Textile dyeing industry is considered as one of the largest generators of toxic chemical wastewater in India. Wastewaters from textile dyeing industries were studied for the decolourization and removal of degradable organics with tapioca sago wastewater as a co-substrate in a pilot scale two-phase Upflow Anaerobic Sludge Blanket (UASB) reactor. The UASB reactor was inoculated with seed sludge from the anaerobic digester treating sago wastewater. The colour and COD removal efficiency was studied by feeding the combined wastewater of sago and textile dyeing industry at different mixing proportion (90:10, 80:20, 75:25. 70:30, 65:35) with COD ranging from 5200 to 6320 mg L-1. The maximum COD removal was about 53.1% in acidogenic reactor (90:10 mixing ratio) and 88.5% in methanogenic reactor (70:30 mixing ratio). In methanogenic reactor at organic loading rate of 5.6 kg COD/m(3) d maximum COD (88.5%) and colour (91.3%) removal were achieved. The value of VFA/alkalinity ratio at the outlet of methanogenic reactor was less than 0.08, proves the process stability of the reactor. The maximum biogas production in methanogenic reactor was achieved at 70:30 mixing ratio. (C) 2010 Elsevier B.V. All rights reserved.