Bioremediation and lipid synthesis through mixotrophic algal consortia in municipal wastewater.

ABSTRACT

Algae grown in outdoor reactors (volume 10 L and depth 20 cm) were fed directly with filtered and sterilised municipal wastewater. The nutrient removal efficiencies were 86%, 90%, 89%, 70% and 76% for TOC, TN, NH4-N, TP and OP, respectively, and lipid content varied from 18% to 28.5% of dry algal biomass. Biomass productivity of ∼122 mg/l/d (surface productivity 24.4 g/m(2)/d) and lipid productivity of ∼32 mg/l/d were recorded. Gas chromatography and mass spectrometry (GC-MS) analyses of the fatty acid methyl esters (FAME) showed a higher content of desirable fatty acids (bearing biofuel properties) with major contributions from saturates such as palmitic acid [C160; ∼40%] and stearic acid [C180; ∼34%], followed by unsaturates such as oleic acid [C181(9); ∼10%] and linoleic acid [C182(9,12); ∼5%]. The decomposition of algal biomass and reactor residues with an exothermic heat content of 123.4 J/g provides the scope for further energy derivation.