Production of bioflocculants from spent brewer's yeast and its application in the treatment of effluents with textile dyes

Advances in chemical synthesis have increased the complexity and degradation resistance of dyes used in textile processes. This fact interferes drastically with conventional biological wastewater treatment and demands further methods to avoid environmental damage. In this sense, this work presents a bioflocculant produced by the alkaline hydrolysis of spent brewer's yeast, a residue from the brewing industry, as well as the evaluation of its performance in the precipitation of recalcitrant dyes. The optimum hydrolysis system was accessed by a full 23 factorial design in terms of NaOH concentration, yeast mass, and temperature, followed by a kinetic study. The solid fraction composition of the produced flocculant agent is 46 % of proteins and 29 % of polysaccharides. The performance of the bioflocculant was evaluated in two different systems, real textile wastewater containing rhodamine and a synthetic solution with flavine. The effects of the flocculation variables pH, temperature, agitation, and flocculant agent dosage were taken into consideration. Color removal outcomes above 80 and 90 % were attained for rhodamine and flavine systems, respectively. Further analysis of real textile wastewater for treated and untreated samples in terms of BOD, COD, TOC, and light metals was performed. A biodegradability test showed the employed treatment could increase microbial assimilation of the sample and reduce its persistent compounds. This work shows, for the first time, the feasibility of the bioflocculant from spent brewer's yeast and features its potential applicability to recalcitrant compounds precipitation in textile wastewaters.