Application of Taguchi experimental design for investigating surfactant enhanced bioremediation of oil contaminated soil

This study was aimed to investigate the influence of five variables (including soil type, surfactant type, surfactant concentration, initial oil concentration, and salinity) on the remediation of oil contaminated soil by using surfactant through the Taguchi experimental design method. The interactions of these five variables were also examined. Each variable was examined with two levels: soil type (loam and sand), surfactant type (rhamnolipid and linear alkylbenzene sulfonates), surfactant concentration (0.5 and 2 CMC), initial oil concentration (low and high), and salinity (0 and 0.1 mol/L NaCl). The experimental results showed that there was a distinct decline of soil total petroleum hydrocarbons (TPH) when using surfactant during the bioremediation period of 45 days. The maximum TPH degradation was observed to be 94%. The analysis of variance (ANOVA) indicated that the five variables showed little effect on the soil TPH biodegradation except for soil type on day 20 and 30 (P ≤ 0.05). The interaction between variable combinations was also not significant (P ≤ 0.05). The soil type was observed to be the most important factor affecting the bioremediation efficiency, but the impacts of other four variables and their interactions were enhanced in the later stage of bioremediation.