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Improved COD Measurements for Organic Content in Flowback Water with High Chloride Concentrations
Author(s) -
Cardona Isabel,
Park Ho Il,
Lin LianShin
Publication year - 2016
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/106143016x14504669767571
Subject(s) - chemical oxygen demand , chemistry , chloride , sulfate , environmental chemistry , environmental engineering , environmental science , wastewater , organic chemistry
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.