Bioremediation of Printing and Dyeing Wastewater by Synechocystis aquatilis: System Construction, Kinetics and Mechanisms

Actual printing and dyeing wastewater (APDW), as one of the most difficult types of wastewater to treat, has become a significant environmental risk due to its toxicity and the challenges associated with its degradation. Microalgae-based treatment of APDW is a promising, eco-friendly, and cost-effective strategy. In this study, a cyanobacterium, Synechocystis aquatilis, was isolated from APDW. The strain demonstrated good environmental tolerance and the capacity to remove pollutants and valorize biomass simultaneously. Under optimized conditions, it removed COD (120.27 mg·L−1·d−1), NH4-N (0.89 mg·L−1·d−1), and total phosphorus (9.52 mg·L−1·d−1), while achieving substantial decolorization. The strain concurrently accumulated lipids (373.08 mg/g), polysaccharides (167.85 mg/g), and proteins (72.05 mg/g). Mechanistic analyses revealed that S. aquatilis microalgae adsorb dyes and impurities via bioadsorption and then biodegrade dyes and nitrogen and phosphorus compounds via NADPH generation, glutamate and butyrate metabolism, and oxidoreductase activity. This study presents a promising application of S. aquatilis as a novel and environmentally friendly treatment method for APDW, enabling simultaneous wastewater treatment and resource recovery.