Efeito de biocatalisador fúngico e/ou biocoagulante magnético na tratabilidade de águas residuárias lácteas

Abstract

The objective of the present study was to evaluate the effect of the fungal biocatalyst and the magnetic biocoagulant on the treatability of dairy wastewater. Fungal lipases of Penicillium polonicum were produced by solid-state fermentation, using sunflower seeds as substrate under the conditions of 96 h of fermentation, at 27 °C, and 55% of humidity. The optimum enzymatic activity of the lipase (biocatalyst) was 32.73 U gSS-1 at pH 7 and a temperature of 37 °C. The biocatalyst was extracted from the fermented solid (crude extract) using a sodium chloride solution (NaCl 2%), reaching 94.51% of enzymatic activity recovery. The effect of the biocatalyst in the bioremediation was initially evaluated in acid dairy wastewater (raw effluent 1 – EB1) and then in alkaline dairy wastewater (raw effluent 2 – EB2). The fermented solid and the crude extract containing the biocatalyst were applied in the bioremediation of the EB1 under conditions of 37 °C, 150 rpm, 500 L-1 , and 168 h. The bioremediation of the EB1 with the fermented solid caused a turbidity increase in the reaction medium, in which the particles released by the fermented solid were verified, and the efficiency in the removal of oils and greases was 26.96%. For the crude extract, the oil and grease content increased almost 9 times, making its application in the bioremediation unfeasible in this treatment process. Only the fermented solid was used in the bioremediation of the EB2 under conditions of 37 °C, 150 rpm, 500 U L-1 , and 96 h. The turbidity also increased at this stage, but the reduction of oils and greases was more expressive (58.77%). For the coagulation/flocculation/sedimentation (C/F/S) experiments, calcium chloride (CaCl2) and potassium chloride (KCl) solutions were tested at the concentration of 0.1 to 0.4 xv M to extract the coagulant protein of Moringa oleífera seeds (MO). To reduce the sedimentation time in the C/F/S process, the MO biocoagulant at concentrations of 1500 and 2000 mg L-1 was functionalized with nanoparticles to obtain the magnetic MO biocoagulant, at a concentration of 60 mg per 20 mL of MO solution. For EB2, the best C/F/S condition was 1500 mg L-1 of biocoagulant extracted with 0.2 M CaCl2, removing 96.53% of turbidity in 20 min, the decrease of oil and grease content was 74.04% at this stage. For the dairy wastewater pre-treated by the bioremediation process (EP2), 1500 1500 mg L-1 of biocoagulant extracted with 0.4 M CaCl2 was required to achieve 88.25% of turbidity removal in 20 min, and the oil and grease content reduced 73.13% in this process. The characterization of the generated sludge in both treatments indicates the presence of nanoparticles, which could lead to the study of their reuse. Both processes presented good results, with positive and negative points, in such a way that the choice of a method must be guided based on the parameter to be improved.