A Somatic Coliphage Threshold Approach To Improve the Management of Activated Sludge Wastewater Treatment Plant Effluents in Resource-Limited Regions

A new understanding of somatic coliphages belonging to the Microviridae family in urban wastewater

Somatic coliphages (SC) and F-specific RNA coliphages (FRNAPH) have been included in regulations or guidelines by several developed countries as a way of monitoring water safety and the microbiological quality of shellfish harvesting waters. SC are highly diverse in their morphology, size and genome. The Microviridae family contains three genera of phages (Alphatrevirus, Gequatrovirus, and Sinsheimervirus), all having a capsid of similar morphology (icosahedral) and size (25-30 nm in diameter) to that of common pathogenic enteric viruses. Three PCR assays specific for each genus of Microviridae were designed to study these phages in raw and treated wastewater (WW) in order to gain knowledge about the diversity and prevalence of Microviridae among SC, as well as their inactivation and removal during WW treatments. Among the four wastewater treatment plants (WWTPs) monitored here, two WWTPs applied disinfection by UV light as tertiary treatment. First, we noticed that Microviridae represented 10 to 30 % of infectious SC in both raw and treated WW. Microviridae appeared to behave in the same way as all SC during these WW treatments. As expected, the highest inactivation, at least 4 log10, was achieved for infectious Microviridae and SC in both WWTPs using UV disinfection. PCR assays showed that the highest removal of Microviridae reached about 4 log10, but the phage removal can vary greatly between WWTPs using similar treatments. This work forms the basis for a broader evaluation of Microviridae as a viral indicator of water treatment efficiency and WW reuse.

Partitioning and inactivation of enveloped and nonenveloped viruses in activated sludge, anaerobic and microalgae-based wastewater treatment systems

Anaerobic and microalgae-based technologies for municipal wastewater treatment have emerged as sustainable alternatives to activated sludge systems. However, viruses are a major sanitary concern for reuse applications of liquid and solid byproducts from these technologies. To assess their capacity to reduce viruses during secondary wastewater treatment, enveloped Phi6 and nonenveloped MS2 bacteriophages, typically used as surrogates of several types of wastewater viruses, were spiked into batch bioreactors treating synthetic municipal wastewater (SMWW). The decay of Phi6 and MS2 in anaerobic and microalgae-based reactors was compared with the decay in activated sludge batch reactors for 96 h (Phi6) and 144 h (MS2). In each reactor, bacteriophages in the soluble and solids fractions were titered, allowing the assessment of virus partitioning to biomass over time. Moreover, the influence of abiotic conditions such as agitation, oxygen absence and light excess in activated sludge, anaerobic and microalgae reactors, respectively, was assessed using dedicated SMWW control reactors. All technologies showed Phi6 and MS2 reductions. Phi6 was reduced in at least 4.7 to 6.5 log10 units, with 0 h concentrations ranging from 5.0 to 6.5 log10 PFU mL-1. Similarly, reductions achieved for MS2 were of at least 3.9 to 7.2 log10 units, from starting concentrations of 8.0 to 8.6 log10 PFU mL-1. Log-logistic models adjusted to bacteriophages' decay indicated T90 values in activated sludge and microalgae reactors of 2.2 and 7.9 h for Phi6 and of 1.0 and 11.5 h for MS2, respectively, all within typical hydraulic retention times (HRT) of full-scale operation. In the case of the microalgae technology, T99 values for Phi6 and MS2 of 12.7 h and 13.6 h were also lower than typical operating HRTs (2-10 d), while activated sludge and anaerobic treatment achieved less than 99 % of Phi6 and 50 % of MS2 inactivation within 12 h of typical HRT, respectively. Thus, the microalgae-based treatment exhibited a higher potential to reduce the disinfection requirements of treated wastewater.

Coliphages as viral indicators in municipal wastewater: A comparison between the ISO and the USEPA methods based on a systematic literature review

The use of traditional faecal indicator bacteria as surrogate organisms for pathogenic viruses in domestic wastewater has been noted as a problematic as concentrations and removal rates of bacteria and viruses do not seem to correlate. In this sense, bacteriophages (phages) emerge as potential viral indicators, as they are commonly found in wastewater in high levels, and can be quantified using simple, fast, low-cost methods. Somatic and F-specific coliphages comprise groups of phages commonly used as indicators of water quality. There are two internationally recognised methods to detect and enumerate coliphages in water samples, the International Standardization Organization (ISO) and the US Environmental Protection Agency (USEPA) methods. Both methods are based on the lysis of specific bacterial host strains infected by phages. Within this context, this systematic literature review aimed at gathering concentrations in raw and treated domestic wastewater (secondary, biological treatment systems and post-treatment systems), and removal efficiencies of somatic and F-specific coliphages obtained by ISO and USEPA methods, and then compare both methods. A total of 33 research papers were considered in this study. Results showed that the ISO method is more commonly applied than the USEPA method. Some discrepancies in terms of concentrations and removal efficiencies were observed between both methods. Higher removal rates were observed for both somatic and F-specific coliphages in activated sludge systems when using the USEPA method compared to the ISO method; in other secondary (biological) treatment systems, this was observed only for F-specific coliphages. The use of different standardised methods available might lead to difficulties in obtaining and comparing phage data in different conditions and locations. Future research comparing both ISO and USEPA methods as well as viral and bacterial pathogens and indicators in WWTP is recommended.

Virus inactivation by sequential ultraviolet-chlorine disinfection: Synergistic effect and mechanism

The COVID-19 outbreak has raised concerns about the efficacy of the disinfection process followed in water treatment plants in preventing the spread of viruses. Ultraviolet (UV) and chlorine multi-barrier disinfection processes are commonly used in water treatment plants; however, their effects on virus inactivation are still unclear. In this study, the effects of different disinfection processes (i.e., UV, free chlorine, and their combination) on waterborne viruses were analyzed using bacteriophage surrogates (i.e., MS2 and PR772) as alternative indicators. The results showed that the inactivation rates of PR772 by either UV or free chlorine disinfection were higher than those of MS2. PR772 was approximately 1.5 times more sensitive to UV disinfection and 8.4 times more sensitive to chlorine disinfection than MS2. Sequential UV-chlorine disinfection had a synergistic effect on virus inactivation, which was enhanced by an increase in the UV dose. As compared with single free chlorine disinfection, UV irradiation at 40 mJ cm^-2 enhanced MS2 and PR772 inactivation significantly with a 2.7-fold (MS2) and a 1.7-fold (PR772) increase in the inactivation rate constants on subsequent chlorination in phosphate buffered saline. The synergistic effect was also observed in real wastewater samples, in which the MS2 inactivation rate increased 1.4-fold on subsequent chlorination following UV irradiation at 40 mJ cm^-2. The mechanism of the synergistic effect of sequential UV-chlorine disinfection was determined via sodium dodecyl sulfate-polyacrylamide gel electrophoresis, using MS2 as an indicator. The results showed that the synergistic effect was due to damage to MS2 surface proteins caused by previous UV disinfection, which enhanced the sensitivity of MS2 to chlorination. This study provides a feasible approach for the efficient inactivation of viruses in water supply and drainage.

Occurrence of Hepatitis A Virus in Water Matrices: A Systematic Review and Meta-Analysis

Hepatitis A is a common form of viral hepatitis. It is usually transmitted through the ingestion of contaminated food and water. This systematic review was carried out to summarise the overall prevalence of Hepatitis A virus (HAV) in different water matrices: untreated and treated wastewater, surface water, groundwater, drinking water, and others (e.g., irrigation water and floodwater). The literature search was performed in four databases: PubMed, Web of Science, Global Index Medicus, and Excerpta Medica Database. Heterogeneity (I2) was assessed using the χ2 test on the Cochran Q statistic and H parameters. A total of 200 prevalence data from 144 articles were included in this meta-analysis. The overall prevalence of HAV in water matrices was 16.7% (95% CI: 13.4−20.3). The prevalence for individual matrix was as follows: 31.4% (95% CI: 23.0−40.4) untreated wastewater, 18.0% (95% CI: 9.5−28.2) treated wastewater, 15.0% (95% CI: 10.1−20.5) surface water, 2.3% (95% CI: 0.1−6.0) in groundwater, 0.3% (95% CI: 0.0−1.7) in drinking water, and 8.5% (95% CI: 3.1−15.6) in other matrices. The prevalence was higher in low-income economies (29.0%). Africa and Eastern Mediterranean were the regions with higher HAV prevalence values. This study showed a high heterogeneity (I2 > 75%) with a significant publication bias (p value Egger test < 0.001). The results of this review suggest that water matrices could be an important route of HAV transmission even in industrialized countries, despite the lower prevalence compared to less industrialized countries, and the availability of advanced water management systems. More effective water/wastewater treatment strategies are needed in developing countries to limit the environmental circulation of HAV.

Quantitative microbial risk assessment of enteroviruses in raw-eatable vegetables irrigated by wastewater: examining different scenarios of washing

Due to the increasing water crisis, the reuse of wastewater deserves attention as a method to reduce the pressure of the water crisis, especially in developing countries. The application of health risk assessment models is a way to estimate disease burdens associated with crop irrigation by wastewater effluents. In this study, a quantitative microbial risk assessment (QMRA) with probabilistic Monte-Carlo simulation was used to estimate the annual risk of enteroviruses (EVs) infection and disease burden for consumers of effluent-irrigated raw vegetables in Tehran, the capital of Iran. Wastewater effluent samples were collected over two seasons: summer and winter. EVs were analyzed in three stages, concentration and separation, cell culture, and real-time PCR (RT-PCR). A questionnaire was used to determine the dominant patterns of vegetable washing by consumers. There were 4 vegetable washing steps: wiping away mud (A), rinsing (B), using detergents (C), using disinfectants (D). 5 patterns of washing were examined in the laboratory and the concentration of enteroviruses was measured in every pattern. pattern 1: just wiping away mud (A), pattern 2: wiping away mud and rinsing (AB), pattern 3: wiping away mud by using detergents and rinsing (ABCB), pattern 4: wiping away mud by using disinfectants and rinsing (ABDB), and pattern 5: wiping away mud by using detergents and disinfectants and rinsing (ABCBDB). For washing pattern 1, pattern 2, and pattern 3, the estimated annual infection risk of EVs was estimated to be 5.6 × 10^-1, 3.6 × 10^-1, 1.7 × 10^-1 (risk/per.day), and burden of disease was calculated as 3 × 10^-2, 2 × 10^-2, and 9 × 10^-3 (burden/year), respectively. The results showed that if vegetables are washed according to method 5, the microbial risk will be minimized and the excess prevalence of viral infections will be eliminated.

Resource recovery in life cycle assessment of sludge treatment: Contribution, sensitivity, and uncertainty

This study focused on the resource recovery of sludge treatment by quantifying the environmental contributions, identifying the influential factors, and comparing different scenarios. Life cycle assessment (LCA) of sewage sludge treatment was carried out to estimate the environmental impacts of six scenarios: (1) co-digestion of sludge and food waste; (2) co-gasification of sludge and woody waste; (3) co-incineration of sludge and used oil; (4) landfilling; (5) incineration; and (6) anaerobic digestion combined with incineration. Results demonstrate that the resource recovery had a substantial contribution to the environmental performance of the sludge treatment, while the degree of contribution was largely affected by various treatment scenarios and diverse impact categories. To gain deep insight into the parameters related to resource recovery, sensitivity analysis was performed to investigate the influence of the parameters on the LCA results, including the organic content, conversion efficiency of organic matter to methane, and other energy conversion efficiencies. After integrating the inventory variation of those parameters into the decision process via the Monte Carlo simulation, results indicate that no obviously superior scenario could be identified. Conversely, when parameter uncertainty was not considered, co-gasification of sludge and woody waste exhibited the most preferable environmental performance. Overall, this study demonstrates that considering the parameter uncertainty of resource recovery will contribute to a more transparent evaluation process, but will inevitably increase the complexity of the decision-making process based on LCA results because it is difficult to determine a sludge treatment scenario that decisively outperforms the others.

Monitoring of human enteric virus and coliphages throughout water reuse system of wastewater treatment plants to irrigation endpoint of leafy greens

One solution to current water scarcity is the reuse of treated wastewater. Water reuse systems have to be examined as a whole, including the efficacy of water-reclamation treatments and the operation steps from the wastewater inlet into the WWTP to the irrigation endpoint, including the irrigated crop. In this study, the monitoring of human enteric viruses and coliphages were assessed in two water reused systems. The presence of hepatitis A virus (HAV) and human noroviruses genogroups I and II (GI and GII) were analyzed by real-time RT-PCR (RT-qPCR) in water (n = 475) and leafy green samples (n = 95). Total coliphages were analyzed by the double-layer agar plaque technique. The prevalence of HAV in water samples was very low (c.a. 2%), mostly linked to raw sewage, while for leafy green samples, none was positive for HAV. In leafy greens, prevalence of norovirus was low (less than 5-6%). The highest reductions for norovirus were observed in samples taken from the water reservoirs used by the growers near the growing field. The virus die-off during water storage due to solar radiation could be considered as an additional improvement. Reclamation treatments significantly reduced the prevalence and the counts of noroviruses GI and GII and coliphages in reclaimed water. However, the coliphage reductions (c.a. 5 log) do not comply with the specifications included in the new European regulation on reclaimed water (≥6.0 log). Correlations between noroviruses GI and GII and coliphages were found only in positive samples with high concentrations (>4.5 log PFU/100 mL). A high percentage of samples (20-25%) negative for total coliphages showed moderate norovirus counts (1-3 logs), indicating that coliphages are not the most suitable indicator for the possible presence of human enteric viruses.

Wastewater-Based Epidemiology of Enteric Viruses and Surveillance of Acute Gastrointestinal Illness Outbreaks in a Resource-Limited Region

Acute gastrointestinal illness (AGI) continues to be an important cause of morbidity and mortality among all ages. This study applied the principles of wastewater-based epidemiology for the preventive identification of potential outbreaks of acute viral gastroenteritis and hepatitis A by analyzing the presence of human enteric viruses in influents of small municipal wastewater treatment plants (WWTPs) handling domestic sewage, together with public health reports of acute diarrheal and hepatitis A disease in Costa Rica during 2013. Raw wastewater samples were collected during four seasonal periods with different rainfall levels. The presence of five human enteric viruses (rotavirus A, norovirus GI, norovirus GII, enterovirus, and hepatitis A virus) was studied by endpoint and real-time polymerase chain reaction in influents of five WWTPs. Cases of AGI were analyzed using historical public health reports of endemic levels and quartile ranges for each administrative and territorial area where the WWTPs are located and for its surrounding counties. A tendency for a higher rate of positive viral tests was present 1 week before an increase of AGI cases. Epidemiological weeks categorized as Outbreak (above the 75th percentile) and Success (below the 25th percentile) showed statistically significant differences in terms of positive viral test rates (Wilcoxon test, P = 0.05). Virological monitoring of wastewater in small WWTPs is an appropriate model for epidemiological surveillance of diarrheal and hepatitis A diseases in low- and middle-resource countries.

Human Fecal Pollution Monitoring and Microbial Risk Assessment for Water Reuse Potential in a Coastal Industrial-Residential Mixed-Use Watershed

Rapid economic development has caused industrial expansion into residential communities, leading to higher fecal pollution loads that could be discharged into aquatic environments. However, little is known regarding the potential microbial impact on human health. This study investigated microbial contamination from coastal industrial–residential community areas in nine sampling sites in waterways during three dry events. A general microbial source tracking (MST) marker, GenBac3, was detected in all samples from all three events, indicating continuing fecal pollution in the area, mostly from human sewage contamination. This was shown by the human-specific genetic marker crAssphage (88.9%) and human polyomavirus (HPyVs; 92.6%) detection. Enteric human adenovirus (HAdV40/41) showed three positive results only from residential sites in the first event. No spatial difference was observed for MST markers and traditional fecal indicators (total coliforms and Escherichia coli) in each event. Still, a significantly lower abundance of GenBac3, HPyVs, and total coliforms in the first sampling event was detected. Spearman’s rho analysis indicated a strong correlation among certain pairs of microbial parameters. Multivariate analysis revealed two clusters of samples separated by land use type (industrial vs. residential). According to factor analysis of mixed data, the land use parameter was more associated with physicochemical parameters (i.e., salinity, conductivity, water temperature, and dissolved oxygen). A Quantitative Microbial Risk Assessment (QMRA) was then conducted to estimate the annual infection risks of HAdV40/41 for non-potable water reuse purposes using predicted concentrations from crAssphage and HPyVs. The highest risks (95th percentiles) were ranked by food crop irrigation, aquaculture, and toilet flushing, at 10^–1, 10^–2, and 10^–3 per person per year (pppy). Required treatment levels to achieve a 10^–4 pppy annual infection risk were estimated. QMRA-based water treatment scenarios were suggested, including chlorination for toilet flushing reuse and depth filtration prior to chlorination for aquaculture and food crop irrigation. Microbial monitoring combined with a QMRA could provide better insights into fecal pollution patterns and the associated risks, facilitating effective water quality management and appropriate prior treatments for water reuse.

Relationships among microbial indicators of fecal pollution, microbial source tracking markers, and pathogens in Costa Rican coastal waters

Tropical coastal waters are understudied, despite their ecological and economic importance. They also reflect projected climate change scenarios for other climate zones, e.g., increased rainfall and water temperatures. We conducted an exploratory microbial water quality study at a tropical beach influenced by sewage-contaminated rivers, and tested the hypothesis that fecal microorganisms (fecal coliforms, enterococci, Clostridium perfringens, somatic and male-specific coliphages, pepper mild mottle virus (PMMoV), Bacteroides HF183, norovirus genogroup I (NoVGI), Salmonella, Cryptosporidium and Giardia) would vary by season and tidal stage. Most microorganisms' concentrations were greater in the rainy season; however, NoVGI was only detected in the dry season and Cryptosporidium was the only pathogen most frequently detected in rainy season. Fecal indicator bacteria (FIB) levels exceeded recreational water quality criteria standards in >85% of river samples and in <50% of ocean samples, regardless of the FIB or regulatory criterion. Chronic sewage contamination was demonstrated by detection of HF183 and PMMoV in 100% of river samples, and in >89% of ocean samples. Giardia, Cryptosporidium, Salmonella, and NoVGI were frequently detected in rivers (39%, 39%, 26%, and 39% of samples, respectively), but infrequently in ocean water, particularly during the dry season. Multivariate analysis showed that C. perfringens, somatic coliphage, male-specific coliphage, and PMMoV were the subset of indicators that maximized the correlation with pathogens in the rivers. In the ocean, the best subset of indicators was enterococci, male-specific coliphage, and PMMoV. We also executed redudancy analyses on environmental parameters and microorganim concentrations, and found that rainfall best predicted microbial concentrations. The seasonal interplay of rainfall and pathogen prevalence undoubtedly influences beach users' health risks. Relationships are likely to be complex, with some risk factors increasing and others decreasing each season. Future use of multivariate approaches to better understand linkages among environmental conditions, microbial predictors (fecal indicators and MST markers), and pathogens will improve prediction of high-risk scenarios at recreational beaches.