key: cord-0959912-ui6aj2jq
authors: Meng, Xianghao; Wang, Xuye; Meng, Shujuan; Wang, Ying; Liu, Hongju; Liang, Dawei; Fan, Wenhong; Min, Hongping; Huang, Wenhai; Chen, Anming; Zhu, Haijun; Peng, Guanping; Liu, Jun; Qiu, Zhenhuan; Wang, Tao; Yang, Linyan; Wei, Yuan; Huo, Peishu; Zhang, Dayi; Liu, Yu
title: A Global Overview of SARS-CoV-2 in Wastewater: Detection, Treatment, and Prevention
date: 2021-09-12
journal: ACS ES T Water
DOI: 10.1021/acsestwater.1c00146
sha: 857050f4eae6c922e43d0c15ba5571a3f02e9f4d
doc_id: 959912
cord_uid: ui6aj2jq

[Image: see text] A novel coronavirus (SARS-CoV-2) causing corona virus disease 2019 (COVID-19) has attracted global attention due to its highly infectious and pathogenic properties. Most of current studies focus on aerosols released from infected individuals, but the presence of SARS-CoV-2 in wastewater also should be examined. In this review, we used bibliometrics to statistically evaluate the importance of water-related issues in the context of COVID-19. The results show that the levels and transmission possibilities of SARS-CoV-2 in wastewater are the main concerns, followed by potential secondary pollution by the intensive use of disinfectants, sludge disposal, and the personal safety of workers. The presence of SARS-CoV-2 in wastewater requires more attention during the COVID-19 pandemic. Thus, the most effective techniques, i.e., wastewater-based epidemiology and quantitative microbial risk assessment, for virus surveillance in wastewater are systematically analyzed. We further explicitly review and analyze the successful operation of a sewage treatment plant in Huoshenshan Hospital in China as an example and reference for other sewage treatment systems to properly ensure discharge safety and tackle the COVID-19 pandemic. This review offers deeper insight into the prevention and control of SARS-CoV-2 and similar viruses in the post-COVID-19 era from a wastewater perspective.

The outbreak of coronavirus infectious disease 2019 is caused by a novel coronavirus (SARS-CoV-2), resulting in symptoms of coughing, sneezing, etc. 1,2 As a single-stranded RNA virus, SARS-CoV-2 has caused an increasing number infections because of its high transmissibility. 3 The influenced countries have taken emergency measures to minimize the spread of SARS-CoV-2, which has become a hot topic around the world. 4, 5 Researches are focusing on the monitoring of SARS-CoV-2 in water, wastewater, sludge, and air and on surfaces to assess the risk of contracting the virus from contaminated environments. 6, 7 People have paid a great deal of attention to the spread of SARS-CoV-2 in aerosols, and the possibility of SARS-CoV-2 being spread in wastewater cannot be ignored. 8, 9 Bhatt et al. summarized the presence of SARS-CoV-2 in wastewater, showing substantial evidence of the existence of SARS-CoV-2 RNA and other pathogenic bacteria in wastewater. 10, 11 SARS-CoV-2 RNA may be released from COVID-19 patients into wastewater 12 and subsequently enter the sewage pipe networks in hospitals or communities, although no confirmed cases from wastewater and fecal−oral transmission have yet been reported. 13−15 During the COVID-19 pandemic, sewage treatment plants face more serious threats from emerging contaminants, including a variety of disinfectants, antibiotics, drugs, and viruses, raising new challenges for wastewater treatment management. 16 The serious threats posed by the fecal−oral route are the main concern for wastewater during the outbreak of COVID-19, and more problems arise from water contaminated by the coronavirus. 17 Theoretically, potential routes of transmission of the virus to humans include directly touching contaminated surface water or groundwater, bathing or swimming in contaminated water, and eating contaminated seafoods or crops in contaminated soils. 18− 20 We used bibliometrics in this study to assess the recent research highlights of this topic and gain a more comprehensive understanding of the presence and spillover of SARS-CoV-2 in water environments. Commonly used surveillance methods like wastewater-based epidemiology (WBE) and quantitative microbial risk assessment (QMRA) are systematically reviewed and analyzed to provide insights into their proper application during the COVID-19 pandemic. Subsequently, the combination of WBE and QMRA is proposed for water safety management in the COVID-19 and post-COVID-19 era. Lastly, the successful operation of sewage treatment facilities and the presence of SARS-CoV-2 in different treatment sectors in Huoshenshan Hospital in China are explicitly discussed to offer a reference for other sewage treatment systems facing the challenges of treating SARS-CoV-2-containing wastewater during the COVID-19 pandemic.

As a widely accepted method for quantifying and analyzing big data by keyword retrieval, bibliometrics offers a good opportunity to carry out a comprehensive study of scientific topics or subjects. 21, 22 Here, we use bibliometrics to visualize the hot points related to coronavirus and discuss the future research trends. The keywords "coronavirus" and "water" were chosen for a search of all literature in the Web of Science on December 31, 2020, and the publication date was set from 2020 without language restrictions. In total, 296 articles were retrieved, and 254 papers were finally selected for further analysis after repetitive and irrelevant articles had been screened out. The "Analytical Search Results tool" was used to analyze these articles, identifying countries and regions that paid a great deal of attention to water-related concerns caused by the coronavirus. WBE and QMRA, as important methods for epidemic surveillance and prevention, were widely applied in the fight against COVID-19. 23−25 They were then both used as the keywords for a search with the same retrieval method to provide insights into their principles and recent applications. All of these papers were thoroughly read and scientifically analyzed in detail.

The number of articles with the keywords of "coronavirus" and "water" in the Web of Science from 2011 to 2020 is illustrated in Figure 1a . It remained at a low level (3−10 articles per year) from 2011 to 2019, and a dramatic increase was found in 2020 when 254 articles were retrieved. Obviously, the COVID-19 pandemic has attracted significant attention to the risks and safety management of water environments. Figure 1b shows the country-based distribution of the 254 retrieved articles. The United States and China together contributed to ∼50% of the relevant publications, indicating that the researchers from these two countries participated most in the investigation of the impacts of coronaviruses on water environments. In addition, the most productive journals (e.g., Science of the Total Environment and International Journal of Environmental Research and Public Health) are closely linked to the "environmental" area , hinting that more attention is being paid to the potential impacts of the coronavirus on the environment and human health ( Figure 1c ).

As tools for monitoring pathogens, WBE ( Figure 2a ) and QMRA (Figure 2b ) have been widely applied for wastewater surveillance and become popular. Considering the requirements of sewage management and monitoring, WBE and QMRA can rapidly detect viruses in the sewage and establish a specific diffusion model to support the epidemiological study of infectious diseases. 23, 26 As shown in Figure 2 , WBE-related publications have significantly grown in 2020, whereas the number articles addressing QMRA has remained relatively stable. This indicates that researchers have recognized the important roles of WBE in SARS-CoV-2 surveillance in wastewater. Although the role of QMRA cannot be denied in the analysis and quantification of harmful microorganisms, including viruses, viral load is normally small and challenges the assessment. Therefore, current QMRA usually optimizes the parameters and assess the risks on the basis of mathematical models (Table 2 ). In addition, application of ACS ES&T Water pubs.acs.org/estwater Review QMRA focuses more on the microbiological risk assessment but lacks a successful case analysis in sewage. 25, 27 Accordingly, WBE is more recommended for epidemiological studies of infectious diseases rather than QMRA in environmental research.

FOR CONTROLLING CORONAVIRUSES 4.1. Impacts of SARS-CoV-2 on the Utilization of Water Resources. Water resources are critical for human life and regional socioeconomic health. 28,29 However, the outbreak of the COVID-19 pandemic increases the risk of water pathogenic contamination and poses a challenge for water utilization. For the cities with superior water resources, often accompanied by high population densities, both water shortage and the possibility of viral transmission increase during the pandemic. 12 More seriously, the regions with limited water resources may be troubled by more severe problems, including water pollution, poor sanitation, a lack of clean water, etc. 30, 31 The process of fetching water resources (such as the process of queuing or the contact of water containers) or washing with water resources that cannot meet the World Health Organization's sanitation standards will bring a greater risk of cross-infection. 32, 33 In addition, countries and regions with water scarcity are more likely to use wastewater for irrigation, which might increase the likelihood of accumulation of the virus in crops or soils. 34, 35 These potential risks in water environments necessitate a systematic review of the current technologies for monitoring and controlling viruses in water and wastewater.

4.2. Persistence and Transmission of SARS-CoV-2 in Water Environments. SARS-CoV-2 causes diarrhea and hampers the gastrointestinal function of humans. 36 A large number of viruses in excreta may be discharged into the municipal sewage network and remain active in the sewage for a prolonged period of time, posing a risk of exposure to operators. 37, 38 During the COVIP-19 pandemic, SARS-CoV-2 genetic materials were widely detected in fecal wastewater. 39−41 More precisely, septic tanks for wastewater (especially hospital wastewater) contain large amounts of fecal debris and suspended solids, which poses significant risks by releasing viruses from these organic solids. 42 Considering the fact that 1.8 billion people worldwide still use cleaned fecalcontaminated water as drinking water, it is very important to take this transmission route into account. 12, 43 Furthermore, it has been found that most fecally transmitted viruses are highly persistent in the aquatic environment. SARS-CoV-2 is an enveloped virus and more likely to be inactivated than non-enveloped viruses. 44−46 However, enveloped viruses have similar persistent rates compared to those of nonenveloped ones in dark water environments as determined by viral decay constants. 47 Additionally, the persistence of SARS-CoV-2 RNA is significantly longer than that of other closely related coronaviruses. For example, SARS-CoV-2 RNA is present in wastewater for 7 days, longer than human coronavirus (HCoV) 229E (∼2 days). 47, 48 The long persistence of SARS-CoV-2 in water leads to the nonneglectable significance of its potential transmission in water environments. Researchers have found that the time that SARS-CoV-2 persists is different in wastewater (>7 days) and groundwater (>10 weeks), indicating that SARS-CoV-2 is subject to environmental factors. 49 Additionally, enveloped SARS-CoV-2 possibly has stronger mobility in the underground aquifer systems and viral adsorption on soil is crucially affected by pH, ion strength, and soil properties, posing challenges in virus detection and control. 50 Consequently, the persistence, transmission, and risks of SARS-CoV-2 in wastewater are affected by many factors, including viral load, viral activity, viral survival time, water type, and organic or microbial matter in water. 44, 51, 52 Correspondingly, pertinent evaluation and detection methods should be adopted according to these real-world scenario, to ensure the accuracy and effectiveness of water surveillance. 53 4.3. Inactivation of SARS-CoV-2 in Water Environments. SARS-CoV-2 can remain stable in feces and wastewater for a long time at low temperatures. 54 To prevent the infectivity of SARS-CoV-2, virus inactivation is imperative. The main methods of inactivating SARS-CoV-2 in a wastewater environment include the following. (1) SARS-CoV-2 is more vulnerable to ultraviolet (UV) (254 nm) exposure than is non-enveloped virus, and the exposure time for effective inactivation is just several seconds. 55 (2) The thermal effect for the inactivation of SARS-CoV-2 is confirmed effectively at 70°C in 5.7 min. 49 (3) Chemical disinfection quenched viral infectivity within a short exposure time as the most effective and economical solution. 56 Thus, a large number of disinfectants (chlorine disinfectants, hypochlorous acid, ozone, etc.) have been applied to inactivate SARS-CoV-2 in wastewater. 57−60 At present, chlorine disinfectants are most widely used, as free chlorine could effectively inactivate SARS- CoV-2 by destroying the proteins on its envelope. 56 Despite the rapid response around the world, SARS-CoV-2 continues to show a pandemic trend due to the shortage of disinfectants. Extensive efforts have been devoted to developing new disinfectants or disinfection alternatives for the effective control of SARS-CoV-2. 11, 61, 62 Unfortunately, the overuse of disinfectants may cause the entrance of the disinfectants into the city sewer network or surrounding water bodies through rainwater or wastewater, which may lead to an accumulation of disinfectants in surface waters during the outbreaks. This would present an emerging problem with a serious concern about the disinfection byproducts (DBPs). Methods for the accurate and swift determination of DBPs should be explored to reduce their risks to human health. 63 4.4. Surveillance and Assessment of SARS-CoV-2. Infectious diseases caused by SARS-CoV-2 and other pathogens have become one of the main threats to public health. Efficient monitoring of viral transmission is critical for the control and prevention of infectious diseases. 64 Although SARS-CoV-2 is considered as a respiratory virus, it also leads to intestinal infections and can be detected in feces and wastewater. 65, 66 As a result, there is growing concern about the transmission of SARS-CoV-2 in water environments. In particular, the greatest risk arises in wastewater discharged from communities where COVID-19 patients, asymptomatic patients, and medical staff are concentrated. 67, 68 It is reported that the presence of coronaviruses in wastewater can be used to qualitatively and quantitatively evaluate the viral load in communities. 24 To meet the needs of virus surveillance in wastewater, cost-effective and real-time monitoring protocols should be proposed. WBE, which can provide comprehensive assessments of the viral load in water environments, has been rapidly developed. 64 In addition, as an optimized protocol for SARS-CoV-2 assessment, the quantitative microbial risk assessment is also limited for exploring a modeling-based approach. As a consequence, standardized information about QMRA is summarized in a table to obtain an implementation scheme of risk assessments from previous studies.

4.4.1. Application of WBE during the COVID-19 Outbreak. Waterborne viruses are the main cause of many diseases. They can be ingested through contaminated drinking water or food, inhaled through droplets or aerosols, or contagiously injested through contact mucosa or wounds, finally leading to infection. As the wastewater environment is reported to shield SARS-CoV-2 over 7 days due to the rich organic matter, 49 the presence of SARS-CoV-2 RNA in wastewater or soil might pose remarkable risks to the surroundings. WBE is a method for analyzing the concentrations of target substances in the sewage of a specific area and then assessing its consumption within the region. 69 It was first applied in the monitoring of illicit drugs since being introduced in 2001. 70−72 Recently, researchers proposed WBE as a strong surveillance tool for monitoring waterborne viruses (such as osteomyelitis virus) and have achieved excellent performance. 73 In tackling COVID-19 pneumonia, it is crucial to detect SARS-CoV-2 and other viruses in water, especially wastewater environments, for effective prevention and control. In particular, the existence of asymptomatic patients carrying SARS-CoV-2 necessitates wider detection. By analyzing SARS-CoV-2 RNA in wastewater, WBE can qualitatively and quantitatively evaluate the health status of residents within a certain area. 74, 75 The introduction of WBE can identify viruses that exist in feces and sewage even when local residents show mild or no symptoms, 76 which might serve as an early warning system during the COVID-19 pandemic. Meanwhile, WBE can work as an tool for long-term surveillance of not only emerging but also re-emerging viruses in a community. 23 As shown in Table 1 , the spatial and temporal accuracy of sampling should be improved for WBE, which can help in confirming the expected critical pathways. 77 In addition, the collection and concentration methods are important in WBE to provide the exact data for viral load evaluation.

Recently, a WBE-based building sewage monitoring system was reported and successfully identified nine potential COVID-19 patients carrying SARS-CoV-2 in Hong Kong. 78 During the entire wastewater monitoring process, they paid more attention to the sampling location, time, and frequency. First, the sampling point should be carefully chosen to locate the specific building clearly. Second, the sampling time is a key factor in WBE because appropriate sampling after discharge of feces can ensure a sufficient viral titer. Thus, the sampling time was 8:00 to 11:00 in the morning, and four samples were collected at hourly intervals. Subsequently, the 12 samples were mixed to be employed as a representative sample. Lastly, virus concentration and extraction are crucial to improve the accuracy of the results. In addition, the support and cooperation from government departments are significant to the success of WBE. As mentioned above, the application of WBE in Hong Kong successfully helped in the identification of COVID-19 patients and prevention of the spread of SARS-CoV-2. This sewage monitoring system for buildings developed by the University of Hong Kong offered an excellent example to fight against COVID-19 with the aid of WBE and imply virus control in water environments. Accordingly, WBE is recommended as an initial warning tool, which can contribute to the diagnosis of COVID-19 patients and the measures for quick response strategies. 46,83−85 4.4.2. Effective Risk Assessment of QMRA. Microbial risk assessment is another method for risk analysis to protect public health. QMRA is a process for identifying and quantifying the adverse effects of exposure to certain microorganisms on human health by using the established scientific data and appropriate experimental methods, eventually providing a description of the risk characteristic. 86 It mainly includes risk assessment, risk management, and risk information. On the basis of scientific evaluation, QMRA carries out hazard identification, hazard characterization, exposure assessment, and risk characterization. 87 QMRA is a valuable tool for supporting water safety plans and could be used to assess human health risks associated with exposure to pathogens in different environmental matrices. 88, 89 Therefore, QMRA is suitable for addressing the following questions raised by the COVID-19 pandemic: (1) to identify the risks of SARS-CoV-2 transmission in different wastewaters by determining the diffusion mode and volatilization rate, (2) As predicted by many experts, the COVID-19 will last irregularly or seasonally for a long period, and SARS-CoV-2 is very likely to coexist with human beings. 97 Therefore, establishing the immunological barrier to SARS-CoV-2 is essential. At present, all countries around the world are actively developing vaccines against COVID-19 for herd immunity, the threshold of which can be achieved only with a high vaccination rate of 60−70% of the population. Some experts have alleged that herd immunity to COVID-19 is probably impossible. 98 Accordingly, before herd immunity can be achieved, SARS-CoV-2 surveillance in water environments is significant in preventing the wide outbreak of the COVID-19 pandemic. WBE can be employed to monitor the spasmodic infection cases in real time. With the expected immunization effect, the application of WBE in the future will be different from the patterns we used now, e.g., lower sampling frequency with the improvement in monitoring sensitivity. In addition to the successful WBE case qualitatively discovering potential patients as described above in Hong Kong, 99 future WBE should provide a quantitative assessment of risks in different regions instead of only the numbers of patients and predict the trends of the COVID-19 outbreak. Furthermore, QMRA can establish the relationships between influential factors and the degree of infection based on a small number of spasmodic cases, providing an effective warning. 89, 93 The interactive risk assessment model obtained by QMRA will be used to trace the source of infection cases with a posteriori probability. Treatment Plants. SARS-CoV-2 RNA has been widely identified in fecal particles and is protected by the surrounding organic matter after being discharged into wastewater. 67 Without sufficient disinfectants, these viruses may again be released into the aqueous water. As a result, the test result can still be positive regardless of whether water has been disinfected. In addition, the overdose of disinfectants can cause the secondary contamination problem in which a large number of DBPs (e.g., chloroform, chlorite, etc.) accumulate in wastewater and pose ecological risks. 67, 100, 101 For example, the residual chlorine can affect the persistence of ecological morphology and damage the respiratory systems or organs. 102 Chlorine-containing disinfectants may even react with organic substances in water to produce BPPs, which pose more serious risks to human health and the ecological environment. 103 Therefore, the use of chlorine-containing disinfectants should be reasonably regulated and substitute disinfectants require further development.

During the COVID-19 outbreak, sewage treatment plants face the problem of sludge disposal. 104 Suspended particles from SARS-CoV-2-containing sludge might be produced and aerosolized into the air during the sludge treatment process. 105 In addition, after being directly transported to a land use area, sludge can release SARS-CoV-2 into surrounding soils, which might maintain infectivity for at least 10 weeks and even cause groundwater pollution. 106, 107 Currently, cement kiln incineration is the most common way to treat sludge from urban sewage treatment plants. 37 During the COVID-19 pandemic, there has been a large gap in sludge disposal due to the suspension of some cement production enterprises. 108 Certainly, sewage treatment plants, as the most important basic facilities in cities, are greatly significant for protecting the water environment and public health. Therefore, the operation of the sewage treatment facilities needs to be standardized, and ACS ES&T Water pubs.acs.org/estwater Review this review comprehensively discusses the details in Huoshenshan Hospital.

At the beginning of the COVID-19 pandemic, China took timely and effective measures to prevent and control the initial spread in Wuhan. 12,109−111 Two specialized emergency hospitals for COVID-19 patients were established in China (Leishenshan Hospital and Huoshenshan Hospital) and received more than 5000 COVID-19 patients. Strict treatment measures were employed to prevent SARS-CoV-2 spillover or spread into the surrounding environment, including wastewater treatment processes. As the two hospitals have the same design capacity of the sewage treatment plant, the design and operation of the facilities for wastewater treatment in Huoshenshan Hospital are representative and described in detail to provide an example and reference for other operational problems of medical wastewater, which is also of great significance for the protection of public health. 112 The building area of Huoshenshan Hospital is 33900 m 2 , and a total of 1000 beds are designed for COVID-19 patients. The drainage pipe network collecting rainwater, sewage from a contaminated area (patient wards), and sewage from a clean area (staff living areas) separately is properly designed and illustrated in panels a and c of Figure 3 . To meet landfill standards, Huoshenshan Hospital uses the high-density polyethylene (HPDE) and the basement adopts impervious "composite geomembrane". Therefore, there is minimal impact or risk of medical activities on groundwater. The treatment process adopted by the Huoshenshan Hospital sewage treatment station is shown in Figure 3b .

The main task of this water treatment station in Huoshenshan Hospital is to disinfect SARS-CoV-2 viruses and ensure the safety of discharged water. Wastewater is first treated in a presterilized contact pool, which has a designed scale of 40 m 3 /h with two groups, an average hydraulic retention time (HRT) of 3 h, and a maximum HRT of ≤5 h for each group. As wastewater contains a large amount of feces debris responsible for virus release, the water treatment station separates suspended solids from the wastewater in the predisinfection tank to avoid the long-term presence of feces particles and virus release. 67 Chlorine dioxide and sodium hypochlorite are used as the disinfectants for wastewater, and the designed dosage is 40 mg/L (in terms of residual chlorine). Wastewater is then transferred into five reinforced fiberglass septic tanks with an effective volume of 100 m 3 to preprecipitate suspended solids. Simultaneously, partial dichlorination is employed in the septic tanks to reduce the stress of regulating the reservoir. Effluent from the septic tank is raised to the regulating reservoir by lifting pumps. Subsequently, the wastewater is treated in the moving bed biofilm reactors (MBBR), which is designed in parallel with an HRT of 5.6 h. Sludge from MBBR is separated in the coagulation and sedimentation tanks, stored in the auxiliary sludge concentration tank, and then treated in the sludge thickener. A sodium hypochlorite solution is added to the sludge thickener by the metering pump for the sludge deactivation. After gravity concentration in a concentration tank, the supernatant is discharged back into the regulating reservoir. The concentrated sludge is transferred into the spiral dewatering machine by the sludge screw pump. When the dewatering machine is started, cationic polyacrylamide (CPAM) is added for conditioning and sludge dehydration. The filtrate from the dewatering machine is pumped into the regulating reservoir again.

The designed flow rate of secondary disinfection is 40 m 3 /h for two groups, with an average residence time of 3 h, a maximum residence time of ≤5 h, and a unit chlorine dosage of 25 mg/L (in terms of available chlorine). Meanwhile, the design of disinfection equipment possesses a certain surplus capacity, which can be adjusted flexibly according to the actual operational situation of the treatment station to fully guarantee the disinfection effects.

The waste gas from the sewage treatment station and patient wards (negative pressure) in Huoshenshan Hospital may contain SARS-CoV-2. 113 Additionally, hydrogen sulfide, ammonia methanethiol, burning soot sulfur, and other toxic waste gases will be generated during the sewage treatment process and the incineration of medical waste. Accordingly, the waste gas requires a careful treatment for avoiding potential risks to the medical staffs and secondary air pollution in the surrounding area. The waste gas from the sewage treatment sector is discharged after the combination of activated carbon adsorption and UV photolysis oxidation. The waste gas from medical waste incineration is first cooled and then treated by desulfurization and deacidification. Afterward, the waste gas is collected using a polyether (PE) microporous dust collector and finally adsorbed by activated carbon. Via the control of the air volume in and out of the wards, pressure gradients are formed between different areas to ensure appropriate air flow from the clean area to the contaminated area. Finally, the ACS ES&T Water pubs.acs.org/estwater Review indoor air pressure is kept 15 Pa lower than outdoors. The exhaust duct is equipped with an antivirus device to sterilize the discharged air to meet the requirements of environmental protection and COVID-19 prevention. The design and operation of the Huoshenshan Hospital exhaust gas treatment system can provide a reference for the exhaust gas treatment of emergency respiratory hospitals for infectious diseases. During the operation of Huoshenshan Hospital, the residual chlorine in effluent and other wastewater quality parameters were monitored in real time to ensure the treatment efficiency and safety of the sewage treatment system. As shown in Figure  4a , the daily treated wastewater did not exceed the maximum designed treatment capacity (1920 m 3 /day). However, the wastewater flux was significantly affected by the rainfall when it exceeded 20 mm a day (February 26 and March 29). As illustrated in Figure 4b , the levels of residual chlorines in the effluent met the standard. The dilution effect of rainwater led to a decrease in the level of of organic matter in influent and caused the carbon level to be insufficient. Thus, the COD removal efficiency in MBBR was decreased.

The presence of SARS-CoV-2 in the sewage treatment system (wastewater, soil, and aerosol) of Huoshenshan Hospital is illustrated in Figure 5 . 114 Among 10 wastewater, three aerosol, and two soil samples collected from all reactors (Figure 3b) , three wastewater samples, one aerosol sample, and one soil sample were positive for SARS-CoV-2. SARS-CoV-2 levels in the first regulating reservoir, MBBR, and sedimentation tank were 633, 505, and 2208 copies/L, respectively. No SARS-CoV-2 was detected in effluents after disinfection, indicating that complete disinfection is greatly important for removing SARS-CoV-2 in wastewater and securing discharge safety. As for aerosol samples, SARS-CoV-2 RNA was detected only in the septic tank (603 copies/m 3 ), suggesting that aerosol SARS-CoV-2 mainly came from the aerosolized droplets from the feces debris of the COVID-19 patients. The soil samples collected from 2 m distance to the first regulating reservoir contained a significant level of SARS-CoV-2 RNA (550 copies/g). Notably, SARS-CoV-2 was not detected in surrounding aerosols and soils of Wuchang Cabin Hospital because of the temporary enclosed system, which effectively prevented the spread of SARS-CoV-2. 114 It is suggested that the appropriate sealing of the wastewater treatment system may prevent the transmission of SARS-CoV-2.

Hand hygiene and ocular protection are critical for preventing COVID-19 cases among staff in sewage treatment plants. 115−117 It is most important to have sufficient COVID-19 personal protective equipment during the operation and maintenance period. For staffs, daily double temperature measurement and regular disinfection should be strictly carried out to ensure their safety. Centralized medical observation for working staff should be arranged after work to ensure no safety accidents.

Although there has been no confirmed case of COVID-19 from SARS-CoV-2 transmission in wastewater to date, a significant number of studies have demonstrated that water safety is a major hidden danger in the prevention and control of the COVID-19 pandemic. Previous studies have focused on the detection of SARS-CoV-2 in wastewater, and the widely accepted methods are WBE and QMRA. From the comprehensive analysis in this review, WBE is the most reliable surveillance method tackling the COVID-19 for its rapid response and thus should be further developed and widely applied. Supplementarily, QMRA provides a strategy for assessing human health risks associated with exposure to pathogens in different environmental matrices. The successful operation of Huoshenshan Hospital helps the successful prevention and control of COVID-19 in China and also provides references for the operation and management of sewage treatment systems around the world for the post-COVID-19 era. 

The authors declare no competing financial interest.

This work was financially supported by National Natural Science Foundation of China Grants 51808019, 52091544, and 42041003.

The architecture of SARS-CoV-2 transcriptome

Can we migrate COVID-19 spreading risk? Front

Characteristics of SARS-CoV-2 and COVID-19

COVID-19 pandemic and its positive impacts on environment: an updated review

Synanthropic rodents as virus reservoirs and transmitters. Revista da Sociedade Brasileira de Medicina Tropical

Detection and survival of SARS-coronavirus in human stool, urine, wastewater and sludge

Investigation of hospital indoor air quality for the presence of SARS-Cov-2

Air and surface contamination in non-health care settings among 641 environmental specimens of 39 COVID-19 cases

COVID-19: gastrointestinal manifestations and potential fecal-oral transmission

Occurrence, fates and potential treatment approaches for removal of viruses from wastewater: A review with emphasis on SARS-CoV-2

Coronavirus disease 2019 (COVID-19) outbreak: some serious consequences with urban and rural water cycle

On water security, sustainability, and the water-food-energy-climate nexus

COVID-19: The environmental implications of shedding SARS-CoV-2 in human faeces

Transmission of SARS-CoV-2 via fecal-oral and aerosols-borne routes: Environmental dynamics and implications for wastewater management in underprivileged societies

2020, 746, 141353. (18) Malenovská, H. Coronavirus Persistence on a Plastic Carrier Under Refrigeration Conditions and Its Reduction Using Wet Wiping Technique, with Respect to Food Safety

Hewson, I. Coronaviruses in the Sea

Beach Tourism in Times of COVID-19 Pandemic: Critical Issues, Knowledge Gaps and Research Opportunities

Disinfection Methods and Survival of SARS-CoV-2 in the Environment and Contaminated Materials: A Bibliometric Analysis

Wastewater and public health: the potential of wastewater surveillance for monitoring COVID-19. Current Opinion in Environmental Science & Health

A review on presence, survival, disinfection/removal methods of coronavirus in wastewater and progress of wastewater-based epidemiology

Implementation of quantitative microbial risk assessment (QMRA) for public drinking water supplies: Systematic review

Pathogen surveillance through monitoring of sewer systems

Application of Quantitative Microbiological Risk Assessment (QMRA) to food spoilage: Principles and methodology

Transparent exopolymer particles (TEPs)-associated protobiofilm: A neglected contributor to biofouling during membrane filtration

Challenges of COVID-19 in children in low-and middle-income countries

Slum health: arresting COVID-19 and improving well-being in urban informal settlements

Potential utilities of mask-wearing and instant hand hygiene for fighting SARS-CoV-2

Contact Dermatitis from Hand Hygiene Practices in the COVID-19 Pandemic

Irrigation System and COVID-19 Recurrence: A Potential Risk Factor in the Transmission of SARS-CoV-2

COVID-19 and Recycled Wastewater Irrigation: A Review of Implications

SARS-CoV-2 induced diarrhoea as onset symptom in patient with COVID-19

Application of Combined Processes of High-Efficiency Sedimentation Tank and Cloth Media Filter for Upgrading and Reconstruction Project of a WWTP

Potential shift of bacterial community structure and corrosion-related bacteria in drinking water distribution pipeline driven by water source switching. Front

Factors associated with COVID-19-related death using OpenSAFELY

Clinical characteristics of 138 hospitalized patients with 2019 novel coronavirus-infected pneumonia in Wuhan, China

Gastrointestinal manifestations of SARS-CoV-2 infection and virus load in fecal samples from the Hong Kong cohort and systematic review and meta-analysis

Potential false-negative nucleic acid testing results for Severe Acute Respiratory Syndrome Coronavirus 2 from thermal inactivation of samples with low viral loads

Fate and risk assessment of emerging contaminants in reclaimed water production processes. Front

Making waves: Coronavirus detection, presence and persistence in the water environment: State of the art and knowledge needs for public health

Current emerging SARS-CoV-2 pandemic: potential direct/indirect negative impacts of virus persistence and related therapeutic drugs on the aquatic compartments

Systematic review and metaanalysis of the persistence and disinfection of human coronaviruses and their viral surrogates in water and wastewater

Post-lockdown detection of SARS-CoV-2 RNA in the wastewater of

Persistence of SARS-CoV-2 in water and wastewater

Frontier review on the propensity and repercussion of SARS-CoV-2 migration to aquatic environment

Coronavirus in water environments: Occurrence, persistence and concentration methods-A scoping review

Concentration and detection of SARS coronavirus in sewage from Xiao Tang Shan Hospital and the 309th Hospital of the Chinese People's Liberation Army

Persistence of SARS-CoV-2 in the environment and COVID-19 transmission risk from environmental matrices and surfaces. Environ. Pollut. 2020, 265, 115010. (54) Cimolai, N. Environmental and Decontamination Issues for Human Coronaviruses and Their Potential Surrogates

UV-C (254 nm) lethal doses for SARS-CoV-2. Photodiagn. Photodyn

Coronavirus in water media: Analysis, fate, disinfection and epidemiological applications

Ozone: A potential oxidant for COVID-19 Virus (SARS-CoV-2)

Acidic electrolyzed water potently inactivates SARS-CoV-2 depending on the amount of free available chlorine contacting with the virus

Biofiltration and disinfection codetermine the bacterial antibiotic resistome in drinking water: A review and meta-analysis. Front

Fast deployment of COVID-19 disinfectant from common ethanol of gas stations in Brazil

Chemical disinfectants of COVID-19: an overview

Disinfection byproducts in drinking water: Occurrence, toxicity and abatement

The potential of wastewater-based epidemiology as surveillance and early warning of infectious disease outbreaks

SARS-CoV-2 from faeces to wastewater treatment: what do we know? A review

Possible transmission of viruses from contaminated human feces and sewage: Implications for SARS-CoV-2

Potential spreading risks and disinfection challenges of medical wastewater by the presence of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) viral RNA in septic tanks of Fangcang Hospital

Open defecation and squat toilets, an overlooked risk of fecal transmission of COVID-19 and other pathogens in developing communities

Pharmaceuticals and personal care products in the environment: overarching issues and overview

Wastewater-based epidemiology: current status and future prospects. Current Opinion in Environmental Science & Health

Cocaine in surface waters: a new evidence-based tool to monitor community drug abuse

Environmental surveillance for polioviruses in the Global Polio Eradication Initiative

Structural changes in hemoglobin during adsorption to solid surfaces: effects of pH, ionic strength, and ligand binding

Wastewater-based epidemiology biomarkers: past, present and future

Making waves: Wastewater-based epidemiology for COVID-19-approaches and challenges for surveillance and prediction

A revised excretion factor for estimating ketamine consumption by wastewaterbased epidemiology -Utilising wastewater and seizure data

Primary concentration-The critical step in implementing the wastewater based epidemiology for the COVID-19 pandemic: A mini-review

Several forms of SARS-CoV-2 RNA can be detected in wastewaters: implication for wastewater-based epidemiology and risk assessment

Ultra-fast and onsite interrogation of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in waters via surface enhanced Raman scattering (SERS)

Prospects and challenges of using electrochemical immunosensors as an alternative detection method for SARS-CoV-2 wastewater-based epidemiology

The international imperative to rapidly and inexpensively monitor community-wide Covid-19 infection status and trends

The presence of SARS-CoV-2 RNA in the feces of COVID-19 patients

Making waves perspectives of modelling and monitoring of SARS-CoV-2 in aquatic environment for COVID-19 pandemic

Predicting pathogen risks to aid beach management: the real value of quantitative microbial risk assessment (QMRA)

Quantitative microbial risk assessment in occupational settings applied to the airborne human adenovirus infection

QMRA and water safety management: review of application in drinking water systems

Quantitative microbial risk assessment of SARS-CoV-2 for workers in wastewater treatment plants

Applying quantitative microbial risk assessment model in developing appropriate standards for irrigation water

Utility of QMRA to compare health risks associated with alternative urban sewer overflow management strategies

Quantitative microbial risk assessment (QMRA) of occupational exposure to SARS-CoV-2 in wastewater treatment plants

SARS-CoV-2 in wastewater: State of the knowledge and research needs

A Case Study Evaluating the Risk of Infection from Middle Eastern Respiratory Syndrome Coronavirus (MERS-CoV) in a Hospital Setting Through Bioaerosols

Microbial exchange via fomites and implications for human health

Method validation for norovirus detection in naturally contaminated irrigation water and fresh produce

Viruses That Can and Cannot Coexist With Humans and the Future of SARS-CoV-2. Front

Five reasons why COVID herd immunity is probably impossible

The first case study of wastewater-based epidemiology of COVID-19 in Hong Kong

Disinfection technology of hospital wastes and wastewater: Suggestions for disinfection strategy during coronavirus Disease 2019 (COVID-19) pandemic in China

Ecotoxicological effects of disinfected wastewater effluents: a short review of in vivo toxicity bioassays on aquatic organisms

Possible effects of COVID-19 on sustainability of aquatic ecosystems: An overview

Hazards and Pollution Status of Chlorinated Disinfection By-Products in Surface Water

Hazards from pathogenic microorganisms in land-disposed sewage sludge

Emission of bacteria and fungi in the air from wastewater treatment plants-a review

The potential exposure and transmission risk of SARS-CoV-2 through sludge treatment and disposal. Resour

Natural host-environmental mediahuman: A new potential pathway of COVID-19 outbreak

Discussion on the Operation of Wastewater Treatment Plants during COVID-19 Epidemic

The SARS-CoV-2 outbreak: what we know

Sentinel surveillance of SARS-CoV-2 in wastewater anticipates the occurrence of COVID-19 cases

Did the COVID-19 Lockdown-Induced Hydrological Residence Time Intensify the Primary Productivity in Lakes? Observational Results Based on Satellite Remote Sensing

Environmental contamination by SARS-CoV-2 in a designated hospital for coronavirus disease 2019

Multi-route transmission potential of SARS-CoV-2 in healthcare facilities

SARS-CoV-2 spillover into hospital outdoor environments

Hand hygiene among health care workers during COVID-19 pandemic: challenges and recommendations

The need for ocular protection for health care workers during SARS-CoV-2 outbreak and a hypothesis for a potential personal protective equipment. Frontiers in Public Health

Challenges and solutions for addressing critical shortage of supply chain for personal and protective equipment (PPE) arising from Coronavirus disease (COVID19) pandemic-Case study from the Republic of Ireland