Study on rock fracture mechanism and hydraulic fracturing propagation law of heterogeneous tight sandstone reservoir.

Hydraulic fracturing technology is an effective way to develop tight sandstone reservoirs with low porosity and permeability. The tight sandstone reservoir is heterogeneous and the heterogeneity characteristics has an important influence on fracture propagation. To investigate hydraulic fracture performance in heterogeneous tight reservoir, the X-ray diffraction experiments are carried out, the Weibull distribution method and finite element method are applied to establish the uniaxial compression model and the hydraulic fracture propagation model of heterogeneous tight sandstone. Meanwhile, the sensitivity of different heterogeneity characterization factors and the multi-fracture propagation mechanism during hydraulic fracture propagation is analyzed. The results indicate that the pressure transfer in the heterogeneous reservoir is non-uniform, showing a multi-point initiation fracture mode. For different heterogeneity characterization factors, the heterogeneity characteristics based on elastic modulus are the most sensitive. The multi-fracture propagation of heterogeneous tight sandstone reservoir is different from that of homogeneous reservoir, the fracture propagation morphology is more complex. With the increase of stress difference, the fracture propagation length increases. With the increase of injection rate, the fracture propagation length increases. With the increase of cluster spacing, the propagation length of multiple fractures tends to propagate evenly. This study clarifies the influence of heterogeneity on fracture propagation and provides some guidance for fracturing optimization of tight sandstone reservoirs.

Interactions between microbial communities and polymers in hydraulic fracturing water cycle: A review.

Hydraulic fracturing (HF) has substantially boosted global unconventional hydrocarbon production but has also introduced various environmental and operational challenges. Understanding the interactions between abundant and diverse microbial communities and chemicals, particularly polymers used for proppant delivery, thickening, and friction reduction, in HF water cycles is crucial for addressing these challenges. This review primarily examined the recent studies conducted in China, an emerging area for HF activities, and comparatively examined studies from other regions. In China, polyacrylamide (PAM) and its derivatives products became key components in hydraulic fracturing fluid (HFF) for unconventional hydrocarbon development. The microbial diversity of unconventional HF water cycles in China was higher compared to North America, with frequent detection of taxa such as Shewanella, Marinobacter, and Desulfobacter. While biodegradation, biocorrosion, and biofouling were common issues across regions, the mechanisms underlying these microbe-polymer interactions differed substantially. Notably, in HF sites in the Sichuan Basin, the use of biocides gradually decreased its efficiency to mitigate adverse microbial activities. High-throughput sequencing proved to be a robust tool that could identify key bioindicators and biodegradation pathways, and help select optimal polymers and biocides, leading to more efficient HFF systems. The primary aim of this study is to raise awareness about the interactions between microorganisms and polymers, providing fresh insights that can inform decisions related to enhanced chemical use and biological control measures at HF sites.

Environmental radon, fracking wells, and lymphoma in dogs.

BACKGROUND: Multicentric lymphoma (ML) in dogs resembles non-Hodgkin lymphoma (NHL) in humans. Human NHL is associated with multiple environmental exposures, including to radon and volatile organic compounds (VOCs). HYPOTHESIS/OBJECTIVES: The objective of this study was to determine whether ML in dogs was associated with environmental radon or proximity to horizontal oil and drilling (fracking), a source of VOC pollution. METHODS: We identified dogs from the Golden Retriever Lifetime Study that developed ML (n = 52) along with matched controls (n = 104). Dog home addresses were categorized by Environmental Protection Agency radon zone and average residential radon by county, as well as by distance from fracking and associated wastewater wells. RESULTS: We found no significant differences in county level radon measurements. Individual household radon measurements were not available. There was no difference in residential proximity to active fracking wells between dogs with ML and unaffected dogs. While dogs with ML lived closer to wastewater wells (123 vs 206 km; P = .01), there was no difference in the percentage of cases vs controls that lived in close proximity (20 km) to a fracking well (11.5% for cases, 6.7% for controls; OR 1.81, 95% CI 0.55 to 5.22; P = .36), or a wastewater well (6.7% for cases, 4.4% for controls; P > .99). CONCLUSIONS AND CLINICAL IMPORTANCE: These data suggest that more proximate sources of chemical exposures need to be assessed in dogs with ML, including measurements of individual household radon and household VOC concentrations.

The human health effects of unconventional oil and gas development (UOGD): A scoping review of epidemiologic studies.

OBJECTIVE: Unconventional oil and gas development (UOGD, sometimes termed "fracking" or "hydraulic fracturing") is an industrial process to extract methane gas and/or oil deposits. Many chemicals used in UOGD have known adverse human health effects. Canada is a major producer of UOGD-derived gas with wells frequently located in and around rural and Indigenous communities. Our objective was to conduct a scoping review to identify the extent of research evidence assessing UOGD exposure-related health impacts, with an additional focus on Canadian studies. METHODS: We included English- or French-language peer-reviewed epidemiologic studies (January 2000-December 2022) which measured exposure to UOGD chemicals directly or by proxy, and where health outcomes were plausibly caused by UOGD-related chemical exposure. Results synthesis was descriptive with results ordered by outcome and hierarchy of methodological approach. SYNTHESIS: We identified 52 studies from nine jurisdictions. Only two were set in Canada. A majority (n = 27) used retrospective cohort and case-control designs. Almost half (n = 24) focused on birth outcomes, with a majority (n = 22) reporting one or more significant adverse associations of UOGD exposure with: low birthweight; small for gestational age; preterm birth; and one or more birth defects. Other studies identified adverse impacts including asthma (n = 7), respiratory (n = 13), cardiovascular (n = 6), childhood acute lymphocytic leukemia (n = 2), and all-cause mortality (n = 4). CONCLUSION: There is a growing body of research, across different jurisdictions, reporting associations of UOGD with adverse health outcomes. Despite the rapid growth of UOGD, which is often located in remote, rural, and Indigenous communities, Canadian research on its effects on human health is remarkably sparse. There is a pressing need for additional evidence.

RéSUMé: OBJECTIF: L'exploitation pétrolière et gazière non conventionnelle (EPGNC, parfois appelée « fracturation ¼ ou « fracturation hydraulique ¼) est un processus industriel d'extraction du méthane et/ou de gisements de pétrole. De nombreux produits chimiques utilisés dans l'EPGNC ont des effets indésirables connus sur la santé humaine. Le Canada est un grand producteur de gaz dérivé de l'EPGNC, dont les puits sont souvent situés à l'intérieur et autour de communautés rurales et autochtones. Nous avons mené une étude de champ pour déterminer l'étendue des données de recherche évaluant les effets sur la santé de l'exposition à l'EPGNC, en nous concentrant plus particulièrement sur les études canadiennes. MéTHODE: Nous avons inclus des études épidémiologiques en anglais ou en français évaluées par les pairs (janvier 2000 à décembre 2022) qui mesuraient l'exposition directe ou indirecte aux produits chimiques de l'EPGNC et dans lesquelles les résultats cliniques étaient plausiblement causés par l'exposition aux produits chimiques liés à l'EPGNC. La synthèse des résultats est descriptive, et les résultats sont ordonnés selon les résultats cliniques et l'approche méthodologique. SYNTHèSE: Nous avons identifié 52 études menées dans neuf juridictions. Deux seulement étaient canadiennes. La majorité (n = 27) faisaient appel à des cohortes rétrospectives ou étaient des études cas-témoins. Près de la moitié (n = 24) portaient sur les issues de la grossesse, et la majorité (n = 22) déclaraient une ou plusieurs associations indésirables significatives entre l'exposition à l'EPGNC et : l'insuffisance de poids à la naissance; la petite taille du bébé pour son âge gestationnel; la naissance avant terme; et une ou plusieurs anomalies congénitales. D'autres études faisaient état d'effets indésirables, dont l'asthme (n = 7), les troubles respiratoires (n = 13), les troubles cardiovasculaires (n = 6), la leucémie aiguë lymphoblastique infantile (n = 2) et la mortalité toutes causes confondues (n = 4). CONCLUSION: Il existe dans différents pays un corpus croissant d'études qui font état d'associations entre l'EPGNC et des résultats sanitaires indésirables. Malgré la croissance rapide de l'EPGNC, souvent présente dans des communautés éloignées, rurales et autochtones, la recherche canadienne sur ses effets sur la santé humaine est remarquablement clairsemée. Il y a un besoin urgent de recueillir d'autres données probantes à ce sujet.

In Silico Acute Aquatic Hazard Assessment and Prioritization Using a Grouped Target Site Model: A Case Study of Organic Substances Reported in Permian Basin Hydraulic Fracturing Operations.

Hydraulic fracturing (HF) is commonly used to enhance onshore recovery of oil and gas during production. This process involves the use of a variety of chemicals to support the physical extraction of oil and gas, maintain appropriate conditions downhole (e.g., redox conditions, pH), and limit microbial growth. The diversity of chemicals used in HF presents a significant challenge for risk assessment. The objective of the present study is to establish a transparent, reproducible procedure for estimating 5th percentile acute aquatic hazard concentrations (e.g., acute hazard concentration 5th percentiles [HC5s]) for these substances and validating against existing toxicity data. A simplified, grouped target site model (gTSM) was developed using a database (n = 1696) of diverse compounds with known mode of action (MoA) information. Statistical significance testing was employed to reduce model complexity by combining 11 discrete MoAs into three general hazard groups. The new model was trained and validated using an 80:20 allocation of the experimental database. The gTSM predicts toxicity using a combination of target site water partition coefficients and hazard group-based critical target site concentrations. Model performance was comparable to the original TSM using 40% fewer parameters. Model predictions were judged to be sufficiently reliable and the gTSM was further used to prioritize a subset of reported Permian Basin HF substances for risk evaluation. The gTSM was applied to predict hazard groups, species acute toxicity, and acute HC5s for 186 organic compounds (neutral and ionic). Toxicity predictions and acute HC5 estimates were validated against measured acute toxicity data compiled for HF substances. This case study supports the gTSM as an efficient, cost-effective computational tool for rapid aquatic hazard assessment of diverse organic chemicals. Environ Toxicol Chem 2024;43:1161-1172. © 2024 ExxonMobil Petroleum and Chemical BV. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Increases in trade secret designations in hydraulic fracturing fluids and their potential implications for environmental health and water quality.

Hydraulic fracturing is an increasingly common method of oil and gas extraction across the United States. Many of the chemicals used in hydraulic fracturing processes have been proven detrimental to human and environmental health. While disclosure frameworks have advanced significantly in the last 20 years, the practice of withholding chemical identities as "trade secrets" or "proprietary claims" continues to represent a major absence in the data available on hydraulic fracturing. Here, we analyze rates of trade secret claims using FracFocus, a nationwide database of hydraulic fracturing data, from January 1, 2014 to December 31, 2022. We use the open-source tool Open-FF, which collates FracFocus data, makes it accessible for systematic analysis, and performs several quality-control measures. We found that the use by mass of chemicals designated as trade secrets has increased over the study time period, from 728 million pounds in 2014 to 2.96 billion pounds in 2022 (or a 43.7% average yearly increase). A total of 10.4 billion pounds of chemicals were withheld as trade secrets in this time period. The water volume used (and therefore total mass of fracturing fluid) per fracturing job has shown a large increase from 2014 to 2022, which partly explains the increase in mass of chemicals withheld as trade secrets over this time period, even as total fracturing jobs and individual counts of proprietary records have decreased. Our analysis also shows increasing rates of claiming proppants (which can include small grains of sand, ceramic, or other mineral substances used to prop open fractures) as proprietary. However, the mean and median masses of non-proppant constituents designated as trade secrets have also increased over the study period. We also find that the total proportion of all disclosures including proprietary designations has increased by 1.1% per year, from 79.3% in 2014 to 87.5% in 2022. In addition, most disclosures designate more than one chemical record as proprietary: trade secret withholding is most likely to apply to 10-25% of all records in an individual disclosure. We also show the top ten reported purposes that most commonly include proprietary designations, after removing vague or multiple entries, the first three of which are corrosion inhibitors, friction reducers, and surfactants. Finally, we report the top ten operators and suppliers using and supplying proprietary chemicals, ranked by mass used or supplied, over our study period. These results suggest the importance of revisiting the role of proprietary designations within state and federal disclosure mechanisms.

Changes in environmental and engineered conditions alter the plasma membrane lipidome of fractured shale bacteria.

IMPORTANCE: Microorganisms inadvertently introduced into the shale reservoir during fracturing face multiple stressors including brine-level salinities and starvation. However, some anaerobic halotolerant bacteria adapt and persist for long periods of time. They produce hydrogen sulfide, which sours the reservoir and corrodes engineering infrastructure. In addition, they form biofilms on rock matrices, which decrease shale permeability and clog fracture networks. These reduce well productivity and increase extraction costs. Under stress, microbes remodel their plasma membrane to optimize its roles in protection and mediating cellular processes such as signaling, transport, and energy metabolism. Hence, by observing changes in the membrane lipidome of model shale bacteria, Halanaerobium congolense WG10, and mixed consortia enriched from produced fluids under varying subsurface conditions and growth modes, we provide insight that advances our knowledge of the fractured shale biosystem. We also offer data-driven recommendations for improving biocontrol efficacy and the efficiency of energy recovery from unconventional formations.

In vivo exposure to electronic waste (e-waste) leachate and hydraulic fracturing fluid adversely impacts the male reproductive system.

Human health effects can arise from unregulated manual disassembly of electronic waste (e-waste) and/or hydraulic fracturing fluid spills. There is limited literature on the effects of e-waste and hydraulic fracturing wastewater exposure on the male reproductive system. Thus, this proof-of-concept study begins to address the question of how wastewater from two potentially hazardous environmental processes could affect sperm quality. Therefore, three groups of eight-week-old adult mice were exposed (5 d/wk for 6 wks) via a mealworm (Tenebrio molitor and Zophabas morio) feeding route to either: (1) e-waste leachate (50% dilution) from the Alaba Market (Lagos, Nigeria); (2) West Virginia hydraulic fracturing flowback (HFF) fluid (50% dilution); or, (3) deionized water (control). At 24-hours (hr), 3 weeks (wk), or 9-wk following the 6-wk exposure period, cohorts of mice were necropsied and adverse effects/persistence on the male reproductive system were examined. Ingestion of e-waste leachate or HFF fluid decreased number and concentration of sperm and increased both chromatin damage and numbers of morphological abnormalities in the sperm when compared to control mice. Levels of serum testosterone were reduced post-exposure (3- and 9-wk) in mice exposed to e-waste leachate and HFF when compared to time-matched controls, indicating the long-term persistence of adverse effects, well after the end of exposure. These data suggest that men living around or working in vicinity of either e-waste or hydraulic fracturing could face harmful effects to their reproductive health. From both a human health and economic standpoint, development of prevention and intervention strategies that are culturally relevant and economically sensitive are critically needed to reduce exposure to e-waste and HFF-associated toxic contaminants.

Environmentally relevant concentrations of chemically complex shale gas wastewater led to reduced fitness of water fleas (Daphnia carinata): Multiple lines of evidence approach.

Shale gas hydraulic fracturing generates flowback waters that pose a threat to aquatic organisms if released into the environment. In order to prevent adverse effects on aquatic ecosystems, multiple lines of evidence are needed to guide better decisions and management actions. This study employed a multi-disciplinary approach, combining direct toxicity assessment (DTA) on the water flea Daphnia carinata and LC-MS metabolomics analysis to determine the impact of a major ion salinity control (SC) and a cumulative flowback shale gas wastewater (SGW) from a well in the Beetaloo Sub-basin, Northern Territory, Australia. The exposures included a culture water control, simply further referred to as 'control', SC at 1% and 2% (v/v) and SGW at 0.125, 0.25, 0.5, 1% and 2% (v/v). The results showed that reproduction was significantly increased at SGW 0.5%, and significantly decreased when exposed to SC 2%. SGW 2% was found to be acutely toxic for the D. carinata (< 48-h). Second generation (F1) of D. carinata exposed to 0.125-1% SGW generally saw reduced activity in four oxidative biomarkers: glutathione S-transferase, lipid peroxidation, reactive oxygen species, and superoxide dismutase. At the metabolomics level, we observed significant changes in 103 metabolites in Daphnia exposed to both SGW and elevated salinity, in comparison to the control group. These changes indicate a range of metabolic disturbances induced by SGW and salinity, such as lipid metabolism, amino acid metabolism, nucleotide synthesis, energy production, and the biosynthesis of crucial molecules like hormones and pigments. These multiple lines of evidence approach not only highlights the complexities of SGW's impact on aquatic ecosystems but also underscores the importance of informed decision-making and management practices to safeguard the environment and its inhabitants.

Prediction criterion and numerical validation for the interaction between hydraulic fractures and bedding planes.

Shale is a kind of sedimentary rock with an obvious bedding structure. The effect of the bedding plane on hydraulic fracture initiation, propagation, and complex fracture network formation is remarkable and a major problem in hydraulic fracturing and shale oil and gas development. In this study, a criterion is established to predict the evolution behavior of hydraulic fractures (HF) under different confining pressure differences and intersection angles. This criterion is intended to predict the types of interaction between HFs and bedding planes (BPs): penetrating, slipping, or dilating. The dependence of crossing on the intersection angle and the principal stress difference is quantitatively presented using the criterion. Meanwhile, 20 simulations with principal stress differences of 2, 4, 6, and 8 MPa and intersection angles of 30°, 45°, 60°, 75°, and 90° were simulated using the RFPA2D-Flow code. Simulation results exhibit good agreement with the criterion results for a wide range of angles. The investigation showed that HFs tend to penetrate BPs under high confining pressure differences and intersection angles and open BPs under low confining pressure differences and intersection angles. In addition to the above two forms, HFs slip due to shear. The criterion can provide relevant reference about the formation of complex fracture networks in shale layers.

Spatial and temporal variation in toxicity and inorganic composition of hydraulic fracturing flowback and produced water.

Hydraulic fracturing for oil and gas extraction produces large volumes of wastewater, termed flowback and produced water (FPW), that are highly saline and contain a variety of organic and inorganic contaminants. In the present study, FPW samples from ten hydraulically fractured wells, across two geologic formations were collected at various timepoints. Samples were analyzed to determine spatial and temporal variation in their inorganic composition. Results indicate that FPW composition varied both between formations and within a single formation, with large compositional changes occurring over short distances. Temporally, all wells showed a time-dependent increase in inorganic elements, with total dissolved solids increasing by up to 200,000 mg/L over time, primarily due to elements associated with salinity (Cl, Na, Ca, Mg, K). Toxicological analysis of a subset of the FPW samples showed median lethal concentrations (LC50) of FPW to the aquatic invertebrate Daphnia magna were highly variable, with the LC50 values ranging from 1.16% to 13.7% FPW. Acute toxicity of FPW significantly correlated with salinity, indicating salinity is a primary driver of FPW toxicity, however organic components also contributed to toxicity. This study provides insight into spatiotemporal variability of FPW composition and illustrates the difficulty in predicting aquatic risk associated with FPW.

Research on the evolution law of hot spots in the field of coal seam hydraulic fracturing based on bibliometric analysis: review from a new scientific perspective.

As an unconventional natural gas, the calorific value of coal seam gas (CSG) is equivalent to that of natural gas. It is a high-quality, clean, and efficient green low-carbon energy source. Coal seam hydraulic fracturing is an important permeability enhancement measure in the process of CSG drainage. In order to further understand the overall research progress in the field of coal seam hydraulic fracturing, the Web of Science (WOS) database is used as a sample source, and the bibliometric analysis of the literature is carried out by CiteSpace software. The visual knowledge maps of the number of publications, the research countries, institutions, and keyword clustering are drawn. The research shows that it has gone through two stages of slow development and rapid growth in terms of time distribution. In terms of cooperation networks, the main active countries include China, the USA, Australia, Russia, and Canada, composed of China University of Mining and Technology, Chongqing University, Henan Polytechnic University, and China University of Petroleum as the core research institutions. Taking keywords as the theme, the coal seam hydraulic fracturing research field mainly involves high-frequency keywords such as hydraulic fracturing, permeability, model, and numerical simulation. The hotspot evolution law and frontier development trend of keywords with time are analyzed and obtained. On this basis, from a new perspective, the "scientific research landscape map" in the field of coal seam hydraulic fracturing is outlined, in order to provide a scientific reference for the research in this field.

Performance and microbial community analysis of combined bioreactors in treating high-salinity hydraulic fracturing flowback and produced water.

The anoxic/oxic systems are a widely used biological strategy for wastewater treatment. However, little is known about the performance and microbial community correlation of different combined bioreactors in the treatment of high-COD and high-salinity hydraulic fracturing flowback and produced water (HF-FPW). In this study, the performance of Up-flow anaerobic sludge bed-bio-contact oxidation reactor (UASB-BCOR) and Fixed-bed baffled reactor (FBR-BCOR) in treating HF-FPW was investigated and compared. The results suggested the FBR-BCOR could efficiently remove COD, SS, NH4+-N, and oil pollutants, and it exhibited better resistance to the negative interference of hydraulic shock load on it. Besides, the correlation analysis first disclosed the key functional genera during the degradation process, including Ignavibacterium, Ellin6067, and Zixibacteria. Moreover, network analysis revealed that the difference of microbial co-occurrence network structure is the main driving factor for the difference of bioreactor processing capacity. This work demonstrates the feasibility and potential of FBR-BCOR in treating HF-FPW.

Toxicity identification evaluation for hydraulic fracturing flowback and produced water during shale gas exploitation in China: Evidence from tissue residues and gene expression.

Hydraulic fracturing flowback and produced water (HF-FPW) from shale gas extraction processes is a highly complex medium with potential threats to the environment. Current research on ecological risks of FPW in China is limited, and the link between major components of FPW and their toxicological effects on freshwater organisms is largely unknown. By integrating chemical and biological analyses, toxicity identification evaluation (TIE) was used to reveal causality between toxicity and contaminants, potentially disentangling the complex toxicological nature of FPW. Here, FPW from different shale gas wells, treated FPW effluent, and a leachate from HF sludge were collected from southwest China, and TIE was applied to obtain a comprehensive toxicity evaluation in freshwater organisms. Our results showed that FPW from the same geographic zone could cause significantly different toxicity. Salinity, solid phase particulates, and organic contaminants were identified as the main contributors to the toxicity of FPW. In addition to water chemistry, internal alkanes, PAHs, and HF additives (e.g., biocides and surfactants) were quantified in exposed embryonic fish by target and non-target tissue analyses. The treated FPW failed to mitigate the toxicity associated with organic contaminants. Transcriptomic results illustrated that organic compounds induced toxicity pathways in FPW-exposed embryonic zebrafish. Similar zebrafish gene ontologies were affected between treated and untreated FPW, again confirming that sewage treatment did not effectively remove organic chemicals from FPW. Thus, zebrafish transcriptome analyses revealed organic toxicant-induced adverse outcome pathways and served as evidence for TIE confirmation in complex mixtures under data-poor scenarios.

Post-injury hydraulic fracturing drives fissure formation in the zebrafish basal epidermal cell layer.

The skin epithelium acts as the barrier between an organism's internal and external environments. In zebrafish and other freshwater organisms, this barrier function requires withstanding a large osmotic gradient across the epidermis. Wounds breach this epithelium, causing a large disruption to the tissue microenvironment due to the mixing of isotonic interstitial fluid with the external hypotonic fresh water. Here, we show that, following acute injury, the larval zebrafish epidermis undergoes a dramatic fissuring process that resembles hydraulic fracturing, driven by the influx of external fluid. After the wound has sealed-preventing efflux of this external fluid-fissuring starts in the basal epidermal layer at the location nearest to the wound and then propagates at a constant rate through the tissue, spanning over 100 µm. During this process, the outermost superficial epidermal layer remains intact. Fissuring is completely inhibited when larvae are wounded in isotonic external media, suggesting that osmotic gradients are required for fissure formation. Additionally, fissuring partially depends on myosin II activity, as myosin II inhibition reduces the distance of fissure propagation away from the wound. During and after fissuring, the basal layer forms large macropinosomes (with cross-sectional areas ranging from 1 to 10 µm2). We conclude that excess external fluid entry through the wound and subsequent closure of the wound through actomyosin purse-string contraction in the superficial cell layer causes fluid pressure buildup in the extracellular space of the zebrafish epidermis. This excess fluid pressure causes tissue to fissure, and eventually the fluid is cleared through macropinocytosis.

Impacts of hydraulic fracturing wastewater from oil and gas industries on drinking water: Quantification of 69 disinfection by-products and calculated toxicity.

Oil and gas production generates large amounts of brine wastewater called "produced water" with various geogenic and synthetic contaminants. These brines are generally used in hydraulic fracturing operations to stimulate production. They are characterized by elevated halide levels, particularly geogenic bromide and iodide. Such salt concentrations in produced water may be as high as thousands of mg/L of bromide and tens of mg/L of iodide. Large volumes of produced water are stored, transported, reused in production operations, and ultimately disposed of by deep well injection into saline aquifers. Improper disposal may potentially contaminate shallow freshwater aquifers and impact drinking water sources. Because conventional produced water treatment typically does not remove halides, produced water contamination of groundwater aquifers may cause the formation of brominated and iodinated disinfection by-products (I-DBPs) at municipal water treatment plants. These compounds are of interest because of their higher toxicity relative to their chlorinated counterparts. This study reports a comprehensive analysis of 69 regulated and priority unregulated DBPs in simulated drinking waters fortified with 1 % (v/v) oil and gas wastewater. Impacted waters produced 1.3×-5× higher levels of total DBPs compared to river water after chlorination and chloramination. Individual DBP levels ranged from (<0.1-122 µg/L). Overall, chlorinated waters formed highest levels, including trihalomethanes that would exceed the U.S. EPA regulatory limit of 80 µg/L. Chloraminated waters had more I-DBP formation and highest levels of haloacetamides (23 µg/L) in impacted water. Calculated cytotoxicity and genotoxicity were higher for impacted waters treated with chlorine and chloramine than corresponding treated river waters. Chloraminated impacted waters had the highest calculated cytotoxicity, likely due to higher levels of more toxic I-DBPs and haloacetamides. These findings demonstrate that oil and gas wastewater if discharged to surface waters could adversely impact downstream drinking water supplies and potentially affect public health.

Persisting Effects in Daphnia magna Following an Acute Exposure to Flowback and Produced Waters from the Montney Formation.

Hydraulic fracturing extracts oil and gas through the injection of water and proppants into subterranean formations. These injected fluids mix with the host rock formation and return to the surface as a complex wastewater containing salts, metals, and organic compounds, termed flowback and produced water (FPW). Previous research indicates that FPW is toxic to Daphnia magna (D. magna), impairing reproduction, molting, and maturation time; however, recovery from FPW has not been extensively studied. Species unable to recover have drastic impacts on populations on the ecological scale; thus, this study sought to understand if recovery from an acute 48 h FPW exposure was possible in the freshwater invertebrate, D. magna by using a combination of physiological and molecular analyses. FPW (0.75%) reduced reproduction by 30% and survivorship to 32% compared to controls. System-level quantitative proteomic analyses demonstrate extensive perturbation of metabolism and protein transport in both 0.25 and 0.75% FPW treatments after a 48 h FPW exposure. Collectively, our data indicate that D. magna are unable to recover from acute 48 h exposures to ≥0.25% FPW, as evidence of toxicity persists for at least 19 days post-exposure. This study highlights the importance of considering persisting effects following FPW remediation when modeling potential spill scenarios.

Coupling iron-carbon micro-electrolysis with persulfate advanced oxidation for hydraulic fracturing return fluid treatment.

Improving the sustainability of the hydraulic fracturing water cycle of unconventional oil and gas development needs an advanced water treatment that can efferently treat flowback and produced water (FPW). In this study, we developed a robust two-stage process that combines flocculation, and iron-carbon micro-electrolysis plus sodium persulfate (ICEPS) advanced oxidation to treat field-based FPW from the Sulige tight gas field, China. Influencing factors and optimal conditions of the flocculation-ICEPS process were investigated. The flocculation-ICEPS system at optimal conditions sufficiently removed the total organic contents (95.71%), suspended solids (92.4%), and chroma (97.5%), but the reaction stoichiometric efficiency (RSE) value was generally less than 5%. The particles and chroma were effectively removed by flocculation, and the organic contents was mainly removed by the ICEPS system. Fourier-transform infrared spectroscopy (FTIR) analysis was performed to track the changes in FPW chemical compositions through the oxidation of the ICEPS process. Multiple analyses demonstrated that PS was involved in the activation of Fe oxides and hydroxides accreted on the surface of the ICE system for FPW treatment, which led to increasing organics removal rate of the ICEPS system compared to the conventional ICE system. Our study suggests that the flocculation-ICEPS system is a promising FPW treatment process, which provides technical and mechanistic foundations for further field application.

Fracking wastewater treatment: Catalytic performance and life cycle environmental impacts of cerium-based mixed oxide catalysts for catalytic wet oxidation of organic compounds.

Water scarcity and the consequent increase of freshwater prices are a cause for concern in regions where shale gas is being extracted via hydraulic fracturing. Wastewater treatment methods aimed at reuse/recycle of fracking wastewater can help reduce water stress of the fracking process. Accordingly, this study assessed the catalytic performance and life cycle environmental impacts of cerium-based mixed oxide catalysts for catalytic wet oxidation (CWO) of organic contaminants, in order to investigate their potential as catalysts for fracking wastewater treatment. For these purposes, MnCeOx and CuCeOx were tested for phenol removal in the presence of concentrated NaCl (200 g L-1), which represented a synthetic fracking wastewater. Removal of phenol in pure ("phenolic") water without NaCl was also considered for comparison. Complete (100 %) phenol and a 94 % total organic carbon (TOC) removal were achieved in both the phenolic and fracking wastewaters by utilising MnCeOx (5 g L-1) and insignificant metal leaching was observed. However, a much lower activity was observed when the same amount of CuCeOx was utilised: 23.3 % and 20.5 % for phenol and TOC removals, respectively, in the phenolic, and 69.1 % and 63 % in the fracking wastewater. Furthermore, severe copper leaching from CuCeOx was observed during stability tests conducted in the fracking wastewater. A life cycle assessment (LCA) study carried out as part of this work showed that the production of MnCeOx had 12-98 % lower impacts than CuCeOx due to the higher impacts of copper than manganese precursors. Furthermore, the environmental impacts of CWO were found to be 94-99 % lower than those of ozonation due to lower energy and material requirements. Overall, the results of this study suggest that the adoption of catalytic treatment would improve both the efficiency and the environmental sustainability of both the fracking wastewater treatment and the fracking process as a whole.

Mixture Toxicity of Three Unconventional Gas Fracking Chemicals, Barium, O-Cresol, and Sodium Chloride, to the Freshwater Shrimp Paratya australiensis.

The 96-h acute toxicity of barium (Ba2+ ), o-cresol, and sodium chloride (NaCl) to Paratya australiensis was assessed in single, binary, and ternary combinations in addition to three biochemical assays: glutathione S-transferase, acetylcholinesterase, and sodium-potassium adenosine triphosphatase. The 96-h lethal concentrations that expressed 50% mortality (LC50) in the single-toxicant exposures were Ba2+ = 23.4 mg/L, o-cresol = 12.2 mg/L, and NaCl = 4198 mg/L. Mortality from o-cresol exposure occurred between 11 and 22 mg/L, whereas Ba2+ was more gradual across 10-105 mg/L, and most of the NaCl mortality occurred between 2050 and 4100 mg/L. Toxic units were used to assess the binary and ternary interactions of the toxicants. A more than additive effect was observed for most combinations in the binary chemical exposures, with the ternary combinations yielding highly synergistic interactions. Greater synergism was observed with the 96-h LC50 of o-cresol in combination with the three concentrations of NaCl (1025, 2050, and 3075 mg/L) compared with Ba2+ , with toxic units of 0.38, 0.48, and 0.10 (o-cresol) and 0.71, 0.67, and 0.50 (Ba2+ ). No notable enzyme activity trends were observed in the enzyme biomarker responses from both individual and mixture exposures. Although acute single-species toxicity tests tend to underestimate the effects of Ba2+ , o-cresol, and NaCl on populations, communities, and ecosystems in seminatural (e.g., mesocosms) and natural systems, there are currently no published acute toxicity data available for P. australiensis and the three toxicants used in the present study. The present study shows that chemicals with different toxicity mechanisms can potentially lead to more synergistic responses. Environ Toxicol Chem 2023;42:481-494. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.