Color Removal

Vinasse-13In general, microbial decolorization is an environmental friendly and low cost alternative to chemical decomposition process. However, the problem still persists because several organisms that have been shown to degrade melanoidin are not best suited for treating molasses containing wastewater. The studies so far can be seen as an early step toward solving the problem. Moreover, most of microbial decolorization studies required effluent dilution for optimal activity. While using microorganisms, use of media supplement create extra load on overall effluent treatment process. Fungus secreting ligninolytic enzymes are capable of degrading pollutants. P. chrysosporium and T.versicolor are the most widely investigated and they resulted in 80% decolorization of diluted anaerobically digested spentwash. T.versicolor produces an extracellular enzyme recognized as peroxidase which is involved in mineralization of melanoidins. The fungus resulted in more than 80% decolorization of diluted anaerobically and aerobically treated effluent. In general fungus was more effective in decolorizing raw molasses spent wash than the anaerobically and aerobically treated streams. This was possibly due to changes in the chemical structure of the melanoidin pigments during anaerobic and aerobic treatment. However, the oxygen demand of the fungus was known to be high. The effects of filamentous fungi have also been studied on fermentation wastewater. Among them Aspergillus spp. is the most popular. These are comparatively slow growing species and more susceptible to infection but the production of a series of extracellular hydrolytic enzymes makes it easier for them to grow on starch and cellulose substrates. They resulted in 60–69% reduction in color. Apart from fungi, yeast has also been studied for fermentation wastewater treatment. Yeast is characterized by quick growth and is less susceptible to contamination by other microorganisms; further, yeast produces biomass with high nutritive value. The yeast Citeromyces resulted in high and stable removal efficiency in both color intensity and organic matter. The decolorization activity of acetogenic bacteria is capable of oxidative decomposition of melanoidins thereby removing low molecular weight compounds in untreated molasses spentwash. The biodegradability of spentwash can be enhanced by enzymatic pre-treatment prior to the aerobic step. The biodegradability was further enhanced by combined ultrasound and enzymatic pre-treatment.