Bioremediation of synthetic intensive aquaculture wastewater by a novel feed-grade composite biofilm

The current challenge in intensive aquaculture is to control the level of nutrient pollutants in the wastewater and provide sustainable sources of proteins for feed. A synthetic lichen type biofilm was developed to have the fungus Mucor indicus and the microalga Chlorella vulgaris grow together on a polymer matrix referred to as a “mycoalgae” biofilm. When the biofilm grows, it takes up phosphorus and nitrogen compounds and converts them to proteins and other cellular products. It cleans the water from nutrient pollutants as the algae are attached to the biofilm leaving purified water at the end of the process. Under 25 mg L⁻¹ total ammonia-N (TAN) conditions, the biofilm reduced TAN to undetectable limits within 48 h with over 69% of the TAN reduction taking place by 24 h. The biofilm reduced levels of phosphate-P from 15 mg to undetectable limits within 24 h. Under the same conditions, 860 mg of dry mycoalgae biomass was generated at the end of the process on 16 cm² of mesh and 100 ml of culture media. This process allows for easy harvesting of the algae with no energy intensive process of separating the algae from the supernatant. The generated biofilm is composed of two organisms that have been shown to positively aid fish health when included as a feed supplement.