## 1 Introduction
### Advanced Treatment Strategies for Emerging Contaminant Mitigation
#### Advanced Oxidation Processes (AOPs)  
AOPs involve the generation of highly reactive species, such as hydroxyl radicals (\(\bullet\)OH), capable of degrading a wide range of organic contaminants [27; 28; 29]. Figure 2: Overview of technologies used for the removal of emerging contaminants, including their targeted pollutant classes, specific treatment methods (e.g., adsorption, advanced oxidation processes, membrane filtration), and a summary of their respective advantages and limitations. The figure highlights the need for integrated approaches to address the complexity of ECs in water treatment systems. * Ozonation (O\({}_{3}\)), UV/H\({}_{2}\)O\({}_{2}\), Fenton, and photo-Fenton processes are widely applied. * Effective in degrading persistent molecules such as artificial sweeteners, antibiotics, and dyes. * Limitations include energy requirements and possible toxic byproduct formation. * Adsorption Techniques  
Adsorption is one of the most effective and widely used techniques for EC removal, due to its simplicity and cost-effectiveness [1; 9; 30]. Activated carbon (powdered or granular) is extensively applied for the uptake of pharmaceuticals, endocrine disruptors, and food additives. * Biochar, carbon nanotubes, and graphene-based materials offer enhanced adsorption capacity, particularly for nanomaterials and microplastics. * Challenges include adsorbent regeneration and disposal. * Membrane Filtration Technologies  
Membrane processes physically remove emerging contaminants based on size exclusion or charge repulsion [31; 32; 33]. * Nanofiltration (NF) and reverse osmosis (RO) are effective for removing low-molecular-weight ECs, including artificial sweeteners and pharmaceuticals. * Ultrafiltration (UF) and microfiltration (MF) can remove microplastics and some nanomaterials when combined with coagulation or flocculation. * Membrane fouling, large scale application limitation, and high operational costs remain concerns. * Biological Treatments  
While traditional biological treatments (e.g., activated sludge) show limited efficacy for many ECs, recent innovations have improved biodegradation capacity [4; 34; 35; 36]. * Membrane bioreactors (MBRs) and moving bed biofilm reactors (MBBRs) show enhanced performance due to longer sludge retention times. * Engineered microbial consortia and microbial cell factories are explored for specific contaminant degradation. * Biological processes are less effective for highly recalcitrant substances like sacralose or nanoplastics. * Electrochemical and Photocatalytic Methods  
Electrochemical oxidation and photocatalysis are gaining attention for the degradation of persistent and non-biodegradable ECs [37; 38; 39; 40]. * Electrochemical oxidation using boron-doped diamond (BDD) or Ti/Pt anodes enables direct electron transfer to degrade pharmaceuticals and food-related ECs. * Heterogeneous photocatalysis using TiO\({}_{2}\), ZnO, and doped semiconductors under UV or solar light are effective in degrading a wide range of ECs, including pesticides and sweeteners. * These methods are costly and energy-intensive, but could be integrated with solar energy for sustainability. * Coagulation-Flocculation and Sedimentation This conventional method is often used as a pre-treatment or in combination with other technologies [41; 42; 43]. * The method alone is ineffective for most ECs, but it can assist in the removal of microplastics, nanomaterials, and particulate-associated pollutants. Use of advanced coagulants (e.g., magnetic flocculants or biocoagulants) enhances efficiency. 2. Hybrid and Integrated Systems  
Combining physical, chemical, and biological methods often enhances removal efficiency and addresses the limitations of single techniques [1; 41; 44]. * Examples include AOP-MBR hybrids, adsorption-photocatalysis systems, and membrane-biochar filters. * Integration allows for targeted removal of both particulate and dissolved ECs. * These combinations can add system complexity and cost implications.