The discharge of colored textile wastewaters containing dyes with different chemical characteristics into the receiving streams is a problem for toxicological, ecological and also esthetical reasons. Most of dyes are stable, and not easily degradable by the conventional treatment methods, so removal of dyes from the textile effluents is a major problem. This study aimed to investigate color removal efficiency of two aerobic filter column reactors operated as sequencing as biological and chemical treatment steps. Biological column reactor (BR) filled with basaltic lava (Scoria) as supporting media for microorganisms, and second column reactor (CR) was filled with lime and textile fly ash mixture (1:3, w/w) used as chemical treatment step especially for phosphate and color removal. The reactors were operated at batch mode to investigate the effect of hydraulic retention times (HRT), aeration time and initial dye concentration (Everzol Blue BB) on treatment efficiencies. The results of the study showed that this system has quite high removal efficiencies for soluble organics and nutrients from wastewater. COD, TOC, NH4-N and PO4-P removal rates were obtained as 94.2 %, 94.8 %, 84.7 % and 97.5% in HRT of 24 h, respectively. In addition, this two-step treatment system reached to quite high color removal efficiencies of 96.4 % Pt/Co, 96.4 % DFZ-436 nm, 99.5 % DFZ-525 nm, and 99.8 % DFZ-620 in initial dye concentration of 800 ppm.
