No abstract

The precise identification of predominant toxic disinfection byproducts (DBPs) from disinfected water is a longstanding challenge. We propose a new acellular analytical strategy, the ‘Thiol Reactome’, to identify thiol-reactive DBPs by employing a thiol probe and nontargeted mass spectrometry (MS) analysis. Disinfected/oxidized water samples had reduced cellular oxidative stress responses of 46 ± 23% in Nrf2 reporter cells when preincubated with glutathione (GSH). This supports thiol-reactive DBPs as the predominant drivers of oxidative stress. This method was benchmarked using seven classes of DBPs including haloacetonitriles, which preferentially reacted with GSH via substitution or addition depending on the number of halogens present. The method was then applied to chemically disinfected/oxidized waters, and 181 tentative DBP-GSH reaction products were detected. The formulas of 24 high abundance DBP-GSH adducts were predicted, among which nitrogenous-DBPs (11) and unsaturated carbonyls (4) were the predominant compound classes. Two major unsaturated carbonyl-GSH adducts, GSH-acrolein and GSH-acrylic acid, were confirmed by their authentic standards. These two adducts were unexpectedly formed from larger native DBPs when reacting with GSH. This study demonstrated the “Thiol Reactome” as an effective acellular assay to precisely identify and broadly capture toxic DBPs from water mixtures.

Prechlorination is the most common strategy for zebra and quagga mussel control in drinking water treatment plant intakes in the Great Lakes region. Although effective and inexpensive, chlorine can form regulated disinfection byproducts. Two potential alternatives to prechlorination were evaluated for mussel control: peracetic acid (PAA) and EarthTec QZ, a copper-based product. Pilot-scale experiments were conducted to test EarthTec QZ for veliger control and to evaluate the efficiency of PAA and EarthTec QZ for adult mussel control. EarthTec QZ doses of 30, 60, and 120 μg/L as copper ions demonstrated dose-dependent veliger control at 12 C. PAA doses of 5, 10, and 25 mg/L were effective for adult mussel control at the low water temperatures tested (4 C). Results from this study indicate that PAA and EarthTec QZ may be an alternative to prechlorination.

The shock response of powdered aluminum compacted by a driver plate was simulated with a one-dimensional Lagrangian continuum mechanics computer program. The porous aluminum was mocked up by a series of flat plates separated by gaps to obtain an initial density of 1.35 g/cm 3 for the "powder." The compaction process was followed in detail for two cases of driver-plate conditions corresponding to two Stanford Research Institute experiments. The calculations showed an approach to equilibrium behind the shock in each of the porous samples. The equilibrium states established were found to be consistent with the Rankine-Hugoniot jump conditions applied to aluminum of density 1.35 g/cm 3 • These states did not lie on the Hugoniot curve of solid-density aluminum. This was shown to be due to the significant internal-energy dependency in the equation of state. The calculated results were in good agreement with the SRI experiments. Application of this computational model to more complex cases is indicated.

A “minicolumn” test approach was recently developed to estimate the performance of preloaded granular activated carbon (GAC) in water treatment plants for micropollutant removal. One of the requirements of this test is that the GAC bed must have a broad mass transfer zone (MTZ) for the contaminant of interest, but this has never been verified. In this study, GAC of different ages harvested from three different bed depths was subjected to lab-scale minicolumn and isotherm tests to measure adsorption kinetics and thermodynamic properties, respectively. The GAC was challenged with micropollutants with a range of adsorption characteristics. The GAC was found to exhibit approximately uniform removal efficiencies for all of the selected micropollutants across the depth, indicating a broad MTZ. Additionally, the MTZ for 2-methylisoborneol and geosmin in a newly installed GAC filter was observed to broaden to beyond the depth of the filter within 7 weeks of installation. This work helps to verify the minicolumn test protocol and supports a novel approach by eliminating the dependence of GAC performance on bed location. With such an approach, utilities may more easily conduct the minicolumn test to establish an accurate GAC replacement schedule and to optimize GAC operation for maximum contaminant removal.