COD Fluctuations in Ozonization Columns for Wastewater Treatment Effects of Intermediate Organic Compounds

Experiments on Chemical Oxygen Demand (COD) performed in an ozonization column for wastewater treatment showed fluctuations following irregular time patterns, which could not be explained only by the experimental uncertainties or by stripping, the last being the cause of fluctuations during the first stages of ozonization procedures. Fluctuations observed in more advanced times of the experiments suggest that changes in the oxidation state of the organic matter also affected the COD values. The effect of intermediate compounds was considered in order to quantify this influence. A mathematical model is proposed in this study, which considers the consequences of intermediate compounds formed during oxidation. The different behaviors observed in the COD results of the ozonization column could be explained applying the model with different sets of adjustable constants. The joint analysis of the experimental results and the mathematical model allows suggesting that fluctuations observed in COD results, superposed to the mean decreasing trend and occurring at larger contact times, are forced by organic intermediate compounds.