Study on Temperature Control Strategy and Energy Saving Effect of Sewage Heat Pump Based on TRNSYS Simulation

To address the issue of decreased biochemical reaction efficiency in wastewater treatment plants during winter due to excessively low water temperatures, this study proposes a sewage heat pump heat extraction and recycling system. The system recovers waste heat from the effluent of the secondary sedimentation tank to heat the influent of the primary sedimentation tank, thereby maintaining a stable temperature in the reaction tank. Using TRNSYS simulation software, two system models were constructed: one with constant-temperature control and one without. Their yearround operational performances were compared and analyzed. Simulation results demonstrate that both systems can elevate the sewage temperature in the reaction tank above $15^{\circ} \mathrm{C}$, meeting the requirements of the $\mathrm{A}^{2} \mathrm{O}$ process. The constanttemperature control system, by dynamically regulating the flow rate, reduces the energy consumption per unit of sewage treated by $50.4 \%$ and increases the annual sewage treatment capacity by $111.3 \%$, performing significantly better than the non-controlled system. The research validates the feasibility and energy-saving potential of the sewage heat pump heat extraction and recycling system, providing a theoretical basis for optimizing thermal energy utilization in wastewater treatment plant located in cold regions.