WHAT IS A WETLAND ALSO KNOWN AS REED BEDS?

WETLAND
They usually consist of a porous medium of gravel, about 0,5 m deep supporting aquatic plants such as reeds, rushes, sedges etc. Water flows through the porus space between the media and plant roots which provide a large surface area for colonization by communities of pollutant removing microbes.

Although the subsurface environment of a Wetland is largely devoid of oxygen, tiny oxygen rich micro-sites exist adjacent to the macrophyts roots. In traveling through the sequence of oxygen-rich and oxygen-poor environments provided by the Wetland, wastewater is subjected to conditions which enhance the removal of a number of important pollutants such as organic carbon (which depletes dissolved oxygen) in aquatic ecosystems and is hence referred to as Biochemical Oxygen Demand (BOD) and nitrogen (which can cause algal blooms in surface waters).

Other pollutants removal mechanisms in Wetlands include filtration, sedimentation and plant uptake of nutrients. Wetlands also have the capacity to lower the concentrations of disease causing pathogens from wastewater.

When is a WETLAND applicable?
Secondary treatment is required in On-Site and Decentralized Wastewater Management Systems when land application is by sub-surface irrigation. It may also be indicated where land application is by trench if available land area is limited or if nitrogen is an issue.

The choice of secondary treatment technology will be governed by a number of factors including:
initial cost, recurrent cost, level of maintenance and user involvement as well as availability of power and land area. The Wetland compares favourably with other approaches on all factors except land area requirement.