Textile industry is faced with serious environmental problems associated with itsrnimmense wastewater discharge, substantial organic load, extreme alkalinity and heavilyrncolored effluent. The overall objective of this study was to evaluate the treatmentrnperformance of pilot anaerobic/ aerobic treatment bioprocess for the removal of organicrnmatter from textile wastewater. This was fed with raw textile wastewater obtained fromrnAwassa Textile factory. The system was inoculated with sludge biomass prepared usingrnsediment slurry samples from alkaline soda lake, Chitu. The performance of the systemrnwas evaluated using COD, BOD5, TN, NH4+-N, NO3-N, SO4 2-, S2-, PO4rn3 - and pHrnconcentrations. Color removal was monitored using spectral analysis of the influent andrneffluent samples. The system was operated at four different organic loading rates (OLR)rn(1.8, 1.5, 1.0 and 0.5 Kg/ m3day).rnResults indicated that the system was able to achieve 86.8, 90.3, 91.5 and 88.47 %rnremoval of COD and 87.1, 90.11, 92, and 87.08 % removal of BOD5 at 1.8, 1.5, 1.0 andrn0.5 Kg/m3day of OLRs, respectively. In addition, TN removal efficiencies were alsornfound to vary from 58.2, 60, 62 and 53.2 % at 1.8, 1.5, 1.0 and 0.5 Kg/m3day of OLRs,rnrespectively. Maximum removal efficiencies were recorded at the third experimental feedrn(OLR of 1.0 Kg/m3.day) where COD, BOD5 and TN concentrations decreased fromrn3140, 957 and 41.33 mg/l to nearly 264, 76, 15.7mg/l, respectively. The increasedrnremoval efficiency was found to be highly related to the increase in biomass of thernsystem. The significance of the anaerobic period was apparent in COD removal and morernthan about 70% of COD was removed in anaerobic phase. The UV-Visible spectrum ofrninfluents and effluents showed remarkable changes confirming the changes in structure ofrnparent dyes. The ammonium nitrogen concentration was increased following anaerobicrntreatment and reduced after the aerobic basin. The variations in the concentration ofrnammonium nitrogen after anaerobic treatment and in the effluent together with the shiftrnin spectral analysis provide an indirect evidence of the biodegradation of dye componentsrnin the wastewater. The results of this study showed the potential application of the systemrnusing alkaline sludge biomass for the treatment of dye containing textile wastewater