Characterization of Organic Matter in Water from Oil and Gas Wells Hydraulically Fractured with Recycled Water.

Liquid chromatography quadrupole time-of-flight mass spectrometry was performed to understand how frac fluid with recycled water (RWA) and frac fluid with fresh water (FWA) compare when subjected to downhole temperature and oxidation conditions. Ethylene oxide and propylated glycol functional units were quantified from both RWA and FWA. Qualitative analysis was performed using Agilent qualitative analysis software B.06.00 based on the exact mass of the chemical compound. Acetone, aldol, alkoxylated phenol formaldehyde resin, diethylbenzene, dipropylene glycol, d-Limonene, ether salt, ethylbenzene, n-dodecyl-2-pyrrolidone, dodecylbenzenesulfonate isopropanolamine, polyethylene glycol, and triethylene glycol were detected in FWA and RWA samples. In the van Krevelen diagram, FWA and RWA show a low degree of oxidation and highly saturated organic compounds. Kendrick mass defect (KMD) analysis was applied using ethylene oxide and propylated glycol units. KMD analysis based on ethylene oxide was scattered between 0 and 0.1, while some KMD analyses based on the propylated glycol are close to 1. FWA had an average carbon number of 32.3 and double bond equivalent (DBE) of 9.8 while RWA had average carbon number of 31.5 and DBE of 9.5. RWA contained predominantly C21-C40 compounds, while FWA had a higher concentration in the over C41 range.

Influence of softening sequencing on electrocoagulation treatment of produced water.

Electrocoagulation has been used to remove solids and some metals from both water and wastewater sources for decades. Additionally, chemical softening is commonly employed in water treatment systems to remove hardness. This paper assesses the combination and sequence of softening and EC methods to treat hydraulic fracturing flowback and produced water from shale oil and gas operations. EC is one of the available technologies to treat produced water for reuse in frac fluids, eliminating not only the need to transport more water but also the costs of providing fresh water. In this paper, the influence of chemical softening on EC was studied. In the softening process, pH was raised to 9.5 and 10.2 before and after EC, respectively. Softening, when practiced before EC was more effective for removing turbidity with samples from wells older than one month (99% versus 88%). However, neither method was successful in treating samples collected from early flowback (1-day and 2-day samples), likely due to the high concentration of organic matter. For total organic carbon, hardness, Ba, Sr, and B removal, application of softening before EC appeared to be the most efficient approach, likely due to the formation of solids before the coagulation process.

Role of lipid oxidation, chelating agents, and antioxidants in metallic flavor development in the oral cavity.

This study investigated the production of metallic flavor, which is a combination of taste and retronasal odor. Chemical reactions in the oral cavity and saliva of healthy subjects were investigated after ingesting iron and copper solutions above and near threshold levels. Significant increase in lipid oxidation (p < 0.001) occurred after metal ingestion, detected as TBARS values. Ferrous ion caused the greatest flavor sensation and lipid oxidation, followed by cupric and cuprous ions. Ferric ion did not cause metallic sensation. Occurrence of oxidation was supported by damage to salivary proteins, detected as protein-carbonyls, and by a significant increase of odorous lipid oxidation related aldehydes. Sensory evaluation demonstrated that antioxidants (vitamins E and C) minimally reduced metallic flavor but that chelating agents (EDTA and lactoferrin) removed the metallic flavor. The role of lipid oxidation is essential for the production of a metallic flavor from ingestion of ferrous, cupric, and cuprous ions.

Retronasal perception and flavour thresholds of iron and copper in drinking water.

Drinking water flavour has a strong role in water quality perception, service satisfaction, willingness to pay and selection of water sources. Metallic flavours are often caused by the dissolved iron and copper, commonly found in groundwater or introduced to tap water by corroding infrastructure. Taste thresholds of iron and copper have been investigated by several studies; however, reported results and test methods vary considerably. This study determined the taste thresholds of ferrous and cuprous ions in room temperature reagent water by using the one-of-five test with multi-nation panellists in the United States. For ferrous and cuprous ions, individual thresholds ranged from 0.003 to >5 mg l(-1) and 0.035 to >5 mg l(-1), respectively. Population thresholds were determined by logistic regression and geometric mean methods as 0.031 and 0.05 mg l(-1) for ferrous ion, and 0.61 mg l(-1) for cuprous ion by both methods. The components of metallic sensation were investigated by use of nose-clips while panellists ingested iron and copper solutions. Results showed that metallic sensation has a significant odour component and should be treated as a flavour instead of a taste. Ferrous, cuprous and cupric ions also produced weak bitter and salty tastes as well as astringent mouthfeel. In comparison, ferric ion produced no sensation.

Determining human exposure and sensory detection of odorous compounds released during showering.

Modeling of human exposure to aqueous algal odorants geosmin (earthy), 2-methylisoborneol (musty), and (trans,cis)-2,6-nonadienal (cucumber, fishy), and the solvent trichloroethylene (sweet chemical), was investigated to improve the understanding of water-air transfer by including humans as sensors to detect contaminants. A mass-transfer model was employed to determine indoor air concentrations when water was used for showering under varying conditions (shower stall volume, water and air flow rate, temperature, aqueous odorant concentration, shower duration). Statistical application of multiple linear regression and tree regression were employed to determine critical model parameters. The model predicted that concentrations detectable to the human senses were controlled by temperature, odor threshold, and aqueous concentration for the steady-state model, whereas shower volume, air flow, and water flow are also important for the dynamic model and initial detection of the odorant immediately after the showering is started. There was excellent agreement of model predictions with literature data for human perception of algal odorants in their homes and complaints to water utilities. TCE performed differently than the algal odorants due to its higher Henry's law constant, in spite of similar gas and liquid diffusivities. The use of nontoxic odorants offers an efficient tool to calibrate indoor air/water shower models.

Taste and odor abnormalities in cancer patients.

Taste and odor abnormalities are major daily concerns for patients with cancer. This review summarizes the common taste and odor disorders of cancer patients and provides insight into their possible causes. Cancer and its therapy, including chemotherapy and radiotherapy, may directly alter and damage taste and odor perception.These alterations affect the daily quality of life of these patients and may lead to patient malnutrition and, in severe cases, significant morbidity. Cancer patients experience decreases in sensitivity to taste and odor, as well as unpleasant metallic and bitter sensations. Complaints relating to taste and odor are not usually addressed, as few, if any, effective interventions are available for these problems. Understanding the types and causes of taste and odor dysfunctions will enable researchers and physicians to develop treatments for these conditions and thereby improve patient quality of life.

Developing hexanal as an odor reference standard for sensory analysis of drinking water.

There are many analytical and sensory methods to analyze drinking water for flavor and off-flavors before it reaches consumers. Flavor profile analysis (FPA) is one of the most comprehensive methods. A well-trained panel is essential for FPA and although taste standards are well established, FPA training lacks an odor reference standard. In search of an odor reference standard, four different panel groups were trained and tested for n-hexanal at various concentrations (1-1000 microg/L) over 14 months. The Weber-Fechner plots for n-hexanal showed a linear and overlapping relationship for all panels. Analytical measurements demonstrated that the headspace concentration of n-hexanal was constant after 5 sniffs at 45 degrees C and it remained constant during FPA sessions for up to 4 h. The panelists liked the grassy odor of n-hexanal, which did not result in fatigue, and testing demonstrated that approximately 95% of the population can detect n-hexanal's odor. n-Hexanal is proposed as an odor reference standard for FPA training to define odor intensities because it is chemically stable, follows Weber-Fechner law, mimics grassy odors found in drinking water, and was acceptable to the human panelists.

Determination of temperature-dependent Henry's law constants of odorous contaminants and their application to human perception.

A new method was developed to measure Henry's law constants at varying temperatures and from these data determine enthalpies of reactions for volatilization of aqueous compounds. The method was applied to 2-methylisoborneol (2-MIB), geosmin, and trans-2,cis-6-nonadienal, which are three of the major odorous compounds found in natural and drinking water. The method used static headspace equilibrium in standard odor analysis flasks and SPME-GC/MS. Dimensionless Henry's law constants were determined at 20, 25, 32, and 39 degrees C in distilled water. Their values ranged from 0.002 to 0.02 and increased with increasing temperature. The study was continued by determining the effects of different concentrations of fulvic acid added to the aqueous media. Decreases of 5-40% in Henry's law constants were observed when fulvic acid was present; however the decrease was not correlated with the fulvic acid concentration. Fulvic acid at any concentration caused a small decrease in constants for geosmin and 2-MIB, yet a more substantial decrease was obtained for nonadienal. Finally, the gas-phase concentrations were predicted using measured Henry's law constants for known aqueous concentrations of 2-MIB, geosmin, and nonadienal at 25 and 45 degrees C. An increase in the gas-phase concentration was not correlated to an increase in human perception as determined by a trained human panel. It is concluded that, after some point, panelists were not able to perceive an increase in the odorant concentration. This has important implications for controlling nuisance odors in the environment.