More than 50% of South Africa’s wetlands have already been destroyed. These are vital habitats for many plants and birds, and other smaller creatures. A wetland is an area of waterlogged soil where only water-tolerant plants can grow. The rich diversity of waterbirds in southern Africa (totalling 130 species) is the result of the many wetlands spread across the subcontinent. A constructed wetland is a man-made system that mimics the natural functions and processes of a wetland. It can be constructed as a horizontal or vertical system, and uses indigeous plants and filtering materials such as gravel and stones to treat and clean greywater.
Constructed wetlands can be used to treat greywater to a standard suitable for use in landscape irrigation. They will also encourage biodiversity into the landscape and reduce the demand for municipal water for irrigation. Indigenous plants that are suitable for use include Juncus oxycarpa, Crinum bulbispermum, and Zantedeschia aethiopica.
These wetlands fall within Sustainable Drainage Systems (SuDS), a concept that uses natural approaches to managing urban drainage, slowing and retaining water to prevent flooding, and simultaneously removing pollutants.
Water Wise has developed a simple, cost-effective, DIY constructed wetland that can be implemented in gardens and landscapes to treat greywater for use in irrigation. Go to the Rand Water website and click on the Water Wise logo for a free, comprehensive guideline on how to build your own wetland.
The wetland can be modified to suit a home garden, school yard, or office landscape, as well as the volume of greywater produced. Tests on the quality of treated water have shown that the wetlands produce water that is suitable for use in landscape irrigation. In fact, coliform bacteria levels were significantly reduced after treatment with the wetlands. As always, take care when working with greywater.