is an integrated approach of EO and biosurfactant addition.