Assessing fish farm wastewater as a sustainable growth medium for Nannochloropsis sp. / Nor Firdia Dayana Mohammad Fadzil

The rapid expansion of aquaculture has led to increased nutrient-rich wastewater generation, posing environmental challenges and necessitating sustainable waste management solutions. This study investigates the feasibility of using fish farm wastewater as a sustainable, cost-effective medium for cultivating Nannochloropsis sp., a promising microalga for biofuel and aquaculture applications. Two formulations were compared: 100% fish farm wastewater (FF) and a blend of 50% fish farm wastewater with 50% commercial media (50%FF+50%CM). Growth profiles, kinetics, and the elemental composition of dried biomass were evaluated over 20 days. The 100% FF medium exhibited a short lag phase (days 0-4) followed by an exponential phase that reached a maximum biomass of 0.4 g I.1 before declining. In contrast, 50%FF+50%CM, with an extended adaptation period, gave a more pronounced exponential phase that produced approximately 0.618 g I.1 biomass. Improved growth kinetics for 50%FF+50%CM was supported by a higher specific growth rate, shorter cell division time, and increased biomass productivity. The elemental profile presented higher nitrogen and carbon in the 50%FF+50%CM biomass, reflecting better nutrient uptake and metabolic activity. Overall, supplementing fish farm wastewater with commercial nutrients can significantly enhance microalgal growth and productivity. This offers a promising integrated approach to aquaculture wastewater treatment in addition to finding a sustainable growth medium for microalgae.