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. 2015 Jun 16;12(6):6894-918.
doi: 10.3390/ijerph120606894.

Mineralization and Detoxification of the Carcinogenic Azo Dye Congo Red and Real Textile Effluent by a Polyurethane Foam Immobilized Microbial Consortium in an Upflow Column Bioreactor

Harshad Lade  1 , Sanjay Govindwar  2 , Diby Paul  3
Affiliations

Mineralization and Detoxification of the Carcinogenic Azo Dye Congo Red and Real Textile Effluent by a Polyurethane Foam Immobilized Microbial Consortium in an Upflow Column Bioreactor

Harshad Lade et al. Int J Environ Res Public Health. .

Abstract

A microbial consortium that is able to grow in wheat bran (WB) medium and decolorize the carcinogenic azo dye Congo red (CR) was developed. The microbial consortium was immobilized on polyurethane foam (PUF). Batch studies with the PUF-immobilized microbial consortium showed complete removal of CR dye (100 mg·L-1) within 12 h at pH 7.5 and temperature 30 ± 0.2 °C under microaerophilic conditions. Additionally, 92% American Dye Manufactureing Institute (ADMI) removal for real textile effluent (RTE, 50%) was also observed within 20 h under the same conditions. An upflow column reactor containing PUF-immobilized microbial consortium achieved 99% CR dye (100 mg·L-1) and 92% ADMI removal of RTE (50%) at 35 and 20 mL·h-l flow rates, respectively. Consequent reduction in TOC (83 and 79%), COD (85 and 83%) and BOD (79 and 78%) of CR dye and RTE were also observed, which suggested mineralization. The decolorization process was traced to be enzymatic as treated samples showed significant induction of oxidoreductive enzymes. The proposed biodegradation pathway of the dye revealed the formation of lower molecular weight compounds. Toxicity studies with a plant bioassay and acute tests indicated that the PUF-immobilized microbial consortium favors detoxification of the dye and textile effluents.

Keywords: Congo red; column bioreactor; decolorization; immobilization; microbial consortium; mineralization.

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Figures

Figure 1
Figure 1
Schematic diagram of the developed upflow column bioreactor.
Figure 2
Figure 2
PCR-DGGE profile of microbial consortium.
Figure 3
Figure 3
Batch studies on the effect of operational variables on the decolorization of CR dye by a PUF-immobilized microbial consortium. (A) Microaerophilic and aerobic incubation; (B) pre-grown culture medium Ph; (C) incubation temperatures and (D) initial CR dye concentrations. The percent decolorization was measured after 12 h of incubation at 30 ± 0.2 °C unless otherwise stated. Data points indicate the mean of three independent replicates; ±Standard errors of mean (SEM) is indicated by error bars.
Figure 4
Figure 4
Batch studies on decolorization of RTE by PUF-immobilized microbial consortium at 30 ± 0.2 °C. (A) Microaerophilic and aerobic incubation; and (B) different RTE concentrations v.z. 25%, 50% and 75%. Decolorization was measured in terms of percent ADMI removal. Data points indicate the mean of three independent replicates; ±SEM is indicated by error bars.
Figure 5
Figure 5
Decolorization of CR dye (100 mg·L−1) and RTE (50%) by PUF-immobilized microbial consortium under upflow column bioreactor conditions at various flow rates. Data points indicate the mean of three independent replicates; ±SEM is indicated by error bars.
Figure 6
Figure 6
HPLC profile of (A) CR dye and (B) its decolorized products obtained after treatment with PUF-immobilized microbial consortium in an upflow column bioreactor.
Figure 7
Figure 7
FTIR profile of (A) CR dye and (B) its decolorized products obtained after treatment with PUF-immobilized microbial consortium in an upflow column bioreactor.
Figure 8
Figure 8
The proposed biodegradation pathway of CR dye by PUF-immobilized microbial consortium in an upflow column bioreactor.
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