Degradação do corante vermelho reativo 239 por ozonização e avaliação do efeito dos subprodutos no desempenho e comunidade microbiana de sistema MBBR

Abstract

This study evaluated the association of the ozonation and biological processes for the degradation of reactive red 239 (RR 239) azo dye and its by-products. Ozonation tests were performed in batch with 50 mg/L the azo dye, 20 mg/L the ozone and at pH 7. The degradation of the RR 239 ozonation products was performed continuously in a single biofilm moving bed reactor (MBBR) and two MBBRs in series. Complete color removal was achieved after 12 min of ozonation. COD (62%) and DOC (35%) removals and increasing ozone consumption indicated incomplete mineralization of RR 239. Absence of dye toxicity using Vibrio fischeri was obtained after 4 min of ozonation. The RR 239 ozonation products identified were aniline, phenol, catechol and 4-amino6-chloro-1,3,5-triazine-ol. The degradation of ozonation by-products by a single MBBR led to the adaptation of heterotrophic bacteria to the ozonated effluent. Ammonium removal (40%) demonstrated the inhibition of nitrification by ozonation by-products. When degradation was performed by two MBBRs in series, the low ammonium removal (40%) revealed that the change from a single to two reactors did not improve nitrification. Tests with dye-free synthetic medium confirmed that the AOB were inhibited by the compound 4-amino-6-chloro-1,3,5-triazin-ol, not metabolized by the MBBR system. The association of ozonation and biological processes was efficient in removing RR 239, however, MBBR was fragile in the presence of triazine compounds, x which is toxic and inhibitory to nitrifiers, as confirmed by microbial community structure analysis through the 16S rRNA gene sequencing of biofilm samples.