Diseño de experimentos

Bioresource Technology 101 (2010) 893–900

Contents lists available at ScienceDirect

Bioresource Technology
journal homepage: www.elsevier.com/locate/biortech

A statistical experiment design approach for optimizing biodegradation of weathered crude oil in coastal sediments
Leila Mohajeri a, Hamidi Abdul Aziz a,*, Mohamed Hasnain Isa b, Mohammad Ali Zahed a
a b

School of CivilEngineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia Civil Engineering Department, Universiti Teknologi PETRONAS, 31750 Tronoh, Perak, Malaysia

a r t i c l e

i n f o

a b s t r a c t
This work studied the bioremediation of weathered crude oil (WCO) in coastal sediment samples using central composite face centered design (CCFD) under response surface methodology (RSM).Initial oil concentration, biomass, nitrogen and phosphorus concentrations were used as independent variables (factors) and oil removal as dependent variable (response) in a 60 days trial. A statistically significant model for WCO removal was obtained. The coefficient of determination (R2 = 0.9732) and probability value (P < 0.0001) demonstrated significance for the regression model. Numericaloptimization based on desirability function were carried out for initial oil concentration of 2, 16 and 30 g per kg sediment and 83.13, 78.06 and 69.92 per cent removal were observed respectively, compare to 77.13, 74.17 and 69.87 per cent removal for un-optimized results. Ó 2009 Elsevier Ltd. All rights reserved.

Article history: Received 23 April 2009 Received in revised form 1 September 2009Accepted 3 September 2009 Available online 20 September 2009 Keywords: Bioremediation Petroleum Nutrient Nitrogen Phosphorus

1. Introduction Hydrocarbons present in the marine environment can originate from natural oil seepage and human activities including extraction, transportation, refining, storage, and utilization of petroleum (crude oil and natural gas) (Ebuehi et al., 2005; Kennish, 2001). Crudeoil causes a variety of risks when released into the environment. It is physically, chemically and biologically harmful to soil because of the presence of many toxic compounds, such as polycyclic aromatic hydrocarbons, benzene and its substituted and cycloalkane rings, in relatively high concentrations. The fate and effects of spilled crude oil and its products in soils have already been thesubject of several studies (Murakami et al., 2008; Ebuehi et al., 2005; Kulakow and Erickson, 2000; Leahy and Colwell, 1990). Biodegradation of hydrocarbon compounds is one of the most important processes involved in the weathering and eventual removal of oil from the environment, particularly for its non-volatile components. Thus, potentially biodegradation can be used for recovery of sensitive areassuch as contaminated shorelines, marshes, and wetlands. Bioremediation technologies have been developed for soils and coastal areas using the addition of nutrients and microbes (Lin and Mendelssohn, 2009; Lei et al., 2008; Joo et al., 2008; Greenwood et al., 2008).

* Corresponding author. Tel.: +60 4 5996203; fax: +60 4 5941009. E-mail address: cehamidi@eng.usm.my (H.A. Aziz). 0960-8524/$ -see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2009.09.013

When a major oil spill occurs in freshwater and marine environments, amount of carbon increase and the availability of nitrogen and phosphorus usually becomes the limiting factor for oil degradation (Leahy and Colwell, 1990). Huang et al. (2008), Borresen and Rike (2007), and Boopathy (2000) determinedoptimum nutrient supplement levels at laboratory incubation experiments. Ongoing research and development seeking to improve methods by minimizing the number of experiments provide information about the direct additive effects of the study variables and interaction effects using design of experiment methods. Recently, this statistical technique has been successfully applied in many fields (Huang...