Analgesics in wastewater matrix: A comprehensive review on occurrence, toxicity, and sustainability assessment of biological, tertiary, and hybrid treatment processes

Over the past few decades, increased consumption of pharmaceuticals has led to the prevalence of the pharmaceuticals and their metabolites in various wastewater matrices. Amongst, analgesics are one of the most consumed classes of medicines. These analgesics have complex molecular structures and physicochemical properties that do not favor degradation by conventional biological processes. Furthermore, they pose significant toxicity towards the non-target species and have the potential to disrupt the aquatic environment. Hence, researchers have focused on advanced or tertiary treatment processes, such as adsorption, photocatalysis, and the Fenton process, to remove these recalcitrant analgesics. Although these processes can remove analgesics with a high removal efficiency of around 85%, they fail to perform well with raw wastewater. Hence, hybrid processes have emerged as a wholesome treatment solution for pharmaceutical-contaminated wastewater. In this context, this review paper covers the performance assessment and sustainability of different biological, advanced, and hybrid processes in treating analgesic-contaminated wastewater. It was observed that the biological process alone could only remove around 60–70%, while the average analgesic removal from synthetic water using adsorption, Fenton, and photocatalysis was more than 80%. However, hybrid processes like a combination of constructed wetlands and photocatalysis exhibited more than 80% removal from real wastewater and were more financially and environmentally sustainable. This review provides a comprehensive idea of how analgesics, in particular, are ubiquitous in the aqueous environment and suggests how they can be removed sustainably by providing a comprehensive overview of all existing treatment systems.