## 2 Materials and Methods  
### Sampling Site Description  
OMW and OMP by-products originate from three-phase olive oil extraction mills. Samples were collected in 2018 from two evaporation ponds located in Agareb (Figure 1a) and Cherarda (Figure 1d), belonging to the governorates of Sfax and Kairouan in Tunisia, respectively (Figure 1, Table 1). This study involves a total of fourteen samples (Table 1) divided into: thirteen OMW samples comprising five samples collected from the evaporation pond of Cherarda, seven samples from the evaporation pond of Agareb, and one sample collected from soil mixed with dried OMW and deposited in a huge pile near to the evaporation pond of Agareb (MA). It was further used for OMW metagenomic analysis of the indigenous microbiota (Table 1, Figure 1b). The 14 th olive mill pomace (OMP) sample was collected from an olive oil industry and used for further tests. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Samples Codes** & **Description** & **Metagenomique** \\ \hline A1 & Sample collected from contaminated area around OMW evaporation pond in Agareb & - \\ \hline A2 & Sample collected from the vicinity of evaporation pond of Agareb with lower level of contamination & - \\ \hline A3 & Sample collected outside of the evaporation pond of Agareb with no sign of contamination (control) & - \\ \hline A4 & Sample collected from the center of dried evaporation pond of Agareb & - \\ \hline A5 & OMW sample collected from the center of dried evaporation pond of Agareb but not fully dried still wet & - \\ \hline MA & Sample collected from soil with dried OMW and deposited in huge piles in Agareb & + \\ \hline C1 & Sample collected from contaminated area around OMW evaporation pond in Cherarda & - \\ \hline C2 & Sample collected from the vicinity of evaporation pond of Cherarda with lower level of contamination & - \\ \hline C3 & Sample collected outside of the evaporation pond of Cherarda with no sign of contamination (control) & - \\ \hline C4 & Sample collected from the center of a completely dried out evaporation pond of Cherarda & - \\ \hline C5 & Sample collected from the center of a completely dried out evaporation pond of Cherarda & - \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Description of the sampling sites of the evaporation ponds of Agareb and Cherarda. Figure 1: (**a,d**) Evaporation ponds situated in Agareb and Cherarda, respectively. (**b**) Pile of soil mixed with dried OMW in Agareb. (**e**) Newly established evaporation pond in Cherarda. (**c,f**) _Atriplex_ plants growing in the vicinity of the evaporation ponds of Agareb and Cherarda, respectively. Briefly, A3 and C3 were the control OMW samples of soil collected from the outside of the evaporation ponds. These samples have no sign of contamination. The remaining samples were taken from contrasting spots situated within (A4, A5, C4 and C5), in the vicinity (A2 and C2) or around (A1 and C1) the 2 evaporation ponds, or even after digging 20 cm (C6) and 50 cm (C7) deep from the center of a completely dried evaporation pond as clearly shown in Table 1 and Figure 2. One additional sample of OMP was collected from an olive oil industry in Sfax (Table 1). Lastly, we have perceived two plants belonging to the _Atriplex_ genus (Figure 1c,f) being able to grow in the vicinity of the two evaporation ponds. Heavy Metal Analysis of OMW Samples Using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES)  
Eleven OMW samples (A1, A2, A3, A4, A5, C1, C2, C3, C5, C6 and C7) were analyzed using the ICP-OES method to determine their composition in heavy metals. Samples