Microbial biotechnology for decolorization of textile wastewaters

Wastewater originating from the textile industry is one of the major sources of pollution for surface and groundwater bodies in countries where textiles and other dye-products are produced. Along with dyes, textile wastewaters also contain varying amounts of metals/metalloids, salts and organic pollutants. Moreover, these wastewaters have high temperatures and varying pH. Various physico-chemical and biological strategies have been devised to remove dye contaminants from such wastewaters. However, biotechnological approaches have attracted worldwide attention for their relative cost-effectiveness and environmentally friendly nature. Most biotechnological approaches rely on the use of microbes that have the potential to enzymatically degrade and decolorize dye-containing textile effluents. During recent years, several microbial cultures as well as microbial enzymes have been characterized and used for removal of dyes from simulated wastewaters having defined chemical compositions. However, there are still many challenges in scaling up microbial and enzymatic technologies for decolorization of raw textile wastewater that contain metals/metalloids, salts and other toxic compounds. The present review article summarizes the findings of recent studies conducted on decolorization of raw textile wastewaters. To the best of our knowledge, this is the only review reporting the biodegradation of azo dyes in raw textile effluents.