Investigation of decolorization kinetics and biodegradation of azo dye Acid Red 18 using sequential process of anaerobic sequencing batch reactor/moving bed sequencing batch biofilm reactor

The purpose of this study was to investigate the application of anaerobic sequencing batch reactor (An-SBR)/moving bed sequencing batch biofilm reactor (MB-SBBR) for treatment of wastewater containing Acid Red 18 (AR18). Based on statistical analysis, COD removal rate and anaerobic biomass concentration were increased with increasing initial AR18 concentration, while the specific COD removal rate was not significantly different among An-SBRs. The results revealed that the decolorization followed first-order kinetics in An-SBR1 receiving AR18 with concentration of 100 mg l(-1). However, in two other reactors with the initial dye concentration of 500 and 1000 mg l(-1), the dye was removed following two successive parts with two different reaction orders. The results showed that the dye decolorization rate increased with increasing its concentration in the feed solution. In MB-SBBRs, the ratio of attached-growth biofilm to suspended biomass concentration was increased gradually during the operation period. This ratio was measured 0.76, 0.70 and 0.51 in MB-SBBR1, 2 and 3 after three months of the reactors operation. Microscopic observations showed a large number of filamentous bacteria in the structure of attached-growth biofilm and suspended biomass in MB-SBBRs which speculated to be the reason for the different Sludge Volume Index (SVI) observed among these reactors. (C) 2012 Elsevier Ltd. All rights reserved.