Decolorization and Biological Degradation of AZO Dye Reactive Red2 in Anaerobic Baffled Reactors

Document Type : Research Paper


1 Faculty Member of Environmental Health, Northern Khorasan School of Medical Sciences

2 Associate Professor of Environmental Health, Isfahan University of Medical Sciences


Azo compounds are molecules with one or more azo (-N=N-) bridges linking substituted aromatic structures. They represent the largest class of dyes used in textile-processing and other industries. In the textile industry, about 15 percent of the dyestuff annually consumed in the dying process finds its way into plant effluent. Release of these compounds into the environment is undesirable because many azo dyes and their products are toxic and/or mutagenic to life. There are several physicochemical and biological methods for dye removal in aquatic environments. Removal of azo dyes in biological systems is based on anaerobic reduction of azo dyes and then mineralization of aromatic amines by aerobic systems. ABR is an anaerobic reactor with a high organic load consisting of 3 to 8 compartments across which wastewater flows. It is the aim of this investigation to study the dye and COD removal efficiencies of the ABR system. An ABR reactor with a capacity of 13.5 L and aretention time of 24 hours was used in this study. After starting up, seeding, and loading with synthetic wastewater, Reactive Red 2 (commonly used in the textile industry) was introduced into the ABR reactor. Following the start-up period, dye and COD removal efficiencies of the reactor were assessed by measuring COD and dye concentrations in the flow using standard methods. Results showed that average dye removal efficiency in the anaerobic baffled system was 89.5 percent while that of COD removal was 54.5 percent. The higher dye removal efficiency of the anaerobic systems is due to their ability to break up azo bonds. It was also revealed that increasing influent dye concentration did not have any considerable effect on COD removal efficiency. The highest dye removal percentage was observed in the primary compartment of the reactor.


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