About

Marc A. Edwards is a University Distinguished Professor at Virginia Tech, serving in the Charles E. Via, Jr. Department of Civil & Environmental Engineering. His research focuses on water treatment, corrosion, arsenic removal, and applied aquatic chemistry. Edwards has held various academic positions at Virginia Tech since 1997, including Lunsford Professor of Civil Engineering and University Distinguished Professor since 2017. His educational background includes a B.S. in Bio-Physics from SUNY Buffalo, an M.S. and Ph.D. in Environmental Engineering from the University of Washington. Throughout his career, Edwards has contributed significantly to the fields of water quality and public health, earning numerous awards and honors such as the Hoover Medal, multiple honorary doctorates, and recognition from organizations like AAAS, IEEE, and the American Society of Civil Engineers. His work has involved addressing critical issues related to water safety, microbial ecology in water systems, and public health advocacy, notably in the context of water crises such as Flint. Edwards is known for his extensive research on microbial and chemical processes in water systems, and his efforts have advanced understanding and solutions for safe drinking water and environmental health.

Research topics

• Artificial Intelligence
• Political Science
• Data Mining
• Computer Science
• Machine Learning
• Epistemology
• Biology
• Water resource management
• Philosophy
• Environmental engineering
• Business
• Environmental protection
• Environmental health
• Environmental planning
• Environmental science
• Medicine
• Ecology

Selected publications

• Countering Growing Distrust in Drinking Water Systems through Truth, Transparency, and Shared Responsibility

  ACS ES&T Water · 2026-02-04

  articleOpen accessSenior author
  PublisherDOI

• Atypical PI3Ks coordinate chemotaxis, signaling dynamics, and multicellular development in <i>Dictyostelium</i>

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-05-14

  articleOpen accessSenior authorCorresponding

  Abstract Phosphoinositide 3-kinase (PI3K) signaling regulates protrusion, polarity, membrane uptake, and multicellular development in Dictyostelium discoideum , but these functions have been interpreted largely through canonical Class I PI3Ks and PI(3,4,5)P₃ production. This framework does not fully explain how PI3K-dependent pathways attenuate Ras activity, organize PI(3,4)P₂-associated polarity states, support cAMP relay, or coordinate development. Here, we identify three atypical PI3K-family enzymes—PikF, PikG, and PikH—as functionally distinct regulators of these processes. PikF constrains Ras–phosphoinositide–actin signaling; pikF⁻ cells show prolonged cAMP-stimulated Ras activation, extended PIP₃ recruitment, delayed PI(3,4)P₂ biosensor recovery, elevated peripheral actin activity, impaired chemotactic precision, and delayed abnormal development. PikG acts through a distinct relay-associated pathway: pikG⁻ cells fail to generate endogenous cAMP oscillations, display disrupted ACA polarity, deposit spatially disorganized ACA-positive vesicle trails, and fail to aggregate. PikH, in contrast, supports efficient phagocytic uptake with little effect on acute chemotactic signaling. Kinase-dead rescue experiments show that conserved catalytic lysines are required for PikF- and PikG-dependent development and PikH-dependent uptake. Together, our results reveal that atypical PI3Ks diversify the Dictyostelium PI3K signaling toolkit, separating protrusive signal attenuation, cAMP relay organization, membrane uptake, and multicellular development into distinct kinase-dependent modules.

  PublisherDOI

• Complexity of Chloramine Decay Kinetics in Premise Plumbing

  ACS ES&T Water · 2026-01-30 · 1 citations

  articleOpen accessSenior author

  Nitrification-driven chloramine decay kinetics have largely been unquantified in premise plumbing, which is particularly vulnerable to opportunistic pathogen growth. Here, we carried out complementary experiments in an at-scale premise plumbing rig with mature biofilms (>4 years age) with influent residuals of <0.2, 0.25, 0.5, 1.0, and 2.5 mg/L as Cl2 and sterile glass jars, with and without an inoculum containing nitrifying bacteria. Chloramine decay was complete after 8 h of stagnation in all PEX rig pipes (n = 16), tested over a range of diameters (1/4–3/4”) and flow rates (0.25–2.2 gpm), with decay rates increasing in situations with higher nitrification rates. The jar experiments revealed that chloramine actually persisted better at higher (37–39 °C) than lower (19–30 °C) temperatures, contrary to standard temperature-adjusted kinetic assumptions, presumably because nitrifiers are inhibited at higher temperatures. Contrary to assumptions made in conventional models, chloramine decay was only effectively modeled as first order in 8/24 cases in the rig experiment (R2 > 0.9). The best fit chloramine decay reaction order varied among the rig pipes from 0.88 to 2.74, depending on chloramine dose and exposure time, hydraulics, and modeling method.

  PublisherDOI

• Microbial Growth Curve Framework Provides Insights for Controlling Opportunistic Pathogens in Building Plumbing

  ACS ES&T Water · 2026-04-10

  articleOpen accessSenior author

  The perception that high water retention time (WRT) in buildings increases microbial and pathogen growth drives costly flushing interventions, which lack a scientific framework to guide effective implementation. Here, we evaluate the effect of WRT from 1 to 21 days in an at-scale building plumbing rig with influent chloramine residuals of <0.2–2.5 mg/L as Cl2 and water heater set points of 40 and 60 °C. We found that the classic microbial growth curve consisting of lag, exponential growth, stationary, and decay phases provided a robust explanation of trends in bulk water total cell counts (TCC) and Legionella pneumophila over a wide range of conditions. We extended this observation to develop a framework to understand how various controls and operating conditions act to stop (e.g., cold temperatures, disinfectant) or reset (e.g., pasteurization in water heaters killing microbes and recycling nutrients) the growth curve as a function of WRT. Bulk water TCC and L. pneumophila reached a consistent peak/plateau at a building WRT of ∼7 days before decaying up to 90% at higher WRT. These findings suggest that recent guidelines recommending weekly flushing of buildings may sometimes be counterproductive and that very high WRT does not necessarily indicate microbial risk.

  PublisherDOI

• Retrospective Analysis of Drinking Water Microcosm Microbiomes Reveals an Apparent Antagonistic Relationship between <i>Neochlamydia</i> and <i>Legionella</i>

  Environmental Science & Technology Letters · 2025-07-17 · 4 citations

  articleOpen accessSenior authorCorresponding

  Legionella pneumophila (Lp) can sometimes establish in drinking water microbial communities and infect individuals inhaling contaminated aerosols. The premise plumbing portion of the drinking water distribution system is often especially vulnerable to Lp growth. Innovative approaches to intentionally manipulate the microbial ecology to control Lp have been proposed but remain elusive. Here, we retrospectively analyzed 16S rRNA gene amplicon sequences and droplet digital PCR data in samples derived from prior drinking water studies, wherein some inexplicable stochastic variations in the Lp occurrence were observed in replicate microcosms. We discovered an apparent antagonistic relationship between Legionella and Neochlamydia. This relationship was noted across three water sources (Flint, Detroit, and Blacksburg) and was at least partially mediated by the presence of copper, through either copper pipes or a dosed range of 0–2000 μg/L total copper. The observations of this study, which was conducted under realistic drinking water conditions harboring mixed microbial communities, are consistent with recent pure culture studies reporting that Legionella amoebic uptake may be inhibited when Neochlamydia are established as amoebal endosymbionts. The findings may help explain the apparent stochastic behavior of Lp in field and research settings and may open a door to new engineered ecological control strategies for Lp.

  PublisherDOI

• A Novel, Metal-Based Approach to Identify Residences with Lead Service Lines

  Environmental Science & Technology Letters · 2025-07-30 · 1 citations

  articleOpen access

  There is an urgent need for rapid, cost-effective approaches to identify residences with lead service lines (LSLs). We evaluated whether analyzing water for corrosion-related metals could accurately identify residences with LSLs without relying on potentially inaccurate property records. We applied principal component analysis logistic regression (PCA-LR) and classification tree models using 28 analytes per bottle (including Pb, Cu, Zn, Fe, Al, and others) measured in 216 water samples collected in Flint, Michigan, in August 2015. The PCA-LR model achieved 87% accuracy (AUROC = 0.93) with 81% sensitivity and 90% specificity, while the classification tree model achieved 80% accuracy (AUROC = 0.77) with 74% sensitivity and 84% specificity. The classification tree provided interpretable decision rules identifying key predictive metals, primarily relying on 1 min flush Pb concentrations with Zn and Al as secondary predictors. It also revealed distinct metal co-occurrence patterns between LSLs and premise plumbing, offering insights into Pb source identification. The tree’s interpretable structure makes it particularly valuable for practical implementation by utilities. Although additional work is needed to extend these models to other water systems, our results suggest that metal analysis provides an accurate, cost-effective, and minimally invasive tool that complements existing approaches for predicting the presence of an LSL.

  PublisherDOI

• A Novel Mechanism of Lead–Tin Solder Spallation in the Presence of Nitrate

  Environmental Science & Technology Letters · 2025-02-10 · 1 citations

  articleOpen accessSenior author

  Elevated 90th percentile water lead levels associated with the release of large chunks of lead–tin solder to drinking water were recently attributed to corrosion by nitrate. A new mechanism of water lead contamination via nitrate-induced spallation of solder was elucidated through surface analyses of new solder coupons and harvested pipe samples, bench-scale testing with lead–tin alloys of varying tin content, and electrochemical tests. Nitrate attack was associated with the formation of ammonia and other reduced nitrogen compounds, causing detinning of solder alloys with more than 40% tin by weight and eventually complete detachment of solder from the point of adhesion to copper pipe via the formation of a corrosive microenvironment. Solder spallation was observed in as little as 6 weeks and resulted in 1.3 times more metal weight loss than could be explained by Faraday’s law for both tin and 50/50 lead–tin solder in 32 h electrochemical tests. Understanding this mechanism of attack can help explain and predict water lead contamination events and inform the development of optimal corrosion control strategies for potable water supplies.

  PublisherDOI

• Influence of Copper Dose on <i>Mycobacterium avium</i> and <i>Legionella pneumophila</i> Growth in Premise Plumbing

  ACS ES&T Water · 2025-10-10 · 1 citations

  articleOpen accessSenior author

  Effects of copper at 0, 4, 30, 250, or 2000 μg/L on microbial communities were examined over an 11 month dosing period using triplicate 120 mL water heater microcosms with PEX-b pipes containing mature biofilms to simulate premise plumbing. Effluent total cell counts (TCCs) and Mycobacterium avium peaked at 250 μg/L, reflecting the dual role of copper as a nutrient and antimicrobial. TCCs and M. avium were relatively consistent among replicate microcosms at each dose, but Legionella pneumophila (Lp) diverged among biological triplicates at 250 μg/L, consistently producing high culturable Lp (average 2.5 log MPN/mL) in one microcosm and low/nondetectable levels in the other two. Repeated cross-inoculations and a reinoculation failed to normalize the microbial community composition across 250 μg/L and other triplicate microcosms. 16S rRNA gene amplicon sequencing revealed that the 250 μg/L replicate with a high Lp was characterized by a distinct microbial community composition relative to the two replicates. At 2000 μg/L copper, microbial diversity and TCCs initially decreased, but then TCCs subsequently increased and ultimately were not statistically different from the 250 μg/L microcosms. This study provides insight into mechanisms underlying nonlinear effects of copper dosing when applied as a disinfectant to premise plumbing for opportunistic pathogen control.

  PublisherDOI

• Household Point-of-Use Faucet Filters for Lead Removal: Field Performance and User Experiences

  ACS ES&T Water · 2025-05-09 · 1 citations

  articleOpen accessSenior authorCorresponding

  Lead certified point of use (POU) faucet filters were field tested in two Louisiana cities in a total of 21 occupied homes during normal use and in two unoccupied homes with very high risk of water lead (Pb) contamination. In an unoccupied home with a 28 m lead service line (LSL) with average lead of 17 μg/L in flushed water, treatment by POU filters generally produced water with <5 μg/L Pb even when tested to 200% of rated capacity. In the unoccupied home with a disturbed LSL, the water had erratic influent particulate lead of 9-3053 μg/L, and the POUs did not consistently produce water with <10 μg/L Pb despite very high percentage removals. When testing POUs in occupied homes known to occasionally have lead over 5 μg/L, POUs always reduced lead to <1 μg/L. In addition, POUs were also effectively removing high levels of iron and manganese present in the water of one city, but this also caused clogging before reaching half of their rated capacity. Laboratory experiments confirmed POU susceptibility to iron clogging.

  PublisherDOI

• Investigation of Organotin Compounds in Drinking Water Contacting Aged PVC Pipes

  ACS ES&T Water · 2025-08-05 · 1 citations

  article

  Polyvinyl chloride (PVC) pipe is commonly used in drinking water distribution systems and building plumbing. Organotin compounds (OTCs) utilized in PVC pipe production are a public health concern. Here, we examined the significance of organotin release into water under different scenarios of temperature and stagnation in complementary laboratory and field studies. Over a two-year laboratory experiment, monomethyltin (MMT) concentrations ranged from 88 to 186 ng/L, and dimethyltin (DMT) ranged from 9 to 75 ng/L. Methyltin was also the main organotin species leached from aged PVC with a biofilm and with the biofilm removed. Laboratory studies revealed that initial leaching rates of MMT and DMT in the segment reactors with a biofilm were about 53% lower in 15 year-old pipe segments compared to 2 year-old segments due to increased rates of biodegradation from mature biofilms. Certain PVC and chlorinated PVC (CPVC) pipe systems can cause consumer exposure to trace organotin compounds from drinking water.

  PublisherDOI

Recent grants

• SusChEM GOALI: Transformative Approach to Sustain Potable Water Infrastructure: Fundamental Mechanisms of In-Situ Autogenous Repair

  NSF · $536k · 2013–2017

• RAPID: Potable water hazards and resource needs in private well communities impacted by extreme flooding events

  NSF · $200k · 2017–2019

• Accelerated Testing of Corrosion

  NSF · $110k · 1993–1996

• RAPID: Recovery of Well Water Quality After the Great Louisiana 2016 Flood

  NSF · $151k · 2016–2018

• RAPID: Synergistic Impacts of Corrosive Water and Interrupted Corrosion Control on Chemical/Microbiological Water Quality: Flint, MI

  NSF · $50k · 2015–2016

Frequent coauthors

• Amy Pruden

  Virginia Tech

  85 shared

• William J. Rhoads

  54 shared

• Kelsey J. Pieper

  Northeastern University

  40 shared

• Jeffrey Parks

  38 shared

• Laurie S. McNeill

  36 shared

• Siddhartha Roy

  33 shared

• Dietmar Glindemann

  Virginia Tech

  28 shared

• Adrienne Katner

  Louisiana State University Health Sciences Center New Orleans

  24 shared