CWs in the last four decades has gained popularity as an alternative treatment to
conventional treatment. Media, water, vegetation, and microbes are the four major
components that make up the CW. The transferring of water is through the filtering
media, and physical mechanisms are used for the removal of contaminants, e.g.,
sedimentation or filtration and microbial degradation as biochemical interaction.
Role of hydrophytes: The wetland plants such as hydrophytes work as sites of
storage for nutrients and carbon and provide mechanism for the gas movement to
and from the hydrosol (wetland soil) (UNEP 2004). The transportation of oxygen
occurs into the rhizome through plants from the air and from the soil too. For
constructed wetland, the preferred plants are those special types of plants (plant
having aerenchyma) which can trap oxygen from the atmosphere with their root
system to incorporate into the soil. The aerenchym tissue which is
non-photosynthetic portion of the hydrophytes ; that are buried in the anoxic
hydrosol ; maintain aerobic respiration is ensure in this process (wetland interland,
2013).The microbes that are associated with rhizome can use some of this oxygen
through symbiotic relationship. A variety of plant species can be grown in
constructed wetlands (De Sousa et al. 2003). This totally depends on plant’s nature
and the purpose of their use, e.g., marsh and deep marsh, shallow marsh lands
(Ulsido 2014).
Role of soil nutrients: In constructed wetland, the soil’s microorganisms and the
grown hydrophytes need nutrients in optimum level. The balance of plants and
microbes growth is controlled or maintained by the level of essential nutrients.
Certain ratio of specific essential nutrients is required by plants in order to achieve
optimum growth. The reason of the badly affected plant growth is the poor and
imbalanced nutrient ratio. For the wastewater treatment, the preferred microbe’s
growth rate is affected badly by the availability of unbalanced nutrients. The
population of microbes can be changed due to unbalanced ratio and is responsible
to generate smelly metabolism as a result of anaerobic pathways with compounds
containing sulfur and nitrogen (Rehm and Reed 1999).
Role of microbes: Microorganisms and their metabolism regulate largely the
function of wetland, which is the fundamental characteristic of wetland (Wetzel
1993). Bacteria, fungi, yeast, rind algae, and protozoa are microorganisms. A major
sink for many nutrients and organic carbon is the microbial biomass (Ulsido 2014).
Microbial transformations are aerobic (require free oxygen), while others are anaerobic (absence of free oxygen). When bacterial species are capable of functioning
under both aerobic and anaerobic conditions, it means that they are facultative
anaerobes in response to changing environmental conditions. Adjustment capabilities are present in microbial population; they adjust to changes in the water delivered
to them. Populations of microbes can expand quickly when presented with material
containing suitable energy. Without suitable environmental conditions, many microorganisms become dormant and can remain dormant for years. Toxic substances
affect microbial community of a constructed wetland, such as heavy metal and
pesticides, and to prevent such chemicals from being introduced at damaging
concentrations, care must be taken. Organic compounds that are water soluble
such as BOD and hydrocarbons are consumed by bacteria of wetland. Suspended
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S. Khan et al.
conventional treatment. Media, water, vegetation, and microbes are the four major
components that make up the CW. The transferring of water is through the filtering
media, and physical mechanisms are used for the removal of contaminants, e.g.,
sedimentation or filtration and microbial degradation as biochemical interaction.
Role of hydrophytes: The wetland plants such as hydrophytes work as sites of
storage for nutrients and carbon and provide mechanism for the gas movement to
and from the hydrosol (wetland soil) (UNEP 2004). The transportation of oxygen
occurs into the rhizome through plants from the air and from the soil too. For
constructed wetland, the preferred plants are those special types of plants (plant
having aerenchyma) which can trap oxygen from the atmosphere with their root
system to incorporate into the soil. The aerenchym tissue which is
non-photosynthetic portion of the hydrophytes ; that are buried in the anoxic
hydrosol ; maintain aerobic respiration is ensure in this process (wetland interland,
2013).The microbes that are associated with rhizome can use some of this oxygen
through symbiotic relationship. A variety of plant species can be grown in
constructed wetlands (De Sousa et al. 2003). This totally depends on plant’s nature
and the purpose of their use, e.g., marsh and deep marsh, shallow marsh lands
(Ulsido 2014).
Role of soil nutrients: In constructed wetland, the soil’s microorganisms and the
grown hydrophytes need nutrients in optimum level. The balance of plants and
microbes growth is controlled or maintained by the level of essential nutrients.
Certain ratio of specific essential nutrients is required by plants in order to achieve
optimum growth. The reason of the badly affected plant growth is the poor and
imbalanced nutrient ratio. For the wastewater treatment, the preferred microbe’s
growth rate is affected badly by the availability of unbalanced nutrients. The
population of microbes can be changed due to unbalanced ratio and is responsible
to generate smelly metabolism as a result of anaerobic pathways with compounds
containing sulfur and nitrogen (Rehm and Reed 1999).
Role of microbes: Microorganisms and their metabolism regulate largely the
function of wetland, which is the fundamental characteristic of wetland (Wetzel
1993). Bacteria, fungi, yeast, rind algae, and protozoa are microorganisms. A major
sink for many nutrients and organic carbon is the microbial biomass (Ulsido 2014).
Microbial transformations are aerobic (require free oxygen), while others are anaerobic (absence of free oxygen). When bacterial species are capable of functioning
under both aerobic and anaerobic conditions, it means that they are facultative
anaerobes in response to changing environmental conditions. Adjustment capabilities are present in microbial population; they adjust to changes in the water delivered
to them. Populations of microbes can expand quickly when presented with material
containing suitable energy. Without suitable environmental conditions, many microorganisms become dormant and can remain dormant for years. Toxic substances
affect microbial community of a constructed wetland, such as heavy metal and
pesticides, and to prevent such chemicals from being introduced at damaging
concentrations, care must be taken. Organic compounds that are water soluble
such as BOD and hydrocarbons are consumed by bacteria of wetland. Suspended
150
S. Khan et al.