Performance and mechanism study of semi-continuous operation of food waste treatment system with microbially reduced graphene oxide modified microbial electrolysis cell cathodes
For the long-term treatment of food waste, the microbial electrolysis cell (MEC) reactor with microbially reduced graphene oxide (MRGO) modified cathode obtained from the optimal strategy preparation was constructed, and the effects of MRGO and different food waste residence times (5, 10, and 15 d) on the performance, resource recovery, and stability of the MEC reactor for treating food waste were investigated. The results showed that the combined stable electron conversion of C3H7COOH and C5H11COOH from MRGO modified MEC cathode reactor was ~2.6 times higher than that of biomodified MEC cathode reactor, and the oxidation peak current of cyclic voltammetry (CV) curve was ~3.2 times higher than that of biomodified MEC cathode reactor. In addition, 10 d was the most suitable residence time for MRGO modified MEC cathode treatment reactor of food waste. MRGO promoted an increase in the abundance of carbon-chain-extending bacterial genera in the MEC cathode biofilm. With the residence time of 10 d, MRGO modified MEC cathode chambers had the highest activity of caproate-producing bacteria and the highest overall expression of carbon chain elongation-related enzyme gene transcript levels. Cluster analysis showed that the functional gene transcript levels of biomodified MEC cathode chamber microorganisms was the least relevant, further elucidating the microbial mechanism of which MRGO enhanced MEC performance more than residence time modulated it, and demonstrating that MRGO modified MEC cathode improved the stability of the food waste treatment system.