Enhanced biodiesel production from glucose-fed activated sludge microbial cultures by addition of nZVI and FeCl3

Abstract

The effect of different iron additives on biodiesel production from activated sludge was investigated under an optimal lipid accumulation condition (pH = 4 & C/N = 100). Iron addition, ranging from 0.1 to 2.5 mmol L⁻¹, had a positive effect on biodiesel production. Among separate iron tests, 0.25 mmol L⁻¹ nZVI and 2.5 mmol L⁻¹ FeCl₃ performed the best. The gravimetric fatty acid methyl ester yields of the two treatments reached 215.3 (0.25 mmol L⁻¹ nZVI) and 274.9 mg g⁻¹ dry sludge (2.5 mmol L⁻¹ FeCl₃) and increased by 36.1% and 74.0% compared with control run (131.0 mg g⁻¹ dry sludge), respectively. At the end of the culture period, the genus Gluconacetobacter (56.4%) was enriched in the sludge under the 2.5 mmol L⁻¹ FeCl₃ treatment while the other treatments were only dominated by Gluconobacter (∼80%). The accumulated lipids mainly contained around 60% of monounsaturated fatty acids, indicating the suitability for biodiesel production. Furthermore, indicators related to production costs showed iron addition could notably improve the biotechnical feasibility.