Journal of Hazardous Materials 140 (2007) 52–59 Biodegradation of effluent contaminated with diesel fuel and gasoline P.A. Vieira a,∗ , R.B. Vieira a , F.P. de Franc ¸a b , V.L. Cardoso a a Universidade Federal de Uberlˆ andia, Faculdade de Engenharia Qu´ ımica, Uberl ˆ andia, MG, Brazil b Universidade Federal do Rio de Janeiro, Escola de Qu´ ımica, Rio de Janeiro, RJ, Brazil Received 17 November 2005; received in revised form 14 June 2006; accepted 15 June 2006 Available online 18 June 2006 Abstract We studied the effects of fuel concentration (diesel and gasoline), nitrogen concentration and culture type on the biodegradation of synthetic effluent similar to what was found at inland fuel distribution terminals. An experimental design with two levels and three variables (2 3 ) was used. The mixed cultures used in this study were obtained from lake with a history of petroleum contamination and were named culture C 1 (collected from surface sediment) and C 2 (collected from a depth of approximately 30 cm). Of the parameters studied, the ones that had the greatest influence on the removal of total petroleum hydrocarbons (TPH) were a nitrogen concentration of 550 mg/L and a fuel concentration of 4% (v/v) in the presence of culture C 1 . The biodegradability study showed a TPH removal of 90 ± 2% over a process period of 49 days. Analysis using gas chromatography identified 16 hydrocarbons. The aromatic compounds did not degrade as readily as the other hydrocarbons that were identified. © 2006 Elsevier B.V. All rights reserved. Keywords: Biodegradation; Mixed cultures; Diesel oil; Gasoline; Hydrocarbons 1. Introduction Leaks and accidental spills are a regular occurrence during the exploration, production, refining, transport and storage of petroleum and petroleum products. In Brazil, the distribution infrastructure for petroleum, petroleum derivatives and ethyl alcohol includes 22 inland terminals (one of which is in the city of Uberlˆ andia), 30 waterway terminals, 6 collector centers for alcohol, 13 refineries and several pipelines [2]. At the inland fuel distribution terminals, countless tank trucks are filled daily with gasoline and diesel fuel for nation-wide distribution. Dur- ing the filling process some fuel may spill on the fill pad, also called a patio. In some cases, the water from washing the patios and the trucks flows into ditches where it is then allowed to run into small lakes or ponds located at the rear of the terminals. The aromatic compounds (including the lighter weight com- pounds known as BTEX, benzene, toluene, ethylbenzene and xylene) make up from 10 to 59% of the gasoline (mass/mass), while the aliphatic hydrocarbons make up from 41 to 62%. Aro- ∗ Corresponding author at: Campus Santa Mˆ onica, Bloco 1K, Caixa Postal 593, CEP 38400-902, Brazil. Tel.: +55 34 3239 4285; fax: +55 34 3239 4249. E-mail addresses: patriciavieiraengq@yahoo.com.br (P.A. Vieira), rafaelbrunovieira@yahoo.com.br (R.B. Vieira), fpfranca@ufrj.br (F.P. de Franc ¸a), vicelma@ufu.br (V.L. Cardoso). matics are usually more toxic than aliphatics with the same number of carbon atoms and they are typically found at higher concentrations in water because their solubility is three to five times greater [7]. Diesel oil or fuel is a complex mixture consist- ing basically of paraffinic, olefinic and aromatic hydrocarbons and, in smaller amounts, molecules containing sulfur, nitrogen, metals, oxygen, etc. Diesel oils are composed of molecules with 8–40 carbon atoms and are usually heavier more viscous and less volatile than gasoline. Reducing hydrocarbon concentrations either in regularly dis- charged effluent, or in media contaminated by accidental fluid releases, is a significant challenge. Mechanical (e.g. skimming) and chemical (e.g. surfactants and dispersants) methods have limited effectiveness and can be expensive. Several researchers have studied the use of microorganism to decompose petroleum products and have shown this to be a promising technological alternative [3,10,15,19,21,27,30; etc.]. Microbiological activ- ity is affected by a number of environmental factors including energy sources, donors and acceptors of electrons, nutrients, pH, temperature and inhibition by the substratum or metabo- lites. These parameters influence how quickly microorganisms adapt to the available substratum [25]. The goal of this study was to adapt two mixed cultures extracted from lake sediment that was contaminated with diesel oil and gasoline and to select the best culture and 0304-3894/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2006.06.048