Lipid production in mixotrophic cultivation of Chlorella vulgaris in a mixture of primary and secondary municipal wastewater

Microalgae's biomass productivity and oil content depend heavily on the method of its cultivation. In this study, nutrient removal from municipal wastewater by Chlorella vulgaris in batch culture was investigated. Carbon dioxide was supplied from sodium hydrogen carbonate. Effect of parameters including light intensity, sodium hydrogen carbonate concentration, and daily illumination time on the productivity of biomass and lipid was investigated. Lipid and biomass production of C. vulgaris increased at higher concentration of sodium hydrogen carbonate concentration and higher light intensity until a certain value and then decreased, but longer daily illumination time, increased both biomass and lipid productivity. Cultivation of C. vulgairs in mixotrophic mode was also studied in a mixture of primary and secondary wastewater with different ratios (25, 50 and 75 volume percent of the primary wastewater). It was observed that using 25% of the primary wastewater results in 100% COD removal, 100% ammonium removal and 82% nitrate elimination. Biomass productivity and lipid productivity of C. vulgaris in a mixture of primary (25%) and secondary wastewater were 138.76 mg/L/d and 45.49 mg/L/d, respectively.