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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.

As global issues such as climate change and diminishing resources become increasingly pressing, water recycling has moved into the focus. However, the successful implementation of Direct Potable Water Reuse (DPR) projects hinges on securing public acceptance, which remains challenging. This paper aims to flesh out possible reasons for the lingering public rejection of DPR. We will do so by conducting a literature review on how public acceptance is understood and what approaches are proposed to enhance it. These approaches are analyzed using Responsible Research and Innovation principles and the `opening up', `closing down' and `leaving ajar' approaches. Our research identifies an overreliance on the controversial information deficit model, closing down large parts of public engagement. We advocate for becoming more inclusive through the `leaving ajar' approach. Particularly, attention should be paid to reflexivity and responsiveness to public concerns to ensure meaningful public engagement.

The state of California, USA, has developed regulations for projects that want to pursue direct potable reuse. One of the most significant requirements is that the treatment train must include ozone and biological activated carbon (ozone/BAC) as pretreatment to a membrane-based treatment train. Ozone/BAC mitigates chemical peaks and diversifies the removal mechanisms of low molecular weight compounds likely to persist in advanced treated water. This paper will present the process benefits of ozone/BAC as pretreatment to the membrane-based treatment train based on testing at a 3,785 m3/d demonstration facility in San Diego, California, USA. One of the most significant benefits of ozone/BAC pretreatment is the improved water quality that benefits not only the product water produced for potable consumption but also the residual stream that is generated with the implementation of the RO process, commonly known as RO concentrate. This improved water quality originates from TOC reduction which is achieved through a combination of chemical oxidation with ozonation and biological growth in the BAC process that results in reduced operating pressures and chemical use for the membrane systems. These process benefits were quantified to develop an overall water cost comparison between a DPR and an indirect potable reuse train. HIGHLIGHTS Benefits of O3/BAC for potable reuse are substantial but underappreciated.; O3/BAC-MF-RO-UV/AOP treatment train provides a greater degree of public health protection.; The experimental DPR treatment train operated at lower O&M costs compared to FAT.; Benefits were quantified for a 30-year basis and show that this train has a similar cost despite higher CAPEX.; O3/BAC-based DPR treatment trains are economically viable.;

Available, effective methods of virus detection adequately address the risks in treating water for potable reuse. [ABSTRACT FROM AUTHOR]

Direct Potable Reuse (DPR) is a method of recycling wastewater to create a potable water source.  DPR is a particularly useful technology in arid, drought-prone regions, including California, because it is a self-sustaining water source.  Despite being safe, efficient, and useful, potable reuse methods, including DPR, have faced intense public opposition.  Such opposition has stopped several projects in California.In January 2018, California State Assembly Bill 574 (AB 574) took effect.  AB 574 requires California’s State Water Resources Control Board to adopt regulations for DPR by 2023, so long as the regulations are found to adequately protect public health.  Once adopted, California would become the first state to have uniform regulations for DPR.  But while uniform regulations will be an important step toward the realization of DPR technology, California’s success in implementing DPR will ultimately depend on public acceptance of DPR as a legitimate source of water.This Comment seeks to provide California’s state and local governments with strategies to garner public support for DPR projects.  First, this Comment provides a framework for gaining public acceptance of DPR.  Second, this Comment explains why California is well-suited to the adoption of DPR technology, and describes California’s history with potable reuse.  Third, this Comment illustrates the main obstacle to DPR—public opposition—through a series of case studies.  Fourth and finally, this Comment applies the framework for gaining public acceptance to the case studies to illustrate a holistic approach to legitimizing DPR. “When was sewage ever classified as being pure?” asked the Revolting Grandmas, a San Diego grassroots group.[1] The Grandmas were revolting against recycling wastewater for potable use, also known as ‘potable reuse.’ They feared waterborne illness, distrusted the purification technology, and were simply disgusted by the idea of drinking water that once went down someone’s toilet.[2] And they were not alone in their concerns.  Public opposition to recycled wastewater has stopped several potable reuse projects in California. Public concerns about recycled wastewater derive, in part, from an ancient human fear of waterborne disease that has complicated mankind’s relationship with water: “[t]here is no life without water.  Indeed, we use its presence as an indicator for the possibility of life beyond the earth.  But drinking water can kill, and always has.”[3] [1].        See Cal. Dep’t of Water Res., Water Recycling 2030: Recommendations of California’s Recycled Water Task Force app. at G-52 (2003), https://water.ca.gov/LegacyFiles/pubs/use/water_recycling_2030/recycled_water_tf_report_2003.pdf [https://perma.cc/9MQ2-Y54H]. [2].        Seeid. app. at G-58. [3].        James Salzman, Drinking Water: A History 21 (2012).

The present study highlights the evolution, progress and prospects of future practices of water reuse in the world. The objective was to produce a comprehensive timeline on the global evolution and progress of water reuse. This was achieved through the analysis of the state of the art on the subject. The present study is a qualitative research, where three aspects have been considered to highlight the global evolution of water reuse: i) Regulations, Standards, Criteria or Guidelines (RSCG); ii) Indirect Potable Reuse Projects (IPR); and iii) Direct Potable Reuse Projects (DPR). The study focused on both legal and practical aspects of water reuse and considered three timelines in the context of RSCG, IPR and DPR: 29 RSCG instruments, institutionalized from 1918 to 2020, where only four instruments were solely dedicated to drinking water reuse; 10 IPR projects; five DPR projects. To achieve good, effective results, the regulatory framework must support the objectives of a structured water reuse policy in addition to guaranteeing legitimacy and maintaining public confidence. Integrated water and wastewater management, based on technological and scientific advances, has become a relevant aspect for implementation of more adequate measures by decision makers to address future global water challenges. HIGHLIGHTS The timeline on Regulation, Criteria or Guidelines spanned from 1918 to 2020.; The timeline on Indirect Potable Water Reuse Projects ranged from 1962 to 2015.; The timeline on Direct Potable Water Reuse Projects was from 1968 to 2014.; The criteria used were initially adopted for agricultural and irrigation uses; Technological advances facilitated the production of better-quality water reuse.;

Given the availability of technological solutions and guidelines for safe drinking water, direct potable reuse of reclaimed water has become a promising option to overcome severe lack of potable water in arid regions. However, the growing awareness of the presence of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARG) in corresponding raw wastes has led to new safety concerns. This study investigated the fate of ARB and intracellular and extracellular ARG after each treatment step of an advanced water treatment facility in Windhoek, Namibia. The New Goreangab Water Reclamation Plant (NGWRP) produces drinking water from domestic secondary wastewater treatment plant effluent and directly provides for roughly a quarter of Windhoek's potable water demand. Procedures to study resistance determinants were based on both molecular biology and culture-based microbiological methods. TaqMan real-time PCR was employed to detect and quantify intracellular resistance genes sul1, ermB, vanA, nptII and nptIII as well as extracellular resistance gene sul1. The NGWRP reduced the amount of both culturable bacterial indicators as well as the resistance genes to levels below the limit of detection in the final product. The main ozonation and the ultrafiltration had the highest removal efficiencies on both resistance determinants. HIGHLIGHTS The final product contained none of the antibiotic resistance genes investigated.; A subsequent series of water treatment steps can decrease antibiotic resistance genes to below LOD.; All steps in the treatment train decreased the abundance of the sul1 resistance gene except for the pre-ozonation and the biological activated carbon.; In the final product, extracellular and intracellular sul1 resistance genes were below LOD.;

Although reclaimed water for potable applications has many potential benefits, it poses concerns for chemical and microbial risks to consumers. We present a quantitative microbial risk assessment (QMRA) Monte Carlo framework to compare a de facto water reuse scenario (treated wastewater-impacted surface water) with four hypothetical Direct Potable Reuse (DPR) scenarios for Norovirus, Cryptosporidium, and Salmonella. Consumer microbial risks of surface source water quality (impacted by 0-100% treated wastewater effluent) were assessed. Additionally, we assessed risks for different blending ratios (0-100% surface water blended into advanced-treated DPR water) when source surface water consisted of 50% wastewater effluent. De facto reuse risks exceeded the yearly 10-4 infections risk benchmark while all modeled DPR risks were significantly lower. Contamination with 1% or more wastewater effluent in the source water, and blending 1% or more wastewater-impacted surface water into the advanced-treated DPR water drove the risk closer to the 10-4 benchmark. We demonstrate that de facto reuse by itself, or as an input into DPR, drives microbial risks more so than the advanced-treated DPR water. When applied using location-specific inputs, this framework can contribute to project design and public awareness campaigns to build legitimacy for DPR.

Under current Spanish law, domestic use of recycled water is only permitted during an officially declared disaster; however, it could be an option from a regulatory perspective. However, would Spaniards be willing to use recycled water in the home if necessary? This study investigates the public acceptance of recycled water use in Spanish households and identifies the determinants of acceptance. In data from 791 questionnaires administered in southern Spain, recycled water is the least acceptable option for alternative sources of water, behind both rainwater collection and desalination. Perceived health risk and environmental awareness explain the differences in acceptance. [ABSTRACT FROM AUTHOR]

The City of Wichita Falls, Texas, made international news in 2014 when its water system became a water reuse pioneer. In response to a historic drought, the city simultaneously planned and implemented direct potable reuse (DPR) and indirect potable reuse (IPR) systems to see it through the drought and respond to future water shortages. Now, the city is a role model for water utilities around the world. [ABSTRACT FROM AUTHOR]

Direct potable reuse (DPR) can be more economic than indirect potable reuse as no environmental buffer is needed and conveyance and blending of the purified water with other potable sources is basically less expensive. Long-term experience in Windhoek (48 years) shows that treated domestic sewage can be safely and cost-efficiently utilized for potable reclamation (0.72 €/m3). A multiple barrier strategy is employed in order to attain the highest possible safety levels. There are three types of barriers: non-treatment, treatment and operational barriers. In recent years, new DPR schemes have been implemented in South Africa and in the USA, and the major difference between all the new reclamation processes and the Windhoek New Goreangab water reclamation plant lies in the employment of desalination process units. This topic and other issues, such as the use of ozone and biological activated carbon filtration, are addressed. Reclamation process optimization (increase in sustainability) and the attainment of greater public acceptance are the major challenges facing the promotion of DPR, which should become a common and widely used water management option within the next 5–10 years.

Advanced treatment facilities for potable water reuse of wastewater are designed to achieve high removal levels of specific pathogens, as well as many other constituents. However, changes to the microbial community throughout treatment, storage, and distribution of this water have not been well characterized. We applied high-throughput amplicon sequencing, read-based, assembly-based, and genome-resolved metagenomics, and flow cytometry to investigate the microbial communities present in a pilot-scale advanced water treatment facility. Advanced treatment of secondary-treated wastewater consisted of ozonation, chloramination, microfiltration, reverse osmosis (RO), advanced oxidation (UV/H2O2), granular activated carbon (GAC) filtration, and chlorination. Treated water was fed into bench-scale simulated distribution systems (SDS). Cell counts and microbial diversity in bulk water decreased until GAC filtration, and the bacterial communities were significantly different following each treatment step. Bacteria grew within GAC media and contributed to a consistent microbial community in the filtrate, which included members of the Rhizobiales and Mycobacteriaceae. After chlorination, some of the GAC filtrate community was maintained within the SDS, and community shifts were associated with stagnation. Putative antibiotic resistance genes and potential opportunistic pathogens were identified before RO and after advanced oxidation, although few if any members of the wastewater microbial community passed through these treatment steps. These findings can contribute to improved design of advanced treatment trains and management of microbial communities in post-treatment steps.

Advanced treatment facilities for potable water reuse of wastewater are designed to achieve high removal levels of specific pathogens, as well as many other constituents. However, changes to the microbial community throughout treatment, storage, and distribution of this water have not been well characterized. We applied high-throughput amplicon sequencing, read-based, assembly-based, and genome-resolved metagenomics, and flow cytometry to investigate the microbial communities present in a pilot-scale advanced water treatment facility. Advanced treatment of secondary-treated wastewater consisted of ozonation, chloramination, microfiltration, reverse osmosis (RO), advanced oxidation (UV/H2O2), granular activated carbon (GAC) filtration, and chlorination. Treated water was fed into bench-scale simulated distribution systems (SDS). Cell counts and microbial diversity in bulk water decreased until GAC filtration, and the bacterial communities were significantly different following each treatment step. Bacteria grew within GAC media and contributed to a consistent microbial community in the filtrate, which included members of the Rhizobiales and Mycobacteriaceae. After chlorination, some of the GAC filtrate community was maintained within the SDS, and community shifts were associated with stagnation. Putative antibiotic resistance genes and potential opportunistic pathogens were identified before RO and after advanced oxidation, although few if any members of the wastewater microbial community passed through these treatment steps. These findings can contribute to improved design of advanced treatment trains and management of microbial communities in post-treatment steps. [ABSTRACT FROM AUTHOR]

Abstract Ensuring safe and effective water treatment, distribution, and reuse requires robust methods for characterizing and monitoring waterborne microbes. Methods widely used today can be limited by low sensitivity, high labor and time requirements, susceptibility to interference from inhibitory compounds, and difficulties in distinguishing between viable and non-viable cells. Flow cytometry (FCM) has recently gained attention as an alternative approach that can overcome many of these challenges. This article critically and systematically reviews for the first time recent literature on applications of FCM in water treatment, distribution, and reuse. In the review, we identify and examine nearly 300 studies published from 2000 to 2018 that illustrate the benefits and challenges of using FCM for assessing source-water quality and impacts of treatment-plant discharge on receiving waters, wastewater treatment, drinking water treatment, and drinking water distribution. We then discuss options for combining FCM with other indicators of water quality and address several topics that cut across nearly all applications reviewed. Finally, we identify priority areas in which more work is needed to realize the full potential of this approach. These include optimizing protocols for FCM-based analysis of waterborne viruses, optimizing protocols for specifically detecting target pathogens, automating sample handling and preparation to enable real-time FCM, developing computational tools to assist data analysis, and improving standards for instrumentation, methods, and reporting requirements. We conclude that while more work is needed to realize the full potential of FCM in water treatment, distribution, and reuse, substantial progress has been made over the past two decades. There is now a sufficiently large body of research documenting successful applications of FCM that the approach could reasonably and realistically see widespread adoption as a routine method for water quality assessment. Graphical abstract Image 1 Highlights • Flow cytometry (FCM) is an accepted tool to characterize microbial water quality. • Nearly 300 studies between 2000 and 2018 applied FCM to water quality assessment. • Research illustrates the value of FCM in water treatment, distribution, and reuse. • FCM-based monitoring can facilitate assessment of treatments for potable reuse. • Automated and standardized FCM data collection and analysis methods are needed. [ABSTRACT FROM AUTHOR]

Abstract Little is known about how introducing recycled water intended for direct potable reuse (DPR) into distribution systems and premise plumbing will affect water quality at the point of use, particularly with respect to effects on microbial communities and regrowth. The examination of potential growth of opportunistic pathogens (OPs) and spread of antibiotic resistance genes (ARGs), each representing serious and growing public health concerns, by introducing DPR water has not previously been evaluated. In this study, the impact of blending purified DPR water with traditional drinking water sources was investigated with respect to treatment techniques, blending location, and blending ratio. Water from four U.S. utility partners was treated in bench- and pilot-scale treatment trains to simulate DPR with blending. Water was incubated in simulated premise plumbing rigs made of PVC pipe containing brass coupons to measure regrowth of total bacteria (16S rRNA genes, heterotrophic plate count), OPs (Legionella spp., Mycobacterium spp., Pseudomonas aeruginosa), ARGs (qnr A, van A), and an indicator of horizontal gene transfer and multi-drug resistance (int I1). The microbial community composition was profiled and the resistome (i.e., all ARGs present) was characterized in select samples using next generation sequencing. While regrowth of total bacteria (16S rRNA genes) from the start of the incubation through week eight consistently occurred across tested scenarios (Wilcoxon, p ≤ 0.0001), total bacteria were not more abundant in the water or biofilm of any DPR scenario than in the corresponding conventional potable condition (p ≥ 0.0748). Regrowth of OP marker genes, qnr A, van A, and int I1 were not significantly greater in water or biofilm for any DPR blends treated with advanced oxidation compared to corresponding potable water (p ≥ 0.1047). This study of initial bacteria colonizing pipes after introduction of blended DPR water revealed little evidence (i.e., one target in one water type) of exacerbated regrowth of total bacteria, OPs, or ARGs in premise plumbing. Graphical abstract Image 1 Highlights • Total bacterial regrowth in direct potable reuse (DPR) comparable to potable water. • No significant difference in Legionella occurrence in DPR versus potable water. • Mycobacterium regrowth was greater in one utility's reuse water than potable water. • No difference in qnr A, van A, or int I1 occurrence in DPR versus potable water. • Appropriate DPR treatment train and optimal blend ratio limits bacterial regrowth. [ABSTRACT FROM AUTHOR]

The Australian Antarctic Division (AAD) operates Australia's Davis Station in the Antarctic. In 2005, Davis Station's wastewater treatment plant failed and since then untreated, macerated effluent has been discharged to the ocean. The objectives of this study were to determine whether an advanced water treatment plant (AWTP) commissioned by the AAD and featuring a multi-barrier process involving ozonation, ceramic microfiltration, biologically activated carbon filtration, reverse osmosis, ultraviolet disinfection and chlorination was capable of producing potable water and a non-toxic brine concentrate that can be discharged with minimal environmental impact. The AWTP was tested using water from a municipal wastewater treatment plant in Tasmania, Australia. We used spot water and passive sampling combined with two multi-residue chromatographic-mass spectrometric methods and a range of recombinant receptor-reporter gene bioassays to screen trace organic chemicals (TrOCs), toxicity and receptor activity in the Feed water, in the environmental discharge (reject water), and product water from the AWTP for six months during 2014–15, and then again for three months in 2016. Across the two surveys we unambiguously detected 109 different TrOCs in the feed water, 39 chemicals in the reject water, and 34 chemicals in the product water. Sample toxicity and receptor activity in the feed water samples was almost totally removed in both testing periods, confirming that the vast majority of the receptor active TrOCs were removed by the treatment process. All the NDMA entering the AWTP in the feed and/or produced in the plant (typically < 50 ng/L), was retained into the reject water with no NDMA observed in the product water. In conclusion, the AWTP was working to design, and releases of TrOCs at the concentrations observed in this study would be unlikely cause adverse effects on populations of aquatic organisms in the receiving environment or users of the potable product water. [ABSTRACT FROM AUTHOR]

An evaluation of surface water augmentation offers insights that can be used in developing public health recommendations for direct potable reuse. [ABSTRACT FROM AUTHOR]

The mechanical reliability of a direct potable reuse (DPR) treatment train—consisting of ozone, biological activated carbon, microfiltration/ultrafiltration, reverse osmosis, and ultraviolet light with advanced oxidation—was evaluated using critical component analysis at the Demonstration Pure Water Facility in San Diego, Calif. Operators maintained logs of all mechanical issues that occurred over a yearlong test period; these were used to calculate several reliability metrics for the unit processes. Mechanical issues were also cross‐referenced with treatment performance data to determine whether any “critical” failures—i.e., those that impacted pathogen reduction performance—occurred. The results demonstrated that no critical failures occurred, though the communication systems experienced critical malfunctions. These malfunctions triggered an immediate system shutdown, mitigating the potential risk to public health. While several components experienced failures, malfunctions, and/or maintenance events, the processes maintained a high degree of availability, demonstrating that DPR facilities can be designed with a high degree of mechanical reliability. [ABSTRACT FROM AUTHOR]

Understanding pathogen risks is a critically important consideration in the design of water treatment, particularly for potable reuse projects. As an extension to our published microbial risk assessment methodology to estimate infection risks associated with Direct Potable Reuse (DPR) treatment train unit process combinations, herein, we (1) provide an updated compilation of pathogen density data in raw wastewater and dose-response models; (2) conduct a series of sensitivity analyses to consider potential risk implications using updated data; (3) evaluate the risks associated with log credit allocations in the United States; and (4) identify reference pathogen reductions needed to consistently meet currently applied benchmark risk levels. Sensitivity analyses illustrated changes in cumulative annual risks estimates, the significance of which depends on the pathogen group driving the risk for a given treatment train. For example, updates to norovirus (NoV) raw wastewater values and use of a NoV dose-response approach, capturing the full range of uncertainty, increased risks associated with one of the treatment trains evaluated, but not the other. Additionally, compared to traditional log-credit allocation approaches, our results indicate that the risk methodology provides more nuanced information about how consistently public health benchmarks are achieved. Our results indicate that viruses need to be reduced by 14 logs or more to consistently achieve currently applied benchmark levels of protection associated with DPR. The refined methodology, updated model inputs, and log credit allocation comparisons will be useful to regulators considering DPR projects and design engineers as they consider which unit treatment processes should be employed for particular projects. [ABSTRACT FROM AUTHOR]

To safely progress toward direct potable reuse (DPR), it is essential to ensure that DPR systems can provide public health protection equivalent to or greater than that of conventional drinking water sources. This study collected data over a one-year period from a full-scale DPR demonstration facility, and used both performance distribution functions (PDFs) and quantitative microbial risk assessment (QMRA) to define and evaluate the reliability of the advanced water treatment facility (AWTF). The AWTF's ability to control enterovirus, Giardia , and Cryptosporidium was characterized using online monitoring of surrogates in a treatment train consisting of ozone, biological activated carbon, microfiltration, reverse osmosis, and ultraviolet light with an advanced oxidation process. This process train was selected to improve reliability by providing redundancy, defined as the provision of treatment beyond the minimum needed to meet regulatory requirements. The PDFs demonstrated treatment that consistently exceeded the 12/10/10-log thresholds for virus, Giardia , and Cryptosporidium , as currently required for potable reuse in California (via groundwater recharge and surface water augmentation). Because no critical process failures impacted pathogen removal performance during the yearlong testing, hypothetical failures were incorporated into the analysis to understand the benefit of treatment redundancy on performance. Each unit process was modeled with a single failure per year lasting four different failure durations: 15 min, 60 min, 8 h, and 24 h. QMRA was used to quantify the impact of failures on pathogen risk. The median annual risk of infection for Cryptosporidium was 4.9 × 10 −11 in the absence of failures, and reached a maximum of 1.1 × 10 −5 assuming one 24-h failure per process per year. With the inclusion of free chlorine disinfection as part of the treatment process, enterovirus had a median annual infection risk of 1.5 × 10 −14 (no failures) and a maximum annual value of 2.1 × 10 −5 (assuming one 24-h failure per year). Even with conservative failure assumptions, pathogen risk from this treatment train remains below the risk targets for both the U.S. (10 −4 infections/person/year) and the WHO (approximately 10 −3 infections/person/year, equivalent to 10 −6 DALY/person/year), demonstrating the value of a failure prevention strategy based on treatment redundancy. [ABSTRACT FROM AUTHOR]

Denitrifying membrane bioreactors (MBRs) are being found useful in water reuse treatment systems, including net-zero water (nearly closed-loop), non-reverse osmosis-based, direct potable reuse (DPR) systems. In such systems nitrogen may need to be controlled in the MBR to meet the nitrate drinking water standard in the finished water. To achieve efficient nitrification and denitrification, the addition of alkalinity and external carbon may be required, and control of the carbon feed rate is then important. In this work, an onsite, two-chamber aerobic nitrifying/denitrifying MBR, representing one unit process of a net-zero water, non-reverse osmosis-based DPR system, was modeled as a basis for control of the MBR internal recycling rate, aeration rate, and external carbon feed rate. Specifically, a modification of the activated sludge model ASM2dSMP was modified further to represent the rate of recycling between separate aerobic and anoxic chambers, rates of carbon and alkalinity feed, and variable aeration schedule, and was demonstrated versus field data. The optimal aeration pattern for the modeled reactor configuration and influent matrix was found to be 30 min of aeration in a 2 h cycle (104 m 3 air/d per 1 m 3 /d average influent), to ultimately meet the nitrate drinking water standard. Optimal recycling ratios (inter-chamber flow to average daily flow) were found to be 1.5 and 3 during rest and mixing periods, respectively. The model can be used to optimize aeration pattern and recycling ratio in such MBRs, with slight modifications to reflect reactor configuration, influent matrix, and target nitrogen species concentrations, though some recalibration may be required. [ABSTRACT FROM AUTHOR]

As reuse of municipal water resource recovery facility (WRRF) effluent becomes vital to augment diminishing fresh drinking water resources, concern exists that conventional barriers may prove deficient, and the upcycling of chemicals of emerging concern (CECs) could prove harmful to human health and aquatic species if more effective and robust treatment barriers are not in place. A multiple month survey, of both primary and secondary effluents, from three (3) WRRFs, for 95 CECs was conducted in 2014 to classify CECs by their persistence through conventional water reclamation processes. By sampling the participating WRRF process trains at their peak performance (as determined by measured bulk organics and particulates removal), a short-list of recalcitrant CECs that warrant monitoring to assess treatment performance at advanced water reclamation and production facilities. The list of identified CECs for potable water reclamation (indirect or direct potable reuse) include a herbicide and its degradants, prescription pharmaceuticals and antibiotics, a female hormone, an artificial sweetener, and chlorinated flame retardants. [ABSTRACT FROM AUTHOR]

Research has been conducted on how to effectively control microbial hazards for an increasing number of water reuse projects in the United States and around the world. Operators play a vital role in today's ever‐evolving water reuse management frameworks. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solar-thermal evaporation directly reuses potable water from domestic wastewater. • Role of reactive oxygen species in avoiding release of contaminants is clarified. • Production of ∼7.65 kg·day−1·m−2 potable water for 2–3 persons' daily usage. • Solar utilization significantly decreases carbon emission and cost of potable reuse. Water scarcity in arid areas requires the exploitation of unconventional water resources like domestic wastewater (DWW). Although direct potable reuse (DPR) of DWW as an alleviation is mature based on membrane and advanced oxidation, it is energy- and carbon-intensive with requirement of well-developed infrastructure. Recently, emerging solar-driven interfacial evaporation for sustainable freshwater reclamation has been practiced on seawater desalination but its feasibility of DPR from DWW has not been investigated. Herein, a solar-absorber of b-TiO 2 -DW was constructed by coating delignified wood (DW) with black reduced TiO 2 (b-TiO 2) to conduct DPR from DWW in a solar-thermal system, wherein b-TiO 2 -DW with anisotropic thermal conductivities and enhanced sunlight absorption facilitates DWW evaporation at air–water interfaces with a DRP rate of ∼1.25 kg·h−1·m−2-absorber in ∼97.5 % photothermal conversion efficiency and ∼90 % evaporation efficiency under simulated illumination (100 mW·cm−2) in the lab. For real solar illumination outdoors (0.8–87.2 mW·cm−2, 10 h), DRP rate reaches ∼7.65 kg·day−1·m−2 that can satisfy the demand of daily drinking water for 2–3 persons. The moderate temperature at evaporation interfaces, physical adsorption, and reactive oxygen species generated by b-TiO 2 -DW synergistically inhibit conventional and emerging (in)volatile contaminants into PRW and prevent biofouling on absorbers. A life cycle assessment (10-years life-cycle amortization) shows that solar-thermal system has lower cost ($ ∼0.027 kg−1 PRW) and carbon footprint (∼0.085 kg CO 2 -eq·kg−1 PRW) than current technologies ($ 0.25–1.14 kg−1 PRW and 0.67–1.17 kg CO 2 -eq·kg−1 PRW). Although DPR efficiency of solar-thermal system needs further enhancement, its flexibility indicates a promising scenario for decentralized DPR in undeveloped areas with laggard infrastructures. [ABSTRACT FROM AUTHOR]

An urban net-zero water treatment system, designed for energy-positive water management, 100% recycle of comingled black/grey water to drinking water standards, and mineralization of hormones and other organics, without production of concentrate, was constructed and operated for two years, serving an occupied four-bedroom, four-bath university residence hall apartment. The system comprised septic tank, denitrifying membrane bioreactor (MBR), iron-mediated aeration (IMA) reactor, vacuum ultrafilter, and peroxone or UV/H 2 O 2 advanced oxidation, with 14% rainwater make-up and concomitant discharge of 14% of treated water (ultimately for reuse in irrigation). Chemical oxygen demand was reduced to 12.9 ± 3.7 mg/L by MBR and further decreased to below the detection limit (<0.7 mg/L) by IMA and advanced oxidation treatment. The process produced a mineral water meeting 115 of 115 Florida drinking water standards that, after 10 months of recycle operation with ∼14% rainwater make-up, had a total dissolved solids of ∼500 mg/L, pH 7.8 ± 0.4, turbidity 0.12 ± 0.06 NTU, and NO 3 -N concentration 3.0 ± 1.0 mg/L. None of 97 hormones, personal care products, and pharmaceuticals analyzed were detected in the product water. For a typical single-home system with full occupancy, sludge pumping is projected on a 12–24 month cycle. Operational aspects, including disinfection requirements, pH evolution through the process, mineral control, advanced oxidation by-products, and applicability of point-of-use filters, are discussed. A distributed, peroxone-based NZW management system is projected to save more energy than is consumed in treatment, due largely to retention of wastewater thermal energy. Recommendations regarding design and operation are offered. [ABSTRACT FROM AUTHOR]

As populations and water demand increase, more sustainable water sources are needed. Wastewater reuse is a major opportunity. Treated wastewater is available for non-potable applications and drinking water production. Direct potable reuse and planned indirect potable reuse provide sustainable drinking water; other reuse applications can offset current drinking water uses at lower cost due to lower end-use quality requirements. There is some public reluctance to choose potable reuse, but planned reuse projects provide drinking water of higher quality than typical natural sources. Guidance is available to assure safe and high-quality reused water. [ABSTRACT FROM PUBLISHER]

Urban water security in Australia’s major cities is now very high, reflecting in part recent policy interventions. Important indirect potable water reuse projects were completed but no direct potable reuse project was undertaken and none seems likely in the near term. Governments have much to learn from decisions to build very large desalination and recycling plants, particularly around timing and scale. Future water reuse decisions are likely to have a much greater commercial focus. Policies and regulations giving more flexibility to decentralized provision of water-related services could result in further growth of climate-resilient water resources and non-potable reuse. [ABSTRACT FROM PUBLISHER]

Water scarcity is a reality, with a recent UN report estimating that about half of the global population could be facing water shortages by 2030. This has focused attention on existing sources and what could be done to maximize potential. Water reuse, in particular direct potable reuse (DPR), has enjoyed a somewhat turbulent history globally. Despite this, the City of Windhoek has been practising DPR for more than 45 years, and this commentary presents globally accepted barriers standing in the way of DPR and attempts to explore ways to overcome these given the experience in Windhoek. [ABSTRACT FROM PUBLISHER]

Essential requirements for remote potable water reuse in small communities include highly automated processes, remote monitoring and control, and high pathogen removal values that can be easily validated. A plant for advanced tertiary water treatment for remote operations using six pathogen barriers has been tested. It can achieve a credible Log Removal Value (LRV) for virus and bacteria well above target values recommended by current guidelines, but not for protozoa since this pathogen type is commonly resistant to most chemical disinfectants. As a result, the required LRV credit requirement for protozoa for the reverse osmosis (RO) barrier of the plant was at least 2 to reach the desired outcome. Furthermore, the maximum certified LRV for protozoa in Australia for RO in recycled water is no greater than 2 due to the lack of recognized integrity testing techniques to validate the process during operation. In this study, a pressure decay test (PDT) for RO systems is presented and verified by particle challenge testing. It is demonstrated with both laboratory scale and single element pilot scale tests that the PDT is more conservative than the particle challenge test. It is also demonstrated that frequent PDTs will not cause physical damage to membranes, based on a sample of 304 PDTs, as well as a visual check of the RO element structure and salt rejection. [ABSTRACT FROM AUTHOR]

This work is motivated by technical advancements related to direct potable reuse (DPR) and the importance of public values when considering alternative water resources. This study involved the distribution of an online survey to residents in four US cities about existing tap water supplies and "purified water," defined as "municipal wastewater that has undergone advanced water treatment processes, thus resulting in water quality that, at a minimum, complies with drinking water regulations." Overall, 50-60% of respondents were in support of using purified water as potable water. Contaminant concerns were highest for taste/smell and microbial contaminants in both current tap water and purified water. Survey results highlight the importance of addressing certain areas when communicating about DPR to the public, such as barriers against microbial contamination, the trustworthiness of utilities, potential improvements over the status quo, and community-specific drivers that necessitate the use of purified water in a given setting. [ABSTRACT FROM AUTHOR]

An osmotic membrane bioreactor (OMBR) and a novel hybrid ultrafiltration OMBR (UFO-MBR) were investigated for extended time. In OMBR, water is drawn by osmosis from activated sludge through a forward osmosis (FO) membrane into a draw solution. OMBRs provide superior rejection of dissolved constituents, including salts and nutrients, compared to conventional UF MBRs, and the FO membranes in OMBR have low fouling propensity. Yet, the high rejection of dissolved constituents in OMBR results in accumulation of salts and nutrients in the activated sludge, with potential detrimental effects on the biological processes. A new strategy for mitigating salt accumulation was investigated using a UF membrane in parallel to the FO membrane in the same bioreactor (UFO-MBR). Results from long-term OMBR and UFO-MBR investigations revealed that the overall removal of chemical oxygen demand, total nitrogen, and total phosphorus were greater than 96%, 82%, and 99%, respectively. We have demonstrated that low salinity in the activated sludge could be maintained, that phosphorus could be recovered through the UF permeate at concentrations greater than 50 mg L − 1 , and that FO membrane fouling was substantially reduced. Additionally, the UFO-MBR was capable of simultaneously producing high quality RO permeate stream and nutrient-rich UF permeate stream from one integrated system. [ABSTRACT FROM AUTHOR]

Droughts have accelerated a drive toward more sustainable water sources, including highly treated wastewater as a source for drinking water. Communities across the southwestern United States are using direct potable reuse to lessen their reliance on dwindling water supplies. [ABSTRACT FROM AUTHOR]

Abstract: Water and wastewater treatment and conveyance account for approximately 4% of US electric consumption, with 80% used for conveyance. Net zero water (NZW) buildings would alleviate demands for a portion of this energy, for water, and for the treatment of drinking water for pesticides and toxic chemical releases in source water. However, domestic wastewater contains nitrogen loads much greater than urban/suburban ecosystems can typically absorb. The purpose of this work was to identify a first design of a denitrifying urban NZW treatment process, operating at ambient temperature and pressure and circum-neutral pH, and providing mineralization of pharmaceuticals (not easily regulated in terms of environmental half-life), based on laboratory tests and mass balance and kinetic modeling. The proposed treatment process is comprised of membrane bioreactor, iron-mediated aeration (IMA, reported previously), vacuum ultrafiltration, and peroxone advanced oxidation, with minor rainwater make-up and H2O2 disinfection residual. Similar to biological systems, minerals accumulate subject to precipitative removal by IMA, salt-free treatment, and minor dilution. Based on laboratory and modeling results, the system can produce potable water with moderate mineral content from commingled domestic wastewater and 10–20% rainwater make-up, under ambient conditions at individual buildings, while denitrifying and reducing chemical oxygen demand to below detection (<3 mg/L). While economics appear competitive, further development and study of steady-state concentrations and sludge management options are needed. [Copyright &y& Elsevier]

Water shortage arising from rapid population growth and relocation has produced an unprecedented degree of stress on regional water resources. Engineered solutions to relieve water stress are frequently based on the use of water of impaired initial quality. Chief among these impaired waters is reclaimed wastewater. For the most part, however, the breadth of both acceptable uses and use-dependent degree of treatment for reclaimed wastewater remain to be established. The chief advantages of direct potable reuse (DPR) relative to other forms of wastewater reclamation and reuse are that (i) all wastewater reclaimed for DPR can be readily used in water-stressed areas and (ii) delivery to points of use does not require a separate distribution system. The drawbacks are related to the need for highly competent, continuous on-line verification of water quality and the cost of treating all reclaimed wastewater to meet potable use requirements when only a small fraction will be used for potable purposes. We have attempted to explore those differences, providing quantitative comparisons where possible, to support selection among water reuse options in water-stressed areas. [ABSTRACT FROM AUTHOR]

Water scarcity, climate change, and population growth have led some water utilities to augment potable water supplies with direct potable reuse (DPR). Predictive analytics can be used to ensure treatment process reliability and encourage public trust in DPR. [ABSTRACT FROM AUTHOR]

The Raw Water Production Facility in Big Spring, Texas, doesn't discharge its treated wastewater effluent into a natural water body before being reused as a supply source, making it the only operating direct potable reuse facility in the United States. Early testing and analysis of the system show promising results. [ABSTRACT FROM AUTHOR]

For decades, the city of Windhoek in Namibia succeeded in stretching their limited potable water resources through strict water management, latterly including wastewater reclamation and direct potable reuse. An integrated approach was followed and proper policies were put in place. This was followed up with appropriate legislation, education, policing and technical and financial measures with the result that extreme water shortages were overcome even in times of severe droughts. [ABSTRACT FROM AUTHOR]