Virus transfer at the skin-liquid interface

Understanding virus transfer between liquid and skin is necessary to estimate transmission during water-related activities. In the present study, we modeled virus transfer from liquid-to-skin and skin-to-liquid. Specifically, we performed human subject studies using unenveloped (MS2, Qβ) and enveloped (Φ6) bacteriophage as pathogenic virus surrogates. Our study shows that transfer from liquid-to-skin is describable by a single, universal model based on 1) virus concentration and 2) volume of liquid remaining on skin. Liquid conditions (pH 6-9, ionic strength 10 - 550 mM), contact times (0.1 - 30 min), and virus species had little to no influence on virus transfer. The model accounts for both; virus adsorbed onto the skin and virus in the liquid retained on skin. In comparison, virus transfer from skin-to-liquid was influenced by the wetness of the skin and by liquid type (water, saliva). Up to 90±19% of the virus inoculated on the skin are transferred to the water when the skin remains wet, compared to and 30 ± 17% when is dry. The transfer from skin-to-liquid was 41% higher when the recipient liquid was water as compared with saliva. This study quantifies virus transfer between liquid and skin, identifies factors influencing transfer, and guides risk assessments of water-related activities

The utility of flow cytometry for potable reuse

Protecting public health from pathogens is critical when treating wastewater to drinking water standards (i.e., planned water reuse). Viruses are a principal concern, yet real-time monitoring strategies do not currently measure virus removal through reuse processes. Flow cytometry (FCM) has enabled rapid and sensitive bacteria monitoring in water treatment applications, but methods for virus and protozoa monitoring remain immature. We discuss recent advances in the FCM field and FCM applications for quantifying microorganisms in water. We focus on flow virometry (FVM) developments, as virus enumeration methods show promise for water reuse applications. Ultimately, we propose FVM for near real-time monitoring across treatment to more accurately validate virus particle removal and for pilot studies to characterize removal through understudied unit processes

Pathogens and pharmaceuticals in source-separated urine in eThekwini, South Africa

In eThekwini, South Africa, the production of agricultural fertilizers from human urine collected from urine-diverting dry toilets is being evaluated at a municipality scale as a way to help finance a decentralized, dry sanitation system. The present study aimed to assess a range of human and environmental health hazards in source-separated urine, which was presumed to be contaminated with feces, by evaluating the presence of human pathogens, pharmaceuticals, and an antibiotic resistance gene. Composite urine samples from households enrolled in a urine collection trial were obtained from urine storage tanks installed in three regions of eThekwini. Polymerase chain reaction (PCR) assays targeted 9 viral and 10 bacterial human pathogens transmitted by the fecal-oral route. The most frequently detected viral pathogens were JC polyomavirus, rotavirus, and human adenovirus in 100%, 34% and 31% of samples, respectively. Aeromonas spp. and Shigella spp. were frequently detected gram negative bacteria, in 94% and 61% of samples, respectively. The gram positive bacterium, Clostridium perfringens, which is known to survive for extended times in urine, was found in 72% of samples. A screening of 41 trace organic compounds in the urine facilitated selection of 12 priority pharmaceuticals for further evaluation. The antibiotics sulfamethoxazole and trimethoprim, which are frequently prescribed as prophylaxis for HIV-positive patients, were detected in 95% and 85% of samples, reaching maximum concentrations of 6800 µg/L and 1280 µg/L, respectively. The antiretroviral drug emtricitabine was also detected in 40% of urine samples. A sulfonamide antibiotic resistance gene (sul1) was detected in 100% of urine samples. By coupling analysis of pathogens and pharmaceuticals in geographically dispersed samples in eThekwini, this study reveals a range of human and environmental health hazards in urine intended for fertilizer production. Collection of urine offers the benefit of sequestering contaminants from environmental release and allows for targeted treatment of potential health hazards prior to agricultural application. The efficacy of pathogen and pharmaceutical inactivation, transformation or removal during urine nutrient recovery processes is thus briefly reviewed

Water and Waste Reuse to Enhance Environmental and Human Health

As strategies in sustainability permeate modern engineering approaches, opportunities to re-engineer our water and sanitation systems in ways that simultaneously address human and ecological needs become apparent. Yet uncertainties remain regarding the human health safety, ecosystem impacts, social acceptance, and economic efficiency of innovative water and waste management infrastructure. I will introduce two areas of my research conducted to reveal opportunities and address uncertainties within this context. First, I will discuss ecological and economic opportunities for using tertiary treated wastewater to renew urban streams. A case study in Pacifica, California demonstrated that the value of ecosystem services provided by a restored stream augmented with recycled water were greater than the additional costs required for implementation. Yet ecological water reuse remains a small portion of California’s water reuse portfolio, just 7% of the volume recycled in 2009. This is due in part to unquantified environmental risks of ecological water reuse. For example, an emerging understanding of the bioaccumulative nature of perfluoroalkyl acids reveals a potential contribution of these persistent micropollutants to ecological risk in such projects. Second, I will present strategies to reduce human and environmental health risks in the scale-up of waste reuse for a city’s decentralized dry sanitation system. In Durban, South Africa, the local municipality aims to recover nutrients from urine to produce agricultural fertilizers. However, source-separated urine also contains excreted pharmaceuticals and pathogens. By evaluating health hazards of collected urine in Durban and treatment efficacy of urine nutrient recovery processes, my work seeks to increase the safety of human waste reuse

Hygiene considerations during the collection, storage and processing of source-separated urine into a marketable fertilizer

Laboratory and field studies along with inactivation data from the literature are used to model bacteria inactivation during urine storage and struvite production. The model is used to evaluate urine storage and struvite drying under the fluctuating temperature and relative humidity. Recommendations are made to enhance microbial inactivation during urine storage and struvite production in low-resource field settings and to promote the safety of using urine-derived fertilizers

Quantifying microbial risks of field-scale struvite production from source-separated urine using first-person videography exposure assessment

This paper quantifies occupational exposures to pathogens in urine during urine collection and processing into fertilizer as well as attendant risks of infection from indirect pathogen exposure. We also detail the microlevel activity time series (MLATS) method, which was used to model disease risks and monitor hygiene. This method employs videography in exposure assessment and is broadly useful for high-resolution modeling of indirect exposures to pathogens

Towards sustainable sanitation: Identifying and mitigating microbial health risks in the production of urine-derived fertilizers

Sanitation systems that systematically recover and reuse waste can promote social enterprise, reduce discharge of harmful nutrients, pathogens and other contaminants to the environment, replace synthetic fertilizer sources, and increase access to sanitation for improved human health. However, one significant obstacle towards successfully modernizing sanitation practices is the need to assure human health safety in the production and application of waste-derived products. This is especially important in resource-poor settings, where an added challenge to safe waste reuse is limited financial capacity for technology implementation. This project seeks to identify and reduce human and environmental health risks in the collection of urine and its processing into a fertilizer (struvite) in a large decentralized sanitation system in Durban, South Africa, where a network of over 80,000 urine-diverting dry toilets (UDDTs) is in place. A screening of fecal pathogens in source-separated urine was conducted to assess microbial health hazards. Rotavirus, Adenovirus and Shigella spp. were identified as the most frequently occurring pathogens. Occupational exposure to Rotavirus in urine via surface-to-hand followed by hand-to-mouth transfer was then evaluated to quantify the relative microbial health risks associated with urine collection and fertilizer production. The microlevel activity time series (MLATS) method was selected for the exposure assessment. First person videography of urine collection and processing was coded into high-resolution data yielding the frequency, duration, and chronology of contacts between each study participant hand and each surface. Additionally, a tracer exposure study was conducted to measure the volume of urine contacted by study participants. A model was constructed using this data to simulate the concentrations expected of pathogens on worker hands and potential dose of pathogens ingested from intermittent hand-to-mouth contacts. Study participants contacted visibly wet, presumably urine-contaminated surfaces more frequently during the production of struvite than during the collection of urine (e.g., 10 vs. 3 wet-surface contacts/hr). The tracer study revealed that during the production of struvite, study participant gloves contacted 0.04 – 50 ml urine per batch of struvite produced. Nevertheless, the probability of Rotavirus infection associated with single dose events from presumed hand-to-mouth contacts was somewhat low during struvite production (e.g., median P(response) [ 95% CI] = 1.5×10-4 [1.4×10-5 , 5.4×10-4] per dose for 10K simulations). This exposure may be unacceptable if urine collection and fertilizer production system is conducted at scale or if multiple hand-to-mouth contacts occur during urine handling. In the context of resource reuse, source-separated urine is often falsely considered “sterile” or nearly so. Urine treatment via storage can reduce pathogen concentrations in struvite reactor influent to reduce exposure. Fertilizer production techniques that reduce human contact with urine during processing such as automated reactors should be favored. This study is unique in its approach to accurately model the time-dependent concentration of pathogens on hands due to urine contamination and to quantify the consequent exposure potential using videography, fecal contamination analysis in urine and on surfaces and a tracer study. Quantitatively identifying risks in this way is an important strategy for identifying and overcoming barriers to safe and sustainable sanitation

White Paper on the Application of Molecular, Spectroscopic, and Other Novel Methods to Monitor Pathogens for Potable Reuse

Direct potable reuse (DPR) is gaining interest in water-scarce and water-conscious regions of the world as a technology capable of treating domestic wastewater to potable water standards. Because wastewater is the source water of such treatment schemes, the removal of harmful biological and chemical contaminants present in wastewater is necessary. One of the primary challenges for water reuse applications is the effective removal of pathogens, including viruses and protozoa. A major limitation for the acceptance of DPR is the inability to actively monitor pathogen levels through potable reuse treatment trains. Although various methods to measure pathogen concentrations exist, the required reduction of these levels through treatment processes means pathogen quantification in finished water is not currently feasible in real-time. The lack of rapid, reliable, and inexpensive methods for monitoring through DPR has also hindered the ability of utilities to confirm sufficient pathogen removal through reuse. In this poster presentation, we will present findings from our collaborative project funded by the Water Environment and Reuse Foundation. WE&RF project 14-17 involves an extensive literature review on the current state of microbiological monitoring methods that have potential relevance in water reuse or application in the future. The white paper is intended to inform the DPR field on how to best monitor for pathogens through water reuse treatment trains. The presentation will present the major topics and conclusions from our collected research. In particular, we will discuss the challenges posed by extremely low pathogen concentrations in most of the DPR treatment train and the potential of concentration techniques coupled with detection methods to detect specific pathogens at various stages of DPR treatment trains. In addition, surrogate monitoring capabilities will be evaluated to determine methods for confirming adequate pathogen removal through treatment. Much of our white paper focuses on novel quantification, concentration, and surrogate monitoring methods that we find most promising for future water reuse applications. Specifically, recent developments in human norovirus (HuNoV) culture methods will surely aid in informing the ability of treatment trains to achieve adequate virus removal for the mitigation of public health risk. Of the many viral pathogens of interest in DPR, HuNoV is of principal concern because of its high concentration in raw wastewater and its large burden of disease. Flow cytometry (FCM) is another technique that will be highlighted in the poster presentation because of its real-time monitoring capabilities. FCM is a high-throughput technology that has been used effectively in real-time bacterial monitoring of environmental matrices. We believe FCM will become an important approach to near real-time virus monitoring in the future. New advances in quantitative PCR techniques also have promise in reuse applications to indicate pathogen contamination. Although not real-time, PCR-based methods are more rapid than culture-based methods. The potential ability of PCR-based methods to differentiate infective and non-infective microorganisms will also be reviewed. The poster presentation will conclude with a review of the most important research topics that are necessary to improve microbiological monitoring and pathogen credit maintenance in DPR applications