Sodium hypochlorite disinfection of SARS-CoV-2 spiked in water and municipal wastewater

Assessment of chlorine and hydrogen peroxide on airborne bacteria: Disinfection efficiency and induction of antibiotic resistance

Airborne pathogens severely threaten public health worldwide. Air disinfection is essential to ensure public health. However, excessive use of disinfectants may endanger environmental and ecological security due to the residual disinfectants and their by-products. This study systematically evaluated disinfection efficiency, induction of multidrug resistance, and the underlying mechanisms of disinfectants (NaClO and H2O2) on airborne bacteria. The results showed that airborne bacteria were effectively inactivated by atomized NaClO (>160 μg/L) and H2O2 (>320 μg/L) after 15 min. However, some bacteria still survived after disinfection by atomized NaClO (0-80 μg/L) and H2O2 (0-160 μg/L), and they exhibited significant increases in antibiotic resistance. The whole-genome sequencing of the resistant bacteria revealed distinct mutations that were responsible for both antibiotic resistance and virulence. This study also provided evidences and insights into possible mechanisms underlying the induction of antibiotic resistance by air disinfection, which involved intracellular reactive oxygen species formation, oxidative stress responses, alterations in bacterial membranes, activation of efflux pumps, and the thickening of biofilms. The present results also shed light on the role of air disinfection in inducing antibiotic resistance, which could be a crucial factor contributing to the global spread of antibiotic resistance through the air.

Wastewater sequencing as a powerful tool to reveal SARS-CoV-2 variant introduction and spread in French Guiana, South America

The origin of introduction of a new pathogen in a country, the evolutionary dynamics of an epidemic within a country, and the role of cross-border areas on pathogen dynamics remain complex to disentangle and are often poorly understood. For instance, cross-border areas represent the ideal location for the sharing of viral variants between countries, with international air travel, land travel and waterways playing an important role in the cross-border spread of infectious diseases. Unfortunately, monitoring the point of entry and the evolutionary dynamics of viruses in space and time within local populations remain challenging. Here we tested the efficiency of wastewater-based epidemiology and genotyping in monitoring Covid-19 epidemiology and SARS-CoV-2 variant dynamics in French Guiana, a tropical country located in South America. Our results suggest that wastewater-based epidemiology and genotyping are powerful tools to monitor variant introduction and disease evolution within a tropical country but the inclusion of both clinical and wastewater samples could still improve our understanding of genetic diversity co-circulating. Wastewater sequencing also revealed the cryptic transmission of SARS-CoV-2 variants within the country. Interestingly, we found some amino acid changes specific to the variants co-circulating in French Guiana, suggesting a local evolution of the SARS-CoV-2 variants after their introduction. More importantly, our results showed that the proximity to bordering countries was not the origin of the emergence of the French Guianese B.1.160.25 variant, but rather that this variant emerged from an ancestor B.1.160 variant introduced by European air plane travelers, suggesting thus that air travel remains a significant risk for cross-border spread of infectious diseases. Overall, we suggest that wastewater-based epidemiology and genotyping provides a cost effective and non-invasive approach for pathogen monitoring and an early-warning tool for disease emergence and spread within a tropical country.

The occurrence, ecological risk, and control of disinfection by-products from intensified wastewater disinfection during the COVID-19 pandemic

Increased disinfection of wastewater to preserve its microbiological quality during the coronavirus infectious disease-2019 (COVID-19) pandemic have inevitably led to increased production of toxic disinfection by-products (DBPs). However, there is limited information on such DBPs (i.e., trihalomethanes, haloacetic acids, nitrosamines, and haloacetonitriles). This review focused on the upsurge of chlorine-based disinfectants (such as chlorine, chloramine and chlorine dioxide) in wastewater treatment plants (WWTPs) in the global response to COVID-19. The formation and distribution of DBPs in wastewater were then analyzed to understand the impacts of these large-scale usage of disinfectants in WWTPs. In addition, potential ecological risks associated with DBPs derived from wastewater disinfection and its receiving water bodies were summarized. Finally, various approaches for mitigating DBP levels in wastewater and suggestions for further research into the environmental risks of increased wastewater disinfection were provided. Overall, this study presented a comprehensive overview of the formation, distribution, potential ecological risks, and mitigating approaches of DBPs derived from wastewater disinfection that will facilitate appropriate wastewater disinfection techniques selection, potential ecological risk assessment, and removal approaches and regulations consideration.

Environmental Persistence and Disinfection of Lassa Virus

Lassa fever, caused by Lassa virus (LASV), is endemic to West Africa, where ≈300,000 illnesses and ≈5,000 deaths occur annually. LASV is primarily spread by infected multimammate rats via urine and fomites, highlighting the need to understand the environmental fate of LASV. We evaluated persistence of LASV Josiah and Sauerwald strains on surfaces, in aqueous solutions, and with sodium hypochlorite disinfection. Tested strains were more stable in deionized water (first-order rate constant [k] for Josiah, 0.23 days; for Sauerwald, k = 0.34 days) than primary influent wastewater (Josiah, k = 1.3 days; Sauerwald, k = 1.9 days). Both strains had similar decay rates on high-density polyethylene (Josiah, k = 4.3 days; Sauerwald, k = 2.3 days) and stainless steel (Josiah, k = 5.3 days; Sauerwald, k = 2.7 days). Sodium hypochlorite was highly effective at inactivating both strains. Our findings can inform future risk assessment and management efforts for Lassa fever.

Wastewater reuse in agriculture: Prospects and challenges

Sustainable water recycling and wastewater reuse are urgent nowadays considering water scarcity and increased water consumption through human activities. In 2015, United Nations Sustainable Development Goal 6 (UN SDG6) highlighted the necessity of recycling wastewater to guarantee water availability for individuals. Currently, wastewater irrigation (WWI) of crops and agricultural land appears essential. The present work overviews the quality of treated wastewater in terms of soil microbial activities, and discusses challenges and benefits of WWI in line with wastewater reuse in agriculture and aquaculture irrigation. Combined conventional-advanced wastewater treatment processes are specifically deliberated, considering the harmful impacts on human health arising from WWI originating from reuse of contaminated water (salts, organic pollutants, toxic metals, and microbial pathogens i.e., viruses and bacteria). The comprehensive literature survey revealed that, in addition to the increased levels of pathogen and microbial threats to human wellbeing, poorly-treated wastewater results in plant and soil contamination with toxic organic/inorganic chemicals, and microbial pathogens. The impact of long-term emerging pollutants like plastic nanoparticles should also be established in further studies, with the development of standardized analytical techniques for such hazardous chemicals. Likewise, the reliable, long-term and extensive judgment on heavy metals threat to human beings's health should be explored in future investigations.

Stability of Monkeypox Virus in Body Fluids and Wastewater

An outbreak of human mpox infection in nonendemic countries appears to have been driven largely by transmission through body fluids or skin-to-skin contact during sexual activity. We evaluated the stability of monkeypox virus (MPXV) in different environments and specific body fluids and tested the effectiveness of decontamination methodologies. MPXV decayed faster at higher temperatures, and rates varied considerably depending on the medium in which virus was suspended, both in solution and on surfaces. More proteinaceous fluids supported greater persistence. Chlorination was an effective decontamination technique, but only at higher concentrations. Wastewater was more difficult to decontaminate than plain deionized water; testing for infectious MPXV could be a helpful addition to PCR-based wastewater surveillance when high levels of viral DNA are detected. Our findings suggest that, because virus stability is sufficient to support environmental MPXV transmission in healthcare settings, exposure and dose-response will be limiting factors for those transmission routes.

Inactivation of SARS-CoV-2 in Water by Chlorination

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is present in both respiratory secretions and feces, creating its potential for transmission by swimming pools. Recreational water activity is known to be at increased risk of respiratory infections and respiratory viruses have caused been detected and have caused outbreaks in swimming pools. However, little is known regarding the chlorine inactivation of SARS-CoV-2 in water typical of swimming pools in the USA. In this study, the inactivation of SARS-CoV-2 Isolate hCoV-19/USA-WA1/2020 was observed in water by chlorination. All experiments were conducted within a BSL-3 laboratory at room temperature. Our results show that the virus was reduced by 3.5 log (> 99.9%) after 30 s of 2.05-mg/L free chlorine contact and greater than 4.17 log (limit of detection) (> 99.99%) within 2 min.

Elucidation of composition of chlorine compounds in acidic sodium chlorite solution using ion chromatography

With the spread of coronavirus infections, the demand for disinfectants, such as a sodium chlorite solution, has increased worldwide. Sodium chlorite solution is a food additive and is used in a wide range of applications. There is evidence that chlorous acid or sodium chlorite is effective against various bacteria, but the actual mechanism is not well understood. One reason for this is that the composition of chlorine-based compounds contained in sodium chlorite solutions has not been clearly elucidated. The composition can vary greatly with pH. In addition, the conventional iodometric titration method, the N,N-diethyl-p-phenylenediamine sulfate (DPD) method and the absorption photometric method cannot clarify the composition. In this study, we attempted to elucidate the composition of a sodium chlorite solution using absorption spectrophotometry and ion chromatography (IC). IC is excellent for qualitative and quantitative analysis of trace ions. Through this, we aimed to develop an evaluation method that allows anyone to easily determine the bactericidal power of sodium chlorite. We found that commercially available sodium chlorite solution is 80% pure, with the remaining 20% potentially containing sodium hypochlorite solution. In addition, when sodium chlorite solution became acidified, its absorption spectrum exhibited a peak at 365 nm. Sodium chlorite solution is normally alkaline, and it cannot be measured by the DPD method, which is only applicable under acidic conditions. The presence of a peak at 365 nm indicates that the acidic sodium chlorite solution contains species with oxidizing power. On the other hand, the IC analysis showed a gradual decrease in chlorite ions in the acidic sodium chlorite solution. These results indicate that chlorite ions may not react with this DPD reagent, and other oxidizing species may be present in the acidic sodium chlorite solution. In summary, when a sodium chlorite solution becomes acidic, chlorine-based oxidizing species produce an absorption peak at 365 nm. Sodium hypochlorite and sodium chlorite solutions have completely different IC peak profiles. Although there are still many problems to be solved, we believe that the use of IC will facilitate the elucidation of the composition of sodium chlorite solution and its sterilization mechanism.

Virus purification highlights the high susceptibility of SARS-CoV-2 to a chlorine-based disinfectant, chlorous acid

Chlorous acid water (HClO2) is known for its antimicrobial activity. In this study, we attempted to accurately assess the ability of chlorous acid water to inactivate SARS-CoV-2. When using cell culture supernatants of infected cells as the test virus, the 99% inactivation concentration (IC99) for the SARS-CoV-2 D614G variant, as well as the Delta and Omicron variants, was approximately 10ppm of free chlorine concentration with a reaction time of 10 minutes. On the other hand, in experiments using a more purified virus, the IC99 of chlorous acid water was 0.41-0.74ppm with a reaction time of 1 minute, showing a strong inactivation capacity over 200 times. With sodium hypochlorite water, the IC99 was 0.54ppm, confirming that these chlorine compounds have a potent inactivation effect against SARS-CoV-2. However, it became clear that when using cell culture supernatants of infected cells as the test virus, the effect is masked by impurities such as amino acids contained therein. Also, when proteins (0.5% polypeptone, or 0.3% BSA + 0.3% sheep red blood cells, or 5% FBS) were added to the purified virus, the IC99 values became high, ranging from 5.3 to 76ppm with a reaction time of 10 minutes, significantly reducing the effect. However, considering that the usual usage concentration is 200ppm, it was shown that chlorous acid water can still exert sufficient disinfection effects even in the presence of proteins. Further research is needed to confirm the practical applications and effects of chlorous acid water, but it has the potential to be an important tool for preventing the spread of SARS-CoV-2.

The disinfectant residues promote the leaching of water contaminants from plastic pipe particles

Disinfection treatment is an indispensable water purification process, but it can leave trace concentrations of disinfectant in the purified water. Disinfectants oxidation can age plastic pipes and release hazardous microplastics and chemicals into drinking water. Lengths of commercially-available unplasticized polyvinyl chloride and polypropylene random copolymer water pipe were ground into particles and exposed to micro-molar concentrations of ClO₂, NaClO, trichloroisocyanuric acid, or O₃ for up to 75 days. The disinfectants aged the plastic and changed its surface morphology and functional groups. Meanwhile, disinfectants could significantly promote the release of organic matter from plastic pipes into the water. ClO₂ generated the highest concentrations of organic matter in the leachates from both plastics. Plasticizers, antioxidants and low molecular weight organic matter were detected in all of the leachates. Leachate samples inhibited the proliferation of CT26 mouse colon cancer and induced oxidative stress in the cells. Even trace concentrations of residual disinfectant can constitute a drinking water risk.

A critical assessment of SARS-CoV-2 in aqueous environment: Existence, detection, survival, wastewater-based surveillance, inactivation methods, and effective management of COVID-19

In early January 2020, the causal agent of unspecified pneumonia cases detected in China and elsewhere was identified as a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and was the major cause of the COVID-19 outbreak. Later, the World Health Organization (WHO) proclaimed the COVID-19 pandemic a worldwide public health emergency on January 30, 2020. Since then, many studies have been published on this topic. In the present study, bibliometric analysis has been performed to analyze the research hotspots of the coronavirus. Coronavirus transmission, detection methods, potential risks of infection, and effective management practices have been discussed in the present review. Identification and quantification of SARS-CoV-2 viral loads in various water matrices have been reviewed. It was observed that the viral shedding through urine and feces of COVID-19-infected patients might be a primary mode of SARS-CoV-2 transmission in water and wastewater. In this context, the present review highlights wastewater-based epidemiology (WBE)/sewage surveillance, which can be utilized as an effective tool for tracking the transmission of COVID-19. This review also emphasizes the role of different disinfection techniques, such as chlorination, ultraviolet irradiation, and ozonation, for the inactivation of coronavirus. In addition, the application of computational modeling methods has been discussed for the effective management of COVID-19.

Exploring possible strategies for treating SARS-CoV-2 in sewage wastewater: A review of current research and future directions

The advent of acute respiratory coronavirus disease (COVID-19) is convoyed by the shedding of the virus in stool. Although inhalation from person-to-person and aerosol/droplet transmission are the main modes of SARS-Coronavirus-2 (SARS-CoV-2) transmission, currently available evidence indicates the presence of viral RNA in the sewerage wastewater, which highlights the need for more effective corona virus treatment options. In the existing COVID-19 pandemic, a substantial percentage of cases shed SARS-CoV-2 viral RNA in their faeces. Hence the treating this sewerage wastewater with proper surveillance is essential to contain this deadly pathogen from further transmission. Since, the viral disinfectants will not be very effective on sewerage waste as organic matter, and suspended solids in water can protect viruses that adsorb to these particles. More effective methods and measures are needed to prevent this virus from spreading. This review will explore some potential methods to treat the SARS-CoV-2 infected sewerage wastewater, current research and future directions.

COVID-19 and Water Variables: Review and Scientometric Analysis

COVID-19 has changed the world since 2020, and the field of water specifically, boosting scientific productivity (in terms of published articles). This paper focuses on the influence of COVID-19 on scientific productivity with respect to four water variables: (i) wastewater, (ii) renewable water resources, (iii) freshwater withdrawal, and (iv) access to improved and safe drinking water. The field's literature was firstly reviewed, and then the maps were built, emphasizing the strong connections between COVID-19 and water-related variables. A total of 94 countries with publications that assess COVID-19 vs. water were considered and evaluated for how they clustered. The final step of the research shows that, on average, scientific productivity on the water topic was mostly conducted in countries with lower COVID-19 infection rates but higher development levels as represented by gross domestic product (GDP) per capita and the human development index (HDI). According to the statistical analysis, the water-related variables are highly significant, with positive coefficients. This validates that countries with higher water-related values conducted more research on the relationship with COVID-19. Wastewater and freshwater withdrawal had the highest impact on the scientific productivity with respect to COVID-19. Access to safe drinking water becomes insignificant in the presence of the development parameters.

Effect of hydraulic retention time on the electro-bioremediation of nitrate in saline groundwater

Bioelectrochemical systems (BES) have proven their capability to treat nitrate-contaminated saline groundwater and simultaneously recover value-added chemicals (such as disinfection products) within a circular economy-based approach. In this study, the effect of the hydraulic retention time (HRT) on nitrate and salinity removal, as well as on free chlorine production, was investigated in a 3-compartment BES working in galvanostatic mode with the perspective of process intensification and future scale-up. Reducing the HRT from 30.1 ± 2.3 to 2.4 ± 0.2 h led to a corresponding increase in nitrate removal rates (from 17 ± 1 up to 131 ± 1 mgNO₃^--N L^-1d^-1), although a progressive decrease in desalination efficiency (from 77 ± 13 to 12 ± 2 %) was observed. Nitrate concentration and salinity close to threshold limits indicated by the World Health Organization for drinking water, as well as significant chlorine production were achieved with an HRT of 4.9 ± 0.4 h. At such HRT, specific energy consumption was low (6.8·10^-2 ± 0.3·10^-2 kWh g^-1NO₃^--N_removed), considering that the supplied energy supports three processes simultaneously. A logarithmic equation correlated well with nitrate removal rates at the applied HRTs and may be used to predict BES behaviour with different HRTs. The bacterial community of the bio-cathode under galvanostatic mode was dominated by a few populations, including the genera Rhizobium, Bosea, Fontibacter and Gordonia. The results provide useful information for the scale-up of BES treating multi-contaminated groundwater.

Disinfection and decontamination in the context of SARS-CoV-2-specific data

Given the high transmissibility of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as witnessed early in the coronavirus disease 2019 (COVID-19) pandemic, concerns arose with the existing methods for virus disinfection and decontamination. The need for SARS-CoV-2-specific data stimulated considerable research in this regard. Overall, SARS-CoV-2 is practically and equally susceptible to approaches for disinfection and decontamination that have been previously found for other human or animal coronaviruses. The latter have included techniques utilizing temperature modulation, pH extremes, irradiation, and chemical treatments. These physicochemical methods are a necessary adjunct to other prevention strategies, given the environmental and patient surface ubiquity of the virus. Classic studies of disinfection have also allowed for extrapolation to the eradication of the virus on human mucosal surfaces by some chemical means. Despite considerable laboratory study, practical field assessments are generally lacking and need to be encouraged to confirm the correlation of interventions with viral eradication and infection prevention. Transparency in the constitution and use of any method or chemical is also essential to furthering practical applications.

Recent advances in aqueous virus removal technologies

The COVID-19 outbreak has triggered a massive research, but still urgent detection and treatment of this virus seems a public concern. The spread of viruses in aqueous environments underlined efficient virus treatment processes as a hot challenge. This review critically and comprehensively enables identifying and classifying advanced biochemical, membrane-based and disinfection processes for effective treatment of virus-contaminated water and wastewater. Understanding the functions of individual and combined/multi-stage processes in terms of manufacturing and economical parameters makes this contribution a different story from available review papers. Moreover, this review discusses challenges of combining biochemical, membrane and disinfection processes for synergistic treatment of viruses in order to reduce the dissemination of waterborne diseases. Certainly, the combination technologies are proactive in minimizing and restraining the outbreaks of the virus. It emphasizes the importance of health authorities to confront the outbreaks of unknown viruses in the future.

Monitoring SARS-CoV-2 in the Wastewater and Rivers of Tapachula, a Migratory Hub in Southern Mexico

The COVID-19 pandemic has been monitored by applying different strategies, including SARS-CoV-2 detection with clinical testing or through wastewater-based epidemiology (WBE). We used the latter approach to follow SARS-CoV-2 dispersion in Tapachula city, located in Mexico's tropical southern border region. Tapachula is a dynamic entry point for people seeking asylum in Mexico or traveling to the USA. Clinical testing facilities for SARS-CoV-2 monitoring are limited in the city. A total of eighty water samples were collected from urban and suburban rivers and sewage and a wastewater treatment plant over 4 months in Tapachula. We concentrated viral particles with a PEG-8000-based method, performed RNA extraction, and detected SARS-CoV-2 particles through RT-PCR. We considered the pepper mild mottle virus as a fecal water pollution biomarker and analytical control. SARS-CoV-2 viral loads (N1 and N2 markers) were quantified and correlated with official regional statistics of COVID-19 bed occupancy and confirmed cases (r > 91%). Our results concluded that WBE proved a valuable tool for tracing and tracking the COVID-19 pandemic in tropical countries with similar water temperatures (21-29 °C). Monitoring SARS-CoV-2 through urban and suburban river water sampling would be helpful in places lacking a wastewater treatment plant or water bodies with sewage discharges.

Reduction and discharge of SARS-CoV-2 RNA in Chicago-area water reclamation plants

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA is commonly excreted in the feces and urine of infected individuals and is, therefore, detected in wastewaters where infection is present in the surrounding population. Water reclamation plants (WRPs) that treat these wastewaters commonly discharge treated effluents into the surrounding environment, yet little is known about the removal or persistence of SARS-CoV-2 RNA through wastewater treatment systems and potential for eventual release into the environment. We collected 361 24-hour composite influent and effluent samples from seven WRPs in the Greater Chicago Area in Illinois. Samples were collected over a period of 21 weeks for three large WRPs (with design max flows of 1.89-2.32 billion gallons per day and serving a combined population of 4.62 million people) and 11 weeks for four smaller WRPs (with design max flows of 96.3-186 million gallons per day and serving a combined population of >0.5 million people). A total of two of the larger WRPs implemented seasonal disinfection (using UV light or chlorination/dechlorination) for 8 weeks of this sampling period. SARS-CoV-2 RNA was quantified in the influent and effluent samples by reverse-transcription quantitative PCR (RT-qPCR) of the N1 and N2 targets of the nucleocapsid (N) gene. Although SARS-CoV-2 RNA was regularly detected in influent and effluent from all WRPs, viral RNA concentrations in the effluent samples were considerably lower, with mean effluent: influent gene copy concentration ratios ranging from 1:160 to 1:2.95 between WRPs. Samples collected while disinfection was active vs. inactive did not show any significant difference in the portion of RNA persisting through the treatment process (P > .05).

Assessing face masks in the environment by means of the DPSIR framework

The use of face masks outside the health care facility dates back a century ago. However, face masks use noticeably soared due to the COVID-19 (Coronavirus disease 2019) pandemic. As a result, an unprecedented influx of discarded face masks is ending up in the environment. This review paper delves into face masks in the environment using the DPSIR (driving forces, pressures, states, impacts, and responses) framework to simplify and communicate the environmental indicators. Firstly, the historical, and briefly the economic trajectory of face masks are discussed. Secondly, the main driving forces of face masks use with an emphasis on public health are explored. Then, the pressures exerted by efforts to fulfill the human needs (driving forces) are investigated. In turn, the state of the environment due to the influx of masks along with the impacts are examined. Furthermore, the upstream, and downstream societal responses to mitigate the environmental damages of the driving forces, pressures, states, and impacts are reviewed. In summary, it has been shown from this review that the COVID-19 pandemic has been causing a surge in face mask usage, which translates to face masks pollution in both terrestrial and aquatic environments. This implies proper usage and disposal of face masks is paramount to the quality of human health and the environment, respectively. Moreover, further research on eco-friendly face masks is indispensable to mitigating the environmental damages occurring due to the mass use of surgical masks worldwide.