Decolorization and degradation analysis of Disperse Red 3B by a consortium of the fungus Aspergillus sp. XJ-2 and the microalgae Chlorella sorokiniana XJK

Abstract

Disperse Red 3B, an anthraquinone dye, was decolorized by a consortium, which was constituted of the fungus (Aspergillus sp. XJ-2) and the microalgae (Chlorella sorokiniana XJK). The consortium performed better than the single system in terms of decolorization and nutrient removal simultaneously in the simulated wastewater of Dispersed Red 3B. The decolorization rate could reach 98.09% by the consortium under the optimized conditions. The removal rate of COD (Chemical Oxygen Demand), TP (Total Phosphorus), and ammonia nitrogen reached 93.9%, 83.9% and 87.6%. Also, the consortium could tolerate higher salt and dye concentration than the single system did. In this co-cultural system, the lignin peroxidase and manganese peroxidase enzyme activities contributed to the degradation of Disperse Red 3B, which reached 86.7 U L^-1 and 122.5 U L^-1. The result of fermentation liquid analysis with UV-vis, FTIR and GC-MS showed that the colored functional group of the dye was broken and the Dispersed Red 3B was degraded into small molecular compounds with low toxicity. It was suggested that degradation plays a major role during the color removal process. The consortium exhibited greater potential in terms of color removal and water pollutant removal than the separate system did.

Fig. 1. Chemical structure of Disperse Red 3B.

Fig. 2. Decolorization rate of simulated wastewater under different conditions. (a) Inoculation ratio of XJ-2 and XJK; (b) inoculation time of XJ-2; (c) pH; (d) temperature; (e) rotation speed of shaker.

Fig. 3. Co-culture morphology of the Aspergillus sp. XJ-2 and Chlorella sorokiniana XJK. (a) Macro morphology; (b) microstructure. (c) Simulation diagram.

Fig. 4. Decolorization rate of simulated wastewater after 4 days treatment by single Chlorella sorokiniana XJK, single Aspergillus sp. XJ-2 and the consortium. (a) Decolorization effect of simulated wastewater; (b) decolorization rate and biomass under used different microbial systems (D: decolorization rate; B: biomass).

Fig. 5. The pollutant removal performances of single Chlorella sorokiniana XJK, single Aspergillus sp. XJ-2 and the consortium. (a) Removal of COD; (b) removal of TP; (c) removal of ammonia nitrogen.

Fig. 6. Decolorization rate of single Chlorella sorokiniana XJK, single Aspergillus sp. XJ-2 and the consortium under different dye concentrations.

Fig. 7. Decolorization rate of simulated wastewater under different NaCl concentrations by single Aspergillus sp. XJ-2, single Chlorella sorokiniana XJK and the consortium.

Fig. 8. Decolorization rate and microbial biomass of simulated wastewater by the consortium of XJ-2 and XJK. (a) Decolorization and biomass; (b) adsorption and degradation (NN: XJ-2 and XJK; IN: XJ-2 of inactivated and XJK; NI: XJ-2 and XJK of inactivated; II: XJ-2 of inactivated and XJK of inactivated; AD: the adsorption capacity of the consortium; DE: the degradation capacity of the consortium; DA: the decolorizing capacity of the consortium).

Fig. 9. Degradation products analysis of Disperse Red 3B by the consortium of Aspergillus sp. XJ-2 and Chlorella sorokiniana XJK on the first second, the second day and the fourth day. (a) UV-vis analysis; (b) FTIR analysis.

Fig. 10. GC-MS analysis of degradation products about Disperse Red 3B.

Fig. 11. Degradation pathway analysis of Disperse Red 3B.