remazol-black-b and reactive-red-2

This work assessed the application of one- and two-stage mesophilic anaerobic systems to colour removal of sulphonated mono and diazo dyes with ethanol as electron donor. The dyes Congo Red (CR), Reactive Black 5 (RB5) and Reactive Red 2 (RR2) were selected as model compounds and tested separately in seven different periods. The one-stage system (R(1)) consisted of a single up-flow anaerobic sludge blanket (UASB) reactor, whereas the two-stage system (R(2)) consisted of an acidogenic UASB reactor (R(A)), a settler and a methanogenic UASB reactor (R(M)). For CR and RB5, no remarkable difference was observed between the colour removal performance of both anaerobic systems R(1) and R(2). The experiments with RR2 revealed that R(2) was more efficient on colour removal than R(1), showing efficiencies almost 2-fold (period VI) and 2.5-fold (period VII) higher than those found by R(1). Additionally, R(2) showed a higher stability, giving a good prospect for application to textile wastewaters. Finally, the acidogenic reactor (R(A)) had an important role in the overall decolourisation achieved by R(2) during the experiments with CR and RB5 (>78 %), whereas for RR2, a more recalcitrant dye, R(A) was responsible for up to 38 % of the total colour removal.

Topics: Anaerobiosis; Bioreactors; Color; Coloring Agents; Congo Red; Electrons; Hydrogen-Ion Concentration; Naphthalenesulfonates; Oxidation-Reduction; Sewage; Textiles; Triazines; Waste Disposal, Fluid; Water Purification

In the present study the degradation of two common azo dyes used in dye houses today, Reactive Black 5 and Reactive Red 2 was evaluated in biofilters. In two experiments, bioreactors performed over 80% decolorization at a hydraulic retention time of only 28.4h with little production of metabolites. Molecular analyses showed a diverse and dynamic bacterial community composition in the bioreactors, including members of the Bacteroidetes, Acinetobacter (Gammaproteobacteria) and Clostridium (Firmicutes) that possess the capacity to reduce azo dyes. Collectively, the results indicate that the development of mixed bacterial communities from natural biomaterials contributes to an efficient and robust degradation performance in bioreactors even at high concentration of dyes.

Topics: Azo Compounds; Biodegradation, Environmental; Bioreactors; Coloring Agents; Microbial Consortia; Naphthalenesulfonates; Oryza; Triazines; Water Pollutants, Chemical