Studies on biodegradation and decolorization of distillery spent wash using fungi and cyanobacteria

Abstract

Ethanol industry is one of the major agro-based industries, which utilize molasses as a raw material for the production of rectified spirit and ethanol. Though the demand for the production of ethanol increases, on the other hand it releases large volume of effluent. Owing to these constrains and many problems faced by the distillery industries, the present work was focused on utilization of microbial activities in two stage sequential manner for the treatment of the Anaerobically treated Distillery Spent Wash (ADSW). Batch experiment was conducted for the optimization of process parameters in treating real ADSW using a single factorial and Response Surface Methodology (RSM). In order to evaluate the combined effect of the extent of biodegradation and decolorization of distillery spent wash in terms of COD reduction and percentage decolorization the present investigation was focused on two stage sequential treatment. Screening test was performed to find the ability of cyanobacteria in decolorizing spent wash. It was found that Phormidium valderianum showed the highest potential to decolorize spent wash when compared to Oscillatoria sp and Synechocystis pevalekii. Batch experiment was conducted in photobioreactor as a second stage for treating the spent wash obtained from the first stage of bioreactor. The process parameters maintained in the reactor were scaled up from the optimized results of the flask level experiment which was performed during RSM study. The change in morphological properties of the organism and transport phenomena of the fermentation broth from the bioreactor was studied using image analyser and viscometer. The best fit with the Herschel-Bulkey model was observed on the 5th day of fermentation broth (R2 value=0.995). Results revealed that the experimental data was best fitted with Andrew s model with R2 value of 0.959. Therefore the two stage sequential treatment using fungi followed by cyanobacteria were proved to be the best process to solve the effluent problems in distillery industries.