Microalgal production and nutrient recovery under mixotrophic mode using cheese whey permeate

Mixotrophic microalgal solutions are efficient nutrient recovery methods, with potential to prolong the cultivation seasons in temperate climates. To improve operation sustainability, the study used landfill leachate for nitrogen source and whey permeate for phosphorus and organic carbon. A non-axenic polyculture, dominated by green algae, was cultivated in mixotrophic mode on glucose or whey permeate compared to a photoautotrophic control in outdoor pilot-scaled raceway ponds during Nordic spring and autumn. The whey permeate treatment had the highest algal growth rate and productivity (0.48 d^-1, 183.8 mg L^-1 d^-1), nutrient removal (total nitrogen: 21.71 mg L^-1 d^-1, total phosphorus: 3.05 mg L^-1 d^-1) and recovery rate (carbon: 85.19 mg L^-1 d^-1, nitrogen: 17.01 mg L^-1 d^-1, phosphorus: 2.58 mg L^-1 d^-1). When grown in whey permeate, algal cultures demonstrated consistent productivity and biochemical composition in high (spring) and low light conditions (autumn), suggesting the feasibility of year-round production in Nordic conditions.