Growth, biomass production, pollutant removal capacity of Chlorella vulgaris cultivated in water polluted with nutrients (PO43- and NO3-) and heavy metal ions (Cd2+ and Pb2+); A strategy for bioremediation, CO2 utilization and simultaneous biodiesel productivity

Abstract

The objective of the work reported herein was to optimize the growth conditions, and study the bioremediation efficiency and simultaneous biomass productivity of Chlorella vulgaris grown in water contaminated with Cd2+, Pb2+ ions and nutrients (NO3− and PO43−). In this regard, Chlorella sp. were cultivated separately in the presence and absence of known concentrations of Cd2+, Pb2+ and PO43− ions in growth media containing 200 mg L− 1 of NO3− for 30 days at ~ 28°C. The biomass, % oil content and the remaining Cd2+, Pb2+ and PO43− concentrations in the growth medium in 30 days after the cultivation were determined. The results revealed that the maximum tolerable Pb2+, Cd2+, total nitrogen (TN) and total prosperous (TP) concentrations were 8 mg L− 1, 2.5 mg L− 1, 200 mg L− 1 and 10 mg L− 1, respectively for living Chlorella sp. Biomass yields (% oil content) of Chlorella sp. grown in the absence of heavy-metal ions, in the presence of Pb2+ and Cd2+ ions in the growth medium were 0.8260 g L− 1 (40.69%), 0.5551 g L− 1 (37.64% ) and 0.2896 g L− 1 (44.80%), respectively, implying no significant reduction in % oil production caused by these metal ions. The extracted bio-oil was almost free from Pb2+ and Cd2+ ions. The bioremediation efficiency of Chlorella sp. was significantly high; 77% PO43− (from 10 mg L− 1), 84% Pb2+ (from 8 mg L− 1) at pH 5 and 72.7% Cd2+ (from 2.5 mg L− 1) at pH 6.