title: Improved COD Measurements for Organic Content in Flowback Water with High Chloride Concentrations.
abstract: An improved method was used to determine chemical oxygen demand (COD) as a measure of organic content in water samples containing high chloride content. A contour plot of COD percent error in the Cl(-)-Cl(-):COD domain showed that COD errors increased with Cl(-):COD. Substantial errors (>10%) could occur in low Cl(-):COD regions (<300) for samples with low (<10 g/L) and high chloride concentrations (>25 g/L). Applying the method to flowback water samples resulted in COD concentrations ranging in 130 to 1060 mg/L, which were substantially lower than the previously reported values for flowback water samples from Marcellus Shale (228 to 21 900 mg/L). It is likely that overestimations of COD in the previous studies occurred as result of chloride interferences. Pretreatment with mercuric sulfate, and use of a low-strength digestion solution, and the contour plot to correct COD measurements are feasible steps to significantly improve the accuracy of COD measurements.
authors.affiliation: Department of Civil and Environmental Engineering, West Virginia University, Morgantown, WV 26505, USA.
authors.forename: Isabel
authors.initials: I
authors.lastname: Cardona
authors.forename: Ho Il
authors.initials: HI
authors.lastname: Park
authors.forename: Lian-Shin
authors.initials: LS
authors.lastname: Lin
mesh_terms: D057919:Biological Oxygen Demand Analysis / Q000379:methods* / Q000592:standards; D001965:Bromides; D002712:Chlorides; D003124:Colorimetry; D017669:Mercury Compounds; D010795:Phthalic Acids; D054712:Salinity; D013431:Sulfates
chemical_list: D001965:Bromides; D002712:Chlorides; D017669:Mercury Compounds; D010795:Phthalic Acids; D013431:Sulfates; C032279:phthalic acid; C028430:mercuric sulfate