title: Experimental design approach to the optimization of PAHs bioremediation from artificially contaminated soil: application of variables screening development.
abstract: BACKGROUND
  The effectiveness of bioremediation systems for PAH-contaminated soil may be constrained by physicochemical properties of contaminants and environmental factors. Information on what is the most effective factor in bioremediation process is essential in the decision of what stimulations can be taken to assist the biodegradation efficacy.
  
  
  METHODS
  In this study, four factors of surfactant (Tween 80), humic acid (HA), salinity and nutrients in a 2(4) full factorial design were screened in bioremediation of phenanthrene contaminated soil by using a consortium of bacteria.
  
  
  RESULTS
  Between the employed levels of the factors only salinity had not significant effect. Optimal concentrations of surfactant, HA and nutrient were obtained by a response surface design. For phenanthrene biodegradation, a central composite face centred design (CCFD) showed that nutrient, surfactant and HA concentrations had highly significant, significant and insignificant effects, respectively. The best conditions with 87.1% phenanthrene biodegradation were 150 mg HA/Kg soil, 12.68 μg/L surfactant, and nutrients as K2HPO4, 0.8; KH2PO4, 0.2 and KNO3, 1 g/L. A high similarity was between the model prediction and experimental results.
  
  
  CONCLUSIONS
  This study showed that nutrient with 81.27% efficiency could be considered as the most effective factor for practical implications of bioremediation process for PAHs contaminated soil cleanup strategies.
authors.affiliation: Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Masoumeh
authors.initials: M
authors.lastname: Ravanipour
authors.affiliation: Department of Environmental Health Engineering, School of Public Health, Iran University of Medical Sciences, Tehran, Iran.
authors.forename: Roshanak Rezaei
authors.initials: RR
authors.lastname: Kalantary
authors.affiliation: Department of Environmental Health Engineering, School of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Anoushiravan
authors.initials: A
authors.lastname: Mohseni-Bandpi
authors.affiliation: Department of Environmental Health Engineering, School of Public Health, Iran University of Medical Sciences, Tehran, Iran.
authors.forename: Ali
authors.initials: A
authors.lastname: Esrafili
authors.affiliation: Department of Environmental Health Engineering, School of Public Health, Iran University of Medical Sciences, Tehran, Iran.
authors.forename: Mahdi
authors.initials: M
authors.lastname: Farzadkia
authors.affiliation: Department of Chemical Engineering, Biotechnology Group, Tarbiat Modares University, Tehran, Iran.
authors.forename: Samireh
authors.initials: S
authors.lastname: Hashemi-Najafabadi
keywords: Bioremediation; Nutrient; Polycyclic Aromatic Hydrocarbons; Response Surface Method; Tween80
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