Enhanced biodegradation and adsorption for treating dye-containing effluents

The aim of this study is to design a biological fixed bed reactor to remove the color of azo dyes continuously. A bacterial consortium able to decolorize azo dyes was firstly isolated from a local dyeing house. The bacterial consortium was further isolated and one of the strains was selected and identified as Aeromonas sp. by 16S rDNA analysis. The decolorization of azo dyes was found to be non-specific, non-growth related and first order reaction. The decolorization works best at 37℃ in a slightly alkaline enriched medium under static condition. Only limited substrate inhibition can be found in the dye concentration (50-400 mg/L) studied. A series of activated carbons were produced from bamboo scaffolding waste by phosphoric acid activation with different conditions. Two high surface area (2123 m2/g) and mesopore volume (1.801 cm3/g) bamboo activated carbons were produced at 600℃ with impregnation ratio of 2 (BACX2) and 6 (BACX6), respectively. These two bamboo activated carbons together with other commercially available adsorbents including peat, bone char and F400 were investigated for their adsorption capacities and reversibilities. The adsorption capacity and reversibility of BACX6 were found to be the highest. It suggests that mesopore volume is important for the adsorption of the large dye molecules and weak attractions were formed between the reactive dyes and BACX6. Finally, BACX6, F400, bone char and one inert glass support (Siran) were selected and immobilized with Aeromonas sp. to investigate their color removal efficiency in the batch and fixed bed system. An enhanced color removal performance was found in the batch system and high azo dye conversion rates were achieved in the small upflow fixed bed bioreactor (UFBR). The UFBR packed with BACX6 showed the highest decolorization efficiency and was successfully removed 1.44 g Reactive Black 5 and Acid Red 18 per day with hydraulic retention time of 6 minutes. The continuous process seems to be a very effective system for the azo dye reduction and is able to overcome different operating shocks