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Membrane Water Treatment   Volume 5, Number 4, October 2014, pages 281-293
Decolorization kinetics and characteristics of the azo dye acid red 18 in MSBR system at various HRTs and SRTs
M. Hasani Zonoozi, M.R. Alavi Moghaddam and R. Maknoon

Abstract     [Buy Article]
    The present work aimed to study the decolorization kinetics and characteristics of a selected azo dye under the influence of two key operational parameters including hydraulic retention time (HRT) and solid retention time (SRT). The decolorization efficiency and the two important criteria of k and normalized k (k/MLSS) were evaluated in lab-scale membrane sequencing batch reactors (MSBRs) at various HRTs of 48, 24 and 16 h (with constant SRT) and in addition, at various SRTs of infinity, 40 and 10 d (with constant HRT). According to the obtained results, both zero and first-order kinetics were properly fitted the decolorization profiles of the selected azo dye in all of the applied HRTs and SRTs. Increase of both HRT and SRT positively affected the decolorization efficiency. More MLSS concentrations corresponded to the lower HRTs and the higher SRTs resulted in higher decolorization rate constants (k). However, the effect of reducing the HRT was not compensated by increase of the MLSS concentration in order to reach higher decolorization efficiency. In addition, increase of the decolorization efficiency, as a consequence of the higher MLSS concentrations at longer SRTs, was restrained by decrease of the time-limited decolorization capability of biomass (represented by normalized k). Evaluation of both k and normalized k is suggested in order to have a more precise study on the decolorization kinetics and characteristics.
Key Words
    decolorization kinetics and characteristics; hydraulic retention time; solid retention time; decolorization rate constant (k); normalized k
Civil and Environmental Engineering Department, Amirkabir University of Technology, Hafez Ave., Tehran15875-4413, Iran.

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