Optimal conditions for bioremediation of oily seawater
Introduction
With advances in biotechnology, bioremediation has become one of the most rapidly developing fields of environmental restoration. Bioremediation methods use microorganisms to reduce the concentration and toxicity of various chemical pollutants, such as petroleum hydrocarbons, polycyclic aromatic hydrocarbons, pesticides, industrial solvents, and metals (Dua et al., 2002).
Hydrocarbon pollution in marine ecosystems has potentially dangerous effects on organism and human health through bioaccumulation and biomagnification via food chains. The majority of petroleum hydrocarbons compounds (i.e., saturates, aromatics) is degradable at different rates, and some components that are recalcitrant to biodegradation may be metabolized over long periods of time. Bioremediation strategies attempt to enhance and accelerate this process. The use of bioremediation for large-scale field application gained significant attention in 1989 when beaches contaminated with crude oil from the Exxon Valdez spill were seeded with fertilizer to promote the growth of hydrocarbon-degrading bacteria (Atlas, 1995).
The addition of dispersant chemicals can affect the environmental cycling processes of petroleum and has been used to treat oil spills in temperate marine environments for many years (Kirby and Law, 2008). Dispersants are a group of chemicals which disseminate organics in aqueous systems and are extensively employed in marine pollution applications (Lee et al., 2008, Hua, 2006). A major reason for using these chemicals is to prevent spilled oil from reaching the shore. Bioremediation, like other biotechnologies has limitations. Bioremediation processes are highly heterogeneous and complex and are correspondingly difficult to characterize. The success of oil spill bioremediation depends on the availability of the appropriate microorganisms, multiple environmental factors and the composition of the oil spilled (Zahed et al., 2010, Gandolfi et al., 2010, Saeki et al., 2009, Zhu et al., 2001).
Response surface methodology (RSM) is a useful mathematical and statistical method for analyzing the effects of several independent variables on process outcomes (response) (Myers and Montgomery, 2002, Draper and John, 1988). In many processes, the relationship between the response and the independent variables is usually unknown; therefore, the first step in RSM is to approximate the function (response) in terms of independent variables. Usually, this process employs a low-order polynomial equation in a pre-determined region of the independent variables, which is subsequently analyzed to identify the optimum values of the independent variables for the best response.
Several studies have been performed on the impact of nitrogen and phosphorus supplementation on bioremediation of crude oil in marine environments (Nikolopoulou and Kalogerakis, 2008, Adesodun and Mbagwu, 2008, Kirkpatrick et al., 2006, Ruiz et al., 2006, Knezevich et al., 2006). However, the optimal duration of treatment and nutrient concentration is still not known for bioremediation of pure and mixed crude oils in seawater. To address these unknowns, the objective of this research was to study the effect of parameters describing the bioremediation of petroleum hydrocarbons in seawater contaminated with a high concentration of crude oil. Classical optimization involves changing one variable at a time while fixing all other variables and studying the effect on the response. This is a time-consuming, expensive, and complicated process for a multi-variable system. Therefore, RSM was employed for design, modeling and optimization of crude oil bioremediation.
In recent years, RSM has been successfully applied to biodegradation optimization (e.g., polycyclic aromatic hydrocarbons (PAH), n-alkanes, diesel fuel) in different matrixes (Mohajeri et al., 2010a, Huang et al., 2008, Vieira et al., 2007; Nasrollahzadeh et al., 2007).
Section snippets
Sampling
Seawater and coastal sediments were collected from the Butterworth Channel, Penang, Malaysia, for both acclimatization and experiments.
Bacterical concertum were isolated from seawater, as follows: 1 L seawater, 10 g soil sample and 1 mL crude oil were transferred to a 2-L conical flask containing growth medium. Bacteria were cultured in a media containing 1 g/L NH4NO3, 1 g/L KH2PO4, 1 g/L K2HPO4, 0.2 g/L MgSO4·7H2O, 0.05 g/L FeCl3, and 0.02 g/L CaCl2 as described by Mohajeri et al., 2010a, Mohajeri et
Statistical testing and mathematical modeling
The experimental data obtained from the design were fitted and analyzed by the response surface regression procedure via Eq. (3), a second-order polynomial equation:where Y denotes the response (TPH removal); β0 is the value of the fixed response at the center point of the design; βi, βii, and βij are the linear, quadratic and interaction-effect (cross-product coefficients) regression terms, respectively; xi and xj are the coded values of
Conclusions
RSM and CCD were employed to optimize biodegradation of dispersed crude oil in seawater samples. Statistical and diagnostics analyses indicated that RSM is a reliable tool to optimize crude oil bioremediation. A significant (R2 = 0.9645, P < 0.0001) quadratic polynomial mathematical model was generated.
Under optimum conditions, 58.6% DCO removal was observed in a 28-day experiment, compared to 53.3% removal in experiments without optimization and 22.6% removal in experiments in which natural
References (33)
- et al.
Biodegradation of waste-lubricating petroleum oil in a tropical alfisol as mediated by animal droppings
Bioresour. Technol.
(2008) Petroleum biodegradation and oil spill bioremediation
Mar. Pollut. Bull.
(1995)- et al.
Biodegradation of crude oil in sandy sediment
Int. Biodeterior. Biodegrad.
(1999) - et al.
Influence of compost amendment on microbial community and ecotoxicity of hydrocarbon-contaminated soils
Bioresour. Technol.
(2010) Biodegradation of dispersed marine fuel oil in sediment under engineered pre-spill application strategy
Ocean Eng.
(2006)- et al.
Optimization of nutrient component for diesel oil degradation by Rhodococcus erythropolis
Mar. Pollut. Bull.
(2008) - et al.
Oil spill treatment products approval: the UK approach and potential application to the Gulf region
Mar. Pollut. Bull.
(2008) - et al.
Biodegradation of petroleum hydrocarbons at low temperature in the presence of the dispersant Corexit 9500
Mar. Pollut. Bull.
(2002) - et al.
Biodegradation of dispersed forties crude and alaskan north slope oils in microcosms under simulated marine conditions
Spill Sci. Technol. Bull.
(2003) - et al.
Crude oil degradation efficiency of a recombinant Acinetobacter baumannii strain and its survival in crude oil-contaminated soil microcosm
FEMS Microb. Lett.
(2004)
A statistical experiment design approach for optimizing biodegradation of weathered crude oil in coastal sediments
Bioresour. Technol.
Enhanced bioremediation of crude oil utilizing lipophilic fertilizers combined with biosurfactants and molasses
Mar. Pollut. Bull.
Bioremediation and toxicity determination of natural seawater polluted with weathered crude oil by salt-tolerant consortia in a SBR
Mar. Pollut. Bull.
Oil spill remediation by using the remediation agent JE1058BS that contains a biosurfactant produced by gordonia sp. strain JE-1058
Bioresour. Technol
Biodegradability of dispersed crude oil at two different temperatures
Mar. Pollut. Bull.
Biodegradation of effluent contaminated with diesel fuel and gasoline
J. Hazard. Mater.
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