Isolation and screening of bacterial isolates from wastewater treatment plants to decolorize azo dyes.

The discharge of dye-contaminated wastewater into natural waterways presents a substantial risk to human and environmental health, therefore necessitating the treatment and removal of toxic dyes from colored wastewaters before their release into the ecosystem. The aim of this study was to isolate and characterize bacterial strains capable of decolorizing and/or degrading azo dyes commonly applied in textile production (monoazo dye Reactive Orange 16 and diazo dye Reactive Green 19) from activated sludge systems used in the treatment of (textile) wastewater. Following a prescreening of 125 isolates for their decolorization potential five strains were retained for further evaluation of decolorization rate and effects of physicochemical parameters using a microtiter plate method. Of those five strains, one strain belonging to the genus Acinetobacter (ST16.16/164) and another belonging to Klebsiella (ST16.16/034) outperformed the other tested strains. Both strains exhibited strong decolorization ability (>80%) within a wide temperature range (20 °C-40 °C) and retained good decolorization activity at temperatures as low as 10 °C (especially strain ST16.16/034). Among the different pH values tested (pH 4, 7 and 10), highest dye removal for both strains occurred at pH 7, with decolorization efficiency remaining relatively high under alkaline conditions (pH 10), and neither isolates decolorization efficiency was negatively impacted by high salt or high dye concentration. Furthermore, both strains displayed the highest rate of decolorization and were able to completely (ST16.16/034) or partly (ST16.16/164) degrade the azo dyes. Altogether, our results support the use of these bacteria in the treatment of industrial wastewaters containing azo dyes.

Meerbergen K ，Willems KA ，Dewil R ，Van Impe J ，Appels L ，Lievens B ... -  《-》

Decolorization and biodegradation of reactive Red 198 Azo dye by a new Enterococcus faecalis-Klebsiella variicola bacterial consortium isolated from textile wastewater sludge.

Eslami H ，Shariatifar A ，Rafiee E ，Shiranian M ，Salehi F ，Hosseini SS ，Eslami G ，Ghanbari R ，Ebrahimi AA ... -  《-》

Oerskovia paurometabola can efficiently decolorize azo dye Acid Red 14 and remove its recalcitrant metabolite.

The biodegradation of dyes remains one of the biggest challenges of textile wastewater. Azo dyes are one of the most commonly employed dye classes, and biological treatment processes tend to generate recalcitrant aromatic amines, which are more toxic than the parent dye molecule. This study aimed to isolate bacterial strains with the capacity to degrade both the azo dye and the resulting aromatic amines towards the development of a simple and reliable treatment approach for dye-laden wastewaters. A mixed bacterial enrichment was first developed in an anaerobic-aerobic lab-scale sequencing batch reactor (SBR) fed with a synthetic textile wastewater containing the model textile azo dye Acid Red 14 (AR14). Eighteen bacterial strains were isolated from the SBR, including members of the Acinetobacter, Pseudomonas and Oerskovia genera, Oerskovia paurometabola presenting the highest decolorization capacity (91% after 24 h in static anaerobic culture). Growth assays supported that this is a facultative bacterium, and decolorization batch tests with 20-100 mg AR14 L-1 in a synthetic textile wastewater supplemented with yeast extract indicated that O. paurometabola has a high color removal capacity for a significant range of AR14 concentrations. In addition, a model typically used to describe biodegradation of xenobiotic compounds was adjusted to the results, to predict AR14 biodegradation time profiles at different initial concentrations. HPLC analysis confirmed that decolorization occurred through azo bond reduction under anaerobic conditions, the azo dye being completely reduced after 24 h of anaerobic incubation for the range of concentrations tested. Interestingly, partial (up to 63%) removal of one of the resulting aromatic amines (4-amino-naphthalene-1-sulfonic acid) was observed when subsequently subjected to aerobic conditions. Overall, this work showed the azo dye biodegradation potential of specific bacterial strains isolated from mixed culture bioreactors, reporting for the first time the decolorization capacity of an Oerskovia sp. with further biodegradation of a recalcitrant sulfonated aromatic amine metabolite.

Franca RDG ，Vieira A ，Carvalho G ，Oehmen A ，Pinheiro HM ，Barreto Crespo MT ，Lourenço ND ... -  《-》

Accelerated decolorization of reactive azo dyes under saline conditions by bacteria isolated from Arabian seawater sediment.

Khalid A ，Kausar F ，Arshad M ，Mahmood T ，Ahmed I ... -  《-》

Microalgal and activated sludge processing for biodegradation of textile dyes.

The textile industry contributes substantially to water pollution. To investigate bioremediation of dye-containing wastewater, the decolorization and biotransformation of three textile azo dyes, Red HE8B, Reactive Green 27, and Acid Blue 29, were considered using an integrated remediation approach involving the microalga Chlamydomonas mexicana and activated sludge (ACS). At a 5 mg L-1 dye concentration, using C. mexicana and ACS alone, decolorization percentages of 39%-64% and 52%-54%, respectively, were obtained. In comparison, decolorization percentages of 75%-79% were obtained using a consortium of C. mexicana and ACS. The same trend was observed for the decolorization of dyes at higher concentrations, but the potential for decolorization was low. The toxic azo dyes adversely affect the growth of microalgae and at high concentration 50 mg L-1 the growth rate inhibited to 50-60% as compared to the control. The natural textile wastewater was also treated with the same pattern and got promising results of decolorization (90%). Moreover, the removal of BOD (82%), COD (72%), TN (64%), and TP (63%) was observed with the consortium. The HPLC and GC-MS confirm dye biotransformation, revealing the emergence of new peaks and the generation of multiple metabolites with more superficial structures, such as N-hydroxy-aniline, naphthalene-1-ol, and sodium hydroxy naphthalene. This analysis demonstrates the potential of the C. mexicana and ACS consortium for efficient, eco-friendly bioremediation of textile azo dyes.

Mustafa G ，Zahid MT ，Kurade MB ，Alvi A ，Ullah F ，Yadav N ，Park HK ，Khan MA ，Jeon BH ... -  《-》