*Enzymatic Bioremediation of Dyes from Textile Industry Effluents DOI: http://dx.doi.org/10.5772/intechopen.103064*


**Table 2.**

*Examples of treatment processes used to remove textile dyes.*

released into the environment. In the United States, according to the Environmental Protection Agency (EPA), the limit value for COD is 163 kg per ton of fabric, however, in practice, cod effluents are up to 15 times higher than the legal standard [27]. Therefore, it is essential to apply efficient treatment strategies that ensure the complete removal of pollutants or that ensure the sustainability of the environment for future generations through physical, chemical, and biological technologies or a combination of them [10].

Physical methods, such as membrane filtration (nanofiltration, reverse osmosis, electrodialysis), sorption techniques, or chemical methods, such as coagulation or flocculation combined with flotation and filtration, flocculation by precipitation, electroflotation, and electrokinetic coagulation, considered for the removal of various dyes, do not degrade them. Such methods simply promote the reduction of the concentration of dyes, converting them from one chemical way to another, thus creating secondary pollution [6]. Among the several processes used for the removal of wastewater dyes, such as chemical oxidation, biodegradation, electrochemical treatment, adsorption, and photocatalytic degradation, the use of photocatalyst provides good

#### *Enzymatic Bioremediation of Dyes from Textile Industry Effluents DOI: http://dx.doi.org/10.5772/intechopen.103064*

results with high efficiency, low cost, speed, and better performance in environmental conditions when sunlight is used in the process [28].

Several natural materials, such as chitosan, are used in physical dye adsorption processes. Chitosan is a modified natural biopolymer, derived from the deacetylation of chitin, which is the most abundant polymer on the planet, derived from important biomass produced by inferior plants and animals, such as arthropods, shells of crustaceans, lobsters, shrimps, crabs, and squid [16]. Adsorption is one of the most efficient methods for removing dyes, however, there is a need for further treatment of the residue resulting from the process.

In addition to the physical and chemical processes aimed at the removal of dyes from wastewater, biological processes also play an important role. Among the biological methods that can be used to remove dyes from industrial wastewater, phytoremediation is a process that has advantages compared to chemical and physical methods of removal. The removal of textile dyes by plants occurs by adsorption, accumulation, and subsequent degradation, mediated by enzymes [29].

In situations where the application of chemical products must be continuous, the use of microorganisms may be considered a simpler and low-cost process, since microorganisms can be added only once in the effluent to be treated, as they have the potential to multiply [30]. Within this context, the activated sludge is commonly used in bioreactors for effluent treatment, which is one of the most used processes by the textile industry [10]. Another possible biological method for the treatment of effluents is the use of bacterial cultures. The isolation of pure cultures from textile wastewater is usually not performed, as it can be a slow and laborious process. Thus, mixed bacterial cultures are commonly used, which, due to cooperation to achieve a potentiated effect, provide better results in discoloration and mineralization of toxic aromatic amines [1].
