## 2 Materials and Methods
### Operating Costs of the EC Process  
The operating costs of the EC process include various components, including material and energy consumption, chemical reagents, sludge disposal, labour, maintenance, and equipment costs [89; 90]. The most important cost factors are the electrode material and electrical energy consumption. Therefore, special emphasis is placed on their calculation as described in Equation (11):  
\[\text{Operating cost = a}\times C_{\text{energy}}+\text{b}\times C_{\text{electrode}} \tag{11}\]  
where \(C_{\text{energy}}\) is the energy consumption per cubic metre of treated wastewater (kWh m\({}^{-3}\)), \(C_{\text{electrode}}\) is the mass of the Al anode consumed per cubic metre of wastewater (kg m\({}^{-3}\)), and a and b approximate the cost of electrical energy (0.1035 EUR/kWh [91]) and Al material (2.25 EUR/kg Al sheet [92; 93]), respectively. The energy consumption is calculated using Equation (12):  
\[C_{\text{energy}}=\frac{U\times I\times t}{V} \tag{12}\]  
where \(U\) is the average voltage, \(I\) is the current, \(t\) is the reaction time, and \(V\) is the volume of treated wastewater. Electrode consumption is determined by measuring mass loss during the EC process. The results are shown in Table 9, which also contains theoretical values for electrode consumption calculated according to [PERSON]'s law for comparison. The energy costs depend on the experimental conditions. They generally increase with increasing  
Figure 9: Three-dimensional surfaces with measured values for each response. current (at a constant initial pH), while they decrease with an increasing initial pH of the solution (at a constant current). The highest energy consumption (61.79 kWh m\({}^{-3}\)) was determined for RUN 5, with the lowest for RUN 16 (1.28 kWh m\({}^{-3}\)). The total consumption of Al material is higher than the theoretical value, which is a consequence of electrochemical and chemical reactions that contribute significantly to the dissolution of the aluminium electrodes and generate Al\({}^{3+}\) coagulant during the EC process. Similar results have been observed in previous studies, referred to as super-faradaic efficiency [62; 66; 89; 94]. Previous research has shown that electrocoagulation can achieve comparable or better contaminant removal than conventional methods like chemical coagulation, often at lower operating costs, particularly when applied to sludge dewatering or greywater treatment [94; 95; 96] A comparative study bt [PERSON] at al. on the treatment of textile wastewater using the EC process and CC showed that the EC process was faster and more economical; it consumed less material and produced less sludge, and the pH of the medium was more stabilised than CC for similar COD and turbidity removal levels [97]. In the present study, the calculated operating costs for TY removal through the EC process are in this range, namely between 0.245 EUR m\({}^{-3}\) (RUN 16) and 7.486 EUR m\({}^{-3}\) (RUN 5). Reducing energy costs can be achieved by coupling the EC process with renewable energy sources such as solar panels and wind turbines. This integration reduces dependency on conventional energy grids and lowers operational costs and carbon emissions. Studies have demonstrated that the incorporation of renewable energy into EC systems can lead  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Experiment** & **U (V)** & \begin{tabular}{c} \(C_{\text{energy}}\) \\ **(kWh m\({}^{-3}\))** \\ \end{tabular}  & \begin{tabular}{c} \(C_{\text{electrode}}\) \\ **(kg m\({}^{-3}\))** \\ \end{tabular}  & \ \begin{tabular}{c} \(C_{\text{electrode},\text{Faraday}}\) \\ **(kg m\({}^{-3}\))** \\ \end{tabular}  & \begin{tabular}{c} **Operating Cost** \\ **(EUR m\({}^{-3}\))** \\ \end{tabular}  \\ \hline RUN 1 & 11.78 & 4.00 & 0.14 & 0.11 & 0.736 \\ \hline RUN 2 & 28.37 & 24.64 & 0.36 & 0.29 & 3.360 \\ \hline RUN 3 & 26.61 & 5.65 & 0.09 & 0.07 &  
to improved efficiency and reduced emissions, aligning sustainable treatment goals.