Vincent DiPietri

All Publications

• Comparison of Halophenol, Halonitrophenol, and Halosalicylic Acid Formation vs 1-2 Carbon DBP Formation during Chlorination and Chloramination of Surface Waters. Environmental science & technology Han, J., Lim, S., DiPietri, V. T., Najm, B., Zhang, X., Mitch, W. A. 2025

  Abstract

  Although haloaromatic disinfection byproducts (DBPs) are considered an important component of nonvolatile, high molecular weight DBPs, little research has compared haloaromatic DBP formation to the conventional 1-2 carbon DBPs during chlorination or chloramination of authentic surface waters. This study compared the concentrations of 15 halophenols, 5 halonitrophenols, and 8 halosalicylic acids to 28 1-2 carbon DBPs in samples collected in two rivers upstream and downstream of wastewater impacts, in a municipal wastewater effluent, and in five algal-impacted reservoirs treated with chlorine alone or chlorine for 1 h followed by chloramination. Halophenols and halosalicylic acids reached ∼10-600 ng/L within 2-12 h during chlorination. Halophenols degraded faster than halosalicylic acids thereafter, and ∼10-30 ng/L halosalicylic acids remained after 5 d. During chlorination/chloramination, both halophenols and halosalicylic acids remained near the levels formed during the first 1 h of chlorine contact. Halonitrophenols formed at ∼10-140 ng/L but were stable during chlorination and chlorination/chloramination. In contrast, 1-2 carbon DBPs formed at ∼50-820 μg/L, accumulating during chlorination but remaining at levels formed during the initial 1 h chlorine contact during chlorination/chloramination. The organic matter in the river samples was more potent at producing aromatic DBPs than the algal-impacted organic matter. Although the trends in halosalicylic acid concentrations during chlorination were consistent with previous observations of overall cytotoxicity, these specific haloaromatic DBPs contributed substantially less to cytotoxicity than the 1-2 carbon DBPs.

  View details for DOI 10.1021/acs.est.5c09818

  View details for PubMedID 40990289

• Toilet Bowl Cleaning Tablets as Sources of Chlorine, Bromine, and Disinfection Byproducts in Wastewater. Environmental science & technology DiPietri, V. T., Grady, Z. S., Frost, A. N., Stitzel, S. E., Sivey, J. D. 2025; 59 (15): 7646-7655

  Abstract

  Commercial toilet bowl cleaning tablets were examined in laboratory systems to characterize their release of active halogens and their potential to form trihalomethanes (THMs) when combined with synthetic sewage. Active halogens (e.g., HOCl, HOBr, and reactive halamines) were quantified via derivatization with 1,3,5-trimethoxybenzene prior to analysis by liquid chromatography. The effects of several variables on halogen release profiles were examined, including pH, ionic strength, temperature, tank solution volume, flushing frequency, and tablet brand. Changes in pH resulted in modest or no appreciable changes in halogen release profiles. Release of active halogens increased as ionic strength decreased and as temperature increased. Tank volume, flushing frequency, and tablet brand had pronounced impacts on halogen release profiles. Maximum measured active chlorine and bromine concentrations in toilet tank water were 189 mg/L as Cl2 and 164 mg/L as Cl2, respectively. Active halogens persisted in toilet bowl water for >24 h. When toilet-tablet-treated water was combined with synthetic sewage, THMs formed at up to 219 ppb with bromine incorporation factors up to 2.86. Active halogens and highly brominated THMs released into wastewater from toilet tablets could have implications for downstream microbial ecology, septic system performance, and overall water quality.

  View details for DOI 10.1021/acs.est.4c12026

  View details for PubMedID 40208265

• Chloride Enhances DNA Reactivity with Chlorine under Conditions Relevant to Water Treatment. Environmental science & technology Szczuka, A., Horton, J., Evans, K. J., DiPietri, V. T., Sivey, J. D., Wigginton, K. R. 2022; 56 (18): 13347-13356

  Abstract

  Free available chlorine (FAC) is widely used to inactivate viruses by oxidizing viral components, including genomes. It is commonly assumed that hypochlorous acid (HOCl) is the chlorinating agent responsible for virus inactivation; however, recent studies have underscored that minor constituents of FAC existing in equilibrium with HOCl, such as molecular chlorine (Cl2), can influence FAC reactivity toward select organic compounds. This study measures the FAC reaction kinetics with dsDNA and ssDNA extracted from representative bacteriophages (T3 and ϕX174) in samples augmented with chloride. Herein, chloride enhances FAC reactivity toward dsDNA and, to a lesser extent, toward ssDNA, especially at pH < 7.5. The enhanced reactivity can be attributed to the formation of Cl2. Second-order rate constants were determined for reactions of ssDNA and dsDNA with HOCl and Cl2. DNA chlorination kinetics followed the reactivity-selectivity principle, where the more-reactive nucleophilic species (ssDNA, ∼100× more reactive than dsDNA) reacted less selectively with electrophilic FAC species. The addition of chloride was also shown to enhance the inactivation of bacteriophage T3 (dsDNA genome) by FAC but did not enhance the inactivation of bacteriophage ϕX174 (ssDNA genome). Overall, the results suggest that Cl2 is an important chlorinating agent of nucleic acids and viruses.

  View details for DOI 10.1021/acs.est.2c03267

  View details for PubMedID 36027047

  View details for PubMedCentralID PMC9494735