School of Municipal and Environmental Engineering, Shandong Jianzhu University, 1000 Fengming Road, Jinan, 250101, China; Shandong Province Co-Innovation Center of Green Building, Jinan, 250101, China; Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao, 266237, China.
School of Municipal and Environmental Engineering, Shandong Jianzhu University, 1000 Fengming Road, Jinan, 250101, China; Shandong Province Co-Innovation Center of Green Building, Jinan, 250101, China.
J Environ Manage. 2020 May 15;262:110356. doi: 10.1016/j.jenvman.2020.110356. Epub 2020 Mar 3.
Anaerobic digestion, the principal method of stabilizing biosolids in wastewater treatment plants (WWTPs), can efficiently and largely attenuate the antibiotic resistances in biosludge. This study aims to investigate the effect of oxidative pretreatment with ultrasound irradiation combined with ozone (US/O) on the mesophilic and thermophilic anaerobic digestion (MAD and TAD) for the biosludge bearing trace fluoroquinolones contaminants-levofloxacin (LEVO) which was widely used in recent years. During the oxidation, the trace-level LEVO was almost completely degraded. The methanogenic activity in US/O pretreated TAD dosed 0.1 mg/L LEVO was much higher than those in single MAD and TAD, therefore leading to a remarkable increase in biogas production. The identification of levofloxacin intermediates during chemical degradation was analyzed using LCMS technique and the reaction pathway based on them was proposed. Hydroxyl radicals provided by US/O contributed to oxidative ring opening of LEVO as well as degradation of other biomacromolecules in the biosludge. Besides, the quinoline resistance genes-qnrA and qnrS declined significantly by 1-2 orders of magnitude in US/O-pretreated TAD, indicating that the active radicals produced by US/O oxidized and degraded LEVO and therefore inactivated the antibiotic resistant bacteria or genes in the biosolids. Meanwhile, the composition and structure of the microbial community altered and the diversity and richness of total bacterial and potential human pathogens decreased, the pattern of which was correlated with LEVO-resistant genes. Among the well-known AD-related phylum including Bacteroidetes, Firmicutes, Methanobacteria as well as Thermotogae which has been previously detected in TAD and performed organic hydrolysis and degradation, the potential LEVO-resistant bacteria were probably affiliated to Actinobacteria, Bacteroidetes, Proteobacteria, Thermotogae. This study revealed the contribution of US/O pretreatment to the anaerobic digestion in terms of ARGs reduction for trace-LEVO- exposed biosludge and could provide useful guidance for controlling the dissemination of ARB and ARGs in sewage sludge.
厌氧消化是污水处理厂（WWTPs）稳定生物固体的主要方法，可有效地大量衰减生物污泥中的抗生素抗性。本研究旨在研究超声辐射与臭氧联合氧化预处理（US/O）对含痕量氟喹诺酮污染物-左氧氟沙星（LEVO）的中温和高温厌氧消化（MAD 和 TAD）的影响，LEVO 近年来被广泛使用。在氧化过程中，痕量的 LEVO 几乎完全降解。在 US/O 预处理的 TAD 中添加 0.1mg/L LEVO 时，产甲烷活性明显高于单一 MAD 和 TAD，从而导致沼气产量显著增加。采用 LCMS 技术分析了左氧氟沙星化学降解过程中的中间产物，并提出了基于它们的反应途径。US/O 提供的羟基自由基有助于 LEVO 的氧化开环以及生物污泥中其他生物大分子的降解。此外，在 US/O 预处理的 TAD 中，喹诺酮抗性基因-qnrA 和 qnrS 显著下降了 1-2 个数量级，表明 US/O 产生的活性自由基氧化和降解了 LEVO，从而使生物污泥中的抗生素抗性细菌或基因失活。同时，微生物群落的组成和结构发生了变化，总细菌和潜在人类病原体的多样性和丰富度降低，其模式与 LEVO 抗性基因相关。在 TAD 中已检测到的众所周知的 AD 相关门，包括拟杆菌门、厚壁菌门、甲烷杆菌门和热变形菌门以及先前检测到的进行有机水解和降解的门，潜在的 LEVO 抗性细菌可能与放线菌门、拟杆菌门、变形菌门和热变形菌门有关。本研究揭示了 US/O 预处理对含痕量 LEVO 暴露的生物污泥厌氧消化的贡献，可为控制污水污泥中 ARB 和 ARGs 的传播提供有用的指导。
