A promising microalgal wastewater cyclic cultivation technology: Dynamic simulations, economic viability, and environmental suitability.

The microalgal wastewater cyclic cultivation technology (AWCT) proposed in this study helps address the challenges surrounding water scarcity and ecological sustainability in a clean, resource-efficient, and affordable manner. A novel microalgae growth model (AGM) elucidating the growth mechanisms of microalgae in the AWCT system was established for dynamic simulations and design optimization. The recycled wastewater accelerated the growth rate of microalgae, and increased biomass and lipids content by 11% and 37.65%, respectively, after 8 batches of cultivation. The accumulated soluble algae products (SAPs) enhanced microalgae growth by providing nutrients and regulating metabolism. In addition, scenario simulations illustrated the excellent long-term performance of the AWCT system. 100% recycling of microalgal wastewater could save 0.3% N and 54.36% P. The techno-economic analysis (TEA) and life cycle assessment (LCA) explored how economic and sustainability principles can be embedded into the life cycle of microalgae production. The AWCT led to outcomes vastly superior to non-cyclic technology by enabling the high-level recovery of resources, providing substantial benefits, enhancing contingency and risk resistance, and offsetting a host of unintended environmental effects.