Decolorization Of Azo Dye By Halophytes Rhizosphere Microorganisms Under Salinity Circumstance

The purpose of this thesis is to investigate the decolorization of azo dye Reactive Brilliant Red X-3B by inoculating salt-tolerant bacteria GTY to plant rhizosphere and the ecotoxicological effects of azo dye on those plants were studied. This thesis belongs to the field of wastewater bioremediation; Knowledge in the field of microorganism and plant rhizosphere was applied on this resarch. The interactions between plants and microorganisms were studied. Results showed that there is a promising future for the application of rhizosphere and microorganisms in dye stuff wastewater treatment.Firstly, the effect of salt and dye concentration on germination, root's length, peroxidase (POD) activity and the amount of total phenolics (ATP) in Sesbania cannabina Pers (SCP) were studied. Results showed that the relative inhibitory rates of germination and root's length were less than 50% when the concentration of NaCl was below 0.6%. There is no obvious effect of dye concentration on germination and root's length of SCP was observed, when the initial dye concentration below than 1000 mg/L, which implied the tolerance of plants on SCP of azo dye. The prohibiting effect of NaCl on POD activity and ATP amount at the beginning of SCP germination, but this restrain was decreased with time. Positive effect was detected of Reactive Brilliant Red X-3B on the activity of POD and ATP. Compared to control treatment, ATP increased by 2-3 times while exposing to high concentration of Reactive Brilliant Red X-3B. And the POD activity increased with high concentrations of Reactive Brilliant Red X-3B, at the meantime, the influence of NaCl on POD activity was reduced. With the appearance of Reactive Brilliant Red X-3B, the influence of POD activity caused by 0.5%NaCl decreased to 26%. Increasing of POD activity and ATP was attributed to the adaption of SCP to environmental stress.Secondly, the performance of salt-tolerant GTY for decolorization of Reactive Brilliant Red X-3B under different conditions was investigated. Results showed that Reactive Brilliant Red X-3B could be decolorized by GTY with a vide range of pH and dye concentration. The best decolorization efficiency was achieved with pH value 7-9, initial dye concentration less than 600 mg/L. and the logarithmic growing stage. High inoculation concentration could increase the decolorization rate, however with less effect on decolorization efficiency. Finally, the effects of plants (e.g. Suaeda salas (L.) pall) and associated root extract on the growth of microorganisms as well as decolorization were studied.Results showed that the root extract improved the Reactive Brilliant Red X-3B declorizaion of GTY in a sequence of Suaeda salas (L.) pall > Medicago sativa > Sesbania cannabina Pers. The increasing of decolorization mainly comes from the promoting growth of microorganism by plants, although plant root could also adsorb/absorb dyes. After 4 days treatments, the azo dye decolorazation rate of sterilized plants was 8.75%, while it reached 89.0% in the co-existance system with plants and microorganisms.