Integrated constructed wetlands

1. Environmental and operational
issues of integrated constructed
wetlands.
Muhammad Ali Raja

2. Contents
• Introduction
• Constructed Wetlands
• Environmental Issues of Constructed Wetlands
• Landscape conservation
• Operational issues of Constructed Wetlands
• Conclusions
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3. Introduction
• The quality of life and sustainability depend upon the quality of the
environment.
• Earth has been the home of uncountable natural resources for a very
long time.
• This belief has led mankind towards the overexploitation of natural
resources, as a result, humanity is now facing a serious problem of
resource depletion.
• For example extensive wars and military operations affecting land
and waterbodies
• Moreover, waterbodies are facing issues like organic pollution.
• Here constructed wetlands come into play.
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4. ConstructedWetlands
• A wetland can be identified by aWater-Logged soil in which
several plants have been grown and the area is covered in water.
• Wetlands can be classified mainly in two categories.
• The constructed wetlands and the natural wetlands. (However,
both have the same role as both help in reducing the pollution
levels and maintain a healthy ecosystem).
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5. Constructed wetland classification based upon the hydrology (Ghermandi et al.)

6. Environmental issues of constructed wetlands
• Environmental issues of constructed wetlands are related to
emissions of GHGs.
• The main focus is to lower emissions of greenhouse gases
(GHGs) and achieving high sustainability goals.
• In several studies comparison between conventional
wastewater treatment systems and integrated constructed
wetlands have been drawn to assess the environmental
impacts of CWs
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7. • There was a research carried out by
(Fuch et al.) in which LCA (life cycle
analysis) was applied to compare
environmental impacts Horizontal
Flow ICW and vertical flow
constructed wetlands.
This figure illustrates that a vertical flow constructed
wetland (VFCW) (with and without gaseous emissions)
have a significantly lesser impact on environment than
horizontal flow constructed wetland (HFCW).
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8. • A study carried out in a city of China, Pan. et al. estimated the emissions of
greenhouse gases.
• Here, instead of comparing an HFCW toVFCW,Vertical Subsurface
ConstructedWetland (VSCW) was compared to conventional wastewater
treatment systems.
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• This figure shows the amount of
greenhouse emissions by vertical
subsurface flow constructed
wetlands (20.2 kg CO2 eq/y) is only
one third (1/3rd) to those of a
conventional wastewater treatment
plant that are around (67.9 kg CO2
eq/y).

9. • Similarly, in a study Chen et al.
analyzed the emissions of GHG
during the construction and
operation phase of a wastewater
treatment plant and a typical
constructed wetland and drew a
comparison between them, in terms
of low carbon emission assessment.
GHG such as (CO2, CH4 and N2O) have been made and units
have been taken in CO2 equivalent. It has been noted in
LRCW that NO2 is of higher fraction, but it has a lower
potential of global warming about 310 times lesser than CO2.
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10. This figure tells about the indirect and direct emission of greenhouse
gases. Here, in LRCW direct emissions account for 41.23% and 23.91%
GHGs and the class.
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11. • In a study byVan derWerf and de Klein, it was noticed, integrated
constructed wetlands work as a carbon dioxide sinks, however, the
amount of carbon dioxide that sinks may vary depending upon some
factors such as, operating conditions, type of vegetation etc.
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12. 12
In Figure a, it is evident that the emissions of
CH4 from a wetland is significant (not only
seasonal but also day and night).
In figure b, denitrification is highly dependent upon
temperature and 91% of the yearly denitrification occurs from
April-September.

13. Land-Scape conservation
• On one hand, high rates of construction and increased urbanization helps to
meet the needs of increasing population, but on the other hand side, it is
decreasing the green cover of the cities throughout the world, which can have
several impacts such as causing suffocation and discomfort to the people.
• In this regard, green infrastructure plays a very important role. Since the
planning and designing of the green infrastructure is emerging from the
recent past as the need to create environmentally friendly places is also
increasing.
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14. Operational Issues of ConstructedWetlands
• Operational issues of constructed wetlands are related to
Monitoring and Harvesting.
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15. Monitoring
• Monitoring provides the data which can be used in the improvement of
the treatment performance and tells about the accumulation of
pollutants that are toxic before they bioaccumulate
• Monitoring should always begin before the bioremediation process,
when intervention can be done.
• At the time of planning of a monitoring program, one thing should be
kept in mind that the intensity of a wetland will depend upon its
complexity of design and its size consequently.
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16. Harvesting
• After harvesting of a ConstructedWetland, nutrients in the plant
biomass are subsequently transported.
• They can be used in animal feedstock or as a fertilizer for agricultural
land. Moreover, they can also act as a feedstock for a biogas plant to
produce energy since they are rich in nutrients and energy.
• The process of harvesting requires extensive care, as it may disturb the
nutrient removal efficiency and the plant may well lose its competitive
strength.
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17. • In a study conducted byVerhofstad et al. (20) two separate ecosystems
of different ponds of (30x15m) were studied with a water depth of
approximately 75cm in the Netherlands.
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This figure explains, harvesting frequency of 1 and
5 times resulted in a lower biomass.
However, the optimal harvesting frequency is
considered from 2-3 times annually, anything
more or less will affect the growth of
macrophytes adversely. (Verhofstad et al.)

18. Conclusions
• However, there are a few limitations of ICWs, but such technologies help a
great deal in reducing greenhouse emissions and doesn’t put burden on the
environment as other conventional wastewater treatment systems.
• Moreover, CWs provide sustainability to the environment, efficiency in
pollution removal and economical convenience.
• CWs have gained popularity worldwide due to these advantages which urged
scientists and researchers to work even more in this regard to improve this
technology to the next level.
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19. References
• (1). Ghermandi,A., Bixio, D., &Thoeye, C. (2007).The role of free water surface constructed
wetlands as polishing step in municipal wastewater reclamation and reuse. Science of theTotal
Environment, 380(1-3), 247-258.
• (2). Saier, M. H., &Trevors, J.T. (2010). Phytoremediation. Water, Air, and Soil Pollution, 205(1), 61-
63.
• (3). Herath, I., &Vithanage, M. (2015). Phytoremediation in constructed wetlands.
In Phytoremediation (pp. 243-263). Springer,Cham.
• (4). Fuchs,V. J., Mihelcic, J. R., & Gierke, J. S. (2011). Life cycle assessment of vertical and
horizontal flow constructed wetlands for wastewater treatment considering nitrogen and carbon
greenhouse gas emissions. Water research, 45(5), 2073-2081.
• (5). Pan,T., Zhu, X. D., &Ye,Y. P. (2011). Estimate of life-cycle greenhouse gas emissions from a
vertical subsurface flow constructed wetland and conventional wastewater treatment plants:A
case study in China. Ecological Engineering, 37(2), 248-254.
• (6). Chen, G. Q., Shao, L., Chen, Z. M., Li, Z., Zhang, B., Chen, H., &Wu, Z. (2011). Low-carbon
assessment for ecological wastewater treatment by a constructed wetland in Beijing. Ecological
Engineering, 37(4), 622-628.
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20. • (7). de Klein, J. J., & van der Werf, A. K. (2014). Balancing carbon sequestration and GHG
emissions in a constructed wetland. Ecological engineering, 66, 36-42.
• (8).Verhofstad, M. J. J. M., Poelen, M.V.,Van Kempen, M. M. L., Bakker, E. S., &
Smolders, A. J. P. (2017). Finding the harvesting frequency to maximize nutrient removal
in a constructed wetland dominated by submerged aquatic plants. Ecological
Engineering, 106, 423-430.
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