Hezegune eraikiak ur grisen tratamendurako (Constructed wetlands for greywater treatment)

Constructed wetlands are low cost, easy to install and sustainable grey-water treatment systems, due to their capacity for removing conventional pollutants. Constructed wetlands are classified as free water surface flow type and subsurface flow type, being the last one more effective for wastewater treatment. Hybrid systems that combine both types of wetlands are increasingly used to harness the best of each wetland type. In order to achieve a satisfactory wastewater purification, an adequate selection of the design parameters is essential, being a key point the adequate choice of plant species. Grey-water fed to the constructed wetland contains large amounts of organic matter and nutrients, being plants and microorganisms responsible for the elimination of these pollutants. Additionally wastewater carries suspended solids and nitrogen compounds. The formers are eliminated by filtration in the gravel bed, while the latter by nitrification and denitrification. In this work, the main characteristics of the constructed wetland types and their advantages and disadvantages have been commented, as well as the characterization of the entering wastewater and a summary of the main physical, chemical and biological processes that are carried out for the purification of water in constructed wetlands.