Cultivation of Chlorella vulgaris in sludge extracts: Nutrient removal and algal utilization.

In order to utilize the excess sludge and reduce the cost of algal cultivation, Chlorella vulgaris was cultivated in increasing proportions of sludge extracts for simultaneous nutrients removal and algal utilization. Results showed that C. vulgaris cultivated in the 100% sludge extract gained the highest total biomass (33.98 ± 0.30 × 106 cells/mL) and showed good results in TOC (absolute value 175 mg/L) and nutrients (TN: 77.1%; TP: 95.0%) removals. According to the Excitation-emission matrix spectra (EEMs) analysis, the 8th day was suggested as the optimal time for biomass harvesting. Although the lipid contents showed a negative correlation with the proportion of sludge extract, the FAME analysis showed that the saturated fatty acids (SFA) contents decreased and the unsaturated fatty acids (UFA) content increased as the concentration of sludge extract increased. The 100% sludge extract could be a desirable alternative medium for the algae cultivation.