Research on the topic Constructed wetland " Waste Water Treatment Plant" . Among the topics of Sanitary Engineering

1. Constructed Wetlands : A low Cost
Waste Water Treatment
System
BAGHDAD UNIVERSITY
SANITARY ENGINEERING DEPARTMENT
M.SC. STUDENT : MARWA MOHAMMED

3. CONSTRUCTED WETLANDS OFFER
SEVERAL ADVANTAGES OVER TRADITION
WATER TREATMENT SYSTEMS:
Wetlands are less expensive to build and operate than
mechanical systems.
There is no energy required to operate a wetland.
Wetlands are passive systems requiring little maintenance.
Normally, the only maintenance required is monitoring of
the water level and rinsing the media every few years to
remove solids and restore adsorption capacity.
Wetlands can also provide wildlife habitat and be more
aesthetically pleasing than other water treatment options.
Subsurface wetlands produce no biosolids or sludge that
requires disposal.

4. WHAT ARE CONSTRUCTED WETLANDS?
Constructed wetlands are small artificial wastewater treatment
systems consisting of one or more shallow treatment cells, with
herbaceous vegetation that flourish in saturated or flooded cells.
They are usually more suitable to warmer climates. In these systems
wastewater is treated by the processes of sedimentation, filtration,
digestion, oxidation, reduction, adsorption and precipitation.
The constructed wetlands
generally consist of six
chambers
◦ Each chamber consists of four cells:
◦ Within each cell are water
hyacinth plants
The constructed wetland
removes solids, dissolved
solids, nutrients, and
pathogens.

5. 4. Perforated drains, drain rock,
texture transition and sand filter
1. Excavation and Forming
2. Waterproofing: Base, geo-textile
membrane
3. Distribution piping
CONSTRUCTION & INSTALLATION

6. TYPES OF CONSTRUCTED
WETLANDS
Surface flow
◦ FWS (Free Water Surface)
Subsurface flow
◦ VSB (Vegetated Submerged Beds)
Vertical flow

7. 1. FREE WATER SURFACE(FWS)
WETLANDS, LIKE MOST NATURAL WETLANDS ARE THOSE
WHERE THE WATER SURFACE IS EXPOSED TO THE
ATMOSPHERE. WATER FLOWS OVER SOIL MEDIA.
A channel (flow bed) is dug and lined with an
impermeable barrier such as clay or geo- textile. The
flow bed is then covered with rocks, gravel and soil.
Vegetation is also planted. It is better to have plants
that are native to the area. After that the wastewater
is let into the flow bed by an inlet pipe. The usual
depth of the wastewater is 10 to 45cm above ground
level. As the water slowly flows through the wetland,
simultaneous processes clean the wastewater and the
cleaned water is released through the outlet pipe.

8. SURFACE FLOW
WETLANDS

9. SURFACE FLOW
WETLANDS

10. • In this, Water flows below
media.
• No water on soil surface but subsoil
is saturated
2. SUBSURFACE
WETLANDS, WHERE THE
WATER SURFACE IS BELOW
GROUND LEVEL.
The use of subsurface
constructed wetlands for water
treatment began in Western
Europe in the 1960’s and in the
U.S. in the 1980’s.

11. HORIZONTAL SUBSURFACE
FLOW WETLANDS

12. VERTICAL FLOW WETLAND

13. Q  KAdh
dl
THE BASIS FOR THE HYDRAULIC
DESIGN OF THE SYSTEM IS DARCY’S
LAW,
Where,
Q = Flow rate in volume per unit time.
K = Hydraulic conductivity of the media.
A = Cross-sectional area of the bed perpendicular to
the flow.
dh/dl = The hydraulic gradient.

14. TYPICAL SUBSURFACEWETLAND SYSTEM
CONSISTS OF :
Liner
Inlet structure
Bed (including media and plants)
Outlet structure
Slope
Systems have been designed with bed slopes of as much 8 percent
to achieve the hydraulic gradient. Newer systems have used a flat
bottom or slight slope and have employed an adjustable outlet to
achieve the hydraulic gradient.
Aspect Ratio
The aspect ratio (length/width) is also important. Ratios of
around 4:1 are preferable. Longer beds have an inadequate
hydraulic gradient and tend to result in water above the bed
surface.

15. Filtration and sedimentation – Larger particles are trapped in the
media or settle to the bottom of the bed as water flows through.
Because these systems are normally used with a pretreatment system,
such as a septic tank or detention pond, this is a small part of the
treatment.
The main treatment processes are,
The breakdown and transformation by the microbial
population clinging to the surface of the media and plant roots
The adsorption of materials and ion exchange at the media and
plant
surfaces.
The plants in the bed also provide oxygen and nutrients to
promote microbial growth. The rest of the bed is assumed to be
anaerobic.
WETLANDS TREAT WATER IN THE
FOLLOWING WAYS

16. THE SUBSURFACE WETLANDS HAVE
PROVED TO BE EFFECTIVE AT
GREATLY REDUCING
CONCENTRATIONS OF FOLLOWING
PARAMETERS :
5-day biochemical oxygen demand (BOD5)
Total suspended solids (TSS)
Nitrogen
Phosphorus
Fecal Coliforms
Wetlands have also shown the ability for reductions
in metals and organic pollutants.

17. PLANTS IN FWS WETLANDS (MACROPHYTES)
In the past monocultures or a combination of two species were
used
Currently more diverse representative of natural ecosystem
plantings occur
The presence of macrophytes is one of the most conspicuous
features of wetlands and their presence distinguishes
constructed wetlands from unplanted soil filters or lagoons.
The macrophytes growing in constructed wetlands have
several properties in relation to the treatment process that
make them an essential component of the design (Brix, 1997).
The type of plant does not matter because primary role
is providing structure for enhancing flocculation,
sedimentation, and filtration of suspended solids
Even though plant type does not matter much, there
are some common varieties-

18. Sedges, Water Hyacinth , Common Cattail , Duckweed, Spatterdock ,
Waterweed

19. ADVANTAGES OF SUBSURFACE
WETLAND(SSW) OVER FREE WATER
SURFACE WETLAND(FWS)
No exposed water surface to attract mosquitoes or for
people to come in contact with.
Fewer odors.
Due to the greater surface area in contact with the water
and greater root penetration of the plants, subsurface
systems can be significantly smaller. Although the media
cost can be expensive, it is usually offset by the smaller
land area required, resulting in a lower cost for the
subsurface system.
Better performance in colder climates due to the
insulating effect of the
• upper media layer.

20.  Increase water quality
 stoppollution
 think for asolution
 Bring out a revolution
 constructed wetlands are referred askidneys
of mother land.
Conclusion :