phylogeny (Song and Ward 2003). Therefore, investigations of both types of
phylogeny will provide different perspectives and additional insights on the bacterial
community composition. DE nitrification is the stepwise reduction of nitrate to
nitrite, in which each step is catalyzed by different enzymes encoded by the genes
nar/nap, nir, nor, and nos. In most cases, only one or two of the enzyme genes nirK,
nirS, norB, or nosZ are investigated when studying the denitrifying bacterial community, because it is assumed that they are all adequately representatives of the true
community composition (Hallin and Lindgren 1999; Hannig et al. 2006; Bremer
et al. 2007). To date, to our knowledge, no study has attempted to ascertain whether
any individual enzyme genes can suffice to characterize the overall community
composition of denitrifying bacteria. To do so, it would be valuable to compare
the occurrence of denitrifying bacterial enzyme genes in a large number of similar
habitats.
Interaction of hydrophytes and microorganisms in constructed wetlands for
wastewater treatment: The plant-water-soil-microorganism interaction plays a
major role in the ecohydrology concept. Plants and microorganism of soil connect
the hydrosphere, lithosphere, and the atmosphere. The strength of the interaction
determines the reliability of the bridge in transferring the contaminated input to
environmentally friendly output (Wetland International 2013). For wastewater treatment, a natural alternative to technical methods is constructed wetlands. There is an
incomplete understanding about the complex process, which is caused by microorganisms, soil matrix, plants, and substances in the wastewater, and their interaction
with each other. In constructed wetland, there is a complex mechanism of both the
microorganism in the root zone and the plants of CW, which come into play while
removing contaminants from wastewater. The wastewater treatment are distributed
within the following order: technological aspects, root growth effect on soil matrix,
transport of gas in helophytes and the discharge of oxygen into the rhizosphere,
bioaccumulation of heavy metals by plants, organic pollutants uptake by plants and
their breakdown, the plant release carbon compounds, and features disturbing the
removal of pathogenic germs (Ulsido 2014).
5.3 Constructed Wetlands and Degradation of Hydrocarbons
in Wastewaters
Like other contaminants, the hydrocarbons are also present in wastewater. The
hydrocarbons consist of a wide range of organic compounds occurred naturally
and also produced anthropogenically, while the characteristics of these compounds
are determined by the arrangement of hydrogen and carbon compounds (ITRC
2003). Hydrocarbons have strong potential to affect not only the function (treatment)
of wetland but also the wetland habitat. There are several pathways involved in the
hydrocarbon removal particularly photo-volatilization, photochemical oxidation,
settling/sedimentation, bioaccumulation, sorption, and biodegradation by plants
and microbes (ITRC 2003).
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S. Khan et al.
phylogeny will provide different perspectives and additional insights on the bacterial
community composition. DE nitrification is the stepwise reduction of nitrate to
nitrite, in which each step is catalyzed by different enzymes encoded by the genes
nar/nap, nir, nor, and nos. In most cases, only one or two of the enzyme genes nirK,
nirS, norB, or nosZ are investigated when studying the denitrifying bacterial community, because it is assumed that they are all adequately representatives of the true
community composition (Hallin and Lindgren 1999; Hannig et al. 2006; Bremer
et al. 2007). To date, to our knowledge, no study has attempted to ascertain whether
any individual enzyme genes can suffice to characterize the overall community
composition of denitrifying bacteria. To do so, it would be valuable to compare
the occurrence of denitrifying bacterial enzyme genes in a large number of similar
habitats.
Interaction of hydrophytes and microorganisms in constructed wetlands for
wastewater treatment: The plant-water-soil-microorganism interaction plays a
major role in the ecohydrology concept. Plants and microorganism of soil connect
the hydrosphere, lithosphere, and the atmosphere. The strength of the interaction
determines the reliability of the bridge in transferring the contaminated input to
environmentally friendly output (Wetland International 2013). For wastewater treatment, a natural alternative to technical methods is constructed wetlands. There is an
incomplete understanding about the complex process, which is caused by microorganisms, soil matrix, plants, and substances in the wastewater, and their interaction
with each other. In constructed wetland, there is a complex mechanism of both the
microorganism in the root zone and the plants of CW, which come into play while
removing contaminants from wastewater. The wastewater treatment are distributed
within the following order: technological aspects, root growth effect on soil matrix,
transport of gas in helophytes and the discharge of oxygen into the rhizosphere,
bioaccumulation of heavy metals by plants, organic pollutants uptake by plants and
their breakdown, the plant release carbon compounds, and features disturbing the
removal of pathogenic germs (Ulsido 2014).
5.3 Constructed Wetlands and Degradation of Hydrocarbons
in Wastewaters
Like other contaminants, the hydrocarbons are also present in wastewater. The
hydrocarbons consist of a wide range of organic compounds occurred naturally
and also produced anthropogenically, while the characteristics of these compounds
are determined by the arrangement of hydrogen and carbon compounds (ITRC
2003). Hydrocarbons have strong potential to affect not only the function (treatment)
of wetland but also the wetland habitat. There are several pathways involved in the
hydrocarbon removal particularly photo-volatilization, photochemical oxidation,
settling/sedimentation, bioaccumulation, sorption, and biodegradation by plants
and microbes (ITRC 2003).
152
S. Khan et al.