Determination of Chemical Oxygen Demand Using UV/O3

In this paper, we report on the development of a simple, fast, and environment-friendly UV/O 3 -based method as an improved alternative to the conventional chemical methods using dichromate or permanganate for determining chemical oxygen demand (COD) in water. In the method through the continuous monitoring of O 3 and CO 2 (concentration and flow rate) before and after reaction, COD can be accurately determined. During the experiment, sample solutions with known COD concentration of 25, 12.5, 5, 2.5, and 1 ppm were first used to validate the feasibility of this new technique. These samples were treated under ambient temperature and pressure for 15 min before the complete digestion time for each sample was measured by analyzing the produced CO 2 concentration. After digestion, residual O 3 dissolved in solution was quantified by the indigo method. A linear relationship between the O 3 consumption and COD value was observed, and the slope of calibration curve was determined to be 0.34 with a R 2 of 0.991. Detection limit of the current experimental setup is 0.81 ppm with a measurement range of 1–25 ppm. The precision of the COD measurement is within 5% of the actual concentration. This developed UV/O 3 method demonstrates viability in being applied to fast, reliable, and accurate COD monitoring.