The traditional model of centralized wastewater treatment is facing substantial strain due to a confluence of global challenges. Consequently, it is imperative to evaluate the impediments and potential advantages associated with the deployment of decentralized wastewater (DW) treatment technologies and systems. Decentralized wastewater (DW) treatment represents a sustainable approach to managing and purifying wastewater across both urban and rural settings. This literature review provides a detailed examination of current advancements and challenges associated with DW treatment technologies. It specifically addresses their operational efficiency, long-term sustainability, and practical implementation across diverse environments. This review critically analyzes recent studies that highlight innovative methodologies, including the deployment of constructed wetlands, anaerobic digestion processes, and predictive models enhanced by artificial intelligence. A critical focus is placed on the ecological and economic advantages of source separation and resource recovery from wastewater streams. The issue of emerging contaminants, such as microplastics, antibiotics, and steroids, is also discussed, emphasizing the continued need for innovation in treatment technologies. Findings from various life cycle assessments are presented to illustrate the environmental impact and feasibility of decentralized systems relative to centralized alternatives. This comprehensive analysis offers valuable insights into the future trajectories of wastewater treatment research and implementation.

CoFe₂O₄ loaded onto red brick powder (CoFe₂O₄@RBP) was synthesized via coprecipitation followed by post-calcination and employed as a heterogeneous catalyst to activate peroxymonosulfate (PMS) for the degradation of methylene blue (MB), thereby valorizing red brick demolition waste within a circular economy pathway and aligning the study with sustainability-oriented resource recovery. The effects of pH, PMS concentration, catalyst dosage, and coexisting substances on MB removal were systematically investigated. Complete MB removal was achieved within 30 min, and the apparent rate constant for the CoFe₂O₄@RBP/PMS system was 0.22 min⁻¹—slightly lower than that of CoFe₂O₄/PMS—while Co leaching was markedly reduced. The process performed well across a broad pH range (3.0–9.0). EPR and radical-quenching experiments indicate that SO₄•⁻ and HO• play a minor role, whereas the Co(II)–PMS complex is primarily responsible for MB degradation; accordingly, common coexisting species (SO₄²⁻, Cl⁻, NO₃⁻, humic acid) exert negligible effects. The catalyst also maintained strong durability across numerous repetitions. These results highlight a cost-efficient route to PMS activation by coupling CoFe₂O₄ with construction waste-derived supports.