## 4 Results and Discussion
Generally, the observed thermal interference is negligible for well with drinking water purposes, and such temperature fluctuations are too limited to contribute to bacterial growth that could harm human health. The last result analyzed is the groundwater temperature distribution of the area of interest, studying the evolution of the thermal perturbation according to seasonal operations of the GSHP system across the Aquifer Group B, where most of the Armi pumping wells are screened. Figure 10 shows the groundwater temperature distribution at the end of the simulation, while the results at the end of the heating and cooling operation are shown in Supplementary Material Figures S1-S6. The groundwater temperature profiles shown in Figure 9 are verified by the analysis of the thermal plume (Figure 10), which reaches only wells n. 5 and n. 8. Well n. 5, located 270 m downgradient of the last BHE, appeared to be most affected due to its proximity to the GSHP system and its location along the groundwater flow direction. Well n. 8 instead is placed more laterally to the main flow direction and at a larger distance from the GSHP system (300 m), showing much smaller oscillations, particularly in Aquifer Group B. In both wells, no thermal perturbation is detected in Aquifer Group C, due to the low groundwater flow velocity of this aquifer (Table 3). No thermal perturbation was observed in any of the other Armi pumping wells. The representation of the thermal perturbation extension at the 3 rd year of simulation (Figure 10) showed how warm and cold plumes alternate in their movement toward S-SE. However, due to the shorter period of operation of the system in cooling mode, the warm plume is visible only immediately downstream of the plant and almost disappears beyond about 500 m. In contrast, two cold plumes are clearly visible, which follow each other spatially, taking on a gradually larger shape and with less pronounced temperature variations than the average as they move away from the GSHP system. At a distance of about 1 km from the system, no temperature increase is expected after 3 years of operation, but a periodic decrease that reaches a maximum value of \(-0.4\)\({}^{\circ}\)C and \(-0.1\)\({}^{\circ}\)C is observed in Aquifer Groups A and B, respectively. Thus, the presence of the GSHP system in the MIA \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Time [d]** & **Period** & **Layer 1 [\({}^{\circ}\)C]** & **Time [d]** & **Layer 5 [\({}^{\circ}\)C]** \\ \hline
328 &
\begin{tabular}{c} Autumn 1 st year \\ (stop operation) \\ \end{tabular} & \(-1.10\) & 271 & \(-1.16\) \\
504 & Heating 2 nd year & +0.60 & 447 & +0.96 \\
690 &
\begin{tabular}{c} Autumn 2 nd year \\ (stop operation) \\ \end{tabular} & \(-1.10\) & 630 & \(-1.17\) \\
864 & Heating 3 rd year & +0.59 & 807 & +0.94 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Groundwater temperature difference in well n. 5 between the maximum or minimum temperature value and the unperturbed temperature value for every year of simulation. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Time [d]** & **Period** & **Layer 1 [\({}^{\circ}\)C]** & **Time [d]** & **Layer 5 [\({}^{\circ}\)C]** \\ \hline
380 & Heating 2 nd year & \(-0.78\) & 311 & \(-0.15\) \\
557 &
\begin{tabular}{c} Spring 2 nd year \\ (stop operation) \\ \end{tabular} & +0.35 & 487 & +0.22 \\
744 & Heating 3 rd year & \(-0.78\) & 678 & \(-0.17\) \\
883 & Heating 3 rd year & +0.34 & 847 & +0.30 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Groundwater temperature difference in well n. 8 between the maximum or minimum temperature value and the unperturbed temperature value for every year of simulation.