Simultaneous nutrients removal and bio-compounds production by cultivating Chlorella sorokiniana SU-1 with unsterilized anaerobic digestate of dairy wastewater

Serving a vital role in the redistribution of energy flux and nutrient cycles in the environment, microalgae have garnered wide attention due to their excellent ability in wastewater phycoremediation with simultaneous resource recovery to synthesize valuable bioproducts for biofuel and other applications. Anaerobic digestate of dairy wastewater is rich in organic carbon and nutrients (P and N), which is well-suited to cultivate microalgae. This study investigated the performance of utilizing untreated anaerobic digestate of dairy wastewater for the cultivation of Chlorella sorokiniana SU-1 to achieve satisfactory removal of nutrients and chemical oxygen demand (COD) as well as the synthesis of biocompounds. High biomass concentration of 4.8 ± 0.08 g/L with compositions of 47.3 ± 1 % carbohydrate, 29.3 ± 11 % protein, and 4.3 ± 3 % lipid content as well as outstanding wastewater treatment performance (91.3 ± 3 % COD removal, 92.1 ± 2 % total phosphorus (TP) removal, and 96.3 ± 1 % total nitrogen (TN) removal) was obtained under the optimal conditions of 100 % wastewater, inoculum size of 1 g/L, and CO₂ aeration rate of 2 vvm. The treated effluent satisfied Taiwan Dairy Wastewater Discharge Standards. This novel approach demonstrated the feasibility of simultaneous treatment of dairy-wastewater anaerobic digestate and valuable biocompounds production.