Integral Approach for Improving the Degradation of Recalcitrant Petrohydrocarbons in a Fixed-Film Reactor Verónica Jiménez & Violeta Bravo & Linda Gonzalez Gutierrez Received: 1 September 2010 / Accepted: 21 January 2011 / Published online: 12 February 2011 # Springer Science+Business Media B.V. 2011 Abstract The degradation of diesel and phenan- threne in waste water was studied in a column combining a submerged trickling-flow with a fixed- film at a determined biofilm thickness with recir- culation. Degradation efficiencies were found to be high with the production of a biofilm thickness of 789 μm structured in a package material with proper adsorption and physicochemical properties necessary to reach a stable state condition for the degradation of recalcitrant components in 78% at a retention time of 3 h. Improved degradation rates were reached with a biofilm built from an adapted inoculum that showed the presence of Pseudomonas sp., Klebsiella sp. Enterobacter in a concentration of 6.45×10 9 CFU mL -1 . Moreover, the biodegradation rate of the inoculumn was quantified. The diesel kinetic experimental data were well described by Gompertz model which provides a specific grow rate (Kb) of 0.76±0.36 h -1 and a correlation of R 2 =0.93. The integral approach study of the variables of a complex degradation process lead to improve the complete operation of the reactor in comparison with other more specific component-based approaches. Keywords Bioremediation . Diesel . Polyaromatics . Fixed-film-reactor . Bioreactors . Biofilm Abbreviations a Log(CFU L -1 ) BOD Biological oxygen demand BTEX Benzene, toluene, ethylbenzene, and xylene C B Cell mass produced C B0 Cell mass at time zero CFU Colony-forming units COD Chemical oxygen demand Kb Specific growth rate FAU Formazin attenuation unit i i sample MSM Mineral salt medium n Number of samples RPM Revolutions per minute R 2 Correlation coefficient tc Hours required to reach inflection point VSS Volatile suspended solids yi Measurement of i sample ŷ Average value of all samples 1 Introduction Diesel is one of the principal subproducts of petro- leum that is commercialized in Mexico. The refineries and petrochemical complexes have well-developed wastewater treatment plants. These plants are Water Air Soil Pollut (2011) 220:301–312 DOI 10.1007/s11270-011-0755-3 V. Jiménez : V. Bravo (*) : L. G. Gutierrez Centro de Investigación y Desarrollo Tecnológico en Electroquímica, Parque Tecnológico Querétaro, Sanfandila, Pedro Escobedo, Querétaro, Mexico C.P. 76703 e-mail: vbravo@cideteq.mx