A droplet-based electricity generators (DEGs) system for harvesting secondary effluent energy

The secondary effluent in municipal wastewater contains considerable amounts of low-frequency and low-energy components that can be effectively harvested using the triboelectric nanogenerator technology. A systematic investigation was conducted into the output performance of diverse droplet-based electricity generators (DEGs). The results showed that the DEGs system could harvest energy from secondary effluents. This energy was then used in the treatment of municipal wastewater to remove ammonium nitrogen (NH₄⁺-N) and chemical oxygen demand (COD), and to degrade the methyl orange (MO) solution. The results demonstrated that a single DEG device can achieve a maximum voltage of 22.47 V, high current of 2.11 µA, and peak power of 15.18 µW. After rectifying the DEGs output, the overall output performance of the DEGs system increased as the number of DEGs in the system increased. Moreover, the study revealed that the DEGs system achieved a removal efficiency of 12 % for NH₄⁺-N and 40 % for COD. Furthermore, after the degradation of MO solution by the DEGs system without external power supply for a period of 42 h, the characteristic peaks of the UV-Visible spectroscopy (271 and 464 nm) of the MO solution exhibited a notable reduction. Additionally, the removal efficiency of 91.31 % for COD and decolorization rate of 96.08 % for MO solution. Thus, this study demonstrates the application of TENG technology in energy harvesting from secondary effluents and presents a novel approach for carbon reduction in municipal wastewater plants.