Abstract

Tetrachloroethylene (PCE) is a chlorinated solvent used in the dry-cleaning industry. PCE is a toxic chemical and is hazardous to humans and the environment. PCE is a dense non-aqueous phase liquid (DNAPL) and once it leaks into the soil, moves downwards and contaminates the soil and the groundwater. Common remediation techniques like soil washing do not easily remediate the soil contaminated with PCE, unless proper additives like surfactants are added to the washing solution. Surfactants reduce the surface and interfacial tension, and increase the solubility of PCE. Surfactants at concentration above the critical micelle concentration (CMC) form micelles and make PCE partition into the micelles, consequently PCE disperses in the aqueous phase and becomes more bioavailable. This study evaluates the effectiveness of rhamnolipid and two surfactant-based products (ASAP (TM) and Degreaser (TM) ) on the bioremediation of PCE. These two agents are non-toxic chemicals. Following the USEPA methods, and gas chromatography analysis, diverse 21 day experiments were conducted. ASAP(TM) and Degreaser(TM) at a ratio to soil of 1:1 showed removal efficiencies of 45% and 52%, respectively. Addition of rhamnolipid with a ratio to soil of 1:1 to these products at the same ratios enhanced the remediation up to 55% and 58%. Conducting microbial analysis, a direct correlation was observed between microbial density and PCE removal, which suggests that degradation, had occurred. The removal trend was: Biological agent + rhamnolipid > biological agent> rhamnolipid > Control.