Sedimentation of mixed cultures using natural coagulants for the treatment of effluents generated in terrestrial fuel distribution terminals

This study evaluated the use of natural coagulants (Moringa oleifera and chitosan) under different conditions with a mixed culture (C1 mixed culture). This culture was used for the biodegradation of hydrocarbons present in the effluent from fuel distribution terminals contaminated with diesel oil and gasoline. The biodegradation was evaluated by two central composite design (CCD) experiments: the first with varying concentrations of Moringa oleifera (MO), drying temperatures (TE) and seed drying times (TI); the second with varying concentrations of chitosan and the hydrochloric acid in which chitosan had been solubilized. The responses monitored in the CCD experiments included the sludge volume index (SVI), the turbidity removal (TR) and the specific rate of oxygen uptake (SOUR). Subsequently, the biodegradation was monitored in a sequencing batch reactor (SBR) under the optimal conditions obtained for each CCD experiment. The results indicated that the best coagulant was chitosan solubilized in 0.25 N HCl at a concentration of 50 mg/L. Within five cycles with chitosan as a coagulant, the total organic carbon (TOC) removal increased from 77 +/- 1.0% to 82 +/- 0.5%, the volatile suspended solids (VSS) increased from 1.4 +/- 0.3 to 2.25 +/- 0.3 g/L and the total petroleum hydrocarbon (TPH) removal increased from 75 +/- 1.0% to 81 +/- 0.5%. (C) 2012 Elsevier B.V. All rights reserved.