LAUSR

Microalgae cultivation using wastewater as the substrate is a sustainable technology for simultaneously microalgae biomass production and pollutant removal. To enhance the overall performance, response surface methodology with a Box–Behnken design was applied to optimize wastewater composition, including chemical oxygen demand (COD), ammonia (NH4–N) and total phosphorus (TP), in batch photobioreactors for mixotrophic cultivation of Chlorella vulgaris. Experimental results showed that under the optimal condition of wastewater composition (COD = 1271 mg/L, NH4–N = 20 mg/L and TP = 18 mg/L), the maximum biomass concentration of C. vulgaris reached 0.52 g/L, while COD and TP were observed to exert more important influence than NH4–N on microalgae growth. Moreover, the growth cycle of C. vulgaris was in the range of 3–5 d. After 5 d batch cultivation, the removal of COD, NH4–N and TP were in the ranges of 70%–83%, 51%–91% and 30%–94%, respectively, depending on initial nutrients composition in wastewater. Positive correlations among C. vulgaris biomass and removed pollutants (especially for COD and TP) were observed. The obtained results were useful for guiding the practical application of microalgae mixotrophic cultivation based processes for wastewater treatment and biomass production.