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Mitch, W.

Publications and source records attributed to Mitch, W..

2 recordsLinked to original sources
bioRxiv2024

Impacts of Disinfection Methods in a Granular Activated Carbon (GAC) Treatment System on Disinfected Drinking Water Toxicity and Antibiotic Resistance Induction Potential

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=154 SRC="FIGDIR/small/608195v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@abf38dorg.highwire.dtl.DTLVardef@102d02dorg.highwire.dtl.DTLVardef@1b14e5dorg.highwire.dtl.DTLVardef@18fd10d_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphic AbstractC_FLOATNO C_FIG Granular activated carbon (GAC) treatment followed by chlorination (GAC/Cl2) and chlorination followed by chloramination (Cl2/NH2Cl) are two methods utilized by drinking water treatment facilities to mitigate the formation of disinfection byproducts (DBPs) in treated water. However, the effectiveness of these methods in reducing the overall toxicity of drinking water, driven by DBPs, remains largely unknown. In this study, we evaluate the total toxicity of water samples from a pilot-scale GAC system with post-chlorination (GAC/Cl2), and occasionally pre-chlorination upstream of GAC (Cl2/GAC/Cl2), compared to water treated by chlorination followed by chloramination (Cl2/NH2Cl). The research was conducted at various bromide and iodide levels and across three GAC bed volumes. To assess DNA stress and oxidative stress in water extracts, we employed the yeast toxicogenomic assay and human cell RT-qPCR assay, along with the DBP analysis from our previous study. Our results indicated that under environmental halogen conditions, GAC/Cl2 typically reduces both genotoxicity and oxidative stress in treated water more effectively than Cl2/NH2Cl and Cl2 treatment. However, Cl2/GAC/Cl2 does not consistently lower toxicity compared to GAC/Cl2. Notably, under high halogen conditions, Cl2/GAC/Cl2 fails to reduce genotoxicity and oxidative stress compared to samples without GAC treatment. Correlation analysis suggested that iodinated DBPs (I-DBPs) and nitrogenous DBPs (N-DBPs) were particularly associated with increased DNA stress and oxidative stress, indicating these classes of DBPs as significant contributors to the observed toxicity. While neither of these two categories of DBPs are regulated by the EPA, it appears that unregulated and unidentified DBPs significantly contribute to the genotoxicity and oxidative stress in drinking water. This research highlights the complex dynamics of water treatment processes and underscores the critical impact of unregulated DBPs on water toxicity.

pharmacology and toxicology↗
bioRxiv2024

Persistence and Free Chlorine Disinfection of Human Coronaviruses and Their Surrogates in Water

The COVID-19 pandemic illustrates the importance of understanding the behavior and control of human pathogenic viruses in the environment. Exposure via water (drinking, bathing, and recreation) is a known route of transmission of viruses to humans, but the literature is relatively void of studies on the persistence of many viruses, especially coronaviruses, in water and their susceptibility to chlorine disinfection. To fill that knowledge gap, we evaluated the persistence and free chlorine disinfection of human coronavirus OC43 (HCoV-OC43) and its surrogates, murine hepatitis virus (MHV) and porcine transmissible gastroenteritis virus (TGEV), in drinking water and laboratory buffer using cell culture methods. The decay rate constants of human coronavirus and its surrogates in water varied depending on virus and water matrix. In drinking water prior to disinfectant addition, MHV showed the largest decay rate constant (2.25 day-1) followed by HCoV-OC43 (0.99 day-1) and TGEV (0.65 day-1); while in phosphate buffer, HCoV-OC43 (0.51 day-1) had a larger decay rate constant than MHV (0.28 day-1) and TGEV (0.24 day-1). Upon free chlorine disinfection, the inactivation rates of coronaviruses were independent of free chlorine concentration and not affected by water matrix, though they still varied between viruses. TGEV showed the highest susceptibility to free chlorine disinfection with the inactivation rate constant of 113.50 mg-1 min-1 L, followed by MHV (81.33 mg-1 min-1 L) and HCoV-OC43 (59.42 mg-1 min-1 L). ImportanceThis study addresses an important knowledge gap on enveloped virus persistence and disinfection in water. Results have immediate practical applications for shaping evidence-based water policies, particularly in the development of disinfection strategies for pathogenic virus control.

microbiology↗