key: cord-330873-hwbdreul authors: Yang, Wan; Cai, Chen; Dai, Xiaohu title: The potential exposure and transmission risk of SARS-CoV-2 through sludge treatment and disposal date: 2020-07-07 journal: Resour Conserv Recycl DOI: 10.1016/j.resconrec.2020.105043 sha: doc_id: 330873 cord_uid: hwbdreul nan The coronavirus disease (COVID-19) is a novel acute pneumonia caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), and the outbreak has been declared to be a pandemic by World Health Organization (WHO). SARS-CoV-2 is a single-stranded, non-segmented RNA virus with an envelope structure. After infectious SARS-CoV-2 was isolated from COVID-19 patients' feces and urines, the corresponding RNA in the wastewater and sewage sludge was also observed (Randazzo et al., 2020) , implying the possibility of transmission of SARS-CoV-2 through the wastewater treatment plants (WWTP). In fact, the enveloped viruses have been proven to survive for days to months in the municipal wastewater system. Sewage sludge, the by-product of WWTPs, is also believed to be the reservoir of this new coronavirus due to the enrichment of 30%-50% of pollutants from sewage. The complex organic matters in the sludge could protect the pathogenic virus from inactivation. It was also reported that the virus HKU1 (i.e., human coronavirus) had been detected in sewage sludge with high abundance (Bibby and Peccia, 2013) . Therefore, it is imperative to understand the potential exposure and transmission risk of this virus in sludge for the sake of public health. The coronavirus spread may occur in specific procedures of the sludge treatment and disposal, and the most noteworthy way of virus transmission and exposure is the direct contact with sludge ( Figure 1 ). In the process of mechanical maintenance, transportation and routine sampling and detecting, workers or operators have high probabilities of being exposed to raw sludge, suggesting that the personal protective 3 equipment and regular disinfection are essential for the epidemic prevention. Furthermore, the inhalation of aerosol is another important exposure route that cannot be ignored. In many procedures of sludge treatment (e.g., biological treatment, sludge dewatering and mechanical agitation), shearing the liquid surface leads to the release of the pathogenic and toxic matrix from sludge into the air in the form of airborne particulate matter. It was found that SARS-CoV-2 could survive in aerosols and remain infectious for several hours (van Doremalen et al., 2020) , indicating the possibility of aerosol transmission. Last but not least, the potential ecological risks are also of great concern post the sludge disposal (e.g., land application). While limited evidence was found that sludge would play an essential role in SARS-CoV-2 transmission, there is still a need to understand the fate of coronaviruses outside the human host, including their persistence and inactivation mechanisms in 5 sludge, which would help to reveal their potential risks during sludge treatment and disposal. Most methods mainly aimed at the detection of enteric viruses, which is not suitable for enveloped viruses due to their vulnerable envelope structure. Also, the presence of natural inhibitors (humic acid, heavy metals, etc.) in sludge may have adverse effects on the gene amplification reaction of viruses, causing false-negative results. Therefore, it is necessary to develop the efficient extraction and detection methods of coronaviruses in sludge. Sludge is a complex mixture of various compounds, which would have effects on the survival and fate of the virus. While the microbial environment in sludge contributes to virus elimination via predation, antagonism and nutrition competition, the extracellular polymeric substances (EPS) may play an essential role in providing protection against the virus. Therefore, it is of considerable significance to explore the occurrence and distribution of coronavirus in sludge and to investigate the exposure and secondary transmission risk of virus in sludge. Although some scenarios have been put forward in the aqueous environment, the persistence in sludge and inactivation with exposure to disinfectants need to be further studied. It is also necessary to evaluate whether the existing sludge sanitation 6 technology would be valid during the epidemic, and to develop novel and efficient technique for the prevention and control of these infectious coronaviruses in sludge. ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Ecological Risk Aerosol Transmission Figure 1 The potential exposure and transmission risk of SARS-CoV-2 through sludge treatment and disposal Identification of Viral Pathogen Diversity in Sewage Sludge by SARS-CoV-2 RNA in wastewater anticipated COVID-19 occurrence in a low prevalence area Assessment of Recommendation for the Containment and Disinfection of Human Excreta in Cholera Treatment Centers Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1 Evaluation of the enterococci indicator in biosolids using culture-based and quantitative PCR assays This work was financially supported by the National Natural Science Foundation of China (NSFC) (Grants 52041003). The authors declare no competing financial interest.