Remediation of Lubricant Contaminated Soils by Cavitation Microjet Shock Wave Soil Washing System with Ozonation

Adopting soil washing to clean up petroleum hydrocarbon contaminated soils with high sand content is considered as a fast and economical method. Cavitation microjet shock wave soil washing system (CMS) enhanced by the use of ozonation was developed for remediation of aged lubricant contaminated soil in this study. Contaminated soil with total petroleum hydrocarbon (TPH) ranging from 1890 mg/kg to 15735 mg/kg were applicable for CMS soil washing system. The impacts of factors including initial TPH concentration hydrocarbon (TPH) concentration, soil particle size, soil washing time, and ozone treatment time onto soil washing were investigated through a 21-month period of field operation. The contaminated soils with particle size between 0.074 mm and 0.25 mm, mainly very fine sand and find sand, demonstrated 31% to 98% of TPH removal by air-injected CMS and 19% to 92% of TPH removal by CMS with ozone addition. The optimal cavitation washing time was 20 minutes. The study indicated that optimal ozone concentration in the slurry was 1.08 mg/L which require air of 27 L/min for ozone produced. However, given the short contact time in the CMS system, ozone addition in the slurry did not improve TPH removal effectively. Considering the compatible TPH removal efficiency and energy cost of ozone addition in the soil washing system, use of air-injected CMS soil washing system may be considered as an alternative way.