Recent trends in the applications of sonochemical reactors as an advanced oxidation process for the remediation of microbial hazards associated with water and wastewater: A critical review

Water is one of the major sources that spread human diseases through contamination with bacteria and other pathogenic microorganisms. This review focuses on microbial hazards as they are often present in water and wastewater and cause various human diseases. Among the currently used disinfection methods, sonochemical reactors (SCRs) that produce free radicals combined with advanced oxidation processes (AOPs) have received significant attention from the scientific community. Also, this review discussed various types of cavitation re-actors, such as acoustic cavitation reactors (ACRs) utilizing ultrasonic energy (UE), which had been widely employed, involving AOPs for treating contaminated waters. Besides ACRs, hydrodynamic cavitation reactors (HCRs) also effectively destroy and deactivate microorganisms to varying degrees. Cavitation is the fundamental phenomenon responsible for initiating many sonochemical reactions in liquids. Bacterial degradation occurs mainly due to the thinning of microbial membranes, local warming, and the generation of free radicals due to cavitation. Over the years, although extensive investigations have focused on the antimicrobial effects of UE (ultrasonic energy), the primary mechanism underlying the cavitation effects in the disinfection process, inac-tivation of microbes, and chemical reactions involved are still poorly understood. Therefore, studies under different conditions often lead to inconsistent results. This review investigates and compares other mechanisms and performances from greener and environmentally friendly sonochemical techniques to the remediation of microbial hazards associated with water and wastewater. Finally, the energy aspects, challenges, and recom-mendations for future perspectives have been provided.

Automated summary

Water is a major source of human diseases due to contamination with bacteria and other pathogenic microorganisms. This review focuses on microbial hazards in water and wastewater, and the use of sonochemical reactors (SCRs) combined with advanced oxidation processes (AOPs) for disinfection. Various types of cavitation reactors, including acoustic cavitation reactors (ACRs) and hydrodynamic cavitation reactors (HCRs), have been employed for the treatment of contaminated waters. Bacterial degradation is primarily caused by thinning of microbial membranes, local warming, and free radical generation due to cavitation. The mechanisms and effects of cavitation in the disinfection process are still poorly understood.