Biodegradation studies on dye effluent and selective remazol dyes by indigenous bacterial species through spectral characterisation

Effluent collected from a dye industry in Tirupur, Tamilnadu, India, was screened for potential indigenous micro-organisms to treat remazol dyes and dye effluents. Out of sixty strains isolated, four strains were found to be potential in degrading the dye effluent and various remazol reactive dyes. The physicochemical characterisation of the dye effluent showed quite high values. Decolourisation studies were performed for two different effluents (I & II) and observed maximum decolourisation of 76.4% at 120 h (Effluent I) and 79.9% at 96 h (Effluent II) by the organism EI25. The synthetic dyes Remazol Red RGB (RR-RGB), Remazol Red RR (RR-RR), Remazol Yellow RGB (RY-RGB) and Remazol Yellow RR (RY-RR) showed complete decolourisation (100%) after 24–72 h by two potential strains (EI05 and EI25). EI25 have shown the maximum efficiency of 87.2, 95.1, 89.4 and 84.4% decolourisation for RR-RGB, RR-RR, RY-RGB and RY-RR, respectively, within a 24 h time period. Morphological characteristics and biochemical screening tests identified the organisms to be Clostridium butyricum and Clostridium acetobutylicum. C. acetobutylicum (EI25) was found to be the most potential strain isolated. Biodegradation of remazol dyes was characterised by spectral analysis using UV–Visible spectroscopy and FTIR spectroscopy. The peak disappearance in UV spectrum is at the λmax 519nm for RR-RGB and RR-RR; whereas, 410nm for RY-RGB and 419nm for RY-RR stands as the proof of decolourisation. In the FTIR spectrum, the shift of several important peaks responsible for the functional groups N=N, S=O and phenolic O–H corresponding to the structure of remazol group of dyes and appearance of new peaks indicating the degradation metabolites observed in the decolourised samples ensures biodegradation. Further, EI25 have also shown marked reduction in the basic wastewater characteristics like COD, BOD, TDS, EC and pH. Thus it is concluded that the Clostridium species on further studies can be well developed into a biological method of textile effluent treatment process.