Environmental Science
G. Manjarrez Paba; R. Baldiris Ávila; D. Baena Baldiris
Abstract
BACKGROUND AND OBJECTIVES:The objective of this study isto present a description of the main characteristics of azo dyes and the different treatment methods used to remove them from water. There is a special emphasis given to the benefits associated with biological treatment, predominantly those related ...
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BACKGROUND AND OBJECTIVES:The objective of this study isto present a description of the main characteristics of azo dyes and the different treatment methods used to remove them from water. There is a special emphasis given to the benefits associated with biological treatment, predominantly those related to the use of bacteria, which has to do with its competitive advantages over other microorganisms in the dye degradation processes.METHODS: The topic to be addressed was first defined through workshops with the research group. The literature review was carried out following several inclusion/exclusion criteria: the year of publication, as the selection was limited to studies published between 2010 and 2020, the focus of the investigation, which had to be related to the efficiency of different techniques for the remediation of ecosystems contaminated with azo dyes and, lastly, that the studies also discussed the use of environmental bacteria in dye degradation processes.FINDING: The efficiency of bacteria to degrade azo dyes ranges from 63-100%, the most efficient being: Marinobacter sp, Sphingobacterium sp, Enterococcus faecalis, Enterococcus casseliflavus. The bacteria that, reportedly, have greater efficiency for simultaneously removing the dye-metal complex are Bacillus circulans and Acinetobacter junii.CONCLUSION: Traditional strategies for the treatment of effluents contaminated with azo dyes are limited to physical and chemical processes that have a high energy and economic cost. For these reasons, current challenges are focused on the use of environmental bacteria capable of transforming dyes into less toxic compounds.
Sh.F. Abd El-Kader; G.A. El-Chaghaby; G.M. Khalafalla; R.I. Refae; H.M. Elshishtawy
Abstract
Congo red is a synthetic azo-dye dye with many industrial applications. The effluents containing azo dyes are causing several environmental hazards and thus should be treated prior to their discharge. The present work investigates the possible use of a novel microbial consortium from sheep compost for ...
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Congo red is a synthetic azo-dye dye with many industrial applications. The effluents containing azo dyes are causing several environmental hazards and thus should be treated prior to their discharge. The present work investigates the possible use of a novel microbial consortium from sheep compost for the decolorization of Congo red dye. The effect of different parameters including contact time, dye concentration and inoculum concentration on dye decolorization were investigated. The kinetic of dye decolorization was also assessed and the biodegradation of the dye was confirmed by different techniques. The results showed that the microbial consortium decolorized about 98% of Congo red (500 mg/L) after 24h. The efficiency of the decolorization decreased from 95% to 62% when the dye concentration increased from 100 to 500mg/L. Also, it was noticed that 75% of Congo red (25 mg/L) was decolorized at an inoculum rate of 2.5%. The kinetic results suggested that the decolorization of Congo red by the studied consortium follows the first order kinetic model. Also the maximum substrate consumption rate (Vmax) according to Michaelis- Menten model was found to be 19.30 mg/h/L and the decolorization rate constant (Km) was 116.93 mg/L. The biodegradation of Congo red was further confirmed by HPLC and GC-Ms analysis which revealed the presence of some spectral differences between the untreated dye sample and the treated one. In conclusion, the results of the present work suggest that microbial consortium from sheep compost could have potential application for bioremediation of industrial effluents containing Congo red dye.