Potable reuse is a critical component of water resource portfolios due to increasing water shortages. Because potable reuse converts wastewater into drinking water, it is critical to understand how it removes viruses. Sub-residual ozone processes are common potable reuse treatments used to transform organic compounds into more biodegradable products for removal during downstream biofiltration. However, no virus reduction credits are currently granted for sub-residual ozone treatment because the Environmental Protection Agency’s Ct framework requires a measurable residual. The purpose of this research is to establish correlations between sub-residual ozone inactivation of viruses and commonly monitored water quality parameters so that corresponding crediting frameworks can be developed.

Effluent samples are collected at multiple wastewater treatment plants and water quality parameters, including pH and total organic carbon (TOC), are measured using standard methods. Virus inactivation experiments are then conducted in the well-characterized samples using bench-scale reactors spiked with a combination of O3:TOC dosages relevant to water reuse, human virus surrogates (e.g., MS2, T4, ΦX174, and Φ6), and a human pathogenic virus (e.g., Enterovirus CVB5). Samples are taken at regular intervals and the ozone residuals are quantified with the indigo colorimetric method and infectious virus concentrations with plaque assay methods. Ultimately, these results will be used to identify a surrogate virus that provides a conservative estimate of human virus inactivation and to generate multiparameter models that will enable researchers and practitioners to assess virus removal in sub-residual ozone systems based on commonly monitored water quality parameters instead of the Ct framework.

With the increasing need of the access to safe drinking water, technologies for removing hazardous components, sustainably and cost-efficiently, are in high demand. Of all kinds of water contaminants, heavy metals are known of being harmful to human health and widely existing in aqueous environment. Adsorptive membranes offer an effective way for selectively removing heavy metals made possible by the synergy of low-cost adsorption and highly scalable filtration. However, the application of adsorptive membranes has been challenged by the instability of membrane in long-time run and limited binding capacity at a reasonable water flux. This study develops a regenerated cellulose based adsorptive membrane by grafting multilayers of covalently bonded polyelectrolytes. The covalent bonding enhances membrane stability and enables the membrane to sustain multi-cycle regeneration without significantly compromising its heavy metal removal efficiency. The maximum adsorption capacity of the active layers reaches up to 194 mg/g, and the pure water flux of the membrane modified with 12 layers of polyelectrolyte is 80 L·m^-2·h^-1 (LMH) operated at 1 bar. The membrane can remove multiple ions such as Cu, Pb, and Cd by adsorption and can be easily regenerated. The strong covalent bonding can extend the membrane lifetime in water purification to remove multiple heavy metals at high efficiency.

Innovative process solutions are required to increase the capacity, robustness, and versatility of water and wastewater treatment plants. Recently, fiber-based materials have been shown to considerably increase the floc size (~7,000 μm) compared to conventional physicochemical treatment using a coagulant and a flocculant (~500 μm). The materials also reduced coagulant usage (up to 40%) and flocculant usage (up to 60%). In this work, super-bridging fiber-based materials were designed and tested for coagulant recovery and reuse in wastewater treatment. Fiber materials were synthesized and optimized to reduce the amount of coagulant and/or flocculant used. The performance of different fiber materials on aluminum retention and adsorption and removal of classical and emerging contaminants was tested. Compared to conventional physicochemical treatment, the fibers drastically increased floc size, hence allowing the replacement of settling by screening, a technology that is more compact than settling tanks. Fibers used in combination with coarse screens (mesh size of ~1000 μm) improved the removal of total suspended solids by ~60% increase from conventional (22%) to fiber-based treatment (81%). When fibers were used in combination with a coagulant and a flocculant, nanoplastics removal increased dramatically. Finally, fibers were proven to be washable and reusable more than five times, which shows potential for operational cost reduction and environmental benefits.

Monodisperse M_reducing/Cu (M_reducing = Pd and Pt) nanoparticles were homogeneously prepared on the surface of primary amine functionalized mesoporous silica nanoparticles to use as highly active reducing catalysts towards nitrate degradation under hydrogen purged process. The size, morphology, and composition of M_reducing/Cu nanocatalysts on the porous silica substrates were finely controlled by various reaction conditions, such as the ratio of the starting precursors and reaction time. The preformed ultra-fine M_reducing/Cu nanocatalysts were further grown larger by the additional metal precursor injection (seed mediated particle growth; M_reducing/Cu/M_reducing types). In nitrate degradation evaluation using the engineered nanocatalysts embedded in mesoporous silica nanoparticles, the reaction kinetics were found to be closely affected by the ratio of M_reducing to Cu. Explicitly, Pd-rich Pd/Cu/Pd nanocatalysts showed the faster nitrate degradation than the Cu-rich counterparts. The selectivity to the final products (ammonium vs. nitrogen) is highly related to the morphology of the engineered nanocatalysts, in which nitrogen dominant selectivity was observed with increase of Pd particle size. Unlike Pd/Cu/Pd combination, Pt/Cu/Pt nanocatalysts showed ammonium dominant selectivity (over 90%) in a wide range of the composition ratios (from Pt-rich to Cu-rich). Lastly homogeneous Pd/Cu/Pd nanocatalysts embedded in mesoporous silica nanoparticles was the exceptionally stable with no catalyst deterioration over the multiple catalytic reduction processes (10 times) with the consistent reaction rate and selectivity. This research provides the better understanding on nitrate reduction in terms of the applied nanocatalysts’ size (dimension) and composition using the monodisperse nanocatalysts (designed with Pd, Pt, and Cu) embedded in chemically stable mesoporous silica nanoparticles (substrate).

Intense harmful algal blooms (HAB) in surface waters and associated algal toxins threaten national water supplies and cost nearly $1B per year in revenues. Microcystins (MCs) are the most common cyanotoxins produced by high frequency cyanobacteria blooms in freshwater lakes and are highly toxic to humans and animals. Despite the heavy investment in HAB mitigation, cyanotoxins continue to be a great challenge for safe drinking water production. This presentation reports the design and fabrication of new functional hydrogel-biochar composite materials as filtration media to selectively capture MC during filtration for drinking water treatment. The results demonstrate the selective MC adsorption by combining complementary strategies of electrostatic interactions, cation-π bonding, π-π stacking, and hydrogen bonding. The kinetics and capacity of the novel nanocomposite surpassed any state-of-the-art adsorbents for MC removal. The experimental results also confirmed that the coupling of nanocomposite materials with MC-degrading bacteria was a promising and effective approach to achieve a sustainable removal of MC through an “adsorption-biodegradation” process. The outcomes of this research will advance water treatment technologies by integrating novel targeted biodegradation with new functional materials as an effective engineering measure.