Removal of Dyes from Wastewaters in Moving Bed Biofilm Reactors: A Review of Biodegradation Pathways and Treatment Performance

Abstract

Dye-containing wastewaters are produced in large quantities worldwide. The bright colors they provide, associated with their potential toxicity, carcinogenicity, and mutagenicity, consist of environmental threats. Therefore, remediation of these waste streams is essential. However, the low biodegradability shown by these compounds constitutes an obstacle to the application of effective and low-cost conventional biological wastewater treatment systems. In this context, other advanced biofilm technologies, such as the moving bed biofilm reactor (MBBR), may consist in an economically viable and eco-friendly alternative for achieving high removal of dyes, while also reaching high performance in the concomitant degradation of other pollutants, such as organic matter and nutrients. In this chapter, the MBBR technology is briefly explained, and recent investigations on the treatment of dyecontaining wastewaters by this biofilm process are described. Moreover, the most influential operational parameters for color removal improvement are discussed. The use of sequential reactors in multistage processes and the association of MBBR with other technologies are also evaluated. Finally, the kinetics of dye degradation in MBBR is presented. Few studies were found in the literature on the application of MBBR for dye removal, mainly consisting of lab-scale or pilot-scale investigations. A single MBBR as a stand-alone technology does not seem to achieve complete dye mineralization. Nonetheless, the use of a series of MBBR or their combination with other physicochemical or biological processes seems to be a good alternative for dyes remediation. It is clear that more studies on MBBR process optimization are needed, especially for real dye-containing wastewaters, to guarantee the effectiveness and sustainability of large-scale treatment plants.