## 3 Results and Discussion
### Removal Rate of Phosphorus and Nitrogen Loads per Time Unit
\begin{tabular}{c} **Synthetic** \\ **Wastewater** \\ **Inflow** \\ \end{tabular}  } & \multicolumn{6}{c}{**RECDC**} & \multicolumn{6}{c}{**REBDC**} \\ \cline{3-14}  & & & \multicolumn{3}{c}{**Electric Current Density [A/m\({}^{2}\)]**} & \multicolumn{3}{c}{**Electric Current Density [A/m\({}^{2}\)]**} \\ \cline{3-14}  & & & **0.63** & **1.25** & **2.50** & **5.00** & **10.00** & **0.63** & **1.25** & **2.50** & **5.00** & **10.00** \\ \hline \multirow{3}{*}{COD} & \multirow{3}{*}{260 *} & 4 h & 28.6 & 27.8 & 27.2 & 25.8 & 22.0 & 30.3 & 34.6 & 30.0 & 41.8 & 56.3 \\  & & 8 h & 25.7 & 25.3 & 24.4 & 23.0 & 21.0 & 27.6 & 33.9 & 27.5 & 27.3 & 55.6 \\  & & 45 ** & 12 h & 22.4 & 21.9 & 21.0 & 20.1 & 19.3 & 26.1 & 26.3 & 27.3 & 24.8 & 32.7 \\  & & 24 h & 18.2 & 18.7 & 17.1 & 16.0 & 14.5 & 19.7 & 21.7 & 24.5 & 24.3 & 28.2 \\ \hline \multirow{3}{*}{Total nitrogen} & \multirow{3}{*}{470} & 4 h & 426.0 & 421.0 & 415.9 & 401.5 & 375.6 & 411.1 & 399.2 & 373.8 & 358.9 & 327.8 \\  & & 8 h & 418.9 & 407.1 & 396.5 & 376.6 & 341.0 & 398.3 & 378.0 & 350.0 & 329.3 & 288.6 \\  & & 12 h & 393.4 & 380.1 & 375.3 & 350.3 & 298.5 & 380.7 & 357.4 & 316.0 & 286.6 & 226.6 \\  & & 24 h & 366.4 & 357.1 & 349.7 & 311.2 & 217.7 & 360.3 & 341.3 & 288.3 & 243.8 & 147.7 \\ \hline \multirow{3}{*}{Nitrate [mg N/L]} & \multirow{3}{*}{453} & 4 h & 408.4 & 408.2 & 403.5 & 389.0 & 330.8 & 409.9 & 397.1 & 371.3 & 353.2 & 304.7 \\  & & 8 h & 403.9 & 395.4 & 387.2 & 365.0 & 307.6 & 396.9 & 376.6 & 348.3 & 323.5 & 265.3 \\  & & 12 h & 379.4 & 370.5 & 366.5 & 339.8 & 256.6 & 380.0 & 356.2 & 314.6 & 282.5 & 215.1 \\  & & 24 h & 355.4 & 353.5 & 343.3 & 304.3 & 189.4 & 359.2 & 340.6 & 287.2 & 240.6 & 142.2 \\ \hline \multirow{3}{*}{Nitrite [mg N/L]} & \multirow{3}{*}{0.015} & 4 h & 0.4 & 0.2 & 0.1 & 0.1 & 30.8 & 1.0 & 1.6 & 2.2 & 5.2 & 21.5 \\  & & 8 h & 1.2 & 0.3 & 0.1 & 0.1 & 23.0 & 0.8 & 0.8 & 1.1 & 4.7 & 20.9 \\  & & 12 h & 1.9 & 0.4 & 0.1 & 0.1 & 35.5 & 0.3 & 0.6 & 0.9 & 3.0 & 10.4 \\  & & 24 h & 6.1 & 1.1 & 0.1 & 0.1 & 27.9 & 0.2 & 0.2 & 0.6 & 2.2 & 5.2 \\ \hline \multirow{3}{*}{Ammonia nitrogen [mg N/L]} & \multirow{3}{*}{18.0} & 4 h & 17.2 & 12.7 & 12.3 & 12.4 & 14.0 & 0.2 & 0.5 & 0.3 & 0.6 & 1.6 \\  & & 8 h & 13.8 & 11.4 & 9.2 & 11.5 & 10.4 & 0.6 & 0.6 & 0.5 & 1.1 & 2.3 \\  & & 12 h & 12.0 & 9.3 & 8.8 & 10.5 & 6.5 & 0.4 & 0.6 & 0 previous investigation [23] and with findings reported by [PERSON] [24], and this agreement could be due to the fact that the electrochemical coagulation of phosphorus observed in bioelectrochemical reactors was accompanied by the removal of this element induced by biofilm biomass growth. In the bioelectrochemical reactor (REBDC), the daily amount of the removed nitrogen load (L\({}^{\text{A}}\)N\({}_{\text{re}}\)) was higher than that in the electrochemical reactor (RECDC) (Figure 3b), because nitrates were removed in the REBDC upon hydrogenotrophic and heterotrophic denitrification as well as electrochemical reduction, while in the RECDC reactor, nitrogen was removed primarily during electrochemical reduction of nitrates [11; 18; 25; 26]. At HRT = 4 h, the nitrogen removal performance was the highest and reached 1.27 and 3.09 g N/m\({}^{2}\cdot\)d at current densities of 0.63 and 10.0 A/m\({}^{2}\), respectively. At HRT = 24 h, the nitrogen removal performance was the lowest, reaching 0.38 and 1.11 g P/m\({}^{2}\cdot\)d, respectively. These results confirmed findings from the experiment with the RECDC, where the HRT extension contributed to a decrease in the daily amount of the removed nitrogen load. At higher electric current densities, the differences between both reactors in daily nitrogen load removed were aggravated. At longer hydraulic retention times, the differences between the reactors successively diminished.