Recycling sludge carbon sources via different iron-based activated PDS into denitrification systems for nitrogen removal: focusing on efficacy, community structure and molecular mechanism - Zhiying Lv; Hong You; Haoran Leng; Hao Sheng; Weirun Li; Feng Liu; Zhipeng Li; Jing Zhu; Guoyu Zhang (Bioresource Technology, 2026)