Effects of bacterial, chemical, physical and meteorological variables on virus removal by a wastewater treatment plant

Effect of Human Adenovirus Type 35 Concentration on Its Inactivation and Sorption on Titanium Dioxide Nanoparticles

Removal of pathogenic viruses from water resources is critically important for sanitation and public health. Nanotechnology is a promising technology for virus inactivation. In this paper, the effects of titanium dioxide (TiO2) anatase nanoparticles (NPs) on human adenovirus type 35 (HAdV-35) removal under static and dynamic (with agitation) batch conditions were comprehensively studied. Batch experiments were performed at room temperature (25 °C) with and without ambient light using three different initial virus concentrations. The virus inactivation experimental data were satisfactorily fitted with a pseudo-first-order expression with a time-dependent rate coefficient. The experimental results demonstrated that HAdV-35 sorption onto TiO2 NPs was favored with agitation under both ambient light and dark conditions. However, no distinct relationships between virus initial concentration and removal efficiency could be established from the experimental data.

Molecular Characterization and Prevalence of Antimicrobial-Resistant Escherichia coli Isolates Derived from Clinical Specimens and Environmental Habitats

Antibiotic-resistant bacteria (ARB) are present in wastewaters as their elimination during treatment in wastewater treatment plants (WWTPs) is often impossible. Water plays an important role in the spread of these microorganisms among humans, animals and the environment. This study aimed to assess the antimicrobial resistance patterns, resistance genes and molecular genotypes by means of phylogenetic groups of E. coli isolates in aquatic habitats, including sewage and receiving water bodies, as well as clinical settings in the Boeotia regional district of Greece. The highest resistance rates among both environmental and clinical isolates were observed to be for penicillins, ampicillin and piperacillin. Resistance patterns related to extended spectrum β-lactamases (ESBL) production and ESBL genes were also detected in both environmental and clinical isolates. Phylogenetic group B2 was predominant in clinical settings and the second most frequent among wastewaters, whereas group A was dominant in all environmental isolates. In conclusion, the studied river water and wastewaters may serve as reservoirs of resistant E. coli isolates that pose potential threats to both human and animal health.

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.

CrAssphage as an indicator of human-fecal contamination in water environment and virus reduction in wastewater treatment

Viral indicators of human-fecal contamination in wastewaters and environmental waters have been getting much attention in the past decade. Cross-assembly phage (crAssphage) is the most abundant DNA virus in human feces. Recently, the usefulness of crAssphage as a microbial source tracking and water quality monitoring tool for human-fecal contamination has been highlighted. Here, we conducted a comprehensive review on crAssphage in water, focusing on detection methodology, concentration range in various waters and wastewaters, specificity to human-fecal contamination, and reduction in wastewater treatment systems. This review highlights that crAssphage is globally distributed in wastewaters and various fecal-contaminated water bodies at high concentrations without seasonal fluctuations. CrAssphage is highly specific to human-fecal contamination and is rarely found in animal feces. It also has a good potential as a performance indicator to ensure virus reduction in wastewater treatment systems. Accordingly, crAssphage could be an effective tool for monitoring of human-fecal contamination and potential presence of fecal pathogenic microbes in environmental waters. Bridging the research gaps highlighted in this review would make crAssphage a powerful tool to support the control of water-related health risks.

Microbiological characterization of stormwater in a high-income neighborhood in Rio de Janeiro, Brazil

Stormwater harvesting and reuse in the urban environment is emerging as an alternative water source, despite human pathogens in the stormwater may represent a hazard to public health. This study presents the results of 1-year monitoring to evaluate the quality of stormwater obtained in a high-income neighborhood in Rio de Janeiro for a set of microbiological parameters as total coliforms, Escherichia coli (E. coli), human adenovirus (HAdV), human JC polyomavirus (JCPyV), Group A rotavirus (RVA), and norovirus GI and GII. Forty-eight stormwater samples obtained from two multiplex units presented total coliforms and E. coli in 91.7% (n = 44) and 58.3% (n = 28) of samples, while HAdV and JCPyV were detected in 20.8% (n = 10) and 12.5% (n = 6), respectively. Viral quantification ranged from 10³ to 10⁴ genomic copies/liter (GC/L) for HAdV and from 10¹ to 10⁴ GC/L for JCPyV. Neither RVA nor norovirus GI and GII was detected. Fifteen out of sixteen (93.8%) samples containing viruses were compliant as per fecal indicator bacteria (FIB) according to Brazilian standards for rainwater reuse and US EPA Guidelines for Water Reuse, suggesting that viruses monitoring should complement the study of bacterial indicators.

Detection of SARS-CoV-2 in Wastewater Northeast of Mexico City: Strategy for Monitoring and Prevalence of COVID-19

A month-long wastewater sampling project was conducted along the northeast periphery of Mexico City, specifically in the state of Hidalgo, to assess the presence of SARS-CoV-2. To determine the prevalence of infection and obtain a range of COVID-19 cases in the main metropolitan zones. Viral RNA residues (0-197,655 copies/L) were measured in wastewater from the five central municipalities in the state. By recording the number of RNA viral copies per liter, micro-basins delimitation, demographic and physiological data, an interval of infected people and virus prevalence was estimated using a Monte Carlo model (with 90% confidence) in the micro-basin of five municipalities with metropolitan influence or industrial activity. Our procedure determined that the percentage of the infected population ranges from 1.4% to 41.7%, while the official data reports 0.1-0.3%. This model is proposed as a helpful method of regional epidemiological monitoring through the analysis of viral prevalence.

Qualitative and Quantitative Analysis of Certain Aspects of the Cytotoxic and Genotoxic Hazard of Hospital Wastewaters by Using a Range of In Vitro Assays

Health care facilities and hospitals generate significant amounts of wastewater which are released into the sewage system, either after a preliminary treatment or without any further treatment. Hospital wastewater may contain large amounts of hazardous chemicals and pharmaceuticals, some of which cannot be eliminated entirely by wastewater treatment plants. Moreover, hospital effluents may be loaded with a plethora of pathogenic microorganisms or other microbiota and microbiome residues. The need to monitor hospital effluents for their genotoxic hazard is of high importance, as detailed information is scarce. DNA-based information can be acquired directly from samples through the application of various molecular methods, while cell-based biomonitoring assays can provide important information about impaired cellular pathways or mechanisms of toxicity without prior knowledge of the identity of each toxicant. In our study, we evaluated samples of chlorinated hospital wastewater discharged into the sewage system after this disinfection process. The assessment of cytotoxicity, genotoxicity and mutagenicity of the hospital effluents was performed in vitro by using a broad battery of biomonitoring assays that are relevant for human health effects. All the tested hospital wastewater samples could be classified as potentially genotoxic, and it is concluded that the microbiota present in hospital wastewater might contribute to this genotoxic potential.

Assessment of socioeconomic inequality based on virus-contaminated water usage in developing countries: A review

Water is an essential resource required for various human activities such as drinking, cooking, and other recreational activities. While developed nations have made significant improvement in providing adequate quality water and sanitation devoid of virus contaminations to a significant percentage of the residences, many of the developing countries are still lacking in these regards, leading to many death cases among the vulnerable due to ingestion of virus-contaminated water and other waterborne pathogens. However, the recent global pandemic of COVID-19 seems to have changed the paradigm by reawakening the importance of water quality and sanitation, and focusing more attention on the pervasive effect of the use of virus-contaminated water as it can be a potential driver for the spread of the virus and other waterborne diseases, especially in developing nations that are characterized by low socioeconomic development. Therefore, this review assessed the socioeconomic inequalities related to the usage of virus-contaminated water and other waterborne pathogens in developing countries. The socioeconomic factors attributed to the various waterborne diseases due to the use of virus-contaminated water in many developing countries are poverty, the standard of living, access to health care facilities, age, gender, and level of education. Some mitigation strategies to address the viral contamination of water sources are therefore proposed, while future scope and recommendations on tackling the essential issues related to socioeconomic inequality in developing nations are highlighted.

Assessment of socioeconomic inequality based on virus-contaminated water usage in developing countries: A review

Water is an essential resource required for various human activities such as drinking, cooking, and other recreational activities. While developed nations have made significant improvement in providing adequate quality water and sanitation devoid of virus contaminations to a significant percentage of the residences, many of the developing countries are still lacking in these regards, leading to many death cases among the vulnerable due to ingestion of virus-contaminated water and other waterborne pathogens. However, the recent global pandemic of COVID-19 seems to have changed the paradigm by reawakening the importance of water quality and sanitation, and focusing more attention on the pervasive effect of the use of virus-contaminated water as it can be a potential driver for the spread of the virus and other waterborne diseases, especially in developing nations that are characterized by low socioeconomic development. Therefore, this review assessed the socioeconomic inequalities related to the usage of virus-contaminated water and other waterborne pathogens in developing countries. The socioeconomic factors attributed to the various waterborne diseases due to the use of virus-contaminated water in many developing countries are poverty, the standard of living, access to health care facilities, age, gender, and level of education. Some mitigation strategies to address the viral contamination of water sources are therefore proposed, while future scope and recommendations on tackling the essential issues related to socioeconomic inequality in developing nations are highlighted.

Potential secondary transmission of SARS-CoV-2 via wastewater

The new coronavirus, SARS-CoV-2, has spread internationally and whilst the current focus of those dealing with the COVID-19 pandemic is understandably restricting its direct transmission, the potential for secondary transmission via wastewater should not be underestimated. The virus has been identified in human fecal and wastewater samples from different countries and potential cases of transmission via wastewater have been reported. Our recommendations for hospital wastewater treatment, municipal wastewater plants, sewage sludge, water reuse and aquatic environments are designed to reduce the risk of such transmission, and contribute to limiting the resurgence of COVID-19 as current restrictions are relaxed. A particular urgent recommendation focusses on supporting low-income countries in tackling the potential for secondary transmission via wastewater.

Quantitative Detection of Human Adenovirus and Human Rotavirus Group A in Wastewater and El-Rahawy Drainage Canal Influencing River Nile in the North of Giza, Egypt

Environmental monitoring is critical in a developing country like Egypt where there is an insufficient framework for recording and tracking outbreaks. In this study, the prevalence of human adenovirus (HAdV), rotavirus group A (RVA) was determined in urban sewage, activated sludge, drainage water, drainage sediment, Nile water, and Nile sediment, using quantitative polymerase chain reaction (qPCR) analysis. HAdV was detected in 50% of urban sewage with viral concentrations ranging from 10³ to 10⁷ genome copies/liter (GC/L), 33% of activated sludge with viral concentrations ranging from 10³ to 10⁷ GC/kilogram (GC/kg), 95% of drainage water with viral concentrations ranging from 10³ to 10⁷ GC/L, 75% of drainage sediment with viral concentrations ranging from 10³ to 10⁷ GC/L, 50% of Nile water with viral concentrations ranging from 10³ to 10⁷ GC/L, and 45% of Nile sediment with viral concentrations ranging from 10³ to 10⁷ GC/kg. RVA was detected in 50% of urban sewage with viral concentrations ranging from 10³ to 10⁷ GC/L, 75% of activated sludge with viral concentrations ranging from 10³ to 10⁷ GC/L, 58% of drainage water with viral concentrations ranging from 10³ to 10⁷ GC/L, 50% of drainage sediment with viral concentrations ranging from 10³ to 10⁷ GC/L, and 45% of Nile water with viral concentrations ranging from 10³ to 10⁷ GC/kg. In conclusion, Abu-Rawash WWTP acts as a source of HAdV and RVA, releasing them into El-Rahawy drain then to the River Nile Rosetta branch.

Viral indicators for tracking domestic wastewater contamination in the aquatic environment

Waterborne enteric viruses are an emerging cause of disease outbreaks and represent a major threat to global public health. Enteric viruses may originate from human wastewater and can undergo rapid transport through aquatic environments with minimal decay. Surveillance and source apportionment of enteric viruses in environmental waters is therefore essential for accurate risk management. However, individual monitoring of the >100 enteric viral strains that have been identified as aquatic contaminants is unfeasible. Instead, viral indicators are often used for quantitative assessments of wastewater contamination, viral decay and transport in water. An ideal indicator for tracking wastewater contamination should be (i) easy to detect and quantify, (ii) source-specific, (iii) resistant to wastewater treatment processes, and (iv) persistent in the aquatic environment, with similar behaviour to viral pathogens. Here, we conducted a comprehensive review of 127 peer-reviewed publications, to critically evaluate the effectiveness of several viral indicators of wastewater pollution, including common enteric viruses (mastadenoviruses, polyomaviruses, and Aichi viruses), the pepper mild mottle virus (PMMoV), and gut-associated bacteriophages (Type II/III FRNA phages and phages infecting human Bacteroides species, including crAssphage). Our analysis suggests that overall, human mastadenoviruses have the greatest potential to indicate contamination by domestic wastewater due to their easy detection, culturability, and high prevalence in wastewater and in the polluted environment. Aichi virus, crAssphage and PMMoV are also widely detected in wastewater and in the environment, and may be used as molecular markers for human-derived contamination. We conclude that viral indicators are suitable for the long-term monitoring of viral contamination in freshwater and marine environments and that these should be implemented within monitoring programmes to provide a holistic assessment of microbiological water quality and wastewater-based epidemiology, improve current risk management strategies and protect global human health.

Environmental and Adaptive Changes Necessitate a Paradigm Shift for Indicators of Fecal Contamination

Changes in the occurrence, distribution, and seasonal variation of waterborne pathogens due to global climate change may increase the risk of human exposure to these microorganisms, thus heightening the need for more reliable surveillance systems. Routine monitoring of drinking water supplies and recreational waters is performed using fecal indicator microorganisms, such as Escherichia coli , Enterococcus spp., and coliphages. However, the presence and numbers of these indicators, especially E. coli and Enterococcus spp., do not correlate well with those of other pathogens, especially enteric viruses, which are a major cause of waterborne outbreaks associated with contaminated water and food, and recreational use of lakes, ponds, rivers, and estuarine waters. For that reason, there is a growing need for a surveillance system that can detect and quantify viral pathogens directly in water sources to reduce transmission of pathogens associated with fecal transmission. In this review, we present an updated overview of relevant waterborne enteric viruses that we believe should be more commonly screened to better evaluate water quality and to determine the safety of water use and reuse and of epidemiological data on viral outbreaks. We also discuss current methodologies that are available to detect and quantify these viruses in water resources. Finally, we highlight challenges associated with virus monitoring. The information presented in this review is intended to aid in the assessment of human health risks due to contact with water sources, especially since current environmental and adaptive changes may be creating the need for a paradigm shift for indicators of fecal contamination.

Evaluating the fate of bacterial indicators, viral indicators, and viruses in water resource recovery facilities

A year-long sampling campaign at nine water resource recovery facilities (WRRFs) was conducted to assess the treatability and fate of bacterial indicators, viral indicators, and viruses. Influent concentrations of viral indicators (male-specific and somatic coliphages) and bacterial indicators (Escherichia coli and enterococci) remained relatively constant, typically varying by one order of magnitude over the course of the year. Annual average bacterial indicator reduction ranged from 4.0 to 6.7 logs, and annual average viral indicator reduction ranged from 1.6 to 5.4 logs. Bacterial and viral indicator reduction depended on the WRRF's treatment processes, and bacterial indicator reduction was greater than viral indicator reduction for many processes. Viral reduction (adenovirus 41, norovirus GI, and norovirus GII) was more similar to viral indicator reduction than bacterial indicator reduction. Overall, this work suggests that viral indicator reduction in WRRFs is variable and depends on specific unit processes. Moreover, for the same unit treatment process, viral indicator reduction and bacterial indicator reduction can vary. PRACTITIONER POINTS: A year-long sampling campaign was conducted at nine water resource recovery facilities (WRRFs). The treatability and fate of bacterial indicators, viral indicators, and viruses were assessed. Viral indicator reduction in WRRFs is variable and depends on specific unit processes. For the same unit treatment process, viral indicator reduction and bacterial indicator reduction can vary.

Occurrence of coliphage in raw wastewater and in ambient water: A meta-analysis

Coliphage have been proposed as indicators of fecal contamination in recreational waters because they better reflect the persistence of pathogenic viruses in the environment and through wastewater treatment than traditional fecal indicator bacteria. Herein, we conducted a systematic literature search of peer-reviewed publications to identify coliphage density data (somatic and male-specific, or MSC) in raw wastewater and ambient waters. The literature review inclusion criteria included scope, study quality, and data availability. A non-parametric two-stage bootstrap analysis was used to estimate the coliphage distributions in raw wastewater and account for geographic region and season. Additionally, two statistical methodologies were explored for developing coliphage density distributions in ambient waters, to account for the nondetects in the datasets. In raw wastewater, the analysis resulted in seasonal density distributions of somatic coliphage (SC) (mean 6.5 log₁₀ plaque forming units (PFU)/L; 95% confidence interval (CI): 6.2-6.8) and MSC (mean 5.9 log₁₀ PFU/L; 95% CI: 5.5-6.1). In ambient waters, 49% of MSC samples were nondetects, compared with less than 5% for SC. Overall distributional estimates of ambient densities of coliphage were statistically higher for SC than for MSC (mean 3.4 and 1.0 log₁₀ PFU/L, respectively). Distributions of coliphage in raw wastewater and ambient water will be useful for future microbial risk assessments.

Human adenoviruses as waterborne index pathogens and their use for Quantitative Microbial Risk Assessment

The current microbial water quality standards are based on the monitoring of fecal indicator organisms, which are mainly bacterial indicators (i.e., Escherichia coli, intestinal enterococci), however epidemiological data indicate that viruses are important etiological agents of waterborne illnesses. Among waterborne viruses, human adenovirus can be considered as an index pathogen, owing to its abundance in sewage and persistence in the environment, as well as its potential infectivity. In this study, data on human adenoviruses from different water matrices (the entrance and exit of a water treatment plant, rivers and seawaters) were analyzed, in parallel with traditional fecal bacterial indicators and somatic coliphages. The results showed a 64% frequency of positive adenovirus samples, decreasing from the sewage system (100% at the entrance and 94% at the exit) to rivers (92% and 72% for different rivers) and seawater (21%). Adenovirus concentrations showed a significant correlation with somatic coliphages in one river and seawater, thus supporting the recent inclusion of coliphages as viral indicators in water safety guidelines. The data collected were used to estimate adenovirus to indicator ratios, which could be used as input in Quantitative Microbial Risk Assessment (QMRA) studies.

Quantitative Microbial Risk Assessment for Workers Exposed to Bioaerosol in Wastewater Treatment Plants Aimed at the Choice and Setup of Safety Measures

Biological risk assessment in occupational settings currently is based on either qualitative or semiquantitative analysis. In this study, a quantitative microbial risk assessment (QMRA) has been applied to estimate the human adenovirus (HAdV) health risk due to bioaerosol exposure in a wastewater treatment plant (WWTP). A stochastic QMRA model was developed considering HAdV as the index pathogen, using its concentrations in different areas and published dose–response relationship for inhalation. A sensitivity analysis was employed to examine the impact of input parameters on health risk. The QMRA estimated a higher average risk in sewage influent and biological oxidation tanks (15.64% and 12.73% for an exposure of 3 min). Sensitivity analysis indicated HAdV concentration as a predominant factor in the estimated risk. QMRA results were used to calculate the exposure limits considering four different risk levels (one illness case per 100, 1.000, 10.000, and 100.000 workers): for 3 min exposures, we obtained 565, 170, 54, and 6 GC/m³ of HAdV. We also calculated the maximum time of exposure for each level for different areas. Our findings can be useful to better define the effectiveness of control measures, which would thus reduce the virus concentration or the exposure time.

Comparative enteric viruses and coliphage removal during wastewater treatment processes in a sub-tropical environment

Microbiological safety of reclaimed water is one of the most important issues in managing potential health risks related to wastewater recycling. Presence and removal of human adenovirus (HAdV), human polyomavirus (HPyV), human torque teno virus (HTtV) and somatic coliphage family Microviridae in three wastewater treatment plants (WWTP) in sub-tropical Brisbane, Australia was investigated. All three WWTPs employ activated sludge process with added on Bardenpho process for nutrient removal. HPyV, HAdV, HTtV and Microviridae were consistently detected in the influent (10⁵ to 10⁶ Genomic copies (GC) L^-1) and secondary treated effluent (10² to 10³GCL^-1). The results of this study suggest that, under appropriate conditions, WWTPs with activated sludge process in sub-tropical climate could be an effective treatment barrier with >3 log₁₀ removal of enteric virus. The geometric mean of pooled data for each virus from all sites showed the highest removal for HPyV (3.65 log₁₀) and lowest for HAdV (2.79 log₁₀) which was statistically significant (p=0.00001). Whereas, the removal rate of HTtV and Microviridae was identical (2.81 log₁₀). A poor correlation between the presence of enteric virus in influent or effluent with routinely monitored physicochemical parameters suggests limited use of physicochemical parameters as predictors of enteric virus presence. High prevalence of HAdV in influent and effluent combined with comparatively low removal suggest that it could be used as a model microorganism for determining enteric virus removal efficacy. Additional tertiary treatment may be required prior to effluent reuse for non-potable purposes or discharge into the recreational waters to prevent exposure of people to health hazards.

Revisiting Antibiotic Resistance Spreading in Wastewater Treatment Plants - Bacteriophages as a Much Neglected Potential Transmission Vehicle

The spread of antibiotic resistance is currently a major threat to health that humanity is facing today. Novel multidrug and pandrug resistant bacteria are reported on a yearly basis, while the development of novel antibiotics is lacking. Focus to limit the spread of antibiotic resistance by reducing the usage of antibiotics in health care, veterinary applications, and meat production, have been implemented, limiting the exposure of pathogens to antibiotics, thus lowering the selection of resistant strains. Despite these attempts, the global resistance has increased significantly. A recent area of focus has been to limit the spread of resistance through wastewater treatment plants (WWTPs), serving as huge reservoirs of microbes and resistance genes. While being able to quite efficiently reduce the presence of resistant bacteria entering any of the final products of WWTPs (e.g., effluent water and sludge), the presence of resistance genes in other formats (mobile genetic elements, bacteriophages) has mainly been ignored. Recent data stress the importance of transduction in WWTPs as a mediator of resistance spread. Here we examine the current literature in the role of WWTPs as reservoirs and hotspots of antibiotic resistance with a specific focus on bacteriophages as mediators of genetic exchange.

Cotransport of human adenoviruses with clay colloids and TiO2 nanoparticles in saturated porous media: Effect of flow velocity

This study focuses on the effects of two clay colloids (kaolinite, KGa-1b and montmorillonite, STx-1b) and titanium dioxide (TiO₂) nanoparticles (NPs) on human adenovirus transport and retention in water saturated porous media at three different pore water velocities (0.38, 0.74, and 1.21cm/min). Transport and cotransport experiments were performed in 30-cm long laboratory columns packed with clean glass beads with 2mm diameter. The experimental results suggested that the presence of KGa-1b, STx-1b and TiO₂ NPs increased human adenovirus inactivation and attachment onto the solid matrix, due to the additional attachment sites available. Retention by the packed column was found to be highest (up to 99%) in the presence of TiO₂ NPs at the highest pore water velocity, and lowest in the presence of KGa-1b. The experimental results suggested that adenoviruses would undergo substantial aggregation or heteroaggregation during cotransport. However, no distinct relationships between mass recoveries and water velocity could be established from the experimental cotransport data. Note that for the cotransport experiments, collision efficiency values were shown to be higher for the higher flow rate examined in this study.

Optimization of sampling strategy to determine pathogen removal efficacy of activated sludge treatment plant

Large-scale wastewater schemes rely on multi-barrier approach for the production of safe and sustainable recycled water. In multi-barrier wastewater reclamation systems, conventional activated sludge process (ASP) often constitutes a major initial treatment step. The main aim of this research was to determine most appropriate sampling approach to establish pathogen removal efficacy of ASP. The results suggest that ASP is capable of reducing human adenovirus (HAdV) and polyomavirus (HPyV) by up to 3 log₁₀. The virus removal data suggests that HAdV removal is comparable to somatic bacteriophage belonging to Microviridae family. Due to the high removal of Escherichia coli (>3 log₁₀) and very poor correlation with the enteric virus, it is not recommended that E. coli be used as a surrogate for enteric virus removal. The results also demonstrated no statistically significant differences (t test, P > 0.05) in calculated log removal values (LRVs) for HAdV, HPyV, and Microviridae from samples collected on hydraulic retention time (HRT) or simultaneous paired samples collected for influent and effluent. This indicates that a more practical approach of simultaneous sampling for influent and effluent could be used to determine pathogen removal efficiency of ASP. The results also suggest that a minimum of 10, preferably 20 samples, are required to fully capture variability in the removal of virus. In order to cover for the potential seasonal prevalence of viruses such as norovirus and rotavirus, sampling should be spread across all seasons.

Quantitative PCR Detection and Characterisation of Human Adenovirus, Rotavirus and Hepatitis A Virus in Discharged Effluents of Two Wastewater Treatment Facilities in the Eastern Cape, South Africa

The occurrence of enteric viruses in reclaimed wastewater, their removal by efficient treatment processes and the public health hazards associated with their release into the environments are of great significance in environmental microbiology. In this study, TaqMan-based real-time polymerase chain reaction (qPCR) was used to assess the prevalence of human adenovirus (HAdV), rotavirus (RV) and hepatitis A virus (HAV) in the final effluents of two wastewater treatment plants in the Eastern Cape Province, South Africa, over a twelve-month sampling period. The correlation between the concentrations of viruses in the effluents samples and faecal coliform (FC) densities were assessed as to validate the use of FC as microbiological indicator in water quality assessment. HAdV was detected in 62.5 % (30/48) of the samples with concentrations ranging between 8.4 × 101 and 1.0 × 105 genome copies/L while HAV and RV were only detected at concentrations below the set detection limits. FCs densities ranged from 1 to 2.7 × 104 CFU/100 ml. Adenovirus species HAdV-B (serotype 2) and HAdV-F (serotype 41) were detected in 86.7 % (26/30) and 6.7 % (2/30) of the HAdV-positive samples, respectively. No consistent seasonal trend was observed in HAdV concentrations, however, increased concentrations of HAdV were generally observed in the winter months. Also, there was no correlation between the occurrence of HAdV and FC at both the treatment plants. The persistent occurrence of HAdV in the discharged treated effluents points to the potential public health risk through the release of HAdV into the receiving watersheds, and the possibility of their transmission to human population.

Quantitative Microbial Risk Assessment in Occupational Settings Applied to the Airborne Human Adenovirus Infection

Quantitative Microbial Risk Assessment (QMRA) methodology, which has already been applied to drinking water and food safety, may also be applied to risk assessment and management at the workplace. The present study developed a preliminary QMRA model to assess microbial risk that is associated with inhaling bioaerosols that are contaminated with human adenovirus (HAdV). This model has been applied to air contamination data from different occupational settings, including wastewater systems, solid waste landfills, and toilets in healthcare settings and offices, with different exposure times. Virological monitoring showed the presence of HAdVs in all the evaluated settings, thus confirming that HAdV is widespread, but with different average concentrations of the virus. The QMRA results, based on these concentrations, showed that toilets had the highest probability of viral infection, followed by wastewater treatment plants and municipal solid waste landfills. Our QMRA approach in occupational settings is novel, and certain caveats should be considered. Nonetheless, we believe it is worthy of further discussions and investigations.

Technical aspects of using human adenovirus as a viral water quality indicator

Despite dramatic improvements in water treatment technologies in developed countries, waterborne viruses are still associated with many of cases of illness each year. These illnesses include gastroenteritis, meningitis, encephalitis, and respiratory infections. Importantly, outbreaks of viral disease from waters deemed compliant from bacterial indicator testing still occur, which highlights the need to monitor the virological quality of water. Human adenoviruses are often used as a viral indicator of water quality (faecal contamination), as this pathogen has high UV-resistance and is prevalent in untreated domestic wastewater all year round, unlike enteroviruses and noroviruses that are often only detected in certain seasons. Standard methods for recovering and measuring adenovirus numbers in water are lacking, and there are many variations in published methods. Since viral numbers are likely under-estimated when optimal methods are not used, a comprehensive review of these methods is both timely and important. This review critically evaluates how estimates of adenovirus numbers in water are impacted by technical manipulations, such as during adenovirus concentration and detection (including culturing and polymerase-chain reaction). An understanding of the implications of these issues is fundamental to obtaining reliable estimation of adenovirus numbers in water. Reliable estimation of HAdV numbers is critical to enable improved monitoring of the efficacy of water treatment processes, accurate quantitative microbial risk assessment, and to ensure microbiological safety of water.

Performance of three small-scale wastewater treatment plants. A challenge for possible re use

The study focused on the assessment of the performance of three WWTPs in Greece by the estimation of the microbiological and chemical quality of influent and effluent sewage. Physicochemical parameters were recorded (temperature, pH, COD, BOD, suspended solids, conductivity), and meteorological data were collected (air temperature, rain). Microbiological parameters were analyzed (Escherichia coli, total coliforms, bacteriophages, Salmonella, human adenoviruses, Candida, Pseudallescheria boydii, helminths, parasites Cryptosporidium ssp., and Giardia spp.). Statistically significant correlations among the various aforementioned parameters were investigated, in an attempt to propose appropriate processing performance indicators. Furthermore, the study aimed to assess current joint ministerial decision (JMD) on wastewater reuse, for irrigation purposes; to evaluate its practicability and its potential for public health protection. In the vast majority, outlet samples from all three studied WWTPs were not appropriate for irrigation reuse purposes based on BOD50 and suspended solids limit values, set by the current JMD, for both limited and unrestricted irrigation applications. Reductions for E. coli, total coliforms, and bacteriophages were found to range between 2-3, 1.5-2.5, and 2-4 log10 values, respectively. Salmonella spp. was detected in outlet sewage samples from Patra (PAT), Arachova (ARH), and Livadeia (LEV), at 23% (3/13), 33% (4/12), and 38% (5/13), respectively. Molds were detected at 92.3% (12/13), 100% (13/13), and 91.6% (11/12), respectively, while Candida was found at 85% (11/13), 67% (8/12), and 46% (6/13). A high prevalence of Pseudallescheria boydii, in outlet samples from all studied WWTPs is an important public health issue, which underlines the need for further studies on this emerging fungal pathogen in wastewater reuse applications. Pseudallescheria boydii was found at 85% (11/13), 67% (8/12), and 46% (6/13), respectively. Helminths were found in both inlet and outlet samples, of all studied WWTPs, at 100%. Human adenoviruses, were detected at high percentages in outlet samples at 76.9% (10/13), 92.3% (12/13), 84.6% (11/13), respectively, while no influence of UV irradiation was recorded on the entry and exit loads of human adenoviruses. No influence of meteorological parameters was found on the microbiological and chemical parameters, with the exception of a weak positive correlation between environmental temperature and bacteriophages. A moderate positive correlation was found between BOD and suspended solids, bacteriophages, and total coliforms, bacteriophages and E. coli, and bacteriophages and adenoviruses. A significant positive correlation was found between total coliforms and E. coli, COD and BOD, and suspended solids and COD. No correlations were proved between human pathogens and bacterial indicator parameters. Collectively, our findings underlined the unsuitability of the current JMD on wastewater reuse in Greece, or public health protection. The study is expected to support the development of a public health risk assessment model based on quantitative risk assessment on the use of treated wastewater for irrigation purposes in Greece.

Interaction of human adenoviruses and coliphages with kaolinite and bentonite

Human adenoviruses (hAdVs) are pathogenic viruses responsible for public health problems worldwide. They have also been used as viral indicators in environmental systems. Coliphages (e.g., MS2, ΦX174) have also been studied as indicators of viral pollution in fecally contaminated water. Our objective was to evaluate the distribution of three viral fecal indicators (hAdVs, MS2, and ΦΧ174), between two different phyllosilicate clays (kaolinite and bentonite) and the aqueous phase. A series of static and dynamic experiments were conducted under two different temperatures (4, 25°C) for a time period of seven days. HAdV adsorption was examined in DNase I reaction buffer (pH=7.6, and ionic strength (IS)=1.4mM), whereas coliphage adsorption in phosphate buffered saline solution (pH=7, IS=2mM). Moreover, the effect of IS on hAdV adsorption under static conditions was evaluated. The adsorption of hAdV was assessed by real-time PCR and its infectivity was tested by cultivation methods. The coliphages MS2 and ΦΧ174 were assayed by the double-layer overlay method. The experimental results have shown that coliphage adsorption onto both kaolinite and bentonite was higher for the dynamic than the static experiments; whereas hAdV adsorption was lower under dynamic conditions. The adsorption of hAdV increased with decreasing temperature, contrary to the results obtained for the coliphages. This study examines the combined effect of temperature, agitation, clay type, and IS on hAdV adsorption onto clays. The results provide useful new information on the effective removal of viral fecal indicators (MS2, ΦX174 and hAdV) from dilute aqueous solutions by adsorption onto kaolinite and bentonite. Factors enabling enteric viruses to penetrate soils, groundwater and travel long distances within aquifers are important public health issues. Because the observed adsorption behavior of surrogate coliphages MS2 and ΦΧ174 is substantially different to that of hAdV, neither MS2 nor ΦΧ174 is recommended as a suitable model for adenovirus.

Viral contamination of aerosol and surfaces through toilet use in health care and other settings

BACKGROUND

The airborne spreading of enteric viruses can occur through the aerosol and droplets produced by toilet flushing. These can contaminate the surrounding environment, but few data exist to estimate the risk of exposure and infection. For this reason environmental monitoring of air and selected surfaces was carried out in 2 toilets of an office building and in 3 toilets of a hospital before and after cleaning operations.

METHODS

To reveal the presence of norovirus, enterovirus, rhinovirus, human rotavirus, and Torque teno virus and to quantify human adenovirus and bacteria counts, molecular and cultural methods were used.

RESULTS

On the whole, viruses were detected on 78% of surfaces and in 81% of aerosol. Among the researched viruses, only human adenovirus and Torque teno virus were found in both surface and air samples. In several cases the same adenovirus strain was concurrently found in all matrices. Bacterial counts were unrelated to viral presence and cleaning did not seem to substantially reduce contamination.

CONCLUSIONS

The data collected in our study confirm that toilets are an important source of viral contamination, mainly in health care settings, where disinfection can have a crucial role in preventing virus spread.