Ozonização convencional e gas stripping no pós-tratamento de efluente sanitário

Abstract

The present research, of experimental character, focused on post-treatment of sanitary effluent through conventional ozonation and gas stripping in bubbling column. The matrix sanitary effluent comes from a city with approximately 700 thousand people, effluent this treated in UASB (Upflow Anaerobic Sludge Blanket) reactor followed by flocculation/flotation. As for the experimental configuration, in the conventional ozonization were applied ozone loads of 2.07, 5.38 and 7.15 gO3/h (surface application rates of 127.4, 382.2 and 636.9 L/min.m2, respectively) to the contact times between the ascending bubbles and the liquid medium of 30 and 60 minutes. Gas stripping experiments maintained the same rates of surface application and contact times. In the conventional ozonation were investigated the pH, color, turbidity, COD, ammoniacal nitrogen, nitrate and E. Coli parameters; while, in the gas stripping, were investigated the pH, color, turbidity, COD, ammoniacal nitrogen and nitrate parameters. The statistical method of Anova allowed to identify which variables (flow rate and contact time) were relevant to the experimental investigations under study. In the ozonation and gas stripping, respectively, there was an increase in pH values (10.39% ± 2.18 e 20.17% ± 1.04) and reductions in color (89.11% ± 4.05 e 42.44% ± 6.97), turbidity (68.28% ± 9.78 e 36.51% ± 18.58), DQO (70.11% ± 8.87 e 35.49% ± 7.37) and ammoniacal nitrogen (10.82% ± 1.55 e 9.25% ± 0.54) and E. Coli (99.82% ± 0.28) parameters; however, nitrate was only raised in the ozonation tests (on the order of 6 times), remaining constant in the gas stripping. For all cases, the physical-chemical and biological parameters were not influenced significantly by the applied gas dosages, but only the contact times. The results obtained allowed to infer that the ozonation is able to promote the removal of the organic compounds present in the study effluent through of the oxidation and of the gas stripping of volatiles organic compounds, while the gas stripping technique is able to remove the volatiles organic compounds and free ammonia. From the experimental results, it is estimated that about 50% of the organic matter removal during the conventional ozonation tests refers to the stripping of volatile organic compounds present in the liquid mass.