Waste sludge is a valuable resource for nitrogen recovery, while electro-fermentation system (EFS) can boost sludge fermentation. However, the simultaneous recovery of nitrogen nutrient during sludge treatment has not been achieved. Herein, we proposed a novel approach for sequential protein-ammonium recovery during sludge treatment by pretreatment-EFS. The results showed that 72.23 % of protein was recovered by alkaline-thermal pretreatment of dewatered sludge. The cascading EFS facilitated the ammonium recovery of 45−80 % in catholyte of pretreated dewatered sludge (EFS-TS) and raw waste sludge. The EFS-TS obtained the highest total chemical oxygen demand removal which increased by 6.39−14.53 % over anaerobic digestion. Metagenomics demonstrated that EFS attributed to the enrichment and interaction of electroactive, fermentative and nitrogen-fixing bacteria, which facilitated the organic degradation pathways, electron transfer, and nitrogen transformation. This study provides insights into syntrophic interaction between biofilm and suspension in the nutrient recovery electro-fermentation and presents a promising approach for processing sludge with full-form nitrogen recovery.

废弃污泥是氮回收的宝贵资源，而电发酵系统（EFS）可以促进污泥发酵。然而，污泥处理过程中氮养分的同步回收尚未实现。在此，我们提出了一种在污泥处理过程中通过预处理-EFS 连续回收蛋白-铵的新方法。结果表明，脱水污泥经碱热预处理后，蛋白质回收率为72.23%。级联 EFS 促进了预处理脱水污泥 (EFS-TS) 和原废污泥的阴极电解液中 45−80% 的铵回收率。EFS-TS 获得了最高的总化学需氧量去除率，比厌氧消化增加了 6.39−14.53%。宏基因组学表明，EFS 归因于电活性、发酵和固氮细菌的富集和相互作用，促进了有机降解途径、电子转移和氮转化。这项研究提供了对营养物回收电发酵中生物膜和悬浮液之间互养相互作用的见解，并提出了一种有前景的全氮回收处理污泥的方法。