Constructed wetlands are one of the most promising treatment options for municipal wastewater with respect to the decentralised settlements, especially in rural and suburban areas, because they are low in cost and maintenance requirements with a good performance. They need more land compared to technical intensive treatment but less space than pond systems.

Constructed wetlands can be installed as two different technological systems according to its hydraulic regime: the free water surface (FWS) and subsurface-flow Constructed wetlands, in which the latter can be further categorized to horizontal and vertical subsurface-flow (HSF and VSF). The FWS system in one sense is similar to a pond system incorporating with the emergent macrophytes. For SF system, the water is maintained below the surface of the wetland bodies, usually made up of gravel planted with the emergent macrophytes. In HSF, the flow is usually continuous thereby creating a saturated condition within the wetland body, whereas in VSF, the media is completely unsaturated due to intermittent feeding.

This lesson discusses the capabilities and limits between these constructed wetland systems and the management requirements to achieve the designed purpose. Design and proper operation are explained for some applications. Some future trends with focus on maximization of efficiency, cost minimisation, ecological sanitation and water reuse are presented as well.