Measurement of chemical oxygen demand (COD) in natural water samples by flow injection ozonation chemiluminescence (FI-CL) technique

COD determination based on ozone oxidation of alpha-naphthol combined with UV radiation (UV-O3) has been studied in the present work. Utilizing the phenomenon that luminol can be oxidized by the dissolved ozone to produce luminescence, we have established a new method of utilizing aqueous chemiluminescence to determine COD. The kinetics and mechanism of the ozonation reaction of alpha-naphthol have been investigated in order to gain a better understanding of the general applicability and limitation of the technique. Real world samples were analyzed and the results show that the relative error of COD(FI-CL) measurement for water samples was < 10%. Compared with the results of the conventional potassium permanganate method, the COD values of the FI-CL method are consistently higher (0-20% relative). The higher COD values suggest that the ozone-UV system is a more effective oxidation technique.