## 3 Results and Discussion  
### Decolorization of Tbanttin Blue (TB)  
Decolorization of TB and current generation in STWW were tested at two initial dye concentrations 300 (STWW1) and 1000 ppm (STWW2) using a concentration of 2000 ppm as a co-substrate and two different sources of halophilic inoculums--SCD and SSM. As shown in (Figure 1A(a)), halophilic inoculum from SCD was able to generate in short time a maximum current density of 12 A/m\({}^{2}\) under salinity of 165 g/L with a decolorization rate of 84% achieved in 12 days for STWW1 (Figure 1B(a)). However, when increasing the concentration of TB from 300 to 1000 ppm (STWW2), the decolorization decreased from 84 to 55%, suggesting that the decolorization rate in STWW1 was more important than in STWW2 (Figure 1B(b)). Consequently, increasing the initial concentration of the dye resulted in a weak decolorization, which may be caused by a greater accumulation of the dye. These results indicate that decolorization performance and electrochemical yield are affected by high dye concentration. [PERSON] et al. [19] also observed a decrease in decolorization rate starting from 800 ppm of azo dye. They attributed this decrease toa bacterial inhibition growth caused by dye toxicity. Recently, [PERSON] et al. [24] used a halotolerant microflora to treat a complex textile effluent composed of five azo dyes. This microflora was able to tolerate a salt concentration ranging from 0 to 80g/L. In comparison with the above-mentioned study, it was found that despite the use of twice the salt concentration, the rate of decolorization was approximately similar, suggesting a high tolerance to the extreme condition.The authors confirmed the advantage of using the extreme halophilic consortia over the moderately halophilic microflora. The effect of the initial dye concentration was also investigated. Indeed, at concentrations maintained between 200-600 mg/L, the decolorization rates exceeded 70% (very close to the rates obtained with STWW 1 in our study). On the other hand, increasing this concentration resulted in a significant decrease in the discoloration rates caused mainly by bacterial toxicity. For experiments using SSM as source of halophilic inoculum, 70% decolorization rate was obtained in 12 days and low maximal current density of 0.1 A/m\({}^{2}\)was recorded when the reactor was fed with STWW1 (Figure 1A(c),B(c)). These findings demonstrated that SSD inoculum may harbor more tenacious and electroactive community than SSM inoculum towards STWW1 experiments. Considering the visual aspects of the two sediments, the SCD appeared more heterogeneous than the SSM with a mixed local hydration, and three different colors (black, brown, and beige). On the other hand, the SSM appears more homogeneous with only one color, and without hydrated zones. Additionally, the sediment chemical analysis showed that the SCD naturally contained more concentrated mineral elements (Table 1). Indeed, the concentrations of calcium, magnesium, potassium, and iron expressed in mg/kg of dried materials in SCD were higher than those of SSM. The difference in azo dye decolorization and anodic electrical production performances of the two sediments could probably be related to their specific difference imminerals composition. In fact, particular mineral composition of SCD leads to more favorable environment for the development of azo dye-degrading microorganisms. When glucose was used as co-substrate with a concentration of 500 ppm under salinity of 165g/L, SCD as inoculum, and 300 ppm of TB, the decolorization rate was 78% after 16 days and current density varied from 3 to 3.7 A/m\({}^{2}\). Experiments performed with acetate under the same conditions showed a very weak rate of decolorization (21%) and current production of 0.7 A/m\({}^{2}\) (Figure 2A,B). These results show that the decolorization rate when acetate is used as a co-substrate was about four times lower compared to its analogue (glucose); acetate may acts as an inhibitor of TB decolorization.