High concentrations of protein wastewater often reduce treatment efficiency due to ammonia inhibition and acid accumulation caused by its low carbon-to-nitrogen ratio (C/N) after digestion, as well as its complex structure. This study investigates the performance of a microbial electrolysis cell (MEC) driving a protein digestion system with gradually increasing organic loading rates (OLR) of bovine serum albumin, elucidating microbial changes and methanogenic metabolic pathways on bioelectrodes under high OLR “inhibited steady-state” (ISS) conditions. The results showed that the accumulation of ammonia nitrogen (AN) from protein hydrolysis under high OLR conditions disrupted microbial growth and caused cell death on the electrode surface, hindering the electron transfer rate. Toxic AN reduced protein hydrolysis, led to propionate accumulation, inhibiting the acetoclastic methanogenesis process and favoring the hydrogenotrophic pathway. As OLR increased from 6 to 11 gCOD/L, cumulative methane production increased significantly from 450.24 mL to 738.72 mL, while average methane yield and production rate decreased by 10.51 % and 50.28 %, from 375.20 mL/gCOD and 75.04 mL/(gCOD·d) to 335.78 mL/gCOD and 37.31 mL/(gCOD·d), respectively. Despite these declines, the system maintained an ISS. Moderate OLR increases can achieve an ISS, boosting protein waste treatment capacity, methane production, and net energy output (NEO), with an OLR of 6 gCOD/L being optimal for maximizing NEO per unit substrate. These findings provide theoretical insights into the methanogenesis pathway of high OLR proteins in MEC-AD systems and offer an effective method for treating high OLR protein wastewater in future practical applications.

中文翻译：

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深入探索微生物电解槽-厌氧消化 （MEC-AD） 产甲烷处理高有机载量蛋白质废水


高浓度的蛋白质废水消化后碳氮比 （C/N） 低，往往会因氨抑制和酸积累而降低处理效率，并且其结构复杂。本研究调查了微生物电解槽 （MEC） 驱动蛋白质消化系统的性能，牛血清白蛋白的有机负荷率 （OLR） 逐渐增加，阐明了在高 OLR“抑制稳态”（ISS） 条件下生物电极上的微生物变化和产甲烷代谢途径。结果表明，在高 OLR 条件下，蛋白质水解产生的氨氮 （AN） 积累破坏了微生物生长并导致电极表面的细胞死亡，阻碍了电子转移速率。毒性 AN 减少了蛋白质水解，导致丙酸盐积累，抑制了乙酰碎屑甲烷生成过程并有利于氢营养途径。当 OLR 从 6 gCOD/L 增加到 11 gCOD/L 时，累积甲烷产量从 450.24 mL 显著增加到 738.72 mL，而平均甲烷产量和产率分别从 375.20 mL/gCOD 和 75.04 mL/（gCOD·d） 下降到 335.78 mL/gCOD 和 37.31 mL/（gCOD·d），分别下降了 10.51 % 和 50.28 %。尽管有这些下降，该系统仍维持了 ISS。适度增加的 OLR 可以实现 ISS，提高蛋白质废物处理能力、甲烷产生和净能量输出 （NEO），6 gCOD/L 的 OLR 是最大化每单位底物 NEO 的最佳选择。这些发现为 MEC-AD 系统中高 OLR 蛋白的甲烷生成途径提供了理论见解，并为未来实际应用中处理高 OLR 蛋白废水提供了一种有效的方法。