A new approach for chemical oxygen demand (COD) measurement at high salinity and low organic matter samples |
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Authors: | Necati Kayaalp Mustafa Evren Ersahin Hale Ozgun Ismail Koyuncu Cumali Kinaci |
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Institution: | (1) Department of Environmental Engineering, Istanbul Technical University Civil Engineering Faculty, Maslak, Istanbul, 34469, Turkey; |
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Abstract: | Background, aim, and scope Chemical oxygen demand (COD) is used as a discharge standard parameter in wastewater treatment plant design, environmental
modelling and many other applications. Chloride interference is an important problem of COD measurement for wastewaters containing
low organic matter and high chloride concentrations. In case of chloride concentrations up to 2,000 mg/L, mercury sulphate
addition at a ratio of 10:1 (HgSO4:Cl−) can adequately mask the interference. When chloride concentration exceeds 2,000 mg/L, this ratio becomes ineffective to
hinder the interference. At this point, it is proposed to use a greater and constant ratio of mercury sulphate addition. However,
this application sometimes results in extra mercury sulphate addition which is not necessary. Even in some cases, greater
addition of mercury sulphate alone is not a solution to erroneous measurement results. The purpose of the study is to determine
optimum HgSO4:Cl− ratios according to the chloride concentrations of the samples and to show the importance of the strength of the digestion
solution for the correct determination of the COD parameter. |
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