## 3 Results and Discussion
### Decolorization of Bezaktiv Red (BR)  
Both sediments SCD and SSM were also tested as microbial inoculum in order to form electro-active microbial bioanode under two different concentrations of BR in synthetic wastewaters named STWW1 (300 ppm) and STWW2 (1000 ppm). A decolorization rate of 55% was recorded in 5 days when STWW1 was treated by SCD as inoculum. During this period, no current density was recorded in front of a total absence of decolorization in the controlled reactor (Figure 4A(a)). Addition of glucose as a co-substrate allowed a significant acceleration in the decolorization of BR (99%) during day 7, with current production of 3.6 A/m\({}^{2}\) stable for 4 days (Figure 4A(a),B(a)). However, we obtained a lower decolorization rate (less than 55%) when used STWW2 and current production less than 0.1 A/m\({}^{2}\) was recorded (Figure 4A(d),B(d)). These findings indicated that increased dye concentration from 300 (STWW1) to 1000 ppm (STWW2) could decrease the performance of the BES. For experiment conductedwith SSM as source of halophilic microorganisms, STWW1, and glucose as co-substrate, the decolorization rate was 70%, with a decrease in efficiency of about 30% compared to results obtained with SCD. In  
Figure 2: (**A**) Evolution of the anodic current recorded on the 6 cm\({}^{2}\) carbon felt working electrode polarized at \(-\)0.1 V/SCE; and (**B**) decolorization rate achieved by bioremediation or bioelectromediation of STWW. (a) Reactor fed with 300 ppm TB, SCD as source of halophilic microorganisms, glucose as co-substrate; (b) Reactor fed with 300 ppm TB, SCD as source of halophilic microorganisms, acetate as co-substrate. these conditions current generation was very weak (less than 0.05A/m\({}^{2}\)), as shown in Figure 4A(b),B(b). Additionally, Figure 4A(c),B(c) summarizes the results of the experiment performed with STWW1 at a salinity of 15 g/L and using SCD as the inoculum source. A current generation of 1A/m\({}^{2}\) was obtained with an almost complete decolorization (98%). These findings confirmed that BR complete decolorization may require the presence of an electron donor co-substrate. Figure 4: (**A**) Evolution of the anodic current recorded on the 6 cm\({}^{2}\) carbon felt working electrode polarized at \(-\)0.1 V/SCE; and (**B**) decolorization rate achieved by bioremediation or bioelectroremediation of STWW. (a) Reactor fed with 300 ppm BR, SCD as source of halophilic microorganisms; (b) Reactor fed with 1000 ppm BR, SCD as source of halophilic microorganisms; (c) Reactor fed with 300 ppm BR, SSM as source of halophilic microorganisms. All experiments have been performed at a salinity of 165 g/L substrate. (d) Reactor fed with 300 ppm BR, SCD as source of halophilic microorganisms at a salinity of 15g/L. Figure 3: Cyclic voltammetries performed on porous carbon felt electrode immersed in reactor contained 300 ppm of TB. (**A**) SCD as inoculum and glucose as co-substrate. (**B**) SSM as inoculum and glucose as co-substrate. CV\({}_{\text{i}}\) (\(-\)), CV\({}_{\text{f}}\) (\(-\)). For TB and BR decolorization, we found that decolorization rate and current production were hindered as soon as the dye concentration was increased. In fact, the decolorization rate decreased from 84 to 69% and from 99 to 55% when concentrations of TB and BR were increased from 300 to 1000 ppm in synthetic wastewaters. Nevertheless, it is interesting to note that with STWW2, the amount of dye material lost during the bioelectrochemical treatment process was two times higher than that observed with STWW1 (99 vs. 55%). In addition, with STWW2, a dramatic inhibition of current generation was noticed. Based on the mechanisms of azo dye degradation involving competition between electron transfer to the electrode or to the N=N bound, more azo dye concentration theoretically leads to low anodic current production. Here, 1000 ppm concentration of BR generated less electron transfer to the anode and consequently decreased current density. Similarly, [PERSON] et al.