Repository for Oil and Gas Energy Research (ROGER)

Abstract:
The global energy landscape has significantly changed in the past several years because horizontal drilling and hydraulic fracturing enable unconventional oil and gas extraction from previously inaccessible shale formations. However, opportunities and challenges coexist. Large volumes of freshwater consumed and wastewater discharge increasingly affect the environment and ecosystem. Much freshwater is pumped into deep formations during hydraulic fracturing process, and flowback with high-salinity brines, producing large volumes of wastewater. Such wastewater contains not only many toxic chemicals and high levels of total dissolved solids, but also abundant stratigraphic minerals and radioactive substances, which may pose a serious risk to the surrounding environment and public health. One of the greatest challenges for current oil and gas extraction is handling those wastewaters in a reasonable and efficient way. This paper described the current methods for dealing with these challenges and put forward some suggestions and expectations for future management of water resources in hydraulic fracturing. Open image in new window Graphical Abstract

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High-quality water is essential for most industrial processes, and many of these processes generate large volumes of contaminated wastewater. Nanotechnology has the potential to make industrial water treatment more efficient and less expensive, though promising technologies must be demonstrated at higher scales to make a real impact.

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Water scarcity severely affects drylands threatening their food security, whereas, the oil and gas industry produces significant and increasing volumes of produced water that could be partly reused for agricultural irrigation in these regions. In this review, we summarise recent research and provide a broad overview of the potential for oil and gas produced water to irrigate food crops in drylands. The quality of produced water is often a limiting factor for the reuse in irrigation as it can lead to soil salinisation and sodification. Although the inappropriate use of produced water in irrigation could be damaging for the soil, the agricultural sector in dry areas is often prone to challenges in soil salinity. There is a lack of knowledge about the main environmental and economic conditions that could encourage or limit the development of irrigation with oil and gas effluents at the scale of drylands in the world. Cheaper treatment technologies in combination with farm-based salinity management techniques could make the reuse of produced water relevant to irrigate high value-crops in hyper-arid areas. This review paper approaches an aspect of the energy-water-food nexus: the opportunities and challenges behind the reuse of abundant oil and gas effluents for irrigation in hydrocarbon-rich but water-scarce and food-unsecured drylands.

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Surface spills of water produced from hydraulic fracturing can expose soil and groundwater to organics such as BTEX and naphthalene (BTEX&N) as well as high concentrations of salt. As an alternative to soil excavation, we evaluated the effectiveness of BTEX&N soil remediation using 2 grasses present in Colorado. Perennial ryegrass and foxtail barley were grown separately in pots in the greenhouse and exposed to salt or a synthesized produced-water slurry containing relevant levels of salt and BTEX&N. Plant biomass was measured 14 days post-spill, and levels of BTEX&N were quantified using GC/MS for soil, roots, and shoots at day 7 and 14 post-spill. Foxtail barley shoot growth was limited by BTEX&N, whereas perennial ryegrass shoot growth was enhanced by salt but not BTEX&N. While BTEX&N in soil associated with foxtail barley mainly decreased over time, the soil associated with perennial ryegrass mainly saw an increase in BTEX&N with time. However, further research is needed to determine the fate of BTEX&N within grasses and soil.

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BACKGROUND: Hydraulically fractured wells produce 2–14 million liters of wastewater, which may contain toxic and radioactive compounds. The wastewater is predominantly disposed of using Class II injection wells. OBJECTIVE: Our objective was to evaluate the relationship between sociodemographic characteristics and injection well locations in Ohio. METHODS: Using state and federal data sources, we classified Ohio census block groups by presence of injection wells, number of hydraulically fractured wells, sociodemographic factors (median household income, % white, population density, % ≥high school education, median age, voter turnout), and geographic information (land area, water area, situated over shale). We modeled the odds of having at least one injection well within a block group with respect to all covariates using three multivariable models incorporating different spatial components to account for similarities in neighboring block groups. RESULTS: In bivariate analyses, block groups with injection wells (n=156) compared with those without (n=9,049) had lower population density (71 vs. 2,210 people/mi2 or 27 vs. 854 people/km2), larger median area (43.5 vs. 1.35 km2), higher median age (42.8 vs. 40.2 y), and higher % white (98.1% vs. 92.1%). After adjustment using a spatial logistic regression model, the odds of a block group containing an injection well were 16% lower per $10,000 increase in median income [odds ratio(OR)=0.837; 95% credible interval (CI): 0.719, 0.961] and 97% lower per 1,000 people/mi2 (or per 386 people/km2) increase (OR=0.030; 95% CI=0.008, 0.072). Block groups on shale and those containing fewer hydraulically fractured wells were more likely to include an injection well. Percentage white, median age, % ≥high school education, and % voter turnout were not significant predictors of injection well presence. CONCLUSION: In Ohio, injection wells were inversely associated with block groups’ median incomes after adjusting for other sociodemographic and geographic variables. Research is needed to determine whether residents in census blocks with injection wells face increased risk of chemical exposures or adverse health outcomes.

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Biological treatment is effective but infrequently used for oil and gas produced water. To date, physical–chemical treatment methods have been favored due to the smaller space requirements and operational simplicity. Changing regulatory requirements and increased interest in recycling and beneficial reuse have led to increased interest in biological treatment. To elucidate its potential role, we reviewed and summarized 59 studies on the biological treatment of produced water. Oilfield produced water was predominantly studied (> 50%). More studies using real produced water were from China than from any other country (37%). Real produced water was used in most studies (73%). Studies were predominantly bench-scale experiments (69%). Fixed-film reactors were most prevalent (27%). Water quality of produced waters treated was variable; median total dissolved solids (TDS) was 28,000 mg L−1 and median chemical oxygen demand (COD) was 1125 mg L−1. Inhibition by salinity was variable according to the treatment system and study design, but efficacy generally decreased when TDS was above 50,000 mg L−1. For studies treating real samples, average COD removal was 73% when TDS was less than 50,000 mg L−1, and 54% when TDS was greater than 50,000 mg L−1. Key issues were microbial acclimation, toxicity, biological fouling, and mineral scaling. Finding an inoculum was not problematic as microorganisms capable of degrading hydrocarbons were isolated from various environments. Treatment performance was better where synthetic produced water was used in lieu of real samples. Biological treatment is promising for producing effluents suitable for reuse, particularly where it functions as part of a larger treatment train.

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Thirteen states in the United States allow the spreading of O&G wastewaters on roads for deicing or dust suppression. In this study, the potential environmental and human health impacts of this practice are evaluated. Analyses of O&G wastewaters spread on roads in the northeastern, U.S. show that these wastewaters have salt, radioactivity, and organic contaminant concentrations often many times above drinking water standards. Bioassays also indicated that these wastewaters contain organic micropollutants that affected signaling pathways consistent with xenobiotic metabolism and caused toxicity to aquatic organisms like Daphnia magna. The potential toxicity of these wastewaters is a concern as lab experiments demonstrated that nearly all of the metals from these wastewaters leach from roads after rain events, likely reaching ground and surface water. Release of a known carcinogen (e.g., radium) from roads treated with O&G wastewaters has been largely ignored. In Pennsylvania from 2008 to 2014, spreading O&G wastewater on roads released over 4 times more radium to the environment (320 millicuries) than O&G wastewater treatment facilities and 200 times more radium than spill events. Currently, state-by-state regulations do not require radium analyses prior to treating roads with O&G wastewaters. Methods for reducing the potential impacts of spreading O&G wastewaters on roads are discussed.

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This research aimed to elucidate the effect of brine salinity and guar gum on the sorption and transport of Ba in dolomite rocks collected from the Arbuckle formation in Oklahoma, USA. Guar gum represents the most important organic additive used in viscosified fracturing fluids, and Ba constitutes the most common and abundant heavy metal found in unconventional oil and gas (UOG) wastewater. Batch experiments conducted using powdered dolomite rocks (500–600 μm particle size) revealed that at brine salinities of UOG wastewater, chloro-complexation reactions between Ba and Cl ions and pH changes that results from dolomite dissolution are the controlling factors of Ba sorption on dolomite. Competition of Ba with common cations (Ca and Mg) for hydration sites of dolomite, plays a secondary role. Core-flooding experiments conducted to analyze the transport of Ba through natural and synthetic dolomite core plugs are in agreement with the batch sorption experimental results. The transport of Ba through dolomite rocks, increases with increasing brine salinity (0–180,000 mg-NaCl/L). The presence guar gum (50–500 mg/L) does not affect the transport of Ba through dolomite rocks of high flow properties (25–29.6% porosity, 9.6–13.7 mD permeability). However, core-flooding experiments conducted using tight dolomite rocks (6.5–8.6% porosity, 0.06–0.3 mD permeability), revealed that guar gum can retard the transport of Ba by clogging high permeability/porosity regions of tight dolomite rocks. The mechanism of Ba sorption on dolomite can be represented by a sorption model that accounts for both surface complexation reactions on three distinct hydration sites (>CaOHo, >MgOHo, and >CO3Ho), and the kinetic dissolution of dolomite. These results are important in understanding and predicting the fate of Ba present in UOG wastewater disposed into deep dolomite saline aquifers.

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Despite a declining trend, California remains a significant oil-producing state. For every barrel of crude oil, an average of 15 barrels of oilfield produced water (OPW) is generated, some of which is used to boost freshwater sources for crop irrigation in the agriculturally important Central Valley. OPW is known to contain salts, metals, hydrocarbons, alkylphenols, naturally radioactive materials, biocides, and other compounds from drilling and production processes. Less is known about the potential uptake and accumulation of these compounds in crops and soil irrigated with OPW. In this study, 23 potted mandarin orange plants were irrigated two to three times weekly (depending on season) with water containing three different concentrations of the known OPW heavy metals barium, chromium, lead, and silver. Seven sets of samples of soil and leaves and 11 fruits were collected and processed using microwave-assisted digestion (EPA Method 3051A). Processed samples were analyzed using inductively coupled plasma-optical emission spectroscopy (ICP-OES). Analysis of variance (ANOVA) and covariance (ANCOVA) coupled with Tukey’s honest significant difference test were used to examine the effects of metal concentrations in the irrigation water and number of watering days, respectively, on the metal concentrations in the soil, leaf, and fruit samples. Accumulation of barium in soil and leaves was strongly positively associated with sample and number of watering days, increasing nearly 2000-fold. Lead also showed an upward trend, increasing up to 560-fold over the baseline level. Total chromium showed an increase in the soil that tapered off, but less consistent results in the leaves and fruit. The silver results were more volatile, but also indicated at least some level of accumulation in the tested media. The smallest absolute accumulation was observed for chromium. Concentrations in the fruit were highest in the peel, followed by pith and juice. Accumulation of all heavy metals was generally highest in the soil and plants that received the highest irrigation water concentration. Considering the potential for adverse human health effects associated with ingesting soluble barium contained in food and drinking water, and to a lesser extent chromium and lead, the study signals that it is important to conduct further research into the accessibility and bioavailability of the tested heavy metals in the soil and whether they pose risks to consumers.

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Due to stricter environmental regulations and lack of other alternatives, saline effluents reuse is becoming necessary in arid regions. Produced water generated in oil and gas exploration is a promising stream for this purpose, since remarkable quantities are available. In order to turn desalination routes into economically attractive options, it is mandatory to choose and to optimize technologies aiming to minimize capital and operational costs. Therefore, several combinations of technologies, involving forward osmosis (FO), reverse osmosis (RO), assisted reverse osmosis (ARO), microfiltration (MF), mechanical vapor compression (MVC), and membrane distillation (MD) were simulated and optimized for different reuse destinations. Results indicated MF-RO as the cheapest route for salinities lower than 90 g/L, while FO-RO had the highest cost and could be unfeasible depending on salinity. For higher salt content, MF-ARO-RO was the cheapest alternative, followed by thermal processes (MF-MVC and FO-MVC, respectively). However, applicability of MVC depends on final water quality due to possible volatiles constraints. MF-ARO-RO process, which is a novel technology, was submitted to a retro-techno-economic analysis (RTEA) to investigate its potentialities. Although membrane parameters had minor influence, external parameters as ARO membrane cost, energy cost and interest rate play important roles on process cost.

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In this study, alginate and polyvinyl alcohol (PVA)-alginate entrapped nanoscale zero-valent iron (nZVI) was tested for structural evolution, chemical transformation, and metals/metalloids removal (Cu(II), Cr(VI), Zn(II), and As(V)) after 1-2 month passivation in model saline wastewaters from hydraulic fracturing. X-ray diffraction analysis confirmed successful prevention of Fe-0 corrosion by polymeric entrapment. Increasing ionic strength (I) from 0 to 4.10 M (deionized water to Day-90 fracturing wastewater (FWW)) with prolonged aging time induced chemical instability of alginate due to dissociation of carboxyl groups and competition for hydrogen bonding with nZVI, which caused high Na (7.17%) and total organic carbon (24.6%) dissolution from PVA-alginate entrapped nZVI after 2-month immersion in Day-90 FWW. Compared to freshly-made beads, 2-month aging of PVA-alginate entrapped nZVI in Day-90 FWW promoted Cu(II) and Cr(VI) uptake in terms of the highest removal efficiency (84.2% and 70.8%), pseudo-second-order surface area-normalized rate coefficient k(sa) (2.09 x 10(-1) L m(-2) h(-1) and 1.84 x 10(-1) L m(-2) h(-1)), and Fe dissolution after 8-h reaction (13.9% and 8.45%). However, the same conditions inhibited Zn(II) and As(V) sequestration in terms of the lowest removal efficiency (31.2% and 39.8%) by PVA-alginate nZVI and ksa (4.74 x 10(-2) Lm(-2) h(-1) and 6.15 x 10(-2) Lm(-2) h(-1)) by alginate nZVI. The X-ray spectroscopic analysis and chemical speciation modelling demonstrated that the difference in metals/metalloids removal by entrapped nZVI after aging was attributed to distinctive removal mechanisms: (i) enhanced Cu(II) and Cr(VI) removal by nZVI reduction with accelerated electron transfer after pronounced dissolution of non-conductive polymeric immobilization matrix; (ii) suppressed Zn(II) and As(V) removal by nZVI adsorption due to restrained mass transfer after blockage of surface-active micropores. Entrapped nZVI was chemically fragile and should be properly stored and regularly replaced for good performance. (C) 2017 Elsevier B.V. All rights reserved.

Abstract:
In this study, alginate and polyvinyl alcohol (PVA)-alginate entrapped nanoscale zero-valent iron (nZVI) was tested for structural evolution, chemical transformation, and metals/metalloids removal (Cu(II), Cr(VI), Zn(II), and As(V)) after 1-2 month passivation in model saline wastewaters from hydraulic fracturing. X-ray diffraction analysis confirmed successful prevention of Fe-0 corrosion by polymeric entrapment. Increasing ionic strength (I) from 0 to 4.10 M (deionized water to Day-90 fracturing wastewater (FWW)) with prolonged aging time induced chemical instability of alginate due to dissociation of carboxyl groups and competition for hydrogen bonding with nZVI, which caused high Na (7.17%) and total organic carbon (24.6%) dissolution from PVA-alginate entrapped nZVI after 2-month immersion in Day-90 FWW. Compared to freshly-made beads, 2-month aging of PVA-alginate entrapped nZVI in Day-90 FWW promoted Cu(II) and Cr(VI) uptake in terms of the highest removal efficiency (84.2% and 70.8%), pseudo-second-order surface area-normalized rate coefficient k(sa) (2.09 x 10(-1) L m(-2) h(-1) and 1.84 x 10(-1) L m(-2) h(-1)), and Fe dissolution after 8-h reaction (13.9% and 8.45%). However, the same conditions inhibited Zn(II) and As(V) sequestration in terms of the lowest removal efficiency (31.2% and 39.8%) by PVA-alginate nZVI and ksa (4.74 x 10(-2) Lm(-2) h(-1) and 6.15 x 10(-2) Lm(-2) h(-1)) by alginate nZVI. The X-ray spectroscopic analysis and chemical speciation modelling demonstrated that the difference in metals/metalloids removal by entrapped nZVI after aging was attributed to distinctive removal mechanisms: (i) enhanced Cu(II) and Cr(VI) removal by nZVI reduction with accelerated electron transfer after pronounced dissolution of non-conductive polymeric immobilization matrix; (ii) suppressed Zn(II) and As(V) removal by nZVI adsorption due to restrained mass transfer after blockage of surface-active micropores. Entrapped nZVI was chemically fragile and should be properly stored and regularly replaced for good performance. (C) 2017 Elsevier B.V. All rights reserved.

Abstract:
Forward osmosis is an emerging membrane based separation technology that could find niche applications in the treatment of oil and gas produced water. Here, the feasibility of treating hydraulic fracturing produced waters using a combined electrocoagulation (EC) and forward osmosis (FO) process has been investigated. EC is shown to be effective in removing suspended solids and organic compounds which foul the membrane during FO. The amount of suspended solids and organic compounds that are removed depends on the EC reaction time. By accounting for internal and external concentration polarization as well as fouling due to deposition on the feed side barrier surface of the FO membrane, the expected flux may be determined. The effectiveness of removal of suspended solids and organic compounds may be modeled as changes in the permeability of the foulant layer that develops on the feed side of the membrane. The results obtained for real produced waters from Southwestern Energy operations in the Fayetteville Shale indicate that combined EC and FO could be an effective method for water recovery from hydraulic fracturing produced waters.

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The state of Oklahoma has experienced a dramatic increase in the amount of measurable seismic activities over the last decade. The needs of a petroleum-driven world have led to increased production utilizing various technologies to reach energy reserves locked in tight formations and stimulate end-of-life wells, creating significant amounts of undesirable wastewater ultimately injected underground for disposal. Using Phased Array L-band Synthetic Aperture Radar (PALSAR) data, we performed a differential Synthetic Aperture Radar Interferometry (InSAR) technique referred to as the Small BAseline Subset (SBAS)-based analysis over east central Oklahoma to identify ground surface deformation with respect to the location of wastewater injection wells for the period of December 2006 to January 2011. Our results show broad spatial correlation between SBAS-derived deformation and the locations of injection wells. We also observed significant uplift over Cushing, Oklahoma, the largest above ground crude oil storage facility in the world, and a key hub of the Keystone Pipeline. This finding has significant implications for the oil and gas industry due to its close proximity to the zones of increased seismicity attributed to wastewater injection. Results southeast of Drumright, Oklahoma represent an excellent example of the potential of InSAR, identifying a fault bordered by an area of subduction to the west and uplift to the east. This differentiated movement along the fault may help explain the lack of any seismic activity in this area, despite the large number of wells and high volume of fluid injected.

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Abstract, Radioactive materials for the medical, technological, and industrial sectors have been effectively regulated in the United States since as early as 1962. The steady increase in the exploration and production of shale gas in recent years has led to concerns about exposures to Naturally Occurring Radioactive Materials (NORM) and Technologically Enhanced Naturally Occurring Radioactive Materials (TENORM) in oil and gas waste streams. This study applied policy surveillance methods to conduct a cross-sectional fifty-state survey of law and regulations of NORM and TENORM waste from oil and gas operations. Results indicated that seventeen states drafted express regulations to reduce exposure to oil and gas NORM and TENORM waste. States with active oil and gas drilling that lack regulations controlling exposure to NORM and TENORM may leave the public and workers susceptible to adverse health effects from radiation. The study concludes with recommendations in regard to regulating oil and gas NORM and TENORM waste.

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Dissolved organic matter (DOM) present in oil and gas (O&G) produced water and fracturing flowback was characterized and quantified by multiple analytical techniques throughout a hybrid biological-physical treatment process. Quantitative and qualitative analysis of DOM by liquid chromatography – organic carbon detection (LC-OCD), liquid chromatography–high-resolution mass spectrometry (LC-HRMS), gas chromatography–mass spectrometry (GC–MS), and 3D fluorescence spectroscopy, demonstrated increasing removal of all groups of DOM throughout the treatment train, with most removal occurring during biological pretreatment and some subsequent removal achieved during membrane treatment. Parallel factor analysis (PARAFAC) further validated these results and identified five fluorescent components, including DOM described as humic acids, fulvic acids, proteins, and aromatics. Tryptophan-like compounds bound by complexation to humics/fulvics were most difficult to remove biologically, while aromatics (particularly low molecular weight neutrals) were more challenging to remove with membranes. Strong correlation among PARAFAC, LC-OCD, LC-HRMS, and GC–MS suggests that PARAFAC can be a quick, affordable, and accurate tool for evaluating the presence or removal of specific DOM groups in O&G wastewater.

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This study evaluates and compares the performance of microbial fuel cells (MFCs) and microbial capacitive deionization cells (MCDCs) fed with wastewater produced from the Bakken shale. The produced water was characterized by high levels of dissolved solids and chemical oxygen demand (COD). Two-compartment MFCs and three-compartment MCDCs were evaluated under batch-fed mode using mixed microbial consortia in the anode, ferricyanide in the cathode, and produced water as the electrolyte in the anode and capacitive deionization units. COD removal in the MFCs was 88%, while that in the MCDCs was limited to 76%. The lower performance of the MCDCs was due to the large impedance (6600 Ω cm2) compared with the MFCs (870 Ω cm2). However, the MCDCs achieved two-fold higher removal of dissolved solids. Both the MFCs and MCDCs suffered from a higher impedance induced by fouling in the latter stages of the operation.

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In Pennsylvania, Appalachian oil and gas wastewaters (OGW) are permitted for release to surface waters after some treatment by centralized waste treatment (CWT) facilities. While this practice was largely discontinued in 2011 for unconventional Marcellus OGW, it continues for conventional OGW. This study aimed to evaluate the environmental implications of the policy allowing the disposal of conventional OGW. We collected stream sediments from three discharge sites receiving treated OGW between 2014-2017 and measured 228Ra, 226Ra, and their decay products, 228Th and 210Pb, respectively. We consistently found elevated activities of 228Ra and 226Ra in stream sediments in the vicinity of the outfall (total Ra = 90-25,000 Bq/kg) compared to upstream sediments (20-80 Bq/kg). In 2015 and 2017, 228Th/228Ra activity ratios in sediments from two disposal sites were relatively low (0.2-0.7), indicating that a portion of the Ra has accumulated in the sediments in recent (<3) years, when no unconventional Marcellus OGW was reportedly discharged. 228Ra/226Ra activity ratios were also higher than what would be expected solely from disposal of low 228Ra/226Ra Marcellus OGW. Based on these variations, we concluded that recent disposal of treated conventional OGW is the source of high Ra in stream sediments at CWT facility disposal sites. Consequently, policies pertaining to the disposal of only unconventional fluids are not adequate in preventing radioactive contamination in sediments at disposal sites, and the permission to release of treated Ra-rich conventional OGW through CWT facilities should be reconsidered.

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Abstract:
Forward osmosis (FO) has proven to be a robust, low-pressure membrane separation process capable of rejecting a broad range of contaminants; thus, providing a high quality diluted brine suitable for further desalination by reverse osmosis (RO). In this study, a pilot-scale FO-RO system treated >10,000 L of raw produced water from the Denver-Julesburg basin (Colorado) over a four-week period using commercially available FO and RO membranes. Overall, the FO-RO pilot system maintained >99% rejection of nearly all measured ions and >95% rejection of hydrocarbons such as semi-volatile linear aliphatic hydrocarbons and polycyclic aromatic hydrocarbons. Although the FO-RO system was able to treat raw produced water, high concentrations of organic compounds severely fouled the FO membrane and substantially reduced water flux by 68% within 21 days. Membrane degradation due to interaction between organic constituents such as aliphatic and aromatic hydrocarbons and the membrane polymer may have compromised the FO membranes, resulting in substantial increase (×15) in reverse salt flux within 21 days. Further investigations of membrane cleaning and pretreatment will be required in order to better understand the overall economic feasibility of treating raw produced water using FO.

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Ozonation, sorption to granular activated carbon and aerobic degradation were compared as potential treatment methods for removal of dissolved organic carbon (DOC) fractions and selected organic compounds from shale gas flowback water after pre-treatment in dissolved air flotation unit. Flowback water was characterised by high chemical oxygen demand and DOC. Low molecular weight (LMW) acids and neutral compounds were the most abundant organic fractions, corresponding to 47% and 35% of DOC respectively. Ozonation did not change distribution of organic carbon fractions and concentrations of detected individual organic compounds significantly. Sorption to activated carbon targeted removal of individual organic compounds with molecular weight >115 Da, whereas LMW compounds remained largely unaffected. Aerobic degradation was responsible for removal of LMW compounds and partial ammonium removal, whereas formation of intermediates with molecular weight of 200–350 Da was observed. Combination of aerobic degradation for LMW organics removal with adsorption to activated carbon for removal of non-biodegradable organics is proposed to be implemented between pre-treatment (dissolved air floatation) and desalination (thermal or membrane desalination) steps.

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Rapid growth of hydraulic fracturing for shale gas within the USA and the possibility of shale developments within Europe has created public concern about the risks of spills and leaks associated with the industry. Reports from the Texas Railroad Commission (1999 to 2015) and the Colorado Oil and Gas Commission (2009 to 2015) were used to examine spill rates from oil and gas well pads. Pollution incident records for England and road transport incident data for the UK were examined as an analogue for potential offsite spills associated with transport for a developing shale industry. The Texas and Colorado spill data shows that the spill rate on the well pads has increased over the recorded time period. The most common spill cause was equipment failure. Within Colorado 33% of the spills recorded were found during well pad remediation and random site inspections. Based on data from the Texas Railroad Commission, a UK shale industry developing well pads with 10 lateral wells would likely experience a spill for every 16 well pads developed. The same well pad development scenario is estimated to require at least 2856 tanker movements over two years per well pad. Considering this tanker movement estimate with incident and spill frequency data from UK milk tankers, a UK shale industry would likely experience an incident on the road for every 12 well pads developed and a road spill for every 19 well pads developed. Consequently, should a UK shale industry be developed it is important that appropriate mitigation strategies are in place to minimise the risk of spills associated with well pad activities and fluid transportation movements.

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This study investigates the flowback water impacts on the corrosion of mild steel pipelines used to transport the saline wastewater generated during fracturing of the Bakken shale. The uniform corrosion rates were high under acidic conditions compared to those under neutral and alkaline conditions. The pitting attack on the flowback water pipelines was 100-fold and 10-fold higher for acidic and alkaline conditions, respectively, than those for the neutral conditions. The corrosion deposits on the mild steel were characterized by a large specific surface area and high reactivity. These results suggest that the flowback water pipelines become a potential source of contaminants that threaten agricultural land and water resources.

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Water touches most segments of the petroleum industry and thus cost-effective water management is a key part of oil & gas industry operations. The water to be managed is either co-produced with the hydrocarbons, generated as a by-product from oil/gas processing, and/or utilized to support production operations. While a majority of the water usually receives basic treatment, there are multiple recent drivers for advanced treatment that should facilitate beneficial water reuse. Hence, a toolbox of advanced technologies needs to be considered to ensure that fit for purpose treatment is deployed. Membrane processes are key components of the technology toolbox since they include some of the best available technologies. This paper provides an overview of the various case studies from ConocoPhillips global projects portfolio, which covered various operations such as gas fields, oil fields, oil sands & shale plays. In these case studies, a wide spectrum of membrane processes, including membrane bioreactors, reverse osmosis, microfiltration, ultrafiltration, nanofiltration, ceramic membranes, forward osmosis, membrane distillation, pressure retarded osmosis, membrane contactors, and/or new innovative membrane materials were either installed at full scale capacity, evaluated via field/lab testing, or investigated through desktop studies. The information presented demonstrates that reverse osmosis and nanofiltration are widely utilized by the industry for water desalination and desulfating, respectively. In addition, membrane filtration and bioreactors are frequently applied as standalone treatments for inorganics and organics removal, respectively; or as pretreatment to desalination membranes. Novel membrane technologies and materials are also being developed by the industry for niche applications.

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Produced water originated from oil and gas production wells was treated by a pilot-scale system including pre-treatment (chemical precipitation), pre-filtration, and post-filtration units. Pre-filtration unit consisted of sand filter, granulated activated carbon (GAC) filter, and ultrafiltration (UF) membrane. Post-filtration unit included reverse osmosis (RO) membrane unit. In this study, two different RO membranes including sea water (SW) and brackish water (BW) membranes were comparatively evaluated in terms of treatment and filtration performance. Besides, a cost analysis was conducted for a real scale RO membrane unit by using the data obtained from the pilot plant study. Average fluxes of 12.7 and 9.4 L/m2 h were obtained by SW and BW membrane units, respectively. Higher COD and conductivity removal efficiencies were obtained by SW membrane in comparison to BW membrane. Total cost of 0.88 €/m3 was estimated for a RO plant treating produced water with a flowrate capacity of 300 m3/d.

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A thin-film composite, bicontinuous cubic lyotropic liquid crystal polymer (TFC Q(I)) membrane with uniformsize, ionic nanopores was studied for the treatment of hydraulic fracturing flowback water. The TFC QI membrane performance was compared to those of a commercial nanofiltration (NF) membrane (NF270) and a commercial reverse osmosis (RO) membrane (SW30HR) for the filtration of flowback water from the Denver-Julesburg Basin. The permeability, salt rejection, and organic solute rejection for each membrane was evaluated. The results illustrate that the TFC QI membrane maintained its performance to a similar degree as the commercial NF and RO membranes while demonstrating a unique selectivity not observed in the commercial membranes. Specifically, the TFC QI membrane rejected 75% of the salt while recovering 9.6% of the dissolved organic carbon (DOC) and 50% of the water. Of particular interest was the recovery of labile DOC, which was assessed through biodegradation experiments. Analysis following biodegradation of the TFC QI membrane permeate demonstrates the membrane's ability to recover labile DOC in a reduced-saline permeate. Improved recovery of labile DOC (increased to 22%) was demonstrated by reducing the pH of the flowback water. Therefore, the selectivity of the TFC QI membrane provides an opportunity to recover resources from hydraulic fracturing flowback.

Abstract:
Hydraulic fracturing (HF) has allowed for the utilization of previously unattainable shale oil and gas (O&G) resources. After HF is complete, the waters used to increase the facies' permeability return uphole as wastewaters. When these waters return to the surface, they are characterized by complex organic and inorganic chemistry, and can pose a health risk if not handled correctly. Therefore, these waters must be treated or disposed of properly. However, the variability of these waters' chemical composition over time is poorly understood and likely limits the applicability of their reuse. This study examines the water chemistry of a hydraulically fractured site in the Niobrara formation throughout the flowback period. Samples were collected every other day for the first 18days, then on a regular basis for three months. We identified HF fluid additives, including benzalkonium chlorides (BACs), alkyl ethoxylates (AEOs), and polyethylene glycols (PEGs), as well as geogenic components present in flowback and produced waters, their overall temporal pattern, and variables affecting the reuse of these waters. Observations indicate that alkalinity and iron may limit the reuse of these waters in HF, while chloride and alkalinity may limit the use of these waters for well-casing cement. The presence of numerous surfactant homologs, including biocides, was also observed, with the highest levels at the beginning of the flowback period. Principal component analysis identified three unique groupings in the chemical data that correspond to different stages in the flowback period: (1) the flowback stage (days 1-2); (2) the transition stage (days 6-21); and (3) the produced water stage (days 21-87). Results from this study will be important when designing decision frameworks for assessing water treatment options, particularly if onsite treatment is attempted. Successful reclamation of these waters may alleviate stress on water resources that continues to negatively impact the U. S.

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Purpose of ReviewIn this study, we compile and curate data from 2012, 2013, and 2014 on flared gas and generated wastewater associated with hydraulic fracturing operations in seven major shale regions of the USA. In the process, we provide an historical perspective of the management practices of flared gas and wastewater prior to the decline in oil prices in 2015. An engineering assessment of the technical potential for repurposing the energy from flared gas for treating hydraulic fracturing wastewater is also considered.Recent FindingsThe seven shale regions were evaluated using mass balances and thermodynamic analysis of the wastewater and flared gas volumes using data compiled from state, federal, and private sources for each region. After curating the publicly available data, we determined that from 2012 through 2014, the Bakken, Marcellus, Utica, and Niobrara flared between 2 and 48 times the amount of natural gas needed to provide energy for treatment of the wastewater produced from the oil and gas industry. The Permian Basin, Eagle Ford, and Haynesville did not have sufficient flared gas to treat the wastewater produced in each respective region and thus would need other energy sources for water and wastewater treatment.SummaryThe findings indicate that novel approaches to managing existing resources and waste streams might have the potential to improve the environmental footprint and economic productivity of select oil and gas sites.

Abstract:
Approximately 81% of the nation's energy demands are supported by hydrocarbons, largely in part to the relatively recent exploration of oil and gas from unconventional shale energy reserves. The extraction of shale energy requires technological ingenuity, such as hydraulic fracturing and horizontal drilling, and significant freshwater resources to successfully recover the previously sequestered hydrocarbons from low porosity formations. As unconventional oil and gas development continues to expand to meet the growing energy demands, it becomes increasingly more important to understand the potential environmental implications and to practice proper environmental stewardship. For example, concerns over water usage and the related consequences have dramatically increased due to the demand for water used in hydraulic fracturing, the increased volumes of wastewater being produced, and the need to dispose of or reuse the wastewater without compromising the surface and subsurface environments. As such, this chapter will cover the life cycle of water in oil and gas development (conventional and unconventional), including water use and waste production in the drilling, stimulation, and production phases; the current waste management strategies and challenges within the various treatment modalities; and the widespread implications of the varying forms of waste management.

Abstract:
One promising water management strategy during hydraulic fracturing is treatment and reuse of flowback/produced water. In particular, the saline flowback water contains many of the chemicals employed for fracking, which need to be removed before possible reuse as “frac water.” This manuscript targets one of the additives; borate-based cross-linkers used to adjust the rheological characteristics of the frac-fluid and turbidity. Alum and ferric chloride were evaluated as coagulants for clarification and boron removal from saline flowback water obtained from a well in the Eagle Ford shale. Extremely high dosages (>9000 mg/L or 333 mM Al and 160 mM Fe) corresponding to Al/B and Fe/B mass ratios of ∼70 and molar ratios of ∼28 and 13 respectively were necessary to remove ∼80% boron. Hence, coagulation does not appear to be feasible for boron removal from high-strength waste streams. X-ray photoelectron spectroscopy revealed BO bonding on surfaces of freshly precipitated Al(OH)3(am) and Fe(OH)3(am) suggesting boron uptake was predominantly via ligand exchange. Attenuated total reflection-Fourier transform infrared spectroscopy provided direct evidence of inner-sphere boron complexation with surface hydroxyl groups on both amorphous aluminum and iron hydroxides. Only trigonal boron was detected on aluminum flocs since possible presence of tetrahedral boron was masked by severe AlO interferences. Both trigonal and tetrahedral conformation of boron complexes were identified on Fe(OH)3 surfaces.

Abstract:
Rising global energy demands associated to unbalanced allocation of water resources highlight the importance of water management solutions for the gas industry. Advanced drilling, completion and stimulation techniques for gas extraction, allow more economical access to unconventional gas reserves. This stimulated a shale gas revolution, besides tight gas and coalbed methane, also causing escalating water handling challenges in order to avoid a major impact on the environment. Hydraulic fracturing allied to horizontal drilling is gaining higher relevance in the exploration of unconventional gas reserves, but a large amount of wastewater (known as “produced water”) is generated. Its variable chemical composition and flow rates, together with more severe regulations and public concern, have promoted the development of solutions for the treatment and reuse of such produced water. This work intends to provide an overview on the exploration and subsequent environmental implications of unconventional gas sources, as well as the technologies for treatment of produced water, describing the main results and drawbacks, together with some cost estimates. In particular, the growing volumes of produced water from shale gas plays are creating an interesting market opportunity for water technology and service providers. Membrane-based technologies (membrane distillation, forward osmosis, membrane bioreactors and pervaporation) and advanced oxidation processes (ozonation, Fenton, photocatalysis) are claimed to be adequate treatment solutions.

Abstract:
The extraction of unconventional hydrocarbons, particularly through hydraulic fracturing (‘fracking’), has generated both support and opposition in many countries around the globe. Along with arguments about economic benefits, decarbonisation, transition fuels and groundwater contamination, etc., the rapid expansion of this industry presents a pressing problem as regards the disposal of the resultant waste – including drilling and cutting material, oil and gas residues, various chemicals used in the process, salts and produced water. One putative solution – ‘landfarming’ – is a disposal process that involves spreading oil and gas waste on to land and mixing it with topsoil to allow bioremediation of the hydrocarbons. This paper examines the case of landfarming in New Zealand where the practice has proved controversial due to its association with fracking, fears about the contamination of agricultural land and potential danger to milk supplies. Drawing upon Gieryn’s notion of cultural cartography and boundary work as well as the literature on the politics of scale it analyses the struggles for epistemic authority regarding the safety of landfarming. The paper concludes that scalar practices were central to the production of knowledge (and ignorance) in these credibility struggles, and that the prevailing cultural cartography of knowledge remained the arbiter and basis for policy. The case has wider implications in terms of the management of waste from unconventional hydrocarbons as well as other environmental issues in which the politics of scale figure in contested knowledge claims.

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The Permian Basin is being transformed by the “shale revolution” from a major conventional play to the world’s largest unconventional play, but water management is critical in this semiarid region. Here we explore evolving issues associated with produced water (PW) management and hydraulic fracturing water demands based on detailed well-by-well analyses. Our results show that although conventional wells produce ∼13 times more water than oil (PW to oil ratio, PWOR = 13), this produced water has been mostly injected back into pressure-depleted oil-producing reservoirs for enhanced oil recovery. Unconventional horizontal wells use large volumes of water for hydraulic fracturing that increased by a factor of ∼10–16 per well and ∼7–10 if normalized by lateral well length (2008–2015). Although unconventional wells have a much lower PWOR of 3 versus 13 from conventional wells, this PW cannot be reinjected into the shale reservoirs but is disposed into nonproducing geologic intervals that could result in overpressuring and induced seismicity. The potential for PW reuse from unconventional wells is high because PW volumes can support hydraulic fracturing water demand based on 2014 data. Reuse of PW with minimal treatment (clean brine) can partially mitigate PW injection concerns while reducing water demand for hydraulic fracturing.

Abstract:
Each of the three earthquake sequences in Oklahoma in 2016—Fairview, Pawnee, and Cushing—appears to have been induced by high-volume wastewater disposal within 10 km. The Fairview M5.1 main shock was part of a 2 year sequence of more than 150 events of M3, or greater; the main shock accounted for about half of the total moment. The foreshocks and aftershocks of the M5.8 Pawnee earthquake were too small and too few to contribute significantly to the cumulative moment; instead, nearly all of the moment induced by wastewater injection was focused on the main shock. The M5.0 Cushing event is part of a sequence that includes 48 earthquakes of M3, or greater, that are mostly foreshocks. The cumulative moment for each of the three sequences during 2016, as well as that for the 2011 Prague, Oklahoma, and nine other sequences representing a broad range of injected volume, are all limited by the total volumes of wastewater injected locally.

Abstract:
Nano-Fe-Co/gamma-Al2O3 catalyst synthesized using the homogeneous precipitation method, and used for heterogeneous Fenton degradation of hydraulic fracturing wastewater in laboratory. The catalysts were characterized by SEM-EDS, XRD, XPS, XRF, BET and FT-IR. The results showed that FeOOH, and CoO are the main catalytically active component. The effects of different reaction parameters such as initial pH, H2O2 dosage and catalyst amount were assessed. Results indicated that maximum removal rate of COD 57.8% occurred at the H2O2 concentration and catalyst dosage were 40 mmolL(-1) 4 gL(-1) and 4 gL(-1), respectively in 90 min. The recycled catalyst was capable of repeating four cycle without a significant decrease in treatment efficiency, and this demonstrated the durability of catalyst. These results indicate the potential of the heterogeneous Fenton system in engineering applications for advanced treatment of fracturing wastewater.

Abstract:
Production of oil from shale and tight reservoirs accounted for almost 50% of 2016 total U.S. production and is projected to continue growing. The objective of our analysis was to quantify the water outlook for future shale oil development using the Eagle Ford Shale as a case study. We developed a water outlook model that projects water use for hydraulic fracturing (HF) and flowback and produced water (FP) volumes based on expected energy prices; historical oil, natural gas, and water-production decline data per well; projected well spacing; and well economics. The number of wells projected to be drilled in the Eagle Ford through 2045 is almost linearly related to oil price, ranging from 20,000 wells at $30/barrel (bbl) oil to 97,000 wells at $100/bbl oil. Projected FP water volumes range from 20% to 40% of HF across the play. Our base reference oil price of $50/bbl would result in 40,000 additional wells and related HF of 265×109 gal and FP of 85×109gal. The presented water outlooks for HF and FP water volumes can be used to assess future water sourcing and wastewater disposal or reuse, and to inform policy discussions.

Abstract:
The use of hydraulic fracturing for shale oil and gas development generates large quantities of flowback and produced (F/P) water as by-products. The current high treatment cost of F/P water inhibits development and profitability of shale oil and gas. The Integrated Precipitative Supercritical (IPSC) process, developed at Ohio University, could remediate F/P water produced from hydraulic fracturing with significantly lower costs than current practices. The objective of this paper is to present results of a techno-economic analysis of the IPSC process using Aspen (R) process software and Microsoft Excel. The Aspen (R) model was used to simulate the IPSC process with its output used as input for the cost analysis. Results indicated an average cost of $6.33 per barrel of F/P water treatment with a possible range from $2.93/bbl to $16.03/bbl determined through sensitivity analyses. The results further indicate that the IPSC process is economically competitive compared to existing practices. (C) 2017 Elsevier Ltd. All rights reserved.

Abstract:
Combining horizontal drilling with high volume hydraulic fracturing has increased extraction of hydrocarbons from low-permeability oil and gas (O accompanied by increased wastewater production. Surface water discharges of O&G wastewater by centralized waste treatment (CWT) plants pose risks to aquatic and human health. We evaluated the impact of surface water disposal of O&G wastewater from CWT plants upstream of the Conemaugh River Lake (dam controlled reservoir) in western Pennsylvania. Regulatory compliance data were collected to calculate annual contaminant loads (Ba, Cl, total dissolved solids (TDS)) to document historical industrial activity. In this study, two CWT plants 10 and 19 km upstream of a reservoir left geochemical signatures in sediments and porewaters corresponding to peak industrial activity that occurred 5 to 10 years earlier. Sediment cores were sectioned for the collection of paired samples of sediment and porewater, and analyzed for analytes to identify unconventional O&G wastewater disposal. Sediment layers corresponding to the years of maximum O&G wastewater disposal contained higher concentrations of salts, alkaline earth metals, and organic chemicals. Isotopic ratios of 226Ra/228Ra and 87Sr/86Sr identified that peak concentrations of Ra and Sr were likely sourced from wastewaters that originated from the Marcellus Shale formation.

Abstract:
Direct contact membrane distillation (DCMD) has immense potential in the desalination of highly saline waste-waters where reverse osmosis is not feasible. This study evaluated the potential of DCMD for treatment of produced water generated during extraction of natural gas from unconventional (shale) reservoirs. Exhaust stream from Natural Gas Compressor Station (NG CS), which has been identified as a potential waste heat source, can be used to operate DCMD thereby providing economically viable option to treat high salinity produced water. An ASPEN Plus simulation of DCMD for the desalination of produced/saline water was developed in this study and calibrated using laboratory-scale experiments. This model was used to optimize the design and operation of large scale systems and estimate energy requirements of the DCMD process. The concept of minimum temperature approach used in heat exchanger design was applied to determine the optimum membrane area for large scale DCMD plants. Energy analysis revealed that the waste heat available from NG CS is sufficient to concentrate all the produced water generated in Pennsylvania to 30 wt% regardless of its initial salinity. (C) 2017 Elsevier B.V. All rights reserved.

Abstract:
Exploration and production of oil and gas (O&G) generates large volumes of wastewater. High salinity and the presence of both dissolved constituents and suspended solids require complex and expensive treatment of O&G produced waters for beneficial reuse (e.g., fracking, irrigation, surface water discharge). Nearly 90% of wastewater produced during the lifetime of O&G wells is currently disposed of due to the high cost of treatment; thus, simple and inexpensive treatment technologies and approaches must be developed to promote water reuse in the O&G industry. In this study we investigated the potential for publicly owned wastewater treatment plants to co-treat produced water and residential waste-water. The removal of organic compounds, nutrients, metals, trace organic compounds, and suspended solids from the combined stream was investigated using a pilot-scale hybrid sequencing batch reactor-membrane bioreactor system. Produced water was initially dosed at 6% by volume, and comparable removal of primary (i.e., chemical oxygen demand, ammonia) and secondary constituents (i.e., trace organic compounds, inorganic contaminants) to control conditions was achieved. When produced water was increased to 20% of the influent by volume, nitrification was lost; however, the dominant biological communities in the bioreactors remained stable, providing evidence of an adaptive system and reliance on non-dominant microorganisms to achieve optimal treatment.

Abstract:
Shale gas drilling flowback fluid (SGDF) generated during shale gas extraction is of great concern due to its high total dissolved solid, radioactive elements and organic matter. To remove the toxic and refractory pollutants in SGDF and improve its biodegradability, a microsacle Fe0/Persulfate/O3 process (mFe0/PS/O3) was developed to pretreat this wastewater obtained from a shale gas well in southwestern China. First, effects of mFe0 dosage, O3 flow rate, PS dosage, pH values on the treatment efficiency of mFe0/PS/O3 process were investigated through single-factor experiments. Afterward, the optimal conditions (i.e., pH = 6.7, mFe0 dosage = 6.74 g/L, PS = 16.89 mmol/L, O3 flow rate = 0.73 L/min) were obtained by using response surface methodology (RSM). Under the optimal conditions, high COD removal (75.3%) and BOD5/COD ratio (0.49) were obtained after 120 min treatment. Moreover, compared with control experiments (i.e., mFe0, O3, PS, mFe0/O3, mFe0/PS, O3/PS), mFe0/PS/O3 system exerted better performance for pollutants removal in SGDF due to strong synergistic effect between mFe0, PS and O3. In addition, the decomposition or transformation of the organic pollutants in SGDF was analyzed by using GC-MS. Finally, the reaction mechanism of the mFe0/PS/O3 process was proposed according to the analysis results of SEM-EDS and XRD. It can be concluded that high-efficient mFe0/PS/O3 process was mainly resulted from the combination effect of direct oxidation by ozone and persulfate, heterogeneous and homogeneous catalytic oxidation, Fenton-like reaction and adsorption. Therefore, mFe0/PS/O3 process was proven to be an effective method for pretreatment of SGDF prior to biological treatment.

Abstract:
High volumes of flowback and produced water are generated everyday as a byproduct of hydraulic fracturing operations and shale gas developments across the United States. Since most shale gas developments are located in semi-arid to arid U.S. regions close to agricultural production, there are many opportunities for reusing these waters as potential alternatives or supplements to fresh water resources for irrigation activities. However, the impacts of high salinity and total organic content of these types of water on crop physiological parameters and plant growth needs to be investigated to determine their utility and feasibility. The aim of the present study was to evaluate the response of switchgrass and rapeseed to treated produced water as an irrigation water source. In this greenhouse study, the influence of produced water at four total organic carbon (TOC) concentrations [1.22, 38.3, 232.2 and 1352.4 mg/l] and three total dissolved solids (TDS) levels [400,3,500, and 21,000 mg/l] on rapeseed (Brassica napus L.) and switchgrass (Panicum virgatum L.), two relatively salt-tolerant, non-food, biofuel crops, was studied. Seedling emergence, biomass yield, plant height, leaf electrolyte leakage, and plant uptake were evaluated. Irrigation water with the highest salinity and TOC concentration resulted in significantly lower growth health and physiological characteristics of both crop species. The organic content of the produced water had a negative impact on biomass yield and physiological parameters of both species. The results of this study could be valuable for regulators and stakeholders in development of treatment standards in which organic matter should be removed to less than 50 mg/l to keep leaf EL (cell damage) to less than 50% and a TOC concentration of less than 5 mg/l required to keep a sustainable biomass production rate.

Abstract:
Organic contaminants in shale gas flowback and produced water (FPW) are traditionally expressed as total organic carbon (TOC) or chemical oxygen demand (COD), though these parameters do not provide information on the toxicity and environmental fate of individual components. This review addresses identification of individual organic contaminants in FPW, and stresses the gaps in the knowledge on FPW composition that exist so far. Furthermore, the risk quotient approach was applied to predict the toxicity of the quantified organic compounds for fresh water organisms in recipient surface waters. This resulted in an identification of a number of FPW related organic compounds that are potentially harmful namely those compounds originating from shale formations (e.g. polycyclic aromatic hydrocarbons, phthalates), fracturing fluids (e.g. quaternary ammonium biocides, 2-butoxyethanol) and downhole transformations of organic compounds (e.g. carbon disulphide, halogenated organic compounds). Removal of these compounds by FPW treatment processes is reviewed and potential and efficient abatement strategies are defined.

Abstract:
This paper is the first of a two-part series designed to assess and summarize extant knowledge regarding hydraulic fracturing water and wastewater management practices using a comparative, multidisciplinary approach. To provide context for both papers, the water and wastewater practices are summarized for the four focus plays: Montney, Duvernay, Barnett, and Marcellus. In Alberta and British Columbia, which host the less-studied Duvernay and Montney plays, play-scale unconventional water and wastewater data are extracted and combined from three databases: FracFocus.ca, geoSCOUT, and AccuMap. A reasonable picture of hydraulic fracturing water use and practices in western Canada emerges from the over 4,000 wells studied. From late 2011 to early 2014, the average number of fracturing stages reported increased from 7 to over 14, while reported cumulative water use approached approximately 15 million m3 in 2013, the first year for which full data in all three databases was available. The majority of wells consuming 10,000 to 50,000 m3 of water are slickwater type, located largely in the two target plays; however, several wells using >50,000 m3 of water appear in the Horn River Formation in BC. While it is possible to identify in the databases wastewater treatment facilities and deep wastewater injection wells, it is at present difficult to constrain wastewater disposal practices and chemistry in Alberta and British Columbia. The analysis points to the need for further coordination between academics, industry, and governmental agencies to develop publicly available, searchable databases that carefully document water sourcing, wastewater recycling/reuse/disposal, and chemistry, in order to properly form hydraulic fracturing water management strategies.

Abstract:
The present study explores the feasibility of using the electrocoagulation (EC) process for the treatment and reuse of wastewater produced during shale gas recovery by hydraulic fracturing. The electrocoagulation process has been evaluated for the removal of suspended solids, total organic carbon (TOC) and scale (hardness) causing divalent cations, which, if untreated, can clog the gas well. Experiments were performed with actual shale gas wastewater (ASWW), synthetic shale gas wastewater prepared with low concentration of dissolved salts (SSWW – LDS) and synthetic shale gas wastewater prepared with a high concentration of dissolved salts (SSWW – HDS). EC is found to be effective for removing TOC and hardness from both the actual and synthetic shale gas wastewaters. The electric energy required per unit mass (EEM) for removal of TOC for ASWW, SSWW – LDS and SSWW – HDS are 243, 102 and 70 kWh/kg respectively. The EEM for removal of hardness for ASWW, SSWW – LDS and SSWW – HDS are 303, 104 and 25 kWh/kg respectively. The high conductivity of SSWW – HDS helps in achieving higher currents and hence the lower reported EEM values for SSWW – HDS. Also, under alkaline conditions, the performance of EC increases significantly. Combination of aeration with EC is also found to increase the performance of EC, especially for wastewater containing high concentrations of chloride ions.

Abstract:
Shale gas has emerged as a potential resource to transform the global energy market. Nevertheless, gas extraction from tight shale formations is only possible after horizontal drilling and hydraulic fracturing, which generally demand large amounts of water. Part of the ejected fracturing fluid returns to surface as flowback water, containing a variety of pollutants. For this reason, water reuse and water recycling technologies have received further interest for enhancing overall shale gas process efficiency and sustainability. Water pre-treatment systems (WPSs) can play an important role for achieving this goal. This paper introduces a new optimization model for WPS simultaneous synthesis, especially developed for flowback water from shale gas production. A multistage superstructure is proposed for the optimal WPS design, including several water pre-treatment alternatives. The mathematical model is formulated via generalized disjunctive programming (GDP) and solved by reformulation as a mixed-integer nonlinear programming (MINLP) problem, to minimize the total annualized cost. Hence, the superstructure allows identifying the optimal pre-treatment sequence with minimum cost, according to inlet water composition and wastewater-desired destination (i.e., water reuse as fracking fluid or recycling). Three case studies are performed to illustrate the applicability of the proposed approach under specific composition constraints. Thus, four distinct flowback water compositions are evaluated for the different target conditions. The results highlight the ability of the developed model for the cost-effective WPS synthesis, by reaching the required water compositions for each specified destination.

Abstract:
We report the 5,425,832 bp draft genome of Pseudomonas sp. strain BDAL1, recovered from a Bakken shale hydraulic fracturing-produced water tank metagenome. Genome annotation revealed several key biofilm formation genes and osmotic stress response mechanisms necessary for survival in hydraulic fracturing-produced water.

Abstract:
This paper introduces a new optimization model for the single and multiple-effect evaporation (SEE/MEE) systems design, including vapor recompression cycle and thermal integration. The SEE/MEE model is specially developed for shale gas flowback water desalination. A superstructure is proposed to solve the problem, comprising several evaporation effects coupled with intermediate flashing tanks that are used to enhance thermal integration by recovering condensate vapor. Multistage equipment with intercooling is used to compress the vapor formed by flashing and evaporation. The compression cycle is driven by electricity to operate on the vapor originating from the SEE/MEE system, providing all the energy needed in the process. The mathematical model is formulated as a nonlinear programming (NLP) problem optimized under GAMS software by minimizing the total annualized cost. The SEE/MEE system application for zero liquid discharge (ZLD) is investigated by allowing brine salinity discharge near to salt saturation conditions. Additionally, sensitivity analysis is carried out to evaluate the optimal process configuration and performance under distinct feed water salinity conditions. The results highlight the potential of the proposed model to cost-effectively optimize SEE/MEE systems by producing fresh water and reducing brine discharges and associated environmental impacts.

Abstract:
Management of shale gas wastewater treatment, disposal, and reuse has become a significant environmental challenge, driven by an ongoing boom in development of U.S. shale gas reservoirs. Systems-analysis based decision support is helpful for effective management of wastewater, and provision of cost-effective decision alternatives from a whole-system perspective. Uncertainties are inherent in many modeling parameters, affecting the generated decisions. In order to effectively deal with the recourse issue in decision making, in this work a two-stage stochastic fracturing wastewater management model, named TSWM, is developed to provide decision support for wastewater management planning in shale plays. Using the TSWM model, probabilistic and nonprobabilistic uncertainties are effectively handled. The TSWM model provides flexibility in generating shale gas wastewater management strategies, in which the first-stage decision predefined by decision makers before uncertainties are unfolded is corrected in the second stage to achieve the whole-system’s optimality. Application of the TSWM model to a comprehensive synthetic example demonstrates its practical applicability and feasibility. Optimal results are generated for allowable wastewater quantities, excess wastewater, and capacity expansions of hazardous wastewater treatment plants to achieve the minimized total system cost. The obtained interval solutions encompass both optimistic and conservative decisions. Trade-offs between economic and environmental objectives are made depending on decision makers’ knowledge and judgment, as well as site-specific information. The proposed model is helpful in forming informed decisions for wastewater management associated with shale gas development.

Abstract:
Hydraulic fracturing used for natural gas extraction from unconventional onshore resources generates large quantities of produced water that needs to be managed efficiently and economically to ensure sustainable development of this industry. Membrane distillation can serve as a cost effective method to treat produced water due to its low energy requirements, especially if waste heat is utilized for its operation. This study evaluated the performance of commercially available hydrophobic microfiltration membranes in a direct contact membrane distillation system for treating very high salinity (i.e., up to 300,000 mg/L total dissolved solids) produced water. Polypropylene and polytetrafluoroethylene membranes yielded the highest permeate flux with membrane distillation coefficient of 5.6 l/m2/hr/kPa (LMH/kPa). All membranes showed excellent rejection of dissolved ions, including naturally occurring radioactive material (NORM), which is a significant environmental concern with this high salinity wastewater. Analysis of membranes after extended testing with actual produced waters revealed unevenly distributed inorganic deposits with significant iron content. A key finding of this study is that the iron oxide fouling layer had negligible effect on membrane performance over extended period of time despite its thickness of up to 12 µm. The results of this study highlight the potential for employing membrane distillation to treat high salinity wastewaters from unconventional gas extraction.