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Rapid industrialization has provided comforts to mankind but has also impacted the environment harmfully. There has been severe increase in the pollution due to several industries, in particular due to dye industry, which generate huge quantities of wastewater containing hazardous chemicals. Although tremendous developments have taken place for the treatment and management of such wastewater through chemical or biological processes, there is an emerging shift in the approach, with focus shifting on resource recovery from such wastewater and also their management in sustainable manner. This review article aims to present and discuss the most advanced and state-of-art technical and scientific developments about the treatment of dye industry wastewater, which include advanced oxidation process, membrane filtration technique, microbial technologies, bio-electrochemical degradation, photocatalytic degradation, etc. Among these technologies, microbial degradation seems highly promising for resource recovery and sustainability and has been discussed in detail as a promising approach. This paper also covers the challenges and future perspectives in this field.

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Industrialization increases use of dyes due to its high demand in paper, cosmetic, textile, leather and food industries. This in turn would increase wastewater generation from dye industrial activities. Various dyes and its structural compounds present in dye industrial wastewater have harmful effects on plants, animals and humans. Synthetic dyes are more resistant than natural dyes to physical and chemical methods for remediation which makes them more difficult to get decolorize. Microbial degradation has been researched and reviewed largely for quicker dye degradation. Genetically engineered microorganisms (GEMs) play important role in achieving complete dye degradation. This paper provides scientific and technical information about dyes & dye intermediates and biodegradation of azo dye. It also compiles information about factors affecting dye(s) biodegradation, role of genetically modified organisms (GMOs) in process of dye(s) degradation and perspectives in this field of research.

In this study, four bench-scale pre-anoxic submerged membrane bioreactors (MBR) were operated simultaneously at different mean cell residence times (MCRTs) (3, 5, 10, and 20 days) to systematically elucidate the contributing factors of membrane fouling. Severe membrane fouling was first observed in the 3-day followed by the 5-day MCRT MBRs. Minimal membrane fouling was detected in the 10 and 20-day MCRT MBRs. The fouling of microfiltration membrane was not controlled by mixed liquor suspended solids concentration or zeta potential of biomass. Instead, membrane fouling rate increased with increasing soluble microbial products and extracellular polymeric substances concentrations, which both increased with decreasing MCRT. Total organic carbon, protein, carbohydrate, and UV254 absorbance in the mixed liquor supernatant increased with decreasing MCRT and were consistently higher than those of the effluent. Accumulation of carbohydrates rather than proteins in the mixed liquor supernatant was found to decrease with increasing MCRT. Normalized capilliary suction time value rather than the capilliary suction time value would indicate membrane fouling potential of a mixed liquor. Image analysis of the fouled membrane using scanning electron microscope and confocal laser scanning microscope showed that biofilm formation was the cause of membrane fouling.