Comparative Anaerobic Decolorization of Azo Dyes by Carbon-Based Membrane Bioreactor

Azael Fabregat,Mohammad Shaiful Alam Amin,Jaume Giralt,Agustin Fortuny,José Font,Frank Stüber

doi:10.3390/w13081060

Azael Fabregat, Mohammad Shaiful Alam Amin + Show 4 more

Open Access

https://doi.org/10.3390/w13081060

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Abstract

This study used a novel integrated technology of ceramic supported carbon membrane (CSCM) to degrade azo dyes through an anaerobic mixed culture. The CSCM worked simultaneously as biofilm support, redox mediator, and nano-filter to enhance the dye decolorization efficiency. The decolorization of Acid Orange 7 (AO7) was initially investigated with and without microorganisms in both ceramic support (CS) and CSCM reactors. The CSCM bioreactor (B-CSCM), operated with microorganisms, gave a maximum decolorization of 98% using a CSCM evolved from 10% weight (wt.) of Matrimid 5218 solution. To know the influence of permeate flow, feed concentration, and dye structure on the decolorization process, different B-CSCMs for dye removal experiments were studied over monoazo AO7, diazo Reactive Black 5 (RB5), and triazo Direct Blue 71 (DB71). The highest color removal, operated with 50 mg·L−1 feed solution and 0.05 L·m−2·h−1 of permeate flux, was 98%, 82%, and 72%, respectively, for AO7, RB5, and DB71. By increasing these parameters to 100 mg·L−1 and 0.1 L·m−2·h−1, the decolorization rate of dye solution still achieved 37% for AO7, 30% for RB5, and 26% for DB71. In addition, the system was run for weeks without apparent loss of activity. These findings make evident that the combined phenomena taking place in CSCM bioreactor result in an efficient, cost-effective, and ecofriendly azo dye decolorization method.

Highlights

Azo dyes represent the largest class of dyestuffs used in textile, paint, food, pharmaceuticals, and cosmetics industries in different stages
Water 2021, 13, 1060 by enhancing the dye removal through the promotion of a stable biofilm; the increase of the biodegradation rate and the retention of products allows deep biodegradation. This study examines these triple roles of carbon membrane on the anaerobic biodegradation of monoazo Acid Orange 7 (AO7), diazo Reactive Black 5 (RB5), and triazo Direct Blue 71 (DB71) dyes from synthetic wastewater under mixed microbial culture at constant flux
The ESEM images represent the morphology of the ceramic support (CS), and ceramic supported carbon membrane (CSCM) resulted from carbonization of 10% wt. polymeric precursor

Summary

Introduction

Azo dyes represent the largest class of dyestuffs used in textile, paint, food, pharmaceuticals, and cosmetics industries in different stages. Approximately a half-million tons of dyes are used worldwide, of which about 15% are later found in the effluent streams This fact poses an enormous threat to the environment, especially due to water pollution [1]. The degraded product or byproduct of the dyes generated from this undesirable discharge poses an adverse effect on the water quality by increasing the color, toxicity, biochemical oxygen demand (BOD), and chemical oxygen demand (COD) [2]. This contaminated water obstructs sunlight transmission, which causes a severe problem for photosynthetic organisms [3]. Wastewater treatments need to be implemented for a safe and healthy aquatic environment by keeping contaminants within permissible limits [7,8]

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