Natural wetlands These have been used for wastewater treatment for many years. In many cases natural wetlands were used for disposal and not treatment and were considered as wastelands.

Although improvement in the quality of wastewater is generally observed as a result of flow through natural wetlands, the extent of their treatment capability is largely unknown. In Tanzania natural wetlands occupy over 7% of the country’s surface area.

Constructed wetlands

These are Designed/man-made systems aimed at achieving removal of pollutants as observed to take place in natural systems. They are sometimes called Reed beds or artificial wetlands but constructed wetlands is an international term-constructed wetlands are increasingly seen as a viable Eco-technology for wastewater treatment due to:

a)Public demand for more stringent wastewater effluent standards,
b)Rapidly escalating costs of construction and operation associated with conventional treatment plants, and
c)Environmental benefits

Classification of Constructed wetlands
These are:
a)Surface Flow Constructed wetlands (popular in USA particularly for Large wastewater flow: This is characterized by Wastewater being exposed
to the atmosphere as it flows through the cell (treatment unit)
b)Subsurface constructed wetlands (Horizontal or vertical flow) widely accepted in Europe, Australia and Africa: This is characterized by Wastewater
being exposed to the atmosphere as it flows through the cell