Biocomplementation of SVE to achieve clean-up goals in soils contaminated with toluene and xylene

Abstract

Soil vapor extraction (SVE) and bioremedia-tion (BR) are two of the most common soil remediation technologies. Their application is widespread; however, both present limitations, namely related to the efficien-cies of SVE on organic soils and to the remediation times of some BR processes. This work aimed to study the combination of these two technologies in order to verify the achievement of the legal clean-up goals in soil remediation projects involving seven different simulated soils separately contaminated with toluene and xylene. The remediations consisted of the application of SVE followed by biostimulation. The results show that the combination of these two technologies is effective and manages to achieve the clean-up goals imposed by the Spanish Legislation. Under the experimental conditions used in this work, SVE is sufficient for the remediation of soils, contaminated separately with toluene and xylene, with organic matter contents (OMC) below 4 %. In soils with higher OMC, the use of BR, as a complementary technology, and when the concentration of contaminant in the gas phase of the soil reaches values near 1 mg/L, allows the achievement of the clean-up goals. The OMC was a key parameter because it hindered SVE due to adsorption phenomena but en-hanced the BR process because it acted as a microor-ganism and nutrient source.

Flowrate and water presence effect on venting/SVE process efficiency

“…This can be explained by the good accessibility of the air to the pores in the case of dry soil. These results confirmed those obtained by Amin et al [4], but differs from the results of Albergaria et al [1,2] and Soares et al [20]. This difference can be due to the size particles of used soils.…”

“…They found that SWC had different impacts on the contaminant removal efficiency which related to the organic content in the soil. Soares et al [20] found that SVE is extremely efficient for the remediation of sandy soils contaminated with toluene and is independent on the SWC. They suggested as Albergaria et al [1] that this result is related to the low organic matter content and high porosity of these types of soils, which are not able to significantly adsorb the contaminants.…”

“…On the other hand, Albergaria et al [1] and Soares et al [20] stated that the use of lower air flowrates will guarantee that the process occurs in equilibrium conditions and that slow diffusion effects are avoided, enhancing the remediation.…”