Review
and comment on constructed wetland design
Introduction
As it was notice that natural
wetlands are able to clean water, it drew scholars and engineers to research on
the wetland system. The first manual wetland experiments appeared in 1950’s (Zhang, 2012). Constructed wetland is a
treatment system. It uses natural processes to improve water quality (US EPA, 2015). The components of a
constructed include vegetation, substrates, biology and microorganism. The
reason to build a constructed wetland is to use a more natural way to deal with
waste water. To
guide developers and avoid environmental disaster by building a constructed
wetland, guideline books were established by authorities. Some governments have
established their own national guideline for developing constructed wetland,
including US, Canada and Australia, etc. Agencies also contribute to
build the
constructed wetlands by establish handbook to provide technical
support. As each country and region has its unique condition, the guideline and
handbook may show some differences. But the framework of each country could be
similar. The US’s,
Canadian and Australian guidelines are more significant to represent the
typical guideline books.
US design and application issues
By reviewing the handbook of constructed wetland from the US
EPA website, the basic framework and considerations could be summarized. The US
EPA handbook shows a whole picture of construction wetland design and
application. There are nine chapters in this handbook covering three categories
of knowledge, including the constructed wetland basics, design consideration
with details and its management from construction to operation. The aim of this
handbook is to guide common constructed wetland developers rather than a
particular region or type of developers. Hence, in this handbook, the content
seemed more like a teaching material. The first three chapters are introduction
to the wetland science. Chapter 4 showed general consideration for the design.
Then in the next three chapters, the main three technical aspects were
indicated. From Chapter 7, it could be seen that the US focused on the surface
flow wetlands and subsurface flow wetlands more than other types of constructed
wetlands. That is probably because these two types constructed wetlands were
the US’s alternatives.
Chapter 8 and 9 gave construction, operation, maintenance
and monitoring guidance. This part showed the importance of pre-activates and
monitoring.
Canadian design and application issues
Other than the US handbook, the Canadian which the author
studied is funded and published by local council in 1999. As the responsible
body is much smaller, it contained more details for this particular region. This
guideline book is more detailed. In the design consideration part, the author
of the guideline particularly claimed the ‘Anaerobic lagoon and facultative
pond design’ and ‘Vegetated filter strip design’ as independent aspects.
It means that these two parts are special for this region. In the construction and
operation part, ‘planting and seeding’ was listed as an aspect which means the
livability of vegetation will be cared in the construction process.
Comparison of US, Canada and Australia
The structure of the guideline book itself may be different,
but the general contents of each country seems to be the same. The core parts
of a guideline are the design consideration and application process. Here lists
the table to compare the general details of these two parts of a constructed
wetland guideline on design and application.
US
|
Canada
|
|
Design Consideration
|
Site Selection
Structure
Permits
& Regulations
System
Lifetimes
Hydrology
Substrates
Vegetation
|
Location
Soil
Hydrology &
Hydraulic
Cell Construction
Control Structure
Anaerobic Lagoon &
Facultative Pond Design
Vegetated Filter strip
design
Irrigation System
Sludge Handling
|
Application
|
Construction
Operation
Maintenance
Monitoring
|
Plans and
Specifications
Site Preparation
Anaerobic Lagoon and
Facultative Pond
Wetland Cells.
Planting and Seeding
Vegetated Filter
Strip.
Construction
Supervision
Operation
Monitoring
|
The similarity of different guidelines is the process. As today, constructed wetland has been a complete subject in both science and engineering. Its guideline book will definitely share the complete process to build the reliable guidance system. The only differences shall be the particular technology and environmental differences considered and applied in particular regions. There might be particular alternatives in different regions or countries. The US’s alternative could be seen as nearly the same as the Canadian alternative. This the because these two countries are neighbors locating on the Northern America continent. Canada is much colder than US. Hence, the particular focus on the livability of vegetation could be significantly different from US.
Conclusion
As constructed wetland technology is to manipulate the water
treatment process by using natural. The instability determines
that any guideline can only give general design suggestion and regulation
baseline. It is quite difficult for scientists and engineers to predict the
unexpected problems in the constructed wetland’s entire life. The coming
difficulty to manipulate the construction function and its water quality will
be solved while its entire life process.
Reference
Zhang, Y. (2012). Design of a Constructed Wetland for
Wastewater Treatment and Reuse in Mount Pleasant, Utah. All Graduate Plan B and
other Reports. Paper 216. Available at: http://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=1232&context=gradreports [Accessed data: April 28th,
2016]
US EPA. (2015). Constructed Wetlands. US EPA. Available
at: https://www.epa.gov/wetlands/constructed-wetlands [Accessed data: April 28th,
2016]
US EPA. (1995). A Handbook of Constructed Wetlands. Office of
Wetlands, Oceans, & Watersheds. Available at: https://www.epa.gov/sites/production/files/2015-10/documents/constructed-wetlands-handbook.pdf [Accessed data: April 28th,
2016]
Tousignant, E. (1999). Guidance Manual
for The Design, Construction and Operations of Constructed Wetlands for Rural
Applications in Ontario. Canadapt Program of the Agricultural Adaptation
Council, Ontario. Avialble at: http://agrienvarchive.ca/bioenergy/download/wetlands_manual.pdf [Accessed data: April 28th,
2016]
