Characterization and modelling of denim-processing wastewaters for activated sludge

The study involved characterization of denim-processing wastewaters, mainly to generate the necessary experimental data for the modelling and evaluati on of the activated sludge process. The striking feature of the wastewater quality was the excessive suspended solids content requiring effective remo val before biological treatment. COD fractionation was, however, typical fo r a textile effluent in general, with a biodegradable fit-action of 90%, a readily biodegradable COD ratio of 20%, a predominantly soluble slowly biod egradable fraction of 55-60% and negligible particulate inert COD. Hydrolys is was identified as the significant step in the biodegradation kinetics wi th rate coefficients quite specific to plant operation. Evaluation of the h ydrolysis kinetics showed that the magnitude of the slowly biodegradable CO D could be reduced with a higher hydraulic detention time, effectively impr oving the quality of the soluble effluent. (C) 2001 Society of Chemical Ind ustry.