No abstract

In this work, the biodegradation of by-products formed by ozonation of the azo dye Reactive Red 239 was evaluated using two MBBRs in series. Two ozone dosages were applied and low carbon removals and increasing ozone consumption observed after discoloration show the formation of oxidation resistant by-products. Five by-products were identified by GC/MS. High COD removal (90%) was observed in the biological process. However, nitrification inhibition was observed with ammonium removal of only 40%. This inhibition was probably caused by 4-amino-6-chloro-1,3,5-triazine-2-ol, which passed unscathed in the MBBRs. The nitrifying activity of the biofilm was restored when the MBBRs in series were fed with synthetic effluent (without by-products), proving the inhibition of nitrifying bacteria by ozonation by-products. The association of ozonation with the biological process was efficient in RR 239 color removal and degradation of some by-products. Higher ozone dosages are required for triazine oxidation, which probably inhibited nitrification in the MBBRs in series. The importance of identifying by-products formed by ozonation and their metabolization or not in a biological process is clear. In addition to partially inhibiting nitrification, special attention should be paid to chemicals that pass undegraded through a biological process and can be released into receiving bodies.

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Clay minerals are widespread in natural systems and have been widely used for the removal of pollutants. In this study, natural expanded vermiculite was used in adsorption tests to remove ammonium nitrogen from landfill leachate. The modification of vermiculite was carried out using NaOH and HCl, and for both modifications the best concentration was 0.1 mol/L. The results produced by XRD (X-ray diffraction) showed that Al replaced K after modification of the vermiculite using HCl and that Mg and Na replaced K after modification using NaOH. It was observed that the adsorption capacity increased as the percentage in mass of K diminished. The Langmuir is the isotherm that presents the best fit of the data, and the values of RL (the Langmuir coefficient) suggest that the adsorption is linear. The thermodynamic parameters indicate that the process is spontaneous and endothermic, that there is a high affinity between the adsorbate and the adsorbent, and that physical adsorption is prevalent.