The influencing mechanism of AD-MEC domesticated sludge to alleviates propionate accumulation and enhances methanogenesis

Magnetic biochar enhanced microbial electrolysis cell with anaerobic digestion for complex organic matter degradation in landfill leachate

Combining microbial electrolytic cells with anaerobic digestion (MEC-AD) was considered as an important method for enhancing complex organic matter degradation. However, the magnetic biochar (MBC) addition would be an effective approach for enhancing biodegradation in MEC-AD. By designing orthogonal experiments, the optimal parameters of MBC-enhanced MEC-AD system for landfill leachate treatment were determined. The results indicated that the optimal conditions were identified as HRT of 72 h, electrode spacing of 2.5 cm, and applied voltage of 0.8 V. Under these conditions, the COD removal efficiency reached a maximum of 54.7 %. Additionally, the UV-vis, 3D-EEM, and GC-MS indicated the macromolecules 13-Docosenamide (Z), Bis(2-ethylhexyl) benzene-1,4-dicarboxylate and bis(2-ethylhexyl) phthalate were degraded. 13-Docosenamide (Z) was almost completely removed under the conditions of 0.8 V applied voltage, 2.5 cm electrode spacing and 24 h HRT, with a removal efficiency of 99.91 %. Significant differences were observed in the microbial core genera among the MEC-AD systems. The core genera in the anodic and cathodic biofilms were primarily fermentative and electroactive bacteria, including Soehngenia (2.2 % - 32.1 %, 3.2 % - 26.4 %) and Desulfomicrobium (1.1 % - 10.2 %, 2.0 % - 29.3 %). Fermentative bacteria, norank_f__Bacteroidetes_vadinHA17, established cooperative relationships with electroactive bacteria Acinetobacter. The enrichment of electrochemically active bacteria optimized microbial interactions, thereby synergistically enhancing the biotransformation of complex organic matter in landfill leachate.

Biogas upgrading performance and underlying mechanism in microbial electrolysis cell and anaerobic digestion integrated system

The productivity and efficiency of two-chamber microbial electrolysis cell and anaerobic digestion integrated system (MEC-AD) were promoted by a complex of anaerobic granular sludge and iron oxides (Fe-AnGS) as inoculum. Results showed that MEC-AD with Fe-AnGS achieved biogas upgrading with a 23%-29% increase in the energy recovery rate of external circuit current and a 26%-31% decrease in volatile fatty acids. The energy recovery rate of MEC-AD remained at 52%-57%, indicating a stable operation performance. The selectively enriched methanogens and electroactive bacteria resulted in dominant hydrogenotrophic and acetoclastic methanogenesis in the cathode and anode chambers. Mechanistic analysis revealed that MEC-AD with Fe-AnGS led to specifically upregulated enzymes related to energy metabolism and electron transfer. Fe-AnGS as inoculum could improve the long-term operation performance of MEC-AD. Consequently, this study provides an efficient strategy for biogas upgrading in MEC-AD.