Treatment of nitrogen and phosphorus for four types of aquaculture wastewater by using nitrogen- and phosphorus-starved Chromochloris zofingiensis

With the gradual increase in the degree of intensification of aquaculture industry, large amounts of aquaculture wastewater (AW) with excess nitrogen (N) and phosphorus (P) are generated. In this study, the treatment feasibility of four types of AW, including the Chinese soft-shelled turtle (Pelodiscus sinensis) AW, the Largemouth bass (Micropterus salmoides) AW, the Pacific white shrimp (Litopenaeus vannamei) AW, and the Hybrid sturgeon (Acipenser baerii ♂ × Acipenser schrenckii ♀) AW by N- and P-starved Chromochloris zofingiensis was assessed. The total N concentration ranged from 14.63 mg L⁻¹ to 63.54 mg L⁻¹, while the total P concentration ranged from 0.36 mg L⁻¹ to 5.78 mg L⁻¹. The removal efficiencies of total N and total P from four types of AW ranged from 79.08 % to 97.54 % and 38.80 % to 83.02 %, respectively. In addition, C. zofingiensis achieved the highest protein content in M. salmoides AW on day 6, reaching 0.46 g g⁻¹. Where it achieved the highest fatty acids and astaxanthin content in Hybrid sturgeon AW, reaching 0.59 g g⁻¹ and 0.95 mg g⁻¹, respectively. In addition, C. zofingiensis exhibited a health-promoting amino acid and fatty acid composition for aquaculture animals after treatment with the four types of AW. Therefore, a recycling scheme AW treatment was proposed. Overall, this study demonstrated the feasibility of using N- and P-starved C. zofingiensis to convert N and P from AW into nutrients, which can be applied as aquafeed additives.