SITE: Petrol station
Geostream Africa supplied, installed and operated a multiphase extraction system for a multinational consultancy company, within their environmental service agreement with a major oil&gas company.
The groundwater contamination from volatile organic compounds and LNAPL (Light Non-Aqueous Phase Liquid) impacted the shallow aquifer and the smear zone downgradient of the underground storage tanks.
The type of contamination and the hydrogeological setting with moderate aquifer permeability represented appropriate conditions for the implementation of Multiphase extraction technology for LNAPL and groundwater recovery and treatment.
The remediation plant was connected to 34 extraction wells to intercept the plume of contamination. It included a vacuum pump, a knock out tank, an oil/water separator, and air stripper and activated carbon filters for the vapour and the treated water, to comply with discharge limits. Small quantities of LNAPL were recovered at the early stages of the operations. The total mass of contaminants removed by the treatment plan was approximately 6000 kg.
The system run in automatic mode for less than 2 years (500 days) until when the concentrations of the contaminants of concern dropped below Site Specific Target Levels and in some cases below laboratory detection limits.