Viruses in disposed sludges may pose potential risks to both environmental ecosystems and humans. In this study, sludges were collected along the entire anaerobic sludge digestion process including anaerobic digestion and 3 related treatment steps (i.e., primary dewatering process, thermal hydrolysis, and final dewatering process after anaerobic digestion) and analyzed using viromic approaches, aiming to evaluate the effectiveness of anaerobic digestion in removing viruses from the sludges. Unclassified viruses were consistently predominant in all sludges, followed by prokaryotic and eukaryotic viral families. The total levels of prokaryotic viruses in sludges ranged from 1.3 × 10 to 5.3 × 10 virus-like particles gram wet sludge (VLPs/g), with being preponderant. By contrast, the total levels of eukaryotic viruses were lower (3.7 × 10 to 1.0 × 10 VLPs/g), and were much more abundant than others. Undergoing all treatment steps, the levels of eukaryotic viruses were reduced by half from the sludges whereas that of prokaryotic viruses was increased by approximately 2.3 times. Thermal hydrolysis step dramatically reduced the level of viruses in the sludge, but the following anaerobic digestion step was an important process for the reconstruction of viral communities. Viruses in the sludges could infect a wide taxonomic range of microbes, mainly including Firmicutes, Bacteroidetes, Proteobacteria, etc. A large variety of auxiliary metabolic genes carried by viruses in the sludges were relevant to the cycling of carbon, sulfur, phosphorus and nitrogen. Overall, it is suggested that the sludge treatment process must be improved for effectively eliminating viruses in the sludges after anaerobic digestion step.

中文翻译：

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使用病毒组学方法揭示厌氧消化过程对活性污泥中病毒群落的影响


处置污泥中的病毒可能对环境生态系统和人类构成潜在风险。本研究收集了整个厌氧污泥消化过程中的污泥，包括厌氧消化和3个相关处理步骤（即初级脱水过程、热水解过程和厌氧消化后的最终脱水过程），并使用病毒学方法进行分析，旨在评估厌氧消化去除污泥中病毒的有效性。未分类的病毒在所有污泥中始终占主导地位，其次是原核和真核病毒家族。污泥中原核病毒总量为1.3×10~5.3×10病毒样颗粒克湿污泥（VLPs/g），以占优势。相比之下，真核病毒的总水平较低（3.7 × 10 至 1.0 × 10 VLP/g），并且比其他病毒丰富得多。经过所有处理步骤，污泥中真核病毒的水平减少了一半，而原核病毒的水平增加了约 2.3 倍。热水解步骤极大地降低了污泥中的病毒水平，但随后的厌氧消化步骤是重建病毒群落的重要过程。污泥中的病毒可感染多种微生物，主要包括厚壁菌门、拟杆菌门、变形菌门等。污泥中的病毒携带多种辅助代谢基因，与碳、硫、磷、氮的循环有关。总体而言，建议必须改进污泥处理工艺，以有效消除厌氧消化步骤后污泥中的病毒。