Mixotrophic growth and biochemical analysis of Chlorella vulgaris cultivated with synthetic domestic wastewater

Domestic wastewater is a potential medium for microbial cultivation because it contains abundant non-toxic inorganic salts and organic nutrients. However, studies of the feasibility of using wastewater as medium have focused on removal rates, while ignoring changes in biomass composition. Therefore, this study investigated the feasibility of growing Chlorella vulgaris in domestic wastewater, while focusing on its nutrient removal rates and biomass composition. Results showed that Chlorella vulgaris growth rate and biomass were significantly promoted by domestic wastewater compared with BG11 medium. The maximum biomass (17.94 × 106 cell L−1) was obtained when 100% domestic wastewater was used. The highest COD removal rate was 93.6% obtained by 75% of wastewater, while the highest NH4+–N and TP removal rates were 98.69% and 86.07% by 25% of wastewater. The harvested biomass was rich in protein (40.9–50.7%) and low in lipids (23.4–28.5%), and both the nutritional quality and quantity of protein and lipid were increased in dilutions. These results indicated that domestic wastewater is a feasible medium for mass-cultivation of Chlorella vulgaris, and 100% dilution is suggested.