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.

As an important alternative to alleviate the shortage of wild fishery resources, mariculture is facing increasing challenges on the wastewater treatment, mainly due to the salinity brought from seawater and low nutrient concentration. In this study, Spirulina platensis (S. platensis) was adopted as the target algae stain for synthetic mariculture wastewater treatment, which exhibited excellent adaptability to high-saline wastewater during a 40 days’ adaptive culture. Then, the microalgae stain was inoculated into photo-bioreactors with different uplift airflow velocity (UAV) to achieve microalgal aggregation. After 10 days of pre-cultivation and a 30-day granulation process, the maximum nutrient removal rates by S. platensis were 86.5% of TN (to 3.4 mg/L), 98.1% of TP (to 0.1 mg/L) and 95.8% of DOC (to 5.5 mg/L), with 3.5 g/L of biomass content in synthetic wastewater. Analysis of phosphorus and EPS content showed that higher protein content in tightly bound EPS and enhanced P accumulation was accompanied with the microalgal aggregation processes, and P was mainly distributed in the residual rather than the EPS part of microalgal aggregates, indicating that the development of aggregates from suspension S. platensis would benefit not only biomass separation, but also phosphorus recovery, being a potential treatment for simultaneously removing nutrients and recovering mariculture wastewater.

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.