Regarding the choices of disinfectant for coronavirus inactivation in water, the use of chlorine still represents the best economic solution.18 However, chlorine reacts with ammonia present in wastewater to form combined chlorine (chloramine), which behaves differently to free chlorine during disinfection. Thus, it is important to understand the chlorine/chloramine speciation and breakpoints specific to the wastewater chemistry for each facility. Furthermore, it is necessary to establish quantitative disinfection kinetics, for example, log inactivation vs. CT values of coronaviruses for traditional disinfectants, including chlorine, chloramine and ozone, and emerging disinfectants, including peracetic acid and hydrogen peroxide. The role of the optimal dose of residual disinfectant is also crucial for drinking water systems. In WWTPs, membrane bioreactors (MBRs) can also play an important role.19,20 Viruses are generally concentrated in suspended solids that are efficiently removed by filtration mechanisms. In MBRs the retention of suspended solids in the bioreactor, combined with the presence of antagonist microorganisms and adverse chemical–physical conditions, leads to the efficient inactivation of enveloped viruses, such as coronaviruses.19,20 Peracetic acid has been found to have some efficacy against some non-enveloped viruses (e.g. norovirus) that are known to be more resistant than enveloped viruses.13,21 Additional research could provide reassurance of the effectiveness of disinfection processes, specifically against coronaviruses and at lower doses and contact times. Additional studies may also be warranted for disinfectants such as peracetic acid and combined chlorine (chloramine), where there is a lack of coronavirus-specific data or the evidence suggests higher bacterial susceptibility to disinfection compared to viruses. list the conclusions

As the current water treatment routine has not been confirmed to remove SARS-CoV-2, it is necessary to take extra steps to ensure the complete removal of these viruses from water. Providing additional treatments to the wastewater before it enters the treatment routine, thus upgrading the existing process, is a well-conceived notion. Home-made treatments such as boiling and large-scale processes such as ultrafiltration, inactivation by ultraviolet irradiation and chlorination are promising tactics that can be used to upgrade the treatment, especially in pandemic hotspots. An investigation of the spread of viruses through biofilms also needs to be better prepared for future situations. Once the countermeasures of social distancing are uplifted and people return to their routine lifestyle, there is a high probability of the reemergence of this virus. Hence, facilities such as a monitoring tool for increased scrutiny of wastewater treatment industries must be enforced to minimize public health risks. An efficient monitoring tool can serve as an alarm when there is an increase in virus particles above the threshold levels, thus allowing us to act faster and contain the infection before it spreads at an alarming rate.list the conclusions

The results of this study indicate that coronaviruses are much more sensitive to temperature than PV-1 and that there is a considerable difference in survivability between PV-1 and the coronaviruses in wastewater. This may bedue in part to the fact that enveloped viruses are less stable in the environment than nonenveloped viruses. Coronaviruses die off very rapidly in wastewater, with a 99.9% reduction in 2–3 days, which is comparable to the data on SARS-CoV survival (Wang et al. 2005a, b). Survival of the coronaviruses in primary wastewater was only slightly longer than secondary wastewater, probably due to the higher level of suspended solids that offer protection from inactivation. PV-1 survived substantially longer than coronaviruses, requiring 10 days for a comparable reduction in primary wastewater and 5 days in secondary wastewater. This study demonstrates that the transmission of coronaviruses would be less than enteroviruses in the aqueous environment due to the fact that coronaviruses are more rapidly inactivated in water and wastewater at ambient temperatures. list the conclusions

The ongoing severe acute respiratory syndrome-coronavirus (SARS-CoV-2) has triggered the coronavirus pandemic (COVID-19) that has claimed hundreds of thousands of lives worldwide. This virus spreads predominantly by human-to-human transmission via respiratory droplets. However, the presence of this virus in the fecal and anal swabs of infected patients has triggered the need for research into its waterborne transmission. The various environmental factors that impact the persistence of coronavirus in different water matrices include temperature, UV exposure, organic matter, disinfectants as well as adversarial microorganisms. This review summarizes the most recent research data on the effect of various factors on coronavirus in aqueous environments. The available data suggest that: (i) increasing temperature decreases the overall persistence of the virus; (ii) the presence of organic matter can increase the survivability of coronavirus; (iii) chlorine is the most effective and economic disinfectant; (iv) membrane bioreactors in wastewater treatment plants are hosts of competitive microorganisms that can inactivate coronaviruses; (v) ultraviolet irradiation is another effective option for virus inactivation. However, the inactivation disinfection kinetics of coronaviruses are yet to be fully understood. Thus, further research is needed to understand its fate and transport with respect to the water cycle so that effective strategies can be adopted to curb its effects. These strategies may vary based on geographic, climatic, technical, and social conditions around the globe. This paper explores possible approaches and especially the conditions that local communities and authorities should consider to find optimal solutions that can limit the spread of this virus. list the conclusions

As for the SARS coronavirus in the 2003 epidemic, the presence of SARS-CoV-2 has been demonstrated in faeces and, in some cases, urine of infected people, as well as in wastewater. This paper proposes a critical review of the state of the art regarding studies on the presence of SARS-CoV-2 in wastewater and sewage sludge, the factors affecting its inactivation and the main proposed treatments. In-vitro tests demonstrated low resistance of SARS-CoV-2 to high temperature, while even significant changes in pH would not seem to determine the disappearance of the virus. In real wastewater and in sewage sludge, to date studies on the influence of the different parameters on the inactivation of SARS-CoV-2 are not available. Therefore, studies involving other HCoVs such as SARS-CoV and HCoV-229E have been also considered, in order to formulate a hypothesis regarding its behaviour in sewage and throughout the steps of biological treatments in WWTPs. Finally, SARS-CoV-2 in wastewater might track the epidemic trends: although being extremely promising, an effective and wide application of this approach requires a deeper knowledge of the amounts of viruses excreted through the faeces and the actual detectability of viral RNA in sewage tell me conclusions of the text one by one

Concerns about possible secondary transmission of the novel SARS-CoV-2 via water are growing with the evidence of its fecal elimination. Moreover, the results of in vitro experiments of prolonged virus survival with declining temperatures suggest that coronavirus excreted in feces could reach wastewater treatment plants in an infective state, especially in cool climates. However, current knowledge is very scarce and fragmentary. Prior to COVID19, interest in this topic was very low owing to the common belief that enveloped viruses cannot survive for extended periods in water. However, the assumption that SARS-CoV-2 is not involved in environmental circulation cannot be accepted without better knowledge, as highlighted by the detection of SARS-CoV-2 RNA in wastewater by six different global research groups. The ongoing SARS-CoV-2 emergency and its rapid spread demands new attention on its detection in water. The scarcity of information on the presence and persistence of coronavirus in the environment merits urgent research. In the meantime, we should respond to the ongoing pandemic by taking precautions and assume that there is a potential for secondary transmission. In particular, we believe that research should address the following:Set up efficient methods to concentrate and detect enveloped viruses (and coronavirus in particular) from water matrices;  Evaluate the survival of these viruses in natural conditions, at different temperatures and in different types of water;  Assess the efficiency of water treatments and disinfection to avoid contamination from urban and hospital wastewater;  Evaluate the implications for water reuse for agriculture including the possibility of food (raw vegetables) contamination;  Establish a surveillance system through sewage monitoring of the potential virus circulation. list the conclusions