The objective of this study is to investigate the feasibility of applying potassium permanganate (KMnO 4 ) as the oxidant in the COD test for highly saline water samples. Initially, the COD values of various glucose standard solutions were determined by three methods, namely the standard closed reflux dichromate (COD Cr ), the acidic permanganate (COD Mn ) and the alkaline permanganate (COD OH ) methods. The results showed that at COD values lower than 20 mg/L, the standard dichromate method was not applicable due to its poor precision (RSD > 10%). The COD OH method was less effective compared to the COD Mn method as the recoveries were 0.71 and 0.89, respectively. The determination of COD OH for the standard solutions of glucose in the presence of Cl -and Br -, respectively, or both Cl -and Br -ions were conducted. The results showed that the COD values only increased 5.1% with the increase in chloride concentrations up to 35000 mg Cl -/L. This shows that the COD OH method is a suitable method for determining the COD of highly saline water samples such as estuarine and coastal waters. The COD test was conducted for river, estuarine and coastal water samples. The results indicated that the COD OH test correlates well with the COD Cr test (R 2 > 0.98). The results also indicated that this COD OH test can be applied in determining the pollution trends for estuarine and coastal waters.