Enhanced Medium-Chain\nFatty Acids Production by Iron–Carbon\nMicroelectrolysis: Performance and Mechanisms

The low biodegradability and slack electron transfer\nof waste-activated\nsludge (WAS) posed significant challenges to medium-chain fatty acids\n(MCFAs) production. Herein, a viable iron–carbon microelectrolysis\n(ICME) technique was proposed to improve the synthesis of MCFAs from\nWAS through accelerating WAS disintegration and substrate transformation\nand increasing the electron transport efficiency, simultaneously.\nResults showed that the maximum MCFAs production in the ICME-mediated\nchain elongation (CE) process was up to 4.4 times that of the control.\nMechanistic exploration revealed that the formation of microscopic\ngalvanic cells drove boosted electron transfer within the ICME, which\ngreatly enhanced the effect of direct interspecies electron transfer\n(DIET), and thus promoted hydrolysis, acidogenesis, and CE processes.\nAdditionally, Fe<sup>2+</sup> formed by ICME facilitated orthophosphate\nremoval through precipitation. Microbial community analysis revealed\nan increase in the number of anaerobic populations associated with\nhydrolysis and acidogenesis. Overall, this study demonstrated the\nviability of ICME for promoting MCFAs production from WAS, offering\na novel avenue for microelectrolysis-aided resource recovery.