A Modified Method For The Determination Of Chemical Oxygen Demand In Sea Water

A modified method for the determination of the chemical oxygen demand in sea water is presented in this paper. The proposed method differs from the alternate method for low COD samples described in the 17th edition of the Standard Methods for the Examination of Water and Wastewater in that it employs a pretreatment step resulting in complete halides removal from the sea water sample. Complete removal of halides is realised by adding 3 g silver sulphate per 30 ml sea water sample in a 50 ml erlenmeyer flask and mixing for 60- 90 min (when a fade lilac colour appears) followed by settling of the precipitates formed for 5-10 min with the flask in a 40 ° inclined position and finally taking slowly and with care the volume of the cleared sea water required for the COD test with a volumetric pipette.