Textile, printing, and dyeing industries in China are expanding annually, resulting in the discharge of significant volumes of wastewater. These effluents have complex compositions and contain diverse pollutants that pose severe hazards to aquatic systems, ecological environments, and nearby flora, fauna, and human populations. The inadequate or rudimentary treatment of these effluents can cause substantial environmental damage. Current technologies for treating textile dyeing wastewater (TDW) include physical, chemical, and biological methods, with biological treatment being noted for its low cost and environmental sustainability. In the realm of biotechnological treatment, microorganisms, such as bacteria, fungi, and algae, exhibit significant potential. This review highlights the urgent need for effective treatment of textile dyeing wastewater (TDW), which poses severe environmental and health risks. It provides a comparative analysis of physical, chemical, and biological treatment methods, with a focus on the unique advantages of biological approaches, such as biodegradation and biosorption, for sustainable wastewater management. Key findings include recent advancements in microbial applications, challenges in scaling up, and integration into existing treatment systems. This review aims to guide future research and practical applications in achieving eco-friendly and cost-effective solutions for TDW remediation.

Reducing nitrous oxide (N₂O) emissions from biological wastewater treatment is critical for achieving low-carbon environmental goals. In this study, a Chlamydomonas reinhardtii -driven algal–bacterial granular sludge system was successfully established in a photo-sequencing batch reactor to enhance nitrogen removal while suppressing N₂O generation. Compact granules formed within 48 days, exhibiting good settling ability (SVI₅/SVI₃₀ = 1.0), an average diameter of 0.5 mm, and a mixed-liquor suspended solid concentration of 2.1 g/L. Algal enrichment was confirmed by an increase in chlorophyll-a to 6.6 mg/g-VSS and substantial accumulation of protein-rich extracellular polymeric substances, which improved granule stability and mass transfer. The system achieved efficient pollutant removal when treating synthetic municipal wastewater, maintaining a chemical oxygen demand removal efficiency of approximately 90% and total nitrogen removal of up to 69.4%, with effluent NH₄⁺-N consistently below 1.6 mg/L. Notably, the N₂O emission factor decreased from 4.2 to 0.4 g N₂O-N/kg N-removed, which is lower than that of conventional activated sludge processes. These results demonstrate the potential of microalgae-driven granulation as a promising low-carbon biotechnology for sustainable wastewater treatment.