Microalgae cultivation in urban wastewater: Nutrient removal and biomass production for biodiesel and methane

The freshwater microalgae species Chlorella kessleri and Chlorella vulgaris, and the marine microalgae species Nannochloropsis oculata were cultivated in urban wastewater. The freshwater species demonstrated the possibility of growing in urban wastewater reaching high biomass production and nutrient removal when cultured in batch mode using a flat-panel airlift photobioreactor. Both microalgae species reached high biomass dry weights, 2.70 +/- 0.08 g/L and 2.91 +/- 0.02 g/L respectively, accompanied by nitrogen concentration reduction around 96% and 95%, and a phosphorous concentration reduction around 99% and 98% respectively. N. oculata was able to uptake nutrients from wastewater to grow but with less efficiency, indicating the need of microalgae acclimation or process optimisation to achieve high nutrient removals. During C. kessleri and C. vulgaris cultivation, the nitrogen consumption led to a progressive N-starvation process which increased the microalgae potential for biofuels production; both species produced 346 +/- 3 mL(CH4)/g(VS) and 415 +/- 2 mL(CH4)/g(VS) during anaerobic digestion, and 7.4 +/- 0.2 g(Biodiesel)/100 g(VS) and 11.3 +/- 0.1 g(Biodiesel)/100 g(VS) respectively. (C) 2015 Elsevier B.V. All rights reserved.