Potential benefit of surfactants in a hydrocarbon contaminated soil washing process: Fluorescence spectroscopy based assessment

Soil washing is an ex situ soil remediation treatment process. The purpose of soil washing is to clean the major gravel and sand fractions, concentrating contamination into the fine silt and clay fractions. The addition of surfactants can improve the efficiency of this method. Here we report the use of UV fluorescence spectroscopy to assess the hydrocarbon cleaning process as a rapid and cost effective alternative to gas chromatography. Three wash solutions were tested on a total petroleum hydrocarbon contaminated soil: water, Sea Power 101 (SP101) at 1% (v/v) and Tween80 at 0.5% (w/v). The most effective to wash the gravel and sand was SP101 (54 and 65% improvement over the water only wash, respectively) which moved contamination to the silt fraction (94% of contaminants). Tween80 appeared not to enhance TPH removal efficiency from the gravel and sand fractions but did concentrate TPH in the effluent (95% more than water wash). In addition to TPH removal from gravel and sand, SP101 also showed potential benefit in the soil washing sedimentation process, enhancing sludge/water volume separation by 10% over the water only wash. In summary, fluorescence spectroscopy proved an effective technique to compare TPH removal efficiencies as part of soil washing laboratory based treatability testing.