Biodegradation of azo dye Orange II using a granular activated carbon (GAC)-biofilm configured biological treatment systems

Abstract

Dyeing industry effluents constitute one of the most problematic wastewaters to be treated not only for their high chemical and biological oxygen demands, suspended solids and content in toxic compounds but also for color, which is the first contaminant to be recognized by human eye. The aim of this study is to investigate the removal of azo dye Orange II by granular activated carbon (GAC)-biofilm configured biological treatment systems, namely GAC-biofilm configured sequencing batch reactor (SBR) and GAC-biofilm configured packed-column. The main advantages of immobilization cells on GAC particles as biofilm compared to the suspended cells include the high biomass hold up, protection of cells against toxic substances and prevention of suspended bacterial biomass in the effluent. It was observed that the GAC-biofilm configured biological systems demonstrated better performance in the removal of color and organic matter compared to the previous study in suspended cells systems especially at high dye concentration (> 600 mg/l). Based on the result obtained, the GAC-biofilm configured SBR system showed better performance in the removal of organic matter compared to GAC-biofilm configured packed column system especially at high organic concentration in feed solution which could be due to the presence of mixed aerobic and anaerobic microbes at different levels in the bioreactor.