Standard method for the measurement of guar gum and other carbohydrates in produced water from the oil and gas industry. Written in compliance with USEPA protocols for the State of California agencies ANALYTE: D-Glucose, CAS#50-99-7 D-Mannose, CAS# 3458-28-4 D-Galactose, CAS#59-23-4 D-Lactose, CAS#63-42-3 Guar Gum, CAS#9000-30-0 INSTRUMENTATION: PerkinElmer Lambda 35 UV/VIS Spectrophotometer 1.0 Scope and Application 1.1 This method covers the determination of mannose, guar gum and other carbohydrates in produced water samples. 1.2 Sugars have varying response factors by this method (Figure 1) and the carbohydrate used for calibration must be specified in the result. 1.3 The method is based on standard curves that are specific for mannose, one of two sugars in commercial guar gum, such that the final carbohydrate concentration is expressed as mannose, mg/L. 1.4 Commercial guar gum should not be used as a calibration standard, due to variability in chemical composition and purity. 1.5 Glucose is not a structural component of guar gum and is therefore not recommended as a calibration standard. 1.6 The method is usable in the 6 to 1000 mg/L as mannose range. Detection range may be variable according to the instrument used. 2.0 Summary of Method Guar gum, a polysaccharide of galactose and mannose, is a common ingredient for hydraulic fracturing fluids [7]. Standard methods for measuring carbohydrates in flow-back and other produced water are needed, particularly in the context of reporting water quality data to regulatory agencies [6]. This method describes standard procedures for carbohydrate measurement that have been validated for use in produced water. Heating produced water with sulfuric acid hydrolyzes polysaccharides and dehydrates monosaccharides to form 2-furaldehyde from pentoses and 5-(hydroxymethyl)-2-furaldehyde from D-glucose and other hexoses [2, 8]. 2-Furaldehyde and 5-(hydroxymethyl)-2-furaldehyde reacts with anthrone to form a green colored compound [1, 2, 3, 5]. Total carbohydrate is quantified by measuring absorbance of known and unknown samples at 625 nm [2].

The authors developed and validated the Korean version of the Experiences in Close Relationships-Short Form (K-ECRR-SF) with the goal of developing a culturally responsive scale. In study 1, a Rasch analysis was conducted on the 36 original items in the ECR-Revised (ECR-R) to select items that best represent anxiety and avoidance subscales by considering cultural equivalence. In study 2, confirmatory factor analysis (CFA) was conducted for the selected 12 items with a different sample. The factor structures of the ECR-R and K-ECRR-SF through CFA were then compared through CFA. In addition, the K-ECRR-SF items were tested for related constructs (i.e., reassurance and support seeking, loneliness, dyadic satisfaction, depression, anxiety, and fear of intimacy) to its criterion evidence. The newly developed K-ECRR-SF is confirmed to be valid and culturally responsive scale in measuring attachment in Korea.

Feed spacers in reverse osmosis systems generate complex fluid flows that limit computational fluid dynamics (CFD) simulations to small length and time scales. That limits our ability to simulate mineral scaling and other membrane fouling phenomena, which occur over longer length and time scales. Thus motivated, we develop a reduced model that replaces the CFD simulation of the velocity field with an analytical model that mimics spacers. This focuses the remaining numerical effort on simulating the advection–diffusion equation governing solute transport. We motivate and validate the model with CFD simulations and bench-scale experiments of spacer filaments in three different arrangements, including cases of unsteady vortex shedding. We show that the model produces a roughly 10,000-fold speedup compared to CFD, and accurately reproduces CFD predictions of not only the average and maximum concentrations, but also the local concentration distribution along the membrane. We also demonstrate the model for simulating a feed channel with a length-to-height ratio of 200. The model provides a simple testbed for exploratory studies of multispecies transport, precipitation, and membrane fouling phenomena for which simulating spacers is often prohibitive.