Efeito de triclosano, glutaraldeído e CTAB na comunidade microbiana e no desempenho de lamas ativadas

Mixed liquor and real sewage were collected from three wastewater treatment plants, the biocides effect being initially assessed in respirometric assays. The biocide effect was also assessed in bench-scale trials, but, in this case, with mixed liquor and real sewage from only one WWTP. In the respirometric assays, all biocides showed a dose-dependent effect in the inhibition of microbial biomass respiration. In bench-scale assays, a biocidal effect was perceptible for triclosan since the lowest concentrations, and for glutaraldehyde and cetyltrimethylammonium bromide (CTAB) only at higher concentrations. The Gram negative Type 0092 was more susceptible to triclosan than to CTAB and glutaraldehyde and the Gram positive Type 0041/0675 was significantly affected by the three biocides. In the viability assays, it was shown that biocides addition gave rise to fragmentation of filamentous bacteria but also to loss of floc structure, which has to be taken in consideration when assessing the overall performance of activated sludge systems. Triclosan and CTAB showed a clear fragmentation effect, mainly on the surface of the flocs, since the beginning, and this effect remained until the end of the assay.