Tratamento biológico de efluente contendo óleo diesel e gasolina

Abstract

The oil industry deal daily with issues related to contamination by petroleum products. With an elaborate logistics distribution of liquid fuels to the consumer market, the oil companies deal with problems related to truck loading, this step can occur any spills of fuels, which results in the generation of waste(effluent). The effluent generated at these sites generally has a high organic load, because they had hydrocarbon constituents of gasoline and diesel oil, promoting contamination of the systems (water and or soil). An alternative treatment of this effluent is the use of mixed cultures, since these microorganisms are capable of providing the elimination or significant reduction of the pollution load which may be present in soil or in a liquid medium. However, the use of mixed cultures in the process presents difficulties in forming flakes, compromising its settleability. As an alternative to this problem, this study investigated the use of ferric chloride in combination with an anionic polyelectrolyte and coagulant natural (Moringa oleifera and chitosan) in the settling of a mixed culture, which was used for the biodegradation of hydrocarbons present in effluent contaminated with diesel oil and gasoline, as well as the biodegradation of hydrocarbon contaminated effluent in a continuous process. Biodegradation was evaluated in four centrals composites designs (CCD), having as variables the first CCD: ferric chloride and polyelectrolyte concentrations, the second ranged concentration of Moringa oleifera, temperature and the drying time of seed. The third Moringa oleifera and polyelectrolyte concentrations and the fourth, varying the chitosan and hydrochloric acid concentrations. The responses monitored in CCD experiments included the sludge volume index (SVI), turbidity, and specific rate of oxygen uptake (SOUR). Subsequently, biodegradation was monitored in a sequencing batch reactor (SBR) to determine the biodegradability under the best conditions obtained in each of the CCDs. The results indicated that the better coagulant was chitosan in concentration of 50 mg/L solubilized in HCl 0.25 N. The results indicated that within five cycles, total organic carbon (TOC) removal increased from 77% to 82%, while the volatile suspended solids (VSS) increased from 1.4 to 2.25 g/L, total petroleum hydrocarbon (TPH) removal increased from 75% to 81% and has not been verified reduction in the amount of living cells, as occurred with the Moringa oleifera, showing that chitosan was an effective coagulant. With the optimized chitosan concentration (50 mg/L) solubilized in 0.25 mol/L of HCl, was conducted experiments on continuous process were monitored residence time of 2, 3 and 4 days in schemes with and without aeration. The best results were obtained at residence time of 4 days with aeration, with turbidity removal of 95% and TPH removal 75% in the reactor and 94% in the clarified and SSV in the reactor within 30 days of operation was 1.8 g/L. These results were interesting because it makes the process of treating wastewater contaminated with hydrocarbons applicable, sustainable and environmentally friendly.