The technological-centered properties of plastics have made them indispensable in everyday applications to facilitate the functioning of numerous needs in today’ society. However, improper management within their use cycle has led to significant environmental challenges, with approximately 10% of the world's plastics entering the ocean, accounting for 60-80% of marine mortality. At the current production rate, it is projected that by 2050, the ocean will contain more plastic than fish. One of the most concerning aspects of plastic pollution is the presence of microplastics—particles smaller than 5 mm—which pose significant threats to marine ecosystems and human health. The findings underscore the importance of integrating chemical engineering, environmental science, and biotechnology to develop sustainable solutions for the better management of microplastic uses and mitigating its pollution. Addressing this complex issue will require strong collaborative efforts across various scientific disciplines and the use of complementary techniques in the removal and degradation of microplastics from wastewater streams. In this contribution, in addition to environmental effects, we also examine the interactions between microplastics and aquatic organisms, highlighting the potential toxicological effects on various species. Special attention is given to the impact on marine food chains, particularly first producers such as microalgae, and the subsequent impact on higher trophic levels, including waterfowl, fish, and humans. The ingestion of microplastics poses significant health risks to marine biota, including gastrointestinal and metabolic disorders, oxidative stress, and potential alterations in behavior and reproduction. Marine animals, particularly those at higher trophic levels, are affected, which can ultimately impact human health as well. Moreover, the role of biodegradation and Advanced Oxidation Process (AOPs) as potential successful techniques to mitigate pollution effects from microplastics particles are overviewed. In this comprehensive review, we investigate the aging of plastic polymers, focusing on the chemical and physical transformations that enhance their environmental persistence and how the potential applications of AOPs in the so called tertiary treatment in wastewater treatment plants could help in managing the pollution originated in the use of microplastic particles. Microplastics pose a dual threat as they can release toxic organic compounds, additives, and metals while also adsorbing contaminants from the surrounding environment. Another pressing issue that will be discussed in this contribution is the adsorption of antibiotics onto microplastic surfaces, facilitating the proliferation of antibiotic-resistant bacteria and the horizontal transfer of resistance genes. The formation of biofilms on microplastics can further promote the activity of microorganisms that secrete enzymes capable of breaking down these polymers through processes such as depolymerization and mineralization, ultimately producing CO₂, H₂O, CH₄, and biomass. The study emphasizes the role of microbial consortia and genetically engineered microorganisms in the biodegradation of microplastics. Various bacterial and fungal species, along with their enzymes, are essential for breaking down these pollutants through processes such as depolymerization and mineralization, ultimately producing harmless byproducts like CO₂ and biomass. Several methods for assessing biodegradation are explored, including weight loss analysis, spectroscopy, and enzyme activity measurement. These techniques are vital for evaluating the effectiveness of remediation strategies and understanding the degradation processes involved. Furthermore, numerous investigations have reported that conventional methods are not reliable in separating MPs due to their small size. This limitation has prompted the exploration of various techniques including biodegradation, adsorption, coagulation/flocculation, filtration, and Advanced Oxidation Processes (AOPs) for either the separation or degradation of microplastics. AOPs have shown promising potential in degrading microplastics into less harmful byproducts through the generation of reactive oxygen species (ROS) such as hydroxyl radicals, sulfate radicals, and superoxide radicals. These highly reactive species facilitate oxidative cleavage of complex polymer chains, ultimately leading to their mineralization into CO₂ and water. AOPs, such as photocatalysis, Fenton and photo-Fenton reactions, ozonation, plasma discharge, and electrochemical oxidation, are increasingly being studied for their effectiveness and environmental compatibility. While these processes offer high degradation efficiency, their application in real-world environmental systems is still under development. Further research is needed to optimize operational parameters, identify cost-effective catalysts, and integrate AOPs with conventional separation technologies. This review outlines the efficacy, benefits, and limitations of current microplastic removal methods and emphasizes the future potential of advanced oxidation technologies for achieving complete microplastic degradation in water, wastewater, and sewage sludge matrices. Our findings emphasize the importance of integrating advanced microbial, enzymatic, and chemical oxidation approaches to develop efficient strategies for mitigating microplastic pollution. Addressing these challenges requires a multidisciplinary approach that combines chemical engineering with environmental science and biotechnology to devise sustainable solutions. This review study provides a comprehensive overview of microplastic pollution by highlighting its environmental impact, toxicological effects, and potential remediation strategies. By focusing on the interactions between microplastics and aquatic organisms, as well as the role of microbial and chemical methods in degradation, we aim to contribute to the development of effective management practices to combat this pressing environmental challenge.
