About

Ernest Blatchley is the Lee A. Rieth Professor in Environmental Engineering at the Lyles School of Civil and Construction Engineering and the School of Sustainability Engineering and Environmental Engineering at Purdue University. His research focuses on environmental engineering, contributing to the fields of sustainability and environmental engineering through his academic and professional work. As a distinguished faculty member, he has made significant contributions to the understanding and advancement of environmental engineering practices, emphasizing sustainable solutions and innovative approaches in his field.

Research topics

• Optics
• Optoelectronics
• Chemistry
• Environmental engineering
• Environmental science
• Materials science
• Organic chemistry
• Waste management
• Environmental chemistry
• Physics
• Engineering
• Process engineering
• Business
• Photochemistry

Selected publications

• Active Air Stripping and Direct Point Exhaust of Trichloramine (NCl3) from Indoor Pools

  SSRN Electronic Journal · 2026-01-01

  preprintOpen access1st authorCorresponding
  PublisherDOI

• Large-scale chamber tests of in-room germicidal ultraviolet (GUV) systems: Review and best practices

  Building and Environment · 2026-02-11

  articleOpen access1st authorCorresponding

  Disease outbreaks, including epidemics and pandemics, can disrupt virtually all aspects of social structure and function. Given the likelihood that additional outbreaks will occur in the future, probably involving airborne pathogens, there is a need to develop and implement strategies to mitigate disease transmission associated with these events. In-room (upper-room and whole-room) germicidal ultraviolet (GUV) systems can play key roles in these mitigation strategies and chamber tests are likely to be important for validation of their performance. At present, no uniform standard exists for conducting large-scale chamber tests or for translating the results of those experiments to application environments. In recognition of these needs, an ad-hoc committee was formed to address these issues. The goals of this effort were to conduct a critical review of the literature related to large-scale tests, to suggest “best practices” for these tests (as possible), and to suggest methods for translation of results from the test environment to the application environment. The review includes a summary of existing standards for large-scale testing. These standards provide recommendations for chamber dimensions, materials of construction, and operating conditions. Challenge agents used in these tests are summarized, including viral (phage), bacterial, and non-microbial agent options and their corresponding methods for culture and analysis. Methods of challenge agent introduction and collection are also summarized. Fluence rate field characterization will play critical roles in interpreting chamber test results and translation to application environments; fluence rate field modeling and measurement methods are reviewed and summarized. The implications of the well-mixed assumption, which is commonly applied, are summarized together with methods that can be used to assess mixing behavior. Basic attributes of health and safety issues related to chamber tests are summarized from the literature and from experience.

  PublisherDOI

• Evaluating tools for predicting and measuring radiometric performance of germicidal ultraviolet systems

  Photochemistry and Photobiology · 2026-02-18

  articleOpen access

  Germicidal ultraviolet (GUV) air treatment technologies can be effective and safe for reducing airborne disease transmission. Today, GUV systems are designed and evaluated using simulation and measurement tools that require further assessment of their accuracy in estimating fluence rate and irradiance. This article reports results from two experiments where two simulation software (Visual Lighting and Photopia) and two measurement techniques (tetrahedron and cubic approximations) were evaluated against chemical actinometry for quantification of GUV fluence rate in a chamber. Additionally, Visual and Photopia were compared to measurements of planar UV-C irradiance for eye and skin exposure. Results showed that overall mean fluence rates were similar between actinometry and both simulation software for WR GUV systems as well as between actinometry and Photopia for UR GUV systems. The tetrahedron approximation better predicted overall mean fluence rate for WR and UR GUV systems, compared to a cubic approximation which tended to overestimate it. Compared to measurements, simulated eye and skin irradiance varied, with higher variability in simulated eye irradiance. The evaluated simulation software can be used to guide the design of GUV systems but must be supplemented with in situ measurements.

  PublisherOA PDFDOI

• Real-Time Monitoring of Dose Distribution and Simplified Indicators of Ultraviolet Reactors with a Buckingham-π Theorem-Based Dual MFSD System

  Environmental Science & Technology · 2025-10-28

  articleCorresponding

  Real-time monitoring of dose delivery is critical for ensuring reliable and energy-efficient ultraviolet (UV) disinfection. However, conventional methods are limited by high cost and inability to capture full dose distribution information. This study presents a novel, cost-effective approach for real-time monitoring of UV dose delivery (including dose distribution and simplified indicators) by integrating a dual microfluorescent silica detector (dual-MFSD) system with Buckingham-π theorem-based scaling. The dual-MFSD system enabled simultaneous and convenient monitoring of real-time water UV transmittance (TRT), as well as a correction factor (CFRT) accounting for lamp output attenuation and sleeve fouling, with an effective optical path-length difference calibrated as 1.01 cm. A dimensionless scaling method based on the Buckingham-π theorem was developed to predict full information of the UV dose distribution using real-time operating parameters (i.e., TRT, flow rate (QRT), and CFRT), allowing rapid calculation of simplified indicators. The predicted doses were validated by computational fluid dynamic (CFD) simulation and biodosimetry at various TRT values (97% and 90%) and QRT values (40, 50, and 60 L min–1) with a measured CFRT (0.754). Additionally, a four-month field test was conducted in a secondary water supply system, demonstrating the practical applicability of this method. This study provides a real-time approach for UV dose monitoring, supporting reliable and energy-efficient UV disinfection.

  PublisherDOI

• Water Disinfection with Dual-Wavelength (222 + 275 nm) Ultraviolet Radiations: Microbial Inactivation and Reactivation

  Environmental Science & Technology · 2025-01-06 · 9 citations

  article

  Emerging mercury-free ultraviolet (UV) sources, such as krypton chloride excimer (KrCl*) lamps and UV light emitting diodes (UV-LEDs), emit diverse wavelengths with distinct inactivation mechanisms. The combined application has the potential to improve disinfection effectiveness through synergism. In this study, a mini-fluidic photoreaction system equipped with a KrCl* lamp (222 nm) and a strip of UV-LEDs (275 nm) was developed, which could individually/simultaneously deliver accurate UV radiation(s) at 222 nm (0.32 mW cm–2) or/and 275 nm (0.50 mW cm–2). Dual-wavelength UV (DWUV) radiations demonstrated a substantial synergistic effect on Escherichia coli (E. coli) inactivation with synergistic coefficients reaching up to 1.92, while no synergistic effect was observed for PR772 bacteriophage (PR772) inactivation. Moreover, DWUV radiations significantly (p < 0.05) suppressed the reactivation of E. coli and PR772 in the subsequent light/dark treatment. For E. coli, the underlying mechanism could be ascribed to the increased level of reactive oxygen species induced by DWUV radiations, which not only enhanced inactivation by damaging proteins and lipids, but also suppressed the reactivation by damaging DNA repair enzymes. For PR772, although the DNA and protein damages caused by DWUV radiations did not yield a synergistic effect, the protein damage prevented the viral DNA from entering host cells for repair, thereby suppressing reactivation. This study helps develop more effective UV disinfection technologies by using DWUV radiations.

  PublisherDOI

• Experimental Observation and Simulation of UV-C-Based Personal-Scale Reactors for Airborne Pathogen Disinfection

  ACS ES&T Engineering · 2025-01-24 · 3 citations

  article

  Airborne infectious disease is often controlled using filtration-based personal protective equipment (PPE), such as masks. However, such disease prevention measures have seen mixed use by the public, can be uncomfortable to wear over long periods of time, and produce significant levels of solid waste. An alternative to traditional masking is to enclose a UV source within a personal-scale reactor that a user breathes through and disinfects the air directly. In this work, a set of prototype personal-scale reactors were developed that utilize UV-C LEDs. Experimental measurements of the UV-C fluence rate within the reactors were conducted using a microfluorescent silica detector. Biological experiments were also conducted, where an aerosolized challenge agent was passed through the reactor, and the fraction of agent inactivation by UV-C exposure was quantified as a function of airflow rate. Experimental results were compared to simulations, in which computational fluid dynamics and optical simulations were used to simulate the inactivation of an infective agent resulting from UV exposure. The disinfection simulation results were similar to the experimental data, showing how computational modeling can be used to inform UV-C-based PPE designs that could be later experimentally investigated. Both simulations and experiments indicated that it is possible to achieve in excess of 1.3 log10 disinfection using personal-scale reactors, making them more effective than an N95 mask, even when disinfecting airflow rates that correspond to human respiration rates during moderate exercise. This is especially true when lining the walls of the reactors with reflective material that allows photon recycling within the reactor. This work presents a proof-of-concept for future UV-based PPE design that can become a standard tool for disease control and prevention.

  PublisherDOI

• Calcium scaling on the quartz sleeve of ultraviolet reactor: On-line measurement and model prediction

  Water Research · 2025-01-26 · 1 citations

  articleCorresponding
  PublisherDOI

• Evaluation and Comparison of the UV-LED Action Spectra for Photochemical Disinfection of Coliphages and Human Pathogenic Viruses

  Microorganisms · 2025-12-09 · 1 citations

  articleOpen access

  Ultraviolet (UV) disinfection is a powerful method for inactivating viruses. However, comparative wavelength-dependent sensitivities among human viruses and bacteriophages remain poorly characterized. Here, we evaluated the virucidal efficiencies of UV-light emitting diode (UV-LED) against multiple coliphages (MS2, Qβ, PhiX174, and T1) and mammalian viruses, including respiratory syncytial virus (RSV) and human metapneumovirus (HMPV). We used a standardized irradiation system equipped with interchangeable UV-LED modules (250–365 nm), a low-pressure mercury lamp (254 nm), and a filtered krypton-chloride excimer lamp (222 nm). All coliphages exhibited wavelength-dependent inactivation with maximal efficiency at 263–270 nm, closely matching the action spectra of RSV and HMPV (r &gt; 0.94, p &lt; 0.001). However, their absolute UV sensitivities were markedly lower: under 254–281 nm irradiation. RSV and HMPV were approximately 21 and 12 times more sensitive than MS2, respectively. In contrast, far-UVC (222 nm) irradiation reduced these differences, indicating simultaneous damage to viral genomes and structural proteins. These results demonstrated that coliphages and human viruses exhibit similar wavelength-dependent sensitivity to UV-LED irradiation but differ in their absolute susceptibility. Therefore, while coliphages can be conservative surrogates for evaluating UV-LED virucidal performance, their applicability to far-UVC assessments should be interpreted with caution.

  PublisherDOI

• Viral Inactivation by Light-Emitting Diodes: Action Spectra Reveal Genomic Damage as the Primary Mechanism

  Viruses · 2025-07-30 · 4 citations

  articleOpen access

  Irradiation with ultraviolet light-emitting diodes (UV-LEDs) represents a promising method for viral inactivation, but a detailed understanding of the wavelength-dependent action spectra remains limited, particularly across different viral components. In this study, we established standardized UV action spectra for infectivity reduction in pathogenic viruses using a system equipped with interchangeable LEDs at 13 different peak wavelengths (250-365 nm). The reduction in viral infectivity induced by UV-LED exposure was strongly related to viral genome damage, whereas no significant degradation of viral structural proteins was detected. Peak virucidal efficiency was observed at 267-270 nm across all tested viruses, representing a slight shift from the traditionally expected 260 nm nucleic acid absorption peak. Enveloped RNA viruses, including influenza A virus, respiratory syncytial virus, and coronavirus, exhibited greater UV sensitivity than nonenveloped viruses such as feline calicivirus and adenovirus. These observations indicate that structural characteristics, such as the presence of an envelope and genome organization, influence UV susceptibility. The wavelength-specific action spectra established in this study provide critical data for optimizing UV-LED disinfection systems to achieve efficient viral inactivation while minimizing energy consumption in healthcare, food safety, and environmental sanitation.

  PublisherOA PDFDOI

• Investigation of a DNA tagged aerosol tracer method for In Situ evaluation of germicidal UV air cleaner effectiveness

  Building and Environment · 2024-07-09 · 7 citations

  article
  PublisherDOI

Frequent coauthors

• D. A. Lyn

  Purdue University West Lafayette

  45 shared

• Chengyue Shen

  Central China Normal University

  40 shared

• Donald E. Bergstrom

  39 shared

• Shiyue Fang

  Michigan Technological University

  37 shared

• Kuang-ping Chiu

  National Cheng Kung University

  34 shared

• P. Savoye

  25 shared

• Zorana Naunović

  University of Belgrade

  24 shared

• Kelly G. Pennell

  22 shared

Labs

• Lyles School of Civil and Construction EngineeringPI

Education

• PhD, Civil Engineering

  University of California Berkeley

Awards & honors

• EPA Training Fellowship, University of California, Berkeley,…
• Chi Epsilon, 1994 - present
• Harold Munson Outstanding Teacher Award, School of Civil Eng…
• Roy E. and Myrna G. Wansik Research Leadership Award, School…
• William Edgar Award for Pioneering Research in Disinfection,…