Abstract
The large volume of sugar cane vinasse generated by alcohol distillation motivated current treatment to reduce vinasse volume by a concentration process and to eliminate pollutants in the wastewater. The vinasse concentration by the coagulation/flocculation process favored the use of the thickened sludge either for fertilizing purposes or for biogas production. The photocatalysis treatment of the clarified vinasse mineralized pollutants and reduced toxicity, with subsequent water reuse. The first series of coagulation/flocculation experiments were carried out in a jar-test apparatus at room temperature with samples of 200 mL and several coagulant concentrations. In the second series of experiments, photocatalysis tests were performed on the clarified vinasse obtained by coagulation/flocculation under conditions optimized in the first series of experiments. The photocatalysis tests were performed for five consecutive days with UV irradiation, using TiO2-P25 as photocatalyst. Significant reduction of toxicity, consistent with the reduction in chemical oxygen demand (COD), was found when the photocatalysis treatment subsequent to coagulation/flocculation process was employed. Further, 98% reduction of turbidity and 87% reduction of color were obtained by the coagulation/flocculation process. Coupled to the photocatalysis process, significant reductions in absorbance, toxicity and COD (80%) were also achieved.
Highlights
Vinasse is a recalcitrant wastewater produced in large amounts in ethanol production from sugar cane
The wastewater is characterized by very high chemical oxygen demand (COD) (60-200 kg m-3) and biochemical oxygen demand (BOD) (25-75 kg m-3), whereas pH, which depends on the Maringá, v. 35, n. 1, p. 89-95, Jan.-Mar., 2013 conditions of sugar cane cultivation, may range between 3.7 and 5.0 (CHAUDHARI et al, 2008; CUNHA et al, 1987; SATYAWALI; BALAKRISHNAN, 2008)
The low efficiency in COD removal when compared to that in color and turbidity removals has been observed in other studies (RIZZO et al, 2008; RODRIGUES et al, 2008). These results demonstrate the efficiency of the method employed and show that a simple process of coagulation/flocculation may decrease the organic load up to 45% without adding toxic components to the already clarified and concentrated vinasse
Summary
Vinasse is a recalcitrant wastewater produced in large amounts in ethanol production from sugar cane. In this process, the fermentation of sugar cane and the subsequent distillation of ethanol generate between 11 and 13 liters of vinasse per liter of ethanol produced. Apart from high organic content rates, distillery wastewater contains nutrients, such as nitrogen (1,660-4,200 mg L-1), phosphorus (2253,038 mg L-1) and potassium (9,600-17,474 mg L-1). 89-95, Jan.-Mar., 2013 conditions of sugar cane cultivation, may range between 3.7 and 5.0 (CHAUDHARI et al, 2008; CUNHA et al, 1987; SATYAWALI; BALAKRISHNAN, 2008) The wastewater is characterized by very high chemical oxygen demand (COD) (60-200 kg m-3) and biochemical oxygen demand (BOD) (25-75 kg m-3), whereas pH, which depends on the Maringá, v. 35, n. 1, p. 89-95, Jan.-Mar., 2013 conditions of sugar cane cultivation, may range between 3.7 and 5.0 (CHAUDHARI et al, 2008; CUNHA et al, 1987; SATYAWALI; BALAKRISHNAN, 2008)
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