Charles Nathan Haas

Drexel University | DU · Department of Civil, Architectural and Environmental Engineering

The coronavirus disease 2019 pandemic highlighted the need for more rapid and routine application of modeling approaches such as quantitative microbial risk assessment (QMRA) for protecting public health. QMRA is a transdisciplinary science dedicated to understanding, predicting, and mitigating infectious disease risks. To better equip QMRA researc...

We used the Delphi method to identify areas of consensus and disagreement in managing building water systems. One hundred and six experts were invited, 25 of whom completed both rounds. More than 95% of experts agreed that current plumbing codes are not adequate and return loop temperature should be monitored. A notably low percentage of experts ag...

To address decreasing water supplies, several US regulatory entities are developing regulations and guidance for the direct potable reuse (DPR) of wastewater, i.e., potable reuse with a limited or no...

This study specifies science-based pathogen treatment requirements for direct potable reuse using high-quality monitoring data and probabilistic approaches to ensure consistent and reliable protection of public health.

Recent water sector safety concerns during the COVID-19 pandemic highlight the need for industry-focused reviews of emerging pathogens to support evidence-based utility decision-making. Between May 7 and August 20, 2022, more than 41 358 cases of human monkeypox were reported globally from over 87 countries in which the disease is not endemic. Give...

Abstract This study examines the influence of chlorine disinfectant type, water use frequency (stagnation time), and water heater temperature on the growth and persistence of microbes, including nontuberculous mycobacteria (NTM), in water heater storage tanks and downstream plumbing. The experimental setup consists of four 50-gallon electric water...

Wastewater surveillance for pathogens using reverse transcription-polymerase chain reaction (RT-PCR) is an effective and resource-efficient tool for gathering additional community-level public health information, including the incidence of coronavirus disease-19 (COVID-19). Surveillance of SARS-CoV-2 in wastewater can provide an early warning signa...

Legionella pneumophila is an opportunistic bacterial respiratory pathogen that is the leading causes of drinking water outbreaks in the United States. Dental offices pose a potential risk for inhalation or aspiration of L. pneumophila due to the high surface area to volume ratio of dental unit water lines—a feature that is conducive to biofilm grow...

Wastewater surveillance for pathogens using the reverse transcription-polymerase chain reaction (RT-PCR) is an effective, resource-efficient tool for gathering additional community-level public health information, including the incidence and/or prevalence and trends of coronavirus disease-19 (COVID-19). Surveillance of SARS-CoV-2 in wastewater may...

In response to COVID-19, the international water community rapidly developed methods to quantify the SARS-CoV-2 genetic signal in untreated wastewater. Wastewater surveillance using such methods has the potential to complement clinical testing in assessing community health. This interlaboratory assessment evaluated the reproducibility and sensitivi...

Computational fluid dynamics (CFD) have been applied to predict the performance of chemical water treatment disinfection systems in recent decades. However, computation times remain sufficiently long and prevent their use in optimal design. As an alternative, the use of an artificial neural network (ANN) metamodel to simulate CFD results was assess...

1 Abstract In response to COVID-19, the international water community rapidly developed methods to quantify the SARS-CoV-2 genetic signal in untreated wastewater. Wastewater surveillance using such methods has the potential to complement clinical testing in assessing community health. This interlaboratory assessment evaluated the reproducibility an...

This study examines the effect of pipe characteristics and stagnation time on nitrification, disinfectant loss, and organic carbon concentrations. Pipe racks consisting of different pipe materials (chlorinated polyvinyl chloride [CPVC], cross-linked polyethylene [PEX-B], and copper), diameters (0.75 and 0.5 in.), and water stagnation times (1 week...

This study develops dose–response models for Ebolavirus using previously published data sets from the open literature. Two such articles were identified in which three different species of nonhuman primates were challenged by aerosolized Ebolavirus in order to study pathology and clinical disease progression. Dose groups were combined and pooled ac...

Brian Pecson and Daniel Gerrity present an Editorial Perspective which focuses on the impact of SARS-CoV-2 on the water industry.

Legionella spp. occurring in hotel hot water systems, in particular Legionella pneumophila, are causing serious pneumonic infections, and water temperature is a key factor to control their occurrence in plumbing systems. We performed a systematic review and meta-analyses of the available evidence on the association between water temperature and Leg...

Naegleria fowleri (N. fowleri) is associated with the occurrence of primary amoebic meningoencephalitis (PAM) infection with a fatality rate of about 98%. Even though the risk of infections caused by N. fowleri is very low, most of the victims of the infections are children or young adults who are more often in good health. A dose-response model fo...

The authors regret to report that the paper “Reverse QMRA as a Decision Support Tool: Setting Acceptable Concentration Limits for Pseudomonas aeruginosa and Naegleria fowleri” contains some erroneous computations [...]

Typical recreational water risk to swimmers is assessed using epidemiologically derived correlations by means of fecal indicator bacteria (FIB). It has been documented that concentrations of FIB do not necessarily correlate well with protozoa and viral pathogens, which pose an actual threat of illness and thus sometimes may not adequately assess th...

Middle Eastern respiratory syndrome, an emerging viral infection with a global case fatality rate of 35.5%, caused major outbreaks first in 2012 and 2015, though new cases are continuously reported around the world. Transmission is believed to mainly occur in healthcare settings through aerosolized particles. This study uses Quantitative Microbial...

Opportunistic premise plumbing pathogens such as Pseudomonas aeruginosa and Naegleria fowleri are a growing concern in building water systems because of their potential risks to human health. The aim of this study was to determine the critical concentrations of P. aeruginosa and N. fowleri in water that are associated with meaningful public health...

The need to prevent possible adverse environmental health impacts resulting from synthetic biology (SynBio) products is widely acknowledged in both the SynBio risk literature and the global regulatory community. To-date, however, discussions of potential risks of SynBio products have been largely speculative, and the limited attempts to characteriz...

Legionella spp. is a key contributor to the United States waterborne disease burden. Despite potentially widespread exposure, human disease is relatively uncommon, except under circumstances where pathogen concentrations are high, host immunity is low, or exposures to small-diameter aerosols occurs. Water quality guidance values for Legionella are...

A broad body of literature has been published regarding roof-harvested rainwater (RHRW) quality around the world. In particular, the presence of fecal indicator bacteria and pathogenic microorganisms has raised concerns regarding the acceptability of rainwater for potable and non-potable uses. As the use of molecular assays has increased our unders...

Here we provide seasonal data on the concentrations of total coliform, Escherichia coli and Enterococcus spp. and six opportunistic pathogens (Acanthamoeba spp., Legionella spp., Legionella pneumophila, Mycobacterium avium, Mycobacterium intracellulare, and Pseudomonas aeruginosa) of public health significance in 24 tank water samples over six mont...

Purpose of review: The global importance of Legionnaires' disease (LD) and Pontiac fever (PF) has grown in recent years. While sporadic cases of LD and PF do not always provide contextual information for evaluating causes and drivers of Legionella risks, analysis of outbreaks provides an opportunity to assess these factors. Recent findings: A re...

Legionella are a major cause of water-associated disease outbreaks with disease transmission occurring following inhalation of bacteria in a fine mist or small aerosols. Legionnaires’ disease has a high mortality rate and presents a significant public health concern. This study focused on understanding how frequently Legionella occur in reclaimed w...

Many infectious disease hazards demonstrate higher susceptibility with regards to younger host ages. This trend of increased susceptibility with decreasing host age can also lead to an increased likelihood of mortality, and prolonged/chronic health effects. For quantitative microbial risk assessment (QMRA) modeling, the ability to quantify the effe...

Potable and non-potable uses of roof-harvested rainwater (RHRW) are increasing due to water shortages. To protect human health risks, it is important to identify and quantify disease-causing pathogens in RHRW so that appropriate treatment options can be implemented. We used a microfluidic quantitative PCR (MFQPCR) system for the quantitative detect...

A study of water quality parameters was conducted in 38 small-scale roof-harvested rainwater barrels (RHRB) located in urban and peri-urban Philadelphia, USA in winter (November–December) 2014 and summer (June–August 2016). Parameters included two fecal indicator bacteria (FIB) (Escherichia coli and Enterococcus spp.) measured using culture-based m...

Experimental time-to-infection data are a useful but often underused material for examining the mechanics of in vivo pathogen growth. The authors incorporated a time–dose–response (TDR) equation into a Shigella flexneri outbreak model. Dose–response and TDR models were generated for Shigella sonnei outbreak model. Dose–response and TDR models were...

The use of reclaimed water brings new challenges for the water industry in terms of maintaining water quality while increasing sustainability. Increased attention has been devoted to opportunistic pathogens, especially Legionella pneumophila, due to its growing importance as a portion of the waterborne disease burden in the United States. Infection...

The transport processes in the mixing of either two gases or two miscible liquids in a T-junction are investigated numerically. Both laminar and turbulent flow fields are considered. The 3-D time-dependent flow fields are calculated for the T-junction (of two circular cross-section pipes that meet orthogonally at the junction). For turbulent flow r...

The inhalation exposure to Stachybotrys chartarum (SC) has been playing a critical role in public health domain due to its ability to produce toxins (trichothecene and other mycotoxins), that are implicated in the cases of acute idiopathic pulmonary hemorrhages (AIPH) in infants. Despite multiple studies reporting an association of exposure to airb...

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...

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 functio...

Research on rainwater quality

Experimental time-to-infection data is a useful, but often underutilized, material for examining the mechanics of in vivo pathogen growth. In this paper, the authors attempt to incorporate a time-dose-response (TDR) equation into a model which predicts the number of ill persons per day in a Giardia lamblia epidemic using data collected from a Pitts...

A quantitative microbial risk assessment (QMRA) of opportunistic pathogens Legionella pneumophila (LP) and Mycobacterium avium complex (MAC) was undertaken for various uses of roof-harvested rainwater (RHRW) reported in Brisbane, Australia to identify appropriate usages and guide risk management practices. Risks from inhalation of aerosols due to s...

Current World Health Organization and Centers for Disease Control and Prevention guidance for the disposal of liquid waste from patients undergoing treatment for Ebola virus disease at hospitals in the U.S. is to manage patient excreta as ordinary wastewater without pretreatment. The potential for Ebolavirus transmission via liquid waste discharged...

Concerns have been raised regarding handling of Ebola virus contaminated wastewater, as well as the adequacy of proposed disinfection approaches. In the current study, we investigate the inactivation of Ebola virus in sterilized domestic wastewater utilizing sodium hypochlorite addition and pH adjustment. No viral inactivation was observed in the o...

Measured and modeled chlorine residuals versus time for added chlorine doses. (DOCX)

Raw data for each replicate for hypochlorite inactivation experiment at a target starting concentration of 5 log TCID50 mL-1. All values log TCID50 mL-1. Limit of detection for each replicate was 0.75 log TCID50 mL-1. (DOCX)

Raw data for each replicate at a target starting concentration of 105 TCID50 mL-1. All values log TCID50 mL-1. Limit of detection for each replicate was 0.75 log10 TCID50 mL-1. (DOCX)

Chlorine residual versus time for 10 mgL-1 dose condition. (DOCX)

Chlorine residual versus applied dose at measured time points. (DOCX)

Chlorine residual versus time for 1 mgL-1 dose condition. No residual detected at later time points. (DOCX)

Chlorine residual versus time for 5 mgL-1 dose condition. (DOCX)

A seasonal study on the occurrence of six opportunistic premise plumbing pathogens (OPPPs) in 24 roof-harvested rainwater (RHRW) tanks repeatedly sampled over six monthly sampling events (n = 144) from August 2015 to March 2016 was conducted using quantitative qPCR. Fecal indicator bacteria (FIB) Escherichia coli (E. coli) and Enterococcus spp. wer...

Mycobacterium avium complex (MAC) is a group of environmentally-transmitted pathogens of great public health importance. This group is known to be harbored, amplified, and selected for more human-virulent characteristics by amoeba species in aquatic biofilms. However, a quantitative microbial risk assessment (QMRA) has not been performed due to the...

Peracetic acid (PAA) is an emerging disinfectant for the treatment of wastewater. While it would be possible to optimize the design of this system using computational fluid dynamics (CFD), the computational intensity would be high. As an alternative, we show that an Artificial Neutral Network (ANN) based metamodel can approximate the CFD solutions...

A study of six potential opportunistic pathogens (Acanthamoeba spp., Legionella spp., Legionella longbeachae, Pseudomonas aeruginosa, Mycobacterium avium and Mycobacterium intracellulare) and an accidental human pathogen (Legionella pneumophila) in 134 roof-harvested rainwater (RHRW) tank samples was conducted using quantitative PCR (qPCR). All fiv...

Reproducible research is a concept that has emerged in data and computationally intensive sciences in which the code used to conduct all analyses, including generation of publication quality figures, is directly available, and preferably in open source manner. This perspective outlines the processes and attributes, and illustrates the execution of...

A career in academics does not mean isolation from practice. In fact, most academic professionals provide a wealth of knowledge, research, and experience within the university halls and outside in the water industry field.

China has had a rapid increase in its economy over the past three decades. However, the economic boom came at a certain cost of depleting air quality. In the study, we aimed to examine the burden of air pollution and its association with climatic factors and health outcomes using data from Chinese national and city-level air quality and public heal...

Importance: The use of roof-harvested rainwater (RHRW) for domestic purposes is a globally accepted practice. The presence of pathogens in rainwater tanks has been reported by several studies supporting the necessity for the management of potential health risks. The sources of fecal pollution in rainwater tanks are unknown. However, the applicatio...

The Bogotá River receives untreated wastewater from the city of Bogotá and many other towns. Downstream from Bogotá, water from the river is used for irrigation of crops. Concentrations of indicator organisms in the river are high, which is consistent with fecal contamination. To investigate the probability of illness due to exposure to enteric pat...

A novel method was used to incorporate in vivo host–pathogen dynamics into a new robust outbreak model for legionellosis. Dose-response and time-dose-response (TDR) models were generated for Legionella longbeachae exposure to mice via the intratracheal route using a maximum likelihood estimation approach. The best-fit TDR model was then incorporate...

Worldwide, high incidences of cryptosporidiosis and giardiasis are attributed to livestock waste. Quantitative microbial risk assessment can be used to estimate the risk of livestock related infections from Cryptosporidium parvum and Giardia lamblia. The objective of this paper was to assess the occupational and public health risks associated with...

Avian and possum fecal droppings may negatively impact roof-harvested rainwater (RHRW) water quality due to the presence of zoonotic pathogens. This study was aimed at evaluating the performance characteristics of a possum feces-associated (PSM) marker by screening 210 fecal and wastewater samples from possums (n = 20) and a range of non-possum hos...

Biological fouling occurs on RO membranes when bacteria and nutrients are present in conditions that are conducive to growth and proliferation of the bacteria. Controlling microbial growth on the membranes is typically limited to biocide application (i.e., disinfectants) in seawater RO plants. However, biological growth and subsequent fouling has n...

Legionella has been identified as the responsible agent for two-thirds of waterborne disease outbreaks in the United States from 2011-2012. The prevention of Legionella in engineered systems presents complex challenges for the drinking water industry due to its persistence, resistance to disinfection, and complex microbial ecology. Not all species...

In the wake of the ongoing 2014/2015 Ebola virus outbreak, significant questions regarding the appropriate handling of Ebola virus-contaminated liquid waste remain, including the persistence of Ebola virus in wastewater. To address these uncertainties, we evaluated the persistence of Ebola virus spiked in sterilized domestic sewage. The viral titer...

We developed two dose–response algorithms for P. aeruginosa pool folliculitis using bacterial and lesion density estimates, associated with undetectable, significant, and almost certain folliculitis. Literature data were fitted to Furumoto & Mickey's equations, developed for plant epidermis-invading pathogens: N l = A ln(1 + BC) (log-linear model);...

Wastewater disinfection processes are typically designed according to heuristics derived from batch experiments where the interaction among wastewater quality, reactor hydraulics and inactivation kinetics is often neglected. In this paper, a CFD study was conducted in a non-deterministic (ND) modeling framework to predict the Escherichia coli inact...

A quantitative microbial risk assessment was conducted to estimate risk of gastrointestinal (GI) illnesses associated with recreational exposure to Philadelphia waterways, under dry and wet weather conditions. Using maximum likelihood estimation, stochastic exposure models were generated for each exposure scenario and Monte Carlo techniques were ap...