Biofilms in Full-Scale Drinking Water Ozone Contactors Contribute Viable Bacteria to Ozonated Water.

Concentrations of viable microbial cells were monitored using culture-based and culture-independent methods across multichamber ozone contactors in a full-scale drinking water treatment plant. Membrane-intact and culturable cell concentrations in ozone contactor effluents ranged from 1200 to 3750 cells/mL and from 200 to 3850 colony forming units/mL, respectively. Viable cell concentrations decreased significantly in the first ozone contact chamber, but rose, even as ozone exposure increased, in subsequent chambers.

Degradation of Extracellular Antibiotic Resistance Genes with UV Treatment.

Disinfected wastewater effluent contains a complex mixture of biomolecules including DNA. If intact genes conveying antibiotic resistance survive the disinfection process, environmental bacteria may take them up. We treated plasmid pWH1266, which contains ampicillin resistance gene bla and tetracycline resistance gene tetA, with UV doses up to 430 mJ/cm and studied the ability of those genes to be acquired by Acinetobacter baylyi.

Life-cycle case study comparison of permeable reactive barrier versus pump-and-treat remediation.

A permeable reactive barrier (PRB) is a passive remediation technology, which over decades of use, may reduce lifetime environmental impacts when compared with a conventional pump-and-treat system (PTS). Greater material production requirements to install PRBs may offset the expected reductions in operational phase impacts and the trade-offs can be investigated in a life-cycle assessment (LCA). The life-cycle environmental impacts of a zerovalent iron (ZVI) containing PRB with a funnel and gate configuration and a PTS were compared in a case study.

Relative reactivity of amino acids with chlorine in mixtures.

The relative reactivity of chlorine with amino acids is an important determinant of the resulting chlorination products in systems where chlorine is the limiting reagent, for example, in the human gastrointestinal tract after consumption of chlorine-containing water, or during food preparation with chlorinated water. Since few direct determinations of the initial reactivity of chlorine with amino acids have been made, 17 amino acids were compared in this study using competitive kinetic principles. The experimental results showed that (1) most amino acids have similar initial reactivities at neutral pH; (2) amino acids with thiol groups such as methionine and cysteine are exceptionally reactive and produce sulfoxides; (3) amino acids without thiol groups primarily undergo monochlorination of the amino nitrogen; and (4) glycine and proline are the least reactive.

Cyanogen chloride precursor analysis in chlorinated river water.

Amino acids have been cited as potential precursors of the disinfection byproduct cyanogen chloride in chlorinated drinking water. Screening experiments with 17 amino acids were performed in this study to comprehensively identify important CNCl precursors. Among this set, only glycine was found to yield detectable CNCl (i.

Mechanism and kinetics of cyanogen chloride formation from the chlorination of glycine.

Glycine is an important precursor of cyanogen chloride (CNCl)--a disinfection byproduct (DBP) found in chlorinated drinking water. To model CNCl formation from glycine during chlorination, the mechanism and kinetics of the reaction between glycine and free chlorine were investigated. Kinetic experiments indicated that CNCI formation was limited by either the decay rates of N,N-dichloroglycine or a proposed intermediate, N-chloroiminocarboxylate, CIN=CHCO2-.

Stability of cyanogen chloride in the presence of free chlorine and monochloramine.

Cyanogen chloride (CNCl) is a disinfection byproduct found in chlorinated and chloraminated drinking water. Although there is an apparent greater association of CNCI with chloraminated water relative to chlorination systems, it was not clear whether these phenomenological observations are explained by differences in the stability or formation potentials of CNCI between the two disinfectants. In this study, the stability of CNCl was examined in the presence of free chlorine and monochloramine using membrane introduction mass spectrometry.