Integrated chromate reduction and azo dye degradation by bacterium.

Ng, Tsz Wai.Thesis (M.Phil.)--Chinese University of Hong Kong, 2010.Includes bibliographical references (leaves 86-98).Abstracts in English and Chinese.Acknowledgements --- p.iAbstract --- p.iiTable of Contents --- p.viiList of Figures --- p.xiiiList of Plates --- p.XVList of Tables --- p.xxiAbbreviations --- p.xxiiChapter 1. --- Introduction --- p.1Chapter 1.1 --- "Pollution, toxicity and environmental impact of azo dye" --- p.1Chapter 1.2 --- Common treatment methods for dyeing effluent --- p.2Chapter 1.2.1 --- Physicochemical methods --- p.2Chapter 1.2.1.1 --- Coagulation/ flocculation --- p.2Chapter 1.2.1.2 --- Adsorption --- p.3Chapter 1.2.1.3 --- Membrane filtration --- p.4Chapter 1.2.1.4 --- Fenton reaction --- p.4Chapter 1.2.1.5 --- Ozonation --- p.5Chapter 1.2.1.6 --- Photocatalytic oxidation --- p.6Chapter 1.2.2 --- Biological treatments --- p.7Chapter 1.2.2.1 --- Degradation of azo dyes by bacteria --- p.8Chapter 1.2.2.1.1 --- Anaerobic conditions --- p.8Chapter 1.2.2.1.2 --- Aerobic conditions --- p.9Chapter 1.2.2.1.3 --- Combined anaerobic and aerobic conditions --- p.10Chapter 1.2.2.2 --- Decolourization of azo dyes by fungi --- p.11Chapter 1.2.2.3 --- Mechanisms of azo dye reduction by microorganisms --- p.12Chapter 1.3 --- "Chromium species, toxicity and their impacts on environment" --- p.14Chapter 1.4 --- Common treatment methods for chromium --- p.16Chapter 1.4.1 --- Chemical and physical methods --- p.16Chapter 1.4.2 --- Biological methods --- p.17Chapter 1.4.2.1 --- Chromium reduction by aerobic bacteria --- p.17Chapter 1.4.2.2 --- Chromium reduction by anaerobic bacteria --- p.18Chapter 1.5 --- Studies concerning azo dye and Cr(VI) co-treatment --- p.19Chapter 1.6 --- Response surface methodology --- p.21Chapter 1.6.1 --- Response surface methodology against one-factor-at-a-time design --- p.22Chapter 1.6.2 --- Phases of response surface methodology --- p.25Chapter 1.6.3 --- 2 - level factorial design --- p.26Chapter 1.6.4 --- Path of steepest ascent --- p.27Chapter 1.6.5 --- Central composite design --- p.28Chapter 2. --- Objectives --- p.30Chapter 3. --- Materials and Methods --- p.31Chapter 3.1 --- Isolation of bacterial strains --- p.31Chapter 3.1.2 --- Azo dye decolourization --- p.33Chapter 3.1.3 --- Chromate reduction --- p.34Chapter 3.2 --- Identification of selected bacterial strains --- p.35Chapter 3.2.1 --- Gram stain --- p.35Chapter 3.2.2 --- Sherlock® Microbial Identification System --- p.35Chapter 3.2.3 --- 16S ribosomal RNA sequencing --- p.37Chapter 3.3 --- Optimization of dye decolourization and chromate reduction efficiency with response surface methodology --- p.38Chapter 3.3.1 --- Minimal-run resolution V design --- p.38Chapter 3.3.2 --- Path of steepest ascent --- p.40Chapter 3.3.3 --- Central composite design --- p.41Chapter 3.3.4 --- Statistical analysis --- p.43Chapter 3.3.5 --- Experimental validation of the optimized conditions --- p.43Chapter 3.4 --- Determination of the performance of the selected bacterium in different conditions --- p.43Chapter 3.5 --- Determination of azoreductase and chromate reductase activities --- p.44Chapter 3.5.1 --- Preparation of cell free extract --- p.44Chapter 3.5.2 --- Azoreductase and chromate reductase assay --- p.45Chapter 3.6 --- Determination and characterization of degradation intermediates --- p.45Chapter 3.6.1 --- Isolation and concentration of the purple colour degradation intermediate --- p.45Chapter 3.6.2 --- Mass spectrometry analysis --- p.47Chapter 3.6.3 --- Atomic absorption spectrometry analysis --- p.48Chapter 4. --- Results --- p.49Chapter 4.1 --- Azo dye decolourizing and chromate reducing ability of the isolated bacterial strain --- p.49Chapter 4.2 --- Identification of selected bacterium --- p.50Chapter 4.3 --- Optimization of dye decolourization and chromate reduction efficiency with response surface methodology --- p.50Chapter 4.3.1 --- Minimal-run resolution V design --- p.50Chapter 4.3.2 --- Path of the steepest ascend --- p.54Chapter 4.3.3 --- Central composite design --- p.55Chapter 4.3.4 --- Validation of the predicted model --- p.62Chapter 4.4 --- Performance of the selected bacterium in different conditions --- p.62Chapter 4.4.1 --- Chromate and dichromate --- p.62Chapter 4.4.2 --- Initial pH --- p.63Chapter 4.4.3 --- Low and high salt concentration --- p.63Chapter 4.4.4 --- Initial K2CrO4 concentration --- p.63Chapter 4.4.5 --- Initial Acid Orange 7 concentration --- p.63Chapter 4.4.6 --- Nutrients limitation --- p.64Chapter 4.5 --- Chromate reductase and azoreductase activities --- p.67Chapter 4.6 --- Determination of degradation intermediates --- p.67Chapter 4.6.1 --- Mass spectrum of the degradation intermediate --- p.68Chapter 4.6.2 --- Chromium content of the degradation intermediate --- p.70Chapter 5. --- Discussion --- p.71Chapter 5.1 --- Characteristic of Brevibacterium linens --- p.71Chapter 5.2 --- Optimization of dye decolourization and chromate reduction with response surface methodology --- p.72Chapter 5.3 --- Performance of Brevibacterium linens under different culture conditions --- p.75Chapter 5.4 --- Postulation of mechanisms --- p.76Chapter 5.4.1 --- Possible reasons of unexpected results of the effect of initial Acid Orange 7 and K2CrO4 concentration --- p.76Chapter 5.4.2 --- Properties of the purple colour degradation intermediate --- p.78Chapter 5.4.3 --- Mechanisms likely responsible for the chromate reduction --- p.80Chapter 5.4.4 --- Explanation of the unexpected results --- p.80Chapter 6. --- Conclusions --- p.83Chapter 7. --- References --- p.86Chapter 8. --- Appendices --- p.99Chapter 8.1 --- Definition and calculation of different terms in 2-level factorial design --- p.99Chapter 8.2 --- Definition and calculation of different terms in ANOVA table --- p.100Chapter 8.3 --- Aliases of terms and resolution --- p.103Chapter 8.4 --- Moving of factors in path of steepest ascent --- p.105Chapter 8.5 --- Estimation of the parameters in linear regression models --- p.106Chapter 8.6 --- Definition and calculation of different terms in test of fitness --- p.10