# Performance of the Dual-Chamber Fungal Fuel Cell in Treating Tannery Wastewater
## 2 Materials and Methods
### Statistical Analysis  
The statistical analysis was performed using a linear regression model. The obtained results indicated that the R\({}^{2}\) of all parameters lies between 97.0 (COD removal in a non-electrolytic cell) and 99.9% (COD removal in an electrolytic cell), which indicates the success of the model to describe the removal performances, and means that the electrolytic cell is preferred for the degradation of a wide range of organic carbon contaminants in excess of the nitrogen and heavy metal removal as described in the previous discussion. Also, the performance of the model using significance values indicated that, in fact, all models successfully described the removal percentages with a \(p\)-value \(<\) 0.001. Furthermore, the significance results indicated that the time parameter is the most important factor affecting the removal efficiency in the presence of produced energy potential. Finally, the statistical model describes the expected removal percentages depending on time after removing X\({}_{2}\) (volt) shown in Table 5.  
\begin{table}
\begin{tabular}{l c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Regression Model**} \\  & \multicolumn{2}{c}{**Electrolytic Cell**} & \multicolumn{4}{c}{**Non-Electrolytic Cell**} \\  & \multicolumn{2}{c}{**Model Summary**} & \multicolumn{4}{c}{**Model Summary**} \\ \hline Method & \multicolumn{4}{c}{Enter} \\ Variables & \multicolumn{4}{c}{Time, and Volt} \\ Dependent & COD & Cr & TN & COD & Cr & TN \\ R & 0.999 & 0.993 & 0.995 & 0.988 & 0.998 & 0.998 \\ R\({}^{2}\) & 0.998 & 0.985 & 0.990 & 0.976 & 0.996 & 0.995 \\ Adjusted R\({}^{2}\) & 0.997 & 0.982 & 0.987 & 0.970 & 0.994 & 0.994 \\ Std. error of the estimate & 0.426 & 2.028 & 0.579 & 1.502 & 0.978 & 0.428 \\  & \multicolumn{4}{c}{ANOVA} \\ Significance & \(<\)0.001 & \(<\)0.001 & \(<\)0.001 & \(<\)0.001 & \(<\)0.001 & \(<\)0.001 \\ F & 1910 & 269 & 384 & 165 & 895 & 857 \\  & \multicolumn{4}{c}{Coefficient} \\ Time “Beta” & 0.099 & 0.315 & 0.116 & 0.166 & 0.271 & 0.152 \\ Time “t” & 13.2 & 8.785 & 11.317 & 5.332 & 13.409 & 17.111 \\ Time “Significance” & \(<\)0.001 & \(<\)0.001 & \(<\)0.001 & \(<\)0.001 & \(<\)0.001 & \(<\)0.001 \\ Volt “Beta” & \(-\)13.6 & 3.922 & 2.905 & \(-\)1.537 & 1.682 & 7.830 \\ Volt “r” & \(-\)9.361 & 0.475 & 1.470 & \(-\)0.264 & 0.444 & 4.712 \\ Volt “Significance” & \(<\)0.001 & 0.647 & 0.180 & 0.799 & 0.669 & 0.002 \\  & \multicolumn{4}{c}{Estimated removal Equation} \\ COD removal Eqn. & \% \(<\) 62.8 \(<\) 0.0993\({}_{1}\)\(-\) 13.596X\({}_{2}\) & \% \(=\) 46.922 & \% \(=\) 1.066X\({}_{1}\)\(-\) 1.537X\({}_{2}\) \\ Cr removal Eqn. & \% \(=\) 17.1 \(+\) 0.315X\({}_{1}\)\(+\) 3.2926X\({}_{2}\) & \% \(=\) 16.795 & \(+\) 0.271X\({}_{1}\)\(+\) 1.6826X\({}_{2}\) \\ TN removal Eqn. & \% \(=\) 74.857 & \(+\) 0.116X\({}_{1}\)\(+\) 2.905X\({}_{2}\) & \% \(=\) 67.736 & \(+\) 0.152X\({}_{1}\)\(+\) 7.830X\({}_{2}\) \\ \hline \hline \end{tabular}
\end{table}
Table 5: Regression model for COD, Cr, and TN for electrolytic and non-electrolytic fungal fuel cells.  
Figure 7: Variation of electrolytic and non-electrolytic FFC treatment performance.  
Supplementary: Figures S1-S3, describe the variation between electrolytic and non-electrolytic fungal fuel cells for COD, Cr, and TN removals. The obtained results indicate that the electrolytic cell is more close to linearity with minimum suggestive errors.