Accelerated acidogenic fermentation and sulfate reduction with mariculture solid waste by magnetite-modified three-dimensional electro-fermentation system.

Electro-fermentation exhibits great potential for mariculture solid waste (MSW) treatment. However, the performance of electro-fermentation is constrained by the low electron transfer efficiency within MSW. In this study, a three-dimensional electro-fermentation system packed with magnetite-modified granular activated carbon was developed to accelerate acidogenic fermentation and sulfate reduction with MSW. The results indicate that optimal performance was achieved at an applied voltage of 0.6 V, leading to a 92.9% enhancement in short-chain fatty acids production and an acetic acid proportion of 84.1%. Elemental sulfur, serving as a low-toxicity electron donor, demonstrated a 6.0-fold rise in yield relative to the control. The MSW structure was disrupted by electro-fermentation, resulting in the efficient release of electron shuttles and biodegradable organic matter. The competition between acidogenesis and sulfidogenesis was alleviated due to the elevated substrate bioavailability, and the acidogenesis-sulfidogenesis efficiency of MSW was also promoted. Furthermore, the physicochemical properties and key enzyme activities were examined to elucidate the underlying mechanisms of the biological pathways. Microbial community investigation confirmed that the acidogenic bacteria and sulfate-reducing bacteria (e.g., Draconibacterium, Halomonas, Enterococcus, Dethiosulfovibrio) were enriched. Overall, the efficiency of acidogenic fermentation and sulfate reduction was improved by the three-dimensional electro-fermentation system, offering a novel approach for sustainable MSW treatment and electron donor recovery.