Bacterial contamination in water is still a critical threat to public health; seeking efficient water disinfection approaches is of great significance. Here, we show that locally enhanced electric field treatment (LEEFT) by electrodes modified with nanoscale tip structures can induce ultrafast bacteria inactivation with nanosecond electrical pulses. A lab-on-a-chip device with gold nanowedges on the electrodes is developed for an operando investigation. Attributed to the lightning-rod effect, the bacteria at the nanowedge tips are inactivated by electroporation. A single 20 ns pulse at 55 kV/cm has achieved 26.6% bacteria inactivation, with ten pulses at 40 kV/cm resulting in 95.1% inactivation. LEEFT lowers the applied electric field by about 8 times or shortens the treatment time by at least 10⁶ times, compared with the system without nanowedges. Both gram-positive and gram-negative bacteria, including antibiotic-resistant bacteria, are inactivated with nanosecond pulses by LEEFT. According to simulation, when the membrane of the cell located at the nanowedge tip is directly charged by the concentrated charges at the tip, it is much faster and to a much higher level, leading to instant electroporation and cell inactivation.

1,4-Dioxane as an emerging environmental contaminant has been widely detected in U.S. drinking water supplies. Toxicity studies show that chronic exposure to 1,4-Dioxane can raise significant health concerns and potential carcinogenic risks to human bodies. Due to its small molecular weight, neutral charge, and hydrophilic property, physical treatment techniques including adsorption, distillation, and membrane filtration have been demonstrated not suitable or effective for removing 1,4-Dioxane. In this study, a modular electrochemical advanced oxidization system was developed for fast and efficient 1,4-Dioxane degradation without additional chemical supplies. A low-cost and robust TiO_x nanotube mesh was developed as anode material, which can oxidize and mineralize 1,4-Dioxane through direct oxidation and reactive species intermediated oxidation. However, the long-term stability of the electrode is still a challenging goal. Thus, a pulsed treatment strategy was applied to minimize structural and morphological changes of the electrodes under electrochemical oxidation operation, especially at high current densities. The periodic polarity reversal of the electrode pair within a short time could effectively remove reactive species and contaminants accumulated on the active sites, regenerate the electrode surface, and extend the electrode lifetime for treatment. Therefore, this technology can potentially provide a promising and cost-effective alternative to point-of-use water treatment.

U.S. agriculture consumes 280 million pounds of glyphosate each year and discharges excessive glyphosate to the aquatic environment. The discharged glyphosate will be transformed into Aminomethyl Phosphonic Acid (AMPA), causing eutrophication, bioaccumulation, and potential embryonic cell damage. To prevent this, early lab studies have explored electrooxidation as a remediation approach to degrade glyphosate or AMPA. However, environmental applications of electrooxidation are challenged by mass transfer constraints and parasitic reactions in diluted water matrices. Our study proposes a stepwise potential fast chronoamperometry (SPFC) technique to tackle these practical challenges when degrading trace-level of AMPA. We find that conventional electrooxidation using a boron-doped diamond anode can degrade over 95% of 0.1mM AMPA. However, its performance is dramatically decreased to 80% when treating 0.01mM AMPA, an environmental concentration that will most likely trigger mass transfer limitation in a heterogenous electrooxidation system. We then switched to the SPFC technique, with an optimized protocol of 50-second oxidation at 2.5 V (vs. Ag/AgCl) and 100-second resting to electrosorb negatively charged AMPA. This SPFC technique boosts AMPA degradation to over 90% when treating 0.01mM AMPA, with a significantly lowered energy input (0.19 kWh g^-1 AMPA) than the conventional electrooxidation (0.28 kWh g^-1 AMPA). We further explore the effects of ionic compositions (e.g., SO₄^2- and Cl^-) and other organic species (e.g., humic acids) on the SPFC system. Their presence does not adversely affect AMPA degradation performance. Our results prove that SPFC can effectively overcome mass transfer constraints in organics degradation and promote a next-generation electrified remediation platform.

1,4-Dioxane is a contaminant of emerging concern that had been commonly detected in groundwater. Due to the high solubility and chemical stability in water, 1,4-dioxane is not effectively removed by conventional water treatment processes. Biodegradation is a cost-effective and environmental-friendly approach and could lead to complete mineralization of 1,4-dioxane without the accumulation of toxic byproducts. A stable and robust 1,4-dioxane degrading enrichment culture was obtained from uncontaminated soil and was used as the seeding consortia for the biological activated filter (BAF) establishment. The enrichment was capable to metabolically degrade 1,4-dioxane at 100 mg/L and environmentally relevant levels (300 μg/L), while the biodegradation ability was severely inhibited with the presence of 1,1-dichloriethene (1,1-DCE) at 1 mg/L, a co-occurring groundwater contaminant. Replicate bench-scale BAFs were constructed by inoculating the enrichment to granular activated carbon (F-300 GAC), and were continuous operated with synthetic groundwater containing 1,4-dioxane at environmental relevant levels (<1,000 μg/L). During one year operation, the BAF was capable of continuously removing >70% of 1,4-dioxane with an influent concentration of 100 μg /L. The effects of 1,4-dioxane loading (216-2160 μg/column/day), Empty bed contact time (EBCT) (1.2-2.4 h), the presence of background natural organic matters (NOM) ( 0.5-1 mg-C/L humic acid) and the presence of co-contaminants (1,1-DCE) (1,1-DCE:1,4-D molar ratio of 1:1 to 10:1) on the BAF system performance for 1,4-dioxane removal were investigated. In addition, the overall microbial abundance, functional microbial species distribution and changes under different operation conditions are currently under investigation.

Insensitive munitions formulations that include 3-nitro-1,2,4-triazol-5-one (NTO) are replacing traditional explosive compounds. While these new formulations have superior safety characteristics, the compounds have greater environmental mobility, raising concern over potential contamination and cleanup of training and manufacturing facilities. Here, we examine the mechanisms and products of NTO photolysis in simulated sunlight to further inform NTO degradation in sunlit surface waters. We demonstrate that NTO produces singlet oxygen, and that dissolved oxygen increases the NTO photolysis rate in deionized water. The rate of NTO photolysis is independent of concentration and decreases slightly in the presence of Suwannee River Natural Organic Matter. The apparent quantum yield of NTO generally decreases as pH increases, ranging from 2.0 × 10^-5 at pH 12 to 1.3 × 10^-3 at pH 2. Bimolecular reaction rate constants for NTO with singlet oxygen and hydroxyl radical were measured to be 1.95±0.15 × 10⁶ and 3.28±0.23 × 10¹⁰ M^-1 s^-1, respectively. Major photolysis reaction products were ammonium, nitrite, and nitrate, with nitrite produced in nearly stoichiometric yield upon the reaction of NTO with singlet oxygen. Environmental half-lives are predicted to span from 1.1 to 5.7 days. Taken together, these data enhance our understanding of NTO photolysis under environmentally relevant conditions.