Bioaugmentation of Azo Dyes

Abstract

Biodegradation is a cost-effective method to remove the residues of azo dyes prior to their discharge in wastewater streams from dye product industries. The efficacy of this treatment method is highly dependent on establishing an effective degrader community and maintaining environmental conditions that support the growth and activity of the degrader organisms. Although activated sludge is commonly used as a source of degrader organisms to start the process, bioaugmentation of the wastewater with highly effective strains provides a much more reliable process in which the process manager can use bacterial strains that target particular dye chemicals and metabolites to achieve complete mineralization. The most effective inoculants are able to degrade dyes over a broad concentration range, tolerate a range of environmental conditions of temperature, pH, and salinity, and persist at high population densities in competition with other microorganisms in mixed microbial cultures. The use of growth supplements such as yeast extract can further enhance the biodegradation activity. The ability to achieve complete mineralization of azo dyes depends on the control of the process in which initial decolorization takes place under microaerophilic conditions with low oxygen, followed by elimination of the dye metabolites using an aeration step. In many cases, this may be best achieved by using a mixture of bacterial strains that sequentially carry out the two-step process. Practical development of bacteria for bioaugmentation requires careful screening that is based not only on their efficacy in pure culture, but also on their ability to compete with the indigenous microbial communities in wastewater streams and ability to be produced and delivered as a stable inoculum. In the future, it may be useful to consider bioaugmentation with bacteria that contain mobile genetic elements that carry catabolic pathways, thereby allowing the genes to be introduced into the indigenous microorganisms. The ability to monitor introduced bacteria or catabolic genes will continue to be important for process optimization both in the laboratory and during operation in fullscale treatment systems.

Lenzites elegans KSG32: A Novel White Rot Fungus for Synthetic Dye Decolourization

“…Synthetic dyes are complex aromatic compounds used in many industries like paper, printing, textile, food and cosmetics [1]. The major synthetic dyes include azo, triphenylmethane, anthraquinone and metal dyes.…”

Fabrication of Green Diatomite/Chitosan-Based Hybrid Foams with Dye Sorption Capacity

“…As shown in Table 1 , the presence of chitosan into the matrix did not affect significantly the density and the porosity of the structure with respect to the pristine PD [ 27 , 42 ]. Moreover, the water absorption (that is directly correlated to the presence of open pores) and the high value of open porosity suggested that the PDC60 is suitable to be applied as an adsorbent for removing toxic compounds from aqueous media, such as the anionic dye Indigo Carmine [ 44 ].…”

Efficacy of Bacterial Strains Isolated from Textile Wastewater for Degradation of Azo Dye Associated Aromatic Amines

“…The intermediate products of first step (decolorization process) are degraded by various bacterial enzymes such as hydroxylase and oxygenase (Pandey et al, 2007;Khalid et al, 2009). Furthermore, the selected bacterial strain has the ability to cleave -N=N-bond, probably with the aid of azoreductase enzyme (McMullan et al, 2001;Khalid et al, 2010).…”