Abstract：
OBJECTIVE: This paper aims to review the main sludge concentration methods used for SARS-CoV-2 detection in sewage sludge samples, discussing the main methods and sample volume related to increased viral load. In addition, we aim to evaluate the countries associated with increased positivity rates for SARS-CoV-2 in sludge samples.
METHODS: This systematic methodology was registered in PROSPERO and followed the PRISMA guidelines. The search was carried out in the SciELO, PubMed/MEDLINE, Lilacs, and Google Scholar databases in January-March 2022. Quantitative studies with conclusive results were included in this review. Concentration methods (polyethylene glycol (PEG), PEG + NaCl, gravity thickening, skimmed milk flocculation, ultrafiltration, filtration using charged filters, primary sedimentation, and anaerobic digestion), as well as detection methods (RTqPCR and reverse transcription droplet digital PCR assay) were evaluated in this review. The SPSS v23 software program was used for statistical analysis.
RESULTS: PEG (with or without NaCl addition) and gravity thickening were the most used sludge concentration methods to detect SARS-CoV-2. The main method associated with increased viral load (>2,02 × 10^4 copies/mL) was PEG + NaCl (p < 0.05, Mann-Whitney test). The average positivity rate for SARS-CoV-2 in sludge samples was 61 %, and a correlation was found between the sludge volume and the viral load (ro 0.559, p = 0.03, Spearman correlation).
CONCLUSIONS: The sludge volume may influence the SARS-CoV-2 load since the virus can adhere to solid particles in these samples. Other factors may be associated with SARS-CoV-2 load, including the methods used; especially PEG + NaCl may result in a high viral load detected in sludge, and may provide a suitable pH for SARS-CoV-2 recovery.
METHODS: This systematic methodology was registered in PROSPERO and followed the PRISMA guidelines. The search was carried out in the SciELO, PubMed/MEDLINE, Lilacs, and Google Scholar databases in January-March 2022. Quantitative studies with conclusive results were included in this review. Concentration methods (polyethylene glycol (PEG), PEG + NaCl, gravity thickening, skimmed milk flocculation, ultrafiltration, filtration using charged filters, primary sedimentation, and anaerobic digestion), as well as detection methods (RTqPCR and reverse transcription droplet digital PCR assay) were evaluated in this review. The SPSS v23 software program was used for statistical analysis.
RESULTS: PEG (with or without NaCl addition) and gravity thickening were the most used sludge concentration methods to detect SARS-CoV-2. The main method associated with increased viral load (>2,02 × 10^4 copies/mL) was PEG + NaCl (p < 0.05, Mann-Whitney test). The average positivity rate for SARS-CoV-2 in sludge samples was 61 %, and a correlation was found between the sludge volume and the viral load (ro 0.559, p = 0.03, Spearman correlation).
CONCLUSIONS: The sludge volume may influence the SARS-CoV-2 load since the virus can adhere to solid particles in these samples. Other factors may be associated with SARS-CoV-2 load, including the methods used; especially PEG + NaCl may result in a high viral load detected in sludge, and may provide a suitable pH for SARS-CoV-2 recovery.
摘要：
目的：本文旨在综述用于污水污泥样品中SARS-CoV-2检测的主要污泥浓缩方法，讨论了与病毒载量增加有关的主要方法和样本量。此外,我们的目标是评估与污泥样品中SARS-CoV-2阳性率增加相关的国家。
方法：该系统方法已在PROSPERO注册，并遵循PRISMA指南。搜索是在SciELO中进行的，PubMed/MEDLINE,丁香花,以及2022年1月至3月的GoogleScholar数据库。本综述包括具有结论性结果的定量研究。浓缩方法(聚乙二醇(PEG)，PEG+NaCl,重力增厚，脱脂乳絮凝,超滤,使用带电过滤器过滤，初级沉降,和厌氧消化)，以及检测方法（RTqPCR和逆转录液滴数字PCR）进行了综述。采用SPSSv23软件进行统计分析。
结果：PEG（添加或不添加NaCl）和重力浓缩是检测SARS-CoV-2的最常用的污泥浓缩方法。与病毒载量增加（>2,02×10^4拷贝/mL）相关的主要方法是PEG+NaCl（p<0.05，Mann-Whitney检验）。污泥样品中SARS-CoV-2的平均阳性率为61％，污泥体积与病毒载量之间存在相关性（ro0.559，p=0.03，Spearman相关性）。
结论：污泥体积可能会影响SARS-CoV-2负荷，因为病毒可以粘附在这些样品中的固体颗粒上。其他因素可能与SARS-CoV-2负荷有关，包括使用的方法;特别是PEG+NaCl可能导致在污泥中检测到高病毒载量，并且可以为SARS-CoV-2回收提供合适的pH。
方法：该系统方法已在PROSPERO注册，并遵循PRISMA指南。搜索是在SciELO中进行的，PubMed/MEDLINE,丁香花,以及2022年1月至3月的GoogleScholar数据库。本综述包括具有结论性结果的定量研究。浓缩方法(聚乙二醇(PEG)，PEG+NaCl,重力增厚，脱脂乳絮凝,超滤,使用带电过滤器过滤，初级沉降,和厌氧消化)，以及检测方法（RTqPCR和逆转录液滴数字PCR）进行了综述。采用SPSSv23软件进行统计分析。
结果：PEG（添加或不添加NaCl）和重力浓缩是检测SARS-CoV-2的最常用的污泥浓缩方法。与病毒载量增加（>2,02×10^4拷贝/mL）相关的主要方法是PEG+NaCl（p<0.05，Mann-Whitney检验）。污泥样品中SARS-CoV-2的平均阳性率为61％，污泥体积与病毒载量之间存在相关性（ro0.559，p=0.03，Spearman相关性）。
结论：污泥体积可能会影响SARS-CoV-2负荷，因为病毒可以粘附在这些样品中的固体颗粒上。其他因素可能与SARS-CoV-2负荷有关，包括使用的方法;特别是PEG+NaCl可能导致在污泥中检测到高病毒载量，并且可以为SARS-CoV-2回收提供合适的pH。
