Dyestuff wastewater treatment using chemical oxidation, physical adsorption and fixed bed biofilm process

Abstract

Fenton's oxidation and activated carbon adsorption were examined as pretreatment processes for dyestuff wastewater having high salinity, colour, and non-biodegradable organic concentrations. In this work, each wastewater stream produced by individual production processes was classified as streams R1, R2, and R3. The stream having a value of BOD5/COD lower than 0.4 was pretreated by Fenton's oxidation or activated carbon adsorption to increase the ratio of BOD5/COD which indicates biodegradability. For Fenton's oxidation with one stream having a value of BOD5/COD lower than 0.4, the optimal reaction pH was 3.0 and the minimum dosing concentration (mg l(-1)) of H2O2:FeSO4. 7H(2)O was 700:3500. Stream R3, which consisted mainly of methanol was efficiently treated by activated carbon adsorption. The ratio of BOD5/COD was also increased to 0.432 and 0.31 from 0.06 in Fenton's oxidation and activated carbon adsorption, respectively. A biological treatment system using a fixed bed reactor was also investigated to enhance biological treatment efficiency at various hydraulic retention times, pretreatment conditions by Fenton's reagent and salt concentrations by dyestuff wastewater. In addition, the efficiency of Fenton's oxidation as a post-treatment system was also investigated to present a total treatment process of dyestuff wastewater. As the influent COD and salinity were increased, the effluent SS and COD were consequently increased. However, as the microorganisms became adapted to the changed influent condition, the treatment efficiency of the fixed bed reactor quickly recovered under the high COD and salinity since the microorganisms were well adapted to toxic influent conditions. A wastewater treatment process consisting of chemical oxidation, activated carbon adsorption, fixed bed biofilm process and Fenton's oxidation as a post-treatment system can be useful to treat dyestuff wastewater having high salinity, colour, and non-biodegradable organic concentration. (C) 1999 Elsevier Science Ltd. All rights reserved.