Textile effluent is characterized by high colour, chemical oxygen demand and conductivity due to presence
of a large number of recalcitrant compounds. The effluent is often discharged without an effective
treatment leading to contamination of water bodies. In the present study, a combination of mediator
assisted laccase and chemical treatment was used for decolorization of effluent from a local textile mill
in a continuous enzyme membrane reactor (EMR). Treatment of the effluent first with laccase and ABTS
(2,2
-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid))lead to about 60% decolorization but was accompanied
by membrane fouling. Addition of alum further coagulated 90% of the residual colour but the
process was associated with dye sludge formation and ABTS could not be recovered from the treated
effluent. Reversal of the treatment sequence was effective in that 85% decolorization was achieved in the
EMR and the process could be operated for over a period of 15 days. No sludge formation was noticed
and membrane fouling was negligible. Most importantly, about 60% ABTS could be recovered from the
treated effluent. Analysis of the treated effluent by mass spectrometery indicated extensive breakdown
of the dye molecules by laccase and ABTS and the breakdown products were neither toxic nor mutagenic
as assessed by measurement of the oxygen consumption rate and the standard Ames test.