Biological and oxidative treatment of cotton textile dye-bath effluents by fixed and fluidized bed reactors

A treatability study for highly polluted and recalcitrant azo, reactive dye-baths from cotton textile dyeing processes was conducted by using fixed and up-flow fluidized bed type reactors packed with brown coal. Ozone oxidation was carried out to assess the combination of biological and chemical oxidation. COD removal efficiencies ranged from 70% to 93%, and up to 99% color removal was attained. At a COD loading rate of 25.5 x 10(-6) gCOD/m(2)-d, COD removal was 85%. Breakthrough of the brown coal used occurred at total organic loading of 0.090 gCOD/g coal. Biodegradable and inert COD fractions of the remazol dye-bath were assessed by BOD28 and oxygen uptake rate (OUR) measurements. 50% of total COD was initially inert. The inert fraction was reduced by adsorption and ozone oxidation by 65% and 40%, respectively. Brown coal is an inexpensive material and the system has economical and operational advantages as compared to treatment options such as advanced oxidation processes (AOPs) using UV, O-3, H2O2 or electrocoagulation. (C) 2009 Elsevier Ltd. All rights reserved.