the anaerobic biodegradation process of hydrocarbons (ITRC 2003). The degradation of the hydrocarbon is less dependent on the processes that occur in the
surrounding ecosystem (Sugai et al. 1997). The volatilization and aerobic biodegradation processes constitute a coupled pathway that contributes significantly to the
natural reduction of hydrocarbon (Lahvis et al. 1999). For best results the experimental design should include the environmental conditions including pH, temperature, dissolved oxygen (DO), and nutrient requirements (i.e., phosphorous and
nitrogen) of the wetland microbes and plants. Contamination due to the manufacture,
transportation, and distribution of petroleum is a major environmental problem
(Atlas and Cerniglia 1995). Oil production process generate large volume of waste
stream including produced and waste waters, when the production process reaches to
the maturity stage, the volume of produced water exceeds up to ten times the total
volume of hydrocarbons produced (Stephenson 1992). The disposal and treatment of
such large volume is of great concern for the environment and for the operators
(Stephenson 1992). The produced water from the oil industry consists of aromatic
hydrocarbons such as ethyl benzene, benzene, xylene (ortho, meta, and para isomers), and toluene which are very soluble, neurotoxic, and cause cancer (Hiegel
2004). Due to high toxicity and persistence, the biodegradation processes and
wetland remediation techniques have attracted great attention (Ilker et al. 2000).
The oil industry used the traditional treatment technologies such as coalescence
hydrocyclones, centrifuges, and flotation, and numerous separators are not operative
regarding the elimination of dissolved organic components plus aromatics in the
dissolved water phase (International Association of Oil and Gas Producers 2002;
Descousse et al. 2004)
Traditionally, the removal of the organic compounds from water has exploited the
density differences between the oils, and water implies that organic compounds can
be removed. In the environment, BTEX compounds occur through aerobic biodegradation and volatilization procedures (Stephenson 1992). The microorganisms
degrade the hydrocarbons in the metabolic process to get energy frequently on
heterotrophic microorganisms that require carbon in the form of moderately complex
and reduced organic compounds (e.g., petroleum hydrocarbons). These microbes
depend on the oxidation of these reduced organic compounds in exothermic degradation reaction sequences that produce energy and the “building blocks” of biosynthesis (Admire et al. 1995). Constructed wetlands are economically and
environmentally friendly technology than other physical and chemical methods
and more efficient results in the degradation of the hazardous compounds
(Ye et al. 2006). Wetland systems are also novel and less expensive treatment
approaches (Rew and Mulamoottil 1999), which eliminate organics such as aromatic
components in the dissolved water phase and inorganic compounds in wastewater
(Wallace and Knight 2006).
The constructed wetland shows the benefits of the natural wetlands, but the
design should be custom-made according to the requirement of individual contaminated site. Despite the effectiveness, the increasing popularity, positive economics,
and environmentally friendly technology, the constructed wetlands are still rare in
the petroleum industry for the treatment of wastewater.
6 Constructed Wetlands: A Clean-Green Technology for Degradation and. . .
155
surrounding ecosystem (Sugai et al. 1997). The volatilization and aerobic biodegradation processes constitute a coupled pathway that contributes significantly to the
natural reduction of hydrocarbon (Lahvis et al. 1999). For best results the experimental design should include the environmental conditions including pH, temperature, dissolved oxygen (DO), and nutrient requirements (i.e., phosphorous and
nitrogen) of the wetland microbes and plants. Contamination due to the manufacture,
transportation, and distribution of petroleum is a major environmental problem
(Atlas and Cerniglia 1995). Oil production process generate large volume of waste
stream including produced and waste waters, when the production process reaches to
the maturity stage, the volume of produced water exceeds up to ten times the total
volume of hydrocarbons produced (Stephenson 1992). The disposal and treatment of
such large volume is of great concern for the environment and for the operators
(Stephenson 1992). The produced water from the oil industry consists of aromatic
hydrocarbons such as ethyl benzene, benzene, xylene (ortho, meta, and para isomers), and toluene which are very soluble, neurotoxic, and cause cancer (Hiegel
2004). Due to high toxicity and persistence, the biodegradation processes and
wetland remediation techniques have attracted great attention (Ilker et al. 2000).
The oil industry used the traditional treatment technologies such as coalescence
hydrocyclones, centrifuges, and flotation, and numerous separators are not operative
regarding the elimination of dissolved organic components plus aromatics in the
dissolved water phase (International Association of Oil and Gas Producers 2002;
Descousse et al. 2004)
Traditionally, the removal of the organic compounds from water has exploited the
density differences between the oils, and water implies that organic compounds can
be removed. In the environment, BTEX compounds occur through aerobic biodegradation and volatilization procedures (Stephenson 1992). The microorganisms
degrade the hydrocarbons in the metabolic process to get energy frequently on
heterotrophic microorganisms that require carbon in the form of moderately complex
and reduced organic compounds (e.g., petroleum hydrocarbons). These microbes
depend on the oxidation of these reduced organic compounds in exothermic degradation reaction sequences that produce energy and the “building blocks” of biosynthesis (Admire et al. 1995). Constructed wetlands are economically and
environmentally friendly technology than other physical and chemical methods
and more efficient results in the degradation of the hazardous compounds
(Ye et al. 2006). Wetland systems are also novel and less expensive treatment
approaches (Rew and Mulamoottil 1999), which eliminate organics such as aromatic
components in the dissolved water phase and inorganic compounds in wastewater
(Wallace and Knight 2006).
The constructed wetland shows the benefits of the natural wetlands, but the
design should be custom-made according to the requirement of individual contaminated site. Despite the effectiveness, the increasing popularity, positive economics,
and environmentally friendly technology, the constructed wetlands are still rare in
the petroleum industry for the treatment of wastewater.
6 Constructed Wetlands: A Clean-Green Technology for Degradation and. . .
155