Cultivation of Chlorella vulgaris on wastewater containing high levels of ammonia for biodiesel production

The feasibility of cultivating Chlorella vulgaris with wastewater containing high ammonia nitrogen concentrations was examined. The average specific growth rate of C. vulgaris was 0.92 d−1 at 17 mg L−1 NH4+-N, but declined to 0.33 d−1 at NH4+-N concentrations of 39–143 mg L−1. At 39 mg L−1 NH4+-N, lipid productivity reached a maximum value (23.3 mg L−1 d−1) and dropped sharply at higher NH4+-N levels, which demonstrated NH4+-N should be controlled for biodiesel production. C16 and C18 fatty acids accounted for 80% of total fatty acids. Increasing NH4+-N from 17 to 207 mg L−1 yielded additional short-chain and saturated fatty acids. Protein content was in positive correlation with NH4+-N content from 17 mg L−1 (12%) to 207 mg L−1 (42%). Carbohydrate in the dried algae cell was in the range of 14–45%, with a peak value occurring at 143 mg L−1 NH4+-N. The results demonstrate that product quality can be manipulated by NH4+-N concentrations of the initial feeds.