Arraste de gases na ozonização convencional e catalítica de esgoto sanitário sintético

Abstract

In the process of sanitary sewage treatment, the biological stage partially meets the standards established by the current environmental legislation. It is therefore of great importance, therefore, to add a third step which aims at polishing in the treatment. Among the various options for the refinement, ozonation presents high oxidative capacity and disinfectant. However, in the process of ozonation by bubbling, besides the removal of the remaining organic material via molecular ozone and hydroxyl, the drag of volatile gases also contributes to the decay of the organic matter, being the quantification of this decay the main objective of this master's study. For this, the removals obtained by conventional and catalytic ozonation with the removals obtained through the entrainment of gases by the bubbling of an inert gas (N2) were compared. Synthetic effluent was tested at uncorrected pH, acid and basic, varying the gas injection rate (O3, and N2) between 60 and 300 L/h (60 L/h interval) and with contact time of the ascending bubbles with the effluent of 5, 10, 20, 40 and 60 min. It was also evaluated the O3 injection with activated carbon, Fe3+ and Mn2+ catalysts, compared to conventional ozone treatment. The analyzed parameters were COD, true color, turbidity, pH and ammonia. It has been observed that the true color reduction efficiency, turbidity and COD has a direct relation with the injected ozone flow rate and the contact time between the ascending ozone bubbles and the effluent. Conventional ozonation achieved removals of 73.4% COD, 86.4% color and 64.1% turbidity. The ozonation catalyzed with activated carbon removed 95.2% COD, 89.1% color and 87.4% turbidity. The Fe3+ catalyzed ozonation obtained the percentages of 37.9; 74.4 and 28.2% for removal of COD, color and turbidity, respectively. The highest removals of COD, color and turbidity obtained by the ozonation catalyzed with Mn2+ were, in this order: 36.8; 89.7 and 47.2%. Gas entrainment promoted 29.5% COD removal, 69.4% color and 61% turbidity. There were no significant ammonia removals in any of the treatments used.