Comprehensive analysis reveals the differentiated influential mechanism of degradable poly (ε-caprolactone) and polybutylene succinate microplastics on nitrogen transformation in aerobic granular sludge systems

•Exposure to 50 mg/L DMPs significantly inhibited the N transformations of AGS system.•PCL microplastics posed more pronounced negative effects on AGS compared to PBS.•DMPs led to excessive production of ROS and destruction of cytomembrane integrity.•DMPs deteriorated ETSA, enzyme activity and gene quantity related to N metabolism.•Mechanism of inhibited N removal performance induced by different DMPs was revealed.