Simultaneous recovery of short-chain fatty acids and phosphorus during lipid-rich anaerobic fermentation with sodium hydroxide conditioning

Anaerobic fermentation (AF) could achieve simultaneous recovery of short-chain fatty acids (SCFAs) and phosphorus (P) when waste activated sludge (WAS) and meat processing waste (MPW) act as co-substrate. However, long-chain fatty acids, the degradation intermediates of lipids, always inhibit anaerobic microbial activity. Therefore, sodium hydroxide (NaOH) conditioning was applied to improve the lipid-rich AF performance in this study. The results demonstrated that 96% WAS (v/v) with NaOH addition that remaining at pH 7.5 could achieve the maximum SCFAs yield (1180.05 mg/g VSfed) at 12 d, and ortho-P content in the AF liquor (AFL) was much more than that of without NaOH addition. Anaerovibrio and Aminobacterium, one kind of lipolytic and proteolytic bacteria, respectively, became the major genus in the lipid-rich AF system. 86% of P in the AFL from 96% WAS + pH 7.5 reactor was recovered through vivianite crystallization method, with 91% of SCFAs remaining in the post-AFL. Meanwhile, analysis results verified vivianite formation in the P precipitate products. Overall, this study provided a new idea to achieve SCFAs and P simultaneous recovery from WAS and MPW through AF with NaOH conditioning and vivianite crystallization.

Automated summary

Anaerobic fermentation (AF) with sodium hydroxide (NaOH) conditioning was used to achieve simultaneous recovery of short-chain fatty acids (SCFAs) and phosphorus (P) from waste activated sludge (WAS) and meat processing waste (MPW). The addition of NaOH improved the AF performance by inhibiting the degradation of long-chain fatty acids. Anaerovibrio and Aminobacterium were identified as the major genera in the lipid-rich AF system. The study also demonstrated successful recovery of P through vivianite crystallization method. Overall, this study provides a new approach for SCFAs and P recovery from WAS and MPW through AF with NaOH conditioning and vivianite crystallization.