## 3 Results and Discussion  
The results on heavy metals are shown in Table 1, as well as the standard limits for discharging treated LL in water bodies [22; 23], reuse for irrigation [23] and discharging in municipal sewers [24]. pH for the raw and treated LL were 8.3 and 8.93, respectively. A very good removal efficiency (greater than 51%) can be observed for all the eight detected heavy metals (As, Ba, Cd, Cr, Fe, Pb, Ni and Zn). The metals Cu, Mn and Se were not detected either in the raw LL or in the treated LL. Therefore, there was not an increase in the concentration of these three metals in the treated LL, because it is known that EC can promote the electro-dissolution of the electrode used in the process. The results show that the treated LL has a quality in agreement with several heavy metals standard limits for discharging in water bodies or irrigation. However, it is not suitable for discharging in public sewers due to higher values for Cr, Fe and Ni. The research has evaluated the possibility of using treated LL in agriculture, since it is an effluent with a high concentration of ammonia [1; 2; 25]. The results of our research pointed out that the irrigation practice with treated LL, obtained through EC with SfE, would bring positive environmental advantages since it would reduce the use of water from surface waters and groundwater for the irrigation of green spaces, such as football fields, squares and gardens. Some studies have analyzed the removal of heavy metals by EC, evaluating parameters such as pH, conductivity and electric current. Although the present study does not aim to analyze these parameters, but the behavior of electrodes produced from metallic residues, some correlations were observed between the cited parameters and the results obtained. A study that used an EC with Fe/Al electrodes for the removal of ions Cr\({}^{3+}\), Cu\({}^{2+}\), Ni\({}^{2+}\) and Zn\({}^{2+}\) showed a removal efficiency above 90% for all metals, in the pH range of 7.89 to 9.56 [26]. Therefore, for the pH range observed in this study (8.3 to 8.93), the removal efficiency of Cr and Zn was lower than the obtained by [26], but it was similar for Ni. The influence of EC on the microbial load of total coliforms was analyzed and is present in Figure 3 and the growth of total coliforms in Petri dishes is shown in Figure 4.  
The initial coliform load of the LL was 10.76 \(\times\) 10\({}^{4}\) CFU/mL, and, after EC treatment using SfE, that load was completely eliminated in the time of 4 h (!1 CFU/mL in the treated LL). Similar results were found in other studies [27; 28]. Research [28] analyzed the influence of _E. coli_ cell density in different treatment technologies applying electro-Fenton, electro-peroxi-coagulation and EC. Regarding the EC technology, these authors observed that the higher the microbial cell density (microbial load), the longer it takes to completely inactivate the microorganisms and, the higher is the current applied for a good inactivation. In the present work, the applied current was 0.1A and it was enough for the almost total coliform inactivation in LL in 4 h treatment with SfE. Therefore, it seems this current and 4 h of contact time is enough to destroy the cytoplasm of the microorganisms present in LL, which makes this sensor very competitive in relation to other disinfection technologies, such as chlorination, with the additional advantage of not leaving by-products in the