## Results and Discussion
### Biotreatment of Support Materials
After studying hydrocarbon degradation in the CorkSorb(tm) 01025 and Barrier Sentec(tm) support materials, TPH concentrations in the materials were not reduced during the experiments (Figure 4). However, GC/MS analysis showed that some hydrocarbon fractions were removed (Figure 5B,C), suggesting the biotransformation of some hydrocarbons, such as alkanes C\({}_{10}\)-C\({}_{20}\), to other linear and/or branched alkanes, as it has been reported by other authors [42]. In addition, the n-C18 alkane/phytane (n-C18/Ph) index revealed microbial degradation of c18 alkenes (Table 4), suggesting the hydrocarbons biotransformation in support materials during the carrier biote treatment phase, especially in the Pad Sentec microcosms where these values decrease to 0.43 after one month of treatment. The linear alkanes are easier to uptake by microorganisms than branched alkanes, thus, the decrease in the value of the n-C18/Ph index is usually related to the first stage of the hydrocarbon microbial degradation [43; 44]. Figure 4: Time course of TPH concentrations (mg/Kg) absorbed to the Pad Sentec(tm), Corksorb(tm) 01025 and Barrier Sentec(tm) carrier during the carrier biote treatment phase at day 7 (end of treatment phase) and after 1, 4 and 8 months. (*) Significant differences between day 7 th, 4 months and 8 months after treatment. (†) Significant differences between 1 month and the other sampling times. Figure 5: Time course of hydrocarbon fraction concentrations (ppm) detected by GC/MS, absorbed to the carrier during the first month of the biotereatment phase (**A**) Pad SentecTM carrier, (**B**) Barrier SentecTM carrier and (**C**) CorksorbTM 01025 carrier. Evidence of hydrocarbon removal in industrial wastewater and the subsequent process of biotreatment in support materials highlight the extremely high efficiency of the bioreactors, especially when Pad Sentec(tm) was used. Consequently, the combination of absorption and biodegradation makes the technology used an effective system for removing hydrocarbons from polluted wastewater. Figure 6 shows, from SEM images, the adhesion of indigenous microbiota to different carriers. When the support materials were examined microscopically, the development of considerable biofilm biomass and the stability of microbiota adhering to the carrier surface were clearly evident, suggesting that this biomass can play an important role in hydrocarbon removal. \begin{table}
\begin{tabular}{c c c c c} \hline
**n-C18/Ph** & **7 Days** & **1 Month** & **4 Months** & **8 Months** \\ \hline Pad Sentec(tm) & \(1.3\pm 0.3\) & \(0.43\pm 0.1\) & ND & ND \\ Corksorb(tm) 01025 & \(1.1\pm 0.2\) & \(0.86\pm 0.01\) & ND & ND \\ Barrier Sentec(tm) & \(1.4\pm 0.2\) & \(1.1\pm 0.2\) & \(0.7\pm 0.3\) & ND \\ \hline \end{tabular}
\end{table} 
Table 4: Time course table for n-C18 alkane/phytane (n-C18/Ph) index associated with the three carriers during the biodegradation phase at day 7 (end of treatment phase) and after 1, 4 and 8 months. Figure 6: _Cont._  
Petroleum and its derivatives are composed of a complex mixture of hydrocarbons that vary depending on physical-chemical and biological environmental factors. There are a large number of hydrocarbon-degrading microorganisms described in the literature as a result of the wide range of scenarios studied [45; 46]. As mentioned, the biodegradability of hydrocarbon fractions varies according to their complexity and the microbial population is modified and influenced by these changes and environmental conditions. In this sense, it has been seen that some microorganisms found in the biofilms of reactors to treat waters highly contaminated with hydrocarbons could be good candidates for study in biodegradation, due to the fact of being present and surviving in these environments [47]. In this study, in order to have knowledge about the composition of the carrier's biofilm, an isolation of bacterial strains was performed at the beginning of biotreatment phase.