Lack of Influence of Extracellular Polymeric Substances (EPS) Level on Hydroxyl Radical Mediated Disinfection of <i>Escherichia coli</i>

Photolysis of nitrate, a prevalent constituent in agriculturally impacted waters, may influence pathogen attenuation in such systems through production of hydroxyl radical (^•OH). This study focuses on the efficacy of ^•OH generated during nitrate photolysis in promoting <i>E. coli</i> die-off as a function of extracellular polymeric substances (EPS) coverage. EPS levels of four <i>E. coli</i> isolates were systematically altered through a sonication extraction method and photochemical batch experiments with a solar simulator examined isolate viability loss as a function of time in nitrate solutions. <i>E. coli</i> viability loss over time exhibited two regimes: an initial induction time, <i>t</i>_s, with little decay was followed by rapid exponential decay characterized by a first-order disinfection rate constant, <i>k</i>. Increasing steady-state ^•OH concentrations enhanced <i>E. coli</i> viability loss, increasing values of <i>k</i> and decreasing <i>t</i>_s values, both of which were quantified with a multitarget bacterial disinfection model. Notably, at a given steady-state ^•OH concentration, values of <i>t</i>_s and <i>k</i> were independent of EPS levels, nor did they vary among the different <i>E. coli</i> strains considered. Results herein show that while ^•OH generated via nitrate photolysis enhances rates of disinfection in surface water, the mechanism by which ^•OH kills <i>E. coli</i> is relatively insensitive to common bacterial variables

Mesoporous, Three-Dimensional Wood Membrane Decorated with Nanoparticles for Highly Efficient Water Treatment

Wood, an earth-abundant material, is widely used in our everyday life. With its mesoporous structure, natural wood is comprised of numerous long, partially aligned channels (lumens) as well as nanochannels that stretch along its growth direction. This wood mesostructure is suitable for a range of emerging applications, especially as a membrane/separation material. Here, we report a mesoporous, three-dimensional (3D) wood membrane decorated with palladium nanoparticles (Pd NPs/wood membrane) for efficient wastewater treatment. The 3D Pd NPs/wood membrane possesses the following advantages: (1) the uniformly distributed lignin within the wood mesostructure can effectively reduce Pd­(II) ions to Pd NPs; (2) cellulose, with its abundant hydroxyl groups, can immobilize Pd NPs; (3) the partially aligned mesoporous wood channels as well as their inner ingenious microstructures increase the likelihood of wastewater contacting Pd NPs decorating the wood surface; (4) the long, Pd NP-decorated channels facilitate bulk treatment as water flows through the entire mesoporous wood membrane. As a proof of concept, we demonstrated the use and efficiency of a Pd NPs/wood membrane to remove methylene blue (MB, C₁₆H₁₈N₃ClS) from a flowing aqueous solution. The turnover frequency of the Pd NPs/wood membrane, ∼2.02 mol_MB·mol_Pd^–1·min^–1, is much higher than the values reported in the literature. The water treatment rate of the 3D Pd NPs/wood membrane can reach 1 × 10⁵ L·m^–2·h^–1 with a high MB removal efficiency (>99.8%). The 3D mesoporous wood membrane with partially aligned channels exhibits promising results for wastewater treatment and is applicable for an even wider range of separation applications