Ultrasound-assisted advanced oxidation removal of contaminants of emerging concern: A review on present status and an outlook to future possibilities
José Fernandes, Paulo J. Ramísio, Stijn Van Hulle, H. Puga
Abstract
The presence of contaminants of emerging concern (CECs) in wastewater poses significant environmental and public health risks. In recent years, increasing efforts have focused on mitigating these risks by reducing CEC concentrations in wastewater treatment plants (WWTPs). Ultrasonic processes, and consequent effects of generated acoustic cavitation, have emerged as a promising solution due to their reliance on physical mechanisms that are considered green. However, it is well established that ultrasound alone achieves limited removal efficiencies for CECs, making its standalone application inadequate for large-scale implementation. This review examines the current progress in ultrasound-based wastewater treatment, emphasizing its integration with oxidants and adsorbents to enhance degradation efficiency. Although research in this field has grown, critical gaps remain, particularly in optimizing operational parameters, understanding the influence of complex water matrices, and bridging the gap between laboratory-scale studies and real-world applications. Most studies indicate that ultrasound has significant potential, especially in reducing chemical usage and treatment time, but remains largely confined to small-scale experiments. Further research is essential to develop pilot-scale studies, refine process conditions, and assess long-term feasibility for full-scale wastewater treatment. Despite these challenges, ultrasound-assisted processes represent a promising green technology that could contribute to more sustainable and efficient WWTPs by reducing reliance on high-footprint treatment methods.