Degradation of a model azo dye in submerged anaerobic membrane bioreactor (SAMBR) operated with powdered activated carbon (PAC)

Abstract

This work investigated the anaerobic degradation of the model azo dye Remazol Yellow Gold RNL in an upflow anaerobic sludge blanket reactor (UASB) and two submerged anaerobic membrane (SAMBR) bioreactors, one of which (SAMBR-1) was operated with powdered activated carbon (PAC) in its interior. The reactors were operated at 35 °C with a hydraulic retention time of 24 h in three operational phases, aimed to assess the effect of external sources of carbon (glucose) or redox mediator (yeast extract) on the removal or color and organic matter. The results showed that removal efficiencies of COD (73-94%) and color (90-94%) were higher for SAMBR-1 when compared to SAMBR-2 (operated without PAC) and UASB reactors. In addition, the presence of PAC in SAMBR-1 increased reactor stability, thereby leading to a lower accumulation of volatile fatty acids (VFA). The microfiltration membrane was responsible for an additional removal of ~50% of soluble residual COD in the form of VFA, thus improving permeate quality. On its turn, PAC exhibited the ability to adsorb byproducts (aromatic amines) of azo dye degradation as well as to act as source of immobilized redox mediator (quinone groups on its surface), thereby enhancing color removal.

Influence of the Applied Organic Load (Olr) on Textile Wastewater Treatment Using Submerged Anaerobic Membrane Bioreactors (Sambr) in the Presence of Redox Mediator and Powdered Activated Carbon (Pac)

“…During phases 4 (with yeast extract) and 5 (without yeast extract) the reactors were fed raw textile wastewater (without dilution) and the presence of yeast extract led to color removal efficiencies 3 times higher in SAMBR-1 and 2.7 higher in SAMBR-2. These results are in accordance with the literature (Baêta et al, 2012;Baêta et al, 2013), confirming that the kinetics of azo dye (one on the many dye classes found in textile wastewater) degradation is accelerated in the presence of redox mediators such as riboflavin, which have intermediate reduction potential values. It is important to highlight that there is only a handful of studies evaluating the effect of redox mediators on color removal of real textile wastewater.…”

“…Other works published by our research group (Baêta et al, 2013) have shown that powdered activated carbon (PAC) can be used as adsorbent of toxic byproducts of anaerobic degradation (e.g., aromatic amines) of textile dyes, as well as of some intermediate VFAs, thereby reducing thermodynamic constraints and enhancing the methanogenic and acetogenic activities. A statistical analysis of COD data (Figure 2) in the reactors SAMBR-1 (with PAC) and SAMBR-2 (without PAC) during phases 1, 2 and 4 shows that PAC influenced only phase 1 since there were no statistically significant differences (p-value > 0.05) for the other phases.…”

“…The first one is related to the PAC capacity of adsorbing dyes and dissolved compounds that interfere with the anaerobic discoloration. The second one is the presence of quinone groups on the PAC surface, which can also act as redox mediators, thereby enhancing color removal, as demonstrated by Baêta et al (2013).…”

Evaluation of soluble microbial products and aromatic amines accumulation during a combined anaerobic/aerobic treatment of a model azo dye

“…Baeta et al [24] showed that PAC had a great capacity to adsorb some intermediate VFA such as acetic (Q max = 5.80 mg/g), butyric (Q max = 5.19 mg/g) and…”

Efficient anaerobic treatment of synthetic textile wastewater in a UASB reactor with granular sludge enriched with humic acids supported on alumina nanoparticles

“…Lately, carbon based materials, such as granular (Van der Zee et al 2003) and powder activated carbon (Baêta et al 2013), black carbon (Xu et al 2013;Gong et al 2014), biochar (Oh et al 2013), activated carbon fibers (Amezquita-Garcia et al 2013;Ríos Del Toro et al 2013), carbon nano-tubes and carbon xerogels (Pereira et al 2014), as well as graphene oxide (Colunga et al 2015) have also been applied as RM to increase the redox conversion of different contaminants.…”