Wetlands are areas that have been flooded and saturated with shallow water long enough to create an oxygen-free (anoxic or anaerobic) environment in their soil. Only plants adapted to these conditions can grow in such a habitat. Collectively, we call them wetland vegetation, and these include, in our conditions, most commonly reed, cattail, sedges, caltha and others. Wetlands are very valuable ecosystems that support a variety of specialized organisms (from bacteria to animals) and provide a range of ecosystem services.
We build artificial wetlands to provide the same ecosystem services as natural wetlands, but under more controlled conditions. Most commonly, artificial wetlands are created as a source of food (e.g., for rice cultivation), nesting sites for waterfowl, for the preservation and enhancement of biodiversity, for flood control, but most importantly for the treatment of various types of waste or drainage water and stormwater runoff. They can be divided into two categories depending on whether the water is on or below the surface of the soil and the gravel substrate. Artificial wetlands in which purification takes place below the surface, i.e., in the root zone of plants, are called root treatment plants.
The root treatment plant for drainage water treatment on Brejlský potok is designed as a combination of two filter fields:
- The first field is primarily for nitrate removal. It is filled with a mixture of gravel and wood chips; anoxic conditions prevail in the filter and water flows horizontally through this field.
- The second field has the task of removing pesticides. It is filled with gravel with an interlayer containing biochar. Water flows vertically through this filter, which increases the degree of aeration and overall efficiency.
