Application of surfactants and biosurfactants in the bioremediation of multi-contaminated soils: microcosms and bench scale bioreactor trials

In the present study, in order to rehabilitate areas multi-contaminated by oil and metals, bioremediation, coupled with bioreactor technologies, was applied. Firstly, a microcosm trial was performed using two synthetic surfactants, TRITON X-100 and TWEEN 80, and a biological one, JBR210, at two different concentrations (0.1 and 1.0 mg. g-1 soil) for 42 days to select the two best surfactants of different natures in order to scale up a solid-phase bench bioreactor under controlled operating conditions. The results obtained with the use of Tween 80 and biosurfactant JBR210 at a concentration of 0.1 mg. g-1 soil, with humidity corrected to 70% of WHC, were a 25.5% and 30.00% removal of THP (Total Petroleum Hydrocarbon), respectively, while control with humidity adjustment alone achieved 20.5% removal. The evaluation of the behavior of microbial activity through next generation sequencing (NGS) of the soil was performed before and after the different treatments in the bioreactor, where the control showed an increase of Actinobacteria population. The treatments with surfactants showed an increase of Alphaproteobacteria and Sphingobacteria in this same period, and a decrease in the abundance of Actinobacteria. The diversity measured by the Shannon index (H') showed a significant decline for the Tween 80 treatment, with no sign of recovery, unlike JBR210 biosurfactant treatment. Therefore, the application of surfactants of different natures has different effects, where both promoted the reduction of diversity, whereas the biosurfactant JBR210 showed a tendency to increase after 42 days, indicating a less intense effect, ie. it is better for the environment.