A Holistic Evaluation of Multivariate Statistical Process Monitoring in a Biological and Membrane Treatment System.

Unsupervised process monitoring for fault detection and data cleaning is underdeveloped for municipal wastewater treatment plants (WWTPs) due to the complexity and volume of data produced by sensors, equipment, and control systems. The goal of this work is to extensively test and tune an unsupervised process monitoring method that can promptly identify faults in a full-scale decentralized WWTP prior to significant system changes. Adaptive dynamic principal component analysis (AD-PCA) is a dimension reduction method modified to address autocorrelation and nonstationarity in multivariate processes and is evaluated in this work for its ability to continuously detect drift, shift, and spike faults. For spike faults, univariate drift faults, and multivariate shift faults, implementing AD-PCA on data that are subset by treatment processes and operating states with significant differences in covariates and whose model parameters use week-long training windows, moderate cumulative variance, and a high threshold for detection was found to detect faults prior to existing operational thresholds. To improve the consistency with which the AD-PCA method detects out-of-control conditions in real time, additional work is needed to remove outliers prior to model fitting and to detect multivariate drift faults in which the covariates change slowly.

Multistage Surface-Heated Vacuum Membrane Distillation Process Enables High Water Recovery and Excellent Heat Utilization: A Modeling Study.

Surface-heated membrane distillation (MD) enhances the energy efficiency of desalination by mitigating temperature polarization (TP). However, systematic investigations of larger scale, multistage, surface-heated MD system with high water recovery and heat recycling are limited. Here, we explore the design and performance of a multistage surface-heated vacuum MD (SHVMD) with heat recovery through a comprehensive finite difference model. In this process, the latent heat of condensation is recovered through an internal heat exchanger (HX) using the retentate from one stage as the condensing fluid for the next stage and an external HX using the feed as the condensing fluid. Model results show that surface heating enhances the performance compared to conventional vacuum MD (VMD). Specifically, in a six-stage SHVMD process, 54.44% water recovery and a gained output ratio (GOR) of 3.28 are achieved with a surface heat density of 2000 W m-2, whereas a similar six-stage VMD process only reaches 18.19% water recovery and a GOR of 2.15. Mass and energy balances suggest that by mitigating TP, surface heating increases the latent heat trapped in vapor. The internal and external HXs capture and reuse the additional heat, which enhances the GOR values. We show for SHVMD that the hybrid internal/external heat recovery design can have GOR value 1.44 times higher than that of systems with only internal or external heat recovery. Furthermore, by only increasing six stages to eight stages, a GOR value as high as 4.35 is achieved. The results further show that surface heating can reduce the energy consumption of MD for brine concentration. The multistage SHVMD technology exhibits a promising potential for the management of brine from industrial plants.

Metabolomics reveals primary response of wheat (Triticum aestivum) to irrigation with oilfield produced water.

The reuse of oilfield produced water (PW) for agricultural irrigation has received increased attention for utility in drought-stricken regions. It was recently demonstrated that PW irrigation can affect physiological processes in food crops. However, metabolomic evaluations are important to further discern specific mechanisms of how PW may contribute as a plant-environmental stressor. Herein, the primary metabolic responses of wheat irrigated with PW and matching salinity controls were investigated. Non-targeted gas chromatography mass spectrometry (GC-MS) metabolomics was combined with multivariate analysis and revealed that PW irrigation altered the primary metabolic profiles of both wheat leaf and grain. Over 600 compounds (183 annotated metabolites) were detected that varied between controls (salinity control and tap water) and PW irrigated plants. While some of these changed metabolites are related to salinity stress, over half were found to be unique to PW. The primary metabolites exhibiting changes in abundance in leaf and grain tissues were amines/amino acids, organic acids, and saccharides. Metabolite pathway analysis revealed that amino acid metabolism, sugar metabolism, and nitrogen remobilization are all impacted by PW irrigation, independent of regular plant responses to salinity stress. These data, when combined with prior physiological studies, support a multi-faceted, physio-metabolic response of wheat to the unique stressor imposed by irrigation with PW.

Desalinating a real hyper-saline pre-treated produced water via direct-heat vacuum membrane distillation.

Membrane distillation (MD) is an emerging thermal desalination technology capable of desalinating waters of any salinity. During typical MD processes, the saline feedwater is heated and acts as the thermal energy carrier; however, temperature polarization (as well as thermal energy loss) contributes to low distillate fluxes, low single-pass water recovery and poor thermal efficiency. An alternative approach is to integrate an extra thermal energy carrier as part of the membrane and/or module assembly, which can channel externally provided heat directly to the membrane-feedwater interface and/or along the feed channel length. This direct-heat delivery has been demonstrated to increase single-pass water recovery and enhance the overall thermal efficiency. We developed a bench-scale direct-heated vacuum MD (DHVMD) process to desalinate pre-treated oil and gas "produced water" with an initial total dissolved solids of 115,500 ppm at a feed temperature ranging between 24 and 32 °C. We evaluated both water flux and specific energy consumption (SEC) as a function of water recovery. The system achieved a 50% water recovery without significant scaling, with an average flux >6 kg m-2 hr-1 and a SEC as low as 2,530 kJ kg-1. The major species of mineral scales (i.e., NaCl, CaSO4, and SrSO4) that limited the water recovery to 68% were modeled in terms of thermodynamics and identified by scanning electron microscopy and energy-dispersive X-ray spectroscopy. In addition, we further developed and employed a physics-based process model to estimate temperature, salinity, water transport and energy flows for full-scale vacuum MD and DHVMD modules. Model results show that a direct-heat input rate of 3,600 W can increase single-pass water recovery from 2.1% to 3.1% while lowering the thermal SEC from 7,800 kJ kg-1 to 6,517 kJ kg-1 in an unoptimized module. Finally, the scaling up potential of DHVMD process is briefly discussed.

Mass Transport in Osmotically Driven Membrane Processes.

Forward osmosis (FO) and pressure retarded osmosis (PRO) are the two operational modes for osmotically driven membrane processes (ODMPs). ODMPs have gained increasing popularity in the laboratory over the years; however, OMDPs have not been applied in very many cases at full scale because they are still emerging technologies that require further development. Computational fluid dynamics (CFD) modeling coupled with solute transport evaluation provides a tool to study hydrodynamics and concentration polarization in FO and PRO. In this study a series of models were developed to predict water flux. The simulation results of empty-channel (with no feed spacer) membrane cells were verified by comparison with experimental results, showing that CFD simulation with solute transport is a reliable tool. Ensuing 2D and 3D models were built to study the impact of feed spacers on the velocity and concentration distribution inside the flow channels, and investigate whether the presence of spacers would enable enhancement of water flux. The results showed that spacers could change the concentration and velocity profile and they could reduce or enhance water flux depending on the inlet flow velocity and distance between the membrane and spacer.

Effect of produced water treatment technologies on irrigation-induced metal and salt accumulation in wheat (Triticum aestivum) and sunflower (Helianthus annuus).

Produced water (PW), a wastewater resulting from hydraulic fracturing and oil and gas production, has been utilized in arid regions for irrigation purposes and potentially presents a new water source for crop irrigation in areas of increasing water scarcity. However, there is a potential for both synthetic and geogenic contaminants in these waters to accumulate in irrigated food crops. This study assessed how water treatment technologies targeted at removal of salinity (i.e., total dissolved solids) and organic chemical content (i.e., dissolved organic carbon) from PW to achieve agricultural irrigation standards altered the impact of inorganic contaminants and nutrient uptake on two salt-tolerant food crops, sunflower (Helianthus annuus) and wheat (Triticum aestivum). The impacts of the treatment technologies on inorganic contaminant loadings in the irrigated soils were also assessed. Treatment technologies to improve PW quality decreased the adverse impacts on plant health; however, plant health was more affected by dilutions of PW than by the treatment technologies employed. Phenotypically, plants irrigated with 90% dilution (low) treatment groups, regardless of treatment technology, were comparable to controls; however, plants watered with high proportions (50%) of raw or treated PW displayed stunted growth, with reduced height and leaf area, and sunflower seed saw 100% yield loss. Although phenotypically similar, plants of the low treatment groups exhibited changes in the ionome, illustrating the influence of PW on plant uptake, translocation, and accumulation of metals, salts, and micronutrients. In addition, bioavailability of metals and nutrients was impacted by the unique and complex PW matrix: bioconcentration factors traditionally used to evaluate risk may therefore over or underestimate accumulation.

A hybrid catalytic hydrogenation/membrane distillation process for nitrogen resource recovery from nitrate-contaminated waste ion exchange brine.

Ion exchange is widely used to treat nitrate-contaminated groundwater, but high salt usage for resin regeneration and management of waste brine residuals increase treatment costs and add environmental burdens. Development of palladium-based catalytic nitrate treatment systems for brine treatment and reuse has showed promising activity for nitrate reduction and selectivity towards the N2 over the alternative product ammonia, but this strategy overlooks the potential value of nitrogen resources. Here, we evaluated a hybrid catalytic hydrogenation/membrane distillation process for nitrogen resource recovery during treatment and reuse of nitrate-contaminated waste ion exchange brines. In the first step of the hybrid process, a Ru/C catalyst with high selectivity towards ammonia was found to be effective for nitrate hydrogenation under conditions representative of waste brines, including expected salt buildup that would occur with repeated brine reuse cycles. The apparent rate constants normalized to metal mass (0.30 ± 0.03 mM min-1 gRu-1 under baseline condition) were comparable to the state-of-the-art bimetallic Pd catalyst. In the second stage of the hybrid process, membrane distillation was applied to recover the ammonia product from the brine matrix, capturing nitrogen as ammonium sulfate, a commercial fertilizer product. Solution pH significantly influenced the rate of ammonia mass transfer through the gas-permeable membrane by controlling the fraction of free ammonia species (NH3) present in the solution. The rate of ammonia recovery was not affected by increasing salt levels in the brine, indicating the feasibility of membrane distillation for recovering ammonia over repeated reuse cycles. Finally, high rates of nitrate hydrogenation (apparent rate constant 1.80 ± 0.04 mM min-1 gRu-1) and ammonia recovery (overall mass transfer coefficient 0.20 m h-1) with the hybrid treatment process were demonstrated when treating a real waste ion exchange brine obtained from a drinking water utility. These findings introduce an innovative strategy for recycling waste ion exchange brine while simultaneously recovering potentially valuable nitrogen resources when treating contaminated groundwater.

Mineral Scale Prevention on Electrically Conducting Membrane Distillation Membranes Using Induced Electrophoretic Mixing.

The growth of mineral crystals on surfaces is a challenge across multiple industrial processes. Membrane-based desalination processes, in particular, are plagued by crystal growth (known as scaling), which restricts the flow of water through the membrane, can cause membrane wetting in membrane distillation, and can lead to the physical destruction of the membrane material. Scaling occurs when supersaturated conditions develop along the membrane surface due to the passage of water through the membrane, a process known as concentration polarization. To reduce scaling, concentration polarization is minimized by encouraging turbulent conditions and by reducing the amount of water recovered from the saline feed. In addition, antiscaling chemicals can be used to reduce the availability of cations. Here, we report on an energy-efficient electrophoretic mixing method capable of nearly eliminating CaSO4 and silicate scaling on electrically conducting membrane distillation (ECMD) membranes. The ECMD membrane material is composed of a percolating layer of carbon nanotubes deposited on porous polypropylene support and cross-linked by poly(vinyl alcohol). The application of low alternating potentials (2 Vpp,1Hz) had a dramatic impact on scale formation, with the impact highly dependent on the frequency of the applied signal, and in the case of silicate, on the pH of the solution.

Emergence and fate of volatile iodinated organic compounds during biological treatment of oil and gas produced water.

Oil and gas (O&G) production in the United States is expected to grow at a substantial rate over the coming decades. Environmental sustainability related to water consumption during O&G extraction can be addressed through treatment and reuse of water returning to the surface after well completion. Water quality is an important factor in reuse applications, and specific treatment technologies must be utilized to remove different contaminants. Among others, biological active filtration can remove dissolved organic matter as a pre-treatment for surface discharge or to facilitate reuse in such applications as hydraulic fracturing, dust suppression, road stabilization, and crop irrigation. Yet, the formation of byproducts during treatment of O&G wastewater remains a concern when evaluating reuse applications. In this study, we investigated the previously unnoticed biotic formation of iodinated organic compounds (IOCs) such as triiodomethane during biological treatment of O&G wastewater for beneficial reuse. Iodide and several IOCs were quantified in O&G produced water before and after treatment in biological active filters filled with different media types over 13 weeks of operation. While iodide and total IOCs were measured at concentrations <53 mg/L and 147 µg/L, respectively, before biological treatment, total IOCs were measured at concentrations close to 4 mg/L after biological treatment. Triiodomethane was the IOC that was predominantly present. IOC formation had a negative strong correlation (r = -0.7 to -0.8, p < 0.05, n = 9) with iodide concentration in the treated O&G wastewater, indicating that iodide introduced to the biological active filter system was utilized in various reactions, including biologically mediated halogenation of organic matter. Additionally, iodide-oxidizing bacteria augmented in the treated produced water pointed towards potential negative environmental implications when releasing biologically treated halide-rich wastewater effluents to the aquatic environment.

Antiwetting and Antifouling Janus Membrane for Desalination of Saline Oily Wastewater by Membrane Distillation.

In this study, we develop Janus membranes comprising a hydrophilic zwitterionic polymer layer and an omniphobic (all-liquid-repelling) porous substrate that simultaneously possess fouling and wetting resistances. An omniphobic membrane was first fabricated by attaching silica nanoparticles (SiNPs) to the fibers of a quartz fiber mat, creating multilevel re-entrant structures, followed by surface fluorination to reduce the surface energy. The Janus membrane was then fabricated by grafting a zwitterionic polymer brush layer via surface-initiated atom-transfer radical-polymerization (ATRP) on the omniphobic substrate. Membrane characterizations, including Fourier-transform infrared spectroscopy, fluorescence microscopy, and contact angle measurements, confirm that the surface hydrophilicity can be finely tuned by adjusting the duration of the ATRP reaction. Also, the zwitterionic polymer brush layer was confined on the top surface of the Janus membrane, rendering the surface hydrophilic, while the remaining part of the Janus membrane remained omniphobic, resisting the wicking of low-surface-tension liquids including ethanol and hexane. A static oil-fouling test showed that crude oil droplets irreversibly fouled an omniphobic membrane (without a hydrophilic top layer) in water. In contrast, oil droplets placed on the Janus membrane in air were immediately desorbed upon its immersion in water. Finally, we performed direct-contact membrane distillation (MD) experiments using a crude-oil-in-saline (NaCl) water emulsion as a feed solution, simulating highly saline oily wastewater. The Janus membrane exhibited superior wetting and fouling resistances, with a stable water flux and nearly perfect salt rejection, while an omniphobic membrane failed in the desalination process. Our work highlights the great potential of antiwetting and antifouling Janus membranes for water reclamation from challenging industrial wastewaters through MD.

Potential for Beneficial Reuse of Oil and Gas-Derived Produced Water in Agriculture: Physiological and Morphological Responses in Spring Wheat (Triticum aestivum).

Produced water (PW) from oil and gas operations is considered a potential resource for food crop irrigation because of increasing water scarcity in dryland agriculture. However, efforts to employ PW for agriculture have been met with limited success. A greenhouse study was performed to evaluate the effects of PW on physiological and morphological traits of spring wheat (Triticum aestivum). Plants were irrigated with water treatments containing 10 and 50% PW (PW10 and PW50, respectively) and compared to a matching 50% salinity (NaCl50) and 100% tap water controls. Compared to controls, plants watered with PW10 and PW50 exhibited developmental arrest and reductions in aboveground and belowground biomass, photosynthetic efficiency, and reproductive growth. Decreases in grain yield ranged from 70 to 100% in plants irrigated with PW compared to the tap water control. Importantly, the PW10 and NaCl50 treatments were comparable for morphophysiological effects, even though NaCl50 contained 5 times the total dissolved solids, suggesting that constituents other than NaCl in PW contributed to plant stress. These findings indicate that despite discharge and reuse requirements focused on total dissolved solids, salinity stress may not be the primary factor affecting crop health. The results of the present study are informative for developing guidelines for the use of PW in agriculture to ensure minimal effects on crop morphology and physiology. Environ Toxicol Chem 2019;38:1756-1769. © 2019 SETAC.

Data-driven performance analyses of wastewater treatment plants: A review.

Recent advancements in data-driven process control and performance analysis could provide the wastewater treatment industry with an opportunity to reduce costs and improve operations. However, big data in wastewater treatment plants (WWTP) is widely underutilized, due in part to a workforce that lacks background knowledge of data science required to fully analyze the unique characteristics of WWTP. Wastewater treatment processes exhibit nonlinear, nonstationary, autocorrelated, and co-correlated behavior that (i) is very difficult to model using first principals and (ii) must be considered when implementing data-driven methods. This review provides an overview of data-driven methods of achieving fault detection, variable prediction, and advanced control of WWTP. We present how big data has been used in the context of WWTP, and much of the discussion can also be applied to water treatment. Due to the assumptions inherent in different data-driven modeling approaches (e.g., control charts, statistical process control, model predictive control, neural networks, transfer functions, fuzzy logic), not all methods are appropriate for every goal or every dataset. Practical guidance is given for matching a desired goal with a particular methodology along with considerations regarding the assumed data structure. References for further reading are provided, and an overall analysis framework is presented.

Removal of per- and polyfluoroalkyl substances using super-fine powder activated carbon and ceramic membrane filtration.

Contamination of drinking water sources with per- and polyfluoroalkyl substances (PFASs) is a major challenge for environmental engineers. While granular activated carbon (GAC) is an effective adsorbent-based treatment technology for long-chained PFASs, GAC is less effective for removal of short-chained compounds, necessitating a more complete treatment strategy. Super-fine powder activated carbon (SPAC; particle diameter <1 um) is potentially a superior adsorbent to GAC due to high specific surface area and faster adsorption kinetics. This study served to evaluate SPAC coupled with ceramic microfiltration (CMF) for PFAS removal in a continuous flow system. Comparison of PFAS mass loading rates onto SPAC and GAC to 10% breakthrough of PFASs using contaminated groundwater indicates that SPAC has nearly double the adsorption potential of GAC. Limitations reaching breakthrough for the SPAC system led to additional higher mass loading experiments where PFAS adsorption onto SPAC reached 2990 µg/g (for quantifiable PFASs), 480x greater than GAC and is thought to be a function of adsorbent size, pore content and PFAS chain length. Additional analysis of system performance through the application of liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF-MS) revealed the presence of additional PFASs in influent samples that were removed by the SPAC/CMF system.

The role of nanotechnology in industrial water treatment.

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.

Enhanced biofiltration of O&G produced water comparing granular activated carbon and nutrients.

Large volumes of water are required for the development of unconventional oil and gas (O&G) wells. Water scarcity coupled with seismicity induced by deep-well disposal promote new O&G wastewater management strategies, specifically treatment and reuse. One technology that has been proven effective for removal of organic matter and solids is biologically active filtration (BAF) with granular active carbon (GAC); however, further optimization is needed to enhance BAF performance. This study evaluated three GAC media (one spent and two new) and two nutrient-mix supplements for enhanced removal of chemical oxygen demand (COD) and dissolved organic carbon (DOC). Biofilm development was also monitored and correlated to BAF performance. The spent GAC with extant biofilm quickly acclimated to PW and demonstrated up to 92% DOC removal (81% COD) in 24h, while little impact by nutrient addition was observed. In addition, virgin GAC was slow to establish a biofilm, indicating that appropriate GAC selection and pre-developed biofilm is critical for efficient BAF performance. Furthermore, the production of high quality BAF effluent (less than 20mg/L DOC) presents the opportunity to apply BAF as a pretreatment for subsequent desalination-expanding the potential for reuse applications of PW.

Assessing the feasibility of using produced water for irrigation in Colorado.

The Colorado Water Plan estimates as much as 0.8 million irrigated acres may dry up statewide from agricultural to municipal and industrial transfers. To help mitigate this loss, new sources of water are being explored in Colorado. One such source may be produced water. Oil and gas production in 2016 alone produced over 300 million barrels of produced water. Currently, the most common method of disposal of produced water is deep well injection, which is costly and has been shown to cause induced seismicity. Treating this water to agricultural standards eliminates the need to dispose of this water and provides a new source of water. This research explores which counties in Colorado may be best suited to reusing produced water for agriculture based on a combined index of need, quality of produced water, and quantity of produced water. The volumetric impact of using produced water for agricultural needs is determined for the top six counties. Irrigation demand is obtained using evapotranspiration estimates from a range of methods, including remote sensing products and ground-based observations. The economic feasibility of treating produced water to irrigation standards is also determined using an integrated decision selection tool (iDST). We find that produced water can make a substantial volumetric impact on irrigation demand in some counties. Results from the iDST indicate that while costs of treating produced water are higher than the cost of injection into private disposal wells, the costs are much less than disposal into commercial wells. The results of this research may aid in the transition between viewing produced water as a waste product and using it as a tool to help secure water for the arid west.

Decision support toolkit for integrated analysis and design of reclaimed water infrastructure.

Planning of water reuse systems is a complex endeavor. We have developed a software toolkit, IRIPT (Integrated Urban Reclaimed Water Infrastructure Planning Toolkit) that facilitates planning and design of reclaimed water infrastructure for both centralized and hybrid configurations that incorporate satellite treatment plants (STPs). The toolkit includes a Pipeline Designer (PRODOT) that optimizes routing and sizing of pipelines for wastewater capture and reclaimed water distribution, a Selector (SelWTP) that assembles and optimizes wastewater treatment trains, and a Calculator (CalcBenefit) that estimates fees, revenues, and subsidies of alternative designs. For hybrid configurations, a Locator (LocSTP) optimizes siting of STPs and associated wastewater diversions by identifying manhole locations where the flowrates are sufficient to ensure that wastewater extracted and treated at an adjacent STP can generate the revenue needed to pay for treatment and delivery to customers. Practical local constraints are also applied to screen and identify STP locations. Once suitable sites are selected, System Integrator (ToolIntegrator) identifies a set of centralized and hybrid configurations that: (1) maximize reclaimed water supply, (2) maximize reclaimed water supply while also ensuring a financial benefit for the system, and (3) maximize the net financial benefit for the system. The resulting configurations are then evaluated by an Analyst (SANNA) that uses monetary and non-monetary criteria, with weights assigned to appropriate metrics by a decision-maker, to identify a preferred configuration. To illustrate the structure, assumptions, and use of IRIPT, we apply it to a case study for the city of Golden, CO. The criteria weightings provided by a local decision-maker lead to a preference for a centralized configuration in this case. The Golden case study demonstrates that IRIPT can efficiently analyze centralized and hybrid water reuse configurations and rank them according to decision-makers' preferences.

Electrochemical Stripping to Recover Nitrogen from Source-Separated Urine.

Recovering nitrogen from separately collected urine can potentially reduce costs and energy of wastewater nitrogen removal and fertilizer production. Through benchtop experiments, we demonstrate the recovery of nitrogen from urine as ammonium sulfate using electrochemical stripping, a combination of electrodialysis and membrane stripping. Nitrogen was selectively recovered with 93% efficiency in batch experiments with real urine and required 30.6 MJ kg N-1 in continuous-flow experiments (slightly less than conventional ammonia stripping). The effects of solution chemistry on nitrogen flux, electrolytic reactions, and reactions with electro-generated oxidants were evaluated using synthetic urine solutions. Fates of urine-relevant trace organic contaminants, including electrochemical oxidation and reaction with electro-generated chlorine, were investigated with a suite of common pharmaceuticals. Trace organics (<0.1 µg L-1) and elements (<30 µg L-1) were not detected at appreciable levels in the ammonium sulfate fertilizer product. This novel approach holds promise for selective recovery of nitrogen from concentrated liquid waste streams such as source-separated urine.

Tracking oil and gas wastewater-derived organic matter in a hybrid biofilter membrane treatment system: A multi-analytical approach.

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.

Temporal characterization and statistical analysis of flowback and produced waters and their potential for reuse.

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.