A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources and Development

Thesis (M.Eng.) - Asian Institute of Technology, 1997

The work presented in this report concerns the application of two stage activation process for treatment of effluents from textile units containing disperse and reactive dyes respectively, for its COD and colour removal . The treatment process is characterized by a high load first stage followed by a low load second stage to obtain removal of biodegradable organics and colour . The first stage emphasizes on rapid colour removal by adsorption while the second stage emphasizes specially on COD removal by the process ofbiodegradation. During the batch process the F/M ratio was varied from 0.58 to 0.79 kgCOD/kgMLSS in first stage for both reactive and disperse dyes and 0.23 to 0.29 kgCOD/kgMLSS for disperse dyes and 0.21 to 0.43 kgCOD/kgMLSS for reactive dyes respectively in second stage aeration. The results of batch process shows that it is possible to obtain a reduction of more than 85% of incoming soluble COD and 80% reduction of the incoming ADMI unit ( colour ), resulting in an effluent quality of 23 lmg/L of soluble COD and 210 ADMI unit for disperse dye effluent and 177mg/L soluble COD and 405 ADMI unit for reactive dye effluent. The remaining fraction of soluble COD measured is considered to be mainly non-biodegradable by conventional biological treatment system. The SVI value between 101 - 108ml/g in the first settling tank indicates better settleability of sludge as compared to second settling tank where SVI value was between 110 - 132ml/g. It was concluded that two stage activation process gives better COD and colour removal than single stage activation process.