Coupling micro-electric field into aerobic granular sludge system for sulfadiazine abatement: Performance, mechanism, toxicity, and microbial characteristics

[Display omitted] •Micro-electric field coupled AGS system was built.•Micro-electric field enhanced the granulation of AGS and the removal of toxicants.•The potential degradation products and pathways of SDZ were proposed.•The main function microbes in e-AGS system for SDZ degradation was revealed. The residual antibiotics in water has aroused ever-growing concern of people. Aerobic granular sludge (AGS) technology shows great application potential for removing toxic organics from wastewater due to its unique features. However, it is still hindered by some bottleneck problems, such as a long culture period and instability of granular sludge. Here, micro-electric field (MEF) coupled AGS (e-AGS) system was established to solve the problems. MEF significantly shortened the cultivation period of AGS (25 days in e-AGS vs. 30 days in control), which mainly related to the production of extracellular polymers. The granular sludge exposed to MEF exhibited a smaller size (3.4 mm), a more compact structure, and high removal rates for sulfadiazine (SDZ, 65 %), ammonia nitrogen (96.49 %), chemical oxygen demand (91.28 %), and total phosphorus (89.31 %). SDZ degradation intermediates and pathways in the e-AGS system were revealed. The eco-toxicity of the effluent was evaluated based on the eco-toxicity of SDZ transformation products. Microbes succession suggested that MEF functioned in a selective role for microorganisms’ growth. At the genus level, Acinetobacter, Bdellovibrio, Leadbetterella, and Aeromonas dominated the degradation of SDZ. This work provides an effective means for the enhancement of the AGS system to treat antibiotic-polluted water and makes provision for the application of AGS.