Wastewater Treatment Plants (WWTPs) encompass a range of processes from preliminary to advanced stages. Conventional treatments are increasingly inadequate for handling emergent pollutants, particularly organic compounds with carcinogenic potential that pose risks to aquifers. Recent advancements prioritize integrating Advanced Oxidation Processes (AOPs) and adsorbents with conventional methods to effectively retain organic pollutants and enhance mineralization. There is a growing preference for non-chemical or minimally chemical approaches. Innovations such as combining ozone and other biological processes with photo-sono-assisted methods, alongside integrating AOPs with adsorbents, are promising. These approaches leverage catalyst-assisted reactions to optimize oxidation efficiency. This review aims to provide a holistic perspective on WWTP processes, spanning wastewater intake to the production of potable water, highlighting key technologies, operational challenges, and future trends. The focus is on advancing sustainable practices and enhancing treatment efficacy to safeguard water quality and address evolving environmental concerns effectively.

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.

This study investigates the characterization of acoustic cavitation in a water-filled, opaque chamber induced by ultrasonic waves at 20 kHz. It examines the effect of different acoustic radiator geometries on cavitation generation across varying electrical power levels. A cost-effective piezoelectric sensor, precisely positioned, quantifies cavitation under assorted power settings. Two acoustic radiator shape configurations, one with holes and another solid, were examined. The piezoelectric sensor demonstrated efficacy, corroborating with existing literature, in measuring acoustic cavitation. This was achieved through the Fast Fourier Transform (FFT) analysis of voltage data, specifically targeting sub-harmonic patterns, thereby providing a robust method for cavitation detection. Results demonstrate that perforated geometries enhance cavitation intensity at lower power levels, while solid shapes predominantly affect cavitation axially, exhibiting decreased activity at minimal power. The findings recommend using two different shape geometries on the acoustic radiator for efficient cavitation detection, highlighting intense cavitation on radial walls and cavitation generation on the bottom. Due to the stochastic nature of cavitation, averaging data is critical. The spatial limitation of the sensor necessitates prioritizing specific areas over complete coverage, with multiple sensors recommended for comprehensive cavitation pattern analysis.