Wastewater Treatment Plants and Microplastic Degradation

Non-degradable microplastics are emerging pollutants and are discharged in huge amounts into the waterbodies with insufficient treatment. Due to their severe threat to biota, various treatment plants for treating wastewater are considered as the last line of defense which forms a barrier between harmful microplastics and the surroundings. As per the literature, various explored primary, secondary, as well as tertiary treatment phases in wastewater treatment plants remove around 65, 14, and 2% microplastic, respectively. Other than conventional treatment methods, herein we mainly explore the recently reported advanced microplastic degradation methods that achieved almost satisfying microplastic degradation activity. Out of these treatment techniques, advanced oxidation processes can only degrade microplastics partially into simpler molecules like CO2 and H2O under laboratory conditions, thus exhibiting a removal efficiency of >99%. A focal point of this review is the detailed analysis of the efficiency of advanced oxidation processes, with a specific emphasis on photocatalytic degradation. Photocatalytic degradation, as a subset of advanced oxidation processes, is dissected to underscore its potential in addressing the persistent nature of microplastic pollutants. The review manuscript further delves into an extensive exploration of various photocatalysts, elucidating their specific roles in the degradation process. The discussion encompasses the generation and utilization of different radicals during photocatalytic reactions, offering insights into the underlying mechanism governing microplastic breakdown.