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Petrochemical wastewater contains inhibitory compounds such as aromatics that are toxic to microorganisms during biological treatment. The compact and layered structure and the high amount of extracellular polymeric substances (EPS) in aerobic granular sludge (AGS) can contribute to protecting microorganisms from the harsh environment. This study evaluated the changes in the granule properties, pollutants removal, microbial metabolic potential and molecular microbial characteristics of the AGS process for petrochemical wastewater treatment. Granules treating petrochemical wastewater had a higher SVI 30 /SVI 5 value (0.94) than that treating synthetic wastewater. An increase in bioactivity and EPS secretion with higher bio-polymer composition, specifically the functional groups such as hydroxyl, alkoxy and amino in protein, was observed, which promoted biomass aggregation. The granules also had more than 2-fold higher specific oxygen utilization rate. The AGS-SBR process obtained an average COD removal of 93% during petrochemical wastewater treatment and an effluent bCOD of below 1 mg L−1. No obvious inhibition of nitrification and denitrification activity was observed in the processes attributed to the layered structure of AGS. The average effluent NH 4 +-N of 5.0 mg L−1 was obtained and TN removal efficiencies of over 80.0% was achieved. Molecular microbial analysis showed that abundant functional genera Stenotrophomonas and Pseudoxanthomonas contributed to the degradation of aromatics and other petroleum organic pollutants. They were enriched with the variation of group behavior while metabolisms of amino acids and carboxylic acids by the relevant functional genera (e.g., Cytophagia) were significantly inhibited. The enrichment of Flavobacterium and Thermomonas promoted nitrification and denitrification, respectively. This research revealed the rapid start-up, enhanced granule structural strength, high inhibition resistance and considerable performance of AGS-SBR for petrochemical wastewater treatment. [Display omitted] • AGS kept stability and high efficiency in petrochemical wastewater treatment. • Average COD removal of 93% and TN removal of over 80% were achieved. • High SVI 30 /SVI 5 and bioactivity with increased EPS secretion were observed. • Stenotrophomonas and Pseudoxanthomonas contributed to petroleum organic degradation. • AGS process showed significant potential for petrochemical wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel heterogeneous Fenton-like process driven by visible light is proposed. • Reactivity is strongly enhanced without the use of reducing agents and TiO 2 modification. • Fe(III) reduction for PS activation can be accomplished via LMCT in organic-TiO 2 -Fe(III). • It can be operated at low iron dosage and neutral conditions against Fenton system. • The excellent and long-lasting catalytic performance is mediated via synergistic effect. Efficient transformation of Fe(III) to Fe(II) enhances the efficiency of persulfate-based Fenton-like process (e.g., Fe(II)-PS system). Here, we developed a novel heterogeneous Fenton-like system driven by visible light (organic-Fe(III)-PS-TiO 2 -Vis) for effective reduction of Fe(III), activation of PS and degradation of organic pollutants without the need for external reducing agents or modifications in TiO 2. The visible light-induced ligand-to-metal (organic-to-TiO 2) charge transfer (LMCT) remarkably boosting Fe(III) reduction to increase reactive oxygen species (ROS) via PS activation, and further enhanced the self-degradation and mineralization of various organics, including phenolics (bisphenol A and phenol), antibiotics (ibuprofen and tetracycline), and dyes (methylene bule and rhodamine B). Compared with traditional Fe(II)-PS and Fe(II)–H 2 O 2 systems, the organic-Fe(III)-PS-TiO 2 -Vis process requires a lower dosage of iron salt. The effective pH range has been broadened to neutral conditions due to effective prevention of Fe(III) precipitation and rapid circulation of Fe(III)/Fe(II). The comprehensive mechanistic study indicated that a synergistic effect was generated via Fe(III) reduction, PS activation, ROS generation and organic decomposition, resulting in sustainable and excellent catalytic performance of this novel Fenton-like process. Further, the results of cycling experiments and tests involving real industrial wastewater highlight the enormous potential of the proposed LMCT-mediated heterogeneous Fenton-like process in environmental remediation. [ABSTRACT FROM AUTHOR]