Effects of bio-surfactants combined with alkaline conditions on volatile fatty acid production and microbial community in the anaerobic fermentation of waste activated sludge

This study investigated the effects of three types of bio-surfactants (BS), namely, saponin (SP), surfactin (SF), and rhamnolipid (RL), with alkaline conditions on volatile fatty acid (VFA) production and microbial community in sludge fermentation. BS combined with a pH of 9 significantly enhanced hydrolase activities, promoted VFA production and inhibited methanation. SP & pH 9 was more efficient in converting organics to VFAs and thus achieved the highest yield of 425.2 mg COD/g VSS, which was 1.5 times that at pH 10. The lower negative effect of SP on metabolic potential and diversity than that of SF or RL was confirmed through a Biolog assay. Illumina-sequencing further proved that the relative abundances of acidogens in SP & pH 9 were higher than those in other tests, including Proteiniclasticum, Fusibacter, Macellibacteroides and Petrimonas et al. This study provided a strategy for plant-derived SP applications in sludge moderate alkaline fermentation to enhance VFA production. (C) 2016 Elsevier Ltd. All rights reserved.