FH WETLAND SYSTEMS Ltd.

Reed Beds and Constructed Wetlands are two terms often used interchangeably. Although international terminology appears to be unagreed, in Ireland the term Constructed Wetland is usually used to describe a soil based marsh system in which the wastewater flows over the soil substrate; while a Reed Bed is usually a gravel based system in which the wastewater flows vertically or horizontally through the gravel substrate.

FH Wetland Systems offers a design service for both Constructed Wetlands and Reed Beds, and we will use the system which is most appropriate to the site conditions.

When it comes to reed beds and constructed wetlands for wastewater treatment, many people assume that they are the same. However there are two principal design types, and they both have advantages and disadvantages for each site:

Other Features often associated with reed beds and constructed wetlands:

Ponds are often incorporated into the design of both soil based constructed wetland systems and gravel based reed bed systems.
Wet woodlands, or evapotranspiration areas are sometimes incorporated into the design of both soil based constructed wetland systems and gravel based reed bed systems.
Wet meadow areas are sometimes incorporated into the design of soil based constructed wetland systems.

Advantages of Constructed Wetland Systems and Gravel Reed Bed Systems over alternative forms of effluent treatment:

Low construction and running costs
Easy management
Excellent reduction of biochemical oxygen demand (BOD5) and suspended solids (SS) from septic tank effluent
Potential for high removal of a wide range of pollutants
Secondary benefits in terms of potential wildlife habitat enhancement
May be used in conjunction with old or overloaded systems to achieve high discharge standards

Principal Differences between Soil and Gravel Systems:

Land area requirements are greater for soil based constructed wetlands
Capital cost are typically greater for reed beds
Maintenance input is greater for reed beds
Preliminary settlement requirements are more stringent for reed beds
Constructed wetlands are considerably easier to desludge in the event of excessive solids inputs
Exposed water/effluent is present in soil based wetlands (to about 200mm depth, with tall plants growing in it), but is covered with gravel in reed beds.
Where a horizontal flow reed bed is used without a vertical flow component, the sewage effluent is completely covered.
Constructed wetlands more closely resemble natural habitats and provide exposed water and are thus more beneficial to wetland wildlife.
While both systems have the potential to have zero energy requirements, constructed wetlands can achieve this with less site slope. The vertical flow reed bed usually requires a pump for most sites.
Constructed wetlands are tolerant of variable loads.

Constructed Wetlands or Reed Beds? Choosing the Most Suitable Option for your Needs

The choice of system depends on site size and soil type, budget, degree of maintenance required, adjacent landuse. The above differences provide a basic background as to the factors to be considered when selecting which system to use. For additional information contact FH Wetland Systems to discuss a specific project.