As cities worldwide face growing freshwater shortages and rising energy demands, it is important to develop new technologies that can simultaneously recover resources and reduce the environmental footprint of wastewater treatment. Considerable amounts of low-frequency and low-energy components have been found in secondary effluents in municipal wastewater that can be harvested by triboelectric nanogenerators (TENGs). While municipal wastewater treatment plants process enormous volumes of water every day, much of the residual mechanical and electrostatic energy contained in treated effluents is lost during discharge. In addition, there is limited research on harvesting energy from municipal wastewater using TENG.
To address this, a team of researchers led by Dr. Beidou Xi from the School of Environmental and Municipal Engineering, Lanzhou Jiaotong University, China, and State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, China, has developed a novel droplet-based electricity generator (DEG) system that converts treated municipal wastewater into usable electrical energy. The study was made available online on May 10, 2025, and was published in Volume 161 of the Journal of Environmental Sciences on March 01, 2026.
“We fabricated several DEG devices using commercially available hydrophobic films, including perfluoroethylenepropylene copolymer (FEP), polytetrafluoroethylene, and polypropylene and investigated the effects of the droplets from various solutions on the output performance of DEGs,” says Dr. Xi.
The fabricated materials formed the contact layer of the generator system, where falling wastewater droplets generated electrical output through triboelectrification and electrostatic induction. Among the tested materials, FEP-based DEG devices demonstrated the strongest performance. A single DEG device achieved a maximum output voltage of 22.47 V, a current of 2.11 μA, and a peak power output of 15.18 μW when operating with secondary wastewater effluents. Remarkably, a single droplet impact was sufficient to illuminate 15 light emitting diodes (LEDs).
The researchers further scaled the technology into a DEG system consisting of multiple devices connected in parallel. After rectification, the system generated enhanced electrical output and efficiently charged capacitors. A six-device DEG system successfully powered an LED continuously without external electricity, demonstrating the technology’s practical energy harvesting capability. Importantly, the study showed that wastewater quality influenced electrical performance. Lower dissolved solids and lower ion concentrations improved electron transfer efficiency between droplets and the hydrophobic film surface, thereby increasing electrical output. However, the researchers found that once secondary effluents met China’s Grade I-A wastewater discharge standard, differences among wastewater treatment methods had little impact on generator performance.
Beyond energy harvesting, the DEG system was also used directly in wastewater treatment applications. For this, the harvested electricity was connected to stainless steel electrodes submerged in municipal wastewater. This configuration enabled electrochemical pollutant removal without relying on an external power source. The DEG-powered treatment system achieved ammonium nitrogen removal efficiencies of approximately 12% and chemical oxygen demand (COD) removal efficiencies exceeding 40%. The researchers observed that tiny bubbles generated during electrolysis promoted electro-flotation, allowing pollutants to attach to bubbles and separate more effectively from the water. Interestingly, alternating current generated by the DEG system appeared to reduce electrode passivation, improving treatment efficiency. Continuous polarity reversal helped prevent mineral accumulation on electrode surfaces, thereby maintaining electrochemical activity during wastewater treatment.
The researchers also explored the system’s capability for dye degradation using methyl orange (MO), a common model pollutant in wastewater treatment research. In experiments conducted without an external power supply, a six-device DEG system powered electrocatalytic degradation of MO solution over 54 hours. During the degradation process, the characteristic ultraviolet-visible absorption peaks associated with MO steadily diminished, indicating destruction of the dye’s aromatic ring and azo bond structures. The system achieved a COD removal efficiency of 91.31% and a decolorization rate of 96.08%, demonstrating strong electrocatalytic performance driven entirely by harvested wastewater energy.
Overall, the findings highlight the broader potential of TENG technology for sustainable environmental engineering applications. By recovering energy directly from treated wastewater streams, wastewater treatment facilities may be able to offset part of their operational energy demands while simultaneously supporting pollutant removal processes. Thus, DEG system may contribute to carbon reduction efforts in municipal wastewater treatment plants by transforming wastewater from an energy-consuming burden into a partially self-powered resource recovery platform.
“Our study demonstrates the application of TENG technology in energy harvesting from secondary effluents and introduces a novel approach to wastewater resource recovery, carbon reduction, and sustainable management,” concludes Dr. Xi.
Reference
DOI: https://doi.org/10.1016/j.jes.2025.05.020
About the Lanzhou Jiaotong University, China
Lanzhou Jiaotong University is located in Lanzhou, a city that lies along the Yellow River. Founded in 1958, the University adheres to the orientation of scientific research towards the frontiers of global science and technology, the main battlefield of the economy, the major needs of the country, and the health of the people. It continuously strengthens basic research and technological development, adheres to the cooperation among industry, academia, and research, and takes the initiative to serve the development of the country, the rail transit industry, and the local economy.
Website: https://en.lzjtu.edu.cn/
About Dr. Beidou Xi from Lanzhou Jiaotong University, China
Dr. Beidou Xi is affiliated to School of Environmental and Municipal Engineering, Lanzhou Jiaotong University, China, and State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, China. He obtained his Bachelor of Engineering in June 1992 and his Master of Engineering in May 1999, both in the School of Environmental Engineering, from Lanzhou Jiaotong University. He earned his Ph.D. in Environmental Engineering from Tsinghua University in July 2002, after which he engaged in postdoctoral research in Canada.
Funding information
This work was supported by Gansu Province University Youth Doctoral Support Project (No. 2023QB-044), the Department of Education of Gansu Province: Major cultivation project of scientific research innovation platform in university (No. 2024CXPT-14), and the Science and Technology Program of Gansu Province (No. 24CXNA029).
Journal of Environmental Sciences
Experimental study
Not applicable
A droplet-based electricity generators (DEGs) system for harvesting secondary effluent energy
1-Mar-2026
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.