Comparison of Predicted Microbiological Human Health Risks Associated with de Facto, Indirect, and Direct Potable Water Reuse

Microbial Treatment Targets for Potable and Nonpotable Water Reuse - A Comprehensive Update and Harmonization

Increasing pressures on traditional sources of water have accelerated the adoption of water reuse throughout the world. A key consideration for communities pursuing water reuse is understanding the amount of treatment that is needed to ensure adequate human health protection. Several U.S. EPA documents describe the importance of managing acute microbial risks and highlight the utility of quantitative microbial risk assessment for developing "fit-for-purpose" treatment targets based on the source of water and end-use. However, there are no U.S. federal water reuse regulations and states are currently considering microbial treatment targets for various applications. Previous publications have yet to address this need by using an updated and consistent set of input parameters to present risk-based microbial treatment targets across a wide range of sources of water, end-use applications, and health benchmarks. This work combines the most current modeling inputs and dose-response parameter values to provide probability of infection and disease burden-based microbial treatment targets for untreated municipal wastewater, untreated onsite wastewater, graywater, stormwater, and roof runoff water used for potable reuse, indoor nonpotable use, and landscape irrigation applications.

Assessing relative risks of municipal wastewater disposal options for Southeast Florida

A comparative assessment of the risks of the three current wastewater effluent disposal options and three other potential options was conducted for Southeast Florida communities. The question was how the risk to humans from the use of potable reuse compares to the other five available wastewater disposal alternatives. The need for this type of risk assessment is due to the potential to use potable reuse as a water supply and the potential resistance from the public as a result of such a proposal. Water quality data relevant to disposal of wastewater treatment plant effluent from South Florida utilities along with water quality data on the receiving waters and drinking water standards were obtained for the project. The comparison of the public health risks associated with these disposal alternatives indicated that health risks associated with deep wells and direct potable reuse were generally lower than those of the other alternatives.

Influence of suspended particles and dissolved organic matters on virus enrichment in reclaimed water by two-step tangential flow ultrafiltration: Phenomena and mechanisms

Enteric virus concentration in large-volume water samples is crucial for detection and essential for assessing water safety. Certain dissolution and suspension components can affect the enrichment process. In this study, tangential flow ultrafiltration (TFUF) was used as an enrichment method for recovering enteric virus in water samples. Interestingly, the bacteriophage MS2 recovery in reclaimed water and the reclaimed water without particles were higher than that in ultrapure water. The simulated reclaimed water experiments showed that humic acid (HA) (92.16% ± 4.32%) and tryptophan (Try) (81.50 ± 7.71%) enhanced MS2 recovery, while the presence of kaolin (Kaolin) inhibited MS2 recovery with an efficiency of 63.13% ± 11.17%. Furthermore, Atomic force microscopy (AFM) revealed that the MS2-HA cluster and the MS2-Try cluster had larger roughness values on the membrane surface, making it difficult to be eluted, whereas MS2-Kaolin cluster had compact surfaces making it difficult to be eluted. Additionally, the MS2-HA cluster is bound to the membrane by single hydrogen bond with SO, whereas both the MS2-Try cluster and the MS2-Kaolin cluster are bound to the membrane by two hydrogen bonds, making eluting MS2 challenging. These findings have potential implications for validating standardized methods for virus enrichment in water samples.

Direct potable reuse and birth defects prevalence in Texas: An augmented synthetic control method analysis of data from a population-based birth defects registry

Background

Direct potable reuse (DPR) involves adding purified wastewater that has not passed through an environmental buffer into a water distribution system. DPR may help address water shortages and is approved or is under consideration as a source of drinking water for several water-stressed population centers in the United States, however, there are no studies of health outcomes in populations who receive DPR drinking water. Our objective was to determine whether the introduction of DPR for certain public water systems in Texas was associated with changes in birth defect prevalence.

Methods

We obtained data on maternal characteristics for all live births and birth defects cases regardless of pregnancy outcome in Texas from 2003 to 2017 from the Texas Birth Defects Registry and birth and fetal death records. The ridge augmented synthetic control method was used to model changes in birth defect prevalence (per 10,000 live births) following the adoption of DPR by four Texas counties in mid-2013, with county-level data on maternal age, percent women without a high school diploma, percent who identified as Hispanic/Latina or non-Hispanic/Latina Black, and rural-urban continuum code as covariates.

Results

There were nonstatistically significant increases in prevalence of all birth defects collectively (average treatment effect in the treated = 53.6) and congenital heart disease (average treatment effect in the treated = 287.3) since June 2013. The estimated prevalence of neural tube defects was unchanged.

Conclusions

We estimated nonstatistically significant increases in birth defect prevalence following the implementation of DPR in four West Texas counties. Further research is warranted to inform water policy decisions.

Estimation of Unintended Treated Wastewater Contributions to Streams in the Yangtze River Basin and the Potential Human Health and Ecological Risk Analysis

"Clean water and sanitation" is one of the United Nations Sustainable Development Goals. One primary objective of wastewater treatment is to remove contaminants such as pathogens, nutrient, and organic matter from wastewater, while not all contaminants could be removed effectively. Wastewater treatment plants would inevitably represent concentrated point sources of residual contaminant loadings into surface waters. This study focuses on the populated Yangtze River Basin where emerging contaminants are frequently detected in the rivers in the recent years. A python-based ArcGIS model is developed to estimate the contributions of effluent discharges in water supply sources and quantify fate and environmental risks of human-derived contaminants in the river network. We find that one-third of the river networks are potentially influenced by the effluents through local or upstream inputs. Average fraction of unintended wastewater reuse in water supply intakes is estimated to be lower than 3% under the average flow scenario with an average traveling time of 0.05 day from the nearest effluent input site to water supply intakes. However, under low flow scenario, the percentage of effluent discharge would increase largely, leading to substantial increases in human health and ecological risks. This study provides a systematic investigation to understand extents of impacts of effluent inputs in river networks as well as identify the opportunities to improve the water management in the densely populated regions.

The status of potable water reuse implementation

A review of the current status of direct and indirect potable water reuse (DPR/IPR) implementation has been conducted, focusing on the regulatory and practical aspects and with reference to the most recent published literature. The review encompasses (a) the principal contaminant types, their required removal and the methods by which their concentration is monitored, (b) regulatory approaches and stipulations in assessing/ratifying treatment schemes and maintaining treated water quality, and (c) existing full-scale installations. Analytical methods discussed include established in-line monitoring tools, such as turbidity measurement, to more recent polymerase chain reaction (PCR)-based assay methods for microbial detection. The key risk assessment tools of quantitative microbial risk assessment (QMRA) and water safety plans (WSPs) are considered in relation to their use in selecting/ratifying treatment schemes, and the components of the treatment schemes from 40 existing IPR/DPR installations summarised. Five specific schemes are considered in more detail. The review reveals:Whilst there are a number of ongoing projects where RO is not used because of the challenge imposed by disposal of RO concentrate, the prevalence of the sequential RO-UV combination implies the importance of quantifying the impact of process upsets on these unit operations.

Microbial community characterization in advanced water reclamation for potable reuse

This study investigated the microbial community structure and composition across two treatment steps used in advanced water reclamation for potable reuse applications, namely Coagulation/Flocculation/Clarification/Granular Media Filtration (CFCGMF) and Ozone-Biological Activated Carbon filtration (O₃/BAC). The study examined the richness, variations, and similarities of the microorganisms involved at each treatment step to better understand the role of ecology and the dynamics on unit process performance and the microbial community developed within it. The bacterial microbiomes at each treatment step were independently characterized using 16S metagenomic sequencing. Combining both treatment steps, a total of 3801 species were detected. From the total species detected, 38% and 98% were identified at CFCGMF and O₃/BAC, respectively. The most abundant phyla were Proteobacteria, Bacteroidetes, Actinobacteria, and Firmicutes in both treatment steps. The identified species were classified based on their preferences to free-living style (59%) vs attached-living style (22%) showing a relatively low richness in the BAC media, but higher diversities. At the taxonomic class level, Betaproteobacteria was the predominant in both system processes. Additionally, a list of eight genera were identified as potential bacterial pathogens present in both process effluents. They are Aeromonas, Clostridium, Enterobacter, Escherichia, Flavobacterium, Legionella, Mycobacterium, and Pseudomonas. CFCGMF effluent yielded less pathogenic bacteria than both the ozone and BAC filter effluent from the O₃/BAC process unit; their relative abundance accounted for about 2% and 8% for CFCGMF and O₃/BAC, respectively. Detailed studies to characterize the microbial communities are crucial in interpreting the mechanisms and synergies between processes performance and microorganisms by identifying the needs and best practices to ensure public health protection. Key points • Microbial communities of two treatment processes are characterized using 16S rRNA sequencing. • Organisms that can tolerate ozone and form biofilms define microbial community in subsequent biofilters. • In relatively low abundances, potential pathogenic bacteria are detected in the treated water.

The occurrence and control of waterborne viruses in drinking water treatment: A review

As the coronavirus disease 2019 continues to spread globally, its culprit, the severe acute respiratory syndrome coronavirus 2 has been brought under scrutiny. In addition to inhalation transmission, the possible fecal-oral viral transmission via water/wastewater has also been brought under the spotlight, necessitating a timely global review on the current knowledge about waterborne viruses in drinking water treatment system - the very barrier that intercepts waterborne pathogens to terminal water users. In this article we reviewed the occurrence, concentration methods, and control strategies, also, treatment performance on waterborne viruses during drinking water treatment were summarized. Additionally, we emphasized the potential of applying the quantitative microbial risk assessment to guide drinking water treatment to mitigate the viral exposure risks, especially when the unregulated novel viral pathogens are of concern. This review paves road for better control of viruses at drinking water treatment plants to protect public health.