Enhanced sorption and destruction of PFAS by biochar-enabled advanced reduction process.

The biochar-enabled advanced reduction process (ARP) was developed for enhanced sorption (by biochar) and destruction of PFAS (by ARP) in water. First, the biochar (BC) was functionalized by iron oxide (FeO), zero valent iron (ZVI), and chitosan (chi) to produce four biochars (BC, FeO-BC, ZVI-chi-BC, and chi-BC) with improved physicochemical properties (e.g.

Conceptualizing future groundwater models through a ternary framework of multisource data, human expertise, and machine intelligence.

Groundwater models are essential for understanding aquifer systems behavior and effective water resources spatio-temporal distributions, yet they are often hindered by challenges related to model assumptions, parametrization, uncertainty, and computational efficiency. Machine intelligence, especially deep learning, promises a paradigm shift in overcoming these challenges. A critical examination of existing machine-driven methods reveals the inherent limitations, particularly in terms of the interpretability and the ability to generalize findings.

Rethinking pump-and-treat remediation as maximizing contaminated groundwater.

For over half a century, the United States has developed water quality regulations (e.g., Safe Drinking Water Act), which has been accompanied by innumerable advances in contaminant transport and fate, site characterization, and remediation.

Mechanistic insight into Cr(VI) retention by Si-containing ferrihydrite.

Hexavalent chromium [Cr(VI)] causes serious harm to the environment due to its high toxicity, solubility, and mobility. Ferrihydrites (Fh) are the main adsorbent and trapping agent of Cr(VI) in soils and aquifers, and they usually coexist with silicate (Si), forming Si-containing ferrihydrite (Si-Fh) mixtures. However, the mechanism of Cr(VI) retention by Si-Fh mixtures is poorly understood.

Impact of chromium (VI) as a co-contaminant on the sorption and co-precipitation of uranium (VI) in sediments under mildly alkaline oxic conditions.

Uranium (U) waste, generated at a variety of mines and nuclear production sites, migrates in the subsurface, posing a serious threat to contaminate groundwater systems. In this study, batch equilibrium and kinetic experiments, geochemical modeling and solid phase characterization were conducted to investigate the impact of Cr(VI), a common co-contaminant, on the adsorption of U(VI) to quartz, plagioclase feldspar, and carbonate-dominated sediment (≤2 mm). Batch experiments were performed under slightly alkaline conditions (7.

PFOS Mass Flux Reduction/Mass Removal: Impacts of a Lower-Permeability Sand Lens within Otherwise Homogeneous Systems.

Perfluorooctane sulfonic acid (PFOS) is one of the most common per- and polyfluoroalkyl substances (PFAS) and is a significant risk driver for these emerging contaminants of concern. A series of two-dimensional flow cell experiments was conducted to investigate the impact of flow field heterogeneity on the transport, attenuation, and mass removal of PFOS. A simplified model heterogeneous system was employed consisting of a lower-permeability fine sand lens placed within a higher-permeability coarse sand matrix.

Datasets associated with the characterization of produced water and Pecos River water in the Permian Basin, the United States.

The data in this report are associated with "Characterization of Produced Water and Surrounding Surface Water in the Permian Basin, the United States" (Jiang et al. 2022) and include raw data on produced water (PW) quality and Pecos River water quality in the Permian Basin, which is one of the major oil and gas producing areas in the U.S.

Global distributions, source-type dependencies, and concentration ranges of per- and polyfluoroalkyl substances in groundwater.

A meta-analysis was conducted of published literature reporting concentrations of per- and polyfluoroalkyl substances (PFAS) in groundwater for sites distributed in 20 countries across the globe. Data for >35 PFAS were aggregated from 96 reports published from 1999 to 2021. The final data set comprises approximately 21,000 data points after removal of time-series and duplicate samples as well as non-detects.

A mechanistic study of ciprofloxacin adsorption by goethite in the presence of silver and titanium dioxide nanoparticles.

The adsorption behaviors of ciprofloxacin (CIP), a fluoroquinolone antibiotic, onto goethite (Gt) in the presence of silver and titanium dioxide nanoparticles (AgNPs and TiONPs) were investigated. Results showed that CIP adsorption kinetics in Gt with or without NPs both followed the pseudo-second-order kinetic model. The presence of AgNPs or TiONPs inhibited the adsorption of CIP by Gt.

Characterization of produced water and surrounding surface water in the Permian Basin, the United States.

A thorough understanding of produced water (PW) quality is critical to advance the knowledge and tools for effective PW management, treatment, risk assessment, and feasibility for beneficial reuse outside the oil and gas industry. This study provides the first step to better understand PW quality to develop beneficial reuse programs that are protective of human health and the environment. In total, 46 PW samples from unconventional operations in the Permian Basin and ten surface water samples from the Pecos River in New Mexico were collected for quantitative target analyses of more than 300 constituents.

Toxicological characterization of produced water from the Permian Basin.

Produced water (PW) is a hypersaline waste stream generated from the shale oil and gas industry, consisting of numerous anthropogenic and geogenic compounds. Despite prior geochemical characterization, the comprehensive toxicity assessment is lacking for evaluating treatment technologies and the beneficial use of PW. In this study, a suite of in vitro toxicity assays using various aquatic organisms (luminescent bacterium Vibrio fischeri, fish gill cell line RTgill-W1, and microalgae Scenedesmus obliquus) were developed to investigate the toxicological characterizations of PW from the Permian Basin.

Analysis and prediction of produced water quantity and quality in the Permian Basin using machine learning techniques.

Appropriate produced water (PW) management is critical for oil and gas industry. Understanding PW quantity and quality trends for one well or all similar wells in one region would significantly assist operators, regulators, and water treatment/disposal companies in optimizing PW management. In this research, historical PW quantity and quality data in the New Mexico portion (NM) of the Permian Basin from 1995 to 2019 was collected, pre-processed, and analyzed to understand the distribution, trend and characteristics of PW production for potential beneficial use.

The Co-Transport of PFAS and Cr(VI) in porous media.

PFAS and Cr are present at some sites as co-contaminants. The objective of this research was to investigate the co-transport behavior of per- and polyfluoroalkyl substances (PFAS) and hexavalent chromium (Cr(VI)) in porous media. Miscible-displacement experiments were conducted using two soils and an aquifer sediment with different geochemical properties.

Transport of PFOS in aquifer sediment: Transport behavior and a distributed-sorption model.

The objectives of this research were to examine the transport of perfluorooctane sulfonic acid (PFOS) in aquifer sediment comprising different geochemical properties, and to compare the behavior to that observed for PFOS transport in soil and sand. PFOS retardation was relatively low for transport in all aquifer media. The PFOS breakthrough curves were asymmetrical and exhibited extensive concentration tailing, indicating that sorption/desorption was significantly nonideal.

Column versus batch methods for measuring PFOS and PFOA sorption to geomedia.

The objective of this study is to compare the consistency between column and batch experiment methods for measuring solid-phase sorption coefficients and isotherms for per and polyfluoroalkyl substances (PFAS). Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are used as representative PFAS, and experiments are conducted with three natural porous media with differing geochemical properties. Column-derived sorption isotherms are generated by conducting multiple experiments with different input concentrations (multi-C method) or employing elution-front integration wherein the entire isotherm is determined from a single breakthrough curve (BTC) elution front.

Natural attenuation method for contaminant remediation reagent delivery assessment for in situ chemical oxidation using aqueous ozone.

A Monitored Natural Attenuation (MNA) assessment approach typically used for contaminant remediation feasibility assessment was developed here for remediation-reagent delivery assessment. Subsurface delivery of oxidants, such as aqueous ozone (O) for in situ chemical oxidation (ISCO) of groundwater contaminants, is naturally attenuated by oxidant demand and reactivity. We compared mixed reactor kinetic experiments, sand column tracer transport experiments, and reactive transport modeling and assessment methods to quantify natural attenuation kinetics, aqueous O solute transport, oxidant demand kinetics, and ISCO reagent delivery limitations.

Nonideal Transport and Extended Elution Tailing of PFOS in Soil.

The objective of this research was to examine the influence of nonideal sorption/desorption on the transport of polyfluorinated alkyl substances (PFASs) in soil, with a specific focus on characterizing and quantifying potential extended, mass-transfer-limited elution behavior. Perfluorooctane sulfonic acid (PFOS) was used as a representative PFAS, and miscible-displacement experiments were conducted with two soils comprising contrasting geochemical properties. The influence of nonlinear, rate-limited, hysteretic, and irreversible sorption/desorption on transport was investigated through experiments and model simulations.

Borehole Diffusive Flux Apparatus for Characterizing Diffusive Mass-transfer in Subsurface Systems.

The concept of the Borehole Diffusive Flux Apparatus (BDFA) is presented herein. The BDFA is an innovative apparatus designed to provide continuous direct access to an undisturbed column of sediment that can be monitored at multiple discrete vertical intervals to provide high-resolution characterization of local-scale mass transfer and attenuation. The conceptual basis and technical design of the device are presented, along with an example of borehole design and installation at a field site.

1,4-Dioxane cosolvency impacts on trichloroethene dissolution and sorption.

Solvent stabilizer 1,4-dioxane, an emerging recalcitrant groundwater contaminant, was commonly added to chlorinated solvents such as trichloroethene (TCE), and the impact of co-disposal on contaminant transport processes remains uncertain. A series of batch equilibrium experiments was conducted with variations of 1,4-dioxane and TCE composition to evaluate aqueous dissolution of the two components and their sorption to aquifer sediments. The solubility of TCE increased with increasing amounts of 1,4-dioxane, indicating that 1,4-dioxane acts as a cosolvent causing solubility enhancement of co-contaminants.

Cyclodextrin-enhanced 1,4-dioxane treatment kinetics with TCE and 1,1,1-TCA using aqueous ozone.

Enhanced reactivity of aqueous ozone (O) with hydroxypropyl-β-cyclodextrin (HPβCD) and its impact on relative reactivity of O with contaminants were evaluated herein. Oxidation kinetics of 1,4-dioxane, trichloroethylene (TCE), and 1,1,1-trichloroethane (TCA) using O in single and multiple contaminant systems, with and without HPβCD, were quantified. 1,4-Dioxane decay rate constants for O in the presence of HPβCD increased compared to those without HPβCD.

Comprehensive retention model for PFAS transport in subsurface systems.

A comprehensive compartment model is presented for PFAS retention that incorporates all potential processes relevant for transport in source zones. Miscible-displacement experiments were conducted to investigate separately the impact of adsorption at the air-water and decane-water interfaces on PFAS retention and transport. Two porous media were used, a quartz sand and a soil, and perfluorooctanesulfonic acid (PFOS) was used as the model PFAS.

Spectroscopic methods for aqueous cyclodextrin inclusion complex binding measurement for 1,4-dioxane, chlorinated co-contaminants, and ozone.

Recalcitrant organic contaminants, such as 1,4-dioxane, typically require advanced oxidation process (AOP) oxidants, such as ozone (O), for their complete mineralization during water treatment. Unfortunately, the use of AOPs can be limited by these oxidants' relatively high reactivities and short half-lives. These drawbacks can be minimized by partial encapsulation of the oxidants within a cyclodextrin cavity to form inclusion complexes.

In situ stabilization of NAPL contaminant source-zones as a remediation technique to reduce mass discharge and flux to groundwater.

Widely used flushing and in-situ destruction based remediation techniques (i.e. pump-and treat, enhanced-solubilization, and chemical oxidation/reduction) for sites contaminated by nonaqueous phase liquid (NAPL) contaminant sources have been shown to be ineffective at complete mass removal and reducing aqueous-phase contaminant of concern (COC) concentrations to levels suitable for site closure.

Chemical structure influence on NAPL mixture nonideality evolution, rate-limited dissolution, and contaminant mass flux.

The influence of chemical structure on NAPL mixture nonideality evolution, rate-limited dissolution, and contaminant mass flux was examined. The variability of measured and UNIFAC modeled NAPL activity coefficients as a function of mole fraction was compared for two NAPL mixtures containing structurally-different contaminants of concern including toluene (TOL) or trichloroethene (TCE) within a hexadecane (HEXDEC) matrix. The results showed that dissolution from the NAPL mixtures transitioned from ideality for mole fractions >0.

Stabilization and prolonged reactivity of aqueous-phase ozone with cyclodextrin.

Recalcitrant organic groundwater contaminants, such as 1,4-dioxane, may require strong oxidants for complete mineralization. However, their efficacy for in-situ chemical oxidation (ISCO) is limited by oxidant decay and reactivity. Hydroxypropyl-β-cyclodextrin (HPβCD) was examined for its ability to stabilize aqueous-phase ozone (O) and prolong oxidation potential through inclusion complex formation.