Sustainable Cultivation of the Microalga Desmodesmus elegans Using Nutrient‐Enriched Duckweed Organic Liquid Fertiliser and Nitrate‐Rich Fish Tank Wastewater

Sustainable cultivation of microalga Desmodesmus elegans was achieved using nutrient enriched duckweed organic liquid fertiliser and nitrate rich fish tank wastewater. The growth was optimised using different concentrations (1:30, 1:60 and 1:200) of the lemna liquid biofertiliser (LLF). The LLF contained all essential nutrients that are present in the standard BG‐11 medium. The highest growth and cell densities of microalgal cultures were achieved at 1:200 dilution of LLF, which was notably higher than the BG‐11 medium. This study demonstrates the development of a sustainable and economical ‘algaeponics’ cultivation system for microalgae growth. This is also the first report on the use of duckweed organic liquid as a complete nutrient source for microalgae. Our ‘algaeponics’ system facilitates the recovery of nitrate as well as the reuse of fish tank wastewater in an eco‐friendly and sustainable manner.