Special Issue "Advanced Technologies for Produced Water Management, Treatment, and Reuse"

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Wastewater Treatment and Reuse".

Deadline for manuscript submissions: 30 June 2021.

Special Issue Editors

Prof. Dr. Pei Xu
E-Mail Website
Guest Editor
Department of Civil Engineering, New Mexico State University, Las Cruces, NM 88003, USA
Interests: desalination; water reuse; membrane processes; photocatalysis; contaminants of emerging concern; produced water treatment; concentrate treatment; advanced nanomaterials for water treatment
Special Issues and Collections in MDPI journals
Dr. Yanyan Zhang
E-Mail Website
Guest Editor
New Mexico State University, Las Cruces, NM 88003, USA
Interests: pathogen detection and inactivation; bacterial adhesion, biofilm, and their resistance to disinfection processes; antibiotic resistance in urban and natural environments; fate and transport of CECs in natural and engineered systems; integrated biochemical and physicochemical treatment systems

Special Issue Information

Dear Colleagues,

Substantial volumes of wastewater are produced every day during oil and natural gas production operations. Produced water is typically disposed of via deep-well injection in oil- and gas-producing regions. Meanwhile, a large amount of fresh water is used for hydraulic fracturing. The reuse of produced water can reduce the volume of water that requires disposal and provide a new source of water for beneficial uses.

This Special Issue is designed to collect original research and review articles focusing on advanced technologies for produced water management, treatment, and use. This Special Issue brings together emerging approaches, challenges, and opportunities related to produced water with the ultimate aim to accelerate the development of innovative technologies, combinations or enhancements of existing technologies, and technological and economic assessment of produced water treatment and reuse. Subject areas may include, but are not limited to, the following:

  • Innovative technologies for the treatment of produced water and fracturing flowback water, such as pretreatment, desalination, advanced oxidation processes, natural treatment systems, etc.;
  • Methods and case studies for produced water management and reuse;
  • Characterization methods for produced water analysis, monitoring, and assessment;
  • Concentrate and waste management;
  • Technologies for resource recovery from produced water;
  • Techno-economic analyses of technologies;

Decision support tools for produced water management.

Dr. Pei Xu
Dr. Yanyan Zhang
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Water is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • produced water
  • oil and gas production
  • treatment technologies
  • water management
  • water reuse
  • desalination
  • advanced oxidation
  • techno-economic analysis
  • water quality analysis

Published Papers (14 papers)

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Research

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Article
Effect of the Aerobic Denitrifying Bacterium Pseudomonas furukawaii ZS1 on Microbiota Compositions in Grass Carp Culture Water
Water 2021, 13(10), 1329; https://doi.org/10.3390/w13101329 - 11 May 2021
Viewed by 389
Abstract
Background: Although functional bacteria are widely used in aquaculture water treatment, whether they affect the indigenous microbiota and whether the impact is persistent remain unclear. Therefore, we aimed to explore the denitrification effect of Pseudomonas furukawaii ZS1 isolated from a grass carp culture [...] Read more.
Background: Although functional bacteria are widely used in aquaculture water treatment, whether they affect the indigenous microbiota and whether the impact is persistent remain unclear. Therefore, we aimed to explore the denitrification effect of Pseudomonas furukawaii ZS1 isolated from a grass carp culture pond in nitrogen-rich aquaculture water, and determine whether its effect on the microbiota structure of the aquaculture water was persistent. Methods: Three each of treatment and control groups were set up, and P. furukawaii ZS1 was added to the treatment group. The concentrations of ammonia nitrogen, nitrite, and nitrate, and the pH of each sample were measured for eight consecutive days. Changes of microbiota composition in the water were analysed via high-throughput sequencing. Results: Ammonia, nitrite, and nitrate concentrations were substantially lower in the treatment group than in the control group. There were significant differences in the microbiota structure between treatment and control groups, especially on days 2–7 after adding P. furukawaii ZS1. Furthermore, significantly enriched bacterial genera in the treatment group were initially higher in number than inhibited genera, but subsequently reverted to being lower in number. Conclusions: These results provide theoretical guidance for the effective use of P. furukawaii ZS1 to control aquaculture water. Full article
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Article
Evaluation of Galdieria sulphuraria and Chlorella vulgaris for the Bioremediation of Produced Water
Water 2021, 13(9), 1183; https://doi.org/10.3390/w13091183 - 25 Apr 2021
Viewed by 483
Abstract
Produced water (PW) is the largest waste stream generated by the oil and gas industry. Traditional treatment of PW burdens the industry with significant expenses and environmental issues. Alternatively, microalgal-based bioremediation of PW is often viewed as an ecologically safe and sustainable platform [...] Read more.
Produced water (PW) is the largest waste stream generated by the oil and gas industry. Traditional treatment of PW burdens the industry with significant expenses and environmental issues. Alternatively, microalgal-based bioremediation of PW is often viewed as an ecologically safe and sustainable platform for treating PW. Moreover, the nutrients in PW could support algal growth. However, significant dilution of PW is often required in algal-based systems due to the presence of complex chemical contaminants. In light of these facts, the current work has investigated the potential of cultivating Galdieria sulphuraria and Chlorella vulgaris in PW using multiple dilutions; 0% PW, 5% PW, 10% PW, 20% PW, 50% PW and 100% PW. While both algal strains can grow in PW, the current results indicated that G. sulphuraria has a higher potential of growth in up to 50% PW (total dissolved solids of up to 55 g L−1) with a growth rate of 0.72 ± 0.05 g L−1 d−1 and can achieve a final biomass density of 4.28 ± 0.16 g L−1 in seven days without the need for additional micronutrients. Additionally, the algae showed the potential of removing 99.6 ± 0.2% nitrogen and 74.2 ± 8.5% phosphorus from the PW. Full article
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Article
Thermal Desalination of Produced Water—An Analysis of the Partitioning of Constituents into Product Streams and Its Implications for Beneficial Use Outside the O&G Industry
Water 2021, 13(8), 1068; https://doi.org/10.3390/w13081068 - 13 Apr 2021
Viewed by 805
Abstract
To understand partitioning of produced water (PW) constituents using thermal desalination, PW from the Delaware Basin was desalinated using a crystallization process and modeled using OLI Systems, Inc. (OLI, Parsippany, NJ, USA) chemistry software. The incorporation of a pretreatment step, steam stripping, prior [...] Read more.
To understand partitioning of produced water (PW) constituents using thermal desalination, PW from the Delaware Basin was desalinated using a crystallization process and modeled using OLI Systems, Inc. (OLI, Parsippany, NJ, USA) chemistry software. The incorporation of a pretreatment step, steam stripping, prior to desalination was predicted to be effective at removing hydrocarbons (across a range of volatilities). As expected, inorganics were almost completely retained in the residual brine which was confirmed by OLI. As evaporation progressed, sparingly soluble compounds such as gypsum and celestite precipitated first and overall solids production at this stage was low (<1% of total solids). Further evaporation resulted in saturation of the residual brine with respect to NaCl, which started to precipitate in bulk up to a practical desalination limit of approximately 68% by mass (approximately 80% by volume). Beyond this point, the residual brine and solids mixture became too viscous to be pumped. Gravimetrically determined total dissolved solids (TDS) for PW, distillate and residual brine was found to be much higher than prediction, potentially due to the presence of neutral species, unstripped gases and organic (likely hydrophilic) constituents. Although the distillate had low TDS, the presence of unknown constituents including organic compounds in the distillate will likely require polishing treatment to mitigate potential toxicity associated with such compounds or transformation products post-release if discharged to the environment. OLI predicted near-complete retention of acetate in the residual brine. In contrast, laboratory tests showed nearly 50% partitioning of acetate into the distillate. Although not modeled, propionate partitioning was even higher at 94%. The inclusion of ammonia as an input species in OLI greatly improved the match between test data and model prediction. Additionally, it was hypothesized that acetic acid/acetate could have formed a volatile adduct with ammonia that increased its volatility and partitioning into the distillate. The findings of this study inform beneficial use by describing the chemical composition of desalination-derived distillate, brine and salt products. This study also identified alternative approaches, both treatment and non-treatment, for managing PW from unconventional operations. Full article
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Article
Rice Physiological Response with Bacillus subtilis and Saccharomyces cerevisiae Inoculation into Soil under Reclaimed Water–Fresh Water Combined Irrigation
Water 2021, 13(6), 773; https://doi.org/10.3390/w13060773 - 12 Mar 2021
Viewed by 393
Abstract
The increasing soil salinity levels under reclaimed water irrigation have a negative effect on plant growth. Greenhouse experiments were conducted in 2018 and 2019 under reclaimed water–fresh water combined irrigation. After transplanting (Day 1), rice was irrigated with clean water (tap water) for [...] Read more.
The increasing soil salinity levels under reclaimed water irrigation have a negative effect on plant growth. Greenhouse experiments were conducted in 2018 and 2019 under reclaimed water–fresh water combined irrigation. After transplanting (Day 1), rice was irrigated with clean water (tap water) for 10 days to facilitate rice root colonisation. Subsequently, rice was irrigated with reclaimed water for 50 days (Day 11 to 60), and then irrigated with clean water. B. subtilis and S. cerevisiae were mixed with clean water (tap water) and irrigated into soil at Day 61. B. subtilis (20 billion colony-forming units/g) and S. cerevisiae (20 billion colony-forming units/g) were mixed at the following proportions: 5 g and 0 (J1), 3.75 g and 1.25 g (J2), 2.5 g and 2.5 g (J3), 1.25 g and 3.75 g (J4), and 0 and 5 g (J5), respectively; rice treated with reclaimed water (CK) and clean water (J0) with no microorganisms applied were also used. We measured NO3--N and NH4+-N concentrations and electrical conductivity (EC) in the soil at 0–5, 5–15, and 15–25 cm layers; root activity; and malondialdehyde (MDA), soluble sugar, superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and glutamine synthetase (GS) activity in leaves at Day 71. B. subtilis and S. cerevisiae combination could promote rice physiological indices, and B. subtilis had a greater effect than S. cerevisiae. There are obvious differences in the physiological performance and soil N between 2018 and 2019 due to the EC of reclaimed water. Redundancy analysis revealed that soil NO3-N and the mass of B. subtilis applied were major factors influencing leaf physiological indices. Five grams of B. subtilis is recommended to facilitate rice growth after irrigation with reclaimed water. Our research provides a new agronomic measure for the safe utilisation of reclaimed water. Full article
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Article
Produced Water Desalination via Pervaporative Distillation
Water 2020, 12(12), 3560; https://doi.org/10.3390/w12123560 - 18 Dec 2020
Cited by 1 | Viewed by 738
Abstract
Herein, we report on the performance of a hybrid organic-ceramic hydrophilic pervaporation membrane applied in a vacuum membrane distillation operating mode to desalinate laboratory prepared saline waters and a hypersaline water modeled after a real oil and gas produced water. The rational for [...] Read more.
Herein, we report on the performance of a hybrid organic-ceramic hydrophilic pervaporation membrane applied in a vacuum membrane distillation operating mode to desalinate laboratory prepared saline waters and a hypersaline water modeled after a real oil and gas produced water. The rational for performing “pervaporative distillation” is that highly contaminated waters like produced water, reverse osmosis concentrates and industrial have high potential to foul and scale membranes, and for traditional porous membrane distillation membranes they can suffer pore-wetting and complete salt passage. In most of these processes, the hard to treat feed water is commonly softened and filtered prior to a desalination process. This study evaluates pervaporative distillation performance treating: (1) NaCl solutions from 10 to 240 g/L at crossflow Reynolds numbers from 300 to 4800 and feed-temperatures from 60 to 85 °C and (2) a real produced water composition chemically softened to reduce its high-scale forming mineral content. The pervaporative distillation process proved highly-effective at desalting all feed streams, consistently delivering <10 mg/L of dissolved solids in product water under all operating condition tested with reasonably high permeate fluxes (up to 23 LMH) at optimized operating conditions. Full article
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Article
Performance, Energy and Cost of Produced Water Treatment by Chemical and Electrochemical Coagulation
Water 2020, 12(12), 3426; https://doi.org/10.3390/w12123426 - 06 Dec 2020
Viewed by 690
Abstract
The separation performance, energy demand, and operating costs of electro-coagulation (EC) are compared to conventional chemical coagulation for oil–water separation using a simulated oil- and gas-produced water matrix. An iron-based chemical coagulant and sacrificial iron electrodes are evaluated. Effluent turbidity, chemical oxygen demand [...] Read more.
The separation performance, energy demand, and operating costs of electro-coagulation (EC) are compared to conventional chemical coagulation for oil–water separation using a simulated oil- and gas-produced water matrix. An iron-based chemical coagulant and sacrificial iron electrodes are evaluated. Effluent turbidity, chemical oxygen demand (COD), total organic carbon (TOC), and oil and grease (O&G) removal were determined for various coagulant concentrations and reaction times and current densities. Chemical coagulation produced superior turbidity removal when scaled by the total iron dose. At lower iron doses (<500 mg/L), chemical coagulation yielded better COD, turbidity, and O&G removal. However, chemical coagulation was unable to effectively remove contaminants to meet the offshore discharge limit of 29 ppm O&G. At higher iron doses, EC was more effective at removing COD and O&G. The energy consumption of EC was found to be much higher even when factoring in the energy of production, transporting, and mixing of chemical coagulants, but the overall cost of EC was approximately half the cost of chemical coagulation, and more effective at O&G removal. Full article
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Article
Techno-Economic Analysis of RO Desalination of Produced Water for Beneficial Reuse in California
Water 2020, 12(7), 1850; https://doi.org/10.3390/w12071850 - 28 Jun 2020
Cited by 1 | Viewed by 817
Abstract
There is approximately 508.7 million cubic meters (3.2 million barrels) of oilfield-produced water generated per year across the oil fields of California. While less than 2% of this produced water receives advanced treatment for beneficial reuse, changing regulations and increasing scarcity of freshwater [...] Read more.
There is approximately 508.7 million cubic meters (3.2 million barrels) of oilfield-produced water generated per year across the oil fields of California. While less than 2% of this produced water receives advanced treatment for beneficial reuse, changing regulations and increasing scarcity of freshwater resources is expected to increase the demand for beneficial reuse. This paper reviews onshore-produced water quality across California, relevant standards and treatment objectives for beneficial reuse, identifies contaminants of concern, and treatment process design considerations. Lastly, we evaluate the capital and operating costs of an integrated membrane system for treating produced water based on data from a field pilot conducted in the coastal region of California. Full article
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Article
Treatment of Produced Water in the Permian Basin for Hydraulic Fracturing: Comparison of Different Coagulation Processes and Innovative Filter Media
Water 2020, 12(3), 770; https://doi.org/10.3390/w12030770 - 11 Mar 2020
Cited by 9 | Viewed by 1561
Abstract
Produced water is the largest volume of waste product generated during oil and natural gas exploration and production. The traditional method to dispose of produced water involves deep well injection, but this option is becoming more challenging due to high operational cost, limited [...] Read more.
Produced water is the largest volume of waste product generated during oil and natural gas exploration and production. The traditional method to dispose of produced water involves deep well injection, but this option is becoming more challenging due to high operational cost, limited disposal capacity, and more stringent regulations. Meanwhile, large volumes of freshwater are used for hydraulic fracturing. The goal of this study is to develop cost-effective technologies, and optimize system design and operation to treat highly saline produced water (120–140 g/L total dissolved solids) for hydraulic fracturing. Produced water was collected from a salt water disposal facility in the Permian Basin, New Mexico. Chemical coagulation (CC) using ferric chloride and aluminum sulfate as coagulants was compared with electrocoagulation (EC) with aluminum electrodes for removal of suspended contaminants. The effects of coagulant dose, current density, and hydraulic retention time during EC on turbidity removal were investigated. Experimental results showed that aluminum sulfate was more efficient and cost-effective than ferric chloride for removing turbidity from produced water. The optimal aluminum dose was achieved at operating current density of 6.60 mA/cm2 and 12 min contact time during EC treatment, which resulted in 74% removal of suspended solids and 53–78% removal of total organic carbon (TOC). The energy requirement of EC was calculated 0.36 kWh/m3 of water treated. The total operating cost of EC was estimated $0.44/m3 of treated water, which is 1.7 or 1.2 times higher than CC using alum or ferric chloride as the coagulant, respectively. The EC operating cost was primarily associated with the consumption of aluminum electrode materials due to faradaic reactions and electrodes corrosions. EC has the advantage of shorter retention time, in situ production of coagulants, less sludge generation, and high mobility for onsite produced water treatment. The fine particles and other contaminants after coagulation were further treated in continuous-flow columns packed with different filter media, including agricultural waste products (pecan shell, walnut shell, and biochar), and new and spent granular activated carbon (GAC). Turbidity, TOC, metals, and electrical conductivity were monitored to evaluate the performance of the treatment system and the adsorption capacities of different media. Biochar and GAC showed the greatest removal of turbidity and TOC in produced water. These treatment technologies were demonstrated to be effective for the removal of suspended constituents and iron, and to produce a clean brine for onsite reuse, such as hydraulic fracturing. Full article
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Article
Detection of Helminth Ova in Wastewater Using Recombinase Polymerase Amplification Coupled to Lateral Flow Strips
Water 2020, 12(3), 691; https://doi.org/10.3390/w12030691 - 03 Mar 2020
Cited by 3 | Viewed by 1678
Abstract
Ascaris lumbricoides is a major soil-transmitted helminth that is highly infective to humans. The ova of A. lumbricoides are able to survive wastewater treatment, thus making it an indicator organism for effective water treatment and sanitation. Hence, Ascaris ova must be removed from [...] Read more.
Ascaris lumbricoides is a major soil-transmitted helminth that is highly infective to humans. The ova of A. lumbricoides are able to survive wastewater treatment, thus making it an indicator organism for effective water treatment and sanitation. Hence, Ascaris ova must be removed from wastewater matrices for the safe use of recycled water. Current microscopic techniques for identification and enumeration of Ascaris ova are laborious and cumbersome. Polymerase chain reaction (PCR)-based techniques are sensitive and specific, however, major constraints lie in having to transport samples to a centralised laboratory, the requirement for sophisticated instrumentation and skilled personnel. To address this issue, a rapid, highly specific, sensitive, and affordable method for the detection of helminth ova was developed utilising recombinase polymerase amplification (RPA) coupled with lateral flow (LF) strips. In this study, Ascaris suum ova were used to demonstrate the potential use of the RPA-LF assay. The method was faster (< 30 min) with optimal temperature at 37 °C and greater sensitivity than PCR-based approaches with detection as low as 2 femtograms of DNA. Furthermore, ova from two different helminth genera were able to be detected as a multiplex assay using a single lateral flow strip, which could significantly reduce the time and the cost of helminth identification. The RPA-LF system represents an accurate, rapid, and cost-effective technology that could replace the existing detection methods, which are technically challenged and not ideal for on-site detection in wastewater treatment plants. Full article
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Article
A Local Model and Experimental Verification of the Crossflow Filtration of a Polydispersed Slurry
Water 2020, 12(2), 489; https://doi.org/10.3390/w12020489 - 11 Feb 2020
Viewed by 800
Abstract
In this paper, we propose a calculation model for a crossflow filtration process that is applicable to polydispersed slurry microfiltration. The deposition velocity of particles in slurry, particle distribution, and resistance of the filter cake on the surface of the filtration media can [...] Read more.
In this paper, we propose a calculation model for a crossflow filtration process that is applicable to polydispersed slurry microfiltration. The deposition velocity of particles in slurry, particle distribution, and resistance of the filter cake on the surface of the filtration media can be predicted by this model, and can be used to predict the variations of filtration velocity. The theoretical prediction matched well with the experimental data, having a difference within 20%, except for the initial few seconds. However, the porosity of the filter cake used in the theoretical prediction was assigned based on the literature. It is revealed by the model that the variations in the crossflow filtration velocity are induced by the gradual domination of particles with small diameters in the filter cake. Meanwhile, the possible direction for the optimization of this model is pointed out. Full article
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Article
Natural Treatment of High-Strength Reverse Osmosis Concentrate by Constructed Wetlands for Reclaimed Water Use
Water 2020, 12(1), 158; https://doi.org/10.3390/w12010158 - 04 Jan 2020
Cited by 3 | Viewed by 1559
Abstract
A pilot study using natural treatment methods such as a horizontal subsurface flow in constructed wetlands to treat the reverse osmosis concentrate (ROC) was conducted to manage nutrient and metals to reclaim the product water for the coastal wetlands and agriculture use. ROC [...] Read more.
A pilot study using natural treatment methods such as a horizontal subsurface flow in constructed wetlands to treat the reverse osmosis concentrate (ROC) was conducted to manage nutrient and metals to reclaim the product water for the coastal wetlands and agriculture use. ROC had a significantly greater concentration of constituents than concentrations typically found in effluent of secondary treated wastewater. During the six-month wetland pilot study, the removal of nutrients from the ROC was monitored. Bulrush (Schoenoplectus californicus), a common wetland plant, tolerated high total dissolved solids (11,000–12,700 mg/L) and provided significant mass removal of nutrients in the concentrate (61% removal of nitrogen and 21% removal of phosphorus) under two hydraulic residence times (HRT1 = 2.5 days and HRT2 = 5 days). Concentration-based reductions of oxidized nitrogen, ammonia-nitrogen, orthophosphate were 63%, 23%, and 23% during HRT1 and 55%, 24%, and 11% during HRT2, respectively. Nutrient mass balance estimates of this microbially dominated wetland system and analysis of mass transformation pathways were also performed. Because of evaporative water loss, mass removal efficiencies were significant. Key processes included denitrification for nitrogen removal, possibly supplemented with Annamox reduction of NO3-N; labile carbon assimilation supporting oxidized nitrogen reduction; and phosphate-P uptake and precipitation within the gravel substrate. The results indicated that engineered wetland treatment offers useful benefits to the management of ROC produced from secondary treated effluent of wastewater through reduction in volume through evapotranspiration and reduction in concentration through biological transformations for beneficial reuse. Full article
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Review

Jump to: Research

Review
A Critical Review of Analytical Methods for Comprehensive Characterization of Produced Water
Water 2021, 13(2), 183; https://doi.org/10.3390/w13020183 - 14 Jan 2021
Cited by 1 | Viewed by 653
Abstract
Produced water is the largest waste stream associated with oil and gas production. It has a complex matrix composed of native constituents from geologic formation, chemical additives from fracturing fluids, and ubiquitous bacteria. Characterization of produced water is critical to monitor field operation, [...] Read more.
Produced water is the largest waste stream associated with oil and gas production. It has a complex matrix composed of native constituents from geologic formation, chemical additives from fracturing fluids, and ubiquitous bacteria. Characterization of produced water is critical to monitor field operation, control processes, evaluate appropriate management practices and treatment effectiveness, and assess potential risks to public health and environment during the use of treated water. There is a limited understanding of produced water composition due to the inherent complexity and lack of reliable and standardized analytical methods. A comprehensive description of current analytical techniques for produced water characterization, including both standard and research methods, is discussed in this review. Multi-tiered analytical procedures are proposed, including field sampling; sample preservation; pretreatment techniques; basic water quality measurements; organic, inorganic, and radioactive materials analysis; and biological characterization. The challenges, knowledge gaps, and research needs for developing advanced analytical methods for produced water characterization, including target and nontarget analyses of unknown chemicals, are discussed. Full article
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Review
Interplay of the Factors Affecting Water Flux and Salt Rejection in Membrane Distillation: A State-of-the-Art Critical Review
Water 2020, 12(10), 2841; https://doi.org/10.3390/w12102841 - 13 Oct 2020
Cited by 2 | Viewed by 627
Abstract
High water flux and elevated rejection of salts and contaminants are two primary goals for membrane distillation (MD). It is imperative to study the factors affecting water flux and solute transport in MD, the fundamental mechanisms, and practical applications to improve system performance. [...] Read more.
High water flux and elevated rejection of salts and contaminants are two primary goals for membrane distillation (MD). It is imperative to study the factors affecting water flux and solute transport in MD, the fundamental mechanisms, and practical applications to improve system performance. In this review, we analyzed in-depth the effects of membrane characteristics (e.g., membrane pore size and distribution, porosity, tortuosity, membrane thickness, hydrophobicity, and liquid entry pressure), feed solution composition (e.g., salts, non-volatile and volatile organics, surfactants such as non-ionic and ionic types, trace organic compounds, natural organic matter, and viscosity), and operating conditions (e.g., temperature, flow velocity, and membrane degradation during long-term operation). Intrinsic interactions between the feed solution and the membrane due to hydrophobic interaction and/or electro-interaction (electro-repulsion and adsorption on membrane surface) were also discussed. The interplay among the factors was developed to qualitatively predict water flux and salt rejection considering feed solution, membrane properties, and operating conditions. This review provides a structured understanding of the intrinsic mechanisms of the factors affecting mass transport, heat transfer, and salt rejection in MD and the intra-relationship between these factors from a systematic perspective. Full article
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Review
A Review of Algae-Based Produced Water Treatment for Biomass and Biofuel Production
Water 2020, 12(9), 2351; https://doi.org/10.3390/w12092351 - 21 Aug 2020
Cited by 6 | Viewed by 1649
Abstract
Produced water (PW), the largest waste stream generated in oil and gas industries, has the potential to be a harmless product rather than being a waste. Biological processes using microorganisms have proven useful to remediate PW contaminated by petroleum hydrocarbons, complex organic chemicals, [...] Read more.
Produced water (PW), the largest waste stream generated in oil and gas industries, has the potential to be a harmless product rather than being a waste. Biological processes using microorganisms have proven useful to remediate PW contaminated by petroleum hydrocarbons, complex organic chemicals, and solvents. In particular, the bioremediation of PW using algae is an eco-friendly and low-cost approach due to algae’s ability to utilize certain pollutants as nutrient sources. Therefore, the utilization of PW as an algal growth medium has a great potential to eliminate chemicals from the PW and minimize the large volumes of freshwater needed for cultivation. Although several reviews describing the bioremediation of PW have been published, to the best of our knowledge, no review has exclusively focused on the algae-based PW treatment. Therefore, the present review is dedicated to filling this gap by portraying the many different facets of the algae cultivation in PW. Several algal species that are known to thrive in a wide range of salinity and the critical steps for their cultivation in hypersaline PW have been identified. Overall, this comprehensive review highlights the PW bioremediation using algae and brings attention to utilizing PW to grow biomass that can be processed to generate biofuels and useful bioproducts. Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

1. Title: Regulatory framework for produced water production, management and reuse in the United States, Part I – Case studies on East of 98th Meridian
Authors: Dr. Pei Xu et al.

2. Title: Regulatory framework for produced water production, management and reuse in the United States, Part II – Case studies on West of 98th Meridian
Authors: Dr. Pei Xu et al.

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