7 Innovative and combined treatment technologies 
Wastewater treatment plants (WWTPs) are transforming because of innovative and combined treatment technologies that improve sustainability, efficiency, and contaminant removal. Combining biological treatment techniques with advanced oxidation processes (AOPs) like photocatalysis and ozonation is a cutting-edge strategy. Reactive species produced by these AOPs, such as hydroxyl radicals, degrade emerging and persistent organic pollutants, which are frequently impervious to standard biological processes (Wang et al., 2012; Vilhunen & Sillanpää, 2010). Another novel combination that merges biological treatment and membrane filtration is the membrane bioreactor (MBR). MBRs are ideal for water reuse applications because they efficiently remove bacteria, suspended solids, and even some dissolved pollutants, resulting in superior effluent quality (Judd, 2011). Additionally, biogas production can be improved while sludge volume is reduced and energy recovery maximized by combining anaerobic digestion with membrane filtration (Appels et al., 2008; Bolzonella et al., 2018). Bioaugmentation involves introducing particular microorganisms into wastewater remedy structures to enhance the elimination of pollutants, which include microplastics. research has demonstrated that bioaugmentation in secondary remedy approaches—such as activated sludge, sequencing batch reactors, and membrane bioreactors—can gain high microplastic removal efficiency, reaching up to 100% with certain polymer-microbe combinations.